ABSTRACT
Objective To investigate the effects of exogenous Apelin-13 on the expression of glucose and fatty acid metabolism related genes in the liver and skeletal muscle of diabetic rats.Methods Forty male Wister rats were randomly divided into a control group (n=8) and an experimental group (n=32).In the experimental group,a rat model of type 2 diabetes mellitus was established by a high glucose and high-fat diet and intraperitoneal injection of streptozotocin (STZ).The diabetic rats were randomized into a diabetic model group and an Apelin-13 treatment group with 14 rats in each group.Rats in the Apelin-13 treatment group were intraperitoneally injected with 0.1 μmol· kg· d-1 Apelin-13 for 10 weeks,while the control group and the diabetic model group were injected with an equal volume of 0.9％ NaCl solution for 10 weeks.At the end of the 10 week treatment,fasting blood glucose values in each group were measured.Levels of mRNA expression of glucose-6-phosphate (G-6-P),phosphoenolpyruvate carboxykinase (PEPCK),peroxisome proliferatoractivated receptor alpha (PPAR-α),acy1 CoA synthetase long-chain family member1 (ACSL1),and carnitine palmitoyltransferase1 (CPT1) in the liver and levels of mRNA expression of PPAR-α and glucose transporter type 4 (GLUT4) in skeletal muscle were detected by real-time fluorescence quantitative polymerase chain reaction (PCR).Results Levels of mRNA expression of liver PPAR-α,liver ACSL1,liver CPT1,and GLUT4 in skeletal muscle were lower in the diabetic model group (0.309±0.073,0.508±0.056,0.389±0.118 and 0.289±0.066,respectively) than in the control group (0.971±0.028,0.990±0.015,0.987±0.015 and 0.994±0.009,respectively) (all P＜0.05);In the Apelin 13 treatment group,their mRNA expression levels (0.663±0.085,0.802±0.079,0.752 ±0.097 and 0.509±0.119,respectively) were higher than in the diabetic model group,but lower than in the control group (all P＜0.05).Liver G-6 P and PEPCK mRNA levels in the diabetic model group (1.727±0.05 and 1.309±0.130) were higher than in the control group (1.002±0.005 and 0.993± 0.010) (both P＜0.05),but lower than in the Apelin13 treatment group (2.586±0.208 and 1.842± 0.234) (both P＜0.05).Skeletal muscle PPAR-α mRNA levels in the diabetic model group (0.477± 0.118) and the Apelin-13 treatment group (0.566±0.0780) were lower than in the control group (0.993±0.013) (both P＜0.05),but showed no significant difference between the two experimental groups (P ＞ 0.05).Conclusions Apelin-13 increases the expression of the PPAR,ACSL1,and CPT1 genes in the liver and,to a certain extent,improves fatty acid oxidation metabolism in the liver in type 2 diabetic rats.It also increases the expression of the G-6-P and PEPCK genes,promotes gluconeogenesis in the liver,and may be related to the development of type 2 diabetes.In skeletal muscle,Apelin 13 increases GLUT4 gene expression,moderately improves skeletal muscle metabolism and may play a role in the regulation of oxidative stress.
