It has been reported that increasingly microRNAs are associated with diseases. However, the patterns among the microRNA-disease associations remain largely unclear. In this study, in order to dissect the patterns of microRNA-disease associations, we performed a comprehensive analysis to the human microRNA-disease association data, which is manually collected from publications. We built a human microRNA associated disease network. Interestingly, microRNAs tend to show similar or different dysfunctional evidences for the similar or different disease clusters, respectively. A negative correlation between the tissue-specificity of a microRNA and the number of diseases it associated was uncovered. Furthermore, we observed an association between microRNA conservation and disease. Finally, we uncovered that microRNAs associated with the same disease tend to emerge as predefined microRNA groups. These findings can not only provide help in understanding the associations between microRNAs and human diseases but also suggest a new way to identify novel disease-associated microRNAs.

Blood lipid levels are heritable, treatable risk factors for cardiovascular disease. We systematically assessed genome-wide coding variation to identify novel lipid genes, fine-map known lipid loci, and evaluate whether low frequency variants with large effect exist. Using an exome array, we genotyped 80,137 coding variants in 5,643 Norwegians. We followed up 18 variants in 4,666 Norwegians to identify 10 loci with coding variants associated with a lipid trait (P < 5×10−8). One coding variant in TM6SF2 (p.Glu167Lys), residing in a GWAS locus for lipid levels, modifies total cholesterol levels and is associated with myocardial infarction. Transient overexpression and knockdown of TM6SF2 in mouse produces alteration in serum lipid profiles consistent with the association observed in humans, identifying TM6SF2 as the functional gene at a large GWAS locus previously known as NCAN/CILP2/PBX4 or 19p13. This study demonstrates that systematic assessment of coding variation can quickly point to a candidate causal gene.

Vascular proliferative disorders, such as atherosclerosis and restenosis, are the most common causes of severe cardiovascular diseases, but a common molecular mechanism remains elusive. Here, we identify and characterize a novel hyperplasia suppressor gene, named HSG (later re-named rat mitofusin-2). HSG expression was markedly reduced in hyper-proliferative vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rat arteries, balloon-injured Wistar Kyoto rat arteries, or ApoE-knockout mouse atherosclerotic arteries. Overexpression of HSG overtly suppressed serum-evoked VSMC proliferation in culture, and blocked balloon injury induced neointimal VSMC proliferation and restenosis in rat carotid arteries. The HSG anti-proliferative effect was mediated by inhibition of ERK/MAPK signalling and subsequent cell-cycle arrest. Deletion of the p21(ras) signature motif, but not the mitochondrial targeting domain, abolished HSG-induced growth arrest, indicating that rHSG-induced anti-proliferation was independent of mitochondrial fusion. Thus, rHSG functions as a cell proliferation suppressor, whereas dysregulation of rHSG results in proliferative disorders.

Abstract-Previous studies have shown that mitofusin 2 (Mfn-2) (or hyperplasia suppressor gene [HSG]) inhibits vascular smooth muscle cell (VSMC) proliferation. Here, we demonstrate that Mfn-2 is a primary determinant of VSMC apoptosis. First, oxidative stress with H 2 O 2 , inhibition of protein kinase C with staurosporine, activation of protein kinase A with forskolin, and serum deprivation concurrently elevate Mfn-2 expression and induce VSMC apoptosis. Second, overexpression of Mfn-2 also triggers apoptosis of VSMCs in culture and in balloon-injured rat carotid arteries, thus contributing to Mfn-2-mediated prevention of neointima formation after angioplasty. Third, Mfn-2 silencing protects VSMCs against H 2 O 2 or Mfn-2 overexpression-induced apoptosis, indicating that upregulation of Mfn-2 is necessary and sufficient for oxidative stress-mediated VSMC apoptosis. The Mfn-2 proapoptotic effect is independent of its role in mitochondrial fusion but mainly mediated by inhibition of Akt signaling and the resultant activation of the mitochondrial apoptotic pathway, as manifested by decreased Akt phosphorylation, increased mitochondrial Bax/Bcl-2 ratio, cytochrome c release, and activation of caspases-9 and caspase-3. Furthermore, Mfn-2-induced apoptosis was blocked by overexpression of an active phosphoinositide 3-kinase mutant or Bcl-xL or inhibition of caspase-9 but not caspases-8. Key Words: PI3K-Akt Ⅲ apoptosis Ⅲ HSG Ⅲ Mfn-2 Ⅲ vascular smooth muscle cells A poptosis is a programmed cell death that is essential for embryonic development and for tissue homeostasis, remodeling, and immune responses. There are 2 major apoptotic signaling cascades: the first is the death receptor (Fas or tumor necrosis factor receptor)-mediated pathway involving activation of caspase-8 and its downstream executioner caspases; the other is the mitochondrial pathway activated by cellular deprivation or stress, and it involves sequentially the release of cytochrome c, the recruitment of apoptotic protease activating factor-1 (Apaf-1), and the activation of caspase-9 and downstream executioner caspases. [1][2][3] Defects (inhibition or exacerbation) of either pathway trigger proliferative or degenerative disorders, including atherosclerosis, restenosis, myocardial infarction, cancers, neurodegenerative diseases, and AIDS. [3][4][5][6][7] Ras, a small GTPase, plays a central role in the regulation of many fundamental biological processes, such as cell proliferation, differentiation, senescence, survival, and growth via activation of a wide array of downstream signaling pathways. Among them, the Ras-Raf-MEK-ERK/ mitogen-activated protein kinase (MAPK) pathway and the Ras-PI3K-Akt (also known as protein kinase [PK]B) pathway are vital for cell proliferation and cell survival. 8 -11 Whereas the Ras-MAPK pathway drives cell cycle progression, 9 the activation of the Ras-PI3K-Akt signaling blocks apoptotic cell death. 11 In particular, Akt-mediated phosphorylation of proapoptotic members of the Bcl-2 family, including Bad and Bax, prevents ...

