Potential Nutrients for Preventing or Treating Bronchopulmonary Dysplasia

A review and guide to nutritional care of the infant with established bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) remains the most common long-term morbidity of premature birth, and the incidence of BPD is not declining despite medical advancements. Infants with BPD are at high risk for postnatal growth failure and are often treated with therapies that suppress growth. Additionally, these infants may display excess weight gain relative to linear growth. Optimal growth and nutrition are needed to promote lung growth and repair, improve long-term pulmonary function, and improve neurodevelopmental outcomes. Linear growth in particular has been associated with favorable outcomes yet can be difficult to achieve in these patients. While there has been a significant clinical and research focus regarding BPD prevention and early preterm nutrition, there is a lack of literature regarding nutritional care of the infant with established BPD. There is even less information regarding how nutritional needs change as BPD evolves from an acute to chronic disease. This article reviews the current literature regarding nutritional challenges, enteral nutrition management, and monitoring for patients with established BPD. Additionally, this article provides a practical framework for interdisciplinary nutritional care based on our clinical experience at the Comprehensive Center for Bronchopulmonary Dysplasia.

PGC-1α activity and mitochondrial dysfunction in preterm infants

Extremely low gestational age neonates (ELGANs) are born in a relatively hyperoxic environment with weak antioxidant defenses, placing them at high risk for mitochondrial dysfunction affecting multiple organ systems including the nervous, respiratory, ocular, and gastrointestinal systems. The brain and lungs are highly affected by mitochondrial dysfunction and dysregulation in the neonate, causing white matter injury (WMI) and bronchopulmonary dysplasia (BPD), respectively. Adequate mitochondrial function is important in providing sufficient energy for organ development as it relates to alveolarization and axonal myelination and decreasing oxidative stress via reactive oxygen species (ROS) and reactive nitrogen species (RNS) detoxification. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) is a master regulator of mitochondrial biogenesis and function. Since mitochondrial dysfunction is at the root of WMI and BPD pathobiology, exploring therapies that can regulate PGC-1α activity may be beneficial. This review article describes several promising therapeutic agents that can mitigate mitochondrial dysfunction through direct and indirect activation and upregulation of the PGC-1α pathway. Metformin, resveratrol, omega 3 fatty acids, montelukast, L-citrulline, and adiponectin are promising candidates that require further pre-clinical and clinical studies to understand their efficacy in decreasing the burden of disease from WMI and BPD in preterm infants.

Targeting the lung endothelial niche to promote angiogenesis and regeneration: A review of applications

Lung endothelial cells comprise the pulmonary vascular bed and account for the majority of cells in the lungs. Beyond their role in gas exchange, lung ECs form a specialized microenvironment, or niche, with important roles in health and disease. In early development, progenitor ECs direct alveolar development through angiogenesis. Following birth, lung ECs are thought to maintain their regenerative capacity despite the aging process. As such, harnessing the power of the EC niche, specifically to promote angiogenesis and alveolar regeneration has potential clinical applications. Here, we focus on translational research with applications related to developmental lung diseases including pulmonary hypoplasia and bronchopulmonary dysplasia. An overview of studies examining the role of ECs in lung regeneration following acute lung injury is also provided. These diseases are all characterized by significant morbidity and mortality with limited existing therapeutics, affecting both young children and adults.

New-generation intravenous fat emulsions and bronchopulmonary dysplasia in preterm infants: a systematic review and meta-analysis

BACKGROUND

Fat emulsion is an important component of parenteral nutrition in premature infants. However, intravenous fat emulsions (IVFE) was reported to be associated with some serious complications, such as bronchopulmonary dysplasia (BPD). Compared to conventional soybean oil-based IVFE, new-generation IVFE may protect against BPD but the results are conflicting.

METHODS

Relevant literatures search was conducted and the summary effect estimates of odds ratio (OR) and 95% confidence interval (CI) were calculated with fixed-effects models.

RESULTS

Of 22 studies involving 3781 infants were selected in this study and BPD was reported as part of the included studies. The pooled estimate for 13 studies, comparing administration of new-generation IVFE with conventional IVFE, indicated that new-generation IVFE was not associated with a reduced risk of BPD in preterm infants, compared with conventional IVFE (OR 0.96; 95% CI 0.80-1.14); the pooled estimate for 18 studies, comparing administration of fish oil-containing IVFE with non-fish oil IVFE, indicated that fish oil-containing IVFE has no protective effect against the occurrence of BPD in preterm infants (OR 0.88; 95% CI 0.71-1.08).

CONCLUSIONS

There is no evidence to support that the new-generation IVFEs could prevent the incidence of BPD or fish oil-containing IVFEs could show a beneficial effect to BPD in premature infants.

Early administration of amino acids with different doses in low birth weight premature infants

Background:

The reasonable use of amino acids (AAs) in parenteral nutrition (PN) is very critical to the growth and development of premature infants. However, the appropriate dose of AAs has not been determined. Our study was designed to investigate the clinical effect of two different doses of AAs in PN for low birth weight premature infants.

Materials and Methods:

This randomized controlled study included 191 preterm infants who admitted to the neonatal intensive care unit of the First Affiliated Hospital of Nanjing Medical University from June 2015 to December 2016 and they were randomly divided into Group 1 (n = 81) and Group 2 (n = 110). In Group 1, the starting dose of AAs dose was 1.0–1.5 g/kg/day, which was increased by 0.5 g/kg with the maximum dose at 3.5 g/kg/day. In Group 2, the starting dose of AAs was 1.8–2.5 g/kg/day and was increased by 1.0 g/kg with the maximum dose at 4.0–4.5 g/kg/day. We analyzed the clinical characteristics, body weight, body length, total calorie intake, nonprotein calorie intake, total protein intake, liver and kidney function, and complications of the two groups of preterm infants.

