Bioactive dipeptides mitigate high-fat and high-fructose corn syrup diet-induced metabolic-associated fatty liver disease via upregulation of Nrf2/HO-1 expressions in C57BL/6J mice

Metabolic-associated fatty liver disease (MAFLD), formerly referred to as non-alcoholic fatty liver disease (NAFLD), is a common liver disease characterized by an abnormal buildup of fat in liver. This study aimed to investigate whether bioactive dipeptides mitigate high-fat and high-fructose corn syrup diet (HFFD)-induced MAFLD in C57BL/6J mice. Sixty male C57BL/6J mice were randomly divided into six groups. The naïve group (untreated) was fed a standard chow diet and other groups were fed with HFFD along with vehicle and bioactive dipeptides treatment throughout experiment period. The control group received vehicle, YF10 and YF50 groups received Tyr-Phe, 10 and 50 mg/kg/day, FY10 and FY50 groups received Phe-Tyr, 10 and 50 mg/kg/day. At the end of experiment, body weight was recorded, and glucose homeostasis was assessed. Mice were sacrificed and blood samples were collected to measure biochemical parameters. Further, liver, visceral fat pads, and other organs were acutely dissected, weighed, and processed. Histopathological and immunohistochemical changes were analyzed. Long-term HFFD feeding resulted in elevated body weight gain, liver weight, visceral adiposity, liver injury, fasting hyperglycemia, hyperinsulinemia, and hyperlipidemia. It also increased severe hepatic steatosis, chronic low-grade inflammation, oxidative stress, mitochondrial dysfunction, and lipid peroxidation. However, bioactive dipeptides dose-dependently alleviated these complications which are associated with MAFLD by modulating adipokines secretion and antioxidant defense system via upregulation of Nrf2/HO-1 expressions. This study highlights potential of bioactive dipeptides as a promising approach for prevention and/or treatment of MAFLD induced by HFFD, providing novel insights into alternative therapeutic strategies.

Bioactive dipeptides enhance the tolerance of lager yeast to ethanol-oxidation cross-stress by regulating the multilevel defense system

Although high gravity brewing technology has been widely used for beer industries due to its economic benefits, yeast cells are subjected to multiple environmental stresses throughout the fermentation process. Eleven bioactive dipeptides (LH, HH, AY, LY, IY, AH, PW, TY, HL, VY, FC) were selected to evaluate their effects on cell proliferation, cell membrane defense system, antioxidant defense system and intracellular protective agents of lager yeast against ethanol-oxidation cross-stress. Results showed that the multiple stresses tolerance and fermentation performance of lager yeast were enhanced by bioactive dipeptides. Cell membrane integrity was improved by bioactive dipeptides through altering the structure of macromolecular compounds of the cell membrane. Intracellular reactive oxygen species (ROS) accumulation was significantly decreased by bioactive dipeptides, especially for FC, decreasing by 33.1%, compared with the control. The decrease of ROS was closely related to the increase of mitochondrial membrane potential, intracellular antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), and glycerol level. In addition, bioactive dipeptides could regulate the expression of key genes (GPD1, OLE1, SOD2, PEX11, CTT1, HSP12) to enhance the multilevel defense systems under ethanol-oxidation cross-stress. Therefore, bioactive dipeptides should be potentially efficient and feasible bioactive ingredients to improve the multiple stresses tolerance of lager yeast during high gravity fermentation.