Esterified Cholesterol Levels Research Articles

Effects of dietary maritime pine (Pinus pinaster)-seed oil on high-density lipoprotein levels andin vitrocholesterol efflux in mice expressing human apolipoprotein A-I

Maritime pine (Pinus pinaster)-seed oil contains two Delta5 unsaturated polymethylene interrupted fatty acids (all cis-5,9, 12-18:3 and all cis-5,11,14-20:3 acids) one of which resembles eicosapentaenoic acid. The goal of the present study was to test whether maritime pine-seed oil consumption affects HDL and apolipoprotein (Apo) A-I levels as well as the ability of serum to promote efflux of cholesterol from cultured cells. To this end, wild type (WT) non-transgenic mice and transgenic mice expressing human ApoA-I (HuA-ITg) were fed on isoenergetic diet containing either 200 g maritime pine-seed oil/kg or 200 g lard/kg for 2 weeks. WT and HuA-ITg mice fed maritime pine-seed oil had lower cholesterol, HDL-cholesterol, LDL-cholesterol and HuA-ITg mice had lower human ApoA-I than those fed lard. The differences in cholesterol (P < 0.0001) and HDL-cholesterol (P < 0.003) levels between mice fed on the two diets were more pronounced in the HuA-ITg than in the WT mice. The ability of HuA-ITg serum to promote cholesterol efflux in cultured cells was greater (P < 0.008) than that of WT animals. However, the maritime pine-seed oil diet was associated with lower (P < 0.005) in vitro cholesterol efflux ability than the lard diet in both mice genotypes. This suggests a negative effect of the maritime pine-seed oil on reverse cholesterol transport. Cholesterol efflux was correlated with serum free or esterified cholesterol and phospholipid levels. The slope of the regression line was smaller in the HuA-ITg than in the WT mice indicating that overexpression of human ApoA-I reduces the negative impact of maritime pine-seed oil on cholesterol efflux. In conclusion, maritime pine-seed oil diet lowers HDL-cholesterol and diminishes in vitro cholesterol efflux. This potentially detrimental effect is attenuated by overexpression of human ApoA-I in mice.

Effects of 4-methylsterols from algae and of β sitosterol on cholesterol metabolism in rats

Male Sprague Dawley rats (8/gp) were fed one of the following diets: AIN-76A (C), C plus 0.5% 4-methylsterols (CM), C plus 0.5% β sitosterol (CS), C plus 0.5% cholesterol (CC), CC plus 0.15% sodium deoxycholate (CB), CB plus 1% 4-methylsterols (CBM) or CB plus 1% β sitosterol (CBS). The 4-methylsterols had no adverse effect on weight gain or organ weight. The 4-methylsterols did not affect serum or liver lipids when added to the control diet or to the cholesterol-bile salt diet. When added to the control diet β sitosterol increased the percentage of serum HDL cholesterol and lowered levels of liver esterified cholesterol. When added to the cholesterol-bile salt diet β sitosterol significantly lowered serum cholesterol and raised HDL-cholesterol levels; β sitosterol also reduced liver total cholesterol.

Reduced Levels of Cholesterol, Phospholipids, and Fatty Acids in Cerebrospinal Fluid of Alzheimer Disease Patients Are Not Related to Apolipoprotein E4

Apolipoprotein E4 (apoE4) has been identified as a major risk factor for Alzheimer disease (AD). Previously it has been reported that levels of apoE are reduced in cerebrospinal fluid (CSF) of AD patients. Because it is known that apoE4 affects plasma lipid metabolism, we examined whether the presence of apoE4 might correlate with an altered lipid metabolism in the CSF of control subjects and AD patients. ApoE and lipid concentrations were determined in postmortem ventricular CSF of 30 neuropathologically confirmed AD cases and 31 age-matched control patients. ApoE genotyping was performed on frozen brain tissue of the same patients. In line with other reports, we found an increased APOE*4 allele frequency in the AD group (0.461) when compared with the control group (0.225). ApoE levels in CSF of AD patients were not significantly reduced when compared with the controls (mean +/-SD: 63+/-55 and 82+/-62 microg/dL for AD and controls, respectively). However, in the CSF of AD patients levels of free and esterified cholesterol (0.13+/-0.09 and 0.25+/-0.19 mg/dL, and 0.25+/-0.19 and 0.42+/-0.34, respectively), phospholipids (0.2+/-0.1 and 3.5+/-5.0 mg/dL) and, suprisingly, also fatty acids (4.5+/-3.2 and 28.0+/-18.5 micromol/L) were found to be significantly reduced. After correction for age, sex, postmortem delay, and pH the levels of phospholipids, fatty acids, and free cholesterol were still significantly reduced (p = 0.021, p = 0.026, andp = 0.012, respectively). The apoE and lipid levels in CSF of AD-and control patients appeared not to be affected by the number of APOE*4 alleles. In conclusion, our results suggest an altered lipid homeostasis in the brain of AD patients that is not related to the presence of apoE4. It is, therefore, unlikely that an effect of apoE4 on brain lipid metabolism is the underlying mechanism behind the role of apoE4 in the development of AD.

