Very low birth weight survivors have reduced peak bone mass and reduced insulin sensitivity

[Association between birth conditions and bone mineral density in adults from the 1982 and 1993 birth cohorts in Pelotas, Rio Grande do Sul State, Brazil]

This study assessed the association of birth weight, gestational age, and intrauterine growth with bone mineral density (BMD) at 22 and 30 years of age in the 1982 and 1993 birth cohorts in Pelotas, Rio Grande do Sul State, Brazil. BMD was measured by dual-energy X-ray absorptiometry (DXA) and the association was assessed using analysis of variance. Multiple linear regression was used to control for confounding factors: sex; household income at birth; maternal smoking during pregnancy; maternal schooling; maternal ethnicity/skin color; and pre-pregnancy body mass index. The study tested whether body fat in adulthood was a mediator of the association analyzed, using the G-computation Formula. A total of 6,803 participants from the 1982 and 1993 cohorts were evaluated at 30 and 22 years of age, respectively. Birth weight was associated with BMD at all sites, with a greater difference at the femoral neck. Individuals born weighing less than 2,000g had on average -0.036g/cm2 (95%CI: -0.064; -0.008) of BMD in the femoral neck than individuals weighing more than 3,500g. Individuals with an intrauterine growth z-score at least 1.28 standard deviation below the mean had an average of -0.013g/cm2 (95%CI: -0.024; -0.002) of BMD in the lumbar spine compared with individuals with an above-average z-score. The mediation analysis showed that body fat in adulthood did not mediate the association. Birth conditions have been associated with BMD in adulthood and the identification of early factors related to bone loss is essential due to the demographic inversion that has been taking place in low- and middle-income countries.

Cardiometabolic health in adults born with very low birth weight-a sibling study

BACKGROUND

Preterm survivors have increased risk for impaired cardiometabolic health. We assessed glucose regulation and cardiometabolic biomarkers in adult very low birth weight (VLBW, <1500 g) survivors, using siblings as controls.

METHODS

VLBW-participants were matched with term-born, same-sex siblings. At mean age 29.2 years (SD 3.9), 74 VLBW-adults and 70 siblings underwent a 2-h 75 g oral glucose tolerance test and blood tests for assessment of cardiometabolic biomarkers.

RESULTS

Of participants, 23 (31%) VLBW and 11 (16%) sibling-controls met World Health Organization criteria for impaired glucose regulation (OR adjusted for age and sex 2.5, 95% CI: 1.1 to 5.8). Adjusting for age and sex, VLBW-participants showed 9.2% higher 2-h glucose (95% CI: 0.4% to 18.8%) than their siblings. Also, fasting (13.4%, -0.3% to 29.0%) and 2-h free fatty acids (15.6%, -2.4% to 36.9%) were higher in VLBW-participants. These differences were statistically significant only after further adjusting for confounders. No statistically significant differences were found regarding other measured biomarkers, including insulin resistance, atherogenic lipid profiles or liver tests.

CONCLUSIONS

VLBW-adults showed more impaired fatty acid metabolism and glucose regulation. Differences in cardiometabolic biomarkers were smaller than in previous non-sibling studies. This may partly be explained by shared familial, genetic, or environmental factors.

IMPACT

At young adult age, odds for impaired glucose regulation were 3.4-fold in those born at very low birth weight, compared to same-sex term-born siblings. Taking into consideration possible unmeasured, shared familial confounders, we compared cardiometabolic markers in adults born preterm at very low birth weight with term-born siblings. Prematurity increased risk for impaired glucose regulation, unrelated to current participant characteristics, including body mass index. In contrast to previous studies, differences in insulin resistance were not apparent, suggesting that insulin resistance may partially be explained by factors shared between siblings. Also, common cardiometabolic biomarkers were similar within sibling pairs.

Quantifying Bone Strength Deficits in Young Adults Born Extremely Preterm or Extremely Low Birth Weight

The long-term bone health of young adults born extremely preterm (EP; <28 weeks' gestation) or extremely low birth weight (ELBW; <1000 g birth weight) in the post-surfactant era (since the early 1990s) is unclear. This study investigated their bone structure and estimated bone strength using peripheral quantitative computed tomography (pQCT)-based finite element modeling (pQCT-FEM). Results using this technique have been associated with bone fragility in several clinical settings. Participants comprised 161 EP/ELBW survivors (46.0% male) and 122 contemporaneous term-born (44.3% male), normal birth weight controls born in Victoria, Australia, during 1991-1992. At age 25 years, participants underwent pQCT at 4% and 66% of tibia and radius length, which was analyzed using pQCT-FEM. Groups were compared using linear regression and adjusted for height and weight. An interaction term between group and sex was added to assess group differences between sexes. Parameters measured included compressive stiffness (kcomp ), torsional stiffness (ktorsion ), and bending stiffness (kbend ). EP/ELBW survivors were shorter than the controls, but their weights were similar. Several unadjusted tibial pQCT-FEM parameters were lower in the EP/ELBW group. Height- and weight-adjusted ktorsion at 66% tibia remained lower in EP/ELBW (mean difference [95% confidence interval] -180 [-352, -8] Nm/deg). The evidence for group differences in ktorsion and kbend at 66% tibia was stronger among males than females (pinteractions  <0.05). There was little evidence for group differences in adjusted radial models. Lower height- and weight-adjusted pQCT-FEM measures in EP/ELBW compared with controls suggest a clinically relevant increase in predicted long-term fracture risk in EP/ELBW survivors, particularly males. Future pQCT-FEM studies should utilize the tibial pQCT images because of the greater variability in the radius possibly related to lower measurement precision. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Bone Status and Early Nutrition in Preterm Newborns with and without Intrauterine Growth Restriction

