Effects of liraglutide on adiponectin and insulin resistance in rats with non-alcoholic fatty liver disease

AIM：To investigate the effects of glucagon-like peptide 1 analog, liraglutide, on adiponectin and insulin resistance in the rats with diet-induced non-alcoholic fatty liver disease (NAFLD). METHODS：Male rats were randomly divided into 3 groups:normal diet (ND) group (n=10), high-fat diet (HFD) group (n=10), and HFD with intraperitoneal injection of liraglutide group (n=10, first 12 weeks with HFD, later 4 weeks with liraglutide). All treatments continued for 16 weeks, and then the rats were killed ethically and the blood samples and liver tissues were collected. The levels of alanine aminotransferase (ALT), fasting blood glucose (FBG), total cholesterol (TC) and triglyceride (TG) were detected by a biochemical automatic analyzer. The levels of free fatty acids (FFAs), fasting insulin (FINS) and adiponectin were measured by RIA and ELISA. RESULTS：Compared with HFD group, the body weight, liver index, homeostasis assessment-insulin resistance (HOMA-IR), the serum levels of TG, TC, ALT and FBG, and the liver levels of TG, TC and FFAs in the rats in liraglutide group were apparently lower, the degree of hepatic steatosis and inflammatory activity significantly decreased (P<0.05), and the level of adiponectin in the serum and liver homogenate increased ob-viously (P<0.05). The level of adiponectin in the liver homogenate was negatively correlated with the levels of FFAs in the liver homogenate. CONCLUSION:Liraglutide is beneficial for NAFLD rats to improve insulin resistance and reduce hepatic steatosis by increasing the level of adiponectin in the serum and liver tissues.     

GLP-1 down-regulates mRNA expression of SOCS-3 and SREBP-1c in rats with nonalcoholic fatty liver disease

AIM: To investigate the effects of glucagon-like peptide-1(GLP-1) on mRNA expression of SOCS-3 and SREBP-1c in the rats with nonalcoholic fatty liver disease. METHODS: Male SD rats were randomly divided into normal control(NC) group, high fat(HF) group and HF+liraglutide(Lira) group. The rats in HF group and HF+Lira group were given high-fat diet for 16 weeks. After 12 weeks of high-fat diet feeding in HF+Lira group, Lira(600 μg·kg^-1·d^-1) was intraperitoneally injected for 4 weeks. At the end of the 16th week, the rats were killed. The pathological changes of the liver were observed under optical microscope. The serum levels of alanine aminotransferase(ALT), aspartate aminotransferase(AST), triglyceride(TG) and total cholesterol(TC) were detected by automatic biochemical analyzer. TG contents of liver were measured by GPO-PAP method. The fasting insulin(FINS) was determined by ELISA, and insulin resistance index was assessed by homeostasis mode assessment(HOMA-IR). The mRNA expression of SOCS-3 and SREBP-1c in the liver tissues was detected by RT-qPCR. RESULTS: Compared with NC group, HOMA-IR, TG of liver, and the serum levels of ALT, AST, TG, TC and FINS in HF group were obviously increased(P<0.01). Compared with HF group, HOMA-IR, TG of liver, and the serum levels of ALT, AST, TG, TC and FINS in HF+Lira group were all obviously decreased(P<0.05 or P<0.01). The mRNA expression of SOCS-3 and SREBP-1c in HF group was significantly higher than that in NC group(P<0.01). The mRNA expression of SOCSV3 and SREBP-1c in HF+Lira group was significantly decreased as compared with HF group(P<0.05). CONCLUSION: Liraglutide may improve the IR and reduce TG of liver through decreasing the mRNA expression of SOCS-3 and SREBP-1c, so as to play a therapeutic role in nonalcoholic fatty liver disease.     

Effect of micronised fenofibrate on lipotoxicity and insulin sensitivity in spontaneously hypertensive rats treated with high-fat diet

