Population Difference in the Associations of KLOTH Promoter Methylation with Mild Cognitive Impairment in Xinjiang Uygur and Han Populations

Hypermethylation at CREBBP Is Associated with Cognitive Impairment in a Mexican American Cohort

BACKGROUND

The aging Mexican American (MA) population is the fastest growing ethnic minority group in the US. MAs have a unique metabolic-related risk for Alzheimer's disease (AD) and mild cognitive impairment (MCI), compared to non-Hispanic whites (NHW). This risk for cognitive impairment (CI) is multifactorial involving genetics, environmental, and lifestyle factors. Changes in environment and lifestyle can alter patterns and even possibly reverse derangement of DNA methylation (a form of epigenetic regulation).

OBJECTIVE

We sought to identify ethnicity-specific DNA methylation profiles that may be associated with CI in MAs and NHWs.

METHODS

DNA obtained from peripheral blood of 551 participants from the Texas Alzheimer's Research and Care Consortium was typed on the Illumina Infinium® MethylationEPIC chip array, which assesses over 850K CpG genomic sites. Within each ethnic group (N = 299 MAs, N = 252 NHWs), participants were stratified by cognitive status (control versus CI). Beta values, representing relative degree of methylation, were normalized using the Beta MIxture Quantile dilation method and assessed for differential methylation using the Chip Analysis Methylation Pipeline (ChAMP), limma and cate packages in R.

RESULTS

Two differentially methylated sites were significant: cg13135255 (MAs) and cg27002303 (NHWs) based on an FDR p < 0.05. Three suggestive sites obtained were cg01887506 (MAs) and cg10607142 and cg13529380 (NHWs). Most methylation sites were hypermethylated in CI compared to controls, except cg13529380 which was hypomethylated.

CONCLUSION

The strongest association with CI was at cg13135255 (FDR-adjusted p = 0.029 in MAs), within the CREBBP gene. Moving forward, identifying additional ethnicity-specific methylation sites may be useful to discern CI risk in MAs.

Epigenetic Peripheral Biomarkers for Early Diagnosis of Alzheimer’s Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and represents the leading cause of cognitive impairment and dementia in older individuals throughout the world. The main hallmarks of AD include brain atrophy, extracellular deposition of insoluble amyloid-β (Aβ) plaques, and the intracellular aggregation of protein tau in neurofibrillary tangles. These pathological modifications start many years prior to clinical manifestations of disease and the spectrum of AD progresses along a continuum from preclinical to clinical phases. Therefore, identifying specific biomarkers for detecting AD at early stages greatly improves clinical management. However, stable and non-invasive biomarkers are not currently available for the early detection of the disease. In the search for more reliable biomarkers, epigenetic mechanisms, able to mediate the interaction between the genome and the environment, are emerging as important players in AD pathogenesis. Herein, we discuss altered epigenetic signatures in blood as potential peripheral biomarkers for the early detection of AD in order to help diagnosis and improve therapy.

PTSD and the klotho longevity gene: Evaluation of longitudinal effects on inflammation via DNA methylation

BACKGROUND

Longevity gene klotho (KL) is associated with age-related phenotypes including lifespan, cardiometabolic disorders, cognition, and brain morphology, in part, by conferring protection against inflammation. We hypothesized that the KL/inflammation association might be altered in the presence of psychiatric stress and operate via epigenetic pathways. We examined KL polymorphisms, and their interaction with posttraumatic stress disorder (PTSD) symptoms, in association with KL DNA methylation in blood. We further examined KL DNA methylation as a predictor of longitudinal changes in a peripheral biomarker of inflammation (C-reactive protein; CRP).

METHODS

The sample comprised 309 white non-Hispanic military veterans (93.5 % male; mean age: 32 years, range: 19-65; 30 % PTSD per structured diagnostic interview); 111 were reassessed approximately two years later.

RESULTS

Analyses revealed a methylation quantitative trait locus at rs9527025 (C370S, previously implicated in numerous studies of aging) in association with a Cytosine-phosphate-Guanine site (cg00129557; B = -.65, p =  1.29 X 10^-20), located within a DNase hypersensitivity site in the body of KL. There was also a rs9527025 x PTSD severity interaction (B = .004, p = .035) on methylation at this locus such that the minor allele was associated with reduced cg00129557 methylation in individuals with few or no PTSD symptoms while this effect was attenuated in those with elevated levels of PTSD. Path models revealed that methylation at cg00129557 was inversely associated with CRP over time (B = -.14, p = .005), controlling for baseline CRP. There was also an indirect effect of rs9527025 X PTSD on subsequent CRP via cg00129557 methylation (indirect B = -.002, p = .033).

