Effects of glucagon-like peptide 1 analogs in combination with insulin on myocardial infarct size in rats with type 2 diabetes mellitus

Inhibiting H2AX Can Ameliorate Myocardial Ischemia/Reperfusion Injury by Regulating P53/JNK Signaling Pathway

Myocardial ischemia-reperfusion (I/R) injury is a significant area of focus in cardiovascular disease research. I/R injury can increase intracellular oxidative stress, leading to DNA damage. H2AX plays a crucial role in DNA repair. This study utilized mouse and cell models of myocardial I/R to investigate the impact of H2AX on cardiomyocytes during I/R. This study initially assessed the expression of H2AX in MI/R mice compared to a sham surgery group. Subsequently, cardiac function, infarct area, and mitochondrial damage were evaluated after inhibiting H2AX in MI/R mice and a negative control group. Furthermore, the study delved into the molecular mechanisms by analyzing the expression of H2AX, P53, p-JNK, SHP2, p-SHP2, p-RAS, parkin, Drp1, Cyt-C, Caspase-3, and Caspase-8 in cardiomyocytes following the addition of JNK or P53 agonists. The results from western blotting in vivo indicated significantly higher H2AX expression in the MI/R group compared to the sham group. Inhibiting H2AX improved cardiac function, reduced myocardial infarct area, and mitigated mitochondrial damage in the MI/R group. In vitro experiments demonstrated that inhibiting H2AX could attenuate mitochondrial damage and apoptosis in myocardial cells by modulating the P53 and JNK signaling pathways. These findings suggested that inhibiting H2AX may alleviate myocardial I/R injury through the regulation of the P53/JNK pathway, highlighting H2AX as a potential target for the treatment of myocardial ischemia/reperfusion injury.

The benefits of oral glucose-lowering agents: GLP-1 receptor agonists, DPP-4 and SGLT-2 inhibitors on myocardial ischaemia/reperfusion injury

Myocardial infarction (MI) is a life-threatening cardiovascular disease that, on average, results in 8.5 million deaths worldwide each year. Timely revascularization of occluded vessels is a critical method of myocardial salvage. However, reperfusion paradoxically leads to the worsening of myocardial damage known as myocardial ischaemia/reperfusion injury (MI/RI). Therefore, reducing the size of myocardial infarction after reperfusion is critical and remains an important therapeutic goal. The susceptibility of the myocardium to MI/RI may be increased by diabetes. Currently, some traditional antidiabetic agents such as metformin reduce MI/RI by decreasing inflammation, inhibiting oxidative stress, and improving vascular endothelial function. This appears to be a new direction for the treatment of MI/RI. Recent cardiovascular outcome trials have shown that several oral antidiabetic agents, including glucagon-like peptide-1 receptor agonists (GLP-1RAs), dipeptidyl peptidase-4 inhibitors (DPP-4is), and sodium-glucose-linked transporter-2 inhibitors (SGLT-2is), not only have good antidiabetic effects but also have a protective effect on myocardial protection. This article aims to discuss the mechanisms and effects of oral antidiabetic agents, including GLP-1RAs, DPP-4is, and SGLT-2is, on MI/RI to facilitate their clinical application.

Preclinical multi-target strategies for myocardial ischemia-reperfusion injury

Despite promising breakthroughs in diagnosing and treating acute coronary syndromes, cardiovascular disease’s high global mortality rate remains indisputable. Nearly half of these patients died of ischemic heart disease. Primary percutaneous coronary intervention (PCI) and coronary artery bypass grafting can rapidly restore interrupted blood flow and become the most effective method for salvaging viable myocardium. However, restoring blood flow could increase the risk of other complications and myocardial cell death attributed to myocardial ischemia-reperfusion injury (IRI). How to reduce the damage of blood reperfusion to ischemic myocardium has become an urgent problem to be solved. In preclinical experiments, many treatments have substantial cardioprotective effects against myocardial IRI. However, the transition from these cardioprotective therapies to clinically beneficial therapies for patients with acute myocardial infarction remains elusive. The reasons for the failure of the clinical translation may be multi-faceted, and three points are summarized here: (1) Our understanding of the complex pathophysiological mechanisms of myocardial IRI is far from enough, and the classification of specific therapeutic targets is not rigorous, and not clear enough; (2) Most of the clinical patients have comorbidities, and single cardioprotective strategies including ischemia regulation strategies cannot exert their due cardioprotective effects under conditions of hyperglycemia, hypertension, hyperlipidemia, and aging; (3) Most preclinical experimental results are based on adult, healthy animal models. However, most clinical patients had comorbidities and received multiple drug treatments before reperfusion therapy. In 2019, COST Action proposed a multi-target drug combination initiative for prospective myocardial IRI; the optimal cardioprotective strategy may be a combination of additive or synergistic multi-target therapy, which we support. By establishing more reasonable preclinical models, screening multi-target drug combinations more in line with clinical practice will benefit the translation of clinical treatment strategies.

