MicroRNA 27a Is a Key Modulator of Cholesterol Biosynthesis

Specific circulating miRNAs are associated with plasma lipids in a healthy American cohort

Low-density lipoprotein cholesterol (LDL-c) is both a therapeutic target and a risk factor for cardiovascular disease (CVD). MicroRNA (miRNA) has been shown to regulate cholesterol homeostasis, and miRNA in blood circulation has been linked to hypercholesterolemia. However, few studies to date have associated miRNA with phenotypes like LDL-c in a healthy population. To this end, we analyzed circulating miRNA in relation to LDL-c in a healthy cohort of 353 participants using two separate bioinformatic approaches. The first approach found that miR-15b-5p and miR-16-5p were upregulated in individuals with at-risk levels of LDL-c. The second approach identified two miRNA clusters, one that positively and a second that negatively correlated with LDL-c. Included in the cluster that positively correlated with LDL-c were miR-15b-5p and miR-16-5p, as well as other miRNA from the miR-15/107, miR-30, and let-7 families. Cross-species analyses suggested that several miRNAs that associated with LDL-c are conserved between mice and humans. Finally, we examined the influence of diet on circulating miRNA. Our results robustly linked circulating miRNA with LDL-c, suggesting that miRNA could be used as biomarkers for hypercholesterolemia or targets for developing cholesterol-lowering drugs.NEW & NOTEWORTHY This study explored the association between circulating microRNA (miRNA) and low-density lipoprotein cholesterol (LDL-c) in a healthy population of 353 participants. Two miRNAs, miR-15b-5p and miR-16-5p, were upregulated in individuals with at-risk LDL-c levels. Several miRNA clusters were positively and negatively correlated with LDL-c and are known to target mRNA involved in lipid metabolism. The study also investigated the influence of diet on circulating miRNA, suggesting potential biomarkers for hypercholesterolemia.

Cellular uptake and trafficking of peptide-based drug delivery systems for miRNA

Today, macromolecular compounds such as microRNAs (miRNAs) are becoming more and more widespread as leading therapeutics. However, their application is limited mostly due to their poor stability, limited cellular uptake, and poor target specificity. Cell-penetrating peptides (CPPs), a group of positively charged peptides, represent a breakthrough as delivery systems for macromolecules. In the present study, we used two types of nanoparticles which differ in the type of CPP used for their manufacturing. The first type is composed of protamine, an arginine rich CPP, which is highly positively charged. The arginine residues are able to form electrostatic interactions with miRNAs, stabilize them, and deliver them to cells. The second type is composed of the N-Ter peptide (also known as MPG), an amphipathic peptide rich in lysine. The positively charged parts of the N-Ter peptide electrostatically stabilize miRNAs, whereas its amphipathic character allows it to successfully traverse cell membranes. We used miRNA-27a, a negative regulator of adipogenesis, to form nanoparticles with the peptides and traced their uptake in 3T3-L1 preadipocytes. Motivated by the lengthy discourse regarding the uptake mechanism of CPPs, the focus of our study was to analyse and understand the internalization of proticles (protamine nanoparticles) and N-Ter complexes. The nanoparticles were characterized regarding size, size distribution, and zeta potential, and their cytotoxicity was tested in 3T3-L1 cells. The uptake studies were performed by varying the experimental conditions such as time, concentration, and temperature, as well as by applying different inhibitors of endocytosis. Furthermore, we assessed the biological effect of miRNA-27a on the pro-adipogenic machinery. The obtained data have shown that protamine and the N-Ter peptide form positively charged nanoparticles through non-covalent complexation. The uptake of proticles and N-Ter complexes was found to be dependent on time, concentration, and temperature, and different uptake pathways were discovered to be involved in the internalization of the different nanoparticles. Furthermore, both types of nanoparticles induced the anti-adipogenic effect of miRNA-27a, demonstrating that this approach can be used as a novel miRNA replacement therapy in the treatment of obesity and obesity-related disorders.

Comprehensive Molecular Evaluation of HNF-1 Alpha, miR-27a, and miR-146 Gene Variants and Their Link with Predisposition and Progression in Type 2 Diabetes Patients

BACKGROUND

Type 2 diabetes (T2D) is a metabolic condition induced by insulin resistance and pancreatic beta cell dysfunction. MicroRNAs (miRNAs) have biological significance because they regulate processes such as the molecular signaling pathways involved in the pathophysiology of diabetes mellitus. The hepatocyte nuclear factor-1 alpha (HNF-1 alpha) is a transcription factor found in hepatocytes and the pancreas. Mutations in the HNF-1 alpha gene were reportedly associated with maturity-onset diabetes of the young (MODY). The objective of the present study was to examine the associations between MiR-27a, MiR-146, and HNF-1 alpha single-nucleotide variations (SNVs) with T2D risk in the Saudi population.

