title: Changes in plasma somatomedin-C in response to ingestion of diets with variable protein and energy content.
abstract: We have attempted to determine the relative importance of dietary intake of protein and energy in restoring plasma immunoreactive somatomedin-C (Sm-C) concentrations after fasting. Ten healthy human volunteers were fasted for 5 days, then divided into two refeeding groups. One group (variable energy) was refed 1.0 g protein/kg ideal body weight, and in 9-day sequences, 11, 18 and 25 kcal of energy/kg. The other group (variable protein) was given 35 kcal energy/kg, and in 9-day sequences, 0.2, 0.4, and 1.0 g protein/kg. When subjects were refed the variable energy diets there was no significant increase in Sm-C at 11 kcal/kg (0.47 +/- 0.13 to 0.45 +/- 0.12 U/ml), suggesting that there is a threshold energy requirement below which optimal protein intake is not sufficient to raise the Sm-C. When subjects were refed 18 and 25 kcal/kg, it became apparent that the more energy added to the diet, the greater the absolute concentration of Sm-C attained (0.66 U/ml on 18 kcal/kg and 0.97 U/ml on 25 kcal/kg). Sm-C correlated with nitrogen balance (r = 0.58) during refeeding with the variable energy diets and was a good indicator of acute directional change in nitrogen balance. However, Sm-C was not a reliable indicator of nitrogen repletion, since it rose almost to control levels on the 25 kcal/kg diet while nitrogen balance remained slightly negative.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000328:Adult; D004044:Dietary Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D002149:Energy Intake; D004734:Energy Metabolism; D005215:Fasting; D005260:Female; D005502:Food; D006801:Humans; D007334:Insulin-Like Growth Factor I; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D013002:Somatomedins / Q000097:blood*
chemical_list: D004044:Dietary Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D009584:Nitrogen