MicroRNA modulation of cholesterol homeostasis

Hypercapnia Increases Influenza A Virus Infection of Bronchial Epithelial Cells by Augmenting Cellular Cholesterol via mTOR and Akt

Hypercapnia, the elevation of CO2 in blood and tissue, is a risk factor for mortality in patients with severe lung disease and pulmonary infections. We previously showed that hypercapnia increases viral replication and mortality in mice infected with influenza A virus (IAV). Elevated CO2 also augmented cholesterol content and pseudo-SARS-CoV-2 entry in bronchial epithelial cells. Interestingly, cellular cholesterol facilitates IAV uptake, replication, assembly, and egress from cells. Here, we report that hypercapnia increases viral protein expression in airway epithelium of mice infected with IAV. Elevated CO2 also enhanced IAV adhesion and internalization, viral protein expression, and viral replication in bronchial epithelial cells. Hypercapnia increased the expression and activation of the transcription factor sterol-regulatory element binding protein 2 (SREBP2), resulting in elevated expression of cholesterol synthesis enzymes, decreased expression of a cholesterol efflux transporter, and augmented cellular cholesterol. Moreover, reducing cellular cholesterol with an SREBP2 inhibitor or statins blocked hypercapnia-induced increases in viral adhesion and internalization, viral protein expression, and IAV replication. Inhibitors of mTOR and Akt also blocked the effect of hypercapnia on viral growth. Our findings suggest that targeting cholesterol synthesis and/or mTOR/Akt signaling may hold promise for reducing susceptibility to influenza infection in patients with advanced lung disease and hypercapnia.

MicroRNA Profile, Putative Diagnostic Biomarkers and RNA-Based Therapies in the Inherited Lipid Storage Disease Niemann-Pick Type C

Lipids are essential for cellular function and are tightly controlled at the transcriptional and post-transcriptional levels. Dysregulation of these pathways is associated with vascular diseases, diabetes, cancer, and several inherited metabolic disorders. MicroRNAs (miRNAs), in particular, are a family of post-transcriptional gene repressors associated with the regulation of many genes that encode proteins involved in multiple lipid metabolism pathways, thereby influencing their homeostasis. Thus, this class of non-coding RNAs (ncRNAs) has emerged as a promising therapeutic target for the treatment of lipid-related metabolic alterations. Most of these miRNAs act at an intracellular level, but in the past few years, a role for miRNAs as intercellular signaling molecules has also been uncovered since they can be transported in bodily fluids and used as potential biomarkers of lipid metabolic alterations. In this review, we point out the current knowledge on the miRNA signature in a lysosomal storage disorder associated with lipid dysfunction, Niemann-Pick type C, and discuss the potential use of miRNAs as biomarkers and therapeutic targets for RNA-based therapies.

Functional significance of cholesterol metabolism in cancer: from threat to treatment

Cholesterol is an essential structural component of membranes that contributes to membrane integrity and fluidity. Cholesterol homeostasis plays a critical role in the maintenance of cellular activities. Recently, increasing evidence has indicated that cholesterol is a major determinant by modulating cell signaling events governing the hallmarks of cancer. Numerous studies have shown the functional significance of cholesterol metabolism in tumorigenesis, cancer progression and metastasis through its regulatory effects on the immune response, ferroptosis, autophagy, cell stemness, and the DNA damage response. Here, we summarize recent literature describing cholesterol metabolism in cancer cells, including the cholesterol metabolism pathways and the mutual regulatory mechanisms involved in cancer progression and cholesterol metabolism. We also discuss various drugs targeting cholesterol metabolism to suggest new strategies for cancer treatment.

The role of microRNA-185 in the pathogenesis of human diseases: A focus on cancer

MicroRNAs (miRNAs) are a widely-studied class of non-coding RNAs characterized by their short length (18-25 nucleotides). The precise functions of miRNAs are not well-elucidated; however, an increasing number of studies suggest their involvement in various physiologic processes and deregulation in pathologic conditions. miRNA-185 (miR-185) is among the mostly-studied miRNAs in human diseases, which is found to play putative roles in conditions like metabolic disorders, asthma, frailty, schizophrenia, and hepatitis. Notably, many cancer studies report the downregulation of miR-185 in cell lines, tumor tissues, and plasma specimens of patients, while it demonstrates a suppressing role on the malignant properties of cancer cells in vitro and in vivo. Accordingly, miR-185 can be considered a tumor suppressor miRNA in human malignancies, while a few studies also report inconsistent findings. Being suggested as a prognostic/diagnostic biomarker, mi-185 is also found to offer clinical potentials, particularly for early diagnosis and prediction of the prognosis of cancer patients. In this review, we have outlined the studies that have evaluated the functions and clinical significance of miR-185 in different human diseases with a particular focus on cancer.

Senescence-responsive miR-33-5p promotes chondrocyte senescence and osteoarthritis progression by targeting SIRT6

Osteoarthritis (OA) is a prevalent disease among elderly individuals that is caused by cartilage degeneration. Chondrocyte senescence involved in the development of OA, and antisenescence therapies have been proposed for OA treatment. In our study, we identified the role of a microRNA, miR-33-5p, in promoting chondrocyte senescence and OA progression. miR-33-5p expression was upregulated under senescence conditions. miR-33-5p-mimic transfection can induce cellular senescence, while transfection of a miR-33-5p-inhibitor in chondrocytes alleviated senescence induced by IL-1β. Moreover, SIRT6 expression was downregulated under IL-1β treatment, and could be restored by miR-33-5p-inhibitor transfection. Luciferase assays revealed that miR-33-5p targeted the SIRT6 mRNA 3' UTR. In addition, SIRT6 mRNA expression showed negative correlations with senescence and OA degree in human cartilage. Bioinformatic analysis also confirmed the pro-senescence effect of miR-33-5p. Furthermore, periodic intraarticular injection of agomiR-33-5p induced cartilage loss and OA-like cartilage changes. To conclude, we revealed the pro-senescence and cartilage-destructive effect of miR-33-5p, whose expression was elevated under various senescence conditions, and showed that SIRT6 was one of its targets. Therefore, miR-33-5p is a potential therapeutic target for treating OA.

Effect of circulating miR‑126 levels on intracranial aneurysms and their predictive value for the rupture of aneurysms: A systematic review and meta‑analysis

Intracranial aneurysm (IA) is a common cerebrovascular disease with a high risk of rupture. At present, the mechanisms underlying the formation and rupture of IAs is not clinically clear. MicroRNAs (miRNAs/miRs) are involved in the development of IAs. The present study aimed to determine the efficacy of circulating miRNA-126 (miR-126) levels as potential biomarkers for predicting aneurysmal ruptures. The present study searched comparative articles involving circulating miR-126 levels and intracranial aneurysms through electronic databases from 1980 to February, 2023. Collected variables included the first author's name, covered study period, publication year, total number of patients and age, and number of males. We collected information about the expression levels of circulating miR-126 in serum. Three articles met the eligibility criteria. The total number of patients was 379 [226 with IA rupture and 153 with non-rupture or/+ controls (healthy)]. The circulating miR-126 can be used as a biomarker for predicting aneurysmal rupture. Interestingly, an aneurysmal size >10 mm was associated with an IA rupture.

ATG5-Mediated Autophagy May Inhibit Pyroptosis to Ameliorate Oleic Acid-Induced Hepatocyte Steatosis

Despite activated autophagy ameliorating hepatocyte steatosis and metabolic associated fatty liver disease (MAFLD), mechanisms underlying the beneficial roles of autophagy in hepatic deregulation of lipid metabolism remain undefined. We explored whether autophagy can ameliorate oleic acid (OA)-induced hepatic steatosis by suppressing pyroptosis. Pyroptosis is involved in hepatocyte steatosis induced by OA. In addition, autophagy flux was blocked in OA-treated hepatocytes. Treatment with OA induced lipid accumulation in liver cell line L-02, which was attenuated by rapamycin (Rap), an autophagy agonist, while aggravated by autophagy inhibitor bafilomycin A1 (Baf A1). Inversely, treatment with pyroptotic agonist Nigericin aggravated OA-induced hepatic steatosis, while pyroptosis antagonist disulfiram ameliorated this effect. Mechanistically, treatment with Rap downregulated the expression of pyroptosis-related proteins, including NLRP3, Caspase-1, IL-18, GSDMD expression evoked by OA, thus improving pyroptosis in hepatic steatosis. Significantly, overexpression of ATG5 obviously downregulated cleaved caspase-1 expressions without altering the total caspase1 expressions in hepatic cell steatosis. Taken together, our studies strongly demonstrated that the activation of ATG5 inhibits pyroptosis to improve hepatic steatosis and suggest autophagy activation as a potential therapeutic strategy for pyroptosis-mediated MAFLD.

