Glucagon-Like Peptide-1 Receptor Agonism and Muscle Health: Vascular and Myocellular Effects on Glucose and Protein...

Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1 RAs) improve glycaemia and reduce body weight, yet their organ-level actions on skeletal muscle remain incompletely defined. Framing skeletal muscle as an integrated unit of vasculature and muscle cells, we synthesize evidence with emphasis on glucose and protein metabolism. GLP-1 and GLP-1 RAs recruit microvasculature in muscle, expanding capillary surface area and increasing delivery of insulin, glucose, and amino acids. Microvascular recruitment increases interstitial insulin availability and potentiates insulin-stimulated glucose uptake and glycogen synthesis, whereas direct effects of GLP-1 on muscle cells remain under investigation. For protein metabolism, microvascular recruitment can enhance muscle protein synthesis when plasma amino acid availability is elevated, whereas effects under basal (fasted) conditions remain unclear. Elucidating the uncertainty regarding GLP-1 receptor localization in human muscle cells will clarify whether direct signaling occurs within muscle cells, thereby improving our understanding of the relative contribution of direct versus perfusion-mediated actions of GLP-1 RAs. Clinically, GLP-1 RAs reduce lean body mass, likely reflecting energy-deficit-mediated effects, but studies directly assessing muscle mass are still limited. Overall, current evidence indicates that GLP-1 RAs exert beneficial effects on muscle vasculature and muscle glucose metabolism. However, their influence on muscle protein turnover remains unclear-primarily due to observed reductions in muscle mass-despite preclinical data suggesting potential favorable effects on muscle protein metabolism that remain to be confirmed in humans.