Hippocampus neuronal metabolic gene expression outperforms whole tissue data in accurately predicting Alzheimer's disease progression

Protective effects of Huang-Lian-Jie-Du-Tang against A25-35-induced memory deficits and oxidative stress in rats

Objective

Huang-Lian-Jie-Du-Tang (HLJDT), a traditional Chinese medicine, improves cognitive ability in rat models of Alzheimer’s disease (AD). The objective of this study was to evaluate the protective effects of HLJDT on learning and memory impairment that are caused by Aβ_25–35.

Methods

Rats were randomly assigned to the following groups: control (water), Aβ_25–35, donepezil hydrochloride 1.05 mg/kg, HLJDT 6 g/kg, HLJDT 3 g/kg, and HLJDT 1.5 g/kg and the corresponding drugs were administered for 28 days by oral gavage. HLJDT for the prevention of Aβ_25–35-induced injury in rats and the underlying mechanisms were assessed. Aβ_25–35 and amyloid precursor protein (APP) levels were measured in the hippocampal specimens. Total superoxide dismutase (T-SOD), glutathione (GSH), and malondialdehyde (MDA) levels in the hippocampus were also measured. The ultrastructure of CA1 hippocampal region was observed using electron microscopy.

Results

HLJDT treatment ameliorated impaired learning and memory significantly, decreased Aβ_25–35, and APP levels in the hippocampus, increased T-SOD and GSH activity and decreased the MDA concentration, and alleviated the nuclear and cytoplasmic abnormalities of the hippocampal CA 1 region that were induced by Aβ_25–35 injection.

Conclusions

HLJDT might decrease hippocampal vulnerability to Aβ_25–35, suggesting its potential neuroprotective effect in AD.

Amyloid β perturbs elevated heme flux induced with neuronal development

Introduction

Heme is a central molecule in mitochondrial respiration and ATP generation in neuronal cells. Thus, we assessed the importance of altered heme metabolism in Alzheimer's disease (AD) pathogenesis.

Methods

To investigate the role of altered heme metabolism in AD, we identified heme-related proteins whose expression is altered in AD patients and mouse models exhibiting amyloid pathology. We detected the levels of proteins involved in heme synthesis, uptake, degradation, and function during neuronal differentiation and characterized the effects of Aβ.

Results

We found that the expression levels of the rate-limiting heme synthetic enzyme ALAS1 and heme degradation enzyme HO-2 are selectively decreased in AD patients and mice. Aβ selectively reduces the levels of HO-2 and heme degradation, which are elevated to support neuronal functions in fully differentiated neuronal cells.

Discussion

Our data show that lowered heme metabolism, particularly the decreased levels of heme degradation and HO-2, is likely a very early event in AD pathogenesis.

The Bioinformatic Analysis of the Dysregulated Genes and MicroRNAs in Entorhinal Cortex, Hippocampus, and Blood for Alzheimer's Disease

Aim

The incidence of Alzheimer's disease (AD) has been increasing in recent years, but there exists no cure and the pathological mechanisms are not fully understood. This study aimed to find out the pathogenesis of learning and memory impairment, new biomarkers, potential therapeutic targets, and drugs for AD.

Methods

We downloaded the microarray data of entorhinal cortex (EC) and hippocampus (HIP) of AD and controls from Gene Expression Omnibus (GEO) database, and then the differentially expressed genes (DEGs) in EC and HIP regions were analyzed for functional and pathway enrichment. Furthermore, we utilized the DEGs to construct coexpression networks to identify hub genes and discover the small molecules which were capable of reversing the gene expression profile of AD. Finally, we also analyzed microarray and RNA-seq dataset of blood samples to find the biomarkers related to gene expression in brain.

Results

We found some functional hub genes, such as ErbB2, ErbB4, OCT3, MIF, CDK13, and GPI. According to GO and KEGG pathway enrichment, several pathways were significantly dysregulated in EC and HIP. CTSD and VCAM1 were dysregulated significantly in blood, EC, and HIP, which were potential biomarkers for AD. Target genes of four microRNAs had similar GO_terms distribution with DEGs in EC and HIP. In addtion, small molecules were screened out for AD treatment.

Conclusion

These biological pathways and DEGs or hub genes will be useful to elucidate AD pathogenesis and identify novel biomarkers or drug targets for developing improved diagnostics and therapeutics against AD.

