Protective effects of Enterococcus faecium strain R30 on transformation of slow to fast fiber under inactive condition

Abstract

Inactivity results in the transformation of slow to fast fiber and mitochondria dysfunction in skeletal muscle. PGC‐1α, a transcriptional factor, can prevent transformation of slow to fast fiber and the reduced oxidative enzyme activity in skeletal muscle. We have confirmed that Enterococcus faecium strain R30 (R30) activated muscle sympathetic nerve and increased blood flow in muscle capillary in our previous study. Several studies report that the increased blood flow induces nitric oxide synthase (eNOS) expression via shear stress, and eNOS expression regulates PGC‐1α protein expression. Also, the activated sympathetic nerve activity increased PGC‐1α protein expression via activation of adrenergic receptor. Therefore, we examined the hypothesis that R30 might prevent the transformation of slow to fast fiber and the reduced oxidative enzyme activity via PGC‐1α protein expression in skeletal muscle under inactive condition. Fifteen male Sprague‐Dawley rats aged 11 weeks old were divided into three groups, that is, 1) control (CON; n = 5), 2) 2 weeks hindlimb unloading (HU; n = 5), and 3) HU+R30 (HU+R30; n = 5). In the experimental periods, we administered orally to R30 (500 mg/kg/day) in the HU+R30 group, and the same amount of physiological saline in the CON and HU groups. After 2 weeks hindlimb unloading, type I fiber composition ratio, citrate synthase (CS) activity, eNOS and PGC‐1α protein expression level were measured. Type I fiber composition ratio and CS activity were significantly higher in the HU+R30 than in the HU group. The expression levels of eNOS and PGC‐1α protein in the HU+R30 group were significantly higher than in the HU group. These results indicate that R30 supplementation could increase the levels of eNOS and PGC‐1α expression in soleus muscle, and prevent the transformation of slow to fast fiber and the reduced oxidative enzyme activity under inactive condition.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.