Insights into Neonatal Oral Feeding through the Salivary Transcriptome

Spectral features of non-nutritive suck dynamics in extremely preterm infants

Background

Non-nutritive suck (NNS) is used to promote ororhythmic patterning and assess oral feeding readiness in preterm infants in the neonatal intensive care unit (NICU). While time domain measures of NNS are available in real time at cribside, our understanding of suck pattern generation in the frequency domain is limited. The aim of this study is to model the development of NNS in the frequency domain using Fourier and machine learning (ML) techniques in extremely preterm infants (EPIs).

Methods

A total of 117 EPIs were randomized to a pulsed or sham orocutaneous intervention during tube feedings 3 times/day for 4 weeks, beginning at 30 weeks post-menstrual age (PMA). Infants were assessed 3 times/week for NNS dynamics until they attained 100% oral feeding or NICU discharge. Digitized NNS signals were processed in the frequency domain using two transforms, including the Welch power spectral density (PSD) method, and the Yule-Walker PSD method. Data analysis proceeded in two stages. Stage 1: ML longitudinal cluster analysis was conducted to identify groups (classes) of infants, each showing a unique pattern of change in Welch and Yule-Walker calculations during the interventions. Stage 2: linear mixed modeling (LMM) was performed for the Welch and Yule-Walker dependent variables to examine the effects of gestationally-aged (GA), PMA, sex (male, female), patient type [respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD)], treatment (NTrainer, Sham), intervention phase [1, 2, 3], cluster class, and phase-by-class interaction.

Results

ML of Welch PSD method and Yule-Walker PSD method measures revealed three membership classes of NNS growth patterns. The dependent measures peak_Hz, PSD amplitude, and area under the curve (AUC) are highly dependent on PMA, but show little relation to respiratory status (RDS, BPD) or somatosensory intervention. Thus, neural regulation of NNS in the frequency domain is significantly different for each identified cluster (classes A, B, C) during this developmental period.

Conclusions

Efforts to increase our knowledge of the evolution of the suck central pattern generator (sCPG) in preterm infants, including NNS rhythmogenesis will help us better understand the observed phenotypes of NNS production in both the frequency and time domains. Knowledge of those features of the NNS which are relatively invariant vs. other features which are modifiable by experience will likewise inform more effective treatment strategies in this fragile population.

The Utility of Speech-Language Biomarkers to Predict Oral Feeding Outcomes in the Premature Newborn

Purpose Successful oral feeding and speech emergence are dependent upon the coordination of shared oral muscles and facial nerves. We aimed to determine if the speech-associated genes, forkhead box P2 (FOXP2), contactin-associated protein-like 2 (CNTNAP2), glutamate receptor, ionotropic, N-methyl D-aspartate 2A (GRIN2A), and neurexin 1, were detectable in neonatal saliva and could predict feeding outcomes in premature newborns. Method In this prospective, observational, preliminary study, saliva collected from 51 premature infants (gestational ages: 30-34 6/7 weeks) at different stages of oral feeding development underwent gene expression analysis. Binary (+/-) expression profiles were explored and examined in relation to days to achieve full oral feeds. Results GRIN2A and neurexin 1 rarely amplified in neonatal saliva and were not informative. Infants who amplified FOXP2 but not CNTNAP2 at the start of oral feeds achieved oral feeding success 3.20 (95% CI [-2.5, 8.9]) days sooner than other gene combinations. Conclusions FOXP2 and CNTNAP2 may be informative in predicting oral feeding outcomes in newborns. Salivary analysis at the start of oral feeding trials may inform feeding outcomes in this population and warrants further investigation.

Optimal Timing to Utilize Olfactory Stimulation with Maternal Breast Milk to Improve Oral Feeding Skills in the Premature Newborn

Background: Olfactory maturation is essential for successful oral feeding. Previous studies have suggested that olfactory stimulation with maternal breast milk may expedite oral feeding skills in the premature infant; however, the optimal developmental window to utilize this intervention and sex-specific responses to stimuli are largely unknown. Objectives: To determine individual responses to olfactory stimulation with mother's own milk (MOM) on feeding outcomes in premature newborns. Materials and Methods: Infants born between 28 0/7 and 33 6/7 weeks' gestation (n = 36) were randomized to receive either MOM or water (sham) stimulus during the learning process of oral feeding. Clinical and feeding outcomes were recorded. Statistical analyses examined the effect of stimulation with MOM on feeding outcomes stratified for age and sex. Results: Overall, there was no significant difference between sham infants compared with MOM infants in mean postmenstrual age of full oral feeds (sham: 35 5/7 versus MOM 36 0/7; p = 0.37). However, when stratified by gestational age (GA), infants born <31 weeks' gestation who received MOM stimulation learned to feed sooner than controls (p = 0.06), whereas infants born ≥31 weeks' gestation learned to feed later than controls (p = 0.20) with a significant interaction (p = 0.02) between the stimulus (MOM versus sham) and dichotomized GA (<31 versus ≥31 weeks). There were no sex differences in response to olfactory stimulus. Conclusions: Infants born <31 weeks' GA who received MOM stimulation learned to feed sooner than control infants and the impact of MOM is significantly different between infants born before or after 31 weeks GA. These data suggest there may be an optimal time in development to utilize maternal breast milk to expedite oral feeding maturation in the premature newborn.

