Population admixture associated with disease prevalence in the Boston Puerto Rican health study

Associations of PON1 and genetic ancestry with obesity in early childhood

Obesity in children has become an epidemic in the U.S. and is particularly prominent in minority populations such as Mexican-Americans. In addition to physical activity and diet, genetics also plays a role in obesity etiology. A few studies in adults and adolescents suggest a link between obesity and paraoxonase 1 (PON1), a multifunctional enzyme that can metabolize organophosphate pesticides and also has antioxidant properties. We determined PON1₁₉₂ genotype and arylesterase levels (ARYase, measure of PON1 enzyme quantity), to characterize the relationship between PON1 and obesity in young Mexican-American children (n = 373) living in an agricultural community in California. Since PON1 polymorphisms and obesity both vary between ethnic groups, we estimated proportional genetic ancestry using 106 ancestral informative markers (AIMs). Among children, PON1₁₉₂ allele frequencies were 0.5 for both alleles, and the prevalence of obesity was high (15% and 33% at ages two and five, respectively). The average proportion of European, African, and Native American ancestry was 0.40, 0.09, and 0.51, yet there was wide inter-individual variation. We found a significantly higher odds of obesity (9.3 and 2.5- fold) in PON1_192QQ children compared to PON1_192RR children at ages two and five, respectively. Similar relationships were seen with BMI Z-scores at age two and waist circumference at age five. After adjusting for genetic ancestry in models of PON1 and BMI Z-score, effect estimates for PON1₁₉₂ genotype changed 15% and 9% among two and five year old children, respectively, providing evidence of genetic confounding by population stratification. However even after adjustment for genetic ancestry, the trend of increased BMI Z-scores with increased number of PON1₁₉₂ Q alleles remained. Our findings suggest that PON1 may play a role in obesity independent of genetic ancestry and that studies of PON1 and health outcomes, especially in admixed populations, should account for differences due to population stratification.

Insulin receptor substrate 1 (IRS1) variants confer risk of diabetes in the Boston Puerto Rican Health Study

OBJECTIVE

Published data concerning associations between IRS1 variants and type 2 diabetes and related traits have been inconsistent. We examined the relationship between common variants in IRS1, type 2 diabetes, and related traits including insulin resistance, hyperglycemia and DNA damage in the Boston Puerto Rican Health Study.

METHODS

We genotyped six common IRS1 variants in an adult Puerto Rican population (n=1132) and tested for association with risk of type 2 diabetes and related traits.

RESULTS

SNPs rs934167 and rs1801123 showed significant association with fasting glucose concentrations (p = 0.005 and p = 0.016, respectively) and rs934167 showed significant association with plasma insulin levels (p = 0.005). Carriers of the rs934167 minor allele had significantly higher HOMA-IR and lower QUICKI (p = 0.001 and p = 0.001, respectively), and a 40% and 58% greater likelihood of being hyperglycaemic or hyperinsulinemic (OR = 1.40 and 1.58; p = 0.013 and 0.002, respectively). However, they exhibited only a marginally significant trend towards having type 2 diabetes (OR=1.27, p = 0.077). Furthermore, carriers of the haplotype C-T of the rs934167 and rs1801123 minor alleles showed consistent patterns of associations after correction for multiple testing. In addition, the G972R (rs1801278) minor allele was significantly associated with higher urinary 8-OHdG concentrations (p = 0.020) and plasma CRP levels (p = 0.035).

CONCLUSIONS

Our results support IRS1 variants associated with type 2 diabetes risk in adult Puerto Ricans. Moreover, we report the novel finding that IRS1 variant G972R (rs1801278) may contribute to oxidative DNA damage and inflammation.

Genetic variants at PSMD3 interact with dietary fat and carbohydrate to modulate insulin resistance

PSMD3 encodes subunit 3 of the 26S proteasome, which is involved in regulating insulin signal transduction, and dietary factors could potentially regulate the function of this gene. We aimed to investigate the associations of PSMD3 variants with glucose-related traits and the interactions of those variants with dietary fat and carbohydrate for glucose-related traits in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study and to replicate the findings in the Boston Puerto Rican Health Study (BPRHS). Ten single nucleotide polymorphisms (SNPs) were selected, covering 90% the genetic variations in or near PSMD3. Minor allele (C) carriers of rs4065321 had higher homeostasis model assessment of insulin resistance (HOMA-IR) than noncarriers in males of both the GOLDN (P = 0.022) and BPRHS (P = 0.036). Minor allele (T) carriers of rs709592 had significantly higher HOMA-IR (P = 0.032) than C homozygotes in the GOLDN, whereas the T allele carriers of rs709592 tended to have higher HOMA-IR (P = 0.08) than C homozygotes in the BPRHS. In the GOLDN, there was an interaction between rs709592 and dietary carbohydrate on HOMA-IR (P = 0.049). Subjects carrying the T allele of rs709592 had higher HOMA-IR compared only with noncarriers with low carbohydrate intake (≤49.1% energy; P = 0.004). SNPs rs4065321 and rs709592 both significantly interacted with dietary MUFAs and carbohydrate on glucose concentrations in the GOLDN. Our study suggests that PSMD3 variants are associated with insulin resistance in populations of different ancestries and that these relationships may also be modified by dietary factors.

Genetics of obesity and type 2 diabetes in African Americans

Obesity and type 2 diabetes are highly prevalent and lead to significant morbidity and mortality. In the United States, the impact of these conditions may be worse on historically underserved minorities, particularly African Americans. Genetic ancestry and differences in physiology are unlikely to be the sole or primary determinants of these disparities. In addition, research in this area has the ethically problematic possibility of conflating race with biology. Despite these important considerations and the challenges of conducting this work, population-based approaches for investigating the etiology of obesity and T2D may yield useful information about the pathophysiology of disease, and have implications that extend to all affected individuals. The purpose of this paper is to describe what is understood about the genetic variation that underlies obesity and T2D in African Americans and other individuals of more recent African descent and to highlight several examples that illustrate how ensuring adequate minority representation in genetic research improves its quality. For a variety of reasons a number of unique insights have been possible as a result of these efforts.

An approach to the etiology of metabolic syndrome

Increased prevalence of obesity in the world, especially accumulation of abnormal amounts of visceral fat predisposes to insulin resistance, which is the central role of metabolic syndrome (MS). Obesity can deregulate the intracellular signaling of insulin due to the production of inflammatory substances, chemoattractant proteins, adipokines and molecules that trigger hormonal mediator potentials for destabilization of signal transduction, leading to metabolic disorders such as hyperglycemia, hypertension, and dyslipidemia. The complexity of the MS and of the genetic mechanisms involved in its etiology derives from the combination of variants on genes involved and environmental factors that predispose it. The purpose of this paper is to review the effects of obesity in molecular and biochemical responses that trigger insulin resistance and its relation to some candidate genes and the ancestral component of the population.