Intrauterine growth restriction (IUGR) together with preterm birth could be harmful to bone health. The aim of the study was to examine bone status in IUGR versus non-IUGR preterms and to analyze the nutritional management best correlated with its improvement. Newborns < 34 weeks of gestational age (wGA), 75 IUGR and 75 non-IUGR, admitted to the Neonatal Intensive Care Unit of the University Hospital of Padova were enrolled and monitored from birth until 36 wGA through anthropometry (weight, length, head circumference, lower limb length (LLL)), biochemistry, bone quantitative ultrasound assessment of bone status (metacarpus bone transmission time, mc-BTT, us) and nutritional intakes monitoring during parenteral nutrition. IUGR compared to non-IUGR showed lower mean mc-BTT (0.45 vs. 0.51, p = 0.0005) and plasmatic phosphate (1.45 vs. 1.79, p < 0.001) at birth. Mc-BTT at 36 wGA, though equal between groups, correlated in IUGR newborns with basal phosphate, mean total energy of the first week and month (positively) and days to reach full enteral feeding (negatively). Lower i.v. vitamin D intake, LLL and prolonged total parenteral nutrition predicted worse mc-BTT at 36 wGA in the enrolled infants. These results suggest that preterms and in particular IUGR newborns need special nutritional care to promote bone development.

Association of Preterm Birth and Low Birthweight with Bone Fractures during Childhood

Preterm birth and low birthweight have been associated with increased fracture risk in children. Our aim was to analyze bone fractures during childhood in preterm, and low-birthweight newborns compared to full-term and normal-birthweight newborns. We conducted a nationwide register-based cohort study in Finland from 1998 to 2017 and utilized the Medical Birth Register and Care Register for Health Care. All newborns alive 28 days after birth were included, and data on all fracture visits in specialized healthcare units were gathered. Incidences per 100,000 person-years with 95% confidence intervals (CI) were calculated, and comparisons were made by incidence rate ratios (IRRs). Kaplan-Meier analysis was used to analyze the timing of fractures during childhood (0-20 years). We included a total of 997,468 newborns and 95,869 fractures; the mean follow-up was 10.0 years, and the overall incidence of fractures was 963 per 100,000 person-years. Very preterm (<32 gestational weeks) newborns had 23% lower fracture incidence than term newborns (IRR 0.77; CI: 0.70-0.85). Preterm newborns (32 to 36 gestational weeks) had a fracture rate (IRR 0.98; CI: 0.95-1.01) similar to that of term newborns. Birthweight showed a linear increase in the fracture rates as newborns with birthweight less than 1000 g had the lowest fracture incidence of 773 per 100,000 person-years and the highest incidence (966 per 100,000 person-years) was among newborns with birthweight 2500 g or more. Children born very preterm or with extremely low birthweight have in general a lower fracture incidence during childhood compared to children born full term and with normal birthweight. These findings possibly reflect, in addition to improvements of neonatal intensive care and early nutrition, the fact that childhood fracture incidences are more dependent on issues other than early life events. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Positive programming of the GC-IGF1 axis mediates adult osteoporosis susceptibility in male offspring rats induced by prenatal dexamethasone exposure

Prenatal dexamethasone exposure (PDE) can lead to offspring long bone dysplasia and continue to postnatal, and this is an important cause of fetal-derived osteoporosis. Studies have confirmed that intrauterine endogenous GC overexposure mediates multiple organ dysplasia and adult-related disease susceptibility in offspring through the glucocorticoid-insulin-like growth factor1 (GC-IGF1) axis. However, it remains unknown if exogenous dexamethasone can regulate bone development in offspring through the GC-IGF1 axis. We determined that the PDE fetal rats exhibited poor osteogenic differentiation, decreased bone mass that continued to adolescence, and increased susceptibility to osteoporosis in adulthood. Concurrently, PDE decreased the serum corticosterone concentration and IGF1 expression in offspring before and after birth, while the increased serum corticosterone concentration induced by chronic stress reversed the inhibition of IGF1 expression induced by PDE. Furthermore, PDE decreased the expression of GRα and miR-130a-5p, increased HDAC4, and decreased H3K27 acetylation in the IGF1 promoter region in bone tissue, and the above changes were negatively compensated after chronic stress. In vitro, a low concentration of corticosterone inhibited the expression of GRα and miR130a-5p, upregulated the expression of HDAC4, inhibited the promoter region H3K27 acetylation, and expression of IGF1 in bone marrow mesenchymal stem cell (BMSCs) osteoblast differentiated cells and inhibited osteogenic differentiation of BMSCs. GRα overexpression, miR-130a-5p mimic treatment, or HDAC4 siRNA exposure reversed the downstream molecular alterations caused by low corticosterone concentrations. In conclusion, PDE-induced intrauterine hypoglucocorticoid exposure could positively program IGF1 expression in bone tissue through the GRα/miR-130a-5p/HDAC4 pathways, thus mediating osteogenic dysdifferentiation and adult osteoporosis susceptibility in male offspring rats.

Outcomes into adulthood of infants born extremely preterm

As survival of infants born extremely preterm increases, more are now reaching adulthood. It is well documented that survivors born extremely preterm experience more developmental delay and disability in multiple domains compared with term-born controls in early childhood and school age. However, with increasing age, health problems involving physical and mental health become more evident. Despite these challenges, it is reassuring that self-reported quality of life remains good. Future directions of research include development of age-appropriate interventions to optimise health and development of individuals born extremely preterm beyond school age.

