Localization of the Q1 mutation by cladistic analysis

The completion of the human genome project appears to be in sight and enormous new information resources will be available. The challenge now facing the scientific community is to use this information. In this paper, we applied cladistic analysis to the sequenced data in a Genetic Analysis Workshop 12 simulation problem. The Q1 mutation was localized to a 5-kb segment, in which the true mutation is located. Our analysis shows that cladistic analysis, which summarizes evolutionary history, can be a powerful tool in gene mapping.

Coronary angiographic findings in African-American and white patients from a single institution

No data exist comparing clinical and angiographic findings in large numbers of contemporary African-American and white patients from the same hospital. Limited angiographic data on African Americans were obtained from hospitals serving predominantly minority patients, making the valid African-American:white comparisons difficult. The study included 2,624 consecutive white and 1,793 African-American patients who had angiography for diagnostic evaluation of presumed coronary artery disease at the Louisiana State University Medical Center in Shreveport between 1990 and 1997. Compared to whites of the same sex, a greater proportion of African-American patients had a history of hypertension, stroke, and heart failure. African Americans also had significantly higher systemic and left ventricular pressure, lower ejection fraction, greater echocardiographic left ventricular mass index, and more concentric hypertrophy. The overall proportion of patients with normal or minimal stenosis of coronary artery (<50% narrowing in the luminal diameter) was greater in African Americans than in whites for both men and women. This difference was predominately found in men aged > or = 55 years or older. Except among older men, African-American patients with coronary heart disease had a similar distribution of 1-, 2-, 3-vessel disease and mean stenosis score compared to whites. In conclusion, a higher frequency of normal coronaries and less frequent coronary stenosis were found in older African-American men. The African-American:white differences in angiographic findings were minimal in younger men and in women. However, African Americans had worse clinical profiles than whites.

Social inequality, ethnicity and cardiovascular disease

BACKGROUND

Epidemiological research on cardiovascular risk factors has led to important advances in prevention science by providing insights that have now resulted in substantial reductions in mortality. This research used the variation in risk among individuals as the guide to causal exposures. Large differentials remain among socio-demographic groups, however, and the causes of these differentials may be distinctly different from those observed at the individual level.

METHODS

Vital statistics and census data from the US and selected regions were used in an ecologic analysis.

RESULTS

In 1996 heart disease mortality in the US varied from 156/100 000 among African-American women to 51/100 000 among Asian women; similar differentials were observed for men. Income equality was correlated with heart disease mortality among the 47 largest US cities (r = -0.4; P = 0.006). Independent of income equality, racial segregation was also associated with risk of death from cardiovascular disease in this sample of cities.

CONCLUSIONS

Social processes generate marked differentials in heart disease mortality among demographic groups. In the US, death rates are currently 2-3 times higher among African Americans compared to Asians. Broadly speaking, this variation results from their separate cultural legacies, based on well-recognized lifestyle factors and dietary patterns. Ecological comparisons across cities that share similar lifestyle patterns suggest that income inequality and patterns of racial discrimination are each associated with large variation in mortality in a similar manner. Racism and social inequality can be conceptualized as social causes of excess cardiovascular mortality that may not be measurable at the individual level.

Commentary: considerations for use of racial/ethnic classification in etiologic research

Numerous authors have critiqued the use of race as an etiologic quantity in medical research. Despite this criticism, the use of variables encoding racial/ethnic categorization has increased in epidemiology, and most researchers agree that important variation in disease risk is captured by this classification system. Previous discussions have generally neglected to articulate guidelines for appropriate use of racial/ethnic information in etiologic research. The authors summarize the logical, conceptual, and practical problems associated with the "ethnic paradigm" as currently applied in biomedical sciences and offer a set of methodological recommendations toward more valid use of racial/ethnic classification in etiologic studies. These suggested guidelines address issues of variable definition, study design, and covariate control, providing a consistent foundation for etiologic research programs that neither ignore racial/ethnic disease disparities nor obfuscate the nature of these disparities through inappropriate analytical approaches. This methodological analysis of racial/ethnic classification as an epidemiologic quantity provides a formal basis for a focus on racism (i.e., social relations) rather than race (i.e., innate biologic predisposition) in the interpretation of racial/ethnic "effects."

