Anthropology of the apoplipoprotein E (apo E) gene: low frequency of apo E4 allele in Basques and in tribal (Baiga) populations of India

Modifiable cardiovascular risk factors and genetics for targeted prevention of dementia

Dementia is a major global challenge for health and social care in the 21st century. A third of individuals >65 years of age die with dementia, and worldwide incidence numbers are projected to be higher than 150 million by 2050. Dementia is, however, not an inevitable consequence of old age; 40% of dementia may theoretically be preventable. Alzheimer's disease (AD) accounts for approximately two-thirds of dementia cases and the major pathological hallmark of AD is accumulation of amyloid-β. Nevertheless, the exact pathological mechanisms of AD remain unknown. Cardiovascular disease and dementia share several risk factors and dementia often coexists with cerebrovascular disease. In a public health perspective, prevention is crucial, and it is suggested that a 10% reduction in prevalence of cardiovascular risk factors could prevent more than nine million dementia cases worldwide by 2050. Yet this assumes causality between cardiovascular risk factors and dementia and adherence to the interventions over decades for a large number of individuals. Using genome-wide association studies, the entire genome can be scanned for disease/trait associated loci in a hypothesis-free manner, and the compiled genetic information is not only useful for pinpointing novel pathogenic pathways but also for risk assessments. This enables identification of individuals at high risk, who likely will benefit the most from a targeted intervention. Further optimization of the risk stratification can be done by adding cardiovascular risk factors. Additional studies are, however, highly needed to elucidate dementia pathogenesis and potential shared causal risk factors between cardiovascular disease and dementia.

Shared Risk Factors between Dementia and Atherosclerotic Cardiovascular Disease

Alzheimer’s disease is the most common form of dementia, and the prodromal phases of Alzheimer’s disease can last for decades. Vascular dementia is the second most common form of dementia and is distinguished from Alzheimer’s disease by evidence of previous stroke or hemorrhage and current cerebrovascular disease. A compiled group of vascular-related dementias (vascular dementia and unspecified dementia) is often referred to as non-Alzheimer dementia. Recent evidence indicates that preventing dementia by lifestyle interventions early in life with a focus on reducing cardiovascular risk factors is a promising strategy for reducing future risk. Approximately 40% of dementia cases is estimated to be preventable by targeting modifiable, primarily cardiovascular risk factors. The aim of this review is to describe the association between risk factors for atherosclerotic cardiovascular disease and the risk of Alzheimer’s disease and non-Alzheimer dementia by providing an overview of the current evidence and to shed light on possible shared pathogenic pathways between dementia and cardiovascular disease. The included risk factors are body mass index (BMI); plasma triglyceride-, high-density lipoprotein (HDL) cholesterol-, low-density lipoprotein (LDL) cholesterol-, and total cholesterol concentrations; hypertension; diabetes; non-alcoholic fatty liver disease (NAFLD); physical inactivity; smoking; diet; the gut microbiome; and genetics. Furthermore, we aim to disentangle the difference between associations of risk factors in midlife as compared with in late life.

APOE ε4 Allele Distribution and Association With Scores of Subjective Cognitive Decline Questionnaire 9 in a Large Chinese Memory Clinic Cohort

Background

Previous reports on APOE ε4 allele distribution in different populations have been inconclusive. The Subjective Cognitive Decline-Questionnaire 9 (SCD-Q9) was developed to identify those at risk of objective cognitive impairment [OCI; including mild cognitive impairment (MCI) and dementia groups), but its association with APOE ε4 and discriminatory powers for SCD_{with subtle cognitive decline} (SCDs) and OCI in memory clinics are unclear.

Objectives

To investigate demographic distribution of APOE ε4, its association with SCD-Q9 scores, and its ability to discriminate SCDs and OCI groups from normal control (NC).

Methods

A total of 632 participants were recruited (NC = 243, SCDs = 298, OCI = 91). APOE ε4 allele distribution and association with SCD-Q9 scores were calculated and the effects on cognitive impairment were analyzed. Receiver operating characteristic (ROC) analysis was applied to identify discriminatory powers for NC, SCDs, and OCI.

