Effects of age, gender, and menopausal status on plasma low density lipoprotein cholesterol and apolipoprotein B levels in the Framingham Offspring Study

Plasma low density lipoprotein (LDL) cholesterol, non-high density lipoprotein (HDL) cholesterol, and apolipoprotein (apo) B, the major protein constituent of LDL, were measured in 1,533 men (mean age 49 +/- 10 years) and 1,597 women (mean age 49 +/- 10 years) participating in the 3rd examination cycle of the Framingham Offspring Study. Mean plasma levels of LDL cholesterol and apoB were higher in men than in women (136 versus 132 mg/dl, P < 0.0001; and 109 versus 95 mg/dl, P < 0.0001, respectively). Increased age was associated with higher plasma LDL cholesterol and apoB levels, especially in women. After adjustment for age and body mass index, LDL cholesterol and apoB levels were still significantly higher in postmenopausal than in premenopausal women, indicating a hormonal effect on LDL metabolism. The associations between coronary heart disease (CHD) and LDL cholesterol, non-HDL cholesterol, apoB, and other plasma lipid and lipoprotein parameters were examined by dividing participants in four groups, based on approximate quartiles for these parameters. Elevated LDL cholesterol levels were not significantly associated with CHD in men, but were in women. This result, at variance with that of several longitudinal studies, is likely due to the cross-sectional design of our analysis. Elevated non-HDL cholesterol and apoB levels were significantly associated with the presence of CHD, in both males and females. A plasma apoB value > or = 125 mg/dl may be associated with an increased risk for CHD. Low plasma levels of HDL cholesterol were also significantly associated with CHD. Plasma triglyceride levels, age and body mass index were strong determinants of LDL cholesterol, non-HDL cholesterol, and apoB levels in men and women. In women, postmenopausal status and elevated blood pressure were also significantly associated with elevated levels of these parameters.     

Plasma remnant-like particle lipid and apolipoprotein levels in normolipidemic and hyperlipidemic subjects

The brain microtubule-associated protein MAP2 family is composed of high-molecular-weight (MAP2a and MAP2b) and low-molecular-weight (MAP2c and MAP2d) isoforms. The common C-terminal region of HMW MAP2 and MAP2c contains three repeated microtubule-binding domains while MAP2d comprises four repeats. MAP2c mRNA is known to be expressed at high levels in the immature brain. We show that in the brains of rat pups, MAP2c mRNAs are indeed expressed at high levels compared with MAP2d. However, in adult rat brains, MAP2d mRNA levels are higher than MAP2c. In order to identify the neural cells expressing MAP2d, we used in situ hybridization. In vivo, we show that MAP2d mRNA is expressed in well-identified neuronal populations of the brain. In primary cultures of hippocampal neurones, double-labelling experiments confirm that MAP2d is clearly expressed in neurones. We also evaluated in this study the subcellular distribution of the MAP2d mRNAs in cultured hippocampal neurones and we report that in contrast with MAP2b mRNAs, mostly localized in dendrites, MAP2d mRNAs are essentially located in neuronal cell bodies.     

Plasma lipoprotein(a) levels in patients with hyperthyroidism

Thyroid function and regulation were studied in 14 consecutive male outpatients with asymptomatic human immunodeficiency virus (HIV) infection (CDC II/III, n = 8) or AIDS (CDC IV, n = 6) who were free of concomitant infections and hepatic dysfunction, and in eight healthy, age- and weight-matched male controls. Blood was sampled every 10 minutes over 24 hours for measurement of thyrotropin (TSH). Thereafter, thyroid hormones and TSH responsiveness to thyrotropin-releasing hormone (TRH) were measured. Triiodothyronine (T3) and thyroxine (T4) did not differ between HIV-infected patients and controls, but HIV patients had lower thyroid hormone-binding index ([THBI] HIV patients, 1.01 +/- 0.02; controls, 1.11 +/- 0.03; P < .02), free thyroxine (FT4) index (94 +/- 3 v 110 +/- 4, P < .01), FT4 (11.8 +/- 0.4 v 14.3 +/- 0.4 pmol/L, P < .01), and reverse triiodothyronine (rT3) values (0.18 +/- 0.01 v 0.26 +/- 0.02 nmol/L, P < .001) and higher thyroxine-binding globulin ([TBG] 20 +/- 1 v 16 +/- 1 mg/L, P < .02) values. Mean 24-hour TSH levels were increased in HIV patients (2.39 +/- 0.33 v 1.44 +/- 0.16 mU/L, P < .05), associated with increased mean TSH pulse amplitude and TSH responsiveness to TRH. No differences were observed between asymptomatic HIV-seropositive and AIDS patients. In conclusion, there is a hypothyroid-like regulation of the pituitary-thyroid axis in stable HIV infection, which differs distinctly from the euthyroid sick syndrome in non-HIV-nonthyroidal illnesses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of apolipoprotein B and lipoprotein lipase gene polymorphism in variability of serum lipid levels

