The MTHFR C677T polymorphism contributes to an increased risk for vascular dementia: A meta-analysis

Plcg2M28L Interacts With High Fat/High Sugar Diet to Accelerate Alzheimer’s Disease-Relevant Phenotypes in Mice

Obesity is recognized as a significant risk factor for Alzheimer’s disease (AD). Studies have supported the notion that obesity accelerates AD-related pathophysiology in mouse models of AD. The majority of studies, to date, have focused on the use of early-onset AD models. Here, we evaluate the impact of genetic risk factors on late-onset AD (LOAD) in mice fed with a high fat/high sugar diet (HFD). We focused on three mouse models created through the IU/JAX/PITT MODEL-AD Center. These included a combined risk model with APOE4 and a variant in triggering receptor expressed on myeloid cells 2 (Trem2^R47H). We have termed this model, LOAD1. Additional variants including the M28L variant in phospholipase C Gamma 2 (Plcg2^M28L) and the 677C > T variant in methylenetetrahydrofolate reductase (Mthfr^{677C >T}) were engineered by CRISPR onto LOAD1 to generate LOAD1.Plcg2^M28L and LOAD1.Mthfr^{677C >T}. At 2 months of age, animals were placed on an HFD that induces obesity or a control diet (CD), until 12 months of age. Throughout the study, blood was collected to assess the levels of cholesterol and glucose. Positron emission tomography/computed tomography (PET/CT) was completed prior to sacrifice to image for glucose utilization and brain perfusion. After the completion of the study, blood and brains were collected for analysis. As expected, animals fed a HFD, showed a significant increase in body weight compared to those fed a CD. Glucose increased as a function of HFD in females only with cholesterol increasing in both sexes. Interestingly, LOAD1.Plcg2^M28L demonstrated an increase in microglia density and alterations in regional brain glucose and perfusion on HFD. These changes were not observed in LOAD1 or LOAD1.Mthfr^{677C >T} animals fed with HFD. Furthermore, LOAD1.Plcg2^M28L but not LOAD1.Mthfr^{677C >T} or LOAD1 animals showed transcriptomics correlations with human AD modules. Our results show that HFD affects the brain in a genotype-specific manner. Further insight into this process may have significant implications for the development of lifestyle interventions for the treatment of AD.

Hyperhomocysteinemia and Dementia Associated With Severe Cortical Atrophy, but No Amyloid Burden

We report a case of a 77 years old patient who was admitted to our memory clinic because of progressive gait impairment and amnestic cognitive decline associated with extrapyramidal symptoms and behavioral changes. The clinical picture was consistent with a possible diagnosis of Alzheimer's Disease associated with parkinsonian symptoms or with a Parkinson Plus syndrome. After a complete investigation, she was found to have a high plasma level of homocysteine due to homozygous methylene-tetrahydrofolate reductase (MTHFR) gene C665 T polymorphism, cognitive and motor impairment were associated with a severe cortical atrophy and mild subcortical vascular disease. PET neuroimaging excluded a significant amyloid load. Clinically, she showed improvement of the movement disorder and functional status after folate integration plus levodopa and memantine administration. We concluded for a primary degenerative dementia with movement impairment associated with persistent hyperhomocysteinemia. We hypothesized that neurodegeneration is driven by mechanisms linked to homocysteine metabolism possibly associated with tauopathy.

Genetic Variants and Oxidative Stress in Alzheimer's Disease

In an aging society, the number of people suffering from Alzheimer's Disease (AD) is still growing. Currently, intensive research is being carried out on the pathogenesis of AD. The results of these studies indicated that oxidative stress plays an important role in the onset and development of this disease. Moreover, in AD oxidative stress is generated by both genetic and biochemical factors as well as the functioning of the systems responsible for their formation and removal. The genetic factors associated with the regulation of the redox system include TOMM40, APOE, LPR, MAPT, APP, PSEN1 and PSEN2 genes. The most important biochemical parameters related to the formation of oxidative species in AD are p53, Homocysteine (Hcy) and a number of others. The formation of Reactive Oxygen Species (ROS) is also related to the efficiency of the DNA repair system, the effectiveness of the apoptosis, autophagy and mitophagy processes as well as the antioxidant potential. However, these factors are responsible for the development of many disorders, often with similar clinical symptoms, especially in the early stages of the disease. The discovery of markers of the early diagnosis of AD may contribute to the introduction of pharmacotherapy and slow down the progression of this disease.

