Association of the Mitochondrial DNA 16189 T to C Variant with Lacunar Cerebral Infarction: Evidence from a Hospital-Based Case-Control Study

G-quadruplex propensity in H. neanderthalensis, H. sapiens and Denisovans mitochondrial genomes

Current methods of processing archaeological samples combined with advances in sequencing methods lead to disclosure of a large part of H. neanderthalensis and Denisovans genetic information. It is hardly surprising that the genome variability between modern humans, Denisovans and H. neanderthalensis is relatively limited. Genomic studies may provide insight on the metabolism of extinct human species or lineages. Detailed analysis of G-quadruplex sequences in H. neanderthalensis and Denisovans mitochondrial DNA showed us interesting features. Relatively similar patterns in mitochondrial DNA are found compared to modern humans, with one notable exception for H. neanderthalensis. An interesting difference between H. neanderthalensis and H. sapiens corresponds to a motif found in the D-loop region of mtDNA, which is responsible for mitochondrial DNA replication. This area is directly responsible for the number of mitochondria and consequently for the efficient energy metabolism of cell. H. neanderthalensis harbor a long uninterrupted run of guanines in this region, which may cause problems for replication, in contrast with H. sapiens, for which this run is generally shorter and interrupted. One may propose that the predominant H. sapiens motif provided a selective advantage for modern humans regarding mtDNA replication and function.

Two Birds One Stone: The Neuroprotective Effect of Antidiabetic Agents on Parkinson Disease-Focus on Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitors

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease affecting more than 1% of the population over 65 years old. The etiology of the disease is unknown and there are only symptomatic managements available with no known disease-modifying treatment. Aging, genes, and environmental factors contribute to PD development and key players involved in the pathophysiology of the disease include oxidative stress, mitochondrial dysfunction, autophagic-lysosomal imbalance, and neuroinflammation. Recent epidemiology studies have shown that type-2 diabetes (T2DM) not only increased the risk for PD, but also is associated with PD clinical severity. A higher rate of insulin resistance has been reported in PD patients and is suggested to be a pathologic driver in this disease. Oral diabetic drugs including sodium-glucose cotransporter 2 (SGLT2) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, and dipeptidyl peptidase-4 (DPP-4) inhibitors have been shown to provide neuroprotective effects in both PD patients and experimental models; additionally, antidiabetic drugs have been demonstrated to lower incidence rates of PD in DM patients. Among these, the most recently developed drugs, SGLT2 inhibitors may provide neuroprotective effects through improving mitochondrial function and antioxidative effects. In this article, we will discuss the involvement of mitochondrial-related oxidative stress in the development of PD and potential benefits provided by antidiabetic agents especially focusing on sglt2 inhibitors.

Pandora's Box: mitochondrial defects in ischaemic heart disease and stroke

Ischaemic heart disease and stroke are vascular events with serious health consequences worldwide. Recent genetic and epigenetic techniques have revealed many genetic determinants of these vascular events and simplified the approaches to research focused on ischaemic heart disease and stroke. The pathogenetic mechanisms of ischaemic heart disease and stroke are complex, with mitochondrial involvement (partially or entirely) recently gaining substantial support. Not only can mitochondrial reactive oxygen species give rise to ischaemic heart disease and stroke by production of oxidised low-density lipoprotein and induction of apoptosis, but the impact on pericytes contributes directly to the pathogenesis. Over the past two decades, publications implicate the causative role of nuclear genes in the development of ischaemic heart disease and stroke, in contrast to the potential role of mitochondrial DNA (mtDNA) in the pathophysiology of the disorders, which is much less understood, although recent studies do demonstrate that the involvement of mitochondria and mtDNA in the development of ischaemic heart disease and stroke is likely to be larger than originally thought, with the novel discovery of links among mitochondria, mtDNA and vascular events. Here we explore the molecular events and mtDNA alterations in relation to the role of mitochondria in ischaemic heart disease and stroke.

