Inhibition of p53 prevents diabetic cardiomyopathy by preventing early-stage apoptosis and cell senescence, reduced glycolysis, and impaired angiogenesis

The triterpene, methyl-3β-hydroxylanosta-9,24-dien-21-oate (RA3), attenuates high glucose-induced oxidative damage and apoptosis by improving energy metabolism

BACKGROUND

Hyperglycemia-induced cardiovascular dysfunction has been linked to oxidative stress and accelerated apoptosis in the diabetic myocardium. While there is currently no treatment for diabetic cardiomyopathy (DCM), studies suggest that the combinational use of anti-hyperglycemic agents and triterpenes could be effective in alleviating DCM.

HYPOTHESIS

To investigate the therapeutic effect of methyl-3β-hydroxylanosta-9,24-dien-21-oate (RA3), in the absence or presence of the anti-diabetic drug, metformin (MET), against hyperglycemia-induced cardiac injury using an in vitro H9c2 cell model.

METHODS

To mimic a hyperglycemic state, H9c2 cells were exposed to high glucose (HG, 33 mM) for 24 h. Thereafter, the cells were treated with RA3 (1 μM), MET (1 μM) and the combination of MET (1 μM) plus RA3 (1 μM) for 24 h, to assess the treatments therapeutic effect.

RESULTS

Biochemical analysis revealed that RA3, with or without MET, improves glucose uptake via insulin-dependent (IRS-1/PI3K/Akt signaling) and independent (AMPK) pathways whilst ameliorating the activity of antioxidant enzymes in the H9c2 cells. Mechanistically, RA3 was able to alleviate HG-stimulated oxidative stress through the inhibition of reactive oxygen species (ROS) and lipid peroxidation as well as the reduced expression of the PKC/NF-кB cascade through decreased intracellular lipid content. Subsequently, RA3 was able to mitigate HG-induced apoptosis by decreasing the activity of caspase 3/7 and DNA fragmentation in the cardiomyoblasts.

CONCLUSION

RA3, in the absence or presence of MET, demonstrated potent therapeutic properties against hyperglycemia-mediated cardiac damage and could be a suitable candidate in the prevention of DCM.

Pathological Relationship between Intracellular Superoxide Metabolism and p53 Signaling in Mice

Intracellular superoxide dismutases (SODs) maintain tissue homeostasis via superoxide metabolism. We previously reported that intracellular reactive oxygen species (ROS), including superoxide accumulation caused by cytoplasmic SOD (SOD1) or mitochondrial SOD (SOD2) insufficiency, induced p53 activation in cells. SOD1 loss also induced several age-related pathological changes associated with increased oxidative molecules in mice. To evaluate the contribution of p53 activation for SOD1 knockout (KO) (Sod1-/-) mice, we generated SOD1 and p53 KO (double-knockout (DKO)) mice. DKO fibroblasts showed increased cell viability with decreased apoptosis compared with Sod1-/- fibroblasts. In vivo experiments revealed that p53 insufficiency was not a great contributor to aging-like tissue changes but accelerated tumorigenesis in Sod1-/- mice. Furthermore, p53 loss failed to improve dilated cardiomyopathy or the survival in heart-specific SOD2 conditional KO mice. These data indicated that p53 regulated ROS-mediated apoptotic cell death and tumorigenesis but not ROS-mediated tissue degeneration in SOD-deficient models.

The regulatory roles of p53 in cardiovascular health and disease

Cardiovascular disease (CVD) remains the leading cause of mortality globally, so further investigation is required to identify its underlying mechanisms and potential targets for its prevention. The transcription factor p53 functions as a gatekeeper, regulating a myriad of genes to maintain normal cell functions. It has received a great deal of research attention as a tumor suppressor. In the past three decades, evidence has also shown a regulatory role for p53 in the heart. Basal p53 is essential for embryonic cardiac development; it is also necessary to maintain normal heart architecture and physiological function. In pathological cardiovascular circumstances, p53 expression is elevated in both patient samples and animal models. Elevated p53 plays a regulatory role via anti-angiogenesis, pro-programmed cell death, metabolism regulation, and cell cycle arrest regulation. This largely promotes the development of CVDs, particularly cardiac remodeling in the infarcted heart, hypertrophic cardiomyopathy, dilated cardiomyopathy, and diabetic cardiomyopathy. Roles for p53 have also been found in atherosclerosis and chemotherapy-induced cardiotoxicity. However, it has different roles in cardiomyocytes and non-myocytes, even in the same model. In this review, we describe the different effects of p53 in cardiovascular physiological and pathological conditions, in addition to potential CVD therapies targeting p53.

A novel role of kallikrein-related peptidase 8 in the pathogenesis of diabetic cardiac fibrosis

Rationale: Among all the diabetic complications, diabetic cardiomyopathy, which is characterized by myocyte loss and myocardial fibrosis, is the leading cause of mortality and morbidity in diabetic patients. Tissue kallikrein-related peptidases (KLKs) are secreted serine proteases, that have distinct and overlapping roles in the pathogenesis of cardiovascular diseases. However, whether KLKs are involved in the development of diabetic cardiomyopathy remains unknown.The present study aimed to determine the role of a specific KLK in the initiation of endothelial-to-mesenchymal transition (EndMT) during the pathogenesis of diabetic cardiomyopathy.

