Effects of gamma-oryzanol and cycloartenol ferulic acid ester on cholesterol diet induced hyperlipidemia in rats

Hypolipidemic effects of gamma-oryzanol (OZ) and cycloartenol ferulic acid ester (CAF) on the hyperlipidemia induced by ingestion of a high cholesterol diet (HCD) in male Sprague-Dawley rats were investigated. The test drugs were given orally and intravenously, daily for 12 days with the HCD feeding. The oral administration with OZ and CAF at 100 mg/kg daily for 6 or 12 days did not apparently prevent the hyperlipidemia induced by HCD-feeding. The intravenous administrations with OZ and CAF at 10 mg/kg for 6 days significantly inhibited the increases in serum total cholesterol (TC), phospholipid (PL) and free cholesterol by HCD. OZ and CAF did not inhibit the decreases of TC in high density lipoprotein (HDL-TC) and HDL-PL by HCD. The increases of atherogenic index [( TC-HDL-TC]/[HDL-TC] and [PL-HDL-PL]/[HDL-PL]) with the HCD feeding were reduced by the intravenous administrations of OZ and CAF. Triglyceride, nonesterified fatty acid, lactate dehydrogenase and transaminase (GOT and GPT) markedly decreased below the control level by the intravenous administrations of OZ and CAF for 12 days. These results suggest that the intravenous administrations of OZ and CAF may have accelerated the excretion of lipids in the blood.     

Effect of gamma-oryzanol on atheroma formation in hypercholesterolemic rabbits

The anti-oxidant action of ferulic acid in gamma-oryzanol was tested in hypercholesterolemic rabbits to determine its effects on the development of atherosclerosis. Eighteen male New Zealand white rabbits were fed a diet containing 1% cholesterol with or without 1% gamma-oryzanol for 10 weeks. The anti-oxidant effect was assessed by the degree of resistance of low density lipoprotein (LDL) to oxidation by copper sulfate and the effect of the copper oxidized LDL on the incorporation of oleate into cholesteryl ester by mouse peritoneal macrophages. In addition, the levels of plasma cholesterol, triglyceride and lipid peroxide were measured before, during and at the end of cholesterol loading. The amount of free ferulic acid and gamma-oryzanol in plasma and LDL and the area of aortic atherosclerotic plaques were determined. It was found that oleate incorporation into cholesteryl ester by macrophages was significantly reduced in the gamma-oryzanol-treated group compared to the non-treated group, and that the reduction was via a mechanism independent of anti-oxidant action. However, no differences were found in the levels of plasma cholesterol, triglyceride, lipid peroxide or in the areas of atherosclerotic plaques between the two groups. It was concluded that gamma-oryzanol has little or no preventive effects on atherosclerosis in rabbits.     

Effect of gamma-oryzanol on cytochrome P450 activities in human liver microsomes

The effects of gamma-oryzanol, a drug mainly used for the treatment of hyperlipidaemia, on several cytochrome P450 (CYP) specific reactions in human liver microsomes were investigated to predict drug interactions with gamma-oryzanol in vivo from in vitro data. The following eight CYP catalytic reactions were used in this study: CYP1A1/2-mediated 7-ethoxyresorufin O-deethylation, CYP2A6-mediated coumarin 7-hydroxylation, CYP2B6-mediated 7-benzyloxyresorufin O-debenzylation, CYP2C8/9-mediated tolbutamide methylhydroxylation, CYP2C19-mediated S-mephenytoin 4'-hydroxylation, CYP2D6-mediated bufuralol 1'-hydroxylation, CYP2E1-mediated chlorzoxazone 6-hydroxylation, and CYP3A4-mediated testosterone 6beta-hydroxylation. gamma-Oryzanol had little inhibitory effects on CYP activities, indicating that this compound would not be expected to cause clinically significant interactions with other CYP-metabolized drugs at expected therapeutic concentrations.     

