In this work, we established a HepG2 cell model of hypercholesterolemia in order to investigate the cholesterol-lowering activity and underlying mechanism of sterols. The levels of total cholesterol (TC), triglycerides (TG) and cholesterol regulation-related proteins were measured in HepG2 cells treated with nothing, simvastatin as a positive control or sterols. The results showed that the four sterol compounds tested could reduce TC and TG levels and mitigate the increase of lipids levels and lipid metabolism disorder in hypercholesterolemic cells. Moreover, they reduced the biosynthesis and absorption of cholesterol, decreased cholesterol esterification and promoted cholesterol excretion to the intestine by down-regulating the expression of Niemann-Pick C1-like 1 (NPC1L1), acetyl-coenzyme A acetyltransferase 2 (ACAT2), 3-hydroxy-3-methylglutaryl-coenzyme A synthase (HMGCS1) and sterol-regulatory element-binding proteins (SREBP2), and up-regulating the expression of ATP-binding cassette transporter G5/8 (ABCG5/8). We concluded that sterols improve lipid levels in hypercholesterolemic cells by affecting the expression of proteins related to cholesterol absorption and metabolism.

In this study, the antitumor properties and the possible molecular mechanisms of Cyclocarya paliurus polysaccharide (CP) and its phosphorylated derivative (P-CP) on CT-26 mouse colon carcinoma cells were investigated. Results found that CP had high inhibition ratio against CT-26 cells. The flow cytometry results found that CP treatment could cause the intracellular acidification, arrest the cell cycle in the S phase and increase reactive oxygen species generation. Additionally, CP treatment triggered mitochondrial membrane potential depolarization and Ca²⁺ overloading, and broke down the balance of antioxidant system, Na⁺/K⁺-ATPase and Ca²⁺-ATPase. Further analysis found CP induced cell apoptosis through improving the activities of caspase-3 and caspase-9, and increasing the level of cytochrome C. Furthermore, the comparative study of antitumor effect on CT-26 cells displayed that the phosphorylation enhanced antitumor activities of polysaccharides. These results suggest CP is a potential natural therapeutic agent for colon cancer and phosphorylation represents an effective method of enhancing the antitumor activity of CP.