(EA02-11-25) Effects of Insulin Infusion on Forearm Amino Acids Kinetics in Lean Humans and Humans With Obesity

Scientific conference where the work was recently presented: ObesityWeek 2024 (The Obesity Society)

Date on which the work was previously presented at the scientific conference listed: November 2, 2024

Objectives: Insulin infusion increases the uptake of plasma amino acids in the muscle of healthy humans, but this effect is observed after non-physiological infusion of insulin for several hours. We determined the kinetics of amino acids across muscle after short-term (i.e., 30 mins) insulin infusion.

Methods: Seventeen subjects (ages 19 to 45 years) were studied: 1) lean subjects (n = 10) with a body mass index (BMI) < 25 and Matsuda Insulin Sensitivity Index (MI) > 7 and 2) subjects (n = 7) with obesity/BMI > 30kg/m² and a MI < 4. Insulin was infused at 1.0 mU/kg/min in the lean, insulin sensitive subjects, and 0.5 mU/kg/min in the subjects with obesity and insulin resistance, resulting in comparable levels of plasma insulin concentrations across subjects. Arterial and venous blood samples were collected simultaneously from a radial artery and a vein draining the forearm muscle before and 30 mins after the insulin infusion to determine arterio-venous (A-V) differences in the concentrations of plasma amino acids. Plasma amino acid concentrations were measured using High Performance Liquid Chromatography.

Results: There was no significant A-V concentration difference (P > 0.05) for the sum of essential amino acids (uM) between insulin infusion and baseline in neither the lean subjects (-50 ± 17 vs -53 ± 15) nor the subjects with obesity (-51 ± 10 vs -45 ± 14). Insulin infusion modified the muscle kinetics of only non-essential amino acids as observed by a decrease in the muscle A-V concentration difference for plasma glutamate (P = 0.005) and increase for plasma alanine and glutamine (P = 0.001 and P = 0.01, respectively), and in the lean subjects only.

Conclusions: Because the A-V concentration differences of essential amino acids across muscle were not affected by the insulin infusion, we conclude that short-term increase in plasma insulin, as typically observed during the postprandial period, is not of physiological significance in inducing muscle anabolism in humans.

Funding Sources: This research was supported by the National Institutes of Health/ National Institute of Diabetes and Digestive and Kidney Diseases.