HLA-DR,DQ and APOE genotypes and gender influence in Sardinian primary progressive MS

Sex-dependent effect of APOE on Alzheimer's disease and other age-related neurodegenerative disorders

The importance of apolipoprotein E (APOE) in late-onset Alzheimer's disease (LOAD) has been firmly established, but the mechanisms through which it exerts its pathogenic effects remain elusive. In addition, the sex-dependent effects of APOE on LOAD risk and endophenotypes have yet to be explained. In this Review, we revisit the different aspects of APOE involvement in neurodegeneration and neurological diseases, with particular attention to sex differences in the contribution of APOE to LOAD susceptibility. We discuss the role of APOE in a broader range of age-related neurodegenerative diseases, and summarize the biological factors linking APOE to sex hormones, drawing on supportive findings from rodent models to identify major mechanistic themes underlying the exacerbation of LOAD-associated neurodegeneration and pathology in the female brain. Additionally, we list sex-by-genotype interactions identified across neurodegenerative diseases, proposing APOE variants as a shared etiology for sex differences in the manifestation of these diseases. Finally, we present recent advancements in 'omics' technologies, which provide a new platform for more in-depth investigations of how dysregulation of this gene affects the development and progression of neurodegenerative diseases. Collectively, the evidence summarized in this Review highlights the interplay between APOE and sex as a key factor in the etiology of LOAD and other age-related neurodegenerative diseases. We emphasize the importance of careful examination of sex as a contributing factor in studying the underpinning genetics of neurodegenerative diseases in general, but particularly for LOAD.

Gender differences in autoimmune disease

Autoimmune diseases are a range of diseases in which the immune response to self-antigens results in damage or dysfunction of tissues. Autoimmune diseases can be systemic or can affect specific organs or body systems. For most autoimmune diseases there is a clear sex difference in prevalence, whereby females are generally more frequently affected than males. In this review, we consider gender differences in systemic and organ-specific autoimmune diseases, and we summarize human data that outlines the prevalence of common autoimmune diseases specific to adult males and females in countries commonly surveyed. We discuss possible mechanisms for sex specific differences including gender differences in immune response and organ vulnerability, reproductive capacity including pregnancy, sex hormones, genetic predisposition, parental inheritance, and epigenetics. Evidence demonstrates that gender has a significant influence on the development of autoimmune disease. Thus, considerations of gender should be at the forefront of all studies that attempt to define mechanisms that underpin autoimmune disease.

Genetics of primary progressive multiple sclerosis

Multiple sclerosis (MS) patients are classified as either having relapsing onset or progressive onset disease, also known as primary progressive MS (PPMS). Relative to relapsing onset patients, PPMS patients are older at disease onset, are equally likely to be men or women, and have more rapid accumulation of disability that does not respond well to treatments used in relapsing onset MS. Although estimates vary, 5-15% of all MS patients have a PPMS disease course. Genetic variance is a proposed determinant of MS disease course. If distinct genes associated with PPMS were identified study of these genes might lead to an understanding of the biology underlying disease progression and neural degeneration that are the hallmarks of PPMS. These genes and their biological pathways might also represent therapeutic targets. This chapter systematically reviews the PPMS genetic literature. Despite the intuitively appealing notion that differences between PPMS and relapsing onset MS are due to genetics, definite differences associated with these phenotypes at the major histocompatibility complex or elsewhere in the genome have not been found. Recent large-scale genome wide screens identified multiple genes associated with MS susceptibility outside the MHC. The genetic variants identified thus far make only weak individual contributions to MS susceptibility. If the genetic effects that contribute to the differences between PPMS and relapsing MS are similar in magnitude to those that distinguish MS from healthy controls then, given the relative scarcity of the PPMS phenotype, very large datasets will be needed to identify PPMS associated genes. International collaborative efforts could provide the means to identify such genes. Alternately, it is possible that factors other than genetics underlie the differences between these clinical phenotypes.

