Location: Obesity and Metabolism ResearchTitle: Effects of endocrine and inflammatory changes on markers of bone turnover following Roux-en-Y gastric bypass surgery
|ROGERS, TARA - University Of California|
|SWARBRICK, MICHAEL - Westmead Millenium Institute Centre For Diabetes And Obesity|
|WOLFE, BRUCE - Oregon Health & Science University|
|ALI, MOHAMED - University Of California|
|BLANKENSHIP, JEANNE - Academy Of Nutrition And Dietetics|
|STANHOPE, KIMBER - University Of California|
|HAVEL, PETER - University Of California|
|Van Loan, Marta|
Submitted to: Medical Science Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2015
Publication Date: 11/25/2015
Citation: Rogers, T.S., Swarbrick, M.M., Wolfe, B.M., Ali, M.R., Blankenship, J., Stanhope, K.L., Havel, P.J., Van Loan, M.D. 2015. Effects of endocrine and inflammatory changes on markers of bone turnover following Roux-en-Y gastric bypass surgery. Medical Science Research. doi: 10.18103/mra.v2i2.329.
Interpretive Summary: For many obese individual bariatric surgery is used to significantly reduce body weight and fat, normalize a variety of endocrine hormones and inflammatory processes. However, the surgery does have its drawbacks. One example is weight loss induced bone loss in a group of individuals at-risk for osteoporosis due to years of "yo-yo" dieting. We examined changes in bone metabolism in a group of 20 obese individuals before and for 1 year following bariatric surgery and the associations with changes in endocrine hormones and inflammatory markers. We found that before surgery bone formation was predicted from body weight and cortisol (a stress hormone) while bone resorption was predicted from insulin and ghrelin - endocrine hormones. However, during the 1 year follow up period we found no consistent set of endocrine or inflammatory markers that tracked changes in bone metabolism suggesting that bone metabolism remained disrupted 12 months following bariatric surgery. These findings suggest that the long-term consequence of RYGB related weight loss on bone metabolism is more complicated than previously believed. Additional research over an extended period of time is needed in order to understand these complex interactions.
Technical Abstract: Bariatric surgery is associated with increased bone turnover. The mechanisms involved are unclear but may involve nutrition, mechanical unloading, altered secretion of gastrointestinal and adipose hormones and changes in inflammatory status leading to weight loss induced bone loss. We assessed markers of bone turnover in obese adults (F=19, M=1; BMI 46.5 + 7.9 kg/m2) following Roux-en-Y gastric bypass surgery (RYGBP), and investigated their relationship to endocrine and inflammatory markers following this procedure. Bone specific alkaline phosphatase (BAP) and N-telopeptide of type I collagen (NTx) were measured as markers of bone formation and resorption, respectively. Repeated measures analysis of variance (ANOVA) was used to evaluate differences over time. Step-wise multiple regression was used to model the contributions of body weight and composition, endocrine and inflammatory markers to bone metabolism (expressed as BAP/NTX). BAP/ NTX declined significantly (p<0.05) within 1 month after surgery and remained low for 12 months post RYGBP. Before surgery, glucose (partial R2 = 0.23, p=0.03) and non-esterified fatty acids (FFA) (partial R2 = 0.12, p=0.09) explained 35% of the variance in BAP/NTX (model R2 = 0.35). Twelve months after RYGBP, 48% of variance in BAP/NTx was explained by glucose (partial R2 = 0.21, p=0.04), insulin (partial R2 = 0.17, p=0.05) and C-reactive protein (CRP) (partial R2 = 0.10, p=0.09; model R2 =0.48). Changes in body weight and composition were not significantly related to the BAP/NTX ratio 12 months after surgery. In conclusion, the use of BAP/Ntx ratio and stepwise regression models can be used to explore the inter-relationships among bone metabolism, endocrine and inflammatory markers following RYGBP related bone loss over an extended period of persistent weight loss.