Apolipoprotein E allele frequencies in chronic and self-limited hepatitis C suggest a protective effect of APOE4 in the course of hepatitis C virus infection

Personalized medicine and nutrition in hepatology for preventing chronic liver disease in Mexico

Chronic liver disease is a global health issue. Patients with chronic liver disease require a fresh approach that focuses on the genetic and environmental factors that contribute to disease initiation and progression. Emerging knowledge in the fields of Genomic Medicine and Genomic Nutrition demonstrates differences between countries in terms of genetics and lifestyle risk factors such as diet, physical activity, and mental health in chronic liver disease, which serves as the foundation for the implementation of Personalized Medicine and Nutrition (PerMed-Nut) strategies. Most of the world's populations have descended from various ethnic groupings. Mexico's population has a tripartite ancestral background, consisting of Amerindian, European, and African lineages, which is common across Latin America's regional countries. The purpose of this review is to discuss the genetic and environmental components that could be incorporated into a PerMed-Nut model for metabolic-associated liver disease, viral hepatitis B and C, and hepatocellular carcinoma in Mexico. Additionally, the implementation of the PerMed-Nut approach will require updated medicine and nutrition education curricula. Training and equipping future health professionals and researchers with new clinical and investigative abilities focused on preventing liver illnesses in the field of genomic hepatology globally is a vision that clinicians and nutritionists should be concerned about.

COVID-19 and the impact on Alzheimer's disease pathology

Coronavirus disease 2019 (COVID-19) has rapidly escalated into a global pandemic that primarily affects older and immunocompromised individuals due to underlying clinical conditions and suppressed immune responses. Furthermore, COVID-19 patients exhibit a spectrum of neurological symptoms, indicating that COVID-19 can affect the brain in a variety of manners. Many studies, past and recent, suggest a connection between viral infections and an increased risk of neurodegeneration, raising concerns about the neurological effects of COVID-19 and the possibility that it may contribute to Alzheimer's disease (AD) onset or worsen already existing AD pathology through inflammatory processes given that both COVID-19 and AD share pathological features and risk factors. This leads us to question whether COVID-19 is a risk factor for AD and how these two conditions might influence each other. Considering the extensive reach of the COVID-19 pandemic and the devastating impact of the ongoing AD pandemic, their combined effects could have significant public health consequences worldwide.

Lower mortality risk in APOE4 carriers with normal cognitive ageing

Abnormal cognitive ageing, including dementia, poses serious challenges to health and social systems in ageing populations. As such, characterizing factors associated with abnormal cognitive ageing and developing needed preventive measures are of great importance. The ε4 allele of the Apolipoprotein E gene (APOE4) is a well-known genetic risk factor for late-onset Alzheimer's disease. APOE4 carriers are also at elevated risk of cardiovascular diseases which are associated with increased risk of cognitive impairment. On the other hand, APOE4 is known to be associated with reduced risk of multiple common types of cancer-a major age-related disease and leading cause of mortality. We conducted the first-ever study of APOE4's opposing effects on cognitive decline and mortality using competing risk models considering two types of death-death with high-amounts versus low-amounts of autopsy-assessed Alzheimer's neuropathology. We observed that APOE4 was associated with decreased mortality risk in people who died with low amounts of Alzheimer's-type neuropathology, but APOE4 was associated with increased mortality risk in people who died with high amounts of Alzheimer's-type neuropathology, a major risk factor of cognitive impairment. Possible preventive measures of abnormal cognitive ageing are also discussed.

Apolipoprotein E and viral infection: Risks and Mechanisms

Apolipoprotein E (ApoE) is a multifunctional protein critical for lipid metabolism and cholesterol homeostasis. In addition to being a well known genetic determinant of both neurodegenerative and cardiovascular diseases, ApoE is frequently involved in various viral infection-related diseases. Human ApoE protein is functionally polymorphic with three isoforms, namely, ApoE2, ApoE3, and ApoE4, with markedly altered protein structures and functions. ApoE4 is associated with increased susceptibility to infection with herpes simplex virus type-1 and HIV. Conversely, ApoE4 protects against hepatitis C virus and hepatitis B virus infection. With the outbreak of coronavirus disease 2019, ApoE4 has been shown to determine the incidence and progression of severe acute respiratory syndrome coronavirus 2 infection. These findings clearly indicate the critical role of ApoE in viral infection. Furthermore, ApoE polymorphism has various or even opposite effects in these infection processes, which are partly related to the structural features that distinguish the different ApoE statuses. In the current review, we summarize the emerging relationship between ApoE and viral infection, discuss the potential mechanisms, and identify future directions that may help to advance our understanding of the link between ApoE and viral infection.

