Racial/ethnic variation in the association of lipid-related genetic variants with blood lipids in the US adult population

Changing the triglyceride diagnostic criteria of metabolic syndrome for African Americans

The incidence and prevalence of metabolic syndrome has been increasing globally with no signs of abating. Individuals with metabolic syndrome are at increased risk of multiple comorbidities, including cardiovascular disease and type 2 diabetes mellitus. Studies show that there is a paradoxical relationship in African Americans however, as they experience a higher rate of cardiovascular disease and type 2 diabetes mellitus despite having a lower prevalence of metabolic syndrome when compared to whites. The triglyceride paradox, an unusual phenomenon in which African Americans consistently express a more normal triglyceride status even when having conditions known to be characterized by high triglyceride levels, is believed to account for this paradoxical relationship. In this manuscript, we review the history and pathophysiology of metabolic syndrome while also discussing the importance of the triglyceride paradox in explaining the inverse relationship that exists between metabolic syndrome, cardiovascular disease, and type 2 diabetes mellitus in African Americans. In addition, we advocate for decreasing the triglyceride cutoff value when diagnosing metabolic syndrome in this population to more precisely determine who is at risk for developing type 2 diabetes mellitus and cardiovascular disease.

A Nutrigenetic Strategy for Reducing Blood Lipids and Low-Grade Inflammation in Adults with Obesity and Overweight

The pathogenesis of obesity and dyslipidemia involves genetic factors, such as polymorphisms related to lipid metabolism alterations predisposing their development. This study aimed to evaluate the effect of a nutrigenetic intervention on the blood lipid levels, body composition, and inflammation markers of adults with obesity and overweight. Eleven genetic variants associated with dyslipidemias in Mexicans were selected, and specific nutrigenetic recommendations for these polymorphisms were found. One hundred and one adults were recruited and assigned to follow either a standard or nutrigenetic diet for eight weeks. Anthropometric, biochemical, body composition, and inflammation markers were evaluated through standardized methods. Weighted genetic risk scores (wGRSs) were computed using the study polymorphisms. After intervention, both diets significantly decreased the anthropometric parameters and body composition (p < 0.05). Only the nutrigenetic diet group showed significant reductions in VLDL-c (p = 0.001), triglycerides (p = 0.002), TG:HDL (p = 0.002), IL-6 (p = 0.002), and TNF-α (p = 0.04). wGRSs had a high impact on the ΔTGs and ΔVLDL-c of both groups (standard diet: ΔTGs: Adj R2 = 0.69, p = 0.03; ΔVLDL-c: Adj R2 = 0.71, p = 0.02; nutrigenetic diet: ΔTGs: Adj R2 = 0.49, p = 0.03 and ΔVLDL-c: R2 = 0.29, p = 0.04). This nutrigenetic intervention improved lipid abnormalities in patients with excessive body weight. Hence, nutrigenetic strategies could be coadjuvant tools and enhance the standard dietary treatment for cardiometabolic diseases.

Genes, environment, and African ancestry in cardiometabolic disorders

The past two decades have been characterized by a substantial global increase in cardiometabolic diseases, but the prevalence and incidence of these diseases and related traits differ across populations. African ancestry populations are among the most affected yet least included in research. Populations of African descent manifest significant genetic and environmental diversity and this under-representation is a missed opportunity for discovery and could exacerbate existing health disparities and curtail equitable implementation of precision medicine. Here, we discuss cardiometabolic diseases and traits in the context of African descent populations, including both genetic and environmental contributors and emphasizing novel discoveries. We also review new initiatives to include more individuals of African descent in genomics to address current gaps in the field.

Total-, LDL-, and HDL-cholesterol, apolipoproteins, and triglycerides with risk of total and fatal prostate cancer in Black and White men in the ARIC study

BACKGROUND

Cholesterol reduction is considered a mechanism through which cholesterol-lowering drugs including statins are associated with a reduced aggressive prostate cancer risk. While prior cohort studies found positive associations between total cholesterol and more advanced stage and grade in White men, whether associations for total cholesterol, low (LDL)- and high (HDL)-density lipoprotein cholesterol, apolipoprotein B (LDL particle) and A1 (HDL particle), and triglycerides are similar for fatal prostate cancer and in Black men, who experience a disproportionate burden of total and fatal prostate cancer, is unknown.

METHODS

We conducted a prospective study of 1553 Black and 5071 White cancer-free men attending visit 1 (1987-1989) of the Atherosclerosis Risk in Communities Study. A total of 885 incident prostate cancer cases were ascertained through 2015, and 128 prostate cancer deaths through 2018. We estimated multivariable-adjusted hazard ratios (HRs) of total and fatal prostate cancer per 1-standard deviation increments and for tertiles (T1-T3) of time-updated lipid biomarkers overall and in Black and White men.

RESULTS

Greater total cholesterol concentration (HR per-1 SD = 1.25; 95% CI = 1.00-1.58) and LDL cholesterol (HR per-1 SD = 1.26; 95% CI = 0.99-1.60) were associated with higher fatal prostate cancer risk in White men only. Apolipoprotein B was nonlinearly associated with fatal prostate cancer overall (T2 vs. T1: HR = 1.66; 95% CI = 1.05-2.64) and in Black men (HR = 3.59; 95% CI = 1.53-8.40) but not White men (HR = 1.13; 95% CI = 0.65-1.97). Tests for interaction by race were not statistically significant.

CONCLUSIONS

These findings may improve the understanding of lipid metabolism in prostate carcinogenesis by disease aggressiveness, and by race while emphasizing the importance of cholesterol control.

Genetic Predictors of the Development of Complications after Coronary Stenting

Due to the fact that there are scientific discussions about the significance of gene polymorphisms in the risk of developing cardiovascular complications after a percutaneous coronary intervention, it is of interest to evaluate the genetic predictors of the development of cardiovascular events. This study is a molecular genetic study. Association with the genes of biomarkers for inflammation and immune response increases the risk of cardiovascular events: rs1234313 (TNFSF4): (A/G, OR-4.57 (2.35-8.87), p ≤ 0.0001), (A/G-A/A, OR-3.14 (1.75-5.63), p ≤ 0.0001), and (A/G, OR = 4.01 (2.19-7.36), p ≤ 0.0001); rs3184504 (SH2D3); ATXN2: (C/T, OR-2.53 (1.28-5.01), T/T, OR-2.99 (1.13-7.92), p = 0.017)), (C/T-T/T, OR-2.61 (1.35-5.07), p = 0.000), and (OR-1.89 (1.15-3.09), p = 0.009)). According to the lipid metabolism biomarker genes, rs2943634: (A/C OR-2.57 (1.18-5.62), p = 0.013); according to the endothelial biomarker genes, rs2713604: (DNAJB8-AS1; GATA2): (C/T, OR-4.27 (2.35-7.76), p ≤ 0.0001), (C/T-C/C, OR-4.13 (2.31-7.40), p ≤ 0.0001), (OR-4.05 (2.24-7.30), p ≤ 0.0001), and (C/T, OR-3.46 (1.99-6.00), p ≤ 0.0001). The regression analysis found that in the presence of the rs2943634 gene polymorphism, the risk of late cardiovascular events increases by 4.007 times with 95% CI (1.502:10.692), p = 0.006. The genes of biomarkers for the risk of cardiovascular events are rs1234313(TNFSF4), rs3184504 (SH2D3; ATXN2), rs2943634, and rs2713604 (DNAJB8-AS1; GATA2). The only predictor of the development of new cardiovascular events was rs2943634, which belongs to the group of lipid metabolism biomarkers.

Is there a relation between plantar fasciitis and total cholesterol levels?

BACKGROUND

The main objective of this study is to investigate the relationship between hypercholesterolemia and Plantar Fasciitis (PF).

