THE EFFECT OF A PROTEIN MEAL WITH AND WITHOUT SUBSEQUENT EXERCISE ON PLASMA INSULIN AND GROWTH HORMONE

¹ Department of Physiology, University of Edinburgh and the Medical Research Council Clinical Endocrinology Research Unit, Edinburgh

Plasma levels of insulin and growth hormone have been measured over a 6-hr. period in ten normal subjects, (a) fasting and resting, (b) after a protein meal and resting, and (c) after a protein meal followed by 2 hr. moderate exercise. Low levels of insulin and growth hormone were found during fasting and the insulin levels fell further throughout the fast. After ingestion of protein, plasma insulin and growth hormone concentrations increased; the rise in insulin secretion preceded the rise in growth hormone. Moderate muscular exercise in the absorptive phase of the meal abolished or markedly diminished the insulin response to protein and enhanced the growth hormone response. It is concluded that dietary protein may have a role in the physiological regulation of insulin and growth hormone release. The metabolic implications of these findings are discussed in terms of the requirements of energy metabolism.

Note:

We are grateful to Dr. J. O'Brien and Professor R. B. Fisher of the Department of Biochemistry, University of Edinburgh, for help with the blood glucose estimations and to Miss M. Black and Dr. J. D. Baird of the Department of Medicine, University of Edinburgh for carrying out the FFA determinations. We are also grateful to the subjects for their cooperation and help.