Evidence for a new pathophysiological mechanism for coronary artery disease regression: hepatic lipase-mediated changes in LDL density. (1/41)

BACKGROUND: Small, dense LDL particles are associated with coronary artery disease (CAD) and predict angiographic changes in response to lipid-lowering therapy. Intensive lipid-lowering therapy in the Familial Atherosclerosis Treatment Study (FATS) resulted in significant improvement in CAD. This study examines the relationship among LDL density, hepatic lipase (HL), and CAD progression, identifying a new biological mechanism for the favorable effects of lipid-altering therapy. METHODS AND RESULTS: Eighty-eight of the subjects in FATS with documented coronary disease, apolipoprotein B levels >/=125 mg/dL, and family history of CAD were selected for this study. They were randomly assigned to receive lovastatin (40 mg/d) and colestipol (30 g/d), niacin (4 g/d) and colestipol, or conventional therapy with placebo alone or with colestipol in those with elevated LDL cholesterol levels. Plasma hepatic lipase (HL), lipoprotein lipase, and LDL density were measured when subjects were and were not receiving lipid-lowering therapy. LDL buoyancy increased with lovastatin-colestipol therapy (7.7%; P<0.01) and niacin-colestipol therapy (10.3%; P<0.01), whereas HL decreased in both groups (-14% [P<0.01] and -17% [P<0.01] with lovastatin-colestipol and niacin-colestipol, respectively). Changes in LDL buoyancy and HL activity were associated with changes in disease severity (P<0.001). In a multivariate analysis, an increase in LDL buoyancy was most strongly associated with CAD regression, accounting for 37% of the variance of change in coronary stenosis (P<0.01), followed by reduction in apolipoprotein Bl (5% of variance; P<0.05). CONCLUSIONS: These studies support the hypothesis that therapy-associated changes in HL alter LDL density, which favorably influences CAD progression. This is a new and potentially clinically relevant mechanism linking lipid-altering therapy to CAD improvement.  (+info)

Role of bile acids and bile acid binding agents in patients with collagenous colitis. (2/41)

BACKGROUND: In a retrospective study bile acid malabsorption was observed in patients with collagenous colitis. AIMS: To study the occurrence of bile acid malabsorption and the effect of bile acid binders prospectively in patients with chronic diarrhoea and collagenous colitis. METHODS: Over 36 months all patients referred because of chronic diarrhoea completed a diagnostic programme, including gastroscopy with duodenal biopsy, colonoscopy with biopsies, and the (75)Se-homocholic acid taurine ((75)SeHCAT) test for bile acid malabsorption. Treatment with a bile acid binder (cholestyramine in 24, colestipol in three) was given, irrespective of the results of the (75)SeHCAT test. RESULTS: Collagenous colitis was found in 28 patients (six men, 22 women), 27 of whom had persistent symptoms and completed the programme. Four patients had had a previous cholecystectomy or a distal gastric resection. The (75)SeHCAT test was abnormal in 12/27 (44%) of the collagenous colitis patients with (75)SeHCAT values 0.5-9.7%, and normal in 15 patients (56%). Bile acid binding treatment was followed by a rapid, marked, or complete improvement in 21/27 (78%) of the collagenous colitis patients. Rapid improvement occurred in 11/12 (92%) of the patients with bile acid malabsorption compared with 10/15 (67%) of the patients with normal (75)SeHCAT tests. CONCLUSION: Bile acid malabsorption is common in patients with collagenous colitis and is probably an important pathophysiological factor. Because of a high response rate without serious side effects, bile acid binding treatment should be considered for collagenous colitis, particularly patients with bile acid malabsorption.  (+info)

Common hepatic lipase gene promoter variant determines clinical response to intensive lipid-lowering treatment. (3/41)

