Direct Inhibition of Osteoclast Formation and Activity by the Vitamin E Isomer gamma-Tocotrienol

Vitamin E homologues, specifically tocotrienols, have been shown to have favorable effects on bone. They possess properties that are indicative of anti-resorptive activity, suggesting the potential for vitamin E in preventing bone loss. To investigate the anti-resorptive activity of the various vitamin E homologues, we cultured human osteoclasts from blood-derived CD14+ cells on collagen, dentin, and calcium phosphate substrates, with some samples supplemented with vitamin E homologues in their cell culture medium. These were compared to the clinically used bisphosphonate, pamidronate. Compounds were either added at the start of culture to study effects on osteoclast formation, or at the start of osteoclastic resorption to determine their effects on activity. The alpha- and gamma-tocotrienol isomers inhibited osteoclast formation without consequent reduction in total cell number. Only gamma-tocotrienol inhibited osteoclast activity without toxicity. Gamma-tocotrienol was the most potent inhibitor of both osteoclast formation and activity and requires further investigation into its anti-resorptive effects on bone.