Does dietary protein intake correlate with markers suggestive of early diabetic nephropathy in children and adolescents with Type 1 diabetes mellitus?

Aims To examine the relationship between dietary protein intake and possible early markers of diabetic nephropathy (creatinine clearance (CrCl), kidney volume and albumin excretion rate (AER)). Methods One hundred and forty-five subjects with diabetes for 5-10 years, divided into three pubertal groups, participated. Kidney volume was measured by ultrasound, and serum creatinine and HbA(1c) were assayed. Two or three 24-h urine collections were obtained for albumin, creatinine and urea excretion rates. Dietary protein intake was estimated from urinary urea nitrogen excretion rate. Glomerular filtration rate was estimated by creatinine clearance. Results Mean protein intake was 1.22 +/- 0.48 g.kg(-1).day(-1) Protein intake was significantly higher in males than females (P < 0.0001) and highest in pre-pubertal compared to mid-pubertal and post-pubertal subjects (P < 0.001). In multiple regression analysis, protein intake was positively associated with CrCl (P < 0.0001), and male sex (P < 0.0001) and negatively associated with body surface area (P = 0.0013) and age (P = 0.01). Kidney volume and AER were not related to dietary protein intake. Conclusions This cross-sectional study failed to show a significant relationship between dietary protein intake and markers of early nephropathy, other than CrCl. However, a longitudinal, prospective study is required to definitively assess the role of protein intake in the evolution of diabetic nephropathy.