Lean mass plays a gender-specific role in familial resemblance for femoral neck bone mineral density in adult subjects

Maternal pre-pregnancy BMI and offspring body composition in young adulthood: the modifying role of offspring sex and birth order

OBJECTIVE

To investigate if the association between maternal pre-pregnancy BMI and offspring's body composition in late adolescence and young adulthood varies by offspring birth order and sex.

DESIGN

Family cohort study, with data from registers, questionnaires and physical examinations. The main outcome under study was offspring body composition (percentage fat mass (%FM), percentage lean mass (%LM)) measured by dual-energy X-ray absorptiometry.

SETTING

Uppsala, Sweden.

SUBJECTS

Two hundred and twenty-six siblings (first-born v. second-born; average age 19 and 21 years) and their mothers.

RESULTS

In multivariable linear regression models, maternal pre-pregnancy BMI was positively associated with daughter's %FM, with stronger estimates for first-born (β=0·97, 95 % CI 0·14, 1·80) v. second-born daughters (β=0·64, 95 % CI 0·08, 1·20). Mother's BMI before her first pregnancy was associated with her second-born daughter's body composition (β=1·05, 95 % CI 0·31, 1·79 (%FM)) Similar results albeit in the opposite direction were observed for %LM. No significant associations were found between pre-pregnancy BMI and %FM (β=0·59, 95 % CI-0·27, 1·44 first-born; β=-0·13, 95 % CI-0·77, 0·52 second-born) or %LM (β=-0·54, 95 % CI-1·37, 0·28 first-born; β=0·11, 95 % CI-0·52, 0·74 second-born) for sons.

CONCLUSIONS

A higher pre-pregnancy BMI was associated with higher offspring %FM and lower offspring %LM in late adolescence and young adulthood, with stronger associations for first-born daughters. Preventing obesity at the start of women's reproductive life might reduce the risk of obesity in her offspring, particularly for daughters.

The association between body composition, 25(OH)D, and PTH and bone mineral density in black African and Asian Indian population groups

CONTEXT AND OBJECTIVE

There are few data on the contribution of body composition to bone mineral density (BMD) in non-Caucasian populations. We therefore studied the contribution of body composition, and possible confounding of 25-hydroxyvitamin D and PTH, to BMD at various skeletal sites in black African (BA) and Asian Indian (AI) subjects.

DESIGN AND SETTING

This was a cross-sectional study in Johannesburg, South Africa.

PARTICIPANTS

BMD, body fat, and lean mass were measured using dual x-ray absorptiometry and abdominal fat distribution by ultrasound in 714 healthy subjects, aged 18-65 years.

RESULTS

Whole-body (subtotal), hip, femoral neck, and lumbar spine (lumbar) BMD were significantly higher in BA than AI subjects (P < .001 for all). Whole-body lean mass positively associated with BMD at all sites in both ethnic groups (P < .001 for all) and partially explained the higher BMD in BA females compared with AI females. Whole-body fat mass correlated positively with lumbar BMD in BA (P = .001) and inversely with subtotal BMD in AI subjects (P < .0001). Visceral adiposity correlated inversely with subtotal BMD in the BA (P = .037) and with lumbar BMD in the AI group (P = .005). No association was found between serum 25-hydroxyvitamin D and BMD. PTH was inversely associated with hip BMD in the BA group (P = .01) and with subtotal (P = .002), hip (P = .001), and femoral BMD (P < .0001) in the AI group.

CONCLUSIONS

Significant differences in whole-body and site-specific BMD between the BA and AI groups were observed, with lean mass the major contributor to BMD at all sites in both groups. The contribution of other components of body composition differed by site and ethnic group.

Gender differences in the heritability of musculoskeletal and body composition parameters in mother-daughter and mother-son pairs

Bone mass and body composition traits are genetically programmed, but the timing and gender and site specificities of their heritability are unclear. Mother-child correlations of bone mineral density (BMD) and bone mineral content, lean mass, and fat mass were studied in 169 premenopausal mothers and their 239 children. Heritability estimates of lean mass, fat mass, BMD, and area were derived for each gender and pubertal stage. There were significant correlations for most densitometry-derived variables at the spine, hip, femoral neck (FN), and total body (r=0.192-0.388) in mother-postmenarcheal daughter pairs, for bone areas at all sites in early puberty (r=0.229-0.508) and for volumetric-derived density at FN and spine (r=0.238-0.368) in mother-son pairs. Fat mass correlations were significant in both genders after puberty (r=0.299-0.324) and lean mass in postmenarcheal girls only (r = 0.299). Heritability estimates varied between 21% and 37% for mother-daughter and 18% and 35% for mother-son pairs for density-derived variables and between 26% and 40% for body composition variables. Maternal inheritance of bone traits is expressed in early-pubertal boys for several skeletal site traits but consistently involves most site traits in girls and boys by late puberty. Body composition inheritance is more variable.