Mitochondrial DNA D-loop AG/TC transition mutation in cortical neurons of mice after long-term exposure to nucleoside analogues

With the wide application of combined antiretroviral therapy, the prognosis of human immunodeficiency virus (HIV)-1 infected patient has been significantly improved. However, long-term administration of antiretroviral drugs can result in various drug-associated toxicities. Among them, nucleoside analogues were confirmed to inhibit DNA polymerase gamma, resulting in mitochondrial toxicity. Our previous study indicated that long-term exposure of mice to nucleoside analogue could induce mitochondria DNA (mtDNA) loss in cortical neurons. Herein, we further identify mitochondrial toxicity of four nucleoside analogues (zidovudine (AZT), stavudine (D4T), lamivudine (3TC), and didanosine (DDI)) by cloning and sequencing mtDNA D-loop region in mice neurons captured with laser capture microdissection. The results showed that mutation of neuronal mtDNA D-loop sequences increased in mice treated with each of the four nucleoside analogues for 4 months and D4T and DDI induced more severe D-loop lesion than the other two nucleoside analogues. The major type of D-loop point mutations induced by four nucleoside analogues was transition, in particular of "A→G" and "T→C" transition, but the point transition sites were variable. Our findings suggest that long-term exposure to nucleoside analogue can result in mtDNA D-loop region lesion in mouse cortical neurons.

The role of the mitochondrial genome in ageing and carcinogenesis

Mitochondrial DNA mutations and polymorphisms have been the focus of intensive investigations for well over a decade in an attempt to understand how they affect fundamental processes such as cancer and aging. Initial interest in mutations occurring in mitochondrial DNA of cancer cells diminished when most were found to be the same mutations which occurred during the evolution of human mitochondrial haplogroups. However, increasingly correlations are being found between various mitochondrial haplogroups and susceptibility to cancer or diseases in some cases and successful aging in others.

The mitochondrial T16189C polymorphism is associated with coronary artery disease in Middle European populations

Background

The pivotal role of mitochondria in energy production and free radical generation suggests that the mitochondrial genome could have an important influence on the expression of multifactorial age related diseases. Substitution of T to C at nucleotide position 16189 in the hypervariable D-loop of the control region (CR) of mitochondrial DNA (mtDNA) has attracted research interest because of its suspected association with various multifactorial diseases. The aim of the present study was to compare the frequency of this polymorphism in the CR of mtDNA in patients with coronary artery disease (CAD, n = 482) and type 2 diabetes mellitus (T2DM, n = 505) from two study centers, with healthy individuals (n = 1481) of Middle European descent in Austria.

Methodology and Principal Findings

CR polymorphisms and the nine major European haplogroups were identified by DNA sequencing and primer extension analysis, respectively. Frequencies and Odds Ratios for the association between cases and controls were calculated. Compared to healthy controls, the prevalence of T16189C was significantly higher in patients with CAD (11.8% vs 21.6%), as well as in patients with T2DM (11.8% vs 19.4%). The association of CAD, but not the one of T2DM, with T16189C remained highly significant after correction for age, sex and body mass index (BMI) and was independent of the two study centers.

Conclusions and Significance

Our results show for the first time a significant association of T16189C with CAD in a Middle European population. As reported in other studies, in patients with T2DM an association with T16189C in individuals of European decent remains questionable.

Mitochondrial haplogroup H1 is protective for ischemic stroke in Portuguese patients

BACKGROUND

The genetic contribution to stroke is well established but it has proven difficult to identify the genes and the disease-associated alleles mediating this effect, possibly because only nuclear genes have been intensely investigated so far. Mitochondrial DNA (mtDNA) has been implicated in several disorders having stroke as one of its clinical manifestations. The aim of this case-control study was to assess the contribution of mtDNA polymorphisms and haplogroups to ischemic stroke risk.

METHODS

We genotyped 19 mtDNA single nucleotide polymorphisms (SNPs) defining the major European haplogroups in 534 ischemic stroke patients and 499 controls collected in Portugal, and tested their allelic and haplogroup association with ischemic stroke risk.

RESULTS

Haplogroup H1 was found to be significantly less frequent in stroke patients than in controls (OR = 0.61, 95% CI = 0.45-0.83, p = 0.001), when comparing each clade against all other haplogroups pooled together. Conversely, the pre-HV/HV and U mtDNA lineages emerge as potential genetic factors conferring risk for stroke (OR = 3.14, 95% CI = 1.41-7.01, p = 0.003, and OR = 2.87, 95% CI = 1.13-7.28, p = 0.021, respectively). SNPs m.3010G>A, m.7028C>T and m.11719G>A strongly influence ischemic stroke risk, their allelic state in haplogroup H1 corroborating its protective effect.

CONCLUSION

Our data suggests that mitochondrial haplogroup H1 has an impact on ischemic stroke risk in a Portuguese sample.

