HDAC3 Inhibitor Prevents Diabetic Cardiomyopathy In Type 1 Diabetic Mice And The Underlying Mechanisms

Background: With the high prevalence of diabetics,the concerns regarding its complications caused by both type 1 and type 2 diabetes are growing,especially the diabetic cardiomyopathy(DCM),which is the most challenging health problem today.Recent studies have shown that activation of histone deacetylases(HDAC)is associated with DCM and total HDAC inhibition attenuated diabetic cardiac injury in the streptozotocin(STZ)-induced diabetic mice.However,there are,at least,4 different types of HDAC and its roles in DCM remain under debate.Aims: To investigate whether HDAC3 inhibitor RGFP966 can prevent the development of DCM,and whether this epigenetic modification produces the phenomenon of “cardiac protective memory”.Method: Male type 1 diabetic OVE26 and wild-type mice were randomized the baseline cardiac function and blood glucose data being collected.Specific HDAC3 inhibitor RGFP966(10 mg/kg,s.c.),pan-inhibitor Valproic acid(VPA,200 mg/kg,s.c.)and vehicle were injected into the mice every other day for 3 months.Animals were divided into six experimental groups: WT + vehicle,WT + RGFP966,WT + VPA,OVE + vehicle,OVE + RGFP966,and OVE + VPA.At the end of the 3-month treatment,the cardiac function of all the mice were examined,then five to seven mice from each group were killed as the time point of 3 months(labeled as 3 M)cohort and heart tissues were collected.The remaining animals(n=5 at least)in each group were kept for another 3 months without HDAC inhibitors’ treatment(labeled as 6 M).After determining the cardiac function at the end of 6 months,,heart tissue were collected for the pathological examination,including the ratio of heart weight and tibia length,total HDAC and HDAC3 activities,hypertrophy,fibrosis,oxidative stress,inflammation.Acetylated Histone H3,acetylated Histone H3K9/14,insulin receptor substrate 1(IRS1),phosphorylated protein kinase B(p-Akt),phosphorylated extracellular signal-regulated kinases 1/2(p-ERK1/2),glucose transporter 4(GLUT4),GLUT1,phosphorylated AMP-activated protein kinase α(p-AMPKα),phosphorylated c-Jun N-terminal kinase(p-JNK),phosphorylated p38 mitogen activated protein kinases(p-p38MAPK),dual specificity phosphatase 5(DUSP5)were detected by Western Blot and real-time PCR method.The acetylated level of histone H3 on the DUSP5 gene promoter region was determined by chromatin immunoprecipitation(Ch IP).Results: In the present study,HDAC3 inhibitor RGFP966 significantly inhibited total HDAC and HDAC3 activity in the typa 1 diabetic OVE26 mice and increased the total acetylated Histone H3 and H3K9/14,but didn’t affect the blood glucose.Pathological and histological examination showed that inhibition of HDAC3 blocked the development of diabetic cardiomyopathy,as evidenced by improved diabetes-induced cardiac dysfunction,hypertrophy,and fibrosis,along with diminishing cardiac oxidative stress,inflammation and insulin resistance.All these cardioprotection of RGFP966 were found at 3M and 6M.Furthermore,phosphorylated ERK 1/2,a well-known initiator of cardiac hypertrophy,was significantly increased,while DUSP5,an ERK1/2 nuclear phosphatase,was substantially decreased in diabetic hearts.Both of these changes were prevented by RGFP966.CHIP assay showed that HDAC3 inhibition elevated histone H3 acetylation on the DUSP5 gene promoter at both two time points.Conclusion: In the type 1 diabetic OVE26 mice,inhibiting HDAC3 significantly prevented the diabetes-induced cardiac dysfunction,hypertrophy,fibrosis,oxidative stress,inflammation and insulin resistance.The possible mechanism might be that inhibition of HDAC3 up-regulates DUSP5 expression via acetylating Histone H3 at DUSP5 gene promoter region,leading to the inactivation of nuclear ERK1/2.These cardioprotection persisted for another 3 months after termination of RFGP966 treatment,which indicates the phenomenon of “cardiac protective memory” induced by epigenetic modification and the potential application of HDAC3 inhibitor for the prevention of DCM.