Methods and Results-By screening gene expression profiles of KLKs, it was found that KLK8 was highly induced in the myocardium of mice with streptozotocin-induced diabetes. KLK8 deficiency attenuated diabetic cardiac fibrosis, and rescued the impaired cardiac function in diabetic mice. Small interfering RNA (siRNA)-mediated KLK8 knockdown significantly attenuated high glucose-induced endothelial damage and EndMT in human coronary artery endothelial cells (HCAECs). Diabetes-induced endothelial injury and cardiac EndMT were significantly alleviated in KLK8-deficient mice. In addition, transgenic overexpression of KLK8 led to interstitial and perivascular cardiac fibrosis, endothelial injury and EndMT in the heart. Adenovirus-mediated overexpression of KLK8 (Ad-KLK8) resulted in increases in endothelial cell damage, permeability and transforming growth factor (TGF)-β1 release in HCAECs. KLK8 overexpression also induced EndMT in HCAECs, which was alleviated by a TGF-β1-neutralizing antibody. A specificity protein-1 (Sp-1) consensus site was identified in the human KLK8 promoter and was found to mediate the high glucose-induced KLK8 expression. Mechanistically, it was identified that the vascular endothelial (VE)-cadherin/plakoglobin complex may associate with KLK8 in HCAECs. KLK8 cleaved the VE-cadherin extracellular domain, thus promoting plakoglobin nuclear translocation. Plakoglobin was required for KLK8-induced EndMT by cooperating with p53. KLK8 overexpression led to plakoglobin-dependent association of p53 with hypoxia inducible factor (HIF)-1α, which further enhanced the transactivation effect of HIF-1α on the TGF-β1 promoter. KLK8 also induced the binding of p53 with Smad3, subsequently promoting pro-EndMT reprogramming via the TGF-β1/Smad signaling pathway in HCAECs. The in vitro and in vivo findings further demonstrated that high glucose may promote plakoglobin-dependent cooperation of p53 with HIF-1α and Smad3, subsequently increasing the expression of TGF-β1 and the pro-EndMT target genes of the TGF-β1/Smad signaling pathway in a KLK8-dependent manner.

Conclusions: The present findings uncovered a novel pro-EndMT mechanism during the pathogenesis of diabetic cardiac fibrosis via the upregulation of KLK8, and may contribute to the development of future KLK8-based therapeutic strategies for diabetic cardiomyopathy.

Role of ferroptosis in the process of diabetes-induced endothelial dysfunction

BACKGROUND

Endothelial dysfunction, a hallmark of diabetes, is a critical and initiating contributor to the pathogenesis of diabetic cardiovascular complications. However, the underlying mechanisms are still not fully understood. Ferroptosis is a newly defined regulated cell death driven by cellular metabolism and iron-dependent lipid peroxidation. Although the involvement of ferroptosis in disease pathogenesis has been shown in cancers and degenerative diseases, the participation of ferroptosis in the pathogenesis of diabetic endothelial dysfunction remains unclear.

AIM

To examine the role of ferroptosis in diabetes-induced endothelial dysfunction and the underlying mechanisms.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with high glucose (HG), interleukin-1β (IL-1β), and ferroptosis inhibitor, and then the cell viability, reactive oxygen species (ROS), and ferroptosis-related marker protein were tested. To further determine whether the p53-xCT (the substrate-specific subunit of system Xc^-)-glutathione (GSH) axis is involved in HG and IL-1β induced ferroptosis, HUVECs were transiently transfected with p53 small interfering ribonucleic acid or NC small interfering ribonucleic acid and then treated with HG and IL-1β. Cell viability, ROS, and ferroptosis-related marker protein were then assessed. In addition, we detected the xCT and p53 expression in the aorta of db/db mice.

RESULTS

It was found that HG and IL-1β induced ferroptosis in HUVECs, as evidenced by the protective effect of the ferroptosis inhibitors, Deferoxamine and ferrostatin-1, resulting in increased lipid ROS and decreased cell viability. Mechanistically, activation of the p53-xCT-GSH axis induced by HG and IL-1β enhanced ferroptosis in HUVECs. In addition, a decrease in xCT and the presence of de-endothelialized areas were observed in the aortic endothelium of db/db mice.

CONCLUSION

Ferroptosis is involved in endothelial dysfunction and p53-xCT-GSH axis activation plays a crucial role in endothelial cell ferroptosis and endothelial dysfunction.

Overexpression of p53 due to excess protein O-GlcNAcylation is associated with coronary microvascular disease in type 2 diabetes

AIMS

We previously reported that increased protein O-GlcNAcylation in diabetic mice led to vascular rarefaction in the heart. In this study, we aimed to investigate whether and how coronary endothelial cell (EC) apoptosis is enhanced by protein O-GlcNAcylation and thus induces coronary microvascular disease (CMD) and subsequent cardiac dysfunction in diabetes. We hypothesize that excessive protein O-GlcNAcylation increases p53 that leads to CMD and reduced cardiac contractility.

