Mitofusin-2 ameliorates high-fat diet-induced insulin resistance in liver of rats

AIM:To investigate the effects of mitofusin-2(MFN2) on insulin sensitivity and its potential targets in the liver of rats fed with a high-fat diet(HFD).METHODS:Rats were fed with a control or HFD for 4 or 8 wk,and were then infected with a control or an MFN2 expressing adenovirus once a week for 3wk starting from the 9th wk.Blood glucose(BG),plasma insulin and insulin sensitivity of rats were determined at end of the 4th and 8th wk,and after treatment with different amounts of MFN2 expressing adenovirus(108,109 or 1010 vp/kg body weight).BG levels were measured by Accu-chek Active Meter.Plasma insulin levels were analyzed by using a Rat insulin enzymelinked immunosorbent assay kit.Insulin resistance was evaluated by measuring the glucose infusion rate(GIR) using a hyperinsulinemic euglycemic clamp technique.The expression or phosphorylation levels of MFN2 and essential molecules in the insulin signaling pathway,such as insulin receptor(INSR),insulin receptor substrate 2(IRS2),phosphoinositide-3-kinase(PI3K),protein kinase beta(AKT2) and glucose transporter type 2(GLUT2) was assayed by quantitative real-time polymerase chain reaction and Western-blotting.RESULTS:After the end of 8wk,the body weight of rats receiving the normal control diet(ND) and the HFD was not significantly different(P>0.05).Compared with the ND group,GIR in the HFD group was significantly decreased(P<0.01),while the levels of BG,triglycerides(TG),total cholesterol(TC) and insulin in the HFD group were significantly higher than those in the ND group(P<0.05).Expression of MFN2 mRNA and protein in liver of rats was significantly downregulated in the HFD group(P<0.01) after 8 wk of HFD feeding.The expression of INSR,IRS2 and GLUT2 were down-regulated markedly(P<0.01).Although there were no changes in PI3K-P85 and AKT2 expression,their phosphorylation levels were decreased significantly(P<0.01).After intervention with MFN2 expressing adenovirus for 3wk,the expression of MFN2 mRNA and protein levels were up-regulated(P<0.01).There was no difference in body weight of rats between the groups.The levels of BG,TG,TC and insulin in rats were lower than those in the Ad group(P<0.05),but GIR in rats infected with Ad-MFN2 was significantly increased(P<0.01),compared with the Ad group.The expression of INSR,IRS2 and GLUT2 was increased,while phosphorylation levels of PI3K-P85 and AKT2 were increased(P<0.01),compared with the Ad group.CONCLUSION:HFDs induce insulin resistance,and this can be reversed by MFN2 over-expression targeting the insulin signaling pathway.

Effect of Soy Isoflavone Crude Extract Supplementation on High Fat Diet-induced Insulin Resistance in Ovariectomized Rats

Female Wister rats aged 8 weeks were randomly divided into sham operation group, ovariectomized （OVX） control group, and 20VX groups fed with soy isoflavone crude extract supplementation. The rats had free access to high fat diet and water for 9 weeks. No significant difference was found in body weight （BW）, total abdominal fat, food intake and food utilization rate between OVX control group and 20VX groups. However, the fasting blood glucose and blood lipid levels were significantly higher in 20VX groups than in OVX control group （P〈0.05）. Intraperitoneal glucose tolerance test （IGTI＂） showed that the area under AUC was smaller in 20VX groups than in OVX control group （P〈0.05）. These findings showed that soy isoflavone crude extract supplementation can improve glucose tolerance and prevent high fat diet-induced insulin resistance in ovariectomized rats.

Apoptosis of Pancreatic Beta Cells in Pregnant Insulin-resistant Rats Fed with High-fat Diet

