Low fibrosis progression of recurrent hepatitis C in apolipoprotein E epsilon4 carriers: relationship with the blood lipid profile

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.

ApoE deficiency promotes hepatic pathology by aggravating Th17/Treg imbalance in murine schistosomiasis japonica

AIMS

The Schistosoma japonicum (S japonicum)-infected ApoE gene deficiency (ApoE^-/- ) mice were used to determine effect of ApoE on hepatic immunopathology.

METHODS

Murine activities and appetite, body weight, and ratio of liver weight to its body weight (Hepatic mass index, HMI) were observed. Worm load and liver egg burden were evaluated as the infection intensity. Number and size of liver egg granulomas and serum levels of alanine aminotransferase (ALT) were investigated. We analysed hepatic fibrosis by markers of fibrosis in tissue, detected hepatic Th17 and Treg frequency by flow cytometry, and measured hepatic expressions of RORγt, Foxp3, IL-17A and TGF-β1 via qPCR. Lipid metabolism was determined by serum levels of cholesterol (TC) and triglyceride (TG) as well as hepatic Oil red O staining.

RESULTS

In the infected ApoE^-/- mice, the increased infection intensity aggravated the hepatic immunopathology (evidenced by increased HMI, elevated egg granulomas and increased ALT levels) and fibrosis (increased hepatic collagen deposition). ApoE deficiency resulted in significantly elevated ratio of hepatic Th17/Treg and higher serum levels of TC and TG, along with higher level of hepatic Oil red O staining.

CONCLUSIONS

ApoE deficiency promotes hepatic pathology and fibrosis by exacerbating Th17/Treg imbalance and altering lipid metabolism in murine schistosomiasis japonica.

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.

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

BACKGROUND & AIMS

Infectious hepatitis C virus (HCV) particles bind to host lipoproteins such as low-density lipoproteins (LDLs). Low-density lipoprotein receptors (LDLR) have been termed candidate receptors for HCV-LDL complexes. Functional host genetic single nucleotide polymorphisms (SNPs) in the apolipoprotein E (APOE) gene encoding apolipoprotein E (apoE) - a major structural LDL component and natural ligand of LDLR - likely influence the course of HCV infection. We investigated the prevalence of APOE SNPs in two large and independent cohorts of patients with chronic HCV infection compared to respective controls.

METHODS

We genotyped 996 chronically HCV-infected patients; 179 patients with spontaneous HCV clearance; 283 individuals with non-HCV-associated liver disease; and 2 234 healthy controls.

RESULTS

APOE genotype proportions in patients with persistent HCV infection significantly differed from healthy controls (P = 0.007) primarily because of a substantial under-representation of APOE4 alleles in chronically HCV-infected patients (10.2%) compared to 13.0% in healthy controls (P = 0.001). The distribution of APOE4 allele positive genotypes (ε2ε4, ε3ε4, ε4ε4) also significantly differed between chronically HCV-infected patients and healthy controls (1.4%, 17%, 1% vs. 2.4%, 20.5%, 1.7%; P = 0.001), suggesting a protective effect of the APOE4 allele in HCV infection. This was confirmed by a significant over-representation of the APOE4 allele in patients with spontaneous HCV clearance (17.6%; P = 0.00008). The APOE4 allele distribution in patients with non-HCV-associated liver disease (14.0%) was very similar to healthy controls and also differed from chronically HCV-infected patients (P = 0.012), suggesting HCV specificity.

CONCLUSIONS

Our findings suggest that the APOE4 allele may confer a protective effect in the course of HCV infection.