Apolipoprotein-ε4 is associated with higher fecundity in a natural fertility population

In many populations, the apolipoprotein-ε4 (APOE-ε4) allele increases the risk for several chronic diseases of aging, including dementia and cardiovascular disease; despite these harmful effects at later ages, the APOE-ε4 allele remains prevalent. We assess the impact of APOE-ε4 on fertility and its proximate determinants (age at first reproduction, interbirth interval) among the Tsimane, a natural fertility population of forager-horticulturalists. Among 795 women aged 13 to 90 (20% APOE-ε4 carriers), those with at least one APOE-ε4 allele had 0.3 to 0.5 more children than (ε3/ε3) homozygotes, while those with two APOE-ε4 alleles gave birth to 1.4 to 2.1 more children. APOE-ε4 carriers achieve higher fertility by beginning reproduction 0.8 years earlier and having a 0.23-year shorter interbirth interval. Our findings add to a growing body of literature suggesting a need for studies of populations living in ancestrally relevant environments to assess how alleles that are deleterious in sedentary urban environments may have been maintained by selection throughout human evolutionary history.

Relationship of Apolipoprotein E with Alzheimer's Disease and Other Neurological Disorders: An Updated Review

Alzheimer's disease (AD) and other neurodegenerative diseases, for which there is no effective cure, cause great social burden. Apolipoprotein E (APOE) is an important lipid transporter, which has been shown to have a close relationship with AD and other neurological disorders in an increasing number of studies, suggesting its potential as a therapeutic target. In this review, we summarize the recent advances in clinical and basic research on the role of APOE in the pathogenesis of multiple neurological diseases, with an emphasis on the new associations between APOE and AD, and between APOE and depression. The progress of APOE research in Parkinson's disease (PD) and some other neurological diseases is briefly discussed.

Effects of APOE Genotype and Western Diet on Metabolic Phenotypes in Female Mice

Western diets high in sugars and saturated fats have been reported to induce metabolic and inflammatory impairments that are associated with several age-related disorders, including Alzheimer's disease (AD) and type 2 diabetes (T2D). The apolipoprotein E (APOE) genotype is associated with metabolic and inflammatory outcomes that contribute to risks for AD and T2D, with the APOE4 genotype increasing risks relative to the more common APOE3 allele. In this study, we investigated the impacts of the APOE genotype on systemic and neural effects of the Western diet. Female mice with knock-in of human APOE3 or APOE4 were exposed to control or Western diet for 13 weeks. In the control diet, we observed that APOE4 mice presented with impaired metabolic phenotypes, exhibiting greater adiposity, higher plasma leptin and insulin levels, and poorer glucose clearance than APOE3 mice. Behaviorally, APOE4 mice exhibited worse performance in a hippocampal-dependent learning task. In visceral adipose tissue, APOE4 mice exhibited generally higher expression levels of macrophage- and inflammation-related genes. The cerebral cortex showed a similar pattern, with higher expression of macrophage- and inflammation-related genes in APOE4 than APOE3 mice. Exposure to the Western diet yielded modest, statistically non-significant effects on most metabolic, behavioral, and gene expression measures in both APOE genotypes. Interestingly, the Western diet resulted in reduced gene expression of a few macrophage markers, specifically in APOE4 mice. The observed relative resistance to the Western diet suggests protective roles of both female sex and young adult age. Further, the data demonstrate that APOE4 is associated with deleterious systemic and neural phenotypes and an altered response to a metabolic stressor, findings relevant to the understanding of interactions between the APOE genotype and risks for metabolic disorders.

The COVID-19 pandemic and Alzheimer’s disease: mutual risks and mechanisms

Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a life-threatening disease, especially in elderly individuals and those with comorbidities. The predominant clinical manifestation of COVID-19 is respiratory dysfunction, while neurological presentations are increasingly being recognized. SARS-CoV-2 invades host cells primarily via attachment of the spike protein to the angiotensin-converting enzyme 2 (ACE2) receptor expressed on cell membranes. Patients with Alzheimer’s disease (AD) are more susceptible to SARS-CoV-2 infection and prone to severe clinical outcomes. Recent studies have revealed some common risk factors for AD and COVID-19. An understanding of the association between COVID-19 and AD and the potential related mechanisms may lead to the development of novel approaches to treating both diseases. In the present review, we first summarize the mechanisms by which SARS-CoV-2 invades the central nervous system (CNS) and then discuss the associations and potential shared key factors between COVID-19 and AD, with a focus on the ACE2 receptor, apolipoprotein E (APOE) genotype, age, and neuroinflammation.

