Cholesterol Burden Research Articles

Cyclodextrin overcomes the transport defect in nearly every organ of NPC1 mice leading to excretion of sequestered cholesterol as bile acid

A mutation in NPC1 leads to sequestration of unesterified cholesterol in the late endosomal/lysosomal compartment of every cell culminating in the development of pulmonary, hepatic, and neurodegenerative disease. Acute administration of 2-hydroxypropyl-beta-cyclodextrin (CYCLO) rapidly overcomes this transport defect in both the 7-day-old pup and 49-day-old mature npc1(-/-) mouse, even though this compound is cleared from the body and plasma six times faster in the mature mouse than in the neonatal animal. The liberated cholesterol flows into the cytosolic ester pool, suppresses sterol synthesis, down-regulates SREBP2 and its target genes, and reduces expression of macrophage-associated inflammatory genes. These effects are seen in the liver and brain, as well as in peripheral organs like the spleen and kidney. Only the lung appears to be resistant to these effects. Forty-eight h after CYCLO administration to the 49-day-old animals, fecal acidic, but not neutral, sterol output increases, whole-animal cholesterol burden is reduced, and the hepatic and neurological inflammation is ameliorated. However, lifespan is extended only when the CYCLO is administered to the 7-day-old animals. These studies demonstrate that CYCLO administration acutely reverses the cholesterol transport defect seen in the NPC1 mouse at any age, and this reversal allows the sequestered sterol to be excreted from the body as bile acid.

Aortic calcifications in familial hypercholesterolemia: Potential role of the low-density lipoprotein receptor gene

We have previously reported premature, extensive aortic calcifications in patients with homozygous familial hypercholesterolemia (hmzFH) due to mutations in the low-density lipoprotein receptor gene (LDL-R). The objective of this study was to measure the degree of aortic calcification in heterozygous FH (htzFH) compared to both hmzFH and controls. We hypothesized that the LDL-R gene may contribute to aortic calcifications in a gene-dosage effect. Patients with htzFH due to the French Canadian mutation (Delta15 kb del. null allele) were selected. All patients underwent computed tomographic scan to measure vascular calcification. We used 22 hmzFH patients from our previous study and patients undergoing computed tomographic virtual colonoscopy as controls. Mean age for htzFH was 50 +/- 15 years; initial cholesterol level before treatment was 10.45 +/- 1.73 mmol/L. Major cardiovascular events occurred in 9 of 17 patients. A strong correlation between age and calcium score was found (r = 0.72, P = .0016). There was a strong correlation between the cholesterol-year score (an index of lifelong cholesterol burden) and the aortic calcium score (r = 0.62, P = .0105). Aortic calcifications in htzFH subjects occurred later than in hmzFH patients, but much earlier than in controls, suggesting a gene-dosage effect of LDL-R mutations and aortic calcium deposition. Aortic calcification was observed in patients with htzFH but presented at a later time and were less extensive than in hmzFH (34 vs 14 years, respectively). Because aortic calcifications may be partly independent of serum cholesterol levels in patients with familial hypercholesterolemia, implications for screening and the timing of treatment initiation may need reassessment.

Aorta of young and middle-aged heterozygous familial hypercholesterolemia patients shows no functional or morphological impairment assessed by MRI

In familial hypercholesterolemia (FH) the level of LDL cholesterol is 2-3 times that of the normal population and leads to accelerated atherosclerosis. Improved care for risk factors has decreased cardiovascular mortality of these patients. We studied subclinical atherosclerotic changes with morphologic and functional aortic magnetic resonance imaging (MRI) in FH patients under the age of 50.39 DNA test-verified heterozygous FH-North Karelia patients, aged 6-48, 28 of them treated with statins, and 25 healthy controls, aged 12 to 50, underwent aortic MRI, carotid ultrasound (US), and risk-factor assessment. No differences in any of the morphologic or functional aortic parameters appeared between patients and controls. Age and gender were independent predictors of the majority of the morphologic and functional measures. Carotid intima-media thickness assessed by US was greater in patients (0.57 mm +/- 0.13 vs. 0.48 +/- 0.13 mm, p = 0.005) as was cholesterol-years score (243 +/- 122 vs. 137 +/- 74, p < 0.001). Patients had thicker intima-media of the common carotid artery and higher cholesterol burden as indicated by their cholesterol-years score. Despite this, no differences existed in morphologic or functional aortic parameters assessed with MRI. The improved care of cardiovascular risk factors, especially statin treatment, may protect the aorta of FH patients. However, larger confirmatory studies are needed.

