Palmitic acid-induced activation of human T-lymphocytes and aortic endothelial cells with production of insulin receptors, reactive oxygen species, cytokines, and lipid peroxidation

Oleic acid triggers metabolic rewiring of T cells poising them for T helper 9 differentiation

T cells are the most common immune cells in atherosclerotic plaques, and the function of T cells can be altered by fatty acids. Here, we show that pre-exposure of CD4+ T cells to oleic acid, an abundant fatty acid linked to cardiovascular events, upregulates core metabolic pathways and promotes differentiation into interleukin-9 (IL-9)-producing cells upon activation. RNA sequencing of non-activated T cells reveals that oleic acid upregulates genes encoding key enzymes responsible for cholesterol and fatty acid biosynthesis. Transcription footprint analysis links these expression changes to the differentiation toward TH9 cells, a pro-atherogenic subset. Spectral flow cytometry shows that pre-exposure to oleic acid results in a skew toward IL-9+-producing T cells upon activation. Importantly, pharmacological inhibition of either cholesterol or fatty acid biosynthesis abolishes this effect, suggesting a beneficial role for statins beyond cholesterol lowering. Taken together, oleic acid may affect inflammatory diseases like atherosclerosis by rewiring T cell metabolism.

Mitochondrial metabolism sustains CD8+ T cell migration for an efficient infiltration into solid tumors

The ability of CD8+ T cells to infiltrate solid tumors and reach cancer cells is associated with improved patient survival and responses to immunotherapy. Thus, identifying the factors controlling T cell migration in tumors is critical, so that strategies to intervene on these targets can be developed. Although interstitial motility is a highly energy-demanding process, the metabolic requirements of CD8+ T cells migrating in a 3D environment remain unclear. Here, we demonstrate that the tricarboxylic acid (TCA) cycle is the main metabolic pathway sustaining human CD8+ T cell motility in 3D collagen gels and tumor slices while glycolysis plays a more minor role. Using pharmacological and genetic approaches, we report that CD8+ T cell migration depends on the mitochondrial oxidation of glucose and glutamine, but not fatty acids, and both ATP and ROS produced by mitochondria are required for T cells to migrate. Pharmacological interventions to increase mitochondrial activity improve CD8+ T cell intratumoral migration and CAR T cell recruitment into tumor islets leading to better control of tumor growth in human xenograft models. Our study highlights the rationale of targeting mitochondrial metabolism to enhance the migration and antitumor efficacy of CAR T cells in treating solid tumors.

Impact of dairy fat manipulation on endothelial function and lipid regulation in human aortic endothelial cells exposed to human plasma samples: an in vitro investigation from the RESET study

PURPOSE

Longer-term intake of fatty acid (FA)-modified dairy products (SFA-reduced, MUFA-enriched) was reported to attenuate postprandial endothelial function in humans, relative to conventional (control) dairy. Thus, we performed an in vitro study in human aortic endothelial cells (HAEC) to investigate mechanisms underlying the effects observed in vivo.

METHODS

This sub-study was conducted within the framework of the RESET study, a 12-week randomised controlled crossover trial with FA-modified and control dairy diets. HAEC were incubated for 24 h with post-intervention plasma samples from eleven adults (age: 57.5 ± 6.0 years; BMI: 25.7 ± 2.7 kg/m2) at moderate cardiovascular disease risk following representative sequential mixed meals. Markers of endothelial function and lipid regulation were assessed.

RESULTS

Relative to control, HAEC incubation with plasma following the FA-modified treatment increased postprandial NOx production (P-interaction = 0.019), yet up-regulated relative E-selectin mRNA gene expression (P-interaction = 0.011). There was no impact on other genes measured.

CONCLUSION

Incubation of HAEC with human plasma collected after longer-term dairy fat manipulation had a beneficial impact on postprandial NOx production. Further ex vivo research is needed to understand the impact of partial replacement of SFA with unsaturated fatty acids in dairy foods on pathways involved in endothelial function.

[Immunometabolism in Sepsis]

Immunometabolism is a fascinating field of research that investigates the interactions between metabolic processes and the immune response. This intricate connection plays a pivotal role in regulating inflammatory reactions and consequently exerts a significant impact on the course of sepsis. The proinflammatory response during an immune reaction is closely tied to a high energy demand in immune cells. As a result, proinflammatory immune cells rapidly require substantial amounts of energy in the form of ATP, necessitating a fundamental and swift shift in their metabolism, i.e., their means of generating energy. This entails a marked increase in glycolysis within the proinflammatory response, thereby promptly meeting the energy requirements and providing essential metabolic building blocks for the biosynthesis of macromolecules. Alongside glycolysis, there is heightened activity in the pentose phosphate pathway (PPP). The PPP significantly contributes to NADPH production within the cell, thus maintaining redox equilibrium. Elevated PPP activity consequently leads to an increased NADPH level, resulting in enhanced production of reactive oxygen species (ROS) and nitric oxide (NO). While these molecules are crucial for pathogen elimination, an excess can also induce tissue damage. Simultaneously, there are dual interruptions in the citric acid cycle. In the cellular resting state, the citric acid cycle acts as a sort of "universal processor", where metabolic byproducts of glycolysis, fatty acid breakdown, and amino acid degradation are initially transformed into NADH and FADH2, subsequently yielding ATP. While the citric acid cycle and its connected oxidative phosphorylation predominantly generate energy at rest, it becomes downregulated in the proinflammatory phase of sepsis. The two interruptions lead to an accumulation of citrate and succinate within cells, reflecting mitochondrial dysfunction. Additionally, the significantly heightened glycolysis through fermentation yields lactate, a pivotal metabolite for sepsis diagnosis and prognosis. Conversely, cells in an anti-inflammatory state revert to a metabolic profile akin to the resting state: Glycolysis is attenuated, PPP is suppressed, and the citric acid cycle is reactivated. Of particular interest is that not only does the immune reaction influence metabolic pathways, but this connection also operates in reverse. Thus, modulation of metabolic pathways also modulates the immunity of the corresponding cell and thereby the state of the immune system itself. This could potentially serve as an intriguing avenue in sepsis therapy.

