Saturated fatty acid palmitate aggravates neointima formation by promoting smooth muscle phenotypic modulation

Effect of Diets with the Addition of Edible Insects on the Development of Atherosclerotic Lesions in ApoE/LDLR-/- Mice

Foods enriched with insects can potentially prevent several health disorders, including cardiovascular diseases, by reducing inflammation and improving antioxidant status. In this study, Tenebrio molitor and Gryllus assimilis were selected to determine the effect on the development of atherosclerosis in ApoE/LDLR-/- mice. Animals were fed AIN-93G-based diets (control) with 10% Tenebrio molitor (TM) and 10% Gryllus assimilis (GA) for 8 weeks. The nutritional value as well as antioxidant activity of selected insects were determined. The lipid profile, liver enzyme activity, and the fatty acid composition of liver and adipose tissue of model mice were evaluated. Quantitative analysis of atherosclerotic lesions in the entire aorta was performed using the en face method, and for aortic roots, the cross-section method was used. The antioxidant status of the GA cricket was significantly higher compared to the TM larvae. The results showed that the area of atherosclerosis (en face method) was not significantly different between groups. Dietary GA reduced plaque formation in the aortic root; additionally, significant differences were observed in sections at 200 and 300 µm compared to other groups. Furthermore, liver enzyme ALT activity was lower in insect-fed groups compared to the control group. The finding suggests that a diet containing edible insect GA potentially prevents atherosclerotic plaque development in the aortic root, due to its high antioxidant activity.

Potassium dehydroandrographolide succinate regulates the MyD88/CDH13 signaling pathway to enhance vascular injury-induced pathological vascular remodeling

Pathological vascular remodeling is a hallmark of various vascular diseases. Previous research has established the significance of andrographolide in maintaining gastric vascular homeostasis and its pivotal role in modulating endothelial barrier dysfunction, which leads to pathological vascular remodeling. Potassium dehydroandrographolide succinate (PDA), a derivative of andrographolide, has been clinically utilized in the treatment of inflammatory diseases precipitated by viral infections. This study investigates the potential of PDA in regulating pathological vascular remodeling. The effect of PDA on vascular remodeling was assessed through the complete ligation of the carotid artery in C57BL/6 mice. Experimental approaches, including rat aortic primary smooth muscle cell culture, flow cytometry, bromodeoxyuridine (BrdU) incorporation assay, Boyden chamber cell migration assay, spheroid sprouting assay, and Matrigel-based tube formation assay, were employed to evaluate the influence of PDA on the proliferation and motility of smooth muscle cells (SMCs). Molecular docking simulations and co-immunoprecipitation assays were conducted to examine protein interactions. The results revealed that PDA exacerbates vascular injury-induced pathological remodeling, as evidenced by enhanced neointima formation. PDA treatment significantly increased the proliferation and migration of SMCs. Further mechanistic studies disclosed that PDA upregulated myeloid differentiation factor 88 (MyD88) expression in SMCs and interacted with T-cadherin (CDH13). This interaction augmented proliferation, migration, and extracellular matrix deposition, culminating in pathological vascular remodeling. Our findings underscore the critical role of PDA in the regulation of pathological vascular remodeling, mediated through the MyD88/CDH13 signaling pathway.

Spatially Resolved Metabolites in Stable and Unstable Human Atherosclerotic Plaques Identified by Mass Spectrometry Imaging

BACKGROUND

Impairments in carbohydrate, lipid, and amino acid metabolism drive features of plaque instability. However, where these impairments occur within the atheroma remains largely unknown. Therefore, we sought to characterize the spatial distribution of metabolites within stable and unstable atherosclerosis in both the fibrous cap and necrotic core.

METHODS

Atherosclerotic tissue specimens from 9 unmatched individuals were scored based on the Stary classification scale and subdivided into stable and unstable atheromas. After performing mass spectrometry imaging on these samples, we identified over 850 metabolite-related peaks. Using MetaboScape, METASPACE, and Human Metabolome Database, we confidently annotated 170 of these metabolites and found over 60 of these were different between stable and unstable atheromas. We then integrated these results with an RNA-sequencing data set comparing stable and unstable human atherosclerosis.

RESULTS

Upon integrating our mass spectrometry imaging results with the RNA-sequencing data set, we discovered that pathways related to lipid metabolism and long-chain fatty acids were enriched in stable plaques, whereas reactive oxygen species, aromatic amino acid, and tryptophan metabolism were increased in unstable plaques. In addition, acylcarnitines and acylglycines were increased in stable plaques whereas tryptophan metabolites were enriched in unstable plaques. Evaluating spatial differences in stable plaques revealed lactic acid in the necrotic core, whereas pyruvic acid was elevated in the fibrous cap. In unstable plaques, 5-hydroxyindoleacetic acid was enriched in the fibrous cap.

CONCLUSIONS

Our work here represents the first step to defining an atlas of metabolic pathways involved in plaque destabilization in human atherosclerosis. We anticipate this will be a valuable resource and open new avenues of research in cardiovascular disease.

Plant-Based Nutrition: Exploring Health Benefits for Atherosclerosis, Chronic Diseases, and Metabolic Syndrome-A Comprehensive Review

Atherosclerosis, chronic non-communicable diseases, and metabolic syndrome are highly interconnected and collectively contribute to global health concerns that reduce life expectancy and quality of life. These conditions arise from multiple risk factors, including inflammation, insulin resistance, impaired blood lipid profile, endothelial dysfunction, and increased cardiovascular risk. Adopting a plant-based diet has gained popularity as a viable alternative to promote health and mitigate the incidence of, and risk factors associated with, these three health conditions. Understanding the potential benefits of a plant-based diet for human health is crucial, particularly in the face of the rising prevalence of chronic diseases like diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer. Thus, this review focused on the plausible advantages of consuming a type of food pattern for the prevention and/or treatment of chronic diseases, emphasizing the dietary aspects that contribute to these conditions and the evidence supporting the benefits of a plant-based diet for human health. To facilitate a more in-depth analysis, we present separate evidence for each of these three concepts, acknowledging their intrinsic connection while providing a specific focus on each one. This review underscores the potential of a plant-based diet to target the underlying causes of these chronic diseases and enhance health outcomes for individuals and populations.