The serum lipid level is determined by the complex interaction of genetic and environmental factors. The genetic component of this system includes apolipoprotein B (apoB) and lipoprotein lipase (LPL) genes. Three RFLP markers (XbaI, MspI, EcoRI) in the apoB gene and PvuII-RFLP in the LPL gene were genotypes and five lipid traits (fasting plasma levels of total cholesterol, triglycerides, HDL-, LDL-, and VLDL- cholesterol) were measured in 122 unrelated individuals without clinical signs of cardiovascular disease. Several alleles and genotypes which were associated with significant effects on cholesterol, triglycerides, and LDL-cholesterol levels were identified. Analysis of intragenotypic variance and multivariate measures of the mean values of lipid concentrations indicate that apoB gene variation may contribute both to the level and variability of plasma lipids.     

Influence of macrophage-derived apolipoprotein E on plasma lipoprotein distribution of apolipoprotein A-I in apolipoprotein E-deficient mice

Two-dimensional multiple-quantum magic angle spinning (MQMAS) NMR and MAS NMR of 11B at various magnetic fields, were applied to elucidate the structure of vitreous (glassy) boron trioxide (v-B2O3), vitreous boron trisulfide (v-B2S3) and crystalline boron trisulfide (c-B2S3). These techniques, when combined with computer simulations of the resulting spectra, provide the isotropic chemical shifts and the quadrupole parameters, as well as a quantitative measure of the intensities of various boron resonances. The MAS NMR of v-B2O3 produced overlapping anisotropic lineshapes corresponding to the -1/2<-->1/2 transition in two distinct types of BO3 units with 3(+/-0.08):] intensity ratio. A combination of MAS and the multiple-quantum method resulted in a better resolved, isotropic 11B spectrum of v-B2O3. A remarkable enhancement of resolution of the MQMAS NMR proved instrumental in finding and identifying various impurities present in v-B2S3 and c-B2S3. In addition to the resonances from boron in two types of BS3 groups, four other structural units, BOS2, BO2S, BO3 and BS4, were elucidated from the spectra of vitreous and crystalline samples. The effects of various experimental parameters, such as the magnitude of the B0 and B1 fields, on the resolution of the MAS and MQMAS techniques are also shown.     

Role of apolipoprotein CIII in triglyceride-rich lipoprotein metabolism

Fibroblast growth factor (FGF) has been reported to increase the volume of callus in a fracture model of rats. There are, however, no reports of successful repair of segmental bony defects by application of an FGF solution. In this study, the effects of basic FGF on the repair of segmental bony defects in the rabbit femur were examined. Minipellet, a new drug delivery system using atelocollagen, was employed to ensure effective delivery of FGF. Segmental bony defects (10 mm in length) were created in the right femurs of 19 rabbits. In pilot studies, no defects of this size healed spontaneously within 6 weeks. Bones were stabilized with miniexternal fixators. Minipellets containing basic FGF were implanted between fragments so as to bridge the two fragments. The healing processes were monitored radiographically and studied histologically. In rabbits in which FGF was added to the defect site at doses of 1.4 microgram or higher, approximately 90% of the defects were filled with new bone and cartilage within 6 weeks after minipellet implantation. In rabbits receiving placebo minipellets, however, approximately 15% of the defects were filled by callus within 6 weeks. Furthermore, this callus did not change into mature bone. An injection of 2 microgram of FGF solution to bony defects had no effect on the repair of segmental bony defects. These findings suggest that FGF plays a role in the production of adequate volumes of callus particularly in the initial stages of fracture healing and that sustained local release enables FGF to be effective at a low dose. In summary, large segmental bony defects healed after insertion of low-dose FGF minipellets. An adequate dose of FGF and an appropriate delivery system are required for successful healing of large bony defects. These findings imply the potential value of FGF minipellets in clinical practice.     