Obesity, Dietary Fats, and Gastrointestinal Cancer Risk-Potential Mechanisms Relating to Lipid Metabolism and Inflammation

Obesity is a major driving factor in the incidence, progression, and poor treatment response in gastrointestinal cancers. Herein, we conducted a comprehensive analysis of the impact of obesity and its resulting metabolic perturbations across four gastrointestinal cancer types, namely, oesophageal, gastric, liver, and colorectal cancer. Importantly, not all obese phenotypes are equal. Obese adipose tissue heterogeneity depends on the location, structure, cellular profile (including resident immune cell populations), and dietary fatty acid intake. We discuss whether adipose heterogeneity impacts the tumorigenic environment. Dietary fat quality, in particular saturated fatty acids, promotes a hypertrophic, pro-inflammatory adipose profile, in contrast to monounsaturated fatty acids, resulting in a hyperplastic, less inflammatory adipose phenotype. The purpose of this review is to examine the impact of obesity, including dietary fat quality, on adipose tissue biology and oncogenesis, specifically focusing on lipid metabolism and inflammatory mechanisms. This is achieved with a particular focus on gastrointestinal cancers as exemplar models of obesity-associated cancers.

The Role of Lipids in the Regulation of Immune Responses

Lipid metabolism plays a major role in the regulation of the immune system. Exogenous (dietary and microbial-derived) and endogenous (non-microbial-derived) lipids play a direct role in regulating immune cell activation, differentiation and expansion, and inflammatory phenotypes. Understanding the complexities of lipid-immune interactions may have important implications for human health, as certain lipids or immune pathways may be beneficial in circumstances of acute infection yet detrimental in chronic inflammatory diseases. Further, there are key differences in the lipid effects between specific immune cell types and location (e.g., gut mucosal vs. systemic immune cells), suggesting that the immunomodulatory properties of lipids may be tissue-compartment-specific, although the direct effect of dietary lipids on the mucosal immune system warrants further investigation. Importantly, there is recent evidence to suggest that lipid-immune interactions are dependent on sex, metabolic status, and the gut microbiome in preclinical models. While the lipid-immune relationship has not been adequately established in/translated to humans, research is warranted to evaluate the differences in lipid-immune interactions across individuals and whether the optimization of lipid-immune interactions requires precision nutrition approaches to mitigate or manage disease. In this review, we discuss the mechanisms by which lipids regulate immune responses and the influence of dietary lipids on these processes, highlighting compelling areas for future research.

Metabolites and Immune Response in Tumor Microenvironments

The remodeled cancer cell metabolism affects the tumor microenvironment and promotes an immunosuppressive state by changing the levels of macro- and micronutrients and by releasing hormones and cytokines that recruit immunosuppressive immune cells. Novel dietary interventions such as amino acid restriction and periodic fasting mimicking diets can prevent or dampen the formation of an immunosuppressive microenvironment by acting systemically on the release of hormones and growth factors, inhibiting the release of proinflammatory cytokines, and remodeling the tumor vasculature and extracellular matrix. Here, we discuss the latest research on the effects of these therapeutic interventions on immunometabolism and tumor immune response and future scenarios pertaining to how dietary interventions could contribute to cancer therapy.

CD8+ T cells contribute to diet-induced memory deficits in aged male rats

We have previously shown that short-term (3-day) high fat diet (HFD) consumption induces a neuroinflammatory response and subsequent impairment of long-term memory in aged, but not young adult, male rats. However, the immune cell phenotypes driving this proinflammatory response are not well understood. Previously, we showed that microglia isolated from young and aged rats fed a HFD express similar levels of priming and proinflammatory transcripts, suggesting that additional factors may drive the exaggerated neuroinflammatory response selectively observed in aged HFD-fed rats. It is established that T cells infiltrate both the young and especially the aged central nervous system (CNS) and contribute to immune surveillance of the parenchyma. Thus, we investigated the modulating role of short-term HFD on T cell presence in the CNS in aged rats using bulk RNA sequencing and flow cytometry. RNA sequencing results indicate that aging and HFD altered the expression of genes and signaling pathways associated with T cell signaling, immune cell trafficking, and neuroinflammation. Moreover, flow cytometry data showed that aging alone increased CD4+ and CD8+ T cell presence in the brain and that CD8+, but not CD4+, T cells were further increased in aged rats fed a HFD. Based on these data, we selectively depleted circulating CD8+ T cells via an intravenous injection of an anti-CD8 antibody in aged rats prior to 3 days of HFD to infer the functional role these cells may be playing in long-term memory and neuroinflammation. Results indicate that peripheral depletion of CD8+ T cells lowered hippocampal cytokine levels and prevented the HFD-induced i) increase in brain CD8+ T cells, ii) memory impairment, and iii) alterations in pre- and post-synaptic structures in the hippocampus and amygdala. Together, these data indicate a substantial role for CD8+ T cells in mediating diet-induced memory impairments in aged male rats.

Decreased cardiovascular risk factors and inflammation with remission of type 2 diabetes in adults with obesity using a high protein diet: Randomized control trial

Objective

The study objective was to determine the effects a high protein (HP) vs. a high carbohydrate (HC) diet on cardiovascular risk factors (CVR), inflammation, metabolic parameters, oxidative stress, weight loss, lean and fat body mass, and remission of Type 2 Diabetes (T2DM) in subjects with obesity.

