| Objective:The incidence of obesity is increasing dramatically, which imposes a heavy burden on the whole society. MicroRNA (miRNA) is a group of highly conserved, non-coding small RNA, functioning as negative gene regulators at post-transcriptional level. Our study was aimed to determine differentially expressed miRNAs of subcutaneous adipose tissue between obese and normal weight women, and to explore possible mechanism of miRNA and their roles in obesity.Methods:3 obese and 5 normal-weight women were enrolled after completing physical examination and blood biochemical tests. Their median age were respectively 40 (30-56) and 49 (37-51) years old. Abdominal subcutaneous adipose tissue was excised, total RNA including miRNA was extracted. Affymetrix miRNA array 4.0 was used to detect the expression profile of miRNA and to identify differentially expressed miRNAs in subcutaneous fat between the two groups. Prediction of target targets was achieved by the conjunctive use of miRanda and Targetscan. Further bioinformatics analysis is performed on the basis of the GO and KEGG databases. The sample size was then enlarged to 8 obese and 9 normal weight women with average age of 34.88±9.67 and 42.11±6.68 years old. Quantitative real-time PCR (qRT-PCR) was applied to verify miRNA expression and to detect the messenger RNA (mRNA) level of some target genes.Results:Statistical differences of body mass index (BMI), weight and waist circumference could be observed between the two groups (P<0.05). MiRNA array revealed a total of 58 markedly changed miRNAs between obese and normal weight subjects, among which,54 miRNAs were down regulated,4 miRNAs were up regulated (Fold>4, P<0.01, FDR<0.05). The co-prediction by miRanda and Targetscan showed that there were 1333 target genes of the differentially expressed miRNAs, causing alterations to 269 biological functions and 89 signaling pathways. Significantly changed functions included DNA-dependent transcription, DNA-dependent transcription regulation, cellular adhesion, small molecule metabolic process, etc. Significantly changed pathways included MAPK signaling pathway, pathways in cancer, PI3K-AKT signaling pathway, ect. The validation results by qRT-PCR indicated that the expression level of miR-143-3p, miR-143-5p, miR-145-5p, let-7a-5p in subcutaneous fat of obese subjects was lower, accounted respectively for 68%(P=0.046),61%(P=0.016),73%(P=0.042), 66%(P=0.006) of normal weight controls, displaying consistency with the miRNA array results. HMGA2, a target gene of let-7a-5p, was proved to be 3.19 times up-regulated in adipose tissue of obese women, while there existed no difference in mRNA level of Thy-1 cell surface antigen (THY1), TAR DNA binding protein (TARDBP), Adaptor protein, phosphotyrosine interaction, PH domain and leucine zipper containing 1 (APPL1), fatty acid transporter-1 (FATP1) (P>0.05), which were all predicted targets of differentially expressed miRNAs.Conclusions:There were in total of 58 differentially expressed miRNAs in subcutaneous adipose tissue of obese women indicated by miRNA array (Fold>4, P<0.01, FDR＜0.05). 93%(54/58) of them were down regulated while 7% (4/58) were up regulated. The predicted target genes of these differentially expressed miRNAs were involved in various biological functions and signaling pathways. The most significantly changed function was DNA transcription and the most significantly changed pathway was MAPK signaling pathway. Low expression of miR-143-3p, miR-143-5p, miR-145-5p, let-7a-5p in obese subcutaneous fat was validated by qRT-PCR. Meanwhile, HMGA2, one of the target genes of let-7a-5p, was up regulated in obese subjects. Hence, miR-143-3p, miR-143-5p, miR-145-5p, let-7a-5p and HMGA2 could be histological biomarkers and potential therapeutic targets for obesity.
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