METHODS AND RESULTS

We conducted in vivo functional experiments in control mice, TALLYHO/Jng (TH) mice, a polygenic type 2 diabetic (T2D) model, and EC-specific O-GlcNAcase (OGA, an enzyme that catalyzes the removal of O-GlcNAc from proteins)-overexpressing TH mice, as well as in vitro experiments in isolated ECs from these mice. TH mice exhibited a significant increase in coronary EC apoptosis and reduction of coronary flow velocity reserve (CFVR), an assessment of coronary microvascular function, in comparison to wild-type mice. The decreased CFVR, due at least partially to EC apoptosis, was associated with decreased cardiac contractility in TH mice. Western blot experiments showed that p53 protein level was significantly higher in coronary ECs from TH mice and T2D patients than in control ECs. High glucose treatment also increased p53 protein level in control ECs. Furthermore, overexpression of OGA decreased protein O-GlcNAcylation and down-regulated p53 in coronary ECs, and conferred a protective effect on cardiac function in TH mice. Inhibition of p53 with pifithrin-α attenuated coronary EC apoptosis and restored CFVR and cardiac contractility in TH mice.

CONCLUSIONS

The data from this study indicate that inhibition of p53 or down-regulation of p53 by OGA overexpression attenuates coronary EC apoptosis and improves CFVR and cardiac function in diabetes. Lowering coronary endothelial p53 levels via OGA overexpression could be a potential therapeutic approach for CMD in diabetes.

Sodium hydrosulfide alleviates dexamethasone-induced cell senescence and dysfunction through targeting the miR-22/sirt1 pathway in osteoblastic MC3T3-E1 cells

Glucocorticoid-induced osteoporosis is characterized by osteoblastic cell and microarchitecture dysfunction, as well as a loss of bone mass. Cell senescence contributes to the pathological process of osteoporosis and sodium hydrosulfide (NaHS) regulates the potent protective effects through delaying cell senescence. The aim of the present study was to investigate whether senescence could contribute to dexamethasone (Dex)-induced osteoblast impairment and to examine the effect of NaHS on Dex-induced cell senescence and damage. It was found that the levels of the senescence-associated markers, p53 and p21, were markedly increased in osteoblasts exposed to Dex. A p53 inhibitor reversed Dex-induced osteoblast injury, a process that was mitigated by NaHS administration through alleviating osteoblastic cell senescence. MicroRNA (miR)-22 blocked the impact of NaHS on Dex-induced osteoblast damage and senescence through targeting the regulation of Sirtuin 1 (sirt1) expression, as shown by the decreased cell viability and alkaline phosphatase activity, as well as an increased expression of p53 and p21. It was revealed that the sirt1 gene was the target of miR-22 in osteoblastic MC3T3-E1 cells through combining the results of dual luciferase reporter assays and reverse transcription-quantitative PCR, as well as western blot analyses. Silencing of sirt1 abolished the protective effect of NaHS against Dex-associated osteoblast senescence and injury. Taken together, the present study showed that NaHS prevents Dex-induced cell senescence and damage through targeting the miR-22/sirt1 pathway in osteoblastic MC3T3-E1 cells.

LncRNA LINC00673 is Downregulated in Diabetic Retinopathy and Regulates the Apoptosis of Retinal Pigment Epithelial Cells via Negatively Regulating p53

BACKGROUND

Long noncoding RNA (LncRNA) LINC00673 has been proven to play critical roles in cancer biology, while its role in other diseases is unknown. It has been reported that LINC00673 could interact with p53, a critical player in diabetes and diabetic complications, suggesting that LINC00673 may also participate in diabetic retinopathy (DR). This study aimed to investigate the role of LINC00673 in DR.

METHODS

The present study included 3 groups of participants, including DR group, diabetes (DB) group, and healthy control (Control) group. Flow cytometry was utilized to determine cell apoptosis. Proteins and messenger RNAs (mRNAs) were estimated by Western blot and quantitative reverse transcription PCR (qRT-PCR), respectively.

RESULTS

LINC00673 was downregulated in plasma samples of DR patients (n=60) in comparison with the healthy controls (n=60) and negatively correlated with p53 only across DR patients but not across the healthy controls. In retinal pigment epithelial cells (RPECs), high glucose treatment downregulated LINC00673. Moreover, LINC00673 overexpression downregulated p53 and decreased RPEC apoptosis, while LINC00673 silencing upregulated p53 and increased RPEC apoptosis. In addition, p53 overexpression reduced the effects of LINC00673 overexpression.

CONCLUSION

LINC00673 is downregulated in DR patients and regulates RPEC apoptosis via negatively regulating p53.

lncRNA ZEB1-AS1 is downregulated in diabetic lung and regulates lung cell apoptosis

The present study aimed to investigate the role of ZEB1-antisense RNA 1 (AS1) in diabetic lung (pneumonia with excluded causes other than diabetes). In the present study, the expression of ZEB1-AS1 in plasma was detected by performing reverse transcription-quantitative PCR. A receiver operating characteristic curve was used for diagnostic analysis. Lung cell apoptosis under the treatment of high glucose was analyzed by a cell apoptosis assay. p53 expression in lung cells was detected by performing western blotting. The present data demonstrated that ZEB1-AS1 was downregulated in the plasma of patients with diabetic lung (DL) compared with diabetic patients without complications (~1.6-fold) and healthy controls (~2.4-fold), and downregulation of ZEB1-AS1 distinguished patients with DL from healthy controls. ZEB1-AS1 in lung cells was downregulated by high glucose treatment, and overexpression of ZEB1-AS1 resulted in inhibited lung cancer cell apoptosis and downregulated p53. p53 overexpression attenuated the effects of ZEB1-AS1 overexpression on lung cell apoptosis. In conclusion, the present study demonstrated that ZEB1-AS1 was downregulated in patients with DL and regulates lung cancer cell apoptosis by downregulating p53.