Apolipoprotein E Genetic Variation and Its Association With Cognitive Function in Rural-Dwelling Older South Africans

Apolipoprotein E (APOE) 𝜀4 allele carrier status is well known for its association with an increased likelihood of developing Alzheimer’s disease, but its independent role in cognitive function is unclear. APOE genetic variation is understudied in African populations; hence, this cross-sectional study in a rural South African community examined allele and genotype frequencies, and their associations with cognitive function. Cognitive function was assessed using two different screening methods to produce a total cognition score and four domain-specific cognition scores for verbal episodic memory, executive function, language, and visuospatial ability. Cognitive phenotype and APOE genotype data were used to determine whether APOE variation was significantly associated with cognitive function in this population. Observed allele frequencies for 1776 participants from the HAALSI study [age 40–80years (mean=56.19); 58.2% female] were 58.1% (𝜀3), 25.4% (𝜀4) and 16.5% (𝜀2). Allele distributions were similar to the African super population, but different from all non-African super populations from the 1,000 Genomes Project. The 𝜀3 homozygous genotype was most common (34.9%) and used as the base genotype for comparison in regression models. Four models were tested for each of the five cognitive phenotypes to explore association of APOE variation with cognitive function. In the first model assessing association with all genotypes for all individuals, marginally significant associations were observed for 𝜀2 homozygotes where executive function scored higher by ~0.5 standard deviations (p=0.037, SE=0.23), and for 𝜀3/𝜀4 heterozygotes where visuospatial ability scores were lower (p=0.046, SE=0.14). These did not survive correction for multiple testing. Regional African population differences were observed at the APOE locus. Marginally, significant associations between APOE genotype, and executive function and visuospatial ability indicate the need for larger studies to better examine these associations in African populations. Furthermore, longitudinal data could shed light on APOE genetic association with rate of change, or decline, in cognitive function.

APOE4 is associated with elevated blood lipids and lower levels of innate immune biomarkers in a tropical Amerindian subsistence population

In post-industrial settings, apolipoprotein E4 (APOE4) is associated with increased cardiovascular and neurological disease risk. However, the majority of human evolutionary history occurred in environments with higher pathogenic diversity and low cardiovascular risk. We hypothesize that in high-pathogen and energy-limited contexts, the APOE4 allele confers benefits by reducing innate inflammation when uninfected, while maintaining higher lipid levels that buffer costs of immune activation during infection. Among Tsimane forager-farmers of Bolivia (N = 1266, 50% female), APOE4 is associated with 30% lower C-reactive protein, and higher total cholesterol and oxidized LDL. Blood lipids were either not associated, or negatively associated with inflammatory biomarkers, except for associations of oxidized LDL and inflammation which were limited to obese adults. Further, APOE4 carriers maintain higher levels of total and LDL cholesterol at low body mass indices (BMIs). These results suggest that the relationship between APOE4 and lipids may be beneficial for pathogen-driven immune responses and unlikely to increase cardiovascular risk in an active subsistence population.

Adherence to a Fish-Rich Dietary Pattern Is Associated with Chronic Hepatitis C Patients Showing Low Viral Load: Implications for Nutritional Management

Hepatitis C virus (HCV) infection is influenced by genetic (e.g., APOE polymorphisms) and environmental factors between the virus and the host. HCV modulates the host’s lipid metabolism but dietary components influence lipids and in vitro HCV RNA replication. Few data exist on the role of dietary features or patterns (DPs) in HCV infection. Herein, we aimed to evaluate the nutritional profiles of chronic HCV (CHC) and spontaneous clearance (SC) Mexican patients in the context of APOE alleles and their correlation with HCV-related variables. The fibrosis-related APOEε3 allele prevailed in CHC and SC patients, who had four DPs (“meat and soft drinks”, DP1; “processed animal and fried foods”, DP2; “Mexican-healthy”, DP3; and “fish-rich”, DP4). In CHC subjects, polyunsaturated fatty acid intake (PUFA ≥ 4.9%) was negatively associated, and fiber intake (≥21.5 g/day) was positively associated with a high viral load (p < 0.036). High adherence to fish-rich DP4 was associated with a higher frequency of CHC individuals consuming PUFA ≥ 4.9% (p = 0.004) and low viral load (p = 0.036), but a lower frequency of CHC individuals consuming fiber ≥21.5 g/day (p = 0.038). In SC and CHC individuals, modifying unhealthy DPs and targeting HCV-interacting nutrients, respectively, could be part of a nutritional management strategy to prevent further liver damage.

