Palmitate-induced inflammatory pathways in human adipose microvascular endothelial cells promote monocyte adhesion and impair insulin transcytosis

DAMPs and DAMP-sensing receptors in inflammation and diseases

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules produced in cellular damage or stress, and they can activate the innate immune system. DAMPs contain multiple types of molecules, including nucleic acids, proteins, ions, glycans, and metabolites. Although these endogenous molecules do not trigger immune response under steady-state condition, they may undergo changes in distribution, physical or chemical property, or concentration upon cellular damage or stress, and then they become DAMPs that can be sensed by innate immune receptors to induce inflammatory response. Thus, DAMPs play an important role in inflammation and inflammatory diseases. In this review, we summarize the conversion of homeostatic molecules into DAMPs; the diverse nature and classification, cellular origin, and sensing of DAMPs; and their role in inflammation and related diseases. Furthermore, we discuss the clinical strategies to treat DAMP-associated diseases via targeting DAMP-sensing receptors.

Palmitate Stimulates Expression of the von Willebrand Factor and Modulates Toll-like Receptors Level and Activity in Human Umbilical Vein Endothelial Cells (HUVECs)

An increased concentration of palmitate in circulation is one of the most harmful factors in obesity. The von Willebrand factor (vWF), a protein involved in haemostasis, is produced and secreted by the vascular endothelium. An increased level of vWF in obese patients is associated with thrombosis and cardiovascular disease. The aim of this study was to investigate a palmitate effect on vWF in endothelial cells and understand the mechanisms of palmitate-activated signalling. Human umbilical vein endothelial cells (HUVECs) incubated in the presence of palmitate, exhibited an increased VWF gene expression, vWF protein maturation, and stimulated vWF secretion. Cardamonin, a Nuclear Factor kappa B (NF-κB) inhibitor, abolished the palmitate effect on VWF expression. The inhibition of Toll-like receptor (TLR) 2 with C29 resulted in the TLR4 overactivation in palmitate-treated cells. Palmitate, in the presence of TLR4 inhibitor TAK-242, leads to a higher expression of TLR6, CD36, and TIRAP. The silencing of TLR4 resulted in an increase in TLR2 level and vice versa. The obtained results indicate a potential mechanism of obesity-induced thrombotic complication caused by fatty acid activation of NF-κB signalling and vWF upregulation and help to identify various compensatory mechanisms related to TLR4 signal transduction.

Diet-derived and diet-related endogenously produced palmitic acid: Effects on metabolic regulation and cardiovascular disease risk

Palmitic acid is the predominant dietary saturated fatty acid (SFA) in the US diet. Plasma palmitic acid is derived from dietary fat and also endogenously from de novo lipogenesis (DNL) and lipolysis. DNL is affected by excess energy intake resulting in overweight and obesity, and the macronutrient profile of the diet. A low-fat diet (higher carbohydrate and/or protein) promotes palmitic acid synthesis in adipocytes and the liver. A high-fat diet is another source of palmitic acid that is taken up by adipose tissue, liver, heart and skeletal muscle via lipolytic mechanisms. Moreover, overweight/obesity and accompanying insulin resistance increase non-esterified fatty acid (NEFA) production. Palmitic acid may affect cardiovascular disease (CVD) risk via mechanisms beyond increasing low-density lipoprotein-cholesterol (LDL-C), notably synthesis of ceramides and possibly through branched fatty acid esters of hydroxy fatty acids (FAHFAs) from palmitic acid. Ceramides are positively associated with incident CVD, whereas the role of FAHFAs is uncertain. Given the new evidence about dietary regulation of palmitic acid metabolism there is interest in learning more about how diet modulates circulating palmitic acid concentrations and, hence, potentially CVD risk. This is important because of the heightened interest in low carbohydrate (carbohydrate controlled) and high carbohydrate (low-fat) diets coupled with the ongoing overweight/obesity epidemic, all of which can increase plasma palmitic acid levels by different mechanisms. Consequently, learning more about palmitic acid biochemistry, trafficking and how its metabolites affect CVD risk will inform future dietary guidance to further lower the burden of CVD.

Free fatty acids and peripheral blood mononuclear cells (PBMC) are correlated with chronic inflammation in obesity

Obesity-related chronic inflammation is closely related to the ability of immune cells to adapt to the body's needs, research has shown that excess FAs can further activate pro-inflammatory transcription factors in the nucleus by interacting with various receptors such as CD36 and TLR4, thereby affecting the inflammatory state of cells. However, how the profile of various fatty acids in the blood of obese individuals is associated with chronic inflammation remains unclear.

OBJECTIVE

The biomarkers associated with obesity were identified from 40 fatty acids (FAs) in the blood, and analyze the relationship between the biomarkers and chronic inflammation. Furthermore, by analyzing the difference in the expression of CD36, TLR4 and NF-κB p65 in peripheral blood mononuclear cells (PBMC) between obese and standard weight people, understand that immunophenotype PBMC is associated with chronic inflammation.

METHODS

This study is a cross-sectional study. Participants were recruited from the Yangzhou Lipan weight loss training camp from May 2020 to July 2020. The sample size was 52 individuals, including 25 in the normal weight group and 27 in the obesity group. Individuals with obesity and controls of normal weight were recruited to identify biomarkers associated with obesity from 40 fatty acids in the blood; correlation analysis was conducted between the screened potential biomarkers FAs and the chronic inflammation index hs-CRP to identify FA biomarkers associated with chronic inflammation. Changes in the fatty acid receptor CD36, inflammatory receptor TLR4, and inflammatory nuclear transcription factor NF-κB p65 in PBMC subsets were used to further test the relationship between fatty acids and the inflammatory state in individuals with obesity.

RESULTS

23 potential FA biomarkers for obesity were screened, eleven of the potential obesity biomarkers were also significantly related to hs-CRP. Compared to the control group, in monocytes the obesity group expressed higher TLR4, CD36, and NF-κB p65 in lymphocytes, the obesity group expressed higher TLR4 and CD36; and in granulocytes the obesity group expressed higher CD36.

CONCLUSION

Blood FAs are associated with obesity and are associated with chronic inflammation through increased CD36, TLR4, and NF-κB p65 in monocytes.

The Role of Palmitic Acid in the Co-Toxicity of Bacterial Metabolites to Endothelial Cells

Introduction

Metabolic endotoxemia most often results from obesity and is accompanied by an increase in the permeability of the intestinal epithelial barrier, allowing co-absorption of bacterial metabolites and diet-derived fatty acids into the bloodstream. A high-fat diet (HFD) leading to obesity is a significant extrinsic factor in developing vascular atherosclerosis. In this study, we evaluated the effects of palmitic acid (PA) as a representative of long-chain saturated fatty acids (LCSFA) commonly present in HFDs, along with endotoxin (LPS; lipopolysaccharide) and uremic toxin indoxyl sulfate (IS), on human vascular endothelial cells (HUVECs).

Methods

HUVECs viability was measured based on tetrazolium salt metabolism, and cell morphology was assessed with fluorescein-phalloidin staining of cells' actin cytoskeleton. The effects of simultaneous treatment of endothelial cells with PA, LPS, and IS on nitro-oxidative stress in vascular cells were evaluated quantitatively with fluorescent probes. The expression of vascular cell adhesion molecule VCAM-1, E-selectin, and occludin, an essential tight junction protein, in HUVECs treated with these metabolites was evaluated in Western blot.

Results

PA, combined with LPS and IS, did not influence HUVECs viability but induced stress on actin fibers and focal adhesion complexes. Moreover, PA combined with LPS significantly enhanced reactive oxygen species (ROS) production in HUVECs but decreased nitric oxide (NO) generation. PA also considerably increased the expression of VCAM-1 and E-selectin in HUVECs treated with LPS or IS but decreased occludin expression.

Conclusion

Palmitic acid enhances the toxic effect of metabolic endotoxemia on the vascular endothelium.

Fatty acids act on vascular endothelial cells and influence the development of cardiovascular disease

Endothelial cells (ECs) maintain the health of blood vessels and prevent the development of cardiovascular disease (CVD). Free saturated fatty acids (FAs) induce EC damage and increase the risk of CVD by promoting arteriosclerosis. Conversely, polyunsaturated FAs (PUFAs), such as docosahexaenoic acid, are thought to suppress EC damage induced during the early stages of CVD. This review describes the effects of multiple dietary FAs on EC disorders involved in the development of CVD. The roles of FAs in atherosclerosis and CVD were analyzed by evaluating articles published in PubMed, Science Direct, and Web of Science. Saturated FAs were found to induce EC damage by reducing the production and action of EC-derived nitric oxide. Oxidative stress, inflammation, and the renin-angiotensin system were found to be involved in EC disorder. Furthermore, n-3 PUFAs were found to reduce EC dysfunction and prevent the development of EC disorder. These results indicate that FAs may affect EC failure induced during the early stages of CVD and reduce the risk of developing the disease.

