Is the heat surrounding adipose tissue mitochondria warranted?

Purpose of review: Mitochondrial uncoupling proteins uncouple oxidative phosphorylation. The physiological role ascribed to this process is thermoregulation. The metabolic consequence of mitochondrial respiration uncoupled from ATP production is increased substrate oxidation and metabolic rate. The recent discovery of uncoupling protein 1 (UCP1) positive mitochondria in human adipose tissue has rekindled interest in the role of UCP1 in energy balance and metabolic health. Recent findings: Recently, there have been numerous reports of functional brown adipose tissue in humans. Further, data from cell and murine studies suggest that beige adipocytes can be induced within white adipose tissue. The presence of brown/beige adipocytes with mitochondria expressing UCP1 negatively correlates with adiposity. Further, activation of these adipocytes alters energy balance and substrate metabolism. However, in humans, brown fat content varies significantly. Further, although beige adipocytes can be induced in white adipose tissue of rodents, whether this is also true in humans remains unclear. Summary: The presence of UCP1-positive mitochondria in human adipose tissue represents an exciting therapeutic target for treating obesity and its metabolic complications. Understanding the mechanisms governing brown fat activation will be crucial if the therapeutic potential of UCP1 is to be realized.