Metformin ameliorates cardiac conduction delay by regulating microRNA-1 in mice

Streptococcus gordonii Supragingival Bacterium Oral Infection-Induced Periodontitis and Robust miRNA Expression Kinetics

Streptococcus gordonii (S. gordonii, Sg) is one of the early colonizing, supragingival commensal bacterium normally associated with oral health in human dental plaque. MicroRNAs (miRNAs) play an important role in the inflammation-mediated pathways and are involved in periodontal disease (PD) pathogenesis. PD is a polymicrobial dysbiotic immune-inflammatory disease initiated by microbes in the gingival sulcus/pockets. The objective of this study is to determine the global miRNA expression kinetics in S. gordonii DL1-infected C57BL/6J mice. All mice were randomly divided into four groups (n = 10 mice/group; 5 males and 5 females). Bacterial infection was performed in mice at 8 weeks and 16 weeks, mice were euthanized, and tissues harvested for analysis. We analyzed differentially expressed (DE) miRNAs in the mandibles of S. gordonii-infected mice. Gingival colonization/infection by S. gordonii and alveolar bone resorption (ABR) was confirmed. All the S. gordonii-infected mice at two specific time points showed bacterial colonization (100%) in the gingival surface, and a significant increase in mandible and maxilla ABR (p < 0.0001). miRNA profiling revealed 191 upregulated miRNAs (miR-375, miR-34b-5p) and 22 downregulated miRNAs (miR-133, miR-1224) in the mandibles of S. gordonii-infected mice at the 8-week mark. Conversely, at 16 weeks post-infection, 10 miRNAs (miR-1902, miR-203) were upregulated and 32 miRNAs (miR-1937c, miR-720) were downregulated. Two miRNAs, miR-210 and miR-423-5p, were commonly upregulated, and miR-2135 and miR-145 were commonly downregulated in both 8- and 16-week-infected mice mandibles. Furthermore, we employed five machine learning (ML) algorithms to assess how the number of miRNA copies correlates with S. gordonii infections in mice. In the ML analyses, miR-22 and miR-30c (8-week), miR-720 and miR-339-5p (16-week), and miR-720, miR-22, and miR-339-5p (combined 8- and 16-week) emerged as the most influential miRNAs.

Perspective and Therapeutic Potential of the Noncoding RNA-Connexin Axis

Noncoding RNAs (ncRNAs) are a class of nucleotide sequences that cannot be translated into peptides. ncRNAs can function post-transcriptionally by splicing complementary sequences of mRNAs or other ncRNAs or by directly engaging in protein interactions. Over the past few decades, the pervasiveness of ncRNAs in cell physiology and their pivotal roles in various diseases have been identified. One target regulated by ncRNAs is connexin (Cx), a protein that forms gap junctions and hemichannels and facilitates intercellular molecule exchange. The aberrant expression and misdistribution of connexins have been implicated in central nervous system diseases, cardiovascular diseases, bone diseases, and cancer. Current databases and technologies have enabled researchers to identify the direct or indirect relationships between ncRNAs and connexins, thereby elucidating their correlation with diseases. In this review, we selected the literature published in the past five years concerning disorders regulated by ncRNAs via corresponding connexins. Among it, microRNAs that regulate the expression of Cx43 play a crucial role in disease development and are predominantly reviewed. The distinctive perspective of the ncRNA-Cx axis interprets pathology in an epigenetic manner and is expected to motivate research for the development of biomarkers and therapeutics.

MicroRNAs: Midfielders of Cardiac Health, Disease and Treatment

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules that play a role in post-transcriptional gene regulation. It is generally accepted that their main mechanism of action is the negative regulation of gene expression, through binding to specific regions in messenger RNA (mRNA) and repressing protein translation. By interrupting protein synthesis, miRNAs can effectively turn genes off and influence many basic processes in the body, such as developmental and apoptotic behaviours of cells and cardiac organogenesis. Their importance is highlighted by inhibiting or overexpressing certain miRNAs, which will be discussed in the context of coronary artery disease, atrial fibrillation, bradycardia, and heart failure. Dysregulated levels of miRNAs in the body can exacerbate or alleviate existing disease, and their omnipresence in the body makes them reliable as quantifiable markers of disease. This review aims to provide a summary of miRNAs as biomarkers and their interactions with targets that affect cardiac health, and intersperse it with current therapeutic knowledge. It intends to succinctly inform on these topics and guide readers toward more comprehensive works if they wish to explore further through a wide-ranging citation list.