Early Nutrition during Hospitalization in Relation to Bone Health in Preterm Infants at Term Age and Six Months Corrected Age

Aim: to evaluate the potential association of macronutrient intake in the first postnatal weeks on bone mineral content (BMC) and bone mineral density (BMD) in extremely and very preterm infants. Methods: fifty-eight extremely and very preterm infants were included. Daily macronutrient intake was calculated in g kg⁻¹ day⁻¹ from birth up to 36 weeks postmenstrual age. A dual-energy X-ray absorptiometry whole body scan was used to assess BMC and BMD in preterm infants at term corrected age (TCA) and six months corrected age (CA). Results: fat intake (g kg⁻¹ day⁻¹) in the first four postnatal weeks was positively associated with BMC and BMD at TCA. At six months CA, protein and fat intake (g kg⁻¹ day⁻¹) in the first weeks of life were both individual predictors for BMD. Fat intake (g kg⁻¹ day⁻¹) in the first four postnatal weeks was significantly associated with BMC at six months CA. Conclusion: the association of macronutrient intake in the first postnatal weeks on BMC or BMD, at TCA and six months CA, suggest that early nutritional intervention immediately after birth and during early infancy is important for bone health in the first months of life.

Bone health in young adult survivors born extremely preterm or extremely low birthweight in the post surfactant era

BACKGROUND

Most infants born extremely preterm (EP; <28 weeks' gestation) or extremely low birthweight (ELBW; <1000 g birthweight) in the post surfactant era (early 1990s) are now surviving into adulthood. Preterm birth/low birthweight are risk factors for reduced bone growth and mineralisation in infants and children. However, little is known about their bone health around peak bone mass and through adult life.

OBJECTIVE

To compare bone health (bone mineral measures, bone structure and strength) in young adults born EP/ELBW with controls (>2499 g birthweight), and within the EP/ELBW group examine perinatal and later variables associated with long term bone health.

METHODS

A geographic cohort comprising all 297 survivors born EP/ELBW in 1991-92 in the state of Victoria, Australia, and 260 contemporaneous controls (>2499 g birthweight) were recruited into a longitudinal study from birth. At age 25 years, investigations included dual energy X ray absorptiometry and peripheral quantitative computed tomography to measure bone, muscle and soft tissue variables, and fasting blood samples to measure serum 25 hydroxyvitamin D (25(OH)D) and bone turnover markers (BTM). Linear regression analysis, with models fitted using generalised estimating equations, was used to compare outcomes between groups, adjusting for height and weight.

RESULTS

Compared with controls (n = 129), young adults born EP/ELBW (n = 162) had lower areal bone mineral density (g/cm²) (mean difference [MD] -0.044; 95% confidence interval [CI] -0.076,-0.013) and Z-scores (MD -0.53; 95% CI -0.75, -0.30) in the femoral neck, and lower total hip Z-score (MD -0.35; 95% CI -0.54, -0.15) after adjusting for height and weight. EP/ELBW males generally displayed more bone and soft tissue deficits than females, compared with their respective controls. Within the EP/ELBW group, early growth, male sex, height and lean mass, muscle measures, 25(OH)D levels, and BTM were independently associated with bone mineral measures, structure or strength.

CONCLUSIONS

Young adults born EP/ELBW had evidence of impaired bone health around the age of peak bone mass compared with controls. Further follow-up of the EP/ELBW groups will determine if they have a heightened low-trauma fracture risk in later life.

Low-activity programming of the PDGFRβ/FAK pathway mediates H-type vessel dysplasia and high susceptibility to osteoporosis in female offspring rats after prenatal dexamethasone exposure

Dexamethasone is a common synthetic glucocorticoid drug that can promote foetal lung maturity. An increasing number of studies have shown that prenatal dexamethasone exposure (PDE) can cause a variety of short-term and long-term hazards to offspring, including bone development toxicity. H-type vessels are a newly discovered subtype of blood vessels associated with promoted bone formation and maintenance of bone mass. In this study, we aimed to explore whether H-type blood vessels are involved in PDE-induced long bone development toxicity in offspring and its mechanism. In vivo, we injected dexamethasone (0.2 mg/kg.d) subcutaneously at gestational days 9-20 and observed the H-type vessel abundance and bone mass at different time points in the offspring rats. In vitro, we investigated the effect of dexamethasone (0, 20, 100, and 500 nM) on the tube formation function of rat bone marrow-derived endothelial progenitor cells (EPCs) and explored its mechanism. Our results showed that the adult PDE female offspring rats were susceptible to osteoporosis. In addition, PDE inhibited bone mass, H-type vessel formation and the expression of bone platelet-derived growth factor receptor β (PDGFRβ)/focal adhesion kinase (FAK) pathway-related genes in antenatal and postnatal female offspring. Moreover, PDE promoted the expression of bone glucocorticoid receptor (GR), CCAAT and enhancer binding protein α (C/EBPα) and miR-34c in female foetuses. Dexamethasone suppressed the tube formation of rat bone marrow-derived EPCs and the activity of the PDGFRβ/FAK pathway, which was mediated by GR/C/EBPα/miR-34c signalling activation. In summary, PDE can cause H-type vessel dysplasia and high susceptibility to osteoporosis in female offspring, and its mechanism is related to the low-activity programming of the PDGFRβ/FAK pathway induced by GR/C/EBPα/miR-34c signalling activation. This study enhances the understanding of the molecular mechanism of dexamethasone-induced bone development toxicity and provides new insights for exploring the early intervention and therapeutic targets of foetal-derived osteoporosis.

Preterm Birth as a Risk Factor for Metabolic Syndrome and Cardiovascular Disease in Adult Life: A Systematic Review and Meta-Analysis

OBJECTIVE

To determine if preterm birth is associated with components of the metabolic syndrome in adult life.

