Obesity: Slim without the gym--the magic of chilling out

Brown adipose tissue and type 2 diabetes

Recent work proposes that a regimen of repeated mild cold exposure may have protective effects against the development of type II diabetes mellitus (T2D) by activating brown adipose tissue (BAT) metabolism. BAT may protect against by increasing whole-body energy expenditure and insulin sensitivity. An evolutionary perspective, however, highlights several limitations of this hypothesis. Some individuals adapt to acute cold stress by constricting their blood vessels, which leads to high blood pressure. Thus, a regimen of repeated mild cooling may have beneficial health effects for some individuals and negative consequences for others. Future research should examine the relationships between low temperature exposure, BAT metabolism, blood pressure, and type II diabetes risk.

p38α blocks brown adipose tissue thermogenesis through p38δ inhibition

Adipose tissue has emerged as an important regulator of whole-body metabolism, and its capacity to dissipate energy in the form of heat has acquired a special relevance in recent years as potential treatment for obesity. In this context, the p38MAPK pathway has arisen as a key player in the thermogenic program because it is required for the activation of brown adipose tissue (BAT) thermogenesis and participates also in the transformation of white adipose tissue (WAT) into BAT-like depot called beige/brite tissue. Here, using mice that are deficient in p38α specifically in adipose tissue (p38αFab-KO), we unexpectedly found that lack of p38α protected against high-fat diet (HFD)-induced obesity. We also showed that p38αFab-KO mice presented higher energy expenditure due to increased BAT thermogenesis. Mechanistically, we found that lack of p38α resulted in the activation of the related protein kinase family member p38δ. Our results showed that p38δ is activated in BAT by cold exposure, and lack of this kinase specifically in adipose tissue (p38δ Fab-KO) resulted in overweight together with reduced energy expenditure and lower body and skin surface temperature in the BAT region. These observations indicate that p38α probably blocks BAT thermogenesis through p38δ inhibition. Consistent with the results obtained in animals, p38α was reduced in visceral and subcutaneous adipose tissue of subjects with obesity and was inversely correlated with body mass index (BMI). Altogether, we have elucidated a mechanism implicated in physiological BAT activation that has potential clinical implications for the treatment of obesity and related diseases such as diabetes.