Diabetic Cardiomyopathy: Clinical and Metabolic Approach

BACKGROUND

Having in mind that diabetes mellitus (DM) and obesity are some of the greatest health challenges of the modern era, diabetic cardiomyopathy (DCM) is becoming more and more recognized in clinical practice. Main Text: Initially, DM is asymptomatic, but it may progress to diastolic and then systolic left ventricular dysfunction, which results in congestive heart failure. A basic feature of this DM complication is the absence of hemodynamically significant stenosis of the coronary blood vessels. Clinical manifestations are the result of several metabolic disorders that are present during DM progression. The complexity of metabolic processes, along with numerous regulatory mechanisms, has been the subject of research that aims at discovering new diagnostic (e.g. myocardial strain with echocardiography and cardiac magnetic resonance) and treatment options. Adequate glycaemic control is not sufficient to prevent or reduce the progression of DCM. Contemporary hypoglycemic medications, such as sodium-glucose transport protein 2 inhibitors, significantly reduce the frequency of cardiovascular complications in patients with DM. Several studies have shown that, unlike the above-stated medications, thiazolidinediones and dipeptidyl peptidase-4 inhibitors are associated with deterioration of heart failure.

CONCLUSION

Imaging procedures, especially myocardial strain with echocardiography and cardiac magnetic resonance, are useful to identify the early signs of DCM. Research and studies regarding new treatment options are still "in progress".

Protective role of NRF2 in macrovascular complications of diabetes

Macrovascular complications develop in over a half of the diabetic individuals, resulting in high morbidity and mortality. This poses a severe threat to public health and a heavy burden to social economy. It is therefore important to develop effective approaches to prevent or slow down the pathogenesis and progression of macrovascular complications of diabetes (MCD). Oxidative stress is a major contributor to MCD. Nuclear factor (erythroid‐derived 2)‐like 2 (NRF2) governs cellular antioxidant defence system by activating the transcription of various antioxidant genes, combating diabetes‐induced oxidative stress. Accumulating experimental evidence has demonstrated that NRF2 activation protects against MCD. Structural inhibition of Kelch‐like ECH‐associated protein 1 (KEAP1) is a canonical way to activate NRF2. More recently, novel approaches, such as activation of the Nfe2l2 gene transcription, decreasing KEAP1 protein level by microRNA‐induced degradation of Keap1 mRNA, prevention of proteasomal degradation of NRF2 protein and modulation of other upstream regulators of NRF2, have emerged in prevention of MCD. This review provides a brief introduction of the pathophysiology of MCD and the role of oxidative stress in the pathogenesis of MCD. By reviewing previous work on the activation of NRF2 in MCD, we summarize strategies to activate NRF2, providing clues for future intervention of MCD. Controversies over NRF2 activation and future perspectives are also provided in this review.

The role of MDM2-p53 axis dysfunction in the hepatocellular carcinoma transformation

Liver cancer is the second most frequent cause of cancer-related death globally. The main histological subtype is hepatocellular carcinoma (HCC), which is derived from hepatocytes. According to the epidemiologic studies, the most important risk factors of HCC are chronic viral infections (HBV, HCV, and HIV) and metabolic disease (metabolic syndrome). Interestingly, these carcinogenic factors that contributed to HCC are associated with MDM2-p53 axis dysfunction, which presented with inactivation of p53 and overactivation of MDM2 (a transcriptional target and negative regulator of p53). Mechanically, the homeostasis of MDM2-p53 feedback loop plays an important role in controlling the initiation and progression of HCC, which has been found to be dysregulated in HCC tissues. To maintain long-term survival in hepatocytes, hepatitis viruses have lots of ways to destroy the defense strategies of hepatocytes by inducing TP53 mutation and silencing, promoting MDM2 overexpression, accelerating p53 degradation, and stabilizing MDM2. As a result, genetic instability, chronic ER stress, oxidative stress, energy metabolism switch, and abnormalities in antitumor genes can be induced, all of which might promote hepatocytes' transformation into hepatoma cells. In addition, abnormal proliferative hepatocytes and precancerous cells cannot be killed, because of hepatitis viruses-mediated exhaustion of Kupffer cells and hepatic stellate cells (HSCs) and CD4+T cells by disrupting their MDM2-p53 axis. Moreover, inefficiency of hepatic immune response can be further aggravated when hepatitis viruses co-infected with HIV. Unlike with chronic viral infections, MDM2-p53 axis might play a dual role in glucolipid metabolism of hepatocytes, which presented with enhancing glucolipid catabolism, but promoting hepatocyte injury at the early and late stages of glucolipid metabolism disorder. Oxidative stress, fatty degeneration, and abnormal cell growth can be detected in hepatocytes that were suffering from glucolipid metabolism disorder, and all of which could contribute to HCC initiation. In this review, we focus on the current studies of the MDM2-p53 axis in HCC, and specifically discuss the impact of MDM2-p53 axis dysfunction by viral infection and metabolic disease in the transformation of normal hepatocytes into hepatoma cells. We also discuss the therapeutic avenues and potential targets that are being developed to normalize the MDM2-p53 axis in HCC.

