*4.13. Statistical Analysis*

Data are presented as mean ± SD. An unpaired two-tailed t-test or Mann–Whitney test was performed; p-values of less than 0.05 were considered statistically significant. (\* *p*-value < 0.05; \*\* *p*-value < 0.01; \*\*\* *p*-value < 0.001).

#### **Supplementary Materials:** Supplementary Materials can be found at http://www.mdpi.com/1422-0067/21/9/3191/s1.

**Author Contributions:** Conceptualization, R.G. and M.E.G.; methodology, T.G.-M., F.Z.D., I.C., L.R.-V., M.-G.H., J.K.-E, H.A. and M.E.G.-; validation, T.G.-M., F.Z.D., I.C., M.-G.H., J.K.-E., E.E., M.A.M., H.A. and M.E.-G.; formal analysis, T.G.-M., H.A. and M.E.G.; investigation, T.G.-M., F.Z.-D., I.C., M.-G.H., L.R.-V. and J.K.-E; project administration, M.E.G.; writing—original draft preparation, T.G.-M., H.A. and M.E.G.; writing—review and editing, E.E., H.A. and M.E.G.; supervision, H.A. and M.E.G.; funding acquisition, R.G., H.A. and M.E.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by 'Fondo de Investigación Sanitaria, Instituto de Salud Carlos III co-funded by European Regional Development Funds', gran<sup>t</sup> number PI15/00484 and PI18/00151 to M.E.G; PI13/00556 and PI16/00789 to R.G. F.Z.-D. received gran<sup>t</sup> support from the Ministerio de Educación, Cultura y Deporte (FPU13/00544). M.E.G. is supported by a 'Miguel Servet' contract (CP16/00046) from Instituto de Salud Carlos III and European Regional Development Funds. HA received support from the Swedish Research Council.

**Acknowledgments:** We are very grateful to Francina Munell for kindly providing us with the patient fibroblasts.

**Conflicts of Interest:** J.K.E. and E.E. have salary from and equity interest in NeuroVive Pharmaceutical, a company active in the field of mitochondrial medicine. The remaining authors declare no potential conflict of interest.