METHODOLOGY

We evaluated the association of SNVs of miR-27a rs895819 A>G, 146a-rs2910164 C>G, and HNF-1 alpha rs1169288 G>T (I27L) with the risk of T2D in Saudi patients with the Amplification Refractory Mutation System PCR (ARMS-PCR). For the miR-27a SNVs, we used 115 cases (82 males, 33 females) and 117 matched healthy controls (HCs); for the Mir-146 SNVs, we used 103 cases (70 males, 33 females) and 108 matched HCs; and for the HNF-1 alpha, we employed 110 patients (80 males, 30 females) and 110 HCs. The blood biochemistry of the participants was essayed using commercial kits, and the methods of statistical analysis used were the Chi-square test, the Fisher exact test, and a multivariate analysis based on logistic regression, like the odds ratio (OD) and risk ratio (RR), with 95% confidence intervals (CIs).

RESULTS

The MiR-27a rs895819 AG genotype was linked to increased T2D susceptibility, with OR = 2.01 and p-value = 0.011, and the miR-146 rs2910164 CG genotype and C allele were linked to an elevated risk of T2D, with OR = 2.75, p-value < 0.0016, OR = 1.77, and p-value = 0.004. The results also showed that the GT genotype and T allele of the HNF-1 alpha (rs1169288) G>T is linked to T2D, with OR = 2.18, p-value = 0.0061, and 1.77, p-value = 0.0059.

CONCLUSIONS

The SNVs in miR-27a, miR-146, and HNF-1 alpha can be potential loci for T2D risk. The limitations of this study include the relatively small sample size and the fact that it was a cross-sectional study. To our knowledge, this is the first study to highlight the association between miR-27a, miR-146, and HNF-1 alpha SNVs and the risk of T2D in the Saudi population. Future large-scale case-control studies, as well as studies on the functions of the proteins and protein interaction studies for HNF-1 alpha, are required to verify our findings. Furthermore, these findings can be used for the identification and stratification of at-risk populations via genetic testing for T2D-prevention strategies.

Early growth response-1: Key mediators of cell death and novel targets for cardiovascular disease therapy

Significance

Cardiovascular diseases are seen to be a primary cause of death, and their prevalence has significantly increased across the globe in the past few years. Several studies have shown that cell death is closely linked to the pathogenesis of cardiovascular diseases. Furthermore, many molecular and cellular mechanisms are involved in the pathogenesis of the cardiac cell death mechanism. One of the factors that played a vital role in the pathogenesis of cardiac cell death mechanisms included the early growth response-1 (Egr-1) factor.

Recent Advances

Studies have shown that abnormal Egr-1 expression is linked to different animal and human disorders like heart failure and myocardial infarction. The biosynthesis of Egr-1 regulates its activity. Egr-1 can be triggered by many factors such as serum, cytokines, hormones, growth factors, endotoxins, mechanical injury, hypoxia, and shear stress. It also displays a pro-apoptotic effect on cardiac cells, under varying stress conditions. EGR1 mediates a broad range of biological responses to oxidative stress and cell death by combining the acute changes occurring in the cellular environment with sustained changes in gene expression.

Future Directions

The primary regulatory role played by the Egr-1-targeting DNAzymes, microRNAs, and oligonucleotide decoy strategies in cardiovascular diseases were identified to provide a reference to identify novel therapeutic targets for cardiovascular diseases.