The influence of enzyme-resistant starch on cholesterol metabolism in rats fed on a conventional diet

Male Wistar rats were fed on a conventional diet containing normal corn starch or 6% enzyme-resistant starch originating from either raw or retrograded high-amylose corn starch. Furthermore, the diets were either cholesterol-free or contained 1% cholesterol and 0.1% cholic acid. The main objective of this study was to investigate whether the addition of enzyme-resistant starch to a rat conventional diet had any effect on cholesterol metabolism. Therefore, plasma and liver cholesterol concentrations, plasma HDL:LDL cholesterol ratios and neutral steroid and bile acid excretion were determined. No significant effect of enzyme-resistant starch feeding on plasma and liver cholesterol concentrations was found. However, consumption of raw or retrograded high-amylose corn starch resulted in a decrease in esterified and total liver cholesterol concentrations of 24 and 22%, respectively. This was accompanied by a reduction in plasma esterified and total cholesterol levels of 4% and a tendency to higher daily faecal coprostanol and total bile acid excretion.

Possible mechanism for the anti-atherosclerotic action of the calcium channel blocker AE0047 in cholesterol-fed rabbits.

1. The present study was designed to investigate the anti-atherosclerotic effect of AE0047, a calcium channel blocker, and to compare it with that of nilvadipine in cholesterol-fed rabbits. Furthermore, the effects of AE0047 on low-density lipoprotein (LDL) oxidation were studied in vitro. 2. A 7 week treatment period with AE0047 (3 and 10 mg/kg, p.o.) led to a dose-dependent reduction in the lipid deposition area by Oil Red-O staining (surface index) without affecting serum lipid levels. There was no reduction in the surface index following treatment with the same dose of nilvadipine (10 mg/kg). 3. In a vehicle-administered high-fat diet group of rabbits, levels of total cholesterol (TC) and esterified cholesterol (EC) and calcium content in the aorta were increased approximately two- to three-fold over those of the normal diet group. Increased levels of TC and EC and calcium content were reduced to the same levels as the normal diet group by AE0047 treatment, whereas nilvadipine did not affect TC and EC levels. 4. In an in vitro study, AE0047 (10 micromol/L) inhibited LDL oxidation and the aggregation of apolipoprotein (Apo) B-100 induced by Cu2+. Furthermore, AE0047 inhibited the degradation of oxidized LDL by macrophages. In contrast, the same dose of nilvadipine (10 micromol/L) did not inhibit either LDL oxidation or the aggregation of ApoB-100. 5. In summary, AE0047 inhibited LDL oxidation, resulting in a decrease of its uptake into macrophages and an inhibition of cholesterol esterification. This leads to an anti-atherosclerotic effect of AE0047. Thus, AE0047 may have therapeutic potential in preventing cardiovascular disease in hypertensive patients.

The β adrenoreceptor antagonist, nipradilol, preserves the endothelial nitric oxide response in atherosclerotic vessels of rabbit

