| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Role of elevated lecithin: cholesterol acyltransferase and cholesteryl ester transfer protein activities in abnormal lipoproteins from proteinuric patients Dullaart, R. P., R. T. Gansevoort, et al. (1993), Kidney Int 44(1): 91-7. Abstract: Lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) are key factors in the esterification of free cholesterol, and the distribution of cholesteryl ester among lipoproteins in plasma. Alterations in these processes may play a role in the lipoprotein abnormalities associated with glomerular proteinuria. The activities of LCAT and CETP were measured using excess exogenous substrate assays in nine patients with nephrotic-range proteinuria and in 18 matched controls. The proteinuria-lowering effect of four weeks of angiotensin converting enzyme (ACE) inhibition with enalapril was also studied. Plasma very low lipoprotein and low density lipoprotein (VLDL and LDL) cholesterol, triacylglycerol and apolipoprotein B levels were significantly elevated in the patients compared with controls. High density lipoprotein (HDL) total cholesterol, free cholesterol, cholesteryl ester and the free cholesterol/cholesteryl ester ratio in HDL were lower. Total plasma apolipoprotein A1 was normal. Plasma LCAT and CETP activities were elevated in the patients by 30% (P < 0.01) and by 39% (P < 0.01), respectively, and were both inversely related to serum albumin. VLDL and LDL cholesterol levels were positively related to LCAT and CETP activities, whereas the HDL free cholesterol content was inversely related to LCAT activity. ACE inhibition resulted in a 40% reduction of proteinuria, a partial normalization of LCAT activity, and a decrease in VLDL and LDL cholesterol. In conclusion, elevated activities of LCAT and CETP may provide a mechanism that contributes to the low proportion of cholesterol in HDL relative to that in VLDL and LDL, as well as to the compositional changes of HDL seen in glomerular proteinuria.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Role of free apolipoprotein A-I in cholesterol efflux. Formation of pre-alpha-migrating high-density lipoprotein particles Asztalos, B., W. Zhang, et al. (1997), Arterioscler Thromb Vasc Biol 17(9): 1630-6. Abstract: This article characterizes products formed by the interaction of purified apolipoprotein (apo) A-I and human fibroblasts. Fibroblasts were incubated with different concentrations of purified apoA-I (1 to 30 micrograms/mL) in tissue culture medium for different periods of time (0 to 24 hours). The medium was then characterized by one- (agarose) and two-dimensional (agarose: polyacrylamide nondenaturing gradient gel) electrophoresis. At any given concentration of apoA-I, the rate of cellular cholesterol efflux appeared linear over 24 hours. Incubating purified apoA-I with fibroblasts for 4 hours, we detected five pre-alpha lipoproteins with particle sizes between 114 and 684 kDa. Formation of pre-alpha lipoproteins was concentration-dependent. At low concentrations (below 5 micrograms/mL apoA-I), all purified apoA-I (with pre-beta mobility) was converted to pre-alpha lipoproteins. At higher concentrations (greater than 5 micrograms/mL apoA-I), more apoA-I remained with pre-beta mobility. The pre-alpha lipoproteins were characterized by colocalization of apoA-I particles with 14C-cholesterol and 32P-phospholipids. Results showed that the pre-alpha particle of lowest molecular weight contained phospholipid and apoA-I but no cholesterol. The remaining pre-alpha particles contained all three substances. When pre-alpha particles were subjected to ultracentrifugation, all particles floated at d < 1.21 g/mL with some of the smallest phospholipid apoA-I only particles being present in the d > 1.21 g/mL fraction. Based on these results, we postulated that in the first stages of reverse cholesterol transport, pre-alpha lipoproteins are formed by the interaction of lipid free apoA-I and peripheral cells. |
