Abstract: The present invention relates to the fields of life sciences and medicine. Specifically, the invention relates to a method for preparing an extract comprising metabolites such as NAD+, NADP+, NADH and NADPH from a sample of a subject and to a method for determining amounts of NAD+, NADP+, NADH, NADPH, NAD+/NADH ratio, NADPH/NADP+ ratio, NAD pool, and/or NADP pool from a sample obtained from a subject. The present invention also relates to an extract comprising metabolites such as NAD+, NADP+, NADH and NADPH. Also, the present invention relates to a kit comprising an extraction solution, a detection system comprising an electron carrier, chromogen and non-ionic detergent for determining amounts of NAD+, NADP+, NADH, NADPH, NAD+/NADH ratio, NADPH/NADP+ ratio, NAD pool, and/or NADP pool, and optionally GSH, GSSG and/or GSH/GSSG ratio, from a sample of a subject.

Abstract: The present invention relates to the fields of life sciences and medicine. Specifically, the invention relates to a method for determining a mitochondrial disorder of a subject or predicting a prognosis of a subject having a mitochondrial disorder, wherein the method comprises determining specific biomarkers from a sample of a subject. Also, the present invention relates to a method of selecting a treatment for a subject having a mitochondrial disorder or following up a treatment of a subject having a mitochondrial disorder, wherein the method comprises determining specific biomarkers from a sample of a subject.

Abstract: The invention relates to a method, of assessing whether a subject is affected with or at risk for developing a dysfunction of the mitochondrial respiratory chain, the method comprising determining the concentration of fibroblast growth factor 21 (FGF21) in a biological sample from the subject, and comparing it to the concentration of FGF21 in a biological sample from at least one normal control, wherein an increase in the concentration of FGF21 in the biological sample from the subject when compared to the concentration of FGF21 in the biological sample from at least one normal control is indicative of occurrence of the dysfunction of the mitochondrial respiratory chain in said subject, or of risk for developing said dysfunction.

Abstract: The present invention provides an in vitro method for diagnosis or prediction of Parkinson's disease in a subject, the method comprising testing for a mutation of a mitochondrial DNA polymerase POLG1 gene of the subject and, where the mutation is detected, diagnosing or predicting Parkinson's disease in the subject. Further, the present invention provides a diagnostic kit for diagnosis or prediction of Parkinson's disease in a subject.