Quantifying diet for nutrigenomic studies

The field of nutrigenomics shows tremendous promise for improved understanding of the effects of dietary intake on health. The knowledge that metabolic pathways may be altered in individuals with genetic variants in the presence of certain dietary exposures offers great potential for personalized nutrition advice. However, although considerable resources have gone into improving technology for measurement of the genome and biological systems, dietary intake assessment remains inadequate. Each of the methods currently used has limitations that may be exaggerated in the context of gene × nutrient interaction in large multiethnic studies. Because of the specificity of most gene × nutrient interactions, valid data are needed for nutrient intakes at the individual level. Most statistical adjustment efforts are designed to improve estimates of nutrient intake distributions in populations and are unlikely to solve this problem. An improved method of direct measurement of individual usual dietary intake that is unbiased across populations is urgently needed.

Association between apolipoprotein E gene polymorphism and the risk of multiple sclerosis: a meta-analysis of 6977 subjects

Epidemiological studies have evaluated the association between apolipoprotein E (ApoE) gene polymorphism and multiple sclerosis (MS) risk. However, the results remain conflicting. Therefore, in order to derive a more precise association of ApoE gene polymorphism with MS risk, we performed this meta-analysis. Systematic searches of electronic databases PubMed, Embase and Web of Science, as well as hand searching of the references of identified articles were performed. Twenty studies were identified, covering a total of 4080 MS cases and 2897 controls. The results showed evidence for significant association between ApoE ε2 mutation and MS risk (for ε2/ε4 versus ε3/ε3: OR=1.74, 95% CI=1.12-2.71, p=0.01; for ε2 allele versus ε3 allele: OR=1.16, 95% CI=1.01-1.35, p=0.04). In the subgroup analysis by ethnicity, the similar results were obtained among Europeans (for ε2/ε4 versus ε3/ε3: OR=1.81, 95% CI=1.14-2.87, p=0.01; for ε2 allele versus ε3 allele: OR=1.19, 95% CI=1.02-1.38, p=0.03). After excluding the outlier studies by observing Galbraith plot, marginal association was found between ApoE ε3/ε4 genotype and the protective factor for MS (for ε3/ε4 versus ε3/ε3: OR=0.86, 95% CI=0.75-0.99, p=0.04). In summary, the present meta-analysis provides evidence that ApoE ε2 mutation is associated with MS risk. In addition, ApoE ε3/ε4 genotype appears to be a protective factor for MS.

Demographic, genetic, and environmental factors that modify disease course

As with susceptibility to disease, it is likely that multiple factors interact to influence the phenotype of multiple sclerosis and long-term disease outcomes. Such factors may include genetic factors, socioeconomic status, comorbid diseases, and health behaviors, as well as environmental exposures. An improved understanding of the influence of these factors on disease course may reap several benefits, such as improved prognostication, allowing us to tailor disease management with respect to intensity of disease-modifying therapies and changes in specific health behaviors, in the broad context of coexisting health issues. Such information can facilitate appropriately adjusted comparisons within and between populations. Elucidation of these factors will require careful study of well-characterized populations in which the roles of multiple factors are considered simultaneously.

The immune-modulatory role of apolipoprotein E with emphasis on multiple sclerosis and experimental autoimmune encephalomyelitis

Apolipoprotein E (apoE) is a 34.2 kDa glycoprotein characterized by its wide tissue distribution and multiple functions. The nonlipid-related properties of apoE include modulating inflammation and oxidation, suppressing T cell proliferation, regulating macrophage functions, and facilitating lipid antigen presentation by CD1 molecules to natural killer T (NKT) cells, and so forth. Increasing studies have revealed that APOE ε allele might be associated with multiple sclerosis (MS), although evidence is still not sufficient enough. In this review, we summarized the current progress of the immunomodulatory functions of apoE, with special focus on the association of APOE ε allele with the clinical features of MS and of its animal model experimental autoimmune encephalomyelitis (EAE).

Genotype-phenotype associations: modulation by diet and obesity

Changes in diet are likely to reduce chronic disorders, but after decades of active research and heated discussion, the question still remains: what is the optimal diet to achieve this elusive goal? Is it a low-fat diet, as traditionally recommended by multiple medical societies? Or a high monounsaturated fat (MUFA) diet as predicated by the Mediterranean diet? Perhaps a high polyunsaturated fat (PUFA) diet based on the cholesterol-lowering effects? The right answer may be all of the above but not for everybody. A well-known phenomenon in nutrition research and practice is the dramatic variability in interindividual response to any type of dietary intervention. There are many other factors influencing response, and they include, among many others, age, sex, physical activity, alcohol, and smoking as well as genetic factors that will help to identify vulnerable populations/individuals that will benefit from a variety of more personalized and mechanistic-based dietary recommendations. This potential could and needs to be developed within the context of nutritional genomics that in conjunction with systems biology may provide the tools to achieve the holy grail of dietary prevention and therapy of chronic diseases and cancer. This approach will break with the traditional public health approach of "one size fits all." The current evidence based on nutrigenetics has begun to identify subgroups of individuals who benefit more from a low-fat diet, whereas others appear to benefit more from high MUFA or PUFA diets. The continuous progress in nutrigenomics will allow some time in the future to provide targeted gene-based dietary advice.

