Glomerular hyperfiltration in NIDDM patients without overt proteinuria

OBJECTIVE--To evaluate the frequency and correlates of glomerular hyperfiltration in NIDDM patients without overt proteinuria. RESEARCH DESIGN AND METHODS--A cross-sectional study was conducted. Seventy-one consecutive NIDDM patients attending an outpatient clinic, with Albustix-tested negative urine and a 24-h AER < 200 micrograms/min, were examined for long-term complications of diabetes. We measured their GFR (51Cr-EDTA single-injection method), 24-h AER (RIA), plasma creatinine, HbA1c, total cholesterol, triglycerides, urinary glucose, and urea. RESULTS--GFR above the upper limit of the normal range for age-matched control subjects (137.1 ml.min-1 x 1.73 m2) was present in 15 of 71 (21%) NIDDM patients. Subjects with normal and hyperfiltration did not differ in terms of age, sex distribution, BMI, duration of NIDDM, BP, AER, or frequency of long-term complications. Plasma glucose was significantly higher in subjects with hyperfiltration (mean [range]: 12.8 [4.3-18.7] vs. 8.7 [2.6-17.5] mM). HbA1c failed to reach statistical significance, although it tended to be higher in the group with hyperfiltration (10.4 [6.7-13.9] vs. 9.4 [4.2-16.5]%, P = 0.10). Age (rS -0.37, P = 0.002), FPG (rS 0.45, P < 0.0005), total cholesterol (rS -0.31, P = 0.008), and glycosuria (rS 0.40, P = 0.001) correlated significantly with GFR. In a stepwise multiple regression analysis, FPG, age, and total cholesterol emerged as significant correlates of the dependent variable GFR. CONCLUSIONS--Hyperfiltration occurred in 21% of NIDDM patients without overt proteinuria. FPG and age significant correlates of the GFR in these patients. Cholesterol is significantly (although only modestly) correlated with the GFR.