Vitamin D binding protein is a key determinant of 25-hydroxyvitamin D levels in infants and toddlers

Circulating 25-hydroxyvitamin D (25-OHD) levels vary among human populations. Only limited information regarding determinants of these measures is available for infants and children, particularly in minority groups at greatest risk for vitamin D deficiency. We identified demographic determinants of circulating 25-OHD in a large cohort of minority children, and now extend our studies to examine potential roles of vitamin D binding protein (DBP) as a determinant of 25-OHD levels. Serum DBP level and common single nucleotide polymorphisms (SNPs) at positions 432 and 436 in the GC gene, encoding DBP, were examined. We confirmed self-reported ancestry using ancestry informative markers (AIMs), and included quantitative AIMs scores in the analysis. The multivariate model incorporated previously identified demographic and nutritional determinants of 25-OHD in this cohort, as well as GC SNPs and circulating DBP. Genetic variants in GC differed by self-reported ancestry. The 1f allele (D432/T436) was enriched in African Americans, occurring in 71%. Homozygosity for the 1f allele (DDTT) occurred in 53% of African Americans but only 6% of Caucasians and 13% of Hispanics. Circulating DBP was significantly correlated with 25-OHD. GC SNPs were associated with both circulating DBP and 25-OHD. It appears that progressive substitution of lysine for threonine at the 436 position results in lower circulating 25-OHD. Multivariate analysis revealed that genetic variance in GC significantly contributes to circulating DBP as well as 25-OHD. Moreover, the effect of GC SNPs on 25-OHD are evident after adjusting for their effects on circulating DBP. Thus in young children genetic variance of the common GC T436K SNP affects circulating levels of the DBP protein, which in turn affects circulating 25-OHD. However, the GC genotype also affects circulating 25-OHD independently of its effect on circulating DBP. These findings provide data that may be important in the interpretation of vitamin D status in children of varying ancestral backgrounds.

Multi-ethnic reference values for spirometry for the 3-95-yr age range: the global lung function 2012 equations

The aim of the Task Force was to derive continuous prediction equations and their lower limits of normal for spirometric indices, which are applicable globally. Over 160,000 data points from 72 centres in 33 countries were shared with the European Respiratory Society Global Lung Function Initiative. Eliminating data that could not be used (mostly missing ethnic group, some outliers) left 97,759 records of healthy nonsmokers (55.3% females) aged 2.5-95 yrs. Lung function data were collated and prediction equations derived using the LMS method, which allows simultaneous modelling of the mean (mu), the coefficient of variation (sigma) and skewness (lambda) of a distribution family. After discarding 23,572 records, mostly because they could not be combined with other ethnic or geographic groups, reference equations were derived for healthy individuals aged 3-95 yrs for Caucasians (n=57,395), African-Americans (n=3,545), and North (n=4,992) and South East Asians (n=8,255). Forced expiratory value in 1 s (FEV(1)) and forced vital capacity (FVC) between ethnic groups differed proportionally from that in Caucasians, such that FEV(1)/FVC remained virtually independent of ethnic group. For individuals not represented by these four groups, or of mixed ethnic origins, a composite equation taken as the average of the above equations is provided to facilitate interpretation until a more appropriate solution is developed. Spirometric prediction equations for the 3-95-age range are now available that include appropriate age-dependent lower limits of normal. They can be applied globally to different ethnic groups. Additional data from the Indian subcontinent and Arabic, Polynesian and Latin American countries, as well as Africa will further improve these equations in the future.

Ethnic and sex disparities in colorectal neoplasia among Hispanic patients undergoing screening colonoscopy

BACKGROUND & AIMS

Colorectal cancer (CRC) has a high prevalence among the US Hispanic population. In Puerto Rico, CRC is the third leading cause of cancer death in men and the second in women. There are limited published data on the prevalence of colorectal neoplasia (CRN) among the US Hispanic population. We determined the prevalence of CRN (colorectal adenomas and cancer) among asymptomatic, Hispanic subjects who were screened in Puerto Rico and evaluated risk factors associated with CRN.

METHODS

We performed a retrospective review of the medical, endoscopic, and pathology records of individuals who underwent first-time screening colonoscopies at an ambulatory gastroenterology practice from January 1, 2008, to December 1, 2009. The prevalence of CRN (overall and advanced), documented by colonoscopy and pathology reports, was calculated for the complete cohort and by sex.

RESULTS

Of the 745 Hispanic individuals who underwent screening colonoscopies during the study period, the prevalence for overall CRN was 25.1% and for advanced CRN (≥ 1 cm and/or with advanced histology) was 4.0%. The prevalence of CRN was higher for men than women (32.0% vs 20.6%; P = .001; odds ratio, 1.92; 95% confidence interval, 1.4-2.6). CRN was more frequently located in the proximal colon (67.7% proximal vs 32.3% distal). A family history of CRC was associated with advanced CRN (odds ratio, 2.73; 95% confidence interval, 1.10-6.79).

CONCLUSIONS

CRN was more common among Hispanic men than women and increased with age. CRNs among Hispanic individuals were predominantly located in the proximal colon. These findings indicate that there are ethnic and sex disparities in patterns of CRN that might be related to genomic admixture and have important implications for screening algorithms for Hispanic individuals.

Genetic predictors for cardiovascular disease in hispanics

A less favorable cardiovascular risk factor profile but paradoxically lower cardiovascular morbidity and mortality have been observed in Hispanics--a pattern often referred to as the Hispanic paradox. It has been proposed that the specific genetic susceptibility of this admixed population and gene-environment interactions may partly explain the paradox. During the past few years, there have been major advances in the identification of genetic risk factors using genome-wide association studies (GWAS) for cardiovascular disease, especially in Caucasians. However, no GWAS of cardiovascular disease have been reported in Hispanics. In the Costa Rican Heart Study, we reported both the consistency and disparity of genetic effects on risk of coronary heart disease (CHD) between Hispanics and other ethnic groups. We demonstrated that the improvement in the identified genetic markers on discrimination of CHD in Hispanics was modest. Future genetic research on Hispanics should consider the diversity in genetic structure, lifestyle, and socioeconomics among various subpopulations and comprehensively evaluate potential gene-environment interactions in relation to cardiovascular risk.

Association of serum lipid components and obesity with genetic ancestry in an admixed population of elderly women

The prevalence of metabolic disorders varies among ethnic populations and these disorders represent a critical health care issue for elderly women. This study investigated the correlation between genetic ancestry and body composition, metabolic traits and clinical status in a sample of elderly women. Clinical, nutritional and anthropometric data were collected from 176 volunteers. Genetic ancestry was estimated using 23 ancestry-informative markers. Pearsons correlation test was used to examine the relationship between continuous variables and an independent samples t-test was used to compare the means of continuous traits within categorical variables. Overall ancestry was a combination of European (57.49%), Native American (25.78%) and African (16.73%). Significant correlations were found for European ancestry with body mass index (r = 0.165; p = 0.037) and obesity (mean difference (MD) = 5.3%; p = 0.042). African ancestry showed a significant correlation with LDL (r = 0.159, p = 0.035), VLDL (r = -0.185; p = 0.014), hypertriglyceridemia (MD = 6.4%; p = 0.003) and hyperlipidemia (MD = 4.8%; p = 0.026). Amerindian ancestry showed a significant correlation with triglyceride levels (r = 0.150; p = 0.047) and hypertriglyceridemia (MD = 4.5%; p = 0.039). These findings suggest that genetic admixture may influence the etiology of lipid metabolism-related diseases and obesity in elderly women.