We evaluated the effects of nipradilol, a β-adrenoreceptor antagonist which contains a nitroxy residue, for vascular response in atherosclerosis of rabbits. Four groups of rabbits received different diets (standard diet; standard diet plus 10 mg/kg/day nipradilol; atherogenic diet [standard diet plus 1% cholesterol]; atherogenic diet plus 10 mg/kg/day nipradilol) for 9 weeks. Plasma lipids, blood pressure, vascular function, nitric oxide (NO), activity of NO synthase, cGMP, and histological atherosclerotic changes were evaluated. Neither the atherogenic diet nor nipradilol treatment affected significantly the animals' body weight, blood pressure, or heart rate. The atherogenic diet increased total cholesterol and triglycerides, which were not altered by nipradilol. The atherogenic diet diminished the acetylcholine-induced NO mediated relaxation. Nipradilol treatment restored this relaxation. Analyses using a NO-sensitive selective electrode showed that nipradilol released NO in the presence of cells and that NO release was greater in atherosclerotic aorta with than without nipradilol treatment. Nipradilol treatment increased the basal NO release as evaluated by the aortic tissue cyclic GMP (cGMP) levels in atherosclerotic vessel, and reduced the esterified cholesterol levels in atherosclerotic vessel. Conclusively, NO released by nipradilol may protect endothelium derived relaxation in atherosclerotic vessels, and may partially inhibit the accumulation of cholesterol in the atherosclerotic lesions.

Acute dyslipoproteinemia induced by interleukin-2: lecithin:cholesteryl acyltransferase, lipoprotein lipase, and hepatic lipase deficiencies.

Recombinant human interleukin-2 (rIL-2) is used to treat refractory cancers. During such treatment, patients develop severe hypocholesterolemia along with striking alterations in the concentration and composition of the circulating lipoproteins. The present study was undertaken to gather information about the pathogenesis of these abnormalities. Patients were studied before-, during- and after a 5-day course of high dose i.v. rIL-2. Whole plasma cholesterol was markedly reduced by rIL-2 administration (52%; P < 0.001), whereas the triglyceride concentration did not change. Thus, the lipoproteins became triglyceride enriched (P = 0.004). Low density lipoprotein cholesterol, apolipoprotein B (apoB), high density lipoprotein cholesterol, and apoA-I concentrations all decreased. Esterified cholesterol levels were markedly reduced. Total plasma apoE increased markedly, and two kinds of abnormal particles appeared: 1) beta-migrating, very low density lipoproteins; and 2) discoidal, apoE- and phospholipid-containing particles with abnormal density and electrophoretic mobility. The activities of two lipoprotein triglyceride hydrolases, lipoprotein lipase and hepatic lipase, fell significantly during treatment and returned promptly to pretreatment levels after rIL-2 was discontinued. Lecithin:cholesteryl acyltransferase (LCAT) activity also decreased significantly (64%) during treatment, but in contrast to the lipases, remained low for at least 5 days after the last dose of rIL-2 (P < 0.001). High dose i.v. rIL-2 induces severe dyslipidemia with deficiencies of both postheparin lipases and acute LCAT deficiency. Most, if not all, of the lipoprotein changes observed are explained by the LCAT deficiency that follows IL-2-induced hepatocellular injury and cholestasis.

Dietary fat amount and carbohydrate type regulate hepatic acyl CoA:cholesterol acyltransferase (ACAT) activity. Possible links between ACAT activity and plasma cholesterol levels

The effects of dietary fat amount and carbohydrate type were evaluated on hepatic acyl CoA:cholesterol acyltransferase (ACAT) activity in guinea pigs to determine whether there was a correlation between plasma LDL cholesterol concentrations induced by diet and rates of hepatic cholesterol esterification. Animals were fed two different fat:carbohydrate ratios: 2.5:58% ( w w ) (low fat) or 25:29% ( w w ) (high fat) with either sucrose or starch as the sole carbohydrate source. Fat contributed 6.9 and 53% of total calories respectively. Consumption of high fat diets resulted in higher plasma cholesterol concentrations (P < 0.001) while simple carbohydrate intake increased plasma triacylglycerol levels (P < 0.01). Animals fed the high fat:sucrose diet exhibited the highest plasma and hepatic cholesterol concentrations. The type of carbohydrate affected the distribution of hepatic cholesterol pools in that animals fed sucrose had higher concentrations of free while those fed starch had higher levels of esterified cholesterol (P < 0.01). Hepatic ACAT activity was up-regulated in animals fed high fat diets (P < 0.01) with no effect due to carbohydrate type. A significant correlation was found between hepatic ACAT activity and plasma LDL cholesterol concentrations (r = 0.69, P < 0.001) and between hepatic ACAT activity and cholesterol influx to the liver (r = 0.97, P < 0.01). These results demonstrate that modifications in hepatic ACAT activity induced by dietary factors could be a response to the influx of cholesterol to the liver or could be related to the rates of incorporation of cholesteryl ester into lipoproteins secreted by the liver.

