Annals of Medicine, 2015; Early Online: 1 © 2015 Informa UK, Ltd. ISSN 0785-3890 print/ISSN 1365-2060 online DOI: 10.3109/07853890.2015.1019917
EDITORIAL
Brown adipose tissue in humans Pirjo Nuutila Turku PET Centre, University of Turku, Kiinamyllynkatu 4–6, 20520 Turku, Finland
Ann Med Downloaded from informahealthcare.com by Kainan University on 04/06/15 For personal use only.
What has been learnt after the ‘rediscovery’ of brown adipose tissue? In spite of the long history of evidence for brown adipose tissue (BAT) in adult humans (1), the evidence of its functionality was missing. The thinking started to change when metabolically active adipose tissue was found in the neck and supraclavicular areas of diagnostic patients imaged with [18F]-fluorodeoxyglucose (FDG) and positron emission tomography (PET). Finally, in 2009, three independent studies demonstrated that these metabolically hot areas corresponded to UCP1-expressing BAT in adult humans (2–4). This Special Section of Annals of Medicine entitled ‘Brown fat’ contains five interesting reviews updating the current knowledge and reporting on recent studies in BAT in humans. The first of those, written by Cereijo, Giralt, and Villarroya (5), gives an excellent introduction into the recent characterization of beige/brite fat. Although the pheochromocytoma serves as a human model for browning, non-sympathetic-related factors are still poorly known and require further research. So-called ‘classical’ BAT and beige/brite fat are thermodynamically rather similar, but their different gene expression profiles suggest different, yet unidentified physiological functions (5). Numerous studies since the first reports (2–4) have indicated that BAT mass and activity are blunted in obesity, suggesting a role of BAT in the battle against overweight. Age-related changes in BAT are highly interesting, as described by Nicole Rogers in her review on BAT during puberty and with aging (6). Contradictory to previous belief, BAT seems to be found in similar anatomical locations in infants and adults. A puberty-associated increase in BAT was reported already in 2005 (7). This peak is associated with an increase in muscle mass, and has a unique potential in understanding the endogenous mechanism that stimulates BAT development. It seems that BAT mass decreases with age, while its cold-induced capacity remains (6). Brown adipose tissue activity is centrally regulated via the sympathetic nervous system. In this section, Contreras and co-workers review comprehensively the peripheral and central regulation of thermogenesis (8). In addition, current knowledge of molecular determinants of browning is updated and illustrated with figures (8). Additional endogenous ways to stimulate BAT in humans are further discussed by Broeders and co-workers (9). Finally, possibilities to activate and recruit BAT are summarized by Takeshi Yoneshiro and Masayuki Saito (10). They are pioneers of BAT imaging and showed in 2009 the association
between BAT activation and increased whole-body energy expenditure (11). Thereafter, using chronic cooling exposure, they have found increased BAT activity and slight weight loss. They have also shown that capsinoids stimulate BAT (12). Here they review the mechanisms via which capsinoids and other food ingredients activate BAT in humans (10). In summary, this Special Section provides highlights of the fascinating story of adipose plasticity. Brown adipose tissue is an intriguing target for life-style and pharmacological interventions against obesity and metabolic diseases. Declaration of interest: The author reports no conflicts of interest.