AIM: To observe the effect of micronised fenofibrate (lipanthyl) on lipotoxicity and insulin sensitivity (IS) in spontaneously hypertensive rats (SHR) with high-fat diet.METHODS: Twenty-seven SHR were randomly divided into three groups: normal chow group (n=9), high-fat diet group (n=9) and micronised fenofibrate treatment group (n=9). Micronised fenofibrate 100 mg·kg-1·d-1 was given orally to SHR, which diet on high-fat diet for three months. Intramuscular lipids were observed and lipids accumulation index (LAI) was calculated. Nonesterified fatty acid, glucose and insulin were determined in all rats.RESULTS: (1) Compared to SHR in normal chow diet group, body weight and the level of serum TG and TC increased significantly and the level of HDL-C decreased significantly in SHR fed with high-fat diet (P<0.05). Micronised fenofibrate significantly decreased systolic blood pressure, body weight, the level of serum TG and TC, increased the level HDL-C (P<0.05). (2) Fasted blood glucose, free fatty acid (FFA), GLU-AUC obviously increased in high-fat diet group compared with normal chow diet group. Insulin sensitivity index (ISI) in high-fat diet group was much lower than that in normal chow diet group (0.0038±0.0007 vs 0.0053±0.0013, P<0.05). No difference was found between fenofibrate-treated group and normal chow diet group. (3) There were more lipid drops in intramuscular cells of SHR treated with high-fat diet than those in fenofibrate-treated group and normal chow diet group (LAI: 6.42±0.59 vs 3.32±0.77 and 1.98±0.97, P<0.05). After covariance analysis, the results above-mentioned also made sense (F=10.46, P<0.05). (4) Inverse association was found between LAI and ISI (r=-0.58, P<0.05). Positive correlations were found between LAI and TG, FFA, body weight.CONCLUSION: In addition to regulating lipid, micronised fenofibrate may reduce BP, body weight, FFA, lipid accumulation in intramuscular cells and improve insulin sensitivity of SHR treated with high-fat diet.     

Protective effect of curcumin analogue L6H4 on diaphragm of type 2 diabetic rats

AIM: To investigate the protective effect of curcumin analogue L6H4 on diaphragm of type 2 diabetic rats.METHODS: SPF male Sprague-Dawley rats (n=40) were randomly divided into 5 groups: normal control (NC) group, high fat (HF) group, high fat+L6H4 treatment (FT) group, diabetes mellitus (DM) group and DM+L6H4 treatment (DT) group. The rats in the later 4 groups were fed with high-fat diet. After 4 weeks of high-fat diet fee-ding, the rats in DM and DT groups were intraperitoneally injected with streptozotocin to induce type 2 diabetes melliutus. The rats in FT and DT groups were given L6H4 by gavage for 8 weeks. Blood glucose and blood lipid levels were detected biochemically. Fasting serum insulin (FINS) level was measured by radioimmunoassay and insulin resistance index (HOMA-IR) was calculated. Serum adiponectin (APN) level was measured by ELISA. The morphological changes of the diaphragm were observed under light and transmission electron microscopes. Lipid deposition and the activity of succinate dehydrogenase (SDH) and NADH-tetrazolium reductase (NADH-TR) were observed by enzyme histochemical staining. The content of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) in the diaphragm were measured by thiobarbituric acid method and hydroxylamine method, respectively. The protein expression of adiponectin receptor 1 (AdipoR1) in the diaphragm was determined by immunohistochemistry and Western blot. RESULTS: The levels of blood lipids, blood glucose, FINS and HOMA-IR in HF and DM groups were higher than those in NC group, but decreased after L6H4 treatment. The serum APN level in HF and DM groups was lower than that in NC group, but increased after treatment with L6H4. The muscle fibers of the diaphragm were shrunk, fat particles accumulated in the muscle fibers, and the mitochondria were slightly swollen in HF and DM groups. The diaphragmatic fibrosis was obvious in DM group. These lesions were relieved after L6H4 treatment. Compared with NC group, the level of MDA and the activity of SDH and NADH-TR in the diaphragm were increased in HF and DM groups, but decreased after treatment with L6H4. The activity of SOD and the expression of AdipoR1 in the diaphragm were lower than those in NC group, but increased after L6H4 treatment.CONCLUSION: The curcumin analogue L6H4 exerts a protective effect on diaphragm in type 2 diabetic rats. The strengthened protein expression of AdipoR1, the increased serum level of APN, and anti-lipid peroxidation may be involved in the process.     