Fasting insulin and apolipoprotein B levels and low-density lipoprotein particle size as risk factors for ischemic heart disease

CONTEXT: Epidemiological studies have established a relationship between cholesterol and low-density lipoprotein cholesterol (LDL-C) concentrations and the risk of ischemic heart disease (IHD), but up to half of patients with IHD may have cholesterol levels in the normal range. OBJECTIVE: To assess the ability to predict the risk of IHD using a cluster of nontraditional metabolic risk factors that includes elevated fasting insulin and apolipoprotein B levels as well as small, dense LDL particles. DESIGN: Nested case-control study. SETTING: Cases and controls were identified from the population-based cohort of the Quebec Cardiovascular Study, a prospective study conducted in men free of IHD in 1985 and followed up for 5 years. PARTICIPANTS: Incident IHD cases were matched with controls selected from among the sample of men who remained IHD free during follow-up. Matching variables were age, smoking habits, body mass index, and alcohol consumption. The sample included 85 complete pairs of nondiabetic IHD cases and controls. MAIN OUTCOME MEASURES: Ability of fasting insulin level, apolipoprotein B level, and LDL particle diameter to predict IHD events, defined as angina, coronary insufficiency, nonfatal myocardial infarction, and coronary death. RESULTS: The risk of IHD was significantly increased in men who had elevated fasting plasma insulin and apolipoprotein B levels and small, dense LDL particles, compared with men who had normal levels for 2 of these 3 risk factors (odds ratio [OR], 5.9; 95% confidence interval [CI], 2.3-15.4). Multivariate adjustment for LDL-C, triglycerides, and high-density lipoprotein cholesterol (HDL-C) did not attenuate the relationship between the cluster of nontraditional risk factors and IHD (OR, 5.2; 95% CI, 1.7-15.7). On the other hand, the risk of IHD in men having a combination of elevated LDL-C and triglyceride levels and reduced HDL-C levels was no longer significant (OR, 1.4; 95% CI, 0.5-3.5) after multivariate adjustment for fasting plasma insulin level, apolipoprotein B level, and LDL particle size. CONCLUSION: Results from this prospective study suggest that the measurement of fasting plasma insulin level, apolipoprotein B level, and LDL particle size may provide further information on the risk of IHD compared with the information provided by conventional lipid variables.     

Racial differences in the distribution of a low density lipoprotein receptor-related protein (LRP) polymorphism and its association with serum lipoprotein, lipid and apolipoprotein levels

We recently demonstrated that granulocyte-macrophage colony-stimulating factor (GM-CSF) is an autocrine growth factor for human osteoblastic (hOB) cells. Since GM-CSF is a member of the heparin-binding factor family, we examined the interactions between GM-CSF and glycosaminoglycans (GAGs) present in the osteoblast microenvironment. Using a bioassay in which the mitogenic activity of recombinant human (rh) GM-CSF was measured after incubation in the presence of an hOB cell layer or extracellular matrix (ECM) produced by these cells, we showed that rhGM-CSF binds to GAG components present in the ECM and that the bound rhGM-CSF retains its ability to stimulate hOB cell proliferation. Heparan sulfate compounds on the hOB cell surface were also found to sequester GM-CSF. Moreover, treatment with sodium chlorate, an inhibitor of GAG sulfation, suppressed the mitogenic activity of rhGM-CSF on hOB cells. This inhibitory effect was rescued by a low dose of heparin. Heparin was also found to promote the effect of rhGM-CSF on hOB cell proliferation, allowing nonmitogenic high doses of rhGM-CSF to stimulate hOB cell growth. Western blot analysis showed that undersulfation of cellular GAGs by chlorate inhibited the increased tyrosine phosphorylation of proteins involved in GM-CSF signaling in cloned immortalized hOB cells. The data demonstrate that GM-CSF binds to proteoglycans on the hOB cell surface and in ECM produced by these cells and that the bound GM-CSF is biologically active. Furthermore, this study shows that cellular proteoglycans play an essential role in GM-CSF signaling and biological activity in hOBs.     

