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Mitochondria play an important role in the etiology of Parkinson's disease (PD). While mutations in the mitochondrial DNA (mtDNA) have been shown to accumulate in PD, no specific mtDNA polymorphisms have been associated with susceptibility or resistance to PD. A cytosine to adenine transversion at base pair 5178 in the mtDNA has been associated with increased longevity and resistance against a number of age related disorders and has been shown to decrease mitochondrial reactive oxygen species (ROS) production. We sought to determine whether 5178A is associated with resistance against PD in a Han Chinese population. To assess its association with PD, we genotyped 484 idiopathic PD patients and 710 control individuals for 5178C/A. Genotyping was performed using restriction fragment length polymorphism (RFLP) analysis. There was no significant association between 5178A and PD (P=0.308) when analyzing the entire population. However, sub-group analysis revealed that in males the frequency of 5178A was significantly lower in PD patients (27.7% in controls vs 20.0% in PD patients, P=0.027). Stratification of the population by age showed that this trend held across age groups but only reached statistical significance in males aged 60-70 (29.1% in controls vs 14.05 in PD patients, P=0.011). In conclusion, we demonstrated that the frequency of 5178A was significantly decreased in male PD patients in a Han Chinese population. This polymorphism may be associated with resistance against the development of PD when in combination with loci on the Y chromosome., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Background: A single nucleotide polymorphism in the mitochondrial gene encoding NADH dehydrogenase subunit 2 (mt-ND2) has been associated with reduced incidence of human type 1 diabetes (T1D). We identified the orthologue of this mitochondrial single nucleotide polymorphism in mouse and using NOD mouse models linked this genetic polymorphism to T1D resistance. The mechanism how this single nucleotide polymorphism affects the development of diabetes is studied using mouse models and beta cell lines., Methods: The impact of this single nucleotide polymorphism on mitochondrial function and resistance to reactive oxygen species was assessed. For these studies we measured oxygen consumption by isolated mitochondria under different doses of nitric oxide. In addition, alloxan sensitivity of beta cell lines was tested using the MTT method to measure cell survival., Results: mt-Nd2a is associated with protection against mouse T1D and alloxan-induced diabetes. Mice with mt-Nd2a exhibited resistance to transfer of diabetes by single clone of diabetogenic CD4+ or CD8+ T cells. Beta cell line with mt-Nd2a resist in vitro attack of diabetogenic CD8+ cytotoxic T cells, as well as free radicals generated by alloxan; isolated mitochondria with mt-Nd2a showed lower reactive oxygen species production and were more resistant to nitric oxide., Conclusion: mt-Nd2a protects against T1D in mouse models. The protection is at beta cell level and is associated with resistance against reactive oxygen species-mediated damage and death., (Copyright © 2011 John Wiley & Sons, Ltd.)

Objective: To investigate whether a single nucleotide polymorphism (SNP) in the mitochondrial gene for NADH dehydrogenase 2 (mt-Nd2) can modulate susceptibility to type 1 diabetes in NOD mice., Research Design and Methods: NOD/ShiLtJ mice conplastic for the alloxan resistant (ALR)/Lt-derived mt-Nd2(a) allele (NOD.mt(ALR)) were created and compared with standard NOD (carrying the mt-Nd2(c) allele) for susceptibility to spontaneous autoimmune diabetes, or to diabetes elicited by reciprocal adoptive splenic leukocyte transfers, as well as by adoptive transfer of diabetogenic T-cell clones. β-Cell lines derived from either the NOD (NIT-1) or the NOD.mt(ALR) (NIT-4) were also created to compare their susceptibility to cytolysis by diabetogenic CD8(+) T-cells in vitro., Results: NOD mice differing at this single SNP developed spontaneous or adoptively transferred diabetes at comparable rates and percentages. However, conplastic mice with the mt-Nd2(a) allele exhibited resistance to transfer of diabetes by the CD4(+) T-cell clone BDC 2.5 as well as the CD8(+) AI4 T-cell clones from T-cell receptor transgenic animals. NIT-4 cells with mt-Nd2(a) were also more resistant to AI4-mediated destruction in vitro than NIT-1 cells., Conclusions: Conplastic introduction into NOD mice of a variant mt-Nd2 allele alone was not sufficient to prevent spontaneous autoimmune diabetes. Subtle nonhematopoietic type 1 diabetes resistance was observed during adoptive transfer experiments with T-cell clones. This study confirms that genetic polymorphisms in mitochondria can modulate β-cell sensitivity to autoimmune T-cell effectors.