Objective The aim of this study is by observing the number change of islets beta cells in gestational rats exposed to high fat diet, tofurther reveal the mechanism of gestational diabetes mellitus. Methods Female Wistar rats were exposed to high fat diet for five weeks, and then became pregnant. During pregnancy dynamically detected indicators of glucose and fat. Until the third trimester of pregnancy evaluated the sensitivity of insulin and glucose tolerance. After executed rats, selected pancreatic tail tissue and fixed, further slides were stained with insulin antibody by immunohistochemistry to confirm the location of beta cells. Image analysis system determined mean area stained positive cells in each islet, which stood for total number of beta cells. The apoptotic beta cells in islet were detected and quantified by the Tunel technology to calculate apoptosis ratio. Results The level of free fatty acids in rats exposed to high fat diet was significantly higher than the control groups, and insulin resistance was more serious. Compared mean stained positive area among each group, the largest was gestational rats fed high fat diet, and gestational rats was larger than virgin rats, but the difference had no statistical significance. About apoptoticratio of beta cells was higher in diet intervened rats, gestational rats were higher than virgin rats. The same trend happened in the number of positive cells, but discrepancy was not remarkable. Conclusion Based on insulin resistance, apoptosis of pancreatic beta cellsincreased in gestational ratstaking high fat diet, through changing the number of beta cells to down regulate the pancreas endocrine function. That may be the mechanism of gestational mellitus.

Modulating Effects of Chlorogenic Acid on Lipids and Glucose Metabolism and Expression of Hepatic Peroxisome Proliferator-activated Receptor-α in Golden Hamsters Fed on High Fat Diet

Objective To examine the effects of chlorogenic acid （CGA） on lipid and glucose metabolism under a high dietary fat burden and to explore the possible role of peroxisome proliferator-activated receptor-α （PPAR-α） in these effects. Methods Twenty male golden hamsters were randomly divided into CGA treatment group （n=10, given peritoneal injection of CGA solution prepared with PBS, 80 mg CGA/kg body weight daily）, and control group （n=10, given PBS i.p. at the average volume of the treatment group）. Animals in both groups were given 15% high fat diet. Eight weeks after treatment with CGA, the level of biochemical parameters in fasting serum and tissues and the expression of hepatic mRNA and protein PPAR-α were determined. Results Eight weeks after treatment with CGA, the levels of fasting serum triglyceride （TG）, free fatty acid （FFA）, total cholesterol （TC）, low density lipoprotein cholesterol （LDL-C）, high density lipoprotein cholesterol （HDL-C）, glucose （FSG）, and insulin （FSI） were significantly lower in the GGA treatment group than in the control group. CGA also led to higher activity of hepatic lipase （HL） lower contents of TG and FFA in liver, and lower activity of lipoprotein lipase （LPL） in skeletal muscle. Furthermore, CGA significantly elevated significantly elevated the expression level of mRNA and protein expression in hepatic PPAR-α. Conclusion CGA can modify lipids and glucose metabolism, which may be attributed to PPAR-α facilitated lipid clearance in liver and improved insulin sensitivity.

Characterization of inflammation and insulin resistance in high-fat diet-induced male C57BL/6J mouse model of obesity

Background: Animal models of diet-induced obesity(DIO) are commonly used in medical research for mimicking human diseases. There is no universal animal model, and careful evaluation of variety of factors needs to be considered when designing new experiments. Here, we investigated the effect of 9 weeks high-fat diet(HFD) intervention, providing 60% energy from fat, on parameters of inflammation and insulin resistance in male C57 BL/6 J mice.Methods: Six weeks old mice were initiated on regular diet(RD) or HFD providing 60 kcal energy from fat for 9 weeks. Fasting blood glucose levels were measured by glucometer, and fasting plasma levels of insulin and proinflammatory cytokines by Luminex assay. Insulin sensitivity was evaluated by using QUICKI and HOMA2 indexes.Results: HFD mice showed ~ 40% higher body weight and ~ 20% larger abdominal circumference, due to an increase in the white adipose tissue mass. Liver examination revealed increased size and higher hepatic lipid accumulation in livers from HFD mice compared to their RD counterparts. Animals from the HFD group were characterized with significantly higher presence of crown-like structures(CLS) in WAT and higher plasma levels of proinflammatory cytokines(TNF-α, IL-6, leptin, MCP-1, PAI-1, and resistin). HFD-fed mice also demonstrated impaired insulin sensitivity(lower QUICKI, higher HOMA-insulin resistance(HOMA-IR), and lower HOMA-percent sensitivity(HOMA-%S)) index values.Conclusion: Male C57 BL/6 J mice on 9 weeks HFD providing 60 kcal energy from fat display impaired insulin sensitivity and chronic inflammation, thus making this DIO mouse model appropriate for studies of early stages of obesity-related pathology.

