RENAL, METABOLIC, AND HORMONAL RESPONSES TO PROTEINS OF DIFFERENT ORIGIN IN NORMOTENSIVE, NONPROTEINURIC TYPE-I DIABETIC-PATIENTS

OBJECTIVE - Whether the differences in renal function found in vegetar ian compared with omnivorous subjects are related to quantity or quali ty of the protein is unknown. We have studied the renal function of ni ne normotensive, nonproteinuric type I diabetic patients who were fed in random order for 4 weeks either an animal protein diet (APD) (prote in intake 1.1 g . kg(-1) . day(-1)) or a vegetable protein diet (APD) (protein intake 0.95 g . kg(-1) . day(-1)). The two diets were isocalo ric. RESEARCH DESIGN AND METHODS - In a crossover study, we measured g lomerular filtration rate (GFR) (inulin clearance), renal plasma flow (RPF) (p-aminohippurate clearance), plasma amino acids, growth hormone , glucagon, insulin-like growth factor I (IGF-I), and microalbuminuria . RESULTS - GFR and RPF were lower with the VPD than with the APD (89. 9 +/- 4.1 vs. 105.6 +/- 5.1 ml . min(-1) . 1.73 m(-2), P < 0.05, and 4 25.7 +/- 22.2 vs. 477.8 +/- 32.2 ml . min(-1) . 1.73 m(-2), P < 0.05, respectively). Renal vascular resistance (RVR) was higher with the VPD than with the APD (101 +/- 25 vs. 91 +/- 10 mmHg . min(-1) . ml(-1), P < 0.05). Filtration fraction (FF) remained unchanged after either di et. Fractional clearance of albumin fell with the VPD to 2.0 +/- 0.65 from 3.4 +/- 1.15 X 10(-6) (P < 0.05). At the end of the APD and VPD, the plasma levels of growth hormone and glucagon did not differ signif icantly. Plasma levels of IGF-I were higher with the APD than with the VPD (1.1 +/- 0.6 vs. 0.9 +/- 0.13 U/ml, P < 0.05). Plasma concentrati ons of valine and lysine were significantly higher with the APD than w ith the VPD (234.6 +/- 30.3 vs. 164.5 +/- 25.4 mmol/l, P < 0.05, and 5 65 +/- 45.1 vs. 430 +/- 56.1 mmol/l, P < 0.05, respectively), whereas plasma valine was strongly correlated to the GFR (r = 0.832, P < 0.01) . No differences were found in other amino acids. CONCLUSIONS - A VPD has significantly different renal effects from an APD equal in protein intake in normotensive, nonproteinuric type I diabetic patients. This could be explained partly by differences in plasma concentrations of amino acids and IGF-I.