Characterization of genome-wide association-identified variants for atrial fibrillation in African Americans

BACKGROUND

Despite a greater burden of risk factors, atrial fibrillation (AF) is less common among African Americans than European-descent populations. Genome-wide association studies (GWAS) for AF in European-descent populations have identified three predominant genomic regions associated with increased risk (1q21, 4q25, and 16q22). The contribution of these loci to AF risk in African American is unknown.

METHODOLOGY/PRINCIPAL FINDINGS

We studied 73 African Americans with AF from the Vanderbilt-Meharry AF registry and 71 African American controls, with no history of AF including after cardiac surgery. Tests of association were performed for 148 SNPs across the three regions associated with AF, and 22 SNPs were significantly associated with AF (P<0.05). The SNPs with the strongest associations in African Americans were both different from the index SNPs identified in European-descent populations and independent from the index European-descent population SNPs (r(2)<0.40 in HapMap CEU): 1q21 rs4845396 (odds ratio [OR] 0.30, 95% confidence interval [CI] 0.13-0.67, P = 0.003), 4q25 rs4631108 (OR 3.43, 95% CI 1.59-7.42, P = 0.002), and 16q22 rs16971547 (OR 8.1, 95% CI 1.46-45.4, P = 0.016). Estimates of European ancestry were similar among cases (23.6%) and controls (23.8%). Accordingly, the probability of having two copies of the European derived chromosomes at each region did not differ between cases and controls.

CONCLUSIONS/SIGNIFICANCE

Variable European admixture at known AF loci does not explain decreased AF susceptibility in African Americans. These data support the role of 1q21, 4q25, and 16q22 variants in AF risk for African Americans, although the index SNPs differ from those identified in European-descent populations.

Adaptive genetic variation and population differences

Since the expansion of modern humans (Homo sapiens) from Africa to the rest of the world between 50,000 and 100,000 years ago, the human genome has been shaped not only by demographic history but also by adaptation to local environments, including regional climate, landscape, food sources, culture, and pathogens. Genetic differences among populations interact with environmental factors, such as diet and lifestyle, leading to differences in nutrient metabolism, which translate into differences in susceptibility to a variety of diseases. Individuals from different populations sharing the same environments can exhibit differences in disease risk, as do individuals from the same population living in various regions of the globe. Therefore, it is important to understand how adaptive genetic variations interact with environments to influence health. This knowledge will provide a broad foundation for designing experiments and approaches in nutrigenomics research and strengthening the knowledge base for dietary recommendations for disease prevention. The objectives of this chapter are to (1) understand the methodology employed in examining adaptive genetic variation across populations, (2) establish the importance of adaptive genetic variation to human health, and (3) discuss the implications for nutrigenomics research and disease prevention.

Association between BDNF rs6265 and obesity in the Boston Puerto Rican Health Study

Brain-derived neurotrophic factor (BDNF) has been associated with regulation of body weight and appetite. The goal of this study was to examine the interactions of a functional variant (rs6265) in the BDNF gene with dietary intake for obesity traits in the Boston Puerto Rican Health Study. BDNF rs6265 was genotyped in 1147 Puerto Rican adults and examined for association with obesity-related traits. Men (n = 242) with the GG genotype had higher BMI (P = 0.009), waist circumference (P = 0.002), hip (P = 0.002), and weight (P = 0.03) than GA or AA carriers (n = 94). They had twice the risk of being overweight (BMI ≥ 25) relative to GA or AA carriers (OR = 2.08, CI = 1.02-4.23, and P = 0.043). Interactions between rs6265 and polyunsaturated fatty acids (PUFA) intake were associated with BMI, hip, and weight, and n-3 : n-6 PUFA ratio with waist circumference in men. In contrast, women (n = 595) with the GG genotype had significantly lower BMI (P = 0.009), hip (P = 0.029), and weight (P = 0.027) than GA or AA carriers (n = 216). Women with the GG genotype were 50% less likely to be overweight compared to GA or AA carriers (OR = 0.05, CI = 0.27-0.91, and P = 0.024). In summary, BDNF rs6265 is differentially associated with obesity risk by sex and interacts with PUFA intake influencing obesity traits in Boston Puerto Rican men.

A high intake of saturated fatty acids strengthens the association between the fat mass and obesity-associated gene and BMI

Evidence that physical activity (PA) modulates the association between the fat mass and obesity-associated gene (FTO) and BMI is emerging; however, information about dietary factors modulating this association is scarce. We investigated whether fat and carbohydrate intake modified the association of FTO gene variation with BMI in two populations, including participants in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study (n = 1069) and in the Boston Puerto Rican Health (BPRHS) study (n = 1094). We assessed energy, nutrient intake, and PA using validated questionnaires. Genetic variability at the FTO locus was characterized by polymorphisms rs9939609 (in the GOLDN) and rs1121980 (in the GOLDN and BPRHS). We found significant interactions between PA and FTO on BMI in the GOLDN but not in the BPRHS. We found a significant interaction between SFA intake and FTO on BMI, which was stronger than that of total fat and was present in both populations (P-interaction = 0.007 in the GOLDN and P-interaction = 0.014 in BPRHS for categorical; and P-interaction = 0.028 in the GOLDN and P-interaction = 0.041 in BPRHS for continuous SFA). Thus, homozygous participants for the FTO-risk allele had a higher mean BMI than the other genotypes only when they had a high-SFA intake (above the population mean: 29.7 ± 0.7 vs. 28.1 ± 0.5 kg/m²; P = 0.037 in the GOLDN and 33.6. ± 0.8 vs. 31.2 ± 0.4 kg/m²; P = 0.006 in BPRHS). No associations with BMI were found at lower SFA intakes. We found no significant interactions with carbohydrate intake. In conclusion, SFA intake modulates the association between FTO and BMI in American populations.

The APOA1/C3/A4/A5 cluster and markers of allostatic load in the Boston Puerto Rican Health Study

BACKGROUND AND AIMS

The APOA1/C3/A4/A5 cluster encodes key regulators of plasma lipids. Interactions between dietary factors and single nucleotide polymorphisms (SNPs) in the cluster have been reported. Allostatic load, or physiological dysregulation in response to stress, has been implicated in shaping health disparities in ethnic groups. We aimed to determine the association between polymorphisms in the APOA1/C3/A4/A5 cluster with allostatic load parameters, alone, and in interaction with dietary fat intake in Puerto Ricans adults.

METHODS AND RESULTS

Data on demographic and anthropometric measures, lifestyle behaviors, and medication use, as well as blood and urine samples for biomarker analysis, were obtained from participants of the Boston Puerto Rican Health Study (n=821, age 45-75 y). The 12 polymorphisms analyzed were not associated with allostatic load parameters. Significant interactions were observed between dietary fat intake and APOA1-75 in association with waist circumference (WC), (P=0.005), APOC3-640 with diastolic blood pressure (DBP), (P=0.003), and APOA4 N147S and APOA5 S19W with systolic blood pressure (SBP), (P=0.001 and P=0.002, respectively). Puerto Ricans homozygous for the common allele of APOA1-75, APOA4 N147S and APOA5 S19W had lower WC and SBP when consuming <31% of total fat from energy, than participants with the minor allele. Participants heterozygous for APOC3-640 had lower DBP at total fat intake ≥31% from energy.

CONCLUSION

SNPs in APOA1/C3/A4/A5, as modulated by dietary fat intake, appear to influence allostatic load parameters in Puerto Ricans.