Palmitic Acid, A Critical Metabolite, Aggravates Cellular Senescence Through Reactive Oxygen Species Generation in Kawasaki Disease

Coronary artery lesions (CALs) are severe complications of Kawasaki disease (KD), resulting in stenosis and thrombogenesis. Metabolomic profiling of patients’ plasma could assist in elucidating the pathogenesis of CALs and identifying diagnostic biomarkers, which are imperative for clinical treatment. The metabolic profiles between KD patients with CALs and without CALs (non-coronary artery lesion, or NCAL, group) indicated the most significantly differentially expressed metabolite, palmitic acid (PA), showed the most massive fold change at 9.879. Furthermore, PA was proven to aggravate endothelial cellular senescence by increasing the generation of reactive oxygen species (ROS) in KD, and those two phenotypes were confirmed to be enriched among the differentially expressed genes between KD and normal samples from GEO datasets. Collectively, our findings indicate that cellular senescence may be one of the mechanisms of vascular endothelial damage in KD. PA may be a biomarker and potential therapeutic target for predicting the occurrence of CALs in KD patients. All things considered, our findings confirm that plasma metabolomics was able to identify promising biomarkers and potential pathogenesis mechanisms in KD. To conclude, Palmitic acid could be a novel target in future studies of CALs in patients with KD.

Immuno-regenerative biomaterials for in situ cardiovascular tissue engineering - Do patient characteristics warrant precision engineering?

In situ tissue engineering using bioresorbable material implants - or scaffolds - that harness the patient's immune response while guiding neotissue formation at the site of implantation is emerging as a novel therapy to regenerate human tissues. For the cardiovascular system, the use of such implants, like blood vessels and heart valves, is gradually entering the stage of clinical translation. This opens up the question if and to what extent patient characteristics influence tissue outcomes, necessitating the precision engineering of scaffolds to guide patient-specific neo-tissue formation. Because of the current scarcity of human in vivo data, herein we review and evaluate in vitro and preclinical investigations to predict the potential role of patient-specific parameters like sex, age, ethnicity, hemodynamics, and a multifactorial disease profile, with special emphasis on their contribution to the inflammation-driven processes of in situ tissue engineering. We conclude that patient-specific conditions have a strong impact on key aspects of in situ cardiovascular tissue engineering, including inflammation, hemodynamic conditions, scaffold resorption, and tissue remodeling capacity, suggesting that a tailored approach may be required to engineer immuno-regenerative biomaterials for safe and predictive clinical applicability.

The Assessment of Changes in the Fatty Acid Profile and Dietary Indicators Depending on the Storage Conditions of Goose Meat

The deterioration of food quality due to lipid oxidation is a serious problem in the food sector. Oxidation reactions adversely affect the physicochemical properties of food, worsening its quality. Lipid oxidation products are formed during the production, processing, and storage of food products. In the human diet, the sources of lipid oxidation products are all fat-containing products, including goose meat with a high content of polyunsaturated fatty acids. This study aims at comparing the fatty acid profile of goose breast muscle lipids depending on the storage conditions: type of atmosphere, temperature, and storage time. Three-way variance analysis was used to evaluate changes in the fatty acids profile occurring in goose meat. The health aspect of fatty acid oxidation of goose meat is also discussed. In general, the fatty acid composition changed significantly during storage in the meat packed in the high-oxygen modified atmosphere at different temperatures (1 °C and 4 °C). Higher temperature led to a higher degree of lipid oxidation and nutrient loss. During the storage of samples in vacuum, no changes in the fatty acid content and dietary indices were found, regardless of the storage temperature, which indicates that the anaerobic atmosphere ensured the oxidative stability of goose meat during 11 days of refrigerated storage.

Anti-Atherosclerotic Potential of Free Fatty Acid Receptor 4 (FFAR4)

Fatty acids (FAs) are considered not only as a basic nutrient, but are also recognized as signaling molecules acting on various types of receptors. The receptors activated by FAs include the family of rhodopsin-like receptors: GPR40 (FFAR1), GPR41 (FFAR3), GPR43 (FFAR2), GPR120 (FFAR4), and several other, less characterized G-protein coupled receptors (GPR84, GPR109A, GPR170, GPR31, GPR132, GPR119, and Olfr78). The ubiquitously distributed FFAR4 can be activated by saturated and unsaturated medium- and long-chain fatty acids (MCFAs and LCFAs), as well as by several synthetic agonists (e.g., TUG-891). The stimulation of FFAR4 using selective synthetic agonists proved to be promising strategy of reduction of inflammatory reactions in various tissues. In this paper, we summarize the evidence showing the mechanisms of the potential beneficial effects of FFAR4 stimulation in atherosclerosis. Based partly on our own results, we also suggest that an important mechanism of such activity may be the modulatory influence of FFAR4 on the phenotype of macrophage involved in atherogenesis.