Comparative study on the difference of obesity model induced by two kinds of high fat diet in Sprague-Dawley rats

Objective: To explore the differences of obese Sprague-Dawley(SD)rats model induced by lard oil high-fat(HF)diet or purified HF diet. Methods: SD weanling rats were randomly divided into three groups: D1 group,where rats were fed by lard oil HF diet;D2 group,where rats were fed by purified HF diet;C group,where rats were fed on chow. After 12 weeks,diet-induced obesity rat(stop 33% based on weight)were selected for further study,and the rest rats from group D1 and D2 were excluded. The food intake and weight were weighted daily and weekly,respectively. The subcutaneous,visceral and total fat contents of rats was measured by 256-row CT scan and the Lee index was calculated accordingly. The kidney,liver,testis,spleen and heart were weighted respectively. Serum leptin and insulin levels were quantified. The pathology in liver and adipose tissues were analyzed by HE staining. Oral glucose tolerance test(OGTT)was used to compare the glucose tolerance ability. Serum total cholestero(lT-CHO),high density lipoprotein(HDL-C),low density lipoprotein(LDL-C),triglyceride(TG)and inflammatory cytokines IL-6,TNF-α were detected as well. Results: After 12 weeks,the body weight,subcutaneous fat,visceral fat,total fat mass,wet weight of liver,kidney and heart,area under blood glucose curve and the levels of serum insulin,leptin,T-CHO,LDL-C,TG,IL-6 and TNF-α in group D2 were significantly increased compared to those of group C and group D1. HDL-C of group D2 was markedly lower than that in group C(P<0. 05). The visceral fat,total fat content and HDL-C in group D1 were significantly different from those of group C(P<0. 05). Steatosis and enlarged adipocyte were found in the livers of rats in group D1 and D2,and the lesions were more significant in group D2. Conclusion: Purified HF diet was more effective in inducing metabolic abnormalities,steatosis,peripheral chronic inflammation in obese SD rat models. But lard oil HF diet was more economical when only inducing visceral steatosis was required.

Elevated glucagon-like peptide-1 on a high-fat diet feeding prevents the incidence of diabetes mellitus in Spontaneously Diabetic Torii <i>Lepr^fa</i>rats

Nutritional regulation plays a critical role to reduce the incidence or progression of diabetes mellitus. In this study, we investigated the effects of a high-fat diet on Spontaneously Diabetic Torii Leprfa (SDT fatty) rats, a novel model for obese type 2 diabetes. The SDT fatty rats were divided into two dietary groups, which were fed a high-fat diet or a standard diet for 18 weeks, from 6 to 24 weeks of age. The calorie intake in the high-fat diet (HF) group was reduced after 10 weeks of age and the group inhibited an incidence of diabetes. Interestingly, the HF induced an increase of serum glucagon-like peptide-1 (GLP-1) levels in SDT fatty rats with refeeding. Fat tissue weights in the HF group increased, but the visceral fat/subcutaneous fat (V/S) ratio decreased. Moreover, histopathological observations revealed an improvement of the pancreatic abnormalities and fatty liver in the HF group. In conclusion, a preventive effect on diabetes in rats fed a high-fat diet has a relation with an increase in incretin hormone, and it might be advantageous for prevention of incidence or progression of diabetes to develop functional foods inducing an increase in incretin hormone.

Effect of mango seed kernel extract on the adipogenesis in 3T3-L1 adipocytes and in rats fed a high fat diet

Mangoes (Mangifera indica L.) are one of the most important tropical foods. The seed is one of the main by-products of mango processing. Therefore, it is important to find an economically viable use for this waste (e.g., as a food additive or supplement with high nutraceutical value). We investigated the anti-obesity effects of mango seed kernel extract with hot water (MSKE-W) in 3T3-L1 adipocytes and in a high fat diet (HFD)-induced obesity rat model. MSKE-W caused a significant decrease in the activity of glycerol 2-phosphate dehydrogenase in 3T3-L1 adipocytes without eliciting cell cytotoxicity and inhibited cellular lipid accumulation through down-regulation of transcription factors such as PPARγ and C/EBPα. In the animal model, rats fed an HFD containing 1% MSKE-W gained less weight than rats fed an HFD alone. The visceral fat mass in rats fed an HFD containing 1% MSKE-W tended to be lower than that in rats fed an HFD alone. Furthermore, histological examination of rat livers from an HFD showed steatohepatitis. However, rats on an HFD containning 1% MSKE-W showed no histopathological changes in liver tissue. Our results indicate that MSKE-W influences anti-obesity effects, both in vitro and in vivo, and suggest that MSKE-W provides a novel preventive potential against obesity.

