ASGR1 deficiency diverts lipids toward adipose tissue but results in liver damage during obesity

BACKGROUND

Asialoglycoprotein receptor 1 (ASGR1), primarily expressed on hepatocytes, promotes the clearance and the degradation of glycoproteins, including lipoproteins, from the circulation. In humans, loss-of-function variants of ASGR1 are associated with a favorable metabolic profile and reduced incidence of cardiovascular diseases. The molecular mechanisms by which ASGR1 could affect the onset of metabolic syndrome and obesity are unclear. Therefore, here we investigated the contribution of ASGR1 in the development of metabolic syndrome and obesity.

METHODS

ASGR1 deficient mice (ASGR1-/-) were subjected to a high-fat diet (45% Kcal from fat) for 20 weeks. The systemic metabolic profile, hepatic and visceral adipose tissue were characterized for metabolic and structural alterations, as well as for immune cells infiltration.

RESULTS

ASGR1-/- mice present a hypertrophic adipose tissue with 41% increase in fat accumulation in visceral adipose tissue (VAT), alongside with alteration in lipid metabolic pathways. Intriguingly, ASGR1-/- mice exhibit a comparable response to an acute glucose and insulin challenge in circulation, coupled with notably decreased in circulating cholesterol levels. Although the liver of ASGR1-/- have similar lipid accumulation to the WT mice, they present elevated levels of liver inflammation and a decrease in mitochondrial function.

CONCLUSION

ASGR1 deficiency impacts energetic homeostasis during obesity leading to improved plasma lipid levels but increased VAT lipid accumulation and liver damage.

A Drosophila model targets Eiger/TNFα to alleviate obesity-related insulin resistance and macrophage infiltration

Obesity is associated with various metabolic disorders, such as insulin resistance and adipose tissue inflammation (ATM), characterized by macrophage infiltration into adipose cells. This study presents a new Drosophila model to investigate the mechanisms underlying these obesity-related pathologies. We employed genetic manipulation to reduce ecdysone levels to prolong the larval stage. These animals are hyperphagic and exhibit features resembling obesity in mammals, including increased lipid storage, adipocyte hypertrophy and high circulating glucose levels. Moreover, we observed significant infiltration of immune cells (hemocytes) into the fat bodies, accompanied by insulin resistance. We found that attenuation of Eiger/TNFα signaling reduced ATM and improved insulin sensitivity. Furthermore, using metformin and the antioxidants anthocyanins, we ameliorated both phenotypes. Our data highlight evolutionarily conserved mechanisms allowing the development of Drosophila models for discovering therapeutic pathways in adipose tissue immune cell infiltration and insulin resistance. Our model can also provide a platform to perform genetic screens or test the efficacy of therapeutic interventions for diseases such as obesity, type 2 diabetes and non-alcoholic fatty liver disease.

Proteomics Studies Suggest That Nitric Oxide Donor Furoxans Inhibit In Vitro Vascular Smooth Muscle Cell Proliferation by Nitric Oxide-Independent Mechanisms

Physiologically, smooth muscle cells (SMC) and nitric oxide (NO) produced by endothelial cells strictly cooperate to maintain vasal homeostasis. In atherosclerosis, where this equilibrium is altered, molecules providing exogenous NO and able to inhibit SMC proliferation may represent valuable antiatherosclerotic agents. Searching for dual antiproliferative and NO-donor molecules, we found that furoxans significantly decreased SMC proliferation in vitro, albeit with different potencies. We therefore assessed whether this property is dependent on their thiol-induced ring opening. Indeed, while furazans (analogues unable to release NO) are not effective, furoxans' inhibitory potency parallels with the electron-attractor capacity of the group in 3 of the ring, making this effect tunable. To demonstrate whether their specific block on G1-S phase could be NO-dependent, we supplemented SMCs with furoxans and inhibitors of GMP- and/or of the polyamine pathway, which regulate NO-induced SMC proliferation, but they failed in preventing the antiproliferative effect. To find the real mechanism of this property, our proteomics studies revealed that eleven cellular proteins (with SUMO1 being central) and networks involved in cell homeostasis/proliferation are modulated by furoxans, probably by interaction with adducts generated after degradation. Altogether, thanks to their dual effect and pharmacological flexibility, furoxans may be evaluated in the future as antiatherosclerotic molecules.

