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PURPOSE OF REVIEW: Contemporary guidelines for the prevention of cardio-metabolic diseases focus on the control of dietary fat intake, because of their adverse metabolic effects. Moreover, fats alter innate immune defenses, by eliciting pro-inflammatory epigenetic mechanisms on the long-living hematopoietic cell progenitors which, in the bone marrow, mainly give rise to short-living neutrophils. Nevertheless, the heterogenicity of fats and the complexity of the biology of neutrophils pose challenges in the understanding on how this class of nutrients could contribute to the development of cardio-metabolic diseases via specific molecular mechanisms activating the inflammatory response. RECENT FINDINGS: The knowledge on the biology of neutrophils is expanding and there are now different cellular networks orchestrating site-specific reprogramming of these cells to optimize the responses against pathogens. The innate immune competence of neutrophil is altered in response to high fat diet and contributes to the development of metabolic alterations, although the precise mechanisms are still poorly understood. SUMMARY: Defining the different molecular mechanisms involved in the fat-neutrophil crosstalk will help to reconcile the sparse data about the interaction of dietary fats with neutrophils and to tailor strategies to target neutrophils in the context of cardio-metabolic diseases.
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Gorduras na Dieta , Neutrófilos , Humanos , Neutrófilos/metabolismo , Neutrófilos/imunologia , Imunidade Inata , Inflamação , Dieta Hiperlipídica/efeitos adversos , Animais , Doenças Cardiovasculares/prevenção & controleAssuntos
Fibrilação Atrial , Mutação com Ganho de Função , Proteína Homeobox PITX2 , Proteínas de Homeodomínio , Fatores de Transcrição , Fibrilação Atrial/genética , Fibrilação Atrial/fisiopatologia , Fibrilação Atrial/diagnóstico , Humanos , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Proteínas de Homeodomínio/genética , Mitocôndrias Cardíacas/genética , Mitocôndrias Cardíacas/metabolismo , Mitocôndrias Cardíacas/patologia , Animais , Potencial da Membrana Mitocondrial/genética , Predisposição Genética para Doença , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/patologia , FenótipoRESUMO
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.
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Receptor de Asialoglicoproteína , Síndrome Metabólica , Animais , Humanos , Camundongos , Tecido Adiposo/metabolismo , Receptor de Asialoglicoproteína/genética , Dieta Hiperlipídica , Inflamação/metabolismo , Lipídeos , Fígado/metabolismo , Síndrome Metabólica/complicações , Camundongos Endogâmicos C57BL , Obesidade/complicaçõesRESUMO
AIMS: Mitochondria are plastic organelles that continuously undergo biogenesis, fusion, fission, and mitophagy to control cellular energy metabolism, calcium homeostasis, hormones, sterols, and bile acids (BAs) synthesis. Here, we evaluated how the impairment of mitochondrial fusion in hepatocytes affects diet-induced liver steatosis and obesity. METHODS AND RESULTS: Male mice selectively lacking the key protein involved in inner mitochondrial fusion, optic atrophy 1 (OPA1) (OPA1ΔHep) were fed a high fat diet (HFD) for 20 weeks. OPA1ΔHep mice were protected from the development of hepatic steatosis and obesity because of reduced lipid absorption; a profile which was accompanied by increased respiratory exchange ratio in vivo, suggesting a preference for carbohydrates in OPA1ΔHep compared to controls. At the molecular level, this phenotype emerged as a consequence of poor mitochondria-peroxisome- endoplasmic reticulum (ER) tethering in OPA1 deficient hepatocytes, which impaired BAs conjugation and release in the bile, thus impacting lipid absorption from the diet. Concordantly, the liver of subjects with non-alcoholic fatty liver disease (NAFLD) presented an increased expression of OPA1 and of the network of proteins involved in mitochondrial function when compared with controls. CONCLUSION: Patients with NAFLD present increased expression of proteins involved in mitochondrial fusion in the liver. The selective deficency of OPA1 in hepatocytes protects mice from HFD-induced metabolic dysfunction by reducing BAs secretion and dietary lipids absorption as a consequence of reduced liver mitochondria-peroxisome-ER tethering.
