Body Composition Across the Adult Lifespan in African Caribbean Men: The Tobago Longitudinal Study of Aging.

Body composition and muscle strength change vary by age and ethnicity, and have a major impact on health and physical function. Little is known about the patterns of these changes in African-ancestry populations. Herein, we examined age-specific (5-year age groups) rates-of-change in lean and fat mass in 1918 African-ancestry men on the Caribbean island of Tobago (baseline age: 62.0±11.8 years, range: 40-99 years). Body composition (DXA) and grip strength were measured at three time points (baseline, 4- and 9-year follow-up). Annualized rates of change were calculated with all 3 time-points using Generalized Estimating Equations. We found that whole body lean mass declined at constant rate until age 65 (-0.72%/year; 95% CI: -0.76, -0.67), which accelerated to -0.92 %/year (-1.02, -0.82) among those 65-69, and again to -1.16 %/year (-1.30, -1.03 ) among those aged 70+. Whole body fat mass increased by a near constant rate of 2.93 %/year (2.72, 3.15%) across the lifespan. Finally, grip strength decline accelerated at age 50, and about 2x faster than lean mass through the lifespan after the age of 50. To conclude, in African-Caribbean men, the acceleration in muscle strength decline precedes the acceleration in lean mass decline by 10-15 years, suggesting decrements in factors other than lean mass drive this initial acceleration in muscle strength decline. We also found that African-Caribbean men undergo a constant shift to a more adipogenic phenotype throughout the adult lifespan (aged 40-99), which likely contributes to age-related loss of muscle and physical function.

Serum Vitamin D and Age-Related Muscle Loss in Afro-Caribbean Men: The Importance of Age and Diabetic Status.

BACKGROUND: Prospective studies examining the potential association of vitamin D with age-related muscle loss have shown inconsistent results. OBJECTIVE: To examine the association between baseline serum 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D), and prospective change in lean mass with aging in African ancestry population. We also determined if associations were modulated by age and diabetes mellitus (DM). DESIGN: Prospective observational cohort study. SETTING: Data were collected from a random sub-sample of 574 men, participants of the Tobago Bone Health Study (TBHS). PARTICIPANTS: 574 Afro-Caribbean men, aged 43+ years (mean age: 59.1 ± 10.5), who were randomly selected as the participants in both the baseline and the follow-up visits. MEASUREMENTS: Baseline fasting serum 25(OH)D was measured using liquid chromatography mass spectrometry (LC-MS/MS), and and 1,25(OH)2D was measured using radioimmunosassay (RIA). Changes in dual-energy X-ray absorptiometry (DXA)-measured appendicular lean mass (ALM), and total body lean mass (TBLM) were measured over an average of 6.0 ± 0.5 years. The associations of 25(OH)D and 1,25(OH)2D with ALM and TBLM were assessed by multiple linear regression model after adjusting for potential confounders. RESULTS: When stratifying all men into two groups by age, greater baseline 25(OH)D and 1,25(OH)2D levels were associated with smaller losses of ALM and TBLM in older (age 60+ years) but not in younger (age 43 - 59 years) men. When stratifying by DM status, the associations of 25(OH)D and 1,25(OH)2D with declines in ALM and TBLM were statistically significant only in prediabetic, but not among normal glycemic or diabetic men. CONCLUSION: Higher endogenous vitamin D concentrations are associated with less lean mass loss with aging among older and prediabetic Afro-Caribbean men independent of potential confounders. Our findings raise a possibility that maintaining high serum vitamin D level might be important for musculoskeletal health in elderly and prediabetic African ancestry men.

Relative influence of heritability, environment and genetics on serum sclerostin.