Targeting of the Lipid Metabolism Impairs Resistance to BRAF Kinase Inhibitor in Melanoma

Drug resistance limits the achievement of persistent cures for the treatment of melanoma, in spite of the efficacy of the available drugs. The aim of the present study was to explore the involvement of lipid metabolism in melanoma resistance and assess the effects of its targeting in cellular models of melanoma with acquired resistance to the BRAF-inhibitor PLX4032/Vemurafenib. Since transcriptional profiles pointed to decreased cholesterol and fatty acids synthesis in resistant cells as compared to their parental counterparts, we examined lipid composition profiles of resistant cells, studied cell growth dependence on extracellular lipids, assessed the modulation of enzymes controlling the main nodes in lipid biosynthesis, and evaluated the effects of targeting Acetyl-CoA Acetyltransferase 2 (ACAT2), the first enzyme in the cholesterol synthesis pathway, and Acyl-CoA Cholesterol Acyl Transferase (ACAT/SOAT), which catalyzes the intracellular esterification of cholesterol and the formation of cholesteryl esters. We found a different lipid composition in the resistant cells, which displayed reduced saturated fatty acids (SFA), increased monounsaturated (MUFA) and polyunsaturated (PUFA), and reduced cholesteryl esters (CE) and triglycerides (TG), along with modulated expression of enzymes regulating biosynthetic nodes of the lipid metabolism. The effect of tackling lipid metabolism pathways in resistant cells was evidenced by lipid starvation, which reduced cell growth, increased sensitivity to the BRAF-inhibitor PLX4032, and induced the expression of enzymes involved in fatty acid and cholesterol metabolism. Molecular targeting of ACAT2 or pharmacological inhibition of SOAT by avasimibe showed antiproliferative effects in melanoma cell lines and a synergistic drug interaction with PLX4032, an effect associated to increased ferroptosis. Overall, our findings reveal that lipid metabolism affects melanoma sensitivity to BRAF inhibitors and that extracellular lipid availability may influence tumor cell response to treatment, a relevant finding in the frame of personalized therapy. In addition, our results indicate new candidate targets for drug combination treatments.

Artichoke and bergamot extracts: a new opportunity for the management of dyslipidemia and related risk factors

The relationship between low LDL-C (cholesterol associated with low-density lipoprotein) and a lower relative risk of developing cardiovascular disease (CVD) has been widely demonstrated. Although from a pharmacological point of view, statins, ezetimibe and PCSK inhibitors, alone or in combination are the front and center of the therapeutic approaches for reducing LDL-C and its CV consequences, in recent years nutraceuticals and functional foods have increasingly been considered as a valid support in the reduction of LDL-C, especially in patients with mild/moderate hyperlipidemia - therefore not requiring pharmacological treatment - or in patients intolerant to statins or other drugs. An approach also shared by the European Atherosclerosis Society (EAS). Of the various active ingredients with hypolipidemic properties, we include the artichoke (Cynara cardunculus, Cynara scolymus) and the bergamot (Citrus bergamia) which, thanks essentially to the significant presence of polyphenols in their extracts, can exert this action associated with a number of other complementary inflammation and oxidation benefits. In light of these evidence, this review aimed to describe the effects of artichoke and bergamot in modifying the lipid and inflammatory parameters described in in vitro, in vivo and clinical studies. The available data support the use of standardized compositions of artichoke and bergamot extracts, alone or in combination, in the treatment of mild to moderate dyslipidemia, in patients suffering from metabolic syndrome, hepatic steatosis, or intolerant to common hypolipidemic treatments.

Oxidized LDL-dependent pathway as new pathogenic trigger in arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is hallmarked by ventricular fibro-adipogenic alterations, contributing to cardiac dysfunctions and arrhythmias. Although genetically determined (e.g., PKP2 mutations), ACM phenotypes are highly variable. More data on phenotype modulators, clinical prognosticators, and etiological therapies are awaited. We hypothesized that oxidized low-density lipoprotein (oxLDL)-dependent activation of PPARγ, a recognized effector of ACM adipogenesis, contributes to disease pathogenesis. ACM patients showing high plasma concentration of oxLDL display severe clinical phenotypes in terms of fat infiltration, ventricular dysfunction, and major arrhythmic event risk. In ACM patient-derived cardiac cells, we demonstrated that oxLDLs are major cofactors of adipogenesis. Mechanistically, the increased lipid accumulation is mediated by oxLDL cell internalization through CD36, ultimately resulting in PPARγ upregulation. By boosting oxLDL in a Pkp2 heterozygous knock-out mice through high-fat diet feeding, we confirmed in vivo the oxidized lipid dependency of cardiac adipogenesis and right ventricle systolic impairment, which are counteracted by atorvastatin treatment. The modulatory role of oxidized lipids on ACM adipogenesis, demonstrated at cellular, mouse, and patient levels, represents a novel risk stratification tool and a target for ACM pharmacological strategies.

