Plasma leptin levels after biliopancreatic diversion: Dissociation with body mass index

Human obesity is associated with increased leptin levels, related to body c omposition and fat mass (FM). Insulin has been suggested to be a regulator of in vivo leptin secretion. To further investigate the relationships betwe en insulin and leptin levels in human obesity, we have studied 10 obese fem ales, aged 26-57 yr [body mass index (BMI), 42.9 +/- 6.3], successfully tre ated by biliopancreatic (BPD) diversion, in an early postoperative period ( 2 months after surgery, post-BPD I; BMI, 37.2 +/- 7.5) and a late postopera tive period (16-24 months after surgery; BMI, 27.6 +/- 3.96). Fourteen norm al female subjects (18-59 yr; BMI, 27.9 +/- 1.4 kg/m(2)) were studied as co ntrols. ln pre-BPD obese subjects, leptin levels were higher than those in controls (60.5 +/- 18.8 vs. 28.7 +/- 4.8 ng/mL; P < 0.001). BMI and insulin levels were also significantly greater (P < 0.0001 and P < 0.03, respectiv ely). After surgery, the three parameters considered significantly decrease d (P = 0.0007 for BMI, P < 0.0001 for leptin, and P = 0.038 for insulin, us ing Friedman's test for repeated data). Concerning the correlation between leptin and FM in our patients, control subjects and pre-BPD subjects confir med the correlation found in the general population (r = 0.78; P < 0.01). O n the contrary, post-BPD patients at 2 months lay outside the general corre lation between FM and leptin; in fact, patients with low leptin levels stil l had a high FM. Moreover, in the post-BPD patients there was no longer a s ignificant correlation between FM and leptin. Concerning the correlation be tween insulin and leptin levels, a significant correlation was present in c ontrol subjects and pre-BPD patients (r = 0.46; P < 0.05). Using correlatio n analysis for repeated measures in surgically treated obese patients, a si gnificant correlation within the subjects was present (r = 0.91; P < 0.0001 ). After operation, BMI and leptin levels had a different pattern of decrea se; leptin decreased rapidly, without correlation with BMT, indicating that body composition is not the only factor regulating leptin levels. The cons istent correlation with insulin levels suggests an important interaction be tween these two hormones in post-BPD obese subjects.