Altered protein glycosylation predicts Alzheimer's disease and modulates its pathology in disease model Drosophila

The pathological hallmarks of Alzheimer's disease (AD) are pathogenic oligomers and fibrils of misfolded amyloidogenic proteins (e.g., β-amyloid and hyper-phosphorylated tau in AD), which cause progressive loss of neurons in the brain and nervous system. Although deviations from normal protein glycosylation have been documented in AD, their role in disease pathology has been barely explored. Here our analysis of available expression data sets indicates that many glycosylation-related genes are differentially expressed in brains of AD patients compared with healthy controls. The robust differences found enabled us to predict the occurrence of AD with remarkable accuracy in a test cohort and identify a set of key genes whose expression determines this classification. We then studied in vivo the effect of reducing expression of homologs of 6 of these genes in transgenic Drosophila overexpressing human tau, a well-established invertebrate AD model. These experiments have led to the identification of glycosylation genes that may augment or ameliorate tauopathy phenotypes. Our results indicate that OstDelta, l(2)not and beta4GalT7 are tauopathy suppressors, whereas pgnat5 and CG33303 are enhancers, of tauopathy. These results suggest that specific alterations in protein glycosylation may play a causal role in AD etiology.

Integrating transcriptomics with metabolic modeling predicts biomarkers and drug targets for Alzheimer's disease

Accumulating evidence links numerous abnormalities in cerebral metabolism with the progression of Alzheimer's disease (AD), beginning in its early stages. Here, we integrate transcriptomic data from AD patients with a genome-scale computational human metabolic model to characterize the altered metabolism in AD, and employ state-of-the-art metabolic modelling methods to predict metabolic biomarkers and drug targets in AD. The metabolic descriptions derived are first tested and validated on a large scale versus existing AD proteomics and metabolomics data. Our analysis shows a significant decrease in the activity of several key metabolic pathways, including the carnitine shuttle, folate metabolism and mitochondrial transport. We predict several metabolic biomarkers of AD progression in the blood and the CSF, including succinate and prostaglandin D2. Vitamin D and steroid metabolism pathways are enriched with predicted drug targets that could mitigate the metabolic alterations observed. Taken together, this study provides the first network wide view of the metabolic alterations associated with AD progression. Most importantly, it offers a cohort of new metabolic leads for the diagnosis of AD and its treatment.

Glia maturation factor expression in hippocampus of human Alzheimer's disease

Alzheimer's disease (AD) is characterized by the presence of neuropathological lesions containing amyloid plaques (APs) and neurofibrillary tangles (NFTs) associated with neuroinflammation and neuronal degeneration. Hippocampus is one of the earliest and severely damaged areas in AD brain. Glia maturation factor (GMF), a known proinflammatory molecule is up-regulated in AD. Here, we have investigated the expression and distribution of GMF in relation to the distribution of APs and NFTs in the hippocampus of AD brains. Our immunohistochemical results showed GMF is expressed specifically in the vicinity of high density of APs and NFTs in the hippocampus of AD patients. Moreover, reactive astrocytes and activated microglia surrounds the APs and NFTs. We further demonstrate that GMF immunoreactive glial cells were increased at the sites of Tau containing NFTs and APs of hippocampus in AD brains. In conclusion, up-regulated expression of GMF in the hippocampus, and the co-localization of GMF and thioflavin-S stained NFTs and APs suggest that GMF may play important role in the pathogenesis of AD.

Analyzing gene expression from whole tissue vs. different cell types reveals the central role of neurons in predicting severity of Alzheimer's disease

Alterations in gene expression resulting from Alzheimer’s disease have received considerable attention in recent years. Although expression has been investigated separately in whole brain tissue, in astrocytes and in neurons, a rigorous comparative study quantifying the relative utility of these sources in predicting the progression of Alzheimer’s disease has been lacking. Here we analyze gene expression from neurons, astrocytes and whole tissues across different brain regions, and compare their ability to predict Alzheimer’s disease progression by building pertaining classification models based on gene expression sets annotated to different biological processes. Remarkably, we find that predictions based on neuronal gene expression are significantly more accurate than those based on astrocyte or whole tissue expression. The findings explicate the central role of neurons, particularly as compared to glial cells, in the pathogenesis of Alzheimer’s disease, and emphasize the importance of measuring gene expression in the most relevant (pathogenically ‘proximal’) single cell types.