Diphlorethohydroxycarmalol isolated from Ishige okamurae improves age-related muscle dysfunction by Ca2+-dependent response via the SirT1/PGC-1α pathway in vitro and in vivo

Abstract

Diphlorethohydroxycarmalol (DPHC), a brown alga tannin isolated from Ishige okamurae, has been reported to stimulate skeletal muscle contraction by promoting the release of calcium ions (Ca²⁺) from the sarcoplasmic reticulum. Although aging is a major cause of skeletal muscle dysfunction, the effect of DPHC on age-related muscle dysfunction remains unclear. This study aims to investigate how DPHC can mitigate skeletal muscle dysfunction induced by D-galactose (D-gal)-mediated aging, utilizing both in vitro and in vivo models, and to elucidate its potential pathways. A skeletal muscle aging model was established by exposing adult zebrafish to D-gal at a concentration of 1% for 6 weeks. This model significantly reduced the zebrafish behavior and muscle mass. In vitro, DPHC treatment significantly increased cell viability in D-gal (200 mM)-induced C2C12 myoblasts, while significantly reducing the activity of the senescence marker senescence-associated β-galactosidase (SA-β-gal). In addition, DPHC also elevated intracellular Ca²⁺ levels, inhibited ROS accumulation, and restored ATP production in D-gal-stimulated C2C12 myoblasts. In vivo, DPHC administration improved the swimming ability and skeletal muscle integrity of zebrafish. It also reduced glycogen accumulation and increased ATP levels in muscle tissue. Mechanistically, DPHC activated calcium/calmodulin-dependent protein kinase kinase 2 (CaMKKβ) in skeletal muscle and promoted AMP-activated protein kinase (AMPK) phosphorylation, thereby upregulating the expression of SirT1 and PGC-1α proteins. Overall, these findings suggest that DPHC attenuates D-gal-induced skeletal muscle dysfunction by enhancing intracellular Ca²⁺ levels to activate the CaMKKβ-AMPK pathway to trigger the SirT1/PGC-1α axis, highlighting its potential as a therapeutic agent against age-related muscle dysfunction.