Differences In Cholesterol Concentrations Research Articles

Cholesterol cytochemistry in cell biology and disease.

Cholesterol localization in membranes, cells, and tissues is a topic of substantial and continuing interest to the biomedical cell biologist. Knowing precisely where and in what amount cholesterol is present offers potentially useful insights into the functional role of this lipid as a constituent of normal membranes, and the part it plays in the pathogenesis of diseases that involve dysfunction of cholesterol homeostasis. The cholesterol content of membranes influences a range of properties, such as fluidity, stability, the activities of membrane-bound enzymes, and the adhesive and electrical properties of the cell surface. Differences in cholesterol content characterize the various specialized membrane systems of the cell; plasma membranes and the membranes of endocytic organelles are normally cholesterol-rich, whereas endoplasmic reticulum, nuclear, and mitochondrial membranes typically have much lower cholesterol levels. Furthermore, the concept that cholesterol distribution may be heterogeneous within a given membrane, reflecting a mosaiclike pattern of functional differentiation, has also been widely debated. Despite the wealth of information from in vitro biophysical studies, however, there remain many gaps in our understanding of the functional significance of cholesterol distrtibution in relation to the diverse membrane-mediated cellular activities that are fundamental to issues function.

Response to a single oral dose of all-rac-alpha-tocopheryl acetate in patients with cystic fibrosis and in healthy individuals

Biochemical vitamin E deficiency and low plasma lipids are frequent findings in patients with cystic fibrosis (CF). The response to a single oral dose of all-rac-alpha-tocopheryl acetate [100 IU (100 mg)/kg body wt] was studied over 24 h in 25 CF patients with exocrine pancreatic insufficiency and in 23 healthy individuals. Patients received pancreatic enzymes together with the vitamin E test dose. At baseline, plasma alpha-tocopherol concentrations correlated with cholesterol concentrations; both were lower in patients than in control subjects, as were erythrocyte alpha-tocopherol concentrations (all P < 0.0001). Plasma and erythrocyte alpha-tocopherol concentrations were significantly higher than baseline concentrations from 3 and 6 h onward, respectively, and peaked most frequently at 6 and 12 h, respectively, in both patients and control subjects. Maximum increases and areas under the concentration time curves for plasma alpha-tocopherol concentrations were smaller in patients than in control subjects (P < 0.0001). When ratios of plasma alpha-tocopherol to cholesterol (to correct for differences in cholesterol concentrations) or erythrocyte alpha-tocopherol concentrations were applied, patients were shown to respond as efficiently as control subjects. On the basis of these results, we recommend vitamin E supplements in doses high enough to achieve vitamin E status in CF patients well within the range of healthy individuals; these supplements should be given with appropriate amounts of pancreatic enzymes. However, for long-term supplementation much lower doses than those used in this test situation may be sufficient.

Serum cholesterol concentraions in parasuicide

To evaluate whether people who have committed parasuicide have low serum cholesterol concentrations. Results of blood tests in subjects admitted to hospital for parasuicide compared with those of a control group of non-suicidal subjects; comparison in subgroup of parasuicide subjects of two sets of blood test results (one set from admission for parasuicide and the other from admission for some other illness). General hospital, Ferrara, Italy. 331 parasuicide subjects aged 44 (SD 21) years (109 with two sets of blood test results) and 331 controls. Serum cholesterol concentrations and possible association with parasuicide, considering sex, violence of method of parasuicide, and underlying psychiatric disorder. Lower serum cholesterol concentrations (4.96 (SD 1.16) mmol/l) were found in the parasuicide subjects than in the controls (5.43 (1.30); P < 0.001), regardless of sex and degree of violence of parasuicide method. Both men and women with two sets of blood test results had lower cholesterol concentrations after parasuicide. Linear regression analysis showed that the difference in cholesterol concentrations was significantly related to the length of time between the taking of the two sets of blood samples. The study showed low cholesterol concentrations after parasuicide. This finding agrees with previous studies, which suggest an association between low cholesterol concentration and suicide.

