EFFECT OF BODY-WEIGHT AND CALORIC RESTRICTION ON SERUM COMPLEMENT PROTEINS, INCLUDING FACTOR-D ADIPSIN - STUDIES IN ANOREXIA-NERVOSA AND OBESITY

Complement plays important roles in host immune defences, and recent s tudies suggest that adipose tissue is an important site of production for some complement proteins. Starvation has been associated with low complement levels, but studied populations have usually had concomitan t opportunistic infections or other conditions which might affect comp lement levels. To determine the impact of body weight and changes in b ody weight on serum complement, we investigated levels of complement p roteins in otherwise healthy patients with a wide range of body weight s, including patients with anorexia nervosa before and after treatment , obese dieters before and after weight loss, and normal weight contro ls. We found that complement proteins of the alternative pathway (C3, B, and D), alternative pathway haemolytic activity (AP50) and the inhi bitors H and I were low in starving anorectics and normalized with wei ght gain. C3a levels were comparable in anorectics at low weight and a fter weight gain, indicating that low serum complement levels were att ributable to hypoproduction and not complement cascade activation with consumption. Further, levels of C3, B, AP50, H and I, but not D, were higher than controls in obese patients and decreased toward normal af ter weight loss. Overall, percentage of ideal body weight, changes in body weight, and serum transferrin were each highly correlated with se rum levels of complement proteins. We conclude that levels of alternat ive pathway complement components are determined in part by factors th at influence body weight and by weight changes, possibly due to change s in production in adipose tissue or at other sites.