MicroRNA miR-378 regulates adipocytokine fate by targeting transcriptional factors in human visceral and subctaneous adipose tissue

Abstract

Purpose: MicroRNAs (miRNA), single-stranded non-protein coding gene products, regulate gene expression through post-transcriptional inhibition, and known to be involved in essential biological processes including obesity and insulin resistance. miR-378 and miR-378*, which are encoded by PGC-1β gene and counterbalance the metabolic actions of PGC-1β. Mice genetically lacking miR-378 and miR-378* are resistant to high fat diet-induced obesity and exhibit enhanced mitochondrial fatty acid metabolism and elevated oxidative capacity of insulin-target tissues. We conducted to elucidate the role of miR378 expression in human adiposity and adipose tissue inflammation. Methods: Pair samples were obtained from subcutaneous (SAT) and visceral adipose tissue (VAT) during elective operation in 71 men and 42 women. Mature miRNA levels were determined by qRT-PCR and normalized to levels of U6 small nuclear ribonucleoprotein. Subcutaneous (SFA) and visceral fat area (VFA) was determined by abdominal multidetector CT scanning. Adipocyte sizing was determined by the osmium-fixed method on a Coulter counter. Results: Study 1 (clinical study): SFA were larger than VFA, and the mean size of adipocytes was greater in SAT than in VAT. In VAT, level of log(miR100) was positively correlated with level of adiponectin, TLR4 and HMGB1, while negatively correlated with CD68, NOX4 and with mean size of adipocyte. In SAT, level of log(miR100) was positively correlated with level of IL18, TLR4 and HMGB1, while negatively correlated with NOX4. Study 2 (in vitro study): expression levels of miR100 as well as PPARγ2 and PGC1α were increased in adipocyte-like 3T3L1 cells during differentiation. Levels of PPARγ2 and PGC1α were inhibited by antisense miRNA transfection. The expression levels of computer-predicted target genes, ACSL1, acyl-CoA synthetase long-chain family member 1 and AGPAT6, 1-acylglycerol-3-phosphate O-acyltransferase 6 (lysophosphatidic acid acyltransferase ζ), were partially inhibited by anti-sense miR-378 overexpression. Conclusion: Adipose tissue miR378 is derived mostly from adipocytes and may play a role in regulating expressions of adipocyte inflammatory cytokines and insulin sensitivity in human. Results suggested that mir-378 regulates adipocytokine expression by targeting transcriptional factors and controls adipose tissue inflammation in human.