Pubertal timing, peak bone mass and fragility fracture risk

Effects of hand preference on digit lengths and digit ratios among children and adults

BACKGROUND

Prenatal sex hormones may not exclusively determine effects of hand preference on digit ratios. Genetic determination is an alternative possibility.

AIM

To study the likelihood of similar effects of hand preference on digit lengths and digit ratios.

METHODS

We selected similar numbers of left-handers and right-handers in samples of kindergarten children (N = 101, age range: 3.5-7 years) and adults (N = 189, age range: 17-28 years) and measured digit lengths (excluding the thumb) directly on the palmar hand.

RESULTS

Compared to right-handers, left-handers had longer digits and lower third-to-fourth (3D:4D) digit ratios among children, whereas an opposite pattern of handedness differences occurred among adults.

CONCLUSIONS

Effects of hand preference on digit lengths and ratios might be genetically/ontogenetically determined. Also discussed are implications of this set of findings for digit ratio research.

Long-term Outcomes of Adolescent Anorexia Nervosa on Bone

PURPOSE

Anorexia nervosa (AN) is a chronic and life-threatening eating disorder that can have a considerable negative impact on the growing skeleton. We hypothesized that the long-term impact on bone health may persist even after normalization of body weight.

METHODS

41 females (mean age 21.2 ± 2.9 years) with a history of adolescent-onset AN attended a follow-up bone health assessment at 5 years (T5, n = 28) or 10 years (T10, n = 13) after their first AN-related hospital admission. Assessment included dual-energy x-ray absorptiometry measurements of the total body, lumbar spine, and proximal femur, peripheral quantitative computed tomography at the radius and tibia, anthropometric measurements, serum biochemistry, fracture history, and a patient questionnaire.

RESULTS

A recovery in body weight and BMI was seen for both the T5 and T10 cohorts (BMI at intake 16.6, BMI at T5-T10 21.2-21.3). Dual-energy x-ray absorptiometry body composition indicated a recovery of fat mass and lean tissue mass. Total BMD was unaffected, but reductions were seen at the femoral neck and arms. Peripheral quantitative computed tomography showed reduced trabecular and cortical bone in the radius, and cortical thinning in the tibia. AN patients showed a statistically significant reduction in measures of radiographic bone health at follow up, although not to a degree that necessitated clinical intervention. Serum insulin-like growth factor 1 was also positively correlated with total BMD and BMC measures. While fracture risk was not increased, a subset of participants (8%) showed multiple (>4) fractures.

CONCLUSION

A longitudinal study of adolescent AN showed persisting negative effects on bone health.

Transcriptional profiling of human femoral mesenchymal stem cells in osteoporosis and its association with adipogenesis

Genetic alterations are major contributing factors in the development of osteoporosis. Osteoblasts and adipocytes share a common origin, mesenchymal stem cells (MSCs), and their genetic determinants might be important in the relationship between osteoporosis and obesity. In the present study, we aimed to isolate differentially expressed genes (DEGs) in osteoporosis and normal controls using human MSCs, and elucidate the common pathways and genes related to osteoporosis and adipogenesis. Human MSCs were obtained from the bone marrow of femurs from postmenopausal women during orthopedic surgeries. RNA sequencing (RNA-seq) was carried out using next-generation sequencing (NGS) technology. DEGs were identified using RNA-seq data. Ingenuity pathway analysis (IPA) was used to elucidate the common pathway related to osteoporosis and adipogenesis. Candidate genes for the common pathway were validated with other independent osteoporosis and obese subjects using RT-PCR (reverse transcription-polymerase chain reaction) analysis. Fifty-three DEGs were identified between postmenopausal osteoporosis patients and normal bone mineral density (BMD) controls. Most of the genetic changes were related to the differentiation of cells. The nuclear receptor subfamily 4 group A (NR4A) family was identified as possible common genes related to osteogenesis and adipogenesis. The expression level of the mRNA of NR4A1 was significantly higher in osteoporosis patients than in controls (p=0.018). The expression level of the mRNA of NR4A2 was significantly higher in obese patients than in controls (p=0.041). Some genetic changes in MSCs are involved in the pathophysiology of osteoporosis. The NR4A family might comprise common genes related to osteoporosis and obesity.