Recombinant LCAT (Lecithin:Cholesterol Acyltransferase) Rescues Defective HDL (High-Density Lipoprotein)-Mediated Endothelial Protection in Acute Coronary Syndrome

Objective- Aim of this study was to evaluate changes in LCAT (lecithin:cholesterol acyltransferase) concentration and activity in patients with an acute coronary syndrome, to investigate if these changes are related to the compromised capacity of HDL (high-density lipoprotein) to promote endothelial nitric oxide (NO) production, and to assess if rhLCAT (recombinant human LCAT) can rescue the defective vasoprotective HDL function. Approach and Results- Thirty ST-segment-elevation myocardial infarction (STEMI) patients were enrolled, and plasma was collected at hospital admission, 48 and 72 hours thereafter, at hospital discharge, and at 30-day follow-up. Plasma LCAT concentration and activity were measured and related to the capacity of HDL to promote NO production in cultured endothelial cells. In vitro studies were performed in which STEMI patients' plasma was added with rhLCAT and HDL vasoprotective activity assessed by measuring NO production in endothelial cells. The plasma concentration of the LCAT enzyme significantly decreases during STEMI with a parallel significant reduction in LCAT activity. HDL isolated from STEMI patients progressively lose the capacity to promote NO production by endothelial cells, and the reduction is related to decreased LCAT concentration. In vitro incubation of STEMI patients' plasma with rhLCAT restores HDL ability to promote endothelial NO production, possibly related to significant modification in HDL phospholipid classes. Conclusions- Impairment of cholesterol esterification may be a major factor in the HDL dysfunction observed during acute coronary syndrome. rhLCAT is able to restore HDL-mediated NO production in vitro, suggesting LCAT as potential therapeutic target for restoring HDL functionality in acute coronary syndrome.

2288Oxidized LDL/CD36/PPARg circuitry is a trigger of adipogenesis in arrhythmogenic cardiomyopathy

Background

Arrhythmogenic Cardiomyopathy (ACM) is a genetic condition hallmarked by ventricular fibro-fatty replacement and arrhythmias. Cardiac mesenchymal stromal cells (C-MSC) differentiate into adipocytes in ACM hearts, through the activation of PPARγ, caused by ACM mutations (e.g. PKP2). The clinical phenotype of ACM is variable for poorly understood reasons. The only recognized cofactor is physical exercise, which is known to increases oxidative stress. An accepted marker of exercise-induced oxidative stress is 13HODE, a component of oxLDL and direct activator of PPARγ. In macrophages, during foam cell formation, 13HODE creates a feed-forward loop increasing both PPARγ and the oxLDL receptor CD36, resulting in fat accumulation.

Purpose

To investigate oxLDL effects on ACM adipogenesis and to dissect the involved pathways.

Methods

We analyzed plasmas (n=42) and ventricular tissues (n=4) of ACM patients and matched healthy controls (HC). For in vitro experiments, ACM and HC C-MSC (n=10) have been used, while in vivo experiments have been conducted in heterozygous Pkp2 knock-out mice (Pkp2+/−; n=10).

Results

We observed higher plasma oxLDL in ACM patients compared to HC (ACM 246.70±55.89 vs HC 102.5±17.95ng/ml; p=0.019). oxLDL levels also discriminate between ACM patients with overt phenotype and their unaffected relatives carriers of the same causative mutations (p=0.03). We observed higher oxidative stress (MDA intensity 40.87±11.76 fold; p=0.015) and CD36 levels (14.72±2.10 fold; p=0.0007) in ACM ventricular tissue, compared to HC.

In basal conditions, ACM C-MSC showed greater oxidative stress (MDA intensity 8.83±2.78 fold p=0.017) and higher expression of PPARγ (1.47±0.14 fold; p=0.009) compared to HC C-MSC. The adipogenic stimulation led to a parallel increase of CD36 and lipid accumulation, mainly in ACM C-MSC (slopes statistically different p=0.016). OxLDL and 13HODE administration increased lipid accumulation in ACM C-MSC (ORO staining ACM vs ACM+oxLDL p=0.01; ACM vs ACM+13HODE p=0.014). On the contrary, the antioxidant N-Acetylcysteine (NAC) prevented lipid accumulation in ACM C-MSC (ORO staining ACM+13HODE vs ACM+13HODE+NAC p=0.0009). Through CD36 silencing of ACM C-MSC, we obtained a significantly lower lipid accumulation than non-silenced cells (ORO staining 0.35±0.10 fold; p=0.003).

Pkp2+/− mice do not spontaneously accumulate adipocytes in the heart, however Pkp2+/− C-MSC are more prone to lipid accumulation in vitro than WT cells (p=0.007). Accordingly, mice have low plasma oxLDL and cardiac oxidative stress. By increasing plasma cholesterol and oxidative stress through high fat diet, we observed fibro-fatty substitution in Pkp2+/− hearts (p=0.046).

Figure 1

Conclusions

These findings reveal a modulatory role of oxidized lipids in ACM adipogenesis at a cellular, tissue and clinical level, enlightening novel targets for pharmacological strategies to prevent adipogenic substitution and consequent ACM clinical phenotypes.