Salvianolic Acid B Protects Against Fatty Acid-Induced Renal Tubular Injury via Inhibition of Endoplasmic Reticulum Stress

Background/Aims: Obesity-related kidney disease is associated with elevated levels of saturated free fatty acids (SFA). SFA lipotoxicity in tubular cells contributes to significant cellular apoptosis and injury. Salvianolic acid B (SalB) is the most abundant bioactive molecule from Radix Salviae Miltiorrhizae. In this study, we investigated the effect of SalB on SFA-induced renal tubular injury and endoplasmic reticulum (ER) stress, in vivo and in vitro. Methods: C57BL/6 mice were assigned to five groups: a control group with normal diet (Nor), high-fat diet group (HFD), and HFD with three different SalB treatment doses, low (SalBL; 3 mg/kg), medium (SalBM; 6.25 mg/kg), and high (SalBH; 12.5 mg/kg) doses. SalB was intraperitoneally injected daily for 4 weeks after 8 weeks of HFD. After 12 weeks, mice were sacrificed and kidneys and sera were collected. Apoptosis and ER stress were induced in human proximal tubule epitelial (HK2) cells by palmitic acid (PA, 0.6 mM), tunicamycin (TM, 1 μg/ml), or thapsigargin (TG, 200 nM) in vitro. Results: C57BL/6 mice fed a high-fat diet (HFD) for 12 weeks exhibited increased apoptosis (Bax and cleaved caspase-3) and ER stress (BIP, P-eIF2α, ATF4, CHOP, ATF6, IRE1α, and XBP1s) markers expression in the kidney, compared with control mice, which were remarkably suppressed by SalB treatment. In vitro studies showed that PA (0.6 mM) induced apoptosis and ER stress in cultured HK2 cells. SalB treatment attenuated all the adverse effects of PA. However, SalB failed to inhibit TM or TG-induced ER stress in HK2 cells. Conclusion: The study indicated that SalB may play an important role in obesity-related kidney injury via mediating SFA-induced ER stress.

The Short Overview on the Relevance of Fatty Acids for Human Cardiovascular Disorders

This review presents existing evidence of the influence of saturated and unsaturated fatty acids on cardiovascular diseases (CVD). Data are discussed regarding the roles of the most relevant fatty acids, such as myristic (C14:0), palmitic (C16:0), stearic (C18:0), palmitoleic (C16:1), oleic (C18:1), linoleic (C18:2), α-linolenic (C18:3, ω-3), γ-linolenic (C18:3, ω-6), arachidonic (C20:4), eicosapentaenoic (C20:5), docosahexaenoic (C22:6), and docosapentaenoic (C22:5) acid. The accumulated knowledge has expanded the understanding of the involvement of fatty acids in metabolic processes, thereby enabling the transition from basic exploratory studies to practical issues of application of these biomolecules to CVD treatment. In the future, these findings are expected to facilitate the interpretation and prognosis of changes in metabolic lipid aberrations in CVD.

Palmitate induces cardiomyocyte death via inositol requiring enzyme-1 (IRE1)-mediated signaling independent of X-box binding protein 1 (XBP1)

Overloading of the saturated fatty acid (SFA) palmitate induces cardiomyocyte death. The purpose of this study is to elucidate signaling pathways contributing to palmitate-induced cardiomyocyte death. Palmitate-induced cardiomyocyte death was induced in Toll-like receptor 2/4 double-knockdown cardiomyocytes to a similar extent as wild-type cardiomyocytes, while cardiomyocyte death was canceled out by triacsin C, a long-chain acyl-CoA synthetase inhibitor. These results indicated that palmitate induced cytotoxicity after entry and conversion into palmitoyl-CoA. Palmitoyl-CoA is not only degraded by mitochondrial oxidation but also taken up as a component of membrane phospholipids. Palmitate overloading causes cardiomyocyte membrane fatty acid (FA) saturation, which is associated with the activation of endoplasmic reticulum (ER) unfolded protein response (UPR) signaling. We focused on the ER UPR signaling as a possible mechanism of cell death. Palmitate loading activates the UPR signal via membrane FA saturation, but not via unfolded protein overload in the ER since the chemical chaperone 4-phenylbutyrate failed to suppress palmitate-induced ER UPR. The mammalian UPR relies on three ER stress sensors named inositol requiring enzyme-1 (IRE1), PKR-like endoplasmic reticulum kinase (PERK), and activating transcription factor 6 (ATF6). Palmitate loading activated only IRE1 and PERK. Knockdown of PERK did not affect palmitate-induced cardiomyocyte death, while knockdown of IRE1 suppressed palmitate-induced cardiomyocyte death. However, knockdown of X-box binding protein 1 (XBP1), the downstream effector of IRE1, did not affect palmitate-induced cardiomyocyte death. These results were validated by pharmacological inhibitor experiments. In conclusion, we identified that palmitate-induced cardiomyocyte death was triggered by IRE1-mediated signaling independent of XBP1.

TLR4 (Toll-Like Receptor 4) Mediates the Development of Intracranial Aneurysm Rupture

Inflammation is emerging as a critical factor in the pathophysiology of intracranial aneurysm. TLR4 (toll-like receptor 4) contributes not only to the innate immune responses but also to the inflammatory processes associated with vascular disease. Therefore, we examined the contribution of the TLR4 pathway to the development of the rupture of intracranial aneurysm. We used a mouse model of intracranial aneurysm. TLR4 inhibition significantly reduced the development of aneurysmal rupture. In addition, the rupture rate and levels of proinflammatory cytokines were lower in TLR4 knockout mice than the control littermates. Macrophage/monocyte-specific TLR4 knockout mice had a lower rupture rate than the control littermate mice. Moreover, the deficiency of MyD88 (myeloid differentiation primary-response protein 88), a key mediator of TLR4, reduced the rupture rate. These findings suggest that the TLR4 pathway promotes the development of intracranial aneurysmal rupture by accelerating inflammation in aneurysmal walls. Inhibition of the TLR4 pathway in inflammatory cells may be a promising approach for the prevention of aneurysmal rupture and subsequent subarachnoid hemorrhage.

