Key Spec Table
|Analytes Available||Species Reactivity||Key Applications||Detection Methods|
|Insulin||M, R||ELISA||Colorimetric, Fluorescent|
|Description||Rat/Mouse Insulin ELISA|
|Background Information||Insulin, a 5.8 kDa hormone, is secreted by the islet beta cells in the pancreas.|
|Detection method||Colorimetric Fluorescent|
|Application||This Rat/Mouse Insulin ELISA is used to measure & quantify Insulin levels in Metabolism & Endocrine research.|
|Application Notes||3 hour assay, room temperature 10 μL sample size|
|Species Reactivity||Mouse Rat|
|Linearity of Dilution||79–133%|
|Standard Curve Range||
|Safety Information according to GHS|
|Storage and Shipping Information|
|Material Size||96-well strip plate|
|PROTOCOL: RAT / MOUSE INSULIN ELISA KIT|
References | 50 Available | See All References
|Reference overview||Pub Med ID|
|Resveratrol attenuates steatosis in obese Zucker rats by decreasing fatty acid availability and reducing oxidative stress. |
S Gómez-Zorita,A Fernández-Quintela,M T Macarulla,L Aguirre,E Hijona,L Bujanda,F Milagro,J A Martínez,M P Portillo
The British journal of nutrition 107 2012
Non-alcoholic fatty liver disease (NAFLD) is one of the most common manifestations of chronic liver disease worldwide. The aim of the present study was to assess the effect of resveratrol on liver fat accumulation, as well as on the activity of those enzymes involved in lipogenesis and fatty acid oxidation in fa/fa Zucker rats. A total of thirty rats were assigned to three experimental groups and orally treated with resveratrol for 6 weeks, or without resveratrol (C: control group; RSV15 group: 15 mg/kg body weight per d; RSV45 group: 45 mg/kg body weight per d). Liver histological analysis was performed by microscopy. Levels of hepatic carnitine palmitoyltransferase-Ia (CPT-Ia), acyl-coenzyme A oxidase (ACO), fatty acid synthase, glucose-6-phosphate dehydrogenase and malic enzyme were assessed by spectrophotometry, and acetyl-CoA carboxylase was assessed by radiometry. Commercial kits were used to determine serum TAG, NEFA, total HDL and non-HDL-cholesterol, glycerol, ketonic bodies, glucose, insulin, adiponectin, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP), hepatic TAG, thiobarbituric acid reactive substrates, GSH (GSSG) and superoxide dismutase. Resveratrol reduced liver weight and TAG content. It did not modify the activity of lipogenic enzymes but it did increase CPT-Ia and ACO activities. NEFA and ALP were reduced in both resveratrol-treated groups. AST/GOT was reduced only by the lowest dose. ALT/GPT, TAG and adiponectin remained unchanged. Resveratrol reduced liver oxidative stress. This study demonstrates that resveratrol can protect the liver from NAFLD by reducing fatty acid availability. Moreover, resveratrol also protects liver from oxidative stress.
|The effect Akt2 deletion on tumor development in Pten(+/-) mice. |
P-Z Xu,M-L Chen,S-M Jeon,X-D Peng,N Hay
Oncogene 31 2012
The serine/threonine kinase Akt is frequently activated in human cancers and is considered an attractive therapeutic target. However, the relative contributions of the different Akt isoforms to tumorigenesis, and the effect of their deficiencies on cancer development are not well understood. We had previously shown that Akt1 deficiency is sufficient to markedly reduce the incidence of tumors in Pten(+/-) mice. Particularly, Akt1 deficiency inhibits endometrial carcinoma and prostate neoplasia in Pten(+/-) mice. Here, we analyzed the effect of Akt2 deficiency on the incidence of tumors in Pten(+/-) mice. Relative to Akt1, Akt2 deficiency had little-to-no effect on the incidence of prostate neoplasia, endometrial carcinoma, intestinal polyps and adrenal lesions in Pten(+/-) mice. However, Akt2 deficiency significantly decreased the incidence of thyroid tumors in Pten(+/-), which correlates with the relatively high level of Akt2 expression in the thyroid. Thus, unlike Akt1 deletion, Akt2 deletion is not sufficient to markedly inhibit tumorigenesis in Pten(+/-) mice in most tested tissues. The relatively small effect of Akt2 deletion on the inhibition of tumorigenesis in Pten(+/-) mice could be explained, in part, by an insufficient decrease in total Akt activity, due to the relatively lower Akt2 versus Akt1 expression, and relatively high blood insulin levels in Pten(+/-)Akt2(-/-) mice. The relatively high blood insulin levels in Pten(+/-)Akt2(-/-) mice may elevate the activity of Akt1, and possibly Akt3, thus, limiting the reduction of total Akt activity and preventing this activity from dropping to a threshold level required to inhibit tumorigenesis.
|Influence of AIN-93 diet on mortality and cardiac remodeling after myocardial infarction in rats. |
Lidiane P Ardisson,Marcos F Minicucci,Paula S Azevedo,Fernanda Chiuso-Minicucci,Beatriz B Matsubara,Luiz S Matsubara,Priscila P Santos,Heloisa B Assalin,Rosangela Novo,Ethel L Novelli,Léa Silvia Sant'ana,Sergio A R Paiva,Leonardo A M Zornoff
International journal of cardiology 156 2012
The AIN-93 diet was proposed by the American Institute of Nutrition with the objective of standardising studies in experimental nutrition. Our objective was to analyze the effects of AIN-93 diet after myocardial infarction in rats.
|Topiramate treatment protects blood-brain barrier pericytes from hyperglycemia-induced oxidative damage in diabetic mice. |
Tulin O Price,Vijay Eranki,William A Banks,Nuran Ercal,Gul N Shah
Endocrinology 153 2012
Diabetes mellitus causes cerebral microvasculature deterioration and cognitive decline. The specialized endothelial cells of cerebral microvasculature comprise the blood-brain barrier, and the pericytes (PC) that are in immediate contact with these endothelial cells are vital for blood-brain barrier integrity. In diabetes, increased mitochondrial oxidative stress is implicated as a mechanism for hyperglycemia-induced PC loss as a prerequisite leading to blood-brain barrier disruption. Mitochondrial carbonic anhydrases (CA) regulate the oxidative metabolism of glucose and thus play an important role in the generation of reactive oxygen species and oxidative stress. We hypothesize that the inhibition of mitochondrial CA would reduce mitochondrial oxidative stress, rescue cerebral PC loss caused by diabetes-induced oxidative stress, and preserve blood-brain barrier integrity. We studied the effects of pharmacological inhibition of mitochondrial CA activity on streptozotocin-diabetes-induced oxidative stress and PC loss in the mouse brain. At 3 wk of diabetes, there was significant oxidative stress; the levels of reduced glutathione were lower and those of 3-nitrotyrosine, 4-hydroxy-2-trans-nonenal, and superoxide dismutase were higher. Treatment of diabetic mice with topiramate, a potent mitochondrial CA inhibitor, prevented the oxidative stress caused by 3 wk of diabetes. A significant decline in cerebral PC numbers, at 12 wk of diabetes, was also rescued by topiramate treatment. These results provide the first evidence that inhibition of mitochondrial CA activity reduces diabetes-induced oxidative stress in the mouse brain and rescues cerebral PC dropout. Thus, mitochondrial CA may provide a new therapeutic target for oxidative stress related illnesses of the central nervous system.
|Hypothalamic JNK1 and IKK? activation and impaired early postnatal glucose metabolism after maternal perinatal high-fat feeding. |
Eva Rother,Ruth Kuschewski,Miguel Angel Alejandre Alcazar,André Oberthuer,Inga Bae-Gartz,Christina Vohlen,Bernhard Roth,Jörg Dötsch
Endocrinology 153 2012
Hypothalamic inflammation has been demonstrated to be an important mechanism in the pathogenesis of obesity-induced type 2 diabetes mellitus. Feeding pregnant and lactating rodents a diet rich in saturated fatty acids has consistently been shown to predispose the offspring for the development of obesity and impaired glucose metabolism. However, hypothalamic inflammation in the offspring has not been addressed as a potential underlying mechanism. In this study, virgin female C57BL/6 mice received high-fat feeding starting at conception until weaning of the offspring at postnatal d 21. The offspring developed increased body weight, body fat content, and serum leptin concentrations during the nursing period. Analysis of hypothalamic tissue of the offspring at postnatal d 21 showed up-regulation of several members of the toll-like receptor 4 signaling cascade and subsequent activation of c-Jun N-terminal kinase 1 and I?B kinase-? inflammatory pathways. Interestingly, glucose tolerance testing in the offspring revealed signs of impaired glucose tolerance along with increased hepatic expression of the key gluconeogenic enzyme phosphoenolpyruvate carboxykinase. In addition, significantly increased hepatic and pancreatic PGC1? expression suggests a role for sympathetic innervation in mediating the effects of hypothalamic inflammation to the periphery. Taken together, our data indicate an important role for hypothalamic inflammation in the early pathogenesis of glucose intolerance after maternal perinatal high-fat feeding.
|Fenretinide prevents lipid-induced insulin resistance by blocking ceramide biosynthesis. |
Benjamin T Bikman,Yuguang Guan,Guanghou Shui,M Mobin Siddique,William L Holland,Ji Yun Kim,Gemma Fabriàs,Markus R Wenk,Scott A Summers,Gemma FabriÃ s
The Journal of biological chemistry 287 2012
Fenretinide is a synthetic retinoid that is being tested in clinical trials for the treatment of breast cancer and insulin resistance, but its mechanism of action has been elusive. Recent in vitro data indicate that fenretinide inhibits dihydroceramide desaturase, an enzyme involved in the biosynthesis of lipotoxic ceramides that antagonize insulin action. Because of this finding, we assessed whether fenretinide could improve insulin sensitivity and glucose homeostasis in vitro and in vivo by controlling ceramide production. The effect of fenretinide on insulin action and the cellular lipidome was assessed in a number of lipid-challenged models including cultured myotubes and isolated muscles strips incubated with exogenous fatty acids and mice fed a high-fat diet. Insulin action was evaluated in the various models by measuring glucose uptake or disposal and the activation of Akt/PKB, a serine/threonine kinase that is obligate for insulin-stimulated anabolism. The effects of fenretinide on cellular lipid levels were assessed by LC-MS/MS. Fenretinide negated lipid-induced insulin resistance in each of the model systems assayed. Simultaneously, the drug depleted cells of ceramide, while promoting the accumulation of the precursor dihydroceramide, a substrate for the reaction catalyzed by Des1. These data suggest that fenretinide improves insulin sensitivity, at least in part, by inhibiting Des1 and suggest that therapeutics targeting this enzyme may be a viable therapeutic means for normalizing glucose homeostasis in the overweight and diabetic.