STRA6 as a possible candidate gene for pathogenesis of osteoporosis from RNA‑seq analysis of human mesenchymal stem cells

To identify novel candidate genes associated with osteoporosis, RNA-sequence analysis of human mesenchymal stem cells (hMSCs) from patients with osteoporosis (G3) and osteopenia (G2), and healthy controls (G1) was performed. Differentially expressed genes (DEGs) from among the three groups were identified. DEGs were separated into nine groups according to their gene expression patterns: UU (up and up), UF (up and flat), UD (up and down), FU (flat and up), FF (flat and flat), FD (flat and down), DU (down and up), DF (down and flat), and DD (down and down). Among the 42 DEGs between G3 and G1, eight candidate genes, namely stimulated by retinoic acid 6 (STRA6), melanophilin, neurotrophic receptor tyrosine kinase 2, cartilage oligomeric matrix protein, collagen type XI α 1 chain, integrin subunit β 2, monooxygenase DBH-like 1 and selenoprotein P, were selected, as they demonstrated consistent gene expression patterns of UU, FU, FD, and DD. Among these eight genes, STRA6 was highly expressed in the osteoporosis group and based on additional data from quantitative polymerase chain reaction analysis, it was selected for further study. In order to investigate whether STRA6 served a functional role in osteoblast or adipocyte differentiation, the effects of STRA6 expression changes in pluripotent stem cell C3H10T1/2, preosteoblast MC3T3-E1 and stromal ST2 cell lines were examined. Bone morphogenetic protein 2 enhanced STRA6 expression only at the early stage of osteoblast differentiation, and overexpression of STRA6 temporally inhibited the expression of osteoblastogenesis markers, including runt related transcription factor 2, bone sialoprotein and osteocalcin. Furthermore, the knockdown of STRA6 slightly enhanced nodule formation at the late stage of osteoblast differentiation, and overexpression of STRA6 in ST2 cells enhanced adipocyte differentiation. Taken together, STRA6 expression could be associated with the pathogenesis of osteoporosis by promoting adipocyte differentiation over osteoblast differentiation in the hMSC population.

Insights into bone health in Duchenne muscular dystrophy

Poor bone health is a significant problem for patients with Duchenne muscular dystrophy (DMD), a progressive, disabling disease. Although the primary focus of DMD disease pathogenesis is degeneration of striated muscle, impairment of bone health likely has a role in the disease that has only been superficially examined to date. Deficiency of bone mineral density and increased incidence of bone fractures are well-recognized clinical components of the DMD phenotype. Furthermore, therapy with corticosteroids, an approved treatment for DMD that prolongs ambulation, may have multiple effects on bone health in DMD patients. This review examines the evidence in preclinical models and in human DMD disease that provides insight into the role performed by bone in the disease pathogenesis and phenotype of DMD. The information reviewed here points toward the need for mechanistic and therapeutic studies to optimize bone health in DMD patients.

Aromatase inhibitors in pediatrics

Aromatase, an enzyme located in the endoplasmic reticulum of estrogen-producing cells, catalyzes the rate-limiting step in the conversion of androgens to estrogens in many tissues. The clinical features of patients with defects in CYP19A1, the gene encoding aromatase, have revealed a major role for this enzyme in epiphyseal plate closure, which has promoted interest in the use of inhibitors of aromatase to improve adult height. The availability of the selective aromatase inhibitors letrozole and anastrozole--currently approved as adjuvant therapy for breast cancer--have stimulated off-label use of aromatase inhibitors in pediatrics for the following conditions: hyperestrogenism, such as aromatase excess syndrome, Peutz-Jeghers syndrome, McCune-Albright syndrome and functional follicular ovarian cysts; hyperandrogenism, for example, testotoxicosis (also known as familial male-limited precocious puberty) and congenital adrenal hyperplasia; pubertal gynecomastia; and short stature and/or pubertal delay in boys. Current data suggest that aromatase inhibitors are probably effective in the treatment of patients with aromatase excess syndrome or testotoxicosis, partially effective in Peutz-Jeghers and McCune-Albright syndrome, but probably ineffective in gynecomastia. Insufficient data are available in patients with congenital adrenal hyperplasia or functional ovarian cysts. Although aromatase inhibitors appear effective in increasing adult height of boys with short stature and/or pubertal delay, safety concerns, including vertebral deformities, a decrease in serum HDL cholesterol levels and increase of erythrocytosis, are reasons for caution.