Pharmacokinetics of Sodium and Calcium Salts of (6S)-5-Methyltetrahydrofolic Acid Compared to Folic Acid and Indirect Comparison of the Two Salts

(6S)-5-Methyltetrahydrofolic acid ((6S)-5-Methyl-THF) salts and folic acid may differ in their abilities to raise plasma (6S)-5-Methyl-THF levels. We compared the area under the curve (AUC), C_max, and T_max of plasma (6S)-5-Methyl-THF after intakes of (6S)-5-Methyl-THF-Na salt (Arcofolin^®) and folic acid. Moreover, we compared the AUCs after intakes of (6S)-5-Methyl-THF-Na and the calcium salt, (6S)-5-Methyl-THF-Ca, that were tested against folic acid in two independent studies. The study was randomized, double blind, and cross over. Twenty-four adults (12 men and 12 women) received a single oral dose of 436 µg (6S)-5-Methyl-THF-Na and an equimolar dose of folic acid (400 µg) on two kinetic days with two weeks washout period in between. The plasma concentrations of (6S)-5-Methyl-THF were measured at 9 time points between 0 and 8 h. We found that the AUC_{0–8 h} of plasma (6S)-5-Methyl-THF (mean (SD) = 126.0 (33.6) vs. 56.0 (25.3) nmol/L*h) and C_max (36.8 (10.8) vs. 11.1 (4.1) nmol/L) were higher after administration of (6S)-5-Methyl-THF-Na than after the administration of folic acid (p < 0.001 for both). These differences were present in men and women. Only administration of folic acid resulted in a transient increase in plasma unmetabolized folic acid (2.5 (2.0) nmol/L after 0.5 h and 4.7 (2.9) nmol/L after 1 h). Intake of (6S)-5-Methyl-THF-Na was safe. The ratios of the AUC_{0–8 h} for (6S)-5-Methyl-THF-Na and (6S)-5-Methyl-THF-Ca to the corresponding folic acid reference group and the delta of these AUC_{0–8 h} did not differ between the studies. In conclusion, a single oral dose of (6S)-5-Methyl-THF-Na caused higher AUC_{0–8 h} and C_max of plasma (6S)-5-Methyl-THF compared to folic acid. The Na- and Ca- salts of (6S)-5-Methyl-THF are not likely to differ in their pharmacokinetics. Further studies may investigate whether supplementation of the compounds for a longer time will lead to differences in circulating or intracellular/tissue folate concentrations.

Genetic architecture of common non-Alzheimer's disease dementias

Frontotemporal dementia (FTD), dementia with Lewy bodies (DLB) and vascular dementia (VaD) are the most common forms of dementia after Alzheimer’s disease (AD). The heterogeneity of these disorders and/or the clinical overlap with other diseases hinder the study of their genetic components. Even though Mendelian dementias are rare, the study of these forms of disease can have a significant impact in the lives of patients and families and have successfully brought to the fore many of the genes currently known to be involved in FTD and VaD, starting to give us a glimpse of the molecular mechanisms underlying these phenotypes. More recently, genome-wide association studies have also pointed to disease risk-associated loci. This has been particularly important for DLB where familial forms of disease are very rarely described. In this review we systematically describe the Mendelian and risk genes involved in these non-AD dementias in an effort to contribute to a better understanding of their genetic architecture, find differences and commonalities between different dementia phenotypes, and uncover areas that would benefit from more intense research endeavors.

MTHFR Gene Mutations Correlate with White Matter Disease Burden and Predict Cerebrovascular Disease and Dementia

The incidence of dementia is on the rise and expected to continue to increase in the foreseeable future. Two of the most common subtypes of dementia are Alzheimer's subtype and vascular dementia. Hyperhomocysteinemia has been shown to serve as a risk factor for dementia due to an associated blood-brain barrier dysfunction and subsequent small-vessel disease pathology. There are varying causes for hyperhomocysteinemia, including genetic and dietary, among others. We highlight the importance of identifying hyperhomocysteinemia as a potential etiologic and therapeutic target for the most common subtypes of dementia.