Results

Total APOE ε4 frequency was 13.1%. This did not vary by demography but was higher in patients with OCI. The SCD-Q9 scores were higher in APOE ε4 carriers than non-carriers in the OCI group. The area under the curve (AUC) for discriminating from OCI using APOE ε4 were 0.587 and 0.575, using SCD-Q9 scores were 0.738 and 0.571 for NC and SCDs groups, respectively. When we combined APOE ε4 and SCD-Q9 scores into the model, the AUC increased to 0.747 for discriminating OCI from NC. However, when OCI group was split into MCI and dementia groups, only total SCD-Q9 score was the independent affecting factor of MCI.

Conclusion

This study demonstrated that the distribution of APOE ε4 alleles did not vary with different demographic characteristics in a large-scale cohort from a memory clinic. APOE ε4 alleles may be associated with scores of SCD-Q9 reflecting the degree of cognitive complaints but their additional contribution to SCD-Q9 scores is marginal in discriminating between NC, SCDs, and OCI.

Apolipoprotein-E Gene Polymorphism and Lipid Composition among IUGR and AGA Neonates

Objective The objective of this study is to study the profile of apolipoprotein E (APOE) gene polymorphism and lipid profile among intrauterine growth restriction (IUGR) and appropriate for gestational age (AGA) neonates. This is an observational study. This study was done at the neonatal unit of a teaching hospital in South India. All consecutively born IUGR neonates (cases) of more than 32 weeks' gestational age and AGA neonates (controls) were enrolled for the study. Genomic DNA extraction was done from a total of 102 peripheral venous blood samples. Genotyping of the APOE rs429358 and rs7412 defining the ε2, ε3, and ε4 alleles was done by polymerase chain reaction–restriction fragment length polymorphism method. Prefeed venous blood was collected and analyzed for lipid profile estimation. The allelic frequencies of cases versus control were ε2—9 (8.7%) versus 3 (2.9%); ε3—88 (84.6%) versus 81 (79.4%); and ε4–7 (6.7%) versus 18 (17.6%). The frequency of ε4 isoform allele, associated with adult onset of metabolic diseases was less among the IUGR group. The mean total cholesterol (TC), Low-Density Lipoprotein (LDL), High-Density Lipoprotein, and triglyceride (TG) were 107.59 ± 35.99, 51.69 ± 24.68, 21.75 ± 9.58, and 151.22 ± 61.84 mg/dL, respectively, in the IUGR group. The mean TC and LDL levels in IUGR group were marginally higher than AGA neonates (107 ± 35.99 vs. 100.37 ± 22.69 mg/dL and 51.69 ± 24.68 versus 46.9 ± 19.51 mg/dL, p > 0.05). In both groups, the mean TC and TGL levels were elevated in the ε4 isoform subgroup (p > 0.05). In our study, the ε2 allele was the second most predominant APOE isoform and the ε4 allele of the APOE gene associated with adult-onset diseases was not increased among IUGR neonates. Neonates with ε4 allele showed an abnormal lipid profile in both study groups suggesting a possible association.

"Association of APOE gene polymorphisms with primary open angle glaucoma in Brazilian patients"

Background: Primary open-angle glaucoma (POAG) is a multifactorial disease that affects 65.5 million people worldwide. In addition to the genetic variants already established as indicators of greater risk for POAG, the apolipoprotein (APOE) gene has been studied in some populations, with controversial results. The aim of this study is to investigate the frequency of the genetic variants of APOE in the Brazilian population, and to evaluate the association between these polymorphisms and the risk of POAG. Methods: APOE variants (rs429358; rs7412) were genotyped in 402 POAG patients and 401 controls. We evaluated the association between APOE genetic variants and the risk for POAG, as well as the correlation between the requirement of glaucoma surgery and the APOE polymorphisms. Results: Among the three APOE gene isoforms, we found a low frequency of APOE alleles ε2 (7.34%) and ε4 (11.76%), but a high frequency of ε3 (80.88%) in our population. When compared to ε3ε3 reference genotype, ε2 allele-carriers (OR = 1.516; p-value = 0.04) and ε2ε3 genotype (OR = 1.655; p-value = 0.02) were associated with a greater risk for POAG. An additive genetic model confirmed the influence of the ε2 allele in the risk of POAG in this sample of the Brazilian population (OR = 1.502; p-value = 0.04). There was no significant association between the analyzed genotypes and the requirement or number of glaucoma surgeries (p > .05). Conclusion: Brazilian individuals carrying the APOEε2 allele may be at an increased risk for the development of POAG.