SUMMARY: We determined factors associated with serum sclerostin in 446 Afro-Caribbean family members. Age, weight, sex, diabetes and kidney function were associated with sclerostin. Sclerostin was heritable, and nine SNPs in the SOST gene region were associated with sclerostin. Variation in serum sclerostin is a heritable factor that is determined by both genetic and environmental factors. INTRODUCTION: Sclerostin, encoded by the SOST gene, is a Wnt inhibitor that regulates bone mineralization and is a candidate gene locus for osteoporosis. However, little is known about the genetic and non-genetic sources of inter-individual variation in serum sclerostin levels. METHODS: Serum sclerostin was measured in 446 Afro-Caribbean men and women aged 18+ from seven large, multigenerational families (mean family size, 64; 3,840 relative pairs). Thirty-six common single nucleotide polymorphisms (SNP) were genotyped within a 100 kb region encompassing the gene encoding sclerostin (SOST). Genetic and non-genetic factors were tested for association with serum sclerostin. RESULTS: Mean serum sclerostin was 41.3 pmol/l and was greater in men than in women (P < 0.05). Factors associated with higher serum sclerostin were increased age and body weight, male sex, diabetes and decreased glomerular filtration rate, which collectively accounted for 25.4 % of its variation. Residual genetic heritability of serum sclerostin was 0.393 (P < 0.0001). Nine SNPs reached nominal significance with sclerostin. Three of those nine SNPs represented independent association signals (rs851056, rs41455049 and rs9909172), which accounted for 7.8 % of the phenotypic variation in sclerostin, although none of these SNPs surpassed a Bonferroni correction for multiple comparisons. CONCLUSIONS: Serum sclerostin is a heritable trait that is also determined by environmental factors including age, sex, adiposity, diabetes and kidney function. Three independent common SNPs within the SOST region may collectively account for a significant proportion of the variation in serum sclerostin.

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.

Genetic analysis of serum osteocalcin and bone mineral in multigenerational Afro-Caribbean families.

UNLABELLED: Osteocalcin is a major component of bone matrix. Concentrations of total, carboxylated, and uncarboxylated osteocalcin, are highly heritable and genetically correlated with bone mineral content (BMC) within African ancestry families. INTRODUCTION: Osteocalcin (OC) is a protein constituent of bone matrix and a marker of bone formation. We characterized the heritability of serum OC measures and identified genomic regions potentially involved in the regulation of OC via high-density genome-wide linkage analysis in African ancestry individuals. METHODS: African ancestry individuals (n = 459) were recruited, without regard to health status, from seven probands (mean family size = 66; 4,373 relative pairs). Residual heritability of serum OC measures was estimated and multipoint quantitative trait linkage analysis was performed using pedigree-based maximum likelihood methods. RESULTS: Residual heritabilities of total OC, uncarboxylated OC, carboxylated OC and percent uncarboxylated OC were 0.74 ± 0.10, 0.89 ± 0.08, 0.46 ± 0.10 and 0.41 ± 0.09, respectively. All OC measures were genetically correlated with whole body BMC. We obtained strong evidence of bivariate linkage for percent uncarboxylated OC and whole body BMC on chromosome 17 (logarithm of the odds [LOD] = 3.15, 99 cM). CONCLUSIONS: All forms of OC were highly heritable and genetically correlated with total body BMC in these African ancestry families. The identified linkage region contains several candidate genes for bone and energy metabolism including COL1A1 and TNFRSF11A. Further studies of this genomic region may reveal novel insight into the genetic regulation of OC and bone mineralization.

Age-related decline in bone density among ethnically diverse older men.

UNLABELLED: We compared rates of BMD decline in older men of diverse ethnic background. The rate of bone loss was statistically equivalent between men of African and Caucasian descent. INTRODUCTION: Race differences in peak bone mineral density (BMD) are well established, but the magnitude of bone loss among non-white men has not been well characterized. Our objective was to compare and contrast the rates of decline in BMD with aging among older men of different race/ethnic groups. METHODS: The rate of decline in hip BMD was measured by dual-energy X-ray absorptiometry (Hologic QDR-4500 W) with an average follow-up of 4.6 years in 3,869 Caucasian, 138 African American, 145 Asian, and 334 Afro-Caribbean men aged ≥ 65 years (Mean ages: 73 ± 5, 70 ± 4, 72 ± 5, 71 ± 5 years, respectively). RESULTS: The annual rate of decline in BMD at the femoral neck was -0.32%, -0.42%, -0.09%, and -0.44%/year for Caucasian, African American, Asian, and Afro-Caribbean men, respectively (p < 0.05 for Caucasian versus Asian). Although men of African ancestry have higher peak BMD than Caucasians, rates of decline in BMD with aging appear to be statistically equivalent in our study. In contrast, Asian men experienced a slower rate of decline in BMD compared with Caucasians and African Americans. CONCLUSION: More studies are needed to better define the natural history of and factors associated with bone loss among non-white men.

Association analysis of 33 lipoprotein candidate genes in multi-generational families of African ancestry.