Comparative effects of two forms of gamma-oryzanol in different sterol compositions on hyperlipidemia induced by cholesterol diet in rats

Hypolipidemic effects of the usual gamma-oryzanol (gamma-OZ) and a new gamma-OZ (N-gamma-OZ) with a different sterol composition from gamma-OZ were investigated on the hyperlipidemia induced by ingestion of a high cholesterol diet (HCD) containing 1% cholesterol for 12 days in male Sprague-Dawley rats. Treatment with gamma-OZ for 6 days significantly inhibited the increase in serum total cholesterol (TC) and phospholipids (PL) induced by HCD, while the treatment with gamma-OZ for 12 days did not inhibit the increase of TC and PL. Treatment with N-gamma-OZ at 100 or 1000 mg/kg for 6 days slightly inhibited the increase of TC by HCD. The decrease of TC in high density lipoprotein (HDL-TC) was markedly inhibited by treatment with N-gamma-OZ for 12 days, but N-gamma-OZ for 6 days and gamma-OZ for 6 and 12 days did not inhibit the decrease of HDL-TC. Treatment with N-gamma-OZ for 12 days significantly inhibited the increase of PL and free cholesterol (FC) by HCD. gamma-OZ at 1000 mg/kg for 12 days also inhibited the increase of FC. N-gamma-OZ significantly reduced the atherogenic index using TC and HDL-TC by affecting the HDL-TC increase. gamma-OZ at 100 mg/kg and N-gamma-OZ at 100 mg/kg for 6 days reduced the atherogenic index using TC and HDL-TC by the inhibition of TC increase. The atherogenic index using PL and HDL-PL was only reduced by the treatment with N-gamma-OZ at 1000 mg/g for 12 days. The increase of triglyceride (TG) by HCD was inhibited by the treatment of N-gamma-OZ for 6 days (all doses) and 12 days (500, 1000 mg/kg), and gamma-OZ at 500 mg/kg for 6 and 12 days also inhibited the increase of TG by HCD. gamma-OZ and N-gamma-OZ had no effects on liver lipid contents. The hypolipidemic effect of N-gamma-OZ was slightly more potent than that of gamma-OZ.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of ketoconazole on cholesterol synthesis and on HMG-CoA reductase and LDL-receptor activities in Hep G2 cells

Ketoconazole, an imidazole derivative, is a member of a class of metabolic inhibitors acting specifically at cytochrome-P450 mediated reactions. We studied the effects of this compound on cholesterol synthesis, and on HMG-CoA reductase and LDL receptor activities, in cultures of human hepatoma cell line Hep G2. Ketoconazole, added in concentrations of 2-100 microM, inhibited cholesterol synthesis, and caused accumulation of lanosterol and dihydrolanosterol. Total mass formation of sterols was depressed. After 20 hr preincubation of the cells with the drug in these concentrations, activity of HMG-CoA reductase was markedly decreased, while the receptor-mediated binding, uptake and degradation of human LDL were increased. This increase is at least partly due to a higher affinity of LDL for its receptor. Ketoconazole prevented the fall in LDL-receptor activity caused by preincubation with LDL, whereas it did not affect the suppression caused by preincubation with exogenous mevalonate. These findings are discussed with respect to the involvement of endogenous sterol and non-sterol effectors of reductase and receptor activities.     

Studies on gamma-oryzanol. III. Influence of gamma-oryzanol on circadian rhythms of serum gastrin, 11-OHCS and gastric secretion in rats (author's transl)]

In the course of investigations of gamma-oryzanol in rats, circadian rhythms in antiulcerogenic action on gamma-oryzanol were observed. Circadian rhythms in several other parameters were investigated and correlated with the antiulcerogenic action. Pretreatment of rats with gamma-oryzanol 100 mg/kg, s.c., for 5 days tended to decrease serum gastrin levels and gastric secretion, and to increase serum 11-OHCS. Suppresive patterns of serum gastrin and gastric secretion following the pretreatment with gamma-oryzanol corresponded to the circadian rhythms in antiulcerogenic action of gamma-oryzanol. A complication of our results suggests that increment of catecholamines in rat brain after gamma-oryzanol plays a role in the above mentioned actions.     

