Biliary cholesterol secretion is a process important for 2 major disease complexes, atherosclerotic cardiovascular disease and cholesterol gallstone disease. With respect to cardiovascular disease, biliary cholesterol...Biliary cholesterol secretion is a process important for 2 major disease complexes, atherosclerotic cardiovascular disease and cholesterol gallstone disease. With respect to cardiovascular disease, biliary cholesterol secretion is regarded as the f inal step for the elimination of cholesterol originating from cholesterol-laden macrophage foam cells in the vessel wall in a pathway named reverse cholesterol transport. On the other hand, cholesterol hypersecretion into the bile is considered the main pathophysiological determinant of cholesterol gallstone formation. This review summarizes current knowledge on the origins of cholesterol secreted into the bile as well as the relevant processes and transporters involved. Next to the established ATP-binding cassette (ABC) transporters mediating the biliary secretion of bile acids (ABCB11), phospholipids (ABCB4) and cholesterol (ABCG5/G8), special attention is given to emerging proteins that modulate or mediate biliary cholesterol secretion. In this regard, the potential impact of the phosphatidylserine flippase ATPase class Ⅰ type 8B member 1, the Niemann Pick C1-like protein 1 that mediatescholesterol absorption and the high density lipoprotein cholesterol uptake receptor, scavenger receptor class B type Ⅰ, is discussed.展开更多
Scavenger receptor class B type Ⅰ (SR-BI) is an important member of the scavenger receptor family of integral membrane glycoproteins. This review highlights studies in SR-BI knockout mice, which concern the role of S...Scavenger receptor class B type Ⅰ (SR-BI) is an important member of the scavenger receptor family of integral membrane glycoproteins. This review highlights studies in SR-BI knockout mice, which concern the role of SR-BI in cholesterol and steroid metabolism. SR-BI in hepatocytes is the sole molecule involved in selective uptake of cholesteryl esters from high-density lipoprotein (HDL). SR-BI plays a physiological role in binding and uptake of native apolipoprotein B (apoB)-containing lipoproteins by hepatocytes, which identif ies SR-BI as a multipurpose player in lipid uptake from the blood circulation into hepatocytes in mice. In adrenocortical cells, SR-BI mediates the selective uptake of HDL-cholesteryl esters, which is eff iciently coupled to the synthesis of glucocorticoids (i.e. corticosterone). SR-BI knockout mice suffer from adrenal glucocorticoid insuff iciency, which suggests that functional SR-BI protein is necessary for optimal adrenal steroidogenesis in mice. SR-BI in macrophages plays a dual role in cholesterol metabolism as it is able to take up cholesterol associated with HDL and apoBcontaining lipoproteins and can possibly facilitate cholesterol efflux to HDL. Absence of SR-BI is associated with thrombocytopenia and altered thrombosis susceptibility, which suggests a novel role for SR-BI in regulating platelet number and function in mice. Transgenic expression of cholesteryl ester transfer protein in humanized SR-BI knockout mice normalizes hepatic delivery of HDL-cholesteryl esters. However, other pathologies associated with SR-BI def iciency, i.e. increased atherosclerosis susceptibility, adrenal glucocorticoid insuffi ciency, and impaired platelet function are not normalized, which suggests an important role for SR-BI in cholesterol and steroid metabolism in man. In conclusion, generation of SR-BI knockout mice has signif icantly contributed to our knowledge of the physiological role of SR-BI. Studies using these mice have identif ied SR-BI as a multi-purpose player in cholesterol and steroid metabolism because it has distinct roles in reverse cholesterol transport, adrenal steroidogenesis, and platelet function.展开更多
Lutein,a type of carotenoids,is found to delay the onset and progression of age-related macular degeneration(AMD).Several lutein supplementation studies showed that after an initial increase,lutein serum levels demons...Lutein,a type of carotenoids,is found to delay the onset and progression of age-related macular degeneration(AMD).Several lutein supplementation studies showed that after an initial increase,lutein serum levels demonstrated a subsequent decrease despite continuous supplementation.In this systematic literature review,this obscure phenomenon was tried to be explained.The subsequent drop in lutein levels was postulated due to down-regulation of lutein receptors scavenger receptor class B typeⅠ(SR-BI)in the gastrointestinal tract,upregulation of lutein degrading enzymeβ-carotene dioxygenase(BCDO2),or perhaps a combination of both.Some single nucleotides polymorphisms(SNPs)that could have influence on the occurrence of this phenomenon.To date,an exact scientific explanation for this phenomenon has not been established.Further research is needed to investigate this phenomenon in depth to reach an irrefutable explanation,giving that lutein is proven to be effective in delaying the onset and progression of AMD and its metabolism in the human body becomes of equal importance.展开更多
基金Supported by A grant from the Netherlands Organization for Scientif ic Research (NWO, VIDI Grant 917-56-358)
文摘Biliary cholesterol secretion is a process important for 2 major disease complexes, atherosclerotic cardiovascular disease and cholesterol gallstone disease. With respect to cardiovascular disease, biliary cholesterol secretion is regarded as the f inal step for the elimination of cholesterol originating from cholesterol-laden macrophage foam cells in the vessel wall in a pathway named reverse cholesterol transport. On the other hand, cholesterol hypersecretion into the bile is considered the main pathophysiological determinant of cholesterol gallstone formation. This review summarizes current knowledge on the origins of cholesterol secreted into the bile as well as the relevant processes and transporters involved. Next to the established ATP-binding cassette (ABC) transporters mediating the biliary secretion of bile acids (ABCB11), phospholipids (ABCB4) and cholesterol (ABCG5/G8), special attention is given to emerging proteins that modulate or mediate biliary cholesterol secretion. In this regard, the potential impact of the phosphatidylserine flippase ATPase class Ⅰ type 8B member 1, the Niemann Pick C1-like protein 1 that mediatescholesterol absorption and the high density lipoprotein cholesterol uptake receptor, scavenger receptor class B type Ⅰ, is discussed.