Reactive oxygen species (ROS) play a critical role in the pathogenesis of human diseases. A cytosine to adenine transversion in the mitochondrially encoded NADH dehydrogenase subunit 2 (mt-ND2, human; mt-Nd2, mouse) gene results in resistance against type 1 diabetes and several additional ROS-associated conditions. Our previous studies have demonstrated that the adenine-containing allele (mt-Nd2(a)) is also strongly associated with resistance against type 1 diabetes in mice. In this report we have confirmed that the cytosine-containing allele (mt-Nd2(c)) results in elevated mitochondrial ROS production. Using inhibitors of the electron transport chain, we show that when in combination with nuclear genes from the alloxan-resistant (ALR) strain, mt-Nd2(c) increases ROS from complex III. Furthermore, by using alamethicin-permeabilized mitochondria, we measured a significant increase in electron transport chain-dependent ROS production from all mt-Nd2(c)-encoding strains including ALR.mt(NOD), non-obese diabetic (NOD), and C57BL/6 (B6). Studies employing alamethicin and inhibitors were able to again localize the heightened ROS production in ALR.mt(NOD) to complex III and identified complex I as the site of elevated ROS production from NOD and B6 mitochondria. Using submitochondrial particles, we confirmed that in the context of the NOD or B6 nuclear genomes, mt-Nd2(c) elevates complex I-specific ROS production. In all assays mitochondria from mt-Nd2(a)-encoding strains exhibited low ROS production. Our data suggest that lowering overall mitochondrial ROS production is a key mechanism of disease protection provided by mt-Nd2(a).

Aims/hypothesis: ALR/Lt, a mouse strain with strong resistance to type 1 diabetes, is closely related to autoimmune type 1 diabetes-prone NOD/Lt mice. ALR pancreatic beta cells are resistant to the beta cell toxin alloxan, combinations of cytotoxic cytokines, and diabetogenic NOD T-cell lines. Reciprocal F1 hybrids between either ALR and NOD or ALR and NON/Lt, showed that alloxan resistance was transmitted to F1 progeny only when ALR was the maternal parent. Here we show that the mitochondrial genome (mtDNA) of ALR mice contributes resistance to diabetes., Methods: When F1 progeny from reciprocal outcrosses between ALR and NOD were backcrossed to NOD, a four-fold lower frequency of spontaneous type 1 diabetes development occurred when ALR contributed the mtDNA. Because of the apparent interaction between nuclear and mtDNA, the mitochondrial genomes were sequenced., Results: An ALR-specific sequence variation in the mt-Nd2 gene producing a leucine to methionine substitution at amino acid residue 276 in the NADH dehydrogenase 2 was discovered. An isoleucine to valine mutation in the mt-Co3 gene encoding COX3 distinguished ALR and NOD from NON and ALS. All four strains were distinguished by variation in a mt-encoded arginyl tRNA polyadenine tract. Shared alleles of mt-Co3 and mt-Tr comparing NOD and ALR allowed for exclusion of these two genes as candidates, implicating the mt-Nd2 variation as a potential ALR-derived type 1 diabetes protective gene., Conclusions/interpretation: The unusual resistance of ALR mice to both ROS-mediated and autoimmune type 1 diabete stresses reflects an interaction between the nuclear and mt genomes. The latter contribution is most likely via a single nucleotide polymorphism in mt-Nd2.