Light plays an essential role in life. Animals and humans possess light-sensing photoreceptors in visual and non-visual organs. We and others recently showed a non-visual role for Opsin3 (Opn3) in regulating adipose function. In this study, we discovered that direct blue light exposure to subcutaneous white adipose tissue (WAT) could reduce lipids accumulation in WAT and improve high-fat diet-induced metabolic abnormalities in an Opn3-dependent manner. Adipose tissue is an orchestrated matrix comprising high innervation that can engage in crosstalk with other organs. Particularly, it communicates with the brain via the sympathetic nervous system (SNS). Using the metabolomic approach, we found that blue light increased circulating levels of histidine, which then triggered the activation of histaminergic neurons in the hypothalamus and turned on brown adipose tissue via SNS. The administration of histidine decarboxylase antagonist blunted the effects of blue light. Taken together, these data demonstrate a novel light-responsive adipose-hypothalamus axis in metabolic regulation and provide a potential light-based therapeutic approach for obesity. Disclosure T.Tsuji: None. T.Huang: None. Y.Zhang: None. M.Lynes: None. G.Profeta: None. N.Narain: None. M.Kiebish: None. Y.Tseng: Consultant; Cellarity, LyGenesis. Funding American Heart Association (903968)
Brown adipocytes hold the potential to mitigate body fat accumulation and type 2 diabetes (T2D) via their specialized function in dissipating energy as heat, a process known as thermogenesis. To fuel their function, brown adipocytes release the bond energy of fat through lipolysis and β-oxidation; then, uncoupling cellular respiration releases this energy as physical heat. In addition to their energy-dissipating function, brown adipocytes can release factors, such as lipids, metabolites, peptides, or microRNA, to regulate metabolism. Signaling lipids have demonstrated roles in regulating thermogenesis in brown adipocytes by regulating lipid uptake and utilization. To further explore these pathways, we performed signaling lipidomics analysis in in vitro differentiated human brown adipocytes and found 15-keto-PGF2α was increased when treated with forskolin, an adenylyl cyclase activator that mimics adrenergic stimulation. Previous studies have shown PGF2α, the parent molecule of 15-keto-PGF2α, inhibits maturation, or adipogenesis, in white adipocyte cell lines by preventing the expression of key adipogenesis genes, such as PPARγ and C/EBPα. Similarly, PGF2α inhibits thermogenic gene expression in brown adipocyte cells. To explore and compare the functional activities of PGF2α and 15-keto-PGF2α, we characterized the dose-response relationship of these lipids on thermogenic gene and protein expression. We found that 15-keto-PGF2α is not as potent as PGF2α at inhibiting both thermogenic gene and protein expression. This suggests the conversion of PGF2α to 15-keto-PGF2α represents a significant signaling event to promote thermogenesis in brown adipocytes. Interestingly, carbonyl reductase 1, an enzyme that catalyzes this conversion, is regulated by treatment with the adrenergic agonist, norepinephrine, in vitro and by cold exposure in vivo. Targeting this conversion may be an attractive approach towards activating thermogenesis to mitigate obesity and T2D. Disclosure E.Fadumiye: None. S.Kodani: None. M.Kiebish: None. V.Bussberg: None. Y.Tseng: Consultant; Cellarity. Funding National Institutes of Health (R01DK122808)
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