0000000000543714
AUTHOR
Leyla C. Ramirez
Effects of peroxisome proliferator-activated receptor alpha activation on pathways contributing to cholesterol homeostasis in rat hepatocytes
International audience; Peroxisome proliferator-activated receptor alpha (PPARa) activation by fibrates controls expression of several genes involved in hepatic cholesterol metabolism. Other genes could be indirectly controlled in response to changes in cellular cholesterol availability. To further understand how fibrates may affect cholesterol synthesis, we investigated in parallel the changes in the metabolic pathways contributing to cholesterol homeostasis in liver. Ciprofibrate increased HMG-CoA reductase and FPP synthase mRNA levels in rat hepatocytes, together with cholesterogenesis from [14C] acetate and [3H] mevalonate. The up-regulation observed in fenofibrate- and WY-14,643-treate…
18-hydroxylation in the Y-1 adrenal cell line: response to ACTH and to culture conditions.
The 18-hydroxylation of deoxycorticosterone in the Y-1 adrenal cell line was studied under various incubation and cell culture conditions and compared to 11 beta-hydroxylation. Repeated incubation of the substrate increased both 18- and 11 beta-hydroxylation in the Y-1 cells. Furthermore, both 18- and 11 beta-hydroxylation were increased with increased serum concentration and prolonged incubation time. While the increase in 11 beta-hydroxylation seemed to be independent of the type of serum, 18-hydroxylation was much more important in cells cultured in fetal or newborn calf serum supplemented medium than in those cultured in horse serum supplemented medium. As expected, ACTH treatment incre…
Stimulation of peroxisomal palmitoyl-CoA oxidase activity by ciprofibrate in hepatic cell lines: comparative studies in Fao, MH1C1 and HepG2 cells.
The response of two rat cell lines, Fao and MH1C1, and one human cell line, HepG2, to the peroxisome proliferator ciprofibrate, was studied. Using a fluorometric assay for palmitoyl-CoA oxidase, the dose- and time-dependent increase of this enzymatic activity was determined. From the lowest concentration (100 microM) stimulation is evident in the two rat cell lines. In the Fao line, the activity was stimulated reaching a seven-fold increase over the control level at 250 microM after 72 h of treatment. In the MH1C1 line, the maximum stimulation, four- to five-fold, was obtained at 250 and 500 microM after 72 h. In the HepG2 cell line, activity increased two-fold at 250 microM after 72 h reac…
Chromatographic and mass spectrometric characteristics of 20-dihydroaldosterone.
The 20 alpha-reduced derivative of aldosterone, 20 alpha-dihydroaldosterone, was needed as reference compound in order to continue the studies on 18-hydroxylation in the Y-1 adrenal cell line. It was obtained by reduction of aldosterone with sodium borohydride. Analysis of the products of the reaction as methoxime trimethylsilyl (MO-TMS) derivatives by gas chromatography (GC) and GC-mass spectrometry (GC-MS) showed three possible forms of the compound. Their identification was confirmed by comparison with the products obtained by stereospecific reduction of aldosterone using 3 alpha,20 beta-hydroxysteroid dehydrogenase. Chromatographic behavior and mass spectra are given for the three forms…
Synthesis and gas chromatographic-mass spectrometric analysis of reduced compounds derived from 6 alpha- and 6 beta-hydroxy-11-deoxycorticosterone.
Abstract A series of thirty two 6-hydroxylated steroids were synthesized by selective reduction of the 4–5 double bond, the 3-oxo group, and/or the 20-oxo group of 6α- and 6β-hydroxyDOC. The different reactions leading to the production of specific isomers are discussed. The gas chromatographic and spectrometric characteristics of the methoxime-trimethylsilyl (MO-TMS) or trimethylsilyl (TMS) derivatives of the isomers obtained are given. The gas chromatographic separation of the syn- and anti -isomers of the methoxime in position 3 was found to be characteristic of the configuration of the hydroxyl in position 6. The difference between methylene unit values of syn- and anti- isomers is much…
Aldosterone synthase activity in the Y-1 adrenal cell line.
The Y-1 adrenal cell line was shown to produce 20 alpha-dihydroaldosterone from deoxycorticosterone. This compound was identified by GC-MS by comparison with the previously synthesized reference compound. Two other 18-hydroxylated metabolites were identified as 11 beta,18-dihydroxy-20 alpha-dihydroprogesterone from endogenous cholesterol and 18-hydroxy-20 alpha-dihydro-11-dehydrocorticosterone from DOC. The conditions necessary for the synthesis of these compounds are culturing in 20% serum-supplemented medium and repeated incubations with the substrate. The production of 11 beta-hydroxylated steroids and that of 18-oxygenated steroids is stimulated differently by ACTH and angiotensin II su…