The role of miRNAs in the diagnosis of stable atherosclerosis of different arterial territories: A critical review

Atherosclerotic disease is a major cause of morbidity and mortality worldwide. Atherosclerosis may be present in different arterial territories and as a single- or multi-territorial disease. The different phenotypes of atherosclerosis are attributable only in part to acquired cardiovascular risk factors and genetic Mendelian inheritance. miRNAs, which regulate the gene expression at the post-transcriptional level, may also contribute to such heterogeneity. Numerous miRNAs participate in the pathophysiology of atherosclerosis by modulating endothelial function, smooth vascular cell function, vascular inflammation, and cholesterol homeostasis in the vessel, among other biological processes. Moreover, miRNAs are present in peripheral blood with high stability and have the potential to be used as non-invasive biomarkers for the diagnosis of atherosclerosis. However, the circulating miRNA profile may vary according to the involved arterial territory, considering that atherosclerosis expression, including the associated molecular phenotype, varies according to the affected arterial territory. In this review, we discuss the specific circulating miRNA profiles associated with atherosclerosis of different arterial territories, the common circulating miRNA profile of stable atherosclerosis irrespective of the involved arterial territory, and the circulating miRNA signature of multi-territorial atherosclerosis. miRNAs may consist of a simple non-invasive method for discriminating atherosclerosis of different arterial sites. The limitations of miRNA profiling for such clinical application are also discussed.

Key regulatory miRNAs in lipid homeostasis: implications for cardiometabolic diseases and development of novel therapeutics

Dysregulation of lipid metabolism is associated with cardiovascular/metabolic diseases, including atherosclerosis, liver diseases and type 2 diabetes mellitus (T2DM). Several miRNAs have been reported as regulators of different stages of lipid homeostasis, including cholesterol/fatty acid biosynthesis, degradation, transport, storage, and low-density (LDL) and high-density lipoprotein (HDL) formation. Indeed, various miRNAs are emerging as attractive therapeutic candidates for metabolic/cardiovascular disease (CVD). Here, we summarize the roles of miR-19b, miR-20a, miR-21, miR-27, miR-29, miR-34a, miR-144, miR-148a, and miR-199a in post-transcriptional regulation of genes involved in lipid metabolism and their therapeutic potential. We also discuss experimental strategies for further development of these miRNAs as novel cardiometabolic therapeutics. Teaser: miRNAs have emerged as crucial regulators of lipid homeostasis. Here, we highlight key miRNAs that regulate lipid metabolism and their therapeutic potential in cardiometabolic disease states.

The miR-23-27-24 cluster: an emerging target in NAFLD pathogenesis

The incidence of non-alcoholic fatty liver disease (NAFLD) is increasing globally, being the most widespread form of chronic liver disease in the west. NAFLD includes a variety of disease states, the mildest being non-alcoholic fatty liver that gradually progresses to non-alcoholic steatohepatitis, fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Small non-coding single-stranded microRNAs (miRNAs) regulate gene expression at the miRNA or translational level. Numerous miRNAs have been shown to promote NAFLD pathogenesis and progression through increasing lipid accumulation, oxidative stress, mitochondrial damage, and inflammation. The miR-23-27-24 clusters, composed of miR-23a-27a-24-2 and miR-23b-27b-24-1, have been implicated in various biological processes as well as many diseases. Herein, we review the current knowledge on miR-27, miR-24, and miR-23 in NAFLD pathogenesis and discuss their potential significance in NAFLD diagnosis and therapy.

MicroRNA hsa-miR-657 promotes retinoblastoma malignancy by inhibiting peroxisome proliferator-activated receptor alpha expression

Retinoblastoma is a familial inherited embryonic neuroretinal malignancy with a low survival rate and poor prognosis. Our study aimed to evaluate the potential interaction between microRNA miR-657 and the peroxisome proliferator-activated receptor alpha (PPARA) in retinoblastoma. Expression of miR-657 and PPARA was analyzed in retinoblastoma tissues and cells using RT-qPCR. Cell proliferation, apoptosis, and migration were measured in retinoblastoma cell lines, and xenografting experiments were performed using nude mice. Our study showed that miR-657 expression was markedly increased, whereas that of PPARA was markedly decreased in retinoblastoma. Additionally, PPARA knockdown enhanced the development of retinoblastoma. miR-657 enhanced the retinoblastoma tumorigenesis by directly inhibiting PPARA expression, suggesting that PPARA targeting by miR-657 facilitates retinoblastoma development by enhancing cell growth. This study provides novel insights into the miR-657- and PPARA-mediated mechanisms underlying retinoblastoma progression and suggests that the interaction between miR-657 and PPARA may serve as an effective target for therapeutic intervention.

Sporadic Alzheimer's Disease- and Neurotoxicity-Related microRNAs Affecting Key Events of Tau-Driven Adverse Outcome Pathway Toward Memory Loss

BACKGROUND

A complex network of aging-related homeostatic pathways that are sensitive to further deterioration in the presence of genetic, systemic, and environmental risk factors, and lifestyle, is implicated in the pathogenesis of progressive neurodegenerative diseases, such as sporadic (late-onset) Alzheimer's disease (sAD).

