RESUMO
BACKGROUND: Mobility limitations are common, with higher prevalence in African Americans compared with whites, and are associated with disability, institutionalization, and death. Aging is associated with losses of lean mass and a shift to central adiposity, which are more pronounced in African Americans. We aimed to examine the association of body composition remodeling with incident mobility limitations in older men of African ancestry. METHODS: Seven-year changes in body composition were measured using peripheral quantitative computed tomography (pQCT) of the calf and whole-body dual x-ray absorptiometry (DXA) in 505 African ancestry men aged ≥60 years and free of self-reported mobility limitations at baseline. Self-reported incident mobility limitations were assessed at 7-year follow-up. Odds of developing mobility limitations associated with baseline and change in body composition were quantified using separate logistic regression models. RESULTS: Seventy-five men (14.9%) developed incident mobility limitations over 6.2 ± 0.6 years. Baseline body composition was not associated with incident mobility limitations. After adjustment for covariates, gaining total and intermuscular fat were associated with incident mobility limitations (odds ratio [OR]: 1.60; 95% confidence interval [CI]: 1.21-2.13; OR: 1.51; 95% CI: 1.18-1.94). Changes in DXA lean mass were not related to mobility limitations; however, maintaining pQCT calf muscle area was protective against mobility limitations (OR: 0.65; 95% CI: 0.48-0.87). CONCLUSIONS: Increases in body fat, and particularly intermuscular fat, and decreases in calf skeletal muscle area were associated with a higher risk of developing mobility limitations. Our findings emphasize the importance of body composition remodeling in the development of mobility limitations among African ancestry men.
Assuntos
População Negra , Composição Corporal , Limitação da Mobilidade , Absorciometria de Fóton , Adulto , Idoso , Estudos de Coortes , Humanos , Incidência , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Autorrelato , Trinidad e TobagoRESUMO
Aging is associated with declining serum levels of androgenic hormones and with increased skeletal muscle fat infiltration, an emerging risk factor for type 2 diabetes mellitus (T2DM). Androgens regulate fat mass and glucose homeostasis, but the effect of androgenic hormones on skeletal muscle fat infiltration is largely unknown. Thus, the aim of the current study was to examine the association of serum androgens and their precursors and metabolites with skeletal muscle fat infiltration and T2DM in a black male population group at high risk of T2DM. Serum androgens, estrogens, and androgen precursors and metabolites were measured using mass spectrometry; and calf skeletal muscle fat distribution (subcutaneous and intermuscular fat; skeletal muscle density) was measured using quantitative computed tomography in 472 Afro-Caribbean men 65 years and older. Bioactive androgens, testosterone, free testosterone, and dihydrotestosterone were associated with less skeletal muscle fat infiltration (r = -0.14 to -0.18, P < .05) and increased skeletal muscle density (r = 0.10 to 0.14, P < .05), independent of total adiposity. In addition, glucuronidated androgen metabolites were associated with less subcutaneous fat (r = -0.11 to -0.15, P < .05). Multivariate logistic regression analysis identified an increased level of 3α-diol-3 glucuronide (odds ratio = 1.38, P < .01) and a decreased level of dihydrotestosterone (odds ratio = 0.66, P < .01) to be significantly associated with T2DM. Our findings suggest that, in elderly black men, independent of total adiposity, bioactive androgens and glucuronidated androgen metabolites may play previously unrecognized role in skeletal muscle fat distribution. Longitudinal studies are needed to further evaluate the relationship between androgens and androgen metabolites with changes in skeletal muscle fat distribution with aging and the incidence of T2DM.
Assuntos
Adiposidade/fisiologia , Envelhecimento/metabolismo , Androgênios/metabolismo , Músculo Esquelético/metabolismo , Idoso , Idoso de 80 Anos ou mais , População Negra , Composição Corporal/fisiologia , Índice de Massa Corporal , Humanos , Resistência à Insulina/fisiologia , Masculino , Sobrepeso/metabolismo , Trinidad e TobagoRESUMO
Although low body weight is a risk factor for osteoporosis-related fractures, conflicting data exist for the association between adiposity and bone mineral density (BMD). Studies examining these relationships have measured body fat and BMD with dual-energy X-ray absorptiometry (DXA), which cannot distinguish subcutaneous adipose tissue area (SAT) from total adiposity or trabecular from cortical bone. To investigate the relationship between adiposity and BMD further, we analyzed body composition and adipose tissue distribution by quantitative computed tomography (QCT) in 1829 Afro-Caribbean men aged 40 years and older from a population-based sample. Cortical volumetric BMD, muscle cross-sectional area, total adipose tissue area (TAT), and percentage SAT were measured at the proximal tibia. Trabecular volumetric BMD was measured at the distal tibia. We used analysis of covariance to test for associations between quartile of the adipose tissue measures and BMD, adjusting for anthropometric, health, and lifestyle factors. Higher TAT was associated with lower cortical BMD in both unadjusted and adjusted models (p < .001). Men with a higher percentage SAT had greater cortical BMD (p < .001). Similar associations were seen between percent SAT and trabecular BMD at the distal tibia. These results indicate that total adiposity is a potentially important correlate of bone mass in older men and that different fat depots may have opposing associations with bone mass. Additional research is needed to better understand the mechanisms underlying the relationship between body fat distribution and bone mass.