Effects of curcumin analogue L6H4 on myocardial tissue of type 2 diabetic rats

AIM: To explore the effects of curcumin analogue L6H4 on the myocardial tissue of type 2 diabetic rats and its mechanism. METHODS: Male Sprague-Dawley rats were randomly divided into normal control (NC) group, high-fat (HF) group, high-fat treatment (FT) group, diabetes mellitus (DM) group and diabetes treatment (DT) group.The rats in the latter 4 groups were fed high-fat diet for 4 weeks, then the rats in DM groups and DT groups were intraperitoneally injected with streptozotocin (STZ) to induce type 2 diabetes, while the rats in FT group and DT group were given L6H4. The blood glucose and lipid levels were detected by biochemical method, and serum adiponectin (APN) levels were detected by ELISA. The serum insulin levels were measured by radioimmunoassay and homeostasis model assessment of insulin resistance (HOMA-IR) were calculated. The morphological changes of myocardium were observed by Masson staining and electron microscopy. The protein expression of adiponectin receptor 1 (AdipoR1) and transforming growth factor β1(TGF-β1) in myocardial tissue were determined by immunohistochemistry. The protein expression of adipoR1 was also detected by Western blot for verification. RESULTS: Compared with NC group, the blood glucose, lipids, insulin, HOMA-IR and TGF-β1 were increased in HF and DM group, but they were decreased after treated with L6H4. Compared with NC group, the concentration of serum APN were decreased and the expression of AdipoR1 in the myocardium were weakened in HF group and DM group, and they increased after treated with L6H4. The myocardial fibrosis was obvious in HF group and DM group, the mitochondria in cardiomyocytes expanded, and the cristae disordered, partial disappeared. These lesions were significantly reduced after L6H4 treatment. CONCLUSION: L6H4 exerts a protective effect on the heart in type 2 diabetic rats. The increased concentration of serum APN, the enhanced expression of AdipoR1, and the expression of TGF-β1 inhibited by APN may be involved in the mechanism of protection.     

Effect of glucagon-like peptide 1 on Sesn2/AMPK/mTOR signaling pathway in liver of obese rats induced by high-fat diet

AIM: To explored the effect of glucagon-like peptide 1 receptor agonist liraglutide on Sesn2/AMPK/mTOR signaling pathway in the liver of obese rats.METHODS: Male SD rats were divided into normal chow (NC) group (n=12) and high-fat diet (HF) group (n=33). After 12 weeks, 5 rats of each group were used to assess establishment of obese rat model. The rats in HF group were divided into 4 subgroups, HF group, low dose of liraglutide (LG) group, middle dose of liraglutide (MG) group, and high dose of liraglutide (HG) group, and treated with various doses of liraglutide (0, 50, 100 and 200 μg/kg) via hypodermic injection twice a day for 4 weeks. The body weight and epididymal fat index of the rats at the 16th week were measured. The liver tissue fatty degeneration was observed. The protein levels of Sesn2, AMPK, p-AMPK, mTOR and p-mTOR were determined by Western blot.RESULTS: The body weight of rats in HF group was obviously higher than that in NC group (P<0.01). Compared with NC group, the levels of Sesn2 and p-AMPK/AMPK were significantly decreased in HF group (P<0.01), while the level of p-mTOR/mTOR was not changed. After treatment with liraglutide for 4-week, the body weight of the rats in LG, MG and HG groups was obviously lower than that in HF group (P<0.01), and epididymal fat index of the rats in MG and HG groups was obviously lower than that in HF group (P<0.01). The protein level of Sesn2 in HG group was obviously higher than that in HF group (P<0.01). The level of p-AMPK/AMPK was significantly increased in MG and HG groups (P<0.01). The level of p-mTOR/mTOR was significantly increased decreased in LG, MG and HG groups (P<0.01).CONCLUSION: Glucagon-like peptide 1 receptor agonist liraglutide affects energy metabolism and improves the state of obesity through Sesn2/AMPK/mTOR signaling pathway.     

Effect of L-glutamine on obesity and insulin resistance in high-fat diet-induced C57BL/6J mice

AIM:To explore the effect of L-glutamine (Gln) on obesity and insulin resistance in high-fat diet(HFD)-induced C57BL/6J mice. METHODS:Male C57BL/6J mice (n=60) were randomly divided into normal control (NC) group, HFD group, HFD+L-alanine (Ala) group and HFD+Gln group. Each group had 15 mice. The body weight of the mice was recorded weekly. Fasting blood glucose (FBG) of the mice was tested after 12-h fasting only with water-drinking at the end of the 16th week. The mice were sacrificed and epididymal fat pad was measured. The levels of insulin (INS), leptin (LEP), adiponectin (APN) and glucagon-like peptide-1 (GLP-1) were measured by ELISA. The insulin resistance index (IRI) and insulin sensitivity index (ISI) were calculated. RESULTS:Compared with NC group, the body weight, epididymal fat pad weight, and the levels of FBG, INS, IRI and LEP increased significantly in HFD group (P<0.05), while the levels of ISI and APN decreased significantly (P<0.05). Compared with HFD group, the body weight, and the levels of FBG, IRI and LEP decreased significantly in HFD+Gln group (P<0.05), while the levels of ISI and APN increased significantly (P<0.05). No significant difference of serum GLP-1 levels the four groups was observed. CONCLUSION:L-glutamine reduces the body weight and attenuates the insulin resistance of HFD-induced mice.     