Dynamic glucose uptake, storage, and release by human microvascular endothelial cells

Endothelia determine blood-to-tissue solute delivery, yet glucose transit is poorly understood. To illuminate mechanisms, we tracked [³H]-2-deoxyglucose (2-DG) in human adipose-tissue microvascular endothelial cells. 2-DG uptake was largely facilitated by the glucose transporters GLUT1 and GLUT3. Once in the cytosol, >80% of 2-DG became phosphorylated and ∼20% incorporated into glycogen, suggesting that transported glucose is readily accessible to cytosolic enzymes. Interestingly, a fraction of intracellular 2-DG was released over time (15-20% over 30 min) with slower kinetics than for uptake, involving GLUT3. In contrast to intracellular 2-DG, the released 2-DG was largely unphosphorylated. Glucose release involved endoplasmic reticulum-resident translocases/phosphatases and was stimulated by adrenaline, consistent with participation of glycogenolysis and glucose dephosphorylation. Surprisingly, the fluorescent glucose derivative 2-NBD-glucose (2-NBDG) entered cells largely via fluid phase endocytosis and exited by recycling. 2-NBDG uptake was insensitive to GLUT1/GLUT3 inhibition, suggesting poor influx across membranes. 2-NBDG recycling, but not 2-DG efflux, was sensitive to N-ethyl maleimide. In sum, by utilizing radioactive and fluorescent glucose derivatives, we identified two parallel routes of entry: uptake into the cytosol through dedicated glucose transporters and endocytosis. This reveals the complex glucose handling by endothelial cells that may contribute to glucose delivery to tissues.

Oleic acid-related anti-inflammatory effects in force-stressed PdL fibroblasts are mediated by H3 lysine acetylation associated with altered IL10 expression

The initiation of a spatially and temporally limited inflammation is essential for tissue and bone remodelling by the periodontal ligament (PdL) located between teeth and alveolar bone. Nutritional components may cause alterations in the inflammatory response of PdL fibroblasts to mechanical stress such as those occurring during orthodontic tooth movement (OTM). Recently, we reported an attenuated pro-inflammatory response of human PdL fibroblasts (HPdLFs) to compressive forces when stimulated with oleic acid (OA), a monounsaturated fatty acid particularly prominent in the Mediterranean diet. Fatty acids could serve as alternative source of acetyl-CoA, thereby affecting epigenetic histone marks, such as histone 3 lysine acetylation (H3Kac) in a lipid metabolism-dependent manner. In this study, we aimed to investigate the extent to which OA exerts its anti-inflammatory effect in compressed HPdLFs via changes in H3Kac. Six-hour compressed HPdLFs showed increased H3Kac when cultured with OA. Inhibition of histone deacetylases resulted in a comparable IL10-increase as observed in compressed OA-cultures. In contrast, inhibition of histone acetyltransferases, particularly p300/CBP, in compressed HPdLFs exposed to OA normalized the inflammatory response to control levels. OA-dependent increased association of H3Kac to IL10 promoter regions in compressed HPdLFs further strengthened the assumption that OA exhibits its anti-inflammatory properties via modulation of this epigenetic mark. In conclusion, our study strongly suggests that nutritional components can directly affect PdL cells via changes in their epigenetic code. Since epigenetic inhibitors are already widely used clinically, they may hold promise for novel approaches for personalized orthodontic treatment that incorporates nutritional and metabolism-related changes.

Clock Gene Bmal1 Disruption in Vascular Smooth Muscle Cells Worsens Carotid Atherosclerotic Lesions

BACKGROUND

Clock system disruptions are associated with cardiovascular diseases. We previously demonstrated Bmal1 (brain muscle aryl nuclear translocase like-1) expression is significantly attenuated in plaque-derived vascular smooth muscle cells (VSMCs). However, the influence of Bmal1 disruption in VSMCs and its molecular targets are still unclear. Here, we aim to define how Bmal1 disruption in VSMCs influences the atherosclerosis lesions.

METHODS

The relationship among Bmal1, neurological symptoms, and plaque stability was investigated. VSMC Bmal1^-/- and VSMC Bmal1^+/+mice were generated and injected with adeno associated virus encoding mutant proprotein convertase subtilisin/kexin type 9 to induce atherosclerosis. Carotid artery ligation and cuff placement were performed in these mice to confirm the role of Bmal1 in atherosclerosis progression. The relevant molecular mechanisms were then explored.

RESULTS

Bmal1 expression in the carotid plague was significantly lower in symptomatic patients as well as in unstable plaques. Moreover, Bmal1 reduction is an independent risk factor for neurological symptoms and plaque instability. Besides, VSMC Bmal1^-/- mice exhibit aggravated atherosclerotic lesions. Further study demonstrated that Bmal1 downregulation in VSMCs increased VSMC migration, monocyte transmigration, reactive oxygen species levels, and VSMCs apoptosis. As for the mechanism, we revealed that Bmal1 suppresses VSMCs migration by inhibiting RAC1 activity in 2 ways: by activating the transcription of RhoGDIα and by interacting with RAC1. Besides, Bmal1 was shown to preserve antioxidant function in VSMCs by activating Nrf2 (nuclear factor erythroid 2-related factor 2) and Bcl-2 transcription.

CONCLUSIONS

Bmal1 disruption in VSMCs worsens atherosclerosis by promoting VSMC migration and monocyte transmigration and impairing antioxidant function. Therefore, Bmal1 may be a potential therapeutic target and biomarker of atherosclerosis in the future.

Palmitate-Triggered COX2/PGE2-Related Hyperinflammation in Dual-Stressed PdL Fibroblasts Is Mediated by Repressive H3K27 Trimethylation

The interrelationships between periodontal disease, obesity-related hyperlipidemia and mechanical forces and their modulating effects on the epigenetic profile of periodontal ligament (PdL) cells are assumed to be remarkably complex. The PdL serves as a connective tissue between teeth and alveolar bone and is involved in pathogen defense and the inflammatory responses to mechanical stimuli occurring during tooth movement. Altered inflammatory signaling could promote root resorption and tooth loss. Hyperinflammatory COX2/PGE2 signaling was reported for human PdL fibroblasts (HPdLFs) concomitantly stressed with Porphyromonas gingivalis lipopolysaccharides and compressive force after exposure to palmitic acid (PA). The aim of this study was to investigate the extent to which this was modulated by global and gene-specific changes in histone modifications. The expression of key epigenetic players and global H3Kac and H3K27me3 levels were quantitatively evaluated in dual-stressed HPdLFs exposed to PA, revealing a minor force-related reduction in repressive H3K27me3. UNC1999-induced H3K27me3 inhibition reversed the hyperinflammatory responses of dual-stressed PA cultures characterized by increased COX2 expression, PGE2 secretion and THP1 adhesion. The reduced expression of the gene encoding the anti-inflammatory cytokine IL-10 and the increased presence of H3K27me3 at its promoter-associated sites were reversed by inhibitor treatment. Thus, the data highlight an important epigenetic interplay between the different stimuli to which the PdL is exposed.

Involvement of Fatty Acids and Their Metabolites in the Development of Inflammation in Atherosclerosis

Despite all the advances of modern medicine, atherosclerosis continues to be one of the most important medical and social problems. Atherosclerosis is the cause of several cardiovascular diseases, which are associated with high rates of disability and mortality. The development of atherosclerosis is associated with the accumulation of lipids in the arterial intima and the disruption of mechanisms that maintain the balance between the development and resolution of inflammation. Fatty acids are involved in many mechanisms of inflammation development and maintenance. Endothelial cells demonstrate multiple cross-linkages between lipid metabolism and innate immunity. In addition, these processes are linked to hemodynamics and the function of other cells in the vascular wall, highlighting the central role of the endothelium in vascular biology.

Integrative Role of Albumin: Evolutionary, Biochemical and Pathophysiological Aspects

Being one of the main proteins in the human body and many animal species, albumin plays a crucial role in the transport of various ions, electrically neutral molecules and in maintaining the colloidal osmotic pressure of the blood. Albumin is able to bind almost all known drugs, many nutraceuticals and toxic substances, determining their pharmaco- and toxicokinetics. However, albumin is not only the passive but also the active participant of the pharmacokinetic and toxicokinetic processes possessing a number of enzymatic activities. Due to the thiol group of Cys34, albumin can serve as a trap for reactive oxygen and nitrogen species, thus participating in redox processes. The interaction of the protein with blood cells, blood vessels, and also with tissue cells outside the vascular bed is of great importance. The interaction of albumin with endothelial glycocalyx and vascular endothelial cells largely determines its integrative role. This review provides information of a historical nature, information on evolutionary changes, inflammatory and antioxidant properties of albumin, on its structural and functional modifications and their significance in the pathogenesis of some diseases.

