The Study On The Effect Of GLP-1 On Hypertension Induced Cardiac Hypertrophy

Objective:1.Observe the effect of GLP-1 on the blood pressure by intervening in spontaneously hypertensive rats;2.Explore the effect of GLP-1 on myocardial hypertrophy induced by hypertension;3.Explore the molecular mechanism of the effect of GLP-1 on myocardial hypertrophy.Methods:8 male Wistar–Kyoto(WKY)rats and 24 male SHRs: weight,200–250 g;age,8weeks.SHRs were divided randomly into three groups: the SHR group(n = 8),liraglutide group(n = 8),and alogliptin group(n = 8).WKY rats were used as the control group.The liraglutide group was subcutaneously injected with liraglutide(300 μg/kg,bid),and the alogliptin group was administered alogliptin(20 mg/kg,Qd.)by gastric gavage.All treatments lasted 7 weeks.At the end of the experimental period,all rats were euthanized with a dose of pentobarbital(100 mg/kg),and the BL-420 data acquisition and analysis system was used to monitor the systolic and diastolic blood pressure of the rats.The heart was harvested and calculate the heart weight(HW)/body weight(BW)ratio.The tissue was fixed,embedded,sliced,stained,and observed histological changes under the microscope;after the tissue protein was extracted,the expression of cardiac hypertrophy marker and pathway proteins was detected by Western-blot.To further assess the role of GLP-1 mediated protection from cardiac hypertrophy,cardiomyocytes were incubated with the AMPK inhibitor compound C or m TOR activator MHY1485,the expression of cardiac hypertrophy marker and pathway proteins was detected;Finally,the data was analyzed.Results:1.GLP-1 reduced blood pressure in SHRsTo observe the effect of GLP-1 on blood pressure in rats,we monitored blood pressure changes after GLP-1 treatment.SBP,DBP,MAP were sigznificantly decreased at 7 weeks after liraglutide or alogliptin treatment compared with the SHR group(P <0.05),and the systolic blood pressure decreased more significantly,and there was no statistical difference in the blood pressure lowering effects of the two drugs.2.GLP-1 attenuated cardiac hypertrophy induced by hypertensionTo investigate the effect of GLP-1 in hypertrophic hearts in vivo,we established a model of cardiac hypertrophy by pressure overload.SHRs were treated with liraglutide or alogliptin for 7 weeks,during which we measured HW and BW and calculated the HW/BW ratio.The HW/BW ratio was obviously increased in SHRs(P < 0.05).Western blot showed that the levels of hypertrophic markers(ANP,BNP,β-MHC)in rat hearts were increased in the SHR group compared with the WKY group(P < 0.05).GLP-1treatment significantly inhibited ANP,BNP,and β-MHC levels and the HW/BW ratio(P< 0.05).Hematoxylin and eosin staining indicated that hypertension remarkably increased the cell cross-sectional area of myocardial tissue,compared with WKY group,cell crosssectional area decreased after liraglutide or alogliptin treatment.Collagen deposition was evaluated using Masson’s trichrome staining.The SHR group showed extensive interstitial fibrosis in the ventricular wall and a significant increase in collagen deposition in both the perivascular region and intermyocardium.Liraglutide or alogliptin administration significantly reversed these changes.TEM showed abundant tight,neatly arranged mitochondria and intact myofibrils in the cytoplasm of cardiomyocytes in the WKY group.In contrast,reduced and swollen mitochondria and ruptured myofibrils were seen in the SHR group.However,these phenomena were reversed by liraglutide or alogliptin treatment.Alterations in morphology were consistent with the gene expression of hypertrophic markers.These results suggest that GLP-1 ameliorates the cardiac hypertrophy induced by hypertension.3.Effects of GLP-1 on the RAAS in SHRsTo evaluate the effect of GLP-1 on the RAAS,we examined components of the RAAS.In this experiment,the concentration of Ang II in serum was measured by ELISA,and the protein expression of Ang II receptors and ACE2 were detected using Western blot.Hypertension caused a significant increase in the levels of Ang II and AT1 R in the heart tissue compared with the WKY group.However,the protein levels of AT2 R and ACE2 were decreased in the SHR group compared with the WKY group(P < 0.05).However,administration of liraglutide or alogliptin reduced the Ang II and AT1 R levels and upregulated the AT2 R and ACE2 levels,as evidenced by a reduced AT1R/AT2 R ratio(P < 0.05).These results indicate that GLP-1 reduces blood pressure and exerts cardiovascular protection by regulating RAAS proteins expression.4.GLP-1 reverses cardiac hypertrophy via the AMPK/m TOR/p70S6 K pathwayTo elucidate the underlying molecular mechanism of the anti-hypertrophic effect of GLP-1,we extracted protein from myocardium in each group and examined the effect of GLP-1 treatment on the expression of proteins involved in the AMPK/m TOR/p70S6 K signaling pathway by Western blot.The results show that decreased p-AMPK levels and increased p-m TOR,p-p70S6 K,and p-4EBP1 levels were observed in the SHR group compared with the WKY group(P < 0.05).However,treatment with liraglutide or alogliptin remarkably increased the p-AMPK level,which prevented activation of pm TOR,p-p70S6 K,and p-4EBP1(P < 0.05).Nevertheless,the levels of total AMPK,m TOR,and p70S6 K proteins showed no obvious differences between the SHR and WKY groups.Meanwhile,along with AMPK activation,the expression level of GLP-1R was increased,so we considered that GLP-1R may participate in the regulation of the AMPK/m TOR pathway.To further assess the role of AMPK/m TOR signaling in GLP-1mediated protection from cardiac hypertrophy,cardiomyocytes were incubated with the AMPK inhibitor compound C or m TOR activator MHY1485 increased expression of hypertrophic markers relative to the Ang II + GLP-1 group,suggesting that the antihypertrophic effect of GLP-1 is abolished by compound C and MHY1485,and increased phosphorylation levels of m TOR,p70S6 K and 4-EBP1.Our results showed that GLP-1ameliorates cardiac remodeling via the AMPK/m TOR/p70S6 K signaling pathway.Conclusion:GLP-1 plays a protective role in cardiac hypertrophy by suppressing the Ang II/AT1R/ACE2 pathway and activating the AMPK/m TOR/p70S6 K pathway.