Pubertal timing and body mass index gain from birth to maturity in relation with femoral neck BMD and distal tibia microstructure in healthy female subjects

Childhood body mass index (BMI) gain is linked to hip fracture risk in elderly. In healthy girls, menarcheal age is inversely related to BMI gain during childhood and to femoral neck areal bone mass density (aBMD) and distal tibia structural components at maturity. This study underscores the importance of pubertal timing in age-related fragility fracture risk.

INTRODUCTION

Recent data point to a relationship between BMI change during childhood and hip fracture risk in later life. We hypothesized that BMI development is linked to variation in pubertal timing as assessed by menarcheal age (MENA) which in turn, is related to peak bone mass (PBM) and hip fracture risk in elderly.

METHODS

We studied in a 124 healthy female cohort the relationship between MENA and BMI from birth to maturity, and DXA-measured femoral neck (FN) aBMD at 20.4 year. At this age, we also measured bone strength related microstructure components of distal tibia by HR-pQCT.

RESULTS

At 20.4 ± 0.6 year, FN aBMD (mg/cm(2)), cortical thickness (μm), and trabecular density (mg HA/cm(3)) of distal tibia were inversely related to MENA (P = 0.023, 0.015, and 0.041, respectively) and positively to BMI changes from 1.0 to 12.4 years (P = 0.031, 0.089, 0.016, respectively). Significant inverse (P < 0.022 to <0.001) correlations (R = -0.21 to -0.42) were found between MENA and BMI from 7.9 to 20.4 years, but neither at birth nor at 1.0 year. Linear regression indicated that MENA Z-score was inversely related to BMI changes not only from 1.0 to 12.4 years (R = -0.35, P = 0.001), but also from 1.0 to 8.9 years, (R = -0.24, P = 0.017), i.e., before pubertal maturation.

CONCLUSION

BMI gain during childhood is associated with pubertal timing, which in turn, is correlated with several bone traits measured at PBM including FN aBMD, cortical thickness, and volumetric trabecular density of distal tibia. These data complement the reported relationship between childhood BMI gain and hip fracture risk in later life.

Velocities of bone mineral accrual in black and white American children

Black adults have higher bone mass than whites in the United States, but it is not clear when black children gain bone mineral faster than white children. We performed a cohort study to compare the growth velocity of total-body bone mineral content (TBMC) between black and white children of the same sex at different ages and stages of sexual maturity. TBMC and total-body area were measured in a cohort of 188 black and white boys and girls aged 5 to 15 years annually for up to 4 years. Rates of change in TBMC and area were found to vary with age and with Tanner stage. For both TBMC and area, growth velocities between black and white children differed significantly across Tanner stages. Age-specific velocities were higher in black children during prepuberty and initial entry into puberty but reversed in subsequent Tanner stages. Despite earlier entry into each Tanner stage, black children spent only an average of only 0.2 year longer in Tanner stages II through IV, and total gain in TBMC from age 5 to 15 was not higher in whites. In conclusion, the higher bone mass in black adults compared with whites cannot be attributed to faster accrual during puberty. It is due to black children's higher rate of bone mineral accrual in prepuberty and plausibly in postpuberty. Most of the racial difference in TBMC velocity can be explained by growth in size.

The influence of pubertal timing on bone mass acquisition: a predetermined trajectory detectable five years before menarche

BACKGROUND

Later menarcheal age (MENA) is a risk factor for osteoporosis. It is associated with low peak bone mass (PBM). Like PBM, MENA is under strong genetic influence. We hypothesized that MENA-related bone mass differences could be predetermined before puberty.

