Abstract:
:This study was undertaken to develop techniques for measuring absolute rates of sterol synthesis in extrahepatic tissues in vitro and to estimate the magnitude of the errors inherent in the use of various 14C-labeled substrates for such measurements. Initial studies showed that significant errors were introduced when rates of synthesis were estimated using [3H]water since about 20 nmol of water were bound to each mg of tissue cholesterol isolated as the digitonide. This source of error could be eliminated by subtracting apparent incorporation rates obtained at 0 degrees C from those obtained at 37 degrees C or by regenerating and drying the free sterol. In a second set of experiments, the H/C incorporation ratio in cholesterol was determined in the liver by measuring the absolute rates of hydrogen and acetyl CoA flux into sterols. The ratio of 0.69 +/- 0.03 was found to be independent of the rate of hepatic cholesterol synthesis, the rate of hepatic acetyl CoA generation, or the source of the acetyl CoA. In a third set of studies, rates of incorporation of [3H]water or 14C-labeled acetate, octanoate, and glucose into digitonin-precipitable sterols were simultaneously measured in nine different extrahepatic tissues. Assuming that the H/C ratio measured in the liver also applied to these tissues, the [3H]water incorporation rates were multipled by the reciprocal of the H/C ratio to give the absolute rates of sterol synthesis in each tissue. When these were compared to the incorporation rates determined with the 14C-labeled substrates the magnitude of the errors in the rates of sterol synthesis obtained with these substrates in each tissue could be assessed. Only [14C]octanoate gave synthesis rates approaching 100% of those obtained with [3H]water and this occurred only in the intestine and kidney; in the other extrahepatic tissues this substrate gave rates of 6--66+ of the absolute rates. Rates of [14C]acetate incorporation in sterols varied from 4 to 62% of the [3H]water incorporation rates while those obtained with [14C]glucose were only 2--88% of the true rates. These studies document the large and highly variable errors inherent in estimating rates of sterol synthesis in extrahepatic tissues using 14C-labeled substrates under in vitro conditions.
journal_name
J Lipid Resjournal_title
Journal of lipid researchauthors
Andersen JM,Dietschy JMsubject
Has Abstractpub_date
1979-08-01 00:00:00pages
740-52issue
6eissn
0022-2275issn
1539-7262journal_volume
20pub_type
杂志文章abstract::Chiral phase high performance liquid chromatographic resolution of sn-1,2(2,3)- and X-1,3-diacylglycerols generated by partial Grignard degradation from natural triacylglycerols was carried out using a chiral column (25 cm x 4.6 mm i.d.) containing (R)-(+)-1-(1-napthyl)ethylamine polymer chemically bonded to 300A wide...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1990-09-01 00:00:00
abstract::ABCG1 and ABCG4 are highly homologous members of the ATP binding cassette (ABC) transporter family that regulate cellular cholesterol homeostasis. In adult mice, ABCG1 is known to be expressed in numerous cell types and tissues, whereas ABCG4 expression is limited to the central nervous system (CNS). Here, we show sig...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/M900250-JLR200
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journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1988-11-01 00:00:00
abstract::The sequences necessary for liver-specific expression of the apolipoprotein (apo) E gene have been shown to reside 3' to the gene, within the apoE/C-I/C-II gene cluster, but have not been precisely characterized. Utilizing a transient transfection reporter gene assay based on the apoC-II promoter, we have localized a ...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1993-10-01 00:00:00
abstract::A colony of New Zealand white rabbits has been developed which, when fed a cholesterol-supplemented diet, exhibit unusual resistance to hypercholesterolemia and atherosclerosis, disorders usually observed in normal cholesterol-fed rabbits. When resistant rabbits (RT) were fed a normal low cholesterol diet (ND), their ...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1989-02-01 00:00:00
abstract::Phospholipids serve as central structural components in cellular membranes and as potent mediators in numerous signaling pathways. There are six main classes of naturally occurring phospholipids distinguished by their distinct polar head groups that contain many unique molecular species with distinct fatty acid compos...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.D051581
更新日期:2014-11-01 00:00:00
abstract::The storage of lipids in the form of triglycerides (TGs) and the de novo synthesis (lipogenesis) of fatty acids from nonlipid precursors [de novo lipogenesis (DNL)] are important functions of adipose tissue (AT) that influence whole-body metabolism. Yet, few studies have reported in vivo estimates of adipose lipid kin...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.P082628
更新日期:2018-09-01 00:00:00
abstract::Oxidized forms of cholesterol (oxysterols) are present in atherosclerotic lesions and may play an active role in lesion development. For example, 7-ketocholesterol (7KC) inhibits cholesterol efflux from macrophage foam cells induced by apolipoprotein A-I (apoA-I). Such oxysterols may promote foam cell formation in ath...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1999-09-01 00:00:00
abstract::Mammalian spermatogenesis is a complex developmental program in which a diploid progenitor germ cell transforms into highly specialized spermatozoa. One intriguing aspect of sperm production is the dynamic change in membrane lipid composition that occurs throughout spermatogenesis. Cholesterol content, as well as its ...
