The Effect And Mechanism Of Liraglutide On Visceral Fat Metabolism In Type 2 Diabetes Mellitus With Obesity

With the development of social economy,the change of people's life style and the population aging,the incidence of type2diabetesmellitus(T2DM)is on an increasing tendency year by year in the world,especially in developing countries and some developed countries.China has the largest disease burden of diabetes in the world.It often occurs some chronic damages of multiple organ on clinic complicated with eye,kidney,nerve,cardiovascular etc.Therefore,pay attention to the obesity problem of the diabetic population,especially the study and intervention of fat has become a hot focusing research in current.Adipose tissue can be divided into white adipose tissue(WAT),brownadipose tissue(BAT)and briteadipose tissue.There is ahuge difference between white adipose tissue and brown adipose tissue of distributionand function in vivo.Brown adipose tissue are mainly distributed in the scapula,nape part,armpit,mediastina and kidney around the human body.It can maintain the balance of body temperature and improveinsulin resistance mainly by non-shivering thermogenesis(NST).Browning of white adipocytes is also a hot issue in the treatment of T2DM and obesity.Therefore,the study of the relationship between brown adipose and metabolism index of adult will provide a new therapeutic strategy for obesity and preventive treatment of metabolic diseases.The classical white fat is widely distributed around the subcutaneous and visceral tissues of the body.As an important energy storage site,triglyceride(TAG)is stored for use when the body needs it.Abdominal fat is mainly white fat,which plays an important role in the occurrence of diabetes and obesity-related diseases.Compared with subcutaneous fat,the increase of visceral fat is more likely to cause a series of adverse conditions such as hypertension,disorder of glucose and lipid metabolism.Through experimental analysis,it is found that-visceral fat is more productive and decomposed.After long-term accumulation,it is easy to produce a variety of products which have adverse effects on human growth and development,such as fatty acids,fat decomposition products,etc.,and pass through the portal vein,and eventually flow into the human liver,enhance glycogenesis and fat synthesis,cause insulin resistance,and ultimately lead to the occurrence of hyperlipidemia and T2DM.Liraglutide,glucagon-like peptide-1(GLP-1)Resemblance.Usually,L cells in the cecum and jejunum secrete a large amount of GLP-1.The gastrointestinal-islet axis is used to regulate the secretion of glucagon and insulin after meals.It has many functions,such as controlling the secretion of glucagon,increasing satiety,inhibiting gastric emptying rate,and so on.It has a positive promoting effect on human body's function,and has a turbulent metabolism with adipose tissue.The treatment of disorderly related diseases has very important practical value and practical significance.At present,the effect of liraglutide on abdominal fat,especially visceral fat and liver fat in patients with T2DM and obesity is not very clear,and its effect on white adipocyte differentiation and browning of white fat and its mechanism need further study.This research mainly explores the relationship between distribution and activity of brown adipose tissue and metabolic index in adult.It compared the effects on the lipid metabolism,islet function,volumeof visceral adipose tissueofpatients with T2DM accompanied with obesity after treatment of GLP-1 analogues liraglutide or insulin glargine.What's more,we observe the influence liraglutide have on the differentiation of white adipose and browning of white adipose.We want to know the potential mechanism in it,which provide a new idea for clinic therapy on patients with T2DM accompanied with obesityPart I.Correlations between brown adipocytes and metabolic indicatorsin adultsObjective:Detection the distribution,volume and activity of BAT in adults,explore its impact on the metabolism index of BMI,FBG,TG,TC,LDL-C,UA etc.And provide new therapeutic target for the prevention and treatment of obesity and metabolic diseases.Method:The image data of 5009 18F-FDG PET/CT patients were analyzed retrospectively and PET/CT images were compared by adopting semi-quantitative method and make quantitative for the BAT on the images.To explore the correlation of metabolism index between detection rate,volume,activity of BAT and blood glucose,blood lipids,UA,and analyze the influencing factors for detection rate,volume and activity of BAT.Result:1.In BAT positive group,it is higher of detection rate,volume,activity of BAT in winter and spring than that in summer and autumn.2.The proportion of female subjects in BAT positive group is significantly higher than that in BAT negative group,moreover the average age,BMI,FBG,TG,TC,LDL-C and UA levels in BAT positive group were significantly lower than that in BAT negative group.3.Regression analysis of logistic showed that season,sex,age,BMI,FBG,TG and LDL-C levels were independent factors of BAT detection rate.4.Multiple linear regression showed that gender and FBG levels were independent factors of BAT volume and activity in BAT positive subjects.Conclusion:The detection rate,volume and activity of BAT in adults are related to multiple metabolism index of BMI,blood glucose,blood lipid and uric acid and moreover,the detection of BAT is influenced by multiple factors such as sex,season,age,BMI,blood sugar and blood lipid.To increase BAT volume and activity and improve glucose and lipid metabolism,which will provide a new therapeutic strategy for obesity and preventive treatment of metabolic diseases.Part II.The role and clinical significance of liraglutide in change of abdominal fat in patients with T2DM accompanied with obesityObjective:To observe and compare after treatment of human GLP-1 analoguesliraglutide and insulin glargine,the change of metabolism index for abdominal fat in patients with T2DM mellitus accompanied with obesity,and explore the effects of GLP-1 RAs on lipid metabolism,islet function,visceral adipose tissue