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, Orexin DEC ) and (ii)>10% Orexin increase (n = 20, Orexin INC ), 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 Orexin DEC 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 Orexin INC group remaining lower than the Orexin DEC 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 Orexin INC group relative to Orexin DEC group. Conclusion Rapid postoperative increases in plasma Orexin are associated with better improvement of glucose and lipid profiles following bariatric surgery.