CONCLUSIONS

Results contribute to our understanding of the epigenetic correlates of inflammation in PTSD and suggest that KL methylation may be a mechanism by which KL genotype confers risk vs. resilience to accelerated aging in those experiencing traumatic stress.

Increased Plasma Level of Longevity Protein Klotho as a Potential Indicator of Cognitive Function Preservation in Patients With Schizophrenia

Cognitive impairments are a core feature of schizophrenia. Klotho is an anti-aging protein with demonstrated cognitive-enhancing effects on the brain. The purpose of this study was to investigate the differences in levels of plasma klotho between patients with schizophrenia and healthy controls, as well as the relationship between klotho level and cognitive function in patients. Forty patients with schizophrenia and 40 gender- and age-matched healthy individuals were recruited. Positive and Negative Syndrome Scale (PANSS) was used to assess the psychopathology of patients. A neuropsychological battery was performed to evaluate the cognitive function of participants. Plasma klotho was measured using enzyme-linked immunosorbent assay. We show that patients with schizophrenia performed worse in the neurocognitive tests than the healthy controls. The levels of plasma klotho were significantly higher in schizophrenia patients than in healthy controls (p < 0.001). In patients, plasma klotho levels were positively correlated with cognitive function with regard to attention (p = 0.010), working memory (p < 0.001), verbal memory (p = 0.044), executive function (p < 0.001), and composite cognitive score (p < 0.001). Stepwise linear regression analysis shows that executive function had the highest correlation with plasma klotho levels (β = 0.896, t = 8.290, p < 0.001). Collectively, these results indicate that anti-aging protein klotho may be implicated in the pathogenesis of schizophrenia, and increased klotho may act as a compensatory factor for the preservation of cognitive function in schizophrenia. Further studies are needed to investigate the dynamic changes of klotho and the mechanisms by which klotho modulates cognition in schizophrenia.

Association of multiple candidate genes with mild cognitive impairment in an elderly Chinese Uygur population in Xinjiang

BACKGROUND

Mild cognitive impairment (MCI) is a high-risk factor for Alzheimer's disease (AD). In the present study, we investigated the association of genetic polymorphisms of five genes (8-oxoguanine DNA glycosylase 1 (OGG1), bridging integrator 1 (BIN1), sortilin-related receptor 1 (SORL1), presenilin 2 (PSEN2) and nerve growth factor (NGF)) with MCI risk in a Xinjiang Uygur population. We also tested the relationship between the promoter methylation of genes OGG1 and dihydrolipoamide S-succinyltransferase (DLST) with MCI.

METHODS

This study involved 43 MCI patients and 125 controls. Genotyping was done by Sanger sequencing. DNA methylation assays used quantitative methylation-specific polymerase chain reaction.

RESULTS

We found that polymorphisms of five genes and the methylation of DLST and OGG1 genes were not associated with MCI (P > 0.05). Further subgroup analysis found that DLST hypomethylation was significantly associated with MCI in the carriers of apolipoprotein E (APOE) ε4 (P = 0.042). In the carriers of non-APOE ε4, DLST methylation levels were significantly lower in the male control group than in the female control group (p = 0.04). Meanwhile, among the non-APOE ε4 carriers younger than 75, OGG1 hypermethylation levels were significantly associated with MCI (P = 0.049). DLST methylation in female controls was significantly lower than that in male controls (P = 0.003). According to gender stratification, there was a significant positive correlation of fasting plasma glucose (FBG) and high-density lipoprotein (HDL) with OGG1 methylation in the female controls (FBG: P = 0.024; HDL: P = 0.033). There was a significant inverse correlation between low-density lipoprotein and DLST methylation in male MCI (P = 0.033). There was a significant positive correlation between HDL and DLST methylation levels in the female controls (P = 0.000).

CONCLUSIONS

This study was the first to discover that DLST promoter methylation interacted with APOE ε4 and thus affected the pathogenesis of MCI. In addition, OGG1 promoter methylation interacted with several other factors to increase the risk of MCI.