Palmitoleic acid on top of HFD ameliorates insulin resistance independent of diacylglycerols and alters gut microbiota in C57BL/6J mice

With the prevalence of obesity and obesity-related metabolic syndrome,such as insulin resistance in recent years,it is urgent to explore effective interventions to prevent the progression of obesity-related metabolic syndrome.Palmitoleic acid is a monounsaturated fatty acid that is available from dietary sources,mainly derived from marine products.P almitoleic acid plays a positive role in maintaining glucose homeostasis and reducing inflammation.However,it is still unknow the mechanism of palmitoleic acid in ameliorating insulin resistance.Here,we investigated the effects of palmitoleic acid on chow diet(CD)-fed and high-fat diet(HFD)-fed mice,which were fed CD or HFD for 12 weeks before administration.We administrated mice with BSA(control),oleic acid,or palmitoleic acid for 6 weeks on top of CD or HFD feeding.We found that palmitoleic acid only improved glucose homeostasis in HFD-fed obese mice by increasing glucose clearance and reducing HOMA-IR.Further study explored that palmitoleic acid changed the composition of gut microbiota by decreasing Firmicutes population and increasing Bacteroidetes population.In colon,palmitoleic acid increased intestinal tight junction integrity and reduced inflammation.Moreover,palmitoleic acid decreased macrophage infiltration in liver and adipose tissue and increase glucose uptake in adipose tissue.Diacylglycerol(DAG)in tissue(for example,liver)is found to positively correlated with HOMA-IR.HFD enhanced the levels of DAGs in liver but not in adipose tissue in this study.Palmitoleic acid did not reverse the high DAG levels induced by HFD in liver.Therefore,in HFD-fed mice,palmitoleic acid reduced insulin resistance by an independent-manner of DAGs.It might be associated with the beneficial effects of palmitoleic acid on altering the gut microbiota composition,improving of intestinal barrier function,and downregulating the inflammation in colon,liver,and adipose tissue.

Effects of Mogroside V on Glucose and Lipid Metabolism in High Fat Diet Mice

[Objectives]To explore the effects and mechanism of mogroside V(MV)on glucose and lipid metabolism in high-fat diet(HFD)mice.[Methods]The experiment fed mice with high-fat diet for 8 weeks,and 40 mice with successful modeling were randomly divided into normal group,model group,and MV dose group(100,200 mg/kg),with 10 mice in each group.From the ninth week,the MV dose group was given intragastric administration,and the normal group and the model group were given an equal volume of distilled water by intragastric administration for 6 weeks,then killed and blood samples and livers were collected.Serum triglycerides(TG),total cholesterol(TC),low density lipoprotein cholesterol(LDL-C),high density lipoprotein cholesterol(HDL-C),free fatty acids(FFA),Advanced glycation end products(AGE-P)-peptides(AGE-P)and glycosylated hemoglobin(HbA1c)content,and TG and hepatic glycogen content in liver were detected by biochemical method.Fasting blood glucose(FBG)was measured by glucose oxidase method.The fasting serum insulin(FINS)content was detected by enzyme-linked immunosorbent assay(ELISA),and the insulin resistance index(HOMA-IR)was calculated.Oil red O staining was used to observe the fat deposition in liver tissue.[Results]MV(100,200 mg/kg)dose groups could significantly down-regulate the contents of TC,TG,LDL-C,FBG,FINS,AGE-P and HbA1c and HOMA-IR,and up-regulate HDL-C and hepatic glycogen content and reduce the fat deposits.[Conclusions]The mechanism of MV regulating glucose and lipid metabolism in mice may be related to the regulation of insulin resistance.

