title: 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.
abstract: This study investigated the regulation of thermogenic capacity in classical brown adipose tissue (BAT) and subcutaneous inguinal (SC Ing) white adipose tissue (WAT) and how it affects whole-body energy expenditure in sedentary and endurance-trained rats fed ad libitum either low fat or high fat (HF) diets. Analysis of tissue mass, PGC-1α and UCP-1 content, the presence of multilocular adipocytes, and palmitate oxidation revealed that a HF diet increased the thermogenic capacity of the interscapular and aortic brown adipose tissues, whereas exercise markedly suppressed it. Conversely, exercise induced browning of the SC Ing WAT. This effect was attenuated by a 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 subcutaneous 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 subcutaneous 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.
authors.affiliation: From the Muscle Health Research Center, School of Kinesiology and Health Science, York University, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Michelle V
authors.initials: MV
authors.lastname: Wu
authors.affiliation: From the Muscle Health Research Center, School of Kinesiology and Health Science, York University, Toronto, Ontario M3J 1P3, Canada.
authors.forename: George
authors.initials: G
authors.lastname: Bikopoulos
authors.affiliation: From the Muscle Health Research Center, School of Kinesiology and Health Science, York University, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Steven
authors.initials: S
authors.lastname: Hung
authors.affiliation: From the Muscle Health Research Center, School of Kinesiology and Health Science, York University, Toronto, Ontario M3J 1P3, Canada roceddia@yorku.ca.
authors.forename: Rolando B
authors.initials: RB
authors.lastname: Ceddia
mesh_terms: D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D059305:Diet, High-Fat; D004041:Dietary Fats / Q000009:adverse effects; D004734:Energy Metabolism / Q000235:genetics*; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism; D008297:Male; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D009765:Obesity / Q000209:etiology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009928:Organ Specificity; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D010805:Physical Conditioning, Animal; D010807:Physical Endurance; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D050507:Subcutaneous Fat, Abdominal / Q000378:metabolism*; D022722:Thermogenesis / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D000071256:Uncoupling Protein 1
chemical_list: D004041:Dietary Fats; C583676:FNDC5 protein, rat; D005353:Fibronectins; D007473:Ion Channels; D024101:Mitochondrial Proteins; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C501429:Ppargc1a protein, rat; D014157:Transcription Factors; C000604373:Ucp1 protein, rat; D000071256:Uncoupling Protein 1
keywords: AMP-activated Kinase (AMPK); Adipose Tissue Metabolism; Exercise; Obesity; Peroxisome Proliferator-activated Receptor γ Coactivator 1-α (PGC-1a) (PPARGC1A); UCP-1, FNDC5, Irisin, Brown Adipocytes, ATGL