Telomere Biology and Human Phenotype

Telomeres are nucleoprotein structures that cap the end of each chromosome arm and function to maintain genome stability. The length of telomeres is known to shorten with each cell division and it is well-established that telomere attrition is related to replicative capacity in vitro. Moreover, telomere loss is also correlated with the process of aging in vivo. In this review, we discuss the mechanisms that lead to telomere shortening and summarise telomere homeostasis in humans throughout a lifetime. In addition, we discuss the available evidence that shows that telomere shortening is related to human aging and the onset of age-related disease

Direct Single-Cell Analysis of Human Polar Bodies and Cleavage-Stage Embryos Reveals No Evidence of the Telomere Theory of Reproductive Ageing in Relation to Aneuploidy Generation

Reproductive ageing in women, particularly after the age of 35, is associated with an exponential increase in the proportion of chromosomally abnormal oocytes produced. Several hypotheses have attempted to explain this observation, including the ‘limited oocyte pool’ hypothesis and the ‘two-hit’ hypothesis, the latter explaining that a depletion in oocyte quality with age results from the multiple opportune stages for errors to occur in meiosis. Recently however, the telomere theory of reproductive ageing in women has been proposed. This suggests that shortened telomeres in oocytes of women of advanced maternal age render oocytes unable to support fertilization and embryogenesis. Despite a credible rationale for the telomere theory of reproductive ageing in women, very few studies have assessed telomere length directly in human oocytes or preimplantation embryos. Therefore, we directly assessed relative telomere length in first polar bodies and blastomeres from cleavage stage (day 3) embryos. In both cell types we tested the hypothesis that (1) older women have shorter telomeres and (2) chromosomally abnormal (aneuploid) gametes/embryos have shorter telomeres. In all cases, we found no evidence of altered telomere length associated with age-related aneuploidy

Late onset vitamin K deficiency bleeding, extreme prematurity and a human milk based diet

An extremely preterm female infant (born at 23+5 weeks; weight 555g) received 0.4mg/kg IM Vitamin K1 (VK). She received an exclusively human milk-based diet and was commenced on a commercially available human-milk fortifier

Less-invasive surfactant administration for neonatal respiratory distress syndrome: a consensus guideline

Introduction: Less-invasive surfactant administration (LISA) is a method of surfactant delivery to preterm infants for treating respiratory distress syndrome (RDS), which can reduce the composite risk of death or bronchopulmonary dysplasia and the time on mechanical ventilation. Methods: A systematic literature search of studies published up to April 2021 on minimally invasive catheter surfactant delivery in preterm infants with RDS was conducted. Based on these studies, with parental feedback sought via an online questionnaire, 9 UK-based specialists in neonatal respiratory disease developed their consensus for implementing LISA. Recommendations were developed following a modified, iterative Delphi process using a questionnaire employing a 9-point Likert scale and an a priori level of agreement/disagreement. Results: Successful implementation of LISA can be achieved by training the multidisciplinary team and following locally agreed guidance. From the time of the decision to administer surfactant, LISA should take <30 min. The comfort of the baby and requirements to maintain non-invasive respiratory support are important. While many infants can be managed without requiring additional sedation/analgesia, fentanyl along with atropine may be considered. Parents should be provided with sufficient information about medication side effects and involved in treatment discussions. Conclusions: LISA has the potential to improve outcomes for preterm infants with RDS and can be introduced as a safe and effective part of UK-based neonatal care with appropriate training

Preterm infants have significantly longer telomeres than their term born counterparts

There are well-established morbidities associated with preterm birth including respiratory, neurocognitive and developmental disorders. However several others have recently emerged that characterise an `aged' phenotype in the preterm infant by term-equivalent age. These include hypertension, insulin resistance and altered body fat distribution. Evidence shows that these morbidities persist into adult life, posing a significant public health concern. In this study, we measured relative telomere length in leukocytes as an indicator of biological ageing in 25 preterm infants at term equivalent age. Comparing our measurements with those from 22 preterm infants sampled at birth and from 31 term-born infants, we tested the hypothesis that by term equivalent age, preterm infants have significantly shorter telomeres (thus suggesting that they are prematurely aged). Our results demonstrate that relative telomere length is highly variable in newborn infants and is significantly negatively correlated with gestational age and birth weight in preterm infants. Further, longitudinal assessment in preterm infants who had telomere length measurements available at both birth and term age (n = 5) suggests that telomere attrition rate is negatively correlated with increasing gestational age. Contrary to our initial hypothesis however, relative telomere length was significantly shortest in the term born control group compared to both preterm groups and longest in the preterm at birth group. In addition, telomere lengths were not significantly different between preterm infants sampled at birth and those sampled at term equivalent age. These results indicate that other, as yet undetermined, factors may influence telomere length in the preterm born infant and raise the intriguing hypothesis that as preterm gestation declines, telomere attrition rate increases

Enteral lactoferrin supplementation for very preterm infants : a randomised placebo-controlled trial