High-fat diet affects plasma membrane GLUT4 content in skeletal muscle from Sprague-Dawley rats

AIM: To explore the change of the amount of GLUT4 protein at the plasma membrane of the rat skeletal muscle after high-fat feeding. METHODS: The animals were divided into three groups (ten for each): group I: control; group II: high-fat feeding; group III: high-fat feeding + dietary treatment. The rat model of insulin resistance (IR) was made by feeding high-fat diet for eight weeks. And then insulin-resistant rats were fed with chow diet for 4 weeks. Fasting plasma glucose and fasting serum insulin levels were measured before and after dietary treatment, respectively. Insulin treatment was achieved by intraperitoneal injection of insulin (10 unit insulin per kg body weight) 15 minutes before killing the animals. The right hindlimb skeletal muscle was rapidly dissected. Then the expression of GLUT4 protein at the plasma membrane in all the animals was assessed with Western bloting. RESULTS: The GLUT4 content at the plasma membrane in high-fat-fed rat skeletal muscle was significantly lower (about 31%) than that in controls (P<0.01). Dietary treatment partly corrected fasting blood glucose [from(6.20±0.39)mmol/L to(5.78±0.74)mmol/L]and fasting serum insulin levels [from(17.19±1.93)mU/L to(11.68±1.28)mU/L] and increased the GLUT4 content at the plasma membrane by 1.14-fold in insulin-resistant rat skeletal muscle. CONCLUSION: High-fat feeding induces IR in Sprague-Dawley rats. The mechanism may be involved in decreased cell-surface level of GLUT4 through affecting intracellular insulin signaling and then decreasing GLUT4 trafficking.     

Effects of blockade of rennin-angiotensin system on expression of uncoupling protein-2 and catalytic subunit of glutamylcysteine ligase in pancreatic islets in rats with insulin resistance and long-term high-fat diet

AIM: To study the mechanism of oxidative stress in rats characteristic of insulin resistance with long-term high-fat diet and to observe the effects of rennin-angiotensin system (RAS) blockade on the functions of RAS, oxidative stress and glucose metabolism.METHODS: Male Wistar rats were randomly divided into 4 groups: normal chow group (NC), high-fat-chow group (HF), perindopril treated group (FP, perindopril and high-fat-chow), and telmisartan treated group (FM, telmisartan and high-fat-chow). At the end of 16 week experiment, the last two groups were treated with perindopril 2 mg·kg-1·d-1 and telmisartan 10 mg·kg-1·d-1, respectively. After 8 week intervention, the glucose infusion rate (GIR) was measured by using euglycemic hyperinsulinemia clamp to evaluate the peripheral insulin resistance. Islet function of all the animals was evaluated by the intravenous glucose tolerance test. The mRNA expression levels of catalytic subunit of glutamylcysteine ligase (GCLC) in the islets were detected by RT-PCR. Immunohistochemical technique with qualitative and (or) quantitative analysis was applied to determine the expression of uncoupling protein-2 (UCP2) in the islets. The contents of malonaldehyde in the pancreatic tissue were determined by chromatometry.RESULTS: Compared to NC group, GIR in HF group was decreased by 31.8%, the relative expression of local GCLC was decreased by 31.5%，the relative content of UCP2 was increased by 17.0% (all P<0.01). The area under the curve of blood insulin between 0 and 10 minutes (AUCI0-10) was (271.8±33.8) vs (282.7±29.8) mIU·L-1·min-1, glucose-stimulated early insulin secretion was decreased, but there was no significant difference. Compared to HF group, the GIR of FP and FM groups was increased by 27.8% and 30.8%, respectively. The relative expression of local GCLC was increased by 26.6% and 26.6%, respectively, the relative content of UCP2 was decreased by 13.0% and 15.6%, respectively (all P<0.01). No significant difference between group FP and FM was found.CONCLUSION: Blockade of rennin-angiotensin system improves insulin resistance and pancreatic islet β-cell function in rats with long-term high-fat diet. The β-cell function may be protected by down-regulating the expression of uncoupling protein-2 (UCP2), up- regulating the expression of catalytic subunit of glutamylcysteine ligase (GCLC) and attenuating oxidative stress.     

