Adipose tissue metabolism in benign symmetric lipomatosis

Type 2 benign symmetric lipomatosis (BSL) is characterized by abnormal grow th of adipose tissue in the upper back, deltoid region, upper arms, hips, a nd upper thigh region. Studies of lipomatous tissue in vitro have suggested that defective lipolysis may account for excess fat accumulation; however, in vivo adipose tissue metabolism has not been evaluated. We measured syst emic adipose tissue lipolysis and regional adipose tissue fatty acid uptake in a patient with type 2 BSL scheduled for elective brachioplasty. We foun d increased, rather than decreased, rates of systemic free fatty acid relea se coupled with normal fatty acid oxidation. The uptake of fatty acids was 19% greater in deltoid region lipomatous tissue than in abdominal sc fat, w hereas in control studies the relative uptake of fatty acids in deltoid fat averaged 29% less than that in abdominal fat. Adipocyte size was smaller t han expected in lipomatous tissue. These results suggest that type 2 BSL is a hyperplastic adipose tissue abnormality that does not impair systemic li polysis. The pathophysiology appears similar to what has been termed hyperp lastic obesity. A better understanding of this condition could lead to insi ghts into the mechanisms of hyperplastic obesity.