Down-Regulation of Renal Gluconeogenesis in Type II Diabetic Rats Following Roux-en-Y Gastric Bypass Surgery: A Potential Mechanism in Hypoglycemic Effect

OBJECTIVE: This study was initiated to evaluate the effects of Roux-en-Y gastric bypass surgery on renal gluconeogenesis in type 2 diabetic rats and its relationship with hormonal parameters. METHODS: Diabetic rats were induced by intraperitoneal injection of streptozotocin (STZ; 35 mg/kg) combined with a high-fat diet. They were then randomly divided into three groups: diabetes model group (DM group, n = 8), sham Roux-en-Y gastric bypass group (SRYGB group, n = 8), and Roux-en-Y gastric bypass group (RYGB group, n = 14). Another 8 normal rats comprised the normal control group (NC group, n = 8). Body weight, glucose, serum lipid, insulin, glucagon-like peptide-1 (GLP-1), leptin, and adiponectin were measured pre- and postoperatively. Glucose-6-phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK), insulin receptor-α (IR-α), insulin receptor-β (IR-β), and glycogen synthase kinase 3 beta (Gsk3b) were measured in renal cortex by using RT-PCR and Western immune-blot analyses on the 4th week after operation. RESULTS: Following RYGB surgery, surgery-treated rats showed significantly improved oral glucose tolerance, dyslipidemia and insulin resistance as well as increased post-gavage insulin levels and serum circulating levels of GLP-1 and adiponectin. RT-PCR and Western immune-blot analyses showed PEPCK and G6Pase protein and mRNA to be significantly decreased in the renal cortex in the RYGB group (p < 0.05 vs. DM or SRYGB group); in addition, IR-α and Gsk3b phosphorylation levels increased in the RYGB group (p < 0.05 vs. DM or SRYGB group). CONCLUSION: Down-regulation of renal gluconeogenic enzymes might be a potential mechanism in hypoglycemia. An improved insulin signal pathway in the renal cortex and increased circulating adiponectin concentrations may contribute to the decline of renal gluconeogenesis following RYGB surgery.