Wei-Jei Lee,Abdullah Almulaifi

Department of Surgery,Min-Sheng General Hospital,National Taiwan University,Taoyuan,Taiwan,China.

Recent advances in bariatric/metabolic surgery:appraisalof clinical evidence

Wei-Jei Lee?,Abdullah Almulaifi

Department of Surgery,Min-Sheng General Hospital,National Taiwan University,Taoyuan,Taiwan,China.

Obesity and associated type 2 diabetes mellitus(T2DM)are becoming a serious medicalissue worldwide. Bariatric surgery has been shown to be the mosteffective and durable therapy for the treatmentof morbid obese patients.Increasing data indicates bariatric surgery as metabolic surgery is an effective and novel therapy for not well controlled obese T2DM patients.The review of recent developments in bariatric/metabolic surgery covers 4 major fields.1)Improvement of safety:recent advances in laparoscopic/metabolic surgery has made this minimal invasive surgery more than ten times safer than a decade ago.The safety profile of laparoscopic/metabolic surgery is compatible with that of laparoscopic cholecystectomy now.2)New bariatric/metabolic surgery:laparoscopic sleeve gastrectomy(LSG)is becoming the leading bariatric surgery because of its simplicity and efficacy.Other new procedures,such as gastric plication,banded plication,single anastomosis(mini)gastric bypass and Duodeno-jejunal bypass with sleeve gastrectomy have all been accepted as treatment modalities for bariatric/metabolic surgery.3) Mechanism of bariatric/metabolic surgery:Restriction is the most important mechanism for bariatric surgery. Weightregain after bariatric surgery is usually associated with loss ofrestriction.Recentstudies demonstrated that gut hormone,microbiota and bile acid changes after bariatric surgery may play an important role in durable weight loss as wellasin T2DM remission.However,weightloss isstillthe cornerstone of T2DMremission aftermetabolic surgery.4)Patient selection:patients who may benefit most from bariatric surgery was found to be patients with insulin resistance.For Asian T2DMpatients,the indication ofmetabolic surgery has been setto those with notwell controlled(HbA1c＞7.5%)disease and with their BMI＞27.5 Kg/m2.A novel diabetes surgicalscore,ABCD score,is a simple system for predicting the success of surgicaltherapy for T2DM.

bariatric surgery,metabolic surgery,type 2 diabetes mellitus,advances

Introduction

Obesity and type 2 diabetes mellitus(T2DM)are becoming epidemic diseases worldwide[1,2].These two diseases are closely related and both are very difficult to treat[3,4].Bariatric surgery,aimed at weightreduction,has been proven to be a viable option for the treatmentof severe obesity in comparison to conservative methods,resulting in long-lasting weight loss, improved quality-of-life,and the resolution of obesityrelated co-morbidities[5].Among all of the obesityrelated co-morbidities,bariatric surgery hasbeen proven especially successfulin treating T2DM[6-8]in morbidly obese patients(BMI＞35 Kg/m2)as wellas preventing the developmentof T2DM[9].Recently,gastrointestinal metabolic surgery has been proposed as a new treatmentmodality for T2DM in patients with body mass index (BMI)＜35 Kg/m2[10].Severalrandomized trials have proven thatmetabolic surgery resulted in better glycemic control compared with medical treatment in T2DM patients with BMI＜35 Kg/m2[11-17].Therefore, itisnotsurprising thatthe numberofbariatric/metabolic surgeries worldwide has grown rapidly over the past decade,including Asia[18-22].The increasing acceptance ofbariatric/metabolic surgery deservesa detailed review and discussion.Therefore,we summarize the currently available randomized controlled trials and review articleson bariatric/metabolic surgery overthe pastdecade. The review will allow current and future bariatric/ metabolic surgeons to build a foundation of bariatric/ metabolic surgery and developmentof furtherclinical trials to provide more powerfulevidence in bariatric/ metabolic surgery.