Heritability of obesity-related traits among Nigerians, Jamaicans and US black people

OBJECTIVE

The mean values for anthropometric traits vary across population groups and this variation is clearly determined for the most part by the environment. The familiarity of anthropometric traits also varies in reports from different populations, although this variation has not been shown to follow a consistent pattern. To examine whether heritability is influenced by socio-cultural factors, we conducted a cross-cultural study of populations of the African diaspora.

PARTICIPANTS

Data were collected on 1868 family members from Nigeria, 623 from Jamaica and 2132 from metropolitan Chicago, IL, USA.

MEASUREMENTS

Height and weight were measured and body mass index (kg/m(2)) calculated. Fat-free mass, fat mass and percentage body fat were estimated using bioelectrical impedance analysis. Plasma leptin concentrations were also measured. The proportion of variance attributable to additive genetic and non-shared environmental components was estimated with the maximum likelihood variance decomposition method.

RESULTS

Mean values for all anthropometric traits increased along the socio-cultural gradient, and obesity increased from 5% in Nigeria to 23% in Jamaica and 39% in the USA. Within populations the relationships among traits both within individuals and within families were highly consistent. Heritability estimates for weight, body mass index, fat mass and percentage body fat were approximately 50% for all groups. Heritability for height was lower in Nigeria (62%) than in Jamaica (74%) or the US (87%).

CONCLUSION

The familial patterns of body size and energy storage appear to be consistent in these genetically related populations across a wide range of environmental conditions.

NUTRITIONALCONSEQUENCES OF THEAFRICANDIASPORA

Along with their foods and dietary customs, Africans were carried into diaspora throughout the Americas as a result of the European slave trade. Their descendants represent populations at varying stages of the nutrition transition. West Africans are in the early stage, where undernutrition and nutrient deficiencies are prevalent. Many Caribbean populations represent the middle stages, with undernutrition and obesity coexisting. African-Americans and black populations in the United Kingdom suffer from the consequences of caloric excess and diets high in fat and animal products. Obesity, non-insulin-dependent diabetes mellitus, hypertension, coronary heart disease, and certain cancers all follow an east-to-west gradient of increasing prevalence. Public health efforts must focus not only on eradicating undernutrition in West Africa and the Caribbean but also on preventing obesity, hypercholesterolemia, and their consequences. Fortunately, a coherent and well-supported set of recommendations exists to promote better nutrition. Implementation of it founders primarily as a result of the influence of commercial and political interests.

Recent changes in the health status of the older U.S. population: findings from the 1984 and 1994 supplement on aging

OBJECTIVES

To examine the changes in the use of health care services, physical functioning, disability, and other aspects of health status in the older U.S. population between 1984 and 1994.

DESIGN AND SETTING

The 1984 and 1994 National Health Interview Survey Supplements on Aging, which were national probability samples of the civilian, noninstitutionalized population age 70 and older.

PARTICIPANTS

A total of 7,541 and 9,447 persons, representing the 17.3 million and 21.8 million U.S. population age 70 and older in 1984 and 1994, respectively.

MEASUREMENTS

Annual bed-limitation days, doctor visits, episodes and days of hospital stays, limitation in 10 measures of physical performance, disability in seven activities of daily living (ADLs) and six instrumental activities of daily living (IADLs), and participation in social activities and exercise.

