Association of polymorphisms in the LRP1 and A2M genes with Alzheimer’s disease in the Northern Chinese Han population

Revealing the mechanisms of blood-brain barrier in chronic neurodegenerative disease: an opportunity for therapeutic intervention

The brain microenvironment is tightly regulated, and the blood-brain barrier (BBB) plays a pivotal role in maintaining the homeostasis of the central nervous system. It effectively safeguards brain tissue from harmful substances in peripheral blood. However, both acute pathological factors and age-related biodegradation have the potential to compromise the integrity of the BBB and are associated with chronic neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD), as well as Epilepsy (EP). This association arises due to infiltration of peripheral foreign bodies including microorganisms, immune-inflammatory mediators, and plasma proteins into the central nervous system when the BBB is compromised. Nevertheless, these partial and generalized understandings do not prompt a shift from passive to active treatment approaches. Therefore, it is imperative to acquire a comprehensive and in-depth understanding of the intricate molecular mechanisms underlying vascular disease alterations associated with the onset and progression of chronic neurodegenerative disorders, as well as the subsequent homeostatic changes triggered by BBB impairment. The present article aims to systematically summarize and review recent scientific work with a specific focus on elucidating the fundamental mechanisms underlying BBB damage in AD, PD, and EP as well as their consequential impact on disease progression. These findings not only offer guidance for optimizing the physiological function of the BBB, but also provide valuable insights for developing intervention strategies aimed at early restoration of BBB structural integrity, thereby laying a solid foundation for designing drug delivery strategies centered around the BBB.

Soluble LRP-1 in Parkinson's disease: clues for paradoxical effects

Background: Low density lipoprotein receptor-related protein-1 (LRP-1) is highly expressed in the central nervous system and plays a role in neurodegenerative disorders. The available data on this subject-matter seem to support the presence of a correlation between LRP-1 levels and abnormal aggregation of a plurality of proteins, including tau, amyloid, and α‑synuclein. Understanding the molecular mechanisms underlying Parkinson's disease (PD) is critical for development of new therapies.

Aim: To investigate serum soluble LRP-1 (sLRP-1) concentrations in patients with PD and explored their potential role as a biomarker in diagnosis and prognosis of disease.

Methods: Based on well-defined inclusion and exclusion criteria, we have included 133 PD patients and 45 healthy controls. The clinical severity was assessed using Hoehn Yahr and Unified PD Rating Scale (UPDRS). Following a fasting period, venous blood samples were taken, and centrifuged. Serum samples were stored until analysis. sLRP-1 was measured by ELISA assay.

Results: The median of serum sLRP-1 levels was higher in PD patients compared to that in healthy controls, but without reaching a statistical significance. There was a positive, but statistically insignificant, correlation between sLRP-1 levels and duration of disease. sLRP-1 levels had a significant correlation with UPDRS Parts I and IV. Patients with hypertension showed lower levels of sLRP-1.

Conclusion: The present study suggests that serum sLRP-1 concentrations are associated with the factors influencing prognosis of PD and disease severity. Further studies are needed to definitively determine whether or not sLRP-1 can be utilized as a diagnostic and prognostic biomarker for PD.

Alpha 2-Macroglobulin Polymorphisms and Susceptibility to Alzheimer's Disease: A Comprehensive Meta-Analysis Based on 62 Studies

Background

The relationship between alpha 2-macroglobulin (A2M) gene and Alzheimer's disease (AD) has been widely studied across populations; however, the results are inconsistent.

Objective

This study aimed to evaluate the association of A2M gene with AD by the application of meta-analysis.

Methods

Relevant studies were identified by comprehensive searches. The quality of each study was assessed using the Newcastle-Ottawa Scale. Allele and genotype frequencies were extracted from each of the included studies. Odds ratio (OR) with corresponding 95% confidence intervals (CI) was calculated using a random-effects or fixed-effects model. The Cochran Q statistic and I2 metric was used to evaluate heterogeneity, and Egger's test and Funnel plot were used to assess publication bias.

Results

A total of 62 studies were identified and included in the current meta-analysis. The G allele of rs226380 reduced AD risk (OR: 0.64, 95% CI: 0.47-0.87, pFDR = 0.012), but carrier with the TT genotype was more likely to develop AD in Asian populations (OR: 1.56, 95% CI: 1.12-2.19, pFDR = 0.0135). The V allele of the A2M-I/V (rs669) increased susceptibility to AD in female population (OR, 95% CI: 2.15, 1.38-3.35, pFDR = 0.0024); however, the II genotype could be a protective factor in these populations (OR, 95% CI: 0.43, 0.26-0.73, pFDR = 0.003). Sensitivity analyses confirmed the reliability of the original results.

Conclusions

Existing evidence indicate that A2M single nucleotide polymorphisms (SNPs) may be associated with AD risk in sub-populations. Future studies with larger sample sizes will be necessary to confirm the results.

