This study was focused on the effects produced by diets with different amino acid proportions on visceral protein synthesis (liver and jejunal mucosa). Eight groups of rats received an enteral modular diet supplemented with different amino acids (Group 1: lie, Leu, Val; Group 2: Phe, Met, Gly; Group 3: Glu, Arg, Gly; Group 4: Gly, Group 5: Orn-Asp, Cys, Pro; Group 6: Lys, Ser, Thr; Group 7: Tyr, His, Ala). Group 8 was the control group. Rats were fed for four days. At the end of this period a flooding dose of 14C-Leu was injected and animals were killed. Liver and jejunal mucosa were removed and protein synthesis rate was determined. Results show a decreased liver protein synthesis in group fed with aromatic amino acids (53.8 ±8.4 vs. 88.6 ±12.1) and Gtti-Arg (68.6±10.9). In jejunal mucosa there was a decrease of protein synthesis in groups fed with aromatic amino acids (98.7 ± 16 vs 160.5 ±49). These changes seem to be related to the intracellular amino acid pool size and its
influence on protein metabolism.
The aim of this work was to study the effects of low energy parenteral diets with different lipid/glucose ratios on rat liver and jejunal mucosa protein synthesis. The studied diets were: LO (100 % glucose, control diet), L25 (25 % lipids: 75 % glucose), L50 (50 % lipids: 50 % glucose) and L75 (75 % lipids: 25 % glucose). All diets were isoenergetic and isonitrogenated, with a standard amino acid content. The diets were assayed in 93 rats with open femoral fracture immobilized by Kirschner pin insertion. The diets were administered for 4 days. On the fifth day, liver and jejunal mucosa protein synthesis were determined. Highest liver protein synthesis rates were obtained with the diet compositions: lipid/carbohydrate ratio: 25 % lipids and 75 % carbohydrates (expressed as energy ratio). A higher proportion of lipids significantly decreases liver protein synthesis (p<0.05). Jejunal mucosa protein synthesis followed the same pattern, with the same statistical differences.
We have studied the effects of hypocaloric diets with different supplements on liver and jejunal mucosa protein synthesis. The supplements assayed were medium chain triglycerides (diet MCT, with 50 % carbohydrates: 25 % long chain triglycerides (LCT): 25 % medium chain triglycerides (MCT), standard amino acids), branched-chain amino acids (diet BCA, identical to control diet L50, with 15.3 % of nitrogen replaced by branched-chain amino acids) and glutamine (diet GLN, identical to diet L50, with 15.3 % of nitrogen replaced by glutamine). The control diet (L50) had 50 % carbohydrates: 50 % LCT and standard amino acids. The diets were assayed on 86 rats with femoral fracture immobilized by Kirschner pin insertion. Nutrition was administered for 4 days. On the fifth day, liver and jejunal mucosa protein synthesis was determined. A branched-chain amino acid supply in a proportion higher than 21.2 % of amino acid nitrogen significantly decreased liver and jejunal mucosa protein synthesis, while the same amount of glutamine did not modify it. MCT had no effect on jejunal mucosa protein synthesis, while it was decreased significantly in the liver.