Pronounced expression of the lipolytic inhibitor G0/G1 Switch Gene 2 (G0S2) in adipose tissue from brown bears (Ursus arctos) prior to hibernation

摘要

Prior to hibernation, the brown bear (Ursus arctos) exhibits unparalleledweight gain. Unlike humans, weight gain in bears is associated with lowerlevels of circulating free fatty acids (FFA) and increased insulin sensitivity.Understanding how free-ranging brown bears suppress lipolysis when gainingweight may therefore provide novel insight toward the development of humantherapies. Blood and subcutaneous adipose tissue were collected from immobilizedfree-ranging brown bears (fitted with GPS-collars) during hibernationin winter and from the same bears during the active period in summer inDalarna, Sweden. The expression of lipid droplet-associated proteins in adiposetissue was examined under the hypothesis that bears suppress lipolysisduring summer while gaining weight by increased expression of negative regulatorsof lipolysis. Adipose triglyceride lipase (ATGL) expression did not differbetween seasons, but in contrast, the expression of ATGL coactivator Comparativegene identification-58 (CGI-58) was lower in summer. In addition, theexpression of the negative regulators of lipolysis, G0S2 and cell-death inducingDNA fragmentation factor-a-like effector (CIDE)C markedly increased duringsummer. Free-ranging brown bears display potent upregulation of inhibitorsof lipolysis in adipose tissue during summer. This is a potential mechanismfor increased insulin sensitivity during weight gain and G0S2 may serve as atarget to modulate insulin sensitivity.