Anti-inflammatory effects of short-term pioglitazone therapy in men with advanced diabetic nephropathy

Patients with diabetic nephropathy have a high rate of cardiovascular events and mortality. Nontraditional cardiovascular risk factors such as oxidative stress and inflammation are thought to be particularly important in mediating these events. Studies suggest that thiazolidinediones (TZDs) can reduce the level of nontraditional cardiovascular risk in people with or without diabetes mellitus. Whether this benefit occurs in patients with diabetic nephropathy is unknown. I hypothesized that the TZD pioglitazone will mitigate oxidative stress and inflammation compared with glipizide in patients with overt diabetic nephropathy. Markers of oxidative stress (plasma and urine albumin carbonyl and total protein carbonyls and malondialdehyde), inflammation [white blood cell (WBC) count, C-reactive protein (CRP), plasma IL-6, TNF-alpha], and plaque stability [matrix metalloproteinase 9 (MMP-9)] were measured in frozen samples obtained from patients with overt diabetic nephropathy participating in a randomized, open-label, blinded end-point, 16-wk trial with glipizide (n = 22) or pioglitazone (n = 22). Pioglitazone therapy in men with advanced diabetic nephropathy reduced WBC count by 1,125/mul (P < 0.001), CRP by 41% (P = 0.042), IL-6 by 38% (P = 0.009), and MMP-9 by 29% (P = 0.016). Specific differential reductions in WBC count of 1,251/mul (P = 0.009) and reduction in IL-6 of 58% with pioglitazone (P = 0.001) were seen compared with glipizide. There were no statistically significant changes observed with plasma TNF-alpha concentrations or markers of oxidative stress with either hypoglycemic agent. In conclusion, pioglitazone reduces proinflammatory markers in patients with overt diabetic nephropathy, which indicates potentially beneficial effects on overall cardiovascular risk. This surrogate end point needs to be confirmed in trials designed to demonstrate cardiovascular protection.