Hypothalamic inflammation in metabolic disorders and aging

The hypothalamus is a critical brain region for the regulation of energy homeostasis. Over the years, studies on energy metabolism primarily focused on the neuronal component of the hypothalamus. Studies have recently uncovered the vital role of glial cells as an additional player in energy balance regulation. However, their inflammatory activation under metabolic stress condition contributes to various metabolic diseases. The recruitment of monocytes and macrophages in the hypothalamus helps sustain such inflammation and worsens the disease state. Neurons were found to actively participate in hypothalamic inflammatory response by transmitting signals to the surrounding non-neuronal cells. This activation of different cell types in the hypothalamus leads to chronic, low-grade inflammation, impairing energy balance and contributing to defective feeding habits, thermogenesis, and insulin and leptin signaling, eventually leading to metabolic disorders (i.e., diabetes, obesity, and hypertension). The hypothalamus is also responsible for the causation of systemic aging under metabolic stress. A better understanding of the multiple factors contributing to hypothalamic inflammation, the role of the different hypothalamic cells, and their crosstalks may help identify new therapeutic targets. In this review, we focus on the role of glial cells in establishing a cause-effect relationship between hypothalamic inflammation and the development of metabolic diseases. We also cover the role of other cell types and discuss the possibilities and challenges of targeting hypothalamic inflammation as a valid therapeutic approach.

Cyanidin-3-O-Glucoside Supplementation Ameliorates Metabolic Insulin Resistance via Restoration of Nitric Oxide-Mediated Endothelial Insulin Transport

SCOPE

Anthocyanin cyanidin-3-O-glucoside (Cy3G) possesses a great potential in prevention of diabetes and its vascular complications while the underlying mechanisms are still far from clear. Accumulating evidence suggests that endothelial insulin transport plays a critical role in regulating metabolic insulin sensitivity. Whether Cy3G can modulate metabolic insulin resistance via regulating endothelial insulin transport is not reported yet.

METHODS AND RESULTS

Palmitic acid (PA)-treated mouse aortic endothelial cells (MAECs) model and high-fat diet (HFD) fed mice model are used. Compared with HFD mice, Cy3G supplementation decrease exogenous insulin content in skeletal muscle and ameliorate metabolic insulin resistance. In culture, Cy3G can directly ameliorate PA-induced impairment on FITC-insulin uptake in MAECs. Mechanistically, Cy3G can effectively decrease inflammatory cytokines and toll-like receptor 4 (TLR4)/nuclear factor-kappa-B inhibitor alpha (IκBα) activation, and restore the attenuated Akt/eNOS signaling pathway. Blunted nitric oxide (NO) synthase with N-nitro-l-arginine methyl ester (L-NAME) can effectively abolish the protective role of Cy3G on endothelial insulin transport and insulin-stimulated glucose utilization in HFD-fed mice.

CONCLUSIONS

These findings suggest that Cy3G supplementation can directly restore the attenuated nitic oxide-mediated endothelial insulin transport and thereby ameliorate metabolic insulin resistance. Our finding can provide a novel explanation for the anti-diabetic effects of Cy3G.

Serum Albumin in Health and Disease: Esterase, Antioxidant, Transporting and Signaling Properties

Being one of the main proteins in the human body and many animal species, albumin plays a decisive role in the transport of various ions-electrically neutral and charged molecules-and in maintaining the colloidal osmotic pressure of the blood. Albumin is able to bind to almost all known drugs, as well as many nutraceuticals and toxic substances, largely determining their pharmaco- and toxicokinetics. Albumin of humans and respective representatives in cattle and rodents have their own structural features that determine species differences in functional properties. However, albumin is not only passive, but also an active participant of pharmacokinetic and toxicokinetic processes, possessing a number of enzymatic activities. Numerous experiments have shown esterase or pseudoesterase activity of albumin towards a number of endogeneous and exogeneous esters. Due to the free thiol group of Cys34, albumin can serve as a trap for reactive oxygen and nitrogen species, thus participating in redox processes. Glycated albumin makes a significant contribution to the pathogenesis of diabetes and other diseases. The interaction of albumin with blood cells, blood vessels and tissue cells outside the vascular bed is of great importance. Interactions with endothelial glycocalyx and vascular endothelial cells largely determine the integrative role of albumin. This review considers the esterase, antioxidant, transporting and signaling properties of albumin, as well as its structural and functional modifications and their significance in the pathogenesis of certain diseases.

Hyperlipidemic Conditions Impact Force-Induced Inflammatory Response of Human Periodontal Ligament Fibroblasts Concomitantly Challenged with P. gingivalis-LPS

In obese patients, enhanced serum levels of free fatty acids (FFA), such as palmitate (PA) or oleate (OA), are associated with an increase in systemic inflammatory markers. Bacterial infection during periodontal disease also promotes local and systemic low-grade inflammation. How both conditions concomitantly impact tooth movement is largely unknown. Thus, the aim of this study was to address the changes in cytokine expression and the secretion of human periodontal ligament fibroblasts (HPdLF) due to hyperlipidemic conditions, when additionally stressed by bacterial and mechanical stimuli. To investigate the impact of obesity-related hyperlipidemic FFA levels on HPdLF, cells were treated with 200 µM PA or OA prior to the application of 2 g/cm² compressive force. To further determine the additive impact of bacterial infection, HPdLF were stimulated with lipopolysaccharides (LPS) obtained from Porphyromonas gingivalis. In mechanically compressed HPdLF, PA enhanced COX2 expression and PGE2 secretion. When mechanically stressed HPdLF were additionally stimulated with LPS, the PGE2 and IL6 secretion, as well as monocyte adhesion, were further increased in PA-treated cultures. Our data emphasize that a hyperlipidemic condition enhances the susceptibility of HPdLF to an excessive inflammatory response to compressive forces, when cells are concomitantly exposed to bacterial components.

Fine particulate matter (PM2.5) inhalation-induced alterations in the plasma lipidome as promoters of vascular inflammation and insulin resistance

Fine particulate matter (PM2.5) air pollution exposure increases the risk of developing cardiovascular disease (CVD). Although the precise mechanisms by which air pollution exposure increases CVD risk remain uncertain, research indicates that PM2.5-induced endothelial dysfunction contributes to CVD risk. Previous studies demonstrate that concentrated ambient PM2.5 (CAP) exposure induces vascular inflammation and impairs insulin and vascular endothelial growth factor (VEGF) signaling dependent on pulmonary oxidative stress. To assess whether CAP exposure induces these vascular effects via plasmatic factors, we incubated aortas from naïve mice with plasma isolated from mice exposed to HEPA-filtered air or CAP (9 days) and examined vascular inflammation and insulin and VEGF signaling. We found that treatment of naïve aortas with plasma from CAP-exposed mice activates NF-κBα and induces insulin and VEGF resistance, indicating transmission by plasmatic factor(s). To identify putative factors, we exposed lung-specific ecSOD-transgenic (ecSOD-Tg) mice and wild-type (WT) littermates to CAP at concentrations of either ∼60 µg/m3 (CAP60) or ∼100 µg/m3 (CAP100) and measured the abundance of plasma metabolites by mass spectrometry. In WT mice, both CAP concentrations increased levels of fatty acids such as palmitate, myristate, and palmitoleate and decreased numerous phospholipid species; however, these CAP-induced changes in the plasma lipidome were prevented in ecSOD-Tg mice. Consistent with the literature, we found that fatty acids such as palmitate are sufficient to promote endothelial inflammation. Collectively, our findings suggest that PM2.5 exposure, by inducing pulmonary oxidative stress, promotes unique lipidomic changes characterized by high levels of circulating fatty acids, which are sufficient to trigger vascular pathology.NEW & NOTEWORTHY We found that circulating plasma constituents are responsible for air pollution-induced vascular pathologies. Inhalation of fine particulate matter (≤PM2.5) promotes a unique form of dyslipidemia that manifests in a manner dependent upon pulmonary oxidative stress. The air pollution-engendered dyslipidemic phenotype is characterized by elevated free fatty acid species and diminished phospholipid species, which could contribute to vascular inflammation and loss of insulin sensitivity.

The involvement of autophagy in the maintenance of endothelial homeostasis: The role of mitochondria

Endothelial mitochondria play important signaling roles critical for the regulation of various cellular processes, including calcium signaling, ROS generation, NO synthesis or inflammatory response. Mitochondrial stress or disturbances in mitochondrial function may participate in the development and/or progression of endothelial dysfunction and could precede vascular diseases. Vascular functions are also strictly regulated by properly functioning degradation machinery, including autophagy and mitophagy, and tightly coordinated by mitochondrial and endoplasmic reticulum responses to stress. Within this review, current knowledge related to the development of cardiovascular disorders and the importance of mitochondria, endoplasmic reticulum and degradation mechanisms in vascular endothelial functions are summarized.

