In conclusion, results of the present study indicate that low-to-moderate caffeine intake may exert some beneficial effects on the skeletal system of mature organisms.

Scope Trigonelline (1‐methylpyridinium‐3‐carboxylate), an alkaloid present in coffee and fenugreek seed, has been reported to exhibit phytoestrogenic activity. The aim of the present study was to investigate the effects of trigonelline on bone mechanical properties of rats with normal estrogen level and estrogen deficiency (developing osteoporosis). Methods and results The experiments were performed on 3‐month‐old nonovariectomized and ovariectomized (estrogen‐deficient) Wistar rats, divided into control rats and rats receiving trigonelline (50 mg/kg p.o. daily) for 4 weeks. The ovariectomy was performed 7–8 days before the start of trigonelline administration. Serum bone turnover markers and bone mineralization, as well as mechanical properties of the tibial metaphysis, femoral diaphysis, and femoral neck were examined. Estrogen deficiency caused worsening of bone mineralization and mechanical properties of the tibial metaphysis, as well as increases in bone turnover markers. Administration of trigonelline did not affect the investigated parameters in nonovariectomized rats, but it worsened the mineralization and mechanical properties of cancellous bone in ovariectomized rats. Conclusion Unfavorable effects of trigonelline on the skeletal system depended on the estrogen status. They were observed only in cancellous bone of estrogen‐deficient rats.

Diosgenin is a steroidal sapogenin present in fenugreek and Dioscorea spp. as glycosides (saponins). Diosgenin has already been reported to inhibit osteoclastogenesis and to stimulate osteogenic activity of osteoblastic cells in vitro, and to exert some antiosteoporotic effects in rats in vivo. The aim of the present study was to investigate the effects of diosgenin administration on the skeletal system of rats with normal estrogen level and with estrogen deficiency induced by bilateral ovariectomy. The experiments were carried out on 3-month-old non-ovariectomized and ovariectomized Wistar rats, divided into control rats and rats receiving diosgenin (50 mg/kg p.o. daily) for 4 weeks. Serum bone turnover markers, bone mass and mineralization, histomorphometric parameters and mechanical properties were studied. Diosgenin improved some investigated parameters in both non-ovariectomized and ovariectomized rats, in which estrogen deficiency induced osteoporotic changes. Diosgenin increased compact bone formation and probably inhibited cancellous bone resorption, which led to improvement of mechanical properties of compact and cancellous bone. In conclusion, this in vivo study demonstrated that diosgenin may be one of sparse compounds increasing bone formation.

Genistein, a major phytoestrogen of soy, is considered a potential drug for prevention and treatment of postmenopausal osteoporosis. The aim of the present study was to compare the effects of genistein, estradiol and raloxifene on the skeletal system in vivo and in vitro. Genistein (5 mg/kg), estradiol (0.1 mg/kg) or raloxifene hydrochloride (5 mg/kg) were administered daily by a stomach tube to mature ovariectomized Wistar rats for 4 weeks. Bone mass, mineral and calcium content, macrometric parameters and mechanical properties were examined. Also the effects of genistein, estradiol and raloxifene (10(-9)-10(-7) M) on the formation of osteoclasts from neonatal mouse bone marrow cells and the activity of osteoblasts isolated from neonatal mouse calvariae were compared. In vivo, estrogen deficiency resulted in the impairment of bone mineralization and bone mechanical properties. Raloxifene but not estradiol or genistein improved bone mineralization. Estradiol fully normalized the bone mechanical properties, whereas genistein augmented the deleterious effect of estrogen-deficiency on bone strength. In vitro, genistein, estradiol and raloxifene inhibited osteoclast formation from mouse bone marrow cells, decreasing the ratio of RANKL mRNA to osteoprotegerin mRNA expression in osteoblasts. Genistein, but not estradiol or raloxifene, decreased the ratio of alkaline phosphatase mRNA to ectonucleotide pyrophosphatase phosphodiesterase 1 mRNA expression in osteoblasts. This difference may explain the lack of genistein effect on bone mineralization observed in ovariectomized rats in the in vivo study. Concluding, our experiments demonstrated profound differences between the activities of genistein, estradiol and raloxifene towards the osseous tissue in experimental conditions.

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