|Hyperglycemic Ins2AkitaLdlr⁻⁻ mice show severely elevated lipid levels and increased atherosclerosis: a model of type 1 diabetic macrovascular disease. |
Zhou C, Pridgen B, King N, Xu J, Breslow JL
Journal of lipid research 52 1483-93. Epub 2011 May 23. 2011
Accelerated atherosclerosis is the leading cause of death in type 1 diabetes, but the mechanism of type 1 diabetes-accelerated atherosclerosis is not well understood, in part due to the lack of a good animal model for the long-term studies required. In an attempt to create a model for studying diabetic macrovascular disease, we have generated type 1 diabetic Akita mice lacking the low density lipoprotein receptor (Ins2(Akita)Ldlr⁻/⁻). Ins2(Akita)Ldlr⁻/⁻ mice were severely hyperglycemic with impaired glucose tolerance. Compared with Ldlr⁻/⁻ mice, 20-week-old Ins2(Akita)Ldlr⁻/⁻ mice fed a 0.02% cholesterol AIN76a diet showed increased plasma triglyceride and cholesterol levels, and increased aortic root cross-sectional atherosclerotic lesion area [224% (P < 0.001) in males and 30% (P < 0.05) in females]. Microarray and quantitative PCR analyses of livers from Ins2(Akita)Ldlr⁻/⁻ mice revealed altered expression of lipid homeostatic genes, including sterol-regulatory element binding protein (Srebp)1, liver X receptor (Lxr)α, Abca1, Cyp7b1, Cyp27a1, and Lpl, along with increased expression of pro-inflammatory cytokine genes, including interleukin (Il)1α, Il1β, Il2, tumor necrosis factor (Tnf)α, and Mcp1. Immunofluorescence staining showed that the expression levels of Mcp1, Tnfα, and Il1β were also increased in the atherosclerotic lesions and artery walls of Ins2(Akita)Ldlr⁻/⁻ mice. Thus, the Ins2(Akita)Ldlr⁻/⁻ mouse appears to be a promising model for mechanistic studies of type 1 diabetes-accelerated atherosclerosis.
|Offspring metabolomic response to maternal protein restriction in a rat model of intrauterine growth restriction (IUGR). |
Alexandre-Gouabau, Marie-Cécile, et al.
J. Proteome Res., 10: 3292-302 (2011) 2011
Intrauterine growth restriction (IUGR), along with postnatal growth trajectory, is closely linked with metabolic diseases and obesity at adulthood. The present study reports the time-dependent metabolomic response of male offspring of rat dams exposed to maternal adequate protein diet during pregnancy and lactation (CC) or protein deprivation during pregnancy only (IUGR with rapid catch-up growth, RC) or through pregnancy and lactation (IUGR with slow postnatal growth, RR). Plasma LC-HRMS metabolomic fingerprints for 8 male rats per group, combined with multivariate statistical analysis (PLS-DA and HCA), were used to study the impact of IUGR and postnatal growth velocity on the offspring metabolism in early life (until weaning) and once they reached adulthood (8 months). Compared with CC rats, RR pups had clear-cut alterations in plasma metabolome during suckling, but none at adulthood; in contrast, in RC pups, alterations in metabolome were minimal in early life but more pronounced in the long run. In particular, our results pinpoint transient alterations in proline, arginine, and histidine in RR rats, compared to CC rats, and persistent differences in tyrosine and carnitine, compared to RC rats at adulthood. These findings suggest that the long-term deregulation in feeding behavior and fatty acid metabolism in IUGR rats depends on postnatal growth velocity.
|Encephalopathy caused by ablation of very long acyl chain ceramide synthesis may be largely due to reduced galactosylceramide levels. |
Ben-David O, Pewzner-Jung Y, Brenner O, Laviad EL, Kogot-Levin A, Weissberg I, Biton IE, Pienik R, Wang E, Kelly S, Alroy J, Raas-Rothschild A, Friedman A, Brügger B, Merrill AH Jr, Futerman AH
The Journal of biological chemistry 286 30022-33. Epub 2011 Jun 24. 2011
Sphingolipids (SLs) act as signaling molecules and as structural components in both neuronal cells and myelin. We now characterize the biochemical, histological, and behavioral abnormalities in the brain of a mouse lacking very long acyl (C22-C24) chain SLs. This mouse, which is defective in the ability to synthesize C22-C24-SLs due to ablation of ceramide synthase 2, has reduced levels of galactosylceramide (GalCer), a major component of myelin, and in particular reduced levels of non-hydroxy-C22-C24-GalCer and 2-hydroxy-C22-C24- GalCer. Noteworthy brain lesions develop with a time course consistent with a vital role for C22-C24-GalCer in myelin stability. Myelin degeneration and detachment was observed as was abnormal motor behavior originating from a subcortical region. Additional abnormalities included bilateral and symmetrical vacuolization and gliosis in specific brain areas, which corresponded to some extent to the pattern of ceramide synthase 2 expression, with astrogliosis considerably more pronounced than microglial activation. Unexpectedly, unidentified storage materials were detected in lysosomes of astrocytes, reminiscent of the accumulation that occurs in lysosomal storage disorders. Together, our data demonstrate a key role in the brain for SLs containing very long acyl chains and in particular GalCer with a reduction in their levels leading to distinctive morphological abnormalities in defined brain regions.
|The antioxidant HDL-associated paraoxonase-1 (PON1) attenuates diabetes development and stimulates β- cell insulin release. |
Koren-Gluzer M, Aviram M, Meilin E, Hayek T
|Influence of fasting, insulin and glucose on ghrelin in the dorsal vagal complex in rats. |
Huang L, Qiu B, Yuan L, Zheng L, Li Q, Zhu S
The Journal of endocrinology 211 257-62. Epub 2011 Sep 19. 2011
The dorsal vagal complex (DVC) is an important site in which ghrelin plays an orexigenic role. However, the relationship between ghrelin expression in DVC and the energy status of the organism is unclear, as well as the role of the vagus nerve in this process. In this study, ghrelin expression in DVC neurons of rats was detected, then levels of ghrelin expression were observed under the conditions of regular diet, fasting, high blood glucose, low blood glucose, and following subdiaphragmatic vagotomy and vagus nerve electrostimulation. The results showed the following: 1) there was positive staining of ghrelin neurons in DVC; 2) ghrelin protein and mRNA levels in DVC increased under fasting condition; 3) Hyperglycemia, induced by glucose production, decreased DVC ghrelin levels and levels did not increase under hypoglycemia induced by insulin injection; 4) the dorsal trunk of the subdiaphragmatic vagus transmits a stimulatory signal to increase DVC ghrelin levels, whereas the ventral trunk transmits inhibitory information; and 5) DVC ghrelin levels decreased with 20 Hz stimulation on the ventral or dorsal trunk of subdiaphragmatic vagus nerves but increased with 1 Hz stimulation on the dorsal trunk. These results indicate that endogenous ghrelin is synthesized in DVC neurons. Conditions such as fasting, hyperglycemia, and hypoglycemia result in changes in DVC ghrelin levels in which the dorsal and ventral trunks of subdiaphragmatic vagus play different modulation roles.
|Ranolazine increases β-cell survival and improves glucose homeostasis in low-dose streptozotocin-induced diabetes in mice. |
Ning Y, Zhen W, Fu Z, Jiang J, Liu D, Belardinelli L, Dhalla AK
The Journal of pharmacology and experimental therapeutics 337 50-8. Epub 2011 Jan 12. 2011
In addition to its anti-ischemic and antianginal effects, ranolazine has been shown to lower hemoglobin A(1c) (HbA(1c)) in patients with coronary artery disease and diabetes. The present study was undertaken to test the hypothesis that ranolazine lowers HbA(1c) because of improved glucose homeostasis in an animal model. Diabetes in mice was induced by giving multiple low doses of streptozotocin. Ranolazine was given twice daily via an oral gavage (20 mg/kg) for 8 weeks. Fasting plasma glucose levels were significantly lower in the ranolazine-treated group (187 ± 19 mg/dl) compared with the vehicle group (273 ± 23 mg/dl) at 8 weeks. HbA(1c) was 5.8 ± 0.4% in the vehicle group and 4.5 ± 0.2% in the ranolazine-treated group (p < 0.05). Glucose disposal during the oral glucose tolerance test (OGTT) and insulin tolerance test were not different between the two groups; however, during OGTT, peak insulin levels were significantly (p < 0.05) higher in ranolazine-treated mice. Mice treated with ranolazine had healthier islet morphology and significantly (p < 0.01) higher β-cell mass (69 ± 2% per islet) than the vehicle group (50 ± 5% per islet) as determined from hematoxylin and eosin staining. The number of apoptotic cells was significantly (p < 0.05) less in the pancreas of the ranolazine-treated group (14 ± 2% per islet) compared with the vehicle group (24 ± 4% per islet). In addition, ranolazine increased glucose-stimulated insulin secretion in rat and human islets in a glucose-dependent manner. These data suggest that ranolazine may be a novel antidiabetic agent that causes β-cell preservation and enhances insulin secretion in a glucose-dependent manner in diabetic mice.
|Berberine protects against high fat diet-induced dysfunction in muscle mitochondria by inducing SIRT1-dependent mitochondrial biogenesis. |
Gomes AP, Duarte FV, Nunes P, Hubbard BP, Teodoro JS, Varela AT, Jones JG, Sinclair DA, Palmeira CM, Rolo AP
Biochimica et biophysica acta 2011
Berberine (BBR) has recently been shown to improve insulin sensitivity in rodent models of insulin resistance. Although this effect was explained partly through an observed activation of AMP-activated protein kinase (AMPK), the upstream and downstream mediators of this phenotype were not explored. Here, we show that BBR supplementation reverts mitochondrial dysfunction induced by High Fat Diet (HFD) and hyperglycemia in skeletal muscle, in part due to an increase in mitochondrial biogenesis. Furthermore, we observe that the prevention of mitochondrial dysfunction by BBR, the increase in mitochondrial biogenesis, as well as BBR-induced AMPK activation, are blocked in cells in which SIRT1 has been knocked-down. Taken together, these data reveal an important role for SIRT1 and mitochondrial biogenesis in the preventive effects of BBR on diet-induced insulin resistance.Copyright © 2011. Published by Elsevier B.V.
