Adaptive thermogenesis in mice requires adipocyte light-sensing via Opsin 3
Almost all life forms can decode light information for adaptive advantage. Examples include the visual system, where photoreceptor signals are interpreted as images, and the circadian system, where light entrains a physiological clock. Here we describe a local, non-visual light response in mice that employs encephalopsin (OPN3, a 480 nm, blue light responsive opsin) to regulate the function of adipocytes. Germ line null and adipocyte-specific conditional null mice show a deficit in thermogenesis that is phenocopied in mice under blue-light deficient conditions. We show that blue light stimulation of adipocytes activates hormone sensitive lipase, the rate limiting enzyme in the lipolysis pathway, and that this is OPN3-dependent. Opn3 adipocyte conditional null mice also use reduced levels of fat mass when fasted and cold exposed further suggesting a lipolysis deficit. These data suggest the hypothesis that in mice, a local, OPN3-dependent light response in adipocytes is a mechanism for regulation of energy homeostasis.