Fat infiltration in muscle: new evidence for familial clustering and associations with diabetes

OBJECTIVE

Increased fat infiltration in skeletal muscle has been associated with diabetes. Quantitative computed tomography (QCT) can be used to measure muscle density, which reflects the lipid content of skeletal muscle such that greater fat infiltration in skeletal muscle is associated with lower muscle density. The relative contribution of genetic and environmental factors to fat infiltration in skeletal muscle has not been assessed. Therefore, our aim is to determine genetic and environmental contributions to measures of skeletal muscle composition, and describe their associations with type 2 diabetes in multigenerational families of African ancestry.

METHODS AND PROCEDURES

Peripheral QCT (pQCT) measures of skeletal muscle density were obtained for the calf in 471 individuals (60% women; mean 43 years) belonging to eight large, multigenerational Afro-Caribbean families (mean family size 51 individuals; 3,535 relative pairs).

RESULTS

The proportion of variance in muscle density due to additive genetic effects (residual heritability) was 35.0% (P < 0.001) and significant covariates (age, gender, BMI, and parity) explained 55.0% of the total phenotypic variation in muscle density. Muscle density was lower (P < 0.001) in 62 diabetics (69.5 mg/cm(3)) than in 339 nondiabetics (74.3 mg/cm(3)) and remained significant after adjusting for age, gender, and BMI (P = 0.005) or age, gender, and waist circumference (P = 0.01).

DISCUSSION

Our results provide new evidence that ectopic lipid deposition in skeletal muscle is a heritable trait and is associated with diabetes, independent of overall and central obesity in families of African heritage. Genome-wide screens and candidate gene studies are warranted to identify the genetic factors contributing to ectopic deposition of skeletal muscle fat.

Correlates of bone mineral density among postmenopausal women of African Caribbean ancestry: Tobago women's health study

Population dynamics predict a drastic growth in the number of older minority women, and resultant increases in the number of fractures. Low bone mineral density (BMD) is an important risk factor for fracture. Many studies have identified the lifestyle and health-related factors that correlate with BMD in Whites. Few studies have focused on non-Whites. The objective of the current analyses is to examine the lifestyle, anthropometric and health-related factors that are correlated with BMD in a population based cohort of Caribbean women of West African ancestry. We enrolled 340 postmenopausal women residing on the Caribbean Island of Tobago. Participants completed a questionnaire and had anthropometric measures taken. Hip BMD was measured by DXA. We estimated volumetric BMD by calculating bone mineral apparent density (BMAD). BMD was >10% and >25% higher across all age groups in Tobagonian women compared to US non-Hispanic Black and White women, respectively. In multiple linear regression models, 35-36% of the variability in femoral neck and total hip BMD respectively was predicted. Each 16-kg (one standard deviation (SD)) increase in weight was associated with 5% higher BMD; and weight explained over 10% of the variability of BMD. Each 8-year (1 SD) increase in age was associated with 5% lower BMD. Current use of both thiazide diuretics and oral hypoglycemic medication were associated with 4-5% higher BMD. For femoral neck BMAD, 26% of the variability was explained by a multiple linear regression model. Current statin use was associated with 5% higher BMAD and a history of breast feeding or coronary heart disease was associated with 1-1.5% of higher BMAD. In conclusion, African Caribbean women have the highest BMD on a population level reported to date for women. This may reflect low European admixture. Correlates of BMD among Caribbean women of West African ancestry were similar to those reported for U.S. Black and White women.

Adipose tissue infiltration in skeletal muscle: age patterns and association with diabetes among men of African ancestry

BACKGROUND

Although obesity is strongly associated with diabetes, the greater prevalence of diabetes in persons of African ancestry than in those of other ancestries cannot be explained simply by differences in total or central adiposity.

OBJECTIVE

We examined whether skeletal muscle composition is associated with diabetes in 1249 men of African ancestry aged >or=40 y.

DESIGN

Anthropometry and fasting serum glucose were measured, and lower-leg skeletal muscle composition was assessed with peripheral quantitative computerized tomography (pQCT).

