Mary J. Berry

Docosahexaenoic Acid and Bronchopulmonary Dysplasia in Preterm Infants

BACKGROUND Studies in animals and in humans have suggested that docosahexaenoic acid (DHA), an n‐3 long‐chain polyunsaturated fatty acid, might reduce the risk of bronchopulmonary dysplasia, but appropriately designed trials are lacking. METHODS We randomly assigned 1273 infants born before 29 weeks of gestation (stratified according to sex, gestational age [<27 weeks or 27 to <29 weeks], and center) within 3 days after their first enteral feeding to receive either an enteral emulsion providing DHA at a dose of 60 mg per kilogram of body weight per day or a control (soy) emulsion without DHA until 36 weeks of postmenstrual age. The primary outcome was bronchopulmonary dysplasia, defined on a physiological basis (with the use of oxygen‐saturation monitoring in selected infants), at 36 weeks of postmenstrual age or discharge home, whichever occurred first. RESULTS A total of 1205 infants survived to the primary outcome assessment. Of the 592 infants assigned to the DHA group, 291 (49.1% by multiple imputation) were classified as having physiological bronchopulmonary dysplasia, as compared with 269 (43.9%) of the 613 infants assigned to the control group (relative risk adjusted for randomization strata, 1.13; 95% confidence interval [CI], 1.02 to 1.25; P=0.02). The composite outcome of physiological bronchopulmonary dysplasia or death before 36 weeks of postmenstrual age occurred in 52.3% of the infants in the DHA group and in 46.4% of the infants in the control group (adjusted relative risk, 1.11; 95% CI, 1.00 to 1.23; P=0.045). There were no significant differences between the two groups in the rates of death or any other neonatal illnesses. Bronchopulmonary dysplasia based on a clinical definition occurred in 53.2% of the infants in the DHA group and in 49.7% of the infants in the control group (P=0.06). CONCLUSIONS Enteral DHA supplementation at a dose of 60 mg per kilogram per day did not result in a lower risk of physiological bronchopulmonary dysplasia than a control emulsion among preterm infants born before 29 weeks of gestation and may have resulted in a greater risk. (Funded by the Australian National Health and Medical Research Council and others; Australian New Zealand Clinical Trials Registry number, ACTRN12612000503820.)

Antenatal corticosteroid exposure at term increases adult adiposity: an experimental study in sheep.

Clinical practice guidelines for elective cesarean section at early‐term gestation (37–38 weeks) recommend antenatal corticosteroids to reduce neonatal respiratory morbidity. However, the long‐term health implications for offspring exposed to corticosteroids at term are unknown and may differ from the effects of preterm corticosteroid exposure. We therefore randomized singleton‐bearing ewes (n = 64) to receive a clinically relevant dose of corticosteroids at term or no treatment. Body composition was assessed in adult offspring using dual‐energy X‐ray absorptiometry. Relative to skeletal size female, but not male, offspring of steroid‐treated ewes had increased weight and a greater fat mass than controls (relative weight: 49.1 ± 1.1 vs. 52.9 ± 1.2 kg/m2, p = 0.02; relative fat mass: 5.4 ± 0.7 vs. 3.4 ± 0.7 kg/m2, p = 0.04). Whether corticosteroid exposure at early‐term gestation increases adult adiposity in humans is unknown and needs further investigation.

Long-term effects of preterm birth on behavior and neurosteroid sensitivity in the guinea pig

Background:Ex-preterm children and adolescents are at risk of developing late-onset neurodevelopmental and behavioral disorders. The mechanisms by which this happens are poorly understood and relevant animal models are required.Methods:Ex-preterm (delivered at 62 d gestation) and term (spontaneously delivered) juvenile guinea pigs underwent behavioral testing at 25 d corrected postnatal age, with tissues collected at 28 d. Neurodevelopmental markers (myelin basic protein (MBP) and glial fibrillary acidic protein (GFAP)) were analyzed in the hippocampus and subcortical white matter by immunohistochemistry. Gamma-aminobutyric acid A (GABAA) receptor subunit mRNA levels were quantified by reverse transcription polymerase chain reaction (RT-PCR), and salivary cortisol measured by enzyme-linked immunosorbent assay.Results:Preterm males travelled greater distances, were mobile for longer, spent more time investigating objects, and approached or interacted with familiar animals more than controls. Myelination and reactive astrocyte coverage was lower in the hippocampus and the subcortical white matter in preterm males. Hippocampal levels of the α5 subunit were also lower in the preterm male brain. Baseline salivary cortisol was higher for preterm males compared to controls.Conclusion:We conclude that juvenile ex-preterm male guinea pigs exhibit a hyperactive phenotype and feature impaired neurodevelopment, making this a suitable model for future therapeutic studies.