Assuntos
Tecido Adiposo/diagnóstico por imagem , População Negra , Densidade Óssea , Adulto , Idoso , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia de Coerência Óptica , Tomografia Computadorizada por Raios X , Trinidad e TobagoRESUMO
Skeletal muscle fat is greater in African ancestry individuals compared with whites, is associated with diabetes, and is a heritable polygenic trait. However, specific genetic factors contributing to skeletal muscle fat in humans remain to be defined. Muscle carnitine palmitoyltransferase-1B (CPT1B) is a key enzyme in the regulation of skeletal muscle mitochondrial beta-oxidation of long-chain fatty acids, and as such is a reasonable biological candidate gene for skeletal muscle fat accumulation. Therefore, we examined the association of three nonsynonymous coding variants in CPT1B (G531L, I66V, and S427C; a fourth, A320G, could not be genotyped) and quantitative computed tomography measured tibia skeletal muscle composition and BMI among 1,774 Afro-Caribbean men aged > or =40, participants of the population-based Tobago Health Study. For all variants, no significant differences were observed for BMI or total adipose tissue. Among individuals who were homozygous for the minor allele at G531L or I66V, intermuscular adipose tissue (IMAT) was 87% (P = 0.03) and 54% lower (P = 0.03), respectively. In contrast, subcutaneous adipose tissue (SAT) was 11% (P = 0.017) and 7% (P = 0.049) higher, respectively, than among individuals without these genotypes. These associations were independent of age, body size, and muscle area. Finally, no individuals with type 2 diabetes were found among those who were homozygous for the minor allele of either at G531L and I66V whereas 14-18% of men with the major alleles had type 2 diabetes (P = 0.03 and 0.007, respectively). Our results suggest a novel association between common nonsynonymous coding variants in CPT1B and ectopic skeletal muscle fat among middle-aged and older African ancestry men.
Assuntos
Adiposidade/genética , Adiposidade/fisiologia , População Negra/genética , Distribuição da Gordura Corporal , Carnitina O-Palmitoiltransferase/genética , Músculo Esquelético/fisiopatologia , Adiposidade/etnologia , Idoso , Alelos , População Negra/etnologia , Estudos de Coortes , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/fisiopatologia , Seguimentos , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Prevalência , Gordura Subcutânea/fisiopatologia , Trinidad e TobagoRESUMO
QCT provides a measure of volumetric BMD (vBMD) and distinguishes trabecular from cortical bone. Few studies have determined the factors related to vBMD in men, especially among men of African heritage. This study evaluated the relationship of anthropometric, medical, and behavioral factors and vBMD in a population-based cohort of men of African ancestry (n = 1901) >or=40 yr of age who had undergone screening for prostate cancer for the first time. Trabecular and cortical vBMD were measured at the radius and tibia by pQCT. Multiple linear regression analysis identified age, height, body weight, cigarette smoking, history of diabetes, fracture, and prostate cancer as the independent correlates of vBMD. However, associations with several variables differed between cortical and trabecular vBMD and between the radius and tibia. Longitudinal studies are needed to gain a better understanding of the mechanisms underlying these differential associations that may show new insight into the etiology of trabecular and cortical bone loss in men.
Assuntos
População Negra , Densidade Óssea , Adulto , Idoso , Idoso de 80 Anos ou mais , Composição Corporal , Osso e Ossos/anatomia & histologia , Humanos , Masculino , Pessoa de Meia-Idade , Índias OcidentaisRESUMO
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.'
Assuntos
Tecido Adiposo/crescimento & desenvolvimento , Tecido Adiposo/fisiologia , Envelhecimento/fisiologia , População Negra , Diabetes Mellitus/epidemiologia , Músculo Esquelético/crescimento & desenvolvimento , Músculo Esquelético/fisiologia , Adulto , Idoso , População Negra/estatística & dados numéricos , Glicemia/análise , Índice de Massa Corporal , Humanos , Masculino , Pessoa de Meia-Idade , Análise de Regressão , Trinidad e TobagoRESUMO
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.'