Protective effects of metformin in various cardiovascular diseases: Clinical evidence and AMPK-dependent mechanisms

Metformin, a well-known AMPK agonist, has been widely used as the first-line drug for treating type 2 diabetes. There had been a significant concern regarding the use of metformin in people with cardiovascular diseases (CVDs) due to its potential lactic acidosis side effect. Currently growing clinical and preclinical evidence indicates that metformin can lower the incidence of cardiovascular events in diabetic patients or even non-diabetic patients beyond its hypoglycaemic effects. The underlying mechanisms of cardiovascular benefits of metformin largely involve the cellular energy sensor, AMPK, of which activation corrects endothelial dysfunction, reduces oxidative stress and improves inflammatory response. In this minireview, we summarized the clinical evidence of metformin benefits in several widely studied cardiovascular diseases, such as atherosclerosis, ischaemic/reperfusion injury and arrhythmia, both in patients with or without diabetes. Meanwhile, we highlighted the potential AMPK-dependent mechanisms in in vitro and/or in vivo models.

The role of MicroRNA networks in tissue-specific direct and indirect effects of metformin and its application

Metformin is a first-line oral antidiabetic agent that results in clear benefits in relation to glucose metabolism and diabetes-related complications. The specific regulatory details and mechanisms underlying these benefits are still unclear and require further investigation. There is recent mounting evidence that metformin has pleiotropic effects on the target tissue development in metabolic organs, including adipose tissue, the gastrointestinal tract and the liver. The mechanism of actions of metformin are divided into direct effects on target tissues and indirect effects via non-targeted tissues. MicroRNAs (miRNAs) are a class of endogenous, noncoding, negative gene regulators that have emerged as important regulators of a number of diseases, including type 2 diabetes mellitus (T2DM). Metformin is involved in many aspects of miRNA regulation, and metformin treatment in T2DM should be associated with other miRNA targets. A large number of miRNAs regulation by metformin in target tissues with either direct or indirect effects has gradually been revealed in the context of numerous diseases and has gradually received increasing attention. This paper thoroughly reviews the current knowledge about the role of miRNA networks in the tissue-specific direct and indirect effects of metformin. Furthermore, this knowledge provides a novel theoretical basis and suggests therapeutic targets for the clinical treatment of metformin and miRNA regulators in the prevention and treatment of cancer, cardiovascular disorders, diabetes and its complications.

Metformin and insulin-resistant related diseases: Emphasis on the role of microRNAs

Metformin is one of the most prescribed drugs in type II diabetes (T2DM) which has recently found new applications in the prevention and treatment of various illnesses, from metabolic disorders to cardiovascular and age-related diseases. Metformin improves insulin resistance (IR) by modulating metabolic mechanisms and mitochondrial biogenesis. Alternation of microRNAs (miRs) in the treatment of IR-related illnesses has been observed by metformin therapy. MiRs are small non-coding RNAs that play important roles in RNA silencing, targeting the 3'untranslated region (3'UTR) of most mRNAs and inhibiting the translation of related proteins. As a result, their dysregulation is associated with many diseases. Metformin may alter miRs levels in the treatment of various diseases by AMPK-dependent or AMPK-independent mechanisms. Here, we summarized the therapeutic role of metformin by modifying the aberrant expression of miRs as potential biomarkers or therapeutic targets in diseases in which IR plays a key role.

Role of MicroRNAs in Human Osteosarcoma: Future Perspectives

Osteosarcoma (OS) is a rare form of cancer with high death rate but is one of the most frequent forms of bone cancer in children and adolescents. MiRNAs are small endogenous RNAs that regulate gene expression post-transcriptionally. The discovery of miRNAs could allow us to obtain an earlier diagnosis, predict prognosis and chemoresistance, and lead to the discovery of new treatments in different types of tumors, including OS. Despite the fact that there is currently only one clinical trial being carried out on a single miRNA for solid tumors, it is very probable that the number of clinical trials including miRNAs as prognostic and diagnostic biomarkers, as well as potential therapeutic targets, will increase in the near future. This review summarizes the different miRNAs related to OS and their possible therapeutic application.

miR-1: A comprehensive review of its role in normal development and diverse disorders

