Unfavorable effect of trigonelline, an alkaloid present in coffee and fenugreek, on bone mechanical properties in estrogen-deficient rats

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.