Human white-fat thermogenesis: Experimental and meta-analytic findings

Petros C Dinas; Argyro Krase; Eleni Nintou; Alexandros Georgakopoulos; Marnie Granzotto; Marinos Metaxas; Elena Karachaliou; Marco Rossato; Roberto Vettor; Panagiotis Georgoulias; Tiago S Mayor; John Koutsikos; Konstantinos Athanasiou; Leonidas G Ioannou; Paraskevi Gkiata; Andres E Carrillo; Yiannis Koutedakis; George S Metsios; Athanasios Z Jamurtas; Sofia Chatziioannou; Andreas D Flouris

doi:10.1080/23328940.2020.1769530

Human white-fat thermogenesis: Experimental and meta-analytic findings

Temperature (Austin). 2020 Jun 5;8(1):39-52. doi: 10.1080/23328940.2020.1769530.

Authors

Petros C Dinas^{1

2}, Argyro Krase¹, Eleni Nintou¹, Alexandros Georgakopoulos³, Marnie Granzotto⁴, Marinos Metaxas³, Elena Karachaliou³, Marco Rossato⁴, Roberto Vettor⁴, Panagiotis Georgoulias⁵, Tiago S Mayor⁶, John Koutsikos⁷, Konstantinos Athanasiou⁷, Leonidas G Ioannou¹, Paraskevi Gkiata¹, Andres E Carrillo⁸, Yiannis Koutedakis^{2

9}, George S Metsios², Athanasios Z Jamurtas⁹, Sofia Chatziioannou³, Andreas D Flouris¹

Affiliations

¹ FAME Laboratory, Department of Exercise Science, University of Thessaly, Trikala, Greece.
² Faculty of Education Health and Wellbeing, University of Wolverhampton, Walsall, UK.
³ PET/CT Department, Biomedical Research Foundation, Academy of Athens, Athens, Greece.
⁴ Department of Medicine - DIMED, Internal Medicine 3, University of Padova, Padova, Italy.
⁵ Nuclear Medicine Laboratory, Medical School, University of Thessaly, Larissa, Greece.
⁶ SIMTECH Laboratory, Transport Phenomena Research Centre, Engineering Faculty of Porto University, Porto, Portugal.
⁷ Nuclear Medicine Department, 401 General Military Hospital, Athens, Greece.
⁸ Department of Movement Science, Chatham University, Pittsburgh, PA, USA.
⁹ School of Physical Education and Exercise Science, University of Thessaly, Trikala, Greece.

Abstract

White adipose tissue (WAT) thermogenic activity may play a role in whole-body energy balance and two of its main regulators are thought to be environmental temperature (T_env) and exercise. Low T_env may increase uncoupling protein one (UCP1; the main biomarker of thermogenic activity) in WAT to regulate body temperature. On the other hand, exercise may stimulate UCP1 in WAT, which is thought to alter body weight regulation. However, our understanding of the roles (if any) of T_env and exercise in WAT thermogenic activity remains incomplete. Our aim was to examine the impacts of low T_env and exercise on WAT thermogenic activity, which may alter energy homeostasis and body weight regulation. We conducted a series of four experimental studies, supported by two systematic reviews and meta-analyses. We found increased UCP1 mRNA (p = 0.03; but not protein level) in human WAT biopsy samples collected during the cold part of the year, a finding supported by a systematic review and meta-analysis (PROSPERO review protocol: CRD42019120116). Additional clinical trials (NCT04037371; NCT04037410) using Positron Emission Tomography/Computed Tomography (PET/CT) revealed no impact of low T_env on human WAT thermogenic activity (p > 0.05). Furthermore, we found no effects of exercise on UCP1 mRNA or protein levels (p > 0.05) in WAT biopsy samples from a human randomized controlled trial (Clinical trial: NCT04039685), a finding supported by systematic review and meta-analytic data (PROSPERO review protocol: CRD42019120213). Taken together, the present experimental and meta-analytic findings of UCP1 and SUV_max, demonstrate that cold and exercise may play insignificant roles in human WAT thermogenic activity. Abbreviations: WAT:White adipose tissue; T_env: Environmental temperature; UCP1: Uncoupling protein one; BAT: Brown adipose tissue; BMI:Body mass index; mRNA: Messenger ribonucleic acid; RCT: Randomized controlled trial; WHR: Waist-to-hip ratio; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-analyses; PET/CT: Positron Emission Tomography and Computed Tomography; REE: Resting energy expenditure; ¹⁸F-FDG: F¹⁸ fludeoxyglucose; VO₂peak:Peak oxygen consumption; 1RM: One repetition maximum; SUV_max: Maximum standardized uptake value; Std: Standardized mean difference.

Keywords: UCP1; Uncoupling protein one; brown-like adipocytes; browning process; thermogenic activity.

Grants and funding

This work was supported by funding from the European Union 7th Framework Program FP7-PEOPLE-2012-IRSES grant no. [319010]; FP7-PEOPLE-2013-IRSES grant no. [612547] and Horizon 2020 ICI-THROUGH grant no [645710].