|Low-level subchronic arsenic exposure from prenatal developmental stages to adult life results in an impaired glucose homeostasis. |
Dávila-Esqueda ME, Morales JM, Jiménez-Capdeville ME, De la Cruz E, Falcón-Escobedo R, Chi-Ahumada E, Martin-Pérez S
Experimental and clinical endocrinology & diabetes : official journal, German Society of Endocrinology [and] German Diabetes Association 119 613-7. Epub 2011 Nov 8. 2011
We evaluated how low-level (3 ppm) subchronic inorganic arsenic (iAs) exposure from prenatal developmental stages until adult life affects glucose homeostasis. Biochemical parameters of glucose and lipid metabolism, pancreatic insulin and glycosylated haemoglobin were determined in 4-month-old female offspring of adult Wistar rats. Pancreatic histology was also performed. Statistical comparisons between control and iAs-treated groups were performed by unpaired two-tailed Student\'s t-test. Statistical significance was set at p<0.05. We found that iAs treatment resulted in an impaired glucose tolerance test, suggestive of impaired glucose metabolism. This group was found to have hyperglycaemia and high levels of HOMA-IR, glycosylated haemoglobin, cholesterol and pancreatic insulin compared to control rats. However, plasma insulin, triglycerides and high-density lipoprotein cholesterol were not different from control rats. Moreover, β-cell damage found in iAs-treated rats consisted of cells with a nucleus with dense chromatin and predominance of eosinophilic cytoplasm, as well as changes in the pancreatic vasculature. The current study provided evidence that subchronic iAs exposure at 3 ppm from prenatal developmental stages to adult life resulted in damage to pancreatic β cells, affected insulin secretion and demonstrated altered glucose homeostasis, thus supporting a causal association between iAs exposure and diabetes.© J. A. Barth Verlag in George Thieme Verlag KG Stuttgart · New York.
|Postnatal growth velocity modulates alterations of proteins involved in metabolism and neuronal plasticity in neonatal hypothalamus in rats born with intrauterine growth restriction. |
Alexandre-Gouabau, Marie-Cécile F, et al.
The Journal of nutritional biochemistry, (2011) 2011
Intrauterine growth restriction (IUGR) due to maternal protein restriction is associated in rats with an alteration in hypothalamic centers involved in feeding behaviour. In order to gain insight into the mechanism of perinatal maternal undernutrition in the brain, we used proteomics approach to identify hypothalamic proteins that are altered in their expression following protein restriction in utero. We used an animal model in which restriction of the protein intake of pregnant rats (8% vs. 20%) produces IUGR pups which were randomized to a nursing regimen leading to either rapid or slow catch-up growth. We identified several proteins which allowed, by multivariate analysis, a very good discrimination of the three groups according to their perinatal nutrition. These proteins were related to energy-sensing pathways (Eno 1, E(2)PDH, Acot 1 and Fabp5), redox status (Bcs 1L, PrdX3 and 14-3-3 protein) or amino acid pathway (Acy1) as well as neurodevelopment (DRPs, MAP2, Snca). In addition, the differential expressions of several key proteins suggested possible shunts towards ketone-body metabolism and lipid oxidation, providing the energy and carbon skeletons necessary to lipogenesis. Our results show that maternal protein deprivation during pregnancy only (IUGR with rapid catch-up growth) or pregnancy and lactation (IUGR with slow postnatal growth) modulates numerous metabolic pathways resulting in alterations of hypothalamic energy supply. As several of these pathways are involved in signalling, it remains to be determined whether hypothalamic proteome adaptation of IUGR rats in response to different postnatal growth rates could also interfere with cerebral plasticity or neuronal maturation.
|Antidiabetic activity of resveratrol, a known SIRT1 activator in a genetic model for type-2 diabetes. |
Sharma S, Misra CS, Arumugam S, Roy S, Shah V, Davis JA, Shirumalla RK, Ray A
Phytother Res 25 67-73. doi 2011
In the present study, resveratrol, a polyphenolic SIRT1 activator was evaluated for its SIRT1 activation in an in vitro fluorescent based assay (EC(50) : 7 μM). The efficacy of resveratrol was also evaluated in ob/ob mice for its antidiabetic and associated metabolic effects. Mice aged 5-8 weeks were included in four groups; control and resveratrol at 5, 15, 50 mg/kg, b.i.d. and were dosed orally. After 4 weeks of drug treatment, body weights were noted and random blood glucose and insulin was estimated for the antidiabetic effect. Animals were also subjected to the oral glucose tolerance test to observe any improvement in the glucose excursion. Triglycerides, total cholesterol, adiponectin and free fatty acid levels were also estimated. The results showed that resveratrol exhibited significant antihyperglycemic activity with an improvement in the insulin levels compared with the control mice. There was also a significant improvement observed in the glucose excursion in the oral glucose tolerance test performed for 120 min; although an insignificant improvement in the triglycerides, total cholesterol, adiponectin and free fatty acid levels was observed at different doses of resveratrol tested. The present findings suggest that resveratrol is an antihyperglycemic agent and drugs similar to resveratrol can be considered as an effective therapeutic adjuvant for the current treatment of diabetes mellitus.Copyright © 2010 John Wiley & Sons, Ltd.
|FoxO1 is involved in the antineoplastic effect of calorie restriction. |
Haruyoshi Yamaza,Toshimitsu Komatsu,Saori Wakita,Carole Kijogi,Seongjoon Park,Hiroko Hayashi,Takuya Chiba,Ryoichi Mori,Tatsuo Furuyama,Nozomu Mori,Isao Shimokawa
Aging cell 9 2010
The FoxO transcription factors may be involved in the antiaging effect of calorie restriction (CR) in mammals. To test the hypothesis, we used FoxO1 knockout heterozygotic (HT) mice, in which the FoxO1 mRNA level was reduced by 50%, or less, of that in wild-type (WT) mouse tissues. The WT and HT mice were fed ad libitum (AL) or 30% CR diets from 12 weeks of age. Aging- and CR-related changes in body weight, food intake, blood glucose, and insulin concentrations were similar between the WT and HT mice in the lifespan study. The response to oxidative stress, induced by intraperitoneal injection of 3-nitropropionic acid (3-NPA), was evaluated in the liver and hippocampus at 6 months of age. Several of the selected FoxO1-target genes for cell cycle arrest, DNA repair, apoptosis, and stress resistance were up-regulated in the WT-CR tissues after 3-NPA injection, while the effect was mostly diminished in the HT-CR tissues. Of these gene products, we focused on the nuclear p21 protein level in the liver and confirmed its up-regulation only in the WT-CR mice in response to oxidative stress. The lifespan did not differ significantly between the WT and HT mice in AL or CR conditions. However, the antineoplastic effect of CR, as indicated by reduced incidence of tumors at death in the WT-CR mice, was mostly abrogated in the HT-CR mice. The present results suggest a role for FoxO1 in the antineoplastic effect of CR through the induction of genes responsible for protection against oxidative and genotoxic stress.
|Cardiac and metabolic changes in long-term high fructose-fat fed rats with severe obesity and extensive intramyocardial lipid accumulation. |
Axelsen LN, Lademann JB, Petersen JS, Holstein-Rathlou NH, Ploug T, Prats C, Pedersen HD, Kjølbye AL
Am J Physiol Regul Integr Comp Physiol 298 R1560-70. Epub 2010 Mar 31. 2010
Metabolic syndrome and obesity-related diseases are affecting more and more people in the Western world. The basis for an effective treatment of these patients is a better understanding of the underlying pathophysiology. Here, we characterize fructose- and fat-fed rats (FFFRs) as a new animal model of metabolic syndrome. Sprague-Dawley rats were fed a 60 kcal/100 kcal fat diet with 10% fructose in the drinking water. After 6, 12, 18, 24, 36, and 48 wk of feeding, blood pressure, glucose tolerance, plasma insulin, glucose, and lipid levels were measured. Cardiac function was examined by in vivo pressure volume measurements, and intramyocardial lipid accumulation was analyzed by confocal microscopy. Cardiac AMP-activated kinase (AMPK) and hepatic phosphoenolpyruvate carboxykinase (PEPCK) levels were measured by Western blotting. Finally, an ischemia-reperfusion study was performed after 56 wk of feeding. FFFRs developed severe obesity, decreased glucose tolerance, increased serum insulin and triglyceride levels, and an initial increased fasting glucose, which returned to control levels after 24 wk of feeding. The diet had no effect on blood pressure but decreased hepatic PEPCK levels. FFFRs showed significant intramyocardial lipid accumulation, and cardiac hypertrophy became pronounced between 24 and 36 wk of feeding. FFFRs showed no signs of cardiac dysfunction during unstressed conditions, but their hearts were much more vulnerable to ischemia-reperfusion and had a decreased level of phosphorylated AMPK at 6 wk of feeding. This study characterizes a new animal model of the metabolic syndrome that could be beneficial in future studies of metabolic syndrome and cardiac complications.
|Metabolic and cardiac changes in high cholesterol-fructose-fed rats. |
Axelsen LN, Pedersen HD, Petersen JS, Holstein-Rathlou NH, Kjolbye AL
Journal of pharmacological and toxicological methods 2010
Introduction: High cholesterol-fructose (HCF) fed rats have previously been described as an animal model of impaired cardiac insulin signaling and decreased contractile performance. In this study, we evaluated the metabolic and cardiac effects of a HCF diet in rats. Methods: Male Sprague-Dawley rats received a HCF diet for 16 to 17weeks. Body weight was measured weekly and mean arterial blood pressure, fasting blood glucose, fasting plasma insulin, glucose tolerance, and blood lipid levels were measured following 15weeks of feeding. One to 2weeks later, while still on the HCF diet, cardiac function was examined by in vivo pressure-volume measurements in the left ventricle. Finally, protein and glucose content in the urine was measured and all organs were weighed at the end of the study. Results: Rats fed a HCF diet showed increased cholesterol and decreased high-density lipoprotein (HDL) levels in serum compared to control fed rats and they had more than a twofold increase in liver weight. However, in contrast to what has previously been reported, HCF diet had no effect on body weight, blood pressure, fasting blood glucose, fasting plasma insulin, glucose tolerance, or cardiac function during unstressed conditions. Discussion: We were unable to reproduce previous findings that a HCF diet causes changes in glucose tolerance and cardiac contractile performance. Therefore, further studies are warranted to evaluate specific interactions between genetic, environmental, and dietary factors on metabolic and cardiovascular disease progression associated with intake of a westernized diet.