Functional and Morphologic Characterization of Thoracic Aorta in Heritable Hyperlipidemic Yoshida Rats of Different Ages

Summary: We investigated serum and aortic tissue lipid content, in vitro aortic response to drugs, and morphology of thoracic aorta in Pittsburgh Yoshida rats (YOS), a new animal model of endogenous hyperlipidemia. Experiments were performed on 2-, 6-, and 18-month-old rats, Normolipidemic Brown Norway rats (BN) were used as controls. Both serum cholesterol and triglycerides increased significantly with age in YOS rats, but remained constantly low in the control group. In YOS rats, absolute serum concentration of high density lipoprotein (HDL)-cholesterol increased significantly with age, although HDL-cholesterol/total-cholesterol ratio decreased. In contrast, no difference in cholesterol content in aortic tissue was detected between the two animal strains or among different age groups. The contractile force generation of thoracic aorta to norepinephrine (NE) and serotonin increased with age in both strains of animals. The endothelium-dependent relaxation induced by acetylcholine (ACh) was significantly reduced in 6- and 18-month-old YOS as compared with 2-month-old YOS but not in BN. ATP-induced relaxation was significantly impaired in YOS thoracic aorta. In contrast, the relaxation induced by NaNO2 acting in smooth muscle did not vary with age in either YOS or BN. Only alterations in endothelial cells, not typical atheromatous injuries in thoracic aorta wall were detected in YOS even at age 18 months. Our data indicate that despite high serum lipid levels, YOS do not develop typical atheromatous lesions or functional and morphologic damage of smooth muscle cells in thoracic aorta, whereas YOS show decreased endothelium-dependent relaxation and morphologic alteration of endothelial cells.

Functional and Morphologic Characterization of Thoracic Aorta in Heritable Hyperlipidemic Yoshida Rats of Different Ages

We investigated serum and aortic tissue lipid content, in vitro aortic response to drugs, and morphology of thoracic aorta in Pittsburgh Yoshida rats (YOS), a new animal model of endogenous hyperlipidemia. Experiments were performed on 2-, 6-, and 18-month-old rats. Normolipidemic Brown Norway rats (BN) were used as controls. Both serum cholesterol and triglycerides increased significantly with age in YOS rats, but remained constantly low in the control group. In YOS rats, absolute serum concentration of high density lipoprotein (HDL)-cholesterol increased significantly with age, although HDL-cholesterol/total-cholesterol ratio decreased. In contrast, no difference in cholesterol content in aortic tissue was detected between the two animal strains or among different age groups. The contractile force generation of thoracic aorta to norepinephrine (NE) and serotonin increased with age in both strains of animals. The endothelium-dependent relaxation induced by acetylcholine (ACh) was significantly reduced in 6- and 18-month-old YOS as compared with 2-month-old YOS but not in BN. ATP-induced relaxation was significantly impaired in YOS thoracic aorta. In contrast, the relaxation induced by NaNO2 acting in smooth muscle did not vary with age in either YOS or BN. Only alterations in endothelial cells, not typical atheromatous injuries in thoracic aorta wall were detected in YOS even at age 18 months. Our data indicate that despite high serum lipid levels, YOS do not develop typical atheromatous lesions or functional and morphologic damage of smooth muscle cells in thoracic aorta, whereas YOS show decreased endothelium-dependent relaxation and morphologic alteration of endothelial cells.

Ischaemic heart disease and cholesterol There's more to heart disease than cholesterol

EDITOR, - We are impressed by the “cholesterol papers.”*RF 1-3* M R Law and colleagues prove that it is highly probable that lowering the serum cholesterol concentration in the population will reduce the risk of ischaemic heart disease without increasing the risk of other disease. The jump from epidemiological evidence to conclusions regarding public health is not, however, as evident as they suggest. Law and colleagues state that lowering serum cholesterol concentration is critical in reducing ischaemic heart disease. It certainly was not so in the past; why should it be in the future? Several Western populations have seen a steeply decreasing mortality from ischaemic heart disease in association with constant or even increasing cholesterol concentrations.4 If we compare the cohort of the British United Provident Association (BUPA), which was recruited in 1975-82, with the Whitehall cohort, which was recruited one decade earlier, we observe higher serum cholesterol concentrations in all the fifths of the BUPA population (fig 12). Despite this, the incidence of ischaemic heart disease was at least three times lower in the BUPA cohort. As far as we can see - the y axis varies tremendously - the incidence of ischaemic heart disease in the patients with the lowest fifth of serum cholesterol concentration in the Whitehall study was still higher than that in the patients with the highest fifth of cholesterol concentration in the BUPA cohort. In the Whitehall study serum cholesterol concentrations were lower in the lower classes, but the risk of ischaemic heart disease was four times higher than that in the highest.5 Differences in cholesterol concentrations may explain the international variation in mortality from ischaemic heart disease but do not explain the variation in middle aged employed men in London. Before it is concluded that cholesterol concentrations must be reduced …