Oral Feeding Success: A Concept Analysis

BACKGROUND

The term "oral feeding success" (OFS) is frequently used in clinical practice and research. However, OFS is inconsistently defined, which impacts the ability to adequately evaluate OFS, identify risk factors, and implement interventions in clinical practice and research.

PURPOSE

To develop the defining attributes, antecedents, and consequences for the concept of OFS in preterm infants during their initial hospitalization.

METHODS

PubMed, CINAHL, and PsycINFO databases were searched for English articles containing the key words "oral feeding success" and "preterm infants." The Walker and Avant method for concept analysis was employed.

RESULTS

Sixteen articles revealed the defining attributes, antecedents, and consequences. Defining attributes included (1) physiologic stability; (2) full oral feeding; and (3) combined criteria of feeding proficiency (≥30% of the prescribed volume during the first 5 minutes), feeding efficiency (≥1.5 mL/min over the entire feeding), and intake quantity (≥80% of the prescribed volume).

IMPLICATIONS FOR PRACTICE

The 3 defining attributes may be used in clinical practice to consistently evaluate OFS. The antecedents of OFS provide clinicians with a frame of reference to assess oral feeding readiness, identify risk factors, and implement effective interventions. The consequences of OFS allow clinicians to anticipate challenges when OFS is not achieved and create a care plan to support the infants.

IMPLICATIONS FOR RESEARCH

The empirical referents of OFS provide consistent and clear operational definitions of OFS for use in research. The antecedents and consequences may guide researchers to select specific measures or covariates to evaluate valid measures of OFS.

Somatosensory Modulation of Salivary Gene Expression and Oral Feeding in Preterm Infants: Randomized Controlled Trial

BACKGROUND

Despite numerous medical advances in the care of at-risk preterm neonates, oral feeding still represents one of the first and most advanced neurological challenges facing this delicate population. Objective, quantitative, and noninvasive assessment tools, as well as neurotherapeutic strategies, are greatly needed in order to improve feeding and developmental outcomes. Pulsed pneumatic orocutaneous stimulation has been shown to improve nonnutritive sucking (NNS) skills in preterm infants who exhibit delayed or disordered nipple feeding behaviors. Separately, the study of the salivary transcriptome in neonates has helped identify biomarkers directly linked to successful neonatal oral feeding behavior. The combination of noninvasive treatment strategies and transcriptomic analysis represents an integrative approach to oral feeding in which rapid technological advances and personalized transcriptomics can safely and noninvasively be brought to the bedside to inform medical care decisions and improve care and outcomes.

OBJECTIVE

The study aimed to conduct a multicenter randomized control trial (RCT) to combine molecular and behavioral methods in an experimental conceptualization approach to map the effects of PULSED somatosensory stimulation on salivary gene expression in the context of the acquisition of oral feeding habits in high-risk human neonates. The aims of this study represent the first attempt to combine noninvasive treatment strategies and transcriptomic assessments of high-risk extremely preterm infants (EPI) to (1) improve oral feeding behavior and skills, (2) further our understanding of the gene ontology of biologically diverse pathways related to oral feeding, (3) use gene expression data to personalize neonatal care and individualize treatment strategies and timing interventions, and (4) improve long-term developmental outcomes.

METHODS

A total of 180 extremely preterm infants from three neonatal intensive care units (NICUs) will be randomized to receive either PULSED or SHAM (non-pulsing) orocutaneous intervention simultaneous with tube feedings 3 times per day for 4 weeks, beginning at 30 weeks postconceptional age. Infants will also be assessed 3 times per week for NNS performance, and multiple saliva samples will be obtained each week for transcriptomic analysis, until infants have achieved full oral feeding status. At 18 months corrected age (CA), infants will undergo neurodevelopmental follow-up testing, the results of which will be correlated with feeding outcomes in the neo-and post-natal period and with gene expression data and intervention status.

RESULTS

The ongoing National Institutes of Health funded randomized controlled trial R01HD086088 is actively recruiting participants. The expected completion date of the study is 2021.

CONCLUSIONS

Differential salivary gene expression profiles in response to orosensory entrainment intervention are expected to lead to the development of individualized interventions for the diagnosis and management of oral feeding in preterm infants.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02696343; https://clinicaltrials.gov/ct2/show/NCT02696343 (Archived by WebCite at http://www.webcitation.org/6r5NbJ9Ym).

