The Developmental Origins of Osteoporosis

Maternal vitamin A and D status in second and third trimester of pregnancy and bone mineral content in offspring at nine years of age

Introduction

Maternal nutritional and vitamin status during pregnancy may have long-term effects on offspring health and disease. The aim of this study was to examine the associations between maternal vitamin A and D status in pregnancy and offspring bone mineral content (BMC) at nine years of age.

Methods

This is a post-hoc study of a randomized control trial including 855 pregnant women from two Norwegian cities; Trondheim and Stavanger. The women were randomized into an exercise intervention or standard antenatal care. Mother and child pairs for the present study were recruited from those still living in Trondheim after 8-10 years. Serum vitamin A (retinol) and vitamin D (25(OH)D) were measured in the 2nd and 3rd trimesters of pregnancy, and active vitamin D (1,25(OH)2D) in serum was measured in a subgroup. Spine BMC and trabecular bone score were measured in the children at nine years of age. Associations were analyzed with linear regression models.

Results

A total of 119 mother and child pairs were included in the analyses. Vitamin A insufficiency (retinol< 1.05 µmol/L) and vitamin D deficiency (25(OH)D< 50 mmol/L) increased from ~7% to ~43% and from ~28% to ~33%, respectively, from the 2nd to the 3rd trimester. An increase in serum 1,25(OH)2D from the 2nd to the 3rd trimester was observed in the subgroup. There was a negative association between serum retinol in the 2nd trimester and spine BMC in the boys, but not in the girls, when adjusted for maternal and child confounders. No other associations between maternal serum vitamin A or D and BMC in the children were found.

Conclusion

We observed a high prevalence of vitamin A insufficiency and vitamin D deficiency during pregnancy. A negative association between mid-pregnancy vitamin A status and spine BMC was observed in boys, but not girls, while no associations were found between maternal vitamin D status and child BMC. The implications of optimal vitamin A and D status in pregnancy for offspring bone health, remains a subject for further investigations.

Epigenetic regulation of bone remodeling and its role in the pathogenesis of primary osteoporosis

Discovery of molecular mechanisms of primary osteoporosis development is fundamental to understand the pathogenesis of musculoskeletal diseases in general and for identifying key links in the genetic and epigenetic regulation of bone remodelling genes. The number of identified molecular genetic markers for osteoporosis is increasing but there is a need to describe their functional interactions. These interactions have been determined to be associated with the control of expression of a number of transcription factors and the differentiation of mesenchymal stem cells through the pathway of osteoblastogenesis or adipogenesis, and monocytic precursors through the pathway of osteoclastogenesis. The results of epigenetic studies have significantly increased the understanding of the role of post-translational modifications of histones, DNA methylation and RNA interference in the osteoporosis pathogenesis and in bone remodelling. However, the knowledge should be systematised and generalised according to the results of research on the role of epigenetic modifiers in the development of osteoporosis, and the influence of each epigenetic mechanism on the individual links of bone remodelling during ontogenesis of humans in general, including the elderly, should be described. Understanding which mechanisms and systems are involved in the development of this nosology is of interest for the development of targeted therapies, as the possibility of using microRNAs to regulate genes is now being considered. Systematisation of these data is important to investigate the differences in epigenetic marker arrays by race and ethnicity. The review article analyses references to relevant reviews and original articles, classifies information on current advances in the study of epigenetic mechanisms in osteoporosis and reviews the results of studies of epigenetic mechanisms on individual links of bone remodelling.

Bone mass in newborns and its predictors

OBJECTIVE

Optimal bone mass (a function of foetal programming and adequate intrauterine bone mineral accrual) is essential for prevention of osteoporosis. The present study was planned with the objectives to describe newborn bone mass (NBBM) and study the associated factors.

DESIGN

Observational study Patients: Singleton pregnant women ≤16 weeks gestation.

MEASUREMENTS

Maternal factors and antenatal events: Dietary assessment (3 days-24-h diet recalls at ≤16 and 32-34 weeks), fetal femoral volume (FFV) assessment at 19 and 34 weeks, serum 25 hydroxyvitamin D (S.25OHD) and placental weight. Newborn anthropometric parameters, cord S.25OHD & IGF-1 level and NBBM by DXA (whole-body bone mineral content (BMC), bone mineral density (BMD) and bone area).