APOE Alleles and Diet in Brain Aging and Alzheimer's Disease

The APOE gene alleles modify human aging and the response to the diet at many levels with diverse pleotropic effects from gut to brain. To understand the interactions of APOE isoforms and diet, we analyze how cellular trafficking of apoE proteins affects energy metabolism, the immune system, and reproduction. The age-accelerating APOE4 allele alters the endosomal trafficking of cell surface receptors that mediate lipid and glucose metabolism. The APOE4 allele is the ancestral human allele, joined by APOE3 and then APOE2 in the human species. Under conditions of high infection, uncertain food, and shorter life expectancy, APOE4 may be adaptive for reducing mortality. As humans transitioned into modern less-infectious environments and longer life spans, APOE4 increased risks of aging-related diseases, particularly impacting arteries and the brain. The association of APOE4 with glucose dysregulation and body weight promotes many aging-associated diseases. Additionally, the APOE gene locus interacts with adjacent genes on chromosome 19 in haplotypes that modify neurodegeneration and metabolism, for which we anticipate complex gene-environment interactions. We summarize how diet and Alzheimer's disease (AD) risk are altered by APOE genotype in both animal and human studies and identify gaps. Much remains obscure in how APOE alleles modify nutritional factors in human aging. Identifying risk variant haplotypes in the APOE gene complex will clarify homeostatic adaptive responses to environmental conditions.

Effect of APOE ε4 allele on survival and fertility in an adverse environment

Background

The apolipoprotein-ε4 allele (APOE-ε4) is strongly associated with detrimental outcomes in affluent populations including atherosclerotic disease, Alzheimer’s disease, and reduced lifespan. Despite these detrimental outcomes, population frequencies of APOE-ε4 are high. We hypothesize that the high frequency of APOE-ε4 was maintained because of beneficial effects during evolution when infectious pathogens were more prevalent and a major cause of mortality. We examined a rural Ghanaian population with a high pathogen exposure for selective advantages of APOE-ε4, to survival and or fertility.

Methods and findings

This rural Ghanaian population (n = 4311) has high levels of mortality from widespread infectious diseases which are the main cause of death. We examined whether APOE-ε4 was associated with survival (total follow-up time was 30,262 years) and fertility after stratifying by exposure to high or low pathogen levels. Households drawing water from open wells and rivers were classified as exposed to high pathogen levels while low pathogen exposure was classified as those drawing water from borehole wells. We found a non-significant, but positive survival benefit, i.e. the hazard ratio per APOE-ε4 allele was 0.80 (95% confidence interval: 0.69 to 1.05), adjusted for sex, tribe, and socioeconomic status. Among women aged 40 years and older (n = 842), APOE-ε4 was not associated with the lifetime number of children. However, APOE-ε4 was associated with higher fertility in women exposed to high pathogen levels. Compared with women not carrying an APOE-ε4 allele, those carrying one APOE-ε4 allele had on average one more child and those carrying two APOE-ε4 alleles had 3.5 more children (p = 0.018).

Conclusions

Contrary to affluent modern-day populations, APOE-ε4 did not carry a survival disadvantage in this rural Ghanaian population. Moreover, APOE-ε4 promotes fertility in highly infectious environments. Our findings suggest that APOE-ε4 may be considered as evolutionarily adaptive. Its adverse associations in affluent modern populations with later onset diseases of aging further characterize APOE-ε4 as an example of antagonistic pleiotropy.

New insights into the distribution of APOE polymorphism in the Iberian Peninsula. The case of Andalusia (Spain)

BACKGROUND

The APOE gene has received much attention due to the remarkable spatial variation patterns of some of its genotypes and alleles in human populations and to its relevance in biomedicine.

AIM

This work was addressed to investigate the extent of APOE polymorphism between autochthonous Andalusians originating from Huelva and Granada provinces. No data on this marker in these southern Spanish coastal populations are available up to date.