Glucose participates in the formation of goose fatty liver by regulating the expression of miRNA-33/CROT

Glucose oversupply promotes formation of fatty liver, and fatty liver is usually accompanied with hyperglycemia. However, the mechanism by which glucose promotes formation of fatty liver is not very clear. In this study, fatty liver was successfully induced in Landes goose by 19 days of overfeeding with corn-based feed, the overfed geese had a significantly higher level of blood glucose than the normally fed geese (control group). In goose primary liver cells, high level of glucose promoted fat deposition and induced the expression of SREBF2(or SREBP2), a key regulator of lipid metabolism, and its intronic gene, miR-33. Moreover, overexpression of miRNA-33(miR-33) promotes lipid accumulation in goose primary liver cells. Consistently, miR-33 inhibitor suppressed glucose induced lipid accumulation in liver cells. Interestingly, the relative abundance of miR-33 in goose fatty liver was significantly higher than that in normal liver, while the relative mRNA and protein abundances of CROT, the target gene of miR-33, in goose fatty liver were significantly lower than those in goose normal liver. Taken together, these findings suggest that miR-33 mediates glucose promotion of lipid accumulation in goose primary liver cells, and that glucose participates in formation of goose fatty liver by regulating the expression of miR-33/CROT.

Nanomaterial-Based Drug Targeted Therapy for Cardiovascular Diseases: Ischemic Heart Failure and Atherosclerosis

Cardiovascular diseases (CVDs) represent the most important epidemic of our century, with more than 37 million patients globally. Furthermore, CVDs are associated with high morbidity and mortality, and also increased hospitalization rates and poor quality of life. Out of the plethora of conditions that can lead to CVDs, atherosclerosis and ischemic heart disease are responsible for more than 2/3 of the cases that end in severe heart failure and finally death. Current therapy strategies for CVDs focus mostly on symptomatic benefits and have a moderate impact on the underlying physiopathological mechanisms. Modern therapies try to approach different physiopathological pathways such as reduction of inflammation, macrophage regulation, inhibition of apoptosis, stem-cell differentiation and cellular regeneration. Recent technological advances make possible the development of several nanoparticles used not only for the diagnosis of cardiovascular diseases, but also for targeted drug delivery. Due to their high specificity, nanocarriers can deliver molecules with poor pharmacokinetics and dynamics such as: peptides, proteins, polynucleotides, genes and even stem cells. In this review we focused on the applications of nanoparticles in the diagnosis and treatment of ischemic heart failure and atherosclerosis.

microRNAs involved in psoriasis and cardiovascular diseases

Psoriasis is a chronic inflammatory disease involving the skin. Both genetic and environmental factors play a pathogenic role in psoriasis and contribute to the severity of the disease. Psoriasis, in fact, has been associated with different comorbidities such as diabetes, metabolic syndrome, gastrointestinal or kidney diseases, cardiovascular disease (CVD), and cerebrovascular diseases (CeVD). Indeed, life expectancy in severe psoriasis is reduced by up to 5 years due to CVD and CeVD. Moreover, patients with severe psoriasis have a higher prevalence of traditional cardiovascular (CV) risk factors, including dyslipidemia, diabetes, smoking, and hypertension. Further, systemic inflammation is associated with oxidative stress increase and induces endothelial damage and atherosclerosis progression. Different miRNA have been already described in psoriasis, both in the skin tissues and in the blood flow, to play a role in the progression of disease. In this review, we will summarize and discuss the most important miRNAs that play a role in psoriasis and are also linked to CVD.

Circulating MicroRNAs as Potential Molecular Biomarkers for Intracranial Aneurysmal Rupture

INTRODUCTION

Diagnosis of the rupture of an intracranial aneurysm (IA) relies on sophisticated neuro-imaging studies, and molecular biomarkers to identify an IA or predict its rupture are still unavailable.

OBJECTIVE

Our objective was to determine the plasma microRNA (miRNA) expression profile in patients with ruptured IA presenting as aneurysmal subarachnoid hemorrhage (aSAH) and identify potential biomarkers of aneurysmal rupture.

METHODS

Plasma miRNA profiling was carried out using quantitative real-time polymerase chain reaction (qRT-PCR) in 20 patients with aSAH and 20 age- and sex-matched healthy controls. Eight differentially expressed miRNAs were validated by qPCR in a larger cohort of 88 patients with aSAH and 110 healthy controls. A receiver operating characteristic (ROC) curve was constructed to evaluate the overall performance of the miRNA-based assay. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was used to determine the potential pathway of miRNA-target genes.

RESULTS

The miRNA profiles were clearly distinct in patients compared with controls. Validation studies showed that three upregulated miRNAs (miR-15a-5p, miR-34a-5p, miR-374a-5p) and five downregulated miRNAs (miR-146a-5p, miR-376c-3p, miR-18b-5p, miR-24-3p, miR-27b-3p) could distinguish patients with aSAH from healthy controls with high predicted probability (0.865 and 0.995, respectively). Further, the expression levels of the eight candidate miRNAs were significantly dysregulated only in aSAH cases and not in patients with SAH due to other causes. Plasma miR-146a-5p and miR-27b-3p were associated with clinical outcomes in patients with aSAH. Functional analysis of the eight differentially expressed miRNA showed that the target genes involved in signaling pathways were related to inflammation.

CONCLUSIONS

Our study determined the plasma miRNA signature of ruptured IAs and identified eight candidate miRNAs that could be useful biomarkers for this condition. We hypothesize that these differentially expressed miRNAs may play pivotal roles in IA pathology.

miR-27b Modulates Insulin Signaling in Hepatocytes by Regulating Insulin Receptor Expression

Insulin resistance (IR) is one of the key contributing factors in the development of type 2 diabetes mellitus (T2DM). However, the molecular mechanisms leading to IR are still unclear. The implication of microRNAs (miRNAs) in the pathophysiology of multiple cardiometabolic pathologies, including obesity, atherosclerotic heart failure and IR, has emerged as a major focus of interest in recent years. Indeed, upregulation of several miRNAs has been associated with obesity and IR. Among them, miR-27b is overexpressed in the liver in patients with obesity, but its role in IR has not yet been thoroughly explored. In this study, we investigated the role of miR-27b in regulating insulin signaling in hepatocytes, both in vitro and in vivo. Therefore, assessment of the impact of miR-27b on insulin resistance through the hepatic tissue is of special importance due to the high expression of miR-27b in the liver together with its known role in regulating lipid metabolism. Notably, we found that miR-27b controls post-transcriptional expression of numerous components of the insulin signaling pathway including the insulin receptor (INSR) and insulin receptor substrate 1 (IRS1) in human hepatoma cells. These results were further confirmed in vivo showing that overexpression and inhibition of hepatic miR-27 enhances and suppresses hepatic INSR expression and insulin sensitivity, respectively. This study identified a novel role for miR-27 in regulating insulin signaling, and this finding suggests that elevated miR-27 levels may contribute to early development of hepatic insulin resistance.

Regulation of ATP binding cassette transporter A1 (ABCA1) expression: cholesterol-dependent and - independent signaling pathways with relevance to inflammatory lung disease

The role of the ATP binding cassette transporter A1 (ABCA1) in maintaining cellular lipid homeostasis in cardiovascular disease is well established. More recently, the important beneficial role played by ABCA1 in modulating pathogenic disease mechanisms, such as inflammation, in a broad range of chronic conditions has been realised. These studies position ABCA1 as a potential therapeutic target in a diverse range of diseases where inflammation is an underlying cause. Chronic respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD) are driven by inflammation, and as such, there is now a growing recognition that we need a greater understanding of the signaling pathways responsible for regulation of ABCA1 expression in this clinical context. While the signaling pathways responsible for cholesterol-mediated ABCA1 expression have been clearly delineated through decades of studies in the atherosclerosis field, and thus far appear to be translatable to the respiratory field, less is known about the cholesterol-independent signaling pathways that can modulate ABCA1 expression in inflammatory lung disease. This review will identify the various signaling pathways and ligands that are associated with the regulation of ABCA1 expression and may be exploited in future as therapeutic targets in the setting of chronic inflammatory lung diseases.

