Mechanical Stretch Inhibits MicroRNA499 via p53 to Regulate Calcineurin-A Expression in Rat Cardiomyocytes

miR-499a rs3746444 A>G Polymorphism Is Correlated with Type 2 Diabetes Mellitus and Diabetic Polyneuropathy in a Romanian Cohort: A Preliminary Study

Type 2 diabetes mellitus (T2DM) is a common metabolic disorder that results from complex interactions of both environmental and genetic factors. Many single nucleotide polymorphisms (SNPs), including noncoding RNA genes, have been investigated for their association with susceptibility to T2DM and its complications, with little evidence available regarding Caucasians. The aim of the present study was to establish whether four miRNA SNPs (miR-27a rs895819 T>C, miR-146a rs2910164 G>C, miR-196a2 rs11614913 C>T, and miR-499a rs3746444 A>G) are correlated with susceptibility to T2DM and/or diabetic polyneuropathy (DPN) in a Romanian population. A total of 167 adult T2DM patients and 324 age- and sex-matched healthy controls were included in our study. miRNA SNPs were detected by real-time PCR using a TaqMan genotyping assay. A significant association with T2DM was observed only for the miR-499a rs3746444 A>G SNP in all the tested models, and the frequencies of both the miR-499a rs3746444 AG and the GG genotypes were higher in the T2DM patients compared to the controls. No correlation was observed for the miR-27a rs895819 T>C, miR-146a rs2910164 G>C, or miR-196a2 rs11614913 C>T SNPs in any genetic model. When we assessed the association of these SNPs with DPN separately, we found a positive association for the miR-499a rs3746444 SNP in both codominant and dominant models (OR 6.47, 95% CI: 1.71-24.47; OR 2.30, 95% CI: 1.23-4.29, respectively). In conclusion, this study shows that miR-499a rs3746444 A>G may influence both T2DM and DPN susceptibility, with carriers of the GG genotype and the G allele being at an increased risk in the Romanian population.

Cardiac-specific overexpression of miR-122 induces mitochondria-dependent cardiomyocyte apoptosis and promotes heart failure by inhibiting Hand2

MicroRNA‐122 (miR‐122) is one of several microRNAs elevated in heart failure patients. To investigate the potential role and mechanism of miR‐122 in heart failure, we constructed a transgenic mouse overexpressing miR‐122 in the heart. This mouse exhibited cardiac dysfunction (as assessed by transthoracic echocardiography), morphological abnormalities of the heart and cardiomyocyte apoptosis characteristic of heart failure. Mechanistically, we identified the Hand2 transcription factor as a direct target of miR‐122 using a dual‐luciferase reporter assay. In Tg‐miR‐122 mice and H9C2 cells with miR‐122 mimics, we detected apoptosis and increased expression of dynamin‐related protein‐1 (Drp1). This effect was blocked with prior knockdown of Hand2 in vitro. Our work suggests that miR‐122 causes cardiomyocyte apoptosis by inhibiting Hand2 and consequently increasing Drp1‐mediated mitochondrial fission. Such a mechanism likely contributes to heart failure and so modulating this pathway could be therapeutically valuable against heart failure.

Cyclic stretching boosts microRNA-499 to regulate Bcl-2 via microRNA-208a in atrial fibroblasts

MicroRNAs that modulate transcription can regulate other microRNAs and are also up-regulated under pathological stress. MicroRNA-499 (miR-499), microRNA-208a (miR-208a) and B-cell lymphoma 2 (Bcl-2) play roles in cardiovascular diseases, such as direct reprogramming of cardiac fibroblast into cardiomyocyte and cardiomyocyte apoptosis. Whether miR208a, miR499 and Bcl-2 were critical regulators in cardiac fibroblast apoptosis under mechanical stretching conditions in human cardiac fibroblasts-adult atrial (HCF-aa) was investigated. Using negative pressure, HCF-aa grown on a flexible membrane base were cyclically stretched to 20% of their maximum elongation. In adult rats, an aortocaval shunt was used to create an in vivo model of volume overload. MiR208a was up-regulated early by stretching and returned to normal levels with longer stretching cycles, whereas the expression of miR499 and Bcl-2 was up-regulated by longer stretching times. Pre-treatment with antagomir-499 reversed the miR-208a down-regulation, whereas Bcl-2 expression could be suppressed by miR-208a overexpression. In the HCF-aa under stretching for 1 h, miR-499 overexpression decreased pri-miR-208a luciferase activity; this inhibition of pri-miR-208a luciferase activity with stretching was reversed when the miR-499-5p binding site in pri-miR-208a was mutated. The addition of antagomir-208a reversed the Bcl-2-3'UTR suppression from stretching for 1 h. Flow cytometric analysis revealed that pre-treatment with miR-499 or antagomir-208a inhibited cellular apoptosis in stretched HCF-aa. In hearts with volume overload, miR-499 overexpression inhibited myocardial miR-208a expression, whereas Bcl-2 expression could be suppressed by the addition of miR-208a. In conclusion, miR-208a mediated the regulation of miR-499 on Bcl-2 expression in stretched HCF-aa and hearts with volume overload.

