The lost correlation between leptin and CRP in type 2 diabetes.

C reactive protein (CRP) is an inflammatory marker believed to be of value in the early prediction of type 2 diabetes (T2DM). Recent studies have shown a positive correlation between leptin and CRP levels. Here, we aimed to study the correlation between leptin and CRP in patients with T2DM. We also studied the effect of metformin therapy on the CRP-leptin correlation in patients with newly diagnosed diabetes. We performed a follow-up study on three groups of participants defined as 1: patients with newly diagnosed T2DM, 2: patients with long-standing T2DM, and 3: healthy controls. Patients with newly diagnosed diabetes were followed for three months after the initiation of metformin therapy. The homeostatic model assessment of insulin resistance (HOMA-IR) decreased, while leptin levels (15.9 ± 1.6 versus 21.4 ± 2.5, p<0.01) increased after metformin therapy. Leptin levels correlated significantly with CRP in healthy controls (r = 0.48; p<0.01); patients with newly diagnosed diabetes before (r = 0.35; p<0.05), and after (r = 0.55, p<0.001) metformin therapy, while there was no significant correlation between leptin and CRP in patients with long-standing diabetes (r = 0.15; p = 0.55). After multiple adjustments for potential confounders, leptin was the best predictor of CRP in controls (β coefficient = 0.433, p<0.01), and patients with newly diagnosed T2DM who received metformin (β coefficient = 0.584, p<0.01). Statin treatment did not have any significant effect on the results. This is the first report demonstrating the restorative role of metformin on the leptin-CRP correlation in patients with newly diagnosed diabetes.