RESULTS

The annual bed-limitation days and hospital stays declined significantly in both men and women between 1984 and 1994. There was a large decrease in the prevalence of limitation in physical performance and a smaller decrease in disability of IADLs. The changes were greater in women than in men. The prevalence of disability in ADLs was not changed in women in general and increased somewhat in men. Significant increases in the proportion of persons participating in certain social activities and regular exercise were found in both men and women. Jointly considering the indicators, including annual bed days and hospital stays, physical performance, ADLs, and IADLs, 4.2% more men and 3.1% more women were physically robust in 1994 than in 1984. Approximately 420,000 more older people would have lived in a severely restricted and disabled state in 1994 if the rate of limitation had not declined.

CONCLUSION

This study provides evidence of an overall improvement in the health status of older Americans but inconsistency in the trends existed for different disability measures and for population subgroups.

Linkage and association analysis of angiotensin I-converting enzyme (ACE)-gene polymorphisms with ACE concentration and blood pressure

Considerable effort has been expended to determine whether the gene for angiotensin I-converting enzyme (ACE) confers susceptibility to cardiovascular disease. In this study, we genotyped 13 polymorphisms in the ACE gene in 1,343 Nigerians from 332 families. To localize the genetic effect, we first performed linkage and association analysis of all the markers with ACE concentration. In multipoint variance-component analysis, this region was strongly linked to ACE concentration (maximum LOD score 7.5). Likewise, most of the polymorphisms in the ACE gene were significantly associated with ACE (P<.0013). The two most highly associated polymorphisms, ACE4 and ACE8, accounted for 6% and 19% of the variance in ACE, respectively. A two-locus additive model with an additive x additive interaction of these polymorphisms explained most of the ACE variation associated with this region. We next analyzed the relationship between these two polymorphisms (ACE4 and ACE8) and blood pressure (BP). Although no evidence of linkage was detected, significant association was found for both systolic and diastolic BP when a two-locus additive model developed for ACE concentration was used. Further analyses demonstrated that an epistasis model provided the best fit to the BP variation. In conclusion, we found that the two polymorphisms explaining the greatest variation in ACE concentration are significantly associated with BP, through interaction, in this African population sample. Our study also demonstrates that greater statistical power can be anticipated with association analysis versus linkage, when markers in strong linkage disequilibrium with a trait locus have been identified. Furthermore, allelic interaction may play an important role in the dissection of complex traits such as BP.

Testing quantitative traits for association and linkage in the presence or absence of parental data

Zhu and Elston developed a transmission disequilibrium test for quantitative traits by defining a linear transformation to condition out founder information. The method tests the null hypothesis of no linkage or association and can be applied to general pedigree structures. However, this method requires both genotype and phenotype parental information, which may be difficult to obtain. In this paper, we describe parametric and non-parametric methods to relax this requirement when only nuclear families are sampled. We show that neither method is affected by population stratification in the absence of linkage. The statistical power and validity of the tests are investigated by simulation. A simple simulation method to calculate the power of the nonparametric method is also discussed. In practice, the data may have some families with parental phenotype and genotype information available and some without. We briefly discuss how all the data may be analyzed jointly.

Distribution and functional consequences of nucleotide polymorphisms in the 3'-untranslated region of the human Sep15 gene

Selenium has been shown to prevent cancer in a variety of animal model systems. Both epidemiological studies and supplementation trials have supported its efficacy in humans. However, the mechanism by which selenium suppresses tumor development remains unknown. Selenium is present in known human selenoproteins as the amino acid selenocysteine (Sec). Sec is inserted cotranslationally in response to UGA codons within selenoprotein mRNAs in a process requiring a sequence within the 3'-untranslated region (UTR), referred to as a Sec insertion sequence (SECIS) element. Recently, a human Mr 15,000 selenoprotein (Sep15) was identified that contains an in-frame UGA codon and a SECIS element in the 3'-UTR. Examination of the available cDNA sequences for this protein revealed two polymorphisms located at position 811 (C/T) and at position 1125 (G/A) located within the 3'-UTR. Here, we demonstrate significant differences in Sep15 allele frequencies by ethnicity and that the identity of the nucleotides at the polymorphic sites influences SECIS function in a selenium-dependent manner. This, together with genetic data indicating loss of heterozygosity at the Sep15 locus in certain human tumor types, suggests that Sep15 may be involved in cancer development, risk, or both.

