GLOMERULAR HYPERFILTRATION IN MICROALBUMINURIC NIDDM PATIENTS

Glomerular hyperfiltration and microalbuminuria are both regarded as r isk factors for the development of diabetic nephropathy in insulin-dep endent diabetic patients. Information on glomerular hyperfiltration is scarse in microalbuminuric non-insulin-dependent diabetic (NIDDM) pat ients. Therefore, we performed a cross-sectional study of glomerular f iltration rate (single i.v. bolus injection of Cr-51- EDTA, plasma cle arance for 4 h) in 158 microalbuminuric NIDDM patients compared to 39 normoalbuminuric NIDDM patients and 20 non-diabetic control subjects. The groups were well-matched with regard to sex, age and body mass ind ex. The uncorrected (ml/min) and the adjusted (ml . min(-1). 1.73 m(-2 )) glomerular filtration rate were both clearly elevated in the microa lbuminuric patients: 139 +/- 29 and 117 +/- 24 as compared to 115 +/- 19 and 99 +/- 15; 111 +/- 23 and 98 +/- 21 in normoalbuminuric NIDDM p atients and control subjects, respectively (p<0.001). The glomerular f iltration rate (ml . min(-1). 1.73 m(-2)) in NIDDM patients who had ne ver received antihypertensive treatment was also clearly elevated in t he microalbuminuric patients (n = 96): 119 +/- 22 as compared to 100 /- 14 and 98 +/- 21 in normoalbuminuric NIDDM patients (n = 27) and co ntrol subjects (n = 20), respectively (p < 0.001). Glomerular hyperfil tration (elevation above mean glomerular filtration rate plus 2 SD in normoalbuminuric NIDDM patients) was demonstrated in 37 (95 % confiden ce interval 30-45)% of the microalbuminuric patients. Multiple regress ion analysis revealed that HbA(1c), 24-h urinary sodium excretion, age and known duration of diabetes were correlated with ,glomerular filtr ation rate in microalbuminuric NIDDM patients (r(2) = 0.21, p < 0.01). Our cross-sectional study indicates that NIDDM patients at high risk of developing diabetic nephropathy are also characterized by an additi onal putative risk factor for progression, glomerular hyperfiltration.