Results:

The start of enteral feeding and the recovery of birth weight in Group 2 were earlier than those in Group 1 (3.83 ± 3.15 day vs. 5.53 ± 5.63 day, P = 0.016 and 6.36 ± 4.88 day vs. 8.48 ± 9.27 day, P = 0.043, respectively). The duration of PN and the time before total enteral nutrition were shorter in Group 2 than in Group 1 (16.46 ± 10.33 day vs. 21.41 ± 18.00 day, P = 0.029 and 15.47 ± 10.54 day vs. 19.47 ± 14.57 day, P = 0.038; respectively). The duration of mechanical ventilation (1.12 ± 2.62 day vs. 3.31 ± 8.13 day, P = 0.028) in Group 2 was shorter than that in Group 1.

Conclusion:

High doses of AAs in the early PN for preterm infants facilitate the promotion of early growth and development, advance recovery of birth weight, reduce the duration of PN, and reduce respiratory support without increasing the incidence of complications.

Present and Future of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is the most common respiratory disorder among infants born extremely preterm. The pathogenesis of BPD involves multiple prenatal and postnatal mechanisms affecting the development of a very immature lung. Their combined effects alter the lung's morphogenesis, disrupt capillary gas exchange in the alveoli, and lead to the pathological and clinical features of BPD. The disorder is ultimately the result of an aberrant repair response to antenatal and postnatal injuries to the developing lungs. Neonatology has made huge advances in dealing with conditions related to prematurity, but efforts to prevent and treat BPD have so far been only partially effective. Seeing that BPD appears to have a role in the early origin of chronic obstructive pulmonary disease, its prevention is pivotal also in long-term respiratory outcome of these patients. There is currently some evidence to support the use of antenatal glucocorticoids, surfactant therapy, protective noninvasive ventilation, targeted saturations, early caffeine treatment, vitamin A, and fluid restriction, but none of the existing strategies have had any significant impact in reducing the burden of BPD. New areas of research are raising novel therapeutic prospects, however. For instance, early topical (intratracheal or nebulized) steroids seem promising: they might help to limit BPD development without the side effects of systemic steroids. Evidence in favor of stem cell therapy has emerged from several preclinical trials, and from a couple of studies in humans. Mesenchymal stromal/stem cells (MSCs) have revealed a reparatory capability, preventing the progression of BPD in animal models. Administering MSC-conditioned media containing extracellular vesicles (EVs) have also demonstrated a preventive action, without the potential risks associated with unwanted engraftment or the adverse effects of administering cells. In this paper, we explore these emerging treatments and take a look at the revolutionary changes in BPD and neonatology on the horizon.

Small for gestational age birth may increase airflow limitation in bronchopulmonary dysplasia

OBJECTIVES

To determine significant indices for assessing the pulmonary function of infants according to bronchopulmonary dysplasia (BPD) severity and to evaluate whether small for gestational age (SGA) could affect pulmonary function in BPD.

METHODS

We evaluated 117 preterm infants who had undergone tidal breathing flow-volume loop and multiple-breath washout analyses within 7 months after birth. We categorized preterm infants according to BPD severity into mild/moderate BPD (n = 86), severe BPD (n = 21), and without BPD (n = 10) and the presence of SGA or appropriate gestational age (AGA) using the Fenton growth chart. We evaluated nine healthy term infants as controls.

RESULTS

The tidal breathing ratio (time to peak expiratory flow/expiratory time [t_PEF /t_E ]) was significantly lower in infants with severe BPD than in those with mild/moderate BPD. Lung clearance index (LCI) was not different based on BPD severity. In the correlation analysis after adjusting for gestational age and sex, t_PEF /t_E was correlated with the duration of mechanical ventilation (r = -0.347, P < .001) and the duration of oxygen supply (r = -0.248, P = .013) in infants with BPD. The proportion of "lower t_PEF /t_E ," defined as below the cut-off value, was greater in SGA infants (P = .017), while no significant difference was seen in the percentage of "higher LCI," defined as above the cut-off value between SGA and AGA infants.

CONCLUSIONS

In infants with BPD, t_PEF /t_E could be a useful pulmonary index which shows lower values in severe BPD. The finding of SGA in infants with BPD could be associated with poor pulmonary function related to the t_PEF /t_E values.

Recent advances in our understanding of the mechanisms of late lung development and bronchopulmonary dysplasia

The objective of lung development is to generate an organ of gas exchange that provides both a thin gas diffusion barrier and a large gas diffusion surface area, which concomitantly generates a steep gas diffusion concentration gradient. As such, the lung is perfectly structured to undertake the function of gas exchange: a large number of small alveoli provide extensive surface area within the limited volume of the lung, and a delicate alveolo-capillary barrier brings circulating blood into close proximity to the inspired air. Efficient movement of inspired air and circulating blood through the conducting airways and conducting vessels, respectively, generates steep oxygen and carbon dioxide concentration gradients across the alveolo-capillary barrier, providing ideal conditions for effective diffusion of both gases during breathing. The development of the gas exchange apparatus of the lung occurs during the second phase of lung development-namely, late lung development-which includes the canalicular, saccular, and alveolar stages of lung development. It is during these stages of lung development that preterm-born infants are delivered, when the lung is not yet competent for effective gas exchange. These infants may develop bronchopulmonary dysplasia (BPD), a syndrome complicated by disturbances to the development of the alveoli and the pulmonary vasculature. It is the objective of this review to update the reader about recent developments that further our understanding of the mechanisms of lung alveolarization and vascularization and the pathogenesis of BPD and other neonatal lung diseases that feature lung hypoplasia.