Relation of C-Reactive Protein and Carotid Intima Media Thickness in Taiwanese With Familial Hypercholesterolemia

The aim of this study was to investigate the potential relationships between the carotid intima media thickness (carotid IMT), high sensitive C-reactive protein (hsCRP), and cholesterol burden in heterozygous familial hypercholesterolemia (FH) subjects. Thirty-two genetically-verified heterozygous patients with FH and 34 healthy controls were recruited into our study in Taiwan. We measured conventional risk factors, hsCRP, and carotid IMT of study subjects. The cholesterol-year score was used to estimate the lifetime cholesterol burden. Subjects with heterozygous FH had significantly elevated total cholesterol, elevated low-density lipoprotein cholesterol, and increased carotid IMT compared with control subjects. Carotid IMT correlated well with the cholesterol-year score. In patients with FH, univariate analysis showed that hsCRP was highly correlated with carotid IMT. Multiple linear regression analysis indicated that hsCRP was the only independent predictor of carotid IMT in patients with FH. In conclusion, patients with heterozygous FH had significantly higher carotid IMT and the level of hsCRP was independently associated with atherosclerotic progression. (R: 0.639, R(2): 0.408, p <0.001).

Ligand activation of LXRβ reverses atherosclerosis and cellular cholesterol overload in mice lacking LXRα and apoE

Liver X receptors (LXRs) alpha and beta are transcriptional regulators of cholesterol homeostasis and potential targets for the development of antiatherosclerosis drugs. However, the specific roles of individual LXR isotypes in atherosclerosis and the pharmacological effects of synthetic agonists remain unclear. Previous work has shown that mice lacking LXRalpha accumulate cholesterol in the liver but not in peripheral tissues. In striking contrast, we demonstrate here that LXRalpha(-/-)apoE(-/-) mice exhibit extreme cholesterol accumulation in peripheral tissues, a dramatic increase in whole-body cholesterol burden, and accelerated atherosclerosis. The phenotype of these mice suggests that the level of LXR pathway activation in macrophages achieved by LXRbeta and endogenous ligand is unable to maintain homeostasis in the setting of hypercholesterolemia. Surprisingly, however, a highly efficacious synthetic agonist was able to compensate for the loss of LXRalpha. Treatment of LXRalpha(-/-)apoE(-/-) mice with synthetic LXR ligand ameliorates the cholesterol overload phenotype and reduces atherosclerosis. These observations indicate that LXRalpha has an essential role in maintaining peripheral cholesterol homeostasis in the context of hypercholesterolemia and provide in vivo support for drug development strategies targeting LXRbeta.

Trends in ATP-III-Defined High Blood Cholesterol Prevalence, Awareness, Treatment and Control Among U.S. Adults

We sought to determine trends in the prevalence, awareness, treatment and control of high low-density lipoprotein (LDL) cholesterol among U.S. adults. Data from 6497 participants of the Third National Health and Nutrition Examination Survey (NHANES) conducted in 1988-1994 and 5626 participants of NHANES 1999-2004 were compared. High LDL cholesterol was defined using risk-specific cut-points from the National Cholesterol Education Program's Adult Treatment Panel III guidelines. The age-standardized percentage of U.S. adults with high LDL cholesterol was 26.6% in 1988-1994 and 25.3% in 1999-2004 (P = 0.28). Between 1988-1994 and 1999-2004, awareness increased from 39.2% to 63.0%, and use of pharmacologic lipid-lowering treatment increased from 11.7% to 40.8% (each p < 0.001). LDL cholesterol control increased from 4.0% to 25.1% among those with high LDL cholesterol (p < 0.001). In 1999-2004, rates of LDL cholesterol control were lower among adults ages 20-49 years compared with those age 65 years or older (13.9% vs. 30.3%; p < 0.001); non-Hispanic blacks and Mexican-Americans compared with non-Hispanic whites (17.2% and 16.5% vs. 26.9%, respectively; p = 0.05 and p = 0.008); and males compared with females (22.6% vs. 28.0%; p = 0.01). Continued efforts are needed to lower the burden of high LDL cholesterol and increase LDL cholesterol control, especially among populations with low control rates.

