Effect of changes in daily protein intake on renal function in chronic renal insufficiency: differences in reaction...

Protein restriction is advocated in patients with chronic renal insufficiency (CRI) in an attempt to slow down further renal function deterioration, with the most obvious effect in patients with chronic glomerulonephritis (GN) and diabetic nephropathy, and much less in other disease entities, such as adult polycystic kidney disease (APKD), tubulointerstitial nephritis (TIN) and nephrosclerosis (NS). The mechanism by which protein restriction slows down the progression of renal failure remains unclear. Decline of hyperfiltration has been implicated. Whether long-term protein restriction in patients with CRI is associated with a decrease in hyperfiltration is not clear. We studied the effects of prolonged protein intake variation (isocaloric diets in 4-week periods of low (goal: 30-40 g protein daily) and high protein intake (goal: 80-90 g daily) on renal function in 51 patients with CRI. Patients were divided into subgroups according to the underlying renal disease (GN, n = 17; APKD, n = 9; TIN, n = 12; NS, n = 13). Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured at the end of each study period. Overall, GFR rose from 39 (9-90) to 46 (9-100) ml/min/1.73 m2 (median and ranges, p < 0.01), and ERPF from 158 (39-558) to 171 (32-676) ml/min/1.73 m2 (p < 0.01). GFR rose significantly in GN (15%, range -23 to 51%), APKD (5%, range -10 to 33%), and NS (8%, range -8 to 25%). ERPF only rose significantly in GN (14%, range -45 to 47%) and APKD (9%, range -9 to 25%).(ABSTRACT TRUNCATED AT 250 WORDS)