High protein intake accelerates glomerulosclerosis independent of effects on glomerular hemodynamics

It is unclear whether glomerular hemodynamic changes always accompany alterations in dietary protein, and whether nonhemodynamic factors associated with a high protein intake can influence glomerular injury. In the present study, uninephrectomized (UNx) male rats were fed either standard (20%) or high (40%) protein diets. Body growth was comparable in the two diet groups. At 30 weeks of age, UNx rats fed high protein had increased albuminuria (36.7 +/- 12.6 mg/24 hr), compared to UNx rats fed standard protein (10.2 +/- 6.2 mg/24 hr; P less than 0.05). The incidence of focal glomerulosclerosis (FGS) at 36 weeks was markedly increased in the high protein rats (19.0 +/- 7.7%), compared to the standard protein rats (3.2 +/- 2.0%; P less than 0.05). Moreover, FGS in the high protein rats correlated with the serum cholesterol level measured at 18, 24, and 30 weeks of age. Glomerular hemodynamics were assessed before glomerular injury developed in separate groups of UNx rats fed either standard or high protein. Single nephron GFR (SNGFR) and single nephron plasma flow (SNPF) were increased in UNx rats, compared to two-kidney rats fed standard protein. SNGFR and SNPF, however, were not different between UNx rats fed standard or high protein. Glomerular capillary pressure (PGC) was not different between UNx rats fed standard protein (51.7 +/- 1.3 mm Hg) and two-kidney controls (53.1 +/- 1.5 mm Hg). Moreover, PGC was not altered in UNx rats fed high protein (51.8 +/- 1.6 mm Hg). We conclude that high dietary protein can accelerate the development of glomerular injury independent of effects on glomerular hemodynamics.