Premature guinea pigs: a new paradigm to investigate the late-effects of preterm birth

Preterm birth is common and the associated short-term morbidity well described. The adult-onset consequences of preterm birth are less clear, but cardiovascular and metabolic health may be adversely affected. Although large animal models of preterm birth addressing important short-term issues exist, long-term studies are hampered by significant logistical constraints. Current small animal models of prematurity require terminal caesarean section of the mother; both caesarean birth and early maternal care modify offspring adult cardio-metabolic function. We describe a novel method for inducing preterm labour in guinea pigs. With support comparable to that received by moderately preterm human infants, preterm pups are viable. Growth trajectories between preterm and term-born pups differ significantly; between term equivalent age and weaning ex-preterm animals demonstrate increased weight and ponderal index. We believe this novel paradigm will significantly improve our ability to investigate the cardio-metabolic sequelae of preterm birth throughout the life course and into the second generation.

Preterm birth has sex-specific effects on autonomic modulation of heart rate variability in adult sheep.

Introduction Globally, 11% of infants are born preterm. In adulthood, individuals born preterm are at increased risk of cardiovascular morbidity and mortality, but the mechanistic basis of this remains unknown. Clinically overt cardiovascular disease may be preceded by altered cardiac autonomic activity characterised by increased sympathetic activity and/or reduced parasympathetic activity. Thus, altered cardiac autonomic activity in survivors of preterm birth may underlie later cardiovascular risk. Objective To investigate the impact of gestational age on cardiac autonomic activity in juvenile and adult sheep. Methods and Results Singleton-bearing ewes were randomised antenatally to spontaneous term birth (TC; n=73) or corticosteroid induced preterm birth (PT; n=60). Cardiac autonomic modulation was assessed using heart rate variability analysis in juvenile and adult offspring. Preterm birth in adult males was associated with altered sympatho-vagal modulation (LFnu: PT 64±4 vs. TC 49±4, p<0.05; LogLF/HF: PT 1.8±0.1 vs. TC 1.5±0.1, p<0.05) and reduced parasympathetic modulation (LogRMSSD: PT 2.9±0.2 vs. TC 3.4±0.1, p<0.05; LogNN50: PT 0.3±0.4 vs. TC 1.6±0.4, p<0.05). Within the range of term birth, each one-day increment in gestational age was associated with a decrement in LFnu in juvenile females and with a decrement in LFnu and LF/HF ratio, but an increment in RMSSD and NN50 in adult females. Conclusions Cardiac autonomic function in adult sheep is affected in a sex-specific manner by gestational age at birth, even within the term range. Altered cardiac autonomic function may contribute to increased later cardiovascular morbidity in those born preterm.

Brief neonatal nutritional supplementation has sex-specific effects on glucose tolerance and insulin regulating genes in juvenile lambs

Background:The nutritional plane and composition during fetal life can impact upon growth and epigenetic regulation of genes affecting pancreatic β-cell development and function. However, it is not clear whether β-cell development can be altered by nutritional factors or growth rate after birth. We therefore investigated the effect of neonatal nutritional supplements on growth, glucose tolerance, and pancreatic development in lambs.Methods:Newborn lambs were randomized to daily nutritional supplements, calculated to increase macronutrient intake to a similar degree as human breast milk fortifier, or an equivalent volume of water, for 2 wk while continuing to suckle ewe milk. Intravenous glucose tolerance test (IVGTT) was performed at 4 mo of age, and pancreata collected for molecular analysis.Results:Supplemented lambs had slower weight gain than controls. In supplemented lambs, insulin response to IVGTT was increased in males but decreased in females, compared to same sex controls, and was unrelated to growth rate. mRNA expression of key genes in β-cell development showed sexually dimorphic effects. Epigenetic change occurred in the promotor region of PDX1 gene with decreased suppression and increased activation marks in supplemented lambs of both sexes.Conclusion:Nutritional interventions in early life have long-term, sex-specific effects on pancreatic function.

Disruptions to the cerebellar GABAergic system in juvenile guinea pigs following preterm birth

Children that are born preterm are at an increased risk of developing cognitive problems and behavioural disorders, such as attention deficit hyperactivity disorder (ADHD). There is increasing interest in the role of the cerebellum in these processes and the potential involvement of GABAergic pathways in neurodevelopmental disorders. We propose that preterm birth, and the associated loss of the trophic intrauterine environment, alters the development of the cerebellum, contributing to ongoing neurobehavioral disorders.

Neonatal milk supplementation in lambs has persistent effects on growth and metabolic function that differ by sex and gestational age.