Improved safety

The most important technique change in bariatric/ metabolic surgery is from open surgery to laparoscopic surgery.Many randomized trialshad proven the superity of laparoscopic bariatric surgery in reducing the impairment of post-operative pulmonary function, intra-operative blood loss,hospital stay,wound infection and incisional hernia rate,and quick return to work[22-24].An additionalbenefitof laparoscopic surgery overopen surgery is the decrease ofpostoperative venous thrombo-embolism[25].However,some adverse effects have been found,such as thatlaparoscopic gastric bypass resulted in decreased intra-operative urine output[26],transient postoperative elevation of liver enzymes[27],and decreased femoral venous flow[28]. These biologic changes may resultfrom the effectof intra-abdominal hypertension caused by pneumo-peritoneum which may influence the respiratory and abdominalorgan function[29].These findings highlight the importance avoiding prolonged operative time in older,more obese patients,and patients with unstable hemodynamic or chronic kidney disease.

A decade ago,the 30 day operation mortality forbariatric/metabolic surgery was up to 2%and 1-year mortality was up to 5%in USA[30].The operative risk was found to be closely related to surgeonˊs experience and hospitalvolume.Improvementin technology and experience has dramatically improved the safety ofthis procedure.Recentreports have confirmed thatbariatric/ metabolic surgery can be performed as safe as laparoscopic cholecystectomy with operation mortality around 0.1%[31,32].However,although the major complication rate was similar between the bariatric and metabolic surgery,patients who already had metabolic syndrome tended to develop more severe complications that resulted in highermortality rates.A recentreportfrom Inabetetal.had found thatbariatric surgery carried a three times higher risk in patients with metabolic syndrome compared with patients withoutmetabolic syndrome[32].The reason for the more severe complication in T2DM patients mightbe related to the compromised cardiovascular system and depressed immunity in patients with poorly controlled diabetes[33,34].

New bariatric/metabolic procedures

Laparoscopic gastric banding and gastric bypass are the two mostcommonly performed bariatric surgeries currently[18].The majorobstacle to laparoscopic adjustable gastric banding(LAGB)is the requirement of patient compliance and a high revision rate,resulting in a rapid decrease in the acceptance of LAGB worldwide[19].Laparoscopic sleeve gastrectomy(LSG),a vertical gastrectomy that leaves a narrow gastric tube along the lesser curvature of the stomach,has been accepted as a primary procedure for morbid obese patients recently because of its simplicity and effectiveness.The American College of Surgeons Bariatric Surgery Center Network has putitin the intermediate position between laparoscopic gastric banding and laparoscopic gastric bypass in term of reduction of BMI,complication rates and resolution of obesity related illness[35].Severalrandomized trials also demonstrated thatLSG has a similarefficacy ofweightreduction comparing to Roux-en-Ygastric bypass(RYGB)at short-to mid-term[36-38].The acceptance of LSGisespecially high in Asia because of the concern of remnant gastric cancer[39].LSG has now consisted more than 50%of the bariatric surgery in Asia and more than 70%in Japan where gastric cancer is the leading cancer death[20,40].However,the main long-term drawback of LSG is the development of gastro-esophagealreflux disease(GERD)in around 15%of the patients[41]. This remains to be an importantissue of LSG[42].

Laparoscopic gastric greater curvature side plication (LGGCP)is a new restrictive technique that was first reported in 1981 by Wilkinson[43]and more recently by Talepourand Amoi[44].Currently,LGGCP has been investigated as a novel bariatric surgery[45-48]and adopted forthe salvage offailed bariatric surgery,such as a dilated sleeve gastrectomy,pouch dilatation after gastric bypass or in adequ ate weigh t loss after LAGB[49].Combination of LAGB with LGGCP (LAGB-P)has recently been reported to increase weightloss after LAGB[50,51].However,long-term data is indicated before acceptthese restrictive novelprocedures as standard bariatric/metabolic surgery.

