Mitophagy in Diabetic Cardiomyopathy: Roles and Mechanisms.

Cardiovascular disease is the leading complication of diabetes mellitus (DM), and diabetic cardiomyopathy (DCM) is a major cause of mortality in diabetic patients. Multiple pathophysiologic mechanisms, including myocardial insulin resistance, oxidative stress and inflammation, are involved in the development of DCM. Recent studies have shown that mitochondrial dysfunction makes a substantial contribution to the development of DCM. Mitophagy is a type of autophagy that takes place in dysfunctional mitochondria, and it plays a key role in mitochondrial quality control. Although the precise molecular mechanisms of mitophagy in DCM have yet to be fully clarified, recent findings imply that mitophagy improves cardiac function in the diabetic heart. However, excessive mitophagy may exacerbate myocardial damage in patients with DCM. In this review, we aim to provide a comprehensive overview of mitochondrial quality control and the dual roles of mitophagy in DCM. We also propose that a balance between mitochondrial biogenesis and mitophagy is essential for the maintenance of cellular metabolism in the diabetic heart.

Anti-Diabetic Effects of Berberis kansuensis Extract on Type 2 Diabetic Rats Revealed by 1 H-NMR-Based Metabolomics and Biochemistry Analysis.

The dried stem bark of Berberis kansuensis C.K.Schneid. (Berberidaceae) was widely used to treat diabetes in traditional Tibetan medicine system. However, its anti-diabetic mechanisms have not been elucidated. In this study, 1 H-NMR-based metabolomics combined with biochemistry assay was applied to investigate the anti-diabetic activities as well as underlying mechanisms of B. kansuensis extract on type 2 diabetic rats. The results showed that after 30 days treatment with B. kansuensis extract, the levels of FBG, GSP, INS, TNF-α, IL-1ß and IL-6 were significantly decreased in B. kansuensis group compared with the model group. Besides, a total of 28 metabolites were identified in rat serum by 1 H-NMR-based metabolomics method, 16 of which were significantly different in the normal group compared with the model group, and eight of them were significantly reversed after B. kansuensis intervention. Further analysis of metabolic pathways indicated that therapeutic effect of B. kansuensis might be predominantly related to their ability to improve glycolysis and gluconeogenesis, citric acid cycle, lipid metabolism, amino acid metabolism and choline metabolism. The results of both metabolomics and biochemical analysis indicated that B. kansuensis extract has a potential anti-diabetic effect on type 2 diabetic rats. Its therapeutic effect may be based on the ability of anti-inflammation, alleviating insulin resistance and restoring several disturbed metabolic pathways.

Gut microbiota-derived trimethylamine N-oxide is associated with poor prognosis in patients with heart failure.

OBJECTIVE: Gut microbiota-produced trimethylamine N-oxide (TMAO) is a risk factor for cardiovascular events. However, conflicting findings regarding the link between plasma TMAO level and prognosis for patients with heart failure have been reported. We examined the association of plasma TMAO concentration with risk of major adverse cardiac events (MACEs) and all-cause mortality in patients with heart failure. STUDY DESIGN: Meta-analysis of prospective clinical studies. DATA SOURCES: We searched electronic databases (PubMed, EMBASE) for published prospective studies examining associations between plasma TMAO level and MACEs and all-cause mortality in adults with heart failure. DATA SYNTHESIS: Hazard ratios (HRs) with 95% confidence intervals for associations between TMAO level and outcomes were estimated in random effects models. In seven eligible studies including a total of 6879 patients (median follow-up, 5.0 years) and adjusted for multiple risk factors, higher plasma TMAO level was associated with greater risks of MACEs (TMAO tertile 3 v tertile 1: HR, 1.68; 95% CI, 1.44-1.96; per SD increment: HR, 1.26; 95% CI, 1.18-1.36) and of all-cause mortality (TMAO tertile 3 v tertile 1: HR, 1.67; 95% CI, 1.17-2.38; per SD increment: HR, 1.26; 95% CI, 1.07-1.48). Higher TMAO level was also associated with greater risk of MACEs after adjusting for estimated glomerular filtration rate (eGFR; six studies included); however, the heterogeneity of studies in which risk was adjusted for eGFR was significant (I2  = 76%). CONCLUSIONS: Elevated plasma TMAO level in patients with heart failure is associated with poorer prognoses. This association is only partially mediated by renal dysfunction.

