Thermogenic capacity is antagonistically regulated in classical brown and white subcutaneous fat depots by high-fat diet and endurance training in rats: Impact on whole-body energy expenditure [Bioenergetics]

October 25th, 2014 by Wu, M. V., Bikopoulos, G., Hung, S., Ceddia, R. B.

ABSTRACT This study investigated the regulation of thermogenic capacity in classical BAT and SC WAT, and how it affects whole-body energy expenditure in sedentary (Sed) and endurance-trained (Ex) rats fed ad libitum either low-fat (LF) or high-fat (HF) diets. Analysis of tissue mass, PGC-1α and UCP-1 content, presence of multilocular adipocytes, and palmitate oxidation revealed that HF diet increased the thermogenic capacity of the interscapular and aortic brown adipose tissues, while exercise markedly suppressed it. Conversely, exercise induced browning of the subcutaneous inguinal (SC Ing) WAT. This effect was attenuated by HF diet. Endurance training neither affected skeletal muscle FNDC5 content nor circulating irisin, but it increased FNDC5 content in SC Ing WAT. This suggests that locally produced FNDC5 rather than circulating irisin mediated the exercise-induced browning effect on this fat tissue. Importantly, despite reducing the thermogenic capacity of classical BAT, exercise increased whole-body energy expenditure during the dark cycle. Therefore, browning of SC WAT, likely exerted a compensatory effect and raised whole-body energy expenditure in endurance-trained rats. Based on these novel findings, we propose that exercise-induced browning of the SC WAT provides an alternative mechanism that reduces thermogenic capacity in core areas and increases it in peripheral body regions. This could allow the organism to adjust its metabolic rate to accommodate diet-induced thermogenesis while simultaneously coping with the stress of chronically increased heat production through exercise.
  • Posted in Journal of Biological Chemistry, Publications
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