A comparison of the 2% and 1% formulations of propofol during anaesthesia for craniotomy

This study investigated the pharmacodynamic and pharmacokinetic equivalence of 1% and 2% propofol emulsions when used for total intravenous anaesthesia for intracranial surgery. The same infusion rate (6.7 mg.kg-1 x h-1) of the two preparations was administered. Induction doses, recovery times, and haemodynamic profiles were identical. Similar propofol concentration profiles were produced and total body clearance of propofol was identical. Both preparations were associated with a similar incidence of injection pain but neither resulted in venous thrombosis or thrombophlebitis at 24 h. Plasma triglyceride concentrations were significantly higher with the 1% solution, but there were no differences in cholesterol concentrations. The 1% and 2% emulsions appeared to be pharmacologically equivalent with similar minor effects on arterial blood pressure and heart rate. Two percent propofol may be preferable to the 1% solution for maintenance of anaesthesia in patients in whom a large lipid load might be considered undesirable.

Hypertension and Hyperlipidemia: A Review

In a recent meta-analysis of 13 studies of antihypertensive treatment, it was demonstrated that the reduction of risk for coronary artery disease was 14% compared with the 20% to 25% expected for a diastolic blood pressure reduction of 5 to 6 mm Hg according to observational studies. In contrast, the obtained effect on stroke reduction was of the same order as that expected for a given blood pressure reduction. A meta-analysis of 22 lipid-lowering studies indicated a reduction in risk of coronary artery disease that is consistent with epidemiologic observations, indicating a difference in risk of 20% to 30% for a 10% difference in cholesterol concentration. Many cross-sectional studies have demonstrated that hypertensive men and women are metabolically different from normotensive subjects. These differences include a disturbed glucose metabolism due to insulin resistance that may also be the basis of the observed lipid abnormalities and even of the hypertension itself. Some of the drugs used in the treatment of hypertension produce changes in metabolism such that insulin resistance becomes worse and lipid abnormalities become still more pronounced. In the case of treatment with beta-blockers, there is a change in lipoprotein composition that may indicate an increased tendency toward oxidation, which may render the lipoproteins more atherogenic. It is obvious that the metabolic profile in hypertensive patients warrants consideration and, furthermore, that the metabolic effects of different drugs should be taken into account when starting treatment.

Effect of dietary fat and cholesterol level on tissue cholesterol concentrations of growing pigs selected for high or low serum cholesterol.

Thirty-six female pigs selected for three generations for high or low serum cholesterol were chosen to evaluate the effects of a high-fat, high-cholesterol diet and a low-fat, low-cholesterol diet provided on an ad libitum basis for 92 d beginning at 12 wk of age on the cholesterol content and percentage of fat in muscle and organ tissues. The pigs were four-way crosses (Chester White x Landrace x Large White x Yorkshire). Samples of cerebrum, heart, ileum, kidney, liver, longissimus muscle, semitendinosus muscle, and subcutaneous fat were collected from each animal for determination of cholesterol concentration. The liver was the only tissue that had a significant difference in cholesterol content and in fat percentage between the genetic groups (high serum cholesterol and low serum cholesterol) and between the two diets (high-fat, high-cholesterol diet and low-fat, low-cholesterol diet). There were no interactions between diet and genetic background on cholesterol accretion or on the percentage of fat in the tissues.

Does plasma cholesterol concentration predict mortality from coronary heart disease in elderly people? 18 year follow up in Whitehall study.