Effect of calories restriction on ER stress in the liver of high fat diet rats

AIM: To study the effect of calories restriction on endoplasmic reticulum(ER) chaperone protein 78-kD glucose regulated protein (GRP78) mRNA expression in the liver of high fat diet rats, in order to explore the mechanism of how calories restriction improves insulin resistance. METHODS: Wistar rats (n=24) were randomly divided into 3 groups: normal chow (NC) group, was fed free normal chow (18.94% of calories as fat) for 12 weeks; high fat group (HF) was fed high fat diet (50.55% of calories as fat) for 12 weeks; calories restriction group (CR) was fed high fat diet for 8 weeks at first, then given 50% of diet consumed by the same age NC group. Changes of body weight, height, and food intake were recorded. At the end of experiment, HOMAIR, the rate of visceral fat (including perirenal fat and epididymal fat) vs weight, plasma protein, blood lipid (including total cholesterol and triglyceride), hepatic GRP78 mRNA and hepatic histological changes (including light microscopic studies and electron microscopic studies) were detected. RESULTS: (1) Animals in HF group had an obviously elevation of fasting insulin (27.51±3.51) mU/L vs (15.46±2.25) mU/L, triglyceride (1.35±0.25) mmol/L vs (0.67±0.10) mmol/L, total cholesterol (2.59±0.34) mmol/L vs (1.41±0.28) mmol/L and insulin resistance index HOMAIR (5.85±0.23 vs 2.85±0.60) compared with NC group, and also had obviously lipid accumulations in the liver. (2) After calories restriction, all the abnormal elevated biochemical indicators were decreased to normal levels, the hepatic lipid accumulations were also improved. (3) The changes of liver ultrastructure in HF group showed rough endoplasmic reticulum enlargement, fragmentation, taking off grain, and with glycogen solution. The changes in CR group were nearly the same as those in NC group. (4) High fat diet induced the expression of GRP78 mRNA, calories restriction might reverse it. CONCLUSION: Reasonable food calories restriction is a good method to improve insulin resistance, partly due to improvement of endoplasmic reticulum stress in liver.     

Influence of metformin on LPIN1 expression and AMPK signaling in high-fat diet-induced insulin resistant rats

AIM: To explore the regulatory mechanism of LPIN1 in hepatic insulin resistance by investigating the influence of metformin on the expression of LPIN1 and AMP-activated protein kinase(AMPK) signaling in the rats with high-fat diet-induced insulin resistance. METHODS: Thirty-six 4-week-old male Wistar rats were randomly divided into 2 groups: control group and high-fat diet (HF) group. The rats in HF group were fed with high-fat diet for 8 weeks and then were randomly divided into 2 subgroups: HF group and metformin intervention group, and the animals were continuously raised for 8 months. The mRNA levels of α1 and α2 subunit of AMPK as well as LPIN1 were measured by real-time RT-PCR. Phospho-AMPKα (Thr-172) was detected by Western blotting to evaluate the activity of AMPK. RESULTS: After 4 months, the rats in HF group showed significant increase in the levels of body weight, fast plasma glucose and insulin, and the levels of triglyceride and total cholesterol significantly elevated.Significant decrease in LPIN1 and phospho-AMPKα (Thr-172) expression in the rat livers were also observed. After treated with metformin, the metabolic indexes of the HF rats were improved. The mRNA and protein expression of AMPKα1 and AMPKα2 had no significant difference among the 3 groups. Metformin treatment also increased the expression of LPIN1 in the liver tissues of HF rats. CONCLUSION: The decrease in LPIN1 expression and AMPK activity may contribute to hepatic insulin resistance in diet-induced obese rats. Metformin improves the LPIN1 expression and AMPK activity through the interaction between LPIN1 and AMPK signal pathways.     