METHODS

We tested this hypothesis in 124 healthy subjects followed from age 7.9 to 20.4 yr with dual-energy x-ray absorptiometry assessment at mean ages of 8.9, 10.0, 12.4, and 16.4 yr. Six sites were measured: radial metaphysis, radial diaphysis, femoral neck, trochanter, femoral diaphysis, and L2-L4. Mean MENA (+/-SD) was 13.0 +/- 1.2 yr. The cohort was segregated by the median of MENA into LATER (14.0 +/- 0.7 yr) and EARLIER (12.1 +/- 0.7 yr) subgroups.

RESULTS

At 20.4 +/- 0.6 yr, areal bone mineral density (aBMD) was lower in the LATER than the EARLIER subgroup at all six sites, with a mean difference of -0.31 Z-score (P = 0.022). Lower Z-scores in the LATER than in the EARLIER subgroup were observed at all sites at mean ages of 10.0, 12.4, and 16.4 yr, and before pubertal maturation, i.e. at 8.9 yr with a mean Z-score difference of -0.34 (P = 0.016). From mean age 8.9 to 20.4 yr, aBMD gains of all sites were similar in LATER and EARLIER subgroups, with mean of +301 and +308 mg/cm(2) (P = 0.402), respectively.

CONCLUSIONS

In prepubertal girls who will experience later menarche, a deficit in aBMD can already be observed before the onset of pubertal maturation, with no further accumulated deficit until PBM compared to girls with earlier menarche. This suggests that shorter estrogen exposure from prepuberty to PBM is not the main factor for increased osteoporosis risk associated with later menarche. Rather common genetic determinants of low bone mass and later puberty could be involved.

Deleterious effect of late menarche on distal tibia microstructure in healthy 20-year-old and premenopausal middle-aged women

Late menarche is a risk factor for fragility fractures. We hypothesized that pubertal timing-dependent alterations in bone structural components would persist from peak bone mass to menopause, independent of premenopausal bone loss. We studied the influence of menarcheal age (MENA) on femoral neck BMD (FN aBMD) by DXA and microstructure of distal tibia by HR-pQCT in healthy young adult (YAD; 20.4 +/- 0.6 [SD] yr, n = 124) and premenopausal middle-aged (PREMENO; 45.8 +/- 3.4 yr, n = 120) women. Median of MENA was 13.0 +/- 1.2 and 13.1 +/- 1.7 yr in YAD and PREMENO, respectively. In YAD and PREMENO (n = 244), FN aBMD (R = -0.29, p = 0.013), as well as total volumetric BMD (Dtot; R = -0.23, p = 0.006) and cortical thickness (Ct.Th; R = -0.18, p = 0.011) of distal tibia were inversely correlated to MENA. After segregation by the median of MENA in EARLY and LATE subgroups, the significant influences of both MENA (p = 0.004) and chronological age (p < 0.0001) were observed for FN aBMD and trabecular bone volume fraction of the distal tibia with similar differences in T-scores between LATE and EARLY subgroups in YAD (-0.36 and -0.31 T-scores) and PREMENO (-0.35 and -0.42 T-scores) women. Ct.Th was negatively influenced by MENA, whereas trabecular thickness (Tb.Th) was negatively influenced by chronological age. There was a striking inverse relationship between cross-sectional area and Ct.Th (R = -0.57, p < 0.001). In conclusion, the negative influence of late menarcheal age at weight-bearing sites as observed by the end of skeletal growth remains unattenuated a few years before menopause and is independent of premenopausal bone loss. Alterations in both bone mineral mass and microstructural components may explain the increased risk of fragility fractures associated with later menarcheal age.

Distal radius strength: a comparison of DXA-derived vs pQCT-measured parameters in adolescent females

Although quantitative computed tomography (QCT) is considered the gold standard for in vivo densitometry, dual-energy X-ray absorptiometry (DXA) scans assess larger bone regions and are more appropriate for pediatric longitudinal studies. Unfortunately, DXA does not yield specific bone architectural output. To address this issue in healthy, postmenarcheal girls, Sievänen's distal radius formulae [1996] were applied to derive indices of bone geometry, volumetric bone mineral density (vBMD), and strength from DXA data; results were compared to peripheral quantitative computed tomography (pQCT) output. Contemporaneous scans were performed on the left, distal radii of 35 gymnasts, ex-gymnasts, and nongymnasts (aged 13.3-20.4 yr, mean 16.6 yr). For 4% and 33% regions, pQCT measured cross-sectional areas (CSAs) and vBMD; comparable DXA indices were generated at ultradistal and 1/3 regions. Index of structural strength in axial compression was calculated from 4% pQCT and DXA output for comparison; 33% pQCT strength-strain index was compared to 1/3 DXA section modulus. Sievänen DXA indices were significantly, positively correlated with pQCT output (R=+0.61 to +0.98; p<0.0001). At the distal radius, in healthy postmenarcheal girls, Sievänen's method yielded potentially useful DXA indices of diaphyseal cortical CSA and bone strength at both the diaphysis (section modulus) and the metaphysis (index of structural strength in axial compression).

