Ingestion of leucine + glycine with glucose produces a partially additive effect on plasma glucose despite a less than additive effect on serum insulin (LB427)

Abstract

Leucine (Leu) is well recognized to stimulate insulin secretion and to reduce the glucose rise when ingested with glucose. Glycine (Gly) reduces the glucose rise, but only weakly stimulates insulin secretion. We have shown that both were particularly potent in their ability to attenuate the glucose response to 25 g glucose. The current study was designed to determine whether the glucose‐attenuating effects would be even greater if Gly and Leu were ingested together with glucose. On 4 separate days, 9 healthy subjects were studied. Test meals were given at 0800 hr. Subjects received water only on day 1, followed by 25 g glucose only, Leu + Gly (1 mmol/kg fat free body mass each), or Leu + Gly with 25 g glucose, on subsequent days in random order. Serum/plasma glucose, insulin and glucagon were measured frequently thereafter for 2.5 hrs. Net areas under the curve were calculated. The glucose area response decreased by 77% (p<0.02) after ingestion of Leu + Gly + glucose compared to ingestion of glucose alone. The insulin area response increased by only 24% (p<0.05). When compared to our previously published data on the individual amino acids, the decrease in glucose response with Leu + Gly + glucose was partially additive. The increase in insulin response was less than additive. The glucagon response was considerably less than additive. Thus, there is a mechanistic interaction between Leu and Gly when ingested with glucose that results in a markedly attenuated glucose response. This occurred in the presence of an attenuated insulin response. Changes in glucagon response could not explain the results. Overall, the way in which ingested amino acids interact with each other and affect glucose metabolism is complex and not well understood. Grant Funding Source: Supported in part by Funds from the Department of Veterans Affairs