Hypothalamic expression of orexin A and lipid metabolism disorder in rats with alimentary obesity

AIM: To evaluate the effect of orexin A in rat hypothalamus on lipid metabolism disorder in rats with alimentary obesity induced by high-fat diet.METHODS: The rat model of alimentary obesity was induced by high-fat diet. The levels of insulin, triglyceride (TG) and total cholesterol (TC) in the serum were detected by luminescent immunoassay and enzymic method. The mRNA expression of orexin A in rat hypothalamus was determined by real-time PCR.RESULTS: There were statistically significant differences of weight, body fat content, and Lee's index between high-fat diet group and control group after 8-week feeding of high-fat diet. Compared to control animals, the levels of insulin, TG and TC in the rats with alimentary obesity significantly increased by 50％, 94％ and 43％, respectively (P<0.05). The expression of orexin A in rat hypothalamus significantly decreased by 57％, and had significant negative correlation with Lee's index, insulin, TG and TC. Their correlation coefficients were r=-0.798 (P<0.05), r=-0.868 (P<0.05), r=-0.981(P<0.05) and r=-0.815 (P<0.05), respectively. CONCLUSION: Alimentary obesity and lipid metabolism disorder induced by high-fat diet are correlated with down-regulation of orexin A expression in rat hypothalamus.     

mRNA expression of insulin receptor and leptin receptor in liver of nonalcoholic fatty liver disease from diabetic rats

AIM: To observe the pathologic changes of liver in diabetic rats and to investigate the role of mRNA expression of insulin receptor and leptin receptor in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). METHODS: Twenty male Sprague-Dawley rats were divided randomly into two groups: normal control group and diabetic group. After fed with high-fat diet for 4 weeks, diabetic rats were injected with streptozotocin at a dosage of 30 mg/kg intraperitoneally to induce NAFLD model of type 2 diabetes mellitus. Then the diabetic animals were fed with high-fat diet continuously for 12 weeks. At the end of the experiment, the rats were sacrificed, the concentrations of blood glucose, serum lipid, ALT and AST were measured biochemically. The levels of serum leptin and serum insulin were detected by enzyme-linked immunosorbent assay (ELISA) and radio immunoassay (RIA), respectively. The pathologic changes of liver were observed under light microscopy (LM) stained with HE, Sudan Ⅲ and Masson trichrome staining, respectively. The ultra-structural changes of liver were observed under transmission electron microscopy (TEM). Additionally, the mRNA expressions of PEPCK, G6Pase, insulin R and leptin R from rat livers were assayed by semi-quantitative RT-PCR. RESULTS: The levels of blood glucose, serum insulin, serum TG, ALT and AST increased significantly (P<0.01), serum TC elevated (P<0.05), and the levels of serum leptin decreased (P<0.01) in diabetic group compared to those in normal control group. Obvious liver fatty degeneration, piecemeal necrosis with accompanying inflammatory infiltration and fibrosis were found under LM. Hepatocytes pyknosis, lots of lipid deposits in cytoplasm of hepatocytes, proliferation of collagen in space of Disse were observed under TEM in diabetic group. The expression of insulin R and leptin R mRNA in liver from diabetic rats increased significantly (P<0.01) while the expression of PEPCK and G6Pase mRNA remained unchanged. CONCLUSION: Insulin resistance plays an important role in the pathogenesis of NAFLD. Low level of serum leptin, up-regulation of mRNA expression of insulin R and leptin R in liver caused by insulin resistance may be involved in this process.     

Effect of non-alcoholic fatty liver disease on metabolic syndrome-rela-ted type 2 diabetes

AIM: To investigate the effect of non-alcoholic fatty liver disease (NAFLD) on metabolic syndrome (MS)- related type 2 diabetes. METHODS: Sixty-four rats were randomly divided into 8 groups: normal control groups of 3 months (3NC), 6 months (6NC), 9 months (9NC) and 12 months (12NC), and high-sucrose and high-fat groups of 3 months (3H), 6 months (6H), 9 months (9H) and 12 months (12H). The serum levels of alanine transaminase (ALT), free fatty acid (FFA), endotoxin (LPS), tumor necrosis factor alpha (TNFα), C-reactive protein (CRP), monocyte chemotactic protein-1 (MCP-1), fasting plasma glucose (FPG) and fasting plasma insulin (FINS) were measured. The insulin resistance index (HOMA-IR) and beta cell function index(HOMA-β) were also calculated. The specimens of liver and pancreas were prepared for microscopic observation with HE and Sudan Ⅳ staining. The visceral adipose specimens were also prepared with HE staining. The apoptosis of islet cells was detected by TUNEL.RESULTS: Compared with normal control groups, the levels of ALT, FFA, LPS, TNFα, CRP, MCP-1, FPG, FINS and HOMA-IR in high-sucrose and high-fat groups of every phase were higher, but the level of HOMA-β in 6H group showed a compensatory increase first and then progressively decreased. Compared with normal control groups, TUNEL results showed that the number of apoptotic islet cells in high-sucrose and high-fat groups gradually increased from the 3rd to the 12th month. CONCLUSION: The NAFLD plays a trigger role in the start of MS-related type 2 diabetes.     

