Blood cholesterol and HDL cholesterol in cigarette smokers.

24 cigarette smokers were investigated for their blood cholesterol and HDL cholesterol. They had elevated total cholesterol compared to age and sex matched controls. 21 smokers out of 24 had significant decrease of HDL cholesterol. It is suggested that smoking, which is a major risk factor for coronary heart disease, might act through its effect on total cholesterol and HDL cholesterol.     

Biosynthesis of cholesterol and cholesterol acetate in dendrobatid arrow poison frogs

The skin of neotropical poison frogs of the genus Dendrobates and Phyllobates presents a series of unique poisons containing decahydroquinoline and perhydro-cyclopentanophenanthrene nuclei respectively. Examples of each class are pumiliotoxin C (2-n-propyl-5-methyl-cis-decahydroquinoline) and batrachotoxin. The biosynthesis of these poisons has now been investigated in Dendrobates pumilio, D. auratus and Phyllobates aurotaenia, using as possible precursors radioactive cholesterol, mevalonate and acetate. Even over periods of up to 14 weeks, significant incorporation of radioactivity into the poisons was not observed. Both acetate and mevalonate were, however, converted to cholesterol and cholesterol acetate.     

Modulation of high-density lipoprotein cholesterol metabolism and reverse cholesterol transport

Low high-density lipoprotein (HDL)-cholesterol (C) is an important risk factor for coronary heart disease. In vitro, HDL exerts several potentially anti-atherogenic effects including reverse cholesterol transport (RCT) from peripheral cells to the liver. Hence, raising HDL-C has become an interesting target for anti-atherosclerotic drug therapy. Levels of HDL-C and the composition of HDL subclasses in plasma are regulated by apolipoproteins, lipolytic enzymes, lipid transfer proteins, receptors, and cellular transporters. The interplay of these factors leads to RCT and determines the composition and thereby the anti-atherogenic properties of HDL. Recent findings suggest that the mechanism of HDL modification rather than a sole increase in HDL-C determines the efficacy of anti-atherosclerotic drug therapy. In several controlled and prospective intervention studies, patients with low HDL-C and additional risk factors benefited from treatment with fibrates or statins. However, in only some of the fibrate trials was prevention of coronary events in patients with low HDL-C and hypertriglyceridaemia related to an increase in HDL-C. This may be because currently available drugs increase HDL-C levels only moderately and because HDL levels per se do not necessarily correlate with the functionality of HDL. However, several novel targets to modify RCT have emerged from the recent understanding of HDL synthesis, maturation and catabolism. The four major targets for an anti-atherogenic strategy in HDL metabolism include stimulation of apoA-I synthesis and secretion, the stimulation of ABCA1 expression, the inhibition of cholesterol ester transfer protein, and the up-regulation of scavenger receptor BI. These and other modulations of HDL metabolism are thought to result in improved RCT making them attractive targets for the development of new regimens of anti-atherogenic drug therapy.     

Inhibition of pancreatic cholesterol esterase reduces cholesterol absorption in the hamster

Background

Type 4 phosphodiesterase (PDE4) inhibitors have been shown to stimulate bone formation in vivo and to stimulate osteoblastic differentiation in vitro. As one possible mechanism for the stimulation of bone formation is the recruitment of osteoprogenitor cells from the bone marrow, we have investigated the effect of the PDE4 inhibitors EMD273316, EMD95833, EMD249615 and EMD 219906 on fibroblastic colony formation by whole bone marrow cells and on the ability of these colonies to adopt an osteoblastic phenotype.

Results

All four agents stimulated colony formation in a concentration dependent manner, however, in the case of EMD273316 & EMD95833, the effect was evident at lower concentrations and the addition of prostaglandin E₂ (PGE₂) was not necessary for maximal stimulation. It was subsequently found that co-incubation with indomethacin reduced the stimulatory effects of EMD273316 & EMD95833 but had no effect on the actions of EMD249615 and EMD 219906 and that EMD273316 & EMD95833 stimulated the synthesis of endogenous PGE₂ by whole bone marrow cells whereas EMD249615 and EMD 219906 had no significant effect.