SLC39A8 is a risk factor for schizophrenia in Uygur Chinese: a case-control study

BACKGROUND

Schizophrenia is a severe mental disease with high morbidity and heritability. The SLC39A8 gene is located in 4q24 and encodes a protein that transports many metal ions. Multiple previous studies found that one of the most pleiotropic single nucleotide polymorphisms (SNPs) in SLC39A8, rs13107325, is associated with schizophrenia in the European population. However, the polymorphism of this locus is rare in other populations. In China, the Han Chinese and the Uygur Chinese are two ethnic populations that originate from different races.

METHODS

A case-control study was conducted with 983 schizophrenia cases and 1230 healthy controls of the Chinese Uygur population. To validate the most promising SNP, meta-analyses were conducted with the Han Chinese and the European PGC2 data sets reported previously.

RESULTS

A susceptible locus, rs10014145 (pallele = 0.014, pallele = 0.098 after correction; pgenotype = 0.004, pgenotype = 0.032 after correction) was identified in case-control study of the Chinese Uygur population. Further, the association between rs10014145 and schizophrenia was supported by a meta-analysis of Han and Uygur Chinese samples (pooled OR [95% CI] =1.10 [1.03-1.17], Z = 2.73, p = 0.006). The association between rs10014145 and schizophrenia was not significant in a meta-analysis of combined Chinese and European samples (pooled OR [95% CI] =1.07 [1.00-1.14], Z = 1.88, and p = 0.06). In addition, the "CCAC" haplotype of rs4698844-rs233814-rs13114343-rs151394 was significantly associated with schizophrenia in Uygur Chinese (P = 0.003, corrected p = 0.012).

CONCLUSIONS

The results of this study support that SLC39A8 is a susceptible gene for schizophrenia in the populations of Han Chinese and Uygur Chinese in China, further studies are suggested to validate the association.

Significant association of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) rs3846662 and sirtuin 1 (SIRT1) rs7895833 and apolipoprotein E (APOE) hypermethylation with mild cognitive impairment (MCI)

Our study investigated the association of five genes with MCI in the Xinjiang Uygur population in China. In addition, we also analyzed the association between APOE methylation and MCI.Forty-three MCI and 125 controls were included in the present study. Genotyping was done by Sanger sequencing. DNA methylation assay was done using quantitative methylation-specific polymerase chain reaction (qMSP).The distribution of HMGCR rs3846662 allele frequencies was significantly different between the MCI group and the control group (P = .04), especially in women (P = .032). Subgroup analysis showed that there was a statistically significant association of HMGCR rs3846662 with MCI in the non-APOE ε4 group (P = .024), especially in the females with non-APOE ε4. Similarly, HMGCR rs3846662 genotype and allele frequency in the ApoE E2 protein group were significantly different in the MCI group and the control group (genotype P = .021; allele P = .007). In addition, SIRT1 rs7895833 genotype frequency in the APOE ε4 group was found to be significantly different between the MCI and the control group (P = .005). We also observed a significant association of SIRT1 rs7895833 with MCI in the ApoE E4 protein subgroup (P = .005). In addition, APOE methylation levels were significantly different between the MCI group and the control group (P = .021), especially in men (P = .006). Subgroup analysis showed that APOE methylation levels were significantly associated with MCI in the non-APOE ε4 group (P = .009), especially in men (P = .015).This study found a significant association of HMGCR rs3846662 with MCI in females independent of APOE ε4. In contrast, we revealed that the association of SIRT1 rs7895833 with MCI was dependent on with APOE ε4. We also showed that hypermethylation of APOE in MCI was independent of APOE ε4.

The longevity gene Klotho is differentially associated with cognition in subtypes of schizophrenia

Cognitive impairment is a core feature of schizophrenia and impacts negatively the functioning of affected individuals. Cognitive decline correlates with aging, and is the primary cause of loss of independence and reduced quality of life. The klotho gene is a key modulator of aging, with expression deficiency resulting in premature aging, while overexpression extends lifespan and enhances cognition. A haplotype and functional human variant of the gene, KL-VS, increases expression and promotes longevity. KL-VS heterozygosity is associated with enhanced cognition and a larger volume of the right dorsolateral prefrontal cortex, a region involved in planning and decision-making, which is especially susceptible to shrinkage with age. We examined the effect of KL-VS heterozygosity on cognition in 497 schizophrenia patients and 316 healthy controls from the Western Australian Family Study of Schizophrenia (WAFSS) who had been comprehensively characterised by neurocognitive tests and classified into cognitively deficient (CD) and cognitively "spared" (CS) clusters. An older, cognitively normal population sample from the Health in Men Study (HIMS) was included to allow assessment of heterozygosity and memory in aged individuals. We show that heterozygosity is associated with better learning and memory in the younger WAFSS healthy controls but not in the aging HIMS sample. However, in schizophrenia patients, KL-VS has a selective effect on memory, with heterozygotes in CD and CS clusters performing worse than non-carriers. This effect was significant and more severe in the CD cluster, reinforcing the utility of subtyping patients into CD and CS clusters that may differ in their genetic underpinnings.