RESULTS

The prevalence of diabetes in this population was high (21%). We observed an age-associated adipose tissue remodeling in skeletal muscle and greater intermuscular (IMAT) and lesser subcutaneous (SAT) adipose tissue area with advancing age (P < 0.0001). Multivariate stepwise logistic regression identified more IMAT and less SAT to be significantly associated with a greater prevalence of diabetes. Even among normal-weight men [body mass index (BMI; in kg/m(2)) < 25], diabetic men had significantly (P = 0.01) more IMAT than did those without diabetes. Greater IMAT was also associated with a greater prevalence of hyperglycemia in men with a family history of diabetes than in those without such history (P for interaction = 0.02).

CONCLUSIONS

These findings underscore the independent associations of subcutaneous and intermuscular fat among men of African ancestry, an effect that may be modified by a family history of diabetes. Further studies are needed to identify the genetic and physiologic mechanisms that influence the distribution and remodeling of adipose tissue in skeletal muscle with aging.'

Sex and genetic effects on upper and lower body fat and associations with diabetes in multigenerational families of African heritage

Very few studies have comprehensively defined the genetic and environmental influences on body fat storage in the arms and legs and their association with diabetes, especially in families of African heritage. We analyzed body fat distribution by dual-energy x-ray absorptiometry (percentage total fat, percentage trunk fat, percentage arm fat, and percentage leg fat) and fasting serum glucose in 471 individuals (mean age, 43 years) from 8 multigenerational Afro-Caribbean families (mean family size = 51; 3535 relative pairs). Diabetes was inversely associated with percentage leg fat (P = .009) and, to some extent, positively associated with percentage arm fat independent of age, sex, and body size (P = .08), but not with anthropometric or dual-energy x-ray absorptiometric measures of total and central adiposity. Furthermore, percentage leg fat was inversely, whereas percentage arm fat was positively, associated with body mass index, waist circumference, and serum glucose (P < .01). Residual heritability (h2r) for arm and leg fat was significant (P < .01) and high: 62% (for percentage arm fat) and 40% (for percentage leg fat). Moreover, sex-specific h2r for leg fat was considerably higher (P = .02) in women than in men (h2r values, 58% vs 17%, respectively). Genetic correlation (rho(G)) between arm and leg fat was -0.61 (P < .01), suggesting that only 37% of the covariation between these 2 adipose tissue depots may be due to shared genetic influences. This study provides new evidence for a strong genetic and sex contribution to upper and lower body fat, with relatively little covariation between these traits due to shared genes. Our findings also suggest that, in this population, leg fat is associated with diabetes independent of overall adiposity.

RNASEL and RNASEL-inhibitor variation and prostate cancer risk in Afro-Caribbeans

BACKGROUND

Afro-Caribbeans from Tobago are at high risk of developing prostate cancer. This elevated risk of prostate cancer is shared by populations of African ancestry living in diverse environments in the Western hemisphere. Variation in the ribonuclease L (RNASEL) gene has recently been reported to be associated with an increased risk of prostate cancer. However, whether RNASEL variation contributes to the increased risk of prostate cancer observed in populations of African ancestry remains unclear.

METHODS

We resequenced the positional candidate gene RNASEL in 48 prostate cancer cases and genotyped the previously reported R462Q and D541E polymorphisms in 230 prostate cancer cases and 458 controls. We also examined the inhibitor of RNASEL (ABCE1) for variation associated with prostate cancer risk.

RESULTS

We found no evidence of association between R462Q and D541E polymorphisms and prostate cancer risk in our case/control analysis. A novel variant (K294E) was identified in a single heterozygous individual with prostate cancer. We also observed a 20 bp insertion/deletion polymorphism 1,109 bp upstream of the initiation codon, but this variant was not associated with prostate cancer. We identified 16 single nucleotide polymorphisms in the ABCE1 gene, only 3 of which had a minor allele frequency >5%. A common A/G transition -1,071 bp from the transcriptional start site was genotyped and showed no evidence of association with prostate cancer.

CONCLUSIONS

Our results suggest that common variation in the putative prostate cancer susceptibility gene, RNASEL, or its inhibitor does not contribute significantly to prostate cancer risk in this Afro-Caribbean population.

