Effects of Dietary Chitosan and Genistein on Calcium and Bone Metabolism in Ovariectomized Rats

研究了壳聚糖（一种阳离子膳食纤维）和染料木素（一种大豆植物雌激素）对去势大鼠骨状态和钙代谢的影响.壳聚糖对骨密度（BMD）的降低作用及其降低BMD的机制;与纤维素相比，壳聚糖导致低钙饮食40天的OVX大鼠股骨和椎骨BMD和刚度显著降低。壳聚糖和纤维素对小肠钙吸收无显著影响，而壳聚糖显著降低小肠磷吸收。壳聚糖组大鼠骨丢失的同时，尿钙排泄量显著增加，血清钙水平显著降低，血清妊高征和25（CH）_2D_3显著升高。壳聚糖还显著增加了十二指肠的维生素D受体和钙结合蛋白D9 K mRNA。结果提示，壳聚糖可能通过抑制磷的吸收，增加尿钙排泄，降低血清无机磷水平，导致妊高征和1，25（CH）_2D_3升高，从而引起骨密度降低。Genistein剂量和阻力行走对绝经后骨丢失的抑制作用：Genistein剂量为5 mg/天，持续4周，可显著降低绝经后股骨BMD的下降，但对椎骨无影响。为了补充染料木黄酮对椎体丢失的预防作用，评价了不同适度运动的效果。抗阻运动包括步行1分钟，休息1分钟，背部负重100 g，连续减少绝经后椎骨BMD下降，但在普通步行的情况下没有。金雀异黄素联合抗阻步行治疗对预防绝经后骨丢失具有独立作用。

Effects of both chitosan, a cationic dietary fiber, and genistein, a soybean phytoestrogen were investigated on bone status and Ca metabolism in ovariectomized (OVX) rats as a model of postmenopausal women.1. Lowering effects of chitosan on the bone mineral density (BMD) and the mechanism by which it decreases BMD; Chitosan caused a significant reduction in BMD and stiffness in femurs and vertebrae of OVX rats fed a low Ca diet for 40 days, as compared to cellulose. There was no remarkable difference in intestinal Ca absorption between chitosan and cellulose, whereas chitosan significantly decreased P absorption. The bone loss in rats fed chitosan was accompanied with a marked increase in urinary Ca excretion and a decrease in serum Ca level, and with a significant increment in serum PIH and 25(CH)_2D_3. Chitosan also significantly increased vitamin D receptor and Ca binding protein D9K mRNAs of the duodenum. These results indicate that dietary chitosan possibly induces the decrease in BMD by enhancing urinary Ca excretion through depressed P absorption, which causes the lowering of serum inorganic P level resulting in the increase in circulating PIH and 1, 25(CH)_2D_3.2. Suppressive effects of genistein dosage and resistance walking on postmenopausal bone loss; Genistein dosage at 5mg/day for 4 weeks to OVX rats significantly lowered the postmenopausal decrease in BMD of femurs, but not of vertebrae. For complementing the preventive function of genistein to vertebrae loss, the effects of different moderate exercises were evaluated. Resistance exercise constituted of 1-min walking interspersed with 1-min rest with 100g weight on the back successively reduced the postmenopausal BMD decrease in vertebrae, but not in the case of ordinary walking. The combined treatment of genistein and resistance walking acted independently to the prevention of postmenopausal bone loss.