Race, ancestry, and development of food-allergen sensitization in early childhood

OBJECTIVE

We examined whether the risk of food-allergen sensitization varied according to self-identified race or genetic ancestry.

METHODS

We studied 1104 children (mean age: 2.7 years) from an urban multiethnic birth cohort. Food sensitization was defined as specific immunoglobulin E (sIgE) levels of ≥ 0.35 kilo-units of allergen (kUA)/L for any of 8 common food allergens. Multivariate logistic regression analyses were used to evaluate the associations of self-identified race and genetic ancestry with food sensitization. Analyses also examined associations with numbers of food sensitizations (0, 1 or 2, and ≥ 3 foods) and with logarithmically transformed allergen sIgE levels.

RESULTS

In this predominantly minority cohort (60.9% black and 22.5% Hispanic), 35.5% of subjects exhibited food sensitizations. In multivariate models, both self-reported black race (odds ratio [OR]: 2.34 [95% confidence interval [CI]: 1.24-4.44]) and African ancestry (in 10% increments; OR: 1.07 [95% CI: 1.02-1.14]) were associated with food sensitization. Self-reported black race (OR: 3.76 [95% CI: 1.09-12.97]) and African ancestry (OR: 1.19 [95% CI: 1.07-1.32]) were associated with a high number (≥ 3) of food sensitizations. African ancestry was associated with increased odds of peanut sIgE levels of ≥ 5 kUA/L (OR: 1.25 [95% CI: 1.01-1.52]). Similar ancestry associations were seen for egg sIgE levels of ≥ 2 kUA/L (OR: 1.13 [95% CI: 1.01-1.27]) and milk sIgE levels of ≥ 5 kUA/L (OR: 1.24 [95% CI: 0.94-1.63]), although findings were not significant for milk.

CONCLUSIONS

Black children were more likely to be sensitized to food allergens and were sensitized to more foods. African ancestry was associated with peanut sensitization.

African ancestry, early life exposures, and respiratory morbidity in early childhood

BACKGROUND

Racial disparities persist in early childhood wheezing and cannot be completely explained by known risk factors.

OBJECTIVE

To evaluate the associations of genetic ancestry and self-identified race with early childhood recurrent wheezing, accounting for socio-economic status (SES) and early life exposures.

METHODS

We studied 1034 children in an urban, multi-racial, prospective birth cohort. Multivariate logistic regression was used to evaluate the association of genetic ancestry as opposed to self-identified race with recurrent wheezing (>3 episodes). Sequential models accounted for demographic, socio-economic factors and early life risk factors. Genetic ancestry, estimated using 150 ancestry informative markers, was expressed in deciles.

RESULTS

Approximately 6.1% of subjects (mean age 3.1 years) experienced recurrent wheezing. After accounting for SES and demographic factors, African ancestry (OR: 1.16, 95% CI: 1.02-1.31) was significantly associated with recurrent wheezing. By self-reported race, hispanic subjects had a borderline decrease in risk of wheeze compared with African Americans (OR: 0.44, 95% CI: 0.19-1.00), whereas white subjects (OR: 0.46, 95% CI: 0.14-1.57) did not have. After further adjustment for known confounders and early life exposures, both African (OR: 1.19, 95% CI: 1.05-1.34) and European ancestry (OR: 0.84, 95% CI: 0.74-0.94) retained a significant association with recurrent wheezing, as compared with self-identified race (OR(whites) : 0.31, 95% CI: 0.09-1.14; OR(hispanic) : 0.47, 95% CI: 0.20-1.08). There were no significant interactions between ancestry and early life factors on recurrent wheezing.

CONCLUSIONS AND CLINICAL RELEVANCE

In contrast to self-identified race, African ancestry remained a significant, independent predictor of early childhood wheezing after accounting for early life and other known risk factors associated with lung function changes and asthma. Genetic ancestry may be a powerful way to evaluate wheezing disparities and a proxy for differentially distributed genetic and early life risk factors associated with childhood recurrent wheezing.

The folate hydrolase 1561C>T polymorphism is associated with depressive symptoms in Puerto Rican adults

OBJECTIVE

To examine the associations between variants of genes involved in the uptake, retention, and metabolism of folate and depressive symptoms and to analyze whether such associations are direct or through mediation by folate or homocysteine.

METHODS

We performed a cross-sectional analysis of data from 976 Puerto Rican adults, aged 45 to 75 years, residing in the greater Boston area, Massachusetts. Twelve single nucleotide polymorphisms (SNPs) in genes involved in folate uptake, retention, and metabolism were investigated. These include FOLH1 (folate hydrolase), FPGS (folate polyglutamate synthase), GGH (γ-glutamyl hydrolase), MTHFR (methylenetetrahydrofolate reductase), MTR (methionine synthase), PCFT (proton-coupled folate transporter), and RFC1 (reduced folate carrier 1). The Center for Epidemiologic Studies Depression Scale (CES-D) was used to measure depressive symptoms.

RESULTS

The FOLH1 rs61886492 C>T (or 1561C>T) polymorphism was significantly associated with lower CES-D score (p = .0025) after adjusting for age, sex, population admixture, smoking, and educational attainment. Individuals with the TT and TC genotypes were 49% less likely (odds ratio = 0.51, 95% confidence interval = 0.29-0.89) to report mild depressive symptoms (CES-D score ≥16 and ≤26) and 64% less likely (odds ratio = 0.36, 95% confidence interval = 0.18-0.69) to report moderate to severe depressive symptoms (CES-D score >26), compared with those with the CC genotype. No significant mediation effects by plasma folate or homocysteine on the associations between this single nucleotide polymorphism and CES-D score were observed.

CONCLUSIONS

The FOLH1 1561C>T polymorphism may be associated with the risk of depressive symptoms.

Methylenetetrahydrofolate reductase variants associated with hypertension and cardiovascular disease interact with dietary polyunsaturated fatty acids to modulate plasma homocysteine in puerto rican adults

Although methylenetetrahydrofolate reductase (MTHFR) genetic variants are associated with plasma homocysteine (Hcy) and cardiovascular disease (CVD), little is known whether dietary fatty acid intake modulates these associations. The goal was to examine the interaction of MTHFR variants with dietary fatty acids influencing plasma Hcy in 995 Boston Puerto Rican adults. We found that plasma Hcy concentration was negatively correlated with (n-3) PUFA intake (r = -0.117; P = 0.022), and the ratio of (n-3):(n-6) PUFA in the diet (r = -0.122; P = 0.009). Further, 2 functional MTHFR variants, 1298A>C and 677C>T, which are not in linkage disequilibrium in this population, were significantly associated with hypertension (OR = 1.72, P = 0.024, and OR = 1.60, P = 0.002, respectively). In addition, the 1298A>C variant was significantly associated with CVD (OR = 3.32; P = 0.030). Importantly, this variant exhibited significant interactions with intakes of total and (n-6) PUFA and the (n-3):(n-6) PUFA ratio of the diet. The plasma Hcy concentration of carriers of risk allele 1298C was greater than that of noncarriers only when participants had consumed a high-PUFA diet (>7.8% energy) but was not greater when they had low intake of PUFA (≤7.8% energy). In addition, participants with combined genotypes of both SNP (677 TT with 1298 AC or CC) who consumed high levels of (n-3) PUFA (>0.66% energy) had lower plasma Hcy compared with those who had the same genotype and consumed low levels of (n-3) PUFA (≤0.66% energy). Our study suggests that dietary PUFA intake modulates the effect of 2 MTHFR variants on plasma Hcy in Boston Puerto Rican adults.