|Interactions Between Age, Stress and Insulin on Cognition: Implications for Alzheimer's Disease. |
Solas M, Aisa B, Mugueta MC, Del RÃo J, Tordera RM, RamÃrez MJ
There is much interest in understanding the mechanisms responsible for interactions among stress, aging, memory and Alzheimer's disease. Glucocorticoid secretion associated with early life stress may contribute to the variability of the aging process and to the development of neuro- and psychopathologies. Maternal separation (MS), a model of early life stress in which rats experience 3 h of daily separation from the dam during the first 3 weeks of life, was used to study the interactions between stress and aging. Young (3 months) MS rats showed an altered hypothalamic-pituitary-adrenal (HPA) axis reactivity, depressive-like behavior in the Porsolt swimming test and cognitive impairments in the Morris water maze and new object recognition test that persisted in aged (18 months) rats. Levels of insulin receptor, phosphorylated insulin receptor and markers of downstream signaling pathways (pAkt, pGSK3beta, pTau, and pERK1 levels) were significantly decreased in aged rats. There was a significant decrease in pERK2 and in the plasticity marker ARC in MS aged rats compared with single MS or aged rats. It is interesting to note that there was a significant increase in the C99 : C83 ratio, Abeta levels, and BACE1 levels the hippocampus of MS aged rats, suggesting that in aged rats subjected to early life stress, there was an increase in the amyloidogenic processing of amyloid precursor protein (APP). These results are integrated in a tentative mechanism through which aging interplay with stress to influence cognition as the basis of Alzheimer disease (AD). The present results may provide the proof-of-concept for the use of glucocorticoid-/insulin-related drugs in the treatment of AD.Neuropsychopharmacology advance online publication, 24 February 2010; doi:10.1038/npp.2010.13.
|Chronic hypoxia increases insulin-stimulated glucose uptake in mouse soleus muscle. |
Gamboa JL, Garcia-Cazarin ML, Andrade FH
Am J Physiol Regul Integr Comp Physiol 2010
People living at high altitude appear to have lower blood glucose levels and decreased incidence of diabetes. Faster glucose uptake and increased insulin sensitivity are likely explanations for these findings: skeletal muscle is the largest glucose sink in the body and its adaptation to the hypoxia of altitude may influence glucose uptake and insulin sensitivity. This study tested the hypothesis that chronic normobaric hypoxia increases insulin-stimulated glucose uptake in soleus muscles and decreases plasma glucose levels. Adult male C57BL/6J mice were kept in normoxia (FIO(2)=21%, Control) or normobaric hypoxia (FIO(2)=10%, Hypoxia) for 4 weeks. Then, we measured blood glucose and insulin levels, in vitro muscle glucose uptake, and indices of insulin signaling. Chronic hypoxia lowered blood glucose and plasma insulin (glucose: Control, 14.3 ± 0.65 vs. Hypoxia, 9.9 ± 0.83 mM, p<0.001; and insulin: 1.2 ± 0.2 vs. 0.7 ± 0.1 ng/ml, control and Hypoxia, p<0.05), and increased insulin sensitivity determined by homeostatic model assessment 2 (HOMA2, Control 21.5±3.8 vs. Hypoxia 39.3±5.7, p<0.03). There was no significant difference in basal glucose uptake in vitro in soleus muscle (1.59±0.24 vs. 1.71±0.15 µmol/g/h; Control and Hypoxia respectively). However, insulin-stimulated glucose uptake was 30% higher in the soleus after 4 weeks of hypoxia (6.24±0.23 µmol/g/h) compared to Control (4.87±0.37 µmol/g/h p<0.02). Muscle glycogen content was not significantly different between the two groups. The content of glucose transporters 4 and 1 (GLUT4 and GLUT1), phosphoinositide 3-kinase (PI3K), glycogen synthase kinase 3 (GSK3), protein kinase B/AKT and AMP-activated protein kinase (AMPK) were not affected by chronic hypoxia. AKT phosphorylation following insulin stimulation in soleus muscle was significantly higher (25% greater in Hypoxia compared to Control, p<0.05). Neither GSK3 nor AMPK phosphorylation changed after 4 weeks of hypoxia. These results demonstrate that the adaptation of skeletal muscles to chronic hypoxia includes increased insulin-stimulated glucose uptake.
|Effects of escin mixture from the seeds of Aesculus hippocastanum on obesity in mice fed a high fat diet. |
Avci G, Küçükkurt I, Küpeli Akkol E, Yeşilada E
Pharm Biol 48 247-52. 2010
Escins, a triterpene glycoside mixture obtained from the ethanol extract of Aesculus hippocastanum L. (Hippocastanaceae) seed, was evaluated for its in vivo effects on the plasma levels of some hormones (leptin, insulin, FT(3), FT(4)) and biochemical parameters (glucose, triglyceride, total cholesterol, HDL-C, LDL-C concentrations) in mice fed with a high fat diet for 5 weeks. A high fat diet induced a remarkable increment in the plasma leptin (p <0.01), total cholesterol (p <0.01) and LDL-C (p <0.001) concentrations compared to control group animals. Combined administration of a high-fat diet with escins decreased leptin (31.6%) (p<0.05) and FT(4) (36.0%) (p<0.05) levels, increased HDL-C concentration (17.0%), while remained ineffective on LDL-C concentration in mice. Results have shown that escins may have beneficial effects in the understanding of obesity.
|Mechanism of action of the stimulatory effect of apigenin-6-C-(2''-O-alpha-l-rhamnopyranosyl)-beta-L-fucopyranoside on 14C-glucose uptake. |
Luisa Helena Cazarolli, Poliane Folador, Henrique Hunger Moresco, Inês Maria Costa Brighente, Moacir Geraldo Pizzolatti, Fátima Regina Mena Barreto Silva
Chemico-biological interactions 179 407-12 2009
There has been a growing interest in hypoglycemic agents from natural products, particularly those derived from plants. Flavonoids are naturally occurring phenolic compounds with a broad range of biological activities and the beneficial effects of flavonoids have been studied in relation to diabetes mellitus, either through their capacity to avoid glucose absorption or to improve glucose tolerance. The purpose of this study was to investigate the mechanism of action of the stimulatory effect of apigenin-6-C-(2''-O-alpha-L-rhamnopyranosyl)-beta-L-fucopyranoside (1), isolated from Averrhoa carambola L. (Oxalidaceae) leaves, on (14)C-glucose uptake. This compound (1) was found to have an acute effect on blood glucose lowering in diabetic rats and stimulated glucose-induced insulin secretion after oral treatment in hyperglycemic rats. A significant stimulatory effect of compound 1 on (14)C-glucose uptake was observed at 50 and 100 microM. The effect of compound 1 on glucose uptake was completely nullified by wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K), RO318220, an inhibitor of protein kinase C (PKC), PD98059, a specific inhibitor of mitogen-activated protein kinase (MEK), cycloheximide, an inhibitor of protein synthesis, and colchicine, a microtubule-depolymerizing agent. Compound 1 (100 microM) and insulin (10 nM) did not show any synergistic effect on glucose uptake. These results suggest that the flavonoid may have a dual target of action, as an insulin-secretagogue and also as an insulin-mimetic agent.
|A Chinese Herbal Decoction, Dang Gui Bu Xue Tang, Prepared from Radix Astragali and Radix Angelicae sinensis, Ameliorates Insulin Resistance Induced by A High-Fructose Diet in Rats. |
IM Liu, TF Tzeng, SS Liou
Evidence-based complementary and alternative medicine : eCAM 2009
Dang Gui Bu Xue Tang (DBT), a Chinese medicinal decoction contains Radix Angelicae sinensis (Danggui) and Radix Astragali (Huangqi) at a ratio of 1:5, is used commonly for treating women's ailments. This study was conducted to explore the effects of this preparation on insulin resistance in rats fed with 6-week diet containing 60% fructose. Similar to the action of rosiglitazone (4 mg kg(-1) per day by an oral administration), repeated oral administration of DBT (2.5 g kg(-1) per day) for 14 days was found to significantly alleviate the hyperglycemia but made no influence on plasma lipid profiles nor weight gain in fructose chow-fed rats. Also, the higher degree of insulin resistance as measured by homeostasis model assessment of basal insulin resistance in fructose chow-fed rats was significantly decreased by repeated DBT treatment. DBT displays the characteristic of rosiglitazone by increasing the whole-body insulin sensitivity in fructose chow-fed rats after 2-week treatment, as evidenced by the marked elevation of composite whole-body insulin sensitivity index during the oral glucose tolerance test. DBT improves insulin sensitivity through increased post-receptor insulin signaling mediated by enhancements in insulin receptor substrate-1-associated phosphatidylinositol 3-kinase step and glucose transporter subtype 4 translocation in soleus muscles of animals exhibiting insulin resistance. DBT is therefore proposed as potentially useful adjuvant therapy for patients with insulin resistance and/or the patients who wish to increase insulin sensitivity.,
|Treatment of type 1 diabetes with adipose tissue-derived stem cells expressing pancreatic duodenal homeobox 1. |
Lin G, Wang G, Liu G, Yang LJ, Chang LJ, Lue TF, Lin CS
Stem cells and development 18 1399-1406 2009
Due to the limited supply of donor pancreas, it is imperative that we identify alternative cell sources that can be used to treat diabetes mellitus (DM). Multipotent adipose tissue-derived stem cells (ADSC) can be abundantly and safely isolated for autologous transplantation and therefore are an ideal candidate. Here, we report the derivation of insulin-producing cells from human or rat ADSC by transduction with the pancreatic duodenal homeobox 1 (Pdx1) gene. RT-PCR analyses showed that native ADSC expressed insulin, glucagon, and NeuroD genes that were up-regulated following Pdx1 transduction. ELISA analyses showed that the transduced cells secreted increasing amount of insulin in response to increasing concentration of glucose. Transplantation of these cells under the renal capsule of streptozotocin-induced diabetic rats resulted in lowered blood glucose, higher glucose tolerance, smoother fur, and less cataract. Histological examination showed that the transplanted cells formed tissue-like structures and expressed insulin. Thus, ADSC-expressing Pdx1 appear to be suitable for treatment of DM.
