1137-OR: Mfsd2a Regulates Lipid Handling and Mitochondrial Function in Brown Adipocytes during Cold Exposure

Introduction and Objective: The major facilitator superfamily domain-containing protein 2a (MFSD2A) is a lysophosphatidylcholine (LPC) transporter whose expression is markedly upregulated in interscapular brown adipose tissue (BAT) during cold exposure. However, its cell-intrinsic role in brown adipocytes remains unclear. This study examined the role of Mfsd2a in BAT lipid remodeling, thermogenic gene expression, and mitochondrial function. Methods: Mfsd2a knockout (KO) and control brown preadipocytes were generated by isolating precursors from flox/flox mice followed by Cre-mediated recombination in vitro. Thermogenic and mitochondrial gene expression was assessed by quantitative PCR, and mitochondrial respiration by Seahorse analysis. For in vivo studies, brown adipocyte-specific Mfsd2a KO mice were generated using UCP1-Cre mice. Metabolic phenotyping included glucose, insulin, and cold tolerance tests. BAT lipidomics was performed in male mice under mild (15°C) and extreme cold (6°C) conditions. Results: In vitro, Mfsd2a KO brown adipocytes exhibited reduced expression of thermogenic (Ucp1, Dio2) and mitochondrial genes (Cox7a, Cox8b), along with decreased maximal FCCP-stimulated respiration. In vivo, glucose tolerance, insulin sensitivity, and cold tolerance were comparable between KO and control mice, while thermogenic and mitochondrial gene expression in BAT was reduced in KO mice, consistent with in vitro findings. Lipidomic analysis of BAT under cold exposure (6°C) revealed significant reductions in DHA-containing phospholipids in KO mice, including PC (18: 0₂2: 6), PC (20: 4₂2: 6), and PE (18: 1₂2: 6), accompanied by increased accumulation of oxidized triglycerides (TGs). Although TG levels did not differ between genotypes at 6°C, KO mice showed a marked reduction in TGs after recovery to 15°C. Conclusion: Mfsd2a regulates mitochondrial function and thermogenic gene expression in brown adipocytes through cold-induced lipid remodeling, thereby supporting mitochondrial integrity and thermogenic capacity in BAT. Disclosure H. Iwasaki: None. Y. Tseng: Consultant; Ended; Paratus Sciences. Consultant; Current; Sofinova Partners. T. Tsuji: None. S. Chen: None. S. Kodani: Employee; Current; SK Pharmteco. L. O. Leiria: None. J. Darcy: None. L. Zangerolamo: None.