METHODS

The study includes patients who presented to the orthopedics outpatient clinic with heel pain and were diagnosed with PF. The control group was composed of patients who came to the orthopedics outpatient clinic, with complaints other than heel pain. The two groups were compared in terms of epidemiological data, total cholesterol (TC) levels, and hypercholesterolemia prevalence. We also performed an in-group analysis of PF patients in terms of age, sex, body mass index, and duration of symptoms.

RESULTS

There were 238 patients (mean age, 46.7) in the PF group and 240 patients (mean age, 47.9) in the control group. There was a significant difference between the PF group and the control group in TC levels (207.6 ± 47.5 versus 195.1 ± 30.1, p = 0.001). Hypercholesterolemia (TC level > 240 mg/dL) was found in 22.7% (n = 54) of the patients in the PF group whereas in the control group this rate was 10.8% (n = 26) (p < 0.001). It was seen that the TC levels were significantly higher in patients over the age of 45 in the PF group (p = 0.038). We also found that TC levels were higher in PF patients with symptoms for longer than a year (p = 0.026).

CONCLUSION

Significantly higher TC levels were found in PF patients in comparison with other orthopedic outpatients. Besides, being over the age of 45 and having a duration of symptoms longer than a year is associated with higher cholesterol levels for PF patients.

LEVEL OF CLINICAL EVIDENCE

4.

Targeted Lipidomics To Measure Phospholipids and Sphingomyelins in Plasma: A Pilot Study To Understand the Impact of Race/Ethnicity in Alzheimer's Disease

The number of people suffering from Alzheimer's disease (AD) is increasing rapidly every year. One aspect of AD that is often overlooked is the disproportionate incidence of AD among African American/Black populations. With the recent development of novel assays for lipidomics analysis in recent times, there has been a drastic increase in the number of studies focusing on changes of lipids in AD. However, very few of these studies have focused on or even included samples from African American/Black individuals samples. In this study, we aimed to determine if the lipidome in AD is universal across non-Hispanic White and African American/Black individuals. To accomplish this, a targeted mass spectrometry lipidomics analysis was performed on plasma samples (N = 113) obtained from cognitively normal (CN, N = 54) and AD (N = 59) individuals from African American/Black (N = 56) and non-Hispanic White (N = 57) backgrounds. Five lipids (PS 18:0_18:0, PS 18:0_20:0, PC 16:0_22:6, PC 18:0_22:6, and PS 18:1_22:6) were altered between AD and CN sample groups (p value < 0.05). Upon racial stratification, there were notable differences in lipids that were unique to African American/Black or non-Hispanic White individuals. PS 20:0_20:1 was reduced in AD in samples from non-Hispanic White but not African American/Black adults. We also tested whether race/ethnicity significantly modified the association between lipids and AD status by including a race × diagnosis interaction term in a linear regression model. PS 20:0_20:1 showed a significant interaction (p = 0.004). The discovery of lipid changes in AD in this study suggests that identifying relevant lipid biomarkers for diagnosis will require diversity in sample cohorts.

The association of prostatic lipids with progression, racial disparity and discovery of biomarkers in prostate cancer

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This study performed lipid profiling on human PCa and BPT tissues matched with patient's age and race, pathological grades and clinical stages.

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The human prostatic lipid profiles were widely associated with the pathogenesis, progression and racial disparity of PCa.

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Neutral lipids had greater impact on pathogenesis, progression and racial disparity of PCa as compared to phospholipids. Cholesteryl ester is the only lipid class significantly higher in PCa than in BPT in all population and stratified AA and CA populations.

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A panel of prostatic lipid parameters in each study population were identified as diagnostic and prognostic biomarkers with high sensitivity, specificity and accuracy simultaneously.

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Lipid profiling on mouse prostatic tissue from mouse PCa model further confirmed the roles of prostatic lipids on the pathogenesis, progression and discovery of diagnostic and prognostic biomarkers of PCa. In addition, this animal model was excellent to investigate prognostic lipid biomarkers in differentiation of indolent from aggressive PCa.

Background

It remains under-investigated whether prostatic lipid profiles are associated with pathogenesis, progression, racial disparity, and discovery of biomarkers in prostate cancer (PCa).

Methods

The electrospray ionization-tandem mass spectrometry was applied to quantitate prostatic lipids in human and mouse PCa and non-cancer prostatic tissues. Biostatistics and bioinformatics were used to compare the concentrations of prostatic lipids at levels of total lipid, group, class and individual species between PCa and benign prostatic tissues, between races, and among pathological conditions of PCa.

Results

Prostatic concentrations of total lipids as well as neutral lipids were significantly higher in PCa than in benign prostatic tissues in all population and Caucasian American population, but not in African American population. The prostatic phospholipid were not statistically different between PCa and benign prostatic tissues in all study populations. Cholesteryl ester is the only lipid class significantly higher in PCa than in benign prostatic tissues in all study populations. A panel of prostatic lipid parameters in each study population was identified as diagnostic and prognostic biomarkers with >60% of sensitivity, specificity and accuracy simultaneously. Lipid profiling on mouse prostatic tissues further confirmed correlation of prostatic lipid profiles to the pathogenesis and progression of PCa. In addition, a few prostatic lipids in mouse can serve as prognostic biomarkers in differentiation of indolent from aggressive PCa.

Conclusion

The prostatic lipids are widely associated with the pathogenesis, progression and racial disparity of PCa. A panel of prostatic lipids can serve as diagnostic, prognostic and race-specific biomarkers for PCa.

Genetic risk scores for cardiometabolic traits in sub-Saharan African populations

BACKGROUND

There is growing support for the use of genetic risk scores (GRS) in routine clinical settings. Due to the limited diversity of current genomic discovery samples, there are concerns that the predictive power of GRS will be limited in non-European ancestry populations. GRS for cardiometabolic traits were evaluated in sub-Saharan Africans in comparison with African Americans and European Americans.

METHODS

We evaluated the predictive utility of GRS for 12 cardiometabolic traits in sub-Saharan Africans (AF; n = 5200), African Americans (AA; n = 9139) and European Americans (EUR; n = 9594). GRS were constructed as weighted sums of the number of risk alleles. Predictive utility was assessed using the additional phenotypic variance explained and the increase in discriminatory ability over traditional risk factors [age, sex and body mass index (BMI)], with adjustment for ancestry-derived principal components.

RESULTS

Across all traits, GRS showed up to a 5-fold and 20-fold greater predictive utility in EUR relative to AA and AF, respectively. Predictive utility was most consistent for lipid traits, with percentage increase in explained variation attributable to GRS ranging from 10.6% to 127.1% among EUR, 26.6% to 65.8% among AA and 2.4% to 37.5% among AF. These differences were recapitulated in the discriminatory power, whereby the predictive utility of GRS was 4-fold greater in EUR relative to AA and up to 44-fold greater in EUR relative to AF. Obesity and blood pressure traits showed a similar pattern of greater predictive utility among EUR.

CONCLUSIONS

This work demonstrates the poorer performance of GRS in AF and highlights the need to improve representation of multiple ethnic populations in genomic studies to ensure equitable clinical translation of GRS.