Crosstalk Between Mitochondrial Hyperacetylation and Oxidative Stress in Vascular Dysfunction and Hypertension

Significance: Vascular dysfunction plays a key role in the development of arteriosclerosis, heart disease, and hypertension, which causes one-third of deaths worldwide. Vascular oxidative stress and metabolic disorders contribute to vascular dysfunction, leading to impaired vasorelaxation, vascular hypertrophy, fibrosis, and aortic stiffening. Mitochondria are critical in the regulation of metabolic and antioxidant functions; therefore, mitochondria-targeted treatments could be beneficial. Recent Advances: Vascular dysfunction is crucial in hypertension pathophysiology and exhibits bidirectional relationship. Metabolic disorders and oxidative stress contribute to the pathogenesis of vascular dysfunction and hypertension, which are associated with mitochondrial impairment and hyperacetylation. Mitochondrial deacetylase Sirtuin 3 (Sirt3) is critical in the regulation of metabolic and antioxidant functions. Clinical studies show that cardiovascular disease risk factors reduce Sirt3 level and Sirt3 declines with age, paralleling the increased incidence of cardiovascular disease and hypertension. An imbalance between mitochondrial acetylation and reduced Sirt3 activity contributes to mitochondrial dysfunction and oxidative stress. We propose that mitochondrial hyperacetylation drives a vicious cycle between metabolic disorders and mitochondrial oxidative stress, promoting vascular dysfunction and hypertension. Critical Issues: The mechanisms of mitochondrial dysfunction are still obscure in human hypertension. Mitochondrial hyperacetylation and oxidative stress contribute to mitochondrial dysfunction; however, regulation of mitochondrial acetylation, the role of GCN5L1 (acetyl-CoA-binding protein promoting acetyltransferase protein acetylation) acetyltransferase, Sirt3 deacetylase, and acetylation of specific proteins require further investigations. Future Directions: There is an urgent need to define molecular mechanisms and the pathophysiological role of mitochondrial hyperacetylation, identify novel pharmacological targets, and develop therapeutic approaches to reduce this phenomenon.

COPD as a Disease of Immunosenescence

Although chronic obstructive pulmonary disease (COPD) is regarded as a chronic inflammatory lung disease, the disease mechanism is still not known. Intriguingly, aging lungs are quite similar to COPD-affected lungs in many ways, and COPD has been viewed as a disease of accelerated premature aging of the lungs. In this paper, based on a literature review, we would like to propose immunosenescence, age-associated decline in immunity, as a critical mechanism for the development of COPD. Immunosenescence can cause a low-grade, systemic inflammation described as inflammaging. This inflammaging may be directly involved in the COPD pathogenesis. The potential contributors to the development of inflammaging in the lungs possibly leading to COPD are discussed in the review paper. A notable fact about COPD is that only 15% to 20% of smokers develop clinically significant COPD. Given that there is a substantial inter-individual variation in inflammaging susceptibility, which is genetically determined and significantly affected by the history of the individual's exposure to pathogens, immunosenescence and inflammaging may also provide the answer for this unexpectedly low susceptibility of smokers to clinically significant COPD.

Palmitate decreases migration and proliferation and increases oxidative stress and inflammation in smooth muscle cells: role of the Nrf2 signaling pathway

Fatty acids are essential to cell functionality and may exert diverging vascular effects including migration, proliferation, oxidative stress, and inflammation. This study examined the effect of palmitate on human coronary artery smooth muscle cell (HCASMC) function. An in vitro wound-healing assay indicated that palmitate decreased HCASMC migration in dose- and time-dependent manners. Furthermore, bromodeoxyuridine incorporation assays indicated that palmitate decreased HCASMC proliferation in a dose-response manner. Palmitate also increased reactive oxygen species formation, malondialdehyde content, and intracellular lipid droplets accompanied with increased fatty acid binding protein 4 expression. Moreover, palmitate induced gene expression (monocyte chemoattractant protein 1, matrix metalloproteinase-2, IL-1β, IL-6, IL-8, and TNF-α) and intracellular protein content (plasminogen activator inhibitor-1 and urokinase plasminogen activator) of inflammatory mediators. Finally, we showed that palmitate activates the transcription factor Nrf2 and the upstream kinases ERK1/2 and Akt in HCASMCs. The inhibitor of Nrf2, trigonelline, significantly attenuated palmitate-induced HCASMC expression of the Nrf2 target gene NQO1. These findings indicate that palmitate might be critically related to HCASMC function by slowing cell migration and proliferation and inducing lipid-laden cells, oxidative stress, and inflammation in part by activation of the Nrf2 transcription factor. Palmitate's activation of proinflammatory Nrf2 signaling may represent a novel mechanism mediating the proatherogenic actions of saturated fatty acids.

Palmitate aggravates proteinuria-induced cell death and inflammation via CD36-inflammasome axis in the proximal tubular cells of obese mice

High levels of serum free fatty acids (FFAs) and proteinuria have been implicated in the pathogenesis of obesity-related nephropathy. CD36, a class B scavenger receptor, is highly expressed in the renal proximal tubules and mediates FFA uptake. It is not clear whether FFA- and proteinuria-mediated CD36 activation coordinates NLRP3 inflammasomes to induce renal tubular injury and inflammation. In this study, we investigated the roles of CD36 and NLRP3 inflammasomes in FFA-induced renal injury in high-fat diet (HFD)-induced obesity. HFD-fed C57BL/6 mice and palmitate-treated HK2 renal tubular cells were used as in vivo and in vitro models. Immunohistochemical staining showed that CD36, IL-1β, and IL-18 levels increased progressively in the kidneys of HFD-fed mice. Sulfo- N-succinimidyl oleate (SSO), a CD36 inhibitor, attenuated the HFD-induced upregulation of NLRP3, IL-1β, and IL-18 and suppressed the colocalization of NLRP3 and ASC in renal tubular cells. In vitro, SSO abolished the palmitate-induced activation of IL-1β, IL-18, and caspase-1 in HK2 proximal tubular cells. Furthermore, treatment with SSO and the knockdown of caspase-1 expression by siRNA both inhibited palmitate-induced cell death and apoptosis in HK2 cells. Collectively, palmitate causes renal tubular inflammation, cell death, and apoptosis via the CD36/NLRP3/caspase-1 axis, which may explain, at least in part, the mechanism underlying FFA-related renal tubular injury. The blockade of CD36-induced cellular processes is therefore a promising strategy for treating obesity-related nephropathy.

