N-Acetyl Cysteine, Selenium, and Ascorbic Acid Rescue Diabetic Cardiac Hypertrophy via Mitochondrial-Associated Redox Regulators

N-Acetylcysteine Alleviates Phenylephrine-Induced Cardiomyocyte Dysfunction via Engaging PI3K/AKT Signaling Pathway

BACKGROUND

Increased reactive oxygen species (ROS) and oxidative stress response lead to cardiomyocyte hypertrophy and apoptosis, which play crucial roles in the pathogenesis of heart failure. The purpose of current research was to explore the role of antioxidant N-acetylcysteine (NAC) on cardiomyocyte dysfunction and the underlying molecular mechanisms.

METHODS AND RESULTS

Compared with control group without NAC treatment, NAC dramatically inhibited the cell size of primary cultured neonatal rat cardiomyocytes (NRCMs) tested by immunofluorescence staining and reduced the expression of representative markers associated with hypertrophic, fibrosis and apoptosis subjected to phenylephrine administration examined by reverse transcription-polymerase chain reaction (RT-PCR) and western blot. Moreover, enhanced ROS expression was attenuated, whereas activities of makers related to oxidative stress response examined by individual assay Kits, including total antioxidation capacity (T-AOC), glutathione peroxidase (GSH-Px), and primary antioxidant enzyme Superoxide dismutase (SOD) were induced by NAC treatment in NRCMs previously treated with phenylephrine. Mechanistically, we noticed that the protein expression levels of phosphorylated phosphatidylinositol 3-kinase (PI3K) and AKT were increased by NAC stimulation. More importantly, we identified that the negative regulation of NAC in cardiomyocyte dysfunction was contributed by PI3K/AKT signaling pathway through further utilization of PI3K/AKT inhibitor (LY294002) or agonist (SC79).

CONCLUSIONS

Collected, NAC could attenuate cardiomyocyte dysfunction subjected to phenylephrine, partially by regulating the ROS-induced PI3K/AKT-dependent signaling pathway.

Effects of Dapagliflozin on Myocardial Gene Expression in BTBR Mice with Type 2 Diabetes

BACKGROUND

Dapagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, is approved for the treatment of type 2 diabetes, heart failure, and chronic kidney disease. DAPA-HF and DELIVER trial results demonstrate that the cardiovascular protective effect of dapagliflozin extends to non-diabetic patients. Hence, the mechanism-of-action may extend beyond glucose-lowering and is not completely elucidated. We have previously shown that dapagliflozin reduces cardiac hypertrophy, inflammation, fibrosis, and apoptosis and increases ejection fraction in BTBR mice with type 2 diabetes.

METHODS

We conducted a follow-up RNA-sequencing study on the heart tissue of these animals and performed differential expression and Ingenuity Pathway analysis. Selected markers were confirmed by RT-PCR and Western blot.

RESULTS

SGLT2 had negligible expression in heart tissue. Dapagliflozin improved cardiac metabolism by decreasing glycolysis and pyruvate utilization enzymes, induced antioxidant enzymes, and decreased expression of hypoxia markers. Expression of inflammation, apoptosis, and hypertrophy pathways was decreased. These observations corresponded to the effects of dapagliflozin in the clinical trials.

Mitochondrion: A bridge linking aging and degenerative diseases

Aging is a natural process, characterized by progressive loss of physiological integrity, impaired function, and increased vulnerability to death. For centuries, people have been trying hard to understand the process of aging and find effective ways to delay it. However, limited breakthroughs have been made in anti-aging area. Since the hallmarks of aging were summarized in 2013, increasing studies focus on the role of mitochondrial dysfunction in aging and aging-related degenerative diseases, such as neurodegenerative diseases, osteoarthritis, metabolic diseases, and cardiovascular diseases. Accumulating evidence indicates that restoring mitochondrial function and biogenesis exerts beneficial effects in extending lifespan and promoting healthy aging. In this paper, we provide an overview of mitochondrial changes during aging and summarize the advanced studies in mitochondrial therapies for the treatment of degenerative diseases. Current challenges and future perspectives are proposed to provide novel and promising directions for future research.

Long-Term Cardiac Damage Associated With Abdominal Irradiation in Mice

Aims: Irradiation is an effective treatment for tumors but has been associated with cardiac dysfunction. However, the precise mechanisms remain incompletely elucidated. This study investigated the long-term cardiac damage associated with abdominal irradiation and explored possible mechanisms.

