PLASMA LEPTIN IN CHRONIC INFLAMMATORY BOWEL-DISEASE AND HIV - IMPLICATIONS FOR THE PATHOGENESIS OF ANOREXIA AND WEIGHT-LOSS

1. Leptin inhibits food intake and is an important regulator of long-t erm energy balance. In rodents, plasma concentrations of leptin are in creased by administration of interleukin-1 and tumour necrosis factor. Hyperleptinaemia may mediate the anorexia and weight loss which is ob served in chronic infections and inflammatory conditions. 2. Plasma le ptin and soluble tumour necrosis factor receptor (sTNF-r55) concentrat ions were measured in patients with inflammatory bowel disease and acq uired immunodeficiency syndrome (AIDS), and healthy controls. 3. The p atients with AIDS were severely wasted [% body fat 12 (9-16); median ( interquartile range)] compared with those with inflammatory bowel dise ase [25.1 (19-31.5)] and control subjects [29.4 (23.6-37.8)]. Leptin c oncentrations were highly correlated with percentage body fat in contr ols (r = 0.74, P < 0.001) and patients with IBD (r = 0.73, P < 0.001) but not in the patients with AIDS (r = -0.024), Leptin concentrations were similar in the inflammatory bowel disease [4.8 (2.6-10.1) ng/ml] and control groups [8.0 (3.1-14.1) ng/ml] but were significantly lower (P < 0.05) in patients with AIDS [1.8 (1.5-2.3) ng/ml] after 23 patie nts were matched for sex and percentage body fat in patients with infl ammatory bowel disease [2.4 (1.8-4.1) ng/ml]. Plasma concentrations of sTNF-r55 were higher in both the patients with inflammatory bowel dis ease [0.19 (0.16-0.23) ng/ml] and those with AIDS [4.8 (2.8-7.3) ng/ml ] compared with controls [0.14 (0.09-0.16) ng/ml] but were not correla ted with either percentage body fat or plasma leptin concentrations. 4 . Hyperleptinaemia does not appear to mediate the anorexia and weight loss associated with inflammatory bowel disease and AIDS. In patients with AIDS with extreme wasting there was no relationship between body fat and leptin and this may be related to the rapid weight loss which occurs in these patients.