RESULTS

Total 224 subjects were studied: 198 full-term and 26 preterm. The mean BMC, BMD and bone area for term newborns was 46.5 g (95% confidence interval [CI]: 45.35-47.66), 0.209 g/cm² (95% CI: 0.206-0.212) and 221.6 cm² (95% CI: 218.52-224.62), respectively. The mean placental weight was 403.2 ± 75.01 g (n = 72) while FFV was 0.71 ± 0.28 ml (19 weeks; n = 59) and 4.4 ± 1.17 ml (34 weeks; n = 33). Factors significantly associated with NBBM -gestational age at delivery, gestational weight gain, FFV at 19 weeks, placental weight, third-trimester maternal serum albumin and newborn anthropometric parameters (univariable analysis) and newborn birth weight, placental weight and FFV at 19 weeks (multivariable analysis).

CONCLUSION

This study described NBBM among term newborns and birth weight, second-trimester FFV and placental weight were the associated factors.

Extracellular Vesicles in Premature Aging and Diseases in Adulthood Due to Developmental Exposures

The developmental origins of health and disease (DOHaD) is a paradigm that links prenatal and early life exposures that occur during crucial periods of development to health outcome and risk of disease later in life. Maternal exposures to stress, some psychoactive drugs and alcohol, and environmental chemicals, among others, may result in functional changes in developing fetal tissues, creating a predisposition for disease in the individual as they age. Extracellular vesicles (EVs) may be mediators of both the immediate effects of exposure during development and early childhood as well as the long-term consequences of exposure that lead to increased risk and disease severity later in life. Given the prevalence of diseases with developmental origins, such as cardiovascular disease, neurodegenerative disorders, osteoporosis, metabolic dysfunction, and cancer, it is important to identify persistent mediators of disease risk. In this review, we take this approach, viewing diseases typically associated with aging in light of early life exposures and discuss the potential role of EVs as mediators of lasting consequences.

Bone Health and Its Positive Relationships with Body Composition in Malaysian Schoolchildren: Findings from a Cross-Sectional Study

Background: Optimal bone health is vital in children to prevent osteoporosis later in life, and body composition plays a crucial role in it. However, the literature reports contradictory results when considering the relationship between body composition and bone health in children. This study aimed to examine the bone health and its relationship with body composition in Malaysian schoolchildren. Methods: In this cross sectional study, body composition data (weight, height, body fat percentage [% fat], fat mass, fat free mass, visceral fat, waist circumference [WC] and body mass index-for-age [BMI z-score]) and bone health data (Z-score and broadband ultrasound attenuation [BUA]) were collected from 415 schoolchildren aged 9–12 years, cluster sampled from randomly selected primary schools in Kuala Lumpur, Malaysia. Results: Girls generally had significantly higher height, body fat percentage, fat mass, visceral fat and Z-score as compared to boys. A steady increase of the mean BUA value was observed with increasing age in both sexes. The mean BUA value of the present study across the population was significantly higher than that of schoolchildren from Nigeria (p < 0.001), Colombia (p < 0.001) and Spain (p = 0.002). Significant positive correlations were found between all the body composition variables and bone outcome variables across the population. Further, BUA was significantly correlated with weight (β = 0.172; p = 0.001), height (β = 0.299; p < 0.001), % fat (β = 0.131; p = 0.007), fat mass (β = 0.130; p = 0.007), fat free mass (β = 0.209; p < 0.001), visceral fat (β = 0.127, p = 0.008), WC (β = 0.165; p = 0.001) and BMI z-score (β = 0.162; p = 0.001), after controlling for sex, age and ethnicity. Similarly, after confounders adjusted, Z-score was significantly predicted by weight (β = 0.160; p = 0.001), height (β = 0.310; p < 0.001), % fat (β = 0.104; p = 0.032), fat mass (β = 0.107; p = 0.026), fat free mass (β = 0.218; p < 0.001), visceral fat (β = 0.107, p = 0.026), WC (β = 0.145; p = 0.002) and BMI z-score (β = 0.150; p = 0.002). Conclusions: Our findings have revealed that body composition variables were positive correlated with bone outcome variables, suggesting that adipose tissue acts to stimulate bone growth. Further clinical and molecular studies in the future is recommended to fully illustrate the complex interactions between adiposity and bone health.

