Sex-Dependent Gene Expression in Infants with Neonatal Opioid Withdrawal Syndrome

Abstract

Objectives To evaluate salivary biomarkers that elucidate the molecular mechanisms by which in utero opioid exposure exerts sex-specific effects on select hypothalamic and reward genes driving hyperphagia, a hallmark symptom of infants suffering from neonatal opioid withdrawal syndrome (NOWS). Study design We prospectively collected saliva from 50 newborns born at ³34 weeks of gestational age with prenatal opioid exposure and 50 sex-and gestational age-matched infants without exposure. Saliva underwent transcriptomic analysis for 4 select genes involved in homeostatic and hedonic feeding regulation (neuropeptide Y2 receptor [NPY2R], proopiomelanocortin [POMC], leptin receptor [LEPR], dopamine type 2 receptor [DRD2]). Normalized gene expression data were stratified based on sex and correlated with feeding volume on day of life 7 and length of stay in infants with NOWS requiring pharmacotherapy. Results Expression of DRD2, a hedonistic/reward regulator, was significantly higher in male newborns compared with female newborns with NOWS (D threshold cycle 10.8 AE 3.8 vs 13.9 AE 3.7, P = .01). In NOWS requiring pharmacotherapy expression of leptin receptor, an appetite suppressor, was higher in male subjects than female subjects (D threshold cycle 8.4 AE 2.5 vs 12.4 AE 5.1, P = .05), DRD2 expression significantly correlated with intake volume on day of life 7 (r = 0.58, P = .02), and expression of NPY2R, an appetite regulator, negatively correlated with length of stay (r = À0.24, P = .05). Conclusions Prenatal opioid exposure exerts sex-dependent effects on hypothalamic feeding regulatory genes with clinical correlations. Neonatal salivary gene expression analyses may predict hyperphagia, severity of withdrawal state, and length of stay in infants with NOWS.

Prenatal Exposures Are Associated With Worse Neurodevelopmental Outcomes in Infants With Neonatal Opioid Withdrawal Syndrome

“…In other studies, male sex is independently associated with poorer neurodevelopmental outcome in infants born preterm, small for gestational age, and infants with hypoxic-ischemic encephalopathy (40). Males are more likely to demonstrate clinical signs of opioid withdrawal and are more likely to require pharmacologic treatment for NOWS (41,42). The exact mechanism of this association has yet to be elucidated but has been attributed to differences in brain organization and genetic, epigenetic, and hormonal factors (42,43).…”

“…Males are more likely to demonstrate clinical signs of opioid withdrawal and are more likely to require pharmacologic treatment for NOWS (41,42). The exact mechanism of this association has yet to be elucidated but has been attributed to differences in brain organization and genetic, epigenetic, and hormonal factors (42,43). This biologic vulnerability of male fetuses to intrauterine adversity remains an important area of future research.…”

Maternal and iatrogenic neonatal opioid withdrawal syndrome: Differences and similarities in recognition, management, and consequences

“…In addition, severity and prevalence of mNOWS could differ between male and female infants. A retrospective study found a higher prevalence in males (Charles et al, 2017), and a prospective pilot study looking at hypothalamic feeding regulatory genes in salivary samples noted increased neonatal withdrawal prevalence and severity in the males and an associated higher expression of dopamine receptor D2, a hedonistic/reward regulator (Yen et al, 2019). Other studies showed no difference between male and female human infants in retrospective (Holbrook & Kaltenbach, 2010) or prospective (secondary) analyses (Unger et al, 2011).…”

Technical Considerations and Protocol Optimization for Neonatal Salivary Biomarker Discovery and Analysis

“…Custom pre-amplification reagents are commercially available and may be manufactured for particular targets of interest. Our laboratory has successfully employed this technique to adapt the interpretation of biomarker levels from binary to relative quantification (22).…”