| Role of glia-derived cholesterol in synaptogenesis: new revelations in the synapse-glia affair Goritz, C., D. H. Mauch, et al. (2002), J Physiol Paris 96(3-4): 257-63. Abstract: Brain development and function relies on the exchange of signals between neurons and glial cells. Here we review a series of recent studies on cultures of purified retinal ganglion cells (RGCs) that point to a new role of glial cells in the formation and plasticity of synaptic connections. The results suggest that neurons must import glia-derived cholesterol via lipoproteins to form numerous and efficient synaptic connections. This finding may explain why throughout the central nervous system (CNS) the main phase of synaptogenesis starts synchronously after glia differentiation and why astrocytes produce apolipoprotein E (apoE) and cholesterol-containing lipoproteins. Experimental tests of these hypotheses may further our understanding of the cholesterol metabolism in the brain and may help to explain neurologic symptoms resulting from defective cholesterol and lipoprotein metabolism. |
| Role of glutamic acid residues 154, 155, and 165 of lecithin:cholesterol acyltransferase in cholesterol esterification and phospholipase A2 activities Wang, J., J. A. DeLozier, et al. (1998), J Lipid Res 39(1): 51-8. Abstract: Previous studies have shown that cholesterol esterification activity by lecithin:cholesterol acyltransferase (LCAT) is progressively inhibited as up to three acidic acid residues are chemically modified. The purpose of this study was to determine whether three glutamic acid residues in LCAT (154, 155, and 165), that align exactly with three acidic acid residues (270, 271, and 281) in the amphipathic phospholipid binding region of apoE, were necessary for enzymatic activity. Site-directed mutagenesis was used to generate mutant constructs of LCAT in which glutamic acid residues 154, 155, and 165 were replaced with glutamine or lysine. Media harvested from transiently transfected COS cells was used as a source of LCAT for cholesterol esterification and phospholipase A2 (PLA2) assays. Cholesterol esterification for all mutant constructs (11-26 nmol CE/h/microg) was similar to or greater than that of wild type LCAT (16 nmol CE/h/microg), except for a triple mutant, in which glutamic acid residues 154, 155, and 165 were changed to lysines (5 nmol CE/h/microg). PLA2 activity followed a similar trend. There was a significant decrease in the cholesterol esterification to PLA2 activity ratio when residue 165 was mutated from its wild type negative charge (E) to an uncharged (Q) or positive (K) charged residue (10.2 vs. 6.0 vs. 4.3, respectively). We conclude that glutamic acid residues 154, 155, and 165 individually or collectively are not necessary for LCAT activity and that residue 165 may be in a region of LCAT that is involved with cholesterol binding or is sensitive to cholesterol binding at the active site of the enzyme. |
| Role of HDL apolipoprotein E in cellular cholesterol efflux: studies in apo E knockout transgenic mice Hayek, T., J. Oiknine, et al. (1994), Biochem Biophys Res Commun 205(2): 1072-8. Abstract: The role of apo E in aspects of reverse cholesterol transport was studied in apolipoprotein E-deficient mice. These animals develop rampant atherosclerosis. The efflux of cholesterol from mouse peritoneal macrophages (MPM) was 40% lower when induced by high density lipoprotein (HDL) from apo E-deficient mice, compared to the effect of HDL from normal mice. On adding apo E to apo E-deficient HDL, cholesterol efflux from the macrophages increased by 35%, approaching the degree of efflux obtained with normal HDL. This HDL (normal or apo E-deficient)-induced cholesterol efflux was similar in peritoneal macrophages derived from both normal and apo E-deficient mice, suggesting that the HDL apo E rather than the macrophage apo E is responsible for the stimulation of cellular cholesterol efflux. On determining cholesterol efflux specifically from the macrophage plasma membrane, the level of efflux was similar for both HDL preparations, suggesting that apo E in HDL is important for cholesterol translocation to the plasma membrane, the initial step in reverse cholesterol transport. It is concluded that the enhanced atherosclerosis in apo E-deficient mice could be related, at least partly, to the impaired efflux of LDL derived cholesterol from macrophages of the arterial wall. |
