Effects Of PTP1B On Disturbance Of Hepatic Glucose Metabolism In Obese Rats Treating With Roux-en-Y Gastric Bypass

Aims: To investigate the effects of Roux-en-Y gastric bypass surgery(RYGB) on hepatic expression of protein tyrosine phosphatase 1B(PTP1B), and its relationship between PTP1 B and hepatic glucose metabolism in obese rats after RYGB. Therefore, this study may provide a theoretical basis for RYGB treating obesity and its related complication.Methods:(1) Sixty SD rats randomly chosen from 70 were fed with high-fat diet, and the left 10 rats which fed with standardized diet were used as normal control group. After 12 weeks induced by HFD.(2) Twenty-eight rats in the HFD group which having body weight at least 20% more than those in normal control rats were divided into three groups: obese group(Ob group, n=8), obese RYGB group(Ob+RYGB group, n=12), obese sham operation group(Ob+Sham group, n=8).(3) Body weight and postprandial blood glucose were regularly monitored each week after surgery; Intraperitoneal glucose, pyruvate, insulin tolerance tests(GTT, PTT and ITT) were performed before and 4, 5, 6weeks after surgery; DEXA was used for detecting body fat ratio; The level of fasting blood glucose, plasma insulin and plasma GLP-1 were measured at 8 weeks after surgery;Blood serum bio-chemical analysis for ALT, AST, TC, TG, HFD-c, LFD-c and HOMA-IR.(4) Hepatic tissue morphology analysis was observed using HE staining; Hepatic glycogen deposition was observed using periodic acid schiff(PAS) staining. RT-PCR analysis for the m RNA levels of Glucose-6-phosphatase(G6Pase), Phosphoenolpyruvate carboxykinase(Pepck), Glycogen synthase kinase-3β(Gsk-3β) and Glycogen synthase(Gs); Western blotting for protein levels of Insulin receptor substrate 1(IRS1), Protein kinase B(Akt), Forkhead box O1(Fox O1) and PTP1 B. Fasting blood glucose(FBG) and plasma levels of insulin also were tested at 8 week after surgery; The intracellular localization of PTP1 B was observed by immunohistochemistry.Results:(1) Comparision of body weight in each groups before and after surgery. There were no significant difference between the two groups at the beginning; At the 4, 8, 12 weeks induced by HFD, body weight in HFD group were significantly increased compared with those in normal control group(P <0.05). At the 2, 4, 6, 8weeks after RYGB surgery, body weight in Ob group and Ob+Sham group were significantly increased compared with those in Ob+RYGB group(P <0.05); At the 4, 6, 8weeks after RYGB surgery, body weight in Ob+RYGB group had no significant difference compared with those in normal control group.(2) Comparision of GTT, PTT, ITT in each groups before and after surgery. After 12 weeks induced by HFD, obese rats were observed glucose intolerance, reduced insulin sensitivity and increased gluconeogenesis. At the 4, 5, 8weeks after RYGB surgery, GTT, PTT and ITT in Ob+RYGB group were observed significantly improved compared with those in Ob+Sham group, AUC of GTT, PTT and ITT analysis were statistical significance(P <0.05).(3) Comparision of FBG, FINS, GLP-1 and HOMA-IR in each groups after surgery. At the 8weeks after RYGB surgery, Compared with Ob group and Ob+Sham group, the FBG, FINS and HOMA-IR in Ob+RYGB group were significantly decreased and the plasma GLP-1 were significantly increased(P <0.05). Compared with normal control group, the GLP-1 in Ob+RYGB group were significantly increased(P <0.05), but the FBG, FINS and HOMA-IR had no significant difference(P>0.05).(4) Serum biochemical indices and body fat ratio analysis in each groups after surgery. At the 8weeks after RYGB surgery, compared with normal control group, the TC, TG, LDL-c and body fat ratio in Ob group and Ob+Sham group were significantly increased(P <0.05), but AST, ALT and HDL-c had no significant difference(P>0.05); Compared with Ob group and Ob+Sham group, the TC, TG, LDL-c body fat ratio in Ob +RYGB group were significantly decreased(P <0.05), but AST, ALT and HDL-c had no significant difference(P>0.05).(5) Hepatic tissue morphology analysis. At the 8weeks after RYGB surgery, compared with normal control group, the Ob group and Ob+Sham group were observed hepatocyte steatosis, the size and the amount of fat physalides were significantly increased, and the hepatic glycogen deposition were significantly decreased(P <0.05); Compared with Ob group and Ob+Sham group, the hepatocyte steatosis and hepatic glycogen deposition in Ob+RYGB group were significantly improved(P <0.05).(6) Comparision of m RNA levels of G6 Pase, Pepck, Gsk-3β, Gs and Ptp1 b in each groups. At the 8weeks after RYGB surgery, compared with normal control group, the m RNA levels of G6 Pase, Pepck, Gsk-3β and Ptp1 b in Ob group and Ob+Sham group were significantly increased(P <0.05), and the m RNA level of Gs were significantly decreased(P <0.05); Compared with Ob group and Ob+Sham group, the m RNA levels of G6Pase, Pepck, Gsk-3β and Ptp1 b in Ob+RYGB group were significantly decreased(P <0.05), and the m RNA level of Gs were significantly increased(P <0.05).(7) Comparision of expression of protein of IRS1, Akt, Fox O1 and PTP1 B. At the 8weeks after RYGB surgery, compared with normal control group, the phosphorylation of IRS1, Akt, Fox O1 in Ob group and Ob+Sham group were significantly decreased, and the expression of PTP1 B were significantly increased(P <0.05); Compared with Ob group and Ob+Sham group, the phosphorylation of IRS1, Akt, Fox O1 in Ob+RYGB group were significantly increased, and the expression of PTP1 B were significantly decreased(P <0.05).Conclusion:(1) Reducing body weight and blood glucose, improving glucose intolerance and increasing insulin sensitivity after RYGB in obese rats, suggested that RYGB have an exactly therapeutic effect for obesity rats.(2) The higher expression of PTP1 B in liver in obese rats suggested that PTP1 B may play a key role in regulation blood lipid and glucose metabolism disorders in obese rats.(3) Down-regulation of PTP1 B might be a potential mechanism in hepatic glucose metabolism improvement in obese rats after RYGB.