An investigation of the neural mechanisms underlying the efficacy of the adjustable gastric band

Background: Bariatric surgery is currently the only effective and durable means of treating morbid obesity. While views of restriction and malabsorption as mechanisms are no longer applied to adjustable gastric banding (AGB), roux-en-Y gastric bypass and sleeve gastrectomy, the exact means via which each is effective remains unclear. The intention of this study is to define the role of sensory vagal fibers in the efficacy of the AGB using capsaicin to eliminate unmyelinated afferent fibers in the vagus nerve. Methods: Two cohorts of obese male Sprague Dawley rats were fitted with a miniaturized AGB at the gastroesophageal junction or were sham operated. A range of parameters were measured in the first of these to assess the metabolic impact of AGB inflation on obese rats. The second group of rats were exposed to capsaicin either intraperitoneally (125mg/kg given in 3 doses over 48 hours), directly applied to the stomach (1% capsaicin) or administered a vehicle solution. The extent of the sensory fiber lesion was determined using the c-fiber mediated reduction in food intake caused by cholecystokinin (CCK, 6μg/kg) and by post mortem analysis of specialized sensory endings (intraganglionic laminar endings). The impact of capsaicin treatment on the efficacy of the AGB in terms of food intake, body weight and fat mass was established. Elevated levels of Fos protein were used as a marker of neural activation following inflation of the AGB. Results: AGB inflation caused a significant reduction in food intake, body weight and fat mass (P<.05) in obese rats. The effect of AGB on these parameters was prevented in capsaicin pre-treated (vagal sensory lesioned) rats. Elevations in neural activity in the nucleus of the solitary tract and parabrachial nucleus following AGB inflation were ameliorated in capsaicin treated rats. Conclusion: Vagal sensory fibers are integral to the efficacy of the AGB