Epigenetic regulation of methionine adenosyltransferase 1A: a role for MicroRNA-based treatment in liver cancer?

Dietary Supplementation of Methyl Donor l-Methionine Alters Epigenetic Modification in Type 2 Diabetes

SCOPE

The aim of the current study is to evaluate whether l-methionine supplementation (l-Met-S) improves type 2 diabetes-induced alterations in glucose and lipid metabolism by modulating one-carbon metabolism and methylation status.

METHODS AND RESULTS

Diabetes is induced in male Sprague-Dawley rats using high-fat diet and low dose streptozotocin. At the end of study, various biochemical parameters, immunoblotting, qRT-PCR and ChIP-qPCR are performed. The first evidence that l-Met-S activates p-AMPK and SIRT1, very similar to "metformin," is provided. l-Met-S improves the altered key one-carbon metabolites in diabetic rats by modulating methionine adenosyl transferase 1A and cystathione β synthase expression. qRT-PCR shows that l-Met-S alleviates diabetes-induced increase in Forkhead transcription factor 1 expression and thereby regulating genes involved in glucose (G6pc, Pdk4, Pklr) and lipid metabolism (Fasn). Interestingly, l-Met-S inhibits the increased expression of DNMT1 and also prevents methylation of histone H3K36me2 under diabetic condition. ChIP assay shows that persistent increase in abundance of histone H3K36me2 on the promoter region of FOXO1 in diabetic rats and it is recovered by l-Met-S.

CONCLUSION

The first evidence that dietary supplementation of l-Met prevents diabetes-induced epigenetic alterations and regulating methionine levels can be therapeutically exploited for the treatment of metabolic diseases is provided.

A nine-miRNA signature as a potential diagnostic marker for breast carcinoma: An integrated study of 1,110 cases

Growing evidence indicates that microRNAs (miRNAs) play critical roles in the initiation and progression of breast carcinoma (BC) and are promising diagnostic biomarkers. In the present study, we aimed to identify a multi-marker miRNA pool with high diagnostic performance for BC. We collected miRNA expression profiles of BC samples and normal breast tissues from The Cancer Genome Atlas (TCGA) and screened differentially expressed miRNAs by conducting two‑sample t-tests and by calculating log2 fold-change (log2FC) ratios. Statistical significance was established at p<0.001 and |log2FC| >1. Then, we generated receiver operating characteristic (ROC) curves, calculated the area under the curve (AUC) with a 95% confidence interval (95% CI), and calculated the diagnostic sensitivity and specificity using MedCalc software. Additionally, we predicted the targets of candidate miRNAs using 10 online databases: TarBase, miRTarBase, TargetScan, TargetMiner, microRNA.org, RNA22, PicTar-vert, miRDB, PITA and PolymiRTS. Target genes that were predicted by at least four algorithms were chosen, and cooperative targets of multiple miRNAs were further selected for GO and KEGG pathway analyses through the DAVID online tool. Eventually, a total of 66 differentially expressed miRNAs were identified after miRNA expression profiles were analyzed in BC and normal breast samples. Of these, we selected nine dysregulated miRNAs as candidate diagnostic markers: seven upregulated miRNAs (hsa-miR-21, hsa-miR-96, hsa-miR-183, hsa-miR‑182, hsa-miR-141, hsa-miR-200a and hsa-miR-429) and two downregulated miRNAs (hsa-miR-139 and hsa-miR‑145). The ROC curve for the combination of these nine differently expressed miRNAs showed extremely high diagnostic accuracy, with an AUC of 0.995 (95% CI, 0.988‑0.999) and diagnostic sensitivity and specificity of 98.7 and 98.9%, respectively. In conclusion, the combination of these nine miRNAs significantly improved the accuracy of breast cancer diagnosis.

Novel immunoassays to detect methionine adenosyltransferase activity and quantify S-adenosylmethionine

We present a novel real-time immunoassay to measure methionine adenosyltransferase (MAT) activity that integrates the MAT-catalyzed reaction of Met and adenosine triphosphate to produce S-adenosylmethionine (SAM) and a highly sensitive immunoassay to specifically quantify SAM simultaneously. The cellular localization of SAM and S-adenosylhomocysteine varies with cell proliferation status: in normal cells, they are found mostly in the cytoplasm, but localize to the nucleus in proliferating cells. MAT-I/III activity is stimulated by Met, but inhibited by S-nitrosoglutathione, and the methylation index (MI) increases after Met stimulation of L02 cells. Met and S-nitrosoglutathione inhibit MAT-II activity, and the MI decreases after Met stimulation of HepG2 cells. The method described provides a significant advancement in the field for the measurement of MAT activity under various conditions.

microRNA-495 inhibits chondrogenic differentiation in human mesenchymal stem cells by targeting Sox9

The chondrogenic differentiation process of human mesenchymal stem cells (hMSCs) passes through multiple stages, which are carried out by various factors and their interactions. Recently, microRNAs that regulate chondrogenic differentiation have been reported. However, microRNA that regulates SRY-related high mobility group-box gene 9 (Sox9), a chondrogenic key factor, has not been identified in hMSC. In this study, we identified that microRNA-495 (miR-495) is an important regulator of hMSC chondrogenic differentiation. In our microarray, miR-495 was downregulated during transforming growth factor (TGF)-β3-induced chondrogenic differentiation of hMSCs in vitro. We found that there is an miR-495 binding site in the 3' untranslated region (3'UTR) of Sox9. We confirmed opposite expression between miR-495 and Sox9 by using real-time polymerase chain reaction. Further, overexpression of miR-495 inhibited Sox9 expression, and repression of miR-495 increased expression of Sox9 in SW1353 cells and hMSCs. Additionally, luciferase analysis revealed that miR-495 directly binds to the Sox9 3'UTR, and we confirmed a seed sequence of miR-495 on the Sox9 3'UTR. Subsequently, overexpression of miR-495 repressed the expression of the extracellular matrix (ECM) protein, such as type II collagen (Col2A1), aggrecan, and proteoglycan products, whereas inhibition of miR-495 increased their expression. Collectively, this study indicates that miR-495 directly targets Sox9, ultimately leading to the regulation of chondrogenic differentiation in hMSCs.