Study Of The Influence Of Blood Glucose Related Factors On Vascular Endothelial Function And The Intervention With Tetramethylpyrazine

Cardiovascular disease(CVD),especially accelerating the development ofatherosclerosis,is a major cause of the high disability rate and mortality in type 2diabetes mellitus(T2DM).Vascular endothelial injury plays a critical role in theoccurrence and development of diabetic cardiovascular complications disease.Theoscillating glucose can have more deleterious influences than constant high glucoseon endothelial function and diabetes chronic cardiovascular complications.The studyon glucose variability has recently become a research focus in the field of diabeticcardiovascular disease.It has an important significance to study the evaluation ofglucose variability and the effect of glucose fluctuation on endothelial dysfunction inthe control of diabetic cardiovascular disease.To investigate its mechanism and theintervention measures should be studied further.This study is divided into three parts:review,clinical study and experimentalresearch.1 Review1.1 Review 1:The changes of strategy in diabetes from focusing on glycosylatedhemoglobin to avoiding cardiovascular events.Several recent trials have led to contradictory outcomes in relation to the issue ofglycemic control and cardiovascular complications in patients with type 2 diabetes.The major target of diabetes treatment is to reduce cardiovascular events.Only relyingon the glycosylated hemoglobin as the"gold standard"of the maintenance of tightglycaemic control should be changed.A multi-pronged approach to address the totalcardiovascular risk factors is imperative.The best practice model for glycemic goalsshould include the quantity,quality and time course of glycemic exposure.1.2 Review 2:Fluctuating high glucose and cardiovascular complications indiabetes mellitus.Type 2 diabetes as a"coronary heart disease equivalent",endothelial dysfunctionplays an important role in the pathogenesis of diabetic cardiovascular complications. High glucose fluctuation induces endothelial dysfunction more obviously thanuncontrolled hyperglycemia.The main mechanisms include inducing endothelial cellapoptosis,improving oxidative stress and increasing the endothelial adhesionmolecules,etc.How to exactly recognize,evaluate and treat fluctuating high glucosemaybe possesses significance in the study of diabetic cardiovascular complications.2 Clinical study2.1 Study on the evaluation parameters of blood glucose and the correlationbetween them in type 2 diabetes patients.Objective:To study the evaluation parameters of blood glucose and thecorrelation between them in type 2 diabetes patients.Methods:25 diagnosed type 2diabetic patients with stable glucose-lowering treatment were enrolled.Seven point(preprandial and 120-min postprandial for each meal and bedtime)capillary glucosewas measured with an ultrasmart glucose meter(Bayer).The following indices ofglycemic variability were calculated from 7-point-daily capillary glucose profiles:mean blood glucose(MBG),large amplitude of glycemic excursions(LAGE),SD ofblood glucose(SDBG),mean amplitude of glycemic excursions(MAGE).HbA_1cwasmeasured by ion-exchange high-performance liquid chromatography.The generalindexes were measured.Then statistics test and correlation regression analysis werepreceded.Results:In simple correlation analysis,HBA_1cand FBG,MBG,LAGE,MAGE had obvious correlations(P＜0.01 or 0.05),MAGE and LAGE,SDBG,HbA_1c,MBG had obvious correlations(P＜0.01 or 0.05).In multivariate analysis,theprimary predictor of HBA_1cwas MBG(R=0.707,P=0.000);the primary predictor ofMAGE was LAGE(R=0.953,P=0.000).All other glucose variables added nothing tothe models.HbA_1c,MAGE and the level of serum total bilirubin had obvious negativecorrelations,with the Pearson correlation coefficient of-0.520(P=0.004)and-0.373(P=0.033)respectively by linear correlation and regression analysis.Conclusions:The different evaluation parameters of blood glucose might reflect the glucose profilefrom different aspects.HBA_1ccorrelates best with MBG and MAGE correlates bestwith LAGE derived from 7-point-daily capillary glucose profiles.The wholeevaluation of blood glucose in diabetes should include both long-term glucose control index and glucose variables.2.2 Relationship between endothelium-dependent vasodilatation and theevaluation parameters of blood glucose in type 2 diabetic patients.Objective:To study the correlation of the endothelium-dependent flow-mediateddilation(EDF)and the evaluation parameters of blood glucose in type 2 diabetespatients.Methods:25 diagnosed type 2 diabetic patients were enrolled.Endothelialfunction was evaluated by flow-mediated dilation measured by ultrasound.Sevenpoint capillary glucose was simultaneously measured and the following indices ofglycemic variability were calculated from 7-point-daily capillary glucose profiles:MBG,LAGE,SDBG,MAGE.HbA_1cwas measured by ion-exchange high-performance liquid chromatography.The general indexes were measured.Thenstatistics test and correlation regression analysis were preceded.Results:EDF andHbA_1c,FBG,MBG showed no significant correlation(P＞0.05).There was significantnegative correlation between EDF and MAGE,LAGE,SDBG(P＜0.05).EDF wasinverse correlation(r=-0.355,P=0.041)with the level of serum uric acid.Conclusions:The correlation of EDF and the glucose variables,including MAGE,LAGE,SDBG,suggests that glucose fluctuations might aggravate vascular endothelialdysfunction.The control of cardiovascular events in diabetes should pay attention tovascular injury which induced not only hyperglycemia but also blood glucosefluctuation.3 Experimental research:Effects of tetramethylpyrazine on human umbilicalvein endothelial cells exposed to constant or intermittent high glucose in vitro.Objective:To explore the effects of constant or intermittent high glucose onhuman umbilical vein endothelial cells(HUVEC),and the effects oftetramethylpyrazine on HUVEC by constant or intermittent high glucose levels.Methods:HUVEC were incubated for 8 days in media containing different glucoseconcentrations:5.56 mmol/1(normal glucose),25 mmol/1(constant high glucose),or adaily alternating 5.56 or 25 mmol/1 glucose(intermittent high glucose).and exposedfor 8 days to conditions of constant or intermittent high glucose levels withtetramethylpyrazine at concentrations of 500μmol/L,100μmol/L and 20μmol/L.Cell viability was measured by MTT method and cell membrane damage was determinedby lactate dehydrogenase(LDH)leakage,Nitric oxide(NO),endothelin-l(ET-1),soluble intercellular adhesion molecule-1(sICAM-1)and tumor necrosis factor-α(TNF-α)concentrations in the cell culture supernatant were measured.The activitiesof superoxide dismutase(SOD),nitric oxide synthetase(NOS)and the contents ofmalondialdehyde(MDA)in the cell lysate were examined by enzyme method orspectrophotometry.Results:The HUVEC viability and LDH leakage were nosignificance difference in different glucose culture conditions with or withouttetramethylpyrazine.Compared with normal glucose group,the activities ofSOD,NOS and the contents of NO were remarkably decreased while the contents ofMDA,ET-1,TNF-αand sICAM-1 were significantly increased in constant highglucose and intermittent high glucose groups(P＜0.01).More interestingly,thechanges of all the detection indexes(except TNF-α)in intermittent high glucosegroups were greater than that in constant high glucose group(P＜0.05 or P＜0.01).500μmol/L,100μmol/L tetramethylpyrazine could partially reverse the changes ofconstant or intermittent high glucose on HUVEC(P＜0.05 or P＜0.01).Conclusions:Both intermittent and constant high glucose can chang the function of endothelialcells.Furthermore,intermittent high glucose can have more deleterious effects thanconstant high glucose on endothelial function,which may be related to oxidativestress,inflammatory reaction and cell adhesion molecule.Tetramethylpyrazine canpartially reverse this impairment.