Correlates of bone mineral density in men of African ancestry: the Tobago bone health study

Correlates of BMD were examined in a cross-sectional analysis of men of West African ancestry. BMD, measured at the total hip and the femoral neck subregion, was associated with age, anthropometric, lifestyle, and medical factors in multiple linear regression models. These models explained 25-27% of the variability in total hip and femoral neck BMD, respectively, and 13% of the variability in estimated volumetric BMD.

OBJECTIVE

To examine the correlates of bone mineral density (BMD) in men of West African ancestry.

METHODS

Two thousand five hundred and one men aged 40 to 93 years were recruited from the Caribbean Island of Tobago. Participants completed a questionnaire and physical examination. We measured hip BMD and body composition, using DXA. Volumetric BMD was estimated as bone mineral apparent density (BMAD).

RESULTS

BMD was 10% and 20% higher in African Caribbean males compared to U.S. non-Hispanic black and white males, respectively. In multiple linear regression models, greater lean mass, history of working on a fishing boat or on a farm, frequent walking, and self-reported diabetes were significantly associated with higher BMD. Fat mass, history of farming, and self-reported hypertension were also associated with higher BMAD. Older age, mixed African ancestry, and history of a fracture were associated with lower BMD and BMAD. Lean body mass explained 20%, 18% and 6% of the variance in BMD at the total hip, femoral neck and BMAD, respectively.

CONCLUSIONS

African Caribbean males have the highest BMD on a population level ever reported. Lean mass was the single most important correlate. Variability in BMD/BMAD was also explained by age, mixed African ancestry, anthropometric, lifestyle, and medical factors.

Genetic and environmental influences on skeletal muscle phenotypes as a function of age and sex in large, multigenerational families of African heritage

The aim of this study was to estimate the heritability of and environmental contributions to skeletal muscle phenotypes (appendicular lean mass and calf muscle cross-sectional area) in subjects of African descent and to determine whether heritability estimates are impacted by sex or age. Body composition was measured by dual-energy X-ray absorptiometry and computed tomography in 444 men and women aged 18 yr and older (mean: 43 yr) from eight large, multigenerational Afro-Caribbean families (family size range: 21-112). Using quantitative genetic methods, we estimated heritability and the association of anthropometric, lifestyle, and medical variables with skeletal muscle phenotypes. In the overall group, we estimated the heritability of lean mass and calf muscle cross-sectional area (h(2) = 0.18-0.23, P < 0.01) and contribution of environmental factors to these phenotypes (r(2) = 0.27-0.55, P < 0.05). In our age-specific analysis, the heritability of leg lean mass was lower in older vs. younger individuals (h(2) = 0.05 vs. 0.23, respectively, P = 0.1). Sex was a significant covariate in our models (P < 0.001), although sex-specific differences in heritability varied depending on the lean mass phenotype analyzed. High genetic correlations (rho(G) = 0.69-0.81; P < 0.01) between different lean mass measures suggest these traits share a large proportion of genetic components. Our results demonstrate the heritability of skeletal muscle traits in individuals of African heritage and that heritability may differ as a function of sex and age. As the loss of skeletal muscle mass is related to metabolic abnormalities, disability, and mortality in older individuals, further research is warranted to identify specific genetic loci that contribute to these traits in general and in a sex- and age-specific manner.

A Randomized Trial of Lycopene Supplementation in Tobago Men with High Prostate Cancer Risk

This unblinded, randomized, Phase I clinical trial was conducted to determine whether lycopene supplementation lowered serum prostate specific antigen (PSA), surrogate endpoint for prostate cancer initiation or progression, in men with elevated prostate cancer risk. Afro-Caribbean men (n=81) with high-grade prostatic intraepithelial neoplasia, atypical foci or repeated non-cancerous biopsies, ascertained in a population-based screening program, were randomized to four months intervention with 30 mg/day lycopene (Lyc-O-Mato) plus a multivitamin, or to multivitamin, only. Serum PSA and lycopene were compared at randomization, 1, and 4 mo using two-sided chi2 and t-tests for independent samples. Treatment groups were similar at baseline. Serum lycopene levels approximately doubled in the lycopene intervention group. Serum PSA declined during the first month of treatment, but returned to randomization level by month 4. The PSA response was nearly identical in both treatment groups. No adverse effects attributed to lycopene supplementation were documented. We conclude that the PSA lowering response to antioxidant supplementation observed in previous 3-wk studies in men awaiting prostatectomy may have been a transient response, perhaps not specific to lycopene. Lowering of serum PSA may not be an appropriate endpoint for the long-term studies needed to evaluate lycopene supplementation for reducing prostate cancer initiation or progression.