Interactions between genetic variants of folate metabolism genes and lifestyle affect plasma homocysteine concentrations in the Boston Puerto Rican population

OBJECTIVE

To investigate genetic and lifestyle factors and their interactions on plasma homocysteine (Hcy) concentrations in the Boston Puerto Rican population.

DESIGN

Cross-sectional study. Plasma concentrations of Hcy, folate, vitamin B12 and pyridoxal phosphate were measured, and genetic polymorphisms were determined. Data on lifestyle factors were collected in interviews.

SETTING

A population survey of health and nutritional measures.

SUBJECTS

A total of 994 Puerto Rican men and women residing in the Boston metropolitan area.

RESULTS

Smoking status was positively associated with plasma Hcy. Genetic polymorphisms MTHFR 677C→T, FOLH1 1561C→T, FOLH1 rs647370 and PCFT 928A→G interacted significantly with smoking for Hcy. MTHFR 1298A→C (P = 0·040) and PCFT 928A→G (P = 0·002) displayed significant interactions with alcohol intake in determining plasma Hcy. Subjects with PCFT 928GG genotype had significantly higher plasma Hcy concentrations compared with carriers of the A allele (AA+AG; P = 0·030) among non-drinking subjects. When consuming alcohol, GG subjects had lower plasma Hcy levels compared with AA+AG subjects. Physical activity interacted significantly with MTR 2756A→G in determining plasma Hcy (P for interaction = 0·002). Smoking interacted with physical activity for plasma Hcy (P for interaction = 0·023).

CONCLUSIONS

Smoking and drinking were associated plasma Hcy concentrations. Genetic variants involved in folate metabolism further modify the effects of lifestyle on plasma Hcy.

Genetic risk score and risk of myocardial infarction in Hispanics

BACKGROUND

Genome-wide association studies have identified loci associated with coronary heart disease in whites of European ancestry. This study evaluated whether genetic markers previously identified in whites are associated with nonfatal acute myocardial infarction (MI) in Hispanics.

METHODS AND RESULTS

Cases (n=1989) with a first nonfatal acute MI and population-based controls (n=2096) living in Costa Rica were studied. Fourteen single-nucleotide polymorphisms were genotyped. Seven single-nucleotide polymorphisms at 3 independent loci showed significant associations with MI. The odds ratios for the loci with the strongest associations were 1.16 (95 confidence interval [CI], 1.05 to 1.27) for rs4977574 (CDKN2A/2B), 1.15 (95 CI, 1.03 to 1.29) for rs646776 (CELSR2-PSRC1-SORT1), and 1.22 (95 CI, 1.08 to 1.38) for rs501120 (CXCL12); the corresponding PARs were 6.8, 10.5, and 15.2; respectively. We developed a genetic risk score by summing the number of the top 3 associated risk alleles. The OR for MI per genetic risk score unit was 1.18 (95 CI, 1.11 to 1.25; P=4.83 × 10(-8)). Discrimination of MI was significantly improved (P=0.02) when the genetic risk score was added to a model including clinical predictors. However, the increase in the area under the receiver-operating characteristic curve after the genetic risk score was added was moderate, from 0.67 (95 CI, 0.65 to 0.69) to 0.68 (95 CI, 0.66 to 0.70).

CONCLUSIONS

These results indicate both the consistency and disparity of genetic effects on risk of MI between Hispanic and white populations. The improvement in the identified genetic markers on discrimination of MI in Hispanics was modest.

Development of two multiplex mini-sequencing panels of ancestry informative SNPs for studies in Latin Americans: an application to populations of the State of Minas Gerais (Brazil)

Admixture occurs when individuals from parental populations that have been isolated for hundreds of generations form a new hybrid population. Currently, interest in measuring biogeographic ancestry has spread from anthropology to forensic sciences, direct-to-consumers personal genomics, and civil rights issues of minorities, and it is critical for genetic epidemiology studies of admixed populations. Markers with highly differentiated frequencies among human populations are informative of ancestry and are called ancestry informative markers (AIMs). For tri-hybrid Latin American populations, ancestry information is required for Africans, Europeans and Native Americans. We developed two multiplex panels of AIMs (for 14 SNPs) to be genotyped by two mini-sequencing reactions, suitable for investigators of medium-small laboratories to estimate admixture of Latin American populations. We tested the performance of these AIMs by comparing results obtained with our 14 AIMs with those obtained using 108 AIMs genotyped in the same individuals, for which DNA samples is available for other investigators. We emphasize that this type of comparison should be made when new admixture/population structure panels are developed. At the population level, our 14 AIMs were useful to estimate European admixture, though they overestimated African admixture and underestimated Native American admixture. Combined with more AIMs, our panel could be used to infer individual admixture. We used our panel to infer the pattern of admixture in two urban populations (Montes Claros and Manhuaçu) of the State of Minas Gerais (southeastern Brazil), obtaining a snapshot of their genetic structure in the context of their demographic history.

CoAIMs: a cost-effective panel of ancestry informative markers for determining continental origins

Background

Genetic ancestry is known to impact outcomes of genotype-phenotype studies that are designed to identify risk for common diseases in human populations. Failure to control for population stratification due to genetic ancestry can significantly confound results of disease association studies. Moreover, ancestry is a critical factor in assessing lifetime risk of disease, and can play an important role in optimizing treatment. As modern medicine moves towards using personal genetic information for clinical applications, it is important to determine genetic ancestry in an accurate, cost-effective and efficient manner. Self-identified race is a common method used to track and control for population stratification; however, social constructs of race are not necessarily informative for genetic applications. The use of ancestry informative markers (AIMs) is a more accurate method for determining genetic ancestry for the purposes of population stratification.

Methodology/Principal Findings

Here we introduce a novel panel of 36 microsatellite (MSAT) AIMs that determines continental admixture proportions. This panel, which we have named Continental Ancestry Informative Markers or CoAIMs, consists of MSAT AIMs that were chosen based upon their measure of genetic variance (F_st), allele frequencies and their suitability for efficient genotyping. Genotype analysis using CoAIMs along with a Bayesian clustering method (STRUCTURE) is able to discern continental origins including Europe/Middle East (Caucasians), East Asia, Africa, Native America, and Oceania. In addition to determining continental ancestry for individuals without significant admixture, we applied CoAIMs to ascertain admixture proportions of individuals of self declared race.

Conclusion/Significance

CoAIMs can be used to efficiently and effectively determine continental admixture proportions in a sample set. The CoAIMs panel is a valuable resource for genetic researchers performing case-control genetic association studies, as it can control for the confounding effects of population stratification. The MSAT-based approach used here has potential for broad applicability as a cost effective tool toward determining admixture proportions.

