Cholesterol efflux from macrophage foam cells is a rate-limiting step in reverse cholesterol transport. In this process cholesterol acceptors like high-density lipoproteins (HDL) and apolipoprotein (apo)A-I must cross the endothelium to get access to the donor cells in the arterial intima. Previously, we have shown that apoA-I passes a monolayer of aortic endothelial cells (ECs) from the apical to the basolateral side by transcytosis, which is modulated by the ATP-binding cassette transporter (ABC)A1. Here, we analyzed the interaction of mature HDL with ECs. ECs bind HDL in a specific and saturable manner. Both cell surface biotinylation experiments and immunofluorescence microscopy of HDL recovered approximately 30% of the cell-associated HDL intracellularly. Cultivated on inserts ECs bind, internalize, and translocate HDL from the apical to the basolateral compartment in a specific and temperature-dependent manner. The size of the translocated particle was reduced, but its protein moiety remained intact. Using RNA interference, we investigated the impact of SR-BI, ABCA1, and ABCG1 on binding, internalization, and transcytosis of HDL by ECs. HDL binding was reduced by 50% and 30% after silencing of SR-BI and ABCG1, respectively, but not at all after diminishing ABCA1 expression. Knock down of SR-BI and, even more so, ABCG1 reduced HDL transcytosis but did not affect inulin permeability. Cosilencing of both proteins did not further reduce HDL binding, internalization, or transport. In conclusion, ECs transcytose HDL by mechanisms that involve either SR-BI or ABCG1 but not ABCA1.

Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy, and until recently prophylactic cranial radiotherapy (CRT) was important for achieving long-term survival. Hypothalamic-pituitary hormone insufficiency is a well-recognized consequence of CRT for childhood cancer. Another problem is increased cardiovascular risk, which has been shown in long-term survivors of other childhood cancers. In the only previously reported study on cardiovascular risk after childhood ALL, obesity and dyslipidemia were recorded in a small subgroup treated with CRT, compared with patients treated with chemotherapy. The mechanisms behind the increase in cardiovascular risk in survivors of childhood cancer are not clarified. The aim of the present study was to elucidate mechanisms of increased cardiovascular risk in former childhood ALL patients. A group of 44 ALL survivors (23 males, median age 25 yr, range 19-32 yr at the time of study) treated with CRT (median 24 Gy, 18-30 Gy) at a median age of 5 yr (1-18 yr) and chemotherapy were investigated for prevalence of GH deficiency and cardiovascular risk factors. Comparison was made with controls randomly selected from the general population and individually matched for sex, age, smoking habits, and residence. All patients and controls underwent a GHRH-arginine test, and patients with a peak GH 3.9 microg/liter or greater were further investigated with an additional insulin tolerance test. Significantly higher plasma levels of insulin (P = 0.002), blood glucose (P = 0.01), and serum levels of low-density lipoprotein cholesterol, apolipoprotein (<em>Apo</em>) B, triglycerides, fibrinogen, and leptin (all P <or= 0.05) were recorded among the ALL patients, compared with controls. Furthermore, the serum levels of high-density lipoprotein cholesterol (P = 0.03) and <em>Apo</em> <em>A1</em> (P = 0.005) were significantly lower among the patients. Compared with controls, the patients had higher body mass index and waist to hip ratio, and body composition measured with dual-energy x-ray absorptiometry showed significantly higher fat mass and lower lean mass (P < 0.001). Forty of 44 ALL patients (91%) were considered GH deficient according to the insulin tolerance test and/or the GHRH-arginine test, and the rest were considered GH insufficient. In patients, peak GH during GHRH-arginine was significantly negatively correlated to total body fat mass measured with dual-energy x-ray absorptiometry (r = -0.48, P = 0.001), waist to hip ratio (r = -0.32, P = 0.03), plasma insulin (r = -0.49, P = 0.001), and leptin (r = -0.46, P = 0.002). Moreover, a significantly positive correlation was recorded with high-density lipoprotein cholesterol (r = 0.38, P = 0.012). Using Doppler echocardiography, a marked reduction in cardiac dimensions and performance (ejection fraction P < 0.001 and fractional shortening P = 0.01), compared with controls, was recorded. In conclusion, at a median 17 yr after treatment with CRT and chemotherapy in former childhood ALL patients, a significant increase in cardiovascular risk factors was recorded. We suggest that GH deficiency, induced by CRT, is a primary cause for this because strong correlations between the stimulated GH peak and several of the cardiovascular risk factors were observed.