MIP-1α Expression Induced by Co-Stimulation of Human Monocytic Cells with Palmitate and TNF-α Involves the TLR4-IRF3 Pathway and Is Amplified by Oxidative Stress

Metabolic inflammation is associated with increased expression of saturated free fatty acids, proinflammatory cytokines, chemokines, and adipose oxidative stress. Macrophage inflammatory protein (MIP)-1α recruits the inflammatory cells such as monocytes, macrophages, and neutrophils in the adipose tissue; however, the mechanisms promoting the MIP-1α expression remain unclear. We hypothesized that MIP-1α co-induced by palmitate and tumor necrosis factor (TNF)-α in monocytic cells/macrophages could be further enhanced in the presence of reactive oxygen species (ROS)-mediated oxidative stress. To investigate this, THP-1 monocytic cells and primary human macrophages were co-stimulated with palmitate and TNF-α and mRNA and protein levels of MIP-1α were measured by using quantitative reverse transcription, polymerase chain reaction (qRT-PCR) and commercial enzyme-linked immunosorbent assays (ELISA), respectively. The cognate receptor of palmitate, toll-like receptor (TLR)-4, was blunted by genetic ablation, neutralization, and chemical inhibition. The involvement of TLR4-downstream pathways, interferon regulatory factor (IRF)-3 or myeloid differentiation (MyD)-88 factor, was determined using IRF3-siRNA or MyD88-deficient cells. Oxidative stress was induced in cells by hydrogen peroxide (H₂O₂) treatment and ROS induction was measured by dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay. The data show that MIP-1α gene/protein expression was upregulated in cells co-stimulated with palmitate/TNF-α compared to those stimulated with either palmitate or TNF-α (P < 0.05). Further, TLR4-IRF3 pathway was implicated in the cooperative induction of MIP-1α in THP-1 cells, and this cooperativity between palmitate and TNF-α was clathrin-dependent and also required signaling through c-Jun and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Notably, ROS itself induced MIP-1α and could further promote MIP-1α secretion together with palmitate and TNF-α. In conclusion, palmitate and TNF-α co-induce MIP-1α in human monocytic cells via the TLR4-IRF3 pathway and signaling involving c-Jun/NF-κB. Importantly, oxidative stress leads to ROS-driven MIP-1α amplification, which may have significance for metabolic inflammation.

The Mechanism of Contrast-Induced Acute Kidney Injury and Its Association with Diabetes Mellitus

Contrast-induced acute kidney injury (CI-AKI) is the third most common hospital-acquired AKI after AKI induced by renal perfusion insufficiency and nephrotoxic drugs, taking great adverse effects on the prognosis and increasing hospital stay and medical cost. Diabetes nephropathy (DN) is a common chronic complication of DM (diabetes mellitus), and DN is an independent risk factor for chronic kidney disease (CKD) and CI-AKI. The incidence of CI-AKI significantly increases in patients with renal injury, especially in DM-related nephropathy. The etiology of CI-AKI is not fully clear, and research studies on how DM becomes a facilitated factor of CI-AKI are limited. This review describes the mechanism from three aspects. ① Pathophysiological changes of CI-AKI in kidney under high-glucose status (HGS). HGS can enhance the oxidative stress and increase ROS which next causes stronger vessel constriction and insufficient oxygen supply in kidney via vasoactive substances. HGS also aggravates some ion pump load and the latter increases oxygen consumption. CI-AKI and HGS are mutually causal, making the kidney function continue to decline. ② Immunological changes of DM promoting CI-AKI. Some innate immune cells and pattern recognition receptors (PRRs) in DM and/or DN may respond to some damage-associated molecular patterns (DAMPs) formed by CI-AKI. These effects overlap with some pathophysiological changes in hyperglycemia. ③ Signaling pathways related to both CI-AKI and DM. These pathways involved in CI-AKI are closely associated with apoptosis, inflammation, and ROS production, and some studies suggest that these pathways may be potential targets for alleviating CI-AKI. In conclusion, the pathogenesis of CI-AKI and the mechanism of DM as a predisposing factor for CI-AKI, especially signaling pathways, need further investigation to provide new clinical approaches to prevent and treat CI-AKI.

Ca2+ signalling in fibroblasts and the therapeutic potential of KCa3.1 channel blockers in fibrotic diseases

The role of Ca²⁺ signalling in fibroblasts is of great interest in fibrosis-related diseases. Intracellular free Ca²⁺ ([Ca²⁺ ]_i ) is a ubiquitous secondary messenger, regulating a number of cellular functions such as secretion, metabolism, differentiation, proliferation and contraction. The intermediate conductance Ca²⁺ -activated K⁺ channel K_Ca 3.1 is pivotal in Ca²⁺ signalling and plays a central role in fibroblast processes including cell activation, migration and proliferation through the regulation of cell membrane potential. Evidence from a number of approaches demonstrates that K_Ca 3.1 plays an important role in the development of many fibrotic diseases, including idiopathic pulmonary, renal tubulointerstitial fibrosis and cardiovascular disease. The K_Ca 3.1 selective blocker senicapoc was well tolerated in clinical trials for sickle cell disease, raising the possibility of rapid translation to the clinic for people suffering from pathological fibrosis. This review after analysing all the data, concludes that targeting K_Ca 3.1 should be a high priority for human fibrotic disease.

TLR2 and TLR4 Surface and Gene Expression in White Blood Cells after Fasting and Oral Glucose, Lipid and Protein Challenges: Influence of Obesity and Sex Hormones

We studied if macronutrients of the diet have different effects on leukocyte activation, and if these effects are influenced by sex hormones or obesity. We analyzed leukocyte cell surface and gene expression of toll-like receptors 2 and 4 (TLR2 and TLR4) during fasting and after macronutrient loads in women with polycystic ovary syndrome and female and male controls. Fasting TLR2 surface expression in neutrophils was higher in men than in women. Obese subjects presented higher TLR2 gene expression than nonobese individuals, particularly in men. In contrast, surface TLR4 expression was lower in men and in obese individuals. Postprandial cell-surface expression decreased similarly after all macronutrient loads. Neutrophil TLR2 decreased only in obese subjects whereas TLR4 showed a greater decrease in nonobese individuals. However, TLR2 gene expression increased after glucose ingestion and decreased during the lipid load, while TLR4 was induced in response to lipids and mostly to glucose. Postprandial TLR gene expression was not influenced by group of subjects or obesity. Both cell-surface and gene postprandial expression inversely correlated with their fasting levels. These responses suggest a transient compensatory response aiming to prevent postprandial inflammation. However, obesity and sex hormones showed opposite influences on surface expression of TLR2 and TLR4, but not on their gene expression, pointing to regulatory posttranscriptional mechanisms.

Shaping of Innate Immune Response by Fatty Acid Metabolite Palmitate

Innate immune cells monitor invading pathogens and pose the first-line inflammatory response to coordinate with adaptive immunity for infection removal. Innate immunity also plays pivotal roles in injury-induced tissue remodeling and the maintenance of tissue homeostasis in physiological and pathological conditions. Lipid metabolites are emerging as the key players in the regulation of innate immune responses, and recent work has highlighted the importance of the lipid metabolite palmitate as an essential component in this regulation. Palmitate modulates innate immunity not only by regulating the activation of pattern recognition receptors in local innate immune cells, but also via coordinating immunological activity in inflammatory tissues. Moreover, protein palmitoylation controls various cellular physiological processes. Herein, we review the updated evidence that palmitate catabolism contributes to innate immune cell-mediated inflammatory processes that result in immunometabolic disorders.

Mechanistic Links Between Obesity, Diabetes, and Blood Pressure: Role of Perivascular Adipose Tissue

Obesity is increasingly prevalent and is associated with substantial cardiovascular risk. Adipose tissue distribution and morphology play a key role in determining the degree of adverse effects, and a key factor in the disease process appears to be the inflammatory cell population in adipose tissue. Healthy adipose tissue secretes a number of vasoactive adipokines and anti-inflammatory cytokines, and changes to this secretory profile will contribute to pathogenesis in obesity. In this review, we discuss the links between adipokine dysregulation and the development of hypertension and diabetes and explore the potential for manipulating adipose tissue morphology and its immune cell population to improve cardiovascular health in obesity.

