Nat Med：过量摄取维生素E或导致骨质疏松

Vitamin E decreases bone mass by stimulating osteoclast fusion

Koji Fujita, Makiko Iwasaki, Hiroki Ochi, Toru Fukuda, Chengshan Ma,, Takeshi Miyamoto, Kimitaka Takitani, Takako Negishi-Koga, Satoko Sunamura, Tatsuhiko Kodama, Hiroshi Takayanagi, Hiroshi Tamai, Shigeaki Kato, Hiroyuki Arai, Kenichi Shinomiya, Hirohi Itoh, Atsushi Okawa & Shu Takeda

Bone homeostasis is maintained by the balance between osteoblastic bone formation and osteoclastic bone resorption. Osteoclasts are multinucleated cells that are formed by mononuclear preosteoclast fusion. Fat-soluble vitamins such as vitamin D are pivotal in maintaining skeletal integrity. However, the role of vitamin E in bone remodeling is unknown. Here, we show that mice deficient in α-tocopherol transfer protein (Ttpa−/− mice), a mouse model of genetic vitamin E deficiency, have high bone mass as a result of a decrease in bone resorption. Cell-based assays indicated that α-tocopherol stimulated osteoclast fusion, independent of its antioxidant capacity, by inducing the expression of dendritic-cell–specific transmembrane protein, an essential molecule for osteoclast fusion, through activation of mitogen-activated protein kinase 14 (p38) and microphthalmia-associated transcription factor, as well as its direct recruitment to the Tm7sf4 (a gene encoding DC-STAMP) promoter. Indeed, the bone abnormality seen in Ttpa−/− mice was rescued by a Tm7sf4 transgene. Moreover, wild-type mice or rats fed an α-tocopherol–supplemented diet, which contains a comparable amount of α-tocopherol to supplements consumed by many people, lost bone mass. These results show that serum vitamin E is a determinant of bone mass through its regulation of osteoclast fusion.