| Role of HDL cholesterol in the prediction of exercise stress test abnormalities in asymptomatic high-risk patients Fourcade, J., J. Ferrieres, et al. (2001), Arch Mal Coeur Vaiss 94(11): 1141-6. Abstract: The diagnosis of coronary artery disease in asymptomatic patients is useful in order to target therapeutic intervention in the patients at highest risk. Systematic testing of all asymptomatic adults with coronary risk factors is not feasible. The aim of this study, carried out in 950 healthy subjects, was to assess the predictive value of classical risk factors for positive exercise stress tests (EE). All subjects underwent stress testing using the Bruce protocol. Statistical analysis was performed by multiple logistic regression on half the samples, then by CART (Classification and Regression Trees) analysis on all subjects. Age, HDL-cholesterol and interaction between lipid lowering treatment and LDL-cholesterol were significantly correlated (p < 0.05) to a positive exercise stress test. In both groups, treated or untreated by lipid lowering drugs. CART identified HDL-cholesterol (< 0.40 g/l) as a predictive factor for positive stress testing. Subgroups of elderly patients (> or = 60 years) with probabilities of 20 to 28% for a positive stress test were identified. The authors conclude that the diagnosis of coronary artery disease by systematic exercise stress testing is potentially valuable in elderly patients with low HDL-cholesterol values. |
| Role of HDL phospholipid in efflux of cell cholesterol to whole serum: studies with human apoA-I transgenic rats Fournier, N., M. de la Llera Moya, et al. (1996), J Lipid Res 37(8): 1704-11. Abstract: Sera of transgenic rats expressing human apoA-I were tested for their ability to stimulate efflux of radiolabeled cholesterol from Fu5AH rat hepatoma cells. Expression of human apoA-I resulted in a dose-dependent increase in HDL, as measured by both HDL-cholesterol and HDL-phospholipid, and produced a decrease in rat apoA-I. In rats expressing high concentrations of human apoA-I (TgRhAIhigh, human apoA-I > 250 mg/dl), the increase in HDL-phospholipid was not proportional to the increase in human apoA-I, as illustrated by a HDL-PL/total apoA-I ratio of 0.84 +/- 0.19 compared to a ratio of 1.28 +/- 0.29 for control rats and of 1.28 +/- 0.39 for rats expressing low levels of human apoA-I (TgRhAIlow, human apoA-I < 250 mg/dl). Compared to sera from control animals, efflux of cell cholesterol was increased by 26% in the sera from TgRhAIlow, and by 76% in the TgRhAIhigh. An examination of the relationships between efflux and HDL-related parameters demonstrated a hyperbolic relationship between efflux and either HDL-cholesterol or HDL-apoA-I. In contrast, there was a strong linear association (r2 = 0.84) between cholesterol efflux and HDL-phospholipid, indicating that this parameter is the component of HDL that best reflects the serum's efflux efficiency. The importance of phospholipids in modulating cholesterol efflux was further explored by measuring the effect of supplementation of serum with dimyristoylphosphatidylcholine (DMPC) vesicles, apoA-I, or both DMPC vesicles and apoA-I. Whereas addition of human apoA-I had no effect on efflux, supplementation with DMPC vesicles produced a substantial increase in efflux that was further stimulated by the combination of DMPC vesicles and apoA-I. These results demonstrate that a major component of HDL that modulates cell cholesterol efflux is phospholipid. |
| Role of hepatic lipase and scavenger receptor BI in clearing phospholipid/free cholesterol-rich lipoproteins in PLTP-deficient mice Kawano, K., S. Qin, et al. (2002), Biochim Biophys Acta 1583(2): 133-40. Abstract: Phospholipid transfer protein knock-out (PLTP0) mice have defective transfer of phospholipids (PL) from triglyceride-rich lipoproteins (TRL) into high-density lipoproteins (HDL). In this study, we examined the role of diet, hepatic lipase (HL) and scavenger receptor BI (SRBI) in determining the accumulation of excess PL and free cholesterol (FC, "surface remnants") in plasma of PLTP0 mice. PL and FC accumulated in the very low-density lipoprotein (VLDL)-LDL region of PLTP0 mice on a highly saturated, coconut oil-based diet, but not on chow or milk-fat based Western diets. Accumulation of PL and FC was dramatically increased in PLTP0/HL0 mice, compared to PLTP0 mice, but only on the coconut oil diet. Turnover studies indicated that the coconut oil diet was associated with delayed catabolism of PL of PL/FC-rich particles. Incubation of these particles with primary hepatocytes in the presence of SRBI neutralizing antibody indicated that SRBI was primarily responsible for removal of FC and PL on the Western diet. In hepatocytes of coconut oil-fed mice, removal of FC and PL from these particles by SRBI was markedly reduced, even though SRBI protein expression levels were unchanged. These studies indicate that HL and SRBI both have major role in the clearance of PL and FC of surface remnants in PLTP0 mice. SRBI appears to be dysfunctional in coconut oil diet-fed animals, possibly related to changes in hepatocyte membrane fatty acid composition. |