Racial differences and the genetics of hypertension

Variation in the prevalence of hypertension among human populations has been used to examine a wide range of research questions. The best known example has always been the twofold greater prevalence among blacks, which has provoked a debate about the relative importance of environmental and genetic factors. This problem is complicated because it requires an understanding of both the genetics of hypertension and the genetic basis of variation among populations. Molecular data accumulated over the past year are beginning to provide new insights into this old question. Modest progress has now been made in the genetics of hypertension. Important advances have been made in understanding rare hypertension syndromes, and large-scale studies of the general population are under way, although the results to date are inconclusive. Markers used to search for hypertension genes can also provide estimates of between-population variability. These data, which are based on genetic variants used for etiologic research, confirm previous evidence of group-specific variation, while underscoring the limited magnitude of this variation. Despite rapid progress, this work is still in its infancy and raises more questions than it answers.

The beta 3-adrenergic receptor gene and obesity in a population sample of African Americans

OBJECTIVE

To examine the role of the Trp64Arg polymorphism in the beta 3-adrenergic receptor gene and the beta 3-adrenergic receptor gene locus in obesity-related traits in African Americans.

SUBJECTS

A total of 687 individuals representing 193 African American families who were residents of metropolitan Chicago.

MEASUREMENTS

Genotyping of the Trp64Arg polymorphism in the beta 3-adrenergic receptor gene and three microsatellite markers flanking the beta 3-adrenergic receptor gene (ADRB3) locus and measuring various obesity-related traits, including body mass index (BMI), fat-free mass, fat mass, percentage fat mass, waist circumference and serum lipid levels.

RESULTS

The prevalence of obesity (defined as body mass index > or = 30 kg/m(2)) in the population was 27.3% and 51.2% in men and women, respectively. The frequency of the Arg64 allele was 10.0%. Multivariate regression analyses confirmed the existence of a significant contribution of familial variance to each of the five obesity-related traits noted above. Likelihood ratio statistics computed in a multivariate regression analysis failed to demonstrate a significant association between the Arg64 allele and any of the five obesity-related traits. Single and multipoint analyses using extended Haseman--Elston regression analyses failed to demonstrate suggestive evidence of linkage of three microsatellite markers that flank the beta 3-adrenergic receptor gene to BMI, percentage body fat, waist circumference or serum leptin levels.

CONCLUSION

Given the contribution of familial variance to obesity-related traits in this population, neither the null finding for the Arg64 allele nor the lack of evidence of linkage of the ADRB3 locus to obesity-related traits could be attributed to lack of transmissibility of the traits suggesting that neither the Arg64 variant of the beta 3-adrenergic receptor gene nor another genetic variant in or near the ADRB3 locus contribute significantly to familial aggregation of obesity-related traits in African Americans. International Journal of Obesity (2001) 25, 54-60

Relationship between premature mortality and socioeconomic factors in black and white populations of US metropolitan areas

OBJECTIVE

examined the association of mortality with selected socioeconomic indicators of inequality and segregation among blacks and whites younger than age 65 in 267 US metropolitan areas. The primary aim of the analysis was to operationalize the concept of institutional racism in public health.

METHODS

Socioeconomic indicators were drawn from Census and vital statistics data for 1989-1991 and included median household income; two measures of income inequality; percentage of the population that was black; and a measure of residential segregation.