Childhood adiposity, adult adiposity, and bone health

IMPORTANCE

Childhood and adolescence are critical periods for lifelong bone mineral accrual, but few studies have determined the impact of childhood adiposity on adult bone density.

OBJECTIVE

To determine the long-term impact of childhood adiposity on adult areal bone mineral density (aBMD) and the effect of adult adiposity on this relationship.

METHODS

We conducted a longitudinal study of 1156 adults (56.3% men), for whom skinfold thickness (SFT) had been measured during childhood (6-18 years) and fat mass percentage (FMP) and aBMD were measured during adulthood (29-43 years). Adult aBMD in the lumbar spine (LS), femoral neck (FN), arms, and legs was measured using dual-energy X-ray absorptiometry. The direct effect of childhood SFT and its indirect effect through adult FMP on adult aBMD were estimated using general linear regression and a causal steps approach.

RESULTS

Significant positive associations between childhood SFT and adult aBMD were found in the LS in men (β = 0.089, P = 0.044) and in all the skeletal sites in women. With respect to the adult fat-bone relationship, high adult FMP was associated with low aBMD in most of the sites in men, but with high FN aBMD in women (β = 0.144, P = 0.002). Moreover, suppressive effects of adult FMP on the associations between childhood SFT and adult aBMD in the LS (-34.8%) and legs (-67.1%) of men, and a positive effect on the FN aBMD in women (17.0%) were identified.

INTERPRETATION

Childhood adiposity appears to have a positive long-term effect on adult aBMD, which may be reduced by adiposity in adult men but reinforced by adiposity in adult women.

The Role of Cannabinoid Receptor Type 2 in the Bone Loss Associated With Pediatric Celiac Disease

OBJECTIVES

In this study, we investigated the role of the cannabinoid receptor type 2 (CB2) in the bone loss associated with celiac disease (CD) evaluating the effect of its pharmacological modulation on osteoclast activity. We previously demonstrated a significant association between the CB2 Q63R variant and CD, suggesting it as a possible disease biomarker. Moreover, CB2 stimulation is beneficial for reducing osteoclast activity in several bone pathologic conditions.

METHODS

In vitro osteoclasts (OCs) were differentiated from peripheral blood mononuclear cells of healthy donors, CD children at diagnosis and after 1 year of gluten-free diet (GFD) and characterized by real-time PCR and western blot for the expression of CB2 and specific osteoclastic markers, TRAP and Cathepsin K. TRAP assay and Bone Resorption assay were performed to evaluate osteoclast activity before and after 48 h exposure to CB2 selective drugs (JWH-133 and AM630) and Vitamin D.

RESULTS

We found in CD patients an osteoclast hyperactivation and low levels of CB2. CB2 stimulation with JWH-133 agonist is more effective than Vitamin D in reducing osteoclast activity whereas CB2 blockade with AM630 increases osteoclast activation. The anti-osteoporotic effect of JWH-133 decreases when used in co-treatment with vitamin D. GFD reduces osteoclast activity without restore CB2 expression.

CONCLUSIONS

CB2 could be a molecular marker to predict the risk of bone alterations in CD and a pharmacological target to reduce bone mass loss in patients who need a direct intervention on bone metabolism, in addition to the GFD.

Fusion Potential of Human Osteoclasts In Vitro Reflects Age, Menopause, and In Vivo Bone Resorption Levels of Their Donors-A Possible Involvement of DC-STAMP

It is well established that multinucleation is central for osteoclastic bone resorption. However, our knowledge on the mechanisms regulating how many nuclei an osteoclast will have is limited. The objective of this study was to investigate donor-related variations in the fusion potential of in vitro-generated osteoclasts. Therefore, CD14⁺ monocytes were isolated from 49 healthy female donors. Donor demographics were compared to the in vivo bone biomarker levels and their monocytes’ ability to differentiate into osteoclasts, showing that: (1) C-terminal telopeptide of type I collagen (CTX) and procollagen type I N-terminal propeptide (PINP) levels increase with age, (2) the number of nuclei per osteoclast in vitro increases with age, and (3) there is a positive correlation between the number of nuclei per osteoclast in vitro and CTX levels in vivo. Furthermore, the expression levels of the gene encoding dendritic cell-specific transmembrane protein (DCSTAMP) of osteoclasts in vitro correlated positively with the number of nuclei per osteoclast, CTX levels in vivo, and donor age. Our results furthermore suggest that these changes in gene expression may be mediated through age-related changes in DNA methylation levels. We conclude that both intrinsic factors and age-induced increase in fusion potential of osteoclasts could be contributing factors for the enhanced bone resorption in vivo, possibly caused by increased expression levels of DCSTAMP.