Acknowledgement/Funding

Telethon Foundation; Italian Ministry of Health

Abstract 035: Recombinant LCAT Restores Defective HDL mediated Endothelial Protection in Acute Coronary Syndrome

Recent evidence suggests that the vasoprotective effects of HDL are impaired in patients during an acute coronary syndrome (ACS). In particular, HDL from ACS patients are defective in promoting nitric oxide (NO) release from cultured endothelial cells (ECs). Lecithin:cholesterol acyltransferase (LCAT) plays a key role in HDL maturation and remodeling, and it is the enzyme responsible for cholesterol esterification in plasma. Very few studies have suggested that LCAT activity is decreased during an acute myocardial infarction, but the possible link between LCAT mass/activity and the HDL dysfunction observed in ACS has never been tested. To test this hypothesis, plasma from 30 STEMI patients was collected at admission, 48 and 72 hours and 30 days after event. LCAT concentration and activity significantly decreased 48 hours after event (-0.49±0.11 μg/ml, P<0.001, and -3.15±1.05 nmol/ml/h, P=0.006) and remained reduced at 72 hours. HDL isolated from STEMI patients lose the capacity to promote NO production in ECs (-0.13 ± 0.06 fold, P=0.04) and the reduction is significantly correlated to decreased LCAT activity (R= 0.52, P=0.003). In vitro studies were performed in which STEMI patients’ plasma was added with rhLCAT and HDL vasoprotective activity assessed by measuring NO production in ECs. In vitro incubation of STEMI patients’ plasma with rhLCAT remodels phospholipids and protein content in HDL and restores HDL ability to promote endothelial NO production (+25%, P=0.03). Impairment of cholesterol esterification may be a major factor in the HDL dysfunction observed during ACS. rhLCAT is able to restore HDL-mediated NO production in vitro, suggesting LCAT as potential therapeutic target for restoring HDL functionality in ACS.

The dataset describes: Phenotypic changes induced by cholesterol loading in smooth muscle cells isolated from the aortae of C57BL/6 mice

The data presented in this article is related to the research article entitled "ABCA1 and HDL₃ are Required to Modulate Smooth Muscle Cells Phenotypic Switch after Cholesterol Loading" (Castiglioni et al., 2017) [1]. This data describes the characterization of the phenotypic changes induced by cholesterol loading in smooth muscle cells (SMCs) isolated from the aortae of C57BL/6 mice. Upon cholesterol loading, there is a significant and concentration-dependent decrease in the expression of Acta2 and a parallel increase in Mac-2, and ATP binding cassette (ABC) transporters Abca1 and Abcg1. Cholesterol incubation causes the transformation of SMCs into foam cells with a 3-fold increase in cellular total cholesterol content and a 2.5-fold stimulation of the activity of the esterifying enzyme Acyl-CoA:cholesterol acyltransferase (ACAT). The addition of the same amount of cholesterol, either dissolved in ethanol or as lipoprotein cholesterol (AcLDL or native LDL) only slightly induces the activity of the enzyme ACAT, and does not cause the accumulation of lipid droplets into SMCs. We describe also the knock down of ABCA1 expression by siRNA treatment in mouse smooth muscle cells.

ABCA1 and HDL3 are required to modulate smooth muscle cells phenotypic switch after cholesterol loading

BACKGROUND AND AIMS

Cholesterol-loaded smooth muscle cells (SMCs) modify their phenotypic behavior becoming foam cells. To characterize the role of ABCA1 and HDL3 in this process, we evaluated HDL3 effects on cholesterol-induced phenotypic changes in SMCs expressing or not ABCA1.

METHODS

SMCs, isolated from the aortae of wild-type (WT) and Abca1 knock-out (KO) mice, were cholesterol-loaded using a "water-soluble cholesterol''.

RESULTS

Cholesterol loading downregulates the expression of Acta2 and calponin (SMC markers), and increases the expression of Mac-2, CD11b and MHCII (inflammation-related genes and surface antigens) and Abca1, Abcg1. HDL3 normalizes SMC marker expression and reduces the expression of inflammation-related genes/proteins in WT cells, an effect not observed with free apoA-I. The effect of HDL3 is almost lost in Abca1 KO cells, as well as when Abca1 is silenced in WT SMC. HDL3 does not differently affect cholesterol downloading in WT or KO cells and stimulates phospholipids removal in WT cells. Similarly, the expression of myocardin and its modulators, such as miR-143/145, is reduced by cholesterol loading in WT and Abca1 KO SMCs; HDL3 normalizes their levels in WT cells but not in KO cells. On the contrary, cholesterol loading induces Klf4 expression while HDL3 restores Klf4 to basal levels in WT cells, but again this effect is not observed in KO cells.

CONCLUSIONS

Our results indicate that HDL3, by interacting with ABCA1, modulates the miR143/145-myocardin axis and prevents the cholesterol-induced gene expression modification in SMCs regardless of its cholesterol unloading capacity.