Regulation of gene expression of ATP-binding cassette transporter (ABC)A1 and ABCG1 by liver X receptor/retinoid X receptor (LXR/RXR) ligands was investigated in the human intestinal cell line CaCo-2. Neither the RXR ligand, 9-cis retinoic acid, nor the natural LXR ligand 22-hydroxycholesterol alone altered ABCA1 mRNA levels. When added together, ABCA1 and ABCG1 mRNA levels were increased 3- and 7-fold, respectively. T0901317, a synthetic non-sterol LXR agonist, increased ABCA1 and ABCG1 gene expression 11- and 6-fold, respectively. ABCA1 mass was increased by LXR/RXR activation. T0901317 or 9-cis retinoic acid and 22-hydroxycholesterol increased cholesterol efflux from basolateral but not apical membranes. Cholesterol efflux was increased by the LXR/RXR ligands to apolipoprotein (apo)A-I or HDL but not to taurocholate/phosphatidylcholine micelles. Actinomycin D prevented the increase in ABCA1 and ABCG1 mRNA levels and the increase in cholesterol efflux induced by the ligands. Glyburide, an inhibitor of ABCA1 activity, attenuated the increase in basolateral cholesterol efflux induced by T0901317. LXR/RXR activation decreased the esterification and secretion of cholesterol esters derived from plasma membranes. Thus, in CaCo-2 cells, LXR/RXR activation increases gene expression of ABCA1 and ABCG1 and the basolateral efflux of cholesterol, suggesting that ABCA1 plays an important role in intestinal HDL production and cholesterol absorption.

BACKGROUND

Glutathione transferases (GSTs) constitute a family of isoenzymes that catalyze the conjugation of the tripeptide glutathione with a wide variety of hydrophobic compounds bearing an electrophilic functional group. Recently, a number of X-ray structures have been reported which have defined both the glutathione- and the substrate-binding sites in these enzymes. The structure of the glutathione-free enzyme from a mammalian source has not, however, been reported previously.

RESULTS

We have solved structures of a human alpha-class GST, isoenzyme A1-1, both in the unliganded form and in complexes with the inhibitor ethacrynic acid and its glutathione conjugate. These structures have been refined to resolutions of 2.5 A, 2.7 A and 2.0 A respectively. Both forms of the inhibitor are clearly present in the associated electron density.

CONCLUSIONS

The major differences among the three structures reported here involve the C-terminal alpha-helix, which is a characteristic of the alpha-class enzyme. This helix forms a lid over the active site when the hydrophobic substrate binding site (H-site) is occupied but it is otherwise disordered. Ethacrynic acid appears to bind in a non-productive mode in the absence of the coenzyme glutathione.

OBJECTIVE

To evaluate the relation between serum thyroid-stimulating hormone (TSH) and lipids.

METHODS

Cross-sectional epidemiological study, nested case-control study, and a placebo-controlled double-blind intervention study.

METHODS

In the 5th Tromsø study serum TSH, total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were measured. Subjects with subclinical hypothyroidism (SHT) and a matching control group were re-examined and apolipoprotein A1 (Apo A1) and apolipoprotein B (Apo B) were also measured. Subjects with SHT were included in an intervention study with thyroxine supplementation for 1 year.

RESULTS

A total of 5143 subjects from the 5th Tromsø study were included. A significant and positive correlation between serum TSH levels and serum TC and LDL-C levels were found in both genders. However, in the females this did not reach statistical significance after adjusting for age and BMI. The serum LDL-C were significantly higher and the Apo A1 levels significantly lower in 84 SHT subjects compared with 145 controls, and in the SHT females the TC levels were also significantly elevated. In the intervention study (32 subjects given thyroxine and 32 subjects given placebo), we observed a significant reduction in the Apo B levels after thyroxine medication. In those that at the end of the study had serum TSH levels in the range 0.2-2.0 mIU L(-1), the serum TC and LDL-C levels were also significantly reduced.

CONCLUSIONS

There is a positive association between serum TSH levels and TC and LDL-C levels. These lipid levels are reduced with thyroxine treatment in subjects with SHT.