Dietary Calcium and Phosphorus Amounts Affect Development and Tissue-Specific Stem Cell Characteristics in Neonatal Pigs

BACKGROUND

Dietary calcium and phosphorus are required for bone and muscle development. Deficiencies of these macrominerals reduce bone mineral and muscle accretion potentially via alterations of mesenchymal stem cell (MSC) and satellite cell (SC) activities.

OBJECTIVES

With increasing interest in the role of early-life events on lifetime health outcomes, we aimed to elucidate the impact of dietary calcium and phosphorus, from deficiency through excess, on MSC and SC characteristics during neonatal development.

METHODS

Neonatal pigs [30 females, 1-d-old, 1.46 ± 0.04 kg body weight (BW)] were fed milk replacers for 16 d that were isonitrogenous and isocaloric with a consistent ratio of calcium to phosphorus, but either 25% deficient (calcium: 0.78%; phosphorus: 0.60%; CaPD), adequate (calcium: 1.08%; phosphorus: 0.84%; CaPA), or 25% in excess (calcium: 1.38%; phosphorus: 1.08%; CaPE) of calcium and phosphorus requirements based on sow-milk composition and extrapolation from NRC requirements for older pigs. BW and feed intake were recorded daily. Blood was collected for serum phosphorus, parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF23) determination. Humeri were collected for MSC isolation and radii/ulnae bone were collected for analysis. Longissimus dorsi muscle was collected for SC isolation and analysis.

RESULTS

There was 4.6% increase in bone ash percentage in CaPE- versus CaPD-fed pigs (P < 0.05). In vivo proliferation indicated a 41.3% increase in MSCs in CaPA compared with CaPD and a 19% increase in SCs in CaPA compared with both CaPE and CaPD. MSCs from CaPD had 2- to 5-fold greater expression of peroxisome proliferator-activated receptor γ (PPARγ), fatty acid-binding protein 4 (FABP4), and lipoprotein lipase (LPL) but lower osteocalcin (BGLAP) and fibronectin (FN1) expression than CaPA (P < 0.05). SCs from CaPD-fed pigs had 19% lower in vivo proliferation than in CaPA-fed pigs.

CONCLUSIONS

These findings demonstrated that feeding a diet marginally deficient in calcium and phosphorus to neonatal pigs had a great impact on bone development, MSC, and SC characteristics. These dietary deficiencies may program future bone health and muscle development by altering MSC and SC activities.

Maternal serum retinol, 25(OH)D and 1,25(OH)2D concentrations during pregnancy and peak bone mass and trabecular bone score in adult offspring at 26-year follow-up

Background

Vitamin A and D deficiency is prevalent in pregnant women worldwide. Both vitamins are involved in fetal skeletal development. A positive association between maternal vitamin D levels and offspring bone mineral density (BMD) at adulthood has been observed. The impact of maternal vitamin A status in pregnancy on offspring peak bone mass remains unclear.

Method and findings

Forty-one mother-child pairs were recruited from a population-based prospective cohort study in Trondheim, Norway, where pregnant women were followed from gestational week 17. Their term-born infants were followed from birth (1986–88). Regression analyses were performed for vitamin A (retinol), 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)₂D] in maternal serum (gestational weeks 17, 33, 37) and cord blood. Offspring BMD and spine trabecular bone score (TBS), a measure of bone quality, were analyzed by dual x-ray absorptiometry at 26 years. Average levels during pregnancy of retinol, 25(OH)D and 1,25(OH)₂D were 1.66 (0.32) μmol/L, 59.0 (20.6) nmol/L, and 251.3 (62.4) pmol/L, respectively. 1,25(OH)₂D levels were similar in those with 25(OH)D levels <30 and >75 nmol/L. After adjustment for maternal age, BMI, smoking, and education, and offspring birth weight, maternal serum retinol was positively associated with offspring spine BMD [mean change 30.8 (CI 7.6, 54.0) mg/cm² per 0.2 μmol/L retinol], and with offspring TBS, although non-significant (p = 0.08). No associations were found between maternal 25(OH)D and 1,25(OH)₂D levels and offspring bone parameters. Vitamin levels in cord blood were not associated with offspring BMD or TBS.

