C-C2W is the physical cause of cholesterol gallstones

Cholesterol gallstones are made up of cholesterol.H20, traces of body temperature cholesterol, and a cholesterol-cholestanol-water adduct (C-C-2W). For the first time C-C-2W has been chemically and optically located in such gallstones, specifically in the nucleus, in the groove, and on the surface. These findings suggest a novel yet rational theory of cholesterol-stone quantitatively related to prevention and dissolution: (1) Bile is chemically abnormal if cholestanolH2O is present as a foreign unwanted substance. (2) When cholestanol.H2O in portal blood approaches 10(-4) mg/ml, precipitation of C-C-2W occurs in the hepatocytes because it finds sufficient cholesterol.H2O to reach the solubility product of the adduct. The resulting C-C-2W microcrystallites flow with bile down the biliary tree and then seed the supersaturated cholesterol solution in the gallbladder. (3) On the other hand, for concentrations of cholestanol.H2O around 10(-5) mg/ml, C-C-2W precipitation occurs exclusively in the gallbladder. (4) The adduct is the physical cause of cholesterol gallstones since however it arrives in the gallbladder, it produces swift crystallization of cholesterol.H20.     

Esterification of cholesterol and cholestanol in the whole body,tissues, and frass of Heliothis zea

The quantity of free and esterified sterols in the whole body, intestine, hemolymph, fat body, and frass of 6th-instar larvae of H. zea, fed cholesterol or cholestanol, was measured in order to determine if there was a difference in the utilization of these two molecules. The principal sterol in the tissues of the larvae was cholestanol or cholesterol, when they were fed diet containing these two molecules, respectively; there was little, if any, metabolism of dietary cholestanol to cholesterol. There was little or no difference in the amount of total sterol in the whole body, tissues, or frass of larvae fed the two different diets, indicating that the absence of a Δ⁵-bond in cholestanol does not prevent the uptake or distribution of this sterol to various tissues. However, the relative percentage of steryl ester was significantly higher in prepupae reared on a diet containing cholestanol instead of cholesterol (6–7-, 4-, 13-, 4-, and 2-fold increase, for the whole body, intestine, hemolymph, fat body, and frass, respectively). The average percentage of total sterol that was esterified in the tissues was greater in the fat body (10.8 ± 15.4 and 44.2 ± 12.3%, respectively, for larvae fed cholesterol and cholestanol) than in the hemolymph (0.5 ± 0.1 and 6.3 ± 0.8%) and intestine (1.2 ± 0.1 and 4.7 ± 1.1%). The percentage of sterol that was esterified in the frass of larvae was large (26.9 ± 3.7 and 48.2 ± 0.5%, respectively, for larvae fed cholesterol and cholestanol). Therefore, the fact that larvae of H. zea fed cholestanol, instead of cholesterol, contain this saturated molecule as their principal tissue sterol and preferentially esterify it may explain, at least in part, why their rate of growth on cholestanol is slower than on cholesterol.     

Cholestanol metabolism in patients with cerebrotendinous xanthomatosis: absorption, turnover, and tissue deposition

To study the metabolism of cholestanol in patients with cerebrotendinous xanthomatosis (CTX), we measured the cholestanol absorption, the cholesterol and cholestanol turnover, and the tissue content of sterols in two patients. Cholestanol absorption was approximately 5.0%. The rapid exchangeable pool of cholestanol was 233 mg, and the total exchangeable pool was 752 mg. The production rate of cholestanol in pool A was 39 mg/day. [4-14C]cholestanol was detected in the xanthomas, but neither [4-14C]cholestanol nor [4-14C]cholesterol was detected in peripheral nerves biopsied at 49 and 97 days after [4-14C]cholesterol given intravenously. Of the 18 tissues analyzed at biopsy and autopsy, the cholestanol content varied from 0.09 mg/g in psoas muscle to 76 mg/g in a cerebellar xanthoma. With the assumption that the cholestanol-to-cholesterol ratio is 1.0, the relative cholestanol-to-cholesterol ratio varied from 1.0 in plasma and liver to 30.0 in the cerebellar xanthoma; cholestanol was especially high in nerve tissue. Our data indicate that CTX patients absorb cholestanol from the diet. They have a higher than normal cholestanol production rate. Cholestanol was derived from cholesterol. In CTX patients, the blood-brain barrier was intact to the passage of [4-14C]cholesterol and [4-14C]cholestanol. The deposition of large amounts of cholestanol (up to 30% of total sterols in cerebellum) in nerve tissues must have an important role in the neurological symptoms in CTX patients. In view of the intact blood-brain barrier, several other explanations for the large amounts of cholestanol in the brain were postulated.     