Apolipoprotein E-ε4 deficiency and cognitive function in hepatitis C virus-infected patients

Hepatitis C virus (HCV) causes not only liver damage in certain patients but can also lead to neuropsychiatric symptoms. Previous studies have shown that the type 4 allele of the gene for apolipoprotein E (APOE) is strongly protective against HCV-induced damage in liver. In this study, we have investigated the possibility that APOE genotype is involved in the action of HCV in brain. One hundred HCV-infected patients with mild liver disease underwent a neurological examination and a comprehensive psychometric testing of attention and memory function. In addition, patients completed questionnaires for the assessment of fatigue, health-related quality of life and mood disturbances. Apolipoprotein E gene genotyping was carried out on saliva using buccal swabs. The APOE-ε4 allele frequency was significantly lower in patients with an impairment of working memory, compared to those with a normal working memory test result (P = 0.003). A lower APOE-ε4 allele frequency was also observed in patients with definitely altered attention ability (P = 0.008), but here, the P-value missed the level of significance after application of the Bonferroni correction. Our data suggest that the APOE-ε4 allele is protective against attention deficit and especially against poor working memory in HCV-infected subjects with mild liver disease. Considering the role of apolipoprotein E in the life cycle of the virus, the findings shed interesting new light upon possible pathomechanisms behind the development of neuropsychiatric symptoms in hepatitis C infection.

Age, gender, and cancer but not neurodegenerative and cardiovascular diseases strongly modulate systemic effect of the Apolipoprotein E4 allele on lifespan

Enduring interest in the Apolipoprotein E (ApoE) polymorphism is ensured by its evolutionary-driven uniqueness in humans and its prominent role in geriatrics and gerontology. We use large samples of longitudinally followed populations from the Framingham Heart Study (FHS) original and offspring cohorts and the Long Life Family Study (LLFS) to investigate gender-specific effects of the ApoE4 allele on human survival in a wide range of ages from midlife to extreme old ages, and the sensitivity of these effects to cardiovascular disease (CVD), cancer, and neurodegenerative disorders (ND). The analyses show that women's lifespan is more sensitive to the e4 allele than men's in all these populations. A highly significant adverse effect of the e4 allele is limited to women with moderate lifespan of about 70 to 95 years in two FHS cohorts and the LLFS with relative risk of death RR = 1.48 (p = 3.6×10⁻⁶) in the FHS cohorts. Major human diseases including CVD, ND, and cancer, whose risks can be sensitive to the e4 allele, do not mediate the association of this allele with lifespan in large FHS samples. Non-skin cancer non-additively increases mortality of the FHS women with moderate lifespans increasing the risks of death of the e4 carriers with cancer two-fold compared to the non-e4 carriers, i.e., RR = 2.07 (p = 5.0×10⁻⁷). The results suggest a pivotal role of non-sex-specific cancer as a nonlinear modulator of survival in this sample that increases the risk of death of the ApoE4 carriers by 150% (p = 5.3×10⁻⁸) compared to the non-carriers. This risk explains the 4.2 year shorter life expectancy of the e4 carriers compared to the non-carriers in this sample. The analyses suggest the existence of age- and gender-sensitive systemic mechanisms linking the e4 allele to lifespan which can non-additively interfere with cancer-related mechanisms.

Discovering genetic origins of healthspan and lifespan could lead to breakthroughs in increasing the years of healthy and long life. In this paper we characterize the association of the e4 allele of the well-studied ApoE gene with lifespan in two generations of participants of large longitudinal studies, the Framingham Heart Study and the Long Life Family Study, and investigate the role of major human diseases such as cardiovascular disease, cancer, and neurodegenerative disorders in this association. This wide range of systemic analyses is possible given the large sample with directly genotyped ApoE polymorphism available from these studies (N = 9841, with 2557 deaths). The analyses show that women's lifespan is more sensitive to the e4 allele than men's in these populations. However, the strongly adverse effect of the e4 allele is not observed for all women, but only for those 70 to 95 years old. Cardiovascular disease, cancer, and neurodegenerative disorders do not mediate the association of the e4 allele with lifespan. However, cancer, but not cardiovascular and neurodegenerative diseases, non-additively enhances this effect resulting in 4.2 years of difference in mean lifespan for the e4 allele carriers compared to the non-carriers.