Effects of single oral doses of scopoletin and aflatoxin B 1 on the bleeding time, serum cholesterol and phospholipid levels of guinea pigs

The bleeding time, serum cholesterol and phospholipid levels were measured in guinea pigs treated to single sublethal oral doses of the coumarin compounds — scopoletin (60ug/kg body wt) and aflatoxin B 1 (50ug/kg body wt). These compounds generally increased the bleeding time (AFB 1 0.5 – 30%, scopoletin 2 – 38%) and the lipid levels relative to the control. However, while the increases elicited by aflatoxin B 1 on the total serum cholesterol, esterified cholesterol and phospholipid levels were statistically significant (P < 0.05), that on free cholesterol levels were not significant (P > 0.05). The increases elicited by scopoletin on all of these lipid fractions were not statistically significant (P > 0.05). Generally, aflatoxin B 1 elicited significantly higher (P < 0.05) increases on the measured serum lipid fractions than scopoletin. These studies highlight the possible roles of dietary scopoletin and AFB 1 in some disorders of blood clotting and lipid metabolism in animals.

Cholesterol metabolism in liver and gallbladder mucosa of patients with cholesterolosis

The objective of this study was to investigate possible pathogenetic factors for cholesterolosis. Liver tissue, gallbladder mucosa, and gallbladder bile were collected in patients with cholesterol gallstones (GS) (14 patients with and 14 patients without cholesterolosis) and gallstone-free (GSF) subjects (11 with and 21 without cholesterolosis) undergoing cholecystectomy. In cholesterolosis, the gallbladder mucosa was characterized by a fivefold increase in esterified cholesterol and normal content of free cholesterol. The hepatic levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, governing cholesterol synthesis, and acyl coenzyme A: acyltransferase activity, catalyzing the esterification of cholesterol, were similar in patients with and without cholesterolosis. Also in the gallbladder mucosa, the 3-hydroxy-3-methylglutaryl coenzyme A reductase activity was similar in patients with and without cholesterolosis. The acyl coenzyme A: acyltransferase activity of the gallbladder mucosa was increased in the GSF subjects with cholesterolosis. The nucleation time of gallbladder bile was shorter in the GSF subjects with cholesterolosis compared with the time of those without cholesterolosis. Occurrence of cholesterol crystals, lipid composition, and cholesterol saturation of gallbladder bile were not significantly influenced by the absence or presence of cholesterolosis. The study has confirmed that cholesterolosis is associated with a several-fold increased level of esterified cholesterol. The data suggest that patients with cholesterolosis have normal hepatic cholesterol formation and esterification. The local synthesis of cholesterol in the gallbladder mucosa seems to be normal. A positive correlation was obtained between the cholesterol saturation of bile and the content of esterified cholesterol in the gallbladder mucosa in the whole series of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol metabolism in liver and gallbladder mucosa of patients with cholesterolosis

The objective of this study was to investigate possible pathogenetic factors for cholesterolosis. Liver tissue, gallbladder mucosa, and gallbladder bile were collected in patients with cholesterol gallstones (GS) (14 patients with and 14 patients without cholesterolosis) and gallstone-free (GSF) subjects (11 with and 21 without cholesterolosis) undergoing cholecystectomy. In cholesterolosis, the gallbladder mucosa was characterized by a fivefold increase in esterified cholesterol and normal content of free cholesterol. The hepatic levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, governing cholesterol synthesis, and acyl coenzyme A: acyltransferase activity, catalyzing the esterification of cholesterol, were similar in patients with and without cholesterolosis. Also in the gallbladder mucosa, the 3-hydroxy-3-methylglutaryl coenzyme A reductase activity was similar in patients with and without cholesterolosis. The acyl coenzyme A: acyltransferase activity of the gallbladder mucosa was increased in the GSF subjects with cholesterolosis. The nucleation time of gallbladder bile was shorter in the GSF subjects with cholesterolosis compared with the time of those without cholesterolosis. Occurrence of cholesterol crystals, lipid composition, and cholesterol saturation of gallbladder bile were not significantly influenced by the absence or presence of cholesterolosis. The study has confirmed that cholesterolosis is associated with a several-fold increased level of esterified cholesterol. The data suggest that patients with cholesterolosis have normal hepatic cholesterol formation and esterification. The local synthesis of cholesterol in the gallbladder mucosa seems to be normal. A positive correlation was obtained between the cholesterol saturation of bile and the content of esterified cholesterol in the gallbladder mucosa in the whole series of patients. However, because cholesterolosis may occur in both GSF subjects and patients with cholesterol GS with or without cholesterol-saturated bile, the uptake of cholesterol from the gallbladder bile may not be the only mechanism for the development of cholesterolosis.