Genetic factors associated with the predisposition to late onset Alzheimer's disease

BACKGROUND

Alzheimer's disease is a progressive, irreversible neurodegenerative disorder characterized by loss of memory and cognitive skills. More than 90% of cases are sporadic and have later age of onset. Many studies have shown a genetic predisposition for late onset Alzheimer's disease (LOAD). The most studied genetic predisposition factor is apolipoprotein E gene besides other susceptibility genes involved in vascular pathologies, homocysteine metabolism, and neuronal growth and differentiation such as methylenetetrahydrofolate reductase (MTHFR), angiotensin-converting enzyme (ACE), APOB and brain derived neurotrophic factor (BDNF).

METHODS

In this study Factor V Leiden (G1691A) and H1299R, prothrombin G20210A, Factor XIII V34L, B-fibrinogen -455G>A, PAI-1 5G/4G, HPA1 b/a, MTHFR C677T, MTHFR A1298C, APOE, ACE I/D, BDNF C270T and G196A polymorphisms were evaluated in 100 LOAD patients and 100 age matched healthy controls.

RESULTS

APOE4 allele, MTHFR CC^A1298C and BDNF TT^C270T genotypes were significantly higher in LOAD patients compared to the control group (p < 0.001, p = 0.04, p = 0.03, respectively). There were no significant associations between other genotypes and allele frequencies. Mini-Mental State Examination (MMSE) scores and age at onset of the patients were also evaluated for each and combined genotypes. Age at onset was significantly lowered by about approximately 4 and 5 years in patients carrying BDNF TT^C270T and MTHFR TT^C677T genotypes, respectively.

CONCLUSION

APOE, MTHFR A1298C and BDNF C270T polymorphisms may be associated with LOAD and BDNF and MTHFR alleles may play a role in the age at onset of the LOAD.

Genetics in vascular dementia

Vascular dementia (VaD) is a common disorder that encompasses heterogeneous entities, which creates challenges in order to reach a global consensus for diagnostic criteria. While the genetic basis for sporadic VaD remains poorly understood, the identification of causal genes in monogenic forms of VaD sheds light on the pathophysiological mechanisms of VaD. This special report describes progress in genetic research on monogenic and sporadic VaD, as well as on associated phenotypes, such as cerebral small vessel disease, stroke and Alzheimer's disease. Methodological issues (e.g., small-size studies) and strategies to overcome these problems (e.g., collaborative consortiums, endophenotypes) are discussed. Lastly, future perspectives in the field and how such work could benefit patients and clinicians are mentioned.

A Validation Study of Vascular Cognitive Impairment Genetics Meta-Analysis Findings in an Independent Collaborative Cohort

Vascular cognitive impairment (VCI), including its severe form, vascular dementia (VaD), is the second most common form of dementia. The genetic etiology of sporadic VCI remains largely unknown. We previously conducted a systematic review and meta-analysis of all published genetic association studies of sporadic VCI prior to 6 July 2012, which demonstrated that APOE (ɛ4, ɛ2) and MTHFR (rs1801133) variants were associated with susceptibility for VCI. De novo genotyping was conducted in a new independent relatively large collaborative European cohort of VaD (nmax = 549) and elderly non-demented samples (nmax = 552). Where available, genotype data derived from Illumina's 610-quad array for 1210 GERAD1 control samples were also included in analyses of genes examined. Associations were tested using the Cochran-Armitage trend test: MTHFR rs1801133 (OR = 1.36, 95% CI 1.16-1.58, p = <0.0001), APOE rs7412 (OR = 0.62, 95% CI 0.42-0.90, p = 0.01), and APOE rs429358 (OR = 1.59, 95% CI 1.17-2.16, p = 0.003). Association was also observed with APOE epsilon alleles; ɛ4 (OR = 1.85, 95% CI 1.35-2.52, p = <0.0001) and ɛ2 (OR = 0.67, 95% CI 0.46-0.98, p = 0.03). Logistic regression and Bonferroni correction in a subgroup of the cohort adjusted for gender, age, and population maintained the association of APOE rs429358 and ɛ4 allele.