SUBJECTS AND METHODS

This study used genomic DNA from healthy, unrelated Andalusians of both sexes (n = 322). All samples were genotyped for two SNPs, rs429358 and rs7412, which determine the three APOE alleles: ε2, ε3 and ε4. For analyses, a TaqMan-based technique was applied using a RT-PCR. Comparisons with other Mediterranean populations were performed based on multivariate analysis.

RESULTS

A relatively high frequency of ε4 in Granada (eastern Andalusia), as well as a low ε2 frequency in Huelva (western Andalusia) were observed. The finding that ε4 allele in Southern Spain and Portugal is higher than expected given its geographical location poses an interesting question for this study, given the well-established APOE-ε4 gradient in Europe.

CONCLUSION

This population study may represent useful information for further prospective anthropological and molecular genetic studies focused on unravelling the relationship between population genetic composition and specific human diseases.

ApoE4 and late onset depression in Indian population

OBJECTIVE

ApoE4 is a 'risk factor' for cognitive disorders like Alzheimer's dementia, and Late Onset Depression (LOD) is a forerunner of dementia. There is thus a need to study the association between ApoE4 allele and LOD.

METHOD

The study assessed the frequency of ApoE4 allele in 31 cases of LOD above the age of 50 years and 31 matched controls. The subjects were assessed on various clinical parameters towards diagnosis.

RESULTS

There was a significant association between the ApoE4 allele and LOD in comparison to controls (Odd's ratio=4.7, Confidence Interval=1.12 to 19.79, P=0.035). ApoE4 allele had no association with the age of onset of depression, cognitive functions and severity of LOD.

CONCLUSION

Individuals with LOD have a significantly higher frequency of the ApoE4 allele. In other words, elderly in India with an ApoE4 allele have 4.7 times more risk of developing depression in old age. Within LOD group there is no difference between those with and without ApoE4 accordingly in age of onset of depression, cognitive functions and severity of LOD.

Apolipoprotein E gene polymorphism and dyslipidaemia in adult Asian Indians: A population based study from Calcutta, India

AIM:

The study was aimed to determine the association of Apolipoprotein E (apo E) gene polymorphisms on lipid levels in Asian Indian population.

METHODS:

A total of 350 (184 males and 166 females) adult (30 years and above) Asian Indians of Calcutta and suburb participated in the study. Anthropometric measures, lipids profiles, and blood glucose measures were collected. Out of 350 subjects, a sample of 70 individuals was selected randomly for genotyping after adjusting for age and sex. The apo E gene polymorphisms were determined by agarose gel electrophoresis.

RESULTS:

The apo E polymorphism showed significant association with dyslipidaemia (P=0.0135) with ε3/4 combination has had the highest occurrence of dyslipidaemia and metabolic syndrome (MS) followed by ε4/4 <ε3/3 <ε2/4 <ε2/3 in decreasing order.

CONCLUSIONS:

The ε4 allele of apo E gene independent of other risk factors is associated with dyslipidaemia in particular with low HDLc and high TC: HDLc ratio.

Recurrent pregnancy loss and apolipoprotein E gene polymorphisms: a case–control study from north India

PROBLEM

the role of apolipoprotein E gene polymorphisms in the etiology of recurrent pregnancy loss (RPL) is not clearly understood. We evaluated this polymorphism in unexplained pregnancy losses among North Indian women.

METHOD OF STUDY

in a retrospective case–control study, 200 well-characterized RPL cases were examined for their APO-E genotypes based on restriction fragment length polymorphism analysis of PCR-amplified fragments including amino acid positions 112 and 158. The observed genotypes were compared with those obtained from an equal number of ethnically matched negative controls.

RESULTS

we found similar APO-E genotypes and E2, E3, and E4 allele frequency distribution among RPL patients and controls. The allele frequencies obtained in patients and controls respectively were as follows:E2 = 7.5% and 9.0% (P = 0.52; OR = 0.81; 95%CI = 0.49–1.35),E3 = 89.7% and 90% (P = 1.00; OR = 0.97; 95%CI = 0.61–1.54), and E4 = 2.8% and 1% (P = 0.12; OR = 2.79; 95%CI = 0.88–8.86).

CONCLUSIONS

our data did not support the association of APO-E gene polymorphisms with recurrent pregnancy loss as reported by some of the previous studies.We endorse adequate characterization of RPL cases, inclusion of appropriate negative controls, and adequate sample size prior to addressing such studies.