Reassessing neurodegenerative disease: immune protection pathways and antagonistic pleiotropy

The antagonistic pleiotropy (AP) theory posits that adaptive evolutionary changes, which facilitate reproduction and individual fitness early in life, can enhance detrimental aging-related processes. Several genes associated with human brain diseases play a protective role in infection, suggesting the relevance of AP in the context of brain aging and neurodegeneration. Relatedly, genetic variants that confer immune protection against pathogens may lead to uncontrolled brain inflammation later in life. Here, we propose a conceptual framework suggesting that the pleiotropic roles of genes in infections and host-pathogen interactions should be considered when studying neurological illnesses. We reinterpret recent findings regarding the impact of neurological disease-associated genetic traits on infections and chronic inflammatory diseases. Identifying the AP pathways shared among these seemingly unrelated conditions might provide further insights into the detrimental role of the immune system in brain disease as well as the mechanisms involved in chronic infections.

Impact of IL10, MTP, SOD2, and APOE Gene Polymorphisms on the Severity of Liver Fibrosis Induced by HCV Genotype 4

Complications of hepatitis C virus (HCV) chronic infection cause ~400,000 deaths worldwide annually. One complication, liver fibrosis, is influenced by host genetic factors. Genes influencing fibrosis include immune, metabolic, oxidative stress, and viral entry genes, such as interleukin 10 (IL10), microsomal triglyceride-transfer protein (MTP), superoxide dismutase-2 (SOD2), and apolipoprotein E (APOE)-encoding genes, respectively. Thus, correlating variations in these genes with HCV-induced fibrosis represents an attractive biomarker for the prognosis of fibrosis severity in chronically infected patients. Here, we aimed to test whether polymorphisms in IL10, MTP, SOD2, and APOE genes correlated with the severity of fibrosis induced by HCV genotype 4 (HCV-gt4) in a cohort of chronically infected Egyptian patients. Our results demonstrate a significant association between the severity of fibrosis and specific SNPs in IL-10, SOD2, and ApoE-encoding genes. Haplotype-combination analysis for IL10, MTP, SOD2, and APOE showed statistically significant associations between specific haplotype combinations and fibrosis severity. Identifying biomarkers correlating with the severity of HCV-gt4-induced fibrosis would significantly impact precision prophylaxis and treatment of patients at risk.

Apolipoprotein E polymorphism influences orthotopic liver transplantation outcomes in patients with hepatitis C virus-induced liver cirrhosis

BACKGROUND

Hepatitis C virus (HCV) infection is responsible for a chronic liver inflammation, which may cause end-stage liver disease and hepatocellular carcinoma. Apolipoprotein E (protein: ApoE, gene: APOE), a key player in cholesterol metabolism, is mainly synthesized in the liver and APOE polymorphisms may influence HCV-induced liver damage.

AIM

To determine whether APOE alleles affect outcomes in HCV-infected patients with liver cirrhosis following orthotopic liver transplantation (OLT).

METHODS

This was a cohort study in which 179 patients, both genders and aged 34-70 years, were included before or after (up to 10 years follow-up) OLT. Liver injury severity was assessed using different criteria, including METAVIR and models for end-stage liver disease. APOE polymorphisms were analyzed by quantitative real-time polymerase chain reaction.

RESULTS

The APOE3 allele was the most common (67.3%). In inflammation severity of biopsies from 89 OLT explants and 2 patients in pre-transplant, the degree of severe inflammation (A3F4, 0.0%) was significantly less frequent than in patients with minimal and moderate degree of inflammation (≤ A2F4, 16.2%) P = 0.048, in patients carrying the APOE4 allele when compared to non-APOE4. In addition, a significant difference was also found (≤ A2F4, 64.4% vs A3F4, 0.0%; P = 0.043) and (A1F4, 57.4% vs A3F4, 0.0%; P = 0.024) in APOE4 patients when compared to APOE3 carriers. The fibrosis degree of the liver graft in 8 of 91 patients and the lack of the E4 allele was associated with more moderate fibrosis (F2) (P = 0.006).

CONCLUSION

Our results suggest that the E4 allele protects against progression of liver fibrosis and degree of inflammation in HCV-infected patients.

Impact of apolipoprotein E genetic polymorphisms on liver disease: An essential review

Cirrhosis is an advanced stage of liver disease, compromising liver function with systemic health implications and poor quality of life. Hepatitis C virus (HCV) infection and alcoholic liver disease are the main causes of this pathology. However, since genetic factors may play a large role in the progression and severity of liver disease, and as apolipoprotein E (apoE) has been recognised to be mainly synthesised in the liver, apoE polymorphism studies are important to better understand the causal mechanisms in liver diseases. In this review, we summarise up-to-date studies addressing how apoE polymorphisms influence liver cirrhosis and liver transplantation outcomes and potential protective mechanisms. Although more clinical studies are needed to support these findings, the apoE ɛ4 allele seems to be protective against the progression of liver cirrhosis in the majority of aetiologies and the postoperative serum apoE phenotype of the transplanted subject receptors was converted to that of the donor, indicating that >90% of apoE in plasma is synthesised in the hepatic system.