High-affinity binding sites for oxygenated sterols in rat liver microsomes: possible identity with antiestrogen binding sites

Oxygenated derivatives of cholesterol are known to exhibit a number of biological activities including the inhibition of cholesterol biosynthesis and of cell proliferation, but their mechanism of action remains unclear. Previous studies have identified a cytosolic protein which binds 25-hydroxycholesterol, as well as several other oxysterols, with high affinity, possibly mediating some of their effects. We now report the existence of a high-affinity oxysterol binding site in rat liver microsomes which is distinct from the cytosolic binding protein. Among the oxygenated sterols examined, 5 alpha-cholestan-3 beta-ol-7-one (7-ketocholestanol) had the highest affinity for this microsomal binding site (Kd = 2.7 nM). Using 7-keto[3H]cholestanol as the radioactive ligand, we found that binding of this oxysterol to the microsomal binding site was saturable and reversible and was displaceable by the following oxysterols in descending order of potency: 7-ketocholestanol greater than 6-ketocholestanol greater than 7 beta-hydroxycholesterol = 7-ketocholesterol greater than cholesten-3 beta,5 alpha, 6 beta-triol = 7 alpha-hydroxycholesterol greater than 4-cholesten-3-one. All other sterols studied, including, notably, 25-hydroxycholesterol, had little or no inhibitory effect on 7-keto[3H]cholestanol binding. Additional studies revealed that the microsomal oxysterol binding site was probably identical to the antiestrogen binding site described by other workers. First, saturation analysis and kinetic studies demonstrated that the antiestrogen tamoxifen competed directly with 7-keto[3H]cholestanol for the same binding site. Second, the ability of different oxysterols and antiestrogens to inhibit 7-keto[3H]cholestanol binding to the microsomal binding site paralleled their ability to inhibit [3H]tamoxifen binding to the antiestrogen binding site. Third, the tissue distribution of binding sites for 7-keto[3H]cholestanol was similar to that of the antiestrogen binding site. We conclude that: (1) in rat liver microsomes there are high-affinity oxysterol binding sites whose ligand specificity is different from that of the cytosolic oxysterol binding protein; and (2) the microsomal oxysterol binding site is probably identical to the antiestrogen binding site. The biological significance of these observations remains to be explored.     

Biosynthesis of cholestanol in higher plants

To understand the early steps of C(27) brassinosteroid biosynthesis, metabolic experiments were performed with Arabidopsis thaliana and Nicotiana tabacum seedlings, and with cultured Catharanthus roseus cells. [26, 28-2H(6)]Campestanol, [26-2H(3)]cholesterol, and [26-2H(3)]cholestanol were administered to each plant, and the resulting metabolites were analyzed by gas chromatography-mass spectrometry. In all the species examined, [2H(3)]cholestanol was identified as a metabolite of [2H(6)]campestanol, and [2H(3)]cholest-4-en-3-one and [2H(3)]cholestanol were identified as metabolites of [2H(3)]cholesterol. This study revealed that cholestanol (C(27) sterol) was biosynthesized from both cholesterol (C(27) sterol) and campestanol (C(28) sterol). It was also demonstrated that cholestanol was converted to 6-oxocholestanol, and campestanol was converted to 6-oxocampestanol.     

The liver plays a key role in whole body sterol accretion of the neonatal Golden Syrian hamster

Neonates have a significant requirement for cholesterol. From -1 to 25 days of age, the liver accrues 6.9 mg cholesterol and the extra-hepatic tissues accrue 107.7 mg cholesterol in the hamster. It is currently unknown if each of these body compartments synthesizes their own cholesterol or if they have alternative source(s) of sterol. Using (3)H(2)O, in vivo hepatic sterol synthesis rates (per g liver per animal) increased between -1 and 5 days of age, decreased by 10 days of age, and increased again by 15 days of age. HMG-CoA reductase (HMGR) expression levels paralleled in vivo synthesis rates. Extra-hepatic sterol synthesis rates followed the same pattern as sterol synthesis rates in the liver. When sterol synthesis rates were converted to the mass of sterol synthesized per day, the liver synthesized 38.9 and the extra-hepatic tissues synthesized 63.9 mg cholesterol in the 26-day neonatal period. Comparing the amount of cholesterol accrued to that synthesized, one can conclude that the liver is a major source of sterol for the whole body during the neonatal period of the hamster. These results may help elucidate the cause(s) of reduced growth rates in neonates with liver disease or in neonates with compromised sterol synthesis rates.     