RESULTS

Age-adjusted premature mortality was 81% higher in blacks than in whites, and median household income was 40% lower. Income inequality, as measured by the Gini coefficient, was greater within the black population (0.45) than within the white population (0.40; p < 0.001). To confirm that the proxy socioeconomic variables were relevant markers of population health status, regression analysis was performed initially on data for the total population. These variables were all independently and significantly related to premature mortality (p < or = 0.01; R(2) = 0.74). Income inequality for the total population was significantly correlated with premature mortality (r = 0.33). Black (r = 0.26) and white (r = 0.20) population-specific correlations between income inequality and premature mortality, while still significant, were smaller. Residential segregation was significantly related to premature mortality and income inequality for blacks (r = 0.38 for both); among whites, however, segregation was modestly correlated with premature mortality (r = 0.19) and uncorrelated with income inequality. Regional analyses demonstrated that the association of segregation with premature mortality was much more pronounced in the South and in areas with larger black populations.

CONCLUSION

Social factors such as income inequality and segregation strongly influence premature mortality in the US. Ecologic studies of the relationships among social factors and population health can measure attributes of the social context that may be relevant for population health, providing the basis for imputing macro-level relationships.

Height and risk of fatal prostate cancer: findings from the National Health Interview Survey (1986 to 1994)

PURPOSE

Height is determined by genetic and nutritional factors mediated through the endocrine system early in life and, thus, may be related to subsequent risk of fatal prostate cancer. This hypothesis was examined in a large representative U.S. national sample.

METHODS

Data from the National Health Interview Survey (NHIS) were analyzed to determine whether height was prospectively related to the risk of fatal prostate cancer in 110,042 men age > or = 50 years old interviewed between 1986 and 1994. Height was self-reported and vital status and causes of death ascertained using the National Death Index. Endpoints were deaths that listed prostate cancer as the underlying cause and deaths with any mention of prostate cancer. Relative risks (RR) and their 95% confidence intervals (CI) were calculated using Cox proportional hazards models adjusted for age, race, weight, and education.

RESULTS

Six hundred and thirty-three deaths listing of prostate cancer as the underlying cause and 910 deaths with any mention of prostate cancer were identified. Height was associated neither with risk of death with prostate cancer listed as the underlying cause nor with risk of death with any mention of prostate cancer (multivariate p for trend = 0.1318 and 0.0698, respectively). Risks were marginally greater among the tallest men compared to the shortest (< or = 171.4 vs. > or = 182.9 cm), but not significantly (RR = 1.21, 95% CI = 0.92 to 1.57, and RR = 1.24, 95% CI = 0.98 to 1.58 for 'underlying cause' and 'any mention', respectively).

CONCLUSIONS

Height alone was not related to risk of fatal prostate cancer in this population.

A first high-density map of 981 biallelic markers on human chromosome 14

As the largest set of sequence variants, single-nucleotide polymorphisms (SNPs) constitute powerful assets for mapping genes and mutations related to common diseases and for pharmacogenetic studies. A major goal in human genetics is to establish a high-density map of the genome containing several hundred thousand SNPs. Here we assayed 3.7 Mb (154,397 bp in 24 alleles) of chromosome 14 expressed sequence tags (ESTs) and sequence-tagged sites, for sequence variation in DNA samples from 12 African individuals. We identified and mapped 480 biallelic markers (459 SNPs and 21 small insertions and deletions), equally distributed between EST and non-EST classes. Extensive research in public databases also yielded 604 chromosome 14 SNPs (dbSNPs), 520 of which could be mapped and 19 of which are common between CNG (i.e., identified at the Centre National de Génotypage) and dbSNP polymorphisms. We present a dense map of SNP variation of human chromosome 14 based on 981 nonredundant biallelic markers present among 1345 radiation hybrid mapped sequence objects. Next, bioinformatic tools allowed 945 significant sequence alignments to chromosome 14 contigs, giving the precise chromosome sequence position for 70% of the mapped sequences and SNPs. In addition, these tools also permitted the identification and mapping of 273 SNPs in 159 known genes. The availability of this SNP map will permit a wide range of genetic studies on a complete chromosome. The recognition of 45 genes with multiple SNPs, by allowing the construction of haplotypes, should facilitate pharmacogenetic studies in the corresponding regions.