volume and hepatic fat content of the patient while controlling blood glucose.Method:Select 132 cases,which is visiting from January 2013 to December 2014 of Department of endocrinology in the first affiliated hospital of soochou university.For the newly diagnosed patient with T2DMaccompanied with obesity,abdominal CT examination is measured to the volume of tummy adipose tissue(TAT),visceral adipose tissue(VAT)and subcutaneous adipose tissue(SAT)to analyze the influencing factor of visceral fat.From June 2015 to December 2017,198 newly diagnosed patients with T2DM mellitus accompanied with obesity or obesity are examined by abdominal magnetic resonance(MR)imaging for liver fat content(LFVF)in the first affiliated hospital of soochou university.To observe the patient's waist circumference,body mass index(BMI),fasting blood glucose(FBG),glycosylated hemoglobin(HbAlc),total cholesterol(TC),triglyceride(TG),high density lipoprotein cholesterol(HDL-C),low density lipoprotein cholesterol(LDL-C),islet function and insulin resistance index(HOMA-IR)and the changes of TAT,VAT,SAT,LFVF,which is based on six months later treatment of metformin separately combined with liraglutide(liraglutide group)or insulin glargine(insulin glargine group).Result:1.The patientwith T2DM accompanied with obesity is in liraglutide treatment group,whose level of FBG,HbAlc,BMI,WHR,FINS and TC,TG,LDL-C is lower than pre-treatment.2.After the treatment of liraglutide,insulin resistance(HOMA-IR)of the patient is also significantly improved,and TAT,VAT and LFVF are obviously lower than pre-treatment,while the volume of visceral adipose tissue(VAT)decrease.3.Compared with the insulin glargine treatment group,there is a significant decrease on the level of HbAlc,BMI,WHR,FINS,LDL-C,HOMA-IR,HOMA-?,TAT,VAT,VAT/SAT and LFVF of the patientwith T2DMaccompanied with obesityConclusion:While formulating the hypoglycemic plan,it is very important for patients with T2DMaccompanied with obesityto reduce the visceral fat volume,which can controlblood glucose and the improvement of insulin resistance.Compared with the group of insulin glargine,liraglutide can significantly reduce blood glucose.At the same time,it can reduce body weight,visceral fat volume and liver fat volume,and promote the redistribution of tummy adipose tissue.Thus,liraglutidereduce inflammation and insulin resistance caused by obesity,which has important clinical value in improving metabolic disorders such as blood glucose and lipids,reducing complications of patients with T2DM accompanied with obesity.Part ?.Effectand mechanism exploring of GLP-1 analogues on adipocyte differentiationObjective:To detect the effect of liraglutide on the differentiation of white adiposeand browning of white adipocytes and to explore its potential mechanism.Method:1.The phenotype and gene expression of the successful differentiation of white adipose:First,induce preadipocyte differentiation into 3T3-L1 through IBMX,DEX and insulin.Observe the accumulation of lipid droplets while differentiating after 0,5,10days.Then detect the gene expressionofdifferentiated cell Ucp1,Cidea,Ap2,Ppary,Glp-1R by Q-PCR after 0,3,6,9 days.Meamwhile,detect and quantify the gene expression of differentiated cellp-ACC,FAS,scdl,ect by westernblot(WB)after 0,3,6,9days.2.The generation and browning of white adipose cells caused by liraglutide:After a 6-day differentiation of preadipocyte,1nM?10 nM?100 nM?1000 nM of liraglutide together with inducer are added into white adipose cellsevery 48 hours.Oil red staining is used to observe lipid droplet of 3T3-11 between liraglutide treatment groupwith different concentrations and the control group onday six.Detect the relative expression level of mRNA of Fgf21,fat synthesis related genes Ap2,Ppary and Scdl,characteristic gene of brown fat cell Ucpl and Prdm16 on 6th day of 3T3-11 differentiation inliraglutide treatment group with different concentrations.Detect the protein expression of FAS?SCD1?PERILIPIN?phospho-PPARy273 and UCP1 on 6th day of 3T3-11 differentiationin liraglutide treatment group with different concentrations.3.The mechanism of the generation and browning of white adipose cells caused by liraglutide:After a 6-day differentiation of preadipocyte,1nM?10 nM?100 nM?1000 nM of liraglutide together with inducer are added into white adipose cells every 48 hours.Detect and quantify the protein expression level of p-m TOR,t-m TOR,p-AMPK,t-AMPK,p-ACC,ACC,p-YAP,t-YAP,p-CREB,t-CREB,p-ERK,ERK by WB.Result:1.Compared with control group,oil red staining shows that there are more lipid droplets accumulated in the differentiated cells of white adipocytes in liraglutide treatment group,and also shows that more of the lipid droplets are accumulated with the increasing of the concentration of liraglutide.2.Compared with the control group,the expression of FGF21 is decreased in the liraglutide treatment group,while fat synthesis related genes Ap2,Ppar gamma and Scdl are all increased.3.The expression of characteristic gene Ucpl and PRDM16 in brown adipocytes increased in a dose-dependent manner.On the level of protein,the phosphorylation sites of FAS,SCD1,PERILIPIN,PPARy273 and the expression of uncoupling protein UCP1 all increased in liraglutide treatment group.4.Compared with the control group,liraglutide increases the level of phosphorylation of CREB,ERK and YAP.Furthermore,liraglutide treatment group decreases phosphorylation site of AMPK to 172 and protein phosphorylation of ACC,increases phosphorylation site of mTOR to 2448.Conclusion:1.GLP-1R has a high level of expression in early differentiation of white adipose.Nevertheless,the expression declines as time goes on during the differentiation.2.iraglutide promotes the differentiation of early white adipose and browning of white adipocytesin a dose-dependent manner.3.Whether on gene level or protein level,liraglutide increases the expression of PPARy transcription factor through up-regulating the phosphorylation levels of CREB,ERK and YAP,which promotes the differentiation of early white adipose.Also,liraglutide may promotebrowning of white adipocytes through the AMPK/mTOR pathway.