Conclusions

These data suggest that EMD249615, EMD 219906, EMD273316 & EMD95833 can promote the recruitment of bone marrow osteoprogenitor cells leading to a stimulation of bone formation via their direct inhibitory effects on PDE4. The actions of EMD273316 & EMD95833 however, are augmented by their ability to stimulate endogenous prostanoids synthesis which acts synergistically with their direct effects on PDE4.     

Effects of NTE-122, a novel acyl-CoA:cholesterol acyltransferase inhibitor, on cholesterol esterification and high-density lipoprotein-induced cholesterol efflux in macrophages

We investigated the effects of a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, NTE-122 (trans-1,4-bis[[1-cyclohexyl-3-(4-dimethylamino phenyl)ureido]methyl]cyclohexane), on ACAT activities in macrophages originating from several species and high-density lipoprotein (HDL)-induced cholesterol efflux in phorbol 12-myristate 13-acetate (PMA)-treated THP-1 cells. NTE-122 inhibited cell-free ACAT activities in human PMA-treated THP-1 cells and mouse J774.1 cells with IC50 values of 0.88 and 360 nM, respectively. NTE-122 competively inhibited the ACAT activity in PMA-treated THP-1 cells. NTE-122 also inhibited cellular ACAT activities in PMA-treated THP-1 cells, rat peritoneal macrophages and J774.1 cells with IC50 values of 3.5, 84 and 6800 nM, respectively. Furthermore, NTE-122 prevented cholesterol accumulation in PMA-treated THP-1 cells incubated with acetylated low density lipoprotein, simultaneously with HDL, while it caused accumulation of a significant amount of free cholesterol in the absence and even in the presence of HDL. NTE-122 also enhanced HDL-induced cholesterol efflux from established foam cells converted from PMA-treated THP-1 cells. These results suggest that NTE-122, capable of inhibiting macrophage ACAT activity in humans more strongly than those in the other species, exhibits anti-atherogenic effects by preventing the foam cell formation and enhancing the foam cell regression in humans.     

Regulation of hepatic cholesterol metabolism in CETP/LDLr mice by cholesterol feeding and by drugs (cholestyramine and lovastatin) that lower plasma cholesterol

1. The hepatic mechanisms involved in the simultaneous regulation of plasma cholesterol concentration and cholesteryl ester transfer protein (CETP) activity were investigated by sharply modifying the hepatic rates of cholesterol synthesis. This was accomplished by cholestyramine, lovastatin and cholesterol feeding in human CETP transgenic mice cross-bred with low-density lipoprotein receptor (LDLr)-knockout mice, generating CETP(+/-)/LDLr(+/-) mice, which present a plasma lipoprotein profile resembling that of humans. 2. Analyses of pooled data showed that the plasma CETP activity correlated positively with plasma total cholesterol concentration, hepatic CETP mRNA and the liver microsomal cholesterol content; a negative correlation was found between plasma CETP activity and the liver 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and LDLr mRNA levels. These coordinated events represent an efficient control system that stabilizes the cell cholesterol content. 3. Nonetheless, not all cholesterol metabolism regulatory systems seem to fit into a coherent pattern of responses, suggesting that other unknown cellular mechanisms play roles depending on the type of pharmacological intervention. 4. For example, microsomal cholesterol content was not affected by cholestyramine, but was increased on cholesterol feeding (as predicted), and, surprisingly, on lovastatin treatment. Furthermore, although both plasma cholesterol-lowering drugs increased CYP7A1 mRNA and had no effect on CYP27 mRNA, other metabolic components were differentially modified. Cholestyramine and lovastatin, respectively, did not modify and increased both HMG-CoA and sterol responsive element binding protein 1c mRNA, did not modify and lowered liver X receptor alpha mRNA, lowered and increased ATP binding cassette A1 mRNA and lowered and did not modify scavenger receptor B1 mRNA. 5. That is, different to unabsorbed cholestyramine, lovastatin, as an absorbed plasma cholesterol-lowering drug, may have modified the activity of other unknown genes that play roles in the interaction of CETP with the metabolism of hepatic cholesterol.     