Genetic and environmental determinants of volumetric and areal BMD in multi-generational families of African ancestry: the Tobago Family Health Study

BMD is higher and fracture risk is lower among individuals of African versus European descent, but little is known about the genetic architecture of BMD in the former group. Heritabilities of areal and volumetric BMD were moderate in our large families of African descent but differed for trabecular and cortical BMD.

INTRODUCTION

Populations of African ancestry have lower osteoporotic fracture risk and higher BMD than other ethnic groups. However, there is a paucity of information regarding the genetic and environmental influences on bone health among populations of African heritage.

MATERIALS AND METHODS

We dissected the genetic architecture of areal BMD measured by DXA at the proximal femur, lumbar spine, and whole body and volumetric BMD measured by pQCT at the distal and proximal radius and tibia in 283 women and 188 men > or =18 years of age (mean, 43 years) from eight multigenerational Afro-Caribbean families (mean family size > 50). Using quantitative genetic methods, we estimated the residual heritability and the effects of anthropometric, demographic, lifestyle, and medical variables on areal and volumetric BMD.

RESULTS

Compared with U.S. non-Hispanic blacks and whites, areal BMD at the femoral neck was highest in the Afro-Caribbean men and women at all ages. Trabecular volumetric BMD decreased linearly with increasing age, whereas cortical volumetric BMD did not decrease until age 40-49, especially in women. Anthropometric, lifestyle, and medical factors accounted for 12-32% of the variation in areal and volumetric BMD, and residual heritabilities (range, 0.23-0.52) were similar to those reported in other ethnic groups. Heritability of cortical BMD was substantially lower than that of areal or trabecular volumetric BMD, although the measured covariates accounted for a similar proportion of the total phenotypic variation.

CONCLUSIONS

Our study is the first comprehensive genetic epidemiologic analysis of volumetric BMD measured by QCT and the first analysis of these traits in extended families of African descent. Genes account for as much or more of the total variation in areal and volumetric BMD than do environmental factors, but these effects seem to differ for trabecular and cortical bone.

High bone density is associated with prostate cancer in older Afro-Caribbean men: Tobago prostate survey

OBJECTIVE

To test the hypothesis that bone mineral density (BMD), a possible surrogate of lifetime exposure to hormone/growth factor/vitamin D/calcium exposure, is higher in prostate cancer cases than controls.

METHODS

Hip BMD was measured by dual X-ray absorptiometry in 222 Afro-Caribbean screening-detected prostate cancer cases and 1,503 screened non-cases, aged 45-79, in the population-based Tobago Prostate Survey. Because possible skeletal metastases may modulate BMD, men with prostate specific antigen >20 ng/ml or highly undifferentiated tumors (Gleason score > or = 8) were excluded. Mean BMD, adjusted for age and body mass index, was compared in cases and non-cases by analysis of variance. Risk across age group-specific BMD quartiles was compared using logistic regression.

RESULTS

Overall, adjusted mean hip BMD was higher in cases (1.157 g/cm2) than non-cases (1.134 g/cm2) (p = 0.02). In men aged 60-79, prostate cancer risk was two-fold higher (OR, 2.12; 95% CI: 1.21-3.71) in the highest BMD quartile compared to the lowest. There was no association in younger men (interaction, p = 0.055).

CONCLUSIONS

High bone density is associated with prostate cancer among older men, consistent with an etiological role for lifetime exposure to factors which modulate bone density. However, other etiologies may dominate prostate cancer risk among younger men.

