β-Carotene stimulates browning of 3T3-L1 white adipocytes by enhancing thermogenesis via the β3-AR/p38 MAPK/SIRT signaling pathway

Background: Natural compounds with medicinal properties are part of a strategic trend in the treatment of obesity. The vitamin A agent, beta-carotene, is a well-known carotenoid, and its numerous functions in metabolism have been widely studied. The activation of thermogenesis by stimulating white fat browning (beiging) has been identified as a treatment for obese individuals. Purpose: The current study was undertaken to unveil the browning activity of beta-carotene in 3T3-L1 white adipocytes. Methods: The effects of beta-carotene were evaluated in 3T3-L1 white adipocytes, and gene/protein expressions were determined by performing quantitative real-time PCR, immunoblot analysis, immunofluorescence assessment, and molecular docking techniques. Results: beta-carotene strikingly increased the expression levels of brown-fat-specific marker proteins (UCP1, PRDM16, and PGC-1 alpha) and beige-fat-specific genes (Cd137, Cidea, Cited1, andTbx1) in 3T3-L1 cells. Exposure to p-carotene also elevated the expressions of key adipogenic transcription factors C/EBP alpha and PPAR gamma in white adipocytes but decreased the expressions of lipogenic marker proteins ACC and FAS. Moreover, lipolysis and fat oxidation were regulated by beta-carotene via upregulation of ATGL, pHSL, ACOX, and CPT1. In addition, molecular docking studies revealed beta-carotene activation of the adenosine A2A receptor and beta 3-AR. beta-Carotene increased the expressions of mitochondrial biogenic markers, stimulated the beta 3-AR and p38 MAPK signaling pathways and its downstream signaling molecules (SIRTs and ATF2), thereby inducing browning. Conclusions: Taken together, our results indicate the potential of beta-carotene as a natural-source therapeutic antiobesity agent.