Apolipoprotein E Effects on Mammalian Ovarian Steroidogenesis and Human Fertility

Apolipoprotein E (ApoE) is a glycoprotein consisting of 299 amino acids, highly produced in the mammalian ovaries. The main function of the ApoE is to transport cholesterol from the peripheral tissues to be metabolized in the liver. In humans, the ApoE gene is polymorphic, with three alleles in a single chromosome-19 locus: APOE2, APOE3, and APOE4. ApoE has also been implicated in cholesterol transport within ovarian follicles to regulate steroidogenesis. Ovarian thecal and granulosa cell cholesterol uptake requires ApoE either by participating in the lipoprotein-receptor complex or lipid endocytosis. In this review, we summarize ApoE role on mammalian ovarian steroidogenesis and on human fertility and discuss recent findings of ApoE4 as an antagonistic pleiotropy gene under adverse environments.

Putative Survival Advantages in Young Apolipoprotein ɛ4 Carriers are Associated with Increased Neural Stress

Inheritance of a single copy of the apolipoprotein E (APOE) ɛ4 allele increases risk of Alzheimer’s disease (AD) by 3-4-fold, with homozygosity associated with a 12-16-fold increase in risk, relative to ɛ3 allele homozygosity. There is a decreased risk associated with the APOE ɛ2 allele. The pathological consequence of APOE genotype has led to intense efforts to understand the mechanistic basis of the interplay between APOE status and loss of synapses. Numerous ɛ4 allele-related associations have been reported with the potential relevance of these associations to the pathogenesis of AD unknown at this time. In primarily young subjects, we have reviewed a representative body of literature on ɛ4 allele-associations related to the following: cardiovascular responses; impacts on reproduction and fetal development; co-morbidities; resistance to infectious disease; responses to head injury; biochemical differences possibly related to neural stress; and brain structure-function differences. In addition, the literature on the association between the ɛ4 allele and cognitive performance has been reviewed comprehensively. The weight-of-the-evidence supports the hypothesis that possession of the ancestral ɛ4 allele in youth is associated with improved fitness during fetal development, infancy, and youth relative to the more recently appearing ɛ3 allele, at the expense of decreased fitness in old age, which is substantially improved by the ɛ3 allele. However, possession of the ɛ4 allele is also associated with higher levels of synaptic macromolecular turnover, which likely stresses basic cellular neuroplasticity mechanisms. Clinical trials of potential AD therapeutics should consider APOE status as an enrollment criterion.

Independent and Correlated Role of Apolipoprotein E ɛ4 Genotype and Herpes Simplex Virus Type 1 in Alzheimer's Disease

The ɛ4 allele of the Apolipoprotein E (APOE) gene in individuals infected by Herpes simplex virus type 1 (HSV-1) has been demonstrated to be a risk factor in Alzheimer's disease (AD). APOE-ɛ4 reduces the levels of neuronal cholesterol, interferes with the transportation of cholesterol, impairs repair of synapses, decreases the clearance of neurotoxic peptide amyloid-β (Aβ), and promotes the deposition of amyloid plaque, and eventually may cause development of AD. HSV-1 enters host cells and can infect the olfactory system, trigeminal ganglia, entorhinal cortex, and hippocampus, and may cause AD-like pathological changes. The lifecycle of HSV-1 goes through a long latent phase. HSV-1 induces neurotropic cytokine expression with pro-inflammatory action and inhibits antiviral cytokine production in AD. It should be noted that interferons display antiviral activity in HSV-1-infected AD patients. Reactivated HSV-1 is associated with infectious burden in cognitive decline and AD. Finally, HSV-1 DNA has been confirmed as present in human brains and is associated with APOEɛ4 in AD. HSV-1 and APOEɛ4 increase the risk of AD and relate to abnormal autophagy, higher concentrations of HSV-1 DNA in AD, and formation of Aβ plaques and neurofibrillary tangles.

APOE ϵ4 modifies the relationship between infectious burden and poor cognition

OBJECTIVE

We investigated whether APOE ϵ4 is an effect modifier of the association between infectious burden (IB) and poor cognition in a multiethnic cohort, the Northern Manhattan Study.

METHODS

IB was assessed by a quantitative weighted index of exposure to common pathogens associated with vascular risk, infectious burden index (IBI), and by serology for individual infections. Cognition was assessed by completion of the Mini-Mental State Examination at baseline and a full neuropsychological test battery after a median follow-up of approximately 6 years. Adjusted linear and logistic regressions estimated the association between IBI and cognition, with a term included for the interaction between APOE ϵ4 and IBI.