Conclusions

This is the first study to show an association between maternal vitamin A status and offspring peak bone mass. Our findings may imply increase future risk for osteoporotic fracture in offspring of mothers with suboptimal vitamin A level. No associations were observed between 25(OH)D and 1,25(OH)₂D and offspring BMD.

Models of Intrauterine growth restriction and fetal programming in rabbits

Intrauterine growth restriction (IUGR) affects approximately 10% of human pregnancies globally and has immediate and life-long consequences for offspring health. However, the mechanisms underlying the pathogenesis of IUGR and its association with later health and disease outcomes are poorly understood. To address these knowledge gaps, the use of experimental animals is critically important. Since the 50's different environmental, pharmacological, and surgical manipulations have been performed in the rabbit to improve our knowledge of the control of fetal growth, fetal responses to IUGR, and mechanisms by which offspring may be programmed by an adverse gestational environment. The purpose of this review is therefore to summarize the utility of the rabbit as a model for IUGR research. It first summarizes the knowledge of prenatal and postnatal development in the rabbit and how these events relate to developmental milestones in humans. It then describes the methods used to induce IUGR in rabbits and the knowledge gained about the mechanisms determining prenatal and postnatal outcomes of the offspring. Finally, it discusses the application of state of the art approaches in the rabbit, including high-resolution ultrasound, magnetic resonance imaging, and gene targeting, to gain a deeper integrative understanding of the physiological and molecular events governing the development of IUGR. Overall, we hope to engage and inspire investigators to employ the rabbit as a model organism when studying pregnancy physiology so that we may advance our understanding of mechanisms underlying IUGR and its consequences in humans and other mammalian species.

Developmental Programming of Body Composition: Update on Evidence and Mechanisms

PURPOSE OF REVIEW

A growing body of epidemiological and experimental data indicate that nutritional or environmental stressors during early development can induce long-term adaptations that increase risk of obesity, diabetes, cardiovascular disease, and other chronic conditions-a phenomenon termed "developmental programming." A common phenotype in humans and animal models is altered body composition, with reduced muscle and bone mass, and increased fat mass. In this review, we summarize the recent literature linking prenatal factors to future body composition and explore contributing mechanisms.

RECENT FINDINGS

Many prenatal exposures, including intrauterine growth restriction, extremes of birth weight, maternal obesity, and maternal diabetes, are associated with increased fat mass, reduced muscle mass, and decreased bone density, with effects reported throughout infancy and childhood, and persisting into middle age. Mechanisms and mediators include maternal diet, breastmilk composition, metabolites, appetite regulation, genetic and epigenetic influences, stem cell commitment and function, and mitochondrial metabolism. Differences in body composition are a common phenotype following disruptions to the prenatal environment, and may contribute to developmental programming of obesity and diabetes risk.

Time since menopause, but not age, is associated with increased risk of osteoporosis

Objectives: This study aimed to determine whether estrogen deficiency is a sole risk factor for osteoporosis or is also associated with age, through indicators such as gender, age, and time since menopause. Methods: A cross-sectional study was conducted evaluating 938 postmenopausal women who underwent bone mineral densitometry. We collected the following data: age, ethnic group, body mass index, smoking, and time since menopause. These data were correlated to the presence of osteoporosis, according to the T-score of the femur and lumbar spine. Results: The prevalence of osteoporosis was 37.8%. Ethnic group (p = 0.47) and smoking habits (p = 0.19) were not associated with osteoporosis. In the group of women with osteoporosis, mean age was significantly higher (p < 0.001), mean body mass index was significantly lower (p < 0.001), and time since menopause was significantly higher (p < 0.001) than in the group of women with no osteoporosis. After multivariate analysis was performed, the only variables that remained independently associated with osteoporosis were body mass index and time since menopause. Higher body mass index was a protective factor (odds ratio = 0.80 [95% confidence interval 0.76; 0.84], p < 0.001). Time since menopause represented a risk factor for osteoporosis (odds ratio = 1.04 [1.02; 1.06], p < 0.001). When divided into categories, the risk increased after 20 years of menopause and gradually every 5 years. Conclusion: Time since menopause and body mass index were the most important factors associated with osteoporosis, confirming that estrogen deficiency, and not age, is the major cause of the disease.