Involvement of insulin receptor substrates in cognitive impairment and Alzheimer’s disease

Type 2 diabetes一associated with impaired insulin/insulin-like growth factor-1 (IGF1) signaling (IIS)一is a risk factor for cognitive impairment and dementia including Alzheimer's disease (AD). The insulin receptor substrate (IRS) proteins are major components of IIS, which transmit upstream signals via the insulin receptor and/or IGF1 receptor to multiple intracellular signaling pathways, including AKT/protein kinase B and extracellular-signal-regulated kinase cascades. Of the four IRS proteins in mammals, IRS1 and IRS2 play key roles in regulating growth and survival, metabolism, and aging. Meanwhile, the roles of IRS1 and IRS2 in the central nervous system with respect to cognitive abilities remain to be clarified. In contrast to IRS2 in peripheral tissues, inactivation of neural IRS2 exerts beneficial effects, resulting in the reduction of amyloid p accumulation and premature mortality in AD mouse models. On the other hand, the increased phosphorylation of IRS 1 at several serine sites is observed in the brains from patients with AD and animal models of AD or cognitive impairment induced by type 2 diabetes. However, these serine sites are also activated in a mouse model of type 2 diabetes, in which the diabetes drug metformin improves memory impairment. Because IRS1 and IRS2 signaling pathways are regulated through complex mechanisms including positive and negative feedback loops, whether the elevated phosphorylation of IRS1 at specific serine sites found in AD brains is a primary response to cognitive dysfunction remains unknown. Here, we examine the associations between IRS 1 /1 RS2-mediated signaling in the central nervous system and cognitive decline.

高脂饮食对小鼠脂质代谢和leptin基因表达水平的影响

目的建立高脂饮食诱导小鼠肥胖模型,分析高脂饲料对小鼠脂质代谢和leptin基因表达水平的影响。方法用高脂饲料饲喂小鼠,每周定时称重和断尾采血一次,分别测定血清中血糖、胆固醇、甘油三酯、胰岛素和leptin的浓度;5周后,分离、称重小鼠体脂并提取腹部脂肪组织RNA,半定量RT-PCR分析leptin基因表达水平。结果从第2周开始,实验组小鼠体重明显高于对照组小鼠,4周后,体重差异显著(P<0.05);血清中血糖、胆固醇、甘油三酯、胰岛素和leptin的含量随体重增加明显增高,4周后,差异显著(P<0.05);实验组体脂含量明显高于对照组(P<0.05),半定量RT-PCR分析表明,肥胖小鼠脂肪组织leptin基因表达水平高于对照组(P<0.05)。结论高脂饮食诱导可建立小鼠肥胖模型,并能够引起高胰岛素和高leptin血症,为进一步研究肥胖的发病机制奠定基础。

高脂饲料诱导的肥胖倾向和肥胖抵抗倾向大鼠内脏脂肪visfatin和AMPK表达及其相互关系

目的:探讨大鼠内脏脂肪组织visfatin和AMPK的表达对肥胖倾向(OP)和肥胖抵抗倾向(ORP)形成的可能作用。方法:20只雄性Wistar大鼠,高脂饲料喂养10周,依据腹脂/体重比值选大鼠进入OP和ORP两组,每组各7只,测定大鼠血脂、血糖、血浆胰岛素和visfatin浓度,肾周脂肪组织中visfatin表达和AMPK活性。结果:与ORP组大鼠相比,OP组大鼠血浆visfatin浓度有升高趋势(P=0.16),肾周脂肪组织visfatin表达显著升高(P<0.05),而AMPK活性显著降低(P<0.05),内脏脂肪visfatin表达与AMPK活性之间存在负相关关系。结论:内脏脂肪组织中visfatin表达升高和AMPK活性降低可能与肥胖倾向有关。Visfatin可能通过负性调节AMPK活化程度影响肥胖倾向的发生。

共轭亚油酸对高脂血症大鼠脂质代谢及visfatin基因表达水平的影响

目的建立高脂血症大鼠模型,分析共轭亚油酸(CLA)对其脂质代谢和visfatin基因表达水平的影响,为进一步研究CLA对脂肪代谢的调控机制奠定基础。方法用高脂饲料饲喂雄性Wistar大鼠,4周后断尾采血测定血清甘油三酯(TG)、总胆固醇(CHO)和血糖(GLU)含量,将构建成功的高脂血症大鼠分为实验组和对照组,实验组每天定时灌胃CLA(0.8 mL/0.1 kg),每周定时称重,记录采食量;4周后眼球采血,测定血清中GLU、CHO、TG、低密度脂蛋白(LDL)、高密度脂蛋白(HDL)水平;断颈处死大鼠,分离体脂并提取肝脏总RNA,半定量RT-PCR分析visfatin基因表达水平。结果高脂饲料饲喂4周后,模型组大鼠血清TG、CHO、GLU明显高于对照组大鼠(P<0.05),表明高脂大鼠模型构建成功。灌胃CLA 4周后,实验组大鼠体重、体脂和采食量低于对照组大鼠(P<0.05),血清中GLU、CHO、TG、LDL含量明显降低,但实验组HDL浓度升高。RT-PCR实验结果表明,实验组大鼠visfatin基因表达水平明显低于对照组大鼠(P<0.05)。结论CLA能降低高脂血症大鼠摄食量,改善高血脂大鼠脂质代谢,并能降低visfatin基因的表达水平。

