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“Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a severe human disease caused by mutations in TYMP, the gene encoding thymidine phosphorylase (TP). It belongs to a broader group of disorders characterized by a pronounced reduction in mitochondrial DNA (mtDNA) copy number in one or more tissues. In most cases, these disorders are caused by mutations in genes involved in deoxyribonucleoside triphosphate (dNTP) metabolism. It is generally accepted that imbalances in mitochondrial dNTP pools resulting from these mutations interfere with mtDNA
selleck inhibitor replication. Nonetheless, the precise mechanistic details of this effect, in particular, how an excess of a given dNTP (e. g., imbalanced dTTP excess observed in TP deficiency) might lead to mtDNA depletion, remain largely unclear. Using an in organello replication experimental model with isolated murine liver mitochondria, we observed that overloads of dATP, dGTP, or dCTP did not reduce the mtDNA replication rate. In contrast, an excess of dTTP decreased mtDNA synthesis, but this effect was due to secondary dCTP depletion rather than to the GDC 941 dTTP excess in itself. This was confirmed
in human cultured cells, demonstrating that our conclusions do not depend on the experimental model. Our results demonstrate that the mtDNA replication rate is unaffected by an excess of any of the 4 separate dNTPs and
is limited by the availability of the dNTP present at the lowest concentration. Therefore, the availability of dNTP is the key factor that leads to mtDNA depletion rather than dNTP imbalances. These results provide the first test of the mechanism that accounts for mtDNA depletion in MNGIE and provide evidence that limited dNTP availability is the common cause of mtDNA depletion due to impaired anabolic or catabolic dNTP pathways. Thus, therapy approaches focusing on restoring the deficient substrates should be explored.”
“Background: ARN-509 The study of muscle metabolism by near-infrared spectroscopy (NIRS) has been poorly implemented in multiple sclerosis (MS). Aims of the study were to compare resting muscle oxygen consumption (rmVO(2)) at gastrocnemius in MS patients and in age-matched healthy controls (HC) measured using NIRS, and to evaluate its possible relationship with patients’ mobility.\n\nMethods: Twenty-eight consecutively enrolled MS patients (male, n = 16; age = 42.7 +/- 14.0 y, Relapsing-Remitting, n = 19; Primary-Progressive, n = 9) and 22 HC (male, n = 13; age = 36.0 +/- 8.2 y) were studied during rest applying the NIRS probes at gastrocnemius, producing a venous occlusion at the thigh using a cuff, and analyzing the slope of the total hemoglobin to calculate rmVO(2). Mobility was assessed by a 6-Minute Walking Test and 6-Minute Walking Distance (6MWD) was recorded.