| Role of hepatic lipases, cholesterol ester transfer proteins and LCAT in the postprandial phase van Tol, A. (1990), Klin Wochenschr 68 Suppl 22: 23-8. Abstract: Hepatic, heparin-releaseable lipase is a multifunctional enzyme that may act on all lipoprotein classes present in plasma from fasted subjects. Recent evidence suggests that the enzyme also plays a role in the metabolism of chylomicronremnants. Its activity is impaired in normolipidemic patients with coronary heart disease, which also have a delayed removal of chylomicronremnants from plasma. Therefore hepatic lipase, in addition to lipoprotein lipase, plays an important role in postprandial lipoprotein metabolism. The activity levels of lecithin: cholesterol acyltransferase (LCAT) and cholesterylester transfer protein (CETP) are virtually unchanged after the ingestion of an oral fat load by normolipidemic subjects. However, the net mass transfer of cholesterylesters out of HDL into apo B-containing lipoproteins (chylomicronremnants, VLDL/IDL/LDL) is strongly increased. All triglyceride-rich lipoprotein fractions accumulate postprandially and, as a result of CETP action, become enriched in cholesterylesters. Defects in hepatic remnant removal may result in influx of remnants into the arterial wall. In patients with hyperlipidemia (and increased risk for atherosclerosis) the CETP-mediated formation of cholesterylester-rich remnants may operate, not only during the postprandial phase, but continuously. |
| Role of high density lipoproteins (HDL) in reverse cholesterol transport Ponsin, G. (1991), Diabete Metab 17(3): 319-24. Abstract: The atheromatous risk is negatively correlated with the plasma concentration of HDL cholesterol. This might be due to the role of HDL in the reverse cholesterol transport. In the first stage, free cholesterol molecules from peripheral cells are taken up by HDL through a receptor-dependent mechanism. In HDL, the esterification of cholesterol is catalysed by the lecithin: cholesterol acyl transferase. The progressive accumulation of cholesterol esters leads to the formation of HDL2. Through the action of cholesterol ester transfer protein, HDL2 become enriched in triglycerides and transfer cholesterol esters to LDL. Finally, cholesterol may be taken up by the liver through two routes which are: the receptor-mediated LDL endocytosis and the direct uptake of cholesterol esters which occurs during the degradation of HDL2 by hepatic lipase. |
| Role of high total protein in gallbladder bile in the formation of cholesterol gallstones Jungst, D., T. Lang, et al. (1991), Gastroenterology 100(6): 1724-9. Abstract: While it is generally accepted that cholesterol supersaturation of bile is of key importance in the rapid formation of cholesterol crystals, the role of total biliary protein and pH in the pathogenesis of cholesterol gallstones is less well understood. The relation of cholesterol saturation, total protein, and pH was studied in 73 gallbladder bile samples with and 35 gallbladder bile samples without cholesterol crystals. In samples containing crystals, a trend to higher values of cholesterol and to a higher cholesterol saturation index was observed. However, significantly (P = 0.02) higher concentrations of total protein were found in samples with crystals 0.80 +/- 0.40 g/dL (8.0 +/- 4.0 g/L) than in samples without crystals 0.63 +/- 0.26 g/dL (6.3 +/- 2.6 g/L). Moreover, of 22 bile samples with total protein concentrations greater than 10.0 g/L, cholesterol crystals were detected in all but 2. Total lipids, bile acids, phospholipids, and pH values were not significantly different in the two groups of bile samples. It was concluded that high biliary protein concentrations are frequently associated with cholesterol crystals and may, therefore, be a possible risk factor in the pathogenesis of cholesterol gallstones. |
