Circulating miRNA Signaling for Fatty Acid Metabolism in Response to a Maximum Endurance Test in Elite Long-Distance Runners

Abstract

Maximal oxygen uptake (VO₂max) is a determining indicator for cardiorespiratory capacity in endurance athletes, and epigenetics is crucial in its levels and variability. This initial study examined a broad plasma miRNA profile of twenty-three trained elite endurance athletes with similar training volumes but different VO₂max in response to an acute maximal graded endurance test. Six were clustered as higher/lower levels based on their VO₂max (75.4 ± 0.9 and 60.1 ± 5.0 mL.kg^-1.min^-1). Plasma was obtained from athletes before and after the test and 15 ng of total RNA was extracted and detected using an SYBR-based 1113 miRNA RT-qPCR panel. A total of 51 miRNAs were differentially expressed among group comparisons. Relative amounts of miRNA showed a clustering behavior among groups regarding distinct performance/time points. Significantly expressed miRNAs were used to perform functional bioinformatic analysis (DIANA tools). Fatty acid metabolism pathways were strongly targeted for the significantly different miRNAs in all performance groups and time points (p < 0.001). Although this pathway does not solely determine endurance performance, their significant contribution is certainly achieved through the involvement of miRNAs. A highly genetically dependent gold standard variable for performance evaluation in a homogeneous group of elite athletes allowed genetic/epigenetic aspects related to fatty acid pathways to emerge.

Keywords: endurance elite athletes; exercise performance; fatty acid metabolism; maximal oxygen uptake; miRNA.

Figure 1

Principal component analysis (PCA) graphs showing “timepoint”−based clustering analysis between (A) all_PRE_vs_POST, (B) HVO2_PRE_vs_POST, and (C) LVO2_PRE_vs_POST comparisons; additional PCA showing “performance”−based clustering analysis between (D) PRE_HVO2_vs_LVO2 and (E) POST_HVO2_vs_LVO2. And finally, a global clustering analysis between (F) all_4_groups. PCA was performed using the relative amount of RNAs significantly detected among groups. Confident intervals are presented inside every colored ellipse.

Figure 2

Heatmaps of significant pathways (Fishers’ exact test and false discovery ratio (FDR) correction) related to crucial miRNAs in response to a maximal graded endurance test (GXT) (timepoint). (A) All athletes (all_PRE_vs_POST); (B) LVO2_PRE_vs_POST; (C) HVO2_PRE_vs_POST; (D) PRE_HVO2_vs_LVO2); (E) POST_HVO2_vs_LVO2; (F) all_4_groups (HVO2_PRE vs. HVO2_POST vs. LVO2_PRE vs. LVO2_POST). Pathways highlighted in red represent fatty acid biosynthesis; in orange, fatty acid metabolism; in purple, Hippo signaling; in gray, TGF-β; in yellow, lysine degradation; and in green, other related pathways.