Skeletal muscle OGT and OGA expression: associations with hormone replacement therapy, physical activity and muscle area in postmenopausal women

Abstract

In skeletal muscle, prolonged increase in O‐GlcNAc transferase (OGT) mediated protein O‐linked N‐acetylglucosaminylation (O‐GlcNAcylation) is associated with age and muscle atrophy. The current study investigated the effects of estrogen based hormone replacement therapy (HRT) and power training (PT) on OGT and O‐GlcNAcase (OGA; enzyme releasing O‐GlcNAc moiety from proteins) gene expression in postmenopausal women and the association of OGT and OGA gene expression with muscle crosssectional area (CSA). Twenty seven 50–57‐year‐old women from a yearlong randomized placebo‐controlled trial formed the three study groups (HRT, n=10; PT, n=8; control, CO, n=9). Following the one year, the ratio of OGT to OGA, reflecting O‐GlcNAcylation capacity, increased 20.0% in the CO group, while in the PT (15.2%) and HRT (−3.9%) group the change was not significant (HRT vs. CO: p=0.004 and PT vs. CO: p=0.54). OGT/OGA correlated negatively with muscle CSA (r= −0.61, p=0.001). Our results suggest that an increase in O‐GlcNAcylation capacity is associated with a decrease in muscle CSA, and that HRT and possibly PT influence muscle OGT and OGA expression, which may be one mechanism by which HRT and PT prevent age‐related loss of muscle mass. Supported by the Academy of Finland, Finnish Ministry of Education and Culture and Finnish Cultural Foundation.