Genetics of vascular dementia - review from the ICVD working group

BACKGROUND

Vascular dementia is a common disorder resulting in considerable morbidity and mortality. Determining the extent to which genes play a role in disease susceptibility and their pathophysiological mechanisms could improve our understanding of vascular dementia, leading to a potential translation of this knowledge to clinical practice.

DISCUSSION

In this review, we discuss what is currently known about the genetics of vascular dementia. The identification of causal genes remains limited to monogenic forms of the disease, with findings for sporadic vascular dementia being less robust. However, progress in genetic research on associated phenotypes, such as cerebral small vessel disease, Alzheimer's disease, and stroke, have the potential to inform on the genetics of vascular dementia. We conclude by providing an overview of future developments in the field and how such work could impact patients and clinicians.

CONCLUSION

The genetic background of vascular dementia is well established for monogenic disorders, but remains relatively obscure for the sporadic form. More work is needed for providing robust findings that might eventually lead to clinical translation.

Meta-Prediction of the Effect of Methylenetetrahydrofolate Reductase Polymorphisms and Air Pollution on Alzheimer's Disease Risk

Background: Alzheimer's disease (AD) is a significant public health issue. AD has been linked with methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, but the findings have been inconsistent. The purpose of this meta-predictive analysis is to examine the associations between MTHFR polymorphisms and epigenetic factors, including air pollution, with AD risk using big data analytics approaches. Methods and Results: Forty-three studies (44 groups) were identified by searching various databases. MTHFR C677T TT and CT genotypes had significant associations with AD risk in all racial populations (RR = 1.13, p = 0.0047; and RR = 1.12, p < 0.0001 respectively). Meta-predictive analysis showed significant increases of percentages of MTHFR C677T polymorphism with increased air pollution levels in both AD case group and control group (p = 0.0021-0.0457); with higher percentages of TT and CT genotypes in the AD case group than that in the control group with increased air pollution levels. Conclusions: The impact of MTHFR C677T polymorphism on susceptibility to AD was modified by level of air pollution. Future studies are needed to further examine the effects of gene-environment interactions including air pollution on AD risk for world populations.

Genetic and environmental factors in vascular dementia: an update of blood brain barrier dysfunction

Vascular dementia (VaD) describes a combination of both cognitive and behavioural manifestations associated with variable brain lesions of vascular origin. While vascular risk factors have been implicated in VaD, the relationship is most evident when the factors are considered together and not individually. This review will examine the significance of the integrity of blood brain barrier (BBB) tight junction (TJ) proteins - occludin and claudins in the pathophysiology of VaD. Specifically, some of the genetic contributors to VaD, namely those responsible for the integrity of the BBB, will be reviewed in detail. Moreover, environmental factors will be considered in conjunction with these genes to examine how the interaction of environmental and genetic factors contributes to one's susceptibility to VaD.

Causes, Consequences and Public Health Implications of Low B-Vitamin Status in Ageing

The potential protective roles of folate and the metabolically related B-vitamins (vitamins B12, B6 and riboflavin) in diseases of ageing are of increasing research interest. The most common cause of folate and riboflavin deficiencies in older people is low dietary intake, whereas low B12 status is primarily associated with food-bound malabsorption, while sub-optimal vitamin B6 status is attributed to increased requirements in ageing. Observational evidence links low status of folate and the related B-vitamins (and/or elevated concentrations of homocysteine) with a higher risk of degenerative diseases including cardiovascular disease (CVD), cognitive dysfunction and osteoporosis. Deficient or low status of these B-vitamins alone or in combination with genetic polymorphisms, including the common MTHFR 677 C → T polymorphism, could contribute to greater disease risk in ageing by causing perturbations in one carbon metabolism. Moreover, interventions with the relevant B-vitamins to optimise status may have beneficial effects in preventing degenerative diseases. The precise mechanisms are unknown but many have been proposed involving the role of folate and the related B-vitamins as co-factors for one-carbon transfer reactions, which are fundamental for DNA and RNA biosynthesis and the maintenance of methylation reactions. This review will examine the evidence linking folate and related B-vitamins with health and disease in ageing, associated mechanisms and public health implications.