MicroRNA-1 (miR-1) is a conserved miRNA with high expression in the muscle tissues. In humans, two discrete genes, MIRN1-1 and MIRN1-2 residing on a genomic region on 18q11.2 produce a single mature miRNA which has 21 nucleotides. miR-1 has a regulatory role on a number of genes including heat shock protein 60 (HSP60), Kruppel-like factor 4 (KLF4) and Heart And Neural Crest Derivatives Expressed 2 (HAND2). miR-1 has critical roles in the physiological processes in the smooth and skeletal muscles as well as other tissues, thus being involved in the pathogenesis of a wide range of disorders. Moreover, dysregulation of miR-1 has been noted in diverse types of cancers including gastric, colorectal, breast, prostate and lung cancer. In the current review, we provide the summary of the data regarding the role of this miRNA in the normal development and the pathogenic processes.

Effects of metformin on atrial and ventricular arrhythmias: evidence from cell to patient

Metformin has been shown to have various cardiovascular benefits beyond its antihyperglycemic effects, including a reduction in stroke, heart failure, myocardial infarction, cardiovascular death, and all-cause mortality. However, the roles of metformin in cardiac arrhythmias are still unclear. It has been shown that metformin was associated with decreased incidence of atrial fibrillation in diabetic patients with and without myocardial infarction. This could be due to the effects of metformin on preventing the structural and electrical remodeling of left atrium via attenuating intracellular reactive oxygen species, activating 5′ adenosine monophosphate-activated protein kinase, improving calcium homeostasis, attenuating inflammation, increasing connexin-43 gap junction expression, and restoring small conductance calcium-activated potassium channels current. For ventricular arrhythmias, in vivo reports demonstrated that activation of 5′ adenosine monophosphate-activated protein kinase and phosphorylated connexin-43 by metformin played a key role in ischemic ventricular arrhythmias reduction. However, metformin failed to show anti-ventricular arrhythmia benefits in clinical trials. In this review, in vitro and in vivo reports regarding the effects of metformin on both atrial arrhythmias and ventricular arrhythmias are comprehensively summarized and presented. Consistent and controversial findings from clinical trials are also summarized and discussed. Due to limited numbers of reports, further studies are needed to elucidate the mechanisms and effects of metformin on cardiac arrhythmias. Furthermore, randomized controlled trials are needed to clarify effects of metformin on cardiac arrhythmias in human.

Atherogenic L5 LDL induces cardiomyocyte apoptosis and inhibits KATP channels through CaMKII activation

Background

Cardiac Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) activation plays a critical role in cardiomyocyte (CM) apoptosis and arrhythmia. Functional ATP-sensitive potassium (K_ATP) channels are essential for cardiac protection during ischemia. In cultured CMs, L5 low-density lipoprotein (LDL) induces apoptosis and QTc prolongation. L5 is a highly electronegative and atherogenic aberrant form of LDL, and its levels are significantly higher in patients with cardiovascular-related diseases. Here, the role of L5 in cardiac injury was studied by evaluating the effects of L5 on CaMKII activity and K_ATP channel physiology in CMs.

Methods

Cultured neonatal rat CMs (NRCMs) were treated with a moderate concentration (ie, 7.5 μg/mL) of L5 or L1 (the least electronegative LDL subfraction). NRCMs were examined for apoptosis and viability, CaMKII activity, and the expression of phosphorylated CaMKIIδ and NOX2/gp91^phox. The function of K_ATP and action potentials (APs) was analyzed by using the patch-clamp technique.

Results

In NRCMs, L5 but not L1 significantly induced cell apoptosis and reduced cell viability. Furthermore, L5 decreased Kir6.2 expression by more than 50%. Patch-clamp analysis showed that L5 reduced the K_ATP current (I_KATP) density induced by pinacidil, a K_ATP opener. The partial recovery of the inward potassium current during pinacidil washout was susceptible to subsequent inhibition by the I_KATP blocker glibenclamide. Suppression of I_KATP by L5 significantly prolonged the AP duration. L5 also significantly increased the activity of CaMKII, the phosphorylation of CaMKIIδ, and the expression of NOX2/gp91^phox. L5-induced apoptosis was prevented by the addition of the CaMKII inhibitor KN93 and the reactive oxygen species scavenger Mn (III)TBAP.

Conclusions

L5 but not L1 induces CM damage through the activation of the CaMKII pathway and increases arrhythmogenicity in CMs by modulating the AP duration. These results help to explain the harmful effects of L5 in cardiovascular-related disease.