Albuminuria in nondiabetic relatives of IDDM patients with and without diabetic nephropathy

Background. In non-insulin-dependent diabetes mellitus (NIDDM), there is a clustering of an elevated urinary albumin excretion rate (U-AER) in nondiabetic relatives of albuminuric patients. Whether this is also the case in insulin-dependent diabetes mellitus (IDDM) is unknown. Methods. Overnight U-AER was measured in 186 nondiabetic first-degree relatives of 80 IDDM patients with diabetic nephropathy (U-AER > 200 mu g/min or 300 mg/24 hours; DN+) and in 52 relatives of 25 IDDM patients without nephropathy (U-AER < 20 mu g/min; DN-). The two groups of relatives were comparable regarding gender distribution, age, obesity, blood pressure, prevalence of antihypertensive therapy, and smoking habits. Results. No difference was found in overnight U-AER between relatives of patients with DN+ and DN- [median (range), 3.4 (0.1 to 372) vs. 4.0 (0.2 to 62) mu g/min, respectively, P = NS]. The proportion of relatives with a U-AER = 10 mu g/min was 12% in DN+ compared with 8% in DN- (P = NS). Among relatives of DN+, those with antihypertensive treatment (AHT+) had higher U-AER compared with those without [AHT+ vs. AHT-, 5.0 (0.5 to 372) vs. 3.4 (0.1 to 26.5) mu g/min, P < 0.01], a phenomenon that was not seen among relatives of DN-[AHT + vs. AHT-, 3.6 (2.1 to 24.3) vs. 4.0 (0.2 to 61.5) mu g/min, P = NS]. However, this analysis was impaired by the small number of relatives of DN- with hypertension (N = 7). Conclusions. In IDDM, we found no clustering of elevated U-AER in nondiabetic relatives of patients with nephropathy. This is different from what has been reported in NIDDM, and suggests heterogeneity in the genesis of albuminuria in diabetes.