Epigenetics and cardiovascular disease

Despite advances in the prevention and management of cardiovascular disease (CVD), this group of multifactorial disorders remains a leading cause of mortality worldwide. CVD is associated with multiple genetic and modifiable risk factors; however, known environmental and genetic influences can only explain a small part of the variability in CVD risk, which is a major obstacle for its prevention and treatment. A more thorough understanding of the factors that contribute to CVD is, therefore, needed to develop more efficacious and cost-effective therapy. Application of the 'omics' technologies will hopefully make these advances a reality. Epigenomics has emerged as one of the most promising areas that will address some of the gaps in our current knowledge of the interaction between nature and nurture in the development of CVD. Epigenetic mechanisms include DNA methylation, histone modification, and microRNA alterations, which collectively enable the cell to respond quickly to environmental changes. A number of CVD risk factors, such as nutrition, smoking, pollution, stress, and the circadian rhythm, have been associated with modification of epigenetic marks. Further examination of these mechanisms may lead to earlier prevention and novel therapy for CVD.

Variants of the CD36 gene and metabolic syndrome in Boston Puerto Rican adults

OBJECTIVE

Puerto Ricans experience a high prevalence of several chronic conditions, including metabolic syndrome. Genetic variants of the CD36 gene have been associated with metabolic syndrome. We aimed to determine the association between 6 single nucleotide polymorphisms (SNPs) for CD36 and metabolic syndrome and its components in Puerto Ricans (45-75 year) living in the Greater Boston area.

METHODS

Associations between each SNP, metabolic syndrome and its components were examined using multivariate logistic regression models. Haplotype trend regression analysis was used to determine associations between haplotypes and metabolic syndrome.

RESULTS

For two SNPs of CD36 (rs1049673 and rs3211931), homozygous subjects of the minor allele (G and T, respectively) were associated with a higher likelihood of metabolic syndrome (odds ratio (OR) (95% confidence interval (CI)): 1.89 (1.0, 3.5) and 1.77 (1.0, 3.1), respectively) relative to carriers of the major allele. Although CD36 haplotypes were not significantly associated with metabolic syndrome overall (global significance, P=0.23), one haplotype (G-C-C vs. C-C-C (reference haplotype)) was marginally associated (P=0.049).

CONCLUSION

SNPs of CD36 were associated with metabolic syndrome in Puerto Ricans. Prospective studies should further explore the role of CD36 variants in the development of this condition.

Differences in albuminuria between Hispanics and whites: an evaluation by genetic ancestry and country of origin: the multi-ethnic study of atherosclerosis

BACKGROUND

Reports show higher prevalence of albuminuria among Hispanics compared with whites. Differences by country of origin or genetic background are unknown.

METHODS AND RESULTS

In Multi-Ethnic Study of Atherosclerosis, we studied the associations of both genetic ancestry and country of origin with albumin to creatinine ratio among 1417 Hispanic versus white participants using multivariable linear regression and back transforming beta coefficients into relative difference (%RD, 95% CI). Percentage European, Native American, and African ancestry components for Hispanics were estimated using genetic admixture analysis. The proportions of European, Native American, and African genetic ancestry differed significantly by country of origin (P<0.0001); Mexican/Central Americans had the highest Native American (41+/-13%), Puerto Ricans had the highest European (61+/-15%), and Dominicans had the highest African (39+/-21%) ancestry. Hispanic ethnicity was associated with higher albumin/creatinine ratio compared with whites, but the association varied with the country of origin (adjusted P interaction=0.04). Mexican/Central Americans and Dominicans had higher albumin/creatinine ratio compared with whites after adjustment (RD 19%, 2% to 40% and RD 27%, 1% to 61%), but not Puerto Ricans (RD 8%, -12% to 34%). Higher Native American ancestry was associated with higher albuminuria after age and sex adjustment among all Hispanics (RD 11%, 1% to 21%) but was attenuated after further adjustment. Higher European ancestry was independently associated with lower albumin/creatinine ratio among Puerto Ricans (-21%, -34% to -6%) but not among Mexican/Central Americans and Dominicans.

CONCLUSIONS

Hispanics are a heterogeneous group with varying genetic ancestry. Risks of albuminuria differ across the country of origin groups. These differences may be due, in part, to differences in genetic ancestral components.

Colloquium paper: genome-wide patterns of population structure and admixture among Hispanic/Latino populations

Hispanic/Latino populations possess a complex genetic structure that reflects recent admixture among and potentially ancient substructure within Native American, European, and West African source populations. Here, we quantify genome-wide patterns of SNP and haplotype variation among 100 individuals with ancestry from Ecuador, Colombia, Puerto Rico, and the Dominican Republic genotyped on the Illumina 610-Quad arrays and 112 Mexicans genotyped on Affymetrix 500K platform. Intersecting these data with previously collected high-density SNP data from 4,305 individuals, we use principal component analysis and clustering methods FRAPPE and STRUCTURE to investigate genome-wide patterns of African, European, and Native American population structure within and among Hispanic/Latino populations. Comparing autosomal, X and Y chromosome, and mtDNA variation, we find evidence of a significant sex bias in admixture proportions consistent with disproportionate contribution of European male and Native American female ancestry to present-day populations. We also find that patterns of linkage-disequilibria in admixed Hispanic/Latino populations are largely affected by the admixture dynamics of the populations, with faster decay of LD in populations of higher African ancestry. Finally, using the locus-specific ancestry inference method LAMP, we reconstruct fine-scale chromosomal patterns of admixture. We document moderate power to differentiate among potential subcontinental source populations within the Native American, European, and African segments of the admixed Hispanic/Latino genomes. Our results suggest future genome-wide association scans in Hispanic/Latino populations may require correction for local genomic ancestry at a subcontinental scale when associating differences in the genome with disease risk, progression, and drug efficacy, as well as for admixture mapping.

MAT1A variants are associated with hypertension, stroke, and markers of DNA damage and are modulated by plasma vitamin B-6 and folate

BACKGROUND

The S-adenosylmethionine synthetase type 1 (MAT1A) gene encodes a key enzyme in one-carbon nutrient metabolism.

OBJECTIVE

This study aimed to determine the association of MAT1A variants with homocysteine, DNA damage, and cardiovascular disease (CVD).

DESIGN

Eight variants of MAT1A were examined for associations with hypertension, stroke, CVD, homocysteine, and DNA damage in 1006 participants of the Boston Puerto Rican Health Study. Two variants were replicated in 1147 participants of the Nutrition, Aging, and Memory in Elders Study.

RESULTS

Two variants and haplotypes were strongly associated with hypertension and stroke, independent of methylenetetrahydrofolate reductase (MTHFR) variants. Homozygotes of the MAT1A d18777A (rs3851059) allele had a significantly greater likelihood of stroke (odds ratio: 4.30; 95% CI: 1.34, 12.19; P = 0.006), whereas 3U1510A (rs7087728) homozygotes had a lower likelihood of hypertension (odds ratio: 0.67; 95% CI: 0.48, 0.95; P = 0.022) and stroke (odds ratio: 0.35; 95% CI: 0.15, 0.82; P = 0.015). A similar trend of association was observed in a second elderly population. Furthermore, strong interactions between MAT1A genotypes and vitamin B-6 status were found. Carriers of the nonrisk allele 3U1510A had a lower 8-hydroxydeoxyguanosine concentration--a biomarker of oxidative DNA damage--when plasma vitamin B-6 was high, whereas homozygotes for the risk-allele 3U1510G had higher 8-hydroxydeoxyguanosine concentrations, regardless of vitamin B-6 status.