The Pivotal Role of the Dysregulation of Cholesterol Homeostasis in Cancer: Implications for Therapeutic Targets

Cholesterol plays an important role in cellular homeostasis by maintaining the rigidity of cell membranes, providing a medium for signaling transduction, and being converted into other vital macromolecules, such as sterol hormones and bile acids. Epidemiological studies have shown the correlation between cholesterol content and cancer incidence worldwide. Accumulating evidence has shown the emerging roles of the dysregulation of cholesterol metabolism in cancer development. More specifically, recent reports have shown the distinct role of cholesterol in the suppression of immune cells, regulation of cell survival, and modulation of cancer stem cells in cancer. Here, we provide a comprehensive review of the epidemiological analysis, functional roles, and mechanistic action of cholesterol homeostasis in regard to its contribution to cancer development. Based on the existing data, cholesterol homeostasis is identified to be a new key player in cancer pathogenesis. Lastly, we also discuss the therapeutic implications of natural compounds and cholesterol-lowering drugs in cancer prevention and treatment. In conclusion, intervention in cholesterol metabolism may offer a new therapeutic avenue for cancer treatment.

Noncoding RNAs in Vascular Diseases

The advent of deep sequencing technologies led to the identification of a considerable amount of noncoding RNA transcripts, which are increasingly recognized for their functions in controlling cardiovascular diseases. MicroRNAs have already been studied for a decade, leading to the identification of several vasculoprotective and detrimental species, which might be considered for therapeutic targeting. Other noncoding RNAs such as circular RNAs, YRNAs, or long noncoding RNAs are currently gaining increasing attention, and first studies provide insights into their functions as mediators or antagonists of vascular diseases in vivo. The present review article will provide an overview of the different types of noncoding RNAs controlling the vasculature and focus on the developing field of long noncoding RNAs.

Brothers in Arms: ABCA1- and ABCG1-Mediated Cholesterol Efflux as Promising Targets in Cardiovascular Disease Treatment

Atherosclerosis is a leading cause of cardiovascular disease worldwide, and hypercholesterolemia is a major risk factor. Preventive treatments mainly focus on the effective reduction of low-density lipoprotein cholesterol, but their therapeutic value is limited by the inability to completely normalize atherosclerotic risk, probably due to the disease complexity and multifactorial pathogenesis. Consequently, high-density lipoprotein cholesterol gained much interest, as it appeared to be cardioprotective due to its major role in reverse cholesterol transport (RCT). RCT facilitates removal of cholesterol from peripheral tissues, including atherosclerotic plaques, and its subsequent hepatic clearance into bile. Therefore, RCT is expected to limit plaque formation and progression. Cellular cholesterol efflux is initiated and propagated by the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. Their expression and function are expected to be rate-limiting for cholesterol efflux, which makes them interesting targets to stimulate RCT and lower atherosclerotic risk. This systematic review discusses the molecular mechanisms relevant for RCT and ABCA1 and ABCG1 function, followed by a critical overview of potential pharmacological strategies with small molecules to enhance cellular cholesterol efflux and RCT. These strategies include regulation of ABCA1 and ABCG1 expression, degradation, and mRNA stability. Various small molecules have been demonstrated to increase RCT, but the underlying mechanisms are often not completely understood and are rather unspecific, potentially causing adverse effects. Better understanding of these mechanisms could enable the development of safer drugs to increase RCT and provide more insight into its relation with atherosclerotic risk. SIGNIFICANCE STATEMENT: Hypercholesterolemia is an important risk factor of atherosclerosis, which is a leading pathological mechanism underlying cardiovascular disease. Cholesterol is removed from atherosclerotic plaques and subsequently cleared by the liver into bile. This transport is mediated by high-density lipoprotein particles, to which cholesterol is transferred via ATP-binding cassette transporters ABCA1 and ABCG1. Small-molecule pharmacological strategies stimulating these transporters may provide promising options for cardiovascular disease treatment.

Atherosclerotic plaque instability in carotid arteries: miR-200c as a promising biomarker

Early recognition of vulnerable carotid plaques could help in identifying patients at high stroke risk, who may benefit from earlier revascularisation. Nowadays, different biomarkers of plaque instability have been unravelled, among these miRNAs are promising tools for the diagnosis and treatment of atherosclerosis. Inflammation, reactive oxygen species (ROS) and endothelial dysfunction play a key role in unstable plaques genesis. We showed that miR-200c induces endothelial dysfunction, ROS production and a positive mechanism among miR-200c and miR-33a/b, two miRNAs involved in atherosclerosis progression. The goal of the present study was to determine whether miR-200c could be an atherosclerosis biomarker. Carotid plaques of patients that underwent carotid endarterectomy (CEA) were assayed for miR-200c expression. miR-200c was up-regulated in carotid plaques (n=22) and its expression was higher in unstable (n=12) compared with stable (n=10) plaques. miR-200c positively correlated with instability biomarkers (i.e. monocyte chemoattractant protein-1, cicloxigenase-2 (COX2), interleukin 6 (IL6), metalloproteinase (MMP) 1 (MMP1), 9 (MMP9)) and miR-33a/b. Moreover, miR-200c negatively correlated with stability biomarkers (i.e. zinc finger E-box binding homoeobox 1 (ZEB1), endothelial nitric oxide (NO) synthase (eNOS), forkhead boxO1 (FOXO1) and Sirtuin1 (SIRT1)) (stable plaques = 15, unstable plaques = 15). Circulating miR-200c was up-regulated before CEA in 24 patients, correlated with miR-33a/b and decreased 1 day after CEA. Interestingly, 1 month after CEA, circulating miR-200c is low in patients with stable plaques (n=11) and increased to control levels, in patients with unstable plaques (n=13). Further studies are needed to establish whether miR-200c represents a circulating biomarker of plaque instability. Our results show that miR-200c is an atherosclerotic plaque progression biomarker and suggest that it may be clinically useful to identify patients at high embolic risk.

Intestinal bile acid sequestration improves glucose control by stimulating hepatic miR-182-5p in type 2 diabetes

Colesevelam is a bile acid sequestrant approved to treat both hyperlipidemia and type 2 diabetes, but the mechanism for its glucose-lowering effects is not fully understood. The aim of this study was to investigate the role of hepatic microRNAs (miRNAs) as regulators of metabolic disease and to investigate the link between the cholesterol and glucose-lowering effects of colesevelam. To quantify the impact of colesevelam treatment in rodent models of diabetes, metabolic studies were performed in Zucker diabetic fatty (ZDF) rats and db/db mice. Colesevelam treatments significantly decreased plasma glucose levels and increased glycolysis in the absence of changes to insulin levels in ZDF rats and db/db mice. High-throughput sequencing and real-time PCR were used to quantify hepatic miRNA and mRNA changes, and the cholesterol-sensitive miR-96/182/183 cluster was found to be significantly increased in livers from ZDF rats treated with colesevelam compared with vehicle controls. Inhibition of miR-182 in vivo attenuated colesevelam-mediated improvements to glycemic control in db/db mice. Hepatic expression of mediator complex subunit 1 (MED1), a nuclear receptor coactivator, was significantly decreased with colesevelam treatments in db/db mice, and MED1 was experimentally validated to be a direct target of miR-96/182/183 in humans and mice. In summary, these results support that colesevelam likely improves glycemic control through hepatic miR-182-5p, a mechanism that directly links cholesterol and glucose metabolism. NEW & NOTEWORTHY Colesevelam lowers systemic glucose levels in Zucker diabetic fatty rats and db/db mice and increases hepatic levels of the sterol response element binding protein 2-responsive microRNA cluster miR-96/182/183. Inhibition of miR-182 in vivo reverses the glucose-lowering effects of colesevelam in db/db mice. Mediator complex subunit 1 (MED1) is a novel, direct target of the miR-96/182/183 cluster in mice and humans.

Antiproliferative potential of miR-33a in laryngeal cancer Hep-2 cells via targeting PIM1

BACKGROUND

Laryngeal cancer is a frequent cause of cancer-associated mortality worldwide with an overall poor prognosis along with high mortality rates. Therefore, comprehensive investigation of underlying molecular mechanisms of laryngeal carcinogenesis remains an important problem.

METHODS

In this study, proliferative and apoptotic features of Hep-2 cells overexpressing microRNA-33a (miR-33a) were evaluated and in silico analysis along with literature search was used to find putative targets of miR-33a. The potential of PIM1 (pim-1 oncogene) as a direct target of miR-33a was tested using quantitative real-time polymerase chain reaction, Western blot, and luciferase assay.