Muscle Loss in Chronic Liver Diseases: The Example of Nonalcoholic Liver Disease

Recent publications highlight a frequent loss of muscle mass in chronic liver diseases, including nonalcoholic fatty liver disease (NAFLD), and its association with a poorer prognosis. In NAFLD, given the role of muscle in energy metabolism, muscle loss promotes disease progression. However, liver damage may be directly responsible of this muscle loss. Indeed, muscle homeostasis depends on the balance between peripheral availability and action of anabolic effectors and catabolic signals. Moreover, insulin resistance of protein metabolism only partially explains muscle loss during NAFLD. Interestingly, some data indicate specific alterations in the liver⁻muscle axis, particularly in situations such as excess fructose/sucrose consumption, associated with increased hepatic de novo lipogenesis (DNL) and endoplasmic reticulum stress. In this context, the liver will be responsible for a decrease in the peripheral availability of anabolic factors such as hormones and amino acids, and for the production of catabolic effectors such as various hepatokines, methylglyoxal, and uric acid. A better understanding of these liver⁻muscle interactions could open new therapeutic opportunities for the management of NAFLD patients.

Palmitate-induced lipotoxicity is crucial for the pathogenesis of nonalcoholic fatty liver disease in cooperation with gut-derived endotoxin

Although previous studies have indicated important roles of palmitate, a saturated fatty acid, in the pathogenesis of nonalcoholic fatty liver disease (NAFLD), it remains unclear how palmitate contributes to inflammation and fibrosis in the liver. Administration of palmitate in high fat diet (HFD)-fed but not basal diet (BD)-fed mice resulted in an increase in serum alanine aminotransferase (ALT) levels. Surprisingly, combined administration of very low dose lipopolysaccharide in palmitate-treated mice led to a marked increase in serum ALT levels despite BD-fed conditions. Administration of palmitate alone in BD-fed mice caused inflammatory cell infiltration and liver fibrosis mediated by the toll-like receptor 4 pathway without ALT elevation. In addition, a significant correlation between serum free fatty acid levels and liver fibrosis stage was observed in patients with NAFLD. These results indicate that palmitate may play crucial roles in the pathogenesis of NAFLD in the presence of gut-derived endotoxin.

Saturated Fatty Acids Undergo Intracellular Crystallization and Activate the NLRP3 Inflammasome in Macrophages

OBJECTIVE

Inflammation provoked by the imbalance of fatty acid composition, such as excess saturated fatty acids (SFAs), is implicated in the development of metabolic diseases. Recent investigations suggest the possible role of the NLRP3 (nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing 3) inflammasome, which regulates IL-1β (interleukin 1β) release and leads to inflammation, in this process. Therefore, we investigated the underlying mechanism by which SFAs trigger NLRP3 inflammasome activation.

APPROACH AND RESULTS

The treatment with SFAs, such as palmitic acid and stearic acid, promoted IL-1β release in murine primary macrophages while treatment with oleic acid inhibited SFA-induced IL-1β release in a dose-dependent manner. Analyses using polarized light microscopy revealed that intracellular crystallization was provoked in SFA-treated macrophages. As well as IL-1β release, the intracellular crystallization and lysosomal dysfunction were inhibited in the presence of oleic acid. These results suggest that SFAs activate NLRP3 inflammasome through intracellular crystallization. Indeed, SFA-derived crystals activated NLRP3 inflammasome and subsequent IL-1β release via lysosomal dysfunction. Excess SFAs also induced crystallization and IL-1β release in vivo. Furthermore, SFA-derived crystals provoked acute inflammation, which was impaired in IL-1β-deficient mice.

CONCLUSIONS

These findings demonstrate that excess SFAs cause intracellular crystallization and subsequent lysosomal dysfunction, leading to the activation of the NLRP3 inflammasome, and provide novel insights into the pathogenesis of metabolic diseases.

Blockade of myeloid differentiation protein 2 prevents obesity-induced inflammation and nephropathy

Obesity is a major and independent risk factor of kidney diseases. The pathogenic mechanisms of obesity‐associated renal injury are recognized to at least involve a lipid‐rich and pro‐inflammatory state of the renal tissues, but specific mechanisms establishing causal relation remain unknown. Saturated fatty acids are elevated in obesity, and known to induce chronic inflammation in kidneys. Myeloid differentiation protein 2 (MD2) is an important protein in lipopolysaccharide‐induced innate immunity response and inflammation. We suggested that obesity‐associated renal injury is regulated by MD2 thereby driving an inflammatory renal injury. The used three mouse models for in vivo study: MD2 knockout mice (KO) maintained on high fat diet (HFD), wild‐type mice on HFD plus L6H21, a specific MD2 inhibitor and KO mice given palmitic acid (PA) by IV injection. The in vitro studies were carried out in cultured renal tubular epithelial cells, mouse mesangial cells and primary macrophages, respectively. The HFD mice presented with increased hyperlipidemia, serum creatinine and proteinuria. Renal tissue from HFD mice had increased fibrosis, inflammatory cytokines, macrophage infiltration, and activation of NF‐κB and MAPKs. This HFD‐induced renal injury profile was not observed in KO mice or L6H21‐treated mice. Mice given PA mimmicked the HFD‐induced renal injury profiles, which were prevented by MD2 knockout. The in vitro data further confirmed MD2 mediates PA‐induced inflammation. MD2 is causally related with obesity‐associated renal inflammatory injury. We believe that MD2 is an attractive target for future therapeutic strategies in obesity‐associated kidney diseases.