A 7-gene signature of the recipient predicts the progression of fibrosis after liver transplantation for hepatitis C virus infection

Fibrosis recurrence after liver transplantation (LT) for hepatitis C virus (HCV) is a universal event and strongly determines a patient's prognosis. The recipient risk factors for fibrosis recurrence are still poorly defined. Here we assess a genetic risk score as a predictor of fibrosis after LT. The cirrhosis risk score (CRS), which comprises allele variants in 7 genes (adaptor-related protein complex 3 S2, aquaporin 2, antizyme inhibitor 1, degenerative spermatocyte homolog 1 lipid desaturase, syntaxin binding protein 5-like, toll-like receptor 4, and transient receptor potential cation channel M5), was calculated for 137 patients who underwent LT for HCV infection and experienced HCV reinfection of the graft. The patients were stratified into 3 CRS categories: <0.5, 0.5 to 0.7, and >0.7. All patients underwent protocol biopsy after LT (median follow-up = 5 years), and liver fibrosis was assessed according to the Desmet and Scheuer score. The data were analyzed with univariate and multivariate analyses. The results showed that the highest CRS category was strongly associated with the presence of F2 or F3 fibrosis in protocol biopsy samples 1, 3, and 5 years after LT (P = 0.006, P = 0.001, and P = 0.02, respectively). Overall, 75.0% of the patients with a CRS > 0.7 developed at least F2 fibrosis, whereas 51.5% developed F3 fibrosis during follow-up. The predictive value of the CRS for fibrosis progression was independent of known clinical risk factors, including the age of the donor, the sex of the recipient, and the occurrence of acute rejection. A Kaplan-Meier analysis confirmed the prognostic value of the CRS with respect to the recurrence of severe liver fibrosis in HCV-infected patients after LT (log rank = 6.23, P = 0.03). In conclusion, the genetic signature of the recipient predicts the likelihood of severe liver fibrosis in the graft after HCV recurrence. The CRS might help with early clinical decision making (eg, the selection of patients for antiviral therapy after LT).

Trade-off in the effects of the apolipoprotein E polymorphism on the ages at onset of CVD and cancer influences human lifespan

Progress in unraveling the genetic origins of healthy aging is tempered, in part, by a lack of replication of effects, which is often considered a signature of false-positive findings. We convincingly demonstrate that the lack of genetic effects on an aging-related trait can be because of trade-offs in the gene action. We focus on the well-studied apolipoprotein E (APOE) e2/3/4 polymorphism and on lifespan and ages at onset of cardiovascular diseases (CVD) and cancer, using data on 3924 participants of the Framingham Heart Study Offspring cohort. Kaplan-Meier estimates show that the e4 allele carriers live shorter lives than the non-e4 allele carriers (log rank = 0.016). The adverse effect was attributed to the poor survival of the e4 homozygotes, whereas the effect of the common e3/4 genotype was insignificant. The e3/4 genotype, however, was antagonistically associated with onsets of those diseases predisposing to an earlier onset of CVD and a later onset of cancer compared to the non-e4 allele genotypes. This trade-off explains the lack of a significant effect of the e3/4 genotype on survival; adjustment for it in the Cox regression model makes the detrimental effect of the e4 allele highly significant (P = 0.002). This trade-off is likely caused by the lipid-metabolism-related (for CVD) and nonrelated (for cancer) mechanisms. An evolutionary rationale suggests that genetic trade-offs should not be an exception in studies of aging-related traits. Deeper insights into biological mechanisms mediating gene action are critical for understanding the genetic regulation of a healthy lifespan and for personalizing medical care.

Apolipoprotein E genotypes modulate fibrosis progression in patients with chronic hepatitis C and persistently normal transaminases

BACKGROUND AND AIM

Carriage of the apolipoprotein E (Apo E) variants, E2, E3 and E4, affects cholesterol metabolism and may be involved in the persistence of hepatitis C virus (HCV) infection. Our aim was to verify whether carriage of specific Apo E variants modulates the course of hepatitis C.

METHODS

We studied a cohort of 116 HCV-positive patients (49 male subjects) with persistently normal transaminases and an Ishak staging score ≤ 2 at an initial biopsy. These untreated patients underwent regular clinical monitoring (median histological follow up: 10 years). Apo E variants were genotyped and results were related to the histological outcome.