References 1. Huttunen P, Hirvonen J, Kinnula V. The occurrence of brown adipose tissue in outdoor workers. Eur J Appl Physiol. 1981;46:339–45. 2. Virtanen KA, Lidell ME, Orava J, Heglind M, Westergren R, Niemi T, et al. Functional brown adipose tissue in healthy adults. N Engl J Med. 2009;360:1518–25. 3. van Marken Lichtenbelt WD, Vanhommerig JW, Smulders NM, Drossaerts JM, Kemerink GJ, Bouvy ND, et al. Cold-activated brown adipose tissue in healthy men. N Engl J Med. 2009;360:1500–8. 4. Cypress AM, Lehman S, Williams G, Tal I, Rodman D, Goldfine AB, et al. Identification and importance of brown adipose tissue in adult humans. N Engl J Med. 2009;360:1509–17. 5. Cereijo R, Giralt M, Villarroya F. Thermogenic brown and beige/brite adipogenesis in humans. Ann Med. 2014 Sep 18:1–9. [Epub ahead of print] 6. Rogers NH. Brown adipose tissue during puberty and with aging. Ann Med. 2014 Jun 3:1–8. [Epub ahead of print] 7. Gelfand MJ, O’Hara SM, Curtwright LA, Maclean JR. Pre-medication to block [(18)F]FDG uptake in the brown adipose tissue of pediatric and adolescent patients. Pediatr Radiol. 2005;35:984–90. 8. Contreras C, Gonzalez F, Fernø J, Diéguez C, Rahmouni K, Nogueiras R, et al. The brain and brown fat. Ann Med. 2014 Jun 10:1–19. [Epub ahead of print] 9. Broeders E, Bouvy ND, van Marken Lichtenbelt WD. Endogenous ways to stimulate brown adipose tissue in humans. Ann Med. 2014 Feb 13. [Epub ahead of print] 10. Yoneshiro T, Saito M. Activation and recruitment of brown adipose tissue as anti-obesity regimens in humans. Ann Med. 2014 Jun 5:1–9. [Epub ahead of print] 11. Saito M, Okamatsu-Ogura Y, Matsushita M, Watanabe K, Yoneshiro T, Nio-Kobayashi J, et al. High incidence of metabolically active brown adipose tissue in healthy adult humans: effects of cold exposure and adiposity. Diabetes. 2009;58:1526–31. 12. Saito M, Yoneshiro T. Capsinoids and related food ingredients activating brown fat thermogenesis and reducing body fat in humans. Curr Opin Lipidol. 2013;24:71–7.
Correspondence: Pirjo Nuutila, Turku PET Centre, University of Turku, Kiinamyllynkatu 4–6, 20520 Turku, Finland. E-mail: [email protected] (Received 10 February 2015; accepted 10 February 2015)
EDITORIAL
Brown adipose tissue in humans Pirjo Nuutila Turku PET Centre, University of Turku, Kiinamyllynkatu 4–6, 20520 Turku, Finland
Ann Med Downloaded from informahealthcare.com by Kainan University on 04/06/15 For personal use only.
What has been learnt after the ‘rediscovery’ of brown adipose tissue? In spite of the long history of evidence for brown adipose tissue (BAT) in adult humans (1), the evidence of its functionality was missing. The thinking started to change when metabolically active adipose tissue was found in the neck and supraclavicular areas of diagnostic patients imaged with [18F]-fluorodeoxyglucose (FDG) and positron emission tomography (PET). Finally, in 2009, three independent studies demonstrated that these metabolically hot areas corresponded to UCP1-expressing BAT in adult humans (2–4). This Special Section of Annals of Medicine entitled ‘Brown fat’ contains five interesting reviews updating the current knowledge and reporting on recent studies in BAT in humans. The first of those, written by Cereijo, Giralt, and Villarroya (5), gives an excellent introduction into the recent characterization of beige/brite fat. Although the pheochromocytoma serves as a human model for browning, non-sympathetic-related factors are still poorly known and require further research. So-called ‘classical’ BAT and beige/brite fat are thermodynamically rather similar, but their different gene expression profiles suggest different, yet unidentified physiological functions (5). Numerous studies since the first reports (2–4) have indicated that BAT mass and activity are blunted in obesity, suggesting a role of BAT in the battle against overweight. Age-related changes in BAT are highly interesting, as described by Nicole Rogers in her review on BAT during puberty and with aging (6). Contradictory to previous belief, BAT seems to be found in similar anatomical locations in infants and adults. A puberty-associated increase in BAT was reported already in 2005 (7). This peak is associated with an increase in muscle mass, and has a unique potential in understanding the endogenous mechanism that stimulates BAT development. It seems that BAT mass decreases with age, while its cold-induced capacity remains (6). Brown adipose tissue activity is centrally regulated via the sympathetic nervous system. In this section, Contreras and co-workers review comprehensively the peripheral and central regulation of thermogenesis (8). In addition, current knowledge of molecular determinants of browning is updated and illustrated with figures (8). Additional endogenous ways to stimulate BAT in humans are further discussed by Broeders and co-workers (9). Finally, possibilities to activate and recruit BAT are summarized by Takeshi Yoneshiro and Masayuki Saito (10). They are pioneers of BAT imaging and showed in 2009 the association
between BAT activation and increased whole-body energy expenditure (11). Thereafter, using chronic cooling exposure, they have found increased BAT activity and slight weight loss. They have also shown that capsinoids stimulate BAT (12). Here they review the mechanisms via which capsinoids and other food ingredients activate BAT in humans (10). In summary, this Special Section provides highlights of the fascinating story of adipose plasticity. Brown adipose tissue is an intriguing target for life-style and pharmacological interventions against obesity and metabolic diseases. Declaration of interest: The author reports no conflicts of interest.