Research design and methods

Twelve women and men with T2D were recruited and randomized to either a HP (30%protein, 30%fat, 40%carbohydrate) (n = 6) or HC (15%protein, 30%fat, 55%carbohydrate) (n = 6) diet feeding study for 6 months in this randomized controlled trial. All meals were purchased at local grocery stores and provided to subjects for 6 months with daily food menus for HP or HC compliance with weekly food pick-up and weight measurements. Oral glucose tolerance and meal tolerance tests with glucose and insulin measurements and DXA scans were done at baseline and after 6 months on the respective diets.

Results

After 6 months on the HP diet, 100% of the subjects had remission of their T2DM to Normal Glucose Tolerance (NGT), whereas only 16.6% of subjects on the HC diet had remission of their T2DM. The HP diet group exhibited significant improvement in a) cardiovascular risk factors (p = 0.004, b) inflammatory cytokines(p = 0.001), c) insulin sensitivity(p = 0.001), d) oxidative stress(p = 0.001), e) increased %lean body mass(p = 0.001) compared to the HC diet group at 6 months.

Conclusions

A significant improvement in cardiovascular risk factors, inflammation, metabolic parameters and 100% remission of T2DM to NGT was achieved with a HP diet compared to a HC diet at 6 months.

Clinicaltrialsgov identifier

NCT01642849.

Immune-metabolic interactions in homeostasis and the progression to NASH

The incidence of non-alcoholic fatty liver disease (NAFLD) has increased significantly over the past two decades. NAFLD ranges from simple steatosis (NAFL) to nonalcoholic steatohepatitis (NASH) and predisposes to fibrosis and hepatocellular carcinoma (HCC). The importance of the immune system in hepatic physiology and in the progression of NAFLD is increasingly recognized. At homeostasis, the liver participates in immune defense against pathogens and in tolerance of gut-derived microbial compounds. Hepatic immune cells also respond to metabolic stimuli and have a role in NAFLD progression to NASH. In this review, we discuss how metabolic perturbations affect immune cell phenotype and function in NAFL and NASH, and then focus on the role of immune cells in liver homeostasis and in the development of NASH.

Fatty Acid Metabolism and T Cells in Multiple Sclerosis

Cellular metabolic remodeling is intrinsically linked to the development, activation, differentiation, function, and survival of T cells. T cells transition from a catabolic, naïve state to an anabolic effector state upon T cell activation. Subsequently, specialization of T cells into T helper (Th) subsets, including regulatory T cells (Treg), requires fine-tuning of metabolic programs that better support and optimize T cell functions for that particular environment. Increasingly, studies have shown that changes in nutrient availability at both the cellular and organismal level during disease states can alter T cell function, highlighting the importance of better characterizing metabolic-immune axes in both physiological and disease settings. In support of these data, a growing body of evidence is emerging that shows specific lipid species are capable of altering the inflammatory functional phenotypes of T cells. In this review we summarize the metabolic programs shown to support naïve and effector T cells, and those driving Th subsets. We then discuss changes to lipid profiles in patients with multiple sclerosis, and focus on how the presence of specific lipid species can alter cellular metabolism and function of T cells.

Tumor microenvironment metabolites directing T cell differentiation and function

Metabolic reprogramming of cancer cells creates a unique tumor microenvironment (TME) characterized by the limited availability of nutrients, which subsequently affects the metabolism, differentiation, and function of tumor-infiltrating T lymphocytes (TILs). TILs can also be inhibited by tumor-derived metabolic waste products and low oxygen. Therefore, a thorough understanding of how such unique metabolites influence mammalian T cell differentiation and function can inform novel anticancer therapeutic approaches. Here, we highlight the importance of these metabolites in modulating various T cell subsets within the TME, dissecting how these changes might alter clinical outcomes. We explore potential TME metabolic determinants that might constitute candidate targets for cancer immunotherapies, ideally leading to future strategies for reprogramming tumor metabolism to potentiate anticancer T cell functions.

The role of nanoparticle format and route of administration on self-amplifying mRNA vaccine potency

The efficacy of RNA-based vaccines has been recently demonstrated, leading to the use of mRNA-based COVID-19 vaccines. The application of self-amplifying mRNA within these formulations may offer further enhancement to these vaccines, as self-amplifying mRNA replicons enable longer expression kinetics and more potent immune responses compared to non-amplifying mRNAs. To investigate the impact of administration route on RNA-vaccine potency, we investigated the immunogenicity of a self-amplifying mRNA encoding the rabies virus glycoprotein encapsulated in different nanoparticle platforms (solid lipid nanoparticles (SLNs), polymeric nanoparticles (PNPs) and lipid nanoparticles (LNPs)). These were administered via three different routes: intramuscular, intradermal and intranasal. Our studies in a mouse model show that the immunogenicity of our 4 different saRNA vaccine formulations after intramuscular or intradermal administration was initially comparable; however, ionizable LNPs gave higher long-term IgG responses. The clearance of all 4 of the nanoparticle formulations from the intramuscular or intradermal administration site was similar. In contrast, immune responses generated after intranasal was low and coupled with rapid clearance for the administration site, irrespective of the formulation. These results demonstrate that both the administration route and delivery system format dictate self-amplifying RNA vaccine efficacy.