ABSTRACT
Objectives To investigate the effects of Apelin 13 on myocardial metabolism in diabetic rats.Methods A total of 40 male Wister rats were randomly divided into normal control group (NC,n=8) and experimental group (n =32).Diabetic rats model were induced by high-sugar and high-fat diet combined with low-dose intraperitoneal injection of streptozotocin (STZ).The wellestablished 28 diabetic model rats were randomly divided into diabetic model group (DM,n=14) and apelin-13 treated group (n=14).In the Apelin-13 group,diabetic rats were administered Apelin-13 [0.1 μmol/(kg · d)]by intraperitoneal injection for 10 weeks,while the control group and diabetic model group were given an equal volume of 0.9％ NaCl.At the end of the 10th week,all rats were sacrificed after fasting glucose measurement.Levels of serum free fatty acids (FFA) and myocardial FFA were measured by ELISA.Expression of myocardial glucose transporter member 4 (GLUT4) were detected by immunohistochemistry.The mRNA expressions of myocardial PPARα,CD36 and CPT-1 were detected by real-time fluorescence quantitative PCR.Results Fasting blood glucose,serum FFA and myocardial FFA were significantly higher in DM group than in NC group (all P＜ 0.05).The level of plasma glucose and myocardial FFA were significant lower(P＞0.05) in Apelin-13 treated group than in DM group;but serum FFA was not significantly lower(P＜0.05).The mRNA expressions of PPARα,CD36,CPT-1 in cardiac myocyte were higher in DM group and Apelin-13 treated group than in control(P＜0.05),and lower in Apelin-13 treated group than in DM group(P＜ 0.05).The expression of myocardial GLUT4 was significantly lower in DM group(1.138±0.316)and in Apelin-13-treated group (4.631 ± 1.832) than in NC group(9.132 ± 2.156),(F=65.507,P＜ 0.05),and higher in Apelin-13-treated group than in DM group(P＜0.05).Conclusions Apelin-13 increases myocardial expression of GLUT4,improves utilization of FFA,and it can effectively reduce the expression of PPARα,CD36 and CPT-1.Therefore,it may play a vital role in the improvement of myocardial metabolism in diabetic rats.
ABSTRACT
Objective To investigate the effect of exogenous apelin-13 on oxidative stress, myocardial inflammatory cytokines and apoptosis in diabetic model rats.Methods A total of 40 male Wistar rats were randomly divided into 2 groups: normal control group (NC, n=8) and experimental group (EX, n=32).Diabetes was induced by feeding with high-sugary and high-fat diet for 8 weeks and a single intraperitoneal injection of streptozotocin (STZ) (30 mg/kg).The wellestablished 28 diabetic model rats were then randomly divided into 2 subgroups: model group (DM, n =14) and apelin-13 administration group (AP, n =14).The rats in AP group were given intraperitoneal administration of apelin-13 at a single dose of 0.1 μtmol · kg-1 · d-1 for 10 weeks, while NC group and DM group were given 0.9％ NaCl in the same way.All rats were sacrificed at the end of the week 10.Blood hydrogen peroxide (H2O2), nitric oxide (NO) and malonaldehyde (MDA) were measured by colorimetry, and superoxide dismutase (SOD) was measured by enzyme-linked immunosorbent assay (ELISA).The expressions of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in rat myocardium were detected by immunohistochemistry.Masson staining was used to observe the myocardial fibrosis in rats of different groups.Cardiomyocyte apoptosis was determined by TUNEL.Results (1) Compared with NC groups, DM group showed that MDA, H2O2 and NO were significantly increased, while SOD was significantly decreased (F=22.400, 6.230, 4.267 and 8.901, all P＜0.0167).There was a statistically significant difference in the levels of MDA, H2O2,SOD between DM group and AP group.(2) The expression of TNF-α and IL-6 was significantly higher inDMgroup than inNCgroup (0.0599±0.0208 vs.0.0076±0.0031, F=35.139;0.0503±0.0243 vs.0.0071± 0.0024, F=15.946, both P＜0.0167).After 10 weeks of apelin-13 administration, the levels of inflammatory cytokines were significantly decreased in AP group than in DM group.(3) The myocardial apoptosis and fibrosis were significantly increased in DM group than in NCgroup [0.0293±0.0061 vs.0.0030-t-0.0013 and 0.0708±0.0420 vs.0.0013±0.0003, F=84.930 and 19.420, both P＜0.0167].The myocardial apoptosis and fibrosis were significantly decreased in AP group than in DM group (both P＜0.0167).Conclusions To some extent, apelin13 reduces the levels of oxidative stress and myocardial inflammation reaction in type 2 diabetes.Moreover, it may play a vital role in the improvement of myocardial apoptosis and fibrosis.