RESULTS

Among those with full neuropsychological test results (n = 569), there were interactions between IBI and APOE ϵ4 (p = 0.07) and herpes simplex virus 1 (HSV-1) and APOE ϵ4 (p = 0.02) for processing speed. IBI was associated with slower processing speed among non-ϵ4 carriers (β = -0.08 per SD change in IBI, 95% confidence interval [CI] -0.16 to -0.01), but not among APOE ϵ4 carriers (β = 0.06 per SD change in IBI, 95% CI -0.08 to 0.19). HSV-1 positivity was associated with slower processing speed among non-ϵ4 carriers (β = -0.24, 95% CI -0.45 to -0.03), but not among APOE ϵ4 carriers (β = 0.27, 95% CI -0.09 to 0.64).

CONCLUSIONS

Potential effect modification by the APOE ϵ4 allele on the relationship of infection, and particularly viral infection, to cognitive processing speed warrants further investigation.

Impact of Apolipoprotein E gene polymorphism during normal and pathological conditions of the brain across the lifespan

The central nervous system (CNS) is the cellular substrate for the integration of complex, dynamic, constant, and simultaneous interactions among endogenous and exogenous stimuli across the entire human lifespan. Numerous studies on aging-related brain diseases show that some genes identified as risk factors for some of the most common neurodegenerative diseases - such as the allele 4 of APOE gene (APOE4) for Alzheimer's disease (AD) - have a much earlier neuro-anatomical and neuro-physiological impact. The impact of APOE polymorphism appears in fact to start as early as youth and early-adult life. Intriguingly, though, those same genes associated with aging-related brain diseases seem to influence different aspects of the brain functioning much earlier actually, that is, even from the neonatal periods and earlier. The APOE4, an allele classically associated with later-life neurodegenerative disorders as AD, seems in fact to exert a series of very early effects on phenomena of neuroplasticity and synaptogenesis that begin from the earliest periods of life such as the fetal ones.We reviewed some of the findings supporting the hypothesis that APOE polymorphism is an early modifier of various neurobiological aspects across the entire human lifespan - from the in-utero to the centenarian life - during both normal and pathological conditions of the brain.

Beyond the CNS: The many peripheral roles of APOE

Apolipoprotein E (APOE) is a multifunctional protein synthesized and secreted by multiple mammalian tissues. Although hepatocytes contribute about 75% of the peripheral pool, APOE can also be expressed in adipose tissue, the kidney, and the adrenal glands, among other tissues. High levels of APOE production also occur in the brain, where it is primarily synthesized by glia, and peripheral and brain APOE pools are thought to be distinct. In humans, APOE is polymorphic, with three major alleles (ε2, ε3, and ε4). These allelic forms dramatically alter APOE structure and function. Historically, the vast majority of research on APOE has centered on the important role it plays in modulating risk for cardiovascular disease and Alzheimer's disease. However, the established effects of this pleiotropic protein extend well beyond these two critical health challenges, with demonstrated roles across a wide spectrum of biological conditions, including adipose tissue function and obesity, metabolic syndrome and diabetes, fertility and longevity, and immune function. While the spectrum of biological systems in which APOE plays a role seems implausibly wide at first glance, there are some potential unifying mechanisms that could tie these seemingly disparate disorders together. In the current review, we aim to concisely summarize a wide breadth of APOE-associated pathologies and to analyze the influence of APOE in the development of several distinct disorders in order to provide insight into potential shared mechanisms implied in these various pathophysiological processes.

Hepatitis C virus clearance and less liver damage in patients with high cholesterol, low-density lipoprotein cholesterol and APOE ε4 allele

BACKGROUND

Cholesterol is related to improvements in the rate of sustained virological response and a robust immune response against the hepatitis C virus (HCV). APOE gene polymorphisms regulate cholesterol levels modifying the course of the HCV infection. The relationship between cholesterol, APOE alleles, and the outcome of HCV infection has not been evaluated in the admixed population of Mexico.

AIM

To investigate the role of APOE -ε2, -ε3, and -ε4 alleles and the metabolic profile in the outcome of HCV infection.

METHODS

A total of 299 treatment-naïve HCV patients were included in this retrospective study. Patients were stratified in chronic hepatitis C (CHC) (n = 206) and spontaneous clearance (SC) (n = 93). A clinical record was registered. Biochemical tests were assessed by dry chemistry assay. APOE genotypes were determined using a Real-Time polymerase chain reaction assay.