Association of interleukin-10 polymorphisms with risk factors of Alzheimer's disease and other dementias (SADEM study)

Some studies have reported a genetic association between single nucleotide polymorphisms (SNPs) in the promoter region of Interleukin (IL) 10 and Alzheimer's disease (AD), with conflicting results. To further investigate the proposed association and to clarify the role of cytokines as a potential cause for AD susceptibility, we analyzed genotypes, allele distributions and haplotypes of IL-10 promoter polymorphisms -1082 (rs1800896) and -819 (rs1800871) in a Mexican population: 986 normal controls and 221 cases divided as follows: 122 with Alzheimer disease (AD), 67 with (VaD) and 32 with mixed dementia (AD/VaD). Patients with dementia showed increased frequency of "ATA, CTG, and CTA" haplotypes when compared to controls. We identified two risk haplotypes: ATA (OR=3.56, 95%CI=2.84-4.45, p<0.0001), and CTA (OR=1.90, 95%CI=1.38-2.62, p<0.0001), and four protection haplotypes: ATG (OR=0.60, 95%CI=0.45-0.82, p=0.0012), CTG (OR=0.38, 95%CI=0.23-0.62, p<0.0001), ACG (OR=0.01, 95%CI=0.002-1.13, p<0.0001), and CCG (OR=0.02, 95%CI=0.004-0.203, p<0.0001). In summary, this is the first study in Mexican population that considers the analysis of IL-10 in patients with AD, VaD and AD/VaD. Our results showed the relevance of the role that IL-10 plays in the pathological mechanisms that result in the development of dementia. In addition, in our study, it was possible to distinguish two protective and two risk haplotypes for the development of dementia.

Genetic susceptibility to vascular cognitive impairment: a pathophysiological view

The heterogeneity of the vascular cognitive impairment (VCI) creates challenges for research on its genetic basis and pathophysiology. Despite well-known monogenic forms may be useful to understand some pathogenic mechanisms leading to VCI, most of VCIs are sporadic disorders resulting from the interaction between environmental, vascular and genetic factors. Genetic investigation for VCI may encompass both candidate genes that affect critical biological processes to VCI and common and rare genetic variants identified across the entire genome study technology, thereby enabling us to confirm or expose new biological mechanisms in VCI and develop new therapeutic and preventive approaches. Notwithstanding genetic susceptibility to VCI remains largely unknown owing to methodological issues. Collaborative efforts emerge as an interesting strategy to overcome these problems.

The relationship between hyperhomocysteinemia and neurodegeneration

Homocysteine (Hcy) is a key junction in methionine metabolism. In inherited forms of hyperhomocysteinemia patients develop early vascular damage and cognitive decline. Hyperhomocysteinemia is a common consequence of dietary, behavioral and pathological conditions and is epidemiologically related to different diseases, among them neurodegenerative ones are receiving progressively more attention in the last years. Several detrimental mechanisms that see in Hcy a possible promoter seem to be implicated in neurodegeneration (protein structural and functional modifications, oxidative stress, cellular metabolic derangements, epigenetic modifications, pathological aggregates deposition, endothelial damage and atherothrombosis). Interventional studies exploring B group vitamins administration in terms of prevention of Hcy-related cognitive decline and cerebrovascular involvement have shown scant results. In this review, current and possible alternative/complementary approaches are discussed.

Vascular dementia

Vascular dementia is one of the most common causes of dementia after Alzheimer's disease, causing around 15% of cases. However, unlike Alzheimer's disease, there are no licensed treatments for vascular dementia. Progress in the specialty has been difficult because of uncertainties over disease classification and diagnostic criteria, controversy over the exact nature of the relation between cerebrovascular pathology and cognitive impairment, and the paucity of identifiable tractable treatment targets. Although there is an established relation between vascular and degenerative Alzheimer's pathology, the mechanistic link between the two has not yet been identified. This Series paper critiques some of the key areas and controversies, summarises treatment trials so far, and makes suggestions for what progress is needed to advance our understanding of pathogenesis and thus maximise opportunities for the search for new and effective management approaches.

