Glycerol: major contributor to the short term protein sparing effect of fat emulsions in normal man

Intravenous glucose, aminoacids, and fat in the postoperative period. A controlled evaluation of each substrate

The metabolic effects of hypocaloric (2-51 MJ), equicalorific quantities of intravenous glucose, crystalline aminoacids, and soyabean emulsion were comapred with those of fasting in 4 groups of male patients (closely matched for age, weight, and fat-free mass) on the day of vagotomy and pylorplasty and on the fast 3 postoperative day. Patients given glucose alone excreted less nitrogen than the fasting patients but nitrogen sparing was greatest in the group given aminoacids alone. There was no evidence of any nitrogen sparing when intravenous fat was the source of energy. There was no difference in blood glucose, free fatty acids, and insulin concentrations among the groups. Ketone-body concentrations rose in the fasting and fat-fed groups but remained low in the groups who received glucose or aminoacids. This study indicates that, in the short term, the increased preservation of protein achieved by the infusion of aminoacids compared with that produced by the traditional infusion of glucose does not warrant the extra cost involved.

Intravenous amino acids as the sole nutritional substrate. Utilization and metabolism in fasting normal human subjects

The fasting normal human volunteer subject provides an ideal experimental setting for the initial investigation of foodstuffs whose use is proposed for the acutely ill surgical patient. In the normal human subject many variables can be controlled; the achievement of an ideal body fuel economy is quite simple; if a favorable utilization of injected foodstuffs cannot be achieved in this setting, it is unlikely, and remains to be proven, that utilization will be satisfactory under the challenges of acute surgical trauma. In this experimental model, employing four normal human volunteer subjects, nutrition has been provided by the intravenous infusion of isotonic amino acids (FreAmine(R) II) at a 3.4% concentration. No other source of calories or nutrients was provided. In this setting, utilization was very poor; the subjects were in negative nitrogen balance throughout. The nitrogen excretion was significantly greater than the total of infused nitrogen. The changes in protein, fat and carbohydrate intermediates, as well as the alteration in hormone concentrations, suggest the following endocrine governance of fuel economy in this setting: a sharp rise in glucagon with maintenance of insulin concentration; rapid gluconeogenesis at the expense of both injected and endogenous amino acids; a progressive ketosis without any associated improvement in protein economy; fat oxidation to meet caloric need. The changes in plasma amino acid concentrations are of outstanding interest. They demonstrate changes appropriate to the infusion gradient with the exception of three amino acids whose concentrations did not respond to high infusate levels (serine, lysine, and alanine); likewise, by the fact that methionine rose remarkably though present in only low concentrations in the infusion. These data, taken with other information reported in the literature, as well as continuing studies in these laboratories, strongly suggest that the utilization of infused amino acids for protein synthesis is favored by the provision of an additional caloric source such as glucose.