Plasma glucagon and α-amino acid nitrogen response to various diets in normal humans

Abstract

The changes in plasma α-amino acid nitrogen (AAN) and glucagon (IRG) in response to a standard mixed diet, and to a high fat, high carbohydrate, and a high protein isocaloric diet consumed as three equal meals 4 hr apart were determined over a 12-hr period. The standard, high fat, and high carbohydrate diets each contained approximately 1.0 g protein/kg body weight. The high protein diet contained 4 g/kg body weight. The AAN rise was modest and similar in all subjects receiving 1.0 g protein/kg. It was considerably higher in subjects who received 4 g/kg. It increased rapidly after the first meal and remained elevated throughout the day in all groups. Calculation of the AAN concentration area over the 12-hr period indicated proportionality between the amount of protein ingested and the AAN area for all diets. The IRG concentration was increased throughout the day in subjects receiving the high protein diet. Changes in IRG in subjects ingesting the standard, high fat and high carbohydrate diets were modest and not statistically significant. However, when the IRG areas over base-line were determined over the 12-hr period, differences between these diets were present and significant. The area was larger with the high fat diet than with the standard diet. The area was negative for subjects on the high carbohydrate diet. These data indicate that the amount of protein commonly present in the diet can stimulate an increase in peripheral IRG which lasts for several hours and that the amount of carbohydrate commonly present can moderate this.