The emerging landscape of salivary diagnostics

Saliva contains a variety of biomolecules, including DNA, coding and noncoding RNA, proteins, metabolites and microbiota. The changes in the salivary levels of these molecular constituents can be used to develop markers for disease detection and risk assessment. Use of saliva as an early-detection tool is a promising approach because collection of saliva is easy and noninvasive. Here, we review recent developments in salivary diagnostics, accomplished using salivaomics approaches, including genomic, transcriptomic, proteomic, metabolomic and microbiomic technologies. Additionally, we illustrate the mechanisms of how diseases distal from the oral cavity can lead to the appearance of discriminatory biomarkers in saliva, and discuss the relevance of these markers for translational and clinical applications.

FOXP2 gene deletion and infant feeding difficulties: a case report

Forkhead box protein P2 (FOXP2) is a well-studied gene known to play an essential role in normal speech development. Deletions in the gene have been shown to result in developmental speech disorders and regulatory disruption of downstream gene targets associated with common forms of language impairments. Despite similarities in motor planning and execution between speech development and oral feeding competence, there have been no reports to date linking deletions within the FOXP2 gene to oral feeding impairments in the newborn. The patient was a nondysmorphic, appropriately and symmetrically grown male infant born at 35-wk gestational age. He had a prolonged neonatal intensive care unit stay because of persistent oral feeding incoordination requiring gastrostomy tube placement. Cardiac and neurological imagings were within normal limits. A microarray analysis found an ∼9-kb loss within chromosome band 7q3.1 that contains exon 2 of FOXP2, demonstrating a single copy of this region instead of the normal two copies per diploid gene. This case study expands our current understanding of the role FOXP2 exerts on motor planning and coordination necessary for both oral feeding success and speech–language development. This case report has important consequences for future diagnosis and treatment for infants with FOXP2 deletions, mutations, and varying levels of gene expression.

Computational gene expression modeling identifies salivary biomarker analysis that predict oral feeding readiness in the newborn

OBJECTIVE

To combine mathematical modeling of salivary gene expression microarray data and systems biology annotation with reverse-transcription quantitative polymerase chain reaction amplification to identify (phase I) and validate (phase II) salivary biomarker analysis for the prediction of oral feeding readiness in preterm infants.

STUDY DESIGN

Comparative whole-transcriptome microarray analysis from 12 preterm newborns pre- and postoral feeding success was used for computational modeling and systems biology analysis to identify potential salivary transcripts associated with oral feeding success (phase I). Selected gene expression biomarkers (15 from computational modeling; 6 evidence-based; and 3 reference) were evaluated by reverse-transcription quantitative polymerase chain reaction amplification on 400 salivary samples from successful (n = 200) and unsuccessful (n = 200) oral feeders (phase II). Genes, alone and in combination, were evaluated by a multivariate analysis controlling for sex and postconceptional age (PCA) to determine the probability that newborns achieved successful oral feeding.

RESULTS

Advancing PCA (P < .001) and female sex (P = .05) positively predicted an infant's ability to feed orally. A combination of 5 genes, neuropeptide Y2 receptor (hunger signaling), adneosine-monophosphate-activated protein kinase (energy homeostasis), plexin A1 (olfactory neurogenesis), nephronophthisis 4 (visual behavior), and wingless-type MMTV integration site family, member 3 (facial development), in addition to PCA and sex, demonstrated good accuracy for determining feeding success (area under the receiver operator characteristic curve = 0.78).

CONCLUSIONS

We have identified objective and biologically relevant salivary biomarkers that noninvasively assess a newborn's developing brain, sensory, and facial development as they relate to oral feeding success. Understanding the mechanisms that underlie the development of oral feeding readiness through translational and computational methods may improve clinical decision making while decreasing morbidities and health care costs.

Great expectorations: the potential of salivary 'omic' approaches in neonatal intensive care

Among those that require critical care, preterm neonates have the greatest limitations on available blood or body fluids for clinical or research-based assessments. Recent technological advancements have improved our ability to detect genetic, proteomic and microbial material at the nanoscale level, making analyte and biomarker assessment from even the smallest quantities possible. Saliva is a unique body fluid that not only may be noninvasively and repeatedly obtained, but also contains multiple serum components, making it promising for noninvasive assessment of the newborn. The integration of high-throughput or 'omic' approaches on neonatal saliva holds great potential to improve diagnostic and prognostic accuracy for a wide range of developmental and pathological conditions affecting the vulnerable preterm neonatal population. Herein, we review the clinical applications and technical considerations regarding the integration of salivary 'omic' technology into the neonatal intensive care unit.