Folate Pathway Gene Methylenetetrahydrofolate Reductase C677T Polymorphism and Alzheimer Disease Risk in Asian Population

The association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and susceptibility to Alzheimers disease (AD) was controversial in previous studies. The present meta-analysis was designed to investigate the association of MTHFR C677T polymorphism with AD. Nine studies were identified by search of PubMed, Google Scholar, Elsevier, Springer Link databases, up to January 2013. Odds ratios (ORs) with corresponding 95 % confidence interval (CI) were calculated using fixed effects model or random effects model. All statistical analysis was done by Mix version 1.7. MTHFR C677T polymorphism had a significant association with susceptibility to AD in all genetic models (for T vs C: OR 1.29, 95 % CI 1.15-1.44, p < 0.0001; for TT + CT vs CC: OR 1.38, 95 % CI 1.16-1.364, p = 0.0002; for TT vs CC: OR 1.60, 95 % CI 1.25-2.04, p = 0.0001; for CT vs CC: OR 1.28, 95 % CI 1.1-1.53, p < 0.008; for TT vs CT + CC: OR 1.37, 95 % CI 1.12-1.67, p = 0.002). Results from present meta-analysis supported that the MTHFR C677T polymorphism was associated with an increased risk of AD in Asian population.

Association Between MTHFR Gene Polymorphisms, Smoking, and the Incidence of Vascular Dementia

This study investigated the relationship between N5,N10-methylene tetrahydrofolic acid reductase (MTHFR) polymorphisms, smoking, and vascular dementia (VD). Polymerase chain reaction-restriction fragment length polymorphism analysis was used to analyze the frequency of the C/T polymorphism at position 677 of the MTHFR gene in 304 VD patients and 300 control patients with nondementia cerebral infarction. The CC, CT, and TT genotype frequencies of the MTHFR gene were 43.42%, 32.57%, and 24.01%, respectively, in the VD group, and 50.67%, 32.00%, and 17.33%, respectively, in the control group. The T allele frequency was significantly higher in the VD group than in the control group ( P < .05). Among patients who smoked, the relative risk of VD in patients with the TT genotype and T allele was higher than in the control group ( P < .05). Therefore, the smoking group with the T allele has the highest risk of VD, and synergy appears to exist between the MTHFR gene polymorphisms and smoking in susceptibility to VD.

Is the prevalence of MTHFR C677T polymorphism associated with ultraviolet radiation in Eurasia?

The methylenetetrahydrofolic acid reductase (MTHFR) C677T polymorphism causes an amino-acid change from alanine to valine and results in the enzyme becoming thermolabile and half decreased activity. Its prevalence varies among global population. We collected data about MTHFR C677T polymorphism prevalence from epidemiology studies, as well as ultraviolet (UV) radiations and some other climatological factors from the internet. The results of the correlation and quadric regression showed that there was inverse U-shape relationship between T allele frequency and UV radiation. The explanatory power of UV radiation was stronger than latitude and all climatological factors. Our results supported the hypothesis that the distribution pattern of MTFHR C677T polymorphism in Eurasia might be the result of interaction of genetic and environmental natural selection, especially the UV radiation.

Pathology supported genetic testing and treatment of cardiovascular disease in middle age for prevention of Alzheimer's disease

Chronic, multi-factorial conditions caused by a complex interaction between genetic and environmental risk factors frequently share common disease mechanisms, as evidenced by an overlap between genetic risk factors for cardiovascular disease (CVD) and Alzheimer's disease (AD). Single nucleotide polymorphisms (SNPs) in several genes including ApoE, MTHFR, HFE and FTO are known to increase the risk of both conditions. The E4 allele of the ApoE polymorphism is the most extensively studied risk factor for AD and increases the risk of coronary heart disease by approximately 40%. It furthermore displays differential therapeutic responses with use of cholesterol-lowering statins and acetylcholinesterase inhibitors, which may also be due to variation in the CYP2D6 gene in some patients. Disease expression may be triggered by gene-environment interaction causing conversion of minor metabolic abnormalities into major brain disease due to cumulative risk. A growing body of evidence supports the assessment and treatment of CVD risk factors in midlife as a preventable cause of cognitive decline, morbidity and mortality in old age. In this review, the concept of pathology supported genetic testing (PSGT) for CVD is described in this context. PSGT combines DNA testing with biochemical measurements to determine gene expression and to monitor response to treatment. The aim is to diagnose treatable disease subtypes of complex disorders, facilitate prevention of cumulative risk and formulate intervention strategies guided from the genetic background. CVD provides a model to address the lifestyle link in most chronic diseases with a genetic component. Similar preventative measures would apply for optimisation of heart and brain health.