African ancestry individuals have a more favorable lipoprotein profile than Caucasians, although the mechanisms for these differences remain unclear. We measured fasting serum lipoproteins and genotyped 768 tagging or potentially functional single nucleotide polymorphisms (SNPs) across 33 candidate gene regions in 401 Afro-Caribbeans older than 18 years belonging to 7 multi-generational pedigrees (mean family size 51, range 21-113, 3,426 relative pairs). All lipoproteins were significantly heritable (P<0.05). Gender-specific analysis showed that heritability for triglycerides was much higher (P<0.01) in women than in men (women, 0.62+/-0.18, P<0.01; men, 0.13+/-0.17, P>0.10), but the heritability for LDL cholesterol (LDL-C) was higher (P<0.05) in men than in women (men, 0.79+/-0.21, P<0.01; women, 0.39+/-0.12, P<0.01). The top 14 SNPs that passed the false discovery rate threshold in the families were then tested for replication in an independent population-based sample of 1,750 Afro-Caribbean men aged 40+ years. Our results revealed significant associations for three SNPs in two genes (rs5929 and rs6511720 in LDLR and rs7517090 in PCSK9) and LDL-C in both the family study and in the replication study. Our findings suggest that LDLR and PCSK9 variants may contribute to a variation in LDL-C among African ancestry individuals. Future sequencing and functional studies of these loci may advance our understanding of genetic factors contributing to LDL-C in African ancestry populations.

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

UNLABELLED: 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.

Distinct distribution of HPV types among cancer-free Afro-Caribbean women from Tobago.

Human papillomavirus (HPV), a sexually transmitted virus causes cervical carcinomas, and is associated with approximately 36% of oropharyngeal tumours where HPV16 is the predominant genotype. The cervical cancer incidence rate in Trinidad and Tobago is about two times higher than the worldwide rate. We have for the first time determined the prevalence and type distribution of cervical HPV infections among cancer-free Afro-Caribbean women from Tobago, and compared it with the HPV subtypes observed in their oral cavity. Thirty-five per cent of the women were cervical HPV positive. The most common high-risk type detected in the cervix was HPV45 rather than HPV16 and 18. The prevalence of HPV infection in the oral mucosa was 6.6%. The distribution of HPV genotypes in healthy Tobagonian women is different from that reported in studies conducted in European and North American populations. This may have important implications for vaccine introduction in this and other Afro-Caribbean countries.

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.

HIV infection in the Caribbean.

The Caribbean is a multi-ethnic region with many different cultural differences. The majority of the population is of African descent, but there are also other ethnic groups present such as Indians, Chinese, Syrians and Europeans. The Caribbean region is influenced by countries such as the USA, Great Britain, France and Holland. The countries of the Caribbean have a serious problem with HIV infection and AIDS. The epidemiology of HIV infection in this region, is different from most other parts of the world in that the mode of spread does not easily fit into any of the three WHO patterns. This review shows that the infection initially started in the homosexual/bisexual community, but since then, it has moved to the heterosexual population and this form of contact is now the main mode of transmission of the virus. The Governments of the Caribbean countries have realized the extent of the problem and have taken measures to try to control the epidemic.

PIP: The Caribbean is a multi-ethnic region of great cultural diversity presently experiencing a serious problem with HIV infection and AIDS. Some of the countries have among the highest annual incidence rates of HIV infection and AIDS in the world. The number of AIDS cases reported keeps rising each year in most Caribbean countries, although the rate of increase is lower than when the epidemic first started. The epidemiology of HIV infection in the Caribbean differs from that of most other parts of the world because the mode of spread does not easily fit into any of the three World Health Organization patterns. This review shows that while HIV infection was initially observed among homosexuals and bisexuals, intercourse between heterosexuals has now become the main mode of HIV transmission in the region. This review further finds that HIV infection and AIDS in the Caribbean affects mainly young to middle-aged adults. Infected males outnumber females, but the gap is narrowing, while the Caribbean has no IV drug abuse problem except for in Bermuda and Puerto Rico. The governments of the Caribbean have realized the extent of the problem and have taken measures to try to control the epidemic. The paper considers the history of the epidemic; its epidemiology in terms of sources, prevalence, age, sex, and risk behaviors; HIV seroprevalence in populations such as homosexual and bisexual men, female prostitutes, intravenous drug users, blood donors, and antenatal clinics; trends; and geographical factors in Trinidad and Tobago, Bahamas, Puerto Rico, Bermuda, Haiti, Dominican Republic, St. Lucia, Cuba, and Guyana. The authors also note the effectiveness of the draconian Cuban policy in controlling the spread of HIV and AIDS, but stress that its severe nature may also drive cases underground, thus leading to an overall understating of the dimensions of the AIDS epidemic in the country.