The genetics of clinical outcome in multiple sclerosis

Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system (CNS), the clinical course of which varies considerably between patients. Genetic complexity and interactions with as yet unknown environmental factors have hindered researchers from fully elucidating the aetiology of the disease. In addition to influencing disease susceptibility, epidemiological evidence suggests that genetic factors may affect phenotypic expression of the disease. Genes that affect clinical outcome may be more effective therapeutic targets than those which determine susceptibility. We present in this review a comprehensive survey of the genes (both MHC- and non-MHC-related) that have been investigated for their role in disease outcome in MS. Recent studies implicating the role of the genotype and epistatic interactions in the MHC in determining outcome are highlighted.

Gender, a significant factor in the cross talk between genes, environment, and health

BACKGROUND

Although men and women share most genetic information, they have significantly different disease susceptibilities that go well beyond the expected gender-specific diseases. Sex influences the risk of nearly all common diseases that affect both men and women, including atherosclerosis and diabetes and their preceding risk factors (eg, hyperlipidemia, insulin resistance, and obesity).

OBJECTIVE

The goal of this article was to examine the interplay between genes, gender, and disease susceptibility, and assess it in the context of the added complexity of environmental factors (ie, dietary habits, smoking, alcohol consumption) in the modulation of the balance between health and disease.

METHODS

Original and review articles published by the author were reexamined for evidence of gene-gender interactions.

RESULTS

Evidence from some key factors in lipid metabolism (apolipoprotein E [APOE])and obesity (perilipin [PLIN]) indicates that the interplay between genes, gender, and environmental factors modulates disease susceptibility. In the Framingham Heart Study, complex interactions have been shown between a promoter polymorphism at the apolipoprotein A1 gene, gender, and dietary poly-unsaturated fatty acid intake that modulate plasma concentrations of high-density lipoprotein cholesterol. Likewise, highly and clinically relevant interactions have been observed between the APOE gene common alleles APOE2 , APOE3, and APOE4 , gender, and smoking that determine cardiovascular disease risk. Most interesting is the gender-dependent association between common polymorphisms at the PLIN locus and obesity risk that has been replicated in several populations around the world.

CONCLUSIONS

These data support the idea that gender-specific differences in morbidity and mortality may be mediated in part by genetic factors and by their differential response to the environment. The new knowledge generated by a more careful and complete elucidation of the complex interactions predisposing to common diseases will result in an increased ability to provide successful personalized behavioral recommendations to prevent chronic disorders.

Apolipoprotein E genotype does not associate with disease severity measured by Multiple Sclerosis Severity Score

OBJECTIVES

During the last years, the association between apolipoprotein E (APOE) polymorphism and disease severity in multiple sclerosis (MS) has been studied with conflicting results. As a result of a considerable individual variation in the clinical course of MS, there is no consensus method for measuring progression using single assessments of disability. Recently, Multiple Sclerosis Severity Score (MSSS) method has been proposed for comparing disease progression using single data. We evaluate in our population if there is any correlation between APOE genotype and severity according to MSSS.

METHODS

We studied 82 patients followed up in our Neurology Unit throughout the year 2005, diagnosed with MS, and with disease duration of at least 2 years. We collected data concerning demographic and clinical variables including age of onset, disease duration, Expanded Disability Status Scale (EDSS) score and the total number of relapses. When reached, we determined the latency to EDSS scores of 4.0 and 6.0. We calculated progression index (PI) and relapse rate (RR). We ascertained MSSS for our patients in the global MSSS table.

RESULTS

We found four patients heterozygous for the E2 allele and 16 for the E4 allele. No patient was homozygous for E2 or E4. RR (P = 0.017 with 95% CI: 0.005-0.57) and PI (P = 0.016 with 95% CI: 0.004-0.38) were significantly lower in E4 carriers. MSSS scores were not associated with carriership of E2 or E4.

