Glomerular hyperfiltration in Koreans with non-insulin-dependent diabetes mellitus

Glomerular hyperfiltration (GHF) may play an important role in the pathogenesis of diabetic nephropathy. The prevalence of GHF in non-insulin-dependent diabetes mellitus (NIDDM) is reported to vary in different populations, ranging from 35% in black Americans with new-onset diabetes to less than 5% in whites. We measured glomerular filtration rate (GFR) by 51Cr-EDTA clearance methods in 284 Korean NIDDM patients without overt nephropathy. Glomerular hyperfiltration (defined as GFR > 140 mL/min/1.73 m2) was found in 25% (71 of 284) of the patients. Thirty percent and 15% of the patients with known duration of diabetes less than 5 years and more than 10 years, respectively, showed GHF. Microalbuminuria (defined as urinary albumin excretion rate 20 to 200 micrograms/min) was found in 23% (64 of 284) of the patients. The mean GFR of the microalbuminuric patients was not significantly different from that of the normoalbuminuric patients (121.5 +/- 30.1 mL/min/1.73 m2 v 124.9 +/- 26.4 mL/min/1.73 m2; P = NS). However, when the patients with microalbuminuria were divided according to the presence or absence of retinopathy, the microalbuminuric patients with retinopathy had a lower GFR compared with the microalbuminuric patients without retinopathy (109.6 +/- 35.5 mL/min/1.73 m2 v 130.0 +/- 26.3 mL/min/1.73 m2; P < 0.01). These results show that the prevalence of GHF in Korean NIDDM patients without overt nephropathy is higher than that reported in whites and that it is similar to that in black Americans. The high prevalence of GHF in Korean NIDDM patients may contribute to the relatively higher prevalence of clinical diabetic nephropathy in this population.