Inherited disorders affecting mitochondrial function are associated with glutathione deficiency and hypocitrullinemia

Department of Genetics, Stanford University, Stanford, CA 94305, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 03/2009; 106(10):3941-5. DOI: 10.1073/pnas.0813409106
Source: PubMed

ABSTRACT Disorders affecting mitochondria, including those that directly affect the respiratory chain function or result from abnormalities in branched amino acid metabolism (organic acidemias), have been shown to be associated with impaired redox balance. Almost all of the evidence underlying this conclusion has been obtained from studies on patient biopsies or animal models. Since the glutathione (iGSH) system provides the main protection against oxidative damage, we hypothesized that untreated oxidative stress in individuals with mitochondrial dysfunction would result in chronic iGSH deficiency. We confirm this hypothesis here in studies using high-dimensional flow cytometry (Hi-D FACS) and biochemical analysis of freshly obtained blood samples from patients with mitochondrial disorders or organic acidemias. T lymphocyte subsets, monocytes and neutrophils from organic acidemia and mitochondrial patients who were not on antioxidant supplements showed low iGSH levels, whereas similar subjects on antioxidant supplements showed normal iGSH. Measures of iROS levels in blood were insufficient to reveal the chronic oxidative stress in untreated patients. Patients with organic acidemias showed elevated plasma protein carbonyls, while plasma samples from all patients tested showed hypocitrullinemia. These findings indicate that measurements of iGSH in leukocytes may be a particularly useful biomarker to detect redox imbalance in mitochondrial disorders and organic acidemias, thus providing a relatively non-invasive means to monitor disease status and response to therapies. Furthermore, studies here suggest that antioxidant therapy may be useful for relieving the chronic oxidative stress that otherwise occurs in patients with mitochondrial dysfunction.

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Available from: Gregory M Enns, Aug 18, 2015
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    • "Decreased activities of mitochondrial complexes I–IV have also been reported in hippocampus of a murine model of SSADH deficiency [16]. Low glutathione levels have been demonstrated in the blood of patients with primary mitochondrial disease [24] as well as in the blood and liver tissue of patients with organic acidemias such as methylmalonic acidemia [24] [25] [26] indicating secondary mitochondrial dysfunction and redox imbalance organic acidemias. Increased lipid peroxidation [14] [15] [23] and low glutathione levels [10] [14] [16] in murine models of SSADH deficiency as well as dicarboxylic aciduria reported in patients [3] and mitochondrial dysfunction in SSADH deficiency, similar to other organic acidemias. "
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    ABSTRACT: The pathophysiology of succinic semialdehyde dehydrogenase (SSADH) deficiency is not completely understood. Oxidative stress, mitochondrial pathology, and low reduced glutathione levels have been demonstrated in mice, but no studies have been reported in humans. We report on a patient with SSADH deficiency in whom we found low levels of blood reduced glutathione (GSH), and elevations of dicarboxylic acids in urine, suggestive of possible redox imbalance and/or mitochondrial dysfunction. Thus, targeting the oxidative stress axis may be a potential therapeutic approach if our findings are confirmed in other patients.
    12/2014; 1:129–132. DOI:10.1016/j.ymgmr.2014.02.005
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    • "It is possible that in diabetic patients with better controlled glycemia, NAC supplementation at the current dosage could be more effective in quenching the oxidative load and an improvement in the GSH ratio might be observed. Although NAC is well known to increase the in-vivo GSH content, most studies in the literature only report the total or free GSH content and did not examine the GSH ratio [24] [31] [32] [38] [42] [43]. In addition, our study provides novel information on how the free GSH content within each immune cell population responds to oral NAC supplementation, with the granulocytes being the most responsive, and T cells the least. "
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    ABSTRACT: Type 2 diabetic patients have increased susceptibility to melioidosis, an infectious disease caused by Burkholderia pseudomallei. We had previously shown that peripheral blood mononuclear cells (PBMCs) from diabetic patients with poor glycemic control had a defective IL-12 and IFNγ response to B. pseudomallei infection, resulting in poor intracellular bacterial control. The impaired IL-12 response was due to glutathione (GSH) deficiency characterized by a low reduced to oxidized glutathione ratio (GSH ratio) and could be restored by the addition of reduced GSH to the infected cells. Our goal is to determine whether N-acetyl cysteine (NAC, a GSH pro-drug) supplementation in diabetic patients could improve their immune control of B. pseudomallei. Type 2 diabetic patients with poor glycemic control were given oral supplementation of NAC for six weeks at 1200mg daily. Their PBMCs and subsets of immune cells showed a significant increase in free GSH concentration. However, the GSH ratio, IL-12 and IFNγ production, and intracellular bacterial killing upon ex-vivo infection did not improve. Thus, oral NAC supplementation in diabetic patients is sufficient to increase intracellular GSH content in blood cells. However, modulating the free GSH content is not sufficient to improve infection outcome as it is the GSH ratio that regulates the IL-12 response in monocytes.
    Microbes and Infection 07/2014; 16(8). DOI:10.1016/j.micinf.2014.07.007 · 2.73 Impact Factor
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    • "LS arises from DNA defects in mitochondrial [3], nuclear [4] [5] [6] or X-linked genes [7] [8] [9] [10] and its pathogenesis is characterized by impaired energy synthesis and enhanced oxidative stress. Despite the fact that mitochondrial dysfunction has been clearly associated with oxidative stress [1], few reports have examined the glutathione levels in blood of patients with LS [11] [12] [13]. "
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    ABSTRACT: BACKGROUND: Genetically defined Leigh syndrome (LS) is a rare, fatal inherited neurodegenerative disorder that predominantly affects children. Although mitochondrial dysfunction has clearly been associated with oxidative stress, few studies have specifically examined Leigh syndrome patients' blood glutathione levels. In this study, we analyzed the balance between oxidized and reduced glutathione in lymphocytes of 10 patients with genetically confirmed LS and monitored the effects of glutathione status following 6months of treatment with EPI-743, a novel redox therapeutic. METHODS: Lymphocytes were obtained from blood samples of 10 children with a genetically confirmed diagnosis of LS and in 20 healthy subjects. Total, reduced, oxidized and protein-bound glutathione levels were determined by HPLC analysis. Erythrocyte superoxide dismutase and glutathione peroxidase enzyme activities were measured by spectrophotometric assays. Plasma total thiols, carbonyl contents and malondialdehyde were assessed by spectrophotometric and fluorometric assays. RESULTS: A significant impairment of all glutathione forms was detected in patients, including a profound decrease of total and reduced glutathione (GSH) associated with high levels of all oxidized glutathione forms (GSSG+GS-Pro; OX). These findings negatively correlated with the glutathione peroxidase activity, which underwent a significant decrease in patients. After treatment with EPI-743, all patients showed a significant increase in reduced glutathione levels and 96% decrease of OX/GSH ratio. CONCLUSIONS: The data presented here strongly support glutathione as a "redox blood signature" in mitochondrial disorders and its use as a clinical trial endpoint in the development of mitochondrial disease therapies.
    Molecular Genetics and Metabolism 03/2013; 109(2). DOI:10.1016/j.ymgme.2013.03.011 · 2.83 Impact Factor
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