Reduced plasma leptin concentrations in bulimia nervosa

Leptin is a protein produced by the ob-ob gene which inhibits food intake. Plasma levels have previously been reported to be altered in obesity and an orexia nervosa (AN) but not bulimia nervosa (BN). We measured fasting plasm a leptin levels by radioimmunoassay in 53 subjects carefully studied at NIM H, including 37 women meeting DSM-III-R criteria for BN [10 with concurrent AN (body mass index (BMI)=14.1+/-1.4), 27 without AN (BMI=20.4+/-1.6)] and 16 normal control women (NCs) (BMI=21.1+/-2.0). Patients were medication-f ree and abstinent from bingeing and purging for three to four weeks prior t o study. Plasma leptin levels were significantly correlated to BMI (r=0.41, P<0.002), weight (kg, r=0.43, P<0.001), and percent average body weight (% ABW, r=0.45, P<0.001) in the total group. Plasma leptin levels were lower i n the BN subjects (3.4+/-2.5 ng/ml) compared to the NCs (6.1+/-2.6 ng/ml, P <0.001, ANCOVA) even after controlling for BMI and weight. There was no sig nificant difference between BN subjects with AN (n=10, 2.6+/-2.6 ng/ml) and those without AN (n=27, 3.8+/-2.4 ng/ml), despite lower BMI in BN with AN. Furthermore, leptin levels were decreased in BN without AN compared with h ealthy controls, even though BMI was comparable in these two subgroups. Pla sma leptin concentrations were negatively correlated with baseline plasma c ortisol levels (n=49, r=-0.49, P<0.001) and positively correlated with prol actin responses following L-tryptophan (n=49, r=0.37, P<0.009) and m-chloro phenylpiperazine (n=52, r=0.24, P<0.09). This is the first known report of decreased plasma leptin levels in BN. The decrement in leptin concentration is not related to BMI, body weight, or the presence or absence of BN. HPA axis activation as well as serotonin dysregulation may be related to decrea sed leptin levels, which may in turn contribute to disinhibited eating in B N. Although current leptin levels were not correlated with self-reported pr evious binge frequency, the role of leptin in the pathophysiology of BN des erves further study. (C) 2000 Elsevier Science Ltd. All rights reserved.