scholarly journals Distinct forms of cytochrome P-450 are responsible for 6β-hydroxylation of bile acids and of neutral steroids

1991 ◽  
Vol 275 (1) ◽  
pp. 105-111 ◽  
Author(s):  
P Zimniak ◽  
E J Holsztynska ◽  
A Radominska ◽  
M Iscan ◽  
R Lester ◽  
...  
Keyword(s):  
Bile Acids ◽  
Steroid Hormones ◽  
Rat Liver ◽  
Lithocholic Acid ◽  
Structural Elements ◽  
Differential Inhibition ◽  
Mutual Inhibition ◽  
Hydroxylation Reaction ◽  
Differential Responses ◽  
Cytochrome P 450

Cytochrome P-450-dependent 6 beta-hydroxylation of bile acids in rat liver contributes to the synthesis of the quantitatively important pool of 6-hydroxylated bile acids, as well as to the detoxification of hydrophobic bile acids. The lithocholic acid 6 beta-hydroxylation reaction was investigated and compared with androstenedione 6 beta-hydroxylation. Differential responses of these two activities to inducers and inhibitors of microsomal P-450 enzymes, lack of mutual inhibition by the two substrates and differential inhibition by antibodies raised against several purified hepatic cytochromes P-450 were observed. From these results it was concluded that 6 beta-hydroxylation of lithocholic acid is catalysed by P-450 form(s) different from the subfamily IIIA cytochromes P-450 which are responsible for the bulk of microsomal androstenedione 6 beta-hydroxylation. Similar, but more tentative, results revealed that the 7 alpha-hydroxylation of lithocholic acid and of androstenedione may be also catalysed by distinct P-450 enzymes. The results indicate that cytochromes P-450 hydroxylating bile acids are distinct from analogous enzymes that carry out reactions of the same regio- and stereo-specificity on neutral steroids (steroid hormones). A comparison of pairs of cytochromes P-450 that catalyse the same reaction on closely related steroid molecules will help to define those structural elements in the proteins that determine the recognition of their respective substrates.

scholarly journals The lithocholic acid 6β-hydroxylase cytochrome P-450, CYP 3A10, is an active catalyst of steroid-hormone 6β-hydroxylation

1993 ◽  
Vol 291 (2) ◽  
pp. 429-433 ◽  
Author(s):  
T K H Chang ◽  
J Teixeira ◽  
G Gil ◽  
D J Waxman
Keyword(s):  
Bile Acid ◽  
Bile Acids ◽  
Steroid Hormones ◽  
Lithocholic Acid ◽  
Liver Microsomes ◽  
Microsomal Protein ◽  
Secondary Bile Acid ◽  
Cos Cells ◽  
Major Activity ◽  
Cytochrome P 450

CYP 3A10 is a hamster liver cytochrome P-450 (P450) that encodes lithocholic acid 6 beta-hydroxylase, an enzyme that plays an important role in the detoxification of the cholestatic secondary bile acid lithocholate. Western-blot analysis revealed that the expression of CYP 3A10 protein is male-specific in hamster liver microsomes, a finding that is consistent with earlier analysis of CYP 3A10 mRNA. Since it has not been established whether the specificities of bile acid hydroxylase P450s, such as CYP 3A10, are restricted to their anionic bile acid substrates, we investigated the role of CYP 3A10 in the metabolism of a series of neutral steroid hormones using cDNA directed-expression in COS cells. The steroid hormones examined, testosterone, androstenedione and progesterone, were each metabolized by the expressed CYP 3A10, with 6 beta-hydroxylation corresponding to a major activity in all three instances. CYP 3A10-dependent steroid hydroxylation was increased substantially when the microsomes were prepared from COS cells co-transfected with NADPH:P450 reductase cDNA. In this case, the expressed P450 actively catalysed the 6 beta-hydroxylation of testosterone (288 +/- 23 pmol of product formed/min per mg of COS-cell microsomal protein), androstenedione (107 +/- 19 pmol/min per mg) and progesterone (150 +/- 7 pmol/min per mg). Other major CYP 3A10-mediated steroid hydroxylase activities included androstenedione 16 alpha-hydroxylation, progesterone 16 alpha- and 21-hydroxylation, and the formation of several unidentified products. CYP 3A10 exhibited similar Vmax. values for the 6 beta-hydroxylation of androstenedione and lithocholic acid (132 and 164 pmol/min per mg respectively), but metabolized the bile acid with a 3-fold lower Km (25 microM, as against 75 microM for androstenedione). Together, these studies establish that the substrate specificity of the bile acid hydroxylase CYP 3A10 is not restricted to bile acids, and further suggest that CYP 3A10 can play a physiologically important role in the metabolism of two classes of endogenous P450 substrates:steroid hormones and bile acids.

scholarly journals Effects of clofibrate on some microsomal hydroxylations involved in the formation and metabolism of bile acids in rat liver

