Therapeutic Evaluation Of Bariatric Surgery Based On Body Composition Measurement

Background:Obesity and type 2 diabetes mellitus(T2DM)is significant public health problems affecting human health.Body composition is strongly associated with the development of obesity and T2DM.Bariatric surgery is the most effective strategy for the treatment of obesity and T2DM,however,the value of body composition measurement in therapeutic evaluation of bariatric surgery has not been well investigated.This project will focus on body composition measurement in a series of studies to explore the significance of body composition measurement in the comparison of surgical procedures,assessment of composition changes,analysis of treatment mechanisms and prediction of clinical outcomes,in order to provide new evidence-based medical evidence for therapeutic evaluation of bariatric surgery.Objectives:(1)To compare the effects of Roux-en-Y gastric bypass(RYGB)and sleeve gastrectomy(SG)on body composition by a meta-analysis.(2)To assess the changes in body composition and distribution after bariatric surgery and their influencing factors and to analyze correlations between body composition and clinical outcomes by a retrospective cohort study.(3)To explore the differential mobilization of site-specific trunk adipose depots after bariatric surgery and to analyze correlations between site-specific fat mobilization and clinical outcomes by a prospective cohort study.(4)To assess the predictive value of body composition and distribution for T2DM remission after bariatric surgery.Methods:(1)By searching Pub Med,EMBASE,the Cochrane,and Clinical Trials ending in December 2021 for all eligible studies,high-quality studies using dual-energy X-ray absorptiometry(DXA)for body composition measurement were included,weighted mean differences and95%confidence intervals were from a random-effects model.(2)T2DM patients assessing changes in body composition with DXA were included to analyze changes in whole-body and regional body composition after bariatric surgery,subgroup analysis was used to explore the effects of bariatric procedures,body mass index(BMI)and gender on changes in body composition,and correlation analysis was used to assess correlations between body composition and clinical outcomes.(3)Patients undergoing bariatric surgery from 24 May 2022 to 20October 2022 were recruited,and magnetic resonance imaging was used to estimate subcutaneous fat area(SFA),visceral fat area(VFA),hepatic and pancreatic proton density fat fraction(PDFF)at baseline and 3 months after surgery.(4)T2DM patients assessing preoperative body composition with DXA were included to analyze the predictive value of body fat percentage(%BF),skeletal muscle index,Android/Gynoid fat ratio and trunk/leg fat ratio for T2DM remission,and develop prediction model based on body composition measurement.Results:(1)Of 17 eligible studies in the meta-analysis,484 patients underwent RYGB and 347 patients underwent SG.For patients with a BMI>35 kg/m~2,RYGB resulted in a more substantial reduction of BMI(-14.13[-14.74,-13.53]kg/m~2 versus-11.96[-12.81,-11.11]kg/m~2,P<0.001)and fat mass(FM)(-26.22[-28.31,-24.12]kg versus-21.50[-25.52,-17.48]kg,P<0.05),and SG resulted in a more substantial reduction of muscle mass(MM)(-10.12[-11.55,-8.68]kg versus-8.28[-9.33,-7.22]kg,P<0.05).(2)A total of 54 T2DM patients were included in this study.After bariatric surgery,both FM and MM significantly decreased,percentage FM losses were more remarkable in Android than in Gynoid,legs and arms,percentage FM losses were more remarkable in trunk than Gynoid,and the proportion of Android FM to whole-body FM was significantly lower.RYGB resulted in a greater percentage%BF loss,especially beneficial to trunk and Android%BF loss.SG resulted in greater percentage losses in MM,trunk fat free mass(FFM),Android FFM and Gynoid FFM.Patients with a BMI≥27.5 kg/m~2 had greater percentage losses in MM,leg FFM,trunk FFM,Android FFM,and Gynoid FFM.Male patients had greater percentage losses in FM and%BF.Trunk FM,Android FM,Δtrunk FM,andΔAndroid FM were significantly and positively associated withΔfasting plasma glucose;Δtrunk FM andΔAndroid FM were significantly and positively associated withΔhomeostatic model assessment of insulin resistance(HOMA-IR).(3)A total of 50 patients were included in the final analysis cohort,the median age was 29.5(23.0-37.0)years,the median BMI was 37.9(33.7-42.2)kg/m~2 and 36%were men.After bariatric surgery,percentage losses in hepatic PDFF,pancreatic PDFF,VFA,and SFA were 69.9%(47.3%-82.4%),51.4%(37.0%-63.4%),36.3%(30.0%-43.6%),and 23.0%(17.2%-32.7%)in sequence,with significantly differential fat mobilization among different sites(P<0.001).Both Pearson correlation analysis and partial correlation analysis indicated that,ΔVFA was positively correlated withΔglycated hemoglobin(r=0.374;partial r=0.446),andΔhepatic PDFF was positively correlated withΔHOMA-IR(r=0.385;partial r=0.402).The percentage hepatic PDFF loss was higher in T2DM patients and pre-T2DM patients than in patients with normal glucose metabolism,and the percentage pancreatic PDFF loss was higher in T2DM patients than in patients with normal glucose metabolism.Patients with a BMI<32.5kg/m~2 had higher percentage losses in SFA,VFA,hepatic PDFF and pancreatic PDFF than patients with BMI≥37.5 kg/m~2,the percentage VFA loss was higher in patients with a BMI<32.5 kg/m~2 than in patients with a 32.5 kg/m~2≤BMI<37.5 kg/m~2,the percentage VFA loss was higher in patients with a 32.5 kg/m~2≤BMI<37.5 kg/m~2 than in patients with a BMI≥37.5 kg/m~2,and the percentage pancreatic PDFF loss was higher in men than in women.(4)A total of 72 T2DM patients were included in this study,40patients(56%)achieved remission.Patients in the remission group had higher%BF and lower trunk/leg fat ratio.According to the area under the receiver operating characteristic curve(AUC),trunk/leg fat ratio(AUC0.784)performed better than BMI(AUC 0.690)and%BF(AUC 0.688)for predicting T2DM remission;the prediction model(AUC 0.883)including age,duration of T2DM,and trunk/leg fat ratio performed better than the ABCD score(AUC 0.809)and the Dia Rem score(AUC 0.792).A nonlinear relationship was observed between trunk/leg fat ratio and BMI.Conclusions:(1)For patients with a BMI>35 kg/m~2,RYGB resulted in a more substantial reduction of BMI and FM,while SG resulted in a more substantial reduction of MM at 1 year after bariatric surgery.(2)Bariatric surgery significantly reduces FM and MM,and preferentially mobilizes trunk FM and Android FM to promote metabolically healthy fat distribution.Bariatric procedures,BMI and gender significantly affects changes in body composition after bariatric surgery.Preferential mobilization of trunk FM and Android FM may be a central factor for bariatric surgery improving glucose metabolism.(3)Bariatric surgery preferentially mobilizes hepatic fat,followed by pancreatic fat and visceral adipose tissue(VAT),while SAT is mobilized to the least extent.Reduction in VAT and hepatic fat has an independent contribution to the improvement of glucose metabolism.The most significant improvement of ectopic fat deposition after bariatric surgery is seen in male patients with a BMI<32.5 kg/m~2 and T2DM.(4)Trunk/leg fat ratio is an effective predictor for T2DM remission after bariatric surgery.The prediction model based on age,duration of T2DM and trunk/leg fat ratio can accurately predict the probability of T2DM remission after bariatric surgery.