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: 9.67). 03/2009; 106(10):3941-5. DOI: 10.1073/pnas.0813409106
Source: PubMed


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.

Download full-text


Available from: Gregory M Enns
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Dec 2014 · Molecular Genetics and Metabolism Reports
  • Source
    • "However, prolonged exposure to elevated mitochondrial ROS can result in the depletion of GSH. Several recent studies showed that cellular GSH level is lower in patients with genetically inherited mitochondrial diseases compared with those of healthy individuals, suggesting that oxidative stress endpoints may also be key indicators of mitochondrial health (Atkuri et al., 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Mitochondrial perturbation has been recognized as a contributing factor to various drug-induced organ toxicities. To address this issue, we developed a high-throughput flow cytometry-based mitochondrial signaling assay to systematically investigate mitochondrial/cellular parameters known to be directly impacted by mitochondrial dysfunction: mitochondrial membrane potential (MMP), mitochondrial reactive oxygen species (ROS), intracellular reduced glutathione (GSH) level, and cell viability. Modulation of these parameters by a training set of compounds, comprised of established mitochondrial poisons and 60 marketed drugs (30 nM to 1mM), was tested in HL-60 cells (a human pro-myelocytic leukemia cell line) cultured in either glucose-supplemented (GSM) or glucose-free (containing galactose/glutamine; GFM) RPMI-1640 media. Post-hoc bio-informatic analyses of IC50 or EC50 values for all parameters tested revealed that MMP depolarization in HL-60 cells cultured in GSM was the most reliable parameter for determining mitochondrial dysfunction in these cells. Disruptors of mitochondrial function depolarized MMP at concentrations lower than those that caused loss of cell viability, especially in cells cultured in GSM; cellular GSH levels correlated more closely to loss of viability in vitro. Some mitochondrial respiratory chain inhibitors increased mitochondrial ROS generation; however, measuring an increase in ROS alone was not sufficient to identify mitochondrial disruptors. Furthermore, hierarchical cluster analysis of all measured parameters provided confirmation that MMP depletion, without loss of cell viability, was the key signature for identifying mitochondrial disruptors. Subsequent classification of compounds based on ratios of IC50s of cell viability:MMP determined that this parameter is the most critical indicator of mitochondrial health in cells and provides a powerful tool to predict whether novel small molecule entities possess this liability. © The Author 2014. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For permissions, please email: [email protected] /* */
    Preview · Article · Aug 2014 · Toxicological Sciences
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Jul 2014 · Microbes and Infection
Show more