The relationship between BMI, plasma leptin, insulin and proinsulin before and after laparoscopic adjustable gastric banding

Background: Morbid obesity is associated with over-secretion of leptin and insulin, and predisposes to development of carbohydrate intolerance. In the current study, we explored the impact of BMI after laparoscopic adjustable gastric banding (LAGB) on leptin, insulin and proinsulin levels. Methods: 23 obese patients (8 males, 15 females) were included in the study. Their mean age was 36±6 yrs (range 21-56 yrs). Blood samples were collected for measurement of plasma leptin, insulin and proinsulin before and 6 and 14 months after LAGB. Results: Mean BMI before surgery was 46.04 ± 4.44 kg/m ², with significant and equal reduction of 18% in each of the follow-up periods, with total BMI reduction of 33% (P<.0001). The levels of circulating leptin, insulin and proinsulin before intervention were 119.3 ± 53.1 ng/ml, 159 ± 13 pmol/l, and 36.36 ± 23.06 pmol/l respectively. Despite an equal BMI reduction in the 2 follow-up periods, the most significant decrease in hormone levels was observed in the immediate post-operative period (54, 53, and 45%, respectively), when compared to the second follow-up period (15,30,10%, respectively). The highest total decline in hormone level of 70% was obtained with insulin, compared to 52% in leptin, and 50% in proinsulin. Despite the significant decrease in proinsulin and insulin levels, their ratio increased from 0.22, to 0.28 and 0.36 after LAGB. Unlike insulin and proinsulin, leptin levels strongly and persistently correlated with BMI during the study. Conclusion: Following LAGB, weight loss was associated with decreased levels of circulating leptin, insulin and proinsulin, most prominent in the first follow-up period. Unlike insulin and proinsulin, leptin showed the most significant and persistent correlation with BMI, suggesting that morbid obesity acts through different feedback hormonal mechanisms which are probably not regulated only by absolute weight loss. Longer follow-up and larger numbers of patients are needed to clarify long-term hormonal profile, as well as the beneficial lasting effects of such interventions.