Abstract 238: ABCA1 and HDL3 are Required to Modulate Smooth Muscle Cells Trandifferentiation in a Myocardin-miR143/145-dependent Process

Cells of the artery wall may accumulate free cholesterol and cholesteryl esters becoming foam cells. Up to 50% of foam cells in human lesions originates from smooth muscle cells (SMCs). Arterial SMCs express the ATP binding cassette (ABC) transporter ABCA1 and, upon cholesterol loading, express macrophage markers and a phagocytic activity. To characterize the role of ABCA1 and HDL3 in this transdifferentiation process, we evaluated the phenotypic changes in SMCs isolated from wild type (WT) and ABCA1 knock out (KO) mice and how HDL3 affects these changes. Cholesterol loading causes the downregulation of the expression of SMC markers including ACTA2, alpha-tropomyosin and myosin heavy chain and increases the expression of macrophage-related genes such as CD68, Mac-2, SRB1, MMPs, ABCG1 and ABCA1. HDL3 treatment in WT cells is able to normalize the expression of ACTA2, while the expression of macrophage-related genes is reduced. On the contrary, the preventive effect of HDL3 is completely lost in ABCA1 KO cells. Interestingly, the presence of HDL3 does not differently affect neutral lipid accumulation in WT or ABCA1 KO cells but stimulates phospholipids removal only in WT cells. ApoAI addition does not reverse the phenotypic changes induced by cholesterol not only in KO but also in WT cells. Moreover, cholesterol loading reduces the expression of myocardin, the master SMC specific-transcriptional coactivator involved in SMC differentiation, by up to 55% (p<0.01 vs respective control) in both cell types. HDL3 normalizes myocardin levels in WT cells while it does not have any effect in ABCA1 KO cells. Similar results are obtained evaluating the levels of miR-143/145, which positively regulate myocardin. The basal expression level of KLF4, a myocardin repressor, is almost double in ABCA1 KO cells compared to WT. After cholesterol loading, KLF4 is slightly reduced in WT cells, while its expression is halved in ABCA1 KO cells. HDL3 restores KLF4 to basal levels in KO cells, but it further reduces them in WT cells. These results indicate that HDL3, modulating the miR143/145-myocardin axis in SMC, prevents the cholesterol-induced gene expression modification regardless of its cholesterol unloading capacity and the presence of ABCA1 is required.

Cyclosporine A impairs the macrophage reverse cholesterol transport in mice by reducing sterol fecal excretion

Despite the efficacy in reducing acute rejection events in organ transplanted subjects, long term therapy with cyclosporine A is associated with increased atherosclerotic cardiovascular morbidity. We studied whether this drug affects the antiatherogenic process of the reverse cholesterol transport from macrophages in vivo. Cyclosporine A 50 mg/kg/d was administered to C57BL/6 mice by subcutaneous injection for 14 days. Macrophage reverse cholesterol transport was assessed by following [³H]-cholesterol mobilization from pre-labeled intraperitoneally injected macrophages, expressing or not apolipoprotein E, to plasma, liver and feces. The pharmacological treatment significantly reduced the amount of radioactive sterols in the feces, independently on the expression of apolipoprotein E in the macrophages injected into recipient mice and in absence of changes of plasma levels of high density lipoprotein-cholesterol. Gene expression analysis revealed that cyclosporine A inhibited the hepatic levels of cholesterol 7-alpha-hydroxylase, concomitantly with the increase in hepatic and intestinal expression of ATP Binding Cassette G5. However, the in vivo relevance of the last observation was challenged by the demonstration that mice treated or not with cyclosporine A showed the same levels of circulating beta-sitosterol. These results indicate that treatment of mice with cyclosporine A impaired the macrophage reverse cholesterol transport by reducing fecal sterol excretion, possibly through the inhibition of cholesterol 7-alpha-hydroxylase expression. The current observation may provide a potential mechanism for the high incidence of atherosclerotic coronary artery disease following the immunosuppressant therapy in organ transplanted recipients.

Adding a statin to a combination of ACE inhibitor and ARB normalizes proteinuria in experimental diabetes, which translates into full renoprotection

The capacity of renin-angiotensin system (RAS) inhibitors to delay progression of diabetic nephropathy depends on the time at which therapy is started. A multimodal intervention is required to afford renoprotection in overt diabetic nephropathy. Here we assessed the effects of maximal RAS inhibition by angiotensin-converting enzyme (ACE) inhibitor plus angiotensin II type 1 receptor blocker (ARB) in combination with statin in rats with overt diabetic nephropathy. Uninephrectomized rats made diabetic by streptozotocin were orally treated from 4 (when proteinuria and renal lesions had developed) to 8 mo with vehicle, lisinopril plus candesartan, lisinopril plus candesartan plus rosuvastatin, or rosuvastatin alone. Systolic blood pressure increased in diabetic rats and was significantly lowered by combined therapies. Dual RAS blockade significantly reduced proteinuria compared with vehicle. Addition of statin further lowered proteinuria to control levels. Glomerulosclerosis was ameliorated by RAS inhibitors or statin, and regression was achieved by the addition of statin. Loss of podocytes of diabetic rats was limited by ACE inhibitor plus ARB while normalized by the three drugs. Defective nephrin expression of diabetes was increased by dual RAS blockade or statin and restored by the triple therapy. Tubular damage, interstitial inflammation, and expression of the fibrotic markers transforming growth factor (TGF)-β1 and phosphorylated Smad 2/3 in tubuli were significantly reduced by the triple regimen. These data suggest a strategy to target proteinuria to try to achieve regression of renal disease in diabetic patients who do not fully benefit from RAS inhibition alone.