Optimizing mechanical stretching protocols for hypertrophic and anti-apoptotic responses in cardiomyocyte-like H9C2 cells

Cardiomyocytes possess the ability to respond to mechanical stimuli by reprogramming their gene expression. This study investigated the effects of different loading protocols on signaling and expression responses of myogenic, anabolic, inflammatory, atrophy and pro-apoptotic genes in cardiomyocyte-like H9C2 cells. Differentiated H9C2 cells underwent various stretching protocols by altering their elongation, frequency and duration, utilizing an in vitro cell tension system. The loading-induced expression changes of MyoD, Myogenin, MRF4, IGF-1 isoforms, Atrogin-1, Foxo1, Fuca and IL-6 were measured by Real Time-PCR. The stretching-induced activation of Akt and Erk 1/2 was also evaluated by Western blot analysis. Low strain (2.7% elongation), low frequency (0.25 Hz) and intermediate duration (12 h) stretching protocol was overall the most effective in inducing beneficial responses, i.e., protein synthesis along with the suppression of apoptosis, inflammation and atrophy, in the differentiated cardiomyocytes. These findings demonstrated that varying the characteristics of mechanical loading applied on H9C2 cells in vitro can regulate their anabolic/survival program.

What Is in the Field for Genetics and Epigenetics of Diabetic Neuropathy: The Role of MicroRNAs

Despite the high prevalence of diabetic neuropathy, its early start, and its impact on quality of life and mortality, unresolved clinical issues persist in the field regarding its screening implementation, the understanding of its mechanisms, and the search for valid biomarkers, as well as disease-modifying treatment. Genetics may address these needs by providing genetic biomarkers of susceptibility, giving insights into pathogenesis, and shedding light on how to select possible responders to treatment. After a brief summary of recent studies on the genetics of diabetic neuropathy, the current review focused mainly on microRNAs (miRNAs), including the authors' results in this field. It summarized the findings of animal and human studies that associate miRNAs with diabetic neuropathy and explored the possible pathogenetic meanings of these associations, in particular regarding miR-128a, miR-155a, and miR-499a, as well as their application for diabetic neuropathy screening. Moreover, from a genetic perspective, it examined new findings of polymorphisms of miRNA genes in diabetic neuropathy. It considered in more depth the pathogenetic implications for diabetic neuropathy of the polymorphism of MIR499A and the related changes in the downstream action of miR-499a, showing how epigenetic and genetic studies may provide insight into pathogenetic mechanisms like mitochondrial dysfunction. Finally, the concept and the data of genotype-phenotype association for polymorphism of miRNA genes were described. In conclusion, although at a very preliminary stage, the findings linking the genetics and epigenetics of miRNAs might contribute to the identification of exploratory risk biomarkers, a comprehensive definition of susceptibility to specific pathogenetic mechanisms, and the development of mechanism-based treatment of diabetic neuropathy, thus addressing the goals of genetic studies.

MicroRNAs: New contributors to mechano-electric coupling and atrial fibrillation

Atrial fibrillation (AF) is a multifactorial disease, which often occurs in the presence of underlying cardiac abnormalities and is supported by electrophysiological and structural alterations, generally referred to as atrial remodeling. Abnormal substrates are commonly encountered in various conditions that predispose to AF, such as hypertension, heart failure, obesity, and sleep apnea, in which atrial stretch plays a key mechanistic role. Emerging evidence suggests a role for microRNAs (small non-coding RNAs) in the pathogenesis of AF, where they can act as post-transcriptional regulators of the genes involved in atrial remodeling. This review summarizes the experimental and clinical evidence that supports the role of microRNAs in the modulation of atrial electrical and structural remodeling with a focus on overload-induced atrial alterations, and discusses the potential contribution of microRNAs to mechano-electrical coupling and AF.