Expression profiling of circular RNAs and their potential role in early‑stage diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a severe cardiovascular complication of diabetes mellitus (DM). Detecting DCM during the early stages of the disease remains a challenge, as the molecular mechanisms underlying early‑stage DCM are not clearly understood. Circular RNA (circRNA), a type of non‑coding RNA, has been confirmed to be associated with numerous diseases. However, it is still unclear how circRNAs are involved in early‑stage DCM. In the present study, heart tissues harvested from BKS‑db/db knock‑out mice were identified through high‑throughput RNA sequencing technology. A total of 58 significantly differentially expressed circRNAs were identified in the db/db sample. Among these, six upregulated circRNAs and seven downregulated circRNAs were detected by reverse transcription‑quantitative PCR and analyzed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. Furthermore, based on the predicted binding site with microRNAs (miRNAs) involved in DCM, five circRNAs (mmu_circ_0000652, mmu_circ_0000547, mmu_circ_0001058, mmu_circ_0000680 and novel_circ_0004285) were shown to serve as competing endogenous (ce)RNAs. The corresponding miRNAs and mRNAs of the ceRNAs were also verified, and two promising circRNA‑miRNA‑mRNA regulatory networks were determined. Finally, internal ribosome entry site prediction combined with open reading frame prediction indicated that it was highly possible that mmu_circ_0001160 encoded a protein. In the present study, a comprehensive analysis of the circRNA expression profile during the early phase of DCM was performed, and two promising circRNA‑miRNA‑mRNA regulatory networks were identified. These results lay the foundation for unravelling the underlying pathogenesis of DCM, and highlight potential biomarkers and therapeutic targets for the treatment of DCM at an early stage.

Connexin 32 deficiency protects the liver against ischemia/reperfusion injury

Hepatic ischemia/reperfusion (I/R) injury is a common complication in the clinical setting. Our previous study has shown that connexin 32 (Cx32) plays a major role in renal I/R injury; however, the role of Cx32 in hepatic I/R injury remains unknown. Liver tissue and serum samples from patients undergoing orthotopic liver transplantation (OLT) were used to evaluate the function of Cx32 in OLT post-reperfusion injury. Then, partial hepatic ischemia was established in global Cx32 knockout mice and wild-type mice followed by reperfusion. Hepatic injury markers were examined. Cx32 small interfering RNA and the p53 inhibitor, pifithrin-α, tenovin-1 were used to examine the relationship between Cx32 and the p53/puma pathways in the BRL-3A and murine primary hepatocytes hypoxia/reoxygenation (H/R) model. Corresponding to liver damage, Cx32 was significantly induced both during OLT in human patients and partial hepatic I/R in mice. Cx32 KO mice exhibited less liver injury than controls. Cx32 deficiency significantly suppressed the p53/puma pathways and hepatocyte apoptosis. Similar results were observed in the BRL-3A and murine primary hepatocytes H/R model. Propofol protected against OLT post-reperfusion injury and hepatocyte apoptosis by inhibiting Cx32. In conclusion Cx32 is a novel regulator of hepatic I/R injury through the modulation of hepatocyte apoptosis and damage, largely via the p53/puma signaling pathway.

Comparative Study of the Effects of GLP1 Analog and SGLT2 Inhibitor against Diabetic Cardiomyopathy in Type 2 Diabetic Rats: Possible Underlying Mechanisms

The present study investigated the possible cardioprotective effects of GLP1 and SGLT2i against diabetic cardiomyopathy (DCM) in type 2 diabetic rats and the possible underlying mechanisms.

METHODS

Thirty-two male Sprague Dawley rats were randomly subdivided into 4 equal groups: a) control group, b) DM group, type 2 diabetic rats with saline daily for 4 weeks, c) DM+ GLP1, as DM group with GLP1 analogue (liraglutide) at a dose of 75 µg/kg for 4 weeks, and d) DM+ SGLT2i as DM group with SGLT2 inhibitor (dapagliflozin) at a dose of 1mg/kg for 4 weeks. By the end of treatment (4 weeks), serum blood glucose, homeostasis model assessment insulin resistance (HOMA-IR), insulin, and cardiac enzymes (LDH, CK-MB) were measured. Also, the cardiac histopathology, myocardial oxidative stress markers (malondialdehyde (MDA), glutathione (GSH) and CAT) and norepinephrine (NE), myocardial fibrosis, the expression of caspase-3, TGF-β, TNF-α, and tyrosine hydroxylase (TH) in myocardial tissues were measured.

RESULTS

T2DM caused significant increase in serum glucose, HOMA-IR, serum CK-MB, and LDH (p < 0.05). Also, DM caused significant myocardial damage and fibrosis; elevation of myocardial MDA; NE with upregulation of myocardial caspase-3, TNF-α, TGF-β, and TH; and significant decrease in serum insulin and myocardial GSH and CAT (p < 0.05). Administration of either GLP1 analog or SGLT2i caused a significant improvement in all studied parameters (p < 0.05).

