Objective Threonine (THR) is an essential amino acid (EAA) utilized in high amounts by the neonatal gut. Intestinal microbes both consume and produce EAA that might impact availability for the host. We hypothesized that treatment with antibiotics or probiotics could influence whole body and intestinal THR metabolism in neonates who require high amounts of protein for growth.
Methods Neonatal pigs were weaned and implanted with vascular and stomach catheters. They were randomized to one of 3 groups (n = 4/group): control (C), probiotics (PRO; Bifidobacterium Breve & Bb12) and intravenously administered antibiotics (AB; ampicillin, gentamycin, metronidazole). After 10 days all piglets underwent a primed, continuous isotope tracer infusion with [1-15N] THR administered intravenously and [U-13C, 1-15N] THR intragastrically to calculate THR kinetics. Piglets were then euthanized and blood samples, intestinal contents and tissues were collected.
Results Proximal small intestinal weight was lower (p = 0.02) and liver weight was higher (p = 0.056) in PRO compared to C and AB. CO2 production, THR oxidation and THR splanchnic uptake were not different amongst groups. In AB, protein fractional and absolute synthesis rates were decreased in gut and liver compared to PRO. However, whole body protein synthesis and breakdown were increased in AB, resulting in a net protein balance that was similar amongst treatment groups.
Conclusions Manipulation of the neonatal gut flora by antibiotics or probiotics altered gut and liver weights, and whole body and intestinal protein synthesis rates. These results show that microbes influence THR kinetics and could impact EAA metabolism necessary for neonatal nutrition.