Do structural differences in statins correlate with clinical efficacy?

PURPOSE OF REVIEW

Statins, by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase, decrease the synthesis not only of cholesterol but also of nonsteroidal mevalonate derivatives. While the first effect translates into plasma cholesterol reductions, the second is related to nonlipid-lowering (pleiotropic) properties. Purpose of this review is to assess the correlation between differences in statin structures and clinical effects. While the cardiovascular benefits of statin chronic therapy are achieved by lowering low-density lipoprotein cholesterol (LDL-C) and should be considered a class effect, the acute ones may reflect structure differences and pleiotropic properties of these drugs.

RECENT FINDINGS

Clinical studies conducted in acute coronary syndrome patients suggest that some benefits achieved by early statin treatment could be related to their pleiotropic properties. Indeed, ex-vivo studies showed the ability of sera from hypercholesterolemic patients treated with a single dose of atorvastatin (but not of simvastatin), to inhibit smooth muscle cell proliferation, independently of LDL-C lowering.

SUMMARY

These findings give a clinical ground to statins' potentially structure-related anti-inflammatory and pleiotropic properties, opening the possibility to control different aspects of atherosclerosis, by choosing the appropriate statin (tailored therapy), particularly in high-cardiovascular-risk patients.

Fibrillar Collagen Inhibits Cholesterol Biosynthesis in Human Aortic Smooth Muscle Cells

Objective— Integrin-mediated cell adhesion to type I fibrillar collagen regulates gene and protein expression, whereas little is known of its effect on lipid metabolism. In the present study, we examined the effect of type I fibrillar collagen on cholesterol biosynthesis in human aortic smooth muscle cells (SMCs).

Methods and Results— SMCs were cultured on either fibrillar or monomer collagen for 48 hours and [ 14 C]-acetate incorporation into cholesterol was evaluated. Fibrillar collagen reduced by 72.9±2.6% cholesterol biosynthesis without affecting cellular cholesterol levels. Fibrillar collagen also reduced 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA) promoter activity (−72.6±7.3%), mRNA (−58.7±6.4%), protein levels (−35.5±8.5%), and enzyme activity (−37.7±2.2%). Intracellular levels of the active form of sterol regulatory element binding proteins (SREBP) 1a was decreased by 60.7±21.7% in SMCs cultured on fibrillar collagen, whereas SREBP2 was not significantly affected (+12.1±7.1%). The overexpression of the active form of SREBP1a rescued the downregulation of fibrillar collagen on HMG-CoA reductase levels. Blocking antibody to α2 integrin partially reversed the downregulation of HMG-CoA reductase mRNA expression. Finally, fibrillar collagen led to an intracellular accumulation of unprenylated Ras.

Conclusions— Our study demonstrated that α2β1 integrin interaction with fibrillar collagen affected the expression of HMG-CoA reductase, which led to the inhibition of cholesterol biosynthesis in human SMCs.

Mice fed a lipogenic methionine-choline-deficient diet develop hypermetabolism coincident with hepatic suppression of SCD-1

Lipogenic diets that are completely devoid of methionine and choline (MCD) induce hepatic steatosis. MCD feeding also provokes systemic weight loss, for unclear reasons. In this study, we found that MCD feeding causes profound hepatic suppression of the gene encoding stearoyl-coenzyme A desaturase-1 (SCD-1), an enzyme whose regulation has significant effects on metabolic rate. Within 7 days of MCD exposure, hepatic SCD-1 mRNA decreased to nearly undetectable levels. By day 21, SCD-1 protein was absent from hepatic microsomes and fatty acids showed a decrease in monounsaturated species. These changes in hepatic SCD-1 were accompanied by signs of hypermetabolism. Calorimetry revealed that MCD-fed mice consumed 37% more energy than control mice (P = 0.0003). MCD feeding also stimulated fatty acid oxidation, although fatty oxidation genes were not significantly upregulated. Interestingly, despite their increased metabolic rate, MCD-fed mice did not increase their food consumption, and as a result, they lost 26% of their body weight in 21 days. In summary, MCD feeding suppresses SCD-1 in the liver, which likely contributes to hypermetabolism and weight loss. MCD feeding also induces hepatic steatosis, by an independent mechanism. Viewed together, these two disparate consequences of MCD feeding (weight loss and hepatic steatosis) give the appearance of an unusual form of lipodystrophy.