To explore the extent to which the relation between plasma cholesterol concentration and risk of death from coronary heart disease in men persists into old age. 18 year follow up of male Whitehall civil servants. Plasma cholesterol concentrations and other risk factors were determined at first examination in 1967-9 when they were aged 40-69. Death of men up to 31 January 1987 was recorded. 18,296 male civil servants, 4155 of whom died during follow up. Cause and age of death. Cholesterol concentration in 1967-9 and number of years elapsed between testing and death. 1676 men died of coronary heart disease. The mean cholesterol concentration in these men was 0.32 mmol/l higher than that in all other men (95% confidence interval 0.26 to 0.37 mmol/l). This difference in cholesterol concentrations fell 0.15 mmol/l with every 10 years' increase in age at screening. The risk of raised cholesterol concentration fell with age at death. Compared with other men cholesterol concentration in those who died of coronary heart disease was 0.44 mmol/l higher in those who died aged less than 60 and 0.26 mmol/l higher in those aged 60-79 (p = 0.03). For a given age at death the longer the gap between cholesterol measurement and death the more predictive the cholesterol concentration, both for coronary heart disease and all cause mortality (trend test p = 0.06 and 0.03 respectively). Reducing plasma cholesterol concentrations in middle age may influence the risk of death from coronary heart disease in old age.

Abnormal proximal tubule apical membrane protein composition in X-linked hypophosphatemic mice

The hypophosphatemic (Hyp) mouse is characterized by an isolated X-linked defect in proximal tubular phosphate (Pi) reabsorption associated with a decreased maximum velocity (Vmax) and a normal affinity (Km). To directly investigate the underlying cellular defect proximal tubular brush-border membranes (BBM) from normal control (Con) and Hyp male littermates were examined for differences in cholesterol content, total and individual phospholipid composition, phospholipid incorporation rates, membrane fluidity, and by two-dimensional sodium dodecyl sulfate (SDS)-polyacrylamide protein electrophoresis. The cholesterol content, total and individual phospholipid profiles, phospholipid incorporation rates, and membrane fluidity of Con and Hyp BBM samples were comparable. However, the two-dimensional gel electrophoreses of Con and Hyp BBM proteins, run simultaneously under identical conditions, revealed a protein with an apparent abnormal isoelectric migration pattern in Hyp BBM samples. This protein had an apparent molecular weight 56,000 and an apparent pI of 7.2 and was consistently evident on Hyp gels (n = 3) but not on Con gels (n = 3). The appearance of this protein band was associated with a diminution in staining of a control protein of comparable apparent molecular weight but markedly lower apparent pI.

Differences in metabolism of three low density lipoprotein subfractions in Hep G2 cells

The metabolism of low density lipoprotein (LDL) subfractions was investigated in the human hepatoma cell line Hep G2. By means of a density gradient ultracentrifugation method three LDL subfractions were isolated from pooled serum of normolipidemic subjects: very light LDL-1A, light LDL-1B and heavy LDL-2, differing in size, relative lipid and protein content. Cell specific association, stimulation of cholesterol esterification and inhibition of sterol synthesis were determined in parallel after incubation of Hep G2 cells with increasing amounts of LDL-protein of the three LDL subfractions. These parallel experiments were repeated four times with freshly prepared LDL subfractions. Response curves were parametrized with the function y = a√ x, depicting the relation between the cellular metabolic event ( y) and the LDL-protein ( x) or LDL-cholesterol ( x) levels. An analysis of covariance model was used to test differences between parameters of the three LDL subfractions. When the results of all four experiments were taken into account, the cell specific association increased more with increasing LDL-protein concentration for LDL-1A than for LDL-2 ( P < 0.05). At the LDL-protein level of 80 μg/ml the cell specific association for LDL-2 amounted to 85.5% of that for LDL-1A. Results for LDL-1B were intermediate between those for LDL-1A and LDL-2. The corresponding cholesteryl ester formation increased more with increasing LDL-protein concentration for LDL-1A than for LDL-1B ( P < 0.001), and for LDL-1B more than for LDL-2 ( P < 0.001). At the LDL-protein level of 70 μg/ml the cholesterol ester accumulation for LDL-2 and LDL-1B was 48.4% and 70.3%, respectively, of that for LDL-1A. These differences between LDL subfractions in cholesteryl esterification were independent of the cholesterol content of the subfractions. Consistent with these findings, the ¦ 14C¦acetate incorporation to sterols decreased more with increasing LDL-protein concentration for LDL-1A and LDL-1B than for LDL-2 ( P < 0.05). At the LDL-protein concentration of 70 μg/ml the decrease in sterol synthesis after incubation with LDL-2 and LDL-1B was 79.2% and 98.0%, respectively, relative to that for LDL-1A. When adjusted for differences in cholesterol content of the LDL subfractions these differences with regard to the 14C-acetate incorporation were not significant. The metabolic differences between LDL subfractions in vitro may have implications for the metabolism and atherogenic potential of the distinct LDL subfractions in vivo. Thus,in the study of atherogenicity of lipoproteins, the existence of subfractions of LDL should be taken into account. Even for normolipidemic subjects the subfractions appear to have different metabolic characteristics.

