[0001] The present invention refers to a method for the treatment, diagnosis and/or prognosis of mitochondrial diseases (i.e., pathologies associated with mitochondrial dysfunction), preferably for the treatment, diagnosis and/or prognosis of neurodegenerative mitochondrial diseases (i.e., treatment, diagnosis and/or prognosis of neuroinflammation and/or neurodegeneration in the context of those mitochondrial diseases).
1. NADPH for use in a method for the treatment of mitochondrial diseases. 2. NADPH for use, according to claim 1, in a method for the treatment of neurodegenerative mitochondrial diseases. 3. NADPH for use, according to any of the previous claims, wherein the method comprises promoting the production of NADPH by increasing the expression and/or activity of enzymes that produce NADPH. 4. NADPH for use, according to any of the previous claims, wherein the method comprises promoting the production of NADPH by increasing the expression and/or activity of enzymes that produce NADPH, preferably by means of the administration of a vector to deliver and enhance the expression and/or activity of enzymes that produce NADPH in the brain or by means of the administration of molecule able to enhance the expression and/or activity of enzymes that produce NADPH in the brain. 5. NADPH for use, according to any of the previous claims, wherein the vector is an adeno-associated virus with tropism to the central nervous system. 6. NADPH for use, according to any of the previous claims, wherein the enzyme that produce NADPH is selected from malic enzyme, isocitrate dehydrogenase 1, or glucose 6 phosphate dehydrogenase. 7. In vitro method for the diagnosis and/or prognosis of mitochondrial diseases which comprises assessing the level of NADPH, or of the expression level and/or activity of enzymes that produce NADPH, in a biological sample obtained from the subject. 8. In vitro use of NADPH, or of an enzyme that produce NADPH, or of a kit comprising reagents for the identification of NADPH, or of an enzyme that produce NADPH, for the diagnosis and/or prognosis of mitochondrial diseases. 9. In vitro method, or in vitro use, according to any of the claims 7 or 8, for the diagnosis and/or prognosis of neurodegenerative mitochondrial diseases. 10. In vitro method, or in vitro use, according to any of the claims 7 to 9, which comprises assessing the level of expression and/or activity of enzymes that produce NADPH, in a biological sample obtained from the subject, selected from malic enzyme 1, isocitrate dehydrogenase 1, or glucose 6 phosphate dehydrogenase. 11. In vitro method, or in vitro use, according to any of the claims 7 to 10, which comprises assessing the level of NADPH or the expression level and/or activity of enzymes that produce NADPH, in a biological sample obtained from the subject, wherein a lower level of NADPH or a lower level of expression and/or activity of enzymes that produce NADPH, as compared to a pre-established threshold level determined in control subjects who are not suffering from neurodegenerative mitochondrial diseases, is an indication that the subject has a pathology associated with mitochondrial dysfunction or a mitochondrial disease or has a poor prognosis. 12. In vitro method, or in vitro use, according to any of the claims 7 to 11, wherein the biological sample is selected from tissue, blood, serum, plasma or cerebrospinal fluid.