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Hepatopatia Gordurosa não Alcoólica , Humanos , Masculino , Camundongos , Animais , Hepatopatia Gordurosa não Alcoólica/genética , Hepatopatia Gordurosa não Alcoólica/prevenção & controle , Hepatopatia Gordurosa não Alcoólica/complicações , Dinâmica Mitocondrial , Fígado/metabolismo , Hepatócitos/metabolismo , Obesidade/metabolismo , Dieta Hiperlipídica , Lipídeos , Metaboloma , Ácidos e Sais Biliares/metabolismo , Camundongos Endogâmicos C57BLRESUMO
Atrial fibrillation (AF) is the most common cardiac arrhythmia worldwide; however, the underlying causes of AF initiation are still poorly understood, particularly because currently available models do not allow in distinguishing the initial causes from maladaptive remodeling that induces and perpetuates AF. Lately, the genetic background has been proven to be important in the AF onset. iPSC-derived cardiomyocytes, being patient- and mutation-specific, may help solve this diatribe by showing the initial cell-autonomous changes underlying the development of the disease. Transcription factor paired-like homeodomain 2 (PITX2) has been identified as a key regulator of atrial development/differentiation, and the PITX2 genomic locus has the highest association with paroxysmal AF. PITX2 influences mitochondrial activity, and alterations in either its expression or function have been widely associated with AF. In this work, we investigate the activity of mitochondria in iPSC-derived atrial cardiomyocytes (aCMs) obtained from a young patient (24 years old) with paroxysmal AF, carrying a gain-of-function mutation in PITX2 (rs138163892) and from its isogenic control (CTRL) in which the heterozygous point mutation has been reverted to WT. PITX2 aCMs show a higher mitochondrial content, increased mitochondrial activity, and superoxide production under basal conditions when compared to CTRL aCMs. However, increasing mitochondrial workload by FCCP or ß-adrenergic stimulation allows us to unmask mitochondrial defects in PITX2 aCMs, which are incapable of responding efficiently to the higher energy demand, determining ATP deficiency.
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A fine balance between uptake, storage, and the use of high energy fuels, like lipids, is crucial in the homeostasis of different metabolic tissues. Nowhere is this balance more important and more precarious than in the heart. This highly energy-demanding muscle normally oxidizes almost all the available substrates to generate energy, with fatty acids being the preferred source under physiological conditions. In patients with cardiomyopathies and heart failure, changes in the main energetic substrate are observed; these hearts often prefer to utilize glucose rather than oxidizing fatty acids. An imbalance between uptake and oxidation of fatty acid can result in cellular lipid accumulation and cytotoxicity. In this review, we will focus on the sources and uptake pathways used to direct fatty acids to cardiomyocytes. We will then discuss the intracellular machinery used to either store or oxidize these lipids and explain how disruptions in homeostasis can lead to mitochondrial dysfunction and heart failure. Moreover, we will also discuss the role of cholesterol accumulation in cardiomyocytes. Our discussion will attempt to weave in vitro experiments and in vivo data from mice and humans and use several human diseases to illustrate metabolism gone haywire as a cause of or accomplice to cardiac dysfunction.
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Insuficiência Cardíaca , Miocárdio , Humanos , Camundongos , Animais , Miocárdio/metabolismo , Metabolismo dos Lipídeos , Coração , Miócitos Cardíacos/metabolismo , Ácidos Graxos/metabolismo , Oxirredução , Metabolismo Energético/fisiologia , Mitocôndrias/metabolismoRESUMO
Background and aim: The primary transcript of fibronectin (FN) undergoes alternative splicing to generate different isoforms, including FN containing the Extra Domain A (FN_EDA+), whose expression is regulated spatially and temporarily during developmental and disease conditions including acute inflammation. The role of FN_EDA+ during sepsis, however, remains elusive. Methods: Mice constitutively express the EDA domain of fibronectin (EDA+/+); lacking the FN EDA domain (EDA-/-) or with a conditional ablation of EDA + inclusion only in liver produced FN (alb-CRE+EDA floxed mice) thus expressing normal plasma FN were used. Systemic inflammation and sepsis were induced by either LPS injection (70 mg/kg) or by cecal ligation and puncture (CLP) Neutrophils isolated from septic patients were tested for neutrophil binding ability. Results: We observed that EDA+/+ were protected toward sepsis as compared to EDA-/- mice. Also alb-CRE+EDA floxed mice presented reduced survival, thus indicating a key role for EDA in protecting toward sepsis. This phenotype was associated with improved liver and spleen inflammatory profile. Ex vivo experiments showed that neutrophils bind to a larger extent to an FN_EDA + coated surface as compared to FN, thus potentially limiting their over-reactivity. Conclusions: Our study demonstrates that the inclusion of the EDA domain in fibronectin dampens the nflammatoryi consequences of sepsis.
