Parenteral nutrition decreases paneth cell function and intestinal bactericidal activity while increasing susceptibility to bacterial enteroinvasion.

INTRODUCTION: Parenteral nutrition (PN) increases the risk of infection in patients with contraindication to enteral feeding. Paneth cells produce and secrete antimicrobial products that protect the mucosa from pathogens. Their loss is associated with increased host-pathogen interactions, mucosal inflammation, and altered microbiome composition. HYPOTHESIS: We hypothesized that PN reduces Paneth cell product expression, and these changes would reduce bactericidal properties of tissue secretions following cholinergic stimulation, increase mucosal enteroinvasion, and shift the intestinal microbiome.
METHOD: Experiment 1: Male ICR mice were randomized to Chow (n = 8) or PN (n = 8). Ileum tissue was collected for Paneth cell antimicrobial expression using RT-PCR, stimulated with a cholinergic agonist degranulate Paneth cells bactericidal activity, or used to assess bacterial enteroinvasion in EVISC. Experiment 2: Mice were randomized to Chow (n = 11) or PN (n = 8) and ileum washing was collected for 16s pyrosequencing analysis.
RESULTS: Compared to Chow, PN decreased tissue expression of REGIII-g (p < 0.002), lysozyme (p < 0.002), and cryptdin-4 (p < 0.03). At the phylum level, PN decreased total Firmicutes but increased total Bacteroidetes, and Proteobacteria. Functionally, secretions from PN tissue was less bactericidal (p < 0.03) and demonstrated increased susceptibility to enteroinvasion by E coli (p < 0.02).
CONCLUSION: PN without enteral nutrition impairs innate mucosal immune function. Tissue expression of Paneth cell antimicrobial proteins decreases associated with compositional shifts to the microbiome, decreased bactericidal activity of mucosal secretions and greater susceptibility of to enteroinvasion by E coli. These changes may explain in-part the increased risk of infection in parenterally fed patients.