Protein synthesis is stimulated in nutritionally obese rats.

To investigate the tissue growth and the protein synthesis in vivo in nutritional obesity we used lipid-rich multichoice diet feeding. Young male rats of the Wistar strain were divided in two groups: control and obese. Control rats were fed pelleted nonpurified diet. Obese rats were fed a multichoice diet based on a variety of highly palatable energy-rich human foods for 30 d. Protein intake was kept equal in the groups to avoid its influence on protein turnover. The tissue growth pattern was evaluated by protein, DNA and RNA contents of liver, kidney, heart, skeletal muscles and small intestine. Protein synthesis in vivo was measured in these tissues by the phenylalanine flooding-dose technique. Rats fed the multichoice diet showed significantly greater body growth when compared with rats fed the nonpurified diet. Adipose and other tissue weights were significantly greater in the obese rats. The tissue growth pattern was characterized mainly by hyperplasia. In most tissues the net protein accretion found in obese rats resulted from an enhancement in the fractional rate of protein synthesis. The greater protein synthesis was due to an increase in the efficiency of ribosomes in kidney, heart and skeletal muscle and to an increase in the synthetic capacity in liver and small intestine. These data suggest that excess energy intake when protein intake is adequate stimulates tissue growth and protein synthesis in rats.