APOE distribution in world populations with new data from India and the UK

BACKGROUND

The APOE gene and its protein product is associated with a number of plasma proteins like very-low density lipoprotein (VLDL), high density lipoprotein (HDL) chylomicrons, chylomicron remnants, and plays a crucial role in lipid metabolism. The APOE gene is polymorphic and common alleles (*E2, *E3 and *E4) have been associated with a number of common and complex diseases in different populations. Due to their crucial role in metabolism and clinical significance, it is imperative that allelic variation in different populations is analysed to evaluate the usage of APOE in an evolutionary and clinical context.

AIM

We report allelic variation at the APOE locus in three European and four Indian populations and evaluate global patterns of genetic variation at this locus. The large, intricate and unexpected heterogeneity of this locus in its global perspective may have insightful consequences, which we have explored in this paper.

SUBJECT AND METHODS

Apolipoprotein E genotypes were determined in four population groups (Punjabi Sikhs, Punjabi Hindus, Maria Gonds and Koch, total individuals = 497) of India and three regionally sub-divided British populations (Nottinghamshire, East Midlands and West Midlands, total individuals = 621). The extent and distribution of APOE allele frequencies were compared with 292 populations of the world using a variety of multivariate methods.

RESULTS

Three alleles, APOE*E2, APOE*E3 and APOE*E4, were observed with contrasting variation, although *E4 was absent in the tribal population of Koch. Higher heterozygosities (>43%) in British populations reflected their greater genetic diversity at this locus. The overall pattern of allelic diversity among these populations is comparable to many European and Indian populations. At a global level, higher frequencies of the *E2 allele were observed in Africa and Oceania (0.099 +/- 0.083 and 0.111 +/- 0.052, respectively). Similarly, *E4 allele averages were higher in Oceania (0.221 +/- 0.149) and Africa (0.209 +/- 0.090), while Indian and Asian populations showed the highest frequencies of *E3 allele. The coefficient of gene differentiation was found to be highest in South America (9.6%), although the highest genetic diversity was observed in Oceania (48.7%) and Africa (46.3%). APOE*E2 revealed a statistically significant decreasing cline towards the north in Asia (r = -0.407, d.f. = 70, p < 0.05), which is not compatible with the coronary heart disease statistics in this continent. APOE*E4 showed a significant increasing cline in North European populations. Spatial autocorrelation analysis shows that the variation at this locus is influenced by 'isolation by distance' with a strong positive correlation for lower distances up to 1313 km.

CONCLUSION

Overall APOE allelic variation in UK and Indian populations is comparable to previous studies but in tribal populations *E4 allele frequency was very low or absent. At a global level allelic variation shows that geography, isolation by distance, genetic drift and possibly pre-historical selection are responsible for shaping the spectrum of genetic variation at the APOE gene. Overall, APOE is a good anthropogenetic and clinical diagnostic marker.

Apolipoprotein E polymorphisms in Mexican patients with coronary artery disease

BACKGROUND

Apolipoprotein E polymorphisms have important effects on plasma lipid levels and in the genetic susceptibility to development of cardiovascular diseases. Thus, the purpose of this study was to investigate the association of apolipoprotein E polymorphisms with coronary artery disease and with plasma lipid levels in a group of Mexican Mestizo patients.

METHODS

Apolipoprotein E polymorphisms were determined in 156 Mexican patients with coronary artery disease and 200 non-related healthy controls using the restriction fragment length polymorphism technique. The correlation of these polymorphisms with lipid profile (total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides) in the patient group was determined.

RESULTS

A similar distribution of allele and genotype frequencies in coronary artery disease patients and healthy controls was found. Higher serum levels of high-density lipoprotein cholesterol and lower levels of low-density lipoprotein cholesterol, triglycerides and glucose were found in patients with the APOE*2/3 genotype when compared to patients with the APOE*3/4 and APOE*3/3 genotypes, although these differences were not significant.

CONCLUSIONS

Our data suggest that genetic variation at the APOE is not a genetic factor related to the genetic susceptibility to coronary artery disease in Mexican individuals, but the role of this polymorphism in determining the lipid profile cannot be excluded.