| Role of in vitro cholesterol depletion in mediating human platelet aggregation Grgurevich, S., R. Krishnan, et al. (2003), J Thromb Haemost 1(3): 576-86. Abstract: We investigated the direct role of cholesterol lowering on human platelet aggregation by in vitro cholesterol depletion using methyl-beta-cyclodextrin. Collagen and thrombin receptor agonist peptide induced maximal aggregation was significantly decreased in cholesterol depleted platelets. In contrast, anti-CD9 antibody, mAb7, or anti-beta(3) antibody, D3, induced percent maximal aggregation was unaffected by cholesterol depletion. Surface and total alpha(IIb)beta(3) levels were equivalent in both groups. Morphological and ultrastructural analysis of collagen induced aggregates revealed that normal and cholesterol depleted platelets changed shape and aggregated; however, cholesterol depletion impaired microtubule ring formation and aggregate size. Cholesterol depletion also diminished the extent of the open canalicular system and collagen induced platelet ATP release. These data suggest cholesterol depletion impairs platelet aggregation by altering platelet ultrastructure critical in mediating secretion. Temporal differences and differences in tyrosine phosphoprotein levels following collagen stimulation were observed, thereby indicating that platelet signaling was concurrently affected by cholesterol depletion. |
| Role of infant dietary long-chain polyunsaturated fatty acids, liposoluble vitamins, cholesterol and lecithin on psychomotor development Cockburn, F. (2003), Acta Paediatr Suppl 92(442): 19-33. |
| Role of isoflavones in the cholesterol reduction by soy proteins in the clinic Sirtori, C. R., E. Gianazza, et al. (1997), Am J Clin Nutr 65(1): 166-7. |
| Role of lecithin:cholesterol acyltransferase and apolipoprotein A-I in cholesterol esterification in lipoprotein-X in vitro O, K. and J. Frohlich (1995), J Lipid Res 36(11): 2344-54. Abstract: Lipoprotein-X (Lp-X) is an abnormal particle present in the plasma of patients with familial lecithin:cholesterol acyltransferase (LCAT) deficiency syndromes or cholestatic liver disease. Compared to other lipoproteins, Lp-X contains a high content of unesterified cholesterol (30%, w/w) to phosphatidylcholine (60%, w/w). The objective of this study was to evaluate the role of LCAT and apolipoprotein A-I (apoA-I) in Lp-X metabolism in vitro and to elucidate the regulation of cholesterol esterification in this unique lipoprotein. Lp-X isolated from sera of patients with obstructive jaundice had a high content of unesterified cholesterol and phosphatidylcholine and contained apolipoprotein E, apoCs, and albumin. Although human recombinant LCAT used as an enzyme source did bind to isolated Lp-X, no cholesterol esterification was detected. However, addition of human apoA-I in the presence of albumin resulted in significant cholesterol esterification in Lp-X (Vmax 0.25 +/- 0.04 nmol/h per microgram LCAT protein). Exogenous apoA-I did not change the size of Lp-X particle as determined by quasi-elastic light scattering analysis. A reduction in Lp-X size was observed when both apoA-I and LCAT were included in the reaction mixture (from 47 nm to 42 nm). Furthermore, addition of apoA-I (but not HDL) dramatically changed the electrophoretic mobility of Lp-X from cathodic to anodic migration. Such changes are not due to displacement of apoC or apoE proteins from Lp-X by apoA-I. While increasing apoA-I concentration (up to 35 micrograms/ml) in the reaction mixture stimulated cholesterol esterification in Lp-X, addition of apoA-I at the concentration of 8 micrograms/ml inhibited cholesterol esterification in VLDL, LDL, and HDL by more than 50%. Albumin was required for the LCAT reaction to Lp-X. Our results suggest that while LCAT binds to isolated Lp-X, apoA-I is needed for the LCAT reaction to proceed. The presence of apoA-I does not result in the displacement of apoCs and apoE from Lp-X and addition of apoA-I changes the electrophoretic mobility but not the size of Lp-X. |
| Role of leukocyte-specific LDL receptors on plasma lipoprotein cholesterol and atherosclerosis in mice Boisvert, W. A., J. Spangenberg, et al. (1997), Arterioscler Thromb Vasc Biol 17(2): 340-7. Abstract: Bone marrow-derived macrophages and lymphocytes express LDL receptors (LDL-R), which allow these cells to take up cholesterol-rich lipoproteins. Although these cells are ubiquitously distributed in the body, it is not known whether they influence plasma cholesterol. Macrophages and T lymphocytes also are found in atherosclerotic lesions, but it is not known whether their LDL-R expression plays a role in atherosclerosis. To address these questions, we subjected LDL-R -/-mice to total body irradiation to eliminate their