OBJECTIVE

The apolipoprotein (apo)A-I mimetic peptide 5A is highly specific for ATP-binding cassette transporter (ABC)A1-mediated cholesterol efflux. We investigated whether the 5A peptide shares other beneficial features of apoA-I, such as protection against inflammation and oxidation. Methods- New Zealand white rabbits received an infusion of apoA-I, reconstituted high-density lipoprotein (HDL) containing apoA-I ([A-I]rHDL), or the 5A peptide complexed with phospholipids (1-palmitoyl-2-linoleoyl phosphatidylcholine [PLPC]), before inserting a collar around the carotid artery. Human coronary artery endothelial cells (HCAECs) were incubated with (A-I)rHDL or 5A/PLPC before stimulation with tumor necrosis factor alpha. Results- ApoA-I, (A-I)rHDL, and 5A/PLPC reduced the collar-mediated increase in (1) endothelial expression of cell adhesion molecules vascular cell adhesion molecule-1 and intercellular adhesion molecule-1; (2) production, as well as the expression of the Nox4 catalytic subunits of the NADPH oxidase; and (3) infiltration of circulating neutrophils into the carotid intima-media. In HCAECs, both 5A/PLPC and (A-I)rHDL inhibited tumor necrosis factor-alpha-induced intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression, as well as the nuclear factor kappaB signaling cascade and production. The effects of the 5A/PLPC complex were no longer apparent in HCAECs knocked down for ABCA1.

CONCLUSIONS

Like apoA-I, the 5A peptide inhibits acute inflammation and oxidative stress in rabbit carotids and HCAECs. In vitro, the 5A peptide exerts these beneficial effects through interaction with ABCA1.

The major apoprotein of rat mesenteric lymph chylomicrons has been isolated and characterized and shown to be identical to apoprotein A1 (apo A1) isolated from serum high density lipoprotein (HDL). During intestinal lipid absorption, active synthesis of apo A1 was demonstrated by radioactive amino acid incorporation into lymph chylomicron A1 as well as lymph HDL. Immunofluorescence studies of intestinal epithelium demonstrated a marked increase in apo A1 fluorescence, confirming an active synthesis of this apoprotein during lipid absorption. Quantitative immunoelectrophoretic methods were used to measure apo A1 in lymph and peripheral blood during various conditions designed to estimate the quantitative importance of intestinal apo A1 to the levels of circulating lipoproteins. During lipid feeding there was an increase in lymph apo A1 that was associated with lymph lipoproteins (50%) of density less than 1.006 g/ml whereas in basal lymph most apo A1 (85%) was in the lipoproteins of density greater than 1.006 g/ml. Lipid feeding in animals without lymph fistulas resulted in a significant increase in serum apo A1 levels; biliary diversion, designed to eliminate intestinal lipoproteins of density less than 1.006 g/ml, resulted in a significant decrease in serum apo A1 levels. These studies demonstrate that the intestine actively synthesizes apo A1 and is a significant source of this apoprotein for circulating lipoproteins.

BACKGROUND

Abnormal blood lipid profiles have been associated with cancer. The objective of this study was to investigate the frequency and clinical significance of altered lipid profiles in children with acute lymphoblastic leukemia (ALL), the most common form of malignant disease in this age group.

METHODS

Fasting blood lipid profiles (cholesterol [C], triglycerides [TG], high density lipoprotein [HDL], low density lipoprotein, very low density lipoprotein, apolipoproteins A1 [apo A1] and B, and lipoprotein a [Lp(a)]) were obtained in 24 children with ALL at diagnosis, 16 children during consolidation therapy with L-asparaginase, and 18 children during maintenance therapy without L-asparaginase. For comparison the authors studied lipid profiles in 15 children previously treated for leukemia, 15 healthy control children, and 17 children with other forms of cancer, both localized and widespread.

RESULTS

An altered blood lipid profile was observed at the time of diagnosis of ALL. Statistically significant values included elevated TG (1.82+/-1.23 mmol/L), reduced HDL-C (0.54+/-0.24 mmol/L), and reduced ApoA1 (0.77+/-0.18 g/L) levels. A wide range of Lp(a) levels (0-1990 mg/L) were observed. Significantly reduced HDL-C (0.55+/-0.20 mmol/L) and ApoA1 (0.69+/-0.22 g/L) were observed in children with widespread but not localized solid tumors at diagnosis. C and TG correlated with serum albumin levels. Significant therapy-related changes in lipid profiles were observed in children with ALL during combination therapy with L-asparaginase (extremely elevated TG levels [3.34+/-2.82 mmol/L] and a striking reduction in Lp(a) levels) that were not observed during combination therapy without L-asparaginase or in children during treatment for solid tumors. In this small study there was no relation between these abnormalities and either thromboembolic events or pancreatitis. Blood lipid profiles in children with ALL returned to normal on completion of therapy.

