PROJECT SUMMARY
Preterm birth is the leading cause of infant mortality in the United States and is associated with long-term
dysfunctions in growth. This is, in part, a result of immature gastrointestinal function and reduced digestive and
metabolic responses to feeding, making it difficult to assimilate enteral nutrition for growth. However,
mechanisms underpinning the blunted response to enteral nutrition and growth dysfunction in preterm neonates
are poorly understood. Fibroblast Growth Factor-19 (FGF19) is a potent fetal growth factor, but postnatally,
FGF19 is secreted by the distal ileum in response to bile acid stimulation and negatively regulates hepatic bile
acid synthesis. Preterm infants have a bile acid pool that is one-third the size of term infants and this smaller bile
acid pool may limit fat digestion and FGF19 secretion. Our recent studies in neonatal pigs showed that the
plasma FGF19 is markedly lower in preterm vs. term, and the lower FGF19 is driven by lower ileal
responsiveness to bile acid stimulation and a smaller hepatic bile acid pool. Pigs born vaginally had plasma
FGF19 levels 35 times greater than term pigs born via cesarean section and 70 times higher than preterm pigs
at birth. Among these groups of pigs, plasma cortisol directly correlated with plasma FGF19 concentrations. This
latter finding may be important since preterm infants are often given glucocorticoids perinatally to improve
respiratory function. In the proposed studies, I hypothesize that glucocorticoids upregulate the developmental
responses to bile acid homeostasis and FGF19 signaling in the perinatal period. In Aim 1A we will characterize
the developmental differences in molecular and cellular signaling pathways in preterm and term hepatocytes and
intestinal enteriods and examine their association with cortisol, bile acid homeostasis and FGF19 signaling. In
Aim 1B we will determine the effect of birth modality (vaginal versus cesarean section) and glucocorticoid
treatment (maternal and neonatal) on gut-liver bile acid homeostasis and FXR-FGF19 signaling in neonatal pigs.
In Aim 2, we will directly assess the effect of an enteral FXR agonist and hydrocortisone on the rate of growth,
tissue protein synthesis and intestinal development in preterm neonatal pigs. The results of these aims will
establish the role of perinatal glucocorticoids on bile acid homeostasis and FGF19 signaling and whether FGF19
functions to improve neonatal growth. My long-term career goal is to establish an independent, academic
research program to interrogate the effects of preterm birth on perinatal hepatic and gastrointestinal development
and physiology. I have assembled an expert mentorship committee to guide my development as an independent
investigator. My mentor, Dr. Doug Burrin has a record of accomplishment using neonatal pigs to model human
infant nutrition and development. Completion of these aims will allow me to pursue additional training and
develop skills in molecular techniques, cell culture, advanced imaging, and bioinformatics.