Effect of an isoflavones-containing red clover preparation and alkaline supplementation on bone metabolism in ovariectomized rats

The aim of this study was to test the combined effect of a quality-controlled red clover extract (RCE) standardized to contain 40% isoflavones by weight (genistein, daidzein, biochanin A, and formononetin present as hydrolyzed aglycones) together with a modified alkaline supplementation on bone metabolic and biomechanical parameters in an experimental model of surgically-induced menopause. Sprague–Dawley female rats were maintained under controlled standard conditions of light and fed with conventional food of standard calcium content and no alfalfa or soybean components. Rats were randomized into four groups: Group A represented normal rats (sham operated) while three other groups were ovariectomized (OVX) and fed for three months as follows: standard food (group B), 6 mg/kg/day food mixed with RCE (Group C), or given 6 mg/kg/day of RCE plus a modified alkaline supplementation (BP) through a nasogastric tube at a dose of 16 mg (group D). The animals were killed 90 days after surgery. As compared to group B, RCE or RCE + BP treatments brought about significantly higher level of estradiol and mitigated the weight loss of the uterus and improved maximum load of the femoral neck. Osteocalcin level showed an over 65% increase in group B but both RCE and RCE + BP treatments prevented such abnormality with a significantly better result in RCE + BP group which virtually normalized such parameter as well as urinary excretion of DPD. Group C and D reduced the over 20% loss of bone mineral density and bone mineral content/body weight ratio observed in untreated post-ovariectomy group. Untreated ovariectomy caused about 48% decrease of cancellous bone mass in the femoral neck while this abnormality was prevented at similar extent by both RCE and RCE + BP treatments. Ovariectomy determined an over 80% increase of bone alkaline phosphatase (BALP) level but both RCE and RCE + BP treatments significantly mitigated such variable. The BALP decrease yielded by the combined RCE + BP treatment was statistically lower than RCE alone. Taken together these data show that red clover preparation in dosages amenable to clinical practice do improve OVX-induced osteoporosis while a mild metabolic alkalosis might further synergize some therapeutic aspects.