Obesity and adipose tissue impact on T-cell response and cancer immune checkpoint blockade therapy

Many different types of cancer are now well known to have increased occurrence or severity in individuals with obesity. The influence of obesity on cancer and the immune cells in the tumor microenvironment has been thought to be a pleiotropic effect. As key endocrine and immune organs, the highly plastic adipose tissues play crucial roles in obesity pathophysiology, as they show alterations according to environmental cues. Adipose tissues of lean subjects present mostly anti-inflammatory cells that are crucial in tissue remodeling, favoring uncoupling protein 1 expression and non-shivering thermogenesis. Oppositely, obese adipose tissues display massive proinflammatory immune cell infiltration, dying adipocytes, and enhanced crown-like structure formation. In this review, we discuss how obesity can lead to derangements and dysfunctions in antitumor CD8+ T lymphocytes dysfunction. Moreover, we explain how obesity can affect the efficiency of cancer immunotherapy, depicting the mechanisms involved in this process. Cancer immunotherapy management includes monoclonal antibodies targeting the immune checkpoint blockade. Exhausted CD8+ T lymphocytes show elevated programmed cell death-1 (PD-1) expression and highly glycolytic tumors tend to show a good response to anti-PD-1/PD-L1 immunotherapy. Although obesity is a risk factor for the development of several neoplasms and is linked with increased tumor growth and aggressiveness, obesity is also related to improved response to cancer immunotherapy, a phenomenon called the obesity paradox. However, patients affected by obesity present higher incidences of adverse events related to this therapy. These limitations highlight the necessity of a deeper investigation of factors that influence the obesity paradox to improve the application of these therapies.

Effects of fatty acids on T cell function: role in atherosclerosis

T cells are among the most common cell types present in atherosclerotic plaques and are increasingly being recognized as a central mediator in atherosclerosis development and progression. At the same time, triglycerides and fatty acids have re-emerged as crucial risk factors for atherosclerosis. Triglycerides and fatty acids are important components of the milieu to which the T cell is exposed from the circulation to the plaque, and increasing evidence shows that fatty acids influence T cell function. In this Review, we discuss the effects of fatty acids on four components of the T cell response - metabolism, activation, proliferation and polarization - and the influence of these changes on the pathogenesis of atherosclerosis. We also discuss how quiescent T cells can undergo a type of metabolic reprogramming induced by exposure to fatty acids in the circulation that influences the subsequent functions of T cells after activation, such as in atherosclerotic plaques.

Long Chain Fatty Acids as Modulators of Immune Cells Function: Contribution of FFA1 and FFA4 Receptors

Long-chain fatty acids are molecules that act as metabolic intermediates and constituents of membranes; however, their novel role as signaling molecules in immune function has also been demonstrated. The presence of free fatty acid (FFA) receptors on immune cells has contributed to the understanding of this new role of long-chain fatty acids (LCFAs) in immune function, showing their role as anti-inflammatory or pro-inflammatory molecules and elucidating their intracellular mechanisms. The FFA1 and FFA4 receptors, also known as GPR40 and GPR120, respectively, have been described in macrophages and neutrophils, two key cells mediating innate immune response. Ligands of the FFA1 and FFA4 receptors induce the release of a myriad of cytokines through well-defined intracellular signaling pathways. In this review, we discuss the cellular responses and intracellular mechanisms activated by LCFAs, such as oleic acid, linoleic acid, palmitic acid, docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA), in T-cells, macrophages, and neutrophils, as well as the role of the FFA1 and FFA4 receptors in immune cells.

The role of peripheral fatty acids as biomarkers for Alzheimer's disease and brain inflammation

Alzheimer's disease (AD) is a complex and heterogeneous neurodegenerative disease. A wide range of techniques have been proposed to facilitate early diagnosis of AD, including biomarkers from the cerebrospinal fluid and blood. Although phosphorylated tau and amyloid beta are amongst the most promising biomarkers of AD, other peripheral biomarkers have been identified and in this review we synthesize the current knowledge on circulating fatty acids. Fatty acids are involved in different biological process including neurotransmission and inflammation. Interestingly, some fatty acids appear to be modulated during disease progression, including long chain saturated fatty acids, and polyunsaturated fatty acids, such as docosahexaenoic acid . However, discrepant results have been reported in the literature and there is the need for further validation and method standardization. Nonetheless, our literature review suggests that fatty acid analyses could potentially provide a valuable source of data to further inform the pathology and progression of AD.

Importance of Dietary Changes During the Coronavirus Pandemic: How to Upgrade Your Immune Response

The new coronavirus pandemic continues to spread causing further public health, social, and economic issues. The disparities in the rates of death between countries poses questions about the importance of lifestyle habits and the immune status of populations. An exploration of dietary habits and COVID-19-related death might unravel associations between these two variables. Indeed, while both nutritional excess and deficiency are associated with immunodeficiency, adequate nutrition leading to an optimally functioning immune system may be associated with better outcomes with regards to preventing infection and complications of COVID-19, as well as developing a better immune response to other pathogenic viruses and microorganisms. This article outlines the key functions of the immune system and how macronutrients, micronutrients, and metabolites from the gut microbiome can be essential in the development of an efficient immune system. In addition, the effects of intermittent fasting on the inflammatory state as well as metabolic parameters will be discussed.

The Influence of Dietary Fatty Acids on Immune Responses

Diet-derived fatty acids (FAs) are essential sources of energy and fundamental structural components of cells. They also play important roles in the modulation of immune responses in health and disease. Saturated and unsaturated FAs influence the effector and regulatory functions of innate and adaptive immune cells by changing membrane composition and fluidity and by acting through specific receptors. Impaired balance of saturated/unsaturated FAs, as well as n-6/n-3 polyunsaturated FAs has significant consequences on immune system homeostasis, contributing to the development of many allergic, autoimmune, and metabolic diseases. In this paper, we discuss up-to-date knowledge and the clinical relevance of the influence of dietary FAs on the biology, homeostasis, and functions of epithelial cells, macrophages, dendritic cells, neutrophils, innate lymphoid cells, T cells and B cells. Additionally, we review the effects of dietary FAs on the pathogenesis of many diseases, including asthma, allergic rhinitis, food allergy, atopic dermatitis, rheumatoid arthritis, multiple sclerosis as well as type 1 and 2 diabetes.

