Modulation of cholesterol 7α-hydroxylase and sterol 27-hydroxylase activities by steroids and physiological conditions in hamster

Souidi, Maâmar; Parquet, Michel; Férézou, Jacqueline; Lutton, C.

doi:10.1016/s0024-3205(99)00089-2

Cited by 44 publications

(37 citation statements)

References 28 publications

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“…Mitochondrial and microsomal fractions were prepared from fresh liver samples (1 g) (28). The microsomal fraction for the assay of HMG-CoA reductase activity was suspended in a modified buffer with 10 mmol/l DTT.…”

Section: Liver Analysesmentioning

confidence: 99%

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Cholesterol-lowering effects of dietary blue lupin (Lupinus angustifolius L.) in intact and ileorectal anastomosed pigs

Martins

Riottot

Abreu

et al. 2005

Journal of Lipid Research

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The present study was undertaken to investigate the effect of cholesterol-enriched casein (CAS) and blue lupin seed (BL) diets on the cholesterol metabolism of intact (INT) and ileorectal anastomosed (IRA) pigs. For 3 weeks, four groups of six pigs were allocated to the treatments (CAS-INT, CAS-IRA, BL-INT, and BL-IRA). Diet-induced hypercholesterolemia was inhibited by the BL through a substantial decrease in plasma LDL-cholesterol. The BL also reduced liver esterified and total cholesterol, increased hepatic LDL receptor synthesis and HMG-CoA reductase activity, and stimulated intestinal bile acid reabsorption. The neutral sterol output was higher in BL-than in CAS-fed pigs. The bile acid output was lower in IRA than in INT pigs. Surgery also prevented steroid microbial transformation, but it did not influence plasma cholesterol levels. These results suggest that the hypocholesterolemic effect of the BL, compared with the CAS, is attributable to impaired intestinal cholesterol absorption, probably involving increased bile acid reabsorption and higher contents of dietary phytosterols, both factors that reduce the micellar solubilization of cholesterol. Furthermore, according to our data, the contribution of the large intestine to cholesterol metabolism is very weak. Hypercholesterolemia and its implications for cardiovascular diseases is a major problem in human health, and much attention has been paid to dietary intervention as a tool for its prevention and treatment (1). Legumes have shown hypocholesterolemic effects in human and animal models (2-4), but these studies have mainly been done with soybean or its components. Therefore, studies involving other legumes, such as lupins, may clarify the mechanism by which plasma cholesterol is reduced and lead to the identification of new functional foods and/or components.Seeds of several species of lupins have been used as food for Ͼ 3,000 years in the Mediterranean area (5). These bitter seeds had to be soaked in water before consumption, to remove most of their alkaloid content (6). From the second half of the 20th century onward, low-alkaloid varieties of white lupin ( Lupinus albus ), yellow lupin ( Lupinus luteus ), and blue lupin ( Lupinus angustifolius ) have been domesticated and selected (7). In 2004, sweet varieties of these three species were mainly cultivated in several parts of Australia, Europe, and South America (8) and used for feed and food applications. Blue lupin seeds have higher nonstarch polysaccharide (6) and protein contents than soybean, with a similar amino acid profile (9). Their use in the food industry is being developed, and lupins are beginning to replace soybean in products such as tempe, miso, fermented sauces, and cooked snack foods (6). Lupin-based fiber supplements, cookies, bread, and spaghetti, with a high sensory quality, are also reported (10).No studies have been undertaken to test the effect of blue lupin seeds on cholesterol metabolism in the pig, an animal model with a plasma lipid profile similar to that of huma...

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Section: Liver Analysesmentioning

confidence: 99%

“…The microsomal cholesterol 7 ␣ -hydroxylase (CYP7A1; EC 1.14.13.17) and mitochondrial sterol 27-hydroxylase (CYP27A1; EC 1.14.13.15) activities were assayed according to Souidi, Parquet, and Lutton (31) and Souidi et al (28), respectively.…”

Section: Liver Analysesmentioning

confidence: 99%

Cholesterol-lowering effects of dietary blue lupin (Lupinus angustifolius L.) in intact and ileorectal anastomosed pigs

Martins

Riottot

Abreu

et al. 2005

Journal of Lipid Research

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“…Microsomal and mitochondrial fractions were isolated according to the procedure described by Einarsson et al [7] and Souidi et al [41]. HMGCoA reductase activity was determined in the microsomal fractions, in the presence of alkaline phosphatase using Phillip and Shapiro's radioisotopic technique [32].…”

Section: Hepatic Enzyme Activitiesmentioning

confidence: 99%

“…CYP7A1 was assayed in the microsomal fractions according to a radioisotopic method using [4-14 C]cholesterol, solubilized and carried by hydroxypropyl-b-cyclodextrin [40]. CYP27A1 was assayed in the mitochondrial fractions according to a radioisotopic method using [4-14 C]cholesterol, solubilized and carried by hydroxypropyl-b-cyclodextrin [41].…”

Section: Hepatic Enzyme Activitiesmentioning

confidence: 99%

Increasing amounts of dietary myristic acid modify the plasma cholesterol level and hepatic mass of Scavenger receptor BI without affecting bile acid biosynthesis in hamsters

Loison

Mendy²,

Sérougne

et al. 2002

Reprod. Nutr. Dev.

