Proteostasis in epicardial versus subcutaneous adipose tissue in heart failure subjects with and without diabetes

Nrf2 protects against myocardial ischemia-reperfusion injury in diabetic rats by inhibiting Drp1-mediated mitochondrial fission

Mitochondrial dysfunction and oxidative stress are considered to be two main drivers of diabetic myocardial ischemia-reperfusion injury (DM + MIRI). Nuclear factor-erythroid 2-related factor 2 (Nrf2) and Dynamin-related protein 1 (Drp1) play central roles in maintaining mitochondrial homeostasis and regulating oxidative stress, but the effects of the Nrf2-Drp1 pathway on DM-MIRI have not been reported. The aim of this study is to investigate the role of the Nrf2-Drp1 pathway in DM + MIRI rats. A rat model of DM + MIRI and H9c2 cardiomyocyte injury were constructed. The therapeutic effect of Nrf2 was assessed by detecting myocardial infarct size, mitochondrial structure, levels of myocardial injury markers and oxidative stress, apoptosis, and Drp1 expression. The results showed that DM + MIRI rats had increased myocardial infarct size and Drp1 expression in myocardial tissue, accompanied by increased mitochondrial fission and oxidative stress. Interestingly, Nrf2 agonist dimethyl fumarate (DMF) could significantly improve cardiac function, mitochondrial fission, and decrease oxidative stress levels and Drp1 expression after ischemia. However, these effects of DMF would be largely counteracted by the Nrf2 inhibitor ML385. Additionally, Nrf2 overexpression significantly suppressed Drp1 expression, apoptosis, and oxidative stress levels in H9c2 cells. Nrf2 attenuates myocardial ischemia-reperfusion injury in DM rats by reducing Drp1-mediated mitochondrial fission and oxidative stress.

LncRNAs and CircRNAs in Endoplasmic Reticulum Stress: A Promising Target for Cardiovascular Disease?

The endoplasmic reticulum (ER) is a principal subcellular organelle responsible for protein quality control in the secretory pathway, preventing protein misfolding and aggregation. Failure of protein quality control in the ER triggers several molecular mechanisms such as ER-associated degradation (ERAD), the unfolded protein response (UPR) or reticulophagy, which are activated upon ER stress (ERS) to re-establish protein homeostasis by transcriptionally and translationally regulated complex signalling pathways. However, maintenance over time of ERS leads to apoptosis if such stress cannot be alleviated. The presence of abnormal protein aggregates results in loss of cardiomyocyte protein homeostasis, which in turn results in several cardiovascular diseases such as dilated cardiomyopathy (DCM) or myocardial infarction (MI). The influence of a non-coding genome in the maintenance of proper cardiomyocyte homeostasis has been widely proven. To date, the impact of microRNAs in molecular mechanisms orchestrating ER stress response has been widely described. However, the role of long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) is just beginning to be addressed given the potential role of these RNA classes as therapeutic molecules. Here, we provide a current state-of-the-art review of the roles of distinct lncRNAs and circRNAs in the modulation of ERS and UPR and their impact in cardiovascular diseases.

Identification of key genes and mechanisms of epicardial adipose tissue in patients with diabetes through bioinformatic analysis

Background

In recent years, peri-organ fat has emerged as a diagnostic and therapeutic target in metabolic diseases, including diabetes mellitus. Here, we performed a comprehensive analysis of epicardial adipose tissue (EAT) transcriptome expression differences between diabetic and non-diabetic participants and explored the possible mechanisms using various bioinformatic tools.

Methods

RNA-seq datasets GSE108971 and GSE179455 for EAT between diabetic and non-diabetic patients were obtained from the public functional genomics database Gene Expression Omnibus (GEO). The differentially expressed genes (DEGs) were identified using the R package DESeq2, then Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment were analyzed. Next, a PPI (protein–protein interaction) network was constructed, and hub genes were mined using STRING and Cytoscape. Additionally, CIBERSORT was used to analyze the immune cell infiltration, and key transcription factors were predicted based on ChEA3.

Results

By comparing EAT samples between diabetic and non-diabetic patients, a total of 238 DEGs were identified, including 161 upregulated genes and 77 downregulated genes. A total of 10 genes (IL-1β, CD274, PDCD1, ITGAX, PRDM1, LAG3, TNFRSF18, CCL20, IL1RN, and SPP1) were selected as hub genes. GO and KEGG analysis showed that DEGs were mainly enriched in the inflammatory response and cytokine activity. Immune cell infiltration analysis indicated that macrophage M2 and T cells CD4 memory resting accounted for the largest proportion of these immune cells. CSRNP1, RELB, NFKB2, SNAI1, and FOSB were detected as potential transcription factors.

Conclusion

Comprehensive bioinformatic analysis was used to compare the difference in EAT between diabetic and non-diabetic patients. Several hub genes, transcription factors, and immune cell infiltration were identified. Diabetic EAT is significantly different in the inflammatory response and cytokine activity. These findings may provide new targets for the diagnosis and treatment of diabetes, as well as reduce potential cardiovascular complications in diabetic patients through EAT modification.