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BACKGROUND: High fat diet (HFD) chronically hyper-activates the myeloid cell precursors, but whether it affects the neutrophil aging is unknown. PURPOSE: We characterized how HFD impacts neutrophil aging, infiltration in metabolic tissues and if this aging, in turn, modulates the development of metabolic alterations. We immunophenotyped neutrophils and characterized the metabolic responses in physiology (wild-type mice, WT) and in mice with constitutively aged neutrophils (MRP8 driven conditional deletion of CXCR4; herein CXCR4fl/flCre+) or with constitutively fresh neutrophils (MRP8 driven conditional deletion of CXCR2; CXCR2fl/flCre+), following 20 weeks of HFD feeding (45 % kcal from fat). FINDINGS: After 20 weeks HFD, the gluco-metabolic profile of CXCR4fl/flCre+ mice was comparable to that of WT mice, while CXCR2fl/flCre+ mice were protected from metabolic alterations. CXCR4fl/flCre+ infiltrated more, but CXCR2fl/flCre+ neutrophils infiltrated less, in liver and visceral adipose tissue (VAT). As consequence, while CXCR4fl/flCre+ resulted into hepatic "suicidal" neutrophils extracellular traps (NETs) and altered immune cell architecture in VAT, CXCR2fl/flCre+ promoted proresolutive hepatic NETs and reduced accumulation of pro-inflammatory macrophages in VAT. In humans, higher plasma levels of Cxcl12 (CXCR4 ligand) correlated with visceral adiposity while higher levels of Cxcl1 (the ligand of CXCR2) correlated with indexes of hepatic steatosis, adiposity and metabolic syndrome. CONCLUSIONS: Neutrophil aging might contribute to the development of HFD induced metabolic disorders.
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Dieta Hiperlipídica , Neutrófilos , Humanos , Camundongos , Animais , Idoso , Neutrófilos/metabolismo , Dieta Hiperlipídica/efeitos adversos , Ligantes , Modelos Animais de Doenças , Envelhecimento , Camundongos Endogâmicos C57BLRESUMO
The mannose receptor C-type 1 (Mrc1) is a C-type lectin receptor expressed on the immune cells and sinusoidal endothelial cells (ECs) of several tissues, including the bone marrow (BM). Parallel to systemic metabolic alterations and hematopoietic cell proliferation, high-fat diet (HFD) feeding increases the expression of Mrc1 in sinusoidal ECs, thus calling for the investigation of its role in bone marrow cell reprogramming and the metabolic profile during obesity. Mrc1-/- mice and wild-type (WT) littermates were fed an HFD (45% Kcal/diet) for 20 weeks. Weight gain was monitored during the diet regimen and glucose and insulin tolerance were assessed. Extensive flow cytometry profiling, histological, and proteomic analyses were performed. After HFD feeding, Mrc1-/- mice presented impaired medullary hematopoiesis with reduced myeloid progenitors and mature cells in parallel with an increase in BM adipocytes compared to controls. Accordingly, circulating levels of neutrophils and pro-inflammatory monocytes decreased in Mrc1-/- mice together with reduced infiltration of macrophages in the visceral adipose tissue and the liver compared to controls. Liver histological profiling coupled with untargeted proteomic analysis revealed that Mrc1-/- mice presented decreased liver steatosis and the downregulation of proteins belonging to pathways involved in liver dysfunction. This profile was reflected by improved glucose and insulin response and reduced weight gain during HFD feeding in Mrc1-/- mice compared to controls. Our data show that during HFD feeding, mannose receptor deficiency impacts BM and circulating immune cell subsets, which is associated with reduced systemic inflammation and resistance to obesity development.