|Overexpression of apolipoprotein A5 in mice is not protective against body weight gain and aberrant glucose homeostasis. |
Nathalie Pamir, Timothy S McMillen, Yu-I Li, Ching-Mei Lai, Howard Wong, Renée C LeBoeuf
Metabolism: clinical and experimental 58 560-7 2009
Apolipoprotein A5 (APOA5) is expressed primarily in the liver and modulates plasma triglyceride levels in mice and humans. Mice overexpressing APOA5 exhibit reduced plasma triglyceride levels. Because there is a tight association between plasma triglyceride concentration and traits of the metabolic syndrome, we used transgenic mice overexpressing human APOA5 to test the concept that these mice would be protected from diet-induced obesity and insulin resistance. Male and female transgenic and wild-type mice on the FVB/N genetic background were fed standard rodent chow or a diet rich in fat and sucrose for 18 weeks, during which time clinical phenotypes associated with obesity and glucose homeostasis were measured. We found that APOA5 transgenic (A5tg) mice were resistant to diet-induced changes in plasma triglyceride but not total cholesterol levels. Body weights were similar between the genotypes for females and males, although male A5tg mice showed a modest but significant increase in the relative size of inguinal fat pads. Although male A5tg mice showed a significantly increased ratio of plasma glucose to insulin, profiles of glucose clearance as evaluated after injections of glucose or insulin failed to reveal any differences between genotypes. Overall, our data showed that there was no advantage to responses to diet-induced obesity with chronic reduction of plasma triglyceride levels as mediated by overexpression of APOA5.Full Text Article
|Reduced antioxidant capacity and diet-induced atherosclerosis in uncoupling protein-2-deficient mice. |
Fatiha Moukdar, Jacques Robidoux, Otis Lyght, Jingbo Pi, Kiefer W Daniel, Sheila Collins
Journal of lipid research 50 59-70 2009
Vascular dysfunction in response to reactive oxygen species (ROS) plays an important role in the development and progression of atherosclerotic lesions. In most cells, mitochondria are the major source of cellular ROS during aerobic respiration. Under most conditions the rates of ROS formation and elimination are balanced through mechanisms that sense relative ROS levels. However, a chronic imbalance in redox homeostasis is believed to contribute to various chronic diseases, including atherosclerosis. Uncoupling protein-2 (UCP2) is a mitochondrial inner membrane protein shown to be a negative regulator of macrophage ROS production. In response to a cholesterol-containing atherogenic diet, C57BL/6J mice significantly increased expression of UCP2 in the aorta, while mice lacking UCP2, in the absence of any other genetic modification, displayed significant endothelial dysfunction following the atherogenic diet. Compared with wild-type mice, Ucp2(-/-) mice had decreased endothelial nitric oxide synthase, an increase in vascular cell adhesion molecule-1 expression, increased ROS production, and an impaired ability to increase total antioxidant capacity. These changes in Ucp2(-/-) mice were associated with increased aortic macrophage infiltration and more numerous and larger atherosclerotic lesions. These data establish that in the vasculature UCP2 functions as an adaptive antioxidant defense to protect against the development of atherosclerosis in response to a fat and cholesterol diet.
|Dietary soy protein isolate attenuates metabolic syndrome in rats via effects on PPAR, LXR, and SREBP signaling. |
Martin J Ronis, Ying Chen, Jamie Badeaux, Thomas M Badger
The Journal of nutrition 139 1431-8 2009
To determine the effects of feeding soy or isoflavones on lipid homeostasis in early development, weanling rats were fed AIN-93G diets made with casein, soy protein isolate (SPI+), isoflavone-reduced SPI+ (SPI-), or casein supplemented with genistein or daidzein for 14 d. PPARalpha-regulated genes and proteins involved in fatty acid degradation were upregulated by SPI+ (P 0.05) accompanied by increased promoter binding and expression of PPARalpha mRNA (P 0.05). Feeding SPI- or pure isoflavones did not alter PPARalpha-regulated pathways. SPI+ feeding had similar effects on PPARgamma signaling. SPI+, SPI-, and casein plus isoflavones all increased liver X-receptor (LXR)alpha-regulated genes and enzymes involved in cholesterol homeostasis. Feeding SPI+ increased promoter binding of LXRalpha, expression of the transcription factor mRNA, and protein (P 0.05). In a second experiment, male Sprague-Dawley rats were fed casein diets from postnatal d (PND) 24 to PND64 or were fed high-fat Western diets containing 5 g x kg(-1) cholesterol made with either casein or SPI+. Insulin resistance, steatosis, and hypercholesterolemia in the Western diet-fed rats were partially prevented by SPI+ (P 0.05). Nuclear sterol receptor element binding protein (SREBP)-1c protein and mRNA and protein expression of enzymes involved in fatty acid synthesis were increased by feeding Western diets containing casein but not SPI+ (P 0.05). These data suggest that activation of PPAR and LXR signaling and inhibition of SREBP-1c signaling may contribute to insulin sensitization and improved lipid homeostasis in SPI+-fed rats after consumption of diets high in fat and cholesterol.
|Ghrelin vaccination decreases plasma MCP-1 level in LDLR(-/-)-mice. |
Kellokoski E, Kummu O, Serpi R, Lehenkari P, Ukkola O, Kesaniemi YA, Horkko S
Peptides 30 2292-2300 2009
Ghrelin is a novel peptide hormone having growth hormone releasing activity and many endocrine and metabolic functions. In rats and pigs, ghrelin immunizations have recently been shown to induce an antibody response against ghrelin simultaneously with a decrease in body weight gain. Our aim was to test the role of ghrelin immunization on atherosclerosis and weight gain in mice. LDLR(-/-)-mice (n=36) were immunized with ghrelin-PADRE, PADRE alone and PBS and then placed on a high fat diet for 22 weeks. Weight gain and food intake were followed throughout the study. Acylated and total ghrelin, cytokines and MCP-1 were analyzed from plasma using commercial kits. Stomach ghrelin was assessed using qRT-PCR and immunohistochemistry. Atherosclerosis was determined from aorta and cross-sections at the end of study. Mice immunized with ghrelin-PADRE developed high plasma IgG titers to ghrelin simultaneously with a significant increase in plasma acylated and total ghrelin levels. Plasma MCP-1 levels decreased in mice immunized with ghrelin-PADRE compared to mice immunized with PADRE and PBS. There were no differences in atherosclerosis determined from aorta and cross-sections as well as in body weights and food intake in LDLR(-/-)-mice between the different immunization groups. Our data indicates that ghrelin-PADRE vaccination induces a strong exclusive IgG response to ghrelin and increases plasma acylated and total ghrelin levels in mice. Ghrelin vaccination decreases plasma MCP-1 levels even though no effects on developing signs of atherosclerosis or weight gain in mice were observed.
|High-fat feeding alters the clock synchronization to light. |
Jorge Mendoza, Paul Pévet, Etienne Challet
The Journal of physiology 586 5901-10 2008
High-fat feeding in rodents leads to metabolic abnormalities mimicking the human metabolic syndrome, including obesity and insulin resistance. These metabolic diseases are associated with altered temporal organization of many physiological functions. The master circadian clock located in the suprachiasmatic nuclei controls most physiological functions and metabolic processes. Furthermore, under certain conditions of feeding (hypocaloric diet), metabolic cues are capable of altering the suprachiasmatic clock's responses to light. To determine whether high-fat feeding (hypercaloric diet) can also affect resetting properties of the suprachiasmatic clock, we investigated photic synchronization in mice fed a high-fat or chow (low-fat) diet for 3 months, using wheel-running activity and body temperature rhythms as daily phase markers (i.e. suprachiasmatic clock's hands). Compared with the control diet, mice fed with the high-fat diet exhibited increased body mass index, hyperleptinaemia, higher blood glucose, and increased insulinaemia. Concomitantly, high-fat feeding led to impaired adjustment to local time by photic resetting. At the behavioural and physiological levels, these alterations include slower rate of re-entrainment of behavioural and body temperature rhythms after 'jet-lag' test (6 h advanced light-dark cycle) and reduced phase-advancing responses to light. At a molecular level, light-induced phase shifts have been correlated, within suprachiasmatic cells, with a high induction of c-FOS, the protein product of immediate early gene c-fos, and phosphorylation of the extracellular signal-regulated kinases I/II (P-ERK). In mice fed a high-fat diet, photic induction of both c-FOS and P-ERK in the suprachiasmatic nuclei was markedly reduced. Taken together, the present data demonstrate that high-fat feeding modifies circadian synchronization to light.Full Text Article
|Conjugated linoleic acid isomers have no effect on atherosclerosis and adverse effects on lipoprotein and liver lipid metabolism in apoE-/- mice fed a high-cholesterol diet. |
Margaret H Cooper, Jessica R Miller, Patricia L Mitchell, Deborah L Currie, Roger S McLeod
Atherosclerosis 200 294-302 2008
Dietary supplementation with conjugated linoleic acid (CLA) has been shown, in several animal models, to decrease the development of atherosclerosis. The mechanism behind the anti-atherogenic properties of CLA is not clear. The objectives of this study were to determine the effect of CLA on atherosclerosis, lipoprotein and liver lipid metabolism, and plasma adiponectin and insulin in apoE(-/-) mice fed an atherogenic (16%, w/w fat; 1.25%, w/w cholesterol) diet. Mice were fed the diet with or without supplementation of linoleic acid (LA), c-9,t-11 CLA, t-10,c-12 CLA, or a 1:1 mixture of the two CLA isomers, at a concentration of 0.5% (w/w), for 12 weeks. Relative to the LA group, CLA supplementation had no significant effect on the lesion area in either en face preparations of the aorta or in aortic root cross-sections. Plasma triacylglycerol and cholesterol concentrations were higher in the t-10,c-12 CLA group than all other treatment groups and liver weight was also increased in this group due to a three-fold increase in liver triacylglycerol. Supplementation with t-10,c-12 CLA or mixed CLA reduced plasma adiponectin levels, whereas t-10,c-12 CLA increased plasma insulin levels. Liver triglycerides correlated directly with blood glucose and plasma insulin and inversely with plasma adiponectin. We conclude that dietary supplementation with CLA does not affect atherosclerosis of the apoE(-/-) mouse on a high-cholesterol diet. Furthermore, t-10,c-12 CLA causes adverse changes in adipocyte function and plasma and liver lipid metabolism, which are partially ameliorated by the inclusion of the c-9,t-11 CLA isomer.
