Association of the LRP1 gene and cognitive performance with amnestic mild cognitive impairment in elderly Chinese

Low-Density Lipoprotein Receptor-Related Protein 1 as a Potential Therapeutic Target in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease impacting the lives of millions of people worldwide. The formation of amyloid β (Aβ) plagues in the brain is the main pathological hallmark of AD. The Aβ deposits are formed due to the imbalance between the production and Aβ clearance in the brain and across the blood-brain barrier (BBB). In this respect, low-density lipoprotein receptor-related protein 1 (LRP1) plays a significant role by mediating both brain Aβ production and clearance. Due to its important role in AD pathogenesis, LRP1 is considered an attractive drug target for AD therapies. In the present review, we summarize the current knowledge about the role of LRP1 in AD pathogenesis as well as recent findings on changes in LRP1 expression and function in AD. Finally, we discuss the advances in utilizing LRP1 as a drug target for AD treatments as well as future perspectives on LRP1 research.

Exome-wide analysis reveals role of LRP1 and additional novel loci in cognition

Cognitive functioning is heritable, with metabolic risk factors known to accelerate age-associated cognitive decline. Identifying genetic underpinnings of cognition is thus crucial. Here, we undertake single-variant and gene-based association analyses upon 6 neurocognitive phenotypes across 6 cognition domains in whole-exome sequencing data from 157,160 individuals of the UK Biobank cohort to expound the genetic architecture of human cognition. We report 20 independent loci associated with 5 cognitive domains while controlling for APOE isoform-carrier status and metabolic risk factors; 18 of which were not previously reported, and implicated genes relating to oxidative stress, synaptic plasticity and connectivity, and neuroinflammation. A subset of significant hits for cognition indicates mediating effects via metabolic traits. Some of these variants also exhibit pleiotropic effects on metabolic traits. We further identify previously unknown interactions of APOE variants with LRP1 (rs34949484 and others, suggestively significant), AMIGO1 (rs146766120; pAla25Thr, significant), and ITPR3 (rs111522866, significant), controlling for lipid and glycemic risks. Our gene-based analysis also suggests that APOC1 and LRP1 have plausible roles along shared pathways of amyloid beta (Aβ) and lipid and/or glucose metabolism in affecting complex processing speed and visual attention. In addition, we report pairwise suggestive interactions of variants harbored in these genes with APOE affecting visual attention. Our report based on this large-scale exome-wide study highlights the effects of neuronal genes, such as LRP1, AMIGO1, and other genomic loci, thus providing further evidence of the genetic underpinnings for cognition during aging.

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.

Role of LRP1 in the pathogenesis of Alzheimer's disease: evidence from clinical and preclinical studies

Among the LDL receptor (LDLR) family members, the roles of LDLR-related protein (LRP)1 in the pathogenesis of Alzheimer's disease (AD), especially late-onset AD, have been the most studied by genetic, neuropathological, and biomarker analyses (clinical studies) or cellular and animal model systems (preclinical studies) over the last 25 years. Although there are some conflicting reports, accumulating evidence from preclinical studies indicates that LRP1 not only regulates the metabolism of amyloid-β peptides (Aβs) in the brain and periphery, but also maintains brain homeostasis, impairment of which likely contributes to AD development in Aβ-independent manners. Several preclinical studies have also demonstrated an involvement of LRP1 in regulating the pathogenic role of apoE, whose gene is the strongest genetic risk factor for AD. Nonetheless, evidence from clinical studies is not sufficient to conclude how LRP1 contributes to AD development. Thus, despite very promising results from preclinical studies, the role of LRP1 in AD pathogenesis remains to be further clarified. In this review, we discuss the potential mechanisms underlying how LRP1 affects AD pathogenesis through Aβ-dependent and -independent pathways by reviewing both clinical and preclinical studies. We also discuss potential therapeutic strategies for AD by targeting LRP1.

Cerebrospinal fluid levels of Alzheimer's disease biomarkers in middle-aged patients with type 1 diabetes

AIMS/HYPOTHESIS

Type 1 diabetes is associated with moderate cognitive decline and cerebral alterations and may lead to an increased risk of dementia, including Alzheimer's disease. This study aimed to investigate the levels of risk markers for Alzheimer's disease in middle-aged patients with type 1 diabetes and controls, and their potential associations with cognitive and cerebral measures.

METHODS

Levels of β-amyloid (Aβ) 42, Tau, phosphorylated Tau (pTau), the soluble form of low-density lipoprotein receptor-related protein 1 (sLRP1) and macrophage colony-stimulating factor (MCSF) were quantified by ELISA in serum and cerebrospinal fluid (CSF) collected from 37 patients with type 1 diabetes and 15 controls. Associations between biomarkers and determinants of cognitive function and white matter integrity were assessed using hierarchical regression analysis controlling for age, HbA1c and estimated intelligence quotient (IQ).

RESULTS

CSF levels of pTau, Aβ42 and LRP1 were higher in patients with type 1 diabetes than in controls (all p < 0.05). There was a trend towards increased Tau levels in patients with type 1 diabetes (p = 0.056), while CSF levels of MCSF were similar between patients with type 1 diabetes and controls. Regression analysis showed that elevated CSF sLRP1 levels were associated with better attention (β = 0.518; p = 0.002) and a better speed of information-processing (β = 0.368; p = 0.034), as well as increased integrity of the white matter of the right inferior fronto-occipital tract (β = 0.395; p = 0.022). Furthermore, elevated Tau levels were associated with decreased integrity of the white matter of right inferior fronto-occipital tract (β = -0.584; p = 0.002).

CONCLUSIONS/INTERPRETATION

CSF levels of biomarkers for Alzheimer's disease are altered in patients with type 1 diabetes compared with controls, but the observed profile does not match the profile characterising pre-Alzheimer's disease patients.

Recent research about mild cognitive impairment in China

The rapid aging of the Chinese population has spurred interest in research about the cause and prevention of dementia and its precursor, mild cognitive impairment (MCI). This review summarizes the last decade of research in China about MCI. Extensive research about the epidemiology, neuropsychological characteristics, diagnosis, genetic etiology, neuroimaging and electrophysiological changes, and treatment of MCI has provided some new insights but few breakthroughs. Further advances in the prevention and treatment of MCI will require a greater emphasis on multi-disciplinary prospective studies with large, representative samples that use standardized methods to assess and monitor changes in cognitive functioning over time.