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BACKGROUND: Cholesterol is central to pancreatic ß-cell physiology and alterations of its homeostasis contribute to ß-cell dysfunction and diabetes. Proper intracellular cholesterol levels are maintained by different mechanisms including uptake via the low-density lipoprotein receptor (LDLR). In the liver, the proprotein convertase subtilisin/kexin type 9 (PCSK9) routes the LDLR to lysosomes for degradation, thus limiting its recycling to the membrane. PCSK9 is also expressed in the pancreas and loss of function mutations of PCSK9 result in higher plasma glucose levels and increased risk of Type 2 diabetes mellitus. Aim of this study was to investigate whether PCSK9 also impacts ß-cells function. METHODS: Pancreas-specific Pcsk9 null mice (Pdx1Cre/Pcsk9 fl/fl) were generated and characterized for glucose tolerance, insulin release and islet morphology. Isolated Pcsk9-deficient islets and clonal ß-cells (INS1E) were employed to characterize the molecular mechanisms of PCSK9 action. RESULTS: Pdx1Cre/Pcsk9 fl/fl mice exhibited normal blood PCSK9 and cholesterol levels but were glucose intolerant and had defective insulin secretion in vivo. Analysis of PCSK9-deficient islets revealed comparable ß-cell mass and insulin content but impaired stimulated secretion. Increased proinsulin/insulin ratio, modifications of SNARE proteins expression and decreased stimulatedcalcium dynamics were detected in PCSK9-deficient ß-cells. Mechanistically, pancreatic PCSK9 silencing impacts ß-cell LDLR expression and cholesterol content, both in vivo and in vitro. The key role of LDLR is confirmed by the demonstration that LDLR downregulation rescued the phenotype. CONCLUSIONS: These findings establish pancreatic PCSK9 as a novel critical regulator of the functional maturation of the ß-cell secretory pathway, via modulation of cholesterol homeostasis.
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Diabetes Mellitus Tipo 2 , Pró-Proteína Convertase 9 , Animais , Glicemia/metabolismo , Cálcio/metabolismo , Colesterol , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Insulina/metabolismo , Lipoproteínas LDL/metabolismo , Camundongos , Camundongos Knockout , Pâncreas/metabolismo , Proinsulina/metabolismo , Pró-Proteína Convertase 9/genética , Pró-Proteína Convertase 9/metabolismo , Receptores de LDL/genética , Receptores de LDL/metabolismo , Proteínas SNARE/metabolismo , Via Secretória , Serina Endopeptidases/genética , Subtilisinas/metabolismoRESUMO
AIMS: Leucocyte telomere length (LTL) shortening is a marker of cellular senescence and associates with increased risk of cardiovascular disease (CVD). A number of cardiovascular risk factors affect LTL, but the correlation between elevated LDL cholesterol (LDL-C) and shorter LTL is debated: in small cohorts including subjects with a clinical diagnosis of familial hypercholesterolaemia (FH). We assessed the relationship between LDL-C and LTL in subjects with genetic familial hypercholesterolaemia (HeFH) compared to those with clinically diagnosed, but not genetically confirmed FH (CD-FH), and normocholesterolaemic subjects. METHODS AND RESULTS: LTL was measured in mononuclear cells-derived genomic DNA from 206 hypercholesterolaemic subjects (135 HeFH and 71 CD-FH) and 272 controls. HeFH presented shorter LTL vs. controls (1.27 ± 0.07 vs. 1.59 ± 0.04, P = 0.045). In particular, we found shorter LTL in young HeFH as compared to young controls (<35 y) (1.34 ± 0.08 vs. 1.64 ± 0.08, P = 0.019); moreover, LTL was shorter in statin-naïve HeFH subjects as compared to controls (1.23 ± 0.08 vs. 1.58 ± 0.04, P = 0.001). HeFH subjects presented shorter LTL compared to LDL-C matched CD-FH (1.33 ± 0.05 vs. 1.55 ± 0.08, P = 0.029). Shorter LTL was confirmed in leucocytes of LDLR-KO vs. wild-type mice and associated with lower abundance of long-term haematopoietic stem and progenitor cells (LT-HSPCs) in the bone marrow. Accordingly, HeFH subjects presented lower circulating haematopoietic precursors (CD34 + CD45dim cells) vs. CD-FH and controls. CONCLUSIONS: We found (i) shorter LTL in genetically determined hypercholesterolaemia, (ii) lower circulating haematopoietic precursors in HeFH subjects, and reduced bone marrow resident LT-HSPCs in LDLR-KO mice. We support early cellular senescence and haematopoietic alterations in subjects with FH.