Green Tea Polyphenol (-)-Epigallocatechin Gallate (EGCG) Attenuates Neuroinflammation in Palmitic Acid-Stimulated BV-2 Microglia and High-Fat Diet-Induced Obese Mice

Obesity is closely associated with neuroinflammation in the hypothalamus, which is characterized by over-activated microglia and excessive production of pro-inflammatory cytokines. The present study was aimed at elucidating the effects of (−)-epigallocatechin gallate (EGCG) on palmitic acid-stimulated BV-2 microglia and high-fat-diet-induced obese mice. The results indicated the suppressive effect of EGCG on lipid accumulation, pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) release, and microglial activation in both cellular and high-fat-diet rodent models. These results were associated with lower phosphorylated levels of the janus kinase 2/signal transducers and activators of transcription 3 (JAK2/STAT3) signaling pathway. In conclusion, EGCG can attenuate high-fat-induced hypothalamic inflammation via inhibiting the JAK2/STAT3 signaling pathways in microglia.

Upregulation of SLAMF3 on human T cells is induced by palmitic acid through the STAT5-PI3K/Akt pathway and features the chronic inflammatory profiles of type 2 diabetes

Metabolic stress-induced low-grade chronic inflammation plays an important role in the development of insulin-resistance and type 2 diabetes (T2D). Emerging evidence highlights the importance of directly elucidating T-cell activation under the obesity-induced metabolic stress condition, as T cells primed under such conditions were found to acquire a unique phenotype and function. Herein, we found a significant upregulation of signaling lymphocytic activation molecule family member 3 (SLAMF3) expression on T cells from T2D patients compared to those of healthy controls. Importantly, SLAMF3 upregulation was associated with an increased ability to produce proinflammatory cytokines. Significantly increased SLAMF3 expression was seen in T2D patient T cells that produce IFN-γ or IL-17 upon short (4-h) stimulation, compared to non-cytokine-producing T cells. In line with this finding, SLAMF3^high T cells were significantly more sensitive than SLAMF3^low T cells to TCR stimulation with anti-CD3/CD28 antibodies. Furthermore, treatment with palmitic acid (PA) led to significant upregulation of SLAMF3 on human T cells primed by anti-CD3/CD28 antibodies and on Jurkat cells, a human T-cell line. RNA sequencing revealed strong activation of the PI3K/Akt signaling pathway in T cells that were primed with PA. Further mechanistic studies showed that inhibition of PI3K/Akt signaling, or its upstream mediator STAT5 can prevent PA-induced SLAMF3 upregulation on T cells. These results indicate that SLAMF3 upregulation is associated with T-cell activation and cytokine production in T2D patients, and suggest that elevated saturated fatty acids in T2D patients may induce SLAMF3 upregulation on T cells via activation of the STAT5-PI3K/Akt signaling pathway.

The Impact of Diet on Immunity and Respiratory Diseases

The Western world has witnessed a tremendous increase in the occurrence of allergy and autoimmunity in the second half of the 20th century. Extensive efforts have been made to explain this phenomenon and various hypotheses have been formulated. Among them, two concepts have attracted the most attention: the "hygiene hypothesis," identifying the reduced exposure to environmental microorganisms as a driving force behind the observed epidemiological trends; and the "diet hypotheses," pointing to the importance of changes in our dietary habits. In this review, we discuss the interplay between the Western diet, microbiota, and inflammatory conditions, with particular emphasis on respiratory diseases. This is followed by an in-depth overview of the immunomodulatory potential of different dietary fatty acids. We conclude by identifying the outstanding questions, which, if answered, could shed further light on the impact of dietary habits on immunity and interconnect it with postulates proposed by the hygiene hypothesis. Linking these two concepts will be an important step towards understanding how Western lifestyle shapes disease susceptibility.

Integration of Metabolomics With Pharmacodynamics to Elucidate the Anti-myocardial Ischemia Effects of Combination of Notoginseng Total Saponins and Safflower Total Flavonoids

Notoginseng (Sanqi), the roots and rhizomes of Panax notoginseng and safflower, the flowers of Carthamus tinctorius, are widely used traditional Chinese medicines (TCMs) for the treatment of cardiovascular diseases. Positive evidences have fueled growing acceptance for cardioprotective effects of the combination of the notoginseng total saponins and safflower total flavonoids (CNS) against myocardial ischemia (MI). However, the underlying cardioprotective mechanisms of CNS are still obscured. Metabolomics is a comprehensive tool for investigating biological mechanisms of disease, monitoring therapeutic outcomes, and advancing drug discovery and development. Herein, we investigated the cardioprotective effects of CNS on the isoproterenol (ISO)-induced MI rats by using plasma and urine metabolomics based on ultra-performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UPLC-Q-TOF/MS) and multiple pharmacodynamics approaches. The results showed that pretreatment with CNS could attenuate the cardiac injury resulting from ISO, as evidenced by decreasing the myocardial infarct size, converting the echocardiographic, histopathological, and plasma biochemical abnormalities, and reversing the perturbations of plasma and urine metabolic profiles, particularly for the 55.0 mg/kg dosage group. In addition, 44 metabolites were identified as the potential MI biomarkers, mainly including a range of free fatty acids (FFAs), sphingolipids, and glycerophospholipids. CNS pretreatment group may robustly ameliorate these potential MI-related biomarkers. The accumulation of LysoPCs and FFAs, caused by PLA₂, may activate NF-κB pathway and increase proinflammatory cytokines. However, our results showed that CNS at 55.0 mg/kg dosage could maximally attenuate the NF-κB signaling pathway, depress the expressions of TNF-α, IL-6, IL-1β, and PLA₂. The results suggested that the anti-inflammatory property of CNS may contribute to its cardioprotection against MI. Our results demonstrate that the integrating of metabolomics with pharmacodynamics provides a reasonable approach for understanding the therapeutic effects of TCMs and CNS provide a potential candidate for prevention and treatment of MI.

