Exercise modulates metabolism acutely by altering the activity of key metabolic enzymes, and in the long-term by inducing transcription of metabolic genes. MicroRNAs (miRNAs) are small non-coding RNAs that suppress target mRNAs, thereby modulating cell functions, including metabolism. The aims of this study were to (1) determine whether exercise training affects the global miRNA profile of adipocytes and, (2) to determine whether the training-responsive miRNAs are important in regulating adipocyte metabolism.
Eleven overweight, sedentary males aged 36 ± 2 years (mean ± SEM) participated in the study. Adipocytes were isolated from the abdominal (ABD) and gluteofemoral (GF) sites prior to, and following, 6 weeks of endurance exercise training. Adipocyte RNA was extracted and purified for small RNA detection. miRNA libraries were subsequently generated using RNA-Seq, and the resulting miRNA profiles were determined using miRDeep2. In separate studies, 3T3-L1 adipocytes were cultured and transfected with miRNAs -10b, -204 and -4532. Lipolysis and fatty acid metabolism were assessed 48 h after transfection
562 miRNAs were identified, with the expression of only three miRNAs (-3613, -204 and -4532) being greater (3-4-fold increase) in GF than ABD adipocytes prior to training. Only miRNA-10b was upregulated in ABD prior to (4.7-fold increase) and after (3-fold increase) exercise training. Subsequent studies in cultured adipocytes showed that overexpression of miRs-10b, -204 and -4532 did not affect lipolysis, though fatty acid oxidation was increased in adipocytes transfected with miRNA-10b and miRNA-4532.
In conclusion, exercise training did not induce striking changes in the miRNA profile of adipocytes, suggesting that stable alterations in the miRNA profile are not a major component of the molecular remodelling observed with endurance training. These studies also provide evidence that the identified ‘training responsive’ miRNAs are not major regulators of lipid metabolism in adipocytes.