| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
| First Page | Previous Page | Next Page | Last Page |
| Rapid formation of cholesterol crystals in gallbladder bile is associated with stone recurrence after laparoscopic cholecystotomy Jungst, D., R. del Pozo, et al. (1997), Hepatology 25(3): 509-13. Abstract: Laparoscopic cholecystotomy (LCT) with subsequent extraction of gallstones and primary closure of the gallbladder has been introduced as an alternative therapy for patients with cholecystolithiasis and preserved gallbladder function. However, stone recurrence has to be considered as a major drawback that might be related to lithogenic factors of gallbladder bile or the composition of gallbladder stones. Therefore, these were studied in relation to stone recurrence within an observation period of 1 to 5 years (median, 3.6 years) in 50 patients after LCT. The concentrations of total and individual bile acids, phospholipids, cholesterol, total lipids, mucin, protein, and the cholesterol saturation indices in gallbladder bile were not significantly different between 10 patients with and 40 patients without stone recurrence. However, the crystal observation time was significantly (P <.02) shorter (range, 1-2 days; median, 1.5) in the bile of patients with stone recurrence compared to those without (range, 1-21 days, median 3.5). Moreover, all 10 stone recurrences were observed in the 28 patients with a crystal observation time in the bile of less than or equal to 2 days (approximate annual risk: 12%-15%), and no recurrences were observed in the 22 patients with a crystal observation time greater than 2 days (P <.0001) or in patients with pigment stones. The rapid formation of cholesterol monohydrate crystals in bile seems to be the major risk factor for recurrent stones after LCT. These are most likely cholesterol stones and, therefore, are amenable to oral bile-acid prevention or treatment. |
| Rapid gas chromatographic method for simultaneous determination of cholesterol and alpha-tocopherol in eggs Botsoglou, N., D. Fletouris, et al. (1998), J AOAC Int 81(6): 1177-83. Abstract: A new method was developed for simultaneous determination of cholesterol and alpha-tocopherol in eggs. It involves rapid and simple sample preparation accomplished in one tube and chromatographic separation that does not require derivatization of analytes. Total analysis time per sample is 40 min. Labor, cost, and use of hazardous chemicals are minimized. To ensure selectivity, accuracy, and precision, critical analytical parameters were investigated. Overall recoveries were 98.8 and 99.2% for cholesterol and alpha-tocopherol, respectively. Linearity was acceptable for both analytes (r = 0.9964 for cholesterol and 0.9996 for alpha-tocopherol) in the fortification range examined. Precision data based on within-day and between-days variation gave overall relative standard deviations of 2.0% for cholesterol and 7.0% for alpha-tocopherol. The method was applied successfully for quantitation of cholesterol and alpha-tocopherol in eggs. |
| Rapid intracellular transport of LDL-derived cholesterol to the plasma membrane in cultured fibroblasts Brasaemle, D. L. and A. D. Attie (1990), J Lipid Res 31(1): 103-12. Abstract: The kinetics of low density lipoprotein (LDL) cholesterol transport to the plasma membrane of Chinese hamster ovary (CHO) cells was studied. LDL was reconstituted with 3Hcholesteryl linoleate and added to CHO cells in a pulse-chase experiment. The internalization and lysosomal cleavage of reconstituted LDL (rLDL) 3Hcholesteryl linoleate to free 3Hcholesterol occurred with a half-time of 37 min after a 30-min lag. The rate of transport of released 3Hcholesterol to the plasma membrane was measured by brief (20-30 sec) cholesterol oxidase treatment of intact, adherent cells: the half-time of transport was 42 min. The similarity in the rate of free cholesterol release from rLDL and transport of this cholesterol to the plasma membrane suggests very rapid transport of rLDL cholesterol from the lysosome to the plasma membrane. Cells were shown to be intact throughout the cholesterol oxidase treatment by the absence of cell-derived lactate dehydrogenase (LDH) activity or K+ in the assay buffer. |