OBJECTIVE

Since sAD pathology and neurotoxicity share microRNAs (miRs) regulating common as well as overlapping pathological processes, environmental neurotoxic compounds are hypothesized to exert a risk for sAD initiation and progression.

METHODS

Literature search for miRs associated with human sAD and environmental neurotoxic compounds was conducted. Functional miR analysis using PathDip was performed to create miR-target interaction networks.

RESULTS

The identified miRs were successfully linked to the hypothetical starting point and key events of the earlier proposed tau-driven adverse outcome pathway toward memory loss. Functional miR analysis confirmed most of the findings retrieved from literature and revealed some interesting findings. The analysis identified 40 miRs involved in both sAD and neurotoxicity that dysregulated processes governing the plausible adverse outcome pathway for memory loss.

CONCLUSION

Creating miR-target interaction networks related to pathological processes involved in sAD initiation and progression, and environmental chemical-induced neurotoxicity, respectively, provided overlapping miR-target interaction networks. This overlap offered an opportunity to create an alternative picture of the mechanisms underlying sAD initiation and early progression. Looking at initiation and progression of sAD from this new angle may open for new biomarkers and novel drug targets for sAD before the appearance of the first clinical symptoms.

Regulation of microRNA miR-197-3p/CDC28 protein kinase regulatory subunit 1B (CKS1B) axis by Circular RNA hsa_circ_0000285 promotes glioma progression

Circular RNA circ_0000285 is differentially expressed in several malignancies; however, its role in gliomas is under investigation. Reverse transcription quantitative polymerase chain reaction was conducted to evaluate the expression of circ_0000285, miR-197-3p, and CDC28 protein kinase regulatory subunit 1B (CKS1B) in glioma tissues and cells. Cell Counting Kit-8 and Transwell invasion assays coupled with Western blotting analysis using anti-Bax and anti-Bcl-2 antibodies were performed to evaluate cell proliferation, invasion, and apoptosis. Luciferase reporter and AGO2 RNA immunoprecipitation assays were conducted to verify the interaction between miR-197-3p and circ_0000285 or CKS1B. Xenograft tumor growth was evaluated in mice. We noted that circ_0000285 was highly expressed in glioma tissues and cells and that circ_0000285-silencing retarded tumor growth both in vitro and in vivo. This effect was mediated by the binding of circ_0000285 to miR-197-3p, which silenced CKS1B, an essential driver of glioma cell proliferation and invasion. Thus, circ_0000285 boosted glioma progression by regulating the miR-197-3p/CKS1B axis, highlighting a novel competing endogenous RNA circuit of glioma progression.

Bilirubin ameliorates murine atherosclerosis through inhibiting cholesterol synthesis and reshaping the immune system

Atherosclerosis is a chronic inflammatory disease caused mainly by lipid accumulation and excessive inflammatory immune response. Although the lipid-lowering and cardioprotective properties of bilirubin, as well as the negative relationship between bilirubin and atherosclerosis, were well documented, it is not yet clear whether bilirubin can attenuate atherosclerosis in vivo. In this study, we investigated the role of bilirubin in improving atherosclerosis. We found that mildly elevated bilirubin significantly reduced the risk factors of atherosclerosis, such as plasma glucose, total cholesterol, and low-density lipoprotein cholesterol, and the formation of atherosclerotic plaques, liver total cholesterol, and cholesterol ester concentration in apolipoprotein E-deficient (ApoE^-/-) mice fed a western-type (high fat) diet. It was further found that bilirubin could promote the degradation of 3-Hydroxy-3-Methylglutaryl-CoA Reductase (HMGCR), a rate-limiting enzyme for endogenous cholesterol synthesis. Using mass cytometry-based high dimensional single cell analysis, we observed a decrease of natural killer cells and an increase of dendritic cells and myeloid-derived suppressor cells, which all are closely associated with atherosclerosis risk factors and contribute to the improvement of atherosclerosis, in ApoE^-/- mice treated with bilirubin. By in-depth analysis, modulation of multiple spleen or peripheral blood T cell clusters exhibiting either positive or negative correlations with total cholesterol or low-density lipoprotein cholesterol was detected after bilirubin treatment. In this study, we demonstrate that bilirubin serves as a negative regulator of atherosclerosis and reduces atherosclerosis by inhibiting cholesterol synthesis and modulating the immune system.

