Research on novel HDL cholesterol excretion mechanism

Too much cholesterol can lead to health problems but cholesterol on high-density lipoprotein (HDL-C) is sometimes referred to as `good´ cholesterol because it is inversely related to cardiovascular disease risk. Junior Associate Professor Maki Tsujita, Department of Biochemistry, Nagoya City University, Japan, is leading a team of researchers conducting studies on the novel high-density lipoprotein (HDL) cholesterol excretion mechanism with a view to obtaining new insights on the link between lipid metabolism and diet. Cholesterol biosynthesis involves more than 30 biosynthetic steps and the body has an efficient absorption mechanism to acquire it from the diet via NPC1L1 in the small intestine. The cholesteryl ester transfer protein (CETP) acts as a key recycling mechanism for cholesterol that mediates the equilibrium of cholesteryl esters (CE), limiting cholesterol excretion. The focus of Tsujita's research is on the movement of free-cholesterol molecules and examining its excretion from the body. Tsujita' wants to clarify whether it is CE or free cholesterol that the SR-B1 receptor takes into the cell when it binds HDL, in order to better understand the details of the metabolism of cholesterol. In her current study, she is using a new approach to investigating the origin of free cholesterol in plasma and has found that radiolabelled FCs are increased in SR-BI deficient mice compared to wild-type mice, suggesting that the conversion of CE to FCs is occurring in the blood.