Background: Data about the relationship of inflammation to nephropathy in type 2 diabetes mellitus are scarce. In the present study, we test the hypothesis that inflammatory parameters are independently related to urinary albumin excretion (UAE) at early stages of nephropathy.
Methods: Sixty-five patients with type 2 diabetes with microalbuminuria (MAB) or mild proteinuria (protein < 1 g/d) were included. We analyzed serum concentrations of high-sensitivity C-reactive protein (hs-CRP) and tumor necrosis factor-alpha (TNF-alpha), as well as urinary level of this cytokine.
Results: Inflammatory parameters were significantly greater in patients with diabetes than controls; furthermore, urinary TNF-alpha levels increased significantly as nephropathy progressed. Median urinary TNF-alpha level was 7 pg/mg in normoalbuminurics, 13 pg/mg in microalbuminurics (P < 0.001), and 18 pg/mg in proteinurics (P < 0.001 versus normoalbuminuria and P < 0.01 versus MAB). Albuminuria was related to hs-CRP (r= 0.68; P < 0.001) and serum (r = 0.45; P < 0.01) and urinary TNF-alpha levels (r = 0.71; P < 0.001), but there was no association between serum and urinary TNF-alpha levels. Partial correlation analysis showed that hs-CRP level, urinary TNF-alpha level, duration of diabetes, and glycated hemoglobin level remained significantly associated with UAE. A stepwise multiple regression analysis showed that UAE was significantly associated with hs-CRP level (P < 0.001), duration of diabetes (P < 0.001), urinary TNF-alpha level (P < 0.01), and glycated hemoglobin level (P < 0.05; adjusted R2 = 0.73; P < 0.001).
Conclusion: Inflammatory parameters in patients with type 2 diabetes at an early stage of nephropathy are independently associated with UAE. In addition to traditional metabolic and hemodynamic factors, it is possible to hypothesize on the participation of inflammation in the pathogenesis of diabetic nephropathy.