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Hipercolesterolemia , Hiperlipoproteinemia Tipo II , Animais , LDL-Colesterol , Humanos , Hipercolesterolemia/genética , Hiperlipoproteinemia Tipo II/diagnóstico , Hiperlipoproteinemia Tipo II/genética , Leucócitos , Camundongos , Telômero/genéticaRESUMO
The molecular pathophysiology of cardiometabolic diseases is known to be influenced by dysfunctional ectopic adipose tissue. In addition to lifestyle improvements, these conditions may be managed by novel nutraceutical products. This study evaluatedthe effects of 11 Cameroonian medicinal spice extracts on triglyceride accumulation, glucose uptake, reactive oxygen species (ROS) production and interleukin secretion in SW 872 human adipocytes after differentiation with 100 µM oleic acid. Triglyceride content was significantly reduced by all spice extracts. Glucose uptake was significantly increased by Tetrapleura tetraptera, Aframomum melegueta and Zanthoxylum leprieurii. Moreover, Xylopia parviflora, Echinops giganteus and Dichrostachys glomerata significantly reduced the production of ROS. Concerning pro-inflammatory cytokine secretion, we observed that Tetrapleura tetraptera, Echinops giganteus, Dichrostachys glomerata and Aframomum melegueta reduced IL-6 secretion. In addition, Xylopia parviflora, Monodora myristica, Zanthoxylum leprieurii, and Xylopia aethiopica reduced IL-8 secretion, while Dichrostachys glomerata and Aframomum citratum increased it. These findings highlight some interesting properties of these Cameroonian spice extracts in the modulation of cellular parameters relevant to cardiometabolic diseases, which may be further exploited, aiming to develop novel treatment options for these conditions based on nutraceutical products.
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Adipócitos/metabolismo , Suplementos Nutricionais , Síndrome Metabólica/terapia , Extratos Vegetais/farmacologia , Especiarias/análise , Linhagem Celular Tumoral , Glucose/metabolismo , Humanos , Interleucinas/metabolismo , Lipossarcoma , Espécies Reativas de Oxigênio/metabolismo , Triglicerídeos/metabolismoRESUMO
AIMS: PCSK9 is secreted into the circulation, mainly by the liver, and interacts with low-density lipoprotein receptor (LDLR) homologous and non-homologous receptors, including CD36, thus favouring their intracellular degradation. As PCSK9 deficiency increases the expression of lipids and lipoprotein receptors, thus contributing to cellular lipid accumulation, we investigated whether this could affect heart metabolism and function. METHODS AND RESULTS: Wild-type (WT), Pcsk9 KO, Liver conditional Pcsk9 KO and Pcsk9/Ldlr double KO male mice were fed for 20 weeks with a standard fat diet and then exercise resistance, muscle strength, and heart characteristics were evaluated. Pcsk9 KO presented reduced running resistance coupled to echocardiographic abnormalities suggestive of heart failure with preserved ejection fraction (HFpEF). Heart mitochondrial activity, following maximal coupled and uncoupled respiration, was reduced in Pcsk9 KO mice compared to WT mice and was coupled to major changes in cardiac metabolism together with increased expression of LDLR and CD36 and with lipid accumulation. A similar phenotype was observed in Pcsk9/Ldlr DKO, thus excluding a contribution for LDLR to cardiac impairment observed in Pcsk9 KO mice. Heart function profiling of the liver selective Pcsk9 KO model further excluded the involvement of circulating PCSK9 in the development of HFpEF, pointing to a possible role locally produced PCSK9. Concordantly, carriers of the R46L loss-of-function variant for PCSK9 presented increased left ventricular mass but similar ejection fraction compared to matched control subjects. CONCLUSION: PCSK9 deficiency impacts cardiac lipid metabolism in an LDLR independent manner and contributes to the development of HFpEF.
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Insuficiência Cardíaca , Pró-Proteína Convertase 9 , Animais , Insuficiência Cardíaca/genética , Masculino , Camundongos , Camundongos Knockout , Pró-Proteína Convertase 9/genética , Receptores de LDL/genética , Volume SistólicoRESUMO
Rivaroxaban (RVX) was suggested to possess anti-inflammatory and vascular tone modulatory effects. The goal of this study was to investigate whether RVX impacts lipopolysaccharide (LPS)-induced acute vascular inflammatory response. Male rats were treated with 5 mg/kg RVX (oral gavage) followed by 10 mg/kg LPS i.p injection. Circulating levels of IL-6, MCP-1, VCAM-1, and ICAM-1 were measured in plasma 6 and 24 hours after LPS injection, while isolated aorta was used for gene expression analysis, immunohistochemistry, and vascular tone evaluation. RVX pre-treatment significantly reduced LPS mediated increase after 6h and 24h for IL-6 (4.4±2.2 and 2.8±1.7 fold), MCP-1 (1.4±1.5 and 1.3±1.4 fold) VCAM-1 (1.8±2.0 and 1.7±2.1 fold). A similar trend was observed in the aorta for iNOS (5.5±3.3 and 3.3±1.9 folds reduction, P<0.01 and P<0.001, respectively), VCAM-1 (1.3±1.2 and 1.4±1.3 fold reduction, P<0.05), and MCP-1 (3.9±2.2 and 1.9±1.6 fold reduction, P<0.01). Moreover, RVX pre-treatment, improved LPS-induced PE contractile dysfunction in aortic rings (Control vs LPS, Emax reduction = 35.4 and 31.19%, P<0.001; Control vs LPS+RVX, Emax reduction = 10.83 and 11.48%, P>0.05, respectively), resulting in 24.5% and 19.7% change in maximal constriction in LPS and LPS+RVX respectively. These data indicate that RVX pre-treatment attenuates LPS-induced acute vascular inflammation and contractile dysfunction.