An evaluation of lipid profile and pro-inflammatory cytokines as determinants of cardiovascular disease in those with diabetes: a study on a Mexican American cohort

Sedentary life styles coupled with high-calorie diets and unhealthy social habits such as smoking, have put an ever-increasing number of people at risk of cardiovascular disorders (CVD), worldwide. A concomitant increase in the prevalence of type 2-diabetes (hyperglycemia), a risk factor for CVD, has further contributed towards escalating CVD-related mortalities. The increase in number of cases of type 2-diabetes underscores the importance of early diagnosis of cardiovascular disease in those with diabetes. In this work, we have evaluated the sensitivity and specificity of dyslipidemia and proinflammatory cytokines to be used as biomarkers for predicting the risk of CVD in those with diabetes. We hypothesize that interplay between dyslipidemia and diabetes-induced low-grade inflammation in those with type 2-diabetes increases the risk of CVD. A total of 215 participants were randomly recruited from the Cameron County Hispanic Cohort (CCHC). Of these, 99% were Mexican Americans living on Texas-Mexico border. Levels of cytokines, adipokines and lipid profile were measured. Cardiovascular disease (CVD) for this study was defined as prior diagnosis of heart attack, angina and stroke, while diabetes was defined by fasting blood glucose (FBG) of > 100 mg/dL and HbA1c of > 6.5, in accordance with American Diabetes Association (ADA) guidelines. Depending on type and distribution of data, various statistical tests were performed. Our results demonstrated higher rates of heart attack (14% vs 11.8%) and stroke (19.8% vs 10%) in those with diabetes as compared to non-diabetes. The odds of having a heart attack were eight times higher in the presence of elevated triglycerides and pro-inflammatory markers (TNFα and IL6) as compared to presence of pro-inflammatory markers only. The odds for heart attack among those with diabetes, increased by 20 fold in presence of high levels of triglycerides, TNFα, and IL6 when coupled with low levels of high-density lipid cholesterol (HDL-C). Lastly, our analysis showed that poorly controlled diabetes, characterized by HbA1c values of > 6.5 increases the odds of stroke by more than three fold. The study quantifies the role of lipid profile and pro-inflammatory markers in combination with standard risk factors towards predicting the risk of CVD in those with type 2-diabetes. The findings from the study can be directly translated for use in early diagnosis of heart disease and guiding interventions leading to a reduction in CVD-associated mortality in those with type 2-diabetes.

A phenome-wide association study (PheWAS) in the Population Architecture using Genomics and Epidemiology (PAGE) study reveals potential pleiotropy in African Americans

We performed a hypothesis-generating phenome-wide association study (PheWAS) to identify and characterize cross-phenotype associations, where one SNP is associated with two or more phenotypes, between thousands of genetic variants assayed on the Metabochip and hundreds of phenotypes in 5,897 African Americans as part of the Population Architecture using Genomics and Epidemiology (PAGE) I study. The PAGE I study was a National Human Genome Research Institute-funded collaboration of four study sites accessing diverse epidemiologic studies genotyped on the Metabochip, a custom genotyping chip that has dense coverage of regions in the genome previously associated with cardio-metabolic traits and outcomes in mostly European-descent populations. Here we focus on identifying novel phenome-genome relationships, where SNPs are associated with more than one phenotype. To do this, we performed a PheWAS, testing each SNP on the Metabochip for an association with up to 273 phenotypes in the participating PAGE I study sites. We identified 133 putative pleiotropic variants, defined as SNPs associated at an empirically derived p-value threshold of p<0.01 in two or more PAGE study sites for two or more phenotype classes. We further annotated these PheWAS-identified variants using publicly available functional data and local genetic ancestry. Amongst our novel findings is SPARC rs4958487, associated with increased glucose levels and hypertension. SPARC has been implicated in the pathogenesis of diabetes and is also known to have a potential role in fibrosis, a common consequence of multiple conditions including hypertension. The SPARC example and others highlight the potential that PheWAS approaches have in improving our understanding of complex disease architecture by identifying novel relationships between genetic variants and an array of common human phenotypes.

The transferability of lipid loci across African, Asian and European cohorts

Most genome-wide association studies are based on samples of European descent. We assess whether the genetic determinants of blood lipids, a major cardiovascular risk factor, are shared across populations. Genetic correlations for lipids between European-ancestry and Asian cohorts are not significantly different from 1. A genetic risk score based on LDL-cholesterol-associated loci has consistent effects on serum levels in samples from the UK, Uganda and Greece (r = 0.23-0.28, p < 1.9 × 10^-14). Overall, there is evidence of reproducibility for ~75% of the major lipid loci from European discovery studies, except triglyceride loci in the Ugandan samples (10% of loci). Individual transferable loci are identified using trans-ethnic colocalization. Ten of fourteen loci not transferable to the Ugandan population have pleiotropic associations with BMI in Europeans; none of the transferable loci do. The non-transferable loci might affect lipids by modifying food intake in environments rich in certain nutrients, which suggests a potential role for gene-environment interactions.

Genome-wide association analysis of HDL-C in a Lebanese cohort

Low serum levels of high-density lipoprotein cholesterol (HDL-C) have been shown to be a risk factor for coronary artery disease independent of low-density lipoprotein cholesterol (LDL-C) in different populations. In this study, we investigated genetic variants through genome-wide association studies to determine their association with HDL-C levels in a sample of 2,700 patients. We identified several SNPs associated with HDL-C levels in the Lebanese population using unadjusted and adjusted by biological factors models. We replicated the association of rs3764261 within CETP with HDL-C levels in the study population, and found other previously unidentified SNPs to be significant at the suggestive level, in both previously identified and unidentified genes. This paper reports the first genome-wide analysis of HDL-C in the Lebanese, Middle Eastern, population and supports the importance of genome-wide association studies across different and minor ethnicities to understand better the etiology of complex human diseases.

Generalizability and applicability of results obtained from populations of European descent regarding the effect direction and size of HDL-C level-associated genetic variants to the Hungarian general and Roma populations

OBJECTIVES

Large-scale association studies that mainly involve European populations identified many genetic loci related to high-density lipoprotein cholesterol (HDL-C) levels, one of the most important indicators of the risk for cardiovascular diseases. The question with intense speculation of whether the effect estimates obtained from European populations for different HDL-C level-related SNPs are applicable to the Roma ethnicity, the largest minority group in Europe with a South Asian origin, was addressed in the present study.

DESIGN

The associations between 21 SNPs (in the genes LIPC(G), CETP, GALNT2, HMGCP, ABCA1, KCTD10 and WWOX) and HDL-C levels were examined separately in adults of the Hungarian general (N = 1542) and Roma (N = 646) populations by linear regression. Individual effects (direction and size) of single SNPs on HDL-C levels were computed and compared between the study groups and with data published in the literature.

RESULTS

Significant associations between SNPs and HDL-C levels were more frequently found in general subjects than in Roma subjects (11 SNPs in general vs. 4 SNPs in Roma). The CETP gene variants rs1532624, rs708272 and rs7499892 consistently showed significant associations with HDL-C levels across the study groups (p ˂ 0.05), indicating a possible causal variant(s) in this region. Although nominally significant differences in effect size were found for three SNPs (rs693 in gene APOB, rs9989419 in gene CETP, and rs2548861 in gene WWOX) by comparing the general and Roma populations, most of these SNPs did not have a significant effect on HDL-C levels. The β coefficients for SNPs in the Roma population were found to be identical both in direction and magnitude to the effect obtained previously in large-scale studies on European populations.

CONCLUSIONS

The effect of the vast majority of the SNPs on HDL-C levels could be replicated in the Hungarian general and Roma populations, which indicates that the effect size measurements obtained from the literature can be used for risk estimation for both populations.

Prediction of Blood Lipid Phenotypes Using Obesity-Related Genetic Polymorphisms and Lifestyle Data in Subjects with Excessive Body Weight

BACKGROUND AND AIM

Individual lipid phenotypes including circulating total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), and triglycerides (TG) determinations are influenced by gene-environment interactions. The aim of this study was to predict blood lipid level (TC, LDL-c, HDL-c, and TG) variability using genetic and lifestyle data in subjects with excessive body weight-for-height.

