Regulation Of JAK2 / STAT3 Pathway On Diabetic Cardiomyopathy And Intervention Effect Of Drugs

BackgroundDiabetic cardiomyopathy (DCM) is defined as a direct negative effect of diabetes mellitus on myocardium occurring independently of a recognized cause such as CAD or hypertension, characterized by the presence of ventricular dysfunction, especially diastolic heart failure. Although several pathological mechanisms have been introduced, there has been limited progress on developing specific treatments. Janus kinase 2/signal transducer and activator of transcription (JAK2/STAT3) pathway is an important pro-inflammatory pathways and cell survival pathway, which is believed to play a compensatory role in the protection of ischemia-reperfusion injury, heart failure and other processes. The pathway is a common way to a variety of cytokines and growth factors in transmitting signals within cells involved in immune responses, a variety of biological activities of vascular cell proliferation, apoptosis and migration. However, the function of JAK2/STAT3 pathway in diabetic cardiomyopathy is currently still unclear. Metformin is one of the first-line routine drugs to control blood glucose. Many clinical trials and basic experiments suggested as an adenosine 5’-monophosphate (AMP)-activated protein kinase (AMPK) agonist, metformin showed benefit for cardiovascular disease besides its hypoglycemia function, while the specific mechanism is not fully elucidated. Sitagliptin is a new therapeutic drug of diabetes, as an inhibitor of dipeptidyl-peptidase 4 (DPP-4) receptor, exerts biological effects with increasing glucagon-like peptide 1 (GLP-1) level. However, whether DPP-4 receptors could exert the protective effect in cardiovascular disease was still inconsistent.Aims1. To observe the changes of JAK2/STAT3 pathway in the progression of diabetic cardiomyopathy and its relationship with the left ventricular remodeling and the degree of inflammation;2. To investigate the intervention of metformin and sitagliptin and the mechanisms may be involved.Methods1.110 male Sprague Dawley (SD) rats (120g±20g) were selected. After 1 week of acclimatization, intraperitoneal insulin tolerance test (IPITT) was performed. The rats were randomly divided into normal diet group (Control, n=34) and high-fat diet group (HFD, n-76). According to the feeding time, each group was further divided into 1 week group (Control-1w, HFD-1w, n=4, each) and 4 week group (Control-4w, HFD-4w, n=4, each), with the rest kept feeding. Four weeks later, IPITT was performed again. HFD rats were randomly divided into two groups, continued high-fat diet group (HFD) and diabetes group (DM). DM group rats were given with a single intraperitoneal injection of STZ (27.5 mg/kg intraperitoneally [ip] in 0.1 mol/1 citrate buffer) to rats with insulin resistance. The control and HFD groups received citrate buffer (ip) alone. One week after STZ administration, rats with FBG>11.1 mmol/L in 2 consecutive analyses, reduced insulin sensitivity and polyuria were considered the diabetic rat model. Normal diet group rats were randomly divided into different feeding duration groups (Control-9w, Control-13w, Control-21w, n=6, each). HFD rats were randomly divided into different feeding duration groups (HFD-9w, HFD-13w, HFD-21w, n=6, each). Diabetic rats were randomly divided into different feeding duration groups and treatment groups (DM-9w, DM-13w, DM-21w, MET, STAG10, STAG20 group, n=8, each). Since the diabetic group successful modeling, MET group rats were given 200mg/kg/day of metformin orally, STAG10 rats given 10mg/kg/day of sitagliptin orally and STAG20 rats were given 20mg/kg/day of sitagliptin orally.2. Before sacrificed, the rats were taken echocardiography to detect left ventricular diastolic diameter (LVID), short axis shrinkage (FS), left ventricular ejection fraction (LVEF), interventricular septum thickness (IVS), diastolic left ventricular posterior wall thickness (LPDW), mitral E/A and tissue Doppler (E’/A’) and other indicators. The rats were taken cardiac catheterization to detect left ventricular end-diastolic pressure (left ventricular end-diastolic pressure, LVEDP). Abdominal aortic blood was collected to detect fasting blood glucose (FBG), glycosylated hemoglobin (HbAlC), lipids, BNP, IL-6 and TNF-a. The of phosphorylation of STAT3 tyrosine sites (Tyr705), JAK2 phosphorylation and the expression of activated caspase3, Bcl-2, Bax, p-ERK and ERK were immunodetected by Western blot. Heart tissues were fixed in 4% paraformaldehyde and embedded in paraffin for morphological experiments of hematoxylin-eosin (HE), masson staining andimmunohistochemistry staining.Results1. Between Control-1w and HFD-lw groups, there was no significant difference.2. Compared with the same feeding duration groups (Control-4w, Control-9w, Control-14w, Control-21w group), HFD rats (HFD-4w, HFD-9w, HFD-14w, HFD-21w group) showed insulin resistance and FBG increased slightly. HFD-9w, HFD-14w and HFD-21w showed left ventricular diastolic dysfunction and HFD-21w rats were significantly left ventricular remodeling. FBG significantly increased in diabetic rats (DM-9w, DM-14w, DM-21w), with significant left ventricular diastolic dysfunction, systolic dysfunction (but still