Circulating MicroRNAs as a New Class of Biomarkers of Physiological Reactions of the Organism to the Intake of Dietary Supplements and Drugs

BACKGROUND

The analysis of individual microRNAs (miRNAs) as a diagnostic and prognostic tool for the effective treatment of various diseases has aroused particular interest in the scientific community. The determination of circulating miRNAs makes it possible to assess biological changes associated with nutritional processes, the intake of dietary supplements and drugs, etc. The profile of circulating miRNAs reflects the individual adaptation of the organism to the effect of specific environmental conditions.

OBJECTIVE

The objective of this study is to systematize the data and show the importance of circulating miRNAs as new potential biomarkers of the organism's response to the intake of various dietary supplements, drugs, and consider the possibility of their use in doping control.

METHODS

A systematic analysis of scientific publications (ncbi.nlm.nih.gov) on the miRNA expression profile in response to the intake of dietary supplements and drugs most often used by athletes, and supposed their role as potential markers in modern doping control was carried out.

RESULTS

The profile of circulating miRNAs is highly dependent on the intake of a particular drug, and, therefore, may be used as a marker of the effects of biologically active supplements and drugs including the substances from the Prohibited List of the World Anti-Doping Agency (WADA).

CONCLUSION

Monitoring of circulating miRNAs can serve as a high-precision marker for detecting doping abuse in elite sports. However, it is necessary to conduct additional studies on the effect of complex drugs on the profile of circulating miRNAs and individual circulating miRNAs on a particular biological process.

Circulating microRNAs from the mouse tibia fracture model reflect the signature from patients with complex regional pain syndrome

INTRODUCTION

Complex regional pain syndrome (CRPS) often results from an initial trauma that later produces a disproportionate amount of pain. The mechanisms underlying CRPS have been studied using a tibia fracture model (TFM) in rodents because this model closely mimics symptoms and has several molecular correlates observed in patients with CRPS.

OBJECTIVE

Here, we determined whether the TFM has alterations in circulating microRNAs (miRNAs) and cytokines transported by small extracellular vesicles (sEVs) that faithfully model previously reported miRNA alterations from patients with CRPS.

METHODS

We isolated and characterized serum-derived sEVs from mice 3 weeks after fracture when symptoms such as pain hypersensitivity develop. Whole-transcriptome profiling was used to determine sEV miRNAs, and Bio-Plex Pro Mouse Cytokine 23-plex assay was used to measure cytokines. Differentially expressed miRNAs from TFM were compared with previously reported circulating miRNA alterations from patients with CRPS.

RESULTS

Although sEV cytokine levels were unchanged, there were significant changes in sEV miRNA profiles. Differentially expressed miRNAs from TFM sEVs significantly overlapped with those previously reported in patients with CRPS. Of the 57 sEV miRNAs dysregulated in the TFM, 30 were previously reported in patients with CRPS compared with healthy control donors both in sEVs and 23 in whole blood.

CONCLUSIONS

These findings enhance the validity of TFM as a model for CRPS and suggest that specific miRNA dysregulation may be a shared feature of CRPS and the TFM. These dysregulated miRNAs could help identify mechanistic targets or serve as biomarker candidates for both diagnosis and treatment responses in clinical trials.

Identification of miR-17, miR-21, miR-27a, miR-106b and miR-222 as endoplasmic reticulum stress-related potential biomarkers in circulation of patients with atherosclerosis

Atherosclerosis and related cardiovascular diseases are among the most common causes of death worldwide. Unfolded protein response, also known as Endoplasmic reticulum stress, has a critical role in many diseases including atherosclerosis. Small non-coding microRNAs (miRNA), which generally suppress gene expression, regulate UPR signalling and they may also be involved in the progression of atherosclerosis. We aim to investigate the expression levels of miR-17, miR-21, miR-27a, miR-106b, miR-222 and CHOP gene in circulation of atherosclerosis patients compared to healthy controls to establish a link between ER stress and atherosclerosis. miRNA containing whole RNA was isolated from blood samples of 25 patients with atherosclerosis and 26 healthy controls. Expression levels of miRNAs and CHOP were measured via Real Time PCR method. miR-17 and miR-106b were significantly increased while miR-21, miR-27a, and miR-222 were significantly decreased in patients compared to controls. CHOP gene was also dramatically and significantly induced in patient samples. miR-17, miR-21, miR-27a, miR-106b, miR-222 and CHOP were significantly differentially expressed in patients with atherosclerosis. Each miRNA and CHOP might regulate atherosclerotic plaque progression and they can be used as a biomarker in the diagnosis and follow-up of atherosclerosis-related cardiovascular diseases.

