| Objective: As a new global epidemic,obesity has become a central issue even in developing countries.It has previously been observed that more than 1/3 adults got overweight or obese.Obesity indicates an increased risk of metabolic diseases such as type 2 diabetes mellitus(T2DM)and nonalcoholic fatty liver disease(NAFLD).In the early 1980 s,it was found that bariatric surgery could reduce the weight of obese patients with T2 DM,and kept the blood sugar normal for a long time.Bariatric surgery can effectively control blood sugar in obese patients with T2 DM,which has been confirmed by many large clinical studies.Hepatic insulin sensitivity is also improved after sleeve gastrectomy(SG)and has played an important role in short-term blood glucose decline and long-term glucose stability.Bariatric surgery has become a major option for severe obesity especially since the advent of lower risk laparoscopic procedures.As an important method of weight reduction,sleeve surgery has been largely recognized for its favorable clinical results.The reduction in fat accumulation after sleeve surgery is a key factor for increasing hepatic insulin sensitivity.However,further research on the effect of sleeve gastrectomy on lipid metabolism is required.In recent years,the changes of adipose tissue metabolism have attracted wide attention.In order to further elucidate the mechanism of energy metabolism changes after weight loss surgery,it is important to envestigate the related effectors and pathways,and to pave the ways for non-invasive intervention of T2 DM.Most of the adipose tissue in animals is white adipose tissue(WAT)and plays a role in energy storage;however,it is also the cause of obesity.Brown adipose tissue(BAT)produces heat efficiently by downregulating fat storage.Previous research has established that under cold or other stressful conditions,the third of adipose tissue,brown-like adipose tissue is observed and was subsequently named beige adipose tissue.This tissue type had a role in heat production.The process of induction and activation of beige adipose tissue is called browning of white adipose tissue.Evidence suggests that browning of white adipose tissue(WAT)plays an important role in energy metabolism.However,it is not clear whether browning of white fat after sleeve gastrectomy(SG)is involved in fat loss and negative glucose balance.Methods: To establish Sprague Dawley(SD)obese rat model of type 2 diabetes mellitus.They were raised on a high-fat diet(HFD).All rats were injected with low-dose Streptozocin.Blood glucose(BG)was measured with whole blood collected from the tail vein by a portable glucometer.Rats with BG levels above 16.7 mmol/l and stable for 4 weeks were considered to be diabetic.Our study contains a blank control group,Sham group with non-restricted diet,Sham group with restricted diet,and sleeve surgery group.we removed the greater curvature of the stomach to create a narrow gastric sleeve(70～80% of the gastric volume was excised).In sham operation group,anterior gastric wall was treated with 1.0cm incision and in situ suture.Four weeks post operation,inguinal adipose tissue was extracted to check the degree of browning.Mice 3T3-L1 cells were kept and induced with insulin,IBMX and DEX into stable differentiated insulin resistant adipocytes.Real-time PCR and Western-blot were used to detect the expression of UCP1,SIRT1,adiponectin,PGC-1α,PPARγ,AMPKα p-AMPKα and beta-actin.The level changes of blood lipid and body fat were detected.UCP1,PGC-1α and PPARγ were detected by immunohistochemical staining.lentivirus vectors were constructed and used for cell infection to establish the stable overexpression and silencing of adiponectin or SIRT1 adipocytes.The browning degree of adipocytes was detected.The rats were injected with AMPK inhibitor(Dorsomorphin,also called compound C)weekly post operation.The expression of heat-producing proteins such as PPARγ,PGC-1αand UCP1 was detected by qRT-PCR and Western blot analysis.Results: 1.Sleeve gastrectomy can relieve obesity and related metabolic disordersIn terms of body weight,Sleeve groups showed a marked and stable reduction compared to other groups(P < 0.05 for all).For fasting blood glucose,Sleeve groups showed a marked reducing tendency(P < 0.05 for all).the Sleeve group showed significantly lower body fat compared to Sham+ad libitum and Sham+FR groups(P < 0.05).2.Sleeve gastrectomy can positively regulate white adipose and beige adipose tissue dynamics in vivoAround 30 days after the operation,In Control and Sham groups,large deposits of adipose tissue were present in inguinal and interscapular regions,whereas these had almost disappeared in Sleeve group rats.Based on a similar food intake,Sham+FR group rats had fatty deposits that looked more like white adipose tissue.The adipose tissues of Sleeve group rats were darker in color and showed increased numbers of blood vessels.PPARγ,UCP1 and PGC-1α mRNA and protein were all markedly up-regulated in tissues from Sleeve group rats compared to tissues from rats of Control and Sham groups(PPARγ P < 0.01;UCP1 and PGC-1α P < 0.05).The expression and distribution of PPARγ,UCP1 and PGC-1α was also studied by immunohistochemistry staining.These three proteins were more positively stained in tissues from rats of the Sleeve group compared to other groups.Cell morphology of Sleeve group is similar to brown adipose tissue.3.Adiponectin/SIRT1 signaling pathway contributes to white adipose browning induced by sleeve gastrectomyPCR of inguinal adipose tissue samples showed that adiponectin and SIRT1 mRNA levels were significantly up-regulated(P < 0.01 for both)Western blots demonstrated that tissues from rats in the Sleeve group showed higher adiponectin and SIRT1 protein expression after the operation(P < 0.01 for both).SIRT1 was markedly up-regulated when adiponectin was overexpressed by about 4-fold(P < 0.05).Adiponectin was significantly up-regulated in SIRT1 overexpressing cells by 1.5-fold(P < 0.05).4.SIRT1 causes white adipose browning by activating AMPKpAMPK was significantly up-regulated in SIRT1-overexpressing 3T3-L1 cells compared to the mock control group(P < 0.01).We gave rats an AMPK inhibitor,compound C,by intraperitoneal injection once per week after the operation.After giving compound C,PGC-1α and UCP1 mRNA and protein expressions were significantly reduced compared with the Sleeve group(Figure 4B–C;P < 0.05 for all).PPARγ showed a reduced tendency,however this was not significant.Conclusions: 1.Sleeve gastrectomy can relieve obesity and related metabolic disorders.Sleeve gastrectomy group showed lower levels of body fat,blood lipid and blood sugar.2.Sleeve gastrectomy can positively regulate white adipose and beige adipose tissue dynamics in vivoSleeve gastrectomy can significantly promote browning of white adipose tissue.Markers of white adipose tissue browning including UCP-1,PPARγ and PGC-1αwere significantly higher in sleeve bariatric surgery group than in sham operation group and control group.3.Adiponectin/SIRT1 signaling pathway contributes to white adipose browning induced by sleeve gastrectomyThe expression of adiponectin and SIRT1 increased significantly in sleeve bariatric surgery group.In 3T3-L1 adipocytes,overexpression of adiponectin and SIRT1 up-regulated the expression of UCP1,PPARγ and PGC-1α.Adiponectin has a positive regulatory effect on SIRT1,and SIRT1 also has a positive feedback effect on adiponectin.4.SIRT1 causes white adipose browning by activating AMPKSIRT1 also promotes browning of white adipose tissue by activating AMPK phosphorylation. |
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