BACKGROUND: The common -514 C-->T polymorphism in the promoter region of the hepatic lipase (HL) gene affects HL activity. The C allele is associated with higher HL activity, more dense and atherogenic LDL, and lower HDL(2) cholesterol. Intensive lipid-lowering therapy lowers HL activity, increases LDL and HDL buoyancy, and promotes coronary artery disease (CAD) regression. We tested the hypothesis that subjects with the CC genotype and a more atherogenic lipid profile experience the greatest CAD regression from these favorable effects. METHODS AND RESULTS: Forty-nine middle-aged men with dyslipidemia and established CAD who were undergoing intensive lipid-lowering therapy were studied. Change in coronary stenosis was assessed by quantitative angiography, HL polymorphism by polymerase chain reaction amplification, HL activity by (14)C-labeled substrate, and LDL buoyancy by density-gradient ultracentrifugation. The response to lipid-lowering therapy was significantly different among subjects with different HL promoter genotypes. Subjects with the C:C genotype had the greatest decrease in HL activity (P<0.005 versus TC and TT by ANOVA) and the greatest improvement in LDL density (P<0.005) and HDL(2)-C (P<0.05) with therapy. These subjects had the greatest angiographic improvement, with 96% of them experiencing CAD regression, compared with 60% of TC and none of the TT patients (P:<0.001). CONCLUSIONS: -In middle-aged men with established CAD and dyslipidemia, the HL gene -514 C-->T polymorphism significantly predicts changes in coronary stenosis with lipid-lowering treatment that appear to involve an HL-associated effect on LDL metabolism. This study identifies a gene polymorphism that strongly influences the lipid and clinical response to lipid-lowering drugs.  (+info)

Determinants of variable response to statin treatment in patients with refractory familial hypercholesterolemia. (4/41)

Interindividual variability in low density lipoprotein (LDL) cholesterol (LDL-C) response during treatment with statins is well documented but poorly understood. To investigate potential metabolic and genetic determinants of statin responsiveness, 19 patients with refractory heterozygous familial hypercholesterolemia were sequentially treated with placebo, atorvastatin (10 mg/d), bile acid sequestrant, and the 2 combined, each for 4 weeks. Levels of LDL-C, mevalonic acid (MVA), 7-alpha-OH-4-cholesten-3-one, and leukocyte LDL receptor and hydroxymethylglutaryl coenzyme A reductase mRNA were determined after each treatment period. Atorvastatin (10 mg/d) reduced LDL-C by an overall mean of 32.5%. Above-average responders (LDL-C -39.5%) had higher basal MVA levels (34.4+/-6.1 micromol/L) than did below-average responders (LDL-C -23.6%, P<0.02; basal MVA 26.3+/-6.1 micromol/L, P<0.01). Fewer good responders compared with the poor responders had an apolipoprotein E4 allele (3 of 11 versus 6 of 8, respectively; P<0.05). There were no baseline differences between them in 7-alpha-OH-4-cholesten-3-one, hydroxymethylglutaryl coenzyme A reductase mRNA, or LDL receptor mRNA, but the latter increased in the good responders on combination therapy (P<0.05). Severe mutations were not more common in poor than in good responders. We conclude that poor responders to statins have a low basal rate of cholesterol synthesis that may be secondary to a genetically determined increase in cholesterol absorption, possibly mediated by apolipoprotein E4. If so, statin responsiveness could be enhanced by reducing dietary cholesterol intake or inhibiting absorption.  (+info)

Growth hormone induces low-density lipoprotein clearance but not bile acid synthesis in humans. (5/41)

OBJECTIVE: Growth hormone (GH) induces hepatic low-density lipoprotein (LDL) receptors and lowers plasma cholesterol. We characterized the influence of GH treatment on plasma LDL clearance in normal humans and investigated the relative role of LDL receptor (LDLR) activity and stimulation of bile acid synthesis in subjects with different LDLR expression. METHODS AND RESULTS: Plasma clearance of autologous 125I-LDL was measured before and during 3 weeks of treatment with GH (0.1 IU/kg per day) in 9 healthy young males. Plasma LDL cholesterol was reduced by 13% and the fractional catabolic rate of LDL increased by 27%. More marked changes were seen in a patient with hypopituitarism substituted with GH (0.07 IU/kg per day) for 3 months. In a second study, GH dose-dependently reduced LDL cholesterol and increased Lp(a) levels in 3 groups of males: younger and elderly healthy subjects and heterozygous familial hypercholesterolemia (FH). No effect on bile acid synthesis measured by the plasma marker 7alpha-hydroxy-4-cholesten-3-one was observed. In an LDLR-deficient FH homozygote, LDL cholesterol was not affected by GH. CONCLUSIONS: GH treatment reduces plasma LDL cholesterol by inducing LDL clearance. In humans, LDLR expression is a prerequisite for this effect, whereas it is not related to stimulation of bile acid synthesis.  (+info)

Hepatic mRNA levels for the LDL receptor and HMG-CoA reductase show coordinate regulation in vivo. (6/41)