Role of Cholesterol and Lipid Rafts in Cancer Signaling: A Promising Therapeutic Opportunity?

Cholesterol is a lipid molecule that plays an essential role in a number of biological processes, both physiological and pathological. It is an essential structural constituent of cell membranes, and it is fundamental for biosynthesis, integrity, and functions of biological membranes, including membrane trafficking and signaling. Moreover, cholesterol is the major lipid component of lipid rafts, a sort of lipid-based structures that regulate the assembly and functioning of numerous cell signaling pathways, including those related to cancer, such as tumor cell growth, adhesion, migration, invasion, and apoptosis. Considering the importance of cholesterol metabolism, its homeostasis is strictly regulated at every stage: import, synthesis, export, metabolism, and storage. The alterations of this homeostatic balance are known to be associated with cardiovascular diseases and atherosclerosis, but mounting evidence also connects these behaviors to increased cancer risks. Although there is conflicting evidence on the role of cholesterol in cancer development, most of the studies consistently suggest that a dysregulation of cholesterol homeostasis could lead to cancer development. This review aims to discuss the current understanding of cholesterol homeostasis in normal and cancerous cells, summarizing key findings from recent preclinical and clinical studies that have investigated the role of major players in cholesterol regulation and the organization of lipid rafts, which could represent promising therapeutic targets.

GPR52 accelerates fatty acid biosynthesis in a ligand-dependent manner in hepatocytes and in response to excessive fat intake in mice

Gpr52 is an orphan G-protein-coupled receptor of unknown physiological function. We found that Gpr52-deficient (Gpr52^−/−) mice exhibit leanness associated with reduced liver weight, decreased hepatic de novo lipogenesis, and enhanced insulin sensitivity. Treatment of the hepatoma cell line HepG2 cells with c11, the synthetic GPR52 agonist, increased fatty acid biosynthesis, and GPR52 knockdown (KD) abolished the lipogenic action of c11. In addition, c11 induced the expressions of lipogenic enzymes (SCD1 and ELOVL6), whereas these inductions were attenuated by GPR52-KD. In contrast, cholesterol biosynthesis was not increased by c11, but its basal level was significantly suppressed by GPR52-KD. High-fat diet (HFD)-induced increase in hepatic expression of Pparg2 and its targets (Scd1 and Elovl6) was absent in Gpr52^−/− mice with alleviated hepatosteatosis. Our present study showed that hepatic GPR52 promotes the biosynthesis of fatty acid and cholesterol in a ligand-dependent and a constitutive manner, respectively, and Gpr52 participates in HFD-induced fatty acid synthesis in liver.

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Hepatosteatosis is inherently an adaptive response to overnutrition to store energy

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On the other hand, it can be a pathological condition causing insulin resistance

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High-fat diet increases PPARγ2 expression and lipogenesis in liver via GPR52

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Gpr52 ablation protects mice from developing hepatosteatosis and insulin resistance

MicroRNA regulation of cholesterol metabolism

MicroRNAs are small noncoding RNAs that regulate gene expression at the posttranscriptional level. Since many microRNAs have multiple mRNA targets, they are uniquely positioned to regulate the expression of several molecules and pathways simultaneously. For example, the multiple stages of cholesterol metabolism are heavily influenced by microRNA activity. Understanding the scope of microRNAs that control this pathway is highly relevant to diseases of perturbed cholesterol metabolism, most notably cardiovascular disease (CVD). Atherosclerosis is a common cause of CVD that involves inflammation and the accumulation of cholesterol-laden cells in the arterial wall. However, several different cell types participate in atherosclerosis, and perturbations in cholesterol homeostasis may have unique effects on the specialized functions of these various cell types. Therefore, our review discusses the current knowledge of microRNA-mediated control of cholesterol homeostasis, followed by speculation as to how these microRNA-mRNA target interactions might have distinctive effects on different cell types that participate in atherosclerosis.

Inhibition of microRNA-128-3p attenuates hypercholesterolemia in mouse model

AIMS

Hypercholesterolemia remains a critical risk factor for cardiovascular diseases and there is an urgent need to develop effective alternative therapeutics. Herein, we investigated the effects of miR-128-3p inhibition on serum cholesterol levels using a hypercholesterolemic mouse model.