Statins effect on smooth muscle cell proliferation

Clinical trials have firmly established that 3-hydroxy-3-methylglutaryl-coenzyme-A reductase inhibitors (statins) can induce regression of vascular atherosclerosis as well as reduction of cardiovascular-related morbidity and death in patients with and without coronary artery disease. These beneficial effects of statins are usually assumed to result from their ability to reduce cholesterol synthesis. However, because mevalonic acid is the precursor not only of cholesterol but also of many nonsteroidal isoprenoid compounds, inhibition of 3-hydroxy-3-methylglutaryl-coenzyme-A reductase may result in pleiotropic effects. Indeed, statins can interfere with major events involved in the formation and the evolution of atherosclerotic lesions, such as arterial myocyte migration and proliferation and cholesterol accumulation, independent of their hypolipidemic properties. The aim of this article is to focus on clinical and experimental data that show that statins possess effects beyond cholesterol lowering, particularly on arterial smooth muscle cell proliferation. The contribution of these direct vascular effects to the reduction of cardiovascular events observed in clinical trials with statins represents one of the major challenges for future studies to understand the antiatherosclerotic benefits of these agents.

Metastasis of breast carcinoma to intracranial meningioma

A patient who had been treated for bilateral breast carcinoma subsequently developed a metastatic breast lesion in a meningioma. Although it is not uncommon for more than one tumor to occur in the same patient, metastases from one tumor into another tumor are rare (''tumor to tumor'' phenomenon). Meningiomas are the most common primary, intracranial tumors to harbor metastases, the majority of which arise from breast and lung carcinomas. Patients with a history of breast cancer and a solitary, intracranial mass with radiological features consistent of meningioma should be evaluated surgically. The lesion may be a primary cerebral malignancy, a metastatic lesion, or a meningioma with or without a metastatic lesion.

Molecular Mechanism for Changes in Proteoglycan Binding on Compositional Changes of the Core and the Surface of Low-Density Lipoprotein–Containing Human Apolipoprotein B100

OBJECTIVE

The aim of this study was to investigate the molecular mechanism for changes in proteoglycan binding and LDL receptor affinity on two compositional changes in LDL that have been associated with atherosclerosis: cholesterol enrichment of the core and modification by secretory group IIA phospholipase A2 (sPLA2) of the surface.

METHODS AND RESULTS

Transgenic mice expressing recombinant apolipoprotein (apo) B and sPLA2 were generated. Recombinant LDL were isolated and tested for their proteoglycan and LDL receptor-binding activity. The results show site A (residues 3148-3158) in apoB100 becomes functional in sPLA2-modified LDL and that site A acts cooperatively with site B (residues 3359-3369), the primary proteoglycan-binding site in native LDL, in the binding of sPLA2-modified LDL to proteoglycans. Our results also show that cholesterol enrichment of LDL is associated with increased affinity for proteoglycans and for the LDL receptor. This mechanism is likely mediated by a conformational change of site B and is independent of site A in apoB100.

CONCLUSIONS

Site A in apoB100 becomes functional in sPLA2-modified LDL and acts cooperatively with site B resulting in increased proteoglycan-binding activity. The increased binding for proteoglycans of cholesterol-enriched LDL is solely dependent on site B.

Effect of S(-) perillic acid on protein prenylation and arterial smooth muscle cell proliferation

A number of proteins post-translationally modified by the covalent attachment of mevalonate-derived isoprene groups farnesol (FOH) or geranylgeraniol (GGOH), play a role in cell proliferation. For this reason, protein farnesyltransferase (PFTase) and protein geranylgeranyltransferases (PGGTases) I and II have gained attention as novel targets for the development of antiproliferative agents. Monoterpenes [limonene, perillic acid (PA) and its derivatives] have been shown to inhibit cell growth and protein prenylation in cancer cells. In the present study, we evaluated the effect of S(-) PA on diploid rat aorta smooth muscle cell (SMC) proliferation as related to protein prenylation. S(-) PA (1-3.5 mM) decreased, in a concentration-dependent manner, rat SMC proliferation as evaluated by cell counting and DNA synthesis. Morphological criteria and flow cytometry analysis excluded the induction of apoptosis as a potential antiproliferative mechanism of S(-) PA on SMC and confirmed a block of the cell cycle progression in G(0)/G(1) phase. The antiproliferative effect of S(-) PA could not be prevented by the addition of mevalonate, FOH, and GGOH to the culture medium and was independent of cholesterol biosynthesis. Densitometric analysis of fluorographed gels, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the cell lysates, further supported that S(-) PA (1-3.5 mM), under the same experimental conditions, concentration-dependently inhibited FOH (up to 70%) and GGOH (up to 70%) incorporation into cellular proteins. We provide evidence that S(-) PA affects protein prenylation, an effect that may contribute to its inhibition of SMC proliferation.