Overexpression of microRNA‑155 alleviates palmitate‑induced vascular endothelial cell injury in human umbilical vein endothelial cells by negatively regulating the Wnt signaling pathway

The present study aimed to investigate the effect of microRNA155 (miR-155) on palmitate-induced vascular endothelial cell injury in human umbilical vein endothelial cells (HUVECs) via the regulation of the Wnt signaling pathway. HUVECs were treated with 0.1 mM palmitate. After transfection with mimic, antagomir or the Wnt pathway inhibitor XAV939, HUVECs were divided into six treatment groups: Control, palmitate, mimic + palmitate, mimic + palmitate + XAV939, antagomir + palmitate, antagomir + palmitate + XAV939. miR-155 expression was detected using reverse transcription-quantitative PCR. The expression levels of the Wnt signaling pathway-related factors β-catenin and Cyclin D, and the inflammatory factors interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), were detected using western blot analysis. MTT and Transwell assays were used to detect the proliferation and migration of cells, respectively. Apoptosis and reactive oxygen species (ROS) levels were determined using flow cytometry. The localization of β-catenin in cells was determined by immunofluorescence. Palmitate reduced the expression level of miR-155 in HUVECs. In palmitate-induced HUVECs, overexpression of miR-155 promoted cell proliferation, reduced the levels of apoptosis, downregulated IL-6 and TNF-α expression, and reduced ROS levels. Inhibition of the Wnt signaling pathway enhanced the anti-endothelial cell injury effect caused by the overexpression of miR-155 in palmitate-induced HUVECs, thereby promoting proliferation, reducing apoptosis, downregulating the levels of inflammatory factors and reducing ROS levels. In summary, overexpression of miR-155 inhibited palmitate-induced apoptosis, ROS production and levels of inflammatory factors, and promoted the proliferation of HUVECs by negatively regulating the Wnt signaling pathway. This present study provides a theoretical basis for the prevention and treatment of cardiovascular diseases associated with endothelial cell injury.

TNF-α in Combination with Palmitate Enhances IL-8 Production via The MyD88- Independent TLR4 Signaling Pathway: Potential Relevance to Metabolic Inflammation

Elevated levels of IL-8 (CXCL8) in obesity have been linked with insulin resistance and type 2 diabetes (T2D). The mechanisms that lead to the profound production of IL-8 in obesity remains to be understood. TNF-α and saturated free fatty acids (FFAs) are increased in obese humans and correlate with insulin resistance. Hence, we sought to investigate whether the cooccurrence of TNF-α and FFAs led to increase the production of IL-8 by human monocytes. We found that co-stimulation of human monocytes with palmitate and TNF-α led to increased IL-8 production as compared to those stimulated with palmitate or TNF-α alone. The synergistic production of IL-8 by TNF-α/palmitate was suppressed by neutralizing anti- Toll like receptor 4 (TLR4) antibody and by genetic silencing of TLR4. Both MyD88-deficient and MyD88-competent cells responded comparably to TNF-α/Palmitate. However, TIR-domain-containing adapter-inducing interferon (TRIF) inhibition or interferon regulatory transcription factor 3 (IRF3) knockdown partly blocked the synergistic production of IL-8. Our human data show that increased adipose tissue TNF-α expression correlated positively with IL-8 expression (r = 0.49, P = 0.001). IL-8 and TNF-α correlated positively with macrophage markers including CD68, CD163 and CD86 in adipose tissue. These findings suggest that the signaling cross-talk between saturated fatty acid palmitate and TNF-α may be a key driver in obesity-associated chronic inflammation via an excessive production of IL-8.

Postprandial inflammatory responses after oral glucose, lipid and protein challenges: Influence of obesity, sex and polycystic ovary syndrome

BACKGROUND & AIMS

Most evidence linking the polycystic ovary syndrome (PCOS) with chronic low-grade inflammation has been obtained in the fasting state. We have studied the postprandial inflammatory response to oral glucose, lipid and protein challenges and the possible influences of obesity, sex and PCOS on these responses.

METHODS

On alternate days, we submitted 17 women with PCOS (9 non-obese, 8 obese), 17 control women (9 non-obese, 8 obese) and 19 control men (10 non-obese, 9 obese) to isocaloric (300 Kcal) oral macronutrient loads. We assayed serum for TNF-α, IL-6, IL-18, IL-10, pentraxin-3 and galectin-3 concentrations and leukocytes for expression of TNF, IL6, IL10 and their receptors TNFRSF1B, IL6R and IL10RA.

RESULTS

Circulating IL-6 levels decreased after glucose and protein ingestion but slightly increased after oral lipid intake. Leukocyte IL6 expression did not change after the ingestion of any macronutrient yet IL6R expression increased during all macronutrient challenges, the largest increase being observed after glucose ingestion. Serum TNF-α similarly decreased during either macronutrient load, whereas TNF expression increased after macronutrient ingestion, the highest increase observed after oral glucose. TNFRSF1B expression also increased after glucose intake but not after lipid or protein ingestion. No global effect of obesity or group on postprandial circulating IL-6, TNF-α, or IL6, IL6R, TNF and TNFRSF1B expression was found. Circulating IL-18 concentrations decreased during all oral challenges, whereas in case of galectin-3 and pentraxin-3 only the protein load caused a reduction in its concentrations. Of the genes studied here, IL10 showed the largest increase in expression throughout all the postprandial curves, particularly after glucose. Obesity blunted the increase in IL10 expression. IL10RA expression decreased after glucose ingestion but remained unchanged during lipid and protein loads.

CONCLUSIONS

Glucose ingestion, as opposed to lipid and protein intake, results into the largest increase in leukocyte gene expression of inflammatory mediators. The expression of the anti-inflammatory cytokine IL10 was the largest observed here, suggesting a compensatory mechanisms against postprandial inflammation that may be blunted in obesity. However, these responses did not translate into the circulating concentrations of these inflammatory mediators during the immediate postprandial phase.

Central and Peripheral Inflammation Link Metabolic Syndrome and Major Depressive Disorder

Metabolic syndrome and major depression are two of the most common and debilitating disorders worldwide, occurring with significant rates of comorbidity. Recent studies have uncovered that each of these conditions is associated with chronic, low-grade inflammation. This is characterized by increased circulating pro-inflammatory cytokines, altered leukocyte population frequencies in blood, accumulation of immune cells in tissues including the brain, and activation of these immune cells. Cytokines that become elevated during obesity can contribute to the progression of metabolic syndrome by directly causing insulin resistance. During chronic stress, there is evidence that these cytokines promote depression-like behavior by disrupting neurotransmitter synthesis and signal transduction. Animal models of obesity and depression have revealed a bi-directional relationship whereby high-fat feeding and chronic stress synergize and exacerbate metabolic dysregulation and behavioral abnormalities. Although far from conclusive, emerging evidence suggests that inflammation in the central and peripheral immune system may link metabolic syndrome to major depressive disorder. In this review, we will synthesize available data supporting this view and identify critical areas for future investigation.

Dietary Fatty Acids and Other Nutrients in Relation to Inflammation and Particularly to Oral Mucosa Inflammation. A Literature Review

Oral mucosa is site of inflammatory process development. When they are chronic, they provide a microenvironment based on cytokines and inflammatory mediators that contribute to cancer initiation, progression, invasion, and metastasis. Certain dietary fatty acids (FAs) have immunomodulatory, inflammatory, and antiinflammatory effects. This review examined the literature on inflammation, mainly referred to the oral mucosa, and its association with dietary FAs and other nutrients. A Pubmed search of studies published in English until June 2018 was carried out. N-3 FAs have shown immunomodulatory and antiinflammatory activity in certain human diseases. These FAs and their mediators may inhibit inflammation, angiogenesis, and cancer via multiple mechanisms. Studies on cellular models of murine and human intestinal mucosa indicate association between dietary n-3 FA intake and the inflammatory state of mucosa membranes. Nevertheless scarce information on the association between dietary FAs and oral inflammation could be found. Based on the evidence, we hypothesize that n-3 FAs reduce the oral mucosa inflammation thus decreasing the risk of developing precancerous lesions and cancer. Molecular and clinical studies referred to this topic should be carried out as a contribution to the oral cancer prevention.

Manifestations and mechanisms of myocardial lipotoxicity in obesity

Environmental and socioeconomic changes over the past thirty years have contributed to a dramatic rise in the worldwide prevalence of obesity. Heart disease is amongst the most serious health risks of obesity, with increases in both atherosclerotic coronary heart disease and heart failure among obese individuals. In this review, we focus on primary myocardial alterations in obesity that include hypertrophic remodelling and diastolic dysfunction. Obesity-associated perturbations in myocardial and systemic lipid metabolism are important contributors to cardiovascular complications of obesity. Accumulation of excess lipid in nonadipose cells of the cardiovascular system can cause cell dysfunction and cell death, a process known as lipotoxicity. Lipotoxicity has been modelled in mice using high-fat diet feeding, inbred lines with mutations in leptin receptor signalling, and in genetically engineered mice with enhanced myocardial fatty acid uptake, altered lipid droplet homoeostasis or decreased cardiac fatty acid oxidation. These studies, along with findings in cell culture model systems, indicate that the molecular pathophysiology of lipid overload involves endoplasmic reticulum stress, alterations in autophagy, de novo ceramide synthesis, oxidative stress, inflammation and changes in gene expression. We highlight recent advances that extend our understanding of the impact of obesity and altered lipid metabolism on cardiac function.