Human osteogenic differentiation in Space: proteomic and epigenetic clues to better understand osteoporosis

In the frame of the VITA mission of the Italian Space Agency (ASI), we addressed the problem of Space osteoporosis by using human blood-derived stem cells (BDSCs) as a suitable osteogenic differentiation model. In particular, we investigated proteomic and epigenetic changes in BDSCs during osteoblastic differentiation induced by rapamycin under microgravity conditions. A decrease in the expression of 4 embryonic markers (Sox2, Oct3/4, Nanog and E-cadherin) was found to occur to a larger extent on board the ISS than on Earth, along with an earlier activation of the differentiation process towards the osteogenic lineage. The changes in the expression of 4 transcription factors (Otx2, Snail, GATA4 and Sox17) engaged in osteogenesis supported these findings. We then ascertained whether osteogenic differentiation of BDSCs could depend on epigenetic regulation, and interrogated changes of histone H3 that is crucial in this type of gene control. Indeed, we found that H3K4me3, H3K27me2/3, H3K79me2/3 and H3K9me2/3 residues are engaged in cellular reprogramming that drives gene expression. Overall, we suggest that rapamycin induces transcriptional activation of BDSCs towards osteogenic differentiation, through increased GATA4 and Sox17 that modulate downstream transcription factors (like Runx2), critical for bone formation. Additional studies are warranted to ascertain the possible exploitation of these data to identify new biomarkers and therapeutic targets to treat osteoporosis, not only in Space but also on Earth.

Structured diet and exercise guidance in pregnancy to improve health in women and their offspring: study protocol for the Be Healthy in Pregnancy (BHIP) randomized controlled trial

BACKGROUND

Evidence from epidemiological and animal studies support the concept of programming fetal, neonatal, and adult health in response to in utero exposures such as maternal obesity and lifestyle variables. Excess gestational weight gain (GWG), maternal physical activity, and sub-optimal and excess nutrition during pregnancy may program the offspring's risk of obesity. Maternal intake of dairy foods rich in high-quality proteins, calcium, and vitamin D may influence later bone health status. Current clinical practice guidelines for managing GWG are not founded on randomized trials and lack specific "active intervention ingredients." The Be Healthy in Pregnancy (BHIP) study is a randomized controlled trial (RCT) designed to test the effectiveness of a novel structured and monitored Nutrition + Exercise intervention in pregnant women of all pre-pregnancy weight categories (except extreme obesity), delivered through prenatal care in community settings (rather than in hospital settings), on the likelihood of women achieving recommended GWG and a benefit to bone status of offspring and mother at birth and six months postpartum.

METHODS

The BHIP study is a two-site RCT that will recruit up to 242 participants aged > 18 years at 12-17 weeks of gestation. After baseline measures, participants are randomized to either a structured and monitored Nutrition + Exercise (intervention) or usual care (control) program for the duration of their pregnancy. The primary outcome of the study is the percent of women who achieve GWG within the Institute of Medicine (IOM) guidelines. The secondary outcomes include: (1) maternal bone status via blood bone biomarkers during pregnancy; (2) infant bone status in cord blood; (3) mother and infant bone status measured by dual-energy absorptiometry scanning (DXA scan) at six months postpartum; (4) other measures including maternal blood pressure, blood glucose and lipid profiles, % body fat, and postpartum weight retention; and (5) infant weight z-scores and fat mass at six months of age.

DISCUSSION

If effective, this RCT will generate high-quality evidence to refine the nutrition guidelines during pregnancy to improve the likelihood of women achieving recommended GWG. It will also demonstrate the importance of early nutrition on bone health in the offspring.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01689961 Registered on 21 September 2012.

Cognitive outcome in childhood of birth weight discordant monochorionic twins: the long-term effects of fetal growth restriction

AIM

Intrauterine growth restriction (IUGR) is associated with poorer outcomes in later life. We used a monochorionic twin model with IUGR in one twin to determine its impact on growth and neurocognitive outcomes.