Plasma lipid concentrations in college students performing self-selected exercise.

Plasma cholesterol and other blood lipids were determined in 64 college juniors and seniors during January and February 1989 (before exercise) and again during April and May 1989 (after exercise). A 14-week period of self-selected exercise was interposed between the before and after exercise cholesterol determinations. Cholesterol concentrations ranged from 127-273 mg/dl (before exercise) to 131-261 mg/dl (after exercise) in this group of students who were 22 +/- 1 years of age. There were no statistically significant differences in cholesterol concentrations between the genders. Students could be further subdivided into groups with low (144 +/- 3 mg/dl, n = 12), medium (176 +/- 6 mg/dl, n = 35), and high (224 +/- 6 mg/dl, n = 17) concentrations of cholesterol. Only students in the high cholesterol group experienced a significant reduction in total cholesterol and low-density-lipoprotein cholesterol after 14 weeks of exercise. High-density-lipoprotein cholesterol concentrations were significantly higher in women than in men in both the medium and high cholesterol subgroups before and after exercise. From these results it appears that a significant fraction of the young adult college population could be at increased risk of coronary heart disease because of inappropriately high concentrations of cholesterol. Moreover, self-selected exercise, if engaged in regularly, can reduce blood cholesterol significantly in students with high cholesterol concentrations.

Histologic, morphometric, and biochemical evolution of vein bypass grafts in a nonhuman primate model: III. Long-term changes and their modification by platelet inhibition with aspirin and dipyridamole

The objectives of this study were to elucidate the long-term influence on vein bypass grafts of platelet inhibition and its late discontinuation. Cephalic vein grafts were interposed bilaterally in the femoral arteries of stump-tailed macaque monkeys fed a diet that sustains plasma cholesterol levels of approximately 225 mg/dl. Fifteen animals were divided into three groups of five animals each. Group I received no medications and served as a control group. Group II received for the full duration of the study a combination of aspirin, 80 mg/day, and dipyridamole, 50 mg/day. Group III received the same regimen of platelet inhibition as in group II during the first 9 months, but were not treated during the subsequent 9-month interval. Grafts were excised for analysis from groups I and II at both 9 and 18 months and from group III at 18 months. Cholesterol content in group I grafts was 470 +/- 89 micrograms/100 mg at 9 months and 388 +/- 127 micrograms/100 mg at 18 months. In group II grafts, cholesterol content was 208 +/- 72 micrograms/100 mg at 9 months (p less than 0.001 compared with group I) and 266 +/- 84 micrograms/100 mg at 18 months. In group III grafts, cholesterol content was 249 +/- 71 micrograms/100 mg at 18 months. Differences in cholesterol content among the three groups of grafts at 18 months were not found to be statistically significant. Stepwise regression analysis at 18 months showed that cholesterol content was best predicted by medial fibrosis (r2 = 0.66) followed by abundance of foam cells (increase in r2 = 0.26) in group I, by fibrin in group II (r2 = 0.63), and by prevalence of macrophages in group III (r2 = 0.74). In all groups, platelets, fibrin, and polymorphonuclear leukocytes were less abundant than they had been at 3 months. Cross-sectional area occupied by the intima was not influenced by platelet inhibition.

