Effects Of Estrogen Deficiency And Isoflavone On Skeletal Muscle Adaptation In Response To Physical Activity

Abstract

The decrease of skeletal muscle performance is a major health risk in postmenopausal women. Loss of skeletal muscle mass is associated with a loss of strength but also with the development of metabolic syndrome. Isoflavone (ISO) supplementation and physical activity have shown some beneficial effects on muscle maintenance. PURPOSE: To determine functional and metabolic adaptations of the skeletal muscle to a specific high-intensity exercise in ovary intact and ovariectomized (OVX) animals as well as its combination with an ISO-enriched diet. METHODS: Female Wistar rats were assigned to five groups: (1) sham-operated (SHAM); (2) SHAM with exercise (SHAM+EX); (3) OVX; (4) OVX+EX; (5) OVX with EX and an ISO-enriched diet (OVX+EX+ISO). A high intensity exercise protocol was designed for the exercise groups. Rats were trained 10 min/time, twice/day, a rest day every four days on a treadmill with an incline of 25°for 61 days and a gradually increasing velocity from 12 to 20 m/min. Lipid (cholesterol and LDL) and leptin levels in serum were measured. Gene expression in soleus muscle was investigated by Real-time PCR. RESULTS: Body weight, visceral fat mass and serum leptin level were about 54%, 20% and 87% increased by OVX compared with SHAM (p<0.05). Exercise significantly decreased all three parameters both in SHAM (37%, 28% and 40%) and in OVX (42%, 31% and 55%) groups (p<0.05). ISO supplementation showed no additive effects. The values of cholesterol and LDL in OVX were about 59% and 64% higher than those of the SHAM rats. Exercise or ISO resulted in no additional effect. Exercise increased PPARγ and MyoD mRNA expressions both in SHAM and OVX groups in soleus muscle. In OVX rats, the gene expression of IGF-1 was also up-regulated by exercise. Additionally, the highest expressions of MyoD and IGF-1 in OVX rats were observed in OVX+EX+ISO group (p<0.05). CONCLUSION: Estrogen deficiency resulted in effects like increasing body weight, visceral fat mass, leptin, cholesterol and LDL. The designed exercise antagonized all increasing effects except for the lipid levels. In soleus muscle, the exercise enhanced gene expressions of PPARγ as a marker for regulation of insulin sensitivity. MyoD and IGF-1 gene expressions, as markers for myogenesis, were increased by exercise and its combination with ISO in OVX rats. Supported by DFG Di 716/12-1