RESULTS

Total cholesterol, low-density lipoprotein cholesterol (LDL-c), triglycerides, and hypercholesterolemia were higher in SC than CHC patients as well as the frequency of the APOE ε4 allele (12.4% vs 7.3%). SC patients were overweight (54.8%). The ε4 allele was associated with SC (OR = 0.55, 95%CI: 0.31-0.98, P = 0.042) and mild fibrosis (F1-F2) in CHC patients (OR 0.091, 95%CI 0.01-0.75, P = 0.020). LDL-c ≥ 101.5 mg/dL (OR = 0.20, 95%CI: 0.10-0.41, P < 0.001) and BMI ≥ 26.6 kg/m2 (OR= 0.37, 95%CI: 0.18-0.76, P < 0.001) were associated with SC status; while ALT ≥ 50.5 IU/L was negatively associated (OR = 5.67, 95%CI: 2.69-11.97, P < 0.001).

CONCLUSION

In SC patients, the APOE ε4 allele and LDL-c conferred a protective effect in the course of the HCV infection in the context of excess body weight.

The Role of ApoE in HCV Infection and Comorbidity

Hepatitis C virus (HCV) is an RNA virus that can efficiently establish chronic infection in humans. The overlap between the HCV replication cycle and lipid metabolism is considered to be one of the primary means by which HCV efficiently develops chronic infections. In the blood, HCV is complex with lipoproteins to form heterogeneous lipo-viro-particles (LVPs). Furthermore, apolipoprotein E (ApoE), which binds to receptors during lipoprotein transport and regulates lipid metabolism, is localized on the surface of LVPs. ApoE not only participate in the attachment and entry of HCV on the cell surface but also the assembly and release of HCV viral particles from cells. Moreover, in the blood, ApoE can also alter the infectivity of HCV and be used by HCV to escape recognition by the host immune system. In addition, because ApoE can also affect the antioxidant and immunomodulatory/anti-inflammatory properties of the host organism, the long-term binding and utilization of host ApoE during chronic HCV infection not only leads to liver lipid metabolic disorders but may also lead to increased morbidity and mortality associated with systemic comorbidities.

The Myth of Optimality in Clinical Neuroscience

Clear evidence supports a dimensional view of psychiatric illness. Within this framework the expression of disorder-relevant phenotypes is often interpreted as a breakdown or departure from normal brain function. Conversely, health is reified, conceptualized as possessing a single ideal state. We challenge this concept here, arguing that there is no universally optimal profile of brain functioning. The evolutionary forces that shape our species select for a staggering diversity of human behaviors. To support our position we highlight pervasive population-level variability within large-scale functional networks and discrete circuits. We propose that, instead of examining behaviors in isolation, psychiatric illnesses can be best understood through the study of domains of functioning and associated multivariate patterns of variation across distributed brain systems.

Impact of Apo E gene polymorphism on HCV therapy related outcome in a cohort of HCV Egyptian patients

The functional apolipoprotein E (Apo E) gene polymorphism could be used as a determinant of outcome of HCV infection. This study aimed to demonstrate the impact of Apo E genotype on the response to HCV combined therapy.

MATERIAL AND METHODS

The study has been implemented on 125 individuals with persistent HCV infection and 120 cases with sustained virologic response (SVR). All participants were genotyped for ApoE gene polymorphism by a real-time quantitative PCR (qPCR).

RESULTS

Statistically significant differences were demonstrated regarding the Apo E genotypes between the two groups (P-value < .001) where the frequency of E3E3 was significantly higher among the chronic HCV-patients while E3E4 and E4E4 genotypes frequencies were higher among the SVR-subjects group and E3E3 genotype was associated with increased risk of chronicity (OR 4.7; 95% CI 1.9-12.1, P-value < .001). Moreover, There were statically significant differences regarding E3 and E4 alleles frequencies, where E3 allele display a higher frequency among the chronic HCV-patient group while the SVR-subjects group showed higher frequency of E4 allele and the carriers of E3 allele have 1.4 times more risk to develop chronicity than those with E4 allele (OR 1.4; 95% CI 1.0-2.0, P-value < .05). Meanwhile the protective E2 allele was absent in all infected participants.

CONCLUSION

This study supports the hypothesis of the protective impact of Apo E4 allele that favors viral clearance of HCV infection and its recovery after combined therapy, while the Apo E3 allele is considered as a particular risk factor for the chronicity in HCV patients and resistance to therapy. Whereas the Apo E2 allele confers a resistance to HCV infection at a time of exposure.

