| BackgroundType2diabetes (T2DM) is an epidemic that is an ever-increasingproportion of the world population. T2DM portends poor prognosis concerningcardiovascular disease complications, which is the prevalent cause of mobilityand mortality induced by diabetes. It has been reported that T2DM has increasedincidence and severity of myocardial infarction (MI).Adiponectin(APN) is an adipocytokine present in plasma at highconcentration up to30μg/ml with anti-inflammatory, anti-atherogenic,anti-diabetic and cardioprotective properties. It has been reported thatadministration of exogenous globular domain of adiponectin (gAPN) canmarkedly ameliorate (MI/R) injury in APN knockout (APN-/-) and diabetic mice.Adiponectin exists mainly in three major oligomeric complexes: trimer (LMW),hexamer (MMW), and a high-molecular-weight form (HMW), and different adiponectin oligomers act on different target tissues and exert distinct biologicalfunctions. Epidemiological studies indicated that the HMW adiponectin wasmarkedly decreased in the patients with diabetes or coronary heart diseases(CHD), and the concentration of plasma HMW adiponectin or the ratio of HMWto total adiponectin（HMW%） was significantly correlated with the degree ofrisk of diabetic coronary heart diseases. Therefore, upregulation of endogenousAPN level and its multimerization are more beneficial to the prevention andtreatment of diabetic cardiovascular diseases.Resveratrol (RSV) is a member of natural, plant-derived chemicals knownas polyphenols and is attracting increased attention due to its diverse healthbenefits especially in case of cardiovascular disease. RSV possesses a range ofadditional cardioprotective and vasoprotective properties includingantiatherosclerotic and vasorelaxation action. This compound also attenuatesMI/R injury. Many studies have revealed that RSV ameliorates MI/R injury bypharmacologically precondition the heart in a nitric oxide (NO)-dependentmanner, but the underlying mechanisms remaim largely unknown. It has beendemonstrated that RSV promotes adiponectin (APN) up-regulation and APNmultimerization in cultured adipocytes and mice. Therefore, APN could be themediator of protection effect of RSV to ischemic myocardium.Accordingly, upregulating endogenous APN level and multimetization byRSV administration might be a new therapy strategy for diabetic coronary heartdiseases. However, it remains completely unknown whether RSV upregulatesadiponectin level and multimerization in T2DM and therefore attenuates MI/Rinjury.Aims 1. To observe whether RSV administration attenuates MI/R injury inT2DM mice.2. To investigate the underlying mechanisms，which might be whetherRSV upregulates APN level and multimerization both in plasma and adiposetissue in T2DM mice, and further protects myocardium against MI/R injury viaactivating APN signaling pathway.Methods1. Establishment of T2DM model in mice T2DM was induced byhigh-fat diet (HD) feeding plus low-dose streptozotocin (STZ) injection. T2DMwas confirmed by detection of body weight, blood glucose, fasting plasmainsulin and oral glucose tolerance test (OGTT).2. Establishment of MI/R model in mice MI/R was produced bytemporarily exteriorizing the heart via a left thoracic incision and placing a6-0silk suture slipknot around the left anterior descending coronary artery. Micewere subjected to30minutes of ischemia and then the slipknot was released for3hours or24hours of reperfusion.3. Route and methods of administration Mice were treated with10mg/kg RSV daily by intragastric administration for3weeks after theestablishment of T2DM. Compound C (an AMPK inhibitor,20mg/kg) wasadministrated by intraperitoneal injection1h before MI/R.4. Determination of MI size and cardiac function Myocardial infarctsize was determined by the Evans blue/2,3,5-triphenyl tetrazolium chloride(TTC) double staining method. Cardiac function was determined byechocardiography. 5. Determination of myocardial apoptosis Myocardial apoptosis wasdetermined by terminal deoxynucleotidyl transferase-mediated dUTP nick endlabeling staining (TUNEL). Caspase-3activity was determined by caspase-3activity assay kit per manufacturer’s instructions.6. Determination of plasma APN level Plasma APN level wasdetermined by mouse APN assay kit per manufacturer’s instructions.7. Immunoblotting Western blot was used to determine myocardiumAMPK, p-AMPK level, adipose tissue DsbA-L level, total APN level and HMWlevel.Results1. HD feeding plus low-dose STZ injection successfully induced T2DM.Compared to normal control, diabetic mice manifested higher body weight andblood glucose level (>11.0mmol/L after8weeks of HD feeding), higher fastingplasma insulin level (P<0.05), lower glucose tolerance in OGTT examination.MI/R model was successfully established which was confirmed by MI size.2. RSV administration alleviated MI/R injury in T2DM mice, as evidencedby decreased infarct size, improved cardiac function，decreased cardiomyocytesapoptosis determined by TUNEL staining and caspase-3activity (P<0.05).3. Compared with control group, MI/R injury was exacerbated in T2DMgroup accompanied by lower APN level (P<0.01). RSV administrationupregulated APN level and APN multimerization (HMW%) both in plasmaand adipose tissue via increasing DsbA-L expression in adipose tissue indiabetic mice (P<0.01). Conversely, administration of AMPK inhibitorCompound C significantly inhibited phosphorylation of myocardiumAMPK(P<0.05), therefore attenuated the cardioprotective effects of RSV（all P<0.05）.Conclusions1. RSV administration significantly attenuated MI/R injury in T2DMmice.2. RSV attenuates MI/R injury in T2DM mice via upregulatingadiponectin level and APN multimerization in both plasma and adipose tissue,and further activating of APN signaling pathway. |
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