Dietary protein intake does not affect IgG synthesis in patients with nephrotic syndrome.

BACKGROUND: Low plasma IgG levels have long been reported as an important complication of the nephrotic syndrome. Few studies in vivo have evaluated IgG synthesis in nephrotic patients and no data are available on the effect of dietary protein restriction on the rate of IgG synthesis. METHODS: We compared the IgG synthesis rates of seven nephrotic patients who assumed, for 4 weeks, either a normal protein diet (NPD) (1.20+/-0.06 g/kg/day) or a low-protein diet (LPD) (0.66+/-0.04 g/kg/day) with those of seven normal subjects (matched for age and body mass index). The post-absorptive fractional synthesis rate (FSR) and absolute synthesis rate (ASR) of IgG were evaluated during the last 120 min of a 5 h 5,5,5-D3-l-leucine infusion. RESULTS: Compared with controls, in nephrotic patients the plasma IgG levels and pool were significantly reduced (P<0.05), while IgG FSR and ASR were increased by 4- and 2.5-fold, respectively (P<0.05). The LPD regimen did not affect plasma IgG FSR, ASR, circulating concentrations and intravascular pool (P = NS). There was a significant negative correlation between plasma IgG FSR and the IgG intravascular pool in nephrotic patients evaluated during both the NPD (r = -0.828; P<0.05) and LPD (r = -0.861; P<0.05) regimens. CONCLUSIONS: Nephrotic syndrome patients with low plasma IgG levels have increased IgG FSR and ASR which are not affected by reduced dietary protein intake.

Increased albumin and fibrinogen synthesis in hemodialysis patients with normal nutritional status.

This study compared the rates of whole-body proteolysis and of albumin and fibrinogen synthesis of seven hemodialysis patients (HD) with those of seven normal matched control subjects (C). HD patients had a normal nutritional and inflammatory status and serum albumin levels >3.5 g/dl. Endogenous leucine flux, albumin and fibrinogen fractional synthesis rate (FSR), and absolute intravascular synthesis rate (ASR) of albumin and fibrinogen all were evaluated by a primed/continuous infusion of 5,5,5-D3-L-leucine. Plasma volume was determined by the Evans blue dye dilution method. Endogenous leucine flux was significantly increased in HD (2.64 +/- 0.08 micromol/kg per min) compared with C (2.17 +/- 0.07 micromol/kg per min, P: < 0.05). Serum albumin concentrations were similar in HD and C. Plasma fibrinogen levels were significantly increased in HD compared with C (P: < 0.05). Plasma volume was greater in HD than in C (P: < 0.05). As a result, total intravascular pool of both albumin (141 +/- 7 versus 114 +/- 3 g/1.73 m(2), P: < 0.05) and fibrinogen (11.7 +/- 1 versus 6.7 +/- 0.5 g/1.73 m(2), P: < 0.05) were greater in HD than in C. Albumin FSR was not statistically different in HD and C. However, albumin ASR was significantly increased in HD than in C (13.7 +/- 2 versus 10.3 +/- 1 g/1.73 m(2) per d, P: < 0.05). Similarly, FSR of fibrinogen did not differ in HD and C groups, whereas ASR of fibrinogen was significantly higher in HD than in C (3.31 +/- 0.6 versus 1.94 +/- 0.3 g/1.73 m(2) per d, P: < 0.05). In summary, normoalbuminemic HD patients have an increased intravascular pool with a greater absolute synthesis rate of both albumin and fibrinogen and an increased rate of whole-body leucine flux.