Familial resemblance of bone turnover rate in men aged 40 and over-the MINOS study

Familial resemblance of bone mineral density (BMD) is well known in both sexes. Fewer data concern the familial resemblance of bone turnover markers (BTMs) and bone size in men. Our aim was to assess the correlation of BMD, bone size, BTM levels and hormones regulating bone turnover in 50 pairs of brothers aged ≥ 40 and 50 pairs of unrelated men matched for age, weight and height. BMD was measured at the lumbar spine, hip, forearm and whole body. We measured serum osteocalcin (OC), bone-specific alkaline phosphatase (bone ALP), N-terminal propeptide of type I procollagen (PINP) and C-terminal telopeptide of type I collagen (CTX-I) as well as urinary free and total deoxypyridinoline (DPD) and CTX-I. After adjustment for age, weight, bioavailable 17β-estradiol, and parathyroid hormone, all the BTMs (except bone ALP) were significantly correlated in the brothers (ICC = 0.36-0.64). Most of these correlations were significantly stronger than in the unrelated men. Bone size correlated significantly between the brothers (ICC = 0.55-0.65). These correlations were significantly stronger than in the unrelated men. BMD correlated between the brothers at most of the skeletal sites and, for some of them, more strongly than in the unrelated men. Serum levels of LDL-cholesterol and triglycerides were significantly correlated in the brothers, but not more strongly than in the unrelated men. BTM levels correlated independently in the brothers aged ≥ 40, when their shared environment was limited. These data suggest a substantial hereditary determinism of the BTM levels in men.

Bone mass and bone size in pre- or early pubertal 10-year-old black and white South African children and their parents

Genetic factors are thought to maintain bone mass in socioeconomically disadvantaged black South Africans. We compared bone mass between environmentally disadvantaged black and advantaged white children and their parents, after determining the most appropriate method by which to correct bone mineral content (BMC) for size. We collected data from 419 healthy black and white children of mean age 10.6 years (range 10.0-10.9), 406 biological mothers, and 100 biological fathers. Whole-body, femoral neck, lumbar spine, and mid- and distal one-third of radius bone area (BA) and BMC were measured by dual-energy X-ray absorptiometry. Power coefficients (PCs) were calculated from the linear-regression analyses of ln(BMC) on ln(BA) and used to correct site-specific BMC for bone size differences. Heritability (½h(2), %) by maternal and paternal descent was estimated by regressing children's Z scores on parents' Z scores. Correcting BMC for height, weight, and BA(PC) accounted for the greatest variance of BMC at all skeletal sites. In so doing, BMC in blacks was up to 2.6 times greater at the femoral neck and lumbar spine. Maternal and paternal heritability was estimated to be ~30% in both black and white subjects. These results may in part explain the lower prevalence of fragility fractures at the hip in black South African children when compared to whites. Heritability was comparable between environmentally disadvantaged black and advantaged white South African children and similar to that reported for Caucasians in other parts of the world.

Evidence for pleiotropic factors in genetics of the musculoskeletal system

There are both theoretical and empirical underpinnings that provide evidence that the musculoskeletal system develops, functions, and ages as a whole. Thus, the risk of osteoporotic fracture can be viewed as a function of loading conditions and the ability of the bone to withstand the load. Both bone loss (osteoporosis) and muscle wasting (sarcopenia) are the two sides of the same coin, an involution of the musculoskeletal system. Skeletal loads are dominated by muscle action; both bone and muscle share environmental, endocrine and paracrine influences. Muscle also has an endocrine function by producing bioactive molecules, which can contribute to homeostatic regulation of both bone and muscle. It also becomes clear that bone and muscle share genetic determinants; therefore the consideration of pleiotropy is an important aspect in the study of the genetics of osteoporosis and sarcopenia. The aim of this review is to provide an additional evidence for existence of the tight genetic co-regulation of muscles and bones, starting early in development and still evident in aging. Recently, important papers were published, including those dealing with the cellular mechanisms and anatomic substrate of bone mechanosensitivity. Further evidence has emerged suggesting that the relationship between skeletal muscle and bone parameters extends beyond the general paradigm of bone responses to mechanical loading. We provide insights into several pathways and single genes, which apparently have a biologically plausible pleiotropic effect on both bones and muscles; the list is continuing to grow. Understanding the crosstalk between muscles and bones will translate into a conceptual framework aimed at studying the pleiotropic genetic relationships in the etiology of complex musculoskeletal disease. We believe that further progress in understanding the common genetic etiology of osteoporosis and sarcopenia will provide valuable insight into important biological underpinnings for both musculoskeletal conditions. This may translate into new approaches to reduce the burden of both conditions, which are prevalent in the elderly population.