STUDY DESIGN

A structured literature search was performed using PubMed. All comparative studies reported metabolic and cardiovascular outcomes in adults (≥18 years of age) born preterm (<37 weeks of gestation) compared with adults born at term (37-42 weeks of gestation) and published through March 2018 were included. The major outcomes assessed were body mass index, waist circumference, waist-to-hip ratio, fat mass, systolic blood pressure (SBP), diastolic blood pressure (DBP), 24-hour SBP, 24-hour DBP, endothelium-dependent brachial artery flow-mediated dilation, carotid intima-media thickness, pulse wave velocity, fasting glucose and insulin, Homeostasis Model Assessment-Estimated Insulin Resistance Index, and lipid profiles. Quality appraisal was performed using a modified version of the Newcastle-Ottawa scale. A meta-analysis was performed for comparable studies which reported sufficient data.

RESULTS

Forty-three studies were included, including a combined total of 18 295 preterm and 294 063 term-born adults. Prematurity was associated with significantly higher fat mass (P = .03), SBP (P < .0001), DBP (P < .0001), 24-hour SBP (P < .001), and 24-hour DBP (P < .001). Furthermore, preterm-born adults presented higher values of fasting glucose (P = .01), insulin (P = .002), Homeostasis Model Assessment-Estimated Insulin Resistance Index (P = .05), and total cholesterol levels (P = .05) in comparison with adults born at term, in random effect models. No statistically significant difference was found between preterm and term-born adults for the other outcomes studied.

CONCLUSIONS

Preterm birth is strongly associated with a number of components of the metabolic syndrome and cardiovascular disease in adult life.

Comparison of physical activity and body composition in a cohort of children born extremely preterm or with extremely low birth weight to matched term-born controls: a follow-up study

OBJECTIVES

To compare physical activity and body composition in a cohort of children born extremely preterm/extremely low birth weight (EP/ELBW) with term-born (TB) controls.

METHODS

A regional cohort of children born during 1999-2000 at gestational age <28 weeks or with birth weight <1000 g and their individually matched TB controls were examined in 2010-2011. Information on physical activity was obtained from parental questionnaires, and body composition was determined by anthropometry and dual X-ray absorptiometry.

RESULTS

Fifty-seven EP/ELBW and 57 TB controls were included at a mean age of 11.6 years. Compared with the TB children, the EP/ELBW-born children exercised less often (22% vs 44% exercised more than 3 days per week), had lower physical endurance and poorer proficiency in sports and play and were less vigorous during exercise (p<0.05). They also had lower values (mean; 95 % CI) for muscle mass (0.9; 0.3-1.5 kg), total bone mineral density z-score (0.30; 0.13-0.52 units) and fat mass ratio (0.14; 0.06-0.21 units). The association between physical activity and bone mineral and skeletal muscle mass accrual was significantly weaker for the EP/ELBW-born than the TB children.

CONCLUSIONS

The EP/ELBW-born children were less physically active, had signs of an unfavourable body composition with less muscle mass and lower bone mineral density than the TB controls. The association between physical activity and the measures of body composition was weaker in the group of EP/ELBW-born children.

Could low birth weight and preterm birth be associated with significant burden of hip osteoarthritis? A systematic review

BACKGROUND

Approaches for the prevention and treatment of hip osteoarthritis (OA) remain limited. There are recent data suggesting that low birth weight (LBW) and preterm birth may be risk factors for hip osteoarthritis. This has the potential to change the current paradigm of hip osteoarthritis prevention by targeting early life factors. The aim of this review was to examine the available evidence for an association of LBW and preterm birth with hip OA. The potential cost implications associated with total hip arthroplasty were also evaluated.

METHODS

Ovid Medline, EMBASE, and Cinahl were searched up until August 2017 using MeSH terms and key words. Methodological quality was evaluated using the National Heart Lung and Blood Institute (NHLBI) quality assessment tool. Qualitative evidence synthesis was performed to summarise the results. Bradford Hill's criteria for causation including the temporal relationship, consistency, strength of the association, specificity, dose-response relationship, and analogy were used to assess the evidence for causation. Economic modelling was used to calculate the potential economic burden associated with LBW or preterm birth related total hip arthroplasty using Australian data from 2012 to 2015.

RESULTS

Five studies, ranging from high to low quality, were included. Hip bone shape abnormalities examined included developmental hip dysplasia and immature hip, and hip osteoarthritis included osteophytes and total hip arthroplasty. A causal link between low birth weight or preterm birth and hip osteoarthritis was found. Of the 30,477 total hip arthroplasties performed for hip osteoarthritis in Australia in 2015, 5791 were estimated to be born preterm and 5273 with low birth weight. This equated to a potential total hip arthroplasty cost of AU$145,136,082 and AU$132,150,222 for these subgroups, respectively.

CONCLUSION

Available data suggest that low birth weight and preterm birth are associated with hip bone shape abnormalities and hip osteoarthritis requiring total hip arthroplasty, with a substantial associated financial burden. Given the current lack of effective treatment and prevention strategies for hip osteoarthritis, this offers a new avenue for reducing the future burden of hip osteoarthritis.