References 1. Huttunen P, Hirvonen J, Kinnula V. The occurrence of brown adipose tissue in outdoor workers. Eur J Appl Physiol. 1981;46:339–45. 2. Virtanen KA, Lidell ME, Orava J, Heglind M, Westergren R, Niemi T, et al. Functional brown adipose tissue in healthy adults. N Engl J Med. 2009;360:1518–25. 3. van Marken Lichtenbelt WD, Vanhommerig JW, Smulders NM, Drossaerts JM, Kemerink GJ, Bouvy ND, et al. Cold-activated brown adipose tissue in healthy men. N Engl J Med. 2009;360:1500–8. 4. Cypress AM, Lehman S, Williams G, Tal I, Rodman D, Goldfine AB, et al. Identification and importance of brown adipose tissue in adult humans. N Engl J Med. 2009;360:1509–17. 5. Cereijo R, Giralt M, Villarroya F. Thermogenic brown and beige/brite adipogenesis in humans. Ann Med. 2014 Sep 18:1–9. [Epub ahead of print] 6. Rogers NH. Brown adipose tissue during puberty and with aging. Ann Med. 2014 Jun 3:1–8. [Epub ahead of print] 7. Gelfand MJ, O’Hara SM, Curtwright LA, Maclean JR. Pre-medication to block [(18)F]FDG uptake in the brown adipose tissue of pediatric and adolescent patients. Pediatr Radiol. 2005;35:984–90. 8. Contreras C, Gonzalez F, Fernø J, Diéguez C, Rahmouni K, Nogueiras R, et al. The brain and brown fat. Ann Med. 2014 Jun 10:1–19. [Epub ahead of print] 9. Broeders E, Bouvy ND, van Marken Lichtenbelt WD. Endogenous ways to stimulate brown adipose tissue in humans. Ann Med. 2014 Feb 13. [Epub ahead of print] 10. Yoneshiro T, Saito M. Activation and recruitment of brown adipose tissue as anti-obesity regimens in humans. Ann Med. 2014 Jun 5:1–9. [Epub ahead of print] 11. Saito M, Okamatsu-Ogura Y, Matsushita M, Watanabe K, Yoneshiro T, Nio-Kobayashi J, et al. High incidence of metabolically active brown adipose tissue in healthy adult humans: effects of cold exposure and adiposity. Diabetes. 2009;58:1526–31. 12. Saito M, Yoneshiro T. Capsinoids and related food ingredients activating brown fat thermogenesis and reducing body fat in humans. Curr Opin Lipidol. 2013;24:71–7.
Correspondence: Pirjo Nuutila, Turku PET Centre, University of Turku, Kiinamyllynkatu 4–6, 20520 Turku, Finland. E-mail: [email protected] (Received 10 February 2015; accepted 10 February 2015)