基金Supported by Top Institute Pharma (TIPharma Project T2-110 Hoekstra M and Van Berkel TJC)+2 种基金Grant 2008T070 from the Netherlands Heart Foundation (Hoekstra M)VIDI Grant 917.66.301 from the Netherlands Organization for Scientific Research (Van Eck M)Van Eck Mis an Established Investigator of the Netherlands Heart Foundation (Grant 2007T056)
文摘Scavenger receptor class B type Ⅰ (SR-BI) is an important member of the scavenger receptor family of integral membrane glycoproteins. This review highlights studies in SR-BI knockout mice, which concern the role of SR-BI in cholesterol and steroid metabolism. SR-BI in hepatocytes is the sole molecule involved in selective uptake of cholesteryl esters from high-density lipoprotein (HDL). SR-BI plays a physiological role in binding and uptake of native apolipoprotein B (apoB)-containing lipoproteins by hepatocytes, which identif ies SR-BI as a multipurpose player in lipid uptake from the blood circulation into hepatocytes in mice. In adrenocortical cells, SR-BI mediates the selective uptake of HDL-cholesteryl esters, which is eff iciently coupled to the synthesis of glucocorticoids (i.e. corticosterone). SR-BI knockout mice suffer from adrenal glucocorticoid insuff iciency, which suggests that functional SR-BI protein is necessary for optimal adrenal steroidogenesis in mice. SR-BI in macrophages plays a dual role in cholesterol metabolism as it is able to take up cholesterol associated with HDL and apoBcontaining lipoproteins and can possibly facilitate cholesterol efflux to HDL. Absence of SR-BI is associated with thrombocytopenia and altered thrombosis susceptibility, which suggests a novel role for SR-BI in regulating platelet number and function in mice. Transgenic expression of cholesteryl ester transfer protein in humanized SR-BI knockout mice normalizes hepatic delivery of HDL-cholesteryl esters. However, other pathologies associated with SR-BI def iciency, i.e. increased atherosclerosis susceptibility, adrenal glucocorticoid insuffi ciency, and impaired platelet function are not normalized, which suggests an important role for SR-BI in cholesterol and steroid metabolism in man. In conclusion, generation of SR-BI knockout mice has signif icantly contributed to our knowledge of the physiological role of SR-BI. Studies using these mice have identif ied SR-BI as a multi-purpose player in cholesterol and steroid metabolism because it has distinct roles in reverse cholesterol transport, adrenal steroidogenesis, and platelet function.
基金Supported by DSR Scholarship Support,King Saud University。
文摘Lutein,a type of carotenoids,is found to delay the onset and progression of age-related macular degeneration(AMD).Several lutein supplementation studies showed that after an initial increase,lutein serum levels demonstrated a subsequent decrease despite continuous supplementation.In this systematic literature review,this obscure phenomenon was tried to be explained.The subsequent drop in lutein levels was postulated due to down-regulation of lutein receptors scavenger receptor class B typeⅠ(SR-BI)in the gastrointestinal tract,upregulation of lutein degrading enzymeβ-carotene dioxygenase(BCDO2),or perhaps a combination of both.Some single nucleotides polymorphisms(SNPs)that could have influence on the occurrence of this phenomenon.To date,an exact scientific explanation for this phenomenon has not been established.Further research is needed to investigate this phenomenon in depth to reach an irrefutable explanation,giving that lutein is proven to be effective in delaying the onset and progression of AMD and its metabolism in the human body becomes of equal importance.