Sex-Specific Skeletal Muscle Fatigability and Decreased Mitochondrial Oxidative Capacity in Adult Rats Exposed to Postnatal Hyperoxia

Premature birth affects more than 10% of live births, and is characterized by relative hyperoxia exposure in an immature host. Long-term consequences of preterm birth include decreased aerobic capacity, decreased muscular strength and endurance, and increased prevalence of metabolic diseases such as type 2 diabetes mellitus. Postnatal hyperoxia exposure in rodents is a well-established model of chronic lung disease of prematurity, and also recapitulates the pulmonary vascular, cardiovascular, and renal phenotype of premature birth. The objective of this study was to evaluate whether postnatal hyperoxia exposure in rats could recapitulate the skeletal and metabolic phenotype of premature birth, and to characterize the subcellular metabolic changes associated with postnatal hyperoxia exposure, with a secondary aim to evaluate sex differences in this model. Compared to control rats, male rats exposed to 14 days of postnatal hyperoxia then aged to 1 year demonstrated higher skeletal muscle fatigability, lower muscle mitochondrial oxidative capacity, more mitochondrial damage, and higher glycolytic enzyme expression. These differences were not present in female rats with the same postnatal hyperoxia exposure. This study demonstrates detrimental mitochondrial and muscular outcomes in the adult male rat exposed to postnatal hyperoxia. Given that young adults born premature also demonstrate skeletal muscle dysfunction, future studies are merited to determine whether this dysfunction as well as reduced aerobic capacity is due to reduced mitochondrial oxidative capacity and metabolic dysfunction.

Bone Accrual in Males with Autism Spectrum Disorder

OBJECTIVE

To test the hypothesis that bone accrual over a 4-year period is reduced in boys with autism spectrum disorder (ASD) compared with typically developing controls.

STUDY DESIGN

Twenty-five boys with ASD and 24 controls were assessed for bone outcomes. Fourteen boys with ASD and 11 controls were assessed both at baseline and after 4 years. The mean subject age was 11.0 ± 1.6 years at study initiation and 14.9 ± 1.6 years at follow-up. Bone mineral density (BMD) was measured at the spine, hip, and whole body using dual-energy X-ray absorptiometry and normalized for age, race, and sex (BMD z-scores). Height adjustments were performed as well. We assessed medical history, physical activity using questionnaires, vitamin D and calcium intake using food records, and serum calcium, phosphorus, 25(OH)-vitamin D, and pubertal hormone levels.

RESULTS

Boys with ASD had lower spine, hip, and whole body BMD z-scores compared with controls. In those subjects assessed both at baseline and after 4 years, bone accrual rates did not differ between the 2 groups; however, spine and hip BMD z-scores remained lower in the boys with ASD than in controls at follow-up. Notably, the ASD group was less physically active at both time points.

CONCLUSION

Although pubertal bone accrual was similar to that in controls, BMD in children with ASD remained low over a 4-year follow-up period, suggesting that low BMD is a consequence of prepubertal factors, such as low physical activity. Studies are needed to investigate the causes and consequences of decreased BMD, to assess BMD in females and adults with ASD, and to evaluate therapeutic interventions.

Diurnal Cortisol Patterns and Dexamethasone Suppression Test Responses in Healthy Young Adults Born Preterm at Very Low Birth Weight

Background

Early life stress, such as painful and stressful procedures during neonatal intensive care after preterm birth, can permanently affect physiological, hormonal and neurobiological systems. This may contribute to altered programming of the hypothalamic-pituitary-adrenal axis (HPAA) and provoke changes in HPAA function with long-term health impacts. Previous studies suggest a lower HPAA response to stress in young adults born preterm compared with controls born at term. We assessed whether these differences in HPAA stress responsiveness are reflected in everyday life HPAA functioning, i.e. in diurnal salivary cortisol patterns, and reactivity to a low-dose dexamethasone suppression test (DST), in unimpaired young adults born preterm at very low birth weight (VLBW; <1500 g).

Methods

The participants were recruited from the Helsinki Study of Very Low Birth Weight Adults cohort study. At mean age 23.3 years (2.1 SD), 49 VLBW and 36 controls born at term participated in the study. For cortisol analyzes, saliva samples were collected on two consecutive days at 0, 15, 30 and 60 min after wake-up, at 12:00 h, 17:00 h and 22:00 h. After the last salivary sample of the first study day the participants were instructed to take a 0.5 mg dexamethasone tablet.

Results

With mixed-effects model no difference was seen in overall diurnal salivary cortisol between VLBW and control groups [13.9% (95% CI: -11.6, 47.0), P = 0.31]. Salivary cortisol increased similarly after awakening in both VLBW and control participants [mean difference -2.9% (29.2, 33.0), P = 0.85]. Also reactivity to the low-dose DST (awakening cortisol ratio day2/day1) was similar between VLBW and control groups [-1.1% (-53.5, 103.8), P = 0.97)].

Conclusions

Diurnal cortisol patterns and reactivity to a low-dose DST in young adulthood were not associated with preterm birth.

Preterm Children Born Small for Gestational Age are at Risk for Low Adult Bone Mass

Cross-sectional studies suggest that premature birth and low birth weight may both be associated with low peak bone mass. We followed bone traits in preterm individuals and controls for 27 years and examined the effects of birth weight relative to gestational age [stratified as small for gestational age (SGA) or appropriate for gestational (AGA)] on adult bone mineral density (BMD). We measured distal forearm BMC (g/cm) and BMD (g/cm(2)) with single-photon absorptiometry (SPA) in 46 preterm children (31 AGA and 15 SGA) at mean age 10.1 years (range 4-16) and in 84 healthy age-matched children. The measurements were repeated 27 years later with the same SPA apparatus but then also with dual energy absorptiometry and peripheral computed tomography (pQCT). Preterm individuals were shorter (p = 0.03) in adulthood than controls. Preterm AGA individuals had similar BMC and BMD height-adjusted Z-scores in adulthood compared to controls. Preterm SGA individuals had lower distal forearm BMC and BMD height-adjusted Z-scores in adulthood than both controls and preterm AGA individuals. Preterm SGA individuals had lower gain from childhood to adulthood in distal forearm BMC height-adjusted Z-scores than controls (p = 0.03). The deficits in preterm SGA individuals in adulthood were also captured by DEXA in height-adjusted femoral neck (FN) BMC Z-score and height-adjusted FN BMD Z-score and by pQCT in tibial cross-sectional area (CSA) Z-score and stress strain index (SSI) Z-score, where all measurements were lower than controls (all p values <0.05). Preterm SGA individuals are at increased risk of reaching low adult bone mass, at least partly due to a deficit in the accrual of bone mineral during growth. In our cohort, we were unable to find a similar risk in preterm AGA individuals.