CONCLUSION

Our results show no effect of the APOE genotype on the severity of MS measured by MSSS, as a recently published meta-analysis has noticed. So, our data do not support a role for APOE in MS severity, in spite of the seeming influence shown using other measures such as PI. MSSS is probably the best method to measure severity with a single measure of disability and should be used more frequently when performing genetic research.

No effect of APOE and PVRL2 on the clinical outcome of multiple sclerosis

Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system unsurpassed for its variability in disease outcome. Apolipoprotein E (APOE) is involved in neuronal remodelling and several studies have attempted to examine the effect of APOE on MS disease severity, but its function in modifying the course of MS is controversial. It has been suggested recently that PVRL2, not APOE, is the locus on chromosome 19 which influences clinical outcome of MS. A cohort of sporadic MS cases, taken from opposite extremes of the putative distribution of long-term outcome using the most stringent clinical criteria to date, was used to determine the role of APOE and PVRL2 on MS disease severity. The MS cases selected represent the prognostic best 5% (benign MS) and worst 5% (malignant MS) of cases in terms of clinical outcome assessed by the EDSS. Genotyping the two sets of MS patients (112 benign and 51 malignant) and a replication cohort from Sardinia provided no evidence to suggest that APOE or PVRL2 have any outcome modifying activity. We conclude that APOE and PVRL2 have little or no effect on the clinical outcome of MS.

Apolipoprotein E gene polymorphism and allele frequencies in the Lebanese population

Apolipoprotein E (ApoE) genotypes were studied in order to determine the prevalence in the Lebanese population and compare it with other populations. DNA from 160 unrelated healthy donors from our HLA-bank was used. ApoE genotype was determined using the CardioVascular Disease (CVD) StripAssay (this assay is based on a Polymerase Chain Reaction-Reverse Hybridization technique). The prevalence of genotypes E3/3, E3/4, and E2/3 was found to be 69%, 26%, and 22%, respectively, and 0.6% for each of E2/4 and E4/4 genotypes. The Lebanese population tested showed similarities to earlier reported ApoE genotypic distributions (high E3 allele frequency) but also peculiar differences especially to some Arabic countries (total absence of E2 allele among Saudis) and other populations. This is the first report from Lebanon that will serve as a template for future investigations of the prevalence of ApoE alleles in association with various clinical entities.

CXCL10 haplotypes and multiple sclerosis: association and correlation with clinical course

CXCL10 (interferon-gamma-inducible protein-10) levels are increased in cerebrospinal fluid of multiple sclerosis (MS) patients with symptomatic attacks of inflammatory demyelination, supporting a role for this molecule in MS pathogenesis. Two hundred and twenty-six patients with MS and 235 controls were genotyped for G --> C and T --> C single nucleotide polymorphisms (SNPs) in exon 4 of CXCL10 gene. Haplotypes were tested for association and correlated with clinical variables. The two SNPs studied were in complete linkage disequilibrium. None of the determined haplotypes was associated with MS. However, carriers of the GGTT haplotype (defined as wild type, according to the sequence in National Centre for Biotechnology Information (NCBI) database) had a significantly lower progression index than non-carriers (P = 0.016). Furthermore, amongst patients who had an initial relapsing remitting (RR) course of the disease, the time between onset and second episode was significantly longer in GGTT carriers (P = 0.021). Considering secondary progressive (SP)-MS patients, the time between the initial RR form and the subsequent worsening to SP was longer in this group (P = 0.08). Therefore, the GGTT haplotype of the CXCL10 gene is not a susceptibility factor for the development of MS, but is probably to influence the course of MS, possibly contributing to slow down the progression of the disease.

APOE genotypes in African American female multiple sclerosis patients

Multiple sclerosis (MS) is a chronic inflammatory CNS disorder, resulting in progressive neurological dysfunction. The disease has a higher incidence in Caucasian Americans (CA) than African Americans (AA); however, the latter may have a more aggressive disease course. We used cluster analysis to determine whether there is a difference in disease progression between the races and whether the APOE AND APOC1 genotypes influence the disease progression. AA female patients were younger and had a higher progression index and MS severity score than CA female MS patients. AA females who were APOE 4/4, 2/4, or 2/3 and APOC1 AA had a younger age-of-onset, had primarily a relapsing remitting disease course, with a higher progression index and MS severity score, as assessed by cluster analysis. Cluster analysis also indicated that CA female patients were of two groups. One group was younger, had the APOE 3/3 genotype with relapsing remitting less severe disease. The second CA group was older, had the APOE 3/4 or 2/3 genotypes with more of the secondary progressive more severe disease phenotype. Thus, the AA MS female patients who were APOE 4 carriers had an earlier age-of-onset and more severe disease course than CA MS female patients.