CONCLUSIONS

MAT1A variants were strongly associated with hypertension and stroke. Improving folate and vitamin B-6 status might decrease the CVD risk of only a subset of the population, depending on genotype. These findings suggest that impairments in methylation activity, independent of homocysteine, have an effect on CVD risk.

West African and Amerindian ancestry and risk of myocardial infarction and metabolic syndrome in the Central Valley population of Costa Rica

Genetic ancestry and environmental factors may contribute to the ethnic differences in risk of coronary heart disease (CHD), metabolic syndrome (MS) or its individual components. The population of the Central Valley of Costa Rica offers a unique opportunity to assess the role of genetic ancestry in these chronic diseases because it derived from the admixture of a relatively small number of founders of Southern European, Amerindian, and West African origin. We aimed to determine whether genetic ancestry is associated with risk of myocardial infarction (MI), MS and its individual components in the Central Valley of Costa Rica. We genotyped 39 ancestral informative markers in cases (n = 1,998) with a first non-fatal acute MI and population-based controls (n = 1,998) matched for age, sex, and area of residence, to estimate individual ancestry proportions. Odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated using conditional (MI) and unconditional (MS and its components) logistic regression adjusting for relevant confounders. Mean individual ancestry proportions in cases and controls were 57.5 versus 57.8% for the Southern European, 38.4 versus 38.3% for the Amerindian and 4.1 versus 3.8% for the West African ancestry. Compared with Southern European ancestry, each 10% increase in West African ancestry was associated with a 29% increase in MI, OR (95% CI) = 1.29 (1.07, 1.56), and with a 30% increase on the risk of hypertension, OR (95% CI) = 1.30 (1.00, 1.70). Each 10% increase in Amerindian ancestry was associated with a 14% increase on the risk of MS, OR (95% CI) = 1.14 (1.00, 1.30), and 20% increase on the risk of impaired fasting glucose, OR (95% CI) = 1.20 (1.01, 1.42). These results show that the high variability of admixture proportions in the Central Valley population offers a unique opportunity to uncover the genetic basis of ethnic differences on the risk of disease.

Apolipoprotein A5 and lipoprotein lipase interact to modulate anthropometric measures in Hispanics of Caribbean origin

Apolipoprotein A5 (APOA5) and lipoprotein lipase (LPL) proteins interact functionally to regulate lipid metabolism, and single-nucleotide polymorphisms (SNPs) for each gene have also been associated independently with obesity risk. Evaluating gene combinations may be more effective than single SNP analyses in identifying genetic risk, but insufficient minor allele frequency (MAF) often limits evaluations of potential epistatic relationships. Populations with multiple ancestral admixtures may provide unique opportunities for evaluating genetic interactions. We examined relationships between LPL m107 (rs1800590) and APOA5 S19W (rs3135506) and lipid and anthropometric measures in Caribbean origin Hispanics (n = 1,019, aged 45-75 years) living in the Boston metropolitan area. Significant interaction terms between LPL m107 and APOA5 S19W were observed for BMI (P = 0.003) and waist circumference (P = 0.019). Higher BMI (P = 0.001), waist (P = 0.011) and hip (P = 0.026) circumference were observed in minor allele (G) carriers for LPL m107 who also carried the APOA5 S19W minor allele (G). Additionally, extreme obesity (BMI > or = 40 kg/m(2)) risk was higher (odds ratio = 4.02; 95% confidence interval: 1.81-8.91; global P = 0.008) for minor allele carriers for both SNPs (LPL TG+GG, APOA5 CG+GG) compared to major allele carriers for both SNPs. In summary, we identified significant interactions for APOA5 S19W and LPL m107 for obesity in Caribbean Hispanics. Population-specific MAFs increase the difficulties of replicating gene-gene interactions, but may support the hypothesis that combinations of frequencies in selected genes could heighten obesity susceptibility in a given population. Analyses of gene-gene interactions may improve understanding of genetically based obesity risk, and underscore the need for further study of groups with multiple ancestral admixtures.

Recent advances of genetic ancestry testing in biomedical research and direct to consumer testing

In the post-Human Genome Project era, the debate on the concept of race/ethnicity and its implications for biomedical research are dependent on two critical issues: whether and how to classify individuals and whether biological factors play a role in health disparities. The advent of reliable estimates of genetic (or biogeographic) ancestry has provided this debate with a quantitative and more objective tool. The estimation of genetic ancestry allows investigators to control for population stratification in association studies and helps to detect biological causation behind population-specific differences in disease and drug response. New techniques such as admixture mapping can specifically detect population-specific risk alleles for a disease in admixed populations. However, researchers have to be mindful of the correlation between genetic ancestry and socioeconomic and environmental factors that could underlie these differences. More importantly, researchers must avoid the stigmatization of individuals based on perceived or real genetic risks. The latter point will become increasingly sensitive as several 'for profit companies' are offering ancestry and genetic testing directly to consumers and the consequences of the spread of the services of these companies are still unforeseeable.

The Emerging Role of Admixture in the Pharmacogenetics of Puerto Rican Hispanics

Admixture is of great relevance to the clinical application of pharmacogenetics and personalized medicine. Preliminary findings in Puerto Ricans further substantiate the argument for admixture as a critical covariate in a customized DNA-guided warfarin dosing algorithm. To this purpose, a genome-wide approach that incorporates admixture as an independent predictor of dose variability in DNA-guided algorithms has been postulated. Admixture is expected to be able to reveal some relevant associations in the genetic epidemiology of Hispanics and will be indispensable to assure that pharmacogenomic research can be pursued in such mixed populations. Consequently, the clinical utility of knowing an individual's genotype before initiating drug treatment in Puerto Ricans, and Hispanics in general, will finally be untangled by developing a "Genetic Prescription Model" that takes admixture into consideration. This approach will help lead physicians and patients to their desired treatment goal, resulting in more effective healthcare in admixed people.

APOA2, dietary fat, and body mass index: replication of a gene-diet interaction in 3 independent populations

BACKGROUND

Nutrigenetics studies the role of genetic variation on interactions between diet and health, aiming to provide more personalized dietary advice. However, replication has been low. Our aim was to study interaction among a functional APOA2 polymorphism, food intake, and body mass index (BMI) in independent populations to replicate findings and to increase their evidence level.

METHODS

Cross-sectional, follow-up (20 years), and case-control analyses were undertaken in 3 independent populations. We analyzed gene-diet interactions between the APOA2 -265T>C polymorphism and saturated fat intake on BMI and obesity in 3462 individuals from 3 populations in the United States: the Framingham Offspring Study (1454 whites), the Genetics of Lipid Lowering Drugs and Diet Network Study (1078 whites), and Boston-Puerto Rican Centers on Population Health and Health Disparities Study (930 Hispanics of Caribbean origin).

RESULTS

Prevalence of the CC genotype in study participants ranged from 10.5% to 16.2%. We identified statistically significant interactions between the APOA2 -265T>C and saturated fat regarding BMI in all 3 populations. Thus, the magnitude of the difference in BMI between the individuals with the CC and TT+TC genotypes differed by saturated fat. A mean increase in BMI of 6.2% (range, 4.3%-7.9%; P = .01) was observed between genotypes with high- (> or =22 g/d) but not with low- saturated fat intake in all studies. Likewise, the CC genotype was significantly associated with higher obesity prevalence in all populations only in the high-saturated fat stratum. Meta-analysis estimations of obesity for individuals with the CC genotype compared with the TT+TC genotype were an odds ratio of 1.84 (95% confidence interval, 1.38-2.47; P < .001) in the high-saturated fat stratum, but no association was detected in the low-saturated fat stratum (odds ratio, 0.81; 95% confidence interval, 0.59-1.11; P = .18).