RESULTS

Induced miR-33a expression significantly inhibited proliferation through inducing apoptosis of Hep-2 cells. Further in vitro tests showed downregulation of PIM1 in messenger ribonucleic acid (mRNA) and protein level upon miR-33a overexpression and confirmed PIM1 as a direct target of miR-33a.

CONCLUSIONS

Mir-33a was demonstrated to act as a tumor suppressor in larnygeal cancer via directly targeting the 3' untranslated region of PIM1.

Dietary compounds have potential in controlling atherosclerosis by modulating macrophage cholesterol metabolism and inflammation via miRNA

Atherosclerosis (AS) is a typical example of a widespread fatal cardiovascular disease. Accumulation of cholesterol-laden macrophages in the artery wall forms the starting point of AS. Increased influx of oxidized low-density lipoprotein to macrophages and decreased efflux of free cholesterol out of macrophages constitute major factors promoting the development of AS. Inflammation further aggravates the development of AS along or via interaction with the cholesterol metabolism. Many microRNAs (miRNAs) are related to the regulation of macrophage in AS in aspects of cholesterol metabolism and inflammation signaling. Dietary compounds perform AS inhibitory effects via miRNAs in the cholesterol metabolism (miR-19b, miR-378, miR-10b, miR-33a, and miR-33b) and two miRNAs in the inflammation signaling (miR-155 and miR-146a). The targeted miRNAs in the cholesterol metabolism vary greatly among different food compounds; however, in inflammation signaling, most food compounds target miR-155. Many receptors are involved in macrophages via miRNAs, including ABCA1 and ABCG1 as major receptors in the cholesterol metabolism, while nuclear factor-κB (NF-κB) and Nrf2 signaling and PI3K/AKT signaling pathways are targeted during inflammation. This article reviews current literature to investigate possible AS therapy with dietary compounds via targeting miRNAs. Currently existing problems were also discussed to guide further studies.

Ablation of carotenoid cleavage enzymes (BCO1 and BCO2) induced hepatic steatosis by altering the farnesoid X receptor/miR-34a/sirtuin 1 pathway

β-Carotene-15, 15'-oxygenase (BCO1) and β-carotene-9', 10'-oxygenase (BCO2) are essential enzymes in carotenoid metabolism. While BCO1/BCO2 polymorphisms have been associated with alterations to human and animal carotenoid levels, experimental studies have suggested that BCO1 and BCO2 may have specific physiological functions beyond the cleavage of carotenoids. In the present study, we investigated the effect of ablation of both BCO1/BCO2 in the development of non-alcoholic fatty liver disease (NAFLD) and its underlying molecular mechanism(s). BCO1/BCO2 double knock out (DKO) mice developed hepatic steatosis (8/8) and had significantly higher levels of hepatic and plasma triglyceride and total cholesterol compared to WT (0/8). Hepatic changes in the BCO1/BCO2 DKO mice were associated with significant: 1) increases in lipogenesis markers, and decreases in fatty acid β-oxidation markers; 2) upregulation of cholesterol metabolism markers; 3) alterations to microRNAs related to TG accumulation and cholesterol metabolism; 4) increases in an hepatic oxidative stress marker (HO-1) but decreases in anti-oxidant enzymes; and 5) decreases in farnesoid X receptor (FXR), small heterodimer partner (SHP), and sirtuin 1 (SIRT1). The present study provided novel experimental evidence that BCO1 and BCO2 could play a significant role in maintaining normal hepatic lipid and cholesterol homeostasis, potentially through the regulation of the FXR/miR-34a/SIRT1 pathway.

Non-coding RNAs in lipid metabolism

Cardiovascular disease (CVD), the leading cause of death and morbidity in the Western world, begins with lipid accumulation in the arterial wall, which is the initial step in atherogenesis. Alterations in lipid metabolism result in increased risk of cardiometabolic disorders, and treatment of lipid disorders remains the most common strategy aimed at reducing the incidence of CVD. Work done over the past decade has identified numerous classes of non-coding RNA molecules including microRNAs (miRNAs) and long-non-coding RNAs (lncRNAs) as critical regulators of gene expression involved in lipid metabolism and CVD, mostly acting at post-transcriptional level. A number of miRNAs, including miR-33, miR-122 and miR-148a, have been demonstrated to play important role in controlling the risk of CVD through regulation of cholesterol homeostasis and lipoprotein metabolism. lncRNAs are recently emerging as important regulators of lipid and lipoprotein metabolism. However, much additional work will be required to fully understand the impact of lncRNAs on CVD and lipid metabolism, due to the high abundance of lncRNAs and the poor-genetic conservation between species. This article reviews the role of miRNAs and lncRNAs in lipid and lipoprotein metabolism and their potential implications for the treatment of CVD.

The phosphodiesterase 5 inhibitor tadalafil regulates lipidic homeostasis in human skeletal muscle cell metabolism

PURPOSE

Tadalafil seems to ameliorate insulin resistance and glucose homeostasis in humans. We have previously reported that tadalafil targets human skeletal muscle cells with an insulin (I)-like effect. We aim to evaluate in human fetal skeletal muscle cells after tadalafil or I: (i) expression profile of I-regulated genes dedicated to cellular energy control, glycolitic activity or microtubule formation/vesicle transport, as GLUT4, PPARγ, HK2, IRS-1, KIF1C, and KIFAP3; (ii) GLUT4, Flotillin-1, and Caveolin-1 localization, all proteins involved in energy-dependent cell trafficking; (iii) activation of I-targeted paths, as IRS-1, PKB/AKT, mTOR, P70/S6K. Free fatty acids intracellular level was measured. Sildenafil or a cGMP synthetic analog were used for comparison; PDE5 and PDE11 gene expression was evaluated in human fetal skeletal muscle cells.

METHODS

RTq-PCR, PCR, western blot, free fatty acid assay commercial kit, and lipid stain non-fluorescent assay were used.

RESULTS

Tadalafil upregulated I-targeted investigated genes with the same temporal pattern as I (GLUT4, PPARγ, and IRS-1 at 3 h; HK2, KIF1C, KIFAP3 at 12 h), re-localized GLUT4 in cell sites positively immune-decorated for Caveolin-1 and Flotillin-1, suggesting the involvement of lipid rafts, induced specific residue phosphorylation of IRS-1/AKT/mTOR complex in association with free fatty acid de novo synthesis. Sildenafil or GMP analog did not affect GLUT4 trafficking or free fatty acid levels.

CONCLUSION

In human fetal skeletal muscle cells tadalafil likely favors energy storage by modulating lipid homeostasis via IRS-1-mediated mechanisms, involving activation of I-targeted genes and intracellular cascade related to metabolic control. Those data provide some biomolecular evidences explaining, in part, tadalafil-induced favorable control of human metabolism shown by clinical studies.

Circulating miR-200c is up-regulated in paediatric patients with familial hypercholesterolaemia and correlates with miR-33a/b levels: implication of a ZEB1-dependent mechanism

Hypercholesterolaemia provokes reactive oxygen species (ROS) increase and is a major risk factor for cardiovascular disease (CVD) development. We previously showed that circulating miR-33a/b expression levels were up-regulated in children with familial hypercholesterolaemia (FH). miR-33a/b control cholesterol homoeostasis and recently miR-33b has been demonstrated to directly target the transcription factor zinc finger E-box-binding homeobox 1 (ZEB1). The latter acts in a negative feedback loop with the miR-200 family. Our previous studies showed that the ROS-dependent miR-200c up-regulation induces endothelial dysfunction and provokes a ZEB1-dependent apoptosis and senescence. In the present study, we aimed to verify whether circulating miR-200c was induced in FH children, and whether a correlation existed with miR-33a/b. Total RNA was extracted from plasma of 28 FH children and 25 age-matched healthy subjects (HS) and miR-200c levels were measured. We found that miR-200c was up-regulated in FH compared with HS (4.00 ± 0.48-fold increase, P<0.05) and exhibited a positive correlation with miR-33a/b. miR-200c did not correlate with plasma lipids, but correlated with C-reactive protein (CRP) plasma levels and glycaemia (GLI). Ordinary least squares (OLS) regression analysis revealed that miR-200c was significantly affected by GLI and by miR-33a (P<0.01; P<0.001 respectively). Moreover, we found that miR-33 overexpression, in different cell lines, decreased ZEB1 expression and up-regulated both the intracellular and the extracellular miR-200c expression levels. In conclusion, circulating miR-200c is up-regulated in FH, probably due to oxidative stress and inflammation and via a miR-33a/b-ZEB1-dependent mechanism. The present study could provide the first evidence to point to the use of miR-33a/b and miR-200c, as early biomarkers of CVD, in paediatric FH.