Impact of intra- and extrauterine growth on bone mineral density and content in the neonatal period of very-low-birth-weight infants

BACKGROUND

Very-low-birthweight infants (VLBWIs) are at high risk for suboptimal bone mineral density (BMD) and bone mineral content (BMC). Small-for-gestational-age (SGA) status also causes reduced bone mineralization in full-term infants. However, the impact of intrauterine and postnatal extrauterine growth on BMD and BMC in VLBWIs is inconclusive.

METHODS

We retrospectively investigated n=68 VLBWIs, comprising 45 appropriate-for-gestational-age (AGA) and 23 SGA infants who underwent lumbar spine dual-energy X-ray absorptiometry at term-equivalent age.

RESULTS

BMD and BMC did not differ between AGA and SGA VLBWIs. Subgroup analyses of infants with birthweight<1000 g vs 1000-1500 g, and GA<27 weeks vs ≥ 27 weeks also showed no differences in BMD and BMC between AGA and SGA infants. In contrast, infants with extrauterine growth restriction (EUGR) showed significantly lower values than those without (BMD: 0.124 ± 0.023 vs 0.141 ± 0.032 g/cm(2), P=0.02; BMC: 0.80 ± 0.26 vs 0.94 ± 0.23 g, P=0.04). There were no differences between AGA and SGA infants with EUGR. However, in the AGA cohort, infants with EUGR showed significantly lower values than those without (BMD: 0.121 ± 0.022; 0.141 ± 0.03 g/cm(2), P=0.02; BMC: 0.73 ± 0.23 vs 0.94 ± 0.23 g, P=0.005). Multiple regression analyses showed GA, weight and head circumference at birth, and weight percentile at term correlated with term BMD. Conversely, only weight percentile at term significantly correlated with term BMC.

CONCLUSION

EUGR, rather than IUGR, is a risk factor for reduced BMD and BMC in the neonatal period in VLBWIs.

Intergenerational transmission of the healthy immigrant effect (HIE) through birth weight: A systematic review and meta-analysis

This review examines intergenerational differences in birth weight among children born to first-generation and second-generation immigrant mothers and the extent to which they vary by country of origin and receiving country. We searched MEDLINE, EMBASE, Web of Science, PubMed, and ProQuest from inception to October 2014 for articles that recorded the mean birth weight (in grams) or odds of low birth weight (LBW) of children born to immigrant mothers and one subsequent generation. Studies were analyzed descriptively and meta-analyzed using Review Manager 5.3 software. We identified 10 studies (8 retrospective cohort and 2 cross-sectional studies) including 158,843 first and second-generation immigrant women. The United States and the United Kingdom represented the receiving countries with the majority of immigrants originating from Mexico and South Asia. Six studies were meta-analyzed for mean birth weight and seven for low birth weight. Across all studies, there was found to be no statistically significant difference in mean birth weight between first and second-generation children. However, the odds of being LBW were 1.21 [95% CI, 1.15, 1.27] times greater among second-generation children. Second-generation children of Mexican descent in particular were at increased odds of LBW (OR = 1.47 [95% CI, 1.28, 1.69]). In the United States, second-generation children were at 34% higher odds of being LBW (OR = 1.34 [95% CI, 1.13, 1.58]) when compared to their first-generation counterparts. This effect was slightly smaller in the United Kingdom (OR = 1.18 [95% CI, 1.13, 1.23]). In conclusion, immigration to a new country may differentially influence low birth weight over generations, depending on the mother's nativity and the country she immigrates to.

Association of low birth weight and preterm birth with the incidence of knee and hip arthroplasty for osteoarthritis

OBJECTIVE

Low birth weight (LBW) and preterm birth have been associated with adverse adult outcomes, including hypertension, insulin resistance, cardiovascular disease, and reduced bone mass. It is unknown whether LBW and preterm birth affect the risk of osteoarthritis (OA). This study aims to examine whether LBW and preterm birth were associated with the incidence of knee and hip arthroplasty for OA.

METHODS

A total of 3,604 participants of the Australian Diabetes, Obesity and Lifestyle Study who reported their birth weight and history of preterm birth and were age >40 years at the commencement of arthroplasty data collection comprised the study sample. The incidence of knee and hip replacement for OA during 2002-2011 was determined by linking cohort records to the Australian Orthopaedic Association National Joint Replacement Registry.

RESULTS

One hundred and sixteen participants underwent knee arthroplasty and 75 underwent hip arthroplasty for OA. LBW (yes versus no; hazard ratio [HR] 2.04, 95% confidence interval [95% CI] 1.11-3.75, P = 0.02) and preterm birth (yes versus no; HR 2.50, 95% CI 1.29-4.87, P = 0.007) were associated with increased incidence of hip arthroplasty independent of age, sex, body mass index, education level, hypertension, diabetes mellitus, smoking, and physical activity. No significant association was observed for knee arthroplasty.

CONCLUSION

Although these findings will need to be confirmed, they suggest that individuals born with LBW or at preterm are at increased risk of hip arthroplasty for OA in adult life. The underlying mechanisms warrant further investigation.

Is very preterm birth a risk factor for adult cardiometabolic disease?