Presenilin gene predisposes to late-onset degenerative but not vascular dementia: a comparative study of PS1 and ApoE genes in a North Indian Cohort

BACKGROUND

Variation in the presenilin gene shifts the cleavage site of amyloid precursor protein producing an insoluble peptide Abeta(42) (instead of Abeta(40), which is soluble when produced in restricted amount), which is prone to aggregation in the brain in the form of amyloid plaques not only in Alzheimer's disease (AD) but also in other degenerative dementias. The role of presenilin 1 (PS1) and apolipoprotein E (ApoE) genes has not been explored in degenerative dementias other than AD.

OBJECTIVE

To study the association of PS1 intron 8 and ApoE epsilon4 gene polymorphism in degenerative and vascular dementia patients in the North Indian population.

DESIGN

A hospital-based association study on degenerative and vascular dementia patients proven on the basis of clinical profile and MRI.

PARTICIPANTS

A group of 107 dementia patients and 162 age- and sex-matched controls from a North Indian cohort participated in the study. All patients had Mini Mental State Examination scores less than 24 and met the DSM-IV criteria for dementia.

RESULTS

The frequency of genotype 1/1 and allele 1 in degenerative dementias (73.12 and 83.70%, respectively) was higher than what had been reported so far in AD. A significant association of PS1 intron 8 polymorphism was found with degenerative dementias but not with vascular dementias (OR 2.50, 95% CI 1.27-5.00). On the other hand, ApoE epsilon4 allele was found to significantly increase the risk for both vascular and degenerative dementias (p = 0.0001, OR 3.45, 95% CI 1.74-6.86).

CONCLUSION

While ApoE epsilon4 allele increases the susceptibility to both degenerative and vascular dementia, PS1 allele 1 increases the susceptibility to degenerative dementias only.

Association of APOE (Hha1) and ACE (I/D) gene polymorphisms with type 2 diabetes mellitus in North West India

Familial and epidemiological studies have shown that genetic factors play a role in the development and progression of type 2 diabetes mellitus (T2DM). Asian Indians have shown an increasing prevalence of T2DM. Apolipoprotein E (APOE) and Angiotensin-1 converting enzyme (ACE) I/D polymorphisms have been associated with T2DM. This study examined the association of APOE and ACE genes with T2DM patients of Punjab, India. APOE (HhaI) and ACE (I/D) genotypes analysed by polymerase chain reaction were available from 90 patients and 97 random healthy controls. All loci and populations are in Hardy-Weinberg equilibrium. There is no significant association of APOE vis-à-vis T2DM, however APOE*4 allele frequency is low in diabetics (3.9% and 8.8%). DD genotype and *D allele of ACE are associated with T2DM (OR=1.90, p<0.05, and OR=1.58, p<0.05, respectively). Recessive and multiplicative mode of inheritance for *D allele provided the strongest support for the association. Height, weight and BMI did not reveal any significant association with APO or ACE. DD-33 and ID-23 combinations (ACE-APOE) showed higher odds of 2.01 and 2.14, respectively. ACE but not APOE polymorphism is positively associated with T2DM in Indian population, however, the synergistic effects of DD-33 and ID-23 are also evident.

Detection of ApoE E2, E3 and E4 alleles using MALDI-TOF mass spectrometry and the homogeneous mass-extend technology

Apolipoprotein (Apo) E is one of the five main types of blood lipoproteins (A–E). It is synthesized primarily in the liver and brain and helps in transporting lipids from one place to another as well as facilitates the clearing of dietary fats, such as triglycerides, from the blood. The ApoE gene exists in three different forms: E2, E3 and E4. E3 is considered to be the normal form. Variants of the ApoE gene have been associated with various diseases. Developing an assay for the genotyping of ApoE variants for use both in clinical and large cohort based association settings would be extremely valuable and would require the use of a platform that has high-throughput capabilities and is highly accurate. Here we describe an assay for the simultaneous genotyping of the ApoE variants in a single bi-plex reaction and a single well using the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and the homogeneous mass-extend (hME) technology. The assay is robust, highly accurate and suitable for both clinical applications and for the genotyping of large disease cohorts. Moreover, the prevalence of ApoE variants in a cohort of Caucasians from the central Wisconsin area is outlined.

