Free cholesterol has been considered to be a critical risk factor of nonalcoholic fatty liver disease (NAFLD). It remains unknown whether dietary intake of condensed tannins (CTs) have distinguishable effects to alleviate liver damage caused by a high cholesterol diet. Male C57BL/6 mice were fed a high cholesterol diet for 6 weeks, and given CTs treatment at a dosage of 200 mg/(kg·day) at the same time. The results indicated that compared with mice fed a normal diet, a high cholesterol diet group resulted in significant weight loss, dysregulation of lipid metabolism in blood and liver, and oxidative stress in the liver, but CTs treatment dramatically reversed these negative effects. Hematoxylin and eosin (H&E) staining and frozen section observation manifested that CTs treatment could effectively reduce the deposition of liver cholesterol and tissue necrosis caused by high cholesterol intake. CTs alleviated liver injury mainly by regulating the expression of related genes in cholesterol metabolism pathway and AMPK phosphorylation. Our results confirmed that CTs have remarkable cholesterol lowering and anti-liver injury effects in vivo.

This study was aimed to analyze the effect of procyanidin B₂ (PC) and tannin acid (TA) on the activities of cholesterol esterase (CEase) and the inhibitory mechanisms of enzymatic activity. The interaction mechanisms were investigated by enzymatic kinetics, multi-spectroscopy methods, thermodynamics analysis, molecular docking, and dynamic simulations. PC and TA could bind with CEase and inhibit the activity of enzyme in a mixed-competitive manner and non-competitive manner, which was verif ied by molecular docking simulations and dynamics simulations. Also, PC and TA showed the synergistic inhibition with orlistat. Fluorescence, UVvis and the thermodynamic analysis revealed that the complexes were formed from CEase and inhibitors by noncovalent interaction. As revealed by the circular dichroism results, both PC and TA decreased enzymatic activities by altering the conformations of CEase. The inhibition of PC and TA on CEase might be one mechanism for its cholesterol-lowering effect.