Toxicological Studies of Pueraria tuberosa, a Potent Antifertility Plant

AbstractToxicity studies with the butanol extract of Pueraria tube-rosa DC. (Leguminosae), a prospective postcoital contraceptive agent, were carried out in rats. A dose of 150 mg/ kg was administered to rats for 6, 12, 18 and 24 days. The level of blood sugar, serum proteins, serum GPT and GOT showed variations within the normal range except at the highest dose regimen. Leucocyte counts and haemoglobin values were within normal limits. Protein content, glycogen content, activity of acid and alkaline phosphatase, level of total and esterified cholesterol, adenosine triphosphatase, and glucose 6-phosphatase activity showed no significant change at initial durations except with the 24 day regimen. However, the adrenal glands showed significant change. In addition, no significant histopathological lesions were observed. In conclusion, the butanol extract appears to be generally safe in rats at these acute and subacute dosage regimens.

Role of liver in the synthesis of cholesterol and the clearance of low density lipoproteins in the cynomolgus monkey

The suitability of the adult male cynomolgus monkey as a model for investigating genetic mechanisms that regulate dietary cholesterolemic response was evaluated by carrying out a systematic characterization of the major aspects of cholesterol metabolism in this species. In monkeys maintained on a diet enriched with saturated fat but low in cholesterol (0.019%, wt/wt), plasma total and low density lipoprotein cholesterol (LDL-C) concentrations were 118 +/- 6 and 45.3 +/- 3.4 mg/dl, respectively. Intestinal cholesterol absorption averaged 54.0 +/- 2.5%, and the rate of whole body sterol synthesis was 10.8 +/- 0.6 mg/day per kg body weight. Only 11.2 +/- 2.6% of this synthesis occurred in the liver. In contrast, the liver was the major site for low density lipoprotein clearance accounting for almost 80% of LDL-C degradation in these animals. The liver, which represented 1.5% of whole body mass, had a total and esterified cholesterol concentration of 4.95 +/- 0.29 and 2.05 +/- 0.30 mg/g, respectively. When challenged with a matching high cholesterol diet (0.19%, wt/wt), the monkeys developed marked hypercholesterolemia that was accounted for mainly by a 7-fold increase in the LDL-C levels. There was, however, wide individual variation among the monkeys in the magnitude of their cholesterolemic response. Hepatic total and esterified cholesterol levels increased 2.5- and 4.6-fold, respectively. Comparative experiments showed that while several of the metabolic characteristics of this species of monkey were similar to those found in the hamster, they were generally very different from those seen in the rat. Thus, the male cynomolgus monkey has many characteristics in common with humans and represents an attractive model for further delineating the genetic mechanisms that dictate variable responsiveness to dietary cholesterol and triacylglycerol.

Coordinate diurnal regulation of hepatic acyl-coenzyme A: cholesterol acyltransferase and cellular levels of esterified cholesterol

Hepatic ACAT, HMG-CoA reductase and both cellular free and esterified cholesterol were measured at 3 h intervals over a 24 h period in the rat. ACAT exhibited a characteristic low amplitude diurnal rhythm with maximum activity at the mid-light phase that was significantly higher than the minimum activity observed at the mid-dark phase. The cellular esterified cholesterol concentration showed a diurnal rhythm that closely paralleled the rhythm of ACAT activity. The cellular free cholesterol concentration was not significantly altered during the 24 h cycle. In rats fed cholesterol, the diurnal rhythm of ACAT was still maintained despite the increase in ACAT activity during the entire 24 h cycle suggesting that the ACAT rhythm is the result of changes in the level of ACAT protein expression. The results also indicate that the diurnal rhythms of ACAT and HMG-CoA reductase are generated by a process independent of the LDL receptor rhythm. All three rhythms are also independent of changes in the level of free cholesterol in the cell.