Distribution of apolipoprotein E alleles in the Omani population

OBJECTIVE

To estimate the apolipoprotein E (apo E) allele distribution in the Omani population and to compare them with those of other populations.

SUBJECTS AND METHODS

One hundred and sixty-two healthy Omanis of Arab Bedouin origin were genotyped by polymerase chain reaction followed by restriction fragment length polymorphism.

RESULTS

The apo E allele frequencies were: epsilon2, 0.052; epsilon3, 0.886; epsilon4, 0.062. This pattern of distribution, characterized by the lowest epsilon4 and among the highest epsilon3 allele frequencies in the world, was very similar to that of Arabs, Southern Europeans of the Mediterranean basin, Indians, and Japanese populations.

CONCLUSION

The results indicate that the allelic distribution of apo E in healthy Omanis is characterized by low Apo epsilon4 and high epsilon3 allele frequencies similar to those of other Arab, Southern European, Japanese and Indian populations. The homogeneous distribution of apo E alleles in this group of populations might have been influenced by diet and/or genetic admixture.

Cord blood apolipoprotein-E genotype distribution and plasma lipid indices in newborns of different ethnicity

We hypothesized that apolipoprotein-E (apo-E) genotypes would be associated with plasma lipid indices in newborns of South Asian (SA) ancestry but not in newborns of African (Afr) ancestry. Cord blood was obtained by consecutive sampling at maternity hospitals in the Caribbean Islands of Trinidad and Curaçao. Apolipoprotein-E genotypes, cholesterol, triglycerides, apo-A, apo-B and Lipoprotein (a) (Lp(a)) were measured in 294 newborns in Trinidad and 234 in Curaçao. The apo-B/apo-AI ratio and an adapted lipid tetrad index (i.e. cholesterol x triglycerides x Lp(a)/apo-AI) were calculated. In Trinidad, apo-E allele frequencies and genotype distributions of Afr and SA were significantly (p < 0.001) different (Afr: n = 71: apo-e2 : e3 : e4 = 10.4 : 66.4 : 23.2%; SA: n = 98; e2 : e3 : e4 = 3.5 : 83.1: 13.4%). The Mixed group (SA + Afr) had apo-E allele frequencies in between those of SA and Afr groups (n = 115; e2 : e3 : e4 = 7 : 76 : 17%). Lipid indices of appropriate for gestational age and term newborns were comparable, except for lower Lp(a) (SA = 29+/-4; Afr = 46+/-5; Mixed = 41+/-5 mg L(-1)) and lower adapted lipid tetrad index (29.4+/-4.8; 41.9+/-5.4; 41.4+/-7.0) in SA. Apo-E allele frequencies of Curaçao newborns were: apo-e2 : e3 : e4 = 10.5 : 72.6 : 16.9%. Their Lp(a) levels were significantly higher (68+/-3 mg L(-1)) than that of the Trinidadian sample (38+/-3; p < 0.0001). Apolipoprotein-E4 had an apo-B-increasing effect and apo-E2 an apo-B-decreasing effect in Afr (r = 0.192, p = 0.003). Among Africans from Trinidad and Curaçao variations in apo-E4 and apo-E2 are associated with an apo-B-increasing effect and an apo-B-decreasing effect, respectively. There was no relationship between apo-E polymorphism and lipids among South Asians.

The evolution of Alzheimer disease, the reproductive schedule, and apoE isoforms

Alzheimer disease (AD)-like neuropathology increases progressively during aging in most primates, and, in some species, is concurrent with reproductive decline in females and cognitive impairments. We consider how the schedule of AD may have evolved in early humans in relation to the apolipoprotein E (apoE) allele system, which is not found in other primates, and to the increasing duration of postnatal care. The delay of independence and the increasing length of maturation required that the schedule of AD-like neurodegeneration be slowed, otherwise parental caregivers would already have become impaired. We hypothesize that the uniquely human apoE epsilon3 allele evolved from the epsilon4 of primate ancestors during human evolution in relation to the rapid increases of brain size and the emergence of grandmothering. In discussing theses possibilities, we review the diverse bioactivities of apoE, which include involvement in hormone systems. The evolution of menopause is also considered in relation to the protective effect of estrogen on AD.