Mechanism Of Cholesterol Absorption Research Articles

Cell scientist to watch – Liang Ge

Liang Ge pursued his PhD in the lab of Dr Bao-Liang Song at the Institutes of Biochemistry and Cell Biology, Chinese Academy of Sciences, where he studied the molecular mechanisms of cholesterol absorption. In 2011 he moved to California for a postdoc and later a research specialist position with Randy Schekman at the University of California, Berkeley. There, he discovered key roles for LC3 lipidation and the ER-Golgi intermediate compartment in autophagosome biogenesis. Liang established his group in the School of Life Sciences at Tsinghua University at the end of 2017, where he combines cell biology and biochemistry techniques, mouse models and computational biology to study the mechanisms of autophagy and unconventional protein secretion.

A Single Meal Containing Phytosterols Does Not Affect the Uptake or Tissue Distribution of Cholesterol in Zebrafish (Danio rerio)

Increased plant oil inclusion in aquaculture feeds has led to higher dietary phytosterol concentrations and speculation about whether this affects the metabolism and health of the fish. The mechanisms of cholesterol absorption and how phytosterols may affect this is unknown in fish. Zebrafish (Danio rerio) were used to study the effects of phytosterols on the uptake and organ distribution of dietary cholesterol in fish. One meal of diets containing a constant addition of cholesterol (cold and [4-14C] cholesterol) and varying types and concentrations of phytosterols were fed to fish in individual compartments. The fish were not previously conditioned on the experimental diets. Activity of 14C was then measured in water and fish tissues to quantify the tissue distribution and excretion of cholesterol. There were no effects of the moderate dietary concentrations of phytosterols on the excretion or tissue distribution of dietary cholesterol 24 hours after the meal.

Expression of Megalin mRNA expression in gallbladder epithelium of patients with cholelithiasis and its significance

Objective To detect and analyze the change of Meaglin mRNA expression in gall-bladder epithelium of the cholelithiasis and gallbladder polyp patients. Methods The expression level of Megalin mRNA was determined in 62 ceses of cholelithiasis and 38 cases of gallbladder polyp by RT-PCR. Results Megalin mRNA was expressed in the gallbladder epithelium and the expression was significantly different between the 2 groups. Conclusion The mechanism of cholesterol absorp-tion in gallbladder epithelium might play an important role in gallstone pathogenesis. Key words: Cholecystitis; Megalin mRNA; Gallbladder epithelium

ABCG5 and ABCG8 are expressed in gallbladder epithelial cells

Gallbladder epithelial cells (GBEC) are exposed to high biliary cholesterol concentrations on their apical (AP) surface. The mechanisms of cholesterol absorption and efflux by these cells are not known. We hypothesized that ABCG5 and ABCG8 are expressed in GBEC and mediate AP cholesterol efflux. Human gallbladder cDNA expressed message for ABCG5 and ABCG8. Cultured murine GBEC also expressed abcg5 and abcg8 mRNA and protein, as did cultured canine GBEC. Interestingly, treatment with model bile containing supersaturating concentrations of cholesterol, or treatment with LXRα/RXR ligands, did not lead to differences in expression of ABCG5 or ABCG8 in the murine or the canine cells. The subcellular localization of ABCG5 and ABCG8 did show alterations, with predominantly intracellular localization at baseline and predominantly AP localization following treatment with model bile or LXRα ligand. GBEC therefore express ABCG5 and ABCG8; these sterol transporters may play a role in mediating AP cholesterol efflux in the gallbladder epithelium.

Cholesterol absorption

Cholesterol absorption is a key regulatory point in human lipid metabolism because it determines the amount of endogenous biliary as well as dietary cholesterol that is retained, thereby influencing whole body cholesterol balance. Plant sterols (phytosterols) and the drug ezetimibe reduce cholesterol absorption and low-density lipoprotein cholesterol in clinical trials, complementing the statin drugs, which inhibit cholesterol biosynthesis. The mechanism of cholesterol absorption is not completely known but involves the genes ABC1, ABCG5, and ABCG8, which are members of the ATP-binding cassette protein family and appear to remove unwanted cholesterol and phytosterols from the enterocyte. ABC1 is upregulated by the liver X (LXR) and retinoid X (RXR) nuclear receptors. Acylcholesterol acytransferase-2 is an intestinal enzyme that esterifies absorbed cholesterol and increases cholesterol absorption when dietary intake is high. New clinical treatments based on better understanding of absorption physiology are likely to substantially improve clinical cholesterol management in the future.

Mechanism of cholesterol absorption by the hydatid cysts of Echinococcus granulosus (Cestoda)

1. 1. The mechanism of cholesterol absorption by hydatid cysts of Echinococcus granulosus was studied in function of time of incubation, size of cysts, temperature of incubation, concentration of cholesterol substrate and presence of metabolic inhibitor. 2. 2. The results indicated that the uptake of cholesterol continuously increased with time of incubation, that small cysts absorbed cholesterol better than large ones, that the optimum temperature for uptake was 25°C and that uptake increased with increase in concentration of substrate. 3. 3. The addition of the metabolic inhibitor 2, 4-dinitrophenol did not affect the process of absorption thus eliminating the participation of the mechanisms of active transport or facilitated diffusion. 4. 4. It was suggested that mechanisms of simple diffusion and possibly exchange diffusion are operating in cholesterol absorption by hydatid cysts.

The mechanism of cholesterol absorption.

The mechanism of cholesterol absorption.

Observations on the mechanism of cholesterol absorption

Observations on the mechanism of cholesterol absorption

Mechanism of Cholesterol Absorption: II. CHANGES IN FREE AND ESTERIFIED CHOLESTEROL POOLS OF MUCOSA AFTER FEEDING CHOLESTEROL-4-C14

Mechanism of Cholesterol Absorption: II. CHANGES IN FREE AND ESTERIFIED CHOLESTEROL POOLS OF MUCOSA AFTER FEEDING CHOLESTEROL-4-C14

Uptake of cholesterol and cholesterol esters by inverted sacs of rat intestine.

Conditions for the use of inverted sacs of rat small intestine for the study of the mechanism of cholesterol absorption are described. Incubation of inverted sacs in albumin-stabilized emulsions of free cholesterol or cholesterol esters, under oxygen-carbon dioxide mixture, led to the disappearance of cholesterol from the external medium and accumulation of free or ester cholesterol in the sacs. Both forms of cholesterol were taken up against a concentration gradient without demonstrable chemical change. The uptake of free cholesterol was quite constant from the lower duodenum to the upper ileum and was independent of the pH of the external medium. Additions of oleic acid, sodium taurocholate or pancreatic extract depressed the uptake of free cholesterol. Comparable but more variable effects were found in respect to cholesterol ester uptake. Addition of pancreatic extract to the external medium increased the proportion of ester in the total cholesterol taken up by the sacs. This was due, in part, to synthesis of cholesterol esters in the mucosa.