Effect of simvastatin (MK-733) on the regulation of cholesterol synthesis in Hep G2 cells

A new antihypercholesterolemic drug, simvastatin (MK-733), which is a prodrug of a potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, inhibited cholesterol synthesis from [14C]acetate concentration dependently without inhibiting it from [3H]mevalonate in Hep G2 cells. Therefore, MK-733 is thought to be converted to L-654,969, the active beta-hydroxy acid form of MK-733 in the cells and/or medium. MK-733 inhibited cholesterol ester synthesis, but did not affect phospholipid, free fatty acid and triacylglycerol synthesis. This compound increased HMG-CoA reductase activity concentration dependently and raised the specific binding, internalization and degradation of 125I-labeled low density lipoprotein by Hep G2 cells. Another HMG-CoA reductase inhibitor, pravastatin (CS-514), also behaved like MK-733. However, its potency was far less than that of MK-733.     

胆固醇合成抑制剂抗动脉粥样硬化研究进展

胆固醇是形成动脉粥样硬化的主要原因之一,通过抑制体内胆固醇的生物合成,可以有效地减少动脉硬化的形成,进而有效地减少因动脉粥样硬化引起的血栓、纤维组织增生以及钙质沉着。目前,胆固醇合成抑制剂是一类重要的抗动脉粥样硬化药物,本文对抑制胆固醇生物合成中所需要的4种主要生物酶抑制剂的研究进展进行综述。     

Effects of gamma-oryzanol on gastric lesions and small intestinal propulsive activity in mice

Effects of gamma-oryzanol were studied on gastric lesions induced by both conditioned emotional stimuli (CES) and REM sleep deprivations and on the facilitation of small intestinal propulsive activity by CES in mice. The CES were given by the communication box method, and the REM sleep deprivations were performed by a modified flower pot method. The incidence of gastric lesions in responder mice induced by CES was reduced by twice p.o. administrations at 6 hr interval of gamma-oryzanol at 200 and 500 mg/kg, oxazolam at 2 mg/kg and atropine at 1-10 mg/kg. The incidence in sender mice was also reduced by gamma-oryzanol at 200 and 500 mg/kg. In addition, the incidence of gastric lesions induced by REM sleep deprivation was also reduced by single administration of gamma-oryzanol at 100 and 200 mg/kg and oxazolam at 5 mg/kg. The facilitation of small intestinal propulsive activity in responder mice induced by CES was suppressed by gamma-oryzanol at 100 and 200 mg/kg and atropine at 10 mg/kg. These results indicate that gamma-oryzanol has an antiulcerative action on gastric lesions induced by CES and REM sleep deprivation, and it has a suppressive action on the facilitation of intestinal propulsion induced by CES.     

Effect of eritadenine on cholesterol metabolism in the rat

Eritadenine, a hypocholesterolemic adenine derivative occurring in the Japanese mushroom Lentinus edodes, had no effect on hepatic cholesterol biosynthesis from 1-¹⁴C-acetate and 2-¹⁴C-mevalonate but accelerated tissue uptake of plasma cholesterol.     

The circadian rhythm of synthesis and catabolism of cholesterol

The circadian rhythms of HMG-CoA reductase and cholesterol-7-hydroxylase (low values during light, rising in the evening with maximum at 12.00 p.m.) are investigated in rats under diverse conditions.Intragastral administration of cholestyramine (bile acid-absorbing resin) leads to an increased rhythm of both enzymes. Feeding of cholic acid (or cholesterol) reduces the activity of both enzymes (of HMG-CoA reductase and cholesterol — 7-hydroxylase, respectively). In starved rats enzyme activities are lowered, too; a damped rhythm reappears after 24 h. A 20% fat diet (containing saturated fatty acids predominantly) markedly reduces the high values.Enzyme activities inhibited after thyroidectomy can be normalized by thyroxin substitution. Thyroxin administration in the normal remains without effect. Four-day insulin treatment of the normal inhibits cholesterol-7-hydroxylase, has no effect on HMG-CoA reductase. In the untreated diabetic rat cholesterol-7-hydroxylase is increased, HMG-CoA reductase significantly inhibited. Insulin treatment of the diabetic animal results in normalized values of HMG-CoA reductase whilst cholesterol-7-hydroxylase is nearly completely suppressed.The rate-limiting enzymes of cholesterol turnover are peripherally regulated by their products via a negative feedback. In contrast, hormones may have synergistic or opposite effects; thus they may represent means of higher regulation. All regulative possibilities discussed (except hypophysectomy) do modify the circadian rhythms. This cannot be demonstrated after hypophysectomy. After hypophysectomy circadian rhythms are not detectable any more.To get valid data about biochemical or pharmacological effects on these enzymes the circadian variations have to be considered by measuring at different times of day (e.g. fat diet); for only the area of enzyme activity and time of day is proportional to the metabolism of a substrate.Read at the Symposium Relevance of Chronobiology for Toxicology and Pharmacology held at the 16th Spring Meeting of the Deutsche Pharmakologische Gesellschaft, Section: Toxicology, March 6, 1975, Mainz     