Another important change of technique is from two anastomosis Roux-en-Y reconstruction to single loop anstomosis technique.The elimination of one anastomosis may reduce operative time and decrease the possibility of surgically related complication. Laparoscopic single anastomosis(mini-)gastric bypass (SAGB),a sleeve gastric tube with a Billroth II loop bypass,had been proven to have a shorter operative time and lower complication rate comparing to RYGB in a randomized trial[52].At longer follow-up, SAGB still had the advantage of less revision surgery for intestinalobstruction comparing to RYGB[53,54].At the same time,another modified duodenal switch (DS)was proposed by Sanchez-Pernaute et al.by doing a single anastomosis DS,called single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-SG)[55,56].However,the major obstacles of DS are technicaldifficulty and the possibility oflong-term nutritional problems.A modified short DS has been proposed by Kasama etal.from Asia with a procedure called duodeno-jejunalbypass with sleeve gastrectomy (DJB-SG)[57].This procedure is specifically designed for metabolic surgery and was especially welcomed in Asia[58].A simplified DJB-SG by single anastomosis,SADJB-SG has also been reported recently[59].

Mechanisms of effect

The mostimportantmechanism for weight reduction is believed to be restriction and the accompanying reduced daily calories intake.A recentstudy has estimated thatthe mostimportantmechanism for the gold standard bariatric surgery,RYGB,is the reduced intake due to restriction and satiety and contributes about 75%of the effect[60].The restriction effect of RYGB is provided by a tiny gastric pouch and small outlet. In SAGB,the restriction is provided by the long sleeve tube,very similar in sleeve gastrectomy.The reason why LSG had a similar result to RYGB is that LSG may provide a better restriction than RYGB[35-37]. Therefore,the reason for weightregain after bariatric surgery is mainly contributed to lost restriction and the goalofrevision surgery is to rebuild the restriction.

The second importantmechanism of RYGB is from the duodeno-jejunal bypass which was estimated to contribute less than 25%of the efficacy[60].Exclusion of the duodenum from food stream may eliminate the physiologic response of duodenal gut hormone and related enzyme secretion(glucagon,cholecystokinin and bilio-pancreatic enzymes).The rapid food transit to distal gut induces a surge of distal gut hormone (GLP-1 and PYY)release[37,61,62].These two gut hormone responses were also called‘‘fore gut theory’’and‘‘hintguttheory’’which help in weightlossaswell T2DM remission[63].

Another mechanism involved is the gut microbiota. Recent studies have shown that the gut microbiota of obese human beings is distinct from thatof healthyweightindividuals[64,65].Changes in the gutmicrobiota might be responsible for the development of nonalcoholic fatty liver disease(NAFLD)and gastrointestinal symptoms[66].Probiotic agents were found to be helpful in treating irritable bowel syndrome and improving outcomes after gastric bypass surgery[67,68].

The mechanism of LSG is also intriguing.LSG was found nota pure restrictive bariatric procedure because some complex gut hormone changes were involved with LSG.The firstone is the markedly reduced ghrelin levelafter complete removalof gastric fundus,site of production of hormone ghrelin,will help in the weightloss[60,62,63].Another one is the quickly elevated ofpost-meal GLP-1 and PYY response induced by the rapid boweltransittime after LSG which may help in weight reduction and metabolic control[37,60,63]. However,a recent study by Randy has shown that neither ghrelin nor GLP-1 played an essential role in LSG.They found that bile acid is the key player in weightloss after LSG[69].Further studies are indicated to elucidate this intrigue question aboutthe mechanism of LSG.

Table 1 Randomized controlled trials for metabolic surgery in T2DM with BMI＜35 Kg/m2

Although LSG had a similar weight loss comparing to gastric bypass,severalrandomized trials have shown that procedure with duodenal exclusion had a higher rate in diabetes remission or off medication than those without duodenal exclusion,especially in lower BMI diabetics[12,13,17].The reason is thatduodenalexclusion may have a significantrole in diabetes treatmentother than weightreduction.The recentstudy has identified some possible duodenal factor related to duodenal exclusion[70].Therefore,although LSG may be the first choice for bariatric surgery,gastric bypass may be a preferred metabolic surgery for the treatment of T2DM in patients with BMI＜35 Kg/m2.Furtherstudies are indicated to elucidate the mechanism of duodenum exclusion and develop possible new treatments for T2DM.