Aims The artery contains numerous cell types which contribute to multiple vascular diseases. However, the heterogeneity and cellular responses of these vascular cells during abdominal aortic aneurysm (AAA) progression have not been well characterized. Methods and results Single-cell RNA sequencing was performed on the infrarenal abdominal aortas (IAAs) from C57BL/6J mice at Days 7 and 14 post-sham or peri-adventitial elastase-induced AAA. Unbiased clustering analysis of the transcriptional profiles from &gt;4500 aortic cells identified 17 clusters representing nine-cell lineages, encompassing vascular smooth muscle cells (VSMCs), fibroblasts, endothelial cells, immune cells (macrophages, T cells, B cells, and dendritic cells), and two types of rare cells, including neural cells and erythrocyte cells. Seurat clustering analysis identified four smooth muscle cell (SMC) subpopulations and five monocyte/macrophage subpopulations, with distinct transcriptional profiles. During AAA progression, three major SMC subpopulations were proportionally decreased, whereas the small subpopulation was increased, accompanied with down-regulation of SMC contractile markers and up-regulation of pro-inflammatory genes. Another AAA-associated cellular response is immune cell expansion, particularly monocytes/macrophages. Elastase exposure induced significant expansion and activation of aortic resident macrophages, blood-derived monocytes and inflammatory macrophages. We also identified increased blood-derived reparative macrophages expressing anti-inflammatory cytokines suggesting that resolution of inflammation and vascular repair also persist during AAA progression. Conclusion Our data identify AAA disease-relevant transcriptional signatures of vascular cells in the IAA. Furthermore, we characterize the heterogeneity and cellular responses of VSMCs and monocytes/macrophages during AAA progression, which provide insights into their function and the regulation of AAA onset and progression.

Nonalcoholic fatty liver disease (NAFLD) including nonalcoholic steatohepatitis (NASH) has reached epidemic proportions with no pharmacological therapy approved. Lower circulating glycine is consistently reported in patients with NAFLD, but the causes for reduced glycine, its role as a causative factor, and its therapeutic potential remain unclear. We performed transcriptomics in livers from humans and mice with NAFLD and found suppression of glycine biosynthetic genes, primarily alanine-glyoxylate aminotransferase 1 (AGXT1). Genetic (Agxt1−/− mice) and dietary approaches to limit glycine availability resulted in exacerbated diet-induced hyperlipidemia and steatohepatitis, with suppressed mitochondrial/peroxisomal fatty acid β-oxidation (FAO) and enhanced inflammation as the underlying pathways. We explored glycine-based compounds with dual lipid/glucose-lowering properties as potential therapies for NAFLD and identified a tripeptide (Gly-Gly-L-Leu, DT-109) that improved body composition and lowered circulating glucose, lipids, transaminases, proinflammatory cytokines, and steatohepatitis in mice with established NASH induced by a high-fat, cholesterol, and fructose diet. We applied metagenomics, transcriptomics, and metabolomics to explore the underlying mechanisms. The bacterial genus Clostridium sensu stricto was markedly increased in mice with NASH and decreased after DT-109 treatment. DT-109 induced hepatic FAO pathways, lowered lipotoxicity, and stimulated de novo glutathione synthesis. In turn, inflammatory infiltration and hepatic fibrosis were attenuated via suppression of NF-κB target genes and TGFβ/SMAD signaling. Unlike its effects on the gut microbiome, DT-109 stimulated FAO and glutathione synthesis independent of NASH. In conclusion, impaired glycine metabolism may play a causative role in NAFLD. Glycine-based treatment attenuates experimental NAFLD by stimulating hepatic FAO and glutathione synthesis, thus warranting clinical evaluation.

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The role of microRNA-1 (miR-1) has been studied in cardiac and skeletal muscle differentiation. However, it remains unexplored in vascular smooth muscle cells (SMCs) differentiation. The aim of this study was to uncover novel targets of and shed light on the function of miR-1 in the context of embryonic stem cell (ESC) differentiation of SMCs in vitro. miR-1 expression is steadily increased during differentiation of mouse ESC to SMCs. Loss-of-function approaches using miR-1 inhibitors uncovered that miR-1 is required for SMC lineage differentiation in ESC-derived SMC cultures, as evidenced by downregulation of SMC-specific markers and decrease of derived SMC population. In addition, bioinformatics analysis unveiled a miR-1 binding site on the Kruppel-like factor 4 (KLF4) 3' untranslated region (3 0 UTR), in a region that is highly conserved across species. Consistently, miR-1 mimic reduced KLF4 3 0 UTR luciferase activity, which can be rescued by mutating the miR-1 binding site on the KLF4 3 0 UTR in the reporter construct. Additionally, repression of the miR-1 expression by miR-1 inhibitor can reverse KLF4 downregulation during ESC-SMC differentiation, which subsequently inhibits SMC differentiation. We conclude that miR-1 plays a critical role in the determination of SMC fate during retinoid acidinduced ESC=SMC differentiation, which may indicate that miR-1 has a role to promote SMC differentiation.