CONCLUSION

For the first time to our knowledge, a gene-diet interaction influencing BMI and obesity has been strongly and consistently replicated in 3 independent populations.

Apolipoprotein A5 polymorphisms interact with total dietary fat intake in association with markers of metabolic syndrome in Puerto Rican older adults

APOA5 -1131T > C and S19W single nucleotide polymorphisms (SNP) have been consistently associated with plasma lipid concentration and metabolic syndrome (MetS), alone and in modulation by dietary factors. Puerto Ricans have a high prevalence of metabolic conditions and high minor allele frequency for these SNP, suggesting a possible role in disease for this population. We aimed to determine the association of APOA5 -1131T > C and S19W with plasma lipids and markers of MetS, alone and in interaction with total fat intake, as a percent of total energy intake, in Puerto Ricans. Anthropometric and demographic data, FFQ, and blood samples were collected at baseline from participants in the Boston Puerto Rican Health Study (n = 802, 45-75 y). APOA5 S19W was associated with plasma HDL cholesterol (HDL-C) (P = 0.044); minor allele carriers had lower HDL-C [1.12 +/- 0.03 (mean +/- SE)] than those with the common variant (1.18 +/- 0.01 mmol/L), even after adjustment for plasma triglycerides (TG) (P = 0.012). Neither polymorphism was associated with TG or other lipids. Interaction of the -1131T > C SNP with total fat energy intake was observed for plasma TG (P = 0.032) and total cholesterol (P = 0.034). APOA5 S19W interacted with total fat intake in association with systolic (P = 0.002) and diastolic (P = 0.007) blood pressure. Neither SNP was associated with MetS in the overall analysis or after stratifying by total energy intake as fat. In conclusion, Puerto Ricans present a distinctive lipid profile in association with APOA5 polymorphisms. Dietary fat intake seems to modulate these associations. The results contribute to the understanding of health disparities in this population.

Disparities in allele frequencies and population differentiation for 101 disease-associated single nucleotide polymorphisms between Puerto Ricans and non-Hispanic whites

Background

Variations in gene allele frequencies can contribute to differences in the prevalence of some common complex diseases among populations. Natural selection modulates the balance in allele frequencies across populations. Population differentiation (F_ST) can evidence environmental selection pressures. Such genetic information is limited in Puerto Ricans, the second largest Hispanic ethnic group in the US, and a group with high prevalence of chronic disease. We determined allele frequencies and population differentiation for 101 single nucleotide polymorphisms (SNPs) in 30 genes involved in major metabolic and disease-relevant pathways in Puerto Ricans (n = 969, ages 45–75 years) and compared them to similarly aged non-Hispanic whites (NHW) (n = 597).

Results

Minor allele frequency (MAF) distributions for 45.5% of the SNPs assessed in Puerto Ricans were significantly different from those of NHW. Puerto Ricans carried risk alleles in higher frequency and protective alleles in lower frequency than NHW. Patterns of population differentiation showed that Puerto Ricans had SNPs with exceptional F_ST values in intronic, non-synonymous and promoter regions. NHW had exceptional F_ST values in intronic and promoter region SNPs only.

Conclusion

These observations may serve to explain and broaden studies on the impact of gene polymorphisms on chronic diseases affecting Puerto Ricans.

Polymorphisms in uracil-processing genes, but not one-carbon nutrients, are associated with altered DNA uracil concentrations in an urban Puerto Rican population

BACKGROUND

Five genes--UNG, SMUG1, MBD4, TDG, and DUT--are involved in the repair or prevention of uracil misincorporation into DNA, an anomaly that can cause mutagenic events that lead to cancer. Little is known about the determinants of uracil misincorporation, including the effects of single nucleotide polymorphisms (SNPs) in the abovementioned genes. Because of their metabolic function, folate and other one-carbon micronutrients may be important factors in the control of uracil misincorporation.

OBJECTIVES

We sought to identify polymorphisms in uracil-processing genes that are determinants of DNA uracil concentration and to establish whether one-carbon nutrient status can further modify their effects.

DESIGN

We examined the relations between 23 selected variants in the 5 uracil-processing genes, uracil concentrations in whole-blood DNA, and one-carbon nutrient (folate, vitamins B-6 and B-12, and riboflavin) status in 431 participants of the Boston Puerto Rican Health Study.

RESULTS

Four SNPs in DUT, UNG, and SMUG1 showed a significant association with DNA uracil concentration. The SNPs in SMUG1 (rs2029166 and rs7296239) and UNG (rs34259) were associated with increased uracil concentrations in the variant genotypes (P = 0.011, 0.022, and 0.045, respectively), whereas the DUT SNP (rs4775748) was associated with a decrease (P = 0.023). In this population, one-carbon nutrient status was not associated with DNA uracil concentration, and it did not modify the effect of these 4 identified SNPs.

CONCLUSION

Because elevated uracil misincorporation may induce mutagenic lesions, possibly leading to cancer, we propose that the 4 characterized SNPs in DUT, UNG, and SMUG1 may influence cancer risk and therefore deserve further investigation.

Apolipoprotein C3 polymorphisms, cognitive function and diabetes in Caribbean origin Hispanics

BACKGROUND

Apolipoprotein C3 (APOC3) modulates triglyceride metabolism through inhibition of lipoprotein lipase, but is itself regulated by insulin, so that APOC3 represents a potential mechanism by which glucose metabolism may affect lipid metabolism. Unfavorable lipoprotein profiles and impaired glucose metabolism are linked to cognitive decline, and all three conditions may decrease lifespan. Associations between apolipoprotein C3 (APOC3) gene polymorphisms and impaired lipid and glucose metabolism are well-established, but potential connections between APOC3 polymorphisms, cognitive decline and diabetes deserve further attention.

METHODS

We examined whether APOC3 single nucleotide polymorphisms (SNPs) m482 (rs2854117) and 3u386 (rs5128) were related to cognitive measures, whether the associations between cognitive differences and genotype were related to metabolic differences, and how diabetes status affected these associations. Study subjects were Hispanics of Caribbean origin (n = 991, aged 45-74) living in the Boston metropolitan area.

RESULTS

Cognitive and metabolic measures differed substantially by type II diabetes status. In multivariate regression models, APOC3 m482 AA subjects with diabetes exhibited lower executive function (P = 0.009), Stroop color naming score (P = 0.014) and Stroop color-word score (P = 0.022) compared to AG/GG subjects. APOC3 m482 AA subjects with diabetes exhibited significantly higher glucose (P = 0.032) and total cholesterol (P = 0.028) compared to AG/GG subjects. APOC3 3u386 GC/GG subjects with diabetes exhibited significantly higher triglyceride (P = 0.004), total cholesterol (P = 0.003) and glucose (P = 0.016) compared to CC subjects.

CONCLUSIONS

In summary, we identified significant associations between APOC3 polymorphisms, impaired cognition and metabolic dysregulation in Caribbean Hispanics with diabetes. Further research investigating these relationships in other populations is warranted.