Piwi-interacting RNAs play a role in vitamin C-mediated effects on endothelial aging.

The underlying mechanisms that mediate the effects of vitamin C on endothelial cell aging are widely unknown. To investigate whether Piwi-interacting RNAs (piRNAs) are involved in this process, an endothelial aging model was induced in vitro using H2O2 in human umbilical vein endothelial cells (HUVECs) and then treated with vitamin C (VC). Untreated HUVECs without H2O2 exposure were used to serve as the negative control group. Cell cycle, cell viability, and aging-associated protein expression were assessed, and RNA sequencing was performed to reveal the piRNA profile. Functional and regulatory networks of the different piRNA target genes were predicted by the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and Gene Ontology (GO) analysis. H2O2 induced G1 phase cell arrest, decreased cell viability, and upregulated the senescence marker p16 in HUVECs. We found that VC treatment inhibited G1 phase cell arrest, increased the number of cells in the S and G2/M phases, increased cell viability, and decreased p16 expression. The piRNA expression profiles revealed that a large proportion of piRNAs that were differentially expressed in H2O2-treated HUVECs were partly normalized by VC. Furthermore, a number of piRNAs associated with the response to VC in H2O2-treated HUVECs were linked with senescence and cell cycle-related pathways and networks. These results indicate that the ability of VC to attenuate H2O2-mediated endothelial cell senescence may be associated with changes in expression of piRNAs that are linked to the cell cycle.

Circular RNA-protein interactions: functions, mechanisms, and identification.

Circular RNAs (circRNAs) are covalently closed, endogenous RNAs with no 5' end caps or 3' poly(A) tails. These RNAs are expressed in tissue-specific, cell-specific, and developmental stage-specific patterns. The biogenesis of circRNAs is now known to be regulated by multiple specific factors; however, circRNAs were previously thought to be insignificant byproducts of splicing errors. Recent studies have demonstrated their activity as microRNA (miRNA) sponges as well as protein sponges, decoys, scaffolds, and recruiters, and some circRNAs even act as translation templates in multiple pathophysiological processes. CircRNAs bind and sequester specific proteins to appropriate subcellular positions, and they participate in modulating certain protein-protein and protein-RNA interactions. Conversely, several proteins play an indispensable role in the life cycle of circRNAs from biogenesis to degradation. However, the exact mechanisms of these interactions between proteins and circRNAs remain unknown. Here, we review the current knowledge regarding circRNA-protein interactions and the methods used to identify and characterize these interactions. We also summarize new insights into the potential mechanisms underlying these interactions.

Role of Sfrps in cardiovascular disease.

Secreted frizzled-related proteins (Sfrps) are a family of secreted proteins that bind extracellularly to Wnt ligands and frizzled receptors. This binding modulates the Wnt signaling cascade, and Sfrps interact with their corresponding receptors. Sfrps are thought to play an important role in the pathological mechanism of cardiac disease such as myocardial infarction, cardiac remodeling, and heart failure. However, the overall role of Sfrps in cardiac disease is unknown. Some members of the Sfrps family modulate cellular apoptosis, angiogenesis, differentiation, the inflammatory process, and cardiac remodeling. In this review, we summarize the evidence of Sfrps association with cardiac disease. We also discuss how multiple mechanisms may underlie Sfrps being involved in such diverse pathologies.

IGF-1 enhances BMSC viability, migration, and anti-apoptosis in myocardial infarction via secreted frizzled-related protein 2 pathway.

