Fooling mother nature: epigenetics and novel treatments for psychiatric disorders

Epigenetics in Alzheimer's Disease: Perspective of DNA Methylation

Research over the years has shown that causes of Alzheimer's disease are not well understood, but over the past years, the involvement of epigenetic mechanisms in the developing memory formation either under pathological or physiological conditions has become clear. The term epigenetics represents the heredity of changes in phenotype that are independent of altered DNA sequences. Different studies validated that cytosine methylation of genomic DNA decreases with age in different tissues of mammals, and therefore, the role of epigenetic factors in developing neurological disorders in aging has been under focus. In this review, we summarized and reviewed the involvement of different epigenetic mechanisms especially the DNA methylation in Alzheimer's disease (AD), late-onset Alzheimer's disease (LOAD), familial Alzheimer's disease (FAD), and autosomal dominant Alzheimer's disease (ADAD). Down to the minutest of details, we tried to discuss the methylation patterns like mitochondrial DNA methylation and ribosomal DNA (rDNA) methylation. Additionally, we mentioned some therapeutic approaches related to epigenetics, which could provide a potential cure for AD. Moreover, we reviewed some recent studies that validate DNA methylation as a potential biomarker and its role in AD. We hope that this review will provide new insights into the understanding of AD pathogenesis from the epigenetic perspective especially from the perspective of DNA methylation.

Male-specific association between dopamine receptor D4 gene methylation and schizophrenia

Objective

The goal of our study was to investigate whether DRD4 gene DNA methylation played an important role in the susceptibility of Han Chinese SCZ.

Methods

Using the bisulphite pyrosequencing technology, DNA methylation levels of 6 CpG dinucleotides in DRD4 CpG island were measured among 30 paranoid SCZ patients, 30 undifferentiated SCZ patients, and 30 age- and gender-matched healthy controls.

Results

Strong correlation was observed among the six CpG sites (r>0.5, P<0.01), thus average methylation levels were applied thereafter. Our results indicated that there was a significant association between DRD4 methylation and the risk of SCZ (P = 0.003), although there was no significant difference in DRD4 methylation between the two SCZ subtypes (P = 0.670). A breakdown analysis by gender showed that the significant association of DRD4 methylation and SCZ was driven by males (P<0.001) but not by females (P = 0.835). DRD4 methylation was significantly associated with p300 in male SCZ patients (r = −0.543, P = 0.005) but not in female SCZ patients (r = 0.110, P = 0.599). Moreover, receiver operating characteristic (ROC) curves showed DRD4 methylation was able to predict the status of SCZ in males [area under curve (AUC) = 0.832, P = 0.002] but not in females (AUC = 0.483, P = 0.876). Finally, a further expression experiment showed that DRD4 methylation in the gene body was positively associated with gene expression, although the exact mechanism of gene regulation remained unknown for this interesting DRD4 methylation.

Conclusion

The gender disparity in the DRD4 DNA methylation provides novel insights into the pathogenesis of SCZ.

Metabolism as a key to histone deacetylase inhibition

There is growing interest in the epigenetic mechanisms that are dysregulated in cancer and other human pathologies. Under this broad umbrella, modulators of histone deacetylase (HDAC) activity have gained interest as both cancer chemopreventive and therapeutic agents. Of the first generation, FDA-approved HDAC inhibitors to have progressed to clinical trials, vorinostat represents a "direct acting" compound with structural features suitable for docking into the HDAC pocket, whereas romidepsin can be considered a prodrug that undergoes reductive metabolism to generate the active intermediate (a zinc-binding thiol). It is now evident that other agents, including those in the human diet, can be converted by metabolism to intermediates that affect HDAC activity. Examples are cited of short-chain fatty acids, seleno-α-keto acids, small molecule thiols, mercapturic acid metabolites, indoles, and polyphenols. The findings are discussed in the context of putative endogenous HDAC inhibitors generated by intermediary metabolism (e.g. pyruvate), the yin-yang of HDAC inhibition versus HDAC activation, and the screening assays that might be most appropriate for discovery of novel HDAC inhibitors in the future.