CONCLUSIONS

The lipid abnormalities observed at diagnosis in children with widespread cancer (ALL or solid tumors) may reflect altered nutritional states or altered lipid metabolism. Reduced concentrations of Lp(a) and elevated TG levels suggest L-asparaginase specific alterations and may provide insight into the toxicity associated with this drug.

High density lipoproteins (HDLs) originate as lipid-free or lipid-poor apolipoproteins that acquire most of their lipid in the extracellular space. They accept phospholipids from cells in a process promoted by the ATP binding cassette A1 transporter to form prebeta-migrating discoidal HDL that are efficient acceptors of cholesterol released from cell membranes. The cholesterol in discoidal HDL is esterified by lecithin:cholesterol acyltransferase (LCAT) in a process that converts the prebeta-migrating disc into an alpha-migrating, spherical HDL. Spherical HDL are further remodelled by cholesteryl ester transfer protein (CETP) that transfers cholesteryl esters from HDL to other lipoproteins and by hepatic lipase that hydrolyses HDL triglyceride in processes that reduce HDL size and lead to the dissociation of prebeta-migrating, lipid-poor apolipoprotein (apo)A-I from the particle. Prebeta-migrating, lipid-poor apoA-I is also generated as a product of the remodelling of HDL by phospholipid transfer protein. Thus, apoA-I cycles between lipid-poor and lipid associated forms as part of a highly dynamic metabolism of HDL. The other main HDL apolipoprotein, apoA-II is incorporated into apoA-I-containing particles in a process of particle fusion mediated by LCAT. Extracellular assembly and remodelling of HDL not only plays a major role in HDL regulation but also provides potential targets for therapeutic intervention. One example of this is the development of inhibitors of CETP.

In addition to its recognized role in bone health, recent studies point to vitamin D functions in other tissues, including the pancreas. We tested the association between the vitamin D status and glucose and lipid homeostasis in a school-based, cross-sectional survey of a representative sample of youth. We measured fasting plasma insulin, glucose, total cholesterol (TC), triglycerides (TG), HDL cholesterol (HDL-C) apolipoproteins (apo) A1 and B, and 25-hydroxyvitamin D [25(OH)D] concentrations in 878 boys and 867 girls. The 25(OH)D concentrations (mean +/- SD) were 45.9 +/- 12.2 nmol/L in boys and 45.9 +/- 13.0 nmol/L in girls. More than 93% of youth had suboptimal (<75 nmol/L) vitamin D concentrations. There was a slightly lower glycemia, -0.5% (P = 0.015) and -0.4% (P = 0.025), and homeostasis model assessment of insulin resistance, -2.8% (P = 0.043) and -2.3% (P = 0.050), for each 10-nmol/L increase in plasma 25(OH)D in boys and girls, respectively. In contrast, in girls only there were modest increases in plasma TC (1.1%; P = 0.017), TG (2.9%; P = 0.004), apoA1 (1.2%; P < 0.001), and apoB (1.5%; P = 0.023). We observed no association between the presence of at least 2 cardiometabolic risk factors (borderline/unfavorable fasting concentrations of apoB, HDL-C, TG, insulin, and glucose) and 25(OH)D concentrations in either boys or girls. Although the observed associations between 25(OH)D concentrations and fasting glucose, and variables of lipid metabolism are modest, they may have a potential long-term impact on cardiovascular risk.

OBJECTIVE

Prior trials with monoclonal antibodies to proprotein convertase subtilizin/kexin type 9 (PCSK9) reported robust low density lipoprotein cholesterol (LDL-C) reductions. However, the ability to detect potentially beneficial changes in other lipoproteins such as lipoprotein (a), triglycerides, high-density lipoprotein cholesterol (HDL-C), and apolipoprotein (Apo) A1, and adverse events (AEs) was limited by sample sizes of individual trials. We report a pooled analysis from four phase 2 studies of evolocumab (AMG 145), a monoclonal antibody to PCSK9.

RESULTS

The trials randomized 1359 patients to various doses of subcutaneous evolocumab every 2 weeks (Q2W) or 4 weeks (Q4W), placebo, or ezetimibe for 12 weeks; 1252 patients contributed to efficacy and 1314, to safety analyses. Mean percentage (95% CI) reductions in LDL-C vs. placebo ranged from 40.2% (44.6%, 35.8%) to 59.3% (63.7%, 54.8%) among the evolocumab groups (all P < 0.001). Statistically significant reductions in apolipoprotein B (Apo B), non-high-density lipoprotein cholesterol (non-HDL-C), triglycerides and lipoprotein (a) [Lp(a)], and increases in HDL-C were also observed. Adverse events (AEs) and serious AEs with evolocumab were reported in 56.8 and 2.0% of patients, compared with 49.2% and 1.2% with placebo. Adjudicated cardiac and cerebrovascular events were reported in 0.3 and 0% in the placebo and 0.9 and 0.3% in the evolocumab arms, respectively.

