The effect of bariatric surgery on serum TRAIL and osteoprotegerin levels in obesity complicated by glucose disorders

SummaryBackground and aimsBariatric surgery improves health outcomes in the obese and reduces some aspects of obesity-associated systemic inflammation. Little is known however about its effects on circulating TNF-related apoptosis-inducing ligand (TRAIL) and osteoprotegerin level, which regulate apoptosis and are implicated in atherogenesis. Our objective was to identify whether circulating TRAIL and osteoprotegerin levels are influenced by the energy restriction and weight loss that follows bariatric surgery in obese patients with glucose disorders.Methods15 morbidly obese individuals with type 2 diabetes mellitus (T2D) or glucose intolerance were recruited for bariatric surgery. Participants were assessed for weight, waist circumference and BMI at baseline, then 2 and 12 weeks following energy restriction with bariatric surgery. Laparoscopic adjustable gastric band placement was performed. Fasted blood samples were collected and an oral glucose tolerance test was performed at each visit. Metabolic parameters and plasma chemistries were assessed. Circulating TRAIL, osteoprotegerin and leptin levels were measured.ResultsA significant increase in circulating TRAIL levels was observed at 12 weeks relative to baseline in participants who suppressed leptin levels. The percentage change in TRAIL was inversely related to the percentage change in fasting insulin and HOMA-β. In contrast, osteoprotegerin levels and the osteoprotegerin:TRAIL ratio were significantly reduced following bariatric surgery. The change in osteoprotegerin:TRAIL ratio positively related to the percentage change in fasting glucose.ConclusionsEnergy restriction after bariatric surgery is associated with increased circulating TRAIL levels and reduced osteoprotegerin levels and osteoprotegerin:TRAIL ratio in obese humans with dysglycaemia. Changes in the TRAIL and osteoprotegerin:TRAIL ratio related to changes in fasting insulin, suggesting a possible role in glucose improvements after bariatric surgery. Mechanistic studies will clarify the role of TRAIL and osteoprotegerin in health and disease.