Effects of Dietary Protein Restriction on the Fractional Rates of Protein Synthesis in Perfused Rat Hindlimb.

Abstract

SummaryThe effects of dietary protein restriction on protein synthe sis were investigated in perfused rat hindlimb. The fractional rate of protein synthesis was measured with [3H] phenylalanine in young adult (7-week-old) rats fed a low protein (5% casein) diet and a protein-free diet for 3 weeks. The low protein diet (LPD) allowed a moderate gain in body weight. The fractional rate of protein synthesis fell to 70% of the control value in LPD group and further fell to less than a half in the protein-free diet (PFD) group. Thus, the protein synthesis rate decreased as the dietary protein content was reduced. The fall of protein synthesis was mainly accompanied by the reduction of RNA activity (mg pro tein/mg RNA/day) rather than RNA concentration (RNA/protein). The rate of protein breakdown was calculated by subtracting growth rate from protein synthesis rate. The breakdown rate was decreased in LPD group and increased slightly in PFD group. From the low rates of protein synthesis and breakdown, it appears that dietary protein restriction, at least allowing a gain in body weight, makes the turnover rate slow down. The overall changes in protein synthesis obtained in the perfused hindlimb are consistent with the reported results in vivo.

Comparison of the effects of food versus protein restriction on selected nutritional and inflammatory markers in rats

“…It is likely that further food restriction below this level would cause greater weight loss and render muscle protein mass inadequate to supply the necessary amino acids to maintain optimal rates of fractional protein synthesis in those rapidly turning over tissues like the viscera and the immune system that require either muscle-derived or dietary protein [12–14]. Thus, with greater food restriction, there might well be an impact on the systemic inflammatory response potential.…”