Genetic determination of adiponectin and its relationship with body fat topography in multigenerational families of African heritage

Adiponectin, an adipose-specific protein, is negatively associated with adiposity, insulin sensitivity, and diabetes. Very few studies have examined the role of heredity in the regulation of adiponectin and its association with body fat among individuals of African heritage. Thus, we measured fasting serum adiponectin levels by radioimmunoassay and body composition by dual-energy x-ray absorptiometry (DEXA) in 402 individuals aged 18 to 103 years belonging to 7 multigenerational families of African heritage in the relatively homogeneous island population of Tobago. Heritability of adiponectin was 33.2% (P < .01), and age, sex, and body mass index explained 23.4% of the variance in adiponectin. Sex-specific heritability was significant in men (heritability, 34%; P < .05), but not in women. The inverse associations between body mass index and percentage of body fat and adiponectin, independent of age and height, were much stronger in women (all P values <.001) than in men. However, percentage of trunk fat was consistently strongly associated with adiponectin in both men (r = -0.40, P < .001) and women (r = -0.44, P < .001), independent of age and height. This study suggests that genetic factors are a significant source of interindividual differences in circulating adiponectin among Afro-Caribbeans. Adiponectin may serve as a promising quantitative intermediate trait in studies designed to map the genes underlying diabetes and obesity in this population.

Lipoprotein subclass and particle size differences in Afro-Caribbeans, African Americans, and white Americans: associations with hepatic lipase gene variation

Despite a higher prevalence of coronary heart disease risk factors, men of African origin have less coronary atherosclerosis, as measured by coronary calcification, than whites. In part, this is thought to be because of the less atherogenic lipoprotein profile observed in men of African origin, characterized by lower triglycerides and higher high-density lipoprotein (HDL) cholesterol. We hypothesized that the -514C>T polymorphism in the hepatic lipase gene (LIPC) plays a significant role in determining a less atherogenic lipoprotein profile observed in men of African origin. Previously conducted studies of the LIPC -514C>T polymorphism in African Americans may have been confounded by a higher level of European admixture; in addition, the results from these studies do not necessarily apply to other African populations because gene-environment interactions may differ. Thus, we compared nuclear magnetic resonance spectroscopy-measured lipoprotein subclass patterns and LIPC -514C>T genotypes in population-based samples of older white American (n = 532) and African American (n = 97) men from the Cardiovascular Health Study to those among older, less admixed, Afro-Caribbean men (n = 205) from the Tobago Health Study. Men of African origin had a more favorable lipoprotein profile than whites. In addition, levels of low-density lipoprotein cholesterol, total cholesterol, and triglyceride, and large and small very low-density lipoprotein, small low-density lipoprotein, as well as very low-density lipoprotein particle size, were remarkably lower in Afro-Caribbean men than in either African American or white men. The frequency of the LIPC -514T allele was much higher in Afro-Caribbeans (0.57) and in African Americans (0.49) than in whites (0.20). The -514T allele in both populations of African origin, but not in whites, was associated with elevated large HDL and greater HDL size. Our findings indicate that the higher frequency of the LIPC -514T allele found in men of African origin living in different environments significantly contributes to the more favorable distribution of HDL subclasses compared with whites.

Estimates of African, European and Native American ancestry in Afro-Caribbean men on the island of Tobago

BACKGROUND/AIMS

The Tobago Afro-Caribbean population is a valuable resource for studying the genetics of diseases that show significant differences in prevalence between populations of African descent and populations of other ancestries. Empirical confirmation of low European and Native American admixture may help in clarifying the ethnic variation in risk for such diseases. We hypothesize that the degree of European and Native American admixture in the Tobago population is low.

METHODS

Admixture was estimated in a random sample of 220 men, from a population-based prostate cancer screening survey of 3,082 Tobago males, aged 40 to 79 years. We used a set of six autosomal markers with large allele frequency differences between the major ethnic populations involved in the admixture process, Europeans, Native Americans and West Africans.

RESULTS

The ancestral proportions of Tobago population are estimated as 94.0+/-1.2% African, 4.6+/-3.4% European and 1.4+/-3.6% Native American.