Localization of a small genomic region associated with elevated ACE

Defining the relationship between multiple polymorphisms in a small genomic region and an underlying quantitative trait locus (QTL) represents a major challenge in human genetics. Pedigree analyses have shown that angiotensin I-converting enzyme (ACE) levels are influenced by a QTL located within or close to the ACE gene and most likely resides in the 3' region of this locus. We genotyped seven polymorphisms spanning 13 kb in the 3' end of ACE in 159 Afro-Caribbean subjects to evaluate the linkage disequilibrium between these sites and to narrow the genomic region associated with an elevated ACE level using a cladistic analysis. The linkage disequilibrium measurement D' and a haplotype tree revealed three distinct haplotype segments, presumably because of recombination. The value of the linkage disequilibrium parameter p(excess) was highest for site 22982, which is located in the middle segment. A series of nested, cladistic analyses confirmed that the other two regions are unlikely to be the ACE-linked QTL and that the variant resides in the middle region. Analyses of the same polymorphisms in 98 unrelated Europeans in the Monitoring Trends and Determinants in Cardiovascular Diseases (MONICA) study resulted in fewer haplotypes than were observed among the Afro-Caribbean subjects, suggesting that populations with greater genetic diversity may be especially informative for fine-scale mapping.

Transvenous pacemaker insertion ipsilateral to chronic subclavian vein obstruction: an operative technique for children and adults

Subclavian vein occlusion limits insertion of pacing electrodes in children and adults. The concern is greatest in children with a long-term need for pacing systems necessitating use of the contralateral vein and potential bilateral loss of access in the future. We describe an operative technique to provide ipsilateral access in chronic subclavian vein occlusion in five consecutive pediatric (n = 4, mean age 6.5 years) and adult (n = 1, age 70 with bilateral subclavian vein occlusion) patients in whom this condition was noted at the time of pacemaker or ICD implant. Occlusion was documented by venography. Pediatric cardiac diagnoses included complete heart block in all patients, tetralogy of Fallot in three, and L-transposition of the great vessels in one. Percutaneous brachiocephalic (innominate) or deep subclavian venous access was achieved by a supraclavicular approach using an 18-gauge Deseret angiocath, a Terumo Glidewire, and dilation to permit one or two 9-11 Fr sheaths. Electrode(s) were positioned in the heart and tunneled (pre- or retroclavicularly) to a pre- or retropectoral pocket. Pacemaker and ICD implants were successful in all without any complication of pneumothorax, arterial or nerve injury, or need for transfusion. Inadvertent arterial access did not occur as compared with prior infraclavicular attempts. One preclavicularly tunneled electrode dislodged with extreme exertion and was revised. Ipsilateral transvenous access for pacemaker or ICD is possible via a deep supraclavicular percutaneous approach when the subclavian venous obstruction is discovered at the time of implant. In children, it avoids the use of the contralateral vein that may be needed for future pacing systems in adulthood. This venous approach provides access large enough to allow even dual chamber pacing in children and can be accomplished safely.

Comparability of resting energy expenditure in Nigerians and U.S. blacks

OBJECTIVE

To determine the influence of environmental factors on resting energy expenditure (REE) and its relationship to adiposity in two populations of West African origin, Nigerians and U.S. blacks.

RESEARCH METHODS AND PROCEDURES

REE and body composition were measured in a cross-sectional sample of 89 Nigerian adults (39 women and 50 men), and 181 U.S. black adults (117 women and 65 men). Both groups represent randomly selected population samples. REE was measured by indirect calorimetry after an overnight fast in both sites using the same instrument. Body composition was estimated using bioelectrical impedance analysis (BIA) in 72 Nigerians and 156 U.S. participants. Multivariate regression analysis was used to determine the significant predictors of REE. The analyses were repeated in a set of 17 Nigerians and 28 U.S. blacks in whom body composition was measured using deuterium dilution.