CONCLUSIONS

In addition to LDL-C reduction, evolocumab, dosed either Q2W or Q4W, demonstrated significant and favourable changes in other atherogenic and anti-atherogenic lipoproteins, and was well tolerated over the 12-week treatment period.

Previous studies have demonstrated that inflammatory cytokines such as interleukin-1beta (IL-1beta) promote lipid accumulation in human mesangial cells (HMC) by dysregulating the expression of lipoprotein receptors. Intracellular lipid accumulation is governed by both influx and efflux; therefore, the effect of IL-1beta on the efflux of lipid from HMC was investigated. IL-1beta was shown to inhibit (3)H-cholesterol efflux from HMC and increase total intracellular cholesterol concentration, probably as a result of reduced expression of the adenosine triphosphate (ATP) binding cassette A1 (ABCA1), a transporter protein involved in apolipoprotein-A1 (apo-A1)-mediated lipid efflux. To ascertain the molecular mechanisms involved, expression of peroxisome proliferator-activated receptors (PPAR) and liver X receptoralpha (LXRalpha) were examined. IL-1beta (5 ng/ml) reduced PPARalpha, PPARgamma, and LXRalpha mRNA expression. Activation of PPARgamma with the agonist prostaglandin J2 (10 micro M) and of PPARalpha with either bezafibrate (100 micro M) or Wy14643 (100 micro M) both increased LXRalpha and ABCA1 gene expression also and enhanced apoA1-mediated cholesterol efflux from lipid-loaded cells, even in the presence of IL-1beta. A natural ligand of LXRalpha, 25-hydroxycholesterol (25-OHC), had similar effects; when used together with PPAR agonists, an additive effect was observed, indicating co-operation between PPAR and LXRalpha in regulating ABCA1 gene expression. This was supported by the observation that overexpression of either PPARalpha or PPARgamma by transfection enhanced LXRalpha and ABCA1 gene induction by PPAR agonists. Taken together with previous data, it appears that, in addition to increasing lipid uptake, inflammatory cytokines promote intracellular lipid accumulation by inhibiting cholesterol efflux through the PPAR-LXRalpha-ABCA1 pathway. These results suggest potential mechanisms whereby inflammation may exacerbate lipid-mediated cellular injury in the glomerulus and in other tissues and indicate that PPAR agonists may have a protective effect.

OBJECTIVE

To evaluate the effects of infliximab and corticosteroid treatment on the lipid profile in patients with active rheumatoid arthritis (RA).

METHODS

Infliximab infusions were given at weeks 0, 2, 6 and then every 8 weeks. Before each infusion, disease activity parameters (Disease Activity Index 28-Joint Score (DAS28)) C reactive protein (CRP) and lipid levels (total cholesterol, high-density lipoprotein (HDL)-cholesterol, triglycerides, apolipoprotein A1 (apo A1) and apolipoprotein B) were measured in 80 consecutive patients with RA, who completed the study period of 48 weeks. Longitudinal analyses were used to investigate (1) the course of lipid levels over a period of time and (2) the relationship between lipids, prednisone dose and disease activity.

RESULTS

Infliximab treatment causes a significant reduction in disease activity and a concomitant decrease in prednisone dose. Although they initially improved significantly, all lipid levels had returned to baseline levels after 48 weeks, except for apo A1. Longitudinal analyses revealed significant yet opposite associations between lipid levels and disease activity and between lipid levels and prednisone dose. DAS28 improvement by 1 point was associated with an increase of 0.016 mmol/l (0.618 mg/dl) total cholesterol and 0.045 mmol/l (1.737 mg/dl) HDL-cholesterol. Reduction of 10 mg prednisone was associated with a decrease of 0.04 mmol/l (1.544 mg/dl) total cholesterol and 0.16 mmol/l (6.177 mg/dl) HDL-cholesterol.

CONCLUSIONS

Overall, no changes in serum lipid levels were observed after 48 weeks of infliximab treatment. The initial beneficial effects of infliximab on the lipid profile, by means of a reduction of disease activity, are attenuated by a concomitant decrease in prednisone dose.

OBJECTIVE

To assess the effect of lipids and lipoproteins on longitudinal cognitive performance and cognitive health in late life and to consider moderating factors such as age and sex that may clarify conflicting prior evidence.