Elevated levels of serum lipoprotein(a) and apolipoprotein(a) phenotype are not related to pre-eclampsia

BACKGROUND: Pre-eclampsia might result from a less effective invasion of trophoblast cells in the myometrium, caused by attenuated immunosuppression in the spiral arteries, resulting from inhibition of plasmin-mediated activation of transforming growth factor-beta-like substances. In vitro evidence indicates that lipoprotein(a) is capable of inhibiting plasmin-mediated activation of transforming growth factor-beta. Thus, high plasma levels of lipoprotein(a) might result in increased incidence of preeclampsia. METHODS: The patient group consisted of 39 patients with a history of pre-eclampsia in a previous pregnancy: Forty-seven women without pre-eclampsia in their history and matched for age were the control group. All participants gave their informed consent. In both the patient and control group blood pressure, CRP, urinalysis, cholesterol, HDL-cholesterol, triglycerides, lipoprotein(a) level and apolipoprotein(a) phenotype were determined. RESULTS: None of the participants had elevated CRP levels, excluding acute phase related elevations of lipoprotein(a). Proteinuria was present in 33% of patients and in 11% of controls (p=0.01). However, no relation was observed between proteinuria and Lp(a) level. Median Lipoprotein(a) levels in both groups were equal (300 mg/l vs. 275 mg/l; p=0.48), as well as the apo(a) phenotype distribution in both groups. CONCLUSIONS: Lipoprotein(a) and apolipoprotein(a) phenotype do not contribute significantly to the pathogenesis of pre-eclampsia.     

Gemfibrozil significantly lowers cynomolgus monkey plasma lipoprotein[a]-protein and liver apolipoprotein[a] mRNA levels

Eight male cynomolgus monkeys (Macaca fascicularis) on a normal chow diet were orally administered gemfibrozil daily using a weekly rising dose protocol for 3 weeks (50, 125, and 200 mg/kg per day). At these drug doses, Lp[a] levels were reduced: 83.7% +/- 3.2 (SEM), (P < 0.024); 63.7% +/- 4.1 (P < 0.013); and 36.2% +/- 1.1 (P < 0.002), respectively, of pretreatment values. Lp[a] reduction was directly related to blood gemfibrozil concentration (range 36-428 microM, r = 0.969) and occurred without concomitant changes in apolipoprotein B. Three weeks posttreatment Lp[a] levels returned to pretreatment values. A specific ribonuclease protection assay demonstrated that liver apolipoprotein[a] (apo[a]) mRNA expression was decreased in all animals to an average of 19.1% +/- 3.0 (P < 0.0026), of pretreatment values after the 200 mg/kg treatment, whereas, albumin, apolipoprotein A-I, apolipoprotein E, and glyceraldehyde-3-phosphate dehydrogenase mRNAs were unchanged. Lp[a] levels were unaffected by gemfibrozil in HepG2 cells permanently transfected with an apo[a] 10-kringle cDNA construct containing partial 5'- and 3'-untranslated sequences and under control of a constitutive CMV promoter. However, both Lp[a] and apo[a] mRNA in primary cynomolgus monkey hepatocytes were coordinately lowered in a dose-dependent fashion by gemfibrozil. Thus, Lp[a] can be regulated by gemfibrozil at the level of apo[a] mRNA expression.     

Plasma levels of lipoprotein(a) are elevated in patients with the antiphospholipid antibody syndrome

The mechanisms underlying clinical abnormalities associated with the antiphospholipid antibody syndrome (APAS) have not been elucidated. We measured plasma levels of lipoprotein(a) [Lp(a)], the active form of plasminogen activator inhibitor (active PAI), thrombin-antithrombin III complex (TAT) and soluble thrombomodulin (TM), to investigate the relationship of these factors to thrombotic events in APAS. Mean plasma levels of Lp(a), TAT, active PAI and TM were all significantly higher in patients with aPL than in a control group of subjects. Plasma levels of Lp(a) and active PAI were significantly higher in patients with aPL and arterial thromboses than in patients with aPL but only venous thromboses. There was a significant correlation between plasma levels of Lp(a) and active PAI in patients with aPL. These findings suggest that patients with aPL are in hypercoagulable state. High levels of Lp(a) in plasma may impair the fibrinolytic system resulting in thromboses, especially in the arterial system.     

