SERUM IMMUNOREACTIVE LEPTIN CONCENTRATIONS IN PATIENTS WITH ANOREXIA-NERVOSA BEFORE AND AFTER PARTIAL WEIGHT RECOVERY

Leptin, the product of the ob gene, is a recently discovered hormone s ecreted by adipocytes. Serum leptin concentrations increase in correla tion with the percentage of body fat, but besides that little is known about the physiological actions of leptin in humans. In order to unde rstand the role of leptin in severe malnutrition, in the present work PO patients recently diagnosed with anorexia nervosa were studied both before and 2 months later, after partial weight recovery, and were co mpared with 18 normal-weight women as controls. Leptin was measured by a newly developed radioimmunoassay and both IGF-I and IGFBP-3 were me asured by commercial radioimmunoassays. The mean (+/-SE) serum leptin concentrations (in mu g/liter) were 18.1 +/- 2.0 in control women with BMI of 21.1 +/- 0.3, significantly higher (P < 0.01) than that in the anorexia nervosa patients at diagnosis (2.2 +/- 0.1, BMI 15.3 +/- 0.6 ). These differences were also observed in IGF-I values (mu g/liter) t hat were 228.0 +/- 14.6 in controls and 157.4 +/- 28.7 in anorexia ner vosa patients (P < 0.02). No differences were observed in IGF-BP3. Aft er treatment, patients with anorexia nervosa experienced an increase i n BMI (17.1 +/- 0.5, P < 0.0001 vs before) although they were still un derweight. The partial recovery in weight led to a complete normalizat ion of IGF-I levels (214.0 +/- 21.0 mu g/liter) and to an enhancement in leptin levels (3.3 +/- 0.5 mu g/liter; P < 8.03 vs before treatment ), though still lower than these in normal-weight women (P < 0.05). In dividually analyzed, a large dispersion was observed in control subjec ts, with leptin levels ranging from 5.5 to 38.7 mu g/liter, while in a ll anorexia nervosa patients leptin levels were under 3 mu g/liter. A treatanent-induced increase in body weight led to an increase in lepti n levels in 7 out of the 10 anorexia nervosa patients studied and the 3 patients with no increase in leptin were all initially under the 14. 5 BMI. In conclusion, leptin levels are severely reduced in anorexia n ervosa patients with severe malnutrition, and a significant rise occur red after partial weight recovery. There seems to be a level of BMI be low which leptin levels do not drop further but also do not increase d espite weight gain, While IGF-I reflects the energy intake of the prev ious few vs weeks, the serum leptin concentration reflects the true st atus of the adipose stores, a fact that has useful clinical implicatio ns. (C) 1997 Academic Press.