Synthetic LXR agonist suppresses endogenous cholesterol biosynthesis and efficiently lowers plasma cholesterol

The liver X receptors (LXRs) are key regulators of genes involved in cholesterol homeostasis. Natural ligands and activators of LXRs are oxysterols. Numerous steroidal and non-steroidal synthetic LXR ligands are under development as potential drugs for individuals suffering from lipid disorders. N,N-dimethyl-3β-hydroxycholenamide (DMHCA) is a steroidal ligand of LXRs that exerts anti-atherogenic effects in apolipoprotein E-deficient mice without causing negative side effects such as liver steatosis or hypertriglyceridemia. In this report, we investigated the consequences of DMHCA treatment on cholesterol homeostasis in vivo and in vitro. Despite its hydrophobicity, DMHCA is readily absorbed by C57BL/6 mice and taken up by intestinal cells, the lung, heart and kidneys, but is undetectable in the brain. DMHCA significantly reduces cholesterol absorption and uptake in duodenum and jejunum of the small intestine and in turn leads to a reduction of plasma cholesterol by 24%. The most striking finding of this study is that DMHCA inhibited the enzyme 3β-hydroxysterol-Δ24-reductase resulting in an accumulation of desmosterol in the plasma and in feces. Thus, the reduction of plasma cholesterol was due to a block in the final step of cholesterol biosynthesis. Taken together, DMHCA is an interesting compound with properties distinct from other LXR ligands and might be used to study desmosterol-mediated effects in cells and tissues.     

Hexadecylphosphocholine disrupts cholesterol homeostasis and induces the accumulation of free cholesterol in HepG2 tumour cells

Hexadecylphosphocholine (HePC) is a synthetic lipid belonging to the alkylphosphocholines (APC), a new group of antiproliferative agents that are proving to be promising candidates in anticancer therapy. We reported in a previous study that HePC interferes with phosphatidylcholine (PC) synthesis in HepG2 cells via both CDP-choline and phosphatidylethanolamine (PE) methylation. We have subsequently extended our studies to show that HePC interferes with sphingolipid metabolism by hindering the formation of sphingomyelin (SM), an effect accompanied by a substantial increase in the incorporation of the exogenous lipogenic precursors into ceramides. Interestingly, we demonstrate for the first time that HePC strongly inhibits the esterification of free cholesterol (FC) by acting at the level of acyl CoA:cholesterol acyltransferase (ACAT) (EC 2.3.1.26) activity. This effect is accompanied by a considerable increase in the synthesis of cholesterol, which leads to a rise in the levels of FC in cells. We are left in no doubt that the imbalance in the metabolism of membrane-lipid components vital to cell survival may well be responsible for the observed DNA fragmentation and activation of caspase-3, an enzyme involved in the cell apoptosis found in this study.     

Rate‐limiting factors of cholesterol efflux in reverse cholesterol transport: Acceptors and donors

1. Plasma levels of high‐density lipoprotein (HDL) are believed to be inversely related to coronary artery disease. High‐density lipoprotein plays a key role in the process of reverse cholesterol transport, by which HDL is able to extract excess cholesterol from peripheral tissues and transfer it to the liver for biliary excretion. 2. Efflux of lipids (cholesterol and phospholipids) is the first step in reverse cholesterol transport. Several cellular membrane transporters, including ABCA1 and ABCG1, as well as scavenger receptor (SR)‐BI receptor, are believed to facilitate the active efflux of cholesterol to lipid‐poor apolipoprotein A‐I and mature HDL, respectively. Furthermore, overexpression or deletion of one or more specific genes supports the view that HDL is involved in cholesterol efflux. 3. In conclusion, current evidence supports a critical role for HDL in atheroprotection via an active efflux pathway through reverse cholesterol transport, with the substantial support of appropriate functions of cell donors.     

