# Dietary Supplementation with Rumen-Protected Arginine or N-Carbamylglutamate Enhances Fetal Liver Development in Nutrient-Restricted Pregnant Hu Ewes

## TL;DR

Supplementing pregnant Hu ewes with arginine or N-carbamylglutamate improves fetal liver development when nutrition is restricted.

## Contribution

This study shows that RP-Arg and NCG supplementation can counteract the negative effects of maternal undernutrition on fetal liver development.

## Key findings

- Maternal undernutrition leads to maldevelopment of fetal liver in Hu ewes.
- Supplementation with RP-Arg or NCG enhances fetal liver growth and reduces apoptosis.
- NCG supplementation improves antioxidant capacity and protein/DNA ratios in fetal livers.

## Abstract

Intrauterine growth restriction (IUGR), defined as the impaired growth and development of a mammalian embryo/fetus or fetal organs during pregnancy, is a significant public health concern worldwide. The fetus is sensitive and responsive to the maternal milieu, and there is evidence that maternal nutritional deficiency has the potential to affect fetal liver development. N-carbamylglutamate (NCG), a stable activator of endogenous Arg synthesis, has been demonstrated to improve fetal survival by increasing the endogenous synthesis of arginine. In this study, we attempted to determine whether supplementation with rumen-protected arginine (RP-Arg) or NCG during late pregnancy in Hu ewes improves fetal liver function by suppressing fetal hepatic abnormalities and apoptosis. We found that maternal undernutrition during pregnancy leads to the maldevelopment of the fetal liver. However, supplementation with RP-Arg and NCG can enhance fetal liver development under such conditions.

This study was conducted in nutrient-restricted pregnant Hu ewes to determine whether rumen-protected arginine (RP-Arg) or N-carbamylglutamate (NCG) supplementation affects fetal liver growth and development. From 35 d to 110 d of gestation, 32 Hu ewes were randomly divided into four groups: a control group (100% of the National Research Council (NRC) requirements), a nutrient-restricted group (50% of the NRC requirements), and two treatment groups (ARG and NCG, 50% of the NRC requirements, supplemented with 20 g/day RP-Arg or 5 g/day NCG, respectively). Fetal body weights, fetal liver growth performance, the capability of antioxidation, and the expression of the mRNA and proteins of apoptosis-related genes in the fetal liver were determined and analyzed at 110 d of gestation. The dry matter, water, fat, protein, and ash components of the fetal livers in the RG group were found to be lower than in the CG group, and these components were significantly higher in the NCG group than in the RG group (p < 0.05). A decrease in DNA, RNA, and protein concentrations and contents, as well as in protein/DNA ratios, was observed in the RG group in comparison to the CG group (p < 0.05). Compared with the RG group, the NCG group had higher concentrations of DNA, RNA, and protein, as well as higher protein/DNA ratios (p < 0.05). The RG group had lower concentrations of cholinesterase, nitric oxide, nitric oxide synthase, superoxide dismutase, alanine aminotransferase, and total protein than the CG group (p < 0.05). The RG group had higher levels of glutathione peroxidase, maleic dialdehyde, and aspartate aminotransferase than the CG group (p < 0.05). In the RG group, the mRNA and protein expression of p53 and Bax was significantly increased (p < 0.05) compared with the CG group, and the gene expression of FasL and Bcl-2, the ratio of Bcl-2 to Bax, and the protein expression of Bcl-2 in the RG group were lower (p < 0.05) than in the CG group. It appears that RP-Arg and NCG supplementation during pregnancy could influence fetal liver growth and development. A nutrition-based therapeutic intervention to alleviate reduced fetal growth can be developed based on this study, which has demonstrated that maternal undernutrition during pregnancy induces the maldevelopment of the fetal liver.