MicroRNA-193b Controls Adiponectin Production in Human White Adipose Tissue

Context: MicroRNAs (miRNAs) are posttranscriptional regulators of gene expression. In white adipose tissue (WAT), recent studies suggest that miRNA levels are altered in various metabolic diseases, including obesity. Objective: The objective of the study was to determine whether adipocyte-expressed miRNAs altered by obesity can regulate adiponectin expression/secretion in fat cells. Design: Eleven miRNAs previously shown to be altered in obese human WAT were overexpressed in human in vitro-differentiated adipocytes followed by assessments of adiponectin levels in conditioned media. Setting: This was cohort study (n = 56) in an academic hospital. Patients: Subcutaneous WAT was obtained from nonobese and obese individuals. Interventions: There were no interventions in this study. Main Outcome Measure(s): Protein and mRNA levels of adiponectin were measured. Results: Of the 11 investigated miRNAs, three (miR-193b/-126/-26a) increased adiponectin secretion when overexpressed in human adipocytes. However, in human WAT only miR-193b expression correlated with adiponectin gene expression and homeostasis model assessment of insulin resistance. Moreover, quantitative PCR of miR-193b in both WAT and isolated adipocytes showed a significant association with serum adiponectin levels. Overexpression of miR-193b altered the gene expression of seven known adiponectin regulators. 3'-untranslated region reporter assays confirmed binding to cAMP-responsive element binding protein 5, nuclear receptor interacting protein 1, and nuclear transcription factor Y alpha. The effects of miR-193b on nuclear transcription factor Y alpha expression were confirmed at the protein level. Transfection with individual miRNA target protectors selective for nuclear transcription factor Y alpha and nuclear receptor interacting protein 1 abolished the stimulatory effect of miR-193b on adiponectin secretion. Conclusions: In human adipocytes, miR-193b controls adiponectin production via pathways involving nuclear transcription factor Y alpha and possibly nuclear receptor interacting protein 1.