Vitamin K₂ improves femoral bone strength without altering bone mineral density in gastrectomized rats

Gastrectomy (GX) induces osteopenia in rats. The present study examined the skeletal effects of vitamin K₂ in GX rats. Thirty male Sprague-Dawley rats (12 wk old) were randomized by the stratifed weight method into the following three groups of 10 animals each: sham operation (control) group; GX group; and GX1oral vitamin K₂ (menatetre-none, 30 mg/kg, 5 d/wk) group. Treatment was initiated at 1 wk after surgery. After 6 wk of treatment, the bone mineral content (BMC), bone mineral density (BMD), and mechanical strength of the femoral diaphysis and distal metaphysis were determined by peripheral quantitative computed tomography and mechanical strength tests, respectively. GX induced decreases in the BMC, BMD, and ultimate force of the femoral diaphysis and distal metaphy-sis. Vitamin K₂ did not signifcantly infuence the BMC or BMD of the femoral diaphysis or distal metaphysis in GX rats, but attenuated the decrease in the ultimate force and increased the stiffness of the femoral diaphysis. The present study showed that administration of vitamin K₂ to GX rats improved the bone strength of the femoral diaphysis without altering the BMC or BMD, suggesting effects of vitamin K₂ on the cortical bone quality.