Cholesterol heterogeneity in bovine rod outer segment disk membranes

Rod outer segment disk membranes have been used to study visual transduction events. Numerous studies have also focused on protein-lipid interactions in these membranes. The possible heterogeneity of the disk membrane composition has not been addressed in such studies. Freeze fracture studies (Andrews, L. D., and Cohn, A. I. (1979) J. Cell Biol. 81, 215-220; Caldwell, R., and McLaughlin, B. (1985) J. Comp. Neurol. 236, 523-537) suggest a difference in cholesterol content between newly formed and old disks. This potential heterogeneity in disk membrane composition was investigated using digitonin. Osmotically intact bovine rod outer segment disk membranes prepared by Ficoll flotation were separated based on the cholesterol content of the disks. The addition of digitonin to disk membrane suspensions in a one-to-one molar ratio with respect to cholesterol produced an increase in the density of the membranes in proportion to the amount of cholesterol present. The digitonin-treated disks were separated into subpopulations using a sucrose density gradient. Disks were shown to vary in cholesterol to phospholipid ratio from 0.30 to 0.05. The ratio of phospholipid to protein remained constant in all disk subpopulations at approximately 65 phospholipids per protein. No significant change in the fatty acid composition of the disks was observed as a function of change in cholesterol content. This work demonstrates compositional heterogeneity in disk membranes which may ultimately affect function.

CT evaluation of gallstones in vitro: correlation with chemical analysis

With the advent of chemical dissolution and lithotripsy for the treatment of gallstones, use of imaging techniques to determine the chemical composition of gallstones has become important. In vitro CT scans were performed on gallstones removed at surgery from 70 patients. The CT appearances were as follows: dense (20%), faint (10%), isodense with saline (nonvisualized) (26%), rimmed (30%), and laminated (14%). Stones from 50 patients were subjected to chemical analysis, and the results were compared with the appearance of the stones on CT. Among stones grouped by CT appearance, a significant difference in cholesterol content was found, but calcium content did not differ significantly among most groups. The inverse correlation between CT attenuation values and cholesterol was stronger (r = -.82) than the correlation between CT attenuation values and calcium (r = .64). The results show that gallstones can be divided into those with high cholesterol content and those with low cholesterol content on the basis of their appearance on in vitro CT. The differences in the CT findings in many gallstones appear to relate more to cholesterol content than to calcium composition.

Neonatal Parenteral Nutrition with a Fat Emulsion Containing Medium Chain Triglycerides

Fifty-one newborn infants requiring parenteral nutrition were randomly assigned to receive a 50% medium chain triglyceride/50% long chain triglyceride lipid emulsion or the conventional 100% long chain triglyceride emulsion. Fat was administered daily for 20 hours, to a maximum of 3 g/kg/day. Plasma triglycerides, cholesterol, free fatty acids, ketones, glucose and capillary blood gases were monitored daily up to the sixth day of fat infusion. There were no significant differences in mean plasma triglycerides and free fatty acids between the two groups. No cases of hyperketonaemia were detected in the infants studied. Hyperglycaemic episodes were detected with similar frequency in both groups. The group who received the emulsion containing medium chain triglycerides had significantly lower mean plasma cholesterol values during the study. After 6 days of intravenous fat administration mean plasma cholesterol was more than 100% higher in the group which received the conventional emulsion. Differences in cholesterol content between the emulsions and a cholesterol lowering effect of medium chain triglycerides are possible explanations for these findings.

Plasma, Tissue and Fecal Cholesterol of Young Pigs Fed Restricted or Liberal Amounts of Beef, Soy or Conventional Diets