Genetic Editing and Pharmacogenetics in Current And Future Therapy Of Neurocognitive Disorders

Dementia is an important issue in western societies, and in the following years, this problem will also rise in the developing regions, such as Africa and Asia. The most common types of dementia in adults are Alzheimer's Disease (AD), Dementia with Lewy Bodies (DLB), Frontotemporal Dementia (FTD) and Vascular Dementia (VaD), of which, AD accounts for more than half of the cases. The most prominent symptom of AD is cognitive impairment, currently treated with four drugs: Donepezil, rivastigmine, and galantamine, enhancing cholinergic transmission; as well as memantine, protecting neurons against glutamate excitotoxicity. Despite ongoing efforts, no new drugs in the treatment of AD have been registered for the last ten years, thus multiple studies have been conducted on genetic factors affecting the efficacy of antidementia pharmacotherapy. The researchers investigate the effects of variants in multiple genes, such as ABCB1, ACE, CHAT, CHRNA7, CYP2C9, CYP2C19, CYP2D6, CYP3A4, CYP3A5, CYP3A7, NR1I2, NR1I3, POR, PPAR, RXR, SLC22A1/2/5, SLC47A1, UGT1A6, UGT1A9 and UGT2B7, associated with numerous pathways: the development of pathological proteins, formation and metabolism of acetylcholine, transport, metabolism and excretion of antidementia drugs and transcription factors regulating the expression of genes responsible for metabolism and transport of drugs. The most promising results have been demonstrated for APOE E4, dementia risk variant, BCHE-K, reduced butyrylcholinesterase activity variant, and CYP2D6 UM, ultrarapid hepatic metabolism. Further studies investigate the possibilities of the development of emerging drugs or genetic editing by CRISPR/Cas9 for causative treatment. In conclusion, the pharmacogenetic studies on dementia diseases may improve the efficacy of pharmacotherapy in some patients with beneficial genetic variants, at the same time, identifying the carriers of unfavorable alleles, the potential group of novel approaches to the treatment and prevention of dementia.

Association between LRP1 C766T polymorphism and Alzheimer's disease susceptibility: a meta-analysis

Low density lipoprotein receptor-related protein 1 (LRP1) C766T polymorphism (rs1799986) has been extensively investigated for Alzheimer’s disease (AD) susceptibility. However, results in different studies have been contradictory. Therefore, we conducted a meta-analysis containing 6455 AD cases and 6304 controls from 26 independent case–control studies to determine whether there was an association between the LRP1 C766T polymorphism and AD susceptibility. The combined analysis showed that there was no significant association between LRP1 C766T polymorphism and AD susceptibility (TT + CT versus CC: OR = 0.920, 95% CI = 0.817–1.037, P = 0.172). In subgroup analysis, significant decreased AD susceptibility was found among Asian population in allele model (T versus C: OR = 0.786, 95% CI = 0.635–0.974, P = 0.028) and dominant model (TT + CT versus CC: OR = 0.800, 95% CI = 0.647–0.990, P = 0.040). Moreover, T allele of LRP1 C766T was statistically associated with late onset of AD (LOAD) (T versus C: OR = 0.858, 95% CI = 0.748–0.985, P = 0.029; TT + CT versus CC: OR = 0.871, 95% CI = 0.763–0.994, P = 0.040). In conclusion, our meta-analysis suggested that LRP1 C766T polymorphism was associated with lower risk of AD in Asian, and could reduce LOAD risk especially. Considering some limitations of our meta-analysis, further large-scale studies should be done to reach a more comprehensive understanding.

Influence of Alpha-2-Macroglobulin 5 bp I/D and Ile1000Val polymorphisms on the susceptibility of Alzheimer's disease: a systematic review and meta-analysis of 52 studies

Accumulating studies have evaluated the association of Alpha-2-Macroglobulin gene (A2M) 5 bp insertion/deletion (5 bp I/D, rs3832852) and Ile1000Val (rs669) polymorphisms with Alzheimer's disease (AD) risk, but the results remain inconclusive. To investigate whether these two polymorphisms facilitate the susceptibility to AD, we conducted a comprehensive systematic review and meta-analysis. Databases of PubMed, Embase, Web of Science, Medline, CNKI, and Google Scholar were searched to get the genetic association studies. All statistical analyses were conducted with Review Manager 5.2 and STATA11.0. Fifty-two articles were included in the final meta-analysis. We performed meta-analysis of 39 studies involving 8,267 cases and 7,932 controls for the 5 bp I/D polymorphism and 27 studies involving 6,585 cases and 6,637 controls for the Ile/Val polymorphism. Overall results did not show significant association between these two polymorphisms and AD risk in dominant, recessive, and multiplicative genetic models. On the stratification analyses by ethnicity and APOE ε4 status with genotypes of polymorphism sites, similar negative associations were found. The meta-analysis suggests that there is no enough evidence for associations of A2M gene polymorphisms (5 bp I/D, Ile1000Val) with AD risk at present, even after stratification by ethnicity and APOE ε4 with genotypes of polymorphism sites. However, due to the heterogeneity in the meta-analysis, the results should be interpreted with caution.

The implications of angiotensin-converting enzymes and their modulators in neurodegenerative disorders: current and future perspectives

Angiotensin converting enzyme (ACE) is a dipeptidyl peptidase transmembrane bound enzyme. Generally, ACE inhibitors are used for the cardiovascular disorders. ACE inhibitors are primary agents for the management of hypertension, so these cannot be avoided for further use. The present Review focuses on the implications of angiotensin converting enzyme inhibitors in neurodegenerative disorders such as dementia, Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, stroke, and diabetic neuropathy. ACE inhibitors such as ramipril, captopril, perindopril, quinapril, lisinopril, enalapril, and trandolapril have been documented to ameliorate the above neurodegenerative disorders. Neurodegeneration occurs not only by angiotensin II, but also by other endogenous factors, such as the formation of free radicals, amyloid beta, immune reactions, and activation of calcium dependent enzymes. ACE inhibitors interact with the above cellular mechanisms. Thus, these may act as a promising factor for future medicine for neurological disorders beyond the cardiovascular actions. Central acting ACE inhibitors can be useful in the future for the management of neuropathic pain due to following actions: (i) ACE-2 converts angiotensinogen to angiotensin(1-7) (hepatapeptide) which produces neuroprotective action; (ii) ACE inhibitors downregulate kinin B1 receptors in the peripheral nervous system which is responsible for neuropathic pain. However, more extensive research is required in the field of neuropathic pain for the utilization of ACE inhibitors in human.