Black pepper and piperine reduce cholesterol uptake and enhance translocation of cholesterol transporter proteins

Black pepper (Piper nigrum L.) lowers blood lipids in vivo and inhibits cholesterol uptake in vitro, and piperine may mediate these effects. To test this, the present study aimed to compare actions of black pepper extract and piperine on (1) cholesterol uptake and efflux in Caco-2 cells, (2) the membrane/cytosol distribution of cholesterol transport proteins in these cells, and (3) the physicochemical properties of cholesterol micelles. Piperine or black pepper extract (containing the same amount of piperine) dose-dependently reduced cholesterol uptake into Caco-2 cells in a similar manner. Both preparations reduced the membrane levels of NPC1L1 and SR-BI proteins but not their overall cellular expression. Micellar cholesterol solubility of lipid micelles was unaffected except by 1 mg/mL concentration of black pepper extract. These data suggest that piperine is the active compound in black pepper and reduces cholesterol uptake by internalizing the cholesterol transporter proteins.     

Correlation of biliary cholesterol, phospholipids and bile acid compositions and the development of cholesterol cholelithiasis in mice

A study was attempted to establish a screening method for detecting cholelitholytic ingredients from a wide variety of natural substances. Although mice were selected as a suitable pathological model of cholelithiasis to detect a small amount of the ingredients, all the conventional lithogenic diets caused unfavorable influence on the animals. Therefore, as the first step we formulated a new lithogenic diet consisting of butter, cholesterol, cholic acid, etc, which was adequate for mice. Subsequently, the pathological characteristics and persistence of cholelithiasis were examined in the animals; the changes in bile compositions including free and conjugated bile acids, cholesterol and phospholipids were observed before and at the onset of cholelithiasis. Following confirmation of the stone formation, a normal diet was substituted for the lithogenic diet to likewise assess the bile compositions 4 and 6 weeks later. An increasing tendency for deoxycholic acid, disappearance of chenodeoxycholic acid and decrease in ursodeoxycholic acid were seen under the condition of cholelithiasis. In addition, the cholic acid-glycine conjugate which should not exist in the normal state and the increase in free and tauring-conjugated cholic acid were noticed. The biliary cholesterol level in treated mice increased to about 4 times higher than that in untreated mice, while the biliary phospholipids and total bile acids levels increased to only about 1.5 and about 2 times the control levels, respectively. The incidence of stone formation rose sharply at an experimental period between 2 and 3 weeks after starting the lithogenic diet. Gallstones die not disappear even at the 6th week after substituting a normal diet for the lithogenic one. However, the cholic acid-glycine conjugate disappeared, and deoxycholic acid as well as chenodeoxycholic acid and ursodeoxycholic acid tended to recover to the normal levels in the bile.     

胆固醇的细菌内毒素检查

目的建立胆固醇细菌内毒素检查方法。方法利用鲎试剂与细菌内毒素产生凝集反应的原理对胆固醇的细菌内毒素进行检查。结果胆固醇的不干扰浓度为 5mg ml,限值确定为每 1mg胆固醇含细菌内毒素量小于0 .1Eu。结论胆固醇的细菌内毒素检查可以用鲎试验法 ,此法灵敏可靠 ,方便经济     

Plasma cholesterol and triglycerides in heroin addicts.

We examined total cholesterolemia, triglyceridemia, high density lipoproteins- (HDL) cholesterolemia, apolipoproteins A1 and B, body mass index, albuminemia and alanine aminotransferase in 60 heroin addicts. After comparing 23 control subjects with the heroin addicts the result was that the latter have significantly lower mean values of total cholesterolemia and of HDL-cholesterolemia and higher values of triglyceridemia. They also have significantly higher prevalences of cases of hypocholesterolemia and of hypo-HDL-cholesterolemia. Within the addict group there is no linear correlation between total cholesterolemia and body mass index; there is, however, an inverse linear correlation between total cholesterolemia and alanine aminotransferase. Therefore, the alterations found in the lipid pattern of heroin addicts are not due to malnutrition but hypothetically to liver diseases which are frequent in these patients.