| Rapid labeling of lipoproteins in plasma with radioactive cholesterol. Application for measurement of plasma cholesterol esterification Yen, F. T. and T. Nishida (1990), J Lipid Res 31(2): 349-53. Abstract: In order to efficiently and rapidly label lipoproteins in plasma with 3Hcholesterol, micelles consisting of lysophosphatidylcholine (lysoPC) and 3Hcholesterol (molar ratio, 50:1) were prepared. When trace amounts of these micelles were injected into plasma, 3Hcholesterol rapidly equilibrated among the plasma lipoproteins, as compared to 3Hcholesterol from an albumin-stabilized emulsion. The distributions of both 3Hcholesterol and unlabeled free cholesterol in plasma lipoproteins were similar in labeled plasma samples. This method of labeling can be used for the measurement of cholesterol esterification, or lecithin:cholesterol acyltransferase activity, in small amounts (20-40 microliters) of plasma samples. |
| Rapid on-line determination of cholesterol distribution among plasma lipoproteins after high-performance gel filtration chromatography Kieft, K. A., T. M. Bocan, et al. (1991), J Lipid Res 32(5): 859-66. Abstract: A high-performance gel chromatography (HPGC) system has been developed which allows the unattended on-line determination of lipoprotein cholesterol distribution (VLDL-C, LDL-C, HDL-C), within 40 min, in microliter quantities of plasma using a single, relatively inexpensive column (Superose 6HR). The FAST cholesterol reagent (Sclavo) and a knitted PFTE Kratos reaction coil (Applied Biosystems) were found to provide optimal sensitivity, linearity, resolution, and dispersion characteristics. Validation is provided by comparison to target values for human quality control reference sera, and by comparing the values obtained by HPGC to the beta-quant method (LRC). The utility of the system is illustrated by comparing profiles from seven different species with normal or elevated plasma cholesterol concentrations. This technique allows rapid analysis of samples, regardless of species, without the use of precipitating agents or the ultracentrifuge. It could also be applied for the direct clinical determination of LDL-cholesterol. |
| Rapid pacing-induced preconditioning is recaptured by farnesol treatment in hearts of cholesterol-fed rats: role of polyprenyl derivatives and nitric oxide Ferdinandy, P., C. Csonka, et al. (1998), Mol Cell Biochem 186(1-2): 27-34. Abstract: We have previously shown that hypercholesterolemia leads to the loss of pacing-induced preconditioning (PC), possibly due to the impairment of cardiac nitric oxide (NO) synthesis. It has been shown that excess exogenous cholesterol inhibits formation of several polyprenyl derivatives involved in signal transduction. In the present study, we examined whether PC and cardiac NO synthesis are restored by treatment with the key polyprenyl product, farnesol, in cholesterol-fed rats. Rats fed 2% cholesterol-enriched/control diet for 24 weeks were given i.p. 5 microM/kg farnesol/vehicle, respectively. An hour later, hearts were isolated and prepared for 'working' perfusion, then subjected to PC/non-PC protocols of 3 intermittent periods of pacing of 5 min duration at 10 Hz, followed by a 10 min coronary occlusion to test the effect of PC. PC increased ischemic aortic flow (AF) from its control value of 15.6+/-1.5 to 27.3+/-1.7 mL/min (p < 0.05). PC was not observed in hearts obtained from hypercholesterolemic rats (AF: 15.7+/-1.2 mL/min), however, it reappeared in the farnesol-treated hypercholesterolemic group (AF: 31.8+/-3.4 mL/ min, p < 0.05). In tissue samples from the left ventricle, cholesterol-diet markedly decreased the intensity of the electron spin resonance spectra of NO obtained after in vivo spin trapping with Fe2+-diethyl-dithio-carbamate complex. Farnesol-treatment did not influence cardiac NO content in the cholesterol-fed or in the control group. These results show that the lost PC can be recaptured by farnesol-treatment in hypercholesterolemia, however, farnesol-treatment does not restore cardiac NO synthesis. |