Simultaneous determination of cholesterol and cholestanol in human serum by high-performance liquid chromatography using 3-(5,6-methylenedioxy-2-phthalimidyl)benzoyl azide as precolumn fluorescent labelling reagent

A fluorescent labelling reagent, 3-(5,6-methylenedioxy-2-phthalimidyl)benzoyl azide, designed for the determination of alcohols by precolumn high-performance liquid chromatography, has been applied to the simultaneous determination of cholesterol and cholestanol in human serum. The reagent reacts with cholesterol and cholestanol at 140°C for 10 min to produce the fluorescent derivatives, which can be separated on a reversed-phase column with acetonitrile—ethanol—water (60:35:7.5, v/v) as eluent. The detection limits for cholesterol and cholestanol were 45 and 50 fmol per injection (20 μl), respectively. The values of cholesterol and cholestanol in normal human sera were 135–212 mg/dl and 137–928 μg/dl, respectively.     

Sterol/steroid metabolism and absorption in a generalist and specialist caterpillar: Effects of dietary sterol/steroid structure,mixture and ratio

Insects cannot synthesize sterols de novo, so they typically require a dietary source. Cholesterol is the dominant sterol in most insects, but because plants contain only small amounts of cholesterol, plant-feeding insects generate most of their cholesterol by metabolizing plant sterols. Plants almost always contain mixtures of different sterols, but some are not readily metabolized to cholesterol. Here we explore, in two separate experiments, how dietary phytosterols and phytosteroids, in different mixtures, ratios, and amounts, affect insect herbivore sterol/steroid metabolism and absorption; we use two caterpillars species – one a generalist (Heliothis virescens), the other a specialist (Manduca sexta). In our first experiment caterpillars were reared on two tobacco lines – one expressing a typical phystosterol profile, the other expressing high amounts/ratios of stanols and 3-ketosteroids. Caterpillars reared on the control tobacco contained mostly cholesterol, but those reared on the modified tobacco had reduced amounts of cholesterol, and lower total sterol/steroid body profiles. In our second experiment, caterpillars were reared on artificial diets containing known amounts of cholesterol, stigmasterol, cholestanol and/or cholestanone, either singly or in various combinations and ratios. Cholesterol and stigmasterol-reared moths were mostly cholesterol, while cholestanol-reared moths were mostly cholestanol. Moth tissue cholesterol concentration tended to decrease as the ratio of dietary cholestanol and/or cholestanone increased. In both moths cholestanone was metabolized into cholestanol and epicholestanol. Interestingly, M. sexta generated much more cholestanol than epicholestanol, while H. virescens did the opposite. Finally, total tissue steroid levels were significantly reduced in moths reared on diets containing very high levels of cholestanol. We discuss how dietary sterol/steroid structural differences are important with respect to sterol/steroid metabolism and uptake, including species-specific differences.     

Biosynthesis of cholestanol from bile acid intermediates in the rabbit and the rat

Biliary 7 alpha-hydroxy-4-cholesten-3-one (an intermediate in bile acid biosynthesis) may be 7 alpha-dehydroxylated in the gut and further metabolized to cholestanol (Skrede, S., and Bj?rkhem, I. (1982) J. Biol. Chem. 257, 8363-8367). We have now evaluated the quantitative importance of pathway(s) to cholestanol with 7 alpha-hydroxylated C27 steroids as intermediates. After feeding conventionally fed rabbits or rats or germ-free rats with [7 alpha-3H]cholesterol and [4-14C]cholesterol, tissue cholestanol could be isolated with about a 20% lower 3H/14C ratio than present in cholesterol. We conclude that there is a pathway to cholestanol involving 7 alpha-hydroxylated intermediates. Intestinal microorganisms are not essential for this pathway, which accounts for at most 20% of the cholestanol formed in these species. In bile fistula rats, there was also a significant conversion of intraperitoneally injected [7 beta-3H]7 alpha-hydroxycholesterol and [4-14C]7 alpha-hydroxy-4-cholesten-3-one into cholestanol. The enzymes involved in the 7 alpha-hydroxylation/dehydroxylation pathway for the biosynthesis of cholestanol are probably located in the liver. Both 7 alpha-hydroxycholesterol and 7 alpha-hydroxy-4-cholesten-3-one may be intermediates.     

