The soy isoflavone genistein inhibits the reduction in Achilles tendon collagen content induced by ovariectomy in rats

The objective of this study was to evaluate effects of genistein and moderate intensity exercise on Achilles tendon collagen and cross-linking in intact and ovariectomized (OVX) female Sprague-Dawley rats. Rats were separated into eight groups (n=9 per group): intact or OVX, treadmill exercised or sedentary, genistein-treated (300 mg•kg−1•day−1) or vehicle. After 6-weeks, tendons were assayed for the collagen-specific amino acid hydroxyproline and hydroxylyslpyridinoline (HP). Collagen content was not influenced by exercise (p=0.40) but was lower (p<0.001) in OVX vehicle rats compared to intact vehicle rats (OVX: 894±35 µg collagen/mg dry weight, intact: 1185±72 µg collagen/mg dry weight). In contrast, collagen content in OVX rats treated with genistein was greater (p=0.010, 1198±121 µg collagen/mg dry weight) when compared to untreated rats and not different from intact rats (p=0.89). HP content was lower in OVX genistein-treated when compared to intact genistein-treated rats, but only within the sedentary animals (p=0.05, intact-treated: 232±39mmol/mol collagen, OVX-treated: 144±21mmol/mol collagen). Our findings suggest that ovariectomy leads to a reduction in tendon collagen, which is prevented by genistein. HP content, however, may not have increased in proportion to the addition of collagen. Genistein may be useful for improving tendon collagen content in conditions of estrogen deficiency.