EFFECT OF LOW PROTEIN-DIET ON THE RENAL RESPONSE TO MEAT INGESTION IN DIABETIC NEPHROPATHY

We measured the renal haemodynamic and proteinuric response to a meat meal (MM) in ten persistently proteinuric insulin-dependent diabetic patients in a randomized cross-over study of 3 weeks on low protein diet (LPD) or normal protein intake (NPD). On LPD, protein intake (0.64 +/- 0.05 vs 1.15 +/- 0.09 g kg-1 body weight (BW) per day, P < 0.001), plasma urea (6.6 +/- 1.3 vs 11.0 +/- 2.0 mmol l-1, P < 0.01) and urea appearance (0.06 +/- 0.01 vs 0.16 +/- 0.03 gN kg-1 body weight per day, P < 0.001) were lower. Baseline glomerular filtration rate (GFR), renal plasma flow (RPF) and renal vascular resistance (RVR) were similar on the two diets and there were no significant average changes in these variables after the meat meal on either diet (NPD, before vs after MM: GFR: 67 +/- 11 vs 71 +/- 13 ml min-1 1.73 m-2; RPF: 479 +/- 70 vs 512 +/- 81 ml min-1 1.73 m-2; RVR: 181 +/- 45 vs 179 +/- 52 mmHg min-1 l-1); (LPD, before vs after MM: GFR: 64 +/- 10 vs 67 +/- 11 ml min-1 1.73 m-2; RPF: 506 +/- 60 vs 533 + 52 ml min-1 1.73 m-2; RVR: 151 +/- 28 vs 146 +/- 32 mmHg min-1 l-1). However, all patients with baseline GFR above 60 ml min-1 1.73 m-2 showed a GFR rise in response to the meat meal on both diets, while patients with lower baseline values tended to reduce their GRF. Baseline fractional albumin clearance was lower on LPD (geometric mean [range]: 1.15 [0.10-50.53] x 10(-4)) than on NPD (1.74[0.17-56.99] x 10(-4)). MM produced a significant increase in the fractional clearance of albumin of almost-equal-to 69% on NPD to 2.94 (0.37-113.42) x 10(-4) (P < 0.02), and of almost-equal-to 62% on LPD to 1.86 (0.13-82.90) x 10(-4) (P < 0.01). The magnitude of these changes was not statistically different. In proteinuric insulin-dependent diabetic patients on NPD the renal vasodilatory response to a meat meal is blunted particularly when basal GFR is depressed. LPD does not restore physiological renal response and, while reducing baseline proteinura, fails to prevent proteinuric effect of meat ingestion.