Mitochondrial DNA Copy Number in Peripheral Blood Is Reduced in Type 2 Diabetes Patients with Polyneuropathy and Associated with a MIR499A Gene Polymorphism

Our aim was to evaluate in a cohort of 125 Italian patients with type 2 diabetes (T2D), who underwent neurological evaluation, the possible differences in the number of mitochondrial DNA copies (mtDNA) comparing positive and negative patients for cardiovascular autonomic neuropathy (CAN) or diabetic peripheral neuropathy (DPN) and comparing them with healthy controls. We also investigated a possible correlation of the number of mtDNA copies with the polymorphism rs3746444 of the MIR499A. T2D patients show a decrease in the number of mtDNA copies compared to healthy controls (p = 2 × 10^-10). Dividing the T2D subjects by neurological evaluation, we found a significant mtDNA decrease in patients with DPN compared with those without (p = 0.02), while no differences were observed between subjects with and without CAN. Furthermore, the homozygous variant genotype for the polymorphism rs3746444 of MIR499A correlates with a decrease in the number of mtDNA copies, particularly in T2D patients (p = 0.009). Our data show a decrease in the number of mtDNA copies in subjects with T2D and suggest that this decrease is more evident in patients who develop DPN. Furthermore, the association of the variant allele of MIR499A with the number of mtDNA copies allows us to hypothesize a possible effect of this polymorphism in oxidative stress.

Plasma miR-208b and miR-499: Potential Biomarkers for Severity of Coronary Artery Disease

Aims

MicroRNAs (miRNAs) are associated with the pathogenesis of coronary artery disease (CAD). The objective of this study is to explore plasma levels of miR-208b and miR-499 in CAD and analyze its association with the severity of CAD.

Materials and Methods

195 consecutive CAD patients who underwent coronary angiography were enrolled in this study. Severity of coronary lesions was evaluated by the synergy between percutaneous coronary intervention with taxus and cardiac surgery score (SYNTAX) score (SS). Plasma levels of miR-208b and miR-499 were assessed by quantitative real-time polymerase chain reaction (qRT-PCR). The relationship between miR-208b and miR-499 and SS was analyzed.

Results

The qRT-PCR results showed that plasma levels of miR-208b and miR-499 in SS > 32 (high SS) group was higher than those in low (SS ≤ 22) and intermediate (22 < SS ≤ 32) groups. Meanwhile, plasma miR-208b and miR-499 levels were significantly positive correlated with the SS (Spearman's r = 0.535 and r = 0.407, respectively; both p < 0.001). Multivariate logistic analysis results showed that miR-208b (odds ratio [OR]: 2.069; 95% confidence interval [CI]: 1.351-3.167; p = 0.001) and miR-499 (OR: 1.652; 95% CI: 1.222-2.233; p = 0.001) were independent predictors of high SS. In receiver operating characteristic curve, the area under the curve of miR-208b and miR-499 in prediction of high SS was 0.775 and 0.713, respectively.

Conclusions

Higher plasma levels of miR-208b and miR-499 were positively associated with the severity of CAD, and plasma miR-208b and miR-499 can act as potential biomarkers for estimating the severity of CAD.

miR-486 is modulated by stretch and increases ventricular growth

Perturbations in biomechanical stimuli during cardiac development contribute to congenital cardiac defects such as hypoplastic left heart syndrome (HLHS). This study sought to identify stretch-responsive pathways involved in cardiac development. miRNA-Seq identified miR-486 as being increased in cardiomyocytes exposed to cyclic stretch in vitro. The right ventricles (RVs) of patients with HLHS experienced increased stretch and had a trend toward higher miR-486 levels. Sheep RVs dilated from excessive pulmonary blood flow had 60% more miR-486 compared with control RVs. The left ventricles of newborn mice treated with miR-486 mimic were 16.9%-24.6% larger and displayed a 2.48-fold increase in cardiomyocyte proliferation. miR-486 treatment decreased FoxO1 and Smad signaling while increasing the protein levels of Stat1. Stat1 associated with Gata-4 and serum response factor (Srf), 2 key cardiac transcription factors with protein levels that increase in response to miR-486. This is the first report to our knowledge of a stretch-responsive miRNA that increases the growth of the ventricle in vivo.