METHODS

Prospective cohort study.

METHODS

A 16-year longitudinal study of health and cognitive aging.

METHODS

Eight hundred nineteen adults from the Swedish Adoption Twin Study of Aging aged 50 and older at first cognitive testing, including 21 twin pairs discordant for dementia.

METHODS

Up to five occasions of cognitive measurements encompassing verbal, spatial, memory, and perceptual speed domains across a 16-year span; baseline serum lipids and lipoproteins including high-density lipoprotein cholesterol (HDL-C), apolipoprotein (apo)A1, apoB, total serum cholesterol, and triglycerides.

RESULTS

The effect of lipids on cognitive change was most evident before age 65. In women, higher HDL-C and lower apoB and triglycerides predicted better maintenance of cognitive abilities, particularly verbal ability and perceptual speed, than age. Lipid values were less predictive of cognitive trajectories in men and, where observed, were in the contrary direction (i.e., higher total cholesterol and apoB values predicted better perceptual speed performance though faster rates of decline). In twin pairs discordant for dementia, higher total cholesterol and apoB levels were observed in the twin who subsequently developed dementia.

CONCLUSIONS

High lipid levels may constitute a more important risk factor for cognitive health before age 65 than after. Findings for women are consistent with clinical recommendations, whereas for men, the findings correspond with earlier age-associated shifts in lipid profiles and the importance of lipid homeostasis to cognitive health.

OBJECTIVE

Our purpose is to review recent publications in the area of marked human HDL deficiency, HDL particles, coronary heart disease (CHD), amyloidosis, the immune response, and kidney disease.

RESULTS

Lack of detectable plasma apolipoprotein (apo) A-I can be due to DNA deletions, rearrangements, or nonsense or frameshift mutations within the APOA1 gene resulting in a lack of apoA-I secretion. Such patients have marked HDL deficiency, normal levels of triglycerides and LDL cholesterol, and can have xanthomas and premature CHD. ApoA-I variants with amino acid substitutions, especially in the region of amino acid residues 50-93 and 170-178, have been associated with amyloidosis. Patients with homozygous Tangier disease have defective cellular cholesterol efflux due to mutations in the adenosine triphosphate-binding cassette transporter A1, detectable plasma apoA-I levels and prebeta-1 HDL in their plasma. They have decreased LDL cholesterol levels and can develop neuropathy and premature CHD. Patients with lecithin: cholesterol acyltransferase deficiency have both prebeta-1 and alpha-4 HDL present in their plasma and develop corneal opacities, anemia, proteinuria, and kidney failure.

CONCLUSIONS

Patients with marked HDL deficiency can have great differences in their clinical phenotype depending on the underlying defect.

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of several autoantibodies. Among the multiple factors involved in SLE development, apoptotic defects and impaired clearance of cellular debris have gained considerable interest, as they contribute to autoantigen overload. Several molecules of the innate immunity, also participate in the removal of damaged and apoptotic cells. Among them are C1q, C-reactive protein (CRP), serum amyloid P protein (SAP), mannose-binding lectin (MBL), and apolipoprotein A1 (APO A1). To evaluate the prevalence of autoantibodies against CRP, SAP, MBL, APO A1, and C1q among SLE patients, and their relationship with disease activity, a total of 150 SLE patients were screened for the presence of elevated antibody titers against C1q, CRP, SAP, MBL, and APO A1, utilizing the enzyme-linked immunosorbent assay (ELISA) method. Disease activity was assessed using the ECLAM or SLEDAI scores. The study population comprised two groups of patients: 100 patients with quiescent disease (median ECLAM score 2) comprised the first group, and 50 patients with active disease (median SLEDAI score 16) comprised group 2. Elevated titers of anti-CRP antibodies were significantly elevated only in group 1 (10% versus 4% of controls). Antibodies against SAP were evaluated only among patients in group 1, and were found at a significant high prevalence (20%). Elevated titers of anti-MBL antibodies were significantly elevated only in group 1 (15% versus 3.6%); and antibodies directed against APO A1 were significantly elevated in 21% of group 1, and 50% of group 2 patients. Elevated titers of anti-C1q were evaluated only in group 2, and were found at a significant prevalence of 66%. Significant correlation with disease activity was found only for anti-APO A1 antibodies, and only in group 1. Several patients harbored more than one of the autoantibodies tested. In patients with SLE, autoantibodies directed against protective molecules, that is, acute-phase proteins involved in the disposal of cellular and nuclear debris, can be detected. These autoantibodies may play a pathogenic role in the development or perpetuation of autoimmunity in SLE.

