Activation of thermogenic adipocytes (brown and beige) has been considered an attractive target for weight loss and treatment of metabolic disease. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC1-alpha) is a master regulator of thermogenic gene expression in thermogenic adipocytes. We previously reported that alpha-tocopherol upregulated PGC-1 alpha gene expression and promoted thermogenic adipocyte differentiation in mammalian adipocytes. In this study, we investigated the effects of the vitamin E analogs (alpha-, gamma- and delta-tocopherol) on PGC-l alpha and uncoupling protein 1 (UCP1) gene expression in 3T3-L1 cells. The expression of PGC-1 alpha and UCP1 increased significantly with the addition of delta-tocopherol. In delta-tocopherol-treated cells, nuclear translocation of PGC-1 alpha increased, as did p38 mitogen-activated protein kinase (MAPK) expression and phosphorylation. Our results suggest that p38 MAPK activation by S-tocopherol contributes to PGC-la activation and UCP1 induction. (C) 2018 Elsevier Inc. All rights reserved.