Differential Effects of -Blockers on Albuminuria in Patients With Type 2 Diabetes

Increases in the cardiovascular risk marker microalbuminuria are attenuated by blood pressure reduction using blockers of the renin-angiotensin system. Such changes in microalbuminuria have not been observed when -blockers are used. A prespecified secondary end point of the Glycemic Effects in Diabetes Mellitus Carvedilol-Metoprolol Comparison in Hypertensives (GEMINI) trial was to examine the effects of different -blockers on changes in albuminuria in the presence of renin-angiotensin system blockade. Participants with hypertension and type 2 diabetes were randomized to either metoprolol tartrate (n 737) or carvedilol (n 498) in blinded fashion after a washout period of all antihypertensive agents except for angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. Blinded medication was titrated to achieve target blood pressure, with a-5 month follow-up period. The current analysis examined microalbuminuria, using spot urine albumin:creatinine, in participants who had values at screening and trial end. A greater reduction in microalbuminuria was observed for those randomized to carvedilol ( 16.2% ; 95% confidence interval, 25.3, 5.9; P 0.003). Of those with normoalbuminuria at baseline, fewer progressed to microalbuminuria on carvedilol versus metoprolol (20 of 302 [6.6%] versus 48 of 431 [11.1%], respectively; P 0.03). Microalbuminuria development was not related to differences in blood pressure or achievement of blood pressure goal (68% carvedilol versus 67%, metoprolol). Presence of metabolic syndrome at baseline was the only independent predictor of worsening albuminuria throughout the study (P 0.004). -Blockers have differential effects on microalbuminuria in the presence of renin-angiotensin system blockade. These differences cannot be explained by effects on blood pressure or 1-antagonism but may relate to antioxidant properties of carvedilol. (Hypertension. 2005; 46:1309-1315.)