RESULTS

U.S. black adults were significantly heavier and had both more fat-free mass (FFM) and body fat than Nigerians. FFM was the only significant determinant of REE in both population groups, whether body composition was measured using BIA or deuterium dilution. The relationship between REE and body composition did not differ by site. There was no relationship between REE and adiposity.

DISCUSSION

Differences in current environmental settings did not impact REE. The differences observed in mean levels of body fat between Nigerians and U.S. blacks were not the result of differences in REE adjusted for body composition.

Abdominal adiposity and clustering of multiple metabolic syndrome in White, Black and Hispanic americans

PURPOSE

The aim of this study was to evaluate the association of abdominal adiposity assessed by waist circumference (WC) with clustering of multiple metabolic syndromes (MMS) in White, Black and Hispanic Americans. MMS was defined as the occurrence of two or more of either hypertension, type 2 diabetes mellitus, dyslipidemia, hypertriglyceridemia or hyperinsulinemia.

METHODS

The number of MMS and fasting insulin (a surrogate measure of MMS) were each used as dependent variables in gender-specific multiple linear regression models, adjusting for age, smoking and alcohol intake. The contribution of WC to interethnic differences in clustering of MMS and fasting insulin concentration was assessed in gender-specific linear regression models. The risk of MMS due to large waist was estimated by comparing odds ratio for men with WC >/= 102 cm with those with WC < 102, and women with WC >/= 88 cm with women with WC < 88 cm in the logistic regression model adjusting for age, smoking and alcohol intake.

RESULTS

WC was positively and independently associated with clustering of MMS and increased fasting insulin concentration adjusting for age, smoking and alcohol intake in the three ethnic groups (p < 0.01). Black ethnicity was associated with clustering of MMS and fasting insulin concentration (p < 0.01). Hispanic ethnicity was also associated with clustering of MMS in men and associated with fasting insulin concentration in both men and women (p < 0.01). In both men and women, the risk of MMS clustering was strongly associated with increased WC in all ethnic groups independent of BMI.

CONCLUSION

WC appears to be a marker for multiple metabolic syndromes in these ethnic groups. The results of this investigation lend support to the view that waist measurement should be considered as a clinical variable for assessing the risk of cardiovascular diseases.

Serum distribution of lipoprotein(a) in African Americans and Nigerians: potential evidence for a genotype-environmental effect

Differences in lipoprotein(a) [Lp(a)] levels across populations have been described and blacks are known to have higher Lp(a) values compared to whites. However, environmental factors which influence Lp(a) levels have been difficult to identify. We took advantage of the large environmental contrast which exists against a common genetic background between U.S. and Nigerian blacks to examine the relationship between Lp(a) and apolipoprotein(a) magnitude of apo(a) isoforms. Although the distribution of Lp(a) and apo(a) isoforms was nearly Gaussian in both populations, mean serum Lp(a) values were significantly higher in the United States than in Nigeria (20.5 vs. 12.7 mg/dl; P = 0.0001) and U.S. blacks had a higher frequency of the large molecular weight isoforms compared to Nigerians. Similar trends in the relationship between apo(a) isoform and Lp(a) concentration were seen in both populations; however, the magnitude of the effect was different. Compared to the Nigerians, U.S. blacks had significantly higher mean Lp(a) values for the same apo(a) isoform. The association of Lp(a) with low density lipoprotein-cholesterol (LDL-C) level was not significant after correcting for the contribution of Lp(a) cholesterol to LDL-C in both populations. Surprisingly, the association between Lp(a) and total-C remained significant (r = 0.20, P = 0.04) after similar correction for the contribution of Lp(a) cholesterol in the U.S. sample. Understanding the relationship between other factors including lifestyle characteristics capable of influencing total-C may help explain the unusually high Lp(a) level observed in this U.S. population.