Effect of pitavastatin on macrophage cholesterol metabolism

OBJECTIVES: Pitavastatin is the first totally synthetic HMG-Co A reductase inhibitor in Japan that significantly reduces LDL cholesterol while raising HDL cholesterol. Clinical trial showed that pitavastatin has potent effects for LDL cholesterol lowering and is expected effectively to prevent atherosclerosis. To clarify the mechanism of reduction of atherosclerosis by pitavastatin, we examined the effect of pitavastatin on foam cell formation of RAW264.7 macrophages. METHODS & RESULTS: Macrophages were cultured with pitavastatin for 24 h and exposed to oxidized LDL with pitavastatin for 3 days. Pitavastatin decreased the cellular cholesteryl ester content in a dose-dependent manner, and this effect was not via inhibition of HMG-CoA reductase because the 3-30 nM pitavastatin did not inhibit [14C]cholesterol synthesis from [14C]acetic acid and the effect was not influenced by addition of mevalonic acid. Pitavastatin increased neutral cholesterol esterase (NCEase) activity and did not affect ACAT activity, and decreased the expression of CD36 and ABCA1 mRNA. The mechanism of the increase of NCEase activity was that pitavastatin directly modified the substrate state, which was cholesterol oleate emulsified with lecithin. CONCLUSION: Clinical blood concentrations of pitavastatin prevent foam cell formation of RAW macrophages by oxidized LDL, and this was not via inhibition of HMG-CoA reductase, and modify substrate condition.     

Influence of trapidil and derivatives on cholesterol synthesis and esterification in cultured cells

The effect of trapidil (Rocornal) and its derivatives AR 12456 and AR 12463 on endogenous cholesterol synthesis and on cholesterol esterification rate was studied in human skin fibroblasts (HSF), in human hepatoma cell line Hep G2 and in primary culture of peritoneal macrophages from mouse (PMM). The cholesterol esterification rate was not influenced by the drugs in the tested cell lines. The incorporation of [14C]acetate into cholesterol in HSF was inhibited by AR 12463 and AR 12456, but not by trapidil. The inhibitory potency of AR 12456 in HSF was enhanced after preincubation of the drug with Hep G2 and removal of the medium to HSF, suggesting that the formed metabolite(s) are more potent inhibitors than the parent substance. The metabolite(s) formed seem(s) to influence the first steps in the endogenous formation of cholesterol, because the incorporation of [14C]mevalonate into cholesterol was not significantly inhibited. These findings suggest that the demonstrated inhibition of the endogenous cholesterol synthesis by AR 12456, especially after transformation into a probably more active substance(s), together with the recently described enhanced expression of LDL receptors in Hep G2 cells may partially explain the hypocholesterolaemic activity of AR 12456.     

Physiological and pharmacological regulation of small intestinal cholesterol synthesis

1. The small intestine is an important site of cholesterol synthesis in the body and at least in experimental animals, it also contributes to the circulating plasma pool of cholesterol. 2. Studies on synthesis regulation have been partly contradictory but it is now concluded that the cellular cholesterol balance is the basic regulatory factor of intestinal cholesterol synthesis. However, the balance is affected differently in various specialized cells and parts of the small intestine. 3. Most data on synthesis regulation are derived from experimental animals but the few human studies suggest that similar regulatory factors function in man, too.