Western diet triggers Toll-like receptor 4 signaling-induced endothelial dysfunction in female Wistar rats

Overconsumption of a diet rich in fat and carbohydrates, called the Western diet, is a major contributor to the global epidemic of cardiovascular disease. Despite previously documented cardiovascular protection exhibited in female rats, this safeguard may be lost under certain metabolic stressors. We hypothesized that female Wistar rats challenged by a Western diet composed of 21% fat and 50% carbohydrate (34.1% sucrose) for 17 wk would develop endothelial dysfunction via endothelial Toll-like receptor 4 (TLR4) signaling. Western diet-fed female rats exhibited dysregulation of metabolism, revealing increased body weight and abdominal fat, decreased expression of adiponectin in white adipose tissue, glucose intolerance, and impaired insulin sensitivity. Western diet exposure increased hepatic triglycerides and cholesterol alongside hepatic steatosis, categorizing nonalcoholic fatty liver disease. Moreover, a Western diet negatively affected vascular function, revealing hypertension, impaired endothelium-dependent vasorelaxation, aortic remodeling, and increased reactive oxygen species (ROS) production. Aortic protein expression of TLR4 and its downstream proteins were markedly increased in the Western diet-fed group in association with elevated serum levels of free fatty acids. In vitro experiments were conducted to test whether free fatty acids contribute to vascular ROS overproduction via the TLR4 signaling pathway. Cultured endothelial cells were stimulated with palmitate in the presence of TAK-242, a TLR4 signaling inhibitor. Palmitate-induced overgeneration of ROS in endothelial cells was abolished in the presence of TAK-242. Our data show that a Western diet induced endothelial dysfunction in female rats and suggest that endothelial TLR4 signaling may play a key role in abolishing female cardiovascular protection. NEW & NOTEWORTHY A Western diet induced elevated levels of free fatty acids, produced nonalcoholic fatty liver disease, and provoked endothelial dysfunction in female rats in association with Toll-like receptor 4 signaling-mediated vascular reactive oxygen species production. Limited consumption of a Western diet in premenopausal women may decrease their risk of cardiovascular complications.

Palmitate induces nitric oxide production and inflammatory cytokine expression in zebrafish

Inflammation markers in zebrafish embryos reflect a toxic response that is common to other animal models and humans. Free fatty acids (FFAs) are known to cause damage in various tissues by inducing inflammation. In this study, we investigated whether a FFA (palmitate) induces inflammation in zebrafish embryos. Nitrous oxide (NO) production and cyclooxygenase-2 (COX-2) mRNA expression were increased in palmitate-treated zebrafish embryos in a dose-dependent manner. mRNA expression of pro-inflammatory cytokines, interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF- α), were also increased. Additionally, the mRNA expression of p65 nuclear factor-kB and I-kB-α were significantly increased after palmitate-treatment. Increased reactive oxygen species (ROS) expression was observed in palmitate-treated zebrafish embryos as well as pericardial edema. Additionally, mRNA expression of pro-inflammatory cytokines were increased in zebrafish liver and pancreas fed with palmitate-contained diet. Taken together, these results indicated that palmitate increases pro-inflammatory mediators in zebrafish embryos, suggesting that zebrafish could be an alternative animal model for inflammatory disease including diabetes.

The role and mechanism of KCa3.1 channels in human monocyte migration induced by palmitic acid

Monocyte migration into diseased tissues contributes to the pathogenesis of diseases. Intermediate-conductance Ca²⁺-activated K⁺ (K_Ca3.1) channels play an important role in cell migration. However, the role of K_Ca3.1 channels in mediating monocyte migration induced by palmitic acid (PA) is still unclear. Using cultured THP-1 cells and peripheral blood mononuclear cells from healthy subjects, we investigated the role and signaling mechanisms of K_Ca3.1 channels in mediating the migration induced by PA. Using methods of Western blotting analysis, RNA interference, cell migration assay and ELISA, we found that PA-treated monocytes exhibited increment of the protein levels of K_Ca3.1 channel and monocyte chemoattractant protein-1 (MCP-1), and the effects were reversed by co-incubation of PA with anti-TLR2/4 antibodies or by specific inhibitors of p38-MAPK, or NF-κB. In addition, PA increased monocyte migration, which was abolished by a specific K_Ca3.1 channel blocker, TRAM-34, or K_Ca3.1 small interfering RNA (siRNA). The expression and secretion of MCP-1 induced by PA was also similarly prevented by TRAM-34 and K_Ca3.1 siRNA. These results demonstrate for the first time that PA upregulates K_Ca3.1 channels through TLR2/4, p38-MAPK and NF-κB pathway to promote the expression of MCP-1, and then induce the trans-endothelial migration of monocytes.

Palmitate induces glycosylation of cyclooxygenase-2 in primary human vascular smooth muscle cells

Vascular basal cyclooxygenase-2 (COX-2) expression and activity can be induced by endotoxin, hypoxia, or ischemia. During vascular pathologies such as atherosclerosis, increases in COX-2 activity result in prostanoid production, a contributor to the development and progression of vascular inflammation leading to unstable atherosclerotic plaques and increased risk for thrombotic events. Recent studies demonstrate that select free fatty acids, such as palmitate, can act as proinflammatory mediators. However, the effect of palmitate on COX-2 expression and activity, and its impact on the development and progression of vascular inflammation, are not well elucidated. We investigated the effect of palmitate on COX-2 expression and function in human vascular smooth muscle cells. Cells were treated with palmitate, COX-2 protein levels were assessed using Western analysis, and activity was assessed via ELISA. We observed that palmitate dose-dependently increased COX-2 levels and specifically enhanced band intensity of the COX-2 74 kDa band (slowest migrating band). This response was attenuated by N-linked glycosylation inhibition, suggesting that palmitate impacts expression of the fully activated glycoform of COX-2. Palmitate-induced increases in COX-2 levels correlated with an increase in prostaglandin E₂ production that was also attenuated by a glycosylation inhibitor. Additionally, palmitate altered cell morphology and increased cell density which were reversed by selective COX-2 inhibition. Thus, we conclude that palmitate acts on COX-2 by two separate mechanisms of action in human vascular smooth muscle. It elicits dose-dependent increases in COX-2 protein expression and modulates regulation of COX-2 activity via modification of posttranslational glycosylation.

Association between plasma phospholipid saturated fatty acids and metabolic markers of lipid, hepatic, inflammation and glycaemic pathways in eight European countries: a cross-sectional analysis in the EPIC-InterAct study

BACKGROUND

Accumulating evidence suggests that individual circulating saturated fatty acids (SFAs) are heterogeneous in their associations with cardio-metabolic diseases, but evidence about associations of SFAs with metabolic markers of different pathogenic pathways is limited. We aimed to examine the associations between plasma phospholipid SFAs and the metabolic markers of lipid, hepatic, glycaemic and inflammation pathways.

METHODS

We measured nine individual plasma phospholipid SFAs and derived three SFA groups (odd-chain: C15:0 + C17:0, even-chain: C14:0 + C16:0 + C18:0, and very-long-chain: C20:0 + C22:0 + C23:0 + C24:0) in individuals from the subcohort of the European Prospective Investigation into Cancer and Nutrition (EPIC)-InterAct case-cohort study across eight European countries. Using linear regression in 15,919 subcohort members, adjusted for potential confounders and corrected for multiple testing, we examined cross-sectional associations of SFAs with 13 metabolic markers. Multiplicative interactions of the three SFA groups with pre-specified factors, including body mass index (BMI) and alcohol consumption, were tested.

RESULTS

Higher levels of odd-chain SFA group were associated with lower levels of major lipids (total cholesterol (TC), triglycerides, apolipoprotein A-1 (ApoA1), apolipoprotein B (ApoB)) and hepatic markers (alanine transaminase (ALT), aspartate transaminase (AST), gamma-glutamyl transferase (GGT)). Higher even-chain SFA group levels were associated with higher levels of low-density lipoprotein cholesterol (LDL-C), TC/high-density lipoprotein cholesterol (HDL-C) ratio, triglycerides, ApoB, ApoB/A1 ratio, ALT, AST, GGT and CRP, and lower levels of HDL-C and ApoA1. Very-long-chain SFA group levels showed inverse associations with triglycerides, ApoA1 and GGT, and positive associations with TC, LDL-C, TC/HDL-C, ApoB and ApoB/A1. Associations were generally stronger at higher levels of BMI or alcohol consumption.

CONCLUSIONS

Subtypes of SFAs are associated in a differential way with metabolic markers of lipid metabolism, liver function and chronic inflammation, suggesting that odd-chain SFAs are associated with lower metabolic risk and even-chain SFAs with adverse metabolic risk, whereas mixed findings were obtained for very-long-chain SFAs. The clinical and biochemical implications of these findings may vary by adiposity and alcohol intake.