| Rapid reduction of MDCK cell cholesterol by methyl-beta-cyclodextrin alters steady state transepithelial electrical resistance Francis, S. A., J. M. Kelly, et al. (1999), Eur J Cell Biol 78(7): 473-84. Abstract: The role of plasma membrane lipids in regulating the passage of ions and other solutes through the paracellular pathway remains controversial. In this study we explore the contribution of cholesterol (CH) in maintaining the barrier function of an epithelial cell line using the CH-solubilizing agent methyl beta-cyclodextrin (MBCD) to stimulate CH efflux. Inclusion of 20 mM MBCD in both apical and basolateral media reduced CH levels by 70-80% with no significant effect on cell viability. Most of that decrease occurred during the first 30 min of incubation. Recovery of CH content to initial values was nearly complete 22 h after removal of MBCD. Within 30 min of adding MBCD to the culture medium, transepithelial electrical resistance (TER) increased, reaching maximum values 30-40% above controls. This early rise in TER occurred when MBCD was added to either side of the monolayer. The later rapid decline in TER was observed only when MBCD bathed the basolateral surface from which, coincidentally, CH efflux was most rapid. Freeze fracture replicas and transmission electron microscopy of monolayers exposed to MBCD for only 30 min revealed no increase in either the average tight junction (TJ) strand number or the dimensions of the lateral intercellular space. There was a statistically significant increase in the number of TJ particles associated with the E fracture face at this time. This raises the interesting possibility that during CH efflux there is a change in the interaction between TJ particles and underlying cytoskeletal elements. There was no change in staining for occludin and ZO-1. After exposing the basolateral surface to MBCD for 2 h, TER fell below control levels. The accompanying increase in mannitol flux suggests strongly that the decrease in TER resulted from an increase in the permeability of the paracellular and not the transcellular pathway. A decrease in immuno-staining for occludin and ZO-1 at TJs, a striking accumulation of actin at tri-cellular areas as well as a decline in the number of parallel strands, as seen in freeze fracture replicas, suggest that changes in cytoskeletal organization during long incubations with MBCD had physically disrupted the TJ network. Data are presented which suggest that the observed changes in paracellular permeability during CH efflux may be related to increased levels of lipid-derived second messengers, some of which may trigger changes in the phosphorylation status of TJ proteins. |
| Rapid reduction of serum cholesterol and blood pressure by a twelve-day, very low fat, strictly vegetarian diet McDougall, J., K. Litzau, et al. (1995), J Am Coll Nutr 14(5): 491-6. Abstract: OBJECTIVE: This study was conducted to demonstrate the effectiveness of a strictly vegetarian, very low-fat diet on cardiac risk factor modification. METHODS: Five hundred men and women, participants in an intensive 12-day live-in program, were studied. The program focused on dietary modification, moderate exercise, and stress management at a hospital-based health-center. RESULTS: During this short time period, cardiac risk factors improved: there was an average reduction of total serum cholesterol of 11% (p < 0.001), of blood pressure of 6% (p < 0.001) and a weight loss of 2.5 kg for men and 1 kg for women. Serum triglycerides did not increase except for two subgroups: females age > or = 65 years with serum cholesterol < 6.5 mmol/L and for females 50 to 64 years with baseline serum cholesterol between 5.2-6.5 mmol/L. High-density lipoprotein cholesterol measured on 66 subjects decreased by 19%. CONCLUSION: A strict, very low-fat vegetarian diet free from all animal products combined with lifestyle changes that include exercise and weight loss is an effective way to lower serum cholesterol and blood pressure. |
