Epicatechin Gallate Regulation of Steroid Hormone Levels Improves Sarcopenia in C57BL/6J Mice

The decline in differentiation capacity during skeletal muscle (SkM) aging contributes to the deterioration of skeletal muscle function and impairs regenerative ability. Epicatechin gallate (ECG), a major functional component of catechins found in tea, has an unclear role in aging-related sarcopenia. In vivo experiments in 54-week-old C57BL/6J mice showed that ECG treatment improved exercise performance, muscle mass, and fiber morphology and downregulated the expression of the testosterone metabolic enzyme gene <i>UGT2A3</i> in aged mice. In vitro experiments with Leydig cells (TM3) demonstrated that ECG upregulated the mRNA and protein expression levels of testosterone synthase genes, including <i>StAR</i>, <i>P450scc</i>, <i>3β-HSD</i>, <i>CYP17a1</i>, and <i>17β-HSD</i>. Network pharmacology analysis further suggested that ECG can influence testosterone secretion through the regulation of cytokines, thereby promoting skeletal muscle differentiation. These findings indicate that ECG enhances the differentiation of skeletal muscle cells by modulating testosterone levels, which helps alleviate age-related muscle function decline.