Epidemiology and natural history of multiple sclerosis: new insights

PURPOSE OF REVIEW

The cause of multiple sclerosis remains elusive. We review recent epidemiological studies of genetic and environmental factors that influence susceptibility to the disease and its clinical course.

RECENT FINDINGS

Genetic advances strengthen the association of multiple sclerosis with the human leukocyte antigen (HLA)-DRB1 allele and interferon-gamma polymorphisms and suggest that apolipoprotein E alleles play an important role. In the environmental realm, nested case-control studies show that prior Epstein-Barr virus exposure is overrepresented in multiple sclerosis. Smoking has been associated with both risk of multiple sclerosis and progressive disease. Vitamin D deficiency might tie together environmental clues with higher multiple sclerosis prevalence rates; dietary vitamin supplementation is also associated with reduced multiple sclerosis risk. Natural history studies demonstrated dissociation between relapses and disease progression, facilitated the ability to distinguish neuromyelitis optica and related syndromes from typical multiple sclerosis, and spawned the exploration of large datasets to model long-term disease activity.

SUMMARY

Our understanding of the contributions of specific genetic and environmental factors that contribute to multiple sclerosis has improved. Further refinements will eventually allow powerful longitudinal studies to assess genetic and environmental interactions with implications for prediction of individual disease susceptibility, clinical course, and response to therapy.

The impact of our genes: consequences of the apolipoprotein E polymorphism in Alzheimer disease and multiple sclerosis

Epidemiological studies provide strong evidence that susceptibility to multiple sclerosis (MS) is in part genetically determined. Likewise the heterogeneity in clinical manifestations, temporal course, severity, and in the pathological processes of MS are probably also influenced by our genes. Apolipoprotein E (apoE) polymorphism has been considered a candidate for impacting on MS because of its numerous functions related to brain tissue and evidence for an association with a variety of cerebral disorders, specifically Alzheimer's disease (AD). The apoE alleles epsilon2, epsilon3, and epsilon4 are known to impact differently on aspects such as neuronal growth and repair, neuroprotection and inflammation. After a review of the strong association of the apoE polymorphism with AD, we review the results on MS. These are far less homogenous but have gained support from morphologic and metabolic measures obtained with magnetic resonance imaging indicating a greater extent of brain destruction with the apoE epsilon4 allele. Evidence for a protective role of the epsilon2 allele in MS is weak. In view of the association with AD it is tempting to speculate that neuropsychologic functioning in MS might be even more strongly related to the apoE polymorphism and especially to the epsilon4 allele than other deficits, but few data on this issue are yet available. While part of the association of the apoE polymorphism with AD is supposed to be caused by apoE-isoform dependent effects on amyloid-beta deposition, no single pathogenetically relevant mechanism has yet been confirmed for MS. In summary we presently may assume only subtle effects of the apoE polymorphism on the course of MS. These effects are probably further modulated by other genes and need further investigation.

Multiple sclerosis genetics: leaving no stone unturned

Compelling epidemiologic and molecular data indicate that genes play a primary role in determining who is at risk for developing multiple sclerosis (MS), how the disease progresses, and how someone responds to therapy. The genetic component of MS etiology is believed to result from the action of allelic variants in several genes. Their incomplete penetrance and moderate individual effect probably reflects epistatic interactions, post-transcriptional regulatory mechanisms, and significant environmental influences. Equally significant, it is also likely that locus heterogeneity exists, whereby specific genes influence susceptibility and pathogenesis in some individuals but not in others. With the aid of novel analytical algorithms, the combined study of genomic, transcriptional, proteomic, and phenotypic information in well-controlled study groups will define a useful conceptual model of pathogenesis and a framework for understanding the mechanisms of action of existing therapies for this disorder, as well as the rationale for novel curative strategies.