Cigarette smoking and increased urine albumin excretion are interrelated predictors of nephropathy progression in in type 2 diabetes

Background: Increased urine albumin excretion, (UAE) predicts nephropathy progression in type 2 diabetes, whereas improved blood pressure (BP) control and angiotensin-converting enzyme (ACE) inhibition ameliorate both albuminuria and nephropathy progression. Cigarette smoking (CS) predicts nephropathy progression in patients with type 2 diabetes despite improved BP control and ACE inhibition. We tested the hypothesis that CS and increased UAE are interrelated predictors of nephropathy progression in patients with type 2 diabetes undergoing improved BP control and ACE inhibition. Methods: We prospectively followed plasma creatinine (P-cr) levels and UAE as albumin-creatinine (alb-cr) ratio for 63.9 +/- 0.6 months in 84 patients with type 2 diabetes undergoing BP control with regimens including ACE inhibitors. Results: Despite ACE inhibition and mean BP reduction from 113.7 +/- 1.8 to 92.3 +/- 0.6 mmHg (P < 0.001), P-cr increased (1.03 +/- 0.02 to 1.25 +/- 0.04 mg/dL [91.1 +/- 1.8 to 110.5 +/- 3.5 μmol/L]; P < 0.001) during follow-up. Regression analysis showed that entry alb-cr ratio, but not CS, predicted nephropathy progression when considering both factors together, but CS predicted progression only when excluding alb-cr ratio. Nephropathy progression was minimal for lower levels of alb-cr ratio at entry, but increased progressively for levels greater than 300. Alb-cr ratio increment during follow-up directly correlated with nephropathy progression (r(2) = 0.307; P < 0.001) and was greater in smokers than nonsmokers (1,878 +/- 346 versus 553 214; P < 0.001). Conclusion: Data show that CS and increased UAE are interrelated predictors of nephropathy progression in patients with type 2 diabetes, and CS increases UAE in these patients despite improved BP control and ACE inhibition.