CONCLUSION

We concluded that both GLP1 and SGLT2i exhibited cardioprotective effects against DCM in T2DM, with the upper hand for SGLT2i. This might be due to attenuation of fibrosis, oxidative stress, apoptosis (caspase-3), sympathetic nerve activity, and inflammatory cytokines (TNF-α and TGF-β).

Cardiomyocyte Senescence and Cellular Communications Within Myocardial Microenvironments

Cardiovascular diseases have become the leading cause of human death. Aging is an independent risk factor for cardiovascular diseases. Cardiac aging is associated with maladaptation of cellular metabolism, dysfunction (or senescence) of cardiomyocytes, a decrease in angiogenesis, and an increase in tissue scarring (fibrosis). These events eventually lead to cardiac remodeling and failure. Senescent cardiomyocytes show the hallmarks of DNA damage, endoplasmic reticulum stress, mitochondria dysfunction, contractile dysfunction, hypertrophic growth, and senescence-associated secreting phenotype (SASP). Metabolism within cardiomyocytes is essential not only to fuel the pump function of the heart but also to maintain the functional homeostasis and participate in the senescence of cardiomyocytes. The senescence of cardiomyocyte is also regulated by the non-myocytes (endothelial cells, fibroblasts, and immune cells) in the local microenvironment. On the other hand, the senescent cardiomyocytes alter their phenotypes and subsequently affect the non-myocytes in the local microenvironment and contribute to cardiac aging and pathological remodeling. In this review, we first summarized the hallmarks of the senescence of cardiomyocytes. Then, we discussed the metabolic switch within senescent cardiomyocytes and provided a discussion of the cellular communications between dysfunctional cardiomyocytes and non-myocytes in the local microenvironment. We also addressed the functions of metabolic regulators within non-myocytes in modulating myocardial microenvironment. Finally, we pointed out some interesting and important questions that are needed to be addressed by further studies.

Nicorandil alleviates apoptosis in diabetic cardiomyopathy through PI3K/Akt pathway

Nicorandil exerts myocardial protection through its antihypoxia and antioxidant effects. Here, we investigated whether it plays an anti‐apoptotic role in diabetic cardiomyopathy. Sprague‐Dawley rats were fed with high‐fat diet; then single intraperitoneal injection of streptozotocin was performed. Rats with fasting blood glucose (FBG) higher than 11.1 mmol/L were selected as models. Eight weeks after the models were built, rats were treated with nicorandil (7.5 mg/kg day and 15 mg/kg day respectively) for 4 weeks. H9c2 cardiomyocytes were treated with nicorandil and then stimulated with high glucose (33.3 mmol/L). TUNEL assay and level of bcl‐2, bax and caspase‐3 were measured. 5‐HD was used to inhibit nicorandil. Also, PI3K inhibitor (Miltefosine) and mTOR inhibitor (rapamycin) were used to inhibit PI3K/Akt pathway. The results revealed that nicorandil (both 7.5 mg/kg day and 15mg/kg day) treatment can increase the level of NO in the serum and eNOS in the heart of diabetic rats compared with the untreated diabetic group. Nicorandil can also improve relieve cardiac dysfunction and reduce the level of apoptosis. In vitro experiments, nicorandil (100 µmol) can attenuate the level of apoptosis stimulated by high glucose significantly in H9C2 cardiomyocyte compared with the untreated group. The effect of nicorandil on apoptosis was blocked by 5‐HD, and it was accompanied with inhibition of the phosphorylation of PI3K, Akt, eNOS, and mTOR. After inhibition of PI3K/Akt pathway, the protective effect of nicorandil is restrained. These results verified that as a NO donor, nicorandil can also inhibit apoptosis in diabetic cardiomyopathy which is mediated by PI3K/Akt pathway.

A therapeutic approach towards microRNA29 family in vascular diabetic complications: A boon or curse?

Diabetes Mellitus (DM) is one of the major metabolic disorders and its severity leads to death. Enhancement in hyperglycaemic conditions of DM gives rise to endothelial impairment in small and large blood vessels contributing towards microvascular and macrovascular complications respectively. The pathogenesis of diabetic complications is associated with interruption of various signal transduction pathways due to epigenetic modifications such as aberrant histone modifications, DNA methylation and expression of miRNAs along with the long non-coding RNAs (lncRNAs). Amongst these epigenetic alterations, modulated expressions of miRNAs confer to apoptosis and endothelial dysfunction of organs that gives rise to vascular complications. In this review, we principally focussed on physiological role of miR29 family in DM and have discussed crosstalk between miR29 family and numerous genes involved in signal transduction pathways of Diabetic vascular complications. Incidences of diabetic retinopathy exploiting the role of miR29 in regulation of EMT process, differential expression patterns of miR29 and promising therapeutic role of miR29 have been discussed. We have summarised the therapeutic role of miR29 in podocyte impairment and how miR29 regulates the expressions of profibrotic, inflammatory and ECM encoding genes in renal fibrosis under diabetic conditions. We have also highlighted impact of miR29 expression patterns in cardiac angiopathy, cardiomyocyte's apoptosis and cardiac fibrosis. Additionally, we have also presented the contradictory actions of miR29 family in amelioration as well as in enhancement of diabetic complications.