The perinatal environment has a major influence on long-term health and disease risk. Preterm birth alters early-life environment and is associated with altered metabolic function in adulthood. Whether preterm birth per se or the early nutritional interventions used to support growth in preterm infants underpins this association is unknown. Lambs born preterm, following dexamethasone induction of labour, or spontaneously at term were randomised to receive nutrient supplementation, analogous to the milk fortifier used clinically or water as a control for the first 2 weeks after birth. Thereafter, nutrition was not different between groups. Growth was monitored, and the glucose-insulin axis function was assessed in juvenile (4 months) and adult life (14 months). Early nutrition influenced adult metabolic function and body composition to a greater extent than preterm birth. In supplemented females, arginine-stimulated insulin secretion was increased in preterm but reduced in term-born juveniles compared with controls (repeated-measures ANOVA P<0·01). In supplemented preterm males, adult weight, ponderal index (PI) and fasting insulin concentrations were elevated compared with preterm controls (weight, 75 (sem 3) v. 69 (sem 2) kg; PI, 48·0 (sem 2·1) v. 43·7 (sem 1·7) kg/m3; fasting insulin, 0·19 (sem 0·02) v. 0·10 (sem 0·02) ng/ml). Conversely, supplemented term-born males had reduced adult weight, PI and fasting insulin concentrations compared with term-born controls (weight, 64 (sem 2) v. 70 (sem 2) kg; PI, 44·4 (sem 1·8) v. 48·2 (sem 1·7) kg/m3; fasting insulin, 0·09 (sem 0·02) v. 0·14 (sem 0·02) ng/ml; all group×supplement interactions P<0·05). Adult metabolic health may reflect both gestational age at birth and early nutrition. Human studies are urgently needed to investigate the adult sex-specific health implications of neonatal nutritional strategies.

Shwachman–Diamond syndrome (SDS) in a preterm neonate

A preterm neonate at 29‐week gestational age was born with intrauterine growth restriction, severe pancytopaenia and gross skeletal dysplasia. Antenatal screening bloods, TORCH/parvovirus tests and karyotype were unremarkable. Postnatally, he had normal microarray comparative genomic hybridization and serum B12/folate levels, and human immunodeficiency virus and cytomegalovirus polymerase chain reaction and antoimmune screening were negative. Targeted gene testing for Shwachman–Diamond syndrome (SDS) revealed the pathognomic mutation (c.183_184delTAinsCT). His postnatal clinical course was complicated by: (i) Ventilator dependency because of a combination of a pathologically compliant chest wall and preterm‐associated chronic lung disease. (ii) Progressive bone marrow failure, resulting in transfusion dependence and profound neutropenia associated with recurrent sepsis. (iii) Gastrointestinal failure and TPN dependency. (iv) Poor postnatal growth with weight/length/head circumference all <3rd centile. (v) Prognostication was complicated by the lack of published literature on the presentation of SDS in a preterm infant. However, because of inexorable progression of multiorgan failure, intensive care was withdrawn on day 54 of life. SDS is a rare autosomal recessive disorder characterised by haematological abnormalities, skeletal dysplasia and exocrine pancreatic dysfunction. Neonatal presentation is thought to be extremely rare. However, with the availability of genetic testing, it has now become clear that because of overlap in clinical presentation, term‐born infants with skeletal dysplasia and severe respiratory distress may initially be misdiagnosed as asphyxiating thoracic dystrophy. This case report highlights the complexities of preterm birth complicating clinical manifestations of SDS.

Inter-individual Relationships Between Sympathetic Arterial Baroreflex Function and Cerebral Perfusion Control in Healthy Males

Maintenance of adequate cerebral perfusion during normal physiological challenges requires integration between cerebral blood flow (CBF) and systemic blood pressure control mechanisms. Previous studies have shown that cardiac baroreflex sensitivity (BRS) is inversely related to some measures of cerebral autoregulation. However, interactions between the sympathetic arterial baroreflex and cerebral perfusion control mechanisms have not been explored. To determine the nature and magnitude of these interactions we measured R–R interval, blood pressure, CBF velocity, and muscle sympathetic nerve activity (MSNA) in 11 healthy young males. Sympathetic BRS was estimated using modified Oxford method as the relationship between beat-to-beat diastolic blood pressure (DBP) and MSNA. Integrated control of CBF was quantified using transfer function analysis (TFA) metrics derived during rest and Tiecks autoregulatory index following bilateral thigh cuff deflation. Sympathetic BRS during modified Oxford trials was significantly related to autoregulatory index (r = 0.64, p = 0.03). Sympathetic BRS during spontaneous baseline was significantly related to transfer function gain (r = −0.74, p = 0.01). A more negative value for sympathetic BRS indicates more effective arterial baroreflex regulation, and a lower transfer function gain reflects greater cerebral autoregulation. Therefore, these findings indicate that males with attenuated CBF regulation have greater sympathetic BRS (and vice versa), consistent with compensatory interactions between blood pressure and cerebral perfusion control mechanisms.