| Rapid turn-over of plasma membrane sphingomyelin and cholesterol in baby hamster kidney cells after exposure to sphingomyelinase Slotte, J. P., A. S. Harmala, et al. (1990), Biochim Biophys Acta 1030(2): 251-7. Abstract: Plasma membrane sphingomyelin in baby hamster kidney (BHK-21) cells was hydrolyzed with sphingomyelinase (Staphylococcus aureus) and the effects on membrane cholesterol translocation and the properties of membrane bound adenylate cyclase and Na+/K(+)-ATPase were determined. Exposure of confluent BHK-21 cells to 0.1 U/ml of sphingomyelinase led to the degradation (at 37 degrees C) of about 60% of cell sphingomyelin. No simultaneous hydrolysis of phosphatidylcholine occurred. The hydrolysis of sphingomyelin subsequently led to the translocation (within 40 min) of about 50-60% of cell 3Hcholesterol from a cholesterol oxidase susceptible pool to an oxidase resistant compartment. The translocation of 3Hcholesterol from the cell surface to intracellular membranes was accompanied by a paralleled increase in 3Hcholesterol ester formation. When cells were first exposed to sphingomyelinase (to degrade sphingomyelin) and then incubated without the enzyme in serum-free media, the mass of cell sphingomyelin decreased initially (by 60%), but then began to increase and reached control levels within 3-4 h. The rapid re-synthesis of sphingomyelin was accompanied by an equally rapid normalization of cell 3Hcholesterol distribution. The re-formation of cell sphingomyelin also led to a decreased content of cellular 3Hcholesterol esters, indicating that unesterified 3Hcholesterol was pulled out of the cholesterol ester cycle and transported to the cell surface. Exposure of BHK-21 cells to sphingomyelinase further led to a dramatically decreased activity of ouabain-sensitive Na+/K(+)-ATPase, whereas forskolin-stimulated adenylate cyclase activity was not affected. The activity of Na+/K(+)-ATPase returned to normal in parallel with the normalization of cell sphingomyelin mass and cholesterol distribution. We conclude that sphingomyelin has profound effects on the steady-state distribution of cell cholesterol, and that manipulations of cell sphingomyelin levels directly and reversibly affects the apparent distribution of cholesterol. Changes in the lipid composition of the plasma membrane also appears to selectively affect important metabolic reactions in that compartment. |
| Rapid ultracentrifugal isolation and imaging detection of cholesterol-phospholipid vesicles Wang, Q. H. (1993), Zhonghua Wai Ke Za Zhi 31(2): 99-101. Abstract: We have utilized ultracentrifugation of bile-metrizamide density gradients to isolate and to quantitate the cholesterol-phospholipid vesicles (CPV) and identified them by transmission electron microscopy and scanning electron microscopy metrizamide was dissolved in bile and continuous density gradients were performed. The distribution of biliary cholesterol, phospholipid and bile salt was studied. The distribution of biliary phospholipid is similar in different fraction of the gradients. Approximately 70% of total biliary cholesterol was concentrated in the lightest fraction of the gradients (density < 1.035g/ml) and 70% of bile salt was found in the heaviest fraction of the gradients (density > 1.035g/ml). CPV harvested in fractions with density < 1.035g/ml and their diameter was 70-90nm. When 15% Metrizamide was dissolved in bile and centrifuged (50,000rpm, 100min, 37 degrees C), two thirds of total biliary cholesterol was concentrated in the top 0.4ml of the 5ml centrifuge tube. A lot of CPV was found in this part of bile and their diameter was 85nm. The advantage of the procedure described in this study is simple, rapid and accurate for pathological and physiological studies of CPV. |
| Rapid westernization of children's blood cholesterol in 3 countries: evidence for nutrient-gene interactions? Couch, S. C., A. T. Cross, et al. (2000), Am J Clin Nutr 72(5 Suppl): 1266S-1274S. Abstract: The aim of this study was to examine potential factors that modify blood cholesterol among children in countries in which dietary and lifestyle habits are becoming westernized. Population data on serum total and lipoprotein cholesterol, anthropometric indexes, and dietary intake were reviewed and compared for children aged 1-18 y from Japan, Spain, and the United States. The data show that total serum cholesterol in Japanese and Spanish children recently exceeded the 75th percentile for US children, primarily reflecting LDL cholesterol, although both LDL and HDL cholesterol contributed. Adiposity indexes do not explain the trends observed. Total and saturated fat intakes increased substantially in both Japan and Spain but in Japan are still lower than intakes in the United States. The Hegsted equation was used to relate differences in serum cholesterol to dietary fat intake. Changes in total serum cholesterol followed established dietary correlations among children in Spain, but not in Japan. Serum cholesterol in Japanese children was predicted to be 0.20-0.32 mmol/L lower than in US children; actual concentrations were considerably higher. These results suggest that a rapid westernization of children's blood cholesterol concentrations has occurred in Japan and Spain. Changes in fat intake predict changes in blood cholesterol in Spain, but not in Japan. Differences in genetic response to diet in certain populations, such as the Japanese, may explain higher blood cholesterol concentrations with lower fat intakes compared with the United States. |
