Dietary components that regulate serum somatomedin-C concentrations in humans.

TLDR

The study examined how different diets affect somatomedin‑C by fasting five normal‑weight adults for five days and then refilling them with three distinct diets. Fasting lowered serum somatomedin‑C from 1.85 to 0.67 U/ml, and refeeding raised it to 1.26 U/ml with a normal diet, 0.90 U/ml with a protein‑deficient diet, and 0.31 U/ml with a diet low in both protein and energy; these changes correlated strongly with nitrogen balance, indicating that protein and energy intake regulate somatomedin‑C and that energy may have a greater influence.

Abstract

Dietary components responsible for the regulation of somatomedin-C in humans were assessed in five adult volunteers of normal weight who were fasted for 5 d on three occasions, then refed three diets of differing composition. The serum somatomedin-C decreased from a mean prefasting value of 1.85 +/- 0.39 U/ml (+/- 1 SD) to 0.67 +/- 0.16 U/ml at the end of fasting (P less than 0.005). After refeeding for 5 d with a normal diet, the mean serum somatomedin-C increased to 1.26 +/- 0.20 U/ml. A protein-deficient (32% of control), isocaloric diet resulted in a significantly smaller increase, to a mean value of 0.90 +/- 0.24 U/ml (P less than 0.05). A diet deficient in both protein and energy led to a further fall 0.31 +/- 0.06 U/ml. The changes in somatomedin-C during fasting and refeeding correlated significantly with mean daily nitrogen balance (r = 0.90). We conclude that both protein and energy intake are regulators of serum somatomedin-C concentrations in adult humans, and energy intake may be of greater importance. The correlation between changes in somatomedin-C and nitrogen balance suggests that the former are directly related to changes in protein synthesis and may be helpful in assessing the response to nutritional therapy.