Bcl-2、Bax、Insulin在高脂诱导C57BL/6J小鼠胰岛损伤中的表达

目的探讨细胞凋亡因子在高脂引起的小鼠胰岛损伤中的表达。方法雄性C57BL/6J小鼠分高脂饮食组(HFD)和低脂饮食对照组(LFD),每组6只,喂养12周时尾部取血进行葡萄糖耐量实验(GTT)及胰岛素耐量实验(ITT)检测胰岛功能。持续喂养至20周时处死取胰腺组织用于透射电镜,苏木素-伊红(haematoxylineosin,HE)染色观察胰岛形态;免疫组化(immunohistochemical,IHC)检测Bcl-2、Bax及Insulin蛋白表达水平。结果喂养12周后,小鼠GTT和ITT显示,HFD组小鼠葡萄糖负荷时的血糖水平高于LFD组(P<0.05)。注射胰岛素后,HFD组小鼠血糖下降缓慢且血糖水平仍较LFD组高(P<0.05)。HE结果显示HFD组小鼠胰岛数量和体积较LFD组减少,形态损伤严重。电镜下观察HFD组胰岛β细胞超微结构受损较LFD组严重,HFD组β细胞形态不规则,细胞核固缩,染色质边集,有大量电子密度较小的脂滴堆积,其中胰岛细胞胞浆内胰岛素分泌颗粒减少。免疫组化的结果显示:HFD组Bcl-2表达低于低脂组,同时HFD组Bax表达高于LFD组,而HFD组胰岛中的Insulin表达低于LFD组(P<0.01)。结论高脂导致C57BL/6J小鼠胰岛细胞结构功能损伤,影响胰岛素的合成与分泌,并且增加细胞凋亡。Bcl-2及Bax在胰岛细胞凋亡中起一定的作用,并可能与高脂饮食有关。

Rosiglitazone reduces fatty acid translocase and increases AMPK in skeletal muscle in aged rats： a possible mechanism to prevent high-fat-induced insulin resistance

Background As an agonist of peroxisome proliferator-activated receptor-gamma （PPARy）, rosiglitazone can prevent acute fatty acid-induced insulin resistance in rats, however, the precise mechanisms by which rosiglitazone alleviates insulin resistance induced by high-fat diet need to be further investigated.Methods Wistar rats aged 23-24 weeks were divided into three groups： （1） aged control group （OC）, （2） high-fat diet （HF） group and （3） high-fat diet plus rosiglitazone maleate tablets （HF＋Rosi） treatment group （n=20 in each group）. Insulin sensitivity was evaluated by conscious hyperinsulinemic-euglycemic clamp technique. mRNA levels of fatty acid translocase （FAT/CD36）, AMP-activated protein kinase α1 （AMPKα1）, AMPKα2 and acetyl CoA carboxylase （ACC） of rat skeletal muscle were determined using real-time PCR, while muscle camitine palmitoyltransferase-1 （CPT-1β） was determined using semi-quantitative PCR. Protein expression levels of FAT/CD36, AMPK phosphorylation （reflecting AMPK activity）, P-ACC （inversely related with ACC activity） and muscle CPT-1M in rat skeletal muscles were measured using Western blotting.Results Aged rats fed by diet rich in fat for more than 8 weeks led to significant increases of plasma lipids, skeletal muscle intramuscular triglyceride and long-chain fatty acyl-CoA （LCACoA） compared to aged rats fed by normal chow diet （OC） （P 〈0.05）, which might correlate with the lower （reduced by 42.4%） whole body insulin sensitivity in HF rats. FAT/CD36 protein concentrations and mRNA levels increased in untreated HF aged rats （P 〈0.01） and high-fat diet induced a significant decrease in P-AMPK, P-ACC, CPT-1M protein concentrations and AMPKα2 and CPT-1β mRNA levels in rat skeletal muscles （P 〈0.05）. No change in AMPKα1 mRNA levels was observed in the HF group.Conclusion High-fat diet in aged rats results in a lipid accumulation and subsequent insulin resistance, while rosiglitazone can alleviate the insulin resistance by reducing fatty acid uptake as well as enhancing lipometabolism.

