Effects of L-Citrulline on microvascular function, skeletal muscle oxygen, and lipolysis in healthy and prediabetic older adults: an exploratory study

Abstract

Background: Prediabetes may increase the risk of endothelial dysfunction and reduce skeletal muscle oxygenation. Increased lipolysis during exercise may reduce fat mass and improve insulin sensitivity. L-citrulline improves endothelial function, although there are no data on lipolysis during exercise in humans. The purpose of this study was to measure the effects of a 2-week L-citrulline supplementation on microvascular function, skeletal muscle oxygenation and exercise lipolysis. Methods: 16 healthy and prediabetic older adults (age=68.8±9.8 yrs) participated in this study. Each intervention involved a two-week supply of L-citrulline or placebo in a double blind, crossover design. Each participant completed an occlusion and submaximal handgrip protocol, and a perceptually regulated exercise test (PRET) before and after each intervention. Results: There were no significant responses in microvascular function, skeletal muscle oxygenation, or lipolysis rates during submaximal exercise to L-citrulline between normal and prediabetic adults. Conclusion: As an exploratory study, there were few significant effects of L-citrulline on efficiency of skeletal muscle oxygenation or rates of fat oxidation during exercise in this population. However, the variables were trending in the direction of our hypotheses. A larger sample size may be needed.