CONCLUSIONS

We conclude that Tobago Afro-Caribbean men are predominantly of West African ancestry, with minimal European and Native American admixture. The Tobago population, thus, may carry a higher burden of high-risk alleles of African origin for certain diseases than the more admixed African-American population. Conversely, this population may benefit from a higher prevalence of protective alleles of African origin.

Association of body composition and physical activity with proximal femur geometry in middle-aged and elderly Afro-Caribbean men: the Tobago bone health study

Osteoporotic fractures are less prevalent in African Americans than in caucasians, possibly because of differences in bone structural strength. Bone structural adaptation can be attributed to changes in load, crudely measured as lean and fat mass throughout life. The purpose of this analysis was to describe the associations of leg lean mass, total body fat mass, and hours walked per week with femoral bone mineral density (BMD) and bone geometry in a cross-sectional sample of 1,748 men of African descent between the ages of 40 and 79 years. BMD, section modulus (Z), cross-sectional area (CSA), and subperiosteal width were measured from dual energy X-ray absortiometry (DXA) scans using the hip structural analysis (HSA) program. Multiple linear regression models explained 35% to 48% of the variance in bending (Z) and axial (CSA) strength at the femoral neck and shaft. Independent of all covariates including total body fat mass, one standard deviation increase in leg lean mass was significantly associated with a 5% to 8% higher Z, CSA, and BMD (P < 0.010) at the neck and shaft. The number of hours walked per week was not a strong or consistent independent predictor of bone geometry or BMD. We have shown that weight is the strongest independent predictor of femur BMD and geometric strength although the effect appears to be mediated by lean mass since leg lean mass fraction and total body fat mass fraction had significant and opposing effects at the narrow neck and shaft in this group of middle aged and elderly men.

Prostate cancer screening parameters in a high-risk African-Caribbean population

OBJECTIVES

To estimate the prostate cancer screening parameters in a population-based study of African-Caribbean men from the Island of Tobago.

METHODS

A total of 2582 men aged 40 to 79 years (50% of all Tobago men in this age group) were screened using both serum prostate-specific antigen (PSA) and digital rectal examination (DRE). Men with an elevated PSA level (4 ng/mL or greater) or abnormal DRE findings were referred for ultrasound-guided sextant biopsy.

RESULTS

The screening results for one or both tests were abnormal in 32% of men. The prevalence of prostate cancer was 10.7 of 100 screened men. The positive predictive value for PSA was 56% compared with 39% for DRE. The positive predictive value for PSA ranged from 6% for those aged 40 to 49 years to 59% for those aged 70 to 79 years. The sensitivity was 71% and the specificity 86% for DRE. The sensitivity for PSA was 80%. The sensitivity was low among men aged 40 to 49 years (20%) and 50 to 59 years (66%). The specificity for PSA declined across age groups from 98% for those aged 40 to 49 years to 70% for those 70 to 79 years.

CONCLUSIONS

The screening parameters in this African-Caribbean population were similar to the sparse data available from other populations of African descent. The screening was highly efficacious, with a positive predictive value of 56% for an elevated PSA level and 40% for an elevated PSA level and/or abnormal DRE findings.

Elevated Seroprevalence of Human Herpesvirus 8 among Men with Prostate Cancer

Background. To investigate any epidemiological association between human herpesvirus (HHV)-8 and prostate cancer, we determined the prevalence of HHV-8 seropositivity among prostate cancer case and control subjects in the United States and Trinidad and Tobago.Methods. Antibodies against HHV-8 were detected in 2 independent laboratories using either indirect immunofluorescence assay (IFA) or a combination of enzyme-linked immunosorbent assay and IFA.Results. Among 138 Tobago men with prostate cancer, HHV-8 seroprevalence was 39.9%-significantly higher than that among 140 age-matched control subjects (22.9%; P=.003; odds ratio [OR], 2.24; 95% confidence interval [CI], 1.29-3.90). Among 100 US men with prostate cancer, seroprevalence was 20%-significantly higher than that of 177 blood donors (5.1%; P=.001; OR, 4.67; 95% CI, 1.91-11.65) and higher than that of 99 men with cancer not related to HHV-8 (13%; P=.253; 95% CI, 0.77-3.54).Conclusions. HHV-8 seropositivity is elevated among men with prostate cancer compared with control subjects, which suggests that HHV-8 plays a role in the development of prostate cancer.