Genetic risk between the CACNA1I gene and schizophrenia in Chinese Uygur population

Background

Schizophrenia (SCZ) is a common mental disorder with high heritability, and genetic factors play a major role in the pathogenesis. Recent researches indicated that the CACNA1I involved in calcium channels probably affect the potential pathogenesis of SCZ.

Results

In this study, we attempted to investigate whether the CACNA1I gene contributes the risk to SCZ in the Uighur Chinese population, and performed a case-control study involving 985 patient samples and 1218 normal controls to analyze nine SNPs within the CACNA1I gene. Among these sites, six SNPs were significantly associated with SCZ in the allele distribution: rs132575 (adjusted P_allele = 0.039, OR = 1.159), rs713860 (adjusted P_allele = 0.039, OR = 0.792), rs738168 (adjusted P_allele = 0.039, OR = 0.785), rs136805 (adjusted P_allele = 0.014, OR = 1.212), rs5757760 (adjusted P_allele = 0.042, OR = 0.873) and rs5750871 (adjusted P_allele = 0.039, OR = 0.859). In addition, two SNPs turned to be risk factors for SCZ not only in the allele distribution, but also in the genotype distribution: rs132575 (adjusted P_genotype = 0.037) and rs136805 (adjusted P_genotype = 0.037).

Conclusions

Overall, the present study provided evidence that significant association exists between the CACNA1I gene and SCZ in the Uighur Chinese population, subsequent validation of functional analysis and genetic association studies are needed to further extend this study.

The relevance of α-KLOTHO to the central nervous system: Some key questions

α-Klotho is well described as an anti-aging protein, with critical roles in kidney function as a transmembrane co-receptor for FGF23, and as a soluble factor in serum. α-Klotho is also expressed in the choroid plexus, where it is released into the cerebrospinal fluid. Nonetheless, α-Klotho is also expressed in the brain parenchyma. Accumulating evidence indicates that this pool of α-Klotho, which we define as brain α-Klotho, may play important roles as a neuroprotective factor and in promoting myelination, thereby supporting healthy brain aging. Here we summarize what is known about brain α-Klotho before focusing on the outstanding scientific questions related to its function. We believe there is a need for in vitro studies designed to distinguish between brain α-Klotho and other pools of α-Klotho, and for a greater understanding of the basic function of soluble α-Klotho. The mechanism by which the human KL-VS variant affects cognition also requires further elucidation. To help address these questions we suggest some experimental approaches that other laboratories might consider. In short, we hope to stimulate fresh ideas and encourage new research approaches that will allow the importance of α-Klotho for the aging brain to become clear.

Rhein reverses Klotho repression via promoter demethylation and protects against kidney and bone injuries in mice with chronic kidney disease

Rhein is an anthraquinone compound isolated from the medicinal plant rhubarb and mainly used in the clinical treatment of diabetic nephropathy. Rhein exhibits various renoprotective functions, but the underlying mechanisms are not fully determined. However, its renoprotective properties recapitulate the role of Klotho, a renal-specific antiaging protein critical for maintaining kidney homeostasis. Here we explored the connections between rhein renoprotection and Klotho in a mouse model of adenine-induced chronic kidney disease. In addition to being an impressive Klotho upregulator, rhein remarkably reversed renal Klotho deficiency in adenine-treated mice. This effect was associated with significant improvement in disturbed serum biochemistry, profibrogenic protein expression, and kidney and bone damage. Further investigation of the molecular basis of Klotho loss revealed that these kidneys displayed marked inductions of DNA methyltransferase DNMT1/DNMT3a and Klotho promoter hypermethylation, whereas rhein treatment effectively corrected these alterations. The renal protective effects of rhein were largely abolished when Klotho was knocked-down by RNA interferences, suggesting that rhein reversal of Klotho deficiency is essential for its renoprotective actions. Thus, our study clarifies how rhein regulation of Klotho expression contributes to its renoprotection and brings new insights into Klotho-targeted strategy for the treatment of kidney diseases of various etiologies.