METHODS

This cross-sectional study enrolled 304 unrelated overweight/obese adults of self-reported European ancestry. A total of 95 single nucleotide polymorphisms (SNPs) related to obesity and weight loss were analyzed by a targeted next-generation sequencing system. Relevant genotypes of each SNP were coded as 0 (nonrisk) and 1 (risk). Four genetic risk scores (GRS) for each lipid phenotype were calculated by adding the risk genotypes. Information concerning lifestyle (diet, physical activity, alcohol drinking, and smoking) was obtained using validated questionnaires. Total body fat (TFAT) and visceral fat (VFAT) were determined by dual-energy X-ray absorptiometry.

RESULTS

Overall, 45 obesity-related genetic variants were associated with some of the studied blood lipids. In addition to conventional factors (age, sex, dietary intakes, and alcohol consumption), the calculated GRS significantly contributed to explain their corresponding plasma lipid trait. Thus, HDL-c, TG, TC, and LDL-c serum concentrations were predicted by approximately 28% (optimism-corrected adj. R 2 = 0.28), 25% (optimism-corrected adj. R 2 = 0.25), 24% (optimism-corrected adj. R 2 = 0.24), and 21% (optimism-corrected adj. R 2=0.21), respectively. Interestingly, GRS were the greatest contributors to TC (squared partial correlation (PC2) = 0.18) and LDL-c (PC2 = 0.18) features. Likewise, VFAT and GRS had a higher impact on HDL-c (PC2 = 0.09 and PC2 = 0.06, respectively) and TG levels (PC2 = 0.20 and PC2 = 0.07, respectively) than the rest of variables.

CONCLUSIONS

Besides known lifestyle influences, some obesity-related genetic variants could help to predict blood lipid phenotypes.

MC1R gene polymorphisms are associated with dysfunctional immune responses and wound infection after burn injury

BACKGROUND

Systemic inflammatory response syndrome (SIRS) is associated with organ failure and infectious complications after major burn injury. Recent evidence has linked melanocortin signaling to anti-inflammatory and wound-repair functions, with mutations in the melanocortin 1 receptor (MC1R) gene leading to increased inflammatory responses. Our group has previously demonstrated that MC1R gene polymorphisms are associated with postburn hypertrophic scarring. Thus, we hypothesized that MC1R single nucleotide polymorphisms (SNPs) would be associated with increased burn-induced SIRS and increased infectious complications.

METHODS

We performed a retrospective cohort study of adults (>18 y of age) admitted to our burn center with >20% total body surface area (TBSA) partial/full thickness burns between 2006 and 2013. We screened for five MC1R SNPs (V60L, V92M, R151C, R163Q, T314T) by polymerase chain reaction from genomic DNA isolated from blood samples. We performed a detailed review of each patient chart to identify age, sex, race, ethnicity, %TBSA burned, burn wound infections (BWIs), and 72-hr intravenous fluid volume, the latter a surrogate for a dysfunctional inflammatory response to injury. Association testing was based on multivariable regression.

RESULTS

Of 106 subjects enrolled, 82 had complete data for analysis. Of these, 64 (78%) were male, with a median age of 39 and median burn size of 30% TBSA. A total of 36 (44%) subjects developed BWIs. The median total administered IV crystalloid in first 72h was 24.6 L. In multivariate analysis, the R151C variant allele was a significant independent risk factor for BWI (adjusted prevalence ratio 2.03; 95% CI: 1.21-3.39; P = 0.007), and the V60L variant allele was independently associated with increased resuscitation fluid volume (P = 0.021).

CONCLUSIONS

This is the first study to demonstrate a significant association between genetic polymorphisms and a nonfatal burn-induced SIRS complication. Our findings suggest that MC1R polymorphisms contribute to dysfunctional responses to burn injury that may predict infectious and inflammatory complications.

Review of biomarkers to assess the effects of switching from cigarettes to modified risk tobacco products

Context: One approach to reducing the harm caused by cigarette smoking, at both individual and population level, is to develop, assess and commercialize modified risk alternatives that adult smokers can switch to. Studies to demonstrate the exposure and risk reduction potential of such products generally involve the measuring of biomarkers, of both exposure and effect, sampled in various biological matrices.Objective: In this review, we detail the pros and cons for using several biomarkers as indicators of effects of changing from conventional cigarettes to modified risk products.Materials and methods: English language publications between 2008 and 2017 were retrieved from PubMed using the same search criteria for each of the 25 assessed biomarkers. Nine exclusion criteria were applied to exclude non-relevant publications.Results: A total of 8876 articles were retrieved (of which 7476 were excluded according to the exclusion criteria). The literature indicates that not all assessed biomarkers return to baseline levels following smoking cessation during the study periods but that nine had potential for use in medium to long-term studies.Discussion and conclusion: In clinical studies, it is important to choose biomarkers that show the biological effect of cessation within the duration of the study.

Cardiovascular Health in African Americans: A Scientific Statement From the American Heart Association

BACKGROUND AND PURPOSE

Population-wide reductions in cardiovascular disease incidence and mortality have not been shared equally by African Americans. The burden of cardiovascular disease in the African American community remains high and is a primary cause of disparities in life expectancy between African Americans and whites. The objectives of the present scientific statement are to describe cardiovascular health in African Americans and to highlight unique considerations for disease prevention and management.

METHOD

The primary sources of information were identified with PubMed/Medline and online sources from the Centers for Disease Control and Prevention.

RESULTS

The higher prevalence of traditional cardiovascular risk factors (eg, hypertension, diabetes mellitus, obesity, and atherosclerotic cardiovascular risk) underlies the relatively earlier age of onset of cardiovascular diseases among African Americans. Hypertension in particular is highly prevalent among African Americans and contributes directly to the notable disparities in stroke, heart failure, and peripheral artery disease among African Americans. Despite the availability of effective pharmacotherapies and indications for some tailored pharmacotherapies for African Americans (eg, heart failure medications), disease management is less effective among African Americans, yielding higher mortality. Explanations for these persistent disparities in cardiovascular disease are multifactorial and span from the individual level to the social environment.

CONCLUSIONS

The strategies needed to promote equity in the cardiovascular health of African Americans require input from a broad set of stakeholders, including clinicians and researchers from across multiple disciplines.

The genomic landscape of African populations in health and disease

A deeper appreciation of the complex architecture of African genomes is critical to the global effort to understand human history, biology and differential distribution of disease by geography and ancestry. Here, we report on how the growing engagement of African populations in genome science is providing new insights into the forces that shaped human genomes before and after the Out-of-Africa migrations. As a result of this human evolutionary history, African ancestry populations have the greatest genomic diversity in the world, and this diversity has important ramifications for genomic research. In the case of pharmacogenomics, for instance, variants of consequence are not limited to those identified in other populations, and diversity within African ancestry populations precludes summarizing risk across different African ethnic groups. Exposure of Africans to fatal pathogens, such as Plasmodium falciparum, Lassa Virus and Trypanosoma brucei rhodesiense, has resulted in elevated frequencies of alleles conferring survival advantages for infectious diseases, but that are maladaptive in modern-day environments. Illustrating with cardiometabolic traits, we show that while genomic research in African ancestry populations is still in early stages, there are already many examples of novel and African ancestry-specific disease loci that have been discovered. Furthermore, the shorter haplotypes in African genomes have facilitated fine-mapping of loci discovered in other human ancestry populations. Given the insights already gained from the interrogation of African genomes, it is imperative to continue and increase our efforts to describe genomic risk in and across African ancestry populations.

