Trisomy 21 results in modest impacts on mitochondrial function and central carbon metabolism

Down syndrome (DS) is the most common genetic cause of intellectual disability. Mechanistically, oxidative stress and mitochondrial dysfunction are reported to be etiological factors for many of the DS-related comorbidities and have previously been reported in a number of in vitro and in vivo models of DS. The purpose of this study was to test for the presence of mitochondrial dysfunction in fibroblast cells obtained via skin biopsy from individuals with DS, and to assess the impact of trisomy 21 on central carbon metabolism. Using extracellular flux assays in matched dermal fibroblasts from euploid and DS individuals, we found that basal mitochondrial dysfunction is quite mild. Stressing the cells with a cocktail of mitochondrial stressors revealed a significant mitochondrial deficit in DS cells compared to euploid controls. Evaluation of extracellular acidification rate did not reveal a baseline abnormality in glycolysis; however, metabolomic assessments utilizing isotopically labeled glucose and glutamine revealed altered central carbon metabolism in DS cells. Specifically, we observed greater glucose dependency, uptake and flux into the oxidative phase of the pentose phosphate pathway in DS fibroblasts. Furthermore, using induced pluripotent stem cells (iPSC) we found that mitochondrial function in DS iPSCs was similar to the previously published studies employing fetal cells. Together, these data indicate that aberrant central carbon metabolism is a candidate mechanism for stress-related mitochondrial dysfunction in DS.