Cholesterol disposition (tissue deposition + fecal excretion) was determined in young pigs fed restricted (trial 1) or liberal (trial 2) amounts of beef-based, soy-based or conventional swine diets. Cholesterol content of diet is greater than average United States consumption per kilogram body weight but is very similar on a per-kilocalorie intake basis. Both beef and soy diets contained more cholesterol (0.09% by weight vs. 0%) and fat (40–50% of calories vs. 8–9%) than did conventional diets. Dried egg yolk was the source of cholesterol in the soy diets. Beef- and soy-fed pigs had greater plasma, HDL and LDL cholesterol concentrations than did conventionally fed pigs; beef-fed pigs had greater plasma, HDL and LDL cholesterol concentrations than did soy-fed pigs in trial 2 only. Final HDL-to-LDL cholesterol ratios did not differ. Neutral steroid and bile acid excretion was twofold greater in soy-fed than in conventionally or beef-fed pigs in trial 2 only. Differences in cholesterol concentrations were found in liver (soy, beef > conventional) and heart (soy > beef, conventional) in trial 1 and in liver (soy, beef > conventional), adipose tissue (soy > conventional > beef) and aorta and other viscera (conventional > soy, beef) in trial 2. In both trials, soy-fed pigs had greatest whole-body cholesterol concentrations. Thus, in both trials, disposition of cholesterol was similar in conventionally fed and beef-fed pigs, despite greater cholesterol intake in the latter, but was greater in soy-fed pigs.

Cholesterol Content and Sensory Analysis of Ground Beef as Influenced by Fat Level, Heating, and Storage

ABSTRACTTwelve treatment combinations including three fat levels, two internal endpoint temperatures, and two storage periods for ground beef patties were studied. Quality and sensory attributes as well as cholesterol content were evaluated. As fat level increased in raw patties, cholesterol content, drip and total cook loss, fat and cholesterol content of cook drip increased whereas red color intensity and evaporative losses decreased. Cholesterol content, evaporative and total losses, and beef‐flavor intensity increased with higher internal endpoint temperature. Red color intensity of raw patties and cholesterol content of raw and cooked patties decreased with storage. No differences in cholesterol content could be attributed to fat content of raw product; therefore, choosing low fat ground beef to lower cholesterol may not be justified.

Effects of high cholesterol diets on rat plasma lipoproteins and lipoprotein-cell interactions.

High fat, high cholesterol diets do not produce atherosclerotic lesions in some animal species such as the rat; however, when combined with experimentally induced hypothyroidism, such diets do produce lesions. While the diets or hypothyroidism each induce significant alterations in plasma lipoproteins, the combination produces marked hypercholesterolemia. If the atherosclerosis is related to the hyperlipidemia, the combination regimen could be provoking changes in the structure or compositions of lipoproteins which are not noted with either regimen alone. To test this hypothesis, Sprague-Dawley male rats (approximately 250 g) were treated as follows: Diet(a) = chow + 5% lard and 0.3% Na taurocholate; Diet(b) = Diet(a) + 2% cholesterol; Diet(c) = Diet(b) + 0.1% propylthiouracil (PTU). The major findings were as follows. 1) With Diet(b), slow floating very low density lipoprotein (VLDL) (pre-beta) enriched in cholesteryl esters accumulated in plasma and low density lipoprotein (LDL) disappeared from its usual flotation position. 2) With Diet(c), changes in plasma concentration were more marked but were also qualitatively different. More VLDL accumulated, and distribution of VLDL was shifted toward even slower floating cholesteryl ester-rich particles. VLDL had "broad beta" mobility. Also, a beta-migrating intermediate density lipoprotein (IDL) population appeared. 3) Lipoprotein (d less than 1.019 g/ml) and zonal subfractions of d less than 1.019 g/ml lipoproteins (isolated from rats on cholesterol Diet (b] stimulated [3H]oleate incorporation into cholesteryl esters of fibroblasts and macrophages, while the d less than 1.019 g/ml fractions of 5% fat (Diet(a]-fed rats did not. 4) The major finding of this study was that identically prepared d less than 1.019 g/ml fractions of Chol + PTU-treated rats (Diet(c] were approximately 2.5-fold more stimulatory than the lipoproteins of cholesterol-fed rats. The results could not be explained by differences in cholesterol contents of the cholesterol-rich lipoproteins, but significant differences in the apoprotein compositions of the fraction were found which could be important. The most active fractions had higher apoBL/apoBS and apoE/apoC ratios than less active fractions. Thus, the combination regimen of cholesterol and PTU produced changes in lipoprotein structure and composition which enhanced the abilities of the lipoproteins to interact with cells. The results suggest that analysis of lipoprotein-cell interactions in vitro may be predictive of the atherogenic potential of lipoproteins in vivo and that euthyroidism in rat protects against atherogenic hyperlipidemia.