Epicardial Adipose Tissue as an Independent Cardiometabolic Risk Factor for Coronary Artery Disease

During the last decades, visceral adiposity has been at the forefront of scientific research because of its complex role in the pathogenesis of cardiovascular diseases. Epicardial adipose tissue (EAT) is the visceral lipid compartment between the myocardium and the visceral pericardium. Due to their unobstructed anatomic vicinity, epicardial fat and myocardium are nourished by the same microcirculation. It is widely known that EAT serves as an energy lipid source and thermoregulator for the human heart. In addition to this, epicardial fat exerts highly protective effects since it releases a great variety of anti-inflammatory molecules to the adjacent cardiac muscle. Taking into account the unique properties of human EAT, it is undoubtedly a key factor in cardiac physiology since it facilitates complex heart functions. Under pathological circumstances, however, epicardial fat promotes coronary atherosclerosis in a variety of ways. Therefore, the accurate estimation of epicardial fat thickness and volume could be utilized as an early detecting method and future medication target for coronary artery disease (CAD) elimination. Throughout the years, several therapeutic approaches for dysfunctional human EAT have been proposed. A balanced healthy diet, aerobic and anaerobic physical activity, bariatric surgery, and pharmacological treatment with either traditional or novel antidiabetic and antilipidemic drugs are some of the established medical approaches. In the present article, we review the current knowledge regarding the anatomic and physiological characteristics of epicardial fat. In addition to this, we describe the pathogenic mechanisms which refer to the crosstalk between epicardial fat alteration and coronary arterial atherosclerosis development. Lastly, we present both lifestyle and pharmacological methods as possible treatment options for EAT dysfunction. 

Adipokine gene expression in adipocytes isolated from different fat depots of coronary artery disease patients

To compare DPP4, LCN2, NAMPT, ITLN1, APLN mRNA levels in adipocytes isolated from the biopsies of subcutaneous, epicardial and perivascular fat obtained from 25 patients with coronary artery disease. Gene expression signature was determined by RT-qPCR with hydrolysis probes. We found DPP4 and APLN mRNA was higher expressed only in adipocytes isolated from epicardial adipose tissue compared to the subcutaneous fat. The ITLN1 gene was overexpressed in epicardial adipose tissue compared to both subcutaneous and perivascular tissues. APLN mRNA expression was positively correlated with total and LDL cholesterol plasma level, and DPP4 mRNA expression - with VLDL cholesterol concentration. Thus, adipocytes isolated from different adipose depots are characterised by differential gene expression of adipokines. Epicardial adipose tissue is of particular interest in the context of its function, molecular and genetic mechanisms of regulation of the cardiovascular system and as a therapeutic target for correction of adipose tissue-induced effects on health.

Can We Decrease Epicardial and Pericardial Fat in Patients With Diabetes?

Diabetes mellitus (DM) is a chronic and complex metabolic disorder and also an important cause of cardiovascular (CV) disease (CVD). Patients with type 2 DM (T2DM) and obesity show a greater propensity for visceral fat deposition (and excessive fat deposits elsewhere) and the link between adiposity and CVD risk is greater for visceral than for subcutaneous (SC) adipose tissue (AT). There is growing evidence that epicardial AT (EAT) and pericardial AT (PAT) play a role in the development of DM-related atherosclerosis, atrial fibrillation (AF), myocardial dysfunction, and heart failure (HF). In this review, we will highlight the importance of PAT and EAT in patients with DM. We also consider therapeutic interventions that could have a beneficial effect in terms of reducing the amount of AT and thus CV risk. EAT is biologically active and a likely determinant of CV morbidity and mortality in patients with DM, given its anatomical characteristics and proinflammatory secretory pattern. Consequently, modification of EAT/PAT may become a therapeutic target to reduce the CV burden. In patients with DM, a low calorie diet, exercise, antidiabetics and statins may change the quantity of EAT, PAT or both, alter the secretory pattern of EAT, improve the metabolic profile, and reduce inflammation. However, well-designed studies are needed to clearly define CV benefits and a therapeutic approach to EAT/PAT in patients with DM.

Linking Arrhythmias and Adipocytes: Insights, Mechanisms, and Future Directions

Obesity and atrial fibrillation have risen to epidemic levels worldwide and may continue to grow over the next decades. Emerging evidence suggests that obesity promotes atrial and ventricular arrhythmias. This has led to trials employing various strategies with the ultimate goal of decreasing the atrial arrhythmic burden in obese patients. The effectiveness of these interventions remains to be determined. Obesity is defined by the expansion of adipose mass, making adipocytes a prime candidate to mediate the pro-arrhythmogenic effects of obesity. The molecular mechanisms linking obesity and adipocytes to increased arrhythmogenicity in both the atria and ventricles remain poorly understood. In this focused review, we highlight areas of potential molecular interplay between adipocytes and cardiomyocytes. The effects of adipocytes may be direct, local or remote. Direct effect refers to adipocyte or fatty infiltration of the atrial and ventricular myocardium itself, possibly causing increased dispersion of normal myocardial electrical signals and fibrotic substrate of adipocytes that promote reentry or adipocytes serving as a direct source of aberrant signals. Local effects may originate from nearby adipose depots, specifically epicardial adipose tissue (EAT) and pericardial adipose tissue, which may play a role in the secretion of adipokines and chemokines that can incite inflammation given the direct contact and disrupt the conduction system. Adipocytes can also have a remote effect on the myocardium arising from their systemic secretion of adipokines, cytokines and metabolites. These factors may lead to mitochondrial dysfunction, oxidative stress, autophagy, mitophagy, autonomic dysfunction, and cardiomyocyte death to ultimately produce a pro-arrhythmogenic state. By better understanding the molecular mechanisms connecting dysfunctional adipocytes and arrhythmias, novel therapies may be developed to sever the link between obesity and arrhythmias.