Insights into brown adipose tissue evolution and function from non-model organisms

Martin Jastroch

Institute for Diabetes and Obesity, Helmholtz Zentrum München, Germany and Philipps University of Marburg, Germany

Brown adipose tissue (BAT) enables adaptive thermoregulation through heat production catalyzed by mitochondrial uncoupling protein 1 (UCP1). Fostered by the discovery of BAT in adult humans, typical model organisms such as mice and rats are frequently studied to target BAT for the treatment of human metabolic diseases. However, complementary studies on multiple non-model species, which are adapted to various ecological niches, may significantly broaden our understanding on BAT function and its physiological role. This review highlights the research on non-model organisms, which was instrumental to shed light on the unique evolutionary history of BAT and UCP1. The blueprint of evolution is reflected in the diversity of extinct and extant species, giving not only fundamental insights into BAT biology, but may bare clues for potential medical access. Fusing research on species diversity, ecology and evolution with comparative physiology and biochemistry, down to functional studies on single protein such as UCP1, unravels conserved and diversified functional changes in BAT and UCP1. As various ecological and physiological roles of BAT and UCP1 have been systemically integrated to maintain metabolic homeostasis during environmental and physiological challenge, comparative studies may also identify key selection processes during mammalian evolution.

While anthropogenic genetic mutations in model organisms are surely pivotal to test functional components of BAT, nature’s selection forces have applied trial and error in innumerable experiments over 500 million years of vertebrate evolution to purify and diversify BAT function. Thus, resolving the complete picture of BAT biology may fail if non-model organisms would be neglected.