Circulating miR-200c is up-regulated in paediatric patients with familial hypercholesterolaemia and correlates with miR-33a/b levels: implication of a ZEB1-dependent mechanism

Hypercholesterolaemia provokes reactive oxygen species (ROS) increase and is a major risk factor for cardiovascular disease (CVD) development. We previously showed that circulating miR-33a/b expression levels were up-regulated in children with familial hypercholesterolaemia (FH). miR-33a/b control cholesterol homoeostasis and recently miR-33b has been demonstrated to directly target the transcription factor zinc finger E-box-binding homeobox 1 (ZEB1). The latter acts in a negative feedback loop with the miR-200 family. Our previous studies showed that the ROS-dependent miR-200c up-regulation induces endothelial dysfunction and provokes a ZEB1-dependent apoptosis and senescence. In the present study, we aimed to verify whether circulating miR-200c was induced in FH children, and whether a correlation existed with miR-33a/b. Total RNA was extracted from plasma of 28 FH children and 25 age-matched healthy subjects (HS) and miR-200c levels were measured. We found that miR-200c was up-regulated in FH compared with HS (4.00 ± 0.48-fold increase, P<0.05) and exhibited a positive correlation with miR-33a/b. miR-200c did not correlate with plasma lipids, but correlated with C-reactive protein (CRP) plasma levels and glycaemia (GLI). Ordinary least squares (OLS) regression analysis revealed that miR-200c was significantly affected by GLI and by miR-33a (P<0.01; P<0.001 respectively). Moreover, we found that miR-33 overexpression, in different cell lines, decreased ZEB1 expression and up-regulated both the intracellular and the extracellular miR-200c expression levels. In conclusion, circulating miR-200c is up-regulated in FH, probably due to oxidative stress and inflammation and via a miR-33a/b-ZEB1-dependent mechanism. The present study could provide the first evidence to point to the use of miR-33a/b and miR-200c, as early biomarkers of CVD, in paediatric FH.

Role of miRNAs in human disease and inborn errors of metabolism

MicroRNAs (miRNAs) are short, noncoding RNAs that regulate gene expression posttranscriptionally by base pairing with target messenger RNAs (mRNAs). They are estimated to target ∼60% of all human protein-coding genes and are involved in regulating key physiological processes and intracellular signaling pathways. They also exhibit tissue specificity, and their dysregulation is linked to the progression of pathology. Identifying disease associated miRNAs and their respective targets provides novel molecular insight into disease, enabling the design of new therapeutic strategies. Notably, miRNAs are present in stable form in biological fluids, making them amenable to routine clinical processing and analysis, which has paved the way for their use as novel biomarkers of disease and response to therapy. One of the most relevant findings in miRNA research concerns the therapeutic modulation of specific miRNA levels in vitro and in vivo, which has led to miRNA-based drugs entering clinical trials. Most studies relative to miRNA profiling, association with pathology, and therapeutical modulation have been conducted for cancer, cardiovascular and neurodegenerative diseases. However, for different monogenic diseases, including inborn errors of metabolism (IEM), research contributing to alterations to physiopathology caused by miRNAs is steadily increasing. Herein, we review the biogenesis pathway and mode of miRNA action, their known roles in disease states, and use of circulating miRNAs as biomarkers, describing the available research tools for basic and clinical studies. In addition, we summarize recent literature on miRNA studies in inherited metabolic diseases.

microRNAs in lipoprotein and lipid metabolism: from biological function to clinical application

microRNAs (miRNAs) are short (~22 nucleotides), non-coding, single-stranded RNA molecules that regulate the expression of target genes by partial sequence-specific base-pairing to the targeted mRNA 3'UTR, blocking its translation, and promoting its degradation or its sequestration into processing bodies. miRNAs are important regulators of several physiological processes including developmental and metabolic functions, but their concentration in circulation has also been reported to be altered in many pathological conditions such as familial hypercholesterolemia, cardiovascular diseases, obesity, type 2 diabetes, and cancers. In this review, we focus on the role of miRNAs in lipoprotein and lipid metabolism, with special attention to the well-characterized miR-33a/b, and on the huge potential of miRNAs for clinical application as biomarkers and therapeutics in the context of cardiometabolic diseases.

Epigenetics and cardiovascular risk in childhood

Cardiovascular disease (CVD) can arise at the early stages of development and growth. Genetic and environmental factors may interact resulting in epigenetic modifications with abnormal phenotypic expression of genetic information without any change in the nucleotide sequence of DNA. Maternal dietary imbalance, inadequate to meet the nutritional needs of the fetus can lead to intrauterine growth retardation, decreased gestational age, low birth weight, excessive post-natal growth and metabolic alterations, with subsequent appearance of CVD risk factors. Fetal exposure to high cholesterol, diabetes and maternal obesity is associated with increased risk and progression of atherosclerosis. Maternal smoking during pregnancy and exposure to various environmental pollutants induce epigenetic alterations of gene expression relevant to the onset or progression of CVD. In children with hypercholesterolemia and/or obesity, oxidative stress activates platelets and monocytes, which release proinflammatory and proatherogenic substances, inducing endothelial dysfunction, decreased Doppler flow-mediated dilation and increased carotid intima-media thickness. Primary prevention of atherosclerosis should be implemented early. It is necessary to identify, through screening, high-risk apparently healthy children and take care of them enforcing healthy lifestyle (mainly consisting of Mediterranean diet and physical activity), prescribing nutraceuticals and eventual medications, if required by a high-risk profile. The key issue is the restoration of endothelial function in the reversible stage of atherosclerosis. Epigenetics may provide new markers for an early identification of children at risk and thereby develop innovative therapies and specific nutritional interventions in critical times.

PKCβ: Expanding role in hepatic adaptation of cholesterol homeostasis to dietary fat/cholesterol

Cholesterol homeostasis relies on an intricate network of cellular processes whose deregulation in response to Western type high-fat/cholesterol diets can lead to several life-threatening pathologies. Significant advances have been made in resolving the molecular identity and regulatory function of transcription factors sensitive to fat, cholesterol, or bile acids, but whether body senses the presence of both fat and cholesterol simultaneously is not known. Assessing the impact of a high-fat/cholesterol load, rather than an individual component alone, on cholesterol homeostasis is more physiologically relevant because Western diets deliver both fat and cholesterol at the same time. Moreover, dietary fat and dietary cholesterol are reported to act synergistically to impair liver cholesterol homeostasis. A key insight into the role of protein kinase C-β (PKCβ) in hepatic adaptation to high-fat/cholesterol diets was gained recently through the use of knockout mice. The emerging evidence indicates that PKCβ is an important regulator of cholesterol homeostasis that ensures normal adaptation to high-fat/cholesterol intake. Consistent with this function, high-fat/cholesterol diets induce PKCβ expression and signaling in the intestine and liver, while systemic PKCβ deficiency promotes accumulation of cholesterol in the liver and bile. PKCβ disruption results in profound dysregulation of hepatic cholesterol and bile homeostasis and imparts sensitivity to cholesterol gallstone formation. The available results support involvement of a two-pronged mechanism by which intestine and liver PKCβ signaling converge on liver ERK1/2 to dictate diet-induced cholesterol and bile acid homeostasis. Collectively, PKCβ is an integrator of dietary fat/cholesterol signal and mediates changes to cholesterol homeostasis.

Functional analysis of new 3' untranslated regions genetic variants in genes associated with genetic hypercholesterolemias

BACKGROUND

Familial hypercholesterolemia (FH) is the best-described autosomal dominant genetic hypercholesterolemia (GH). Mutations in candidate genes can explain a high proportion of FH cases, but for many, no causative mutations are detected (designed non-FG-GH), suggesting the existence of additional genetic variants associated with the disease.

OBJECTIVE

We aimed to identify new single-nucleotide variants (SNVs) located at the 3' untranslated regions (3'UTRs) of the low-density lipoprotein receptor, low-density lipoprotein receptor-related protein-associated protein 1, ATP-binding cassette sub-family G member 5, and sterol regulatory element-binding protein 2 genes in non-FH-GH individuals and investigated whether the association of these SNVs with non-FH-GH could be explained by changes in the affinity of regulatory microRNAs (miRNA) targeting the sequences modified by the SNVs.

METHODS

The study includes probands with non-FH-GH attending 2 lipid clinics in Spain. We performed functional analyses of selected variants using a luciferase reporter system. Through in silico target-prediction tools, we identified miRNAs, which binding to the 3'UTR could be affected by the presence of specific SNVs. We used analogs and inhibitors of these miRNAs to test this possibility.