Fas/FasL-mediated cell death in rat's diabetic hearts involves activation of calcineurin/NFAT4 and is potentiated by a high-fat diet rich in corn oil

This study investigated if calcineurin/nuclear factor of activated T cells (NFAT) axis mediates the cardiac apoptosis in rats with type 1 diabetes mellitus (T1DM)-induced rats or administered chronically high-fat diet rich in corn oil (CO-HFD). Also, it investigated the impact of chronic administration of CO-HFD on Fas/Fas ligand (Fas/FasL)-induced apoptosis in the hearts of T1DM-induced rats. Adult male Wistar rats (140-160 g) were classified as control: (10% fat) CO-HFD: (40% fat), T1DM, and T1DM + CO-HFD (n=20/each). In vitro, cardiomyocytes were cultured in either low glucose (LG) or high glucose (HG) media in the presence or absence of linoleic acid (LA) and other inhibitors. Compared to the control, increased reactive oxygen species (ROS), protein levels of cytochrome C, cleaved caspase-8 and caspase-3, myocardial damage and impeded left ventricular (LV) function were observed in the hearts of all treated groups and maximally in T1DM + CO-HFD-treated rats. mRNA of all NFAT members (NFAT1-4) were not affected by any treatment. CO-HFD or LA significantly up-regulated Fas levels in both LVs and cultured cardiomyocytes in a ROS dependent mechanism and independent of modulating intracellular Ca²⁺ levels or calcineurin activity. T1DM or hyperglycemia significant up-regulated mRNA and protein levels of Fas and FasL by activating Ca²⁺/calcineurin/NFAT-4 axis. Furthermore, Fas/FasL cell death induced by recombinant FasL (rFasL) or HG media was enhanced by pre-incubating the cells with LA. In conclusion, activation of the Ca²⁺/calcineurin/NFAT4 axis is indispensable for hyperglycemia-induced Fas/FasL cell death in the cardiomyocytes and CO-HFD sensitizes this by up-regulation of Fas.

Offspring of mothers with hyperglycaemia in pregnancy: The short term and long-term impact. What is new?

The continuing rise in the global prevalence of diabetes and overweight or obesity has become a major burden for global health, as the pandemic is affecting both high and low-middle income countries (LMIC). At the same time, a similar pattern has been observed for all forms of hyperglycemia in pregnancy (HIP), diabetes during pregnancy and gestational diabetes. The offspring of mothers with HIP and/or overweight-obesity is receiving increasing attention as advances in early detection and treatment of HIP did not completely prevent macrosomia and its associated short-term perinatal disorders, whilst long term consequences are observed in the mother and in offspring as it reaches adulthood. This review discusses the current developments in the consequences of HIP in the offspring, with a particular focus on its long-term health at adulthood, and on intergenerational and transgenerational effects. HIP is emerging as one of the factors that can contribute, during the window of sensitivity to environmental cues constituted by the preconception, pregnancy, and early childhood, and as an amplifying factor linked to reproduction, to the current global epidemic of diabetes and non-communicable diseases (NCDs).

LncRNA HOTAIR functions as a competing endogenous RNA to upregulate SIRT1 by sponging miR-34a in diabetic cardiomyopathy

The HOX transcript antisense RNA (HOTAIR) long noncoding RNA (lncRNA), a highly abundant and conserved imprinted gene, has been implicated in many essential biological processes and diseases. However, to date, the significance of HOTAIR in diabetic cardiomyopathy (DCM) has never been investigated. The current study was designed to determine whether DCM can be regulated by HOTAIR and to elucidate the related mechanism. In vivo, streptozotocin (STZ) was injected intraperitoneally to induce type 1 diabetes in mice. Cardiomyocyte specific HOTAIR overexpression was achieved using an adeno-associated virus system 12 weeks after STZ injection. In vitro, H9c2 were used to explore the potential molecular mechanism of HOTAIR in the regulation of high-glucose-induced cardiomyocyte injury. Luciferase reporter assay and RNA immunoprecipitation (RIP) were performed to explore the relationship between HOTAIR, microRNA-34a (miR-34a), and Sirtuin 1 (SIRT1). HOTAIR expression was significantly decreased in diabetic mice hearts. Knockdown of HOTAIR in high glucose-induced H9c2 resulted in increased oxidative injury, inflammation, and apoptosis in vitro. Cardiomyocyte-specific overexpression of HOTAIR improved cardiac function, decreased oxidative stress and inflammation, and attenuated myocyte death in mice treated with STZ. Mechanistically, the expression of SIRT1/forkhead box protein O1 was significantly increased in the HOTAIR-overexpressing hearts compared with the control hearts treated with STZ. Moreover, we found HOTAIR functioned as a molecular sponge of miR-34a in H9c2 and SIRT1 was identified as a target of miR-34a. Furthermore, the protective effects of HOTAIR on DCM was abolished in SIRT1 deficiency mice in vivo. HOTAIR protected against DCM via activation of the SIRT1 expression by sponging miR-34a.