journal_title:Journal of lipid research
pub_type: 杂志文章,评审
doi:10.1194/jlr.R032326
更新日期:2013-01-01 00:00:00
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journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.RA120000950
更新日期:2020-07-09 00:00:00
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journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.D070565
更新日期:2016-10-01 00:00:00
abstract::Achilles tendon xanthomas are associated with increased cardiovascular risk in patients with familial hypercholesterolemia (FH). Oxidized low density lipoprotein (OxLDL), the antibodies against OxLDL, and the LDL-associated phospholipase A(2) (Lp-PLA(2)) may play important roles in atherogenesis. We investigated the p...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.M600109-JLR200
更新日期:2006-10-01 00:00:00
abstract::The following data have been obtained from comparative studies on the metabolism of cholesterol, cholestanol, and beta-sitosterol by L-cell mouse fibroblasts. (1) When the sterols are added to the growth medium under similar conditions, cellular incorporation of cholesterol > cholestanol > beta-sitosterol; (2) only li...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1971-11-01 00:00:00
abstract::LDL-associated phospholipids (PLs) may be transferred into platelets. In this work, we characterized the role of VLDLs as PL donors. VLDL transferred radiolabeled PLs to platelets in a temperature- and concentration-dependent manner. LPL stimulated this process through its action on VLDL lipolysis, because it was abol...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.M500209-JLR200
更新日期:2006-02-01 00:00:00
abstract::Previous studies have shown that reduced levels of the adipocyte fatty acid binding protein (FABP)4 (AFABP/aP2), result in metabolic improvement including potentiated insulin sensitivity and attenuated atherosclerosis. Mechanistically, pharmacologic or genetic inhibition of FABP4 in macrophages upregulates UCP2, atten...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.M074542
更新日期:2017-07-01 00:00:00
abstract::Lipoprotein lipase (LPL) and hepatic lipase (HL) mediate the hydrolysis of triglycerides and phospholipids present in circulating lipoprotein particles and are essential for normal lipid metabolism. Both enzymes have a similar primary amino acid structure and share requirements for intact catalytic, lipid binding, and...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1993-08-01 00:00:00
abstract::Human apolipoprotein (apo) E occurs as three common isoforms (apoE4, E3, and E2), all of which influence plasma cholesterol levels. Although both apoE4 and E3 bind with equal effectiveness to the low density lipoprotein receptor, they associate preferentially with different classes of plasma lipoproteins: apoE4 with v...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1990-08-01 00:00:00
abstract::Incubation of 125I-labeled very low density lipoprotein (VLDL) with lipoprotein lipase-rich (postheparin) plasma obtained from intact or supradiaphragmatic rats resulted in the transfer of more than 80% of apoprotein C from VLDL to high density lipoprotein (HDL), whereas apoprotein B was associated with lipoprotein of...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1975-09-01 00:00:00
abstract::The lipids of intact human platelets were labeled in vitro with acetate-1-(14)C, and the distribution of radioactivity in individual fatty acids and in lipid classes was examined in platelet subcellular fractions separated by sucrose density gradient ultracentrifugation. The distribution of newly formed fatty acids am...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1971-01-01 00:00:00
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journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1998-08-01 00:00:00
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journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.M073270
更新日期:2017-08-01 00:00:00
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journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.M500203-JLR200
更新日期:2006-02-01 00:00:00
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journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1988-01-01 00:00:00
abstract::Thyroid hormone lowers serum cholesterol and alters sterol metabolic processes. This laboratory has previously reported increased biliary lipid secretion as an early effect of triiodothyronine (T3) in the rat. To evaluate whether the bile lipid action of T3 is a primary or secondary effect, the isolated-perfused rat l...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1992-10-01 00:00:00
abstract::Activation of cultured hepatic stellate cells correlated with an enhanced expression of proteins involved in uptake and storage of fatty acids (FA translocase CD36, Acyl-CoA synthetase 2) and retinol (cellular retinol binding protein type I, CRBP-I; lecithin:retinol acyltransferases, LRAT). The increased expression of...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.M200376-JLR200
更新日期:2003-02-01 00:00:00
abstract::We report the characterization of eight mutations of sterol 27-hydroxylase gene (CYP27) in five Italian patients with cerebrotendinous xanthomatosis, who were found to be compound heterozygotes. Four mutations (C --> T at nt 45 of exon 4, G(+1) --> A in intron 6, G(+5) --> T in intron 7, and G(-1) --> A in intron 7) a...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1997-11-01 00:00:00
abstract::SREBP cleavage-activating protein (Scap) is an endoplasmic reticulum membrane protein required for cleavage and activation of sterol regulatory element-binding proteins (SREBPs), which activate the transcription of genes in sterol and fatty acid biosynthesis. Liver-specific loss of Scap is well tolerated; hepatic synt...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.M059709
更新日期:2015-08-01 00:00:00
abstract::Sterol 27-hydroxylase, the mitochondrial enzyme that catalyzes the first step in oxidation of the sterol side chain in hepatic bile acid synthesis, also catalyzes the synthesis of 27-hydroxycholesterol from cholesterol. We have developed a high performance liquid chromatography (HPLC) assay for this enzyme, using eith...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1993-04-01 00:00:00
abstract::Cell death-inducing DFF45-like effector b (Cideb), an endoplasmic reticulum (ER)- and lipid droplet (LD)-associated protein, has been shown to play a critical role in maintaining hepatic lipid homeostasis by promoting the lipidation and maturation of VLDL particles. Here, we observed that Cideb is expressed in the jej...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:10.1194/jlr.M046482
更新日期:2014-07-01 00:00:00
abstract::Fatty acid translocase (FAT/CD36) is a membrane protein putatively involved in the transmembrane transport of long-chain fatty acids. We tested the hypothesis that expression of this protein in H9c2, a rat heart cell line normally not expressing FAT, would increase cellular palmitate uptake. We were able to stably tra...
journal_title:Journal of lipid research
pub_type: 杂志文章
doi:
更新日期:1998-10-01 00:00:00