RESULTS

We identified 11 new SNVs showing significant association with non-FH-GH. We show that the presence of 4 of these SNVs leads to significant changes in the transcriptional levels of the reporter gene. Through mechanistic analysis, we identified 2 miRNAs (miR-27a and miR-133-3p) targeting the 3'UTR of sterol regulatory element-binding protein 2 and an additional miRNA (miR-92a) targeting the 3'UTR of low-density lipoprotein receptor-related protein-associated protein 1.

CONCLUSION

Our findings reveal novel regulatory links between certain miRNAs and key genes regulating cholesterol homeostasis. They also highlight the potential of miRNAs as therapeutic targets for the treatment of FH.

Interplay of mitochondrial metabolism and microRNAs

Mitochondria are important organelles in cellular metabolism. Several crucial metabolic pathways such as the energy producing electron transport chain or the tricarboxylic acid cycle are hosted inside the mitochondria. The proper function of mitochondria depends on the import of proteins, which are encoded in the nucleus and synthesized in the cytosol. Micro-ribonucleic acids (miRNAs) are short non-coding ribonucleic acid (RNA) molecules with the ability to prevent messenger RNA (mRNA)-translation or to induce the degradation of mRNA-transcripts. Although miRNAs are mainly located in the cytosol or the nucleus, a subset of ~150 different miRNAs, called mitomiRs, has also been found localized to mitochondrial fractions of cells and tissues together with the subunits of the RNA-induced silencing complex (RISC); the protein complex through which miRNAs normally act to prevent translation of their mRNA-targets. The focus of this review is on miRNAs and mitomiRs with influence on mitochondrial metabolism and their possible pathophysiological impact.

Small GTPase ARF6 Regulates Endocytic Pathway Leading to Degradation of ATP-Binding Cassette Transporter A1

OBJECTIVE

ABCA1 (ATP-binding cassette transporter A1) is the principal protein responsible for cellular cholesterol efflux. Abundance and functionality of ABCA1 is regulated both transcriptionally and post-translationally, with endocytosis of ABCA1 being an important element of post-translational regulation. Functional ABCA1 resides on the plasma membrane but can be internalized and either degraded or recycled back to the plasma membrane. The interaction between the degradative and recycling pathways determines the abundance of ABCA1 and may contribute to the efflux of intracellular cholesterol.

APPROACH AND RESULTS

Here, we show that the principal pathway responsible for the internalization of ABCA1 leading to its degradation in macrophages is ARF6-dependent endocytic pathway. This pathway was predominant in the regulation of ABCA1 abundance and efflux of plasma membrane cholesterol. Conversely, the efflux of intracellular cholesterol was predominantly controlled by ARF6-independent pathways, and inhibition of ARF6 shifted ABCA1 into recycling endosomes enhancing efflux of intracellular cholesterol.

CONCLUSIONS

We conclude that ARF6-dependent pathway is the predominant route responsible for the ABCA1 internalization and degradation, whereas ARF6-independent endocytic pathways may contribute to ABCA1 recycling and efflux of intracellular cholesterol.

Aberrant expression of plasma microRNA-33a in an atherosclerosis-risk group

In order to investigate whether plasma microRNA-33a (miR-33a) can be a biomarker for the early detection of atherosclerosis and to reexamine the assumption that miR-33a represses the expression of ABCA1, we compared the expression levels of miR-33a and ATP-binding cassette A1 (ABCA1) using human plasma and supernatants of macrophage cultured media. We first separated ample number of plasma samples from left-over whole blood samples based on the criteria for normal or dyslipidemia, and stored them at -20 °C until use. Then we selected 18 plasma samples for each normal, athero-risk and treated group using a metabolic disease cohort in which candidate subjects have participated. For classifying into three groups, we primarily relied on the records of physicians' comments, prescriptions, treatment history, lipid profiles and test results from medical equipment aimed at the diagnosis for atherosclerosis or cardiovascular disease. After collecting the final 54 plasma samples, we analyzed and compared the expression levels of miR-33a and ABCA1 at the plasma levels. In the comparison of plasma levels of the three groups, the miR-33a expression level of athero-risk group was 5.01-fold higher than that of normal group. Meanwhile, in the culture of foam cells transfected with anti-miR-33a oligonucleotides, the miR-33a level significantly decreased, while ABCA1 level significantly increased. The results suggest that enhanced expression of miR-33a might induce cholesterol accumulation and aggravate inflammation in vessel walls by suppressing the expression of ABCA1 in macrophages. Thus, plasma miR-33a can be considered as a candidate biomarker of atherosclerosis.

Deregulated hepatic microRNAs underlie the association between non-alcoholic fatty liver disease and coronary artery disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) appears to be a new risk factor for the development of coronary artery disease (CAD). Members of a class of non-coding RNAs, termed microRNAs (miRNAs), have been identified as post-transcriptional regulators of cholesterol homoeostasis and can contribute to the development of NAFLD. The aims of this study were to (i) to assess the relationship between NAFLD and sudden cardiac death (SCD) from severe CAD in forensic autopsies and (ii) to quantify several hepatic miRNAs previously associated with lipid metabolism and NAFLD to correlate their expression with the presence of NAFLD, CAD, obesity parameters and postmortem lipid profile.

METHODS

A total of 133 cases of autopsies with SCD and established CAD (patient group, CAD-SCD) and 106 cases of non-CAD sudden death (control group, non-CAD-SD) were included. miRNAs were quantified in frozen liver tissues.

RESULTS

Males predominated in both groups. Patients more frequently exhibited NAFLD and necroinflammatory steatohepatitis (NASH) than controls (62% vs 26%, P = 0.001 and 42% vs 26%, P = 0.001 respectively). In both groups, the presence of NAFLD correlated with body mass index and abdominal circumference (P < 0.05). An increase in miR-34a-5p and a decrease in miR-122-5p and -29c-3p in patients with NASH vs controls without NAFLD were observed (P < 0.05). Finally, significant correlations between miR-122-5p and unfavourable lipid profile and also hs-CRP and miR-34a-5p were noted.

CONCLUSIONS

CAD is associated with NAFLD and NASH. The hepatic miRNAs studied appear to be associated with NAFLD severity and may promote CAD through lipid metabolism alteration and/or promotion of the systemic inflammation.

TXNIP regulates myocardial fatty acid oxidation via miR-33a signaling

Myocardial fatty acid β-oxidation is critical for the maintenance of energy homeostasis and contractile function in the heart, but its regulation is still not fully understood. While thioredoxin-interacting protein (TXNIP) has recently been implicated in cardiac metabolism and mitochondrial function, its effects on β-oxidation have remained unexplored. Using a new cardiomyocyte-specific TXNIP knockout mouse and working heart perfusion studies, as well as loss- and gain-of-function experiments in rat H9C2 and human AC16 cardiomyocytes, we discovered that TXNIP deficiency promotes myocardial β-oxidation via signaling through a specific microRNA, miR-33a. TXNIP deficiency leads to increased binding of nuclear factor Y (NFYA) to the sterol regulatory element binding protein 2 (SREBP2) promoter, resulting in transcriptional inhibition of SREBP2 and its intronic miR-33a. This allows for increased translation of the miR-33a target genes and β-oxidation-promoting enzymes, carnitine octanoyl transferase (CROT), carnitine palmitoyl transferase 1 (CPT1), hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase/enoyl-CoA hydratase-β (HADHB), and AMPKα and is associated with an increase in phospho-AMPKα and phosphorylation/inactivation of acetyl-CoA-carboxylase. Thus, we have identified a novel TXNIP-NFYA-SREBP2/miR-33a-AMPKα/CROT/CPT1/HADHB pathway that is conserved in mouse, rat, and human cardiomyocytes and regulates myocardial β-oxidation.

MicroRNA-33 promotes the replicative senescence of mouse embryonic fibroblasts by suppressing CDK6

MicroRNAs are a large class of tiny noncoding RNAs, which have emerged as critical regulators of gene expression, and thus are involved in multiple cellular processes, including cellular senescence. MicroRNA-33 has previously been established to exert crucial effect on cell proliferation, lipid metabolism and cholesterol metabolism. Nonetheless, the association between microRNA-33 and cellular senescence and its underlying molecular mechanism are far to be elucidated. The present study has attempted to probe into the effect of microRNA-33 on MEFs senescence. Our data unveiled that microRNA-33 was dramatically down-regulated in senescent MEFs compared to the young MEFs, and ectopic expression of microRNA-33 promoted MEFs senescence, while knock-down of microRNA-33 exhibited a protective effect against senescence phenotype. Moreover, we verified CDK6 as a direct target of microRNA-33 in mouse. Silencing of CDK6 induced the premature senescence phenotype of MEFs similarly as microRNA-33, while enforced expression of CDK6 significantly reverse the senescence-induction effect of microRNA-33. Taken together, our results suggested that microRNA-33 enhanced the replicative senescence of MEFs potentially by suppressing CDK6 expression.