Current lipid-altering agents that lower low density lipoprotein cholesterol (LDL-C) primarily through increased hepatic LDL receptor activity include statins, bile acid sequestrants/resins and cholesterol absorption inhibitors such as ezetimibe, plant stanols/sterols, polyphenols, as well as nutraceuticals such as oat bran, psyllium and soy proteins; those currently in development include newer statins, phytostanol analogues, squalene synthase inhibitors, bile acid transport inhibitors and SREBP cleavage-activating protein (SCAP) activating ligands. Other current agents that affect lipid metabolism include nicotinic acid (niacin), acipimox, high-dose fish oils, antioxidants and policosanol, whilst those in development include microsomal triglyceride transfer protein (MTP) inhibitors, acylcoenzyme A: cholesterol acyltransferase (ACAT) inhibitors, gemcabene, lifibrol, pantothenic acid analogues, nicotinic acid-receptor agonists, anti-inflammatory agents (such as Lp-PLA(2) antagonists and AGI1067) and functional oils. Current agents that affect nuclear receptors include PPAR-alpha and -gamma agonists, while in development are newer PPAR-alpha, -gamma and -delta agonists, as well as dual PPAR-alpha/gamma and 'pan' PPAR-alpha/gamma/delta agonists. Liver X receptor (LXR), farnesoid X receptor (FXR) and sterol-regulatory element binding protein (SREBP) are also nuclear receptor targets of investigational agents. Agents in development also may affect high density lipoprotein cholesterol (HDL-C) blood levels or flux and include cholesteryl ester transfer protein (CETP) inhibitors (such as torcetrapib), CETP vaccines, various HDL 'therapies' and upregulators of ATP-binding cassette transporter (ABC) A1, lecithin cholesterol acyltransferase (LCAT) and scavenger receptor class B Type 1 (SRB1), as well as synthetic apolipoprotein (Apo)E-related peptides. Fixed-dose combination lipid-altering drugs are currently available such as extended-release niacin/lovastatin, whilst atorvastatin/amlodipine, ezetimibe/simvastatin, atorvastatin/CETP inhibitor, statin/PPAR agonist, extended-release niacin/simvastatin and pravastatin/aspirin are under development. Finally, current and future lipid-altering drugs may include anti-obesity agents which could favourably affect lipid levels.

Smooth muscle cells (SMCs) are the main cell type in intimal thickenings and some stages of human atherosclerosis. Like monocyte-derived macrophages, SMCs accumulate excess lipids and contribute to the total intimal foam cell population. In contrast, apolipoprotein (Apo)E-deficient and LDL receptor-deficient mice develop atherosclerotic lesions that are macrophage- as opposed to SMC-rich. The lesser contribution of SMCs to lesion development in these mouse models has distracted attention away from the importance of SMC cholesterol homeostasis in the artery wall. Intimal SMCs accumulate excess amounts of cholesteryl esters when compared with medial layer SMCs, possibly explained by reduced ATP-binding cassette transporter A1 expression and ApoA-I binding to intimal-type SMCs. The aim of this review is to compare the relative contribution of monocyte-derived macrophages and SMCs to human vs. mouse atherosclerosis, and describe what is known about lipid uptake and removal mechanisms contributing to arterial macrophage and SMC foam cell formation. An increased understanding of the contribution of these cell types to lesion development will help to delineate their relative importance in atherogenesis and as potential therapeutic targets.

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.

Apoptotic defects and impaired clearance of cellular debris are considered key events in the development of autoimmunity, as they can contribute to autoantigen overload, and may initiate an autoimmune response. The pentraxins are a group of highly conserved proteins including the short pentraxins, C-reactive protein (CRP) and serum amyloid-P (SAP), and the long pentraxin-3 (PTX3), which are all involved in innate immunity and in acute-phase responses. Mannan-binding lectin (MBL) is an activator of the complement system, and Apolipoprotein A-1 (Apo A-1) is pivotal in the cholesterol homeostasis and has anti-inflammatory properties. In addition to their role in innate immunity and inflammation, each of these five proteins participates in the removal of damaged and apoptotic cells. In this review, we discuss the clinical significance of different levels of these proteins, their role in the induction or protection from autoimmunity, and the presence of specific autoantibodies against them in the different autoimmune diseases.

