2017 年 66 巻 2 号 p. 171-179
Thermogenic adipocytes that are distinct from classical brown adipocytes (beige adipocytes) were identified in 2012. Beige adipocytes are also called inducible brown adipocytes because their differentiation is induced by a number of physiological stimuli, including adrenaline or myokines. PPARγ is the master regulator of adipogenesis and promotes thermogenic adipocyte differentiation. A PPARγ agonist also promotes thermogenic adipocyte differentiation in mouse white adipose tissues. The vitamin E analog α-tocopherol promotes PPARγ expression and induces mRNA expression of target genes. This study investigated the effects of vitamin E analogs on thermogenic adipocyte differentiation in mouse preadipocytes and rat white adipose tissues. We determined the effects of vitamin E analogs (α-tocopherol and γ-tocopherol) on PPARγ, PGC-1α, and uncoupling protein 1 (UCP1) gene expression in 3T3-L1 cells. UCP1 expression and the mitochondrial contents were confirmed in the cells using immunofluorescence. In an in vivo study, male SD-IGS rats were fed a high-fat diet (HFD), α-tocopherol-enriched HFD, or γ-tocopherol-enriched HFD for 8 weeks before the analysis of PPARγ, PGC-1α, UCP1, and CD137 gene expression, and pathological examinations of white adipose tissues. The expression of PPARγ, PGC-1α, and UCP1 increased in 3T3-L1 cells following α-tocopherol treatment in a concentration-dependent manner. UCP1 expression and mitochondrial content also increased in α-tocopherol-treated cells. According to the histopathological examinations of rat white adipose tissues, multilocular cells were observed in the α-tocopherol intake group. Furthermore, the gene expression levels of PGC-1α, UCP1, and CD137 increased in the α-tocopherol intake group. Our results suggest that α-tocopherol promotes thermogenic adipocyte differentiation in mammalian white adipose tissues.
