80-OR: A New Cytoskeleton-Based Mechanism for Regulating Brown Adipose Tissue Physiology

Human genetic variants in ANK2, encoding the scaffold protein ankyrin-B (AnkB), increase risk for T2D. We characterized the role of AnkB in white adipose tissue (WAT) in mice with AnkB deficiency in both WAT and brown adipose tissue (BAT) (AT-AnkB KO). We found that AnkB loss led to obesity and insulin resistance driven by its role in clathrin mediated endocytosis of GLUT4 in WAT. AT-AnkB KO mice also had lipid accumulation in BAT. However, the cell-autonomous roles of AnkB in BAT and its contribution to energy balance is unknown. To elucidate AnkB’s roles in BAT, we developed mice lacking AnkB in BAT (BAT-AnkB KO). Histology and TEM revealed lipid accumulation in BAT of 4-month-old BAT-AnkB KO mice housed at thermoneutrality. Consistent with this finding, brown adipocytes from AnkB deficient mice also have enlarged lipid droplets, suggesting an AnkB cell-autonomous role in BAT lipid homeostasis. Proteomic-MS revealed that AnkB forms complexes with lipolysis factors Atgl, Hsl and Plin1, and regulators of the PKA pathway, suggesting AnkB plays a role regulating BAT lipolysis. Interestingly, Hsl and Plin1 are elevated in BAT despite the enlarged LDs of BAT-AnkB KO mice, implying either lipolytic deficits or compensatory effects. These findings support RNA sequencing that revealed downregulation of PKA signaling genes, ATPase subunits, and mitochondrial calcium signaling genes in BAT of BAT-AnkB KO mice. Last, peri-droplet mitochondria (PDM), a mitochondria subpopulation with reduced beta-oxidation capacity that contacts LDs, form longer contact sites with BAT LDs from BAT-AnkB KO mice. Together, these findings suggest that early alterations in mitochondrial bioenergetics and lipolysis contribute to BAT LD accumulation. Along with this data, we will present findings on thermogenic regulation in vivo and physiological assays evaluating lipolysis and its major regulators.