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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.

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: L0 (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.

To investigate the effect of glutamine-enriched total parenteral nutrition (TPN) on the protein synthesis and morphology of jejunal mucosa in non-hypercatabolic stress, sixty-two male Sprague-Dawley rats were subjected to surgical stress by femoral fracture. The rats were divided into 3 groups and received TPN for 8 days. One group received a standard amino acid solution without glutamine, the second group a standard solution enriched with glycine and glutamic acid, and the third group a standard solution enriched with glycyl-glutamine. All regimens were isocaloric and isonitrogenous-nitrogen (2.2 g/kg.day), glucose (150 Kcal/kg.day), and lipids (150 Kcal/kg.day). There were no statistically significant differences in jejunal mucosal thickness, DNA content, protein content, fractional synthesis rate or absolute protein synthesis among the groups after eight days of parenteral nutrition. In conclusion, the addition of glutamine to TPN did not influence either protein metabolism or morphology of the jejunal mucosa in non-hypercatabolic surgical stress.

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: Ile, 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 Glu-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.