| Rapidly progressive stroke in a young adult with very low high-density lipoprotein cholesterol Zivkovic, S. A., O. L. Lopez, et al. (2000), J Neuroimaging 10(4): 233-6. Abstract: Ischemic strokes can affect young adults (15-45 years old). Most such strokes are caused by cardioembolic events, small vessel disease, or illicit drug use, and less frequently by large vessel atherosclerosis. Large vessel cerebral atherosclerosis is usually associated with high levels of low-density lipoprotein (LDL) cholesterol, but a low level of high-density lipoprotein (HDL) is also a risk factor for ischemic strokes. The magnitude of increased risk is unclear, particularly with extremely low HDL levels found only in various genetic and inherited disorders. Advanced atherosclerosis developed in the patient in this study, with HDL of 3 mg/dL, leading to rapidly progressive stroke with a fatal outcome. The disease primarily affected the posterior circulation. The course of this case illustrates that very low HDL may be associated with advanced cerebrovascular atherosclerosis and fatal stroke, and as such should be considered in young individuals with stroke. |
| Rat liver peroxisomes catalyze the initial step in cholesterol synthesis. The condensation of acetyl-CoA units into acetoacetyl-CoA Thompson, S. L. and S. K. Krisans (1990), J Biol Chem 265(10): 5731-5. Abstract: In the last few years, it has been demonstrated by this group and others that rat liver peroxisomes participate in cholesterol synthesis. It has been shown that the key regulatory enzyme of isoprenoid biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A reductase, is present in liver cells not only in the endoplasmic reticulum but also within peroxisomes. It has been also demonstrated that rat liver peroxisomes in the presence of cytosolic proteins in vitro are able to convert 14Cmevalonic acid to 14Ccholesterol. In addition, a recent study demonstrated that the largest cellular concentration of sterol carrier protein-2 is inside peroxisomes. It is of interest, therefore, to inquire whether other proteins known to be involved in cholesterol biogenesis are also present in peroxisomes. In this study we investigated the first step in cholesterol synthesis, the condensation of two acetyl-CoA units to acetoacetyl-CoA. It was demonstrated that peroxisomal thiolase, purified by DEAE-phosphocellulose chromatography from gemfibrozil-treated rats, is active not only toward acetoacetyl-CoA and 3-ketoacyl-CoA, consistent with literature reports, but is also capable of converting acetyl-CoA units to acetoacetyl-CoA. This is the first demonstration of condensation activity in rat liver peroxisomes. |
| Rat plasma cholesterol after particulate triacylglycerol clearance Quarfordt, S. H., B. S. Oswald, et al. (1991), Biochim Biophys Acta 1082(3): 247-50. Abstract: Following clearance of plasma cholesterol-rich triacylglycerol emulsions, lower-density lipoprotein cholesterol increased minimally in chow and considerably in cholesterol-fed rats. Cholesterol-poor chylomicrons and enteral triacylglycerol produced similar lipoprotein cholesterol increases in cholesterol-fed rats indicating tissue cholesterol recruitment after particulate triacylglycerol clearance. No plasma cholesterol increment was found after chylomicron clearance in anhepatic cholesterol fed rats demonstrating the liver as the major tissue source. The post triacylglycerol clearance was not due to the influx of fatty acid into the liver since larger hepatic free fatty acid loads produced no plasma cholesterol increment. This plasma cholesterol response to particulate triacylglycerol flux occurs only when the liver has excess cholesterol and if applicable to man, may be a factor explaining the large plasma cholesterol differences between diets rich and poor in lipid. |
