INFLUENCE OF DIETARY-PROTEIN ON GLOMERULAR-FILTRATION AND URINARY ALBUMIN EXCRETION IN INSULIN-DEPENDENT DIABETES

We investigated the effects of dietary constituents on glomerular filtration (GFR) and albumin excretion rates (AERs) in a cross-sectional study in 39 young subjects with insulin-dependent diabetes. Dietary protein intake correlated significantly in patients with GFRs < 150 mL/min per 1.73 m2 (r = 0.53, n = 23, P = 0.009), but not with AER. GFR also correlated with mean blood glucose at a concentration < 12.0 mmol/L (r = 0.61, P = 0.0035). Protein and fat intakes were similar in patients with and without microalbuminuria (AER > 20 mg/L) but long-term glycemic control was worse in the former [HbA1 12.4 +/- 2.9% (xBAR +/- SD) and 10.6 +/- 2.1 %, respectively, P = 0.043]. In seven patients, short-term reduction of dietary protein from 2.0 to 1.0 to 0.5 g . kg-1 . d-1 produced a progressive fall in GFR by 11.6 +/- 6.0 and 9.6 +/- 5.9 mL/min, respectively (P < 0.05), but did not consistently affect AER. We conclude that both dietary protein and glycemic control influence GFR but neither alone appears to explain glomerular hyperfiltration. Microalbuminuria was associated with poor glycemic control but not with dietary fat or protein consumption.