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Anti-Inflamatórios/administração & dosagem , Rivaroxabana/administração & dosagem , Vasculite/tratamento farmacológico , Vasoconstrição/efeitos dos fármacos , Administração Oral , Animais , Aorta/efeitos dos fármacos , Aorta/imunologia , Modelos Animais de Doenças , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/imunologia , Humanos , Lipopolissacarídeos/imunologia , Masculino , Ratos , Vasculite/sangue , Vasculite/imunologia , Vasoconstrição/imunologiaRESUMO
AIMS: It has been hypothesized that the activity of lysosomal acid lipase (LAL), a key enzyme involved in lipid metabolism, is involved in the NAFLD phenotype. To clarify the role of LAL in NAFLD, we studied 164 consecutive patients with biopsy-proven NAFLD and fat-loaded HepG2 cells. METHODS: LAL activity was measured (i) on dried blood spots (DBS) from NAFLD patients and dyslipidemic subjects without fatty liver and (ii) on liver biopsies from NAFLD patients. LAL activity and expression were evaluated in HepG2 cells cultured in the presence of free fatty acids (FAs), with or without a PPAR-alpha agonist. RESULTS: LAL activity was significantly reduced in patients with NAFLD compared to dyslipidemic subjects. LAL activity measured in liver biopsies from NAFLD patients was highly correlated to that measured on DBS and was independent of LAL expression in the liver. In a fully adjusted model, LAL activity on DBS was associated only with platelets and, when normalized by platelet count, it did not differ according to fibrosis stage. In vitro, FA loading of HepG2 fully replicated the impairment of LAL activity observed in NALFD patients. In these cells, the activation of PPAR-alpha receptors prevented and corrected FA-induced LAL impairment, by stimulating FA oxidation and LAL expression. CONCLUSIONS: LAL activity is reduced in NAFLD patients, independently from disease progression. In vitro, impaired LAL activity induced by FA loading was rescued by PPAR-alpha activation. These data suggest that the pharmacological modulation of LAL should be explored in the management of NAFLD patients.
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Hepatócitos/metabolismo , Metabolismo dos Lipídeos , Hepatopatia Gordurosa não Alcoólica/metabolismo , Esterol Esterase/metabolismo , Adulto , Ácidos Graxos/metabolismo , Feminino , Células Hep G2 , Hepatócitos/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Hepatopatia Gordurosa não Alcoólica/patologia , PPAR alfa/metabolismoRESUMO
Cholesterol plays an essential role in determining cell membrane physico-chemical characteristics and functions. A proper membrane structure is critical in pancreatic ß-cells for glucose-mediated insulin secretion, and alterations in cellular cholesterol content may negatively affect this process, leading to ß-cell dysfunction. The low density lipoprotein receptor (LDL-R) appears to play a relevant role in ß-cell dysfunction due to cholesterol accumulation. This observation raised the question of whether hypocholesterolemic drugs which increase LDL-R expression might bear diabetogenic properties, thus increasing the risk of new-onset diabetes or worsen glycaemic parameters in diabetic patients. Being at higher cardiovascular risk, diabetic patients are usually treated with hypolipidemic drugs to correct the atherogenic dyslipidemia characteristic of this pathological condition. Statin therapy has been associated with an increased incidence of new-onset diabetes (NOD), being the diabetogenic effect depending on the type and dose of statin. However, it is worth noting that the benefits on cardiovascular mortality largely exceed the increased risk associated with the development of diabetes. Although genetic variants associated with lower levels of LDL-C are also associated with an increased NOD risk, clinical trials with lipid-lowering drugs other than statins, namely ezetimibe or monoclonal antibodies against PCSK9, did not observe an increase of developing diabetes. In summary, molecular evidence clearly points to a key role for cholesterol homeostasis in pancreatic ß-cell function which, in humans, is negatively affected by statins. Available data exclude that this could be the case for other hypocholesterolemic approaches, but long-term studies are warranted to explore this critical aspect.