A sensitive solution hybridization assay using autologous cRNA probes was developed with the aim to study the simultaneous regulation of hepatic mRNA levels, on a quantitative basis, for the LDL receptor (LDLr), HMG-CoA reductase, and cholesterol 7 alpha-hydroxylase (Cho-7-hx) in C57BL/6J mice. With the purpose to suppress and stimulate transcript levels respectively, animals received established high fat diets, cholesterol-enriched diets, and a diet supplemented with mevinolin and colestipol. One hundred nineteen animals were investigated in six separate experiments. In spite of an eightfold increase in hepatic cholesterol induced by a high fat diet, the LDLr and the HMG-CoA reductase mRNA levels were only reduced to 60-70% and 25-50% of control values, respectively. When the data from all animals were analyzed, a strong positive correlation was obtained between the mRNA levels for the LDLr and HMG-CoA reductase (r = 0.79, P less than 0.001). A significant relation remained when control animals only were analyzed (n = 42, r = 0.59, P less than 0.001). Cho-7-hx mRNA showed a regulatory pattern that differed from that of the LDLr and HMG-CoA reductase; feeding cholesterol at 1.7% and 5% but not at 0.4% elevated the mRNA levels for Cho-7-hx while the LDLr and HMG-CoA reductase mRNA levels were maximally suppressed already at 0.4% of dietary cholesterol. The results show that the mRNA levels for the LDLr and HMG-CoA reductase are regulated in parallel in the liver in vivo during various metabolic perturbations as well as at normal physiologic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)  (+info)

Comparison of computer- and human-derived coronary angiographic end-point measures for controlled therapy trials. (7/41)

The Cholesterol Lowering Atherosclerosis Study, a randomized angiographic clinical trial, demonstrated the beneficial effect of niacin/colestipol plus diet therapy on coronary atherosclerosis. Outcome was determined by panel-based estimates (viewed in both still and cine modes) of percent stenosis severity and change in native artery and bypass graft lesions. Computer-based quantitative coronary angiography (QCA) was also used to measure lesion and bypass graft stenosis severity and change in individual frames closely matched in orientation, opacification, and cardiac phase. Both methods jointly evaluated 350 nonoccluded lesions. The correlation between QCA and panel estimates of lesion size was 0.70 (p less than 0.0001) and for change in lesion size was 0.28 (p = 0.002). Agreement between the two methods in classifying lesion changes (i.e., regression, unchanged, or progression) occurred for 60% (210 of 350) of the lesions kappa +/- SEM = 0.20 +/- 0.05, p less than 0.001). The panel identified 442 nonoccluded lesions for which QCA stenosis measurements could not be obtained. Lesions not measurable by QCA included those with stenosis greater than 85% that could not be reliably edge tracked, segments with diffuse or ecstatic disease that had no reliable reference diameter, and segments for which matched frames could not be located. Seventy-nine lesions, the majority between 21% and 40% stenosis, were identified and measured by QCA but were not identified by the panel. This comparison study demonstrates the need to consider available angiographic measurement methods in relation to the goals of their use.  (+info)

Liver X receptor alpha interferes with SREBP1c-mediated Abcd2 expression. Novel cross-talk in gene regulation. (8/41)

The peroxisomal ATP binding cassette (ABC) transporter adrenoleukodystrophy-related protein, encoded by ABCD2, displays functional redundancy with the X-linked adrenoleukodystrophy-associated protein, making ABCD2 up-regulation of therapeutic value. Cholesterol lowering activates human ABCD2 in cultured cells. To investigate in vivo regulation by sterols, we first characterized a sterol regulatory element (SRE) in the murine Abcd2 promoter that is directly bound by SRE-binding proteins (SREBPs). Intriguingly, this element overlaps with a direct repeat 4, which serves as binding site for liver X receptor (LXR)/retinoid X receptor heterodimers, suggesting novel cross-talk between SREBP and LXR/retinoid X receptor in gene regulation. Using fasting-refeeding and cholesterol loading, SREBP accessibility to the SRE/direct repeat 4 was tested. Results suggest that adipose Abcd2 is induced by SREBP1c, whereas hepatic Abcd2 expression is down-regulated by concurrent activation of LXRalpha and SREBP1c. In cell culture, SREBP1c-mediated Abcd2 induction is counteracted by ligand-activated LXRalpha. Finally, hepatic Abcd2 expression in LXRalpha,beta-deficient mice is inducible to levels vastly exceeding wild type. Together, we identify LXRalpha as negative modulator of Abcd2, acting through a novel regulatory mechanism involving overlapping SREBP and LXRalpha binding sites.  (+info)

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