Methods and Results: Wild-type C57BL6/J mice were divided into two groups: untreated controls (Con) and treatment group receiving 15 Gy of abdominal gamma irradiation (AIR). Both groups received normal feeding for 12 months. The AIR group showed reductions in left ventricular ejection fraction (LVEF), fractional shortening (FS), left ventricular end-diastolic internal diameter (LVID; d), left ventricular end-diastolic volume (LV Vol. diastolic volume (LV Vol; d) and mitral transtricuspid flow late diastolic filling velocity (MV A). It also showed increased fibrosis, reduced conduction velocity and increased conduction heterogeneity. Non-targeted metabolomics showed the differential metabolites were mainly from amino acid metabolism. Further KEGG pathway annotation and enrichment analysis revealed that abnormalities in arginine and proline metabolism, lysine degradation, d-arginine and d-ornithine metabolism, alanine, aspartate and glutamate metabolism, and arginine biosynthesis.

Conclusion: Abdominal irradiation causes long-term damage to the non-irradiated heart, as reflected by electrical and structural remodeling and mechanical dysfunction associated with abnormal amino acid biosynthesis and metabolism.

Signaling Pathways Related to Oxidative Stress in Diabetic Cardiomyopathy

Diabetes is a chronic metabolic disease that is increasing in prevalence and causes many complications. Diabetic cardiomyopathy (DCM) is a complication of diabetes that is associated with high mortality, but it is not well defined. Nevertheless, it is generally accepted that DCM refers to a clinical disease that occurs in patients with diabetes and involves ventricular dysfunction, in the absence of other cardiovascular diseases, such as coronary atherosclerotic heart disease, hypertension, or valvular heart disease. However, it is currently uncertain whether the pathogenesis of DCM is directly attributable to metabolic dysfunction or secondary to diabetic microangiopathy. Oxidative stress (OS) is considered to be a key component of its pathogenesis. The production of reactive oxygen species (ROS) in cardiomyocytes is a vicious circle, resulting in further production of ROS, mitochondrial DNA damage, lipid peroxidation, and the post-translational modification of proteins, as well as inflammation, cardiac hypertrophy and fibrosis, ultimately leading to cell death and cardiac dysfunction. ROS have been shown to affect various signaling pathways involved in the development of DCM. For instance, OS causes metabolic disorders by affecting the regulation of PPARα, AMPK/mTOR, and SIRT3/FOXO3a. Furthermore, OS participates in inflammation mediated by the NF-κB pathway, NLRP3 inflammasome, and the TLR4 pathway. OS also promotes TGF-β-, Rho-ROCK-, and Notch-mediated cardiac remodeling, and is involved in the regulation of calcium homeostasis, which impairs ATP production and causes ROS overproduction. In this review, we summarize the signaling pathways that link OS to DCM, with the intention of identifying appropriate targets and new antioxidant therapies for DCM.

Quercetin alleviates diastolic dysfunction and suppresses adverse pro-hypertrophic signaling in diabetic rats

INTRODUCTION

Quercetin (Que) is a potent anti-inflammatory and antioxidant flavonoid with cardioprotective potential. However, very little is known about the signaling pathways and gene regulatory proteins Que may interfere with, especially in diabetic cardiomyopathy. Therefore, we aimed to study the potential cardioprotective effects of Que on the cardiac phenotype of type 2 diabetes mellitus (T2DM) accompanied by obesity.

METHODS

For this experiment, we used Zucker Diabetic Fatty rats (fa/fa) and their age-matched lean controls (fa/+) that were treated with either vehicle or 20 mg/kg/day of Que for 6 weeks. Animals underwent echocardiographic (echo) examination before the first administration of Que and after 6 weeks.

RESULTS

After the initial echo examination, the diabetic rats showed increased E/A ratio, a marker of left ventricular (LV) diastolic dysfunction, in comparison to the control group which was selectively reversed by Que. Following the echo analysis, Que reduced LV wall thickness and exhibited an opposite effect on LV luminal area. In support of these results, the total collagen content measured by hydroxyproline assay was decreased in the LVs of diabetic rats treated with Que. The follow-up immunoblot analysis of proteins conveying cardiac remodeling pathways revealed that Que was able to interfere with cardiac pro-hypertrophic signaling. In fact, Que reduced relative protein expression of pro-hypertrophic transcriptional factor MEF2 and its counter-regulator HDAC4 along with pSer²⁴⁶-HDAC4. Furthermore, Que showed potency to decrease GATA4 transcription factor, NFAT3 and calcineurin, as well as upstream extracellular signal-regulated kinase Erk5 which orchestrates several pro-hypertrophic pathways.

DISCUSSION

In summary, we showed for the first time that Que ameliorated pro-hypertrophic signaling on the level of epigenetic regulation and targeted specific upstream pathways which provoked inhibition of pro-hypertrophic signals in ZDF rats. Moreover, Que mitigated T2DM and obesity-induced diastolic dysfunction, therefore, might represent an interesting target for future research on novel cardioprotective agents.