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.