The common belief is that macrophages, a class of white blood cells, play a major role in thermogenesis, how the body regulates its production of heat, but a new study suggests that the main driver of thermogenesis is the sympathetic nervous system, which is chiefly controlled by the brain.
The ability to generate heat is critical for the survival of warm-blooded animals, including humans, as it prevents death by hypothermia. The new study focused on catecholamines, hormones released by the sympathetic nervous system to activate brown fat tissue. Brown adipose tissue is a type of fat tissue that burns energy to produce heat and keep us warm. Catecholamines can also convert white fat tissue, the more familiar kind of fat tissue that stores lipids, into a tissue that resembles brown fat.
The researchers tested whether macrophages could provide an alternative source of catecholamines, as had been proposed in recent years. According to Christoph Buettner, MD, PhD, senior author of the study in Nature Medicine and Professor of Medicine at Mount Sinai, while a lot of effort has been invested in targeting the immune system to cure diabetes and insulin resistance, as of yet there are no anti-inflammatory drugs that have been shown to work well in humans with metabolic disease. "Our study suggests that perhaps the key to combating the devastating effects of diabetes and obesity in humans is to restore the control of thermogenesis and metabolism by the brain and the autonomic nervous system."