A growing body of evidence has indicated that high-fat diet-induced nonalcoholic fatty liver disease is usually accompanied by oxidized low-density lipoprotein (ox-LDL) deposited in the liver. The current study aimed to investigate the effect of quercetin on high-fat diet-induced ox-LDL accumulation in the liver and to explore the potential underlying mechanisms. The results demonstrate that quercetin supplementation for 24 weeks significantly alleviated high-fat diet-induced liver damage and reduced hepatic cholesterol and ox-LDL level. Quercetin notably inhibited both mRNA and protein expression of CD36 (reduced by 53% and 71%, resp.) and MSR1 (reduced by 25% and 45%, resp.), which were upregulated by high-fat diet. The expression of LC3II was upregulated by 2.4 times whereas that of p62 and mTOR was downregulated by 57% and 63% by quercetin treatment. Therefore, the significantly improved autophagy lysosomal degradation capacity for ox-LDL may be implicated in the hepatoprotective effect of quercetin; scavenger receptors mediated ox-LDL uptake might also be involved.

Diets containing various docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratios protect against liver damage in mice fed with a high‐fat diet (HFD). However, it is unclear whether these beneficial roles of DHA and EPA are associated with alterations of fatty acid (FA) composition in the liver. This study evaluated the positive impacts of n‐6/n‐3 polyunsaturated fatty acids (PUFAs) containing different DHA/EPA ratios on HFD‐induced liver disease and alterations of the hepatic FA composition. ApoE^−/− mice were fed with HFDs with various ratios of DHA/EPA (2 : 1, 1 : 1, and 1 : 2) and an n‐6/n‐3 ratio of 4 : 1 for 12 weeks. After treatment, the serum and hepatic FA compositions, serum biochemical parameters, liver injury, and hepatic lipid metabolism‐related gene expression were determined. Our results demonstrated that dietary DHA/EPA changed serum and hepatic FA composition by increasing contents of n‐6 and n‐3 PUFAs and decreasing amounts of monounsaturated fatty acids (MUFAs) and the n‐6/n‐3 ratio. Among the three DHA/EPA groups, the DHA/EPA 2 : 1 group tended to raise n‐3 PUFAs concentration and lower the n‐6/n‐3 ratio in the liver, whereas DHA/EPA 1 : 2 tended to raise n‐6 PUFAs concentration and improve the n‐6/n‐3 ratio. DHA/EPA supplementation reduced the hepatic impairment of lipid homeostasis, oxidative stress, and the inflammatory responses in HFD‐fed mice. The DHA/EPA 2 : 1 group had lower serum levels of total cholesterol, triglycerides, and low‐density lipoprotein cholesterol and higher levels of adiponectin than HFD group. The DHA/EPA 1 : 2 group had elevated serum levels of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase, without significant change the expression of genes for inflammation or hepatic lipid metabolism among the three DHA/EPA groups. The results suggest that DHA/EPA‐enriched diet with an n‐6/n‐3 ratio of 4 : 1 may reverse HFD‐induced nonalcoholic fatty liver disease to some extent by increasing n‐6 and n‐3 PUFAs and decreasing the amount of MUFAs and the n‐6/n‐3 ratio.

Melon seeds have received considerable attention in recent years because of their high protein content, but they have not yet been fully used. The modification of melon seed protein (MSP) using ultrasound-assisted pH-shifting treatment was investigated in this study by analyzing structural characteristics and functional properties. The particle size, free sulfhydryl content, surface hydrophobicity, solubility, secondary structure, water-holding capacity, oil-holding capacity, emulsification activity index, and emulsification stability index of MSP were determined. MSP treated with ultrasound-assisted, pH-shifting had a smaller particle size, lower free sulfhydryl content, higher surface hydrophobicity, and solubility increased from 43.67 % to 89.12 %. The secondary structure of MSP was affected by ultrasonic treatment, manifesting as an α-helix increase and β-helix, β-turn, and random coil content decrease, which may be the reason why the protein structure became more compact after treatment. The water and oil holding capacities of MSP increased from 2.74 g/g and 3.14 g/g in untreated samples to 3.19 g/g and 3.97 g/g for ultrasound-treated samples, and further increased to 3.97 g/g and 5.02 g/g for ultrasound-assisted, pH-shifting treatment at pH 9.0, respectively. The emulsification activity index of MSP was 21.11 m²/g before treatment and reached a maximum of 32.34 m²/g after ultrasound-assisted, pH-shifting treatment at pH 9.0. The emulsification stability of MSP was maximized by ultrasonic treatment at pH 7.0. Ultrasound-assisted, pH-shifting treatment can effectively improve the functional properties of MSP by modifying the protein structure, which improves the potential application of melon seed protein in the food industry.