Effect of dietary cholesterol on erythrocyte peroxidant stress in vitro and in vivo

The effect of dietary variation of plasma cholesterol concentrations on the susceptibility of erythrocytes to in vitro and in vivo peroxidant stress was studied in rats. Malonyldialdehyde, produced in vivo (endogenous malonyldialdehyde) or following in vitro exposure of cells to 10 mM H2O2 (H2O2 malonyldialdehyde), was used as a measure of peroxidant stress. After 5 weeks, the plasma cholesterol concentrations in rats receiving 1.2% cholesterol + 0.6% cholic acid in their diet rose to 6-times that of control rats receiving a diet without added cholesterol; at the same time, erythrocyte H2O2 malonyldialdehyde in the cholesterol-fed rats decreased significantly relative to the control rats. During subsequent exposure of both groups to in vivo peroxidant stress with phenylhydrazine in two separate dose trials, erythrocyte peroxidant stress remained significantly lower in the cholesterol-fed rats: at a dose of 100 mumol/100 g body weight, H2O2 malonyldialdehyde was lower; at a dose of 25 mumol/100 g body weight, both endogenous and H2O2 malonyldialdehyde were lower. Erythrocyte membrane cholesterol concentrations were 12% higher in the cholesterol-fed rats than in controls. The effects of in vivo peroxidant stress on plasma cholesterol were also studied. In vivo peroxidant stress at the higher dose of phenylhydrazine produced a decrease in plasma cholesterol concentrations of control rats. The lower dose had no effect on this group and the plasma cholesterol concentrations were unchanged in the cholesterol-fed rats during both treatments. The data suggest that elevated plasma cholesterol concentrations are protective against erythrocyte peroxidant stress. The mechanism of cholesterol's protective effect is probably mediated through elevated membrane cholesterol concentrations.     

Bile acid production in human subjects: rate of oxidation of [24,25-3H]cholesterol compared to fecal bile acid excretion

Bile acid production has been quantitated in seven subjects by methods that compare the results of two independent approaches, namely, quantitation of cholesterol side-chain oxidation and fecal bile acid excretion. Six hypertriglyceridemic (HT) subjects and one normolipidemic control were studied by both techniques. A further control subject was studied by the cholesterol side-chain oxidation method alone. Cholesterol side-chain oxidation was quantitated by measuring the appearance of 3H2O after intravenous administration of [24,25-3H]cholesterol, using multicompartmental analysis of plasma cholesterol and [3H]water specific activity. Body water kinetics were independently defined by use of oral D2O. Two HT subjects were restudied while they were taking cholestyramine, 16 g/day. In all ten studies, multicompartmental analysis closely simulated the observed appearance of 3H2O. Values obtained for bile acid production suggest that cholesterol oxidation, or bile acid input, was significantly greater than fecal bile acid output in the HT subjects (P less than 0.05). Cholesterol side-chain oxidation rates in the two normal subjects were lower than those encountered in HT subjects, being similar to published values for normal subjects both for bile acid synthesis as determined by isotope dilution kinetics and fecal bile acid excretion. Studies conducted with two, synthetically different, preparations of [24,25-3H]cholesterol indicated that, in one of the two preparations, approximately 20% of the tritium label was at positions proximal to C24. In the other preparation examined, all of the tritium was located at, or distal to, C24. Further studies revealed that 0.055-0.24% of the dose was present as labile tritium by virtue of its appearance as 3H2O following in vitro incubation with human plasma. Provided these isotope effects are taken into account, multicompartmental analysis of plasma [24,25-3H]cholesterol and body water appears to be a useful technique for quantitating cholesterol oxidation in human subjects.     