| Rate and adequacy of cholesterol screening in patients admitted to a large rehabilitation unit after stroke Bogar, M. D., J. R. Basford, et al. (2005), Arch Phys Med Rehabil 86(1): 69-72. Abstract: OBJECTIVE: To assess cholesterol screening and intervention among patients admitted with acute ischemic stroke to an inpatient rehabilitation unit. DESIGN: Descriptive retrospective study. SETTING: Rehabilitation unit of a large midwestern teaching hospital. PARTICIPANTS: All patients over the age of 18 years admitted to a rehabilitation unit between January 1, 1999, and December 30, 2000, with acute ischemic stroke. One hundred fourteen patients (60 men, 54 women) with a median age of 74.4 years (range, 31.6-96.1y) met the inclusion criteria. Patients with a coexisting illness likely to lead to near-term death were excluded from analysis. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The proportion of patients with lipid profiles obtained at admission or within the year preceding admission, the proportion of patients with documented hyperlipidemia on lipid treatment, and the proportion of patients being treated who met National Cholesterol Education Program (NCEP) guidelines for low-density lipoprotein cholesterol control. RESULTS: Of the 114 subjects, 29 (25%) underwent cholesterol screening within the first 48 hours of hospitalization, and 27 (32%) had been screened within the preceding year. Of the 67 patients diagnosed with hyperlipidemia, 33 (49%) were taking cholesterol-lowering medical therapy when admitted, and 38 (57%) were under treatment when discharged from the rehabilitation unit. Three of the 5 patients diagnosed with hyperlipidemia before their hospitalization who were taking lipid-lowering medical therapy and were screened at admission met the NCEP prevention goals. CONCLUSIONS: Cholesterol monitoring and treatment intervention in patients hospitalized in US rehabilitation units after acute stroke may be inadequate. More research and health care provider education is warranted. |
| Rate of gastric emptying influences dietary cholesterol absorption efficiency in selected inbred strains of mice Kirby, R. J., P. N. Howles, et al. (2004), J Lipid Res 45(1): 89-98. Abstract: This study compared the physiological process of cholesterol absorption in different strains of inbred mice with the goal of identifying novel mechanism(s) by which cholesterol absorption can be controlled. The rate and amount of cholesterol absorption were evaluated based on 14Ccholesterol appearance in plasma after feeding a meal containing 14Ccholesterol and by the percentage of 14C-cholesterol absorbed over a 24 h period. Results showed that the rate of 14Ccholesterol appearance in plasma was slower in 129P3/J mice than in SJL/J mice. However, more dietary cholesterol was absorbed over a 24 h period by 129P3/J mice than by SJL/J mice. In both strains of mice, cholesterol delivered with medium-chain triglyceride was absorbed less efficiently than cholesterol delivered with olive oil. The strain- and vehicle-dependent differences in cholesterol absorption efficiency correlated negatively with stomach-emptying rates. Furthermore, inhibition of gastric emptying with nitric oxide synthase inhibitor increased cholesterol absorption efficiency in SJL/J mice. These results document that stomach-emptying rate contributes directly to the rate of dietary cholesterol absorption, which is inversely correlated with the total amount of cholesterol absorbed from a single meal. Additionally, genetic factor(s) that influence gastric emptying may be an important determinant of cholesterol absorption efficiency. |