Plasma apolipoprotein profiles of male and female rats

To determine if sex differences exist in the apolipoprotein profile of the rat, the concentrations of the major apolipoproteins and lipids of 12-week-old male and female rats were measured in the plasma as well as in the individual lipoprotein fractions. Plasma apo B, triglyceride, and cholesterol concentrations were significantly higher in male rats than in female rats. Plasma concentrations of apo A-I, apo E, apo A-IV, and apo C-III did not differ between the sexes. Male rats had higher concentrations of apo B in the very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL), and the low density lipoproteins (LDL). These results further support the evidence that sex hormones influence lipoprotein metabolism in the rat.     

Lipoproteins, apolipoproteins, and low-density lipoprotein size among diabetics in the Framingham offspring study

Diabetes mellitus has been shown to be associated with lipid abnormalities. Prior studies have indicated that women with diabetes have a risk of coronary heart disease similar to that of men. We compared lipid parameters in diabetic and nondiabetic participants in cycle 3 of the Framingham Offspring Study. Values for plasma total cholesterol (TC), triglyceride, lipoprotein, cholesterol, apolipoprotein (apo) A1, B, apo and lipoprotein(a) [Lp(a)] and low-density lipoprotein (LDL) particle size were analyzed in 174 diabetic and 3,757 nondiabetic subjects. Data from a total of 2,025 men and 2,042 women participating in the third examination (1983 to 1987) of the Framingham Offspring Study were subjected to statistical analysis. Male and female diabetics showed lower high-density lipoprotein (HDL) cholesterol, higher triglycerides, higher very-low-density lipoprotein (VLDL) cholesterol, lower apo A1, and higher LDL particle scores, indicating smaller size, than nondiabetics. Female diabetics also showed significantly higher TC and apo B values than nondiabetics. The results remained statistically significant after controlling for obesity and menopausal status. The presence of small dense LDL particles (pattern B) was highly associated with diabetes and hypertriglyceridemia in both sexes, and the relative odds for pattern B remained significant in women but not in men after adjustment for age and hypertriglyceridemia. No differences in apo E isoform distribution were found for diabetics and nondiabetics. Diabetes was not associated with elevated LDL cholesterol levels. In conclusion, diabetics have lower HDL cholesterol and higher triglyceride levels and are more likely to have small dense LDL particles. Diabetes is not a secondary cause of elevated LDL cholesterol. Lipid screening of diabetics should include full quantification of lipids for proper assessment of potential atherosclerotic risk.     

An abnormal triglyceride-rich lipoprotein containing excess sialylated apolipoprotein C-III

An abnormal triglyceride-rich lipoprotein has been isolated from some patients with chronic renal failure or severe hypertriglyceridemia. The abnormal lipoprotein was characterized by an increased content of apolipoprotein (apo) C-III-2 (57.5% of total apo C-III peptides compared with 35.5% for controls, P less than 0.001) as characterized by isoelectric focusing and scanning densitometry. As determined by a substrate competition assay, the abnormal lipoprotein was a less efficient substrate for purified bovine milk lipoprotein lipase than control lipoproteins. Neuraminidase digestion of abnormal or control lipoprotein resulted in a reduction of the apo C-III-2 band with a corresponding increase in the region of apo C-III-0, which suggests that the increased content of apo C-III-2 in the abnormal is due to excessive sialylation of the C-III peptide. Limited incubation of the abnormal lipoproteins with neuraminidase caused a partial loss of sialic acid and resulted in a triglyceride-rich lipoprotein with a normal C-III-2:C-III-1 ratio. This preparation displayed normal substrate interaction with lipoprotein lipase. Three severely hypertriglyceridemic patients with the abnormal lipoprotein showed a marked reduction in serum triglyceride concentration, which is associated with a reversion to a normal C-peptide profile after dietary therapy. The results suggest that the extent of sialylation of the apo C-III peptide carried on triglyceride-rich lipoproteins may be critical for their interaction with lipoprotein lipase.     

