Citrulline supplementation leads to increased immune suppression and more severe outcomes in infected newborn piglets

Background: Preterm infants are at high risk of infection and sepsis, which is associated with arginine (ARG) deficiency. Optimal nutrition for preterm newborns suspected with infection is critical to prevent sepsis development. Citrulline (CIT) supplementation is known to prevent sepsis in adult rodents, by maintaining sufficient blood ARG levels and vascular stabilization. We hypothesized that CIT therapy improve sepsis outcomes in infected preterm newborns via CIT and ARG metabolism.Results: After infection, oral CIT supplementation led to higher mortality, blood bacterial load, and circulating and hepatic inflammation, compared with the infected controls. Intravenous CIT administration also showed increased inflammation and bacterial burdens without increased mortality. Liver transcriptomics and data from in vitro blood stimulation indicated that CIT induces enhanced immunosuppression, which may impair resistance response to bacteria at early stage of infection and later cause excessive inflammation and tissue damage. Conclusion: Early stage of CIT supplementation exacerbates sepsis severity in infected preterm pigs, likely via induced enhanced systemic immunosuppression. Caesarean-delivered, parentally nourished preterm pigs were treated with CIT (1g/kg) via an oral bolus (ORA_CIT) or continuous intravenous supplement (IV_CIT), then inoculated with Staphylococcus epidermidis or saline (SE/CON) and cared for 14h. Clinical outcomes were monitored, while blood, liver and spleen samples were collected for analysis. Liver RNA was used for RNAseq.