Lack of association between a biallelic polymorphism in the adducin gene and blood pressure in whites and African Americans

Population-based candidate gene association analyses are becoming increasingly popular as a result of a greater number of genes and gene polymorphisms having been identified for which some functional information is available. Because many biochemical and physiologic systems impact blood pressure regulation and hypertension susceptibility, many of these identified genes and polymorphisms are candidates for population-level association studies involving blood pressure levels or hypertension status. Recent studies have suggested that the alpha-adducin gene may harbor polymorphisms that influence blood pressure level. Therefore, we embarked on a study to test one such polymorphism in two large US samples: one from an urban African American population (Maywood, IL) and another from a rural white population (Tecumseh, MI). We used both family-based association tests and tests that consider the impact of additional measured factors beyond adducin gene variation on blood pressure levels. We found no evidence for a significant effect of the chosen adducin polymorphism on blood pressure variation in either sample. We also found no association between Adducin genotypes and antihypertensive use. These facts, together with similar findings in companion studies, suggest that the alpha-adducin gene polymorphism does not have a pronounced effect on blood pressure variation in the populations studied. This does not suggest, however, that the alpha-adducin gene does not have a role in blood pressure regulation and hypertension susceptibility.

The Idikan adult mortality study

The Idikan adult mortality study is designed to explore the usefulness of the verbal autopsy methodology in the determination of cause-specific adult mortality. Such data have been largely unavailable in developing countries. Members of a stable urban community (4333 adults) were registered in their family units and followed up every 3 months to ascertain deaths, exits and new entries to the study population. Deaths were investigated by means of a verbal autopsy, which was administered by a trained interviewer to the relative closest to the decedent. Two physicians independently studied the results and assigned a cause of death, and these were then confirmed or resolved by a senior physician colleague. Hospitals where deaths occurred were visited and assignable cause of death was obtained where available and compared with the cause assigned by verbal autopsy. Only 8 of the 60 investigated deaths were confirmed to have occurred in a hospital in the first 2 years of the study. The cause of death assigned by verbal autopsy agreed moderately both between the independent coders as well as with the hospital assigned cause of death using the Kappa statistics for agreement beyond chance. We therefore concluded that verbal autopsies appear moderately useful for adult death statistics (Kappa = 0.23 to 0.1). Accumulation of more hospital deaths is needed, however, to make more definite conclusions about the validity of the technique.

Heritability of angiotensin-converting enzyme and angiotensinogen: A comparison of US blacks and Nigerians

Angiotensinogen (AGT) and angiotensin I-converting enzyme (ACE) are heritable traits, but whether the environmental context influences heritability has not been examined. Known genetic factors explain only a portion of variation in AGT and ACE, and levels of both proteins are influenced by the environment. The African diaspora provides an opportunity to compare these traits in genetically related populations in contrasting environments. As part of a study of the genetics of hypertension, we examined families that included 1449 Nigerians and 1147 African Americans. Body mass index (weight [kg]/height [m](2)) was 21 kg/m(2) in Nigeria and 29 kg/m(2) in the United States, which is consistent with a large environmental contrast. AGT was considerably higher among African Americans (1919 versus 1396, P<0.01), whereas ACE was higher in Nigerians (630 versus 517, P<0.01). A household effect was observed among the Nigerian families (spouse correlations 0.30 for AGT, 0.18 for ACE), and correlations among first-degree relatives were large (0.42 to 0. 51 and 0.36 to 0.38 for AGT and ACE, respectively). Among African Americans, the familial aggregations of AGT and ACE were very limited, and the familial correlation for AGT was not different from zero. Heritability was 77% for AGT and 67% for ACE in Nigeria and 18% for AGT and ACE in the United States. The familial patterns of body mass index and blood pressure were similar among both family sets. In conclusion, less familial aggregation was observed for AGT and ACE in the United States than in Nigeria, most likely reflecting a greater random individual environmental effect on these traits. Variation in heritability of traits could influence the power of epidemiological studies to identify genetic effects.