Long Non-Coding RNA Associated with Cholesterol Homeostasis and Its Involvement in Metabolic Diseases

Plasma Extracellular MicroRNAs Associated With Cardiovascular Disease Risk Factors in Middle-Aged and Older Adults

BACKGROUND

Extracellular microRNAs (miRNAs) are a class of noncoding RNAs that remain stable in the extracellular milieu, where they contribute to various physiological and pathological processes by facilitating intercellular signaling. Previous studies have reported associations between miRNAs and cardiovascular diseases (CVDs); however, the plasma miRNA signatures of CVD and its risk factors have not been fully elucidated at the population level.

METHODS AND RESULTS

Plasma miRNA levels were measured in 4440 FHS (Framingham Heart Study) participants. Linear regression analyses were conducted to test the cross-sectional associations of each miRNA with 8 CVD risk factors. Prospective analyses of the associations of miRNAs with new-onset obesity, hypertension, type 2 diabetes, CVD, and all-cause mortality were conducted using proportional hazards regression. Replication was carried out in 1999 RS (Rotterdam Study) participants. Pathway enrichment analyses were conducted and target genes were predicted for miRNAs associated with ≥5 risk factors in the FHS. In the FHS, 6 miRNAs (miR-193b-3p, miR-122-5p, miR-365a-3p, miR-194-5p, miR-192-5p, and miR-193a-5p) were associated with ≥5 risk factors. This miRNA signature was enriched for pathways associated with CVD and several genes annotated to these pathways were predicted targets of the identified miRNAs. Furthermore, miR-193b-3p, miR-194-5p, and miR-193a-5p were each associated with ≥2 risk factors in the RS. Prospective analysis revealed 8 miRNAs associated with all-cause mortality in the FHS.

CONCLUSIONS

These findings highlight associations between miRNAs and CVD risk factors that may provide valuable insights into the underlying pathogenesis of CVD.

The mechanisms behind the dual role of long non-coding RNA (lncRNA) metastasis suppressor-1 in human tumors: Shedding light on the molecular mechanisms

When the expression levels of metastasis suppressor-1 (MTSS1) were discovered to be downregulated in a metastatic cancer cell line in 2002, it was proposed that MTSS1 functioned as a suppressor of metastasis. The 755 amino acid long protein MTSS1 connects to actin and organizes the cytoskeleton. Its gene is located on human chromosome 8q24. The suppressor of metastasis in metastatic cancer was first found to be MTSS1. Subsequent reports revealed that MTSS1 is linked to the prevention of metastasis in a variety of cancer types, including hematopoietic cancers like diffuse large B cell lymphoma and esophageal, pancreatic, and stomach cancers. Remarkably, conflicting results have also been documented. For instance, it has been reported that MTSS1 expression levels are elevated in a subset of melanomas, hepatocellular carcinoma associated with hepatitis B, head and neck squamous cell carcinoma, and lung squamous cell carcinoma. This article provides an overview of the pathological effects of lncRNA MTSS1 dysregulation in cancer. In order to facilitate the development of MTSS1-based therapeutic targeting, we also shed light on the current understanding of MTS1.

LINC01123 acts as an oncogenic driver in lung adenocarcinoma by regulating the miR-4766-5p/PYCR1 axis

BACKGROUND

Lung adenocarcinoma remains one of the most significant threats to human life as it involves multiple etiologies, including alteration of oncogenes or tumor-inhibitory genes. Long non-coding RNAs (lncRNAs) have been reported to have both cancer promoting and cancer inhibiting effects. In this work, we investigated the function and mechanism of lncRNA LINC01123 in lung adenocarcinoma.

METHODS

The expression of LINC01123, miR-4766-5p, and PYCR1 (pyrroline-5-carboxylate reductase 1) mRNA was analyzed by RT-qPCR. The protein expression levels of PYCR1 and the apoptosis-related proteins (Bax and Bcl-2) were determined by western blotting. Cell proliferation and migration were determined by CCK-8 and wound-healing assays, respectively. Tumor growth in nude mice and Ki67 immunohistochemical staining were used to determine the in vivo role of LINC01123. The putative binding relationships miR-4766-5p has with LINC01123 and PYCR1, which had been identified by analysis of public databases, were validated through RIP and dual-luciferase reporter assays.

RESULTS

LINC01123 and PYCR1 overexpression and miR-4766-5p downregulation were shown to occur in lung adenocarcinoma samples. LINC01123 depletion repressed lung adenocarcinoma cell growth and migration and blocked the development of solid tumors in an animal model. Moreover, LINC01123 bound directly to miR-4766-5p, the downregulation of which attenuated the anticancer effects of LINC01123 depletion in lung adenocarcinoma cells. MiR-4766-5p directly targeted downstream PYCR1 to suppress PYCR1 expression. The repressive effects of PYCR1 knockdown on the migration and proliferation of lung adenocarcinoma cells were also partly abolished by miR-4766-5p downregulation.