Prostate cancer risk is three-fold higher among men, aged 50-64, of African descent compared with men of Asian-Indian descent in Trinidad and Tobago

OBJECTIVE

To test the hypothesis that the screening-detected prevalence of prostate cancer is higher among men of African descent than among men of Asian-Indian descent living in Trinidad & Tobago.

DESIGN

Population-based prostate cancer screening study among men aged 50-64.

SETTING

Caribbean islands of Trinidad and Tobago.

PARTICIPANTS

Tobago, population-based sample of 1196 male residents of African descent; Trinidad, 173 agricultural workers of Asian-Indian descent.

INTERVENTIONS

Serum prostate specific antigen (PSA, Abbot AxSYM) and digital rectal exam (DRE) were used to screen men for prostate cancer. Men with elevated PSA (> or = 4 ng/mL) and/or abnormal DRE were offered an ultrasound guided sextant biopsy of the prostate gland.

MAIN OUTCOME MEASURES

Prevalence of abnormal screen; prevalence of prostate cancer.

RESULTS

Elevated PSA and/or abnormal DRE were observed in 29% (348/1196) of Afro-Tobagonian men. Three hundred sixteen men underwent biopsies. Screening-detected prostate cancer prevalence was: 4.9% (23/468) for those aged 50-55; 7.7% (28/366) for those aged 55-59; and 13.3% (48/362) for those aged 60-64 years. Screening was abnormal in 18% (31/173) of Asian-Indian men; 25 underwent biopsies. Prostate cancer prevalence in Asian Indian men was: 1.6% (1/63) for those aged 50-54; 1.4% (1/71) for those aged 55-59; and 5.1% (2/39) for those aged 60-64 years. Mantel-Haenszel age-adjusted rate ratio was 3.4, 95% CI 1.3-9.0.

CONCLUSIONS

This study establishes a high prevalence of screening-detected prostate cancer among Afro-Tobagonians compared with Indo-Trinidadians. Comparison of candidate genes, environmental, and lifestyle factors between these populations may identify factors that increase risk for, or provide protection against, prostate cancer.

Relation of risk of systemic lupus erythematosus to west African admixture in a Caribbean population

Risk of systemic lupus erythematosus (SLE) is higher in people of west African descent than in Europeans. The objective of this study was to distinguish between genetic and environmental explanations for this ethnic difference by examining the relationship of disease risk to individual admixture (defined as the proportion of the genome that is of west African ancestry); 124 cases of SLE and 219 matched controls resident in Trinidad were studied. Analysis of admixture was restricted to 52 cases and 107 controls who reported no Indian or Chinese ancestry. These individuals were typed with a panel of 26 single-nucleotide polymorphisms and five insertion/deletion polymorphisms chosen to have large allele frequency differentials between west African, European and Native American populations. A Bayesian model for population admixture, individual admixture and locus ancestry was fitted by Markov chain simulation. Mean west African admixture (M) was 0.81 in cases and 0.74 in controls (P=0.01). The risk ratio for SLE associated with unit change in M was estimated as 32.5 with a 95% confidence interval (CI) of 2.0-518. Adjustment for measures of socioeconomic status (household amenities in childhood and years of education) altered this risk ratio only slightly (adjusted risk ratio: 28.4, 95% CI 1.7-485). These results support an additive genetic model for the ethnic difference in risk of SLE between west Africans and Europeans, rather than an environmental explanation or an "overdominant" model in which risk is higher in heterozygous than in homozygous individuals. This conclusion lays a basis for localizing the genes underlying this ethnic difference in risk of SLE by admixture mapping.