Predicting the structure of apolipoprotein A-I in reconstituted high-density lipoprotein disks

In reconstituted high-density lipoproteins, apolipoprotein A-I and phosphatidylcholines combine to form disks in which the amphipathic alpha-helices of apolipoprotein A-1 bind to the edge of a lipid bilayer core, shielding the hydrophic lipid tails from the aqueous environment. We have employed experimental data, sequence analysis, and molecular modeling to construct an atomic model of such a reconstituted high-density lipoprotein disk consisting of two apolipoprotein A-I proteins and 160 palmitoyloleoylphosphatidylcholine lipids. The initial globular domain (1-47) of apolipoprotein A-I was excluded from the model, which was hydrated with an 8-A shell of water molecules. Molecular dynamics and simulated annealing were used to test the stability of the model. Both head-to-tail and head-to-head forms of a reconstituted high-density lipoprotein were simulated. In our simulations the protein contained and adhered to the lipid bilayer while providing good coverage of the lipid tails.     

Plasma lipid, apolipoprotein and Lp(a) levels in elderly normolipidemic women: relationships with coronary heart disease and longevity

The relation between plasma lipids and coronary heart disease (CHD) in the elderly is still debated, as well as the proposed role of lipoproteins as markers of longevity. In this study both normolipidemic elderly and middle-aged women with CHD showed higher triglycerides and apolipoprotein B levels and lower high-density lipoprotein (HDL)-cholesterol and apolipoprotein A-I levels in comparison with age-matched subjects without CHD. In the middle-aged group, hypertension and HDL-cholesterol levels and, in the elderly group, only HDL-cholesterol levels were independently associated with CHD. No significant difference was found between a group of healthy centenarians and elderly and middle-aged subjects without CHD. These data suggest that plasma lipids are also related to CHD in the elderly and that, even if at present we are not able to consider them as predictors of longevity, some lipoprotein features may contribute to select subgroups of subjects in which other factors play a further role in life expectancy.     

Interaction of apolipoprotein AII with the putative high-density lipoprotein receptor

There is strong evidence to indicate that binding of HDL by cells is due to recognition of apoproteins residing on the surface of the lipoprotein by the putative HDL receptor(s). Although both of the major HDL apoproteins, AI and AII, are recognized by the putative receptor, the nature of the binding interaction and the domains of the apoproteins involved are largely unknown. Previous data from this laboratory led to the proposal of a model to explain how HDL particles containing AII interacted with the HDL receptor in a different manner as compared to HDL particles which contain apoAI but not apoAII [Vadiveloo, P. K., & Fidge, N. H. (1992) Biochem. J. 284, 145-151]. The model predicted that each chain of the apoAII homodimer contained a binding domain capable of interacting with the HDL receptor. This model was tested in the current study by preparing apoAII monomers, complexing them with phospholipid, and determining the ability of these complexes to bind to putative HDL receptors in rat liver plasma membranes (RLPM) and bovine aortic endothelial cell membranes (BAECM) by ligand blotting. The data showed that these complexes were bound by HB1 and HB2 from RLPM, and to the 110-kDa HDL binding protein from BAECM, providing critical evidence to support the model. Further investigation into the binding interaction revealed that apoAII complexed with phospholipid (apoAII-PC) bound more than delipidated apoAII, which bound more than delipidated apoAII monomers. Thus, optimum binding required the presence of lipid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Estrogen increases low-density lipoprotein receptor-independent catabolism of apolipoprotein B in hyperlipidemic rabbits

Estrogen has been reported to increase the catabolism of low-density lipoprotein (LDL) apolipoprotein (apo) B by increasing LDL receptor activity. To determine the effect of estrogen on LDL receptor-independent pathways, paired turnover studies of native LDL and chemically modified LDL (methyl-LDL) were performed before and during estrogen administration in female New Zealand rabbits consuming a diet containing 0.5% (wt/wt) cholesterol. Rabbits were matched by plasma cholesterol concentration and assigned randomly to receive estrogen (estradiol cypionate 0.5 mg/kg/wk) or placebo. The residence time of both the native LDL apo B tracer and the methyl-LDL apo B tracer in plasma was decreased by estrogen but not by placebo. Multicompartmental modeling of the paired, double-labeled turnover studies indicated that an increase in fractional catabolic rate (FCR) of the fast-turnover pool, a kinetically distinct LDL subpopulation in plasma, accounted for the observed decrease in residence time in plasma for both tracers. These data support the hypothesis that, in addition to any effect on the LDL receptor, estrogen promotes the activity of LDL receptor-independent pathways.