Vitamin D prenatal programming of childhood metabolomics profiles at age 3 y

Background: Vitamin D deficiency is implicated in a range of common complex diseases that may be prevented by gestational vitamin D repletion. Understanding the metabolic mechanisms related to in utero vitamin D exposure may therefore shed light on complex disease susceptibility.Objective: The goal was to analyze the programming role of in utero vitamin D exposure on children's metabolomics profiles.Design: First, unsupervised clustering was done with plasma metabolomics profiles from a case-control subset of 245 children aged 3 y with and without asthma from the Vitamin D Antenatal Asthma Reduction Trial (VDAART), in which pregnant women were randomly assigned to vitamin D supplementation or placebo. Thereafter, we analyzed the influence of maternal pre- and postsupplement vitamin D concentrations on cluster membership. Finally, we used the metabolites driving the clustering of children to identify the dominant metabolic pathways that were influential in each cluster.Results: We identified 3 clusters of children characterized by 1) high concentrations of fatty acids and amines and low maternal postsupplement vitamin D (mean ± SD; 27.5 ± 11.0 ng/mL), 2) high concentrations of amines, moderate concentrations of fatty acids, and normal maternal postsupplement vitamin D (34.0 ± 14.1 ng/mL), and 3) low concentrations of fatty acids, amines, and normal maternal postsupplement vitamin D (35.2 ± 15.9 ng/mL). Adjusting for sample storage time, maternal age and education, and both child asthma and vitamin D concentration at age 3 y did not modify the association between maternal postsupplement vitamin D and cluster membership (P = 0.0014). Maternal presupplement vitamin D did not influence cluster membership, whereas the combination of pre- and postsupplement concentrations did (P = 0.03).Conclusions: Young children can be clustered into distinct biologically meaningful groups by their metabolomics profiles. The clusters differed in concentrations of inflammatory mediators, and cluster membership was influenced by in utero vitamin D exposure, suggesting a prenatal programming role of vitamin D on the child's metabolome. This trial was registered at clinicaltrials.gov as NCT00920621.

Cooperative stimulation of atherogenesis by lipopolysaccharide and palmitic acid-rich high fat diet in low-density lipoprotein receptor-deficient mice

BACKGROUND AND AIMS

Either lipopolysaccharide (LPS) or high-fat diet (HFD) enriched with saturated fatty acid (SFA) promotes atherosclerosis. In this study, we investigated the effect of LPS in combination with SFA-rich HFD on atherosclerosis and how LPS and SFA interact to stimulate inflammatory response in vascular endothelial cells.

METHODS

Low-density lipoprotein receptor-deficient (LDLR^-/-) mice were fed a low-fat diet (LFD), HFD with low palmitic acid (PA) (LP-HFD), or HFD with high PA (HP-HFD) for 20 weeks. During the last 12 weeks, half mice received LPS and half received PBS. After treatment, metabolic parameters and aortic atherosclerosis were analyzed. To understand the underlying mechanisms, human aortic endothelial cells (HAECs) were treated with LPS and/or PA and proinflammatory molecule expression was quantified.

RESULTS

The metabolic study showed that LPS had no significant effect on cholesterol, triglycerides, free fatty acids, but increased insulin and insulin resistance. Both LP-HFD and HP-HFD increased body weight and cholesterol while LP-HFD increased glucose and HP-HFD increased triglycerides, insulin, and insulin resistance. Analysis of aortic atherosclerosis showed that HP-HFD was more effective than LP-HFD in inducing atherosclerosis and LPS in combination with HP-HFD increased atherosclerosis in the thoracic aorta, a less common site for atherosclerosis, as compared with LPS or HP-HFD. To understand the mechanisms, results showed that LPS and PA synergistically upregulated adhesion molecules and proinflammatory cytokines in HAECs.

CONCLUSIONS

LPS and PA-rich HFD cooperatively increased atherogenesis in the thoracic aorta. The synergy between LPS and PA on proinflammatory molecules in HAECs may play an important role in atherogenesis.

Zoledronate dysregulates fatty acid metabolism in renal tubular epithelial cells to induce nephrotoxicity

Zoledronate is a bisphosphonate that is widely used in the treatment of metabolic bone diseases. However, zoledronate induces significant nephrotoxicity associated with acute tubular necrosis and renal fibrosis when administered intravenously. There is speculation that zoledronate-induced nephrotoxicity may result from its pharmacological activity as an inhibitor of the mevalonate pathway but the molecular mechanisms are not fully understood. In this report, human proximal tubular HK-2 cells and mouse models were combined to dissect the molecular pathways underlying nephropathy caused by zoledronate treatments. Metabolomic and proteomic assays revealed that multiple cellular processes were significantly disrupted, including the TGFβ pathway, fatty acid metabolism and small GTPase signaling in zoledronate-treated HK-2 cells (50 μM) as compared with those in controls. Zoledronate treatments in cells (50 μM) and mice (3 mg/kg) increased TGFβ/Smad3 pathway activation to induce fibrosis and kidney injury, and specifically elevated lipid accumulation and expression of fibrotic proteins. Conversely, fatty acid transport protein Slc27a2 deficiency or co-administration of PPARA agonist fenofibrate (20 mg/kg) prevented zoledronate-induced lipid accumulation and kidney fibrosis in mice, indicating that over-expression of fatty acid transporter SLC27A2 and defective fatty acid β-oxidation following zoledronate treatments were significant factors contributing to its nephrotoxicity. These pharmacological and genetic studies provide an important mechanistic insight into zoledronate-associated kidney toxicity that will aid in development of therapeutic prevention and treatment options for this nephropathy.

Deconstructing metabolic inflammation using cellular systems

Over the past years, we have embarked in a systematic analysis of the effect of obesity or fatty acids on circulating monocytes, microvascular endothelial cells, macrophages, and skeletal muscle cells. With the use of cell culture strategies, we have deconstructed complex physiological systems and then reconstructed "partial equations" to better understand cell-to-cell communication. Through these approaches, we identified that in high saturated fat environments, cell-autonomous proinflammatory pathways are activated in monocytes and endothelial cells, promoting monocyte adhesion and transmigration. We think of this as a paradigm of the conditions promoting immune cell infiltration into tissues during obesity. In concert, it is possible that muscle and adipose tissue secrete immune cell chemoattractants, and indeed, our tissue culture reconstructions reveal that myotubes treated with the saturated fatty acid palmitate, but not the unsaturated fatty acid palmitoleate, release nucleotides that attract monocytes and other compounds that promote proinflammatory classically activated "(M1)-like" polarization in macrophages. In addition, palmitate directly triggers an M1-like macrophage phenotype, and secretions from these activated macrophages confer insulin resistance to target muscle cells. Together, these studies suggest that in pathophysiological conditions of excess fat, the muscle, endothelial and immune cells engage in a synergistic crosstalk that exacerbates tissue inflammation, leukocyte infiltration, polarization, and consequent insulin resistance.

Endothelial Transcytosis of Insulin: Does It Contribute to Insulin Resistance?

Most research on insulin resistance has focused on impaired signaling at the level of target tissues like skeletal muscle. Insulin delivery is also important and includes recruitment and perfusion of capillaries bearing insulin, but also the transit of insulin across the capillary endothelium. The mechanisms of this second stage (insulin transcytosis) and whether it contributes to insulin resistance remain uncertain.

Knockout of Vasohibin-1 Gene in Mice Results in Healthy Longevity with Reduced Expression of Insulin Receptor, Insulin Receptor Substrate 1, and Insulin Receptor Substrate 2 in Their White Adipose Tissue

Vasohibin-1 (Vash1), originally isolated as an endothelium-derived angiogenesis inhibitor, has a characteristic of promoting stress tolerance in endothelial cells (ECs). We therefore speculated that the lack of the vash1 gene would result in a short lifespan. However, to our surprise, vash1^−/− mice lived significantly longer with a milder senescence phenotype than wild-type (WT) mice. We sought the cause of this healthy longevity and found that vash1^−/− mice exhibited mild insulin resistance along with reduced expression of the insulin receptor (insr), insulin receptor substrate 1 (irs-1), and insulin receptor substrate 2 (irs-2) in their white adipose tissue (WAT) but not in their liver or skeletal muscle. The expression of vash1 dominated in the WAT among those 3 organs. Importantly, vash1^−/− mice did not develop diabetes even when fed a high-fat diet. These results indicate that the expression of vash1 was required for the normal insulin sensitivity of the WAT and that the target molecules for this activity were insr, irs1, and irs2. The lack of vash1 caused mild insulin resistance without the outbreak of overt diabetes and might contribute to healthy longevity.

