Brown fat fuel use and regulation of energy homeostasis.

PURPOSE OF REVIEW: New evidence has recently supported the notion that brown adipose tissue (BAT) is present in adult humans and can play a prominent role in the regulation of body weight and metabolism. This has renewed the efforts to understand the physiologic mechanisms by which BAT is activated, which in turn could provide new therapeutic strategies for obesity and diabetes. RECENT FINDINGS: BAT mass and activity are positively correlated with measures of metabolic health in rodents and humans; however, the amount of functional BAT in adult humans is highly variable with less found in overweight and obese individuals. The impact of BAT in the uptake and utilization of circulating nutrients is systemic, with major effects on whole-body insulin sensitivity and glucose tolerance as illustrated by BAT transplantation in rodents. Furthermore, a host of physiologic conditions and novel peptides/hormones have been implicated in the activation of BAT thermogenesis and/or 'browning' of white adipocytes. SUMMARY: These new findings open the way for novel strategies aimed at increasing BAT mass and activity in obese humans as an important clinical goal in the midst of unprecedented high prevalence of obesity and associated metabolic disorders.