Palmitate induces VSMC apoptosis via toll like receptor (TLR)4/ROS/p53 pathway

BACKGROUND AND AIMS

Toll-like receptor 4 (TLR4) has been implicated in vascular inflammation, as well as in the pathogenesis of atherosclerosis and diabetes. Vascular smooth muscle cell (VSMC) apoptosis has been shown to induce plaque vulnerability in atherosclerosis. Previous studies reported that palmitate induced apoptosis in VSMCs; however, the role of TLR4 in palmitate-induced apoptosis in VSMCs has not yet been defined. In this study, we investigated whether or not palmitate-induced apoptosis depended on the activation of the TLR4 pathway.

METHODS

VSMCs were treated with or without palmitate, CRISPR/Cas9z-mediated genome editing methods were used to deplete TLR4 expression, while NADPH oxidase inhibitors were used to inhibit reactive oxygen species (ROS) generation. Cell apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, ROS was measured using the 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) method, the mRNA and protein expression levels of caspase 3, caspase 9, BCL-2 and p53 were studied by real-time polymerase chain reaction (RT-PCR) and ELISA.

RESULTS

Palmitate significantly promotes VSMC apoptosis, ROS generation, and expression of caspase 3, caspase 9 and p53; while NADPH oxidase inhibitor pretreatment markedly attenuated these effects. Moreover, knockdown of TLR4 significantly blocked palmitate-induced ROS generation and VSMC apoptosis accompanied by inhibition of caspase 3, caspase 9, p53 expression and restoration of BCL-2 expression.

CONCLUSIONS

Our results suggest that palmitate-induced apoptosis depends on the activation of the TLR4/ROS/p53 signaling pathway, and that TLR4 may be a potential therapeutic target for the prevention and treatment of atherosclerosis.

Elongation of Long-Chain Fatty Acid Family Member 6 (Elovl6)-Driven Fatty Acid Metabolism Regulates Vascular Smooth Muscle Cell Phenotype Through AMP-Activated Protein Kinase/Krüppel-Like Factor 4 (AMPK/KLF4) Signaling

BACKGROUND

Fatty acids constitute the critical components of cell structure and function, and dysregulation of fatty acid composition may exert diverging vascular effects including proliferation, migration, and differentiation of vascular smooth muscle cells (VSMCs). However, direct evidence for this hypothesis has been lacking. We investigated the role of elongation of long-chain fatty acid member 6 (Elovl6), a rate-limiting enzyme catalyzing the elongation of saturated and monounsaturated long-chain fatty acid, in the regulation of phenotypic switching of VSMC.

METHODS AND RESULTS

Neointima formation following wire injury was markedly inhibited in Elovl6-null (Elovl6-/-) mice, and cultured VSMCs with siRNA-mediated knockdown of Elovl6 was barely responsive to PDGF-BB. Elovl6 inhibition induced cell cycle suppressors p53 and p21 and reduced the mammalian targets of rapamycin (mTOR) phosphorylation and VSMC marker expression. These changes are ascribed to increased palmitate levels and reduced oleate levels, changes that lead to reactive oxygen species (ROS) production and resulting AMP-activated protein kinase (AMPK) activation. Notably, Elovl6 inhibition robustly induced the pluripotency gene Krüppel-like factor 4 (KLF4) expression in VSMC, and KLF4 knockdown significantly attenuated AMPK-induced phenotypic switching of VSMC, indicating that KLF4 is a bona fide target of AMPK.

CONCLUSIONS

We demonstrate for the first time that dysregulation of Elovl6-driven long-chain fatty acid metabolism induces phenotypic switching of VSMC via ROS production and AMPK/KLF4 signaling that leads to growth arrest and downregulation of VSMC marker expression. The modulation of Elovl6-mediated cellular processes may provide an intriguing approach for tackling atherosclerosis and postangioplasty restenosis.

Macrophages in age-related chronic inflammatory diseases

Chronic inflammation is the common pathological basis for such age-associated diseases as cardiovascular disease, diabetes, cancer and Alzheimer’s disease. A multitude of bodily changes occur with aging that contribute to the initiation and development of inflammation. In particular, the immune system of elderly individuals often exhibits diminished efficiency and fidelity, termed immunosenescence. But, although immune responses to new pathogens and vaccines are impaired, immunosenescence is also characterized by a basal systemic inflammatory state. This alteration in immune system function likely promotes chronic inflammation. Changes in the tissue microenvironment, such as the accumulation of cell debris, and systemic changes in metabolic and hormonal signals, also likely contribute to the development of chronic inflammation. Monocyte/macrophage lineage cells are crucial to these age-associated changes, which culminate in the development of chronic inflammatory diseases. In this review, we will summarize the diverse physiological and pathological roles of macrophages in the chronic inflammation underlying age-associated diseases.

Regulation of Vascular Smooth Muscle Cell Dysfunction Under Diabetic Conditions by miR-504

OBJECTIVE

Diabetes mellitus accelerates proatherogenic and proinflammatory phenotype of vascular smooth muscle cell (VSMC) associated with vascular complications. Evidence shows that microRNAs (miRNAs) play key roles in VSMC functions, but their role under diabetic conditions is unclear. We profiled miRNAs in VSMC from diabetic mice and examined their role in VSMC dysfunction.