Depression, daily stressors and inflammatory responses to high-fat meals: when stress overrides healthier food choices

Depression, stress and diet can all alter inflammation. This double-blind, randomized crossover study addressed the impact of daily stressors and a history of major depressive disorder (MDD) on inflammatory responses to high-fat meals. During two separate 9.5 h admissions, 58 healthy women (38 breast cancer survivors and 20 demographically similar controls), mean age 53.1 years, received either a high saturated fat meal or a high oleic sunflower oil meal. The Daily Inventory of Stressful Events assessed prior day stressors and the Structured Clinical Interview for DSM-IV evaluated MDD. As expected, for a woman with no prior day stressors, C-reactive protein (CRP), serum amyloid A (SAA), intercellular adhesion molecule-1 (sICAM-1) and vascular cell adhesion molecule-1 (sVCAM-1) were higher following the saturated fat meal than the high oleic sunflower oil meal after controlling for pre-meal measures, age, trunk fat and physical activity. But if a woman had prior day stressors, these meal-related differences disappeared-because the stressors heightened CRP, SAA, sICAM-1 and sVCAM-1 responses to the sunflower oil meal, making it look more like the responses to the saturated fat meal. In addition, women with an MDD history had higher post-meal blood pressure responses than those without a similar history. These data show how recent stressors and an MDD history can reverberate through metabolic alterations, promoting inflammatory and atherogenic responses.

CD36 is upregulated in mice with periodontitis and metabolic syndrome and involved in macrophage gene upregulation by palmitate

BACKGROUND

We reported that high-fat diet (HFD)-induced metabolic syndrome (MetS) exacerbates lipopolysaccharide (LPS)-stimulated periodontitis and palmitate, the major saturated fatty acid in the HFD, amplified LPS-stimulated gene expression in vitro. As CD36 is a major receptor for fatty acids, we investigated periodontal CD36 expression in mice with periodontitis and MetS, and the role of CD36 in inflammatory gene expression in macrophages stimulated by palmitate.

METHODS

MetS and periodontitis were induced in mice by HFD and periodontal injection of LPS, respectively. The periodontal CD36 expression and its relationship with alveolar bone loss were studied using immunohistochemistry, real-time PCR, and correlation analysis. The role of CD36 in upregulation of inflammatory mediators by LPS and palmitate in macrophages was assessed using pharmacological inhibitor and small interfering RNA.

RESULTS

Periodontal CD36 expression was higher in mice with both MetS and periodontitis than that in mice with periodontitis or MetS alone and was correlated with osteoclastogenesis and alveolar bone loss. In vitro studies showed that CD36 expression in macrophages was upregulated by LPS and palmitate, and targeting CD36 attenuated palmitate-enhanced gene expression.

CONCLUSION

CD36 expression is upregulated in mice with periodontitis and MetS and involved in gene expression in macrophages stimulated by palmitate and LPS.

Fatty acid synthase plays a positive role in shrimp immune responses against Vibrio parahaemolyticus infection

Fatty acid synthase (FAS) is an important enzyme that catalyzes the synthesis of fatty acids. In this study, the role of the FAS gene from pacific white shrimp Litopenaeus vannamei (LvFAS) in immune responses against Vibrio parahaemolyticus infection was studied. The expression of LvFAS could be up-regulated upon infection of V. parahaemolyticus and stimulation of lipopolysaccharide and poly (I:C). The promoter of LvFAS was predicted to harbor a NF-κB binding site and dual-luciferase reporter assays demonstrated that the NF-κB family proteins Relish, sRelish and Dorsal could activate the transcription of LvFAS. After knockdown of LvFAS expression using RNAi strategy, both the mortality of V. parahaemolyticus infected shrimps and the bacterial load in shrimp tissues were significantly increased. Meanwhile, the expression of many immune-responsive genes, such as antimicrobial peptides, C-type lectins (CTLs), lysozyme and hemolin, was down-regulated. These suggested that LvFAS could play a positive role in anti-V. parahaemolyticus responses in shrimp. To our knowledge, this is the first study that investigates the role of FAS in antibacterial immunity in animals, which may indicate the relationship between the anabolism of fatty acids and immune responses in crustaceans.

Hepatic inflammatory cytokine production can be regulated by modulating sphingomyelinase and ceramide synthase 6

Chronic inflammation is associated with the pathogenesis of type 2 diabetes and diabetic complications, and palmitate has been nominated as a candidate for the molecular link between these disorders. Recently, a crucial role of ceramide in inflammation and metabolic diseases has been reported. Therefore, in this study, we investigated whether ceramide formation is involved in palmitate‑induced hepatic inflammation in vitro and in vivo. Ceramide can be generated either by the de novo pathway or by sphingomyelin degradation, and six different ceramide synthases (CerS) determine the specific acyl chain length of ceramide in mammals. We examined the roles of CerS and sphingomyelinases (SMases) in the secretion of inflammatory cytokines, such as tumour necrosis factor (TNF)‑α, interleukin (IL)‑1β, and IL‑6 in Hep3B cells. Among the six CerS, CerS6 overexpression uniquely elevated TNF‑α secretion via p38 mitogen‑activated protein kinase (MAPK) activation. In addition, the treatment of CerS6 overexpressing cells with palmitate synergistically increased cytokine secretion. However, neither palmitate treatment nor CerS6 overexpression altered lipopolysaccharide (LPS)-induced cytokine secretion. Instead, the activation of acidic (A)‑SMase was involved in LPS‑induced cytokine secretion via the MAPK/NF‑κB pathway. Finally, the suppression of ceramide generation via A‑SMase inhibition or de novo ceramide synthesis decreased high‑fat diet‑induced hepatic cytokine production in vivo. On the whole, our results revealed that CerS6 played a role in TNF‑α secretion, and palmitate augmented inflammatory responses in pathophysiological conditions in which CerS6 is overexpressed. In addition, A‑SMase activation was shown to be involved in LPS‑induced inflammatory processes, suggesting that the modulation of CerS6 and A‑SMase may be a therapeutic target for controlling hepatic inflammation.

Rab17 mediates differential antigen sorting following efferocytosis and phagocytosis

Macrophages engulf and destroy pathogens (phagocytosis) and apoptotic cells (efferocytosis), and can subsequently initiate adaptive immune responses by presenting antigens derived from engulfed materials. Both phagocytosis and efferocytosis share a common degradative pathway in which the target is engulfed into a membrane-bound vesicle, respectively, termed the phagosome and efferosome, where they are degraded by sequential fusion with endosomes and lysosomes. Despite this shared maturation pathway, macrophages are immunogenic following phagocytosis but not efferocytosis, indicating that differential processing or trafficking of antigens must occur. Mass spectrometry and immunofluorescence microscopy of efferosomes and phagosomes in macrophages demonstrated that efferosomes lacked the proteins required for antigen presentation and instead recruited the recycling regulator Rab17. As a result, degraded materials from efferosomes bypassed the MHC class II loading compartment via the recycling endosome - a process not observed in phagosomes. Combined, these results indicate that macrophages prevent presentation of apoptotic cell-derived antigens by preferentially trafficking efferocytosed, but not phagocytosed, materials away from the MHC class II loading compartment via the recycling endosome pathway.

Endothelial FoxO proteins impair insulin sensitivity and restrain muscle angiogenesis in response to a high-fat diet

Skeletal muscle microvascular dysfunction contributes to disease severity in type 2 diabetes. Recent studies indicate a role for Forkhead box O (FoxO) transcription factors in modulating endothelial cell phenotype. We hypothesized that a high-fat (HF) diet generates a dysfunctional vascular niche through an increased expression of endothelial FoxO. FoxO1 protein increased (+130%) in the skeletal muscle capillaries from HF compared to normal chow-fed mice. FoxO1 protein was significantly elevated in cultured endothelial cells exposed to the saturated fatty acid palmitate or the proinflammatory cytokine TNF-α. In HF-fed mice, endothelium-directed depletion of FoxO1/3/4 (FoxO(Δ)) improved insulin sensitivity (+110%) compared to that of the controls (FoxO(L/L)). The number of skeletal muscle capillaries increased significantly in the HF-FoxO(Δ) mice. Transcript profiling of skeletal muscle identified significant increases in genes associated with angiogenesis and lipid metabolism in HF-FoxO(Δ) vs. HF-FoxO(L/L) mice. HF-FoxO(Δ) muscle also was characterized by a decrease in inflammation-related genes and an enriched M2 macrophage signature. We conclude that endothelial FoxO proteins promote insulin resistance in HF diet, which may in part result from FoxO proteins establishing an antiangiogenic and proinflammatory microenvironment within skeletal muscle. These findings provide mechanistic insight into the development of microvascular dysfunction in the progression of type 2 diabetes.-Nwadozi, E., Roudier, E., Rullman, E., Tharmalingam, S., Liu, H.-Y., Gustafsson, T., Haas, T. L. Endothelial FoxO proteins impair insulin sensitivity and restrain muscle angiogenesis in response to a high-fat diet.