|Hyperinsulinemia and insulin resistance in Wrn null mice fed a diabetogenic diet. |
Gina Moore, Susan Knoblaugh, Kathryn Gollahon, Peter Rabinovitch, Warren Ladiges
Mechanisms of ageing and development 129 201-6 2008
Werner syndrome (WS) is an autosomal recessive progeroid syndrome caused by mutations in the Werner (Wrn) gene. WS patients have increased incidence of a number of chronic conditions including insulin resistance and type 2 diabetes. Since ingestion of foods that are high in fat and sugar is associated with increased incidence of diabetes, we examined if Wrn mutations might affect metabolic response to a diabetogenic diet. Four-month-old mice with a null mutation for the Wrn gene were fed a diet consisting of 36% fat (lard), 33% table sugar, and 20% protein plus balanced vitamins and minerals. Wrn null mice had significantly increased body weights, increased serum insulin levels, impaired glucose tolerance, and insulin resistance during 4 months of eating the diabetogenic diet. Diffuse fatty infiltration of the liver and pancreatic islet hyperplasia was characteristic morphological features. These observations suggest that Wrn null mice have impaired glucose homeostasis and fat metabolism, and may be a useful model to investigate metabolic conditions associated with aging.Full Text Article
|Release of acetylcholine by syringin, an active principle of Eleutherococcus senticosus, to raise insulin secretion in Wistar rats. |
Ko Yu Liu, Yang-Chang Wu, I-Min Liu, Wen Chen Yu, Juei-Tang Cheng
Neuroscience letters 434 195-9 2008
The present study is designed to screen the effect of syringin, an active principle purified from the rhizome and root parts of Eleutherococcus senticosus (Araliaceae), on the plasma glucose and investigate the possible mechanisms. Plasma glucose decreased in a dose-dependent manner 60 min after intravenous injection of syringin into fasting Wistar rats. In parallel to the decrease of plasma glucose, increases of plasma insulin level as well as the plasma C-peptide was also observed in rats receiving same treatment. Both the plasma glucose lowering action and the raised plasma levels of insulin and C-peptide induced by syringin were also inhibited by 4-diphenylacetoxy-N-methylpiperdine methiodide (4-DAMP), the antagonist of the muscarinic M3 receptors, but not affected by the ganglionic nicotinic antagonist, pentolinium or hexamethonium. Moreover, disruption of synaptic available acetylcholine (ACh) using an inhibitor of choline uptake, hemicholinium-3, or vesicular acetylcholine transport, vesamicol, abolished these actions of syringin. Also, physostigmine at concentration sufficient to inhibit acetylcholinesterase enhanced the actions of syringin. Mediation of ACh release from the nerve terminals to enhance insulin secretion by syringin can thus be considered. The results suggest that syringin has an ability to raise the release of ACh from nerve terminals, which in turn to stimulate muscarinic M3 receptors in pancreatic cells and augment the insulin release to result in plasma glucose lowering action.
|SirT1 regulates energy metabolism and response to caloric restriction in mice. |
Gino Boily, Erin L Seifert, Lisa Bevilacqua, Xiao Hong He, Guillaume Sabourin, Carmen Estey, Cynthia Moffat, Sean Crawford, Sarah Saliba, Karen Jardine, Jian Xuan, Meredith Evans, Mary-Ellen Harper, Michael W McBurney
PloS one 3 e1759 2008
The yeast sir2 gene and its orthologues in Drosophila and C. elegans have well-established roles in lifespan determination and response to caloric restriction. We have studied mice carrying two null alleles for SirT1, the mammalian orthologue of sir2, and found that these animals inefficiently utilize ingested food. These mice are hypermetabolic, contain inefficient liver mitochondria, and have elevated rates of lipid oxidation. When challenged with a 40% reduction in caloric intake, normal mice maintained their metabolic rate and increased their physical activity while the metabolic rate of SirT1-null mice dropped and their activity did not increase. Moreover, CR did not extend lifespan of SirT1-null mice. Thus, SirT1 is an important regulator of energy metabolism and, like its orthologues from simpler eukaryotes, the SirT1 protein appears to be required for a normal response to caloric restriction.Full Text Article
|Prolonged interleukin-6 administration enhances glucose tolerance and increases skeletal muscle PPARalpha and UCP2 expression in rats. |
Anna G Holmes, Jose L Mesa, Bronwyn A Neill, Jason Chung, Andrew L Carey, Gregory R Steinberg, Bruce E Kemp, Robert J Southgate, Graeme I Lancaster, Clinton R Bruce, Matthew J Watt, Mark A Febbraio
The Journal of endocrinology 198 367-74 2008
Chronic elevations in interleukin (IL)-6 have been associated with insulin resistance, but acute IL-6 administration can enhance insulin sensitivity. Our aim was to exogenously administer IL-6 to rats to elicit either chronic or repeated acute elevations in systemic IL-6. We hypothesized that a continuous elevation of IL-6 would inhibit glucose tolerance and insulin sensitivity while acute intermittent elevations would improve it. Male Wistar rats were treated for 14d with recombinant human IL-6 (2.4 microy) or saline administered either by miniosmotic pump (continuous IL-6) or via twice-daily injection (intermittent IL-6). Glucose and insulin tolerance tests were performed following 14-d treatment and 24 h later rats were administered a bolus of insulin (150 mU/g) or saline intraperitoneally. Approximately, 10 min after insulin injection soleus, gastrocnemius and liver were excised and rapidly frozen in liquid nitrogen for subsequent metabolic measures. Irrespective of the mode of delivery, IL-6 treatment increased basal insulin sensitivity, as measured by the homeostatic model assessment of insulin resistance, and enhanced glucose clearance during an i.p. glucose tolerance test. IL-6 increased circulating fatty acids, but did not increase triglyceride accumulation in either skeletal muscle or liver, while it increased the protein expression of both PPARalpha and UCP2 in skeletal muscle, suggesting that IL-6 can enhance fat oxidation via mitochondrial uncoupling. These data demonstrate that, irrespective of the mode of delivery, IL-6 administration over 2 weeks enhances glucose tolerance. Our results do not support the notion that prolonged chronically elevated IL-6 impairs insulin action in vivo.
|Differentiation of mouse nuclear transfer embryonic stem cells into functional pancreatic beta cells. |
W Jiang, Z Bai, D Zhang, Y Shi, J Yong, S Chen, M Ding, H Deng
Diabetologia 51 1671-9 2008
AIMS/HYPOTHESIS: Therapeutic cloning has been reported to have potential in the treatment of several degenerative diseases. However, it has yet to be determined whether mouse nuclear transfer-embryonic stem cells (NT-ESCs) can be differentiated into pancreatic beta cells and used to reverse diabetes in an animal model. METHODS: We first used the somatic nuclear transfer technique to generate mouse NT-ESCs and then developed a chemically defined stepwise protocol to direct the NT-ESCs into functional pancreatic beta cells. We examined the gene expression pattern of the differentiated NT-ESCs and transplanted the NT-ESC-derived insulin-producing cells into recipient diabetic mice. RESULTS: Four mouse NT-ESC lines were first established using an improved nuclear transfer technique and insulin-producing cells were efficiently generated from NT-ESCs by mimicking pancreatic in vivo development. Most of the insulin-producing cells that we generated co-produced pancreatic and duodenal homeobox 1, but not glucagon at the final stage of this differentiation method, which differed from the insulin and glucagon co-production reported by other groups. The differentiated NT-ESCs were able to release insulin in response to glucose stimuli and normalise the blood glucose level of diabetic mice for at least 2 months. CONCLUSIONS/INTERPRETATION: These results demonstrate the potential of therapeutic cloning for cell therapy of type 1 diabetes in a mouse model.
|Epigallocatechin gallate attenuates experimental non-alcoholic steatohepatitis induced by high fat diet. |
Nalan Kuzu, Ibrahim Halil Bahcecioglu, Adile Ferda Dagli, Ibrahim Hanifi Ozercan, Bilal Ustündag, Kazim Sahin
Journal of gastroenterology and hepatology 23 e465-70 2008
BACKGROUND AND AIM: In the present study, we examined the preventive role of epigallocatechin gallate (EGCG) in an experimental non-alcoholic steatohepatitis model induced by a high fat diet. METHODS: The study included 21 male Sprague-Dawley rats, which were equally divided into three groups. The first group was fed on a standard rat diet, the second group on a high fat diet (HFD), and the third group on a HFD + EGCG. The study concluded after 6 weeks. Histopathological examination was performed. Plasma and tissue MDA levels, glucose, insulin, alanine aminotransferase (ALT), aspartate aminotransferase, gamma glutamyltransferase, alkaline phosphatase, triglyceride, and cholesterol levels were studied. Insulin resistance was calculated by the homeostasis model of insulin resistance method. RESULTS: Steatosis, inflammation, ballooning degeneration, and necrosis increased significantly in the HFD group, compared to the control group (P 0.01). Steatosis and inflammation decreased in the HFD + EGCG group, in comparison to the HFD group (P 0.05, for each). There was a significant decline in ALT (P 0.01), triglyceride (P 0.01), insulin (P 0.05), and glucose (P 0.05) levels in the HFD + EGCG group, when compared to the HFD group. Plasma and liver MDA levels in the HFD + EGCG group were lower than those of the HFD group; the difference was significant (P 0.01 for each). Glutathione levels in the HFD + EGCG group was significantly higher those in the HFD group. CYP 2E1 and alpha-smooth muscle actin expression decreased in the HFD + EGCG group, in comparison to the HFD group (P 0.01, P 0.05, respectively). CONCLUSION: EGCG reduces the development of experimental non-alcoholic steatohepatitis induced by a high fat diet. It seems to exercise this effect through its effect on lipid metabolism and antioxidant characteristics.
|Dioscorea as the principal herb of Die-Huang-Wan, a widely used herbal mixture in China, for improvement of insulin resistance in fructose-rich chow-fed rats. |
Jen-Hao Hsu, Yang-Chang Wu, I-Min Liu, Juei-Tang Cheng
Journal of ethnopharmacology 112 577-84 2007
The present study was designed to clarify the principal herb responsible for the improvement of insulin resistance produced by Die-Huang-Wan, a mixture of six herbs, in rats fed with fructose-rich chow for 4 weeks. A decrease in plasma glucose was observed in fructose-rich chow-fed rats received an oral administration of Die-Huang-Wan at 26 mg/kg for 60 min but it disappeared with the deletion of dioscorea (Dioscoreae rhizoma) while this action was not modified by the deletion of other five herbs. The decrease of plasma glucose in fructose-rich chow-fed rats produced by dioscorea was similar to that treated with Die-Huang-Wan at same dosing; while the other five herbs failed to produce same influence. Similar to the effect of Die-Huang-Wan, dioscorea improved the fructose-induced decrement of insulin-stimulated glucose disposal rate after 3 days of treatment. Also, oral administration of dioscorea at effective dose (4.2 mg/kg per administration, three times daily) into streptozotocin-induced diabetic rats for 10 days increased the response to exogenous insulin, approaching to that induced by Die-Huang-Wan in same treatment. However, these effects failed to induce in the dioscorea-deleted formula of Die-Huang-Wan or other five herbs of this mixture. These results suggest that dioscorea is the major herb for the improvement of insulin sensitivity produced by Die-Huang-Wan. This can be applied to use as an adjuvant for subjects who need to increase insulin sensitivity.