Dynamics of total volume of pancreatic α- and β -cells under the influence sulfonylureas and their combination with dipeptidyl peptidase-4 inhibitors

Objective

Sulfonylureas and dipeptidyl peptidase‐4 inhibitors have a multidirectional effect on pancreatic cells. We aimed to evaluate the effects of these drugs on β‐ and α‐cells in rats aged 12 months with type 2 diabetes mellitus when administered in combination with various sulfonylureas.

Methods

Streptozotocin‐nicotinamide induced type 2 diabetes mellitus was induced in rats aged 12 months. Animals received the sulfonylureas gliclazide or glibenclamide for 24 weeks alone or in combination with the dipeptidyl peptidase‐4 inhibitor vildagliptin or vildagliptin monotherapy. Blood glucose and animal weights were measured before and during the experiment. The oral glucose tolerance test was conducted before therapy initiation. Immunohistochemical analyses were conducted after the end of the experiment using glucagon and insulin antibodies. The total volumes of α and β cells were estimated in relation to the volume of the pancreatic islets.

Results

The total volumes of β‐cells did not differ between the sulfonylurea group and the untreated type 2 diabetes mellitus group. The addition of dipeptidyl peptidase‐4 inhibitors to sulfonylureas normalized the total volumes of β cells. The total volumes of α‐cells in the gliclazide group and combination of gliclazide with dipeptidyl peptidase‐4 inhibitor was comparable to that in the control group of intact animals, in contrast with the glibenclamide group.

Conclusion

The combination of vildagliptin to both sulfonylureas contributed to the normalisation of β‐cells number. Normalisation of the total volumes of α‐cells was observed with gliclazide therapy and combination of gliclazide with dipeptidyl peptidase‐4 inhibitor.

Xuan Bi Tong Yu Fang Promotes Angiogenesis via VEGF-Notch1/Dll4 Pathway in Myocardial Ischemic Rats

OBJECTIVE

To investigate the effect of Xuan Bi Tong Yu Fang (XBTYF) on angiogenesis via the vascular endothelial growth factor- (VEGF-) Notch1/delta-like 4 (Dll4) pathway. Materials and Methods. Sixty Sprague-Dawley rats were randomly divided into six groups: control, sham-operated, myocardial ischemia model, and XBTYF treatment at 3.2, 1.6, and 0.8 g/kg. Electrocardiography was performed to evaluate the successful establishment of the model. Hematoxylin-eosin staining and transmission electron microscopy were carried out to observe the morphology and mitochondrial structure in myocardial cells, respectively. TUNEL staining was performed to assess the degree of cell apoptosis. The expression of VEGF-A, Notch1, Dll4, Bcl2, Bax, caspase 3, caspase 9, and cytochrome-c (Cyt-c) was observed by western blot.

RESULTS

XBTYF inhibited changes to the morphology and mitochondrial structure in cardiomyocyte and reduced cell apoptosis. Compared with the model group, XBTYF at all doses (3.2, 1.6, and 0.8 g/kg) reduced the expression of Notch1, Dll4, Bax, caspase 3, caspase 9, and Cyt-c, whereas expression of VEGF-A and Bcl2 was increased.

CONCLUSION

XBTYF attenuated mitochondrial damage and cell apoptosis while promoting the angiogenesis of cardiomyocyte. The associated mechanism may be related to the VEGF-Notch1/Dll4 pathway.

DPP-4 inhibition by linagliptin prevents cardiac dysfunction and inflammation by targeting the Nlrp3/ASC inflammasome

We compared the effects of linagliptin (Lina, a DPP4 inhibitor) and GLP-1 receptor activation by exenatide followed by exendin-4 in an infusion pump (EX) on infarct size (IS), post-infarction activation of the inflammasome and remodeling in wild-type (WT) and db/db diabetic mice. Mice underwent 30 min ischemia followed by 24 h reperfusion. IS was assessed by TTC. Additional mice underwent permanent coronary artery occlusion. Echocardiography was performed 2w after infarction. Activation of the inflammasome in the border zone of the infarction was assessed by rt-PCR and ELISA 2w after reperfusion. Further in vitro experiments were done using primary human cardiofibroblasts and cardiomyocytes exposed to simulated ischemia-reoxygenation. Lina and EX limited IS in both the WT and the db/db mice. Lina and EX equally improved ejection fraction in both the WT and the db/db mice. mRNA levels of ASC, NALP3, IL-1β, IL-6, Collagen-1, and Collagen-3 were higher in the db/db mice than in the WT mice. Infarction increased these levels in the WT and db/db mice. Lina more than EX attenuated the increase in ASC, NALP3, IL-1β, IL-6, Collagen-1 and Collagen-3, TNFα and IL-1β, and decreased apoptosis, especially in the db/db mice. In vitro experiments showed that Lina, but not EX, attenuated the increase in TLR4 expression, an effect that was dependent on p38 activation with downstream upregulation of Let-7i and miR-146b levels. Lina and EX had similar effects on IS and post-infarction function, but Lina attenuated the activation of the inflammasome and the upregulation of collagen-1 and collagen-3 more than direct GLP-1 receptor activation. This effect depends on p38 activation with downstream upregulation of miR-146b levels that suppresses TLR4 expression.