Vascular stiffness in familial hypercholesterolaemia is associated with C‐reactive protein and cholesterol burden

Familial hypercholesterolaemia (FH) is characterized by very high serum cholesterol and premature coronary atherosclerosis. Arterial stiffness and atherosclerosis are two major underlying pathophysiologies of arterial disease that are predictive of future cardiovascular events. The aims of this study were to quantify atherosclerosis and arterial stiffness and to evaluate their relationship with high sensitive C-reactive protein (hs-CRP) and the level of exposure to high serum cholesterol in FH patients. We measured traditional risk factors, hs-CRP, intima-media thickness (IMT) of carotid artery, and brachial-ankle pulse wave velocity (baPWV) in 35 heterozygous FH subjects and 17 healthy control subjects. Cholesterol-year score (CYS) was calculated to estimate the lifetime cholesterol burden in FH subjects. FH subjects had significantly elevated total cholesterol, low-density lipoprotein cholesterol, and carotid IMT compared with those without mutations. Among FH patients, the baPWV and carotid IMT were higher in cases with high cholesterol burden than those without. Similarly, the baPWV and carotid IMT were also higher in cases with elevated hs-CRP (> 1 mg L(-1)) than those without. Multiple linear regression analysis demonstrated CYS and hs-CRP were significant independent predictors of baPWV and IMT in FH patients. Both high cholesterol burden and vascular inflammation are not only associated with atherosclerosis, but also contribute to the development of arterial stiffness in FH patients. Early detection of hypercholesterolaemia in FH patients is warranted to prevent the untoward pathophysiologies.

Familial Hypercholesterolemia Patients Treated With Statins at No Increased Risk for Intracranial Vascular Lesions Despite Increased Cholesterol Burden and Extracranial Atherosclerosis

To correlate known vascular disease risk factors and the signs of extracranial and intracranial changes of vascular origin in young patients with heterozygous familial hypercholesterolemia (FH). 39 DNA test-verified heterozygous FH North Karelian patients (FH-NK), aged 6 to 48, 28 of them treated with statins, and 25 healthy controls underwent brain magnetic resonance imaging (MRI) and carotid ultrasound. Common carotid intima-media thickness was significantly greater in the patients (P=0.005). MR angiography showed no pathological changes, other than 1 incidental aneurysm. The number and size of white matter hyperintensities on T2-weighted MR images, considered as markers of microvascular alterations, did not differ between patients and controls. FH-NK patients treated with statins seem to be at no increased risk for brain infarcts or other brain lesions of vascular origin when younger than age 50.

The P-407-induced murine model of dose-controlled hyperlipidemia and atherosclerosis: a review of findings to date.

We are continuing to both elucidate underlying mechanisms and identify clinical applications for a chemically induced murine model of dose-controlled hyperlipidemia and atherosclerosis. This murine model neither utilizes genetically modified mice nor a high-fat, cholate-containing diet, although simultaneous ingestion of a high-fat, cholate-enriched diet potentiates the hyperlipidemic response and the number and size of aortic atherosclerotic lesions formed in C57BL/6 mice. The chemical agent used to induce hyperlipidemia is poloxamer 407 (P-407), a nonionic surface-active-agent. To date, we have investigated the effect of P-407 on the biologic activity of a variety of key enzymes involved with lipid metabolism and transport. These enzymes include 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, lipoprotein lipase (LPL), cholesterol 7alpha-hydoxylase (C7alphaH), sterol 27-hydroxylase (S27H), lecithin cholesterol acyltransferase (LCAT), cholesteryl-ester-transfer-protein (CETP), hepatic lipase (HL), and endothelial lipase (EL). P-407 directly inhibits the heparin-releasable fraction of LPL and HL and indirectly increases the biologic activity of CETP and LCAT. Long-term (> 4 months) administration of P-407 to C57BL/6 mice appears to have no effect on the biologic activity of S27H and HMG-CoA reductase, but decreases the activity of C7alphaH. This would suggest that hypertriglyceridemia and hypercholesterolemia result from inhibition of LPL and C7alphaH, respectively, while the biologic activity of CETP and LCAT are indirectly increased to compensate for the increased cholesterol burden. The above model has proven useful for predicting the therapeutic efficacy of existing and possibly newer statin drugs, as well as evaluating the potential of one statin drug (atorvastatin calcium) to cause the regression of P-407-induced atherosclerotic lesions in mice. The P-407-induced murine model of atherogenesis represents an alternative to the use of either genetically modified or diet-induced models and may also prove beneficial for the evaluation of newer classes of antihyperlipidemic agents such as antioxidants, CETP inhibitors, and liver X receptor (LXR) agonists.

