Adipose tissue metabolism in benign symmetric lipomatosis

Type 2 benign symmetric lipomatosis (BSL) is characterized by abnormal growth of adipose tissue in the upper back, deltoid region, upper arms, hips, and 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 systemic adipose tissue lipolysis and regional adipose tissue fatty acid uptake in a patient with type 2 BSL scheduled for elective brachioplasty. We found increased, rather than decreased, rates of systemic free fatty acid release coupled with normal fatty acid oxidation. The uptake of fatty acids was 19% greater in deltoid region lipomatous tissue than in abdominal sc fat, whereas in control studies the relative uptake of fatty acids in deltoid fat averaged 29% less than that in abdominal fat. Adipocyte size was smaller than expected in lipomatous tissue. These results suggest that type 2 BSL is a hyperplastic adipose tissue abnormality that does not impair systemic lipolysis. The pathophysiology appears similar to what has been termed hyperplastic obesity. A better understanding of this condition could lead to insights into the mechanisms of hyperplastic obesity.