MiR-499 inhibited hypoxia/reoxygenation induced cardiomyocytes injury by targeting SOX6

Objective

MiR-499 has been reported to be expressed only in cardiomyocytes, and its expression would increase after acute myocardial infarction (AMI). miR-499 plays a role in the process of cardiomyocytes injury induced by hypoxia/reoxygenation (H/R), however, it still remains unclear.

Results

Hypoxia inhibited miR-499-5p expression and H/R induced apoptosis. SOX6 was a target gene of miR-499-5p, and high expression of miR-499-5p inhibited the expression of SOX6. MiR-499-5p reduced H9c2 cells injury by inhibiting the expression of SOX6, overexpression of which could reverse the effect of miR-499-5p on H9c2 cells. MiR-499-5p inhibited the levels of LDH and MDA, while overexpression of miR-499-5p inhibited H/R-induced cell apoptosis. MiR-499-5p could up-regulate the level of Bcl-2 and down-regulate the expression levels of Bax and caspase-3. However, SOX6 partially reversed these effects of miR-499-5p.

Conclusion

We proved that miR-499-5p inhibited H/R-induced cardiomyocytes injury by targeting SOX6. Our results suggested that miR-499-5p/SOX6 pathway may present a potential therapeutic target for the treatment of AMI.

Association between a MIR499A polymorphism and diabetic neuropathy in type 2 diabetes

AIMS

Diabetic polyneuropathy (DPN) and cardiovascular autonomic neuropathy (CAN) affect a large percentage of diabetic people and impact severely on quality of life. As it seems that miRNAs and their variations might play a role in these complications, we investigated whether the rs3746444 SNP in the MIR499A gene could be associated with susceptibility to DPN and/or CAN.

METHODS

We analyzed 150 participants with type 2 diabetes. DNA was extracted from peripheral blood samples and genotyping was performed by TaqMan genotyping assay. Cardiovascular tests, MNSI-Q and MDNS for neuropathic symptoms and signs, VPT, and thermal thresholds were used for CAN and DPN assessment. We performed a genotype-phenotype correlation analysis.

RESULTS

We observed that the GG genotype was associated with a higher risk of developing CAN (P=0.002 and OR=16.08, P=0.0005 and OR=35.02, for early and confirmed CAN, respectively) and DPN (P=0.037 and OR=6.56), after correction for BMI, sex, age, HbA1c and disease duration. Moreover, the GG genotype was associated with worse values of MDNS (P=0.017), VPT (P=0.01), thermal thresholds (P=0.01), and CAN score (P<0.001). A logistic multivariate analysis confirmed that MIR499A GG genotype, disease duration and HbA1c contributed to early CAN (R²=0.26), while the same variables and age contributed to DPN (R²=0.21). With a multiple linear regression, we observed that GG genotype (P=0.001) and disease duration (P=0.035) were the main variables contributing to the CAN score (R²=0.35).

CONCLUSIONS

We described for the first time that the MIR499A genetic variation could be involved in diabetic neuropathies susceptibility. In particular, patients carrying the rs3746444 GG genotype had a higher risk of CAN development, together with a more severe form of CAN.

The role of microRNAs in heart failure

MicroRNAs are small non-coding RNA molecules that regulate gene expression by inhibiting mRNA translation and/or inducing mRNA degradation. In the past decade, many in vitro and in vivo studies have explored the involvement of microRNAs in various cardiovascular diseases. In this paper, studies focused upon the target genes and functionality of miRNAs in the pathophysiological processes of heart failure are reviewed. The selected miRNAs are categorized according to the biological relevance of their target genes in relation to four cardiovascular pathologies, namely angiogenesis, cardiac hypertrophy, fibrosis and apoptosis. This review illustrates the involvement of miRNAs in different biological signaling pathways and provides an overview of current understanding of the roles of miRNAs in cardiovascular health and diseases. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure - edited by Jun Ren & Megan Yingmei Zhang.

Correction: Mechanical Stretch Inhibits MicroRNA499 via p53 to Regulate Calcineurin-A Expression in Rat Cardiomyocytes

[This corrects the article DOI: 10.1371/journal.pone.0148683.].