Suppression of Connective Tissue Growth Factor Mediates the Renoprotective Effect of Sitagliptin Rather Than Pioglitazone in Type 2 Diabetes Mellitus

Aim: Diabetic nephropathy (DN) is a leading cause of end-stage renal disease, and thus, the ability of antidiabetic drugs to ameliorate renal microvascular disease may be as important as their ability to control blood glucose. Therefore, we investigated the reno-protective effect of the antidiabetic drugs, Sitagliptin and Pioglitazone, versus combined Metformin/Enalapril in a rat model of type 2 diabetes.

Method: Male Wistar rats were randomly assigned to be either normal control or diabetic. Induction of type 2 diabetes was done by intraperitoneal injection of\ low dose streptozotocin (35mg/kg) on top of 2 weeks of high fat diet. Hyperglycemic animals were divided into 4 groups: untreated diabetic, Sitagliptin (10mg/kg), Pioglitazone (10mg/kg) and Metformin/Enalapril (500, 10mg/kg, respectively) treated. After 6 weeks, fasting blood glucose, plasma insulin, β-cell function, insulin resistance, serum lipids, urea & creatinine, albuminurea, kidney weight, renal oxidative stress, plasma connective tissue growth factor (CTGF) and renal histopathology were assessed.

Key Findings: Sitagliptin decreased microalbuminurea, urea & creatinine, renal tropism, oxidative stress and CTGF to levels similar to Metformin/Enalapril group. It also preserved near normal renal histology. Although Pioglitazone treatment reduced urea, creatinine, renal tropism and oxidative stress, it did not improve renal pathological changes or significantly alter CTCF.

Significance: Early Sitagliptin treatment in type 2 diabetes can equally ameliorate renal functions and structural changes as combined Metformin/Enalapril. Moreover Sitagliptin is a better renoprotective than Pioglitazone, probably due to its suppressor effect on CTGF, a key factor mediating diabetic renal injury.