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-The purpose of this study was to analyze the effects of increasing amounts of dietary myristic acid (0.03 to 4.2% of the total dietary energy) on the plasma and hepatic cholesterol metabolism. Six groups of hamsters received semi-purified diets containing 0.05% cholesterol and 12.5% lipids and differing only by the nature of the triglycerides (Safflower oil, lard, lard/coconut oil (1:1), milk fat, milk fat/coconut oil (1:1), coconut oil) for 3 weeks. A positive regression between the plasma cholesterol level and the dietary myristic acid level was observed (r = 0.60, P < 0.0001). However, it is noteworthy that the increase in plasma total cholesterol only reflects an increase in the level of HDL-cholesterol. In parallel, the mass SR-BI decreased linearly with the increased level of myristic acid in the diet, whereas the LDL-R did not change. This study shows that increasing amounts of myristic acid (0.03 to 4.2%) do not alter the cholesterol or bile acid metabolism and increase only the HDL-C. myristic acid / cholesterol / LDL receptor / SR-B1 / hamsterRésumé -Des doses croissantes d'acide myristique dans l'alimentation modifient la concentration plasmatique du cholestérol et la quantité de SR-BI, sans affecter la biosynthèse des acides biliaires chez le hamster. Le but de cette étude était d'analyser les effets de doses croissantes d'acide myristique (0,03 à 4,2 % de l'apport énergétique total) sur le métabolisme plasmatique et hépatique du cholestérol. Six groupes de hamsters ont reçu des régimes semi-synthétiques contenant 0,05 % de cholestérol et 12,5 % de lipides (carthame, saindoux, saindoux/huile de coco (1:1),

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“…Sterol 27-Hydroxylase Activity-The activity of mitochondrial sterol 27-hydroxylase in the liver was measured as described by Souidi et al (22). Briefly, the livers were homogenized, and the mitochondria were isolated by differential centrifugation.…”

Section: Materials-[␣-mentioning

confidence: 99%

In Vivo and in Vitro Regulation of Sterol 27-Hydroxylase in the Liver during the Acute Phase Response

Memon

Moser

Shigenaga

et al. 2001

Journal of Biological Chemistry

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The host response to infection is associated with several alterations in lipid metabolism that promote lipoprotein production. These changes can be reproduced by lipopolysaccharide (LPS) administration. LPS stimulates hepatic cholesterol synthesis and suppresses the conversion of cholesterol to bile acids. LPS down-regulates hepatic cholesterol 7␣-hydroxylase, the rate-limiting enzyme in the classic pathway of bile acid synthesis. We now demonstrate that LPS markedly decreases the activity of sterol 27-hydroxylase, the rate-limiting enzyme in the alternate pathway of bile acid synthesis, in the liver of Syrian hamsters. Moreover, LPS progressively decreases hepatic sterol 27-hydroxylase mRNA levels by 75% compared with controls over a 24-h treatment period. LPS also decreases oxysterol 7␣-hydroxylase mRNA levels in mouse liver. In vitro studies in HepG2 cells demonstrate that tumor necrosis factor and interleukin (IL)-1 decrease sterol 27-hydroxylase mRNA levels by 48 and 80%, respectively, whereas IL-6 has no such effect. The IL-1-induced decrease in sterol 27-hydroxylase mRNA expression occurs early, is sustained for 48 h, and requires very low doses. In vivo IL-1 treatment also lowers hepatic sterol 27-hydroxylase mRNA levels in Syrian hamsters. Studies investigating the molecular mechanisms of LPS-induced decrease in sterol 27-hydroxylase show that LPS markedly decreases mRNA and protein levels of hepatocyte nuclear factor-1 (HNF-1), a transcription factor that regulates sterol 27-hydroxylase, in the liver. Moreover, LPS decreases the binding activity of HNF-1 by 70% in nuclear extracts in hamster liver, suggesting that LPS may down-regulate sterol 27-hydroxylase by decreasing the binding of HNF-1 to its promoter. Coupled with our earlier studies on cholesterol 7␣-hydroxylase, these data indicate that LPS suppresses both the classic and alternate pathways of bile acid synthesis. A decrease in bile acid synthesis in liver would reduce cholesterol catabolism and thereby contribute to the increase in hepatic lipoprotein production that is induced by LPS and cytokines.

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Modulation of cholesterol 7α-hydroxylase and sterol 27-hydroxylase activities by steroids and physiological conditions in hamster

Cited by 44 publications

References 28 publications

Cholesterol-lowering effects of dietary blue lupin (Lupinus angustifolius L.) in intact and ileorectal anastomosed pigs

Cholesterol-lowering effects of dietary blue lupin (Lupinus angustifolius L.) in intact and ileorectal anastomosed pigs

Increasing amounts of dietary myristic acid modify the plasma cholesterol level and hepatic mass of Scavenger receptor BI without affecting bile acid biosynthesis in hamsters

In Vivo and in Vitro Regulation of Sterol 27-Hydroxylase in the Liver during the Acute Phase Response

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