Low sit-to-stand performance is associated with low femoral neck bone mineral density in healthy women

Bone mass may be adjusted to control the strains produced by muscular activity. We assessed the relationship between maximum rising strength (MRS), a new measurement of sit-to-stand performance, and femoral neck (FN) bone mineral density (BMD), taking into account possible confounding variables. The study population consisted of 249 healthy women aged 18-76. We measured MRS with a dynamometer fixed on the ground and connected by an adjustable nonelastic cord to a padded belt. FN BMD was measured by dual X-ray absorptiometry. Women in the first quartile of FN BMD (<0.702 g/cm(2)) had significantly lower values of MRS, body weight, height, lean mass, past 5-year physical activity expenditures, blood 17 beta estradiol (E2), 25-hydroxyvitamin D (25(OH)D), dehydroepiandrosterone sulfate (DHEAS), and insulin like growth factor 1, and higher values of age and parathyroid hormone than other women. In the logistic regression model, FN BMD values in the lowest quartile were associated with age (adjusted odds ratio [OR(a)] per 10-year increase = 1.84, 95% confidence interval [95% CI] = 1.33-2.54, P < 0.001), body weight (OR(a) per 10-kg decrease = 3.67, 95% CI = 2.08-6.47, P < 0.001), MRS (OR(a) per 20-kg decrease = 1.17, 95% CI = 1.02-1.34, P = 0.03), serum DHEAS (OR(a) < 0.5 mg/ml vs > or =0.5 mg/ml = 2.83, 95% CI = 1.3-6.12, P = 0. 01), and serum E2 (OR(a) per 10-pmol/l decrease = 1.02, 95% CI = 1.01-1.03, P = 0.03). The present study suggests a significant association between low FN BMD and low sit-to-stand performance in healthy women, independent of possible confounding variables.

Paternal skeletal size predicts intrauterine bone mineral accrual

BACKGROUND

We have previously demonstrated that maternal body build and lifestyle factors predict neonatal bone mineral accrual. However, the paternal determinants of neonatal bone mass are not known. In this study we explored the relationship between a father's bone mass and that of his offspring.

METHODS

A total of 278 pregnancies (142 male and 136 female neonates) were recruited from the Southampton Women's Survey, a unique, well-established cohort of women, aged 20-34 yr, who had been assessed before and during pregnancy. The neonates and their fathers underwent whole body dual-x-ray absorptiometry (DXA) within 2 wk of birth using a Lunar DPX (General Electric Corp., Madison, WI) and Hologic Discovery instrument (Hologic Inc., Bedford, MA), respectively; correlation and regression methods were used to explore the parental determinants of neonatal bone mass.

RESULTS

After adjusting the paternal DXA indices for father's age and the neonatal for baby's gestational age and age at DXA scan, there were highly significant positive associations between baby's whole body bone area, bone mineral content, and bone mineral density and the corresponding indices in the father (P = 0.003, 0.0002, 0.046, respectively) among female infants. These relationships were independent of maternal height and fat stores. The associations for male infants with paternal DXA indices did not achieve statistical significance.

CONCLUSIONS

The father's skeletal size predicts skeletal size more strongly in female than male offspring, independently of the mother's body build. These data point toward the importance of considering paternal genotype in studies exploring the developmental origins of osteoporotic fracture and raise intriguing mechanistic questions about the gender specificity of influences on intrauterine bone mineral accrual.

Linkage of genes to total lean body mass in normal women

BACKGROUND

Total lean body mass (LEAN-tot) is one of the three major components of body weight. Its deterioration is a risk factor for frailty. Despite this, there are few studies examining the contribution of genetic factors.

OBJECTIVE

Our objective was to examine the contribution of genetic factors for LEAN-tot variation, including a genome-wide search for the genes.

RESEARCH METHODS

Dual-energy x-ray absorptiometry measurements of LEAN-tot were obtained from each of the 3180 United Kingdom females (509 monozygotic and 1081 dizygotic twin pairs). Contribution of genetic factors was assessed using variance component analysis. A genome-wide linkage analysis was performed on the dizygotic twins using a modified version of the Haseman-Elston method.

RESULTS

Age, body height, total fat, and bone mass were correlated with LEAN-tot, and commonly explained 52% of the LEAN-tot variation. The crude heritability estimate was 74.0 +/- 4.0%, after adjustment for the aforementioned factors; 65.2 +/- 4.6% was attributable to independent genetic effects. Significant (P < 0.001) genetic correlations were found between LEAN-tot and bone mass, and LEAN-tot and total fat. Adjusted only for age, LEAN-tot showed no significant linkage. After adjustment for all covariates, significant linkage (LOD = 4.49 and 3.62) was observed at chromosome 12q24.3 and 14q22.3, respectively. Additional peaks of interest were on 7p15.3-15.1 (LOD = 2.86) and 8p22 (LOD = 2.83).

CONCLUSIONS

LEAN-tot measured by dual-energy x-ray absorptiometry is highly heritable, independent of other body measures. This first genomic search for genes associated with the lean component of body mass suggests significant linkage to quantitative trait loci on chromosomes 12 and 14.