Ameliorative Effect of Macadamia Nut Protein Peptides on Acetaminophen-Induced Acute Liver Injury in Mice

This study aims to examine the ameliorative effect of macadamia nut protein peptides (MPP) on acetaminophen (APAP)-induced liver injury (AILI) in mice, and develop a new strategy for identifying hepatoprotective functional foods. The molecular weight distribution and amino acid composition of MPP were first studied. Forty mice were then randomized into four groups: control group (CON), APAP model group, APAP+MPP low-dose group (APAP+L-MPP), and APAP+MPP high-dose group (APAP+H-MPP). The APAP+L-MPP (320 mg/kg per day) and APAP+H-MPP (640 mg/kg per day) groups received continuous MPP gavage for 2 weeks. A 12 h of APAP (200 mg/kg) gavage resulted in liver damage. Pathological alterations, antioxidant index levels, expression of toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-kappa B), and associated inflammatory factors were determined for each treatment group. The results revealed that the total amino acid content of MPP was 39.58 g/100 g, with Glu, Arg, Asp, Leu, Tyr, and Gly being the major amino acids. The molecular weight range of 0-1000 Da accounted for 73.54%, and 0-500 Da accounted for 62.84% of MPP. MPP ameliorated the pathological morphology and reduced the serum levels of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase of AILI in mice. MPP significantly increased the activities of superoxide dismutase and glutathione peroxidase in the liver compared with the APAP group. MPP inhibited the expression of TLR4, NF-kappa B, interleukin-1 beta (IL-1 beta), and tumor necrosis factor-alpha (TNF-alpha) genes in AILI mice. MPP also inhibited the expression levels of inflammatory factors (TNF-alpha and IL-6). Our study concludes that MPP alleviates AILI in mice by enhancing antioxidant capacity and inhibiting TLR4/NF-kappa B pathway-related gene activation.