Antidiabetic and Anti-oxidative Effects of Honokiol on Diabetic Rats Induced by High-fat Diet and Streptozotocin

Objective To study the antidiabetic and anti-oxidative effects of honokiol （Hon） in Magnolia officinalis and its underlying molecular mechanism in diabetic rats induced by high-fat diet （HFD） and streptozotocin （STZ）. Methods After ig administration with Hon [25, 50, and 100 mg/（kg.d）] to diabetic rats for consecutive 10 weeks, the levels of blood glucose （BG）, oral glucose tolerance （OGT）, blood lipids including total cholesterol （TC）, triglyceride （TG）, high density lipoprotein-cholesterol （HDL-C）, and low density lipoprotein-cholesterol （LDL-C）, hepatic oxidative stress including the activities of superoxide dismutase （SOD）, catalase （CAT）, glutathione peroxidase （GSH-Px）, methane dicarboxylic aldehyde （MDA）, and cytochrome P4502E1 （CYP2E1） in diabetic rats were measured. Results Compared to the diabetic control rats, ig administration of Hon resulted in significant decrease in BC, TC, TG, and LDL-C levels in serum, as well as hepatic CYP2E] activity and MDA content in diabetic rats, whereas the level of OGT and activities of hepatic CAT, SOD, and CSH-Px in diabetic rats were significantly increased. Conclusion Hon could alleviate hyperglycemia, hyperlipemia, hepatic oxidative damage, and insulin resistance in diabetic rats by inhibiting hepatic CYP2E1 activity.

Effects of octreotide on glucose transporter type 2expression in obese rat small intestine

AIM： TO investigate the effects of the somatostatin analogue, octreotide, on maltose and sucrase activities and expression of glucose transporter type 2 （GLUT2） in obese rat intestinal mucosa. METHODS： We divided 49 Sprague-Dawley rats into a group of 31 high fat diet-induced obese rats and a group of 18 normal controls. The obese rats were separated into an octreotide treated group 9f 16 rats and an obese group of 15. The intervention （：jroup was injected with octreotide at 40 ±g/kg body weight every 12 h for 8 d. Rat body weight was measured weekly to calculate Lee＇s index. After euthanization, maltase and sucrase activities in the small intestine were measured by activity assays, and the fasting plasma glucose level was measured. The expression of GLUT2 in small intestinal mucosa was analyzed by immunohistochemistry, reverse transcriptase polymerase chain reaction and Western blotting assays. RESULTS： Body weight, Lee＇s index, fasting plasma glucose level, maltase activity in small intestinal mucosa, mucosa and apical GLUT2, GLUT2 mRNA and protein expression levels were all significantly higher in the obese group than in the normal control group （605.61 ± 141.00 vs 378.54 ±111.75, 337.61 ± 10.82 vs 318.73 ± 20.10, 8.60± 1.38 vs 7.33 ± 0.70, 156.01 ± 58.81 vs 50.43 ± 30.49, 390 744.2± 62 469.21 vs 170 546.50 ± 50 646.14, 26 740.18 ±3809.60 vs 354.98± 57.19, 0.26± 0.11 vs 0.07± 0.02, and 2.08 ± 0.59 vs 1.27 ± 0.38, respectively, all P 〈 0.01）. Sucrase activity did not differ between the two groups. Octreotide intervention significantly decreased the body weight and fasting plasma glucose level of obese rats （508.27 ± 94.39 vs 605.61 ± 141.00, 7.58 ± 1.51 vs 8.60±1.38, respectively, all P 〈 0.05）. The intestinal mucosa and apical GLUT2, expression of GLUT2 mRNA and protein were also significantly lower in the octreotide intervention group than in the obese group （269 975.2 ± 53 730.94 vs 390 744.2 ± 62 469.21, 3758.06 ± 364.51 vs 26 740.18 ± 3809.60, 0.08 ± 0.02 vs 0.26 ±0.11, and 1.31 ± 0.27 vs 2.08 ±0.59, respectively, all P 〈 0.01）. CONCLUSION： High fat dietinduced obesity is associated with elevated intestinal maltase activity, GLUT2 expression, and permanent apical GLUT2 in the small intestinal mucosa of rats. Octreotide can inhibit these effects.