| Rate of low-density lipoprotein cholesterol and apolipoprotein B changes on initiation and discontinuation of atorvastatin treatment Stern, R. H. and R. B. Abel (1997), J Clin Pharmacol 37(4): 291-6. Abstract: In a clinical trial, the changes in LDL cholesterol and in total apolipoprotein B with time were analyzed using a one-compartment model with constant input rate and first-order elimination rate constant after the initiation and discontinuation of treatment with atorvastatin. After initiation of treatment, input rate for total apoplipoprotein B (21 mg/dL/day) and elimination rate constants for both total apoplipoprotein B (0.36 days-1) and low-density lipoprotein (LDL) cholesterol (0.24 days-1) were similar to those reported for LDL-apolipoprotein B at steady state during treatment with other HMG-CoA reductase inhibitors. However, after discontinuation of treatment, very low elimination rate constants of 0.09 days-1 for LDL cholesterol and 0.07 days-1 for total apolipoprotein B are obtained. A likely explanation is that the model incorrectly assumes an immediate return to the pretreatment state, whereas transient stimulation of hepatic cholesterol synthesis on discontinuation of therapy with HMG-CoA reductase inhibitors is known to occur. |
| Rates of cholesterol esterification and esterified cholesterol net mass transfer between high-density lipoproteins and apolipoprotein B-containing lipoproteins in Type 1 diabetes Valabhji, J., J. Donovan, et al. (2002), Diabet Med 19(5): 424-8. Abstract: AIMS: Type 1 diabetes is associated with a high incidence of coronary heart disease (CHD) despite paradoxically normal or high high-density lipoprotein (HDL) cholesterol concentrations. Triglyceride (TG) concentrations have been shown to be important determinants of two aspects of HDL metabolism: cholesterol esterification rate and esterified cholesterol (EC) net mass transfer rate between HDL and the apolipoprotein B-containing lipoproteins. In order to try to explain the paradox, we aimed to assess the relationships between plasma TG and these two processes in Type 1 diabetic compared with non-diabetic subjects. METHODS: Rates of cholesterol esterification and EC net mass transfer between HDL and the apolipoprotein B-containing lipoproteins were assessed by incubating whole plasma at 37 degrees C; intra-assay coefficients of variation were 6% and 30%, respectively. RESULTS: Ten Type 1 diabetic and 10 non-diabetic subjects, with similar ages, sex distributions, body mass indices and total cholesterol and TG concentrations, were assessed. Apolipoprotein A1, HDL unesterified cholesterol, and HDL phospholipid concentrations were greater in the Type 1 diabetic subjects. There were no significant differences in the rates of cholesterol esterification or EC net mass transfer between the groups. There were strong associations between plasma TG and the rate of cholesterol esterification and between plasma TG and the rate of EC net mass transfer in Type 1 diabetic subjects (r = 0.83, P = 0.0027 and r = 0.88, P = 0.0009, respectively) and in non-diabetic subjects (r = 0.91, P = 0.0002 and r = 0.79, P = 0.0070, respectively). However, the slopes of the associations with plasma TG were significantly steeper in the Type 1 diabetic subjects (analyses of covariance P = 0.0053 and P = 0.0146, respectively). CONCLUSIONS: Increases in TG may therefore promote more EC enrichment of atherogenic apolipoprotein B-containing lipoproteins in Type 1 diabetes while also promoting more cholesterol esterification, thereby maintaining HDL cholesterol concentrations. This could contribute to the paradox of high CHD incidence despite normal or high HDL cholesterol concentrations in Type 1 diabetes. |
| Rates of cholesterol, ubiquinone, dolichol and dolichyl-P biosynthesis in rat brain slices Andersson, M., P. G. Elmberger, et al. (1990), FEBS Lett 269(1): 15-8. Abstract: Slices from the brain and liver of rats were prepared and upon incubation exhibited a continuous and high capacity for incorporation of radioactive precursors into proteins and lipids. Using 3Hmevalonate as precursor, the rates of biosynthesis of cholesterol, ubiquinone, dolichol and dolichyl-P in brain slices were determined and found to be 5.5, 0.25, 0.0093 and 0.0091 nmol/h/g, respectively. Dolichol and dolichyl-P accumulate to a limited extent, but almost all of these lipids in the brain originate from de novo synthesis. The calculated half-lives for cholesterol, ubiquinone, dolichol and dolichyl-P were 4076, 90, 1006 and 171 h, respectively. The results indicate that lipids formed via the mevalonate pathway in the brain have an active and independently regulated biosynthesis. |
| Ratio of low-density lipoprotein cholesterol to ubiquinone as a coronary risk factor Giral, P. and E. Bruckert (1992), N Engl J Med 326(6): 416-7. |