RESULTS

The mean ± standard deviation staging scores were 0.9 ± 0.7 at entry versus 1.9 ± 1.2 at the end of follow up, P < 0.0001. Initial and final staging scores in the E3/E3 homozygotes (n = 74) were 1.0 ± 0.7 versus 2.1 ± 1.3, P < 0.0001, while in the remaining patients (n = 42) they were 0.9 ± 0.6 versus 1.5 ± 1.0, P < 0.002. A synergistic effect was observed between Apo E polymorphisms and baseline serum cholesterol values: patients not carrying any E3 allele, as well as carriers of a single E3 allele with serum cholesterol concentration > 190 mg/dL were more likely to have a favorable outcome (final vs initial staging score increased in 7/66, did not change in 10/46, and decreased in 3/4, P <0.005).

CONCLUSIONS

Some of the variability in the natural history of patients with persistently normal transaminases with initially mild hepatitis C can be related to their Apo E genetic background.

Inflammatory gene variants in the Tsimane, an indigenous Bolivian population with a high infectious load

The Tsimane of lowland Bolivia are an indigenous forager-farmer population living under conditions resembling pre-industrial European populations, with high infectious morbidity, high infection and inflammation, and shortened life expectancy. Analysis of 917 persons ages 5 to 60+ showed that allele frequencies of 9 SNPs examined in the apolipoprotein E (apoE), C-reactive protein (CRP), and interleukin-6 (IL-6) genes differed from some European, African, and north Asian-derived populations. The apoE2 allele was absent, whereas four SNPs related to CRP and IL-6 were monomorphic: CRP (rs1800947, rs3093061, and rs3093062) and IL-6 (rs1800795). No significant differences in apoE, CRP, and IL-6 variants across age were found CRP levels were higher in carriers of two CRP proinflammatory SNPs, whereas they were lower in carriers of apoE4. Taken together the evidence for (1) different allele frequencies between the Tsimane and other populations and (2) the correlations of CRP and apoE alleles with blood CRP may suggest that these variants are under selection in response to a high infection environment.

Genetic polymorphism at the apolipoprotein E locus affects the outcome of chronic hepatitis B

Apolipoprotein E (ApoE) and H (ApoH) genotypes are known to affect plasma lipoprotein concentrations. By modulating transport and entry of the hepatitis B virus into hepatocytes, apolipoproteins may influence the course of infection. To verify this hypothesis, 105 patients with chronic HBV infection were examined. Sixty-two of the patients were followed-up for a median time of 21 years. One hundred two controls were included. ApoE and ApoH genotypes were determined by the restriction fragment length polymorphism method. A trend was found for progressive overrepresentation of ApoE3/E3 among patients with advanced liver disease: 13/27 (48%) of inactive HBV carriers, 36/61 (59%) of chronic hepatitis B patients and 16/17 (94%) of patients who received liver transplants (P < 0.005). Being an E3/* carrier was associated with a lower probability of loss of HBsAg: 9/56 (16%) versus 3/6 (50%) (P < 0.05); it was also associated with a longer time before HBsAg loss (P < 0.05). No influence of ApoH genotypes on clinical outcomes was found. The probability of disease progression was higher, and that of loss of HBsAg was lower, among patients with the ApoE3 allelic variant. Downregulation and/or reduced binding of the LDL receptor may explain the more benign course of hepatitis B among carriers of ApoE2-E4.

Apolipoprotein E genotype and hepatitis C, HIV and herpes simplex disease risk: a literature review

Apolipoprotein E is a polymorphic and multifunctional protein with numerous roles in lipoprotein metabolism. The three common isoforms apoE2, apoE3 and apoE4 show isoform-specific functional properties including different susceptibilities to diseases. ApoE4 is an accepted risk factor for Alzheimer's disease and cardiovascular disorders. Recently, associations between apoE4 and infectious diseases have been demonstrated. This review summarises how apoE4 may be involved in the infection incidence and associated pathologies of specific infectious diseases, namely hepatitis C, human immunodeficiency virus disease and herpes simplex.ApoE4 seems to be protective against chronic hepatitis C virus infection and retards fibrosis progression. In contrast apoE4 enhances the fusion rate of human immunodeficiency virus with target cell membranes, resulting in accelerated cell entry and faster disease progression. Its association with human immunodeficiency virus-associated dementia remains controversial. Regarding herpes simplex virus infection, apoE4 intensifies virus latency and is associated with increased oxidative damage of the central nervous system, and there is some evidence that herpes simplex virus infection in combination with the apoE4 genotype may be associated with an increased risk of Alzheimer's disease. In addition to reviewing available data from human trials, evidence derived from a variety of cell culture and animal models are considered in this review in order to provide mechanistic insights into observed association between apoE4 genotype and viral disease infection and pathology.

