A sideways glance: does the color matter? A revised model of the origin of white and brown fat cells

Abstract

Springer-Verlag 2008 Obesity, a major factor in the development of common medical conditions like type 2 diabetes, dislipidemias, atherosclerosis and cardiovascular disease, has become a global epidemic. These conditions occur mainly as a result of insulin resistance induced by obesity. Obesity develops when energy intake exceeds energy expenditure, although it depends not only on the balance between food intake and calories utilization, but also on the balance between white adipose tissue where energy is stored, and brown adipose tissue where calories are burned. In the past 20 years much information has been published on the role of factors controlling food intake and energy expenditure in body weight regulation, yet little information is available to understand the mechanistic differences between brown and white fat cells. These two cell types give rise to separate tissues, although sometimes they are intermingled. White adipose tissue in humans is dispersed throughout the body with major intraabdominal depots around the omentum, intestines, perirenal areas, as well as in subcutaneous depots in the buttocks, thighs and abdomen. Brown fat is commonly found in infants mostly concentrated in the interscapular region. This latter cell type helps generating enough heat for the child’s survival, but it is difficult to find in adults, where it is concentrated in small amount in the cervical, supraclavicular and paravertebral areas. White fat cells accumulate energy from food as tryglycerides stored within a large fat droplet for later use. Brown fat cells also take up energy from food and generate heat by leaking hydrogen ions across the inner membrane of the mito