Effects of celiprolol vs. nifedipine on serum lipoproteins in patients with mild to moderate hypertension

During a double-blind, randomized study in hypertensive patients, changes in plasma lipid and lipoprotein levels during treatment with celiprolol were compared with those occurring during nifedipine treatment. Fifty-three patients (28 men and 25 women) with mild-to-moderate hypertension, aged 20-64 years, were studied. After a 1-month placebo run-in period, patients were randomly assigned to receive either nifedipine (40 mg daily) or celiprolol (200 mg daily), each time using a double-dummy technique. After 6 weeks, dosages of each drug could be doubled. After 6 weeks, there were no differences in plasma lipids between the two treatment groups. However, the changes after 12 weeks of treatment were different (p < 0.05) between the groups, leading to lower levels of plasma esterified cholesterol, low-density lipoprotein (LDL) cholesterol, and apoprotein AI, AII, and B in the celiprolol group. Plasma lecithin cholesterol acyltransferase activity (LCAT) was not modified. The present study showed that celiprolol was at least equivalent to nifedipine in terms of secondary effects on plasma lipids and lipoprotein.

Is the antiatherosclerotic potency of HDL modulated by the origin of HDL?

Different HDL preparations from rabbit blood were injected intravenously (10 mg HDL protein/injection and animal) into cholesterol fed rabbits twice a week for 8 weeks. The composition of the used high density lipoprotein (HDL) was modified by dietary pretreatment. HDL-1 was taken from rabbits after 8 weeks pellet diet, HDL-2 after 8 weeks fish-oil rich diet and HDL-3 after 8 weeks of cholesterol rich diet. The animals treated with HDL-1 and HDL-2 had a significantly smaller area of intima covered with fatty streaks than the control animals (injection of saline instead of HDL). The injection of HDL-3 was without influence. These differences were correlated with changes in the level of free and esterified cholesterol (FC and CE) in kidney, liver and aorta of the rabbits, but not with the level of cholesterol in the serum lipoproteins. We investigated simultaneously the influence of the different HDL preparations on the cholesterol content in rabbit skin fibroblasts (RSF), rabbit smooth muscle cells (SMC) and human hepatoma cell line Hep G2. Additionally the influence on the proliferation of SMC was studied. HDL-1 diminished the level of FC in cholesterol enriched RSF and rabbit SMC, whereas both other HDL preparations had no effect. The level of FC in Hep G2 was not influenced. HDL-1 and HDL-3 stimulated the proliferation of rabbit SMC, whereas HDL-2 had no such influence. The data support the antiatherosclerotic role of HDL injections in cholesterol fed rabbits, but the composition of the used HDL seems to modify this influence, probably by different effects on the biochemical changes induced by the HDL.

Effect of lipoprotein(a) on lipid metabolism of cultured human intimal aortic cells

The effect of Lp(a) on lipid metabolism in cells cultured from unaffected human aortic intima has been investigated. Lp(a) isolated from the blood of healthy subjects failed to alter intracellular neutral lipid content. On the other hand, Lp(a) obtained from coronary atherosclerosis patients induced a 1.5- to 2.5-fold increase in intracellular levels of free and esterified cholesterol and triglycerides. The sialic acid content of patients' Lp(a) was 2.5-fold lower as compared with that of healthy subjects' Lp(a). Healthy donors' Lp(a) in vitro desialylated with neuraminidase were able to accumulate lipids within the cells. Using lectin-chromatography on Ricinus Communis agglutinin-agarose, Lp(a) was divided into subfractions differing by sialic acid content. Desialylated (sialic acid-poor) Lp(a), but not sialylated lipoproteins, were capable of increasing the intracellular content of total cholesterol. Desialylated but not sialylated Lp(a) formed aggregates during incubation under cell culture conditions. Isolated aggregates of desialylated Lp(a) induced lipid accumulation in cells. Elimination of Lp(a) aggregates from cultural medium prevented the increase of intracellular lipids. Complexes of Lp(a) with the matrix components and antibodies increased lipid level in cultured cells. We assume that formation of large particles of desialylated Lp(a) aggregates or Lp(a)-containing complexes is a necessary step for lipid accumulation in human intimal cells.