Studies have illustrated some patients whose T2DM remission after surgery experienced a recurrence of theirdisease overtime[71-73].DiGiorgietal.have shown that beyond 3 years after gastric bypass,24%of patients with initial remission of their T2DM had reemergence of diabetes[72].The recurrence of T2DM was usually associated with weight regain and longer duration of T2DM[73].Other studies also showed that weight reduction is the most important predictor of T2DM remission after bariatric/metabolic surgery[74]. Even in low BMI T2DM patients,weight reduction is still the most important deciding factor of T2DM remission[75,76].Therefore,patients receiving metabolic surgery for their T2DM required long-term follow-up and education for life style modification in order to prevent weight regain.

Patient selection

Although nota perfectone,the BMI,surrogate of obesity,isnow the mostimportantindicatorofbariatricsurgery as wellas metabolic surgery fordiabetes treatment.Indication for bariatric surgery was universally accepted for BMI＞35 Kg/m2with co-morbidities and BMI may be lowered to 32 in Asian because of the tendency of centralobesity for Asian[20].However, recent study has shown that BMI did notpredictthe effectofbariatric surgery on mortality orcardiovascular disease and patients who may benefitfrom bariatric surgery are those with insulin resistance[7,71,77].These findings are very importantin patientselection and may be incorporated into indication forbariatric/metabolic surgery in the future.We shallselectthose patients who are mostlikely to benefitfrom bariatric surgery,and more importance should be given to metabolic variables and less to BMI.

Table 2 Variables and point values used for the computation of the age,body-mass index,c-peptide, duration of diabetes(ABCD)score.★

Table 3 Remission rate of T2DM according to ABCD score

Recently,gastrointestinal metabolic surgery has been proposed as a new treatment modality for T2DM in patients with BMI＜35 Kg/m2[78].Several randomized trials have proven that metabolic surgery resulted in a better glycemic control compared with medical treatment in T2DM patients with BMI＜35 Kg/m2[11-17].Table 1 disclosed the magnitude of HbA1c reduction in various treatment arms of these randomized trials.International Diabetes Federation (IDF)guideline has recommended that surgery is an eligible treatmentfor Asian patients with notwellcontrolled T2DM(HbA1c＞7.5%)and BMI＞27.5 kg/ m2[10].However,previous study also disclosed that T2DM remission after bariatric surgery was progressively decreased associated with the lower of BMI[79]. Therefore,itis mandatory to select patients who are bestsuited to the surgery and those who willpredictably have a poor resultare excluded to avoid the unnecessaryexposure to the surgical risk.To be able to make such decisions,we need preoperative information on the association between possible predictors and outcome. A simple scoring system consisted of four variablesthe age,BMI,C-peptide and duration of diabetes-was developed forpredicting the successofT2DMtreatment after metabolic surgery;the ABCD Diabetes Surgery Score was previously reported[80].This simple multidimensionalgrading system can predict the success of T2DM treatmen t and is clinically recommended (Table 2and 3).

Conclusion

Laparoscopic bariatric/metabolic surgery is becoming a safe and effective treatment for morbid obesity and obese T2DM.LSG and many new procedures have been developed and adapted into the treatmentmodalities of bariatric/metabolic surgery.Good patient selection and durable weight loss remain the cornerstones of the success of bariatric/metabolic surgery.

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?Corresponding author:Dr.Weijei Lee,Min-Sheng General Hospital, Taiwan,No.168,Chin Kuo Road,Taoyuan,Taiwan,China.Tel/Fax: 886-3-3179599 ext1598/886-3-3469291,E-mail:wjlee-obessurg-tw@ yahoo.com.tw.

Received 30 August 2014,Revised 16 September 2014,Accepted 05 November 2014,Epub 01 December 2014

The authors reported no conflict of interests.

?2015 by the Journal of Biomedical Research.All rights reserved.

10.7555/JBR.28.20140120