Uncoupling proteins as a therapeutic target to protect the diabetic heart

Myocardial remodeling and dysfunction caused by accelerated oxidative damage is a widely reported phenomenon within a diabetic state. Altered myocardial substrate preference appears to be the major cause of enhanced oxidative stress-mediated cell injury within a diabetic heart. During this process, exacerbated free fatty acid flux causes an abnormal increase in mitochondrial membrane potential leading to the overproduction of free radical species and subsequent cell damage. Uncoupling proteins (UCPs) are expressed within the myocardium and can protect against free radical damage by modulating mitochondrial respiration, leading to reduced production of reactive oxygen species. Moreover, transgenic animals lacking UCPs have been shown to be more susceptible to oxidative damage and display reduced cardiac function when compared to wild type animals. This suggests that tight regulation of UCPs is necessary for normal cardiac function and in the prevention of diabetes-induced oxidative damage. This review aims to enhance our understanding of the pathophysiological mechanisms relating to the role of UCPs in a diabetic heart, and further discuss known pharmacological compounds and hormones that can protect a diabetic heart through the modulation of UCPs.

Novel ASK1 inhibitor AGI-1067 improves AGE-induced cardiac dysfunction by inhibiting MKKs/p38 MAPK and NF-κB apoptotic signaling

Heart failure has been identified as one of the clinical manifestations of diabetic cardiovascular complications. Excessive myocardium apoptosis characterizes cardiac dysfunctions, which are correlated with an increased level of advanced glycation end products (AGEs). In this study, we investigated the participation of reactive oxygen species (ROS) and the involvements of apoptosis signal-regulating kinase 1 (ASK1)/mitogen-activated protein kinase (MAPK) kinases (MKKs)/p38 MAPK and nuclear factor κB (NF-κB) pathways in AGE-induced apoptosis-mediated cardiac dysfunctions. The antioxidant and therapeutic effects of a novel ASK1 inhibitor, AGI-1067, were also studied. Myocardium and isolated primary myocytes were exposed to AGEs and treated with AGI-1067. Invasive hemodynamic and echocardiographic assessments were used to evaluate the cardiac functions. ROS formation was evaluated by dihydroethidium fluorescence staining. A terminal deoxynucleotidyl transferase dUTP nick end labelling assay was used to detect the apoptotic cells. ASK1 and NADPH activities were determined by kinase assays. The association between ASK1 and thioredoxin 1 (Trx1) was assessed by immunoprecipitation. Western blotting was used to evaluate the phosphorylation and expression levels of proteins. Our results showed that AGE exposure significantly activated ASK1/MKKs/p38 MAPK, which led to increased cardiac apoptosis and cardiac impairments. AGI-1067 administration inhibited the activation of MKKs/p38 MAPK by inhibiting the disassociation of ASK1 and Trx1, which suppressed the AGE-induced myocyte apoptosis. Moreover, the NF-κB activation as well as the ROS generation was inhibited. As a result, cardiac functions were improved. Our findings suggested that AGI-1067 recovered AGE-induced cardiac dysfunction by blocking both ASK1/MKKs/p38 and NF-κB apoptotic signaling pathways.

Cellular senescence links aging and diabetes in cardiovascular disease

Aging is a powerful independent risk factor for cardiovascular diseases such as atherosclerosis and heart failure. Concomitant diabetes mellitus strongly reinforces this effect of aging on cardiovascular disease. Cellular senescence is a fundamental mechanism of aging and appears to play a crucial role in the onset and prognosis of cardiovascular disease in the context of both aging and diabetes. Senescent cells are in a state of cell cycle arrest but remain metabolically active by secreting inflammatory factors. This senescence-associated secretory phenotype is a trigger of chronic inflammation, oxidative stress, and decreased nitric oxide bioavailability. A complex interplay between these three mechanisms results in age- and diabetes-associated cardiovascular damage. In this review, we summarize current knowledge on cellular senescence and its secretory phenotype, which might be the missing link between aging and diabetes contributing to cardiovascular disease.

MDM2 controls NRF2 antioxidant activity in prevention of diabetic kidney disease

Oxidative stress and P53 contribute to the pathogenesis of diabetic kidney disease (DKD). Nuclear factor erythroid 2-related factor 2 (NRF2) is a master regulator of cellular antioxidant defense system, is negatively regulated by P53 and prevents DKD. Recent findings revealed an important role of mouse double minute 2 (MDM2) in protection against DKD. However, the mechanism remained unclear. We hypothesized that MDM2 enhances NRF2 antioxidant signaling in DKD given that MDM2 is a key negative regulator of P53. The MDM2 inhibitor nutlin3a elevated renal P53, inhibited NRF2 signaling and induced oxidative stress, inflammation, fibrosis, DKD-like renal pathology and albuminuria in the wild-type (WT) non-diabetic mice. These effects exhibited more prominently in nutlin3a-treated WT diabetic mice. Interestingly, nutlin3a failed to induce greater renal injuries in the Nrf2 knockout (KO) mice under both the diabetic and non-diabetic conditions, indicating that NRF2 predominantly mediates MDM2's action. On the contrary, P53 inhibition by pifithrin-α activated renal NRF2 signaling and the expression of Mdm2, and attenuated DKD in the WT diabetic mice, but not in the Nrf2 KO diabetic mice. In high glucose-treated mouse mesangial cells, P53 gene silencing completely abolished nutlin3a's inhibitory effect on NRF2 signaling. The present study demonstrates for the first time that MDM2 controls renal NRF2 antioxidant activity in DKD via inhibition of P53, providing MDM2 activation and P53 inhibition as novel strategies in the management of DKD.