Blood DNA Methylation in Nuclear and Mitochondrial Sequences Links to Malnutrition and Poor Prognosis in ALS: A Longitudinal Study

<b>Background</b>: Malnutrition in amyotrophic lateral sclerosis (ALS) is associated with disease severity, and epigenetic regulation may be involved. The aim of this study was to assess the methylation levels of specific DNA sequences from the nuclear and mitochondrial genomes in a population with ALS to elucidate their relationship with nutritional status and the evolution of the disease. <b>Methods</b>: Patients with ALS were evaluated between 2013 and 2021 (<i>n</i> = 66). They were categorized according to their nutritional status, using the Global Leadership Initiative on Malnutrition (GLIM) criteria, and disease progression, using the ALS Functional Rating (ALSFRS-R) Scale. DNA samples were extracted from leukocytes at the time of diagnosis for analysis of DNA methylation levels of markers of oxidative stress, mitochondrial function and global methylation (D-loop, GSTP1, and LINE-1). <b>Results</b>: According to the GLIM criteria, 29 (43.9%) patients had malnutrition (22.7%-moderate; 21.2%-severe), which was positively correlated with ALS disease progression (r = 0.414; <i>p</i> < 0.01) and death (r = 0.687; <i>p</i> < 0.01). Mortality occurred in 43.9% of the patients (median time to death, 18.7 (1.7-82.7) months). A significant association was observed between DNA methylation levels of the D-loop, GSTP1, and the CpG1 site of LINE-1 and malnutrition, disease progression at diagnosis, and death. The D-loop was the best predictor of malnutrition (AUC, 0.79; <i>p</i> < 0.01), disease progression (AUC, 0.70; <i>p</i> < 0.01), and mortality (AUC, 0.71; <i>p</i> < 0.01). <b>Conclusions</b>: This study revealed, for the first time, the early detection of D-loop methylation levels as a potential biomarker of nutritional status in patients with ALS, which may be useful for personalized nutritional management aimed at counteracting disease progression.