Impact of age on host responses to diet-induced obesity:Development of joint damage and metabolic set points

Background:Osteoarthritis is one of the leading causes of pain and disability worldwide,and a large percentage of patients with osteoarthritis are individuals who are also obese.In recent years,a series of animal models have demonstrated that obesity-inducing diets can result in synovial joint damage(both with and without the superimposition of trauma),which may be related to changes in percentage of body fat and a series of low-level systemic inflammatory mediators.Of note,there is a disparity between whether the dietary challenges commence at weaning,representing a weanling onset,or at skeletal maturity,representing an adult onset of obesity.We wished to evaluate the effect ofthe dietary exposure time and the age at which animals are exposed to a high-fat and high-sucrose(HFS) diet to determine whether these factors may result in disparate outcomes,as there is evidence suggesting that these factors result in differential metabolic disturbances.Based on dietary exposure time,we hypothesized that rats fed an HFS diet for 14 weeks from weaning(HFS Weanling) would demonstrate an increase in knee joint damage scores,whereas rats exposed to the HFS diet for 4 weeks,starting at 12 weeks of age(HFS Adult) and rats exposed to a standard chow diet(Chow)would not display an increase in knee joint damage scores.Methods:Male Sprague-Dawley rats were fed either an HFS diet for 14 weeks from weaning(HFS Weanling) or an HFS diet for 4 weeks,starting at 12 weeks of age(HFS Adult).At sacrifice,joints were scored using the modified Mankin Criteria,and serum was analyzed for a defined subset of inflammatory markers(Interleukin-6,leptin,monocyte chemoattractant protein-1,and tumor necrosis factorα).Results:When the HFS Weanling and HFS Adult groups were compared,both groups had a similar percent of body fat,although the HFS Weanling group had a significantly greater body mass than the HFS Adult group.The HFS Weanling and HFS Adult animals had a significant increase in body mass and percentage of body fat when compared to the Chow group.Although knee joint damage scores were low in all 3 groups,we found,contrary to our hypothesis,that the HFS Adult group had statistically significant greater knee joint damage scores than the Chow and HFS Weanling groups.Furthermore,we observed that the HFS Weanling group did not have significant differences in knee joint damage scores relative to the Chow group.Conclusion:These findings indicate that the HFS Weanling animals were better able to cope with the dietary challenge of an HFS diet than the HFS Adult group.Interestingly,when assessing various serum proinflammatory markers,no significant differences were detected between the HTS Adult and HFS Weanling groups.Although details regarding the mechanisms underlying an increase in knee joint damage scores in the HFS Adult group remain to be elucidated,these findings indicate that dietary exposure time maybe less important than the age at which an HFS diet is introduced.Moreover,increases in serum proinflammatory mediators do not appear to be directly linked to knee joint damage scores in the HFS Weanling group animals but may be partially responsible for the observed knee joint damage in the adults over the very short time of exposure to the HFS diet.

HIGH-FAT-DIET INDUCED OBESITY IN RATS AND EFFECTS OF ENDURANCE TRAINING ON THE BODY FAT CONTENT OF OBESE RATS

To study the high-fat-diet induced rat obesity and the of fect of endurance training on the body fat content of obese rats, we randomly divided 66 male weanling SD rats into control(16 rats) and high fat diet group(50 rats). After 10 weeks, we chose diet-induced obese rats(DIO, 26 rats) and divided them into endurance training group(DIO-T, 8 rats) and DIO groups(DIO, 18 rats) randomly. Aner 8 weeks, endurance training, all rats were killed. The results showed that nosignificant difference was found between groups in body weight, the feed efficiency of DIO groups was higher than control groups, tke carass fat con tent of DIO-T group was significantlylower than DIO group, and plasma insulin concentration of DIO group was higher than control and DIO-T groups. It was suggested that rats’ obesity was induced obesity by high fat diet, dietary obesity had relation to higher eding efficiency and hyperinsulinemia. Endurance training can effectively reduce the body fat content of high-fat-diet induced obese rats by improving its hyper-insulinemia. Plasma TCH and TG of all rats had no significant difference.