ELAC2 and prostate cancer risk in Afro-Caribbeans of Tobago

To test the hypothesis that variation in the putative prostate cancer susceptibility gene ELAC2 contributes to the elevated risk of prostate cancer in Afro-Caribbean males from Tobago, we genotyped the S217L and A514T polymorphisms, previously reported to be associated with prostate cancer risk in a large sample of cases and controls. The frequency of the high-risk Leu allele at the S217L site was the same in cases and controls. Both cases and controls were homozygous for the low-risk Ala allele at the A514T site. In addition, we sequenced the exons and 3'- and 5'-flanking regions of ELAC2 in 24 individuals with histologically confirmed prostate cancer. We identified 17 new single nucleotide polymorphisms. An A(-1196)T polymorphism, which alters a predicted TATA box consensus sequence, was tested in cases and controls, and no significant difference in allele or genotype frequencies was observed. The absence of ELAC2 mutations and lack of association between polymorphisms in ELAC2 and prostate cancer in cases and controls leads us to conclude that ELAC2 does not contribute significantly to the elevated prevalence of prostate cancer in Afro-Caribbean males of Tobago.

High prevalence of screening-detected prostate cancer among Afro-Caribbeans: the Tobago Prostate Cancer Survey

Risk for prostate cancer is high among African Americans. We hypothesized that risk for prostate cancer is also high in other populations of African descent. Our objective was to determine the screening-detected prevalence of prostate cancer in the predominantly Afro-Caribbean population on the island of Tobago. Male residents, ages 40-79 years, were invited to participate in a population-based screening for prostate cancer using serum prostate-specific antigen (PSA) and digital rectal exam (DRE). Men with elevated PSA (>or=4 ng/ml) or abnormal DRE were offered an ultrasound-guided sextant biopsy of the prostate gland. Men (2484), ages 40-79 years, underwent prostate cancer screening between September 1997 and June 2001. Mean age was 55.9, SD was 10.6 years, and median was 54 years. Mean serum PSA was 14.8 ng/ml, SD was 376 [excluding 4 values >or= 2 SD above the mean (1,112, 1,317, 1,818, and 18,330 ng/ml) mean PSA was 5.5 ng/ml and SD was 29.6], and median PSA was 1.2 ng/ml. Elevated PSA and/or abnormal DRE were observed in 31% (759 of 2484) overall, and in age groups 40-49 (87 of 843, 10%), 50-59 (201 of 729, 28%), 60-69 (262 of 584, 45%), and 70-79 (209 of 328, 64%). Of 681 men biopsied, 259 (38%, or 10% of the 2484 screened) were diagnosed with prostate cancer. Age-specific rates of screening detected prostate cancer were: 1%, ages 40-79 years; 7%, ages 50-59 years; 18%, ages 60-69 years; and 28%, ages 70-79 years. These screening results indicate a very high screening-detected prevalence of prostate cancer in this population of West African descent. These data support the hypothesis that populations of African descent share genetic and/or lifestyle factors that contribute to their elevated risk for prostate cancer.

Kawasaki disease in an adult Trinidadian male

Since Kawasaki in 1967 described the first case of mucocutaneous lymph node syndrome which presented as an acute febrile illness in young children, the syndrome has occasionally been reported in adults in the U.S.A. The present communication describes the first adult case reported from the West Indies.

Cutaneous histoplasmosis in the acquired immune deficiency syndrome--a report of three cases from Trinidad

Three cases are reported of patients with the Acquired Immune Deficiency Syndrome (AIDS) and cutaneous histoplasmosis. Their initial presentation was that of a generalised maculopapular rash. Two patients were bisexual males and the third was an unmarried female. The range of opportunistic infections seen in AIDS patients in Trinidad is mentioned and clinicians are alerted to the fact that in areas endemic for Histoplasma capsulatum maculopapular rash in patients with AIDS may suggest disseminated histoplasmosis. The value of skin biopsy is mentioned.

Kaposi sarcoma in the acquired immune deficiency syndrome (AIDS), presenting as lymphogranuloma venereum (LGV) in a promiscuous trinidadian male

A 27-year-old promiscuous male who denied homosexuality, intravenous drug abuse or having received blood transfusions, had disseminated Kaposi sarcoma. The aggressive nature of the tumor in a young man with the Acquired Immune Deficiency Syndrome (AIDS) presenting as lymphogranuloma venereum (LGV) is highlighted. The relation of the HTLV III virus to a diffuse membranoproliferative glomerulonephritis with sclerosis and associated hyaline degenerative changes in the juxtaglomerular apparatus are discussed.