Interethnic Differences in Serum Lipids and Implications for Cardiometabolic Disease Risk in African Ancestry Populations

African Americans generally have a healthier lipid profile (lower triglycerides and higher high-density lipoprotein cholesterol concentration) compared with those of other ethnicities. Paradoxically, African Americans do not experience a decreased risk of the cardiometabolic diseases that serum lipids are expected to predict. This review explores this mismatch between biomarker and disease among African ancestry individuals by investigating the presence of interethnic differences in the biological relationships underlying the serum lipids-disease association. This review also discusses the physiologic and genomic factors underlying these interethnic differences. Additionally, because of the importance of serum lipids in assessing disease risk, interethnic differences in serum lipids have implications for identifying African ancestry individuals at risk of cardiometabolic disease. Where possible, data from Africa is included, to further elucidate these ancestral differences in the context of a different environmental background.

Genetic associations with lipoprotein subfraction measures differ by ethnicity in the multi-ethnic study of atherosclerosis (MESA)

A recent genome-wide association study associated 62 single nucleotide polymorphisms (SNPs) from 43 genomic loci, with fasting lipoprotein subfractions in European-Americans (EAs) at genome-wide levels of significance across three independent samples. Whether these associations are consistent across ethnicities with a non-European ancestry is unknown. We analyzed 15 lipoprotein subfraction measures, on 1677 African-Americans (AAs), 1450 Hispanic-Americans (HAs), and 775 Chinese-Americans (CHN) participating in the multi-ethnic study of atherosclerosis (MESA). Genome-wide data were obtained using the Affymetrix 6.0 and Illumina HumanOmni chips. Linear regression models between genetic variables and lipoprotein subfractions were adjusted for age, gender, body mass index, smoking, study center, and genetic ancestry (based on principal components), and additionally adjusted for Mexican/Non-Mexican status in HAs. A false discovery rate correction was applied separately within the results for each ethnicity to correct for multiple testing. Power calculations revealed that we did not have the power for SNP-based measures of association, so we analyzed phenotype-specific genetic risk scores (GRSs), constructed as in the original genome-wide analysis. We successfully replicated all 15 GRS-lipoprotein associations in 2527 EAs. Among the 15 significant GRS-lipoprotein associations in EAs, 11 were significant in AAs, 13 in HAs, and 1 in CHNs. Further analyses revealed that ethnicity differences could not be explained by differences in linkage disequilibrium, lipid lowering drugs, diabetes, or gender. Our study emphasizes the importance of ethnicity (here indexing genetic ancestry) in genetic risk for CVD and highlights the need to identify ethnicity-specific genetic variants associated with CVD risk.

The C1431T polymorphism of peroxisome proliferator activated receptor γ (PPARγ) is associated with low risk of diabetes in a Pakistani cohort

BACKGROUND

Diabetes is a socioeconomic burden in Pakistan. International diabetes federation reported 6.9 million cases of diabetes and 87,548 deaths due to diabetes in Pakistan in 2014. Peroxisome proliferators-activated receptors are transcription factors, regulating several physiological processes.

AIM

The aim of the current study was to determine the prevalence of silent variant C1431T in exon 6 of PPAR-y and analyze its effect on various anthropometric and biochemical parameters in a Pakistani cohort.

METHODS

We collected 926 samples, 500 healthy controls (fasting blood sugar <99 mg/dL, random blood sugar <126 mg/dL) and 426 cases with diabetes (fasting blood sugar >99 mg/dL, random blood sugar >126 mg/dL). The genotyping was done by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) and serum biochemical parameters were determined by commercially available kits.

RESULTS

The genotyping results by RLFP showed allelic frequency C = 61.2 % and T = 38.8 % in controls while C = 74.5 % and T = 25.5 % in cases (OR 0.536, CI 0.439-0.655, p = 8.2 × 10(-10)) and genotypic frequency CC = 38.8 %, CT = 44.7 %, TT = 16.5 % in controls. While CC = 53.6 %, CT = 41.4 %, TT = 5.1 % in cases (OR 0.544, CI 0.408-0.726, p = 2.3 × 10(-10)). The rare T allele appeared to be a protective allele i.e., the presence of rare allele lowered the risk of diabetes in the studied cohort. The biochemical and anthropometric parameters were analyzed for any significant association with the SNP showing that C1431T variant has an association with BMI, weight, fasting glucose and LDLC. However, no significant association was found with age, gender, height, HDLC, TC, triglycerides and leptin.

CONCLUSION

In conclusion, the presence of minor allele lowers the risk of diabetes and the effect may involve modulating certain serum parameters.

Transethnic Genetic-Correlation Estimates from Summary Statistics

The increasing number of genetic association studies conducted in multiple populations provides an unprecedented opportunity to study how the genetic architecture of complex phenotypes varies between populations, a problem important for both medical and population genetics. Here, we have developed a method for estimating the transethnic genetic correlation: the correlation of causal-variant effect sizes at SNPs common in populations. This methods takes advantage of the entire spectrum of SNP associations and uses only summary-level data from genome-wide association studies. This avoids the computational costs and privacy concerns associated with genotype-level information while remaining scalable to hundreds of thousands of individuals and millions of SNPs. We applied our method to data on gene expression, rheumatoid arthritis, and type 2 diabetes and overwhelmingly found that the genetic correlation was significantly less than 1. Our method is implemented in a Python package called Popcorn.

Effect of SORT1, APOB and APOE polymorphisms on LDL-C and coronary heart disease in Pakistani subjects and their comparison with Northwick Park Heart Study II

Background

Many SNPs have been identified in genes regulating LDL-C metabolism, but whether their influence is similar in subjects from different ethnicities is unclear. Effect of 4 such SNPs on LDL-C and coronary heart disease (CHD) was examined in Pakistani subjects and was compared with middle aged UK men from Northwick Park Heart Study II (NPHSII).

Methods

One thousand nine hundred sixty-five (1770 non CHD, 195 CHD) UK and 623 (219 non CHD, 404 CHD) Pakistani subjects were enrolled in the study. The SNPs SORT1 rs646776, APOB rs1042031 and APOE rs429358, rs7412 were genotyped by TaqMan/KASPar technique and their gene score was calculated. LDL-C was calculated by Friedewald equation, results were analyzed using SPSS.

Results

Allele frequencies were significantly different (p = <0.05) between UK and Pakistani subjects. However, the SNPs were associated with LDL-C in both groups. In UK non CHD, UK CHD, Pakistani non CHD and Pakistani CHD respectively, for rs646776, per risk allele increase in LDL-C(mmol/l) was 0.18(0.04), 0.06(0.11), 0.15(0.04) and 0.27(0.06) respectively. For rs1042031, per risk allele increase in LDL-C in four groups was 0.11(0.04), 0.04(0.14), 0.15(0.06) and 0.25(0.09) respectively. For APOE genotypes, compared to Ɛ3, each Ɛ2 decreased LDL-C by 0.11(0.06), 0.07(0.15), 0.20(0.08) and 0.38(0.09), while each Ɛ4 increased LDL-C by 0.43(0.06), 0.39(0.21), 0.19(0.11) and 0.39(0.14) respectively. Overall gene score explained a considerable proportion of sample variance in four groups (3.8 %, 1.26 % 13.7 % and 12.3 %). Gene score in both non-CHD groups was significantly lower than CHD subjects.

Conclusions

The SNPs show a dose response association with LDL-C levels and risk of CHD in both populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0253-0) contains supplementary material, which is available to authorized users.