The first infants to experience modern pre- and neonatal care are now in their thirties, an age at which the incidence of cardiometabolic disease is low. However, data from cohorts born preterm prior to the introduction of modern care suggest an increased risk of type 2 diabetes. For young adult cohorts of former very small or very preterm infants, there is accumulating evidence of increased risk factors for later cardiovascular disease, including higher blood pressure, lower lean body mass, impaired glucose regulation, and perhaps a more atherogenic lipid profile. Regarding lifestyle, adults born very small or very preterm undertake less non-conditioning physical activity and may have a lower intake of fruit and milk products. Any intervention reducing risk factors, in particular blood pressure and low physical activity, would have a substantial potential to reduce the lifetime disease burden in small preterm infants. There are now enough data to warrant an expert evaluation of the level of evidence for cardiometabolic disease in individuals born very small or very preterm, which has possible public health implications.

Birth weight and adult bone metabolism are unrelated: results from birth weight-discordant monozygotic twins

Low birth weight (BW) has been associated with poor bone health in adulthood. The aim of this study was to investigate the association between BW and bone mass and metabolism in adult BW-discordant monozygotic (MZ) twins. A total of 153 BW-extremely discordant MZ twin pairs were recruited from the Danish Twin Registry. Serum vitamin D (25-hydroxyvitamin D [25OHD]) and bone turnover markers (BTMs) amino-terminal propeptide of type I procollagen (P1NP), pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (1CTP), and cross-linked C-telopeptide (CTX) were quantified. Femoral neck (FN), total hip (TH), lumbar spine (LS), and whole-body (WB) bone mineral density (BMD) (ie, FN-BMD, TH-BMD, LS-BMD, and WB-BMD, respectively) were measured using dual-energy X-ray absorptiometry (DXA). Twins were studied as single individuals using regression analyses with or without adjustment for height, weight, age, sex, and intrapair correlation. Within-pair differences were assessed using Student's t test and fixed-regression models. BW was not associated with BTMs, LS-BMD, TH-BMD, FN-BMD, or WB-BMD, but BW was associated with WB-BMC, and WB-Area after adjustments. Compared to the co-twin, twins with the highest BW were heavier and taller in adulthood (mean differences ± SD): 3.0 ± 10.5 kg; 1.6 ± 2.6 cm; both p < 0.001). Within-pair analyses showed that LS-BMD, TH-BMD, and FN-BMD tended to be higher in twins with highest BW (for all: mean difference 0.01 ± 0.1 g/cm(2) ; p = 0.08, 0.05, and 0.10, respectively). No difference was observed after adjustment for adult body size. Intrapair differences in BW were not associated with differences in any of the biochemical parameters or BMD. Small differences between twins in BMD were explained by dissimilarities in body size. These results suggest that BW and adult bone metabolism are unrelated.

Maternal preeclampsia and bone mineral density of the adult offspring

OBJECTIVE

Preterm birth at very low birthweight (<1500 g) is associated with cardiometabolic risk factors and reduced bone mineral density in the adult offspring. Preeclampsia is a frequent cause of preterm birth and is also associated with cardiometabolic risk factors in the offspring. Whether it is associated with bone mineral density is not known.

STUDY DESIGN

We evaluated skeletal health in participants of the Helsinki Study of Very Low Birthweight Adults: 144 born at very low birthweight and 139 born at term. From the very low birthweight and term offspring a respective 32 and 11 were born from pregnancy complicated by preeclampsia. We measured bone mineral density at age 18.5 to 27.1 years by dual X-ray absorptiometry.

RESULTS

Very low birthweight adults exposed to maternal preeclampsia had higher lumbar spine Z score (mean -0.44, compared with -1.07 in very low birthweight unexposed adults, P = .002), femoral neck Z score (-0.05 vs -0.53, P = .003) and whole body bone mineral density Z score (-0.14 vs -0.72, P = .001). Corresponding Z scores for those born at term were -0.02 (preeclampsia) and -0.45 (no preeclampsia) for lumbar spine (P = .2), 0.78 and 0.08 for femoral neck (P = .02) and 0.02 and -0.31 for whole body bone mineral density Z score (P = .08). The results survived adjustment for offspring current height, body mass index, leisure time physical activity, socioeconomic position, smoking, and maternal smoking during pregnancy, and maternal prepregnancy body mass index.

CONCLUSION

Young adults exposed to maternal preeclampsia have higher bone mineral density than those not exposed. This difference is seen among those born at very low birthweight and seems also to be present among those born at term.

Maternal birthweight is associated with subsequent risk of vitamin D deficiency in early pregnancy

BACKGROUND

Maternal low birthweight and vitamin D deficiency in pregnancy are associated with a similar spectrum of adverse pregnancy outcomes including pre-eclampsia and gestational diabetes. However, the relationship between maternal birthweight and subsequent vitamin D concentrations in early pregnancy is largely unknown.

METHODS

We assessed whether self-reported maternal birthweight was associated with risk of early pregnancy vitamin D deficiency (≤20 ng/mL) among a pregnancy cohort (n = 658). Serum 25-hydroxyvitamin D [25(OH)D] was measured using liquid chromatography-tandem mass spectroscopy.

RESULTS

Adjusting for maternal characteristics and month of blood draw, a 100-g higher maternal birthweight was associated with a 5.7% decreased risk of early pregnancy 25(OH)D deficiency [odds ratio (OR) = 0.94; 95% confidence interval (CI) 0.90, 0.99]. Low-birthweight (<2500 g) women were 3.7 times as likely to have early pregnancy 25(OH)D deficiency compared with normal-birthweight women [OR = 3.69; 95% CI 1.63, 8.34]. These relationships were not modified by either pre-pregnancy overweight status [body mass index (BMI) ≥25 kg/m(2)] or adulthood weight trajectory (BMI change ≥2 kg/m(2) from age 18 to pre-pregnancy).

