Human brown adipose tissue as a target for obesity management; beyond cold-induced thermogenesis

Elevating energy expenditure via adaptive thermogenesis in brown adipose tissue (BAT) is a potential strategy to reverse obesity. Much early enthusiasm for this approach, based on rodent studies, was tempered by the belief that BAT was relatively inconsequential in healthy adult humans. Interest was reinvigorated a decade ago when a series of studies re-identified BAT, primarily in upper thoracic regions, in adults. Despite the ensuing explosion of pre-clinical investigations and identification of an extensive list of potential target molecules for BAT recruitment, our understanding of human BAT physiology remains limited, particularly regarding interventions which might hold therapeutic promise. Cold-induced BAT thermogenesis (CIT) has been well studied, although is not readily translatable as an anti-obesity approach, whereas little is known regarding the role of BAT in human diet-induced thermogenesis (DIT). Furthermore, human studies dedicated to translating known pharmacological mechanisms of adipose browning from animal models are sparse. Several lines of recent evidence suggest that molecular regulation and physiology of human BAT differ to that of laboratory rodents, which form the majority of our knowledge base. This review will summarize knowledge on CIT and expand upon the current understanding and evidence gaps related to human adaptive thermogenesis via mechanisms other than cold.