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Colesterol/metabolismo , Células Secretoras de Insulina/metabolismo , Transportador 1 de Cassete de Ligação de ATP/genética , Transportador 1 de Cassete de Ligação de ATP/metabolismo , Doenças Cardiovasculares/tratamento farmacológico , LDL-Colesterol/sangue , Diabetes Mellitus Tipo 2/etiologia , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patologia , Humanos , Inibidores de Hidroximetilglutaril-CoA Redutases/efeitos adversos , Inibidores de Hidroximetilglutaril-CoA Redutases/uso terapêutico , Pró-Proteína Convertase 9/genética , Receptores de LDL/genética , Receptores de LDL/metabolismoRESUMO
Aims: PCSK9 loss of function genetic variants are associated with lower low-density lipoprotein cholesterol but also with higher plasma glucose levels and increased risk of Type 2 diabetes mellitus. Here, we investigated the molecular mechanisms underlying this association. Methods and results: Pcsk9 KO, WT, Pcsk9/Ldlr double KO (DKO), Ldlr KO, albumin AlbCre+/Pcsk9LoxP/LoxP (liver-selective Pcsk9 knock-out mice), and AlbCre-/Pcsk9LoxP/LoxP mice were used. GTT, ITT, insulin and C-peptide plasma levels, pancreas morphology, and cholesterol accumulation in pancreatic islets were studied in the different animal models. Glucose clearance was significantly impaired in Pcsk9 KO mice fed with a standard or a high-fat diet for 20 weeks compared with WT animals; insulin sensitivity, however, was not affected. A detailed analysis of pancreas morphology of Pcsk9 KO mice vs. controls revealed larger islets with increased accumulation of cholesteryl esters, paralleled by increased insulin intracellular levels and decreased plasma insulin, and C-peptide levels. This phenotype was completely reverted in Pcsk9/Ldlr DKO mice implying the low-density lipoprotein receptor (LDLR) as the proprotein convertase subtilisin/kexin Type 9 (PCSK9) target responsible for the phenotype observed. Further studies in albumin AlbCre+/Pcsk9LoxP/LoxP mice, which lack detectable circulating PCSK9, also showed a complete recovery of the phenotype, thus indicating that circulating, liver-derived PCSK9, the principal target of monoclonal antibodies, does not impact beta-cell function and insulin secretion. Conclusion: PCSK9 critically controls LDLR expression in pancreas perhaps contributing to the maintenance of a proper physiological balance to limit cholesterol overload in beta cells. This effect is independent of circulating PCSK9 and is probably related to locally produced PCSK9.
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Diabetes Mellitus Experimental , Diabetes Mellitus Tipo 2/genética , Intolerância à Glucose/metabolismo , Secreção de Insulina/fisiologia , Pró-Proteína Convertase 9/metabolismo , Receptores de LDL/metabolismo , Animais , Apoptose , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patologia , Camundongos , Camundongos Knockout , Pâncreas/metabolismo , Pâncreas/patologiaRESUMO
Cholesterol homeostasis has a pivotal function in regulating immune cells. Here we show that apolipoprotein E (apoE) deficiency leads to the accumulation of cholesterol in the cell membrane of dendritic cells (DC), resulting in enhanced MHC-II-dependent antigen presentation and CD4+ T-cell activation. Results from WT and apoE KO bone marrow chimera suggest that apoE from cells of hematopoietic origin has immunomodulatory functions, regardless of the onset of hypercholesterolemia. Humans expressing apoE4 isoform (ε4/3-ε4/4) have increased circulating levels of activated T cells compared to those expressing WT apoE3 (ε3/3) or apoE2 isoform (ε2/3-ε2/2). This increase is caused by enhanced antigen-presentation by apoE4-expressing DCs, and is reversed when these DCs are incubated with serum containing WT apoE3. In summary, our study identifies myeloid-produced apoE as a key physiological modulator of DC antigen presentation function, paving the way for further explorations of apoE as a tool to improve the management of immune diseases.