MTHFR (677 and 1298) and IL-6-174 G/C genes in pathogenesis of Alzheimer's and vascular dementia and their epistatic interaction

Genetic risk factors play an important role in the pathogenesis of Alzheimer disease (AD) and vascular dementia (VaD). In this case-control study, we examined C677T and A1298C (rs1801133 and rs1801131) polymorphism in the methylenetetrahydrofolate reductase (MTHFR) genes and their correlation with plasma levels of homocysteine (Hcy) in AD and VaD cases and evaluated the gene-gene interaction (epistasis) with IL-6-174 G/C (rs1800795). CC genotype was associated with elevated levels of plasma homocysteine (p = 0.004) as compared with genotype AA of rs1801131. In AD, we observed a significant (p = 0.04) association with C alleles of rs1801131. Regression analysis revealed that the presence of both rs1801133 T and rs1800795 C alleles increased the odds of developing AD by 2.5 and VaD by 3.7-fold. While rs1800795 (CC or GC) genotypes alone increased the odds of developing VaD by 2.2-fold, the presence of CC genotype of rs1801131 nullified this effect. The findings support the hypothesis that multiple genes are involved to alter the odds of developing AD and VaD.

Pharmacological investigations on potential of peroxisome proliferator-activated receptor-gamma agonists in hyperhomocysteinemia-induced vascular dementia in rats

The present study has been designed to investigate the potential of peroxisome proliferator-activated receptor-gamma ([PPAR]-γ) agonists, pioglitazone, and rosiglitazone in hyperhomocysteinemia-induced vascular dementia of rats. l-methionine was administered for 8 weeks to induce hyperhomocysteinemia and associated vascular dementia. Pioglitazone and rosiglitazone were administered to l-methionine-treated rats for 4 weeks (starting from 5th to 8th weeks of methionine treatment). Donepezil served as a positive control in this study. On 52nd day onward, the animals were exposed to Morris water maze (MWM) for testing learning and memory abilities. Vascular endothelial function, serum nitrite/nitrate levels, brain thiobarbituric acid reactive species (TBARS), brain reduced glutathione (GSH) levels, and brain acetylcholinesterase (AChE) activity were also measured. l-methionine-treated animals have shown impairment of learning, memory, endothelial function, decrease in serum nitrite/nitrate levels, and brain GSH levels along with increase in brain TBARS levels and AChE activity. Pioglitazone, rosiglitazone, and donepezil significantly improved hyperhomocysteinemia-induced impairment of learning, memory, endothelial dysfunction, and changes in various biochemical parameters. It is concluded that pioglitazone and rosiglitazone may be considered as potential pharmacological agents for the management of hyperhomocysteinemia-induced vascular dementia.

The -1082G/A polymorphism in IL-10 gene is associated with risk of Alzheimer's disease: a meta-analysis

BACKGROUND

The -1082G/A polymorphism in IL-10 gene has been extensively investigated for association to Alzheimer's disease (AD), however, results of different studies have been inconsistent. The objective of this study is to assess the relationship of IL-10 -1082G/A polymorphism and AD risk by using meta-analysis.

METHODS

All eligible case-control studies were searched in Pubmed and Embase. Odds ratios (OR) with the 95% confidence intervals (CI) were used to assess the association.

RESULTS

A total of 2158 cases and 2088 controls in 12 case-control studies were included. The results indicated that the A allele carriers (AA+AG) had a 27% increased risk of AD, when compared with the homozygote GG (OR=1.27, 95%CI=1.02-1.58 for AA+AG vs. GG). In the subgroup analysis by ethnicity, significant elevated risks were associated with A allele carriers in Europeans (OR=1.27 and 95%CI=1.01-1.59 for AA+AG vs. GG), but not in Asians (OR=1.37 and 95%CI=0.32-5.88 for AA+AG vs. GG).

CONCLUSIONS

This meta-analysis suggested that the -1082G/A polymorphism of IL-10 gene would be a risk factor for AD. To further evaluate gene-to-gene and gene-to-environmental interactions between polymorphisms of IL-10 gene and AD risk, more studies with large groups of patients are required.