|Body composition and selected blood parameters in mice fed a combination of fibre and conjugated linoleic acid. |
M Javadi, M J H Geelen, H Everts, A G Lemmens, A C Beynen
Journal of animal physiology and animal nutrition 91 492-7 2007
Feeding mice conjugated linoleic acid (CLA) reduces body fat. Soluble fibre decreases apparent lipid digestibility. The objective of the present study was to examine whether a combination of dietary CLA and soluble fibre would further decrease the proportion of body fat than a diet with CLA alone. Therefore, we fed mice diets with CLA and different amounts of Nutrim, containing 10% soluble fibre. CLA was added to the control diet at the expense of high oleic acid sunflower oil (HOSF) component and Nutrim was added at the expense of an isoenergetic combination of starch, dextrose and cellulose. The diets were fed for 28 days. Weight gain after 28 days was less in CLA-fed animals than in HOSF-fed animals. Both CLA and Nutrim increased the body water content. CLA reduced total body fat and epidydymal fat but Nutrim did not. No interaction of CLA and fibre was detected. We, therefore, must conclude that under the present experimental conditions dietary CLA and fibre do not interact to reduce body fat deposition.
|Impact of endurance training on murine spontaneous activity, muscle mitochondrial DNA abundance, gene transcripts, and function. |
Lisa S Chow,Laura J Greenlund,Yan W Asmann,Kevin R Short,Shelly K McCrady,James A Levine,K Sreekumaran Nair
Journal of applied physiology (Bethesda, Md. : 1985) 102 2007
We hypothesized that enhanced skeletal muscle mitochondrial function following aerobic exercise training is related to an increase in mitochondrial transcription factors, DNA abundance [mitochondrial DNA (mtDNA)], and mitochondria-related gene transcript levels, as well as spontaneous physical activity (SPA) levels. We report the effects of daily treadmill training on 12-wk-old FVB mice for 5 days/wk over 8 wk at 80% peak O(2) consumption and studied the training effect on changes in body composition, glucose tolerance, muscle mtDNA muscle, mitochondria-related gene transcripts, in vitro muscle mitochondrial ATP production capacity (MATPC), and SPA levels. Compared with the untrained mice, the trained mice had higher peak O(2) consumption (+18%; P < 0.001), lower percentage of abdominal (-25.4%; P < 0.02) and body fat (-19.5%; P < 0.01), improved glucose tolerance (P < 0.04), and higher muscle mitochondrial enzyme activity (+19.5-43.8%; P < 0.04) and MATPC (+28.9 to +32.4%; P < 0.01). Gene array analysis showed significant differences in mRNAs of mitochondria-related ontology groups between the trained and untrained mice. Training also increased muscle mtDNA (+88.4 to +110%; P < 0.05), peroxisome proliferative-activated receptor-gamma coactivator-1alpha protein (+99.5%; P < 0.04), and mitochondrial transcription factor A mRNA levels (+21.7%; P < 0.004) levels. SPA levels were higher in trained mice (P = 0.056, two-sided t-test) and significantly correlated with two separate substrate-based measurements of MATPC (P < 0.02). In conclusion, aerobic exercise training enhances muscle mitochondrial transcription factors, mtDNA abundance, mitochondria-related gene transcript levels, and mitochondrial function, and this enhancement in mitochondrial function occurs in association with increased SPA.
|Increase of acetylcholine release by Panax ginseng root enhances insulin secretion in Wistar rats. |
Chih-Fen Su, Juei-Tang Cheng, I-Min Liu
Neuroscience letters 412 101-4 2007
The present study was designed to ascertain the effect of Panax ginseng root on plasma glucose and investigate the possible mechanisms for the effect. Ninety minutes after the oral administration of P. ginseng root to fasting Wistar rats, plasma glucose decreased in a dose-dependent manner. Simultaneous with the reduction in plasma glucose, an increase in the plasma level of insulin and C-peptide was also observed. Moreover, disruption of the available synaptic acetylcholine (ACh), using the inhibitor for choline uptake (hemicholinium-3), or the inhibitor for vesicular choline transport (vesamicol), abolished the metabolic actions of P. ginseng root. Conversely, physostigmine, at a concentration sufficient to inhibit acetylcholinesterase, enhanced the metabolic effect of P. ginseng root. It is possible that P. ginseng root mediates the release of ACh from nerve terminals to enhance insulin secretion. Blockade of the actions of P. ginseng root by 4-diphenylacetoxy-N-methylpiperdine methiodide (4-DAMP) suggested that the site of action is the muscarinic M(3) receptor. Taken together, the results suggest that P. ginseng root has the ability to increase the release of ACh from nerve terminals in rats so as to stimulate muscarinic M(3) receptors activity located in the pancreatic cells for the secretion of insulin, which in turn lower plasma glucose.
|Study of iron metabolism disturbances in an animal model of insulin resistance. |
Guillaume Le Guenno, Emilie Chanséaume, Marc Ruivard, Béatrice Morio, Andrzej Mazur
Diabetes research and clinical practice 77 363-70 2007
The relationship between iron and insulin-resistance (IR) is documented by the positive correlation between iron stores and IR. Moreover, some patients exhibited a hepatic iron overload associated with IR (HIO-IR) but the mechanism involved in this overload is not known. Thus, we studied the iron metabolism disturbances in an animal model of IR and the influence of provoked hyperglycemia/hyperinsulinemia on plasma iron parameters. Wistar rats were fed a control or a high-fat/high-energy (HF/HE) diet. Plasma glucose, insulin, iron, transferrin and transferrin saturation (TS) were measured during intra-peritoneal glucose test tolerance (IPGTT) compared to saline. Hemogram, tissue iron concentrations and hepatic hepcidin mRNA expression were determined at the end of experiment. HF/HE rats exhibited higher body and liver weights, increased IR-index and hemoglobin concentration. Iron content was lower in the spleen of HF/HE rats and tended to decrease in the liver as compared to controls. Transferrin values were higher and these of TS lower in HF/HE group. The hepcidin mRNA was 3.5-fold lower in HF/HE rats than in controls. IPGTT had no effect on iron status parameters in both groups. As reflected by higher hemoglobin concentration, IR could increase erythropoïesis which enhances iron requirement. Iron stores and TS value decreased leading to a down-regulation of hepcidin expression which increased iron absorption. Hepcidin expression should be investigated in metabolic syndrome and hepatic iron overload associated with IR.
|Hypothalamic apolipoprotein A-IV is regulated by leptin. |
Ling Shen, Patrick Tso, Stephen C Woods, Randall R Sakai, W Sean Davidson, Min Liu
Endocrinology 148 2681-9 2007
Apolipoprotein A-IV (apo A-IV) is a satiety factor involved in the control of food intake and body weight. Our previous studies demonstrated that apo A-IV is present in areas of the hypothalamus where leptin acts to influence energy homeostasis. In the present studies, we found that leptin-deficient obese (ob/ob) mice have significantly reduced hypothalamic apo A-IV mRNA levels. Intragastric infusion of a lipid emulsion significantly stimulated hypothalamic apo A-IV gene expression in lean controls but not in ob/ob mice. Daily ip administration of leptin (3 microg/g) for 5 d significantly increased hypothalamic apo A-IV mRNA levels of ob/ob mice relative to pair-fed controls. In addition, centrally administered leptin raised the reduced apo A-IV gene expression induced by fasting. Using immunohistochemistry, we demonstrated that apo A-IV is present in leptin-sensitive phosphorylated signal transducer and activator of transcription 3 (pSTAT3)-positive cells of the arcuate nucleus of the hypothalamus. Knockdown of STAT3 expression by small interfering RNA significantly attenuated the stimulatory effect of leptin on apo A-IV protein expression in cultured primary hypothalamic neurons, implying that the hypothalamic apo A-IV is regulated by leptin, at least partially, via the STAT3 signaling pathway. Third-ventricular (intracerebroventricular) administration of a subthreshold dose of leptin (1 microg) potentiated apo A-IV-induced (subthreshold dose, 0.5 microg) reduction of feeding, indicating the existence of a functional synergistic interaction between leptin and apo A-IV, leading to suppression of food intake.
|Increasing the fat-to-carbohydrate ratio in a high-fat diet prevents the development of obesity but not a prediabetic state in rats. |
Natalia Sinitskaya, Sylviane Gourmelen, Carole Schuster-Klein, Béatrice Guardiola-Lemaitre, Paul Pévet, Etienne Challet
Clinical science (London, England : 1979) 113 417-25 2007
Metabolic disorders induced by high-fat feeding in rodents evoke some, if not all, of the features of human metabolic syndrome. The occurrence and severity of metabolic disorders, however, varies according to rodent species, and even strain, as well as the diet. Therefore, in the present study, we investigated the long-term obesogenic and diabetogenic effects of three high-fat diets differing by their fat/carbohydrate ratios. Sprague-Dawley rats were fed a control high-carbohydrate and low-fat diet [HCD; 3:16:6 ratio of fat/carbohydrate/protein; 15.48 kJ/g (3.7 kcal/g)], a high-fat and medium-carbohydrate diet [HFD1; 53:30:17 ratio of fat/carbohydrate/protein; 19.66 kJ/g (4.7 kcal/g)], a very-high-fat and low-carbohydrate diet [HFD2; 67:9:24 ratio of fat/carbohydrate/protein; 21.76 kJ/g (5.2 kcal/g)] or a very-high-fat and carbohydrate-free diet [HFD3; 75:0:25 ratio of fat/carbohydrate/protein; 24.69 kJ/g (5.9 kcal/g)] for 10 weeks. Compared with the control diet (HCD), rats fed with high-fat combined with more (HFD1) or less (HFD2) carbohydrate exhibited higher BMI (body mass index; +13 and +10% respectively; P0.05) and abdominal fat (+70% in both HFD1 and HFD2; P0.05), higher plasma leptin (+130 and +135% respectively; P0.05), lower plasma adiponectin levels (-23 and -30% respectively; P0.05) and impaired glucose tolerance. Only the HFD1 group had insulin resistance. By contrast, a very-high-fat diet devoid of carbohydrate (HFD3) led to impaired glucose tolerance, insulin resistance and hypoadiponectinaemia (-50%; P0.05), whereas BMI, adiposity and plasma leptin did not differ from respective values in animals fed the control diet. We conclude that increasing the fat-to-carbohydrate ratio to the uppermost (i.e. carbohydrate-free) in a high-fat diet prevents the development of obesity, but not the prediabetic state (i.e. altered glucose tolerance and insulin sensitivity).