CONCLUSION

Downregulation of LINC01123 represses lung adenocarcinoma progression. This suggests that LINC01123 functions as an oncogenic driver in lung adenocarcinoma by controlling the miR-4766-5p/PYCR1 axis.

Long noncoding RNA lincsc5d regulates hepatic cholesterol synthesis by modulating sterol C5 desaturase in large yellow croaker

Although long noncoding RNA (lncRNA) plays a vital role in cholesterol metabolism, very little information is available in fish. Thus, a 10-week feeding experiment was performed to estimate the effects of lncRNA on cholesterol metabolism in large yellow croaker fed with fish oil (FO), soybean oil (SO), olive oil (OO), and palm oil (PO) diets. Results showed that fish fed with OO and PO diets had higher liver total cholesterol (TC) and cholesterol ester (CE) contents compared with fish fed with FO diets. Analysis of the KEGG pathway showed that the steroid biosynthesis pathway was enriched in comparisons FO vs SO, FO vs OO, and FO vs PO. Meanwhile, sterol C5 desaturase (SC5D), a cholesterol synthase, was up-regulated in the steroid biosynthesis pathway. SC5D was widely expressed in all tissues examined, and the highest expression of SC5D was detected in brain. More importantly, a novel lncRNA associated with sc5d gene was identified by RNA sequencing and named as lincsc5d. The tissue distribution of lincsc5d was similar to that of sc5d. A nuclear/cytoplasmic RNA separation assay showed that lincsc5d was a nucleus-enriched lncRNA. qRT-PCR results demonstrated that lincsc5d was markedly up-regulated in the SO, OO, and PO groups. Furthermore, the results of TC content and the lincsc5d and sc5d expression in hepatocytes agreed with in vivo results. In conclusion, this study indicated that vegetable oils, especially OO and PO, increased hepatic cholesterol levels by promoting cholesterol synthesis, and lncRNA lincsc5d and sc5d might be involved in cholesterol synthesis.

Epigenetic regulation and T-cell responses in endometriosis – something other than autoimmunity

Endometriosis is defined as the presence of endometrial-like glands and stroma located outside the uterine cavity. This common, estrogen dependent, inflammatory condition affects up to 15% of reproductive-aged women and is a well-recognized cause of chronic pelvic pain and infertility. Despite the still unknown etiology of endometriosis, much evidence suggests the participation of epigenetic mechanisms in the disease etiopathogenesis. The main rationale is based on the fact that heritable phenotype changes that do not involve alterations in the DNA sequence are common triggers for hormonal, immunological, and inflammatory disorders, which play a key role in the formation of endometriotic foci. Epigenetic mechanisms regulating T-cell responses, including DNA methylation and posttranslational histone modifications, deserve attention because tissue-resident T lymphocytes work in concert with organ structural cells to generate appropriate immune responses and are functionally shaped by organ-specific environmental conditions. Thus, a failure to precisely regulate immune cell transcription may result in compromised immunological integrity of the organ with an increased risk of inflammatory disorders. The coexistence of endometriosis and autoimmunity is a well-known occurrence. Recent research results indicate regulatory T-cell (Treg) alterations in endometriosis, and an increased number of highly active Tregs and macrophages have been found in peritoneal fluid from women with endometriosis. Elimination of the regulatory function of T cells and an imbalance between T helper cells of the Th1 and Th2 types have been reported in the endometria of women with endometriosis-associated infertility. This review aims to present the state of the art in recognition epigenetic reprogramming of T cells as the key factor in the pathophysiology of endometriosis in the context of T-cell-related autoimmunity. The new potential therapeutic approaches based on epigenetic modulation and/or adoptive transfer of T cells will also be outlined.

Genetics and regulation of HDL metabolism

The inverse association between plasma HDL cholesterol (HDL-C) levels and risk for cardiovascular disease (CVD) has been demonstrated by numerous epidemiological studies. However, efforts to reduce CVD risk by pharmaceutically manipulating HDL-C levels failed and refused the HDL hypothesis. HDL-C levels in the general population are highly heterogeneous and are determined by a combination of genetic and environmental factors. Insights into the causes of HDL-C heterogeneity came from the study of monogenic HDL deficiency syndromes but also from genome wide association and Μendelian randomization studies which revealed the contribution of a large number of loci to low or high HDL-C cases in the general or in restricted ethnic populations. Furthermore, HDL-C levels in the plasma are under the control of transcription factor families acting primarily in the liver including members of the hormone nuclear receptors (PPARs, LXRs, HNF-4) and forkhead box proteins (FOXO1-4) and activating transcription factors (ATFs). The effects of certain lipid lowering drugs used today are based on the modulation of the activity of specific members of these transcription factors. During the past decade, the roles of small or long non-coding RNAs acting post-transcriptionally on the expression of HDL genes have emerged and provided novel insights into HDL regulation and new opportunities for therapeutic interventions. In the present review we summarize recent progress made in the genetics and the regulation (transcriptional and post-transcriptional) of HDL metabolism.

