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APPETITE, OBESITY, DIGESTION, AND METABOLISM

Short photoperiod exposure increases adipocyte sensitivity to noradrenergic stimulation in Siberian hamsters

¹Molecular and Cellular Biology and Pathobiology Program, Medical University of South Carolina, Charleston, South Carolina; ²Pennington Biomedical Research Center, Baton Rouge, Louisiana; ³Department of Foods and Nutrition, University of Georgia, Athens, Georgia; and ⁴Department of Biology and Center for Behavioral Neuroscience, Georgia State University, Atlanta, Georgia

Submitted 23 November 2004 ; accepted in final form 13 January 2005

Siberian hamsters (Phodopus sungorus) exhibit a naturally occurring, reversible seasonal obesity with body fat peaking in long "summerlike" days (LDs) and reaching a nadir in short "winterlike" days (SDs). These SD-induced decreases in adiposity are mediated largely via sympathetic nervous system (SNS) innervation of white adipose tissue (WAT), as indicated by increased WAT norepinephrine (NE) turnover. We examined whether SDs also increase sensitivity to NE-stimulated lipolysis. This was accomplished by measuring NE- and ₃-adrenoceptor (₃-AR) agonist (BRL-37344)-induced lipolysis (glycerol release) as well as NE-induced cAMP accumulation by inguinal, epididymal, and retroperitoneal WAT (IWAT, EWAT, and RWAT) in isolated adipocytes of LD- and SD-housed hamsters. SDs increased potency/efficacy of NE-triggered lipolysis in a temporally and fat pad-specific manner. Thus when WAT pad mass decreased most rapidly (5 wk of SDs), potency (sensitivity/EC₅₀) and efficacy (maximal response asymptote) of NE-stimulated lipolysis were increased for all WAT pads and also at 10 wk for IWAT compared with their LD counterparts. SD enhancement of lipolysis was similar for NE and BRL-37344 in IWAT adipocytes. These results, coupled with our previous demonstration that SDs upregulate WAT ₃-AR mRNA expression, suggest that increased ₃-ARs mediated the SD-induced increased NE sensitivity. NE-stimulated adipocyte accumulation of cAMP was greater after 5 wk of SDs for IWAT and EWAT and after 10 wk of SDs for IWAT compared with LDs, with no photoperiod effect for RWAT. Therefore, the SD-induced increase in SNS drive to WAT and increased sensitivity to this drive may work together to increase lipolysis in SDs.

lipolysis; body fat; BRL-37344; body weight; sympathetic

This article has been cited by other articles:

				N. A. Brito, M. N. Brito, and T. J. Bartness Differential sympathetic drive to adipose tissues after food deprivation, cold exposure or glucoprivation Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2008; 294(5): R1445 - R1452. [Abstract] [Full Text] [PDF]