Association between Eight Functional Polymorphisms and Haplotypes in the Cholesterol Ester Transfer Protein (CETP) Gene and Dyslipidemia in National Minority Adults in the Far West Region of China

We have investigated the relationship between the polymorphisms and haplotypes in the CETP gene, and dyslipidemia among the Xinjiang Kazak and Uyghur populations in China. A total of 712 patients with dyslipidemia and 764 control subjects of CETP gene polymorphism at rs12149545, rs3764261, rs1800775, rs711752, rs708272, rs289714, rs5882, and rs1801706 loci were studied by the Snapshot method, linkage disequilibrium analysis and haplotype construction. The results are as follows: (1) the minor allele of eight loci of frequencies in the two groups were different from other results of similar studies in other countries; (2) In the linear regression analysis, the HDL-C levels of rs708272 TT, rs1800775 AA, rs289714 CC and rs711752 AA genotypes were significantly higher than those of other genotypes, however, the rs3764261 GG and rs12149545 GG genotypes were significantly lower than those of other genotypes in the two ethnic groups. The HDL-C levels of the rs12149545 GG genotype were lower than those of other genotypes; (3) in the control group, the rs708272 CT genotype of TG levels were lower than in the CC genotype, the T genotype of LDL-C levels were lower than in the CC genotype, and the HDL-C levels were higher than in the CT genotype; the rs1800775 AC genotype of TG levels were higher than in the AA genotype, the rs711752 AG genotype of TG levels were lower than in the GG genotype, the AA genotype LDL-C levels were lower than in the GG genotype, and the HDL-C levels were higher than in the AG genotype; the rs1800775 AC genotype of TG levels were higher than in the AA genotype. In the dyslipidemia group, the rs708272 TT genotype of TC and LDL-C levels were higher than in the CT genotype and the rs3764261 TT genotype of TC levels were higher than in the GG genotype. The rs711752 AA genotype of TC and LDL-C levels were higher than in the AG genotype, and the rs12149545 AA genotype of TC and LDL-C levels were higher than in the GG genotype; (4) perfect Linkage Disequilibrium was observed for two sets of two SNPs: rs3764261 and rs12149545; rs711752 and rs708272. (5) Using SHEsis software analysis, the five A/T/A/A/T/C/A/G, A/T/A/A/T/T/G/A, G/G/A/G/C/C/G/G, G/G/C/G/C/C/A/G and G/G/C/G/C/T/G/G haplotypes were between dyslipidemia group and control group statistically significantly different (p < 0.05 in each case). The polymorphism of CETP genes rs708272, rs3764261, rs1800775, rs711752, rs12149545 was closely related to the dyslipidemia in the Xinjiang Uyghur and Kazakh ethnic groups; and the rs708272 T, rs3764261 T, rs711752 A, and rs12149545 A alleles could reduce risk of dyslipidemia in the Uyghur and Kazakh populations, however, the rs1800775 C allele showed risk factors.

Genetic Susceptibility to Lipid Levels and Lipid Change Over Time and Risk of Incident Hyperlipidemia in Chinese Populations

BACKGROUND

Multiple genetic loci associated with lipid levels have been identified predominantly in Europeans, and the issue of to what extent these genetic loci can predict blood lipid levels increases over time and the incidence of future hyperlipidemia remains largely unknown.

METHODS AND RESULTS

We conducted a meta-analysis of genome-wide association studies of lipid levels in 8344 subjects followed by replication studies including 14 739 additional individuals. We replicated 17 previously reported loci. We also newly identified 3 Chinese-specific variants in previous regions (HLA-C, LIPG, and LDLR) with genome-wide significance. Almost all the variants contributed to lipid levels change and incident hyperlipidemia >8.1-year follow-up among 6428 individuals of a prospective cohort study. The strongest associations for lipid levels change were detected at LPL, TRIB1, APOA1-C3-A4-A5, LIPC, CETP, and LDLR (P range from 4.84×10(-4) to 4.62×10(-18)), whereas LPL, TRIB1, ABCA1, APOA1-C3-A4-A5, CETP, and APOE displayed significant strongest associations for incident hyperlipidemia (P range from 1.20×10(-3) to 4.67×10(-16)). The 4 lipids genetic risk scores were independently associated with linear increases in their corresponding lipid levels and risk of incident hyperlipidemia. A C-statistics analysis showed significant improvement in the prediction of incident hyperlipidemia on top of traditional risk factors including the baseline lipid levels.

CONCLUSIONS

These findings identified some evidence for allelic heterogeneity in Chinese when compared with Europeans in relation to lipid associations. The individual variants and those cumulative effects were independent risk factors for lipids increase and incident hyperlipidemia.

Associations of lipid levels susceptibility loci with coronary artery disease in Chinese population

Background

Recent genome-wide association studies (GWAS) have identified several single nucleotide polymorphisms (SNPs) that were associated with blood lipid levels in Caucasians. This study investigated whether these loci influenced lipid levels and whether they were associated with the risk of coronary artery disease (CAD) and its angiographic severity in Chinese population.

Methods

Six SNPs were genotyped in 1100 CAD cases and 1069 controls using the high-resolution melting (HRM) method. Coronary atherosclerosis severity was assessed by the vessel scores and the Gensini scoring system.

Results

Among the 6 SNPs and the genetic risks scores (GRS), the minor alleles of HNF1A rs1169288 (odd ratio (OR) = 1.18, 95 % confidence interval (CI) 1.05–1.33, P = 0.006) and MADD-FOLH1 rs7395662 (OR = 1.20, 95 % CI 1.07–1.36, P = 0.002) as well as the GRS (P = 1.06 × 10^-5) were significantly associated with increased risk of CAD after false discovery rate (FDR) correction. The vessel (P = 0.013) and Gensini scores (β = 0.113, P = 0.002) differed among CAD patients with different SNP rs1169288 C > T genotypes. The multiple linear regression analyses using an additive model revealed that the minor allele C of SNP rs1169288 (β = 0.060, P = 0.001) and the GRS (β = 0.033, P = 3.59 × 10^-4) were significantly associated with increased total cholesterol (TC) levels, the minor allele A of SNP rs7395662 (β = -0.024, P = 0.007) and the GRS (β = -0.013, P = 0.004) were significantly associated with decreased high-density lipoprotein cholesterol (HDL-c) levels.

Conclusions

The present study demonstrated that SNPs rs1169288, rs7395662 and the GRS were significantly associated with lipid levels and the risk of CAD in Chinese population. Furthermore, the allele C of SNP rs1169288 increased the odds of coronary atherosclerosis severity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-015-0079-1) contains supplementary material, which is available to authorized users.

Prevalence of dyslipidaemia and associated risk factors in a rural population in South-Western Uganda: a community based survey

BACKGROUND

The burden of dyslipidaemia is rising in many low income countries. However, there are few data on the prevalence of, or risk factors for, dyslipidaemia in Africa.

METHODS

In 2011, we used the WHO Stepwise approach to collect cardiovascular risk data within a general population cohort in rural south-western Uganda. Dyslipidaemia was defined by high total cholesterol (TC) ≥ 5.2 mmol/L or low high density lipoprotein cholesterol (HDL-C) <1 mmol/L in men, and <1.3 mmol/L in women. Logistic regression was used to explore correlates of dyslipidaemia.

RESULTS

Low HDL-C prevalence was 71.3% and high TC was 6.0%. In multivariate analysis, factors independently associated with low HDL-C among both men and women were: decreasing age, tribe (prevalence highest among Rwandese tribe), lower education, alcohol consumption (comparing current drinkers to never drinkers: men adjusted (a)OR=0.44, 95%CI=0.35-0.55; women aOR=0.51, 95%CI=0.41-0.64), consuming <5 servings of fruit/vegetable per day, daily vigorous physical activity (comparing those with none vs those with 5 days a week: men aOR=0.83 95%CI=0.67-1.02; women aOR=0.76, 95%CI=0.55-0.99), blood pressure (comparing those with hypertension to those with normal blood pressure: men aOR=0.57, 95%CI=0.43-0.75; women aOR=0.69, 95%CI=0.52-0.93) and HIV infection (HIV infected without ART vs. HIV negative: men aOR=2.45, 95%CI=1.53-3.94; women aOR=1.88, 95%CI=1.19-2.97). The odds of low HDL-C was also higher among men with high BMI or HbA1c ≤ 6%, and women who were single or with abdominal obesity. Among both men and women, high TC was independently associated with increasing age, non-Rwandese tribe, high waist circumference (men aOR=5.70, 95%CI=1.97-16.49; women aOR=1.58, 95%CI=1.10-2.28), hypertension (men aOR=3.49, 95%CI=1.74-7.00; women aOR=1.47, 95%CI=0.96-2.23) and HbA1c >6% (men aOR=3.00, 95%CI=1.37-6.59; women aOR=2.74, 95%CI=1.77-4.27). The odds of high TC was also higher among married men, and women with higher education or high BMI.