|Improvement of insulin sensitivity in obese Zucker rats by myricetin extracted from Abelmoschus moschatus. |
I-Min Liu,Thing-Fong Tzeng,Shorong-Shii Liou,Ting-Wei Lan
Planta medica 73 2007
In an attempt to develop new substances for treating insulin resistance, obese Zucker rats were employed to screen the effect of myricetin, an active principle of Abelmoschus moschatus (Malvaceae), on insulin resistance. Myricetin purified from the aerial portion of the plant was administered intravenously ( I. V.) into animals. A dose-dependent decrease in the plasma glucose concentration of obese Zucker rats was observed 30 min following an I. V. injection. Moreover, repeated I. V. injection of myricetin (1 mg/kg) into obese Zucker rats 3 times daily for 1 week reduced the value of the glucose-insulin index, an index of insulin resistance calculated from the areas under the curve of glucose and insulin during the intraperitoneal glucose tolerance test. Additionally, repeated myricetin treatments overturned the inability of insulin to increase the expression of glucose transporter subtype 4 (GLUT 4) and to increase the protein levels and phosphorylation of insulin receptor substrate-1 (IRS-1) in soleus muscle of these obese rats. The inability of insulin to increase expression of the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3-kinase) and to promote Akt serine phosphorylation in soleus muscle of these rats were also overturned by repeated myricetin treatments. These findings indicate that myricetin improves insulin sensitivity through increased post-receptor insulin signaling mediated by enhancements in IRS-1-associated PI3-kinase and GLUT 4 activity in muscles of obese Zucker rats. Myricetin might be used as a model substance for the development of antidiabetic compounds.
|Release of acetylcholine by Hon-Chi to raise insulin secretion in Wistar rats. |
Chang-Chih Chen, I-Min Liu
Neuroscience letters 404 117-21 2006
The mandarin Hon-Chi is the red yeast rice fermented with Monascus pilous and Monascus purpureus. The present study is designed to screen the effect of Hon-Chi on plasma glucose and investigate the possible mechanisms. After oral administration into fasting Wistar rats for 90min, Hon-Chi decreased the plasma glucose in a dose-dependent manner. In parallel to the reduction of plasma glucose, an increase of plasma level of insulin or C-peptide was also observed in rats receiving same treatment. Moreover, disruption of synaptic available acetylcholine (ACh) using an inhibitor of choline uptake, hemicholinium-3, or vesicular acetylcholine transport, vesamicol, abolished these actions of Hon-Chi. Also, physostigmine at concentration sufficient to inhibit acetylcholinesterase enhanced the actions of Hon-Chi. Mediation of ACh release from the nerve terminals to enhance insulin secretion by Hon-Chi can thus be considered. Both the plasma glucose lowering action and the raised plasma levels of insulin and C-peptide induced by Hon-Chi were also inhibited by 4-diphenylacetoxy-N-methylpiperdine methiodide (4-DAMP), but not affected by the ganglionic nicotinic antagonist, pentolinium or hexamethonium, indicating the mediation of muscarinic M(3) receptors. The results suggest that Hon-Chi has an ability to raise the release of ACh from nerve terminals, which in turn to stimulate muscarinic M(3) receptors in pancreatic cells and augment the insulin release to result in plasma glucose lowering action. Thus, Hon-Chi seems suitable to employ as the health food for increase of insulin secretion in the prevention of type-2 diabetes.
|Increase of insulin secretion by ginsenoside Rh2 to lower plasma glucose in Wistar rats. |
Wen-Kung Lee, Shung-Te Kao, I-Min Liu, Juei-Tang Cheng
Clinical and experimental pharmacology physiology 33 27-32 2006
1. The aim of the present study was to clarify the role of ginsenoside Rh2 as the active compound in Panax ginseng root for lowering plasma glucose in animals. 2. Plasma glucose was assessed using the glucose oxidase method. Changes in the levels of insulin and C-peptide in plasma were measured by ELISA using commercially available kits. 3. After intravenous injection into fasting Wistar rats for 60 min, ginsenoside Rh2 (0.1-1.0 mg/kg) decreased plasma glucose in a dose-dependent manner. In parallel with the decrease in plasma glucose, increases in plasma insulin levels, as well as plasma C-peptide, were observed in rats receiving the same treatment. These effects of Rh2 were reversed by atropine (0.1-1.0 mg/kg), but not affected by the ganglionic nicotinic antagonists pentolinium or hexamethonium (both at 7.5 mg/kg). 4. Disruption of synaptically available acetylcholine (ACh) using an inhibitor of choline uptake (hemicholinium-3; 1-10 microg/kg) or an inhibitor of vesicular ACh transport (vesamicol; 1.5-3.5 mg/kg) abolished the actions of Rh2. In addition, physostigmine (0.1-0.5 mg/kg), at a concentration sufficient to inhibit acetylcholinesterase, enhanced the actions of the ginsenoside Rh2. Thus, mediation of the effects of Rh2 to enhance insulin secretion by ACh released from nerve terminals can be considered. 5. Blockade of the increase in plasma insulin and the plasma glucose-lowering action of Rh2 by 4-diphenylacetoxy-N-methylpiperdine methiodide (4-DAMP; 5-10 microg/kg) indicates the participation of muscarinic M(3) receptors. Increases in plasma C-peptide level induced by Rh2 were also sensitive to 4-DAMP. 6. The results of the present study suggest that ginsenoside Rh2 has the ability to increase insulin secretion as a result of the release of ACh from nerve terminals that then stimulates muscarinic M(3) receptors in pancreatic cells. This finding shows the mechanism for the plasma glucose-lowering action of ginsenoside Rh2, that is one of the major principles contained in P. ginseng root. Thus, ginsenoside Rh2 may be applied as an adjuvant for the management of diabetes.
|Increase of adiponectin receptor gene expression by physical exercise in soleus muscle of obese Zucker rats. |
Shih-Pei Chang, Yu-Hsuan Chen, Weng-Cheng Chang, I-Min Liu, Juei-Tang Cheng
European journal of applied physiology 97 189-95 2006
Aerobic exercise, including treadmill running has been widely used to treat insulin resistance and type 2 diabetes. We studied the effects of endurance training on gene expression of adiponectin receptor 1 (AdipoR1) in skeletal muscle of obese Zucker rats: the 8-week moderate exercise program consisted of treadmill running at 20 m/min and 0 degrees gradient for 1 h/day, 7 days/week. After 8 weeks, insulin action on glucose disposal rate was measured by glucose-insulin index, the product of the areas under the curve of glucose and insulin during intraperitoneal glucose tolerance testing. In contrast to results for sedentary obese rats, exercise training decreased plasma levels of insulin and glucose as well as the glucose-insulin index in obese rats, indicating the merit of regular moderate exercise for improvement of insulin sensitivity in this insulin-resistant animal model. Also, diabetes-related reductions in mRNA and protein content of AdipoR1 in soleus muscle were observed in obese rats at baseline; they were markedly reversed after the 8-week exercise program. However, such exercise training did not alter plasma levels of insulin and glucose in lean Zucker rats. Also, AdipoR1 gene expression in soleus muscle was not changed by exercise in lean Zucker rats compared with the sedentary, lean littermates. These results suggest that long-term exercise training may reverse reduced AdipoR1 gene expression in soleus muscle and improve insulin sensitivity in the obese Zucker rats. Thus, an endurance exercise training is probably helpful clinically for obese individuals with insulin resistance.
|Effects of DGAT1 deficiency on energy and glucose metabolism are independent of adiponectin. |
Ryan S Streeper, Suneil K Koliwad, Claudio J Villanueva, Robert V Farese
American journal of physiology. Endocrinology and metabolism 291 E388-94 2006
Mice lacking acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1), an enzyme that catalyzes the terminal step in triacylglycerol synthesis, have enhanced insulin sensitivity and are protected from obesity, a result of increased energy expenditure. In these mice, factors derived from white adipose tissue (WAT) contribute to the systemic changes in metabolism. One such factor, adiponectin, increases fatty acid oxidation and enhances insulin sensitivity. To test the hypothesis that adiponectin is required for the altered energy and glucose metabolism in DGAT1-deficient mice, we generated adiponectin-deficient mice and introduced adiponectin deficiency into DGAT1-deficient mice by genetic crosses. Although adiponectin-deficient mice fed a high-fat diet were heavier, exhibited worse glucose tolerance, and had more hepatic triacylglycerol accumulation than wild-type controls, mice lacking both DGAT1 and adiponectin, like DGAT1-deficient mice, were protected from diet-induced obesity, glucose intolerance, and hepatic steatosis. These findings indicate that adiponectin is required for normal energy, glucose, and lipid metabolism but that the metabolic changes induced by DGAT1-deficient WAT are independent of adiponectin and are likely due to other WAT-derived factors. Our findings also suggest that the pharmacological inhibition of DGAT1 may be useful for treating human obesity and insulin resistance associated with low circulating adiponectin levels.Full Text Article
|Insulin resistance in the Zucker diabetic fatty rat: a metabolic characterisation of obese and lean phenotypes. |
B L Leonard, R N Watson, K M Loomes, A R J Phillips, G J Cooper
Acta diabetologica 42 162-70 2005
The Zucker diabetic fatty (ZDF) rat is a commonly used animal model of type 2 diabetes yet complete descriptions of insulin resistance in this model are limited. We present a full characterisation of in vivo insulin resistance in obese (fa/fa) animals compared to lean (+/?) littermates. Anaesthetised, ten-week old, obese ZDF rats and their lean littermates underwent a hyperinsulinaemic euglycaemic glucose clamp. Compared with lean littermates, obese ZDF rats required an 89% lower glucose infusion rate to maintain euglycaemia and showed a 35% decrease in peripheral glucose disposal. Insulin-stimulated glucose uptake (R(g')) in obese animals was also significantly less in all skeletal muscles studied. R(g') in cardiac and white adipose tissue was not different between the two groups. Total glycogen content in skeletal and cardiac muscle was significantly less in obese animals, while total glycogen content in the liver was significantly greater than in lean littermates. Glycogen synthesis was also decreased in skeletal muscle of obese animals. Compared with lean animals, total triglyceride content was significantly greater in skeletal muscle, heart and liver of obese ZDF rats. Obese animals also showed significantly increased glucose incorporation into lipid in all of these tissues, indicating an increase in lipogenesis. Collectively, these results provide an integrated characterisation of in vivo insulin resistance in obese ZDF rats and a direct comparison with lean littermates.
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