MATERIALS AND METHODS

Five injections of anti-miR-128-3p (AM-128) treatment were given, and the cholesterol profile in serum and liver was quantified. We validated the underlying gene network using qRT-PCR, western blotting, ELISA, and dual luciferase assays.

KEY FINDINGS

AM-128 treatment inhibits cholesterol biosynthesis by upregulating INSIG1 and downregulating HMGCR (3-hydroxy-3-methylglutaryl-CoA reductase) expression. The serum cholesterol clearance by SR-B1 (scavenger receptor class B member 1) and LDLR (low density lipoprotein receptors) was also increased. Furthermore, the catabolism of cholesterol by CYP7A1 (cytochrome P450 family 7 subfamily A member 1) was increased.

SIGNIFICANCE

Our results confirmed a critical role of miR-128-3p inhibition in lowering serum cholesterol and suggest its potential therapeutic implications in reversing hypercholesterolemia.

The Role of microRNAs in Metabolic Syndrome-Related Oxidative Stress

Oxidative stress (OxS) is the cause and the consequence of metabolic syndrome (MetS), the incidence and economic burden of which is increasing each year. OxS triggers the dysregulation of signaling pathways associated with metabolism and epigenetics, including microRNAs, which are biomarkers of metabolic disorders. In this review, we aimed to summarize the current knowledge regarding the interplay between microRNAs and OxS in MetS and its components. We searched PubMed and Google Scholar to summarize the most relevant studies. Collected data suggested that different sources of OxS (e.g., hyperglycemia, insulin resistance (IR), hyperlipidemia, obesity, proinflammatory cytokines) change the expression of numerous microRNAs in organs involved in the regulation of glucose and lipid metabolism and endothelium. Dysregulated microRNAs either directly or indirectly affect the expression and/or activity of molecules of antioxidative signaling pathways (SIRT1, FOXOs, Keap1/Nrf2) along with effector enzymes (e.g., GPx-1, SOD1/2, HO-1), ROS producers (e.g., NOX4/5), as well as genes of numerous signaling pathways connected with inflammation, insulin sensitivity, and lipid metabolism, thus promoting the progression of metabolic imbalance. MicroRNAs appear to be important epigenetic modifiers in managing the delicate redox balance, mediating either pro- or antioxidant biological impacts. Summarizing, microRNAs may be promising therapeutic targets in ameliorating the repercussions of OxS in MetS.

Bone marrow deficiency of mRNA decaying protein Tristetraprolin increases inflammation and mitochondrial ROS but reduces hepatic lipoprotein production in LDLR knockout mice

Tristetraprolin (TTP), an mRNA binding and decaying protein, plays a significant role in controlling inflammation by decaying mRNAs encoding inflammatory cytokines such as TNFalpha. We aimed to test a hypothesis that TTP in bone marrow (BM) cells regulates atherogenesis by modulating inflammation and lipid metabolism through the modulation of oxidative stress pathways by TTP target genes. In a BM transplantation study, lethally irradiated atherogenic LDLR^-/- mice were reconstituted with BM cells from either wild type (TTP^+/+) or TTP knockout (TTP^-/-) mice, and fed a Western diet for 12 weeks. We made the following observations: (1) TTP^-/- BM recipients display a significantly higher systemic and multi-organ inflammation than TTP^+/+ BM recipients; (2) BM TTP deficiency modulates hepatic expression of genes, detected by microarray, involved in lipid metabolism, inflammatory responses, and oxidative stress; (3) TTP^-/- BM derived macrophages increase production of mitochondrial reactive oxygen species (mtROS); (4) BM-TTP^-/- mice display a significant reduction in serum VLDL/LDL levels, and attenuated hepatic steatosis compared to controls; and (5) Reduction of serum VLDL/LDL levels offsets the increased inflammation, resulting in no changes in atherosclerosis. These findings provide a novel mechanistic insight into the roles of TTP-mediated mRNA decay in bone marrow-derived cells in regulating systemic inflammation, oxidative stress, and liver VLDL/LDL biogenesis.

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.

Circulating miR-27a-3p as a candidate for a biomarker of whole grain diets for lipid metabolism

Circulating miR-27a-3p was involved in the process of lipid synthesis under the dietary patterns of whole grain diets, and the expression of miR-27a-3p was decreased in serum, while it was elevated both in liver and ileum.