A new adipocyte-specific long non-coding RNA engages impaired fatty acid sensing and dyslipidaemia in obese subjects (RNA-seq)

The relevance of adipose-derived long noncoding RNAs (lncRNAs) to the regulation of gene expression patterns related to the obese phenotype remains elusive. Here, the analysis of transcriptomes of adipose tissue before-after significant weight loss led to the identification of 496 putative lncRNAs (FDR p-values <0.05). Only the nonconserved linc-GALNTL6-4 displayed a fold-change above 2 plus adjusted p-value <0.0001. Exploration of additional omental and subcutaneous fat samples confirmed diminished linc-GALNTL6-4 in obese subjects, while lncRNA-mRNA co-expression analyses highlighted its association with fatty acid metabolism. Concurrently, the expression of this unique lncRNA towered in ex vivo isolated and in vitro differentiated adipocytes, being compromised under conditions that mimicked inflammation in obese adipocytes. On the other hand, the knockdown of linc-GALNTL6-4 in fat cell progenitors conveys impaired differentiation, fostering deranged expression patterns in differentiated adipocytes, including the increased expression of genes devoted to the transport of lipids, such as Apolipoprotein C1 (APOC1) and the intracellular fatty acid-binding protein FABP3. Conversely, overexpression of linc-GALNTL6-4 ameliorated adipocyte performance through the specific control of the short-chain fatty acid receptor FFAR3. Current data unveil the unforeseen relevance of linc-GALNTL6-4 as a modulator of fatty acid sensing in adipocytes deeply challenged by body weight and meta-inflammation. To induce the adipogenic conversion of adipocyte progenitors, human preadipocytes (SP-F-1, Zen-Bio, Inc.) were led to grow as a monolayer in preadipocyte medium (PM-1) until reaching confluence, and then incubated with adipocyte differentiation medium (DM-2) for 7 days. This media is composed of DMEM / Ham’s F-12 (1:1), HEPES, FBS, biotin, pantothenate, insulin, dexamethasone, IBMX, PPARγ agonist, penicillin, streptomycin and amphotericin B. Thereafter, differentiating adipocytes were maintained in adipocyte maintenance medium (AM-1) for 7 additional days (DM-2 without dexamethasone, IBMX and PPARγ agonists). During this process, the shape of preadipocytes evolves from the flattened form to rounded cells containing abundant lipid droplets, and are thus considered differentiated, mature adipocytes (~12th day and thereafter). Once differentiated, we challenged these cultures of primary human adipocytes with the ectopic presence of synthetic small interfering (si-)RNAs directed against our lncRNA candidate. 8 samples were analysed (Control=4, siLINC2=4)