SAT430 Effect Of Organochlorine Pesticides On Brown Adipose Thermogenesis

Abstract

Abstract Disclosure: S. Huang: None. J.A. Jugan: None. J. Harrigan: None. A. Singla: None. V. Huang: None. C.M. Mann: None. M. La Merrill: None. Mammalian non-shivering thermogenesis is canonically controlled by β-adrenergic signaling in brown adipose tissue. The β-adrenergic receptors Adrb1, Adrb2, and Adrb3 receive the signals from upstream sympathetic neurons, activate adenylyl cyclase, and increase the expression of uncoupled protein-1 (UCP1) which dissipates energy to produce heat. The banned but persistent pesticide dichlorodiphenyltrichloroethane (DDT) along with its metabolite, dichlorodiphenyldichloroethylene (DDE), jointly referred to as DDX, are consistently associated with increased risk of present-day obesity and type II diabetes. In addition, DDX reduced body temperature by reducing sympathetic axons innervation in mice. However, the effect of DDX on the expression of β-adrenergic receptors and thermogenesis in brown adipocytes and other mammals is unclear. Therefore, the association between DDX exposure and the expression of β-adrenergic receptors and thermogenesis in vitro and in vivo was investigated. To this aim, Sprague-Dawley (SD) rats were fed high-fat diet and gavage of either a very low dose DDX mixture (5.6μg/kg weekly for 4 weeks) or olive oil vehicle control. DDX caused a significant reduction in body temperature after two weeks without significant changes in caloric intake or food efficiency. Notably, among all the β-adrenergic receptors, only Adrb3, and Ucp1 were downregulated in the brown adipose of DDX-treated rats. These results suggest that DDX reduces body temperature by attenuating Adrb3 expression in rat brown adipose tissue. To test whether this could explain the previously observed risk of human obesity associated with DDX exposure, we used immortalized human brown adipocytes to evaluate the effect of DDX on the RNA expression of β-adrenergic receptors, UCP1, and thermogenic function. As observed in rat brown adipose, DDT and DDE each reduced the expression of ADRB3 and UCP1, but not ADRB1 or ADRB2 in immortalized human brown adipocytes. Further, DDT and DDE each decreased heat produced by the human brown adipocytes. In addition, the reduced expression of UCP1 in DDX-treated human brown adipocytes was dependent on the presence of adenylyl cyclase (AC) activator, forskolin, demonstrating that the expression of UCP1 can be rescued by bypassing the upstream β3-adrenergic receptor. In conclusion, this evidence supports the hypothesis that obesogenic pesticides, DDT and DDE, attenuate thermogenesis by impairing brown adipocyte expression of the β3-adrenergic receptor and UCP1 in several mammalian species. Presentation: Saturday, June 17, 2023