Mitochondrial haplogroup A is a genetic risk factor for atherothrombotic cerebral infarction in Japanese females

Mitochondrion-derived reactive oxygen species possibly play an important role in the pathogenesis of atherosclerosis and atherothrombotic cerebral infarction, because mitochondria in vascular endothelial cells are the major site of superoxide production. In the present study, we surveyed mitochondrial haplogroups associated with atherothrombotic cerebral infarction in 1081 Japanese subjects. Twenty-six mitochondrial single nucleotide polymorphisms of 11 major mitochondrial haplogroups (F, B, A, N9a, M7a, M7b, M7c, G1, G2, D4, and D5) were determined by use of 28-plex PCR and fluorescent beads combined with sequence-specific oligonucleotide probes. Multivariate logistic regression analysis with adjustment for conventional risk factors revealed that mitochondrial haplogroup A was associated with atherothrombotic cerebral infarction in female subjects (P< 0.05). However, no significant association was detected for males. Our study shows that haplogroup A confers an increased risk of atherothrombotic cerebral infarction in Japanese females. Validation of our findings will require additional studies with independent subject panels.

Increased Oxidative Damage with Altered Antioxidative Status in Type 2 Diabetic Patients Harboring the 16189 T to C Variant of Mitochondrial DNA

A transition of T to C at nucleotide position 16189 in mitochondrial DNA (mtDNA) has attracted biomedical researchers for its probable correlation with the development of diabetes mellitus in adult life. In diabetes, persistent hyperglycemia may cause high production of free radicals. Reactive oxygen species are thought to play a role in a variety of physiologic and pathophysiologic processes in which increased oxidative stress may play an important role in disease mechanisms. The aim of the present study was to clarify the degree of oxidative damage and plasma antioxidant status in diabetic patients and to see the potential influence of the 16189 variant of mtDNA on the oxidative status in these patients. An indicative parameter of lipid peroxidation, malondialdehyde (MDA), and total free thiols were measured from plasma samples of 165 type 2 diabetic patients with or without this variant and 168 normal subjects. Here we report an increase in the plasma levels of MDA and total thiols in type 2 diabetic patients compared with control subjects. The levels of plasma thiols in diabetic patients with the 16189 variant of mtDNA were not different from those in controls. These results suggest an increase in the oxidative damage and a compensatory higher antioxidative status in patients with type 2 diabetes. Harboring the 16189 mtDNA variant may impair the ability of a cell to respond properly to oxidative stress and oxidative damage.

Mitochondrial microheteroplasmy and a theory of aging and age-related disease

We implicate a recently described form of mitochondrial mutation, mitochondrial microheteroplasmy, as a candidate for the principal component of aging. Microheteroplasmy is the presence of hundreds of independent mutations in one organism, with each mutation usually found in 1-2% of all mitochondrial genomes. Despite the low abundance of single mutations, the vast majority of mitochondrial genomes in all adults are mutated. This mutational burden includes inherited mutations, de novo germline mutations, as well as somatic mutations acquired either during early embryonic development or later in adult life. We postulate that microheteroplasmy is sufficient to explain the pathomechanism of several age-associated diseases, especially in conditions with known mitochondrial involvement, such as diabetes (DM), cardiovascular disease, Parkinson's disease (PD), and Alzheimer's disease (AD) and cancer. The genetic properties of microheteroplasmy reconcile the results of disease models (cybrids, hypermutable PolG variants and mitochondrial toxins), with the relatively low levels of maternal inheritance in the aforementioned diseases, and provide an explanation of their delayed, progressive course.

Gene polymorphism of platelet glycoprotein I balpha in Chinese patients with large- and small-artery subtypes of ischemic stroke

The platelet surface glycoprotein (GP) I balpha, an important part of the GP I b-IX-V complex, participates in the formation of thrombosis by initially mediating platelet adhesion under high shear stress. The purpose of present study was to investigate the association between gene polymorphism of GP I balpha (human platelet antigen 2, HPA2) and ischemic stroke in a matched case-control study. One hundred patients and 100 matched controls were enrolled in the study. The cases were divided into large- and small-vessel subtypes of ischemic stroke according to Trial of Org10172 in Acute Stroke Treatment criteria. Genotyping for GP I balpha polymorphism was documented by polymerase chain reaction amplification and restriction enzyme analysis. There were no statistically significant differences in the GP I balpha HPA2 genotype distribution between ischemic stroke group, large-vessel subtype group, small-vessel subtype group and corresponding control groups. The heterozygote genotype of GP I balpha HPA2 was more frequent in the large-vessel subtype group (16.1%) than in the small-vessel subtype group (10.1%), but the difference was not statistically significant. Ourresults suggest that the polymorphism of the GP I balpha HPA2 genotype might not be a genetic risk factor of ischemic stroke.