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Mol Med. 2016 Oct;22:548-559. doi: 10.2119/molmed.2016.00122. Epub 2016 Jun 30.

Altered redox mitochondrial biology in the neurodegenerative disorder fragile X-tremor/ataxia syndrome: use of antioxidants in precision medicine.

Author information

1
Department of Molecular Biosciences, School of Veterinary Medicine, Davis, CA 95616.
2
Medical Investigations of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, CA 95817.
3
Department of Pediatrics, University of California Davis Medical Center, Sacramento CA 95817.
4
Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, CA 95817.

Abstract

A 55-200 expansion of the CGG nucleotide repeat in the 5'-UTR of the fragile X mental retardation 1 gene (FMR1) is the hallmark of the triplet nucleotide disease known as the "premutation" as opposed to those with >200 repeats, known as the full mutation or fragile X syndrome. Originally, premutation carriers were thought to be free of phenotypic traits; however, some are diagnosed with emotional and neurocognitive issues and, later in life, with the neurodegenerative disease fragile X-associated tremor/ataxia syndrome (FXTAS). Considering that mitochondrial dysfunction has been observed in fibroblasts and post-mortem brain samples from carriers of the premutation, we hypothesized that mitochondrial dysfunction-derived ROS may result in cumulative oxidative-nitrative damage. Fibroblasts from premutation carriers (n=31, all FXTAS-free except 8), compared to age- and sex-matched controls (n=25), showed increased mitochondrial ROS production, impaired Complex I activity, lower expression of MIA40 (rate-limiting step of the redox-regulated mitochondrial-disulfide-relay-system), increased mtDNA deletions, and increased biomarkers of lipid and protein oxidative-nitrative damage. Most of the outcomes were more pronounced in FXTAS-affected individuals. Significant recovery of mitochondrial mass and/or function was obtained with superoxide or hydroxyl radicals' scavengers, a glutathione peroxidase analog, or by overexpressing MIA40. The effects of ethanol (a hydroxyl radical scavenger) were deleterious, while others (by N-acetyl-cysteine, quercetin and epigallocatechin-3-gallate) were outcome- and/or carrier-specifics. The use of antioxidants in the context of precision medicine is discussed with the goal of improving mitochondrial function in carriers with the potential of decreasing the morbidity and/or delaying FXTAS onset.

KEYWORDS:

Neurodegenerative disorders; antioxidants; free radicals; metabolism; mitochondria; neurobiology; neurodegeneratio; neurodegeneration; oxidative stress; personalized medicine; reactive oxygen species; triplet nucleotide disease

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