#1870 Uninephrectomized diabetic rats delay onset of hyperglycemia via down-regulation of SGLT2 mRNA

Abstract

Abstract Background and Aims The kidney is essential for glucose metabolism. Reabsorption of almost all the glucose filtered by the glomerulus is performed by the sodium-glucose cotransporters (the SGLTs) in the proximal tubules, with SGLT2 responsible for about 90%. In addition, the kidney, along with the liver, plays an important role in gluconeogenesis, especially in the long fasting state. SGLT2 inhibitors originally developed for the treatment of type 2 diabetes mellitus (DM) are clinically very effective drugs halting chronic kidney disease progression. The underlying mechanisms are, however, not fully understood. Furthermore, SGLT2 expression in diabetic patients has been reported to increase and decrease but remains unclear. Therefore, this study aimed to evaluate how uninephrectomy (UNx) and SGLT2 inhibitor treatment affects the dynamics of blood glucose and SGLTs in SDT fatty rats with obese type 2 DM (leptin receptor mutation), which is hyperglycemic from an early stage. Method 24 male SDT fatty rats were divided into four groups: sham + placebo group (n=6); sham + dapagliflozin (dapa, 1.5 mg/kg/day) group (n=6); UNx + placebo group (n=6); UNx + dapa group (n=6). UNx or sham operations were undergone at week 6. Measurements included body weight, food intake, water consumption, urine output, blood pressure, serum creatinine, and blood glucose in the experiment. At week 12, the rats were sacrificed, and the kidneys were sampled to measure SGLT1 and SGLT2 mRNA in the renal cortex by real-time PCR quantification. Results Blood glucose levels continued to rise from week 7 in the sham + placebo group, but the rate of increase was still slower in the UNx + placebo group, and the increase in blood glucose levels was mostly suppressed with dapa administration (Fig. 1). Only the Sham + placebo group showed increased urinary volume and weight loss after week 10 due to hyperglycemia. There were no significant differences in serum creatinine or blood pressure during the study. Real-time PCR results showed that SGLT2 mRNA in the renal cortex was significantly decreased by 26% in the UNx group (P=0.0386), but SGLT1 mRNA was not significantly different. Conclusion Uninephrectomized diabetic rats delayed onset of hyperglycemia and reduced SGLT2 mRNA; SGLT2 inhibitor treatment further delayed the onset of hyperglycemia but did not alter SGLT2 mRNA expression. In animal models of diabetes, renal glucose reabsorption appeared to be a major contributor to the development of hyperglycemia.