Prediction of acute GVHD and relapse by metabolic biomarkers after allogeneic hematopoietic stem cell transplantation

BACKGROUND

There are very few studies investigating metabolic biomarkers to predict acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (HSCT). Metabolic models can provide a framework for analyzing the information-rich omics data sets in this setting.

METHODS

Four hundred and fifty-six samples from one hundred and fourteen consecutive patients who underwent HSCT from January 2012 to May 2014 were collected for this study. The changes in serum metabolite levels were investigated using a gas chromatography-mass spectrometry-based metabolomics approach and underwent statistical analysis.

RESULTS

Significant metabolic changes were observed on day 7. The stearic acid/palmitic acid (SA/PA) ratio was effective in the diagnosis of grade II-IV aGVHD. Multivariate analysis showed that patients with high SA/PA ratios on day 7 after HSCT were less likely to develop II-IV aGVHD than patients with low SA/PA ratios (odds ratio [OR] = 0.06, 95% CI 0.02-0.18, P < 0.001). After the adjustment for clinical characteristics, the SA/PA ratio had no significant effect on overall survival (hazard ratio [HR] = 1.95, 95% CI 0.92-4.14, P = 0.08), and patients in the high SA/PA ratio group were significantly more likely to relapse than those in the low ratio group (HR = 2.26, 95% CI 1.04-4.91, P = 0.04).

CONCLUSION

Our findings suggest that the SA/PA ratio on day 7 after HSCT is an excellent biomarker to predict both aGVHD and relapse. The serum SA/PA ratio measured on day 7 after transplantation may improve risk stratification for aGVHD and relapse after allogeneic stem cell transplantation.

FUNDING

National Natural Science Foundation of China (81470346, 81773361), Priority Academic Program Development of Jiangsu Higher Education Institutions, Jiangsu Natural Science Foundation (BK20161204), Innovation Capability Development Project of Jiangsu Province (BM2015004), Jiangsu Medical Junior Talent Person award (QNRC2016707), and NIH (AI129582 and NS106170).

Bioavailability of Bergamot (Citrus bergamia) Flavanones and Biological Activity of Their Circulating Metabolites in Human Pro-Angiogenic Cells

Myeloid angiogenic cells (MACs) play a key role in endothelial repairing processes and functionality but their activity may be impaired by the lipotoxic effects of some molecules like stearic acid (SA). Among the dietary components potentially able to modulate endothelial function in vivo, (poly)phenolic compounds represent serious candidates. Here, we apply a comprehensive multidisciplinary approach to shed light on the prospects of Bergamot (Citrus bergamia), a citrus fruit rich in flavanones and other phenolic compounds, in the framework of lipotoxicity-induced MACs impairment. The flavanone profile of bergamot juice was characterized and 16 compounds were identified, with a new 3-hydroxy-3-methylglutaryl (HMG) flavanone, isosakuranetin-7-O-neohesperidoside-6″-O-HMG, described for the first time. Then, a pilot bioavailability study was conducted in healthy volunteers to assess the circulating flavanone metabolites in plasma and urine after consumption of bergamot juice. Up to 12 flavanone phase II conjugates (sulfates and glucuronides of hesperetin, naringenin and eriodyctiol) were detected and quantified. Finally, the effect of some of the metabolites identified in vivo, namely hesperetin-7-O-glucuronide, hesperetin-3′-O-glucuronide, naringenin-7-O-glucuronide and naringenin-4′-O-glucuronide, was tested, at physiological concentrations, on gene expression of inflammatory markers and apoptosis in MACs exposed to SA. Under these conditions, naringenin-4′-O-glucuronide and hesperetin-7-O-glucuronide were able to modulate inflammation, while no flavanone glucuronide was effective in curbing stearate-induced lipoapoptosis. These results demonstrate that some flavanone metabolites, derived from the in vivo transformation of bergamot juice phenolics in humans, may mitigate stearate-induced inflammation in MACs.

Stearic acid at physiologic concentrations induces in vitro lipotoxicity in circulating angiogenic cells

BACKGROUND AND AIMS

Saturated free fatty acids (SFAs) can induce lipotoxicity in different cells. No studies have investigated the effects of SFA in circulating angiogenic cells (CACs), which play a key role in endothelial repair processes. The aim of the study was to assess the effects of SFAs, specifically stearic acid (SA), on viability and function of CACs and to investigate potential underlying molecular mechanisms.

METHODS

CACs were isolated from healthy subjects by established methods. CACs were incubated with BSA-complexed stearate (100 μM) to assess the time course (from 8 to 24 h exposure) of the effects on viability and apoptosis (activation of caspases 3/7), angiogenic function (tube formation assay), pro-inflammatory cytokine (IL-1β, IL-6, IL-8, MCP-1 and TNFα) gene expression (qPCR) and secretion (ELISA), activation of MAPK (JNK, p38 and Erk1/2) by Western blot and endoplasmic reticulum (ER) stress marker (CHOP, BIP, ATF4, XBP-1 and sXBP-1) gene expression by qPCR.

RESULTS

Stearic acid activates effector caspases in CACs in a dose- and time-dependent manner. SA also impairs CAC function and increases pro-inflammatory molecule (IL-1β, IL-6, IL-8, MCP-1 and TNFα) gene expression and secretion in CACs starting from 3 h of incubation. The activation of JNK by SA mediates pro-inflammatory response, but it may be not necessary for apoptosis. Moreover, SA induces the expression of ER stress markers across the three branches of the ER stress response.