Evolution in health and medicine Sackler colloquium: Evolution of the human lifespan and diseases of aging: roles of infection, inflammation, and nutrition

Humans have evolved much longer lifespans than the great apes, which rarely exceed 50 years. Since 1800, lifespans have doubled again, largely due to improvements in environment, food, and medicine that minimized mortality at earlier ages. Infections cause most mortality in wild chimpanzees and in traditional forager-farmers with limited access to modern medicine. Although we know little of the diseases of aging under premodern conditions, in captivity, chimpanzees present a lower incidence of cancer, ischemic heart disease, and neurodegeneration than current human populations. These major differences in pathology of aging are discussed in terms of genes that mediate infection, inflammation, and nutrition. Apolipoprotein E alleles are proposed as a prototype of pleiotropic genes, which influence immune responses, arterial and Alzheimer's disease, and brain development.

Disease progression in chronic hepatitis C: modifiable and nonmodifiable factors

The hepatic complications of chronic hepatitis C (CHC) usually occur only after progression to cirrhosis has taken place. Progression to cirrhosis, however, is extremely variable and depends on a broad set of host and viral factors that modify the rate at which fibrosis develops in a given individual. Despite their inherent limitations, studies of the natural history of CHC have identified several nonmodifiable factors associated with disease progression. These include age at acquisition of infection, sex, and race. More recent reports suggest important roles for host genetic polymorphisms and viral factors. Of greater immediate relevance to patients and their clinicians are the potentially modifiable factors, which include excessive alcohol consumption; smoking (tobacco and marijuana); insulin resistance; and coinfection with hepatitis B virus, human immunodeficiency virus type 1, or schistosomiasis. Unfortunately, to date, there are no reliable predictive models that can accurately estimate the risk of CHC disease progression.

Sex-related influence of angiotensin-converting enzyme polymorphisms on fibrosis progression due to recurrent hepatitis C after liver transplantation

BACKGROUND

Experimental evidence and clinical studies suggest that the renin-angiotensin system and its inhibitors may play a role in regulating the mechanisms of liver fibrosis development. The present study aimed to verify whether carriage of specific angiotensin-converting enzyme (ACE) insertion (I)/deletion (D) allelic variants, modulating angiotensin II generation, could affect the outcome of recurrent hepatitis C after liver transplantation, via several metabolic pathways.

METHODS

Forty-five (29 men) recipients, with a median histological follow-up of 60 months after orthotopic liver transplantation (OLT), were studied. ACE gene I/D polymorphism was assessed by means of a polymerase chain reaction procedure. Fibrosis progression was evaluated annually during the follow-up.

RESULTS

Weight gain 1 year post-OLT (defined as an increase in body mass index, BMI, of >0.5 kg/m(2)) was significantly more common among D/ carriers (22/22 vs. 16/23, P < 0.005); patients who 1 year after OLT had an increase in their BMI value of >0.5 kg/m(2) more frequently had a triglycerides/cholesterol ratio of <or= 0.7 (16/22 vs. 8/23, chi-squared test P < 0.02). This association was stronger in men. Female D/D homozygotes had the highest probability of showing significant liver fibrosis (7/10) in comparison with men (11/29) and I/ women (1/6) (P < 0.01).

CONCLUSIONS

In patients with recurrent hepatitis C, carriers of the D allele appeared to gain more weight after liver transplantation, and in male liver recipients, the D allele was associated with a peculiar lipid profile that was associated with a slower rate of allograft fibrosis progression. Among female recipients, carriage of the D allele may favor more severe allograft fibrosis.