BACKGROUND: Bone marrow mesenchymal stem cell (BMSC) transplantation represents a promising therapeutic strategy for ischemic heart disease. However, its effects are hampered by the poor viability of transplanted cells and the hostile microenvironment of the ischemic region. Insulin-like growth factor-1 (IGF-1) is an important paracrine growth factor of BMSC and plays an important role in the properties of BMSC. Here, we investigated whether overexpressing IGF-1 could enhance the BMSC viability, migration, anti-apoptosis, and protective effects of cardiomyocytes, and explore the underlying mechanisms' focus on the role of the AKT/secreted frizzled-related protein 2 (SFRP2)/ß-catenin pathway. METHODS: We constructed BMSCs overexpressing insulin-like growth factor-1 (BMSCs-IGF-1) or empty vector (BMSCs-NC) using lentivirus, and evaluated cell survival, proliferation, and migration under normoxic and hypoxic conditions. Co-culture of rat cardiomyoblasts with BMSCs was performed to explore the paracrine effect of BMSCs-IGF-1 for rescuing cardiomyoblasts under hypoxia. Transplantation of BMSCs in acute myocardial infarction rats was used to explore the effect of BMSCs-IGF-1 therapy. RESULTS: BMSCs-IGF-1 exhibited a higher cell proliferation rate, migration capacity, and stemness, and were more resistant to apoptosis under hypoxia. Overexpression of IGF-1 upregulated the expression of total and nuclear ß-catenin via the AKT-secreted frizzled-related protein 2 (SFRP2) pathway, which enhanced cell survival. Inhibition of AKT or SFRP2 knockdown by siRNA significantly antagonized the effect of IGF-1 and decreased the expression of ß-catenin. The expression of ß-catenin target genes, including cyclin D1 and c-Myc, were accordingly decreased. Moreover, BMSCs-IGF-1 could rescue cardiomyoblasts from hypoxia-induced apoptosis and preserve cell viability under hypoxia. Transplantation of BMSCs-IGF-1 into myocardial infarction rats greatly reduced infarct volume than BMSCs-NC, with significantly greater expression of SFRP2 and ß-catenin. CONCLUSIONS: These results suggest that in BMSCs overexpressing IGF-1, SFRP2 is an important mediator for the enhancement of stem cell viability via activating, rather than antagonizing, the Wnt/ß-catenin pathway.

Treatment of Myocardial Infarction with Gene-modified Mesenchymal Stem Cells in a Small Molecular Hydrogel.

The effect of transplanted rat mesenchymal stem cells (MSCs) can be reduced by extracellular microenvironment in myocardial infarction (MI). We tested a novel small-molecular hydrogel (SMH) on whether it could provide a scaffold for hepatocyte growth factor (HGF)-modified MSCs and alleviate ventricular remodeling while preserving cardiac function after MI. Overexpression of HGF in MSCs increased Bcl-2 and reduced Bax and caspase-3 levels in response to hypoxia in vitro. Immunocytochemistry demonstrated that cardiac troponin (cTnT), desmin and connexin 43 expression were significantly enhanced in the 5-azacytidine (5-aza) with SMH group compared with the 5-aza only group in vitro and in vivo. Bioluminescent imaging indicated that retention and survival of transplanted cells was highest when MSCs transfected with adenovirus (ad-HGF) were injected with SMH. Heart function and structure improvement were confirmed by echocardiography and histology in the Ad-HGF-SMHs-MSCs group compared to other groups. Our study showed that: HGF alleviated cell apoptosis and promoted MSC growth. SMHs improved stem cell adhesion, survival and myocardial cell differentiation after MSC transplantation. SMHs combined with modified MSCs significantly decreased the scar area and improved cardiac function.

Resveratrol Ameliorates Cardiac Dysfunction by Inhibiting Apoptosis via the PI3K/Akt/FoxO3a Pathway in a Rat Model of Diabetic Cardiomyopathy.

The aim of this study was to explore the effect and mechanism of action of resveratrol (RSV) on cardiac function in diabetic cardiomyopathy (DCM). Hyperglycemia-induced apoptosis contributes to the pathogenic changes in DCM. RSV treatment inhibited high glucose-induced apoptosis of neonatal rat ventricular myocytes. Additionally, high glucose decreased cell viability, prevented serine-threonine kinase (Akt) and FoxO3a phosphorylation, and suppressed cytoplasmic translocation of FoxO3a. However, these effects of apoptosis were reversed by 10 µM of RSV. The PI3K inhibitor LY294002 abolished the RSV protective effect in vitro. RSV (5 or 50 mg·kg·d orally for 8 weeks) prevented the deterioration of cardiac function and structural cardiomyopathy in a streptozotocin-induced rat model of diabetes and reduced apoptosis in diabetic myocardium. Furthermore, it restored streptozotocin-impaired phosphorylation of Akt and FoxO3a (p-Akt and p-FoxO3a) and suppressed nuclear translocation of FoxO3a in vivo. Together, these data indicate that RSV has therapeutic potential against DCM by inhibiting apoptosis via the PI3K/Akt/FoxO3a pathway.