CONCLUSIONS

In humans, both function and viability of CACs are exquisitely vulnerable to physiologic concentrations of stearate; lipotoxic impairment of endothelial repair processes may be implicated in vascular damage caused by SFAs.

Starving for survival-how catabolic metabolism fuels immune function

Infections disturb homeostasis and often induce a switch to catabolic organismal metabolism. During catabolism, increased systemic availability of glucose, fatty acids and ketone bodies is observed, and recent evidence indicates that these metabolites might serve an immunomodulatory function. However, whereas our understanding of direct pathogen recognition by the host immune system is quite detailed, much less is known about the immunobiology of the metabolic host response to infection. In this review article we briefly discuss how pathogens induce 'dys-homeostasis' systemically, locally, and within cells, and provide examples of how such changes can shape immune-functionality during the course of an infection.

Nutritional effects on T-cell immunometabolism

T cells are highly influenced by nutrient uptake from their environment, and changes in overall nutritional status, such as malnutrition or obesity, can result in altered T-cell metabolism and behavior. In states of severe malnutrition or starvation, T-cell survival, proliferation, and inflammatory cytokine production are all decreased, as is T-cell glucose uptake and metabolism. The altered T-cell function and metabolism seen in malnutrition is associated with altered adipokine levels, most particularly decreased leptin. Circulating leptin levels are low in malnutrition, and leptin has been shown to be a key link between nutrition and immunity. The current view is that leptin signaling is required to upregulate activated T-cell glucose metabolism and thereby fuel T-cell activation. In the setting of obesity, T cells have been found to have a key role in promoting the recruitment of inflammatory macrophages to adipose depots along with the production of inflammatory cytokines that promote the development of insulin resistance leading to diabetes. Deletion of T cells, key T-cell transcription factors, or pro-inflammatory T-cell cytokines prevents insulin resistance in obesity and underscores the importance of T cells in obesity-associated inflammation and metabolic disease. Altogether, T cells have a critical role in nutritional immunometabolism.

Deficiency of stearoyl-CoA desaturase-1 aggravates colitogenic potential of adoptively transferred effector T cells

Stearoyl-CoA desaturase-1 (SCD1) is a lipogenic enzyme involved in the de novo biosynthesis of oleate (C18:1, n9), a major fatty acid in the phospholipids of lipid bilayers of cell membranes. Accordingly, Scd1KO mice display substantially reduced oleate in cell membranes. An altered SCD1 level was observed during intestinal inflammation; however, its role in modulating inflammatory bowel disease remains elusive. Herein, we investigated the colitogenic capacity of Scd1KO effector T cells by employing the adoptive T-cell transfer colitis model. Splenic effector T cells (CD4⁺CD25^-) from age- and sex-matched wild-type (WT) and Scd1KO mice were isolated by FACS and intraperitoneally administered to Rag1KO mice, which were monitored for the development of colitis. At day 60 postcell transfer, Rag1KO mice that received Scd1KO CD4⁺CD25^- T cells displayed accelerated and exacerbated colitis than mice receiving WT CD4⁺CD25^- T cells. Intriguingly, Scd1KO CD4⁺CD25^- T cells display augmented inflammatory cytokine profile and cellular membrane fluidity with a concomitant increase in proinflammatory saturated fatty acids, which we postulate to potentially underlie their augmented colitogenic potential.

The genetic variant rs4073 A→T of the Interleukin-8 promoter region is associated with the earlier onset of exudative age-related macular degeneration

Purpose

To study the association of the single nucleotide polymorphism (SNP) rs4073 in the interleukin‐8 (IL‐8) promoter region with the diagnosis and age of onset of exudative age‐related macular degeneration (AMD) in association with the known genetic risk factors for AMD and tobacco smoking.

Methods

Medical records, smoking history and angiograms or fundus photographs of 301 patients with exudative AMD, 72 patients with dry AMD and 119 control subjects were analysed retrospectively. The associations of IL‐8 rs4073 A→T, CFH rs1061170 T→C, ARMS2 rs10490924 G→T and C3 rs2230199 C→G SNPs with the presence of AMD and with the age of onset of exudative AMD were analysed.

Results

Younger age of exudative AMD onset was associated with the homozygous AA genotype of IL‐8 rs4073 (p = 0.009, Mann–Whitney U‐test), CC genotype of CFH rs1061170 (p = 0.016), TT genotype of ARMS2 rs10490924 (p = 0.001) and with current smoking (p = 0.002). The risk alleles C in CFH rs1061170 (p < 0.0001, Pearson chi‐square) and T in ARMS2 rs10490924 (p < 0.0001), as well as smoking (p < 0.0001), were more prevalent in AMD patients compared with controls. No association was found between the IL‐8 rs4073 genotype and the presence of AMD.

Conclusion

Out of the factors associated with the earlier onset of exudative AMD, only the genotype of IL‐8 rs4073 did not appear as a risk factor for AMD in general. IL‐8 may have a role in accelerating the development of the choroidal neovascularization in exudative AMD.

Role of lipids in the metabolism and activation of immune cells

Immune cell plasticity has extensive implications in the pathogenesis and resolution of metabolic disorders, cancers, autoimmune diseases and chronic inflammatory disorders. Over the past decade, nutritional status has been discovered to influence the immune response. In metabolic disorders such as obesity, immune cells interact with various classes of lipids, which are capable of controlling the plasticity of macrophages and T lymphocytes. The purpose of this review is to discuss lipids and their impact on innate and adaptive immune responses, focusing on two areas: (1) the impact of altering lipid metabolism on immune cell activation, differentiation and function and (2) the mechanism by which lipids such as cholesterol and fatty acids regulate immune cell plasticity.