METHODS

Monochorionic twins with ≥20% birth weight discordance born in the north of England were eligible. Cognitive function was assessed using the British Ability Scales. The Strength and Difficulties Questionnaire was used to identify behavioural problems. Auxological measurements were collected. Generalised estimating equations were used to determine the effects of birth weight on cognition.

RESULTS

Fifty-one monochorionic twin pairs were assessed at a mean age of 6.3 years. Mean birth weight difference was 664 g at a mean gestation of 34.7 weeks. The lighter twin had a General Conceptual Ability (GCA) score that was three points lower (Twin^L -105.4 vs Twin^H -108.4, 95% CI -0.9 to -5.0), and there was a significant positive association (B 0.59) of within-pair birth weight differences and GCA scores. Mathematics and memory skills showed the largest differences. The lighter twin at school age was shorter (mean difference 2.1 cm±0.7) and lighter (mean difference 1.9 kg±0.6). Equal numbers of lighter and heavier twins were reported to have behavioural issues.

CONCLUSIONS

In a monochorionic twin cohort, fetal growth restriction results in lower neurocognitive scores in early childhood, and there remain significant differences in size. Longer term follow-up will be required to determine whether growth or cognitive differences persist in later child or adulthood, and whether there are any associated longer term metabolic sequelae.

Epigenetics of Skeletal Diseases

PURPOSE OF REVIEW

Epigenetic mechanisms modify gene activity in a stable manner without altering DNA sequence. They participate in the adaptation to the environment, as well as in the pathogenesis of common complex disorders. We provide an overview of the role of epigenetic mechanisms in bone biology and pathology.

RECENT FINDINGS

Extensive evidence supports the involvement of epigenetic mechanisms (DNA methylation, post-translational modifications of histone tails, and non-coding RNAs) in the differentiation of bone cells and mechanotransduction. A variety of epigenetic abnormalities have been described in patients with osteoporosis, osteoarthritis, and skeletal cancers, but their actual pathogenetic roles are still unclear. A few drugs targeting epigenetic marks have been approved for neoplastic disorders, and many more are being actively investigated. Advances in the field of epigenetics underscore the complex interactions between genetic and environmental factors as determinants of osteoporosis and other common disorders. Likewise, they help to explain the mechanisms by which prenatal and post-natal external factors, from nutrition to psychological stress, impact our body and influence the risk of later disease.

Sexual Dimorphism and the Origins of Human Spinal Health

Recent observations indicate that the cross-sectional area (CSA) of vertebral bodies is on average 10% smaller in healthy newborn girls than in newborn boys, a striking difference that increases during infancy and puberty and is greatest by the time of sexual and skeletal maturity. The smaller CSA of female vertebrae is associated with greater spinal flexibility and could represent the human adaptation to fetal load in bipedal posture. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities. This review summarizes the potential endocrine, genetic, and environmental determinants of vertebral cross-sectional growth and current knowledge of the association between the small female vertebrae and greater risk for a broad array of spinal conditions across the lifespan.

Effect of human milk formula with bovine colostrum supplementation on bone mineral density in infant cynomolgus macaques

Insulin-like growth factor 1 (IGF1) is a regulator of human growth during infancy and childhood, known to promote bone and muscle growth as well as lipid accumulation. This study aimed to investigate the effects of formula milk with or without IGF1 supplementation (in the form of pure IGF1 or bovine colostrum) on growth and body composition in infant cynomolgus macaques during the first 6 months of life. Three groups of infants were nursery-reared and received formula milk with or without IGF1 or bovine colostrum supplementation for 4 months, and a fourth group consisting of breast-fed infants was included for comparison (n=6 for each group). Ranked-based analysis of covariance was used to detect differences between adjusted means for sex. No differences in weight, height, fat mass, and fat-free mass could be detected between groups. However, bone mineral density (BMD) was significantly different between groups at the end of formula feeding. Infants that received bovine colostrum supplementation displayed higher mean BMD than infants of all other groups, with no differences between the latter three groups. In conclusion, our results suggest that supplementation with bovine colostrum can enhance BMD in formula-fed infants, an effect that apparently does not depend on IGF1. Bovine colostrum supplementation could be beneficial for long-term bone health in infants with suboptimal bone growth.