Effects Of Roux-en-Y Gastric Bypass Surgery On Bone Metabolism In Obese Chinese With Type 2 Diabetes

Objective We aim to assess the effects of Roux-en-Y gastric bypass surgery(RYGB)on bone metabolism on Chinese obese individuals with type 2 diabetes mellitus(T2DM).Two ghrelin gene products,namely unacylated ghrelin(UAG)and obestatin,were evaluated the roles in this pathological process to provide a theoretical basis for the prevention and treatment of abnormal bone metabolism after RYGB.Methods It was a single-center,retrospective cohort study.From January 2013 to January 2017,30 patients with obesity and T2DM who had undergone RYGB were enrolled in the Sixth People’s Hospital affiliated to Shanghai Jiaotong University.Blood samples were collected from each patient preoperatively,6,12 and 24 months postoperatively.Changes in anthropometric parameters,metabolic indexes and serum UAG and obestatin were assessed.BMD at lumbar spine(LS),femoral neck(FN)and total hip(TH)were identified by Dual-energy X-ray absorptiometry(DXA).Results RYGB resulted in statistical reductions of BMD in three different skeletal parts.After the first 6 months,BMD began to reduce and maintained a declining trend until 24 months postoperatively.Comparing to baseline,the maximal reduction of BMD was as high as 10.28%in total hip.The plasma concentration of UAG increased after 6 months(51.61±55.21 versus 71.95±64.91 pg/ml;p<0.01),as well as the serum obestatin level(1.65±0.88 versus 1.71±0.99 ng/ml;p>0.05).Although there was a slight drop of both two peptides in the first year,but were still above the baseline.Notably,in the second year,UAG and obestatin rose to their peak values respectively(91.90±77.11 pg/ml and 1.74±1.09 ng/ml).Additionally,Postoperative serum β-CTX,N-MID,PTH,ALP and 25(OH)D were significantly elevated,but there was no significant difference in blood calcium and blood phosphorus.There was a negative correlation between UAG and BMD in all sites.Multiple linear regression analysis showed that the UAG level was the independent parameter associated with BMD at baseline(FN:β=-0.407,p=0.012 and TH:β=-0.396,p=0.030 respectively),as well as the changes of UAG was independently related with reduction percentage of LS BMD after 24 months(p=-0.379,p=0.046).Conclusions The reduction of BMD in obese Chinese with T2DM was observed after RYGB.The pronounced increase of serum UAG acts as an independent risk factor for the decrease of BMD.