CONCLUSION

Low HDL-C prevalence in this relatively young rural population is high whereas high TC prevalence is low. The consequences of dyslipidaemia in African populations remain unclear and prospective follow-up is required.

Leveraging Multi-ethnic Evidence for Mapping Complex Traits in Minority Populations: An Empirical Bayes Approach

Elucidating the genetic basis of complex traits and diseases in non-European populations is particularly challenging because US minority populations have been under-represented in genetic association studies. We developed an empirical Bayes approach named XPEB (cross-population empirical Bayes), designed to improve the power for mapping complex-trait-associated loci in a minority population by exploiting information from genome-wide association studies (GWASs) from another ethnic population. Taking as input summary statistics from two GWASs-a target GWAS from an ethnic minority population of primary interest and an auxiliary base GWAS (such as a larger GWAS in Europeans)-our XPEB approach reprioritizes SNPs in the target population to compute local false-discovery rates. We demonstrated, through simulations, that whenever the base GWAS harbors relevant information, XPEB gains efficiency. Moreover, XPEB has the ability to discard irrelevant auxiliary information, providing a safeguard against inflated false-discovery rates due to genetic heterogeneity between populations. Applied to a blood-lipids study in African Americans, XPEB more than quadrupled the discoveries from the conventional approach, which used a target GWAS alone, bringing the number of significant loci from 14 to 65. Thus, XPEB offers a flexible framework for mapping complex traits in minority populations.

Racial differences in levels of serum lipids and effects of exposure to persistent organic pollutants on lipid levels in residents of Anniston, Alabama

Serum lipid levels are major risk factors for cardiovascular disease. In addition to diet, exercise, genetics, age and race, serum concentrations of persistent organic pollutants (POPs) influence concentrations of serum lipids. We investigated associations between fasting concentrations of 35 polychlorinated biphenyl (PCB) congeners and nine organochlorine pesticides in relation to total serum lipids, total cholesterol, low-density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol and triglycerides in 525 Caucasian and African American residents of Anniston, Alabama, who were not on any lipid-lowering medication. In Model 1, data were adjusted for age, age quadratic, gender, BMI, alcohol consumption, smoking and exercise, while in Model 2, additional adjustment was done for other POPs. As compared to Caucasians, African Americans had lower levels of total lipids and triglycerides with higher concentrations of HDL cholesterol, but higher concentrations of PCBs and pesticides. Total pesticides were more strongly associated with elevations in serum lipids than were total PCBs, and the associations were stronger in African Americans. Total DDTs were not associated with serum lipids after adjustment for other POPs in either racial group, while the strongest positive associations were seen for hexachlorobenzene (HCB) in both racial groups. Racial differences in lipid profiles, concentrations of POPs and associations between POP concentrations and serum lipids are relevant to racial differences in rates of cardiovascular disease.

Genetic determinants of age-related macular degeneration in diverse populations from the PAGE study

PURPOSE

Substantial progress has been made in identifying susceptibility variants for AMD in European populations; however, few studies have been conducted to understand the role these variants play in AMD risk in diverse populations. The present study aims to examine AMD risk across diverse populations in known and suspected AMD complement factor and lipid-related loci.

METHODS

Targeted genotyping was performed across study sites for AMD and lipid trait-associated single nucleotide polymorphism (SNPs). Genetic association tests were performed at individual sites and then meta-analyzed using logistic regression assuming an additive genetic model stratified by self-described race/ethnicity. Participants included cases with early or late AMD and controls with no signs of AMD as determined by fundus photography. Populations included in this study were European Americans, African Americans, Mexican Americans, and Singaporeans from the Population Architecture using Genomics and Epidemiology (PAGE) study.

RESULTS

Index variants of AMD, rs1061170 (CFH) and rs10490924 (ARMS2), were associated with AMD at P=3.05×10(-8) and P=6.36×10(-6), respectively, in European Americans. In general, none of the major AMD index variants generalized to our non-European populations with the exception of rs10490924 in Mexican Americans at an uncorrected P value<0.05. Four lipid-associated SNPS (LPL rs328, TRIB1 rs6987702, CETP rs1800775, and KCTD10/MVK rs2338104) were associated with AMD in African Americans and Mexican Americans (P<0.05), but these associations did not survive strict corrections for multiple testing.

CONCLUSIONS

While most associations did not generalize in the non-European populations, variants within lipid-related genes were found to be associated with AMD. This study highlights the need for larger well-powered studies in non-European populations.

Gene-based sequencing identifies lipid-influencing variants with ethnicity-specific effects in African Americans

Although a considerable proportion of serum lipids loci identified in European ancestry individuals (EA) replicate in African Americans (AA), interethnic differences in the distribution of serum lipids suggest that some genetic determinants differ by ethnicity. We conducted a comprehensive evaluation of five lipid candidate genes to identify variants with ethnicity-specific effects. We sequenced ABCA1, LCAT, LPL, PON1, and SERPINE1 in 48 AA individuals with extreme serum lipid concentrations (high HDLC/low TG or low HDLC/high TG). Identified variants were genotyped in the full population-based sample of AA (n = 1694) and tested for an association with serum lipids. rs328 (LPL) and correlated variants were associated with higher HDLC and lower TG. Interestingly, a stronger effect was observed on a "European" vs. "African" genetic background at this locus. To investigate this effect, we evaluated the region among West Africans (WA). For TG, the effect size among WA was the same in AA with only African local ancestry (2-3% lower TG), while the larger association among AA with local European ancestry matched previous reports in EA (10%). For HDLC, there was no association with rs328 in AA with only African local ancestry or in WA, while the association among AA with European local ancestry was much greater than what has been observed for EA (15 vs. ∼ 5 mg/dl), suggesting an interaction with an environmental or genetic factor that differs by ethnicity. Beyond this ancestry effect, the importance of African ancestry-focused, sequence-based work was also highlighted by serum lipid associations of variants that were in higher frequency (or present only) among those of African ancestry. By beginning our study with the sequence variation present in AA individuals, investigating local ancestry effects, and seeking replication in WA, we were able to comprehensively evaluate the role of a set of candidate genes in serum lipids in AA.

Interethnic Variation in Lipid Profiles: Implications for Underidentification of African-Americans at risk for Metabolic Disorders

Interethnic differences exist in the distribution of serum lipids, with African Americans (AA) generally having a healthier lipid profile than other US ethnic groups. Similar lipid distributions are observed among other African ancestry groups with distinct lifestyle characteristics, suggesting the importance of inherited factors. Despite healthier serum lipids, AA experience a disproportionate burden of Type 2 Diabetes and Cardiovascular Disease. As evidence of a different relationship between serum lipids and disease exists, the characterization of metabolic risk using lipid concentration (as in Metabolic Syndrome criteria) may lead to the under-identification of AA at risk. Given the disproportionately high rate of metabolic disorders in AA, understanding interethnic differences in the association between serum lipids and disease should be a research priority, as better appreciation of these differences will enhance knowledge of disease etiology, improve intervention targeting, and may lead to mechanisms to ameliorate debilitating health disparities in the US and globally.