CONCLUSIONS

Further research on shared developmental mechanisms that determine birthweight and vitamin D homeostasis may help identify targets and related preventative measures for adverse pregnancy and birth outcomes.

Total and carboxylated osteocalcin associate with insulin levels in young adults born with normal or very low birth weight

OBJECTIVE

Osteocalcin (OC), a bone-derived protein, has been implicated in the regulation of glucose and energy metabolism. Young adults born with very low birth weight (VLBW) have altered glucose regulation and lower bone mineral density (BMD) compared with those born at term. The aim of this study was to explore the association between bone and glucose metabolism in healthy young adults born prematurely or at term.

METHODS

The cohort of this cross-sectional study comprised 332 non-diabetic young adults (age 18 to 27 years) born either preterm with VLBW (n = 163) or at term (n = 169). OC, carboxylated osteocalcin (cOC) and markers of glucose metabolism were measured at fasting and after a 75-g oral glucose tolerance test (OGTT).

RESULTS

VLBW adults were shorter, had lower BMD (p<0.001) and higher fasting OC (p = 0.027) and cOC (p = 0.005) than term-born subjects. They also had higher 2-hour insulin (p = 0.001) and glucose (p = 0.037) concentrations. OGTT induced a significant reduction in OC (p<0.001), similar in both groups. OC reduction was not associated with OGTT-induced increases in insulin (p = 0.54). However, fasting total OC and cOC correlated negatively with fasting insulin after adjustment for age, gender, BMD and VLBW status (r = -0.182, p = 0.009 and r = -0.283, p<0.001, respectively).

CONCLUSION

Adults born with VLBW have higher OC and cOC than their peers born at term. This may in part reflect the mechanisms that underlie their lower BMD and decreased insulin sensitivity. Serum OC appears to be negatively associated with long-term glucose regulation whereas acute changes during OGTT may be mediated via other mechanisms.

A temporary decrease in mineral density in perinatal mouse long bones

Fetal and postnatal bone development in humans is traditionally viewed as a process characterized by progressively increasing mineral density. Yet, a temporary decrease in mineral density has been described in the long bones of infants in the immediate postnatal period. The mechanism that underlies this phenomenon, as well as its causes and consequences, remain unclear. Using daily μCT scans of murine femora and tibiae during perinatal development, we show that a temporary decrease in tissue mineral density (TMD) is evident in mice. By monitoring spatial and temporal structural changes during normal growth and in a mouse strain in which osteoclasts are non-functional (Src-null), we show that endosteal bone resorption is the main cause for the perinatal decrease in TMD. Mechanical testing revealed that this temporary decrease is correlated with reduced stiffness of the bones. We also show, by administration of a progestational agent to pregnant mice, that the decrease in TMD is not the result of parturition itself. This study provides a comprehensive view of perinatal long bone development in mice, and describes the process as well as the consequences of density fluctuation during this period.

Small-for-gestational-age preterm-born infants already have lower bone mass during early infancy

BACKGROUND

In preterm-born infants, low birth weight and diminished bone accretion deteriorate peak bone mass. Whether low birth weight is already associated with decreased bone mass during infancy is unknown.

OBJECTIVE

To study the effect of birth weight on bone accretion between term age (40 weeks postmenstrual age) and six months post-term in preterm-born infants.

DESIGN

In 139 preterm-born infants (51% male, gestational age 30.3±1.5 weeks, birth weight 1341±288g) weight and whole-body bone mineral content (BMC, gram) were measured at term age and six months post-term. At birth, infants were small-for-gestational-age (SGA, n=33, weight and/or length<-2 SDS) or appropriate-for-gestational-age (AGA, n=98, weight and length≥-2 SDS).

RESULTS

At term age and six months post-term, BMC adjusted for gender and gestational age was lower in SGA than AGA infants (term age: 38.1±9.5 versus 48.6±10.1g, β=-0.26, 95% CI -0.37; -0.16, p<0.001; six months: 130.1±25.7 versus 145.4±22.9g, β=-0.16, 95% CI -0.25; -0.08, p<0.001). At six months post-term, BMC remained lower in SGA infants after adjustment for actual weight and length. Between term age and six months post-term, BMC gain adjusted for gender and gestational age was lower in SGA than AGA infants (91.7±22.8 versus 98.2±20.7g; β=-0.12, 95% CI -0.24; -0.003, p=0.044). BMC gain remained lower in SGA infants after adjustment for weight and length gain.

CONCLUSION

The first six months post-term, SGA preterms have lower bone accretion, independent of body size, suggesting that prenatal conditions for bone accretion cannot be replicated postnatally.

The clinical need for a method of identification of embryos destined to become a blastocyst in assisted reproductive technology cycles

PURPOSE

To provide a rationale for continuation of efforts to improve the outcome of Assisted Reproductive Technology outcomes, thereby increasing the likelihood of the live birth of healthy neonates.

METHODS

Description of rationale and a framework leading to improvement in Assisted Reproductive Technology outcomes.

RESULTS

The opportunity for improvement in the success rate for Assisted Reproductive Technology outcome is predicated on selection of the highest quality embryo(s) for transfer. However, such approaches must be balanced by a limit to the number of embryos transferred so as to reduce the risk for multiple births and particularly higher order multiple gestations. Blastocyst transfer offers one such successful approach, but is confounded by suggestions of an increased risk of both pregnancy complications and epigenetic disorders.

CONCLUSION

There is a need for development of approaches which, individually or in combination, may assist in the early detection of embryos destined to develop into blastocysts.