[Evaluation of Naturally Occurring Compounds Regulating Brown/Beige Adipocyte Differentiation]

Brown adipose tissue is a critical regulator of metabolic health, and contributes to thermogenesis by uncoupling oxidative phosphorylation through the action of mitochondrial uncoupling protein 1 (Ucp1). Recent studies have shown that cold exposure and the stimulation of β3-adrenergic receptors induce the development of brown cell-like "beige" adipocytes in white adipose tissue. Brown and/or beige adipocyte-mediated thermogenesis suppresses high-fat diet-associated obesity. Therefore, the development of brown/beige adipocytes may prevent obesity and metabolic diseases. In the present study, we elucidated whether naturally occurring compounds contribute to regulating the cellular differentiation of brown/beige adipocytes. We screened for the up-regulated expression of Ucp1 during beige adipogenesis using extracts of crude herbal drugs frequently used in Kampo prescriptions (therapeutic drugs in Japanese traditional medicine). This screening revealed that the extract prepared from Citri Unshiu Pericarpium [the peel of Citrus unshiu (Swingle) Marcov.] increased the expression of Ucp1 in beige adipocytes. We also focused on the function of clock genes in regulating brown/beige adipogenesis. Therefore, another aim of the present study was to evaluate naturally occurring compounds that regulate brain and muscle Arnt-like 1 (Bmal1) gene expression. In this review, we focus on naturally occurring compounds that affect regulatory processes in brown/beige adipogenesis, and discuss better preventive strategies for the management of obesity and other metabolic disorders.