Effects of dietary pectin on the hepatic activities of hydroxymethyl glutaryl CoA reductase and acyl CoA cholesterol acyltransferase in cholesterol supplemented mice

Plasma lipoprotein cholesterol and hepatic activities of hydroxymethyl glutaryl CoA reductase (HMGR) and acyl CoA cholesterol acyltransferase (ACAT) in mice fed a semi-synthetic diet supplemented with 5% low methoxyl pectin with or without addition of 0.5% cholesterol for 4 weeks were examined. While plasma concentrations of total cholesterol and triglycerides were significantly reduced, the hepatic levels of total and esterified cholesterol were markedly increased, and triglyceride levels remained unaffected when cellulose in the diet was substituted for by pectin in the cholesterol-enriched diet. The administration of 0.5% cholesterol to control animals resulted in a 50% reduction in the hepatic HMGR activity. This activity was restored to its control level when cellulose was substituted by pectin in the diet. The hepatic ACAT activity, on the other hand, was significantly increased when fed a diet containing 0.5% cholesterol. This effect remained unchanged when pectin was administered. The hypolipidemic action of pectin does not appear to be mediated through inhibition of cholesterol synthesis. It is possible that the decreased plasma level of cholesterol is the reflection of its accumulation in the liver.

Atherosclerosis in Young White Males: Arterial Collagen and Cholesterol

As part of a muticenter study on atherosclerosis, we examine defined segments of thoracic and abdominal aortas from 118 white males, age 15–34 years, who died from external causes. One half o each aorta specimen was graded or lesions. Intima-media preparations were assayed for collagen an cholesterol in two standardized regions (dorsal and ventral) derived from the alternate half of each segment. Even though the mean extent of intimal surface involvement with raise lesions remained minimal (0–6%), the data revealed a remarkable transition in vessel wall chemistry over this time span. For example, the amount of collagen per unit surface area increases with age in all vessel segments except the ventral domain of the thoracic aorta. The amount of collagen as a percent of total vessel protein rises with age only in the ventral and dorsal regions of the abdominal aorta. Free and esterified cholesterol levels per unit surface area increase with age in all vessel segments. There is a significant correlation between collagen and esterified cholesterol per unit surface area in all vessel regions with the exception of the abdominal ventral segment. In the latter segment increases in collagen per unit surface area occur without a corresponding increase in cholesterol level suggesting that connective tissue proliferation may actually precede lipid deposition in the genesis of atherosclerosis. Esterified cholesterol is present at higher levels in the dorsal domains of the thoracic and abdominal aortas than in the ventral domains. These findings provide chemical data confirming that the dorsal domain is the most lesion-prone region of these vessel segments. The most pronounced changes in aorta chemistry become apparent in the 25–29 year age range. Thus, the results suggest that for white males, preventive measures for atherosclerosis such as dietary restrictions should be instituted at the beginning of the third decade.

Progesterone blocks cholesterol translocation from lysosomes.

Fluorescent microscopic examination of fibroblasts cultured with low density lipoprotein (LDL) and progesterone (10 micrograms/ml) for 24 h revealed extensive filipin-cholesterol staining of perinuclear lysosomes. Levels of unesterified cholesterol were 2-fold greater than in fibroblasts cultured with LDL alone. Progesterone strongly blocked cholesteryl ester synthesis. When cellular uptake of LDL was monitored in the presence of 58035, a specific inhibitor of acyl-CoA:cholesterol acyltransferase, excess unesterified cholesterol was not stored in lysosomes. Discontinuation of LDL uptake in conjunction with progesterone washout markedly reversed the filipin-cholesterol staining of lysosomes. Reversal of the lysosomal cholesterol lipidosis was associated with a rapid burst of cholesteryl ester synthesis and a normalization of the cellular levels of free and esterified cholesterol. In contrast to normal cells, progesterone removal from Niemann-Pick C fibroblasts did not reverse the lysosomal cholesterol accumulation of these mutant cultures. The metabolic precursor of progesterone, pregnenolone, also induced extensive accumulation of cholesterol in lysosomes. Other steroids induced less vacuolar cholesterol accumulation in the following decreasing order: corticosterone and testosterone, promegestone, RU 486. The relative inhibition of cellular cholesterol esterification by the steroids paralleled their respective abilities to sequester cholesterol in lysosomes rather than their inhibition of acyl-CoA:cholesterol acyltransferase activity in cell-free extracts. The progesterone-related inhibition and restoration of lysosomal cholesterol trafficking is a useful experimental means of studying intracellular cholesterol transport. A particularly important feature of its utility is the facile reversibility of the steroid-induced block. The lysosomal cholesterol lipidosis established with a hydrophobic amine, U18666A, was not as readily reversed.