Acute Post-Bariatric Surgery Increase in Orexin Levels Associates with Preferential Lipid Profile Improvement

Context: Orexin is a recently identified neuropeptide hormone. Objectives: Acute and long-term post-bariatric changes in Orexin and relationship to post-operative metabolic outcomes. Design and Participants: Men and women undergoing biliopancreatic diversion with duodenal switch bariatric surgery (n = 76, BMI >= 35 kg/m(2)) were evaluated for body composition and plasma parameters at baseline, acutely (1 and 5 days) and long-term (6 and 12 months) post-surgery. Setting: University Hospital Centre, Canada. Interventions and Main Outcome Measures: Groups were subdivided based on acute (average 1 and 5 day) changes in Orexin prior to weight loss: (i). 10% Orexin decrease (n = 33, OrexinDEC) and (ii). 10% Orexin increase (n = 20, OrexinINC), to evaluate impact on long-term changes. Results: Both groups had comparable preoperative Orexin levels, BMI, age, sex distribution, diabetes and lipid lowering medication, plasma glucose and lipid parameters except for apolipoproteinB (p < 0.007). Orexin increase was rapid and maintained throughout one year, while OrexinDEC subjects remained significantly lower throughout. Over 12 months, changes in BMI, fat mass, and % fat mass were comparable. Fasting glucose and insulin increased immediately 1-day post-operatively, decreasing rapidly (5-day) and declining thereafter with the OrexinINC group remaining lower than the OrexinDEC group throughout (p = 0.001). Similarly, plasma cholesterol, triglyceride, LDL-C and HDL-C decreased at 1-day, increased slightly (5-day), except HDL-C, then decreased over 1 year, with greater decreases in OrexinINC group relative to OrexinDEC group. Conclusion: Rapid postoperative increases in plasma Orexin are associated with better improvement of glucose and lipid profiles following bariatric surgery.