Sitagliptin reduces urinary microalbumin in experimental model of diabetic nephropathy

The term Diabetic kidney disease (DKD) refers to any disease of the kidney that is a result of long-term hyperglycemia caused either by diabetes mellitus type 1 (DT1) or type 2 (DT2). When DKD coexists with macro albuminuria or proteinuria the condition is called diabetic nephropathy. DKD is the primary cause of renal failure since it is responsible for the 44% of new cases presented in the U.S.A. in 2008. Sitagliptin is an inhibitor of the enzyme dipeptidyl peptidase and is used as a treatment for diabetes since 2006. Through the inhibition of the enzyme's action sitagliptin prevents the degradation of GLP-1 which is an endogenous peptide with significant hypoglycemic actions, particularly postprandial. The proven hypoglycemic actions of sitagliptin led the researchers to further study the possible effects sitagliptin may have on the complications of diabetes mellitus such as diabetic nephropathy. The purpose of the study is to examine the effect of sitagliptin on diabetic nephropathy using biochemical parameters for assessment.

27db/db mice were used in total. They were about 4 weeks old. The mice were randomly divided into 3 groups each one consisting of 9 mice, the first 2 groups received sitagliptin treatment over a period of 32 weeks while the third did not receive any treatment. In the first group the mice received 200mg sitagliptin per Kg of body weight and in the second 10mg per Kg. At the end of the 32 weeks period the serum glucose, urea, creatinine, cholesterol, LDL, HDL, hsCRP and triglycerides as well as the urinary creatinine and microalbumin were measured in all 3 groups.

The first group (received 200mg/kg) in comparison to the third group (control group) exhibited a reduction in the biochemical parameters measured: glucose -12.35% (P=0.16), urea -17.18% (P=0.61), creatinine -0.81% (P=0.95 ), cholesterol -19.28% (P=0,09), HDL -12,25% (P=0.26), LDL -31.2% (P=0.25), triglycerides -13,9% (P=0.37), hsCRP -49.8% (P=0.06), microalbumin -37.8% (P<0.0001).

The administration of sitagliptin reduces in a statistically significant manner the urinary microalbumin. In addition, hsCRP was greatly reduced but the reduction did not reach the required significance level. The other biochemical data presented a reduction which could not be considered as statistically significant. However, it should be mentioned that the exact mechanisms by which sitagliptin achieves this reduction in the biochemical parameters measured, except for the glucose reduction, remain unclear. Although it is suggested that the reduction of glucotoxicity due to sitagliptin treatment is the main reason for those results, the effects of sitagliptin on inflammation, protection of the endothelium and reduction of arterial blood pressure might play a facilitating role.