Ferroelectricity in the arterial wall: A new physical component of atherosclerosis

The appearance of two electric potentials in the aorta is explained by the blood pulse and the remote steps of atherosclerosis are elucidated from the physical point of view. When the first C-C-2W is deposited in the intimamedia, the primary cause of their retention is the stress-induced polarization of the membrane. C-C-2W possesses a permanent dipole moment which may be reversed by the field produced by the radial expansion/contraction of the arteries.The initial C-C-2W increases the polarization of the aorta walls, favoring accumulation of more oriented material on top of the first. C-C-2W is also ferroelectric and constitutes a polar continuum with the membranes. By the time fatty streaks appear, the entire aorta wall is ferroelectric and energy has been stored in the walls under the form of residual polarization. This storage gradually destroys the wall, leading to aneurism. The biological significance of the new theory is summarized in Table 2.     

Lethal atherosclerosis associated with abnormal plasma and tissue sterol composition in sitosterolemia with xanthomatosis

Tissue sterol composition was determined in an 18-year-old male with sitosterolemia with xanthomatosis who died suddenly and whose coronary and aortic vessels showed extensive atherosclerosis and, for comparison, in an 18-year-old male with minimal atherosclerosis who died accidently. Sterols in the control tissues (plasma, erythrocytes, cardiac muscle, lung, liver, aorta, and brain) contained cholesterol with only trace amounts of cholestanol. In contrast, sterols in corresponding tissues of the sitosterolemic subject (except brain) were composed of cholesterol, increased amounts of plant sterols, campesterol and sitosterol, and 5 alpha-saturated stanols, cholestanol, 5 alpha-campestanol, and 5 alpha-sitostanol, that were deposited in approximately the same ratio as present in plasma. However, sitosterolemic brain sterol composition resembled that of the control brain with cholesterol and only trace amounts (less than 1%) of cholestanol and phytosterols. The sitosterolemic aorta was extensively atherosclerotic and contained more than twice the quantity of sterols as the control aorta (5.6 mg/g versus 2.6 mg/g) with increased amounts of cholesterol, plant sterols, and 5 alpha-saturated stanols. These results indicate that cholesterol, plant sterols, and 5 alpha-stanols are deposited prematurely and are associated with accelerated atherosclerosis in subjects with sitosterolemia with xanthomatosis.     

Distribution and dynamic state of sterols and steroids in the tissues of an insect, the roach Eurycotis floridana

The total concentrations of sterols in the tissues of the roach, Eurycotis floridana, reared under aseptic conditions and on semisynthetic diets, are similar to, but somewhat lower than, those of tissues of vertebrates. Total concentrations of tissue sterols are relatively independent of dietary concentration of sterols whether the diet contains 0.1% cholesterol as the sole sterol, or a "minimal cholesterol" mixture (0.1% cholestanol together with 0.005% cholesterol). Under the latter conditions the cholesterol is incorporated preferentially into most tissues and remains almost exclusively unesterified, while the cholesterol-sparing sterol is esterified to varying degree, depending upon the tissue. The turnover of tissue sterols has been studied. Cholesterol of the tissues of adult insects grown on a diet containing this sterol alone may be displaced by cholestanol fed as 5% of the total diet, initially at an appreciable rate but later much less rapidly. In growing insects that have received a diet containing cholestanol together with minimal cholesterol, the unesterified cholesterol turns over slowly in all tissues and immeasurably slowly in some. The unesterified sparing sterol, on the other hand, turns over at a much greater rate. The turnover of sterols during growth is accompanied by a shift of sterols from the unesterified to the esterified pool in all tissues. The fat body of the growing insect stores sterols (apparently as their esters) that have been displaced from other tissues. The fat body of the adult does not show evidence of sterol storage. Polar derivatives of sterols are present in minor amount in all tissues of the insect, most abundantly in the mid-intestine and gastric caeca. These compounds seem likely to be C(27) steroids.     

Increased plasma cholestanol and 5 alpha-saturated plant sterol derivatives in subjects with sitosterolemia and xanthomatosis

We have measured plasma sterol composition in 14 subjects with sitosterolemia and xanthomatosis. In addition to elevated plasma phytosterol (campesterol 16 +/- 7 mg/dl and sitosterol 35 +/- 16 mg/dl) and normal to moderately high cholesterol levels (258 +/- 96 mg/dl), concentrations of 5 alpha-saturated stanols, cholestanol, 5 alpha-campestanol, and 5 alpha-sitostanol were at least 10 times greater than controls. Diets contained plentiful quantities of cholesterol and plant sterols, but only trace amounts of cholestanol (less than 2 mg/day) and no detectable 5 alpha-campestanol and 5 alpha-sitostanol, which indicated that the 5 alpha-saturated stanols were formed endogenously. Treatment with cholestyramine reduced plasma cholesterol and phytosterol levels by 45% and 5 alpha-saturated stanols by 55%. These results indicate that abnormally high plasma concentrations of cholestanol, 5 alpha-campestanol, and 5 alpha-sitostanol are found in subjects with sitosterolemia and xanthomatosis, and that treatment with cholestyramine effectively reduced elevated plasma sterol levels.     