Additive genetic variation in schizophrenia risk is shared by populations of African and European descent

To investigate the extent to which the proportion of schizophrenia's additive genetic variation tagged by SNPs is shared by populations of European and African descent, we analyzed the largest combined African descent (AD [n = 2,142]) and European descent (ED [n = 4,990]) schizophrenia case-control genome-wide association study (GWAS) data set available, the Molecular Genetics of Schizophrenia (MGS) data set. We show how a method that uses genomic similarities at measured SNPs to estimate the additive genetic correlation (SNP correlation [SNP-rg]) between traits can be extended to estimate SNP-rg for the same trait between ethnicities. We estimated SNP-rg for schizophrenia between the MGS ED and MGS AD samples to be 0.66 (SE = 0.23), which is significantly different from 0 (p(SNP-rg = 0) = 0.0003), but not 1 (p(SNP-rg = 1) = 0.26). We re-estimated SNP-rg between an independent ED data set (n = 6,665) and the MGS AD sample to be 0.61 (SE = 0.21, p(SNP-rg = 0) = 0.0003, p(SNP-rg = 1) = 0.16). These results suggest that many schizophrenia risk alleles are shared across ethnic groups and predate African-European divergence.

Skeletal muscle adiposity is associated with serum lipid and lipoprotein levels in Afro-Caribbean men

OBJECTIVE

When compared with other ethnic groups, African ancestry individuals have lower triglycerides and higher High-density lipoprotein cholesterol (HDL-C) levels, although the mechanisms for these differences remain unclear. A comprehensive array of factors potentially related to fasting serum lipid and lipoprotein levels in African ancestry men was evaluated.

DESIGN AND METHODS

Men (1,821) underwent dual-energy X-ray absorptiometry measures of total body fat and quantitative computed tomography assessments of calf skeletal muscle adiposity [subcutaneous and intermuscular adipose tissue (AT), and muscle density as a measure of intra-muscular AT].

RESULTS

Multivariable linear regression analysis identified age (-), total body fat (+), subcutaneous AT (-), fasting glucose (+), fasting insulin (+), diastolic blood pressure (+), and non-African ancestry (+) as independent correlates of triglycerides (all P < 0.05). Total body fat (+), intra-muscular AT (-), and diastolic blood pressure (+) were independent correlates of Low-density lipoprotein cholesterol (LDL-C) (all P < 0.001). Age (+), waist circumference (-), fasting insulin (-), physical activity (+), and alcohol intake (+) were independent correlates of HDL-C (all P < 0.05).

CONCLUSIONS

A novel relationship between skeletal muscle adiposity and serum lipid and lipoprotein levels in African ancestry men, independent of total and central adiposity was illuminated. In African ancestry populations, genetic factors are likely a significant determinant of triglycerides levels.

A multiethnic replication study of plasma lipoprotein levels-associated SNPs identified in recent GWAS

Genome-wide association studies (GWAS) have identified a number of loci/SNPs associated with plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG) levels. The purpose of this study was to replicate 40 recent GWAS-identified HDL-C-related new loci in 3 epidemiological samples comprising U.S. non-Hispanic Whites (NHWs), U.S. Hispanics, and African Blacks. In each sample, the association analyses were performed with all 4 major lipid traits regardless of previously reported specific associations with selected SNPs. A total of 22 SNPs showed nominally significant association (p<0.05) with at least one lipid trait in at least one ethnic group, although not always with the same lipid traits reported as genome-wide significant in the original GWAS. The total number of significant loci was 10 for TC, 12 for LDL-C, 10 for HDL-C, and 6 for TG levels. Ten SNPs were significantly associated with more than one lipid trait in at least one ethnic group. Six SNPs were significantly associated with at least one lipid trait in more than one ethnic group, although not always with the same trait across various ethnic groups. For 25 SNPs, the associations were replicated with the same genome-wide significant lipid traits in the same direction in at least one ethnic group; at nominal significance for 13 SNPs and with a trend for association for 12 SNPs. However, the associations were not consistently present in all ethnic groups. This observation was consistent with mixed results obtained in other studies that also examined various ethnic groups.

Association of genetic variants influencing lipid levels with coronary artery disease in Japanese individuals

Background/Objective

In Japanese populations, we performed a replication study of genetic loci previously identified in European-descent populations as being associated with lipid levels and risk of coronary artery disease (CAD).

Methods

We genotyped 48 single nucleotide polymorphisms (SNPs) from 22 candidate loci that had previously been identified by genome-wide association (GWA) meta-analyses for low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and/or triglycerides in Europeans. We selected 22 loci with 2 parallel tracks from 95 reported loci: 16 significant loci (p<1×10⁻³⁰ in Europeans) and 6 other loci including those with suggestive evidence of lipid associations in 1292 GWA-scanned Japanese samples. Genotyping was done in 4990 general population samples, and 1347 CAD cases and 1337 controls. For 9 SNPs, we further examined CAD associations in an additional panel of 3052 CAD cases and 6335 controls.

Principal Findings

Significant lipid associations (one-tailed p<0.05) were replicated for 18 of 22 loci in Japanese samples, with significant inter-ethnic heterogeneity at 4 loci–APOB, APOE-C1, CETP, and APOA5–and allelic heterogeneity. The strongest association was detected at APOE rs7412 for LDL-C (p = 1.3×10⁻⁴¹), CETP rs3764261 for HDL-C (p = 5.2×10⁻²⁴), and APOA5 rs662799 for triglycerides (p = 5.8×10⁻⁵⁴). CAD association was replicated and/or verified for 4 loci: SORT1 rs611917 (p = 1.7×10⁻⁸), APOA5 rs662799 (p = 0.0014), LDLR rs1433099 (p = 2.1×10⁻⁷), and APOE rs7412 (p = 6.1×10⁻¹³).

Conclusions

Our results confirm that most of the tested lipid loci are associated with lipid traits in the Japanese, further indicating that in genetic susceptibility to lipid levels and CAD, the related metabolic pathways are largely common across the populations, while causal variants at individual loci can be population-specific.

Gender and single nucleotide polymorphisms in MTHFR, BHMT, SPTLC1, CRBP2, CETP, and SCARB1 are significant predictors of plasma homocysteine normalized by RBC folate in healthy adults

Using linear regression models, we studied the main and 2-way interaction effects of the predictor variables gender, age, BMI, and 64 folate/vitamin B-12/homocysteine (Hcy)/lipid/cholesterol-related single nucleotide polymorphisms (SNP) on log-transformed plasma Hcy normalized by RBC folate measurements (nHcy) in 373 healthy Caucasian adults (50% women). Variable selection was conducted by stepwise Akaike information criterion or least angle regression and both methods led to the same final model. Significant predictors (where P values were adjusted for false discovery rate) included type of blood sample [whole blood (WB) vs. plasma-depleted WB; P < 0.001] used for folate analysis, gender (P < 0.001), and SNP in genes SPTLC1 (rs11790991; P = 0.040), CRBP2 (rs2118981; P < 0.001), BHMT (rs3733890; P = 0.019), and CETP (rs5882; P = 0.017). Significant 2-way interaction effects included gender × MTHFR (rs1801131; P = 0.012), gender × CRBP2 (rs2118981; P = 0.011), and gender × SCARB1 (rs83882; P = 0.003). The relation of nHcy concentrations with the significant SNP (SPTLC1, BHMT, CETP, CRBP2, MTHFR, and SCARB1) is of interest, especially because we surveyed the main and interaction effects in healthy adults, but it is an important area for future study. As discussed, understanding Hcy and genetic regulation is important, because Hcy may be related to inflammation, obesity, cardiovascular disease, and diabetes mellitus. We conclude that gender and SNP significantly affect nHcy.