Effect of resveratrol on level of brain-derived neurotrophic factor in hippocampus of obese rats induced by ovariectomy and high-fat diet

AIM：To explore the effects of resveratrol on the level of brain-derived neurotrophic factor (BDNF) and the mRNA expression of estrogen receptor α (ERα) and estrogen receptor β (ERβ) in hippocampus of obese rats induced by ovariectomy and high-fat diet. METHODS：Fifty female Wistar rats, aged 3 months, were randomly divided into 5 groups: control (C) group, sham operation plus high-fat diet (H) group, ovariectomy plus normal diet (O) group, ovariectomy plus high-fat diet (O+H) group, and ovariectomy plus high-fat diet and treated with resveratrol (40 mg·kg-1·d-1) (O+H+R) group. Three months later, the blood was collected from the femoral artery to detect the serum concentrations of total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and estradiol (E2). The mRNA expression of ERα, ERβ and BDNF in the hippocampus was determined by real-time PCR. The protein level of BDNF in hippocampal tissues was detected by ELISA and Western blotting. RESULTS：Compared with C group, the serum levels of TC and LDL-C in H group were increased, and the hippocampal level of BDNF was decreased. The rats in O group had higher concentration of serum TC, and lower levels of serum E2 and the mRNA expression of ERα, ERβ and BDNF in the hippocampus than those in C group. Compared with C,H and O groups, the level of serum TC was higher, and the level of serum E2 and the expression of BDNF in the hippocampus was lower in O+H group. The mRNA expression of ERα and ERβ in hippocampus was also reduced as compared with C group and H group. After treated with resveratrol, the rats in O+H+R group showed lower level of serum TC, and higher levels of serum E2, hippocampal BDNF and mRNA expression of ERα and ERβ than those in O+H group. CONCLUSION：Ovariectomy combined with high-fat diet decreases the mRNA expression of ERαand ERβ and the level of BDNF in the rat hippocampus. Resveratrol improves the blood lipid metabolism and up-regulates the mRNA expression of ERα/ERβ and the level of BDNF in the hippocampus in obese rats induced by ovariectomy and high-fat diet.     

Effect of GLP-1 on insulin resistance and PKCε in rats with nonalcoholic fatty liver disease induced by high fat diet

AIM: To observe the therapeutic effect of glucagon-like peptide 1 (GLP-1) analog on nonalcoholic fatty liver disease of rats and to investigate the underlying mechanism.METHODS: SD rats (n=21) were used to establish a nonalcoholic fatty liver disease model by feeding a high fat diet for 12 weeks, and other 11 rats were fed with a normal diet for 16 weeks. The model rats were randomly divided into 2 equal groups:one group was treated with glucagon-like peptide 1 analog (0.6 mg·kg^-1·d^-1) by intraperitoneal injection for 4 weeks, the other group using saline as a control. After treatment, fasting blood glucose, serum insulin, blood lipids, liver function and the pathological changes of the hepatic tissues were evaluated and the expression of PKCε at mRNA and protein levels in the liver tissues was detected by real-time PCR and Western blot, respectively.RESULTS: Compared with model group, the intervention of GLP-1 significantly reduced insulin resistance index (HOMA-IR), improved the liver function (P<0.05), decreased the liver index and blood lipids (P<0.05). HE staining showed obvious pathological changes of the hepatic tissues in model group, and the intervention of GLP-1 significantly reduced lipid droplets in the hepatocytes and improved the structural damage of the liver. The expression of hepatic protein kinase Cε (PKCε) at mRNA and protein levels significantly decreased which were reversed by treating with GLP-1.CONCLUSION: GLP-1 shows good therapeutic effect on nonalcoholic fatty liver disease of rats, possibly by controlling lipid metabolism and reducing insulin resistance, which may be related to PKCε expression.     