Brachymeria lasus and Pachycrepoideus vindemiae: Sterol requirements during larval growth of two hymenopterous insect parasites reared in vitro on chemically defined media

Brachymeria lasus and Pachycrepoideus vindemiae failed to develop in vitro on sterol-free artificial media, and dietary acetate and squalene failed to maintain and/or support growth. The sterols, cholesterol, cholestanol, β-sitosterol, 7-dehydrocholesterol, and cholesterol linoleate were all utilized and maintained larvae of both species. Larval survival and development rate were greatest with cholesterol followed by cholestanol, β-sitosterol and 7-dehydrocholesterol. Although cholesterol linoleate maintained larvae little growth occurred and mortality was high. Cholestanol followed by β-sitosterol and 7-dehydrocholesterol displayed partial cholesterol sparing activity. Cholesterol linoleate had little effect on larval growth when fed with suboptimal levels of cholesterol or cholestanol. Both species contained 5 to 10% of the total body lipids as free sterol with traces of sterol ester. The major free sterol appears to be cholesterol.     

Baseline serum cholestanol as predictor of recurrent coronary events in subgroup of Scandinavian simvastatin survival study

Objectives: To investigate whether baseline serum cholestanol:cholesterol ratio, which is negatively related to cholesterol synthesis, could predict reduction of coronary events in the Scandinavian simvastatin survival study. Design: Follow up of patients with coronary heart disease in whom baseline ratios were related to major coronary events. Setting: Four universities in Finland. Subjects: A subgroup of 868 patients with coronary heart disease selected from the Scandinavian simvastatin survival study. Intervention: Treatment with simvastatin or placebo. Main outcome measures: Serum concentrations of low density lipoprotein and high density lipoprotein cholesterol, total triglyceride concentration, and cholesterol:cholestanol ratio. Major coronary events. Results: With increasing baseline quarter of cholestanol distribution the reduction in relative risk increased gradually from 0.623 (95% confidence interval 0.395 to 0.982) to 1.166 (0.791 to 1.72). The risk of recurrence of major coronary events increased 2.2-fold (P<0.01) by multiple logistic regression analysis between the lowest and highest quarter of cholestanol. The ratio of cholestanol was related inversely to the body mass index and directly to high density lipoprotein cholesterol and triglyceride concentrations but their quarters of distribution were not related to risk reduction.Conclusions: Measurement of serum cholestanol concentration revealed a subgroup of patients with coronary heart disease in whom coronary events were not reduced by simvastatin treatment. Thus, patients with high baseline synthesis of cholesterol seem to be responders whereas those with low synthesis of cholesterol are non-responders.

Key messages

• Recurrence of major coronary events is reduced by statin treatment in about one third of patients with coronary heart disease, to predict those who will not respond has not been possible from baseline lipid concentrations in the Scandinavian simvastatin survival.
• This study showed that increasing quarters of cholestanol:cholesterol ratio, reflecting decreasing synthesis of cholesterol, were related to recurrence of major coronary events during simvastatin treatment in a Finnish subgroup (n=868) of the Scandinavian study.
• The subjects with lowest baseline quarters of cholestanol were associated with significantly reduced relative risk of major coronary events, while the risk in the highest quarter was unchanged and 2.2 times higher than in the lowest one.
• Cholestanol:cholesterol ratios were related inversely to the body mass index and directly to high density lipoprotein cholesterol and triglyceride concentrations, but their quarters were unrelated to risk reduction.
• The findings suggest that patients with coronary disease who have high absorption (high basal cholestanol:cholesterol) and low synthesis of cholesterol do not benefit from statin treatment alone and that they can be identified by measuring serum cholestanol concentration before treatment.

