Circulating long non-coding RNAs (lncRNAs) serve as valuable biomarkers in a number of human diseases. However, lncRNA biomarkers have yet to be identified in obesity. We aim to characterize circulating lncRNA expression in obese and non-obese human subjects. First, we assessed the genome-wide circulating lncRNA expression profiles in blood from 3 obese and 3 non-obese human subjects. We found a significant decrease in circulating levels of three lncRNAs (lncRNA-p5549, lncRNA-p21015 and lncRNA-p19461) in obese human subjects only. Next, using RT-PCR we measured the expression levels of these three lncRNAs in 33 obese and 33 non-obese human subjects and found similar differences. Moreover, we found a negative correlation between circulating levels of these three lncRNAs and body mass index (BMI), waist circumference, waist to hip ratio and fasting insulin. There was also a significant negative correlation between expression of lncRNA-p19461 and homeostasis model assessment-estimated insulin resistance. Finally, we tested the circulating levels of these three lncRNAs in 8 obese human subjects after a 12-week diet-induced weight loss program. We found that only lncRNA-p19461 expression level significantly increased. In summary, circulating lncRNAs are deregulated in obesity. Weight loss-induced changes in this profile support this observation and suggest a potential mechanistic relevance.
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