endogenous bone marrow-derived cells and repopulated them with either LDL-R-expressing wild-type bone marrow (treated mice) or LDL-R -/- bone marrow (control mice). Thus, the only difference between the two groups of mice was the ability of the bone marrow-derived cells to express the LDL-R in the treated mice. Plasma cholesterol levels were similar in the two groups of mice at 8 and 16 weeks after transplantation. Chromatographic separation of the lipoproteins revealed similar lipoprotein cholesterol distributions. Although the extent of lesion area in the aortic valves of the high-fat-diet-fed mice was more severe than that in the chow-fed mice, lesions appeared similar between control and treated mice given either chow or high-fat diet. Abundant LDL-R expression was detected in the lesions of treated mice, whereas the lesions of control mice showed no LDL-R expression, indicating that donor-derived leukocytes had migrated into the lesions of the recipient mice. Thus, bone marrow transplantation can be used as a tool to replace the endogenous bone marrow-derived cells in the artery wall with those of the donor origin. |
| Role of lipases, lecithin:cholesterol acyltransferase and cholesteryl ester transfer protein in abnormal high density lipoprotein metabolism in insulin resistance and type 2 diabetes mellitus de Vries, R., S. E. Borggreve, et al. (2003), Clin Lab 49(11-12): 601-13. Abstract: Dyslipidaemia, hallmarked by low HDL cholesterol and high plasma triglycerides, is a feature of insulin resistance and type 2 diabetes mellitus. These lipoprotein abnormalities represent major cardiovascular risk factors in these conditions. Among other factors, lipoprotein lipase (LPL), hepatic lipase (HL), lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) play an important role in an abnormal HDL metabolism in insulin resistance and type 2 diabetes mellitus. LPL hydrolyses lipoprotein triglycerides, thus providing lipids for HDL formation. In insulin resistant states, a decreased post-heparin plasma LPL activity contributes to a low HDL cholesterol, whereas an increased activity of HL reduces HDL particle size by hydrolysing its triglycerides and phospholipids. High HL activity coincides with low HDL cholesterol. The esterification of free cholesterol by LCAT increases HDL particle size. Subsequent CETP action results in transfer of cholesteryl esters from HDL towards triglyceride-rich lipoproteins. This cholesteryl ester transfer process results in lower HDL cholesterol and indirectly decreases HDL size. Plasma cholesterol esterification is unaltered or increased, whereas cholesteryl ester transfer is enhanced in type 2 diabetes mellitus, abnormalities which are probably related to the degree of hypertriglyceridaemia. It is plausible that a low LPL activity contributes to premature atherosclerosis as observed in insulin resistance and type 2 diabetes mellitus, but the effects of high HL activity and altered plasma cholesterol esterification on atherosclerosis development are uncertain. Since the cholesteryl ester transfer process between lipoproteins provides a metabolic intermediate between low HDL cholesterol and high plasma triglycerides, hypertriglyceridaemia-associated accelerated transfer of cholesteryl ester out of HDL may be pathogenetically involved in the development of cardiovascular disease in insulin resistance and type 2 diabetes mellitus. |
| Role of lipoproteins and triglycerides in cholesterol lithogenesis Mansurov, K., F. Mansurova, et al. (1994), Klin Med (Mosk) 72(5): 31-3. Abstract: Serum lipoprotein spectrum was evaluated in 63 patients with cholelithiasis at various stages versus 10 healthy subjects as control. The patients were found to develop lipoprotein shifts as early as a physicochemical stage of the disease. Abnormal proportions of lipoproteins and triglycerides, changes in the formation of free radical products justify correction of dyslipoproteinemia early in cholelithiasis course. |
| Role of liver in the maintenance of cholesterol and low density lipoprotein homeostasis in different animal species, including humans Dietschy, J. M., S. D. Turley, et al. (1993), J Lipid Res 34(10): 1637-59. |
| Role of liver in the synthesis of cholesterol and the clearance of low density lipoproteins in the cynomolgus monkey Turley, S. D., D. K. Spady, et al. (1995), J Lipid Res 36(1): 67-79. Abstract: 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. |