     

On the structural specificity in the regulation of the hydroxymethylglutaryl-CoA reductase and the cholesterol-7 alpha-hydroxylase in rats. Effects of cholestanol feeding

The effect of feeding 2% cholestanol or cholesterol on cholesterol-7 alpha-hydroxylase activity and hydroxymethylglutaryl (HMG)-CoA reductase activity was studied in rats. The rate of 7 alpha-hydroxylation of a trace amount of labelled cholesterol increased by about 80% after the cholestanol feeding, whereas the 7 alpha-hydroxylation of endogenous microsomal cholesterol increased by about 40%. The latter conversion was measured with an accurate technique based on isotope dilution-mass spectrometry. After cholesterol feeding, the corresponding figures were about 50 and 60%, respectively. The cholestanol feeding had no significant effect on the HMG-CoA reductase activity, whereas the cholesterol feeding decreased the activity by about 80%. From the results obtained, it is concluded that the increased 7 alpha-hydroxylation observed after cholesterol feeding can not be explained only by a simple expansion of the substrate pool. The similar effect of both cholesterol and cholestanol on the cholesterol 7 alpha-hydroxylase activity and the diverging effect on the HMG-CoA reductase activity show that there is no coupling between cholesterol synthesis and degradation under the conditions employed. The lack of effect of cholestanol on the HMG-CoA reductase activity indicates a high structural specificity of the receptor involved in regulation of the enzyme. If a receptor mechanism is involved in the stimulation of the cholesterol-7 alpha-hydroxylase by cholesterol and cholestanol, these receptor(s) must be different from those involved in the regulation of the HMG-CoA reductase.     

Polymorphisms in the ABCG5 and ABCG8 genes associate with cholesterol absorption and insulin sensitivity

The roles of polymorphisms of the sitosterolemia genes ABCG5 and ABCG8 in the regulation of cholesterol metabolism and insulin sensitivity were studied in mildly hypercholesterolemic noncoronary subjects (n = 263, 144 men and 119 women) divided into tertiles by baseline serum cholestanol-to-cholesterol ratio (< or = 118.3 and > or = 147.7 10(2) x mmol/mol cholesterol), a surrogate marker of cholesterol absorption efficiency. The lowest cholestanol tertile was associated with high body mass index (BMI), plasma glucose, serum insulin and triglycerides, and cholesterol synthesis markers (cholestenol, desmosterol, lathosterol) and low HDL cholesterol and cholesterol absorption markers (campesterol, sitosterol) (P < 0.01 for all). The 19H allele of the ABCG8 gene accumulated in the lowest cholestanol tertile (P < 0.001) and was associated with low total and LDL cholesterol and absorption markers and with high synthesis markers (P < 0.05 for all). The 604E allele of the ABCG5 gene in men was associated with high BMI, plasma insulin, low serum sitosterol, and high serum cholestenol levels (P < 0.05 for all). In a subgroup of 71 men, the 604E allele was associated with insulin resistance measured with the hyperinsulinemic euglycemic clamp. In conclusion, low cholesterol absorption efficiency was associated with characteristics of the metabolic syndrome. Low serum cholesterol and cholesterol absorption were linked to the D19H polymorphism of the ABCG8 gene, and characteristics of the insulin resistance syndrome in men were linked with the Q604E polymorphism of the ABCG5 gene.     

Grape seed and skin extract mitigates garlic-induced oxidative stress in rat liver

Garlic is a commonly used spice in folk medicine that can exert adverse health effects when given at a high dose. Grape seed and skin extract (GSSE) exhibits a variety of beneficial effects even at a high dose. In the present study we evaluated the toxicity of high-dose garlic treatment on liver and the protective effect of GSSE. Rats were intraperitoneally administered either with garlic extract (5 g·(kg body weight)(-1)) or GSSE (500 mg·(kg body weight)(-1)) or a combination of garlic and GSSE at the same doses daily for 1 month. Plasma and hepatic levels of cholesterol, triacylglycerol, and transaminases and liver antioxidant status were evaluated. Data showed that a high garlic dose induced liver toxicity and a pro-oxidative status characterized by increased malondialdehyde and decreased antioxidant enzyme activities as catalase, peroxidase, and superoxide dismutase. Garlic increased intracellular H(2)O(2) but decreased free iron and Ca(2+). GSSE alone or in co-treatment with garlic had the reverse effect and counteracted almost all garlic-induced deleterious impacts to near control levels. In conclusion, a high garlic dose induced a pro-oxidative state characterized by the Fenton reaction between H(2)O(2) and free iron, inducing Ca(2+) depletion, while GSSE exerted antioxidant properties and Ca(2+) repletion.