Mobilization of cytoplasmic CE droplets by overexpression of human macrophage cholesteryl ester hydrolase

The obligatory first step in the removal of cholesterol from foam cells is the hydrolysis of stored cholesteryl esters (CEs) to release free cholesterol (FC). Neutral cholesteryl ester hydrolase (CEH) catalyzes this hydrolysis, and limiting levels of CEH could play a role in determining the susceptibility to atherosclerosis. We have recently reported the first identification and cloning of cDNA for human macrophage CEH. In the present study, we tested the hypothesis that systematically varied levels of overexpression of human macrophage CEH results in a proportional degree of reduction in cellular CE content in a cell system with known and reproducible amounts of CE accumulation. CEH expression was confirmed by demonstrating the presence of CEH mRNA and protein with an increase in CEH activity. A significant reduction in intracellular lipid droplets was observed in CEH-expressing cells, together with a decrease in cellular CE mass and a 2-fold increase in FC efflux. These results demonstrate that when human macrophage CEH is expressed in lipid-laden cells, hydrolysis and mobilization of CE (stored as lipid droplets) occur. These data establish the possibility that increased CE hydrolysis, mediated by CEH up-regulation, could represent an important mechanism to reduce the cholesterol burden of foam cells.

Childhood Precursors of High Blood Pressure and Elevated Cholesterol

For several decades, high blood pressure and elevated cholesterol have been established as risk factors for atherosclerosis and, thus, for most cardiovascu­ lar morbidity and mortality of industrialized countries. More recently, de­ veloping countries are recognizing the public health burden of high blood pressure and elevated cholesterol, as a result of demographic changes, which have seen increasing proportions of populations reach the sixth decade of life and beyond, and social and behavioral changes, which have fostered the development of the risk factors (12). Thus, the consequences of high blood pressure and elevated cholesterol, in addition to cigarette smoking and other factors, now constitute a global public health problem. The causes of coronary heart disease and other complications of atheroscle­ rosis and hypertensive disease must be sought earlier in life than the age range in which these events become especially common, i.e. at age 40 and older. The theoretical foundation for this concept is reinforced strongly by patholog­ ical evidence, including that from postmortem examinations of young military casualties. These examinations show that the vascular lesions of atherosclero­ sis commonly are present in the coronary arteries and aorta before age 20 (see, for example, Ref. 40). Geographically widespread evidence that aortic

Copper deficiency and cholesterol metabolism in the rat

The influence of copper deficiency on both 3H incorporation into plasma and liver lipids following [ 3H]mevalonate injection, and the excretion of biliary steroids from cannulated bile ducts was examined in the rat in two separate experiments. Copper-deficient rats exhibited a significant hypercholesterolemia (129% increase, P < 0.001) at 181 days. Four hours after [ 3H]mevalonate injection, 3H incorporation into plasma free and esterified cholesterol was elevated 162% ( P < 0.005) and 80% ( P < 0.025), respectively, and 3H incorporation into liver total lipids and cholesterol esters was depressed 18% ( P < 0.04) and 43% ( P < 0.005, respectively, in copper-deficient rats. Hepatic copper concentration of deficient rats showed a significant negative correlation with 3H incorporation into plasma cholesterol ( r= −0.83, P < 0.02) and cholesterol ester ( r = −0.70, P < 0.08). Total hepatic cholesterol remained unchanged by deficiency despite the significant increase in total plasma cholesterol burden of copper deficient rats (82%, P < 0.001). Copper deficiency failed to impair biliary steroid excretion. The 56% ( P < 0.001) increase in bile acid excretion in the first 8 hours was paralleled by the 62% ( P < 0.005) increase in plasma cholesterol concentration of deficient rats. The observations suggest a more rapid synthesis and clearance of cholesterol to the plasma pool, with this cholesterol being unavailable for excretion as biliary steroids, in copper-deficient rats.