1976 ◽  
Vol 156 (2) ◽  
pp. 445-448 ◽  
Author(s):  
B O Angelin ◽  
I Björkhem ◽  
K Einarsson
Keyword(s):  
Bile Acid ◽  
Bile Acids ◽  
Rat Liver ◽  
Lithocholic Acid ◽  
Present Knowledge ◽  
Acid Formation ◽  
Microsomal Metabolism ◽  
Endogenous Cholesterol

1. The liver microsomal metabolism of [4-14C]cholesterol, endogenous cholesterol, 7 α-hydroxy-4-[6 β-3H]cholesten-3-one, 5-β-[7 β-3H]cholestane-3 α, 7 α-diol and [3H]lithocholic acid was studdied in control and clofibrate (ethyl p-chlorophenoxyisobutyrate)-treated rats. 2. The extent of 7 α-hydroxylation of exogenous [414C]cholesterol and endogenous cholesterol, the latter determined with a mass fragmentographic technique, was the same in the two groups of rats. The extent of 12 α-hydroxylation of 7 α-hydroxy-4-cholesten-3-one and 5 β-cholestane-3 α, 7 α-diol was increased by about 60 and 120% respectively by clofibrate treatment. The 26-hydroxylation of 5 β-cholestane-3 α, 7 α-diol was not significantly affected by clofibrate. The 6 β-hydroxylation of lithocholic acid was about 80% higher in the clofibrate-treated animals than in the controls. 3. The results are discussed in the context of present knowledge about the liver microsomal hydroxylating system and bile acid formation in patients with hypercholesterolaemia, treated with clofibrate.

scholarly journals Binding of bile acids by 100 000g supernatants from rat liver

1977 ◽  
Vol 162 (3) ◽  
pp. 659-664 ◽  
Author(s):  
R C Strange ◽  
I A Nimmo ◽  
I W Percy-Robb
Keyword(s):  
Molecular Weight ◽  
Bile Acids ◽  
Rat Liver ◽  
Chenodeoxycholic Acid ◽  
Lithocholic Acid ◽  
Equilibrium Dialysis ◽  
Acid Transport ◽  
Binding Characteristics ◽  
Glycocholic Acid ◽  
Prominent Peak

1. The binding of glycocholic acid, chenodeoxycholic acid and lithocholic acid to rat liver 1000 000g supernatants was studied by equilibrium dialysis. 2. The binding characteristics of the bile acids suggest that the binding components are involved in bile acid transport. 3. When mixtures of [14C]lithocholic acid and liver supernatants were eluted from columns of Sephadex G-75, a prominent peak of [14C]lithocholic acid appeared with proteins of mol.wt. approx. 40000. A second, smaller, peak of [14C]lithocholic acid was eluted with proteins of mol.wt. approx. 100000. 4. The inclusion of cholic acid, glycocholic acid or chenodeoxycholic acid in the eluting buffer decreased the amount of [14C]lithocholic acid that was eluted with the higher-molecular-weight component.

scholarly journals Changes in the Metabolism of Steroid Hormones by the Rat Liver Cytochrome P-450 System after Induction with trans-Stilbene Oxide.

1981 ◽  
Vol 35b ◽  
pp. 151-153 ◽  
Author(s):  
Johan Meijer ◽  
Joseph W. DePierre ◽  
Klaus Mosbach ◽  
Gian Maria Pacifici ◽  
Anders Rane
Keyword(s):  
Steroid Hormones ◽  
Rat Liver ◽  
Liver Cytochrome ◽  
Trans Stilbene ◽  
Cytochrome P 450

Pharmacological effects of secondary bile acid microparticles in diabetic murine model

2020 ◽  
Vol 16 ◽  
Author(s):  
Armin Mooranian ◽  
Nassim Zamani ◽  
Bozica Kovacevic ◽  
Corina Mihaela Ionescu ◽  
Giuseppe Luna ◽  
...  
Keyword(s):  
Bile Acid ◽  
Blood Glucose ◽  
Bile Acids ◽  
Lithocholic Acid ◽  
Diabetes Treatment ◽  
Secondary Bile Acid ◽  
Glucose Levels ◽  
Anti Inflammatory ◽  
Antidiabetic Effects

Aim: Examine bile acids effects in Type 2 diabetes. Background: In recent studies, the bile acid ursodeoxycholic acid (UDCA) has shown potent anti-inflammatory effects in obese patients while in type 2 diabetics (T2D) levels of the pro-inflammatory bile acid lithocholic acid were increased, and levels of the anti-inflammatory bile acid chenodeoxycholic acid were decreased, in plasma. Objective: Hence, this study aimed to examine applications of novel UDCA nanoparticles in diabetes. Methods: Diabetic balb/c adult mice were divided into three equal groups and gavaged daily with either empty microcapsules, free UDCA, or microencapsulated UDCA over two weeks. Their blood, tissues, urine, and faeces were collected for blood glucose, inflammation, and bile acid analyses. UDCA resulted in modulatory effects on bile acids profile without antidiabetic effects suggesting that bile acid modulation was not directly linked to diabetes treatment. Results: UDCA resulted in modulatory effects on bile acids profile without antidiabetic effects suggesting that bile acid modulation was not directly linked to diabetes treatment. Conclusion: Bile acids modulated the bile profile without affecting blood glucose levels.

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