Citrulline supplementation attenuates the development of non-alcoholic steatohepatitis in female mice through mechanisms involving intestinal arginase

Abstract

Non-alcoholic fatty liver disease (NAFLD) is by now the most prevalent liver disease worldwide. The non-proteogenic amino acid l -citrulline (L-Cit) has been shown to protect mice from the development of NAFLD. Here, we aimed to further assess if L-Cit also attenuates the progression of a pre-existing diet-induced NAFLD and to determine molecular mechanisms involved. Female C57BL/6J mice were either fed a liquid fat-, fructose- and cholesterol-rich diet (FFC) or control diet (C) for 8 weeks to induce early stages of NASH followed by 5 more weeks with either FFC-feeding +/- 2.5 g L-Cit/kg bw or C-feeding. In addition, female C57BL/6J mice were either pair-fed a FFC +/- 2.5 g L-Cit/kg bw +/- 0.01 g/kg bw i.p. N(ω)-hydroxy-nor- l -arginine (NOHA) or C diet for 8 weeks. The protective effects of supplementing L-Cit on the progression of a pre-existing NAFLD were associated with an attenuation of 1) the increased translocation of bacterial endotoxin and 2) the loss of tight junction proteins as well as 3) arginase activity in small intestinal tissue, while no marked changes in intestinal microbiota composition were prevalent in small intestine. Treatment of mice with the arginase inhibitor NOHA abolished the protective effects of L-Cit on diet-induced NAFLD. Our results suggest that the protective effects of L-Cit on the development and progression of NAFLD are related to alterations of intestinal arginase activity and intestinal permeability.

Aspartate induces metabolic changes and improves the host's ability to fight against Aeromonas hydrophila infection in Cyprinus carpio

“…These results indicated that aspartate is an effective modulator in combating A. hydrophila infection, which is consistent with the current findings in innate immunity by amino acids (e.g. glutamine, arginine, and citrulline) that have been reported (Hu et al, 2015; Rajcic et al, 2021; Zheng et al, 2019).…”

Inhibition of GCN2 alleviates hepatic steatosis and oxidative stress in obese mice: Involvement of NRF2 regulation

“…Here, we showed that GCN2iB increased the GSH/GSSG ratio and total glutathione levels in the livers of HFD-fed mice, which was associated with the upregulation of glutathione metabolic genes. GCN2iB also increased the abundance of citrulline and taurine, which exert beneficial effects in NAFLD animal models [ 44 , 45 ].…”

Alterations of nitric oxide homeostasis as trigger of intestinal barrier dysfunction in non‐alcoholic fatty liver disease

“…Arginase activity was measured in proximal intestinal tissue of mice and in serum of NAFL patients and healthy controls as detailed previously 22 …”

“…Arginase activity was measured in proximal intestinal tissue of mice and in serum of NAFL patients and healthy controls as detailed previously. 22 To determine arginase activity in tissue samples, proximal small intestine was homogenized in 10 mM Tris-HCl containing 0.4% (w/v) Triton X-100 and protease inhibitor cocktail. Levels of NO 2 − in proximal small intestine were detected using Griess assay (Promega).…”

“…After 8 weeks of feeding, FFC-fed mice had developed obvious signs of steatosis and beginning hepatic inflammation with the higher number of infiltrating neutrophils, NAS and plasma activities of ALT and AST (p < 0.05, Figure 1A-E). Expression of Tlr4 and myeloid differentiation primary response 88 (Myd88) mRNA in liver tissue, as well as bacterial endotoxin levels in portal plasma, being all indicative of intestinal barrier dysfunction, 19,22 were also significantly higher in mice fed the FFC in comparison to C-fed mice (Figure 1F-H). In addition, ZO-1 protein levels in small intestinal tissue were significantly lower in FFC-fed mice compared to C-fed mice (Figure 1I,J).…”