Plasma Arginine Depletion Prevents Necrotizing Enterocolitis in Formula-fed Preterm Pigs

Background: Necrotizing enterocolitis (NEC) is a gastrointestinal disease characterized by ischemic insult to the intestinal mucosa, leading to severe inflammation and necrosis. Current targeted treatments for NEC are limited to empiric antibiotic therapy and surgery. Arginine metabolism has been implicated in the pathogenesis of NEC, given that arginine functions as a precursor for nitric oxide (NO) which mediates both vascular function and the proinflammatory immune response. The objective of this project is to manipulate the circulating arginine concentration using a single, intramuscular injection of pegylated arginine deiminase (ADI-PEG20) which rapidly metabolizes plasma arginine to citrulline. We postulate that arginine and its downstream metabolites play a significant role in driving the dysfunctional hyperinflammatory phenotype that is integral to NEC. Thus, the removal of arginine from circulation has a potent anti-inflammatory effect that blocks NEC pathogenesis. Approach: A total of 34 piglets were delivered on gestation day 104 (analogous to 30 weeks of human gestation) by cesarean section. Piglets were assigned to one of three treatments: preterm infant formula (CTL), donor human milk (DHM), or one intramuscular injection of ADIPEG-20 (ADIPEG; 1.2 mg/kg) followed by preterm infant formula. Pigs were monitored for clinical signs of NEC and euthanized when they reached clinical endpoints. Gross and histologic sections of the stomach, proximal jejunum, distal ileum and colon were scored for NEC severity using an established scale. Plasma and tissue were analyzed for amino acid levels. Results: NEC incidence was greatest in the CTL (57%, n=8/14) pigs, and lowest in the ADIPEG (20%, n=2/10) and DHM (30%, n=3/10) pigs. Plasma arginine decreased from 230 uM on day 2 to 4 uM on day 3 24 hr after ADIPEG treatment. Plasma arginine was lower in ADIPEG pigs throughout the study compared to CTL and DHM pigs. Tissue arginine levels were similar in ADIPEG, CTL, and DHM across treatments in the liver, lung, kidney, distal ileum, skeletal muscle and heart. Plasma citrulline increased in the ADIPEG pigs on Day 2 (107 uM to 750uM) of the study and remained high until the end of the study compared to CTL and DHM pigs (~87 uM and 94 uM). Citrulline levels in the liver, lung, ileum, heart, and skeletal muscle was highest in the ADIPEG pigs compared to other treatments. Conclusion: Depletion of plasma arginine from circulation may be an effective strategy to prevent NEC. NIH/ NIGMS R01GM108940, NIH/NIDDK 1K08DK135845 and USDA/ARS 3092-51000-065 supported this work. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.