Background: Infections acquired in hospital are an important cause of morbidity and mortality in very preterm infants. Several small trials have suggested that supplementing the enteral diet of very preterm infants with lactoferrin, an antimicrobial protein processed from cow's milk, prevents infections and associated complications. Methods: In this randomised, placebo-controlled trial, very preterm infants (born before 32 weeks' gestation) in 37 UK hospitals were allocated randomly (1:1) within 72 hours after birth to receive enteral bovine lactoferrin (150 mg/kg/day; maximum 300 mg/day) versus sucrose (same dose) once daily until 34 weeks' postmenstrual age. Web-based randomisation minimised for recruitment site, gestation (completed weeks), sex, and single versus multifetal pregnancy. Parents, caregivers and outcomes assessors were unaware of group assignment. The primary outcome was microbiologically-confirmed or clinically-suspected lateonset infection (occurring >72 hours after birth). The trial was registered with the International Standard Randomised Controlled Trial Number 88261002. Findings: We recruited 2203 participants between May 2014 and September 2017. Four infants had consent withdrawn or unconfirmed leaving 1098 infants in the lactoferrin group and 1101 in the sucrose group. Primary outcome data for 2182 infants were available for inclusion in the intention-to-treat analyses. In the intervention group, 316/1093 (28.9%) infants acquired a late-onset infection versus 334/1089 (30.7%) in the control group: risk ratio (RR) adjusted for minimisation factors 0.95 (95% confidence interval [CI] 0.86, 1.04). Pre-specified subgroup analyses did not show statistically significant interactions for gestation at birth (completed weeks') or type of enteral milk received (human, formula, or both). Interpretation: Enteral supplementation with bovine lactoferrin does not reduce the incidence of late-onset infection in very preterm infants. Funding: UK National Institute for Health Research Health Technology Assessment programme (10/57/49)

Enteral lactoferrin supplementation for very preterm infants : a randomised placebo-controlled trial

Background: Infections acquired in hospital are an important cause of morbidity and mortality in very preterm infants. Several small trials have suggested that supplementing the enteral diet of very preterm infants with lactoferrin, an antimicrobial protein processed from cow's milk, prevents infections and associated complications. Methods: In this randomised, placebo-controlled trial, very preterm infants (born before 32 weeks' gestation) in 37 UK hospitals were allocated randomly (1:1) within 72 hours after birth to receive enteral bovine lactoferrin (150 mg/kg/day; maximum 300 mg/day) versus sucrose (same dose) once daily until 34 weeks' postmenstrual age. Web-based randomisation minimised for recruitment site, gestation (completed weeks), sex, and single versus multifetal pregnancy. Parents, caregivers and outcomes assessors were unaware of group assignment. The primary outcome was microbiologically-confirmed or clinically-suspected lateonset infection (occurring >72 hours after birth). The trial was registered with the International Standard Randomised Controlled Trial Number 88261002. Findings: We recruited 2203 participants between May 2014 and September 2017. Four infants had consent withdrawn or unconfirmed leaving 1098 infants in the lactoferrin group and 1101 in the sucrose group. Primary outcome data for 2182 infants were available for inclusion in the intention-to-treat analyses. In the intervention group, 316/1093 (28.9%) infants acquired a late-onset infection versus 334/1089 (30.7%) in the control group: risk ratio (RR) adjusted for minimisation factors 0.95 (95% confidence interval [CI] 0.86, 1.04). Pre-specified subgroup analyses did not show statistically significant interactions for gestation at birth (completed weeks') or type of enteral milk received (human, formula, or both). Interpretation: Enteral supplementation with bovine lactoferrin does not reduce the incidence of late-onset infection in very preterm infants. Funding: UK National Institute for Health Research Health Technology Assessment programme (10/57/49)

Pregnancy and neonatal outcomes of COVID-19: The PAN-COVID study

Objective To assess perinatal outcomes for pregnancies affected by suspected or confirmed SARS-CoV-2 infection. Methods Prospective, web-based registry. Pregnant women were invited to participate if they had suspected or confirmed SARS-CoV-2 infection between 1st January 2020 and 31st March 2021 to assess the impact of infection on maternal and perinatal outcomes including miscarriage, stillbirth, fetal growth restriction, pre-term birth and transmission to the infant. Results Between April 2020 and March 2021, the study recruited 8239 participants who had suspected or confirmed SARs-CoV-2 infection episodes in pregnancy between January 2020 and March 2021. Maternal death affected 14/8197 (0.2%) participants, 176/8187 (2.2%) of participants required ventilatory support. Pre-eclampsia affected 389/8189 (4.8%) participants, eclampsia was reported in 40/ 8024 (0.5%) of all participants. Stillbirth affected 35/8187 (0.4 %) participants. In participants delivering within 2 weeks of delivery 21/2686 (0.8 %) were affected by stillbirth compared with 8/4596 (0.2 %) delivering ≥ 2 weeks after infection (95 % CI 0.3–1.0). SGA affected 744/7696 (9.3 %) of livebirths, FGR affected 360/8175 (4.4 %) of all pregnancies. Pre-term birth occurred in 922/8066 (11.5%), the majority of these were indicated pre-term births, 220/7987 (2.8%) participants experienced spontaneous pre-term births. Early neonatal deaths affected 11/8050 livebirths. Of all neonates, 80/7993 (1.0%) tested positive for SARS-CoV-2. Conclusions Infection was associated with indicated pre-term birth, most commonly for fetal compromise. The overall proportions of women affected by SGA and FGR were not higher than expected, however there was the proportion affected by stillbirth in participants delivering within 2 weeks of infection was significantly higher than those delivering ≥ 2 weeks after infection. We suggest that clinicians’ threshold for delivery should be low if there are concerns with fetal movements or fetal heart rate monitoring in the time around infection

The influence of nutrition on the preterm phenotype at term

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