Brown fat or brown adipose tissue (BAT) is metabolically active fat. It contains mitochondria, which contribute the brown color due to their iron content. Much has been learned about brown fat in the past 5-10 years, including that there is more than one type of this adipose tissue.

Not only is there brown, but also beige fat, or as the authors of this work (Schultz T.J., et al.) call it, recruitable brown adipose tissue (rBAT). The authors contrast the two brown fats by noting that constitutive brown adipose tissue (cBAT) is embryonic in origin and is found in the interscapular region of mice. rBAT is found in white adipose tissue (WAT) and in skeletal muscle in mice.

Furthermore,  these two  brown fats are from different cellular ancestors, cBAT coming from progenitors of skeletal muscle, while rBAT is derived from a non-myogenic lineage.

Bone morphogenetic proteins (BMPs) regulate the formation and thermoregulatory activity of BAT. In this report, the authors blocked a receptor for BMP, BMPR1A, by generating a mouse model that was missing BMPR1A in all cells carrying the myogenic marker Myf5+. Continue reading “Browning of Fat as a Tool in Obesity Resistance”