Role of Lipid Accumulation and Inflammation in Atherosclerosis: Focus on Molecular and Cellular Mechanisms

Atherosclerosis is a chronic lipid-driven and maladaptive inflammatory disease of arterial intima. It is characterized by the dysfunction of lipid homeostasis and signaling pathways that control the inflammation. This article reviews the role of inflammation and lipid accumulation, especially low-density lipoprotein (LDL), in the pathogenesis of atherosclerosis, with more emphasis on cellular mechanisms. Furthermore, this review will briefly highlight the role of medicinal plants, long non-coding RNA (lncRNA), and microRNAs in the pathophysiology, treatment, and prevention of atherosclerosis. Lipid homeostasis at various levels, including receptor-mediated uptake, synthesis, storage, metabolism, efflux, and its impairments are important for the development of atherosclerosis. The major source of cholesterol and lipid accumulation in the arterial wall is proatherogenic modified low-density lipoprotein (mLDL). Modified lipoproteins, such as oxidized low-density lipoprotein (ox-LDL) and LDL binding with proteoglycans of the extracellular matrix in the intima of blood vessels, cause aggregation of lipoprotein particles, endothelial damage, leukocyte recruitment, foam cell formation, and inflammation. Inflammation is the key contributor to atherosclerosis and participates in all phases of atherosclerosis. Also, several studies have shown that microRNAs and lncRNAs have appeared as key regulators of several physiological and pathophysiological processes in atherosclerosis, including regulation of HDL biogenesis, cholesterol efflux, lipid metabolism, regulating of smooth muscle proliferation, and controlling of inflammation. Thus, both lipid homeostasis and the inflammatory immune response are closely linked, and their cellular and molecular pathways interact with each other.

LncRNAs as Therapeutic Targets and Potential Biomarkers for Lipid-Related Diseases

Lipid metabolism is an essential biological process involved in nutrient adjustment, hormone regulation, and lipid homeostasis. An irregular lifestyle and long-term nutrient overload can cause lipid-related diseases, including atherosclerosis, myocardial infarction (MI), obesity, and fatty liver diseases. Thus, novel tools for efficient diagnosis and treatment of dysfunctional lipid metabolism are urgently required. Furthermore, it is known that lncRNAs based regulation like sponging microRNAs (miRNAs) or serving as a reservoir for microRNAs play an essential role in the progression of lipid-related diseases. Accordingly, a better understanding of the regulatory roles of lncRNAs in lipid-related diseases would provide the basis for identifying potential biomarkers and therapeutic targets for lipid-related diseases. This review highlighted the latest advances on the potential biomarkers of lncRNAs in lipid-related diseases and summarised current knowledge on dysregulated lncRNAs and their potential molecular mechanisms. We have also provided novel insights into the underlying mechanisms of lncRNAs which might serve as potential biomarkers and therapeutic targets for lipid-related diseases. The information presented here may be useful for designing future studies and advancing investigations of lncRNAs as biomarkers for diagnosis, prognosis, and therapy of lipid-related diseases.

Non-Coding RNAs: Novel Players in Insulin Resistance and Related Diseases

The rising prevalence of metabolic diseases related to insulin resistance (IR) have stressed the urgent need of accurate and applicable tools for early diagnosis and treatment. In the last decade, non-coding RNAs (ncRNAs) have gained growing interest because of their potential role in IR modulation. NcRNAs are variable-length transcripts which are not translated into proteins but are involved in gene expression regulation. Thanks to their stability and easy detection in biological fluids, ncRNAs have been investigated as promising diagnostic and therapeutic markers in metabolic diseases, such as type 2 diabetes mellitus (T2D), obesity and non-alcoholic fatty liver disease (NAFLD). Here we review the emerging role of ncRNAs in the development of IR and related diseases such as obesity, T2D and NAFLD, and summarize current evidence concerning their potential clinical application.

Translating genetic association of lipid levels for biological and clinical application

PURPOSE OF REVIEW

This review focuses on the foundational evidence from the last two decades of lipid genetics research and describes the current status of data-driven approaches for transethnic GWAS, fine-mapping, transcriptome informed fine-mapping, and disease prediction.

RECENT FINDINGS

Current lipid genetics research aims to understand the association mechanisms and clinical relevance of lipid loci as well as to capture population specific associations found in global ancestries. Recent genome-wide trans-ethnic association meta-analyses have identified 118 novel lipid loci reaching genome-wide significance. Gene-based burden tests of whole exome sequencing data have identified three genes-PCSK9, LDLR, and APOB-with significant rare variant burden associated with familial dyslipidemia. Transcriptome-wide association studies discovered five previously unreported lipid-associated loci. Additionally, the predictive power of genome-wide genetic risk scores amalgamating the polygenic determinants of lipid levels can potentially be used to increase the accuracy of coronary artery disease prediction.

CONCLUSIONS

Lipids are one of the most successful group of traits in the era of genome-wide genetic discovery for identification of novel loci and plausible drug targets. However, a substantial fraction of lipid trait heritability remains unexplained. Further analysis of diverse ancestries and state of the art methods for association locus refinement could potentially reveal some of this missing heritability and increase the clinical application of the genomic association results.