Protective effect on hepatic insulin resistance of Astragalus polysaccharide in the high fat-fed mice model

AIM: To investigate the effect and mechanism of Astragalus polysaccharide (APS) on the amelioration of hepatic insulin resistance in high fat-fed mouse model.METHODS: C57BL/6J mice (n=26) were divided into three groups randomly: C group (an animal model for control,n=10);IR group ( an animal model of insulin resistance,n=8) and IA group (an animal model in high-fat diet with APS treatment for12 weeks,700mg·kg^-1·d^-1,ig).High-fat diet was used to induce the formation of insulin resistant.The parameters and insulin sensitivity of the animals were observed.The pathological features of the liver were presented through microscope and TEM.The expression changes of hepatic GSK3β were measured by Western blotting.RESULTS: In this study,the fat-fed mouse model of insulin resistance was established successfully.The mice in IA group responded to the 12-week APS therapy with a significant decrease in the level of blood glucose,plasma insulin,body weight,hepatic TG/FFA and improved glucose tolerance compared with those in IR group.In addition,the expression and the activity of GSK3β were lower in IA group (vs IR group，P<0.05).We also found the hepatic steatosis could be significantly alleviated with APS therapy.CONCLUSION: These results indicate that APS prevents the occurrence of insulin resistance and the hepatic steatosis induced by high-fat diet,at least in part by inhibiting the expression and activity of the hepatic GSK3β.     

Serum levels of inflammatory factors and adiponectin in type 2 diabetic retinopathy patients

AIM: To investigate the serum levels of inflammatory factors and adiponectin in type 2 diabetic retinopathy (DR) patients.METHODS: One hundred and ten cases of type 2 diabetic patients were divided into 3 groups: no diabetic retinopathy group (DM, n=35), non-proliferative diabetic retinopathy group (NPDR, n=45), and proliferative diabetic retinopathy group (PDR, n=30). Other 40 normal persons served as controls (NC group). The physical examinated was performed for each patient. Serum levels of fasting plasma glucose (FPG), glycated hemoglobin A1c (HbA1c), 2 h postprandial plasma glucose (2hPG), fasting insulin (FINS), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), adiponectin, intercellular adhesion molecule-1(ICAM-1), tumor necrosis factor-α (TNF-α) and high-sensitivity C-reactive protein (hs-CRP) were measured. Insulin resistance index (HOMA-IR) was also calculated.RESULTS: The systolic blood pressure, body-mass index, waist-hip ratio, serum levels of TG, LDL-C, FPG, 2hPG, HbA1c, ICAM-1, TNF-α, hs-CRP and HOMA-IR were significantly higher in DM group, NPDR group and PDR group than those in NC group (P<0.05). The systolic blood pressure, serum levels of ICAM-1, TNF-α, hs-CRP and HOMA-IR were higher in NPDR group and PDR group than those in DM group (P<0.05). The serum concentration of adiponectin was lower in DM group, NPDR group and PDR group than that in NC group (P<0.05), and that was also lower in NPDR group and PDR group than that in DM group (P<0.05). The negative correlations between adiponectin and ICAM-1 (r=-0.735,P<0.01), TNF-α (r=-0.781,P<0.01), hs-CRP (r=-0.768, P<0.01) or HOMA-IR (r=-0.752, P<0.01) were observed. The relationships between HOMA-IR and ICAM-1 (r=0.857,P<0.01), TNF-α (r=-0.906, P<0.01) or hs-CRP (r=-0.888,P<0.01) were positive.CONCLUSION: The results suggest that inflammatory refactors and adiponectin play important roles in the pathophysiology and progression of DR. The protective effects of adiponectin on DR may be related with its anti-inflammatory reactions to improve insulin resistant.     

Effect of electroacupuncture in different intensities on endoplasmic reti-culum stress in adipose tissues from high-fat diet-induced obese rats

AIM: To investigate the effect of electroacupuncture (EA) in different intensities on unfolded protein response (UPR) signaling pathway in adipose tissues from high-fat diet-induced obese rats. METHODS: Sixty SD rats were randomly divided into 2 groups: common diet group (n=10) and high-fat diet group (n=50). Thirty obese rats in high-fat diet group were chosen and divided into high-fat diet group, 5 mA EA group and 1 mA EA group (n=10 each). EA at frequency of 20 Hz and intensities of 5 mA or 1 mA was applied to ST 36 and SP 6 for 15 min once daily for 2 weeks. The body weight was detected once a week. The expression of p-PERK and CHOP/GADD153 in epididymal adipose tissues was determined by Western blotting. The content of Bcl-2 and caspase-12 in the adipose tissues was measured by ELISA. RESULTS: After EA, the body weight and the expression of p-PERK and CHOP/GADD153 in obese rats were significantly decreased (P<0.01 or P<0.05). The rats in 5 mA EA group exhibited a better improvement on the protein expression than the rats in 1 mA EA group.CONCLUSION: EA has a beneficial regulatory effect on the rats with simple obesity. Moreover, the EA density of 5 mA is superior to 1 mA.