4.1 Pilot study 2018
Eight of the miRNAs (miR-494, -369, -122, -146a, -30e, -135a, -22 and -20a) measured in the miRCURY LNA miRNA PCR Human Panel I changed significantly (p < 0.05) because of the intervention. Four of these miRNAs (miR-146a, -30e, -22 and -20a) changed in all 12 samples. These miRNAs and four others (miR-19b, -101, -505 and -378a; p < 0.07), which also changed in all samples, were then analyzed in the sports intervention study. Furthermore, Line-1 methylation (p = 0.003) increased significantly.
4.2 Intervention study 2019 – 2020
The selected miRNAs and DNA methylation sites were analyzed in the control group and intervention group before (T0) and after (T1) 12 weeks and to assess the persistent consequence of the intervention, analysis was also done 10 months after the intervention (T2) in the follow-up group. SNP genotyping was only carried out in the intervention group.
4.2.1 Results of the selected miRNAs and Line-1 methylation
Intervention group: Five of the selected miRNAs showed an altered expression level after the sports intervention. Three miRNAs (miR-20a, p = 0.017, 0.95-fold; miR-22, p = 0.012, 0.95-fold and miR-505, p = 0.006, 0.95-fold) were significantly downregulated and two (miR-30e, p = 0.075, 0.97-fold and miR-146a, p = 0.066, 0.97-fold) showed a downregulation trend (Table 1). However, to quantify the effect of the intervention, we evaluated a “fitness sore”, which depends on the strength / p-values of the individual miRNAs in the intervention and control group. Whereby a high score means better fitness and as can be seen in Figure 2, the “fitness score” increased significantly in the entire intervention group (p = 0.000), in men (p = 0.005) and women (p = 0.009), while it did not change in the control group (p = 0.740). Furthermore, the methylation of Line-1 showed no change after 12-week intervention.
Control group: In the control group, only one miRNA had a changed expression after 12 weeks. The miR-20a showed a significant upregulation (p = 0.020, 1.48-fold), whereas in the intervention group a significant downregulation was observed. When the intervention and the control group are compared, they showed a significantly different expression of miR-20a (p = 0.042) before the intervention (T0) and significantly different expressions of miR-22 (p = 0.000), -30e (p = 0.015) and -146a (p = 0.047) after 12 weeks (T1). If considering the fold changes of the two groups, they differ significantly in miR-20a (p = 0.012) and miR-22 (p = 0.046).
Follow-up group: In the follow-up group we observed an upregulated miR-378a 10 months after the sports intervention (T2), compared to immediately after the intervention (T1) (p = 0.050). When comparing before the intervention (T0) and 10 months after the intervention (T2), there are no differences in the expression levels of these miRNAs.
4.2.2 Results of the SNP genotyping
Table 2 shows the distribution of the selected single nucleotide polymorphism (SNPs) in the respective genes of our study participants in the intervention group (n = 61).
Differences between genotypes and selected miRNAs: Polymorphisms in the ACE gene seem to influence the expression of miR-101 (p = 0.019). Participants with a CC genotype had a significantly higher expression after the intervention compared to participants with a CG or GG phenotype, with no differences between CG and GG (Figure 3A). Furthermore, polymorphisms in the ACTN3 gene appear to have an influence on the expression of miR-20a (p = 0.027), miR-22 (p = 0.033) and miR-101 (p = 0.004), see Figure 3B-D. Participants with a CC genotype had a significant higher expression of these miRNAs after 12 weeks than those with a TC genotype. Whereas the participants with a TT genotype showed a higher expression of miR-101 than TC genotypes. Furthermore, the polymorphism in the FTO gene also seems to influence the expression of miR-22 (p = 0.008). However, only the GG genotype differed from the AA genotype. Participants with a GG genotype showed a higher expression after the intervention than those with an AA genotype (Figure 3E).
4.2.3 Results of the body composition measurement (BIA)
The Intervention resulted in significant changes in the anthropometric data. There was an increase in metabolic rate at rest (p = 0.000), phase angle (p = 0.004), LBM (p = 0.000), BCM (p = 0.007) as well as ICW (p = 0.007) and ECW (p = 0.015), and a decrease in BFM (p = 0.000), see Table 3.
Epigenetic and genetic markers and anthropometric data: We were also able to determine significant correlations between miRNAs, Line-1 methylation and anthropometric data. Between miR-22 (linear regression = -0.277, p = 0.031), miR-101 and LBM (linear regression = -0.267, p = 0.038). Among miR-505 and BFM (linear regression = 0.290, p = 0.024), between Line-1 methylation and ECW (linear regression = -0.267, p = 0.037) and among the fitness score and BFM (linear regression = -0.343, p = 0.007), see Figure 4. For example, the participants who gained more LBM had a lower expression of miR-22 (Figure 4A) and miR-101 (Figure 4C), and participants who lost more BFM had a lower expression of miR-505 and a higher fitness score (Figure 4B and D).
Furthermore, we could observe correlations between ACTN3 gene, LBM (p = 0.039), ICW (p = 0.040) and BMI (p = 0.072). The participants with a TC genotype showed a higher gain in LBM and ICW compared to participants with a TT genotype.
4.2.4 Results of epigenetic markers, nutrition and lifestyle
In the intervention group, we were able to determine a significant correlation between the intake of B vitamins (B vitamin complex, cobalamin and folic acid) and miR-19b (p = 0.033) and miR-101 (p = 0.047). Participants who supplemented with B vitamins had a higher expression of these miRNAs compared to participants who did not supplement. A similar correlation could be established with the intake of magnesium and miR-19b (p = 0.052). Furthermore, we were able to observe an association between miR-378a and iron supplementation (p = 0.017). The participants who supplemented iron had a significant higher expression of miR-378a. In addition, the participants who had a higher fluid intake (2-3 liters a day) showed an upregulation of miR-378a (p = 0.003). Furthermore, the participants who reported consuming whole grain products daily or several times a day showed higher expression level of miR-101 (p = 0.002) than those who consumed less. Whereas miR-146a correlated with stress (p = 0.029). The participants who reported having an increased stress level had a significantly lower expression of miR-146a.