Effect of valsartan on angiotensin II-induced plasminogen activator inhibitor-1 biosynthesis in arterial smooth muscle cells

Previous studies have shown that angiotensin II stimulates the synthesis of plasminogen activator inhibitor-1 in cultured vascular cells, which suggests that activation of the renin-angiotensin system may impair fibrinolysis. We have investigated the effects of angiotensin II and of valsartan, a recently developed angiotensin II antagonist that is highly specific and selective for the angiotensin II subtype 1 receptor, on plasminogen activator inhibitor-1 secretion by smooth muscle cells isolated from rat and human vessels. Angiotensin II induced a time- and concentration-dependent increase of plasminogen activator inhibitor activity in supernatants of rat aortic cells, which reached a plateau after 6 hours of incubation with 100 nmol/L angiotensin II (2.4+/-0.6-fold over control value; P:<0.001). The angiotensin II-induced plasminogen activator inhibitor activity was inhibited, in a concentration-dependent manner, by valsartan with an IC(50) value of 21 nmol/L. Valsartan fully prevented the angiotensin II-induced increase in plasminogen activator inhibitor-1 protein and mRNA. Furthermore, angiotensin II doubled the secretion of plasminogen activator inhibitor-1 by smooth muscle cells obtained from human umbilical and internal mammary arteries, and valsartan fully prevented it. Angiotensin II did not affect the secretion of tissue plasminogen activator antigen by any of the cell systems tested. Thus, valsartan effectively inhibits angiotensin II-induced plasminogen activator inhibitor-1 secretion without affecting that of tissue plasminogen activator in arterial rat and human smooth muscle cells.

Pleiotropic effects of statins in atherosclerosis and diabetes

OBJECTIVE

To investigate the direct anti-atherosclerotic properties of statins.

RESEARCH DESIGN AND METHODS

Using in vitro and ex vivo models, the effect of different statins on key events involved in atherogenesis has been investigated. We studied the ability of statins to modulate modified LDL-induced cholesterol esterification, metalloproteinase secretion by macrophages, and arterial myocyte migration and proliferation. The mechanisms underlying the inhibitory effect of statins have also been explored. Finally, the antiproliferative effect of sera from statin-treated patients has been confirmed in a cell culture system.

RESULTS

Fluvastatin, simvastatin, lovastatin, atorvastatin, and cerivastatin, but not pravastatin, dose-dependently decrease smooth muscle cell (SMC) migration and proliferation. Moreover, statins are able to reduce cholesterol accumulation in macrophages in vitro by blocking cholesterol esterification and endocytosis of modified lipoproteins and matrix-degrading enzyme secretion. This in vitro inhibition was completely prevented by mevalonate and partially by all-trans farnesol and all-trans geranylgeraniol, confirming the specific role of isoprenoid metabolites (probably through prenylated protein[s]) in regulating these cellular events. The inhibitory effect of statins on SMC proliferation has been shown in different models of proliferating cells, such as cultured arterial myocytes and rapidly proliferating carotid and femoral intimal lesions in rabbits, independently of their ability to reduce plasma cholesterol. Finally, ex vivo studies showed that sera from fluvastatin-treated patients interfere with SMC proliferation.

CONCLUSIONS

These results suggest that 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors exert a direct anti-atherosclerotic effect in the arterial wall, beyond their effects on plasma lipids that could translate into a more significant prevention of cardiovascular disease. These findings provide a basis for the beneficial effect of statins in clinical trials also involving diabetic patients--a population with a higher absolute risk of recurrent cardiovascular events.

Direct effects of statins on the vascular wall

The beneficial effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) on coronary events have generally been attributed to their hypocholesterolemic properties. Mevalonate and other intermediates of cholesterol synthesis (isoprenoids) are necessary for cell proliferation and other important cell functions; thus effects other than cholesterol reduction may help to explain the antiatherosclerotic properties of statins. Recently we provided in vitro and in vivo evidence of decreased smooth-muscle cell (SMC) proliferation and migration by fluvastatin and simvastatin, but not by pravastatin, independent of plasma cholesterol reduction. The ability of fluvastatin to interfere with arterial SMC proliferation at therapeutic concentrations (0.1-1 microM) prompted us to investigate the pharmacologic activity of sera from 10 patients treated with fluvastatin, 40 mg once daily, on the proliferation of cultured human arterial myocytes. Pravastatin, 40 mg once daily, displays a lipid-lowering activity similar to that of fluvastatin without affecting SMC proliferation and was investigated as a control for assessing this non-lipid-related effect of fluvastatin. Fluvastatin and pravastatin, given for 6 days to patients with type IIa hypercholesterolemia, resulted in a similar decrease in low-density-lipoprotein (LDL) cholesterol. However, the addition of 15% whole-blood sera from patients treated with fluvastatin to the culture medium resulted in a 43% inhibition of cholesterol synthesis in SMCs (p < 0.01) that mirrored the pharmacokinetic profile of fluvastatin. When SMC proliferation was investigated, a significant inhibition of cell growth (-30%; p < 0.01) was detected with sera obtained 6 h after the last dose. No effect on SMC proliferation or cholesterol biosynthesis was observed when sera from patients treated with pravastatin were evaluated. These results suggest that statins exert a direct antiproliferative effect on the arterial wall, beyond their effects on plasma lipids, which could prevent significant cardiovascular disease.