at a normal level) and increased left ventricular end-diastolic pressure. DM-14w and DM-21w rats became significantly left ventricular remodeling.3. After feeding for 9 weeks, serum TG, TC, IL-6 and TNF-α in HFD rats (HFD-9w, HFD-14w, HFD-21w) were significantly increased compared with control rats (P<0.05). Compared with HFD rats, serum IL-6 and serum TNF-α were significantly increased in DM-14w and DM-21 w rats (P<0.05).4. After feeding for 4 weeks, JAK2/STAT3 pathway in HFD rats cardiomyocytes activated significantly and consistently compared with control rats. JAK2/STAT3 pathway activated in DM-9w and DM-14w rats, while down-regulated in DM-21 w rats compared with control rats.5. After feeding for 9 weeks, Bax/Bcl-2 ratio and cleaved caspase3 significantly increased in HFD group compared with control group. Compared with HFD group, Bax/Bcl-2 ratio and cleaved caspase3 significantly increased in DM rats.6. The levels of HbA1C were decreased in MET, STAG10 or STAG20 group comparing with DM-21w group, while sill higher than Control-21w group. The inflammation levels in MET, STAG10 or STAG20 were reduced and there were no statistically significant differences among the three groups. Rats in MET, STAG10 or STAG20 group had less heart apoptosis, interstitial fibrosis and left ventricular remodeling comparing with rats in DM-21w group. MET improved diabetic cardiomyopathy pathologic courses much more than STAG10 and STAG20. There was no statistical difference between STAG10 and STAG20 group. JAK2/STAT3 pathway activated significantly in MET group but not obviously in STAG10 and STAG20.Conclusions1. Inflammatory was activated in DCM rats and HFD rats with increased left ventricular remodeling. JAK2/STAT3 pathway was consistently activated in HFD rats, while activated in the early phase in DCM rats, down-regulated in the later-stage and inhibited in final-stage. The activation of JAK2/STAT3 pathway may be a compensatory self-protection response to inflammation. However, it’s dysregulated in DCM heart and caused more serious injury compared with HFD ones.2. Both of metformin and sitagliptin could improve cardiac remodeling in DCM rats. Metformin showed its superiority in exerting hear protection. The protective effect of metformin may partly owe to the activation of JAK2/STAT3 pathway.Metformin ameliorates hyperglycemia-induced cardiomyocyte apoptosis through promoting STAT3 activationBackground:Metformin (MET) has been proved to provide cardioprotective effects in patients with diabetic disease. However, the mechanisms appear diverse and remain unclear.Purpose:We aimed to determine whether MET could ameliorate cardiomyocyte apoptosis by promoting STAT3 activation under high glucose condition.Methods and Results:Neonatal primary cardiomyocytes were prepared and cultured with high glucose and different concentrations of MET. MET significantly decreased HG-induced cell apoptosis by reducing the ratio of Bcl2-associated X protein to B-cell lymphoma/leukemia-2 (bax/bcl-2). Meanwhile, STAT3 tyrosine phosphorylation was markedly decreased after 24 h of hyperglycaemia (P< 0.05), which was significantly activated by MET, especially at the 1mM concentration (P< 0.05).Conclusion:MET could reduce high glucose-induced cardiomyocytes injury, which may be associated with STAT3 activation.Objective:We aimed to evaluate the impact of diabetes duration on long-term clinical outcomes after drug-eluting stent (DES) implantation or coronary artery bypass grafting (CABG).Methods:A total of 820 diabetic patients treated with initial DES (n=451) or CABG (n=369) were consecutively included in this single-center follow-up study. Main outcomes included repeat revascularization, major adverse cardiac events (MACEs) [ie, death, nonfatal myocardial infarction (MI), repeat revascularization], and major adverse cardiac or cerebrovascular events (MACCEs). Cox regression analysis with propensity adjustment was used for data analysis.Results:After adjusting for potential covariates,3-year risks of MACEs were significantly higher in the DES group compared with the CABG group regardless of the diabetes durations less or more than 5 years (HR 2.27,95% CI 1.19-4.31, p=0.01; HR 3.73,95% CI 2.72-10.12, p<0.01; p for interaction=0.28). A similar trend was observed for repeat revascularization. However, CABG was associated withincreased risk of stroke, especially in the patients with diabetes duration ≥5 years (HR 0.02,95% CI 0.002-0.12, p<0.01).3-year risk of MACCEs was significantly higher in the DES group in patients with diabetes duration≥ 5 years (HR 2.13,95% CI 1.34-3.39,p<0.01), but not for those < 5 years (HR 1.03,95% CI 0.65-1.63, p=0.91). A statistically significant interaction between diabetes duration and treatment strategy was found for MACCEs (p for interaction=0.04). Although a similar trend was observed for death and nonfatal MI, the interaction did not reach statistical significance (p for interaction=0.16,0.23 respectively).Conclusions: These findings suggested that short diabetes duration (< 5 years) was associated with equal risk of MACCEs among stable CAD patients with PCI and CABG, emphasizing the need to consider the diabetes duration for the choice of best strategy in subjects undergoing coronary revascularization.