Leptin and the sympathetic connection of fat to bone

Loss of body weight is associated with bone loss, and body weight gain is associated with increased bone formation. The molecular mechanisms linking body weight, body composition, and bone density are now better understood. Lean mass is likely to have a significant, local effect on bone modeling and remodeling through mechanotransduction pathways. In contrast to the local regulation of bone formation and resorption by muscle-derived stimuli, peripheral body fat appears to influence bone mass via secretion of systemic, endocrine factors that link body weight to bone density even in non-weight bearing regions (e.g., the forearm). The cytokine-like hormone leptin, which is secreted by fat cells, is an important candidate molecule linking changes in body composition with bone formation and bone resorption. Increases in body fat increase leptin levels and stimulate periosteal bone formation through its direct anabolic effects on osteoblasts, and through central (CNS) effects including the stimulation of the GH-IGF-1 axis and suppression of neuropeptide Y, a powerful inhibitor of bone formation. Stimulation of beta2-adrenergic receptors through central (hypothalamic) leptin receptors does, however, increase remodeling of trabecular bone, resulting in a lower cancellous bone volume that may be better adapted to a concomitantly larger cortical bone compartment. These findings suggest that body weight and body fat can regulate bone mass and structure through molecular pathways that are independent of load-bearing. Furthermore, pharmacological manipulation of the signaling pathways activated by leptin may have significant potential for the treatment and prevention of bone loss.

Influence of age at menarche on forearm bone microstructure in healthy young women

BACKGROUND

Shorter estrogen exposure from puberty onset to peak bone mass attainment may explain how late menarche is a risk factor for osteoporosis. The influence of menarcheal age (MENA) on peak bone mass, cortical, and trabecular microstructure was studied in 124 healthy women aged 20.4 +/- 0.6 (sd) yr.

METHODS

At distal radius, areal bone mineral density (aBMD) was measured by dual-energy x-ray absorptiometry, and volumetric bone mineral density (BMD) and microstructure were measured by high-resolution peripheral computerized tomography, including: total, cortical, and trabecular volumetric BMD and fraction; trabecular number, thickness, and spacing; cortical thickness (CTh); and cross-sectional area (CSA).

RESULTS

Median MENA was 12.9 yr. Mean aBMD T score of the whole cohort was slightly positive. aBMD was inversely correlated to MENA for total radius (R = -0.21; P = 0.018), diaphysis (R = -0.18; P = 0.043), and metaphysis (R = -0.19; P = 0.031). Subjects with MENA more than the median [LATER: 14.0 +/- 0.7 (+/-sd) yr] had lower aBMD than those with MENA less than the median (EARLIER: 12.1 +/- 0.7 yr) in total radius (P = 0.026), diaphysis (P = 0.042), and metaphysis (P = 0.046). LATER vs. EARLIER displayed lower total volumetric BMD (315 +/- 54 vs. 341 +/- 56 mg HA/cm(3); P = 0.010), cortical volumetric BMD (874 +/- 49 vs. 901 +/- 44 mg HA/cm(3); P = 0.003), and CTh (774 +/- 170 vs. 849 +/- 191 microm; P = 0.023). CTh was inversely related to CSA (R = -0.46; P < 0.001). In LATER reduced CTh was associated with 5% increased CSA.

CONCLUSIONS

In healthy young adult women, a 1.9-yr difference in mean MENA was associated with lower radial aBMD T score, lower CTh without reduced CSA, a finding compatible with less endocortical accrual. It may explain how late menarche is a risk factor for forearm osteoporosis.