APPROACH AND RESULTS

High throughput small RNA-sequencing identified 135 differentially expressed miRNAs in VSMC from type 2 diabetic db/db mice (db/dbVSMC) versus nondiabetic db/+ mice. Several of these miRNAs were known to regulate VSMC functions. We further focused on miR-504, because it was highly upregulated in db/dbVSMC, and its function in VSMC is unknown. miR-504 and its host gene Fgf13 were significantly increased in db/dbVSMC and in aortas from db/db mice. Bioinformatics analysis predicted that miR-504 targets including signaling adaptor Grb10 and transcription factor Egr2 could regulate growth factor signaling. We experimentally validated Grb10 and Egr2 as novel targets of miR-504. Overexpression of miR-504 in VSMC inhibited contractile genes and enhanced extracellular signal-regulated kinase 1/2 activation, proliferation, and migration. These effects were blocked by miR-504 inhibitors. Grb10 knockdown mimicked miR-504 functions and increased inflammatory genes. Egr2 knockdown-inhibited anti-inflammatory Socs1 and increased proinflammatory genes. Furthermore, high glucose and palmitic acid upregulated miR-504 and inflammatory genes, but downregulated Grb10.

CONCLUSIONS

Diabetes mellitus misregulates several miRNAs including miR-504 that can promote VSMC dysfunction. Because changes in many of these miRNAs are sustained in diabetic VSMC even after in vitro culture, they may be involved in metabolic memory of vascular complications. Targeting such mechanisms could offer novel therapeutic strategies for diabetic complications.

Isolation, Culture, and Characterization of Vascular Smooth Muscle Cells

Smooth muscle cells (SMC) are the predominant cell type involved in the pathogenesis of atherosclerosis, vascular calcification and restenosis after angioplasty; however, they are also important in the de novo formation of blood vessels through differentiation of mesenchymal cells under the influence of mediators secreted by endothelial cells. In angiogenesis, vascular SMC are formed by proliferation of existing SMC or maturation and differntiation of pericytes. Experimental findings have demonstrated a potential role of putative smooth muscle progenitor cells in the circulation or within adult tissues and the perivascular adventitia in the development of atherosclerotic plaques, restenosis and angiogenesis. Modulation of vascular smooth muscle phenotype, SMC migration and hypertrophy are now recognized as key events in the development of vascular diseases. This has led to an increase in experimental research on SMC function in response to growth factors, extracellular matrix components, modified lipoproteins, biomechanical forces and other pro-atherogenic and pro-angiogenic mediators to address the cellular mechanisms involved. This chapter highlights well established methodologies used for vascular SMC and pericyte isolation and culture as well as their characterisation. A better understanding of vascular SMC and pericyte biology and their phenotypic modulation is required to identify therapeutic strategies to target angiogenesis and treat cardiovascular diseases.

Protective role of oleic acid against cardiovascular insulin resistance and in the early and late cellular atherosclerotic process

BACKGROUND

Several translational studies have identified the differential role between saturated and unsaturated fatty acids at cardiovascular level. However, the molecular mechanisms that support the protective role of oleate in cardiovascular cells are poorly known. For these reasons, we studied the protective role of oleate in the insulin resistance and in the atherosclerotic process at cellular level such as in cardiomyocytes (CMs), vascular smooth muscle cells (VSMCs) and endothelial cells (ECs).

METHODS

The effect of oleate in the cardiovascular insulin resistance, vascular dysfunction, inflammation, proliferation and apoptosis of VSMCs were analyzed by Western blot, qRT-PCR, BrdU incorporation and cell cycle analysis.

RESULTS

Palmitate induced insulin resistance. However, oleate not only did not induce cardiovascular insulin resistance but also had a protective effect against insulin resistance induced by palmitate or TNFα. One mechanism involved might be the prevention by oleate of JNK-1/2 or NF-κB activation in response to TNF-α or palmitate. Oleate reduced MCP-1 and ICAM-1 and increased eNOS expression induced by proinflammatory cytokines in ECs. Furthermore, oleate impaired the proliferation induced by TNF-α, angiotensin II or palmitate and the apoptosis induced by TNF-α or thapsigargin in VSMCs.

CONCLUSIONS

Our data suggest a differential role between oleate and palmitate and support the concept of the cardioprotector role of oleate as the main lipid component of virgin olive oil. Thus, oleate protects against cardiovascular insulin resistance, improves endothelial dysfunction in response to proinflammatory signals and finally, reduces proliferation and apoptosis in VSMCs that may contribute to an ameliorated atherosclerotic process and plaque stability.

GPR40/FFA1 and neutral sphingomyelinase are involved in palmitate-boosted inflammatory response of microvascular endothelial cells to LPS

OBJECTIVES

Increased levels of both saturated fatty acids (SFAs) and lipopolysaccharide (LPS) are associated with type 2 diabetes. However, it remains largely unknown how SFAs interact with LPS to regulate inflammatory responses in microvascular endothelial cells (MIC ECs) that are critically involved in atherosclerosis as a diabetic complication. In this study, we compared the effects of LPS, palmitic acid (PA), the most abundant saturated fatty acid, or the combination of LPS and PA on interleukin (IL)-6 expression by MIC ECs and explored the underlying mechanisms.

METHODS

Human cardiac MIC ECs were treated with LPS, PA and LPS plus PA and the regulatory pathways including receptors, signal transduction, transcription and post-transcription, and sphingolipid metabolism for IL-6 expression were investigated.

RESULTS

G protein-coupled receptor (GPR)40 or free fatty acid receptor 1 (FFA1), but not toll-like receptor 4, was involved in PA-stimulated IL-6 expression. PA not only stimulated IL-6 expression by itself, but also remarkably enhanced LPS-stimulated IL-6 expression via a cooperative stimulation on mitogen-activated protein kinase and nuclear factor kappa B signaling pathways, and both transcriptional and post-transcriptional activation. Furthermore, PA induced a robust neutral sphingomyelinase (nSMase)-mediated sphingomyelin hydrolysis that was involved in PA-augmented IL-6 upregulation.