Cognitive Dysfunction and Single Nucleotide Polymorphisms in Hepatitis C Virus-Infected Persons: A Systematic Review

The aim of this study was to realize a systematic review to identify data reported in the literature involving people infected by hepatitis C virus (HCV) with cognitive dysfunctions and single nucleotide polymorphisms (SNPs). The research was realized in six databases and the selection of studies was performed in two stages. Initially, we searched indexed articles from the following electronic databases: SciELO, MEDLINE, PubMed, HighWire, LILACS, and ScienceDirect. Then the articles were completely read and those that did not meet the eligibility criteria were excluded. Therefore, 5,669 articles were obtained and, of these, 25 were selected. Finally, one article involving people with HCV and cognitive impairment was included in the review. The frequency of the APOE-ɛ4 allele in people with HCV and mild liver disease was significantly lower in those with work memory impairment (p = 0.003) and attention (p = 0.008). This situation differs from other studies that showed an association between ɛ4 allele high frequency and cognitive decline. Thus, studies with larger samples involving people with HCV, cognitive alterations, and SNPs are necessary, in view of the lack of this theme in the literature and the divergences in the findings.

Genetic, Transcriptome, Proteomic, and Epidemiological Evidence for Blood-Brain Barrier Disruption and Polymicrobial Brain Invasion as Determinant Factors in Alzheimer's Disease

Diverse pathogens are detected in Alzheimer's disease (AD) brains. A bioinformatics survey showed that AD genome-wide association study (GWAS) genes (localized in bone marrow, immune locations and microglia) relate to multiple host/pathogen interactomes (Candida albicans, Cryptococcus neoformans, Bornavirus, Borrelia burgdorferri, cytomegalovirus, Ebola virus, HSV-1, HERV-W, HIV-1, Epstein-Barr, hepatitis C, influenza, Chlamydia pneumoniae, Porphyrymonas gingivalis, Helicobacter pylori, Toxoplasma gondii, Trypanosoma cruzi). These interactomes also relate to the AD hippocampal transcriptome and to plaque or tangle proteins. Upregulated AD hippocampal genes match those upregulated by multiple bacteria, viruses, fungi, or protozoa in immunocompetent cells. AD genes are enriched in GWAS datasets reflecting pathogen diversity, suggesting selection for pathogen resistance, as supported by the old age of AD patients, implying resistance to earlier infections. APOE4 is concentrated in regions of high parasitic burden and protects against childhood tropical infections and hepatitis C. Immune/inflammatory gain of function applies to APOE4, CR1, and TREM2 variants. AD genes are also expressed in the blood-brain barrier (BBB), which is disrupted by AD risk factors (age, alcohol, aluminum, concussion, cerebral hypoperfusion, diabetes, homocysteine, hypercholesterolemia, hypertension, obesity, pesticides, pollution, physical inactivity, sleep disruption, smoking) and by pathogens, directly or via olfactory routes to basal-forebrain BBB control centers. The BBB benefits from statins, NSAIDs, estrogen, melatonin, memantine, and the Mediterranean diet. Polymicrobial involvement is supported by upregulation of bacterial, viral, and fungal sensors/defenders in the AD brain, blood, or cerebrospinal fluid. AD serum amyloid-β autoantibodies may attenuate its antimicrobial effects favoring microbial survival and cerebral invasion leading to activation of neurodestructive immune/inflammatory processes, which may also be augmented by age-related immunosenescence. AD may thus respond to antibiotic, antifungal, or antiviral therapy.

Apolipoprotein E4 is associated with improved cognitive function in Amazonian forager-horticulturalists with a high parasite burden

The apolipoprotein E4 (E4) allele is present worldwide, despite its associations with higher risk of cardiovascular morbidity, accelerated cognitive decline during aging, and Alzheimer's disease (AD). The E4 allele is especially prevalent in some tropical regions with a high parasite burden. Equatorial populations also face a potential dual burden of high E4 prevalence combined with parasitic infections that can also reduce cognitive performance. We examined the interactions of E4, parasite burden, and cognitive performance in a traditional, nonindustrialized population of Amazonian forager-horticulturalists (N = 372) to test whether E4 protects against cognitive decline in environments with a heavy pathogen burden. Contrary to observations in industrial populations, older adult E4 carriers with high parasite burdens either maintained or showed slight improvements in cognitive performance, whereas non-E4 carriers with a high parasite burden showed reduced cognitive performance. Being an E4 carrier is the strongest risk factor to date of AD and cognitive decline in industrial populations; it is associated with greater cognitive performance in individuals facing a high parasite and pathogen load, suggesting advantages to the E4 allele under certain environmental conditions. The current mismatch between postindustrial hygienic lifestyles and active parasite-rich environs may be critical for understanding genetic risk for cognitive aging.-Trumble, B. C., Stieglitz, J., Blackwell, A. D., Allayee, H., Beheim, B., Finch, C. E., Gurven, M., Kaplan, H. Apolipoprotein E4 is associated with improved cognitive function in Amazonian forager-horticulturalists with a high parasite burden.