The role of low-density lipoprotein (LDL) cholesterol in coronary artery disease (CAD) and the impact of therapeutic agents on LDL cholesterol are well established. Less is known about the role of high-density lipoprotein (HDL) cholesterol and even less about the role of the different HDL subspecies in CAD. HDL particles vary in size and density, mainly because of differences in the number of apolipoprotein (apo) particles and the amount of cholesterol ester in the core of HDL. Apo A-I is essential and, together with lipid, sufficient for the formation of HDL particles. Apo A-I-containing HDL particles play a primary role in cholesterol efflux from membranes, at least in part through interactions with the adenosine triphosphate-binding cassette transporter A1 (ABCA1). Patients with Tangier disease have mutations in the gene encoding ABCA1, which result in functionally impaired protein, a marked deficiency in HDL cholesterol, and a high risk of premature CAD. Our studies of apo A-I-containing HDL subpopulations in various patient populations reveal that patients homozygous for Tangier disease have only the pre-beta(1) HDL subspecies. Tangier heterozygotes are severely depleted in the larger alpha- and pre-alpha-mobility subspecies. Patients with low HDL cholesterol levels and those with CAD also show deficiencies in the alpha(1) and pre-alpha(1-3) HDL subspecies. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) increase the levels of the large alpha(1) and pre-alpha(1) subpopulations and decrease the level of the small alpha(3) subpopulation. Thus, atorvastatin, for example, significantly moves the distribution of HDL particles toward normal, followed by simvastatin, pravastatin, and lovastatin in decreasing order of efficiency. A new statin, rosuvastatin, produces greater increases in HDL cholesterol than atorvastatin, but its effect on HDL particle distribution is yet to be determined.

We have studied the frequency of DNA polymorphisms in and around the apolipoprotein A-1 (Apo-A1) and apolipoprotein CIII (Apo-CIII) gene loci in 53 persons of Caucasian descent with genetic hyperlipidemias. Three restriction-fragment-length polymorphisms (RFLPs) have previously been located 5' and 3' to the Apo-A1 gene and in the Apo-CIII gene and were detected after digestion with XmnI, PstI, and SstI, respectively, and hybridization with a 2.2-kb fragment of the Apo-A1 gene. These RFLPs are in linkage equilibrium. The rare variant sites for XmnI (X2) and SstI (S2) were more frequent in familial combined hyperlipidemia (FCH) than in controls and persons with other genetic hyperlipidemias. When considered as a haplotype, this difference was significant (P less than .03). The findings in this study suggest that the previously reported association between S2 and hypertriglyceridemia may be accounted for, in part, by inclusion of numerous patients with FCH. Our data provide further evidence that these RFLPs around and within the Apo-A1/Apo-CIII genes do not participate in unmasking clinical expression in persons with familial dysbetalipoproteinemia.

Apolipoprotein A1 is the major polypeptide of the human plasma high density lipoprotein (HDL). The structure and function of the apo A1 gene are of interest because of the inverse correlation shown between HDL levels and coronary heart disease. We have determined the nucleotide sequence of the apo A1 gene previously isolated. Its coding sequence is interrupted by two introns of 185 and 588 base pairs. As there may be one or more introns in the 5' non coding region, the 5' end of the gene could not be precisely located. The human apo A1 has an unusual propeptide segment very similar to its rat counterpart. The data reported here provide an essential basis for future studies of structural and functional alleles of the apo A1 gene.

The ability of mammalian cytidine deaminases encoded by the APOBEC3 (A3) genes to restrict a broad number of endogenous retroelements and exogenous retroviruses, including murine leukemia virus and human immunodeficiency virus (HIV)-1, is now well established. The RNA editing family member apolipoprotein B (apo B)-editing catalytic subunit 1 (APOBEC1; A1) from a variety of mammalian species, a protein involved in lipid transport and which mediates C-U deamination of mRNA for apo B, has also been shown to modify a range of exogenous retroviruses, but its activity against endogenous retroelements remains unclear. Here, we show in cell culture-based retrotransposition assays that A1 family proteins from multiple mammalian species can also reduce the mobility and infectivity potential of LINE-1 (long interspersed nucleotide sequence-1, L1) and long-terminal repeats (LTRs) retrotransposons (or endogenous retroviruses), such as murine intracisternal A-particle (IAP) and MusD sequences. The anti-L1 activity of A1 was mainly mediated by a deamination-independent mechanism, and was not affected by subcellular localization of the proteins. In contrast, the inhibition of LTR-retrotransposons appeared to require the deaminase activity of A1 proteins. Thus, the AID/APOBEC family proteins including A1s employ multiple mechanisms to regulate the mobility of autonomous retrotransposons in several mammalian species.