Restorative effects of epicatechin on ovariectomy induced loss of skeletal muscle structure-function: Underlying mechanisms.

Early menopause occurs in women under age 45 and is seen in ~5% of women. Women who experience estrogen deficiency at an early age (before menopause) are known to be at increased overall risk for premature morbidity and mortality. Also, higher rates of physical limitation are known to occur in surgically menopausal vs. naturally menopausal women. To the extent that muscle mass and strength decreases, it can foster lesser levels of overall physical activity which, can promote a further deterioration of the musculoskeletal system including bone density. We previously documented the capacity of the cacao flavanol (-)-epicatechin (Epi) to restore skeletal muscle (SkM) mass and strength in various models of disease. Our research group implemented a female Wistar rat model whereby ovariectomy (OVX) was used to assess its impact on SkM structure/function as well as on modulators of muscle mass (atrophy). Using this model, we tested the hypothesis that Epi can restore SkM structure and function and recognized modulators of muscle mass. For these experiments, female rats at the age of 6 months (n=9-10/subgroups) were subjected to OVX and allowed to evolve for a period of 12 weeks. A subgroup was treated with Epi at the dose of 1 mg/kg/day (by gavage in water) 8 weeks after OVX. Intact animals subjected to a sham OVX and vehicle (water) were used as controls. Front limb strength (in Newtons =N) was assessed weekly resulting in a significant progressive drop in force with OVX that was fully restored with 4 weeks of Epi treatment (figure 1 top graphs). Overall exercise capacity was assessed by treadmill (bottom panels) demonstrating a decrease with OVX and an improvement in total treadmill time (in minutes) with Epi that was greater vs. controls. At the time of sacrifice, muscle weight of gastrocnemius was recorded and values normalized to tibial length demonstrating the development of significant atrophy with OVX and the restoring effects of Epi treatment. An assessment of factors recognized to induce a loss of muscle mass was pursued. Myostatin levels were measured in blood by ELISA while the relative protein levels for the recognized inducers of muscle atrophy Murf-1 and atrogin-1 by Western blots of gastrocnemius lysates. Relative changes were normalized for loading differences using GAPDH. Blood levels of the muscle atrophy inducer factor myostatin were significantly increased with OVX and were fully normalized by Epi. OVX led to the significant upregulation of Murf-1 and atrogin-1 and the normalization of such effects with Epi. OXV led to significant increases in pro-inflammatory cytokines TNF-α, IL-1β, IL-2 and IFN-γ andf plasma oxidative stress leveles (protein carbonylation) that were completely normalized with Epi. Altogether, results demonstrate that OVX can significantly compromise SkM structure and function which can be fully reversed by the use of Epi. These effects are likely the results of the effects on recognized modulators of inflammation, oxidative stress and atrophy. Clinical trials are warranted as per the recognized safety profile of Epi in humans.