CONCLUSION

PA boosted inflammatory response of microvascular endothelial cells to LPS via GPR40 and nSMase.

Novel potential targets for prevention of arterial restenosis: insights from the pre-clinical research

Restenosis is the pathophysiological process occurring in 10-15% of patients submitted to revascularization procedures of coronary, carotid and peripheral arteries. It can be considered as an excessive healing reaction of the vascular wall subjected to arterial/venous bypass graft interposition, endarterectomy or angioplasty. The advent of bare metal stents, drug-eluting stents and of the more recent drug-eluting balloons, have significantly reduced, but not eliminated, the incidence of restenosis, which remains a clinically relevant problem. Biomedical research in pre-clinical animal models of (re)stenosis, despite its limitations, has contributed enormously to the identification of processes involved in restenosis progression, going well beyond the initial dogma of a primarily proliferative disease. Although the main molecular and cellular mechanisms underlying restenosis have been well described, new signalling molecules and cell types controlling the progress of restenosis are continuously being discovered. In particular, microRNAs and vascular progenitor cells have recently been shown to play a key role in this pathophysiological process. In addition, the advanced highly sensitive high-throughput analyses of molecular alterations at the transcriptome, proteome and metabolome levels occurring in injured vessels in animal models of disease and in human specimens serve as a basis to identify novel potential therapeutic targets for restenosis. Molecular analyses are also contributing to the identification of reliable circulating biomarkers predictive of post-interventional restenosis in patients, which could be potentially helpful in the establishment of an early diagnosis and therapy. The present review summarizes the most recent and promising therapeutic strategies identified in experimental models of (re)stenosis and potentially translatable to patients subjected to revascularization procedures.

A novel adipocytokine, omentin, inhibits platelet-derived growth factor-BB-induced vascular smooth muscle cell migration through antioxidative mechanism

Omentin is a novel adipocytokine expressed in visceral adipose tissue. Secretion and blood concentration of omentin decrease in the obese subjects. We previously demonstrated that omentin is anti-inflammatory in vascular smooth muscle cells (SMCs). While vascular remodeling via migration of SMCs is also important for hypertension development, it remains to be clarified whether omentin affects this process. Here we examined whether omentin controls SMC migration. Omentin (300 ng/ml, 2 h) significantly inhibited platelet-derived growth factor (PDGF)-BB (10 ng/ml, 6 h)-induced migration of rat mesenteric arterial SMCs, as determined by Boyden chamber assay. Omentin (300 ng/ml, 2 h) significantly inhibited PDGF-BB (10 ng/ml, 30 min)-induced phosphorylation of p38 and heat shock protein (HSP) 27. Omentin (300 ng/ml, 2 h) significantly inhibited PDGF-BB (10 ng/ml, 30 min)-induced NADPH oxidase (NOX) activation as determined by lucigenin assay. Omentin (300 ng/ml, 24 h) significantly inhibited fetal bovine serum (5%, 4 days)-induced SMC outgrowth from rat isolated mesenteric artery. In vivo, omentin significantly inhibited carotid intimal hyperplasia in mouse ligation model. In summary, we for the first time demonstrate that omentin prevents PDGF-BB-induced SMC migration by preventing NOX/O2−/p38/HSP27 pathways, which might be at least partly responsible for the preventive effects on neointimal hyperplasia. Our data suggest that omentin may be protective against hypertension development by inhibiting vascular structural remodeling.

The ω-3 polyunsaturated fatty acid, eicosapentaenoic acid, attenuates abdominal aortic aneurysm development via suppression of tissue remodeling

Abdominal aortic aneurysm (AAA) is a prevalent vascular disease that can progressively enlarge and rupture with a high rate of mortality. Inflammation and active remodeling of the aortic wall have been suggested to be critical in its pathogenesis. Meanwhile, ω-3 polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) are known to reduce cardiovascular events, but its role in AAA management remains unclear. Here, we show that EPA can attenuate murine CaCl₂-induced AAA formation. Aortas from BALB/c mice fed an EPA-diet appeared less inflamed, were significantly smaller in diameter compared to those from control-diet-fed mice, and had relative preservation of aortic elastic lamina. Interestingly, CT imaging also revealed markedly reduced calcification of the aortas after EPA treatment. Mechanistically, MMP2, MMP9, and TNFSF11 levels in the aortas were reduced after EPA treatment. Consistent with this finding, RAW264.7 macrophages treated with EPA showed attenuated Mmp9 levels after TNF-α simulation. These results demonstrate a novel role of EPA in attenuating AAA formation via the suppression of critical remodeling pathways in the pathogenesis of AAAs, and raise the possibility of using EPA for AAA prevention in the clinical setting.

Toll-like receptor, lipotoxicity and chronic inflammation: the pathological link between obesity and cardiometabolic disease

The epidemic growth in the prevalence of obesity has made the impact of metabolic syndrome on cardiovascular events increasingly significant. Elevated visceral adiposity, the indispensable component of metabolic syndrome, is thought to play a primary role in the increasing incidence of cardiometabolic disorders. Importantly, obesity is not merely the simple expansion of adipose tissue mass; it also involves the activation of inflammatory processes within visceral adipose tissue. Adipose tissue inflammation on the one hand enhances the production of proinflammatory adipokines and on the other hand increases the release of free fatty acids via the activation of lipolysis. The adipokines and free fatty acids secreted from visceral fat then contribute to a cardiometabolic pathology. We herein summarize recent advances in our understanding of the mechanisms by which visceral obesity leads to the activation of inflammation in cardiovascular and metabolic tissues and promotes cardiometabolic disease. Our focus is on Toll-like receptor 4 signaling and free fatty acids as mediators of chronic inflammation in patients with metabolic syndrome and atherosclerosis.