High blood sugar levels significantly impact the prognosis of colorectal cancer patients through down-regulation of microRNA-16 by targeting Myb and VEGFR2

The high prevalence of type 2 diabetes mellitus in colorectal cancer patients is a crucial public health issue worldwide. The deregulation of microRNAs has been shown to be associated with the progression of CRC; however, the effects of high blood sugar levels on miR deregulation and, in turn, CRC remain unexplored. In this study, 520 CRC patients were classified into two groups according to their blood sugar levels (≧110 or <110 mg/dL). Clinicopathologic features, clinical outcomes, and serum miR-16 levels of the two groups were then analyzed, while cell cycles, cell proliferation, migration, and cellular miR-16 expression were investigated via D-(+)-glucose administration. Additionally, the target genes of miR-16 were identified. Through multivariate analysis, both the disease-free survival and overall survival of the CRC patients were found to be associated with the UICC stage, perineural invasion, and blood glucose levels (P < 0.05). Serum miR-16 levels were significantly lower in the high blood glucose patients than in the normal blood glucose patients (P = 0.0329). With D-(+)-glucose administration, the proliferation and migration of CRC cells in vitro increased remarkably (P < 0.05), while their accumulation in the G1 phase decreased significantly. Cellular miR-16 expression was suppressed by D-(+)-glucose administration. The expression levels of two target genes, Myb and VEGFR2, were affected significantly by miR-16, while glucose administration inhibited miR-16 expression and enhanced tumor cell proliferation and migration. Hyperglycemia can impact the clinical outcomes of CRC patients, likely by inhibiting miR-16 expression and the expression of its downstream genes Myb and VEGFR2.

Cholesterol in Pancreatic β-Cell Death and Dysfunction: Underlying Mechanisms and Pathological Implications

The mechanisms or causes of pancreatic β-cell death as well as impaired insulin secretion, which are the principal events of diabetic etiopathology, are largely unknown. Diabetic complications are known to be associated with abnormal plasma lipid profile, mainly elevated level of cholesterol and free fatty acids. However, in recent years, elevated plasma cholesterol has been implicated as a primary modulator of pancreatic β-cell functions as well as death. High-cholesterol diet in animal models or excess cholesterol in pancreatic β-cell causes transporter desensitization and results in morphometric changes in insulin granules. Moreover, cholesterol is also held responsible to cause oxidative stress, mitochondrial dysfunction, and activation of proapoptotic markers leading to β-cell death. The present review focuses on the pathways and molecularevents that occur in the β-cell under the influence of excess cholesterol that hampers the basal physiology of the cell leading to the progression of diabetes.

Macrophage miRNAs in atherosclerosis

The discovery of endogenous microRNAs (miRNAs) in the early 1990s has been followed by the identification of hundreds of miRNAs and their roles in regulating various biological processes, including proliferation, apoptosis, lipid metabolism, glucose homeostasis and viral infection Esteller (2011), Ameres and Zamore (2013) [1,2]. miRNAs are small (~22 nucleotides) non-coding RNAs that function as "rheostats" to simultaneously tweak the expression of multiple genes within a genetic network, resulting in dramatic functional modulation of biological processes. Although the last decade has brought the identification of miRNAs, their targets and function(s) in health and disease, there remains much to be deciphered from the human genome and its complexities in mechanistic regulation of entire genetic networks. These discoveries have opened the door to new and exciting avenues for therapeutic interventions to treat various pathological diseases, including cardiometabolic diseases such as atherosclerosis, diabetes and obesity. In a complex multi-factorial disease like atherosclerosis, many miRNAs have been shown to contribute to disease progression and may offer novel targets for future therapy. This article is part of a Special Issue entitled: MicroRNAs and lipid/energy metabolism and related diseases edited by Carlos Fernández-Hernando and Yajaira Suárez.

The Unfolded Protein Response and Cholesterol Biosynthesis Link Luman/CREB3 to Regenerative Axon Growth in Sensory Neurons

We recently revealed that the axon endoplasmic reticulum resident transcription factor Luman/CREB3 (herein called Luman) serves as a unique retrograde injury signal in regulation of the intrinsic elongating form of sensory axon regeneration. Here, evidence supports that Luman contributes to axonal regeneration through regulation of the unfolded protein response (UPR) and cholesterol biosynthesis in adult rat sensory neurons. One day sciatic nerve crush injury triggered a robust increase in UPR-associated mRNA and protein expression in both neuronal cell bodies and the injured axons. Knockdown of Luman expression in 1 d injury-conditioned neurons by siRNA attenuated axonal outgrowth to 48% of control injured neurons and was concomitant with reduced UPR- and cholesterol biosynthesis-associated gene expression. UPR PCR-array analysis coupled with qRT-PCR identified and confirmed that four transcripts involved in cholesterol regulation were downregulated >2-fold by the Luman siRNA treatment of the injury-conditioned neurons. Further, the Luman siRNA-attenuated outgrowth could be significantly rescued by either cholesterol supplementation or 2 ng/ml of the UPR inducer tunicamycin, an amount determined to elevate the depressed UPR gene expression to a level equivalent of that observed with crush injury. Using these approaches, outgrowth increased significantly to 74% or 69% that of injury-conditioned controls, respectively. The identification of Luman as a regulator of the injury-induced UPR and cholesterol at levels that benefit the intrinsic ability of axotomized adult rat sensory neurons to undergo axonal regeneration reveals new therapeutic targets to bolster nerve repair.

Relationships among injury, fibrosis, and time in human kidney transplants

BACKGROUND

Kidney transplant biopsies offer an opportunity to understand the pathogenesis of organ fibrosis. We studied the relationships between the time of biopsy after transplant (TxBx), histologic fibrosis, diseases, and transcript expression.

METHODS

Expression microarrays from 681 kidney transplant indication biopsies taken either early (n = 282, <1 year) or late (n = 399, >1 year) after transplant were used to analyze the molecular landscape of fibrosis in relationship to histologic fibrosis and diseases.

RESULTS

Fibrosis was absent at transplantation but was present in some early biopsies by 4 months after transplant, apparently as a self-limited response to donation implantation injury not associated with progression to failure. The molecular phenotype of early biopsies represented the time sequence of the response to wounding: immediate expression of acute kidney injury transcripts, followed by fibrillar collagen transcripts after several weeks, then by the appearance of immunoglobulin and mast cell transcripts after several months as fibrosis appeared. Fibrosis in late biopsies correlated with injury, fibrillar collagen, immunoglobulin, and mast cell transcripts, but these were independent of time. Pathway analysis revealed epithelial response-to-wounding pathways such as Wnt/β-catenin.

CONCLUSION

Fibrosis in late biopsies had different associations because many kidneys had potentially progressive diseases and subsequently failed. Molecular correlations with fibrosis in late biopsies were independent of time, probably because ongoing injury obscured the response-to-wounding time sequence. The results indicate that fibrosis in kidney transplants is driven by nephron injury and that progression to failure reflects continuing injury, not autonomous fibrogenesis.

TRIAL REGISTRATION

INTERCOM study (www.clinicalTrials.gov; NCT01299168).

FUNDING

Canada Foundation for Innovation and Genome Canada.

Association between ErbB3 genetic polymorphisms and coronary artery disease in the Han and Uyghur populations of China

BACKGROUND

ErbB3 is a member of the epidermal growth factor receptor (EGFR/ERBB) family of receptor tyrosine kinases. Recent research has shown that amplification of this gene is related to prostate, bladder and breast cancers, as well as low-density lipoprotein cholesterol (LDL-C) metabolism. LDL-C plays a considerable role in the development of cardiovascular disease. Thus, the present study assessed the association between human ErbB3 gene polymorphisms and coronary artery disease (CAD) in Han and Uygur populationsin China.

METHODS

We performed two independent case-control studies with a Han population (339 CAD patients and 395 control subjects) and a Uygur population (306 CAD patients and 325 control subjects). All of the CAD patients and controls were genotyped for the same three single nucleotide polymorphisms (rs877636, rs705708, and rs10783779) in the ErbB3 gene by real-time PCR.

