Glucagon and insulin responses after ingestion of different amounts of intact and hydrolysed proteins

Ingestion of dietary protein is known to induce both insulin and glucagon secretion. These responses may be affected by the dose and the form (intact or hydrolysed) in which protein is ingested. The aim of the study was to investigate the effect of different amounts of intact protein and protein hydrolysate of a vegetable (soya) and animal (whey) protein on insulin and glucagon responses and to study the effect of increasing protein loads for both intact protein and protein hydrolysate in man. The study employed a repeated-measures design with Latin-square randomisation and single-blind trials. Twelve healthy non-obese males ingested three doses (0-3, 0-4 and 0-6 g/kg body weight) of intact soya protein (SPI) and soya protein hydrolysate (SPH). Another group of twelve healthy male subjects ingested three doses (0-3, 0.4 and 0.6 g/kg body weight) of intact whey protein (WPI) and whey protein hydrolysate (WPH). Blood was sampled before (t = 0) and 15, 30, 60, 90 and 120 min after protein ingestion for insulin, glucagon and glucose determination. SPI induced a higher total area under the curve for insulin and glucagon than SPH while no difference between WPI and WPH was found. Insulin and glucagon responses increased with increasing protein load for SPI, SPH, WPI and WPH., but the effect was more pronounced for glucagon. A higher dose of protein or its hydrolysate will result in a lower insulin:glucagon ratio, an important parameter for the control of postprandial substrate metabolism. In conclusion, insulin and glucagon responses were protein and hydrolysate specific.