RESULTS

In the Han population, rs877636 polymorphisms were associated with CAD on the basis of the genotypes, dominant model, additive model, and allele frequency (for genotypes: P = 0.008; for dominant model: P = 0.003; for additive model: P = 0.004; for allele: P = 0.008), and these significant difference was retained (all P < 0.05) after adjusting for the major confounding factors.

CONCLUSION

The CT genotype and C allele of rs877636 in the ErbB3 gene could be a genetic marker of CAD risk for the Han population in China.

Circulating miR-33a and miR-33b are up-regulated in familial hypercholesterolaemia in paediatric age

Circulating miR-33a and miR-33b are up-regulated in familial hypercholesterolaemic children. miR-33a and miR-33b positively correlate with total cholesterol, LDL-cholesterol, LDL-cholesterol/HDL-cholesterol ratio, apolipoprotein B, C-reactive protein and glycaemia. miR-33 could be a novel prognostic marker and therapeutic target for cardiovascular diseases associated with paediatric hypercholesterolaemia.

MicroRNA-27a decreases the level and efficiency of the LDL receptor and contributes to the dysregulation of cholesterol homeostasis

RATIONALE

A strong risk factor for atherosclerosis- the leading cause of heart attacks and strokes- is the elevation of low-density lipoprotein cholesterol (LDL-C) in blood. The LDL receptor (LDLR) is the primary pathway for LDL-C removal from circulation, and their levels are increased by statins -the main treatment for high blood LDL-C. However, statins have low efficiency because they also increase PCSK9 which targets LDLR for degradation. Since microRNAs have recently emerged as key regulators of cholesterol homeostasis, our aim was to identify potential microRNA-based therapeutics to decrease blood LDL-C and prevent atherosclerosis.

METHODS AND RESULTS

We over expressed and knocked down miR-27a in HepG2 cells to assess its effect on the expression of key players in the LDLR pathway using PCR Arrays, Elisas, and Western blots. We found that miR-27a decreases LDLR levels by 40% not only through a direct binding to its 3' untranslated region but also indirectly by inducing a 3-fold increase in PCSK9, which enhances LDLR degradation. Interestingly, miR-27a also directly decreases LRP6 and LDLRAP1, two other key players in the LDLR pathway that are required for efficient endocytosis of the LDLR-LDL-C complex in the liver. The inhibition of miR-27a using lock nucleic acids induced a 70% increase in LDLR levels and, therefore, it would be a more efficient treatment for hypercholesterolemia because of its desirable effects not only on LDLR but also on PCSK9.

CONCLUSION

The results presented here provide evidence supporting the potential of miR-27a as a novel therapeutic target for the prevention of atherosclerosis.

'Micro-managers' of hepatic lipid metabolism and NAFLD

Nonalcoholic fatty liver disease (NAFLD) is tightly associated with insulin resistance, type 2 diabetes, and obesity. As the defining feature of NAFLD, hepatic steatosis develops as a consequence of metabolic dysregulation of de novo lipogenesis, fatty acid uptake, fatty acid oxidation, and triglycerides (TG) export. MicroRNAs (miRNAs), a class of endogenous small noncoding RNAs, play critical roles in various biological processes through regulating gene expression at post-transcriptional level. A growing body of evidence suggests that miRNAs not only maintain hepatic TG homeostasis under physiological condition, but also participate in the pathogenesis of NAFLD. In this review, we focus on the current knowledge of the hepatic miRNAs associated with the development of liver steatosis and the regulatory mechanisms involved, which might be helpful to further understand the nature of NAFLD and provide a sound scientific basis for the drug development.

Long-term supplementation with a low dose of proanthocyanidins normalized liver miR-33a and miR-122 levels in high-fat diet-induced obese rats

Deregulation of miR-33 and miR-122, as major regulators of lipid metabolism in liver, has been related to obesity and metabolic syndrome. Proanthocyanidins repress these microRNAs in healthy animals. Hence, we hypothesized that long-term consumption of dietary proanthocyanidins can normalize the expression of miR-33a and miR-122. Therefore, the objective of this work was to determine whether the long-term consumption of proanthocyanidins could effectively normalize the expression of miR-33a and miR-122 in rats made obese by a high-fat diet and to determine the effective dose. Rats were maintained on the high-fat diet with or without supplementation with a grape seed proanthocyanidin extract at low, medium, or high dose in relation to human consumption. Results show that 3 weeks of supplementation with grape seed proanthocyanidin extract normalized the overexpression of miR-33a and miR-122 in obese rats' liver for all doses studied, with no dose-dependent outcome, and also reduced the levels of plasma and liver lipids in a dose-dependent manner. In conclusion, a low sustained dose of proanthocyanidins, lower than the estimated mean intake for a European population, is enough to normalize miR-33a and miR-122 levels in the livers of obese rats. Therefore, a proanthocyanidin-rich diet during obesity can improve some of the metabolic syndrome symptoms at least at the molecular level.

Lipid abnormalities in alpha/beta2-syntrophin null mice are independent from ABCA1

The syntrophins alpha (SNTA) and beta 2 (SNTB2) are molecular adaptor proteins shown to stabilize ABCA1, an essential regulator of HDL cholesterol. Furthermore, SNTB2 is involved in glucose stimulated insulin release. Hyperglycemia and dyslipidemia are characteristic features of the metabolic syndrome, a serious public health problem with rising prevalence. Therefore, it is important to understand the role of the syntrophins herein. Mice deficient for both syntrophins (SNTA/B2-/-) have normal insulin and glucose tolerance, hepatic ABCA1 protein and cholesterol. When challenged with a HFD, wild type and SNTA/B2-/- mice have similar weight gain, adiposity, serum and liver triglycerides. Hepatic ABCA1, serum insulin and insulin sensitivity are normal while glucose tolerance is impaired. Liver cholesterol is reduced, and expression of SREBP2 and HMG-CoA-R is increased in the knockout mice. Scavenger receptor-BI (SR-BI) protein is strongly diminished in the liver of SNTA/B2-/- mice while SR-BI binding protein NHERF1 is not changed and PDZK1 is even induced. Knock-down of SNTA, SNTB2 or both has no effect on hepatocyte SR-BI and PDZK1 proteins. Further, SR-BI levels are not reduced in brown adipose tissue of SNTA/B2-/- mice excluding that syntrophins directly stabilize SR-BI. SR-BI stability is regulated by MAPK and phosphorylated ERK2 is induced in the liver of the knock-out mice. Blockage of ERK activity upregulates hepatocyte SR-BI showing that increased MAPK activity contributes to low SR-BI. Sphingomyelin which is well described to regulate cholesterol metabolism is reduced in the liver and serum of the knock-out mice while the size of serum lipoproteins is not affected. Current data exclude a major function of these syntrophins in ABCA1 activity and insulin release but suggest a role in regulating glucose uptake, ERK and SR-BI levels, and sphingomyelin metabolism in obesity.

Mechanistic Role of MicroRNAs in Coupling Lipid Metabolism and Atherosclerosis

MicroRNAs (miRNAs, miRs) represent a group of powerful and versatile posttranscriptional regulators of gene expression being involved in the fine control of a plethora of physiological and pathological processes. Besides their well-established crucial roles in the regulation of cell cycle, embryogenesis or tumorigenesis, these tiny molecules have also been shown to participate in the regulation of lipid metabolism. In particular, miRs orchestrate cholesterol and fatty acids synthesis, transport, and degradation and low-density and high-density lipoprotein (LDL and HDL) formation. It is thus not surprising that they have also been reported to affect the development and progression of several lipid metabolism-related disorders including liver steatosis and atherosclerosis. Mounting evidence suggests that miRs might represent important "posttranscriptional hubs" of lipid metabolism, which means that one miR usually targets 3'-untranslated regions of various mRNAs that are involved in different steps of one precise metabolic/signaling pathway, e.g., one miR targets mRNAs of enzymes important for cholesterol synthesis, degradation, and transport. Therefore, changes in the levels of one key miR affect various steps of one pathway, which is thereby promoted or inhibited. This makes miRs potent future diagnostic and even therapeutic tools for personalized medicine. Within this chapter, the most prominent microRNAs involved in lipid metabolism, e.g., miR-27a/b, miR-33/33*, miR-122, miR-144, or miR-223, and their intracellular and extracellular functions will be extensively discussed, in particular focusing on their mechanistic role in the pathophysiology of atherosclerosis. Special emphasis will be given on miR-122, the first microRNA currently in clinical trials for the treatment of hepatitis C and on miR-223, the most abundant miR in lipoprotein particles.