Rapid linkage of innate immunological signals to adaptive immunity by the brain-fat axis

Innate immunity signals induced by pathogen/damage-associated molecular patterns are essential for adaptive immune responses, but it is unclear if the brain plays a role in this process. Here we show that while tumor necrosis factor (TNF) quickly increased in the brain of mice following bacterial infection, intra-brain TNF delivery mimicked bacterial infection to rapidly increase peripheral lymphocytes, especially in the spleen and fat. Multiple mouse models revealed that hypothalamic responses to TNF were accountable for this increase of peripheral lymphocytes in response to bacterial infection. Finally, hypothalamic induction of lipolysis was found to mediate the brain's action in promoting this increase in peripheral adaptive immune response. Thus, the brain-fat axis is important for rapidly linking innate immunity to adaptive immunity.

Niacin receptor activation improves human microvascular endothelial cell angiogenic function during lipotoxicity

OBJECTIVE

Niacin (nicotinic acid) as a monotherapy can reduce vascular disease risk, but its mechanism of action remains controversial, and may not be dependent on systemic lipid modifying effects. Niacin has recently been shown to improve endothelial function and vascular regeneration, independent of correcting dyslipidemia, in rodent models of vascular injury and metabolic disease. As a potential biosynthetic precursor for NAD(+), niacin could elicit these vascular benefits through NAD(+)-dependent, sirtuin (SIRT) mediated responses. Alternatively, niacin may act through its receptor, GPR109A, to promote endothelial function, though endothelial cells are not known to express this receptor. We hypothesized that niacin directly improves endothelial cell function during exposure to lipotoxic conditions and sought to determine the potential mechanism(s) involved.

METHODS AND RESULTS

Angiogenic function in excess palmitate was assessed by tube formation following treatment of human microvascular endothelial cells (HMVEC) with either a relatively low concentration of niacin (10 μM), or nicotinamide mononucleotide (NMN) (1 μM), a direct NAD(+) precursor. Although both niacin and NMN improved HMVEC tube formation during palmitate overload, only NMN increased cellular NAD(+) and SIRT1 activity. We further observed that HMVEC express GRP109A. Activation of this receptor with either acifran or MK-1903 recapitulated niacin-induced improvements in HMVEC tube formation, while GPR109A siRNA diminished the effect of niacin.

CONCLUSION

Niacin, at a low concentration, improves HMVEC angiogenic function under lipotoxic conditions, likely independent of NAD(+) biosynthesis and SIRT1 activation, but rather through niacin receptor activation.

Fatty acids, lipid mediators, and T-cell function

Research toward the mechanisms underlying obesity-linked complications has intensified during the last years. As a consequence, it has become clear that metabolism and immunity are intimately linked. Free fatty acids and other lipids acquired in excess by current feeding patterns have been proposed to mediate this link due to their immune modulatory capacity. The functional differences between saturated and unsaturated fatty acids, in combination with their dietary intake are believed to modulate the outcome of immune responses. Moreover, unsaturated fatty acids can be oxidized in a tightly regulated and specific manner to generate either potent pro-inflammatory or pro-resolving lipid mediators. These oxidative derivatives of fatty acids have received detailed attention during the last years, as they have proven to have strong immune modulatory capacity, even in pM ranges. Both fatty acids and oxidized fatty acids have been studied especially in relation to macrophage and T-cells functions. In this review, we propose to focus on the effect of fatty acids and their oxidative derivatives on T-cells, as it is an active area of research during the past 5 years. The effect of fatty acids and their derivatives on activation and proliferation of T-cells, as well as the delicate balance between stimulation and lipotoxicity will be discussed. Moreover, the receptors involved in the interaction between free fatty acids and their derivatives with T-cells will be summarized. Finally, the mechanisms involved in modulation of T-cells by fatty acids will be addressed, including cellular signaling and metabolism of T-cells. The in vitro results will be placed in context of in vivo studies both in humans and mice. In this review, we summarize the latest findings on the immune modulatory function of lipids on T-cells and will point out novel directions for future research.

Deranged fatty acid composition causes pulmonary fibrosis in Elovl6-deficient mice

Despite the established role of alveolar type II epithelial cells for the maintenance of pulmonary function, little is known about the deregulation of lipid composition in the pathogenesis of pulmonary fibrosis. The elongation of long-chain fatty acids family member 6 (Elovl6) is a rate-limiting enzyme catalysing the elongation of saturated and monounsaturated fatty acids. Here we show that Elovl6 expression is significantly downregulated after an intratracheal instillation of bleomycin (BLM) and in human lung with idiopathic pulmonary fibrosis. Elovl6-deficient (Elovl6⁻/⁻) mice treated with BLM exhibit severe fibroproliferative response and derangement of fatty acid profile compared with wild-type mice. Furthermore, Elovl6 knockdown induces a change in fatty acid composition similar to that in Elovl6⁻/⁻ mice, resulting in induction of apoptosis, TGF-β1 expression and reactive oxygen species generation. Our findings demonstrate a previously unappreciated role for Elovl6 in the regulation of lung homeostasis, and in pathogenesis and exacerbation of BLM-induced pulmonary fibrosis.

Effect of α -Lipoic Acid on Oxidative Stress in End-Stage Renal Disease Patients Receiving Intravenous Iron

Oxidative stress is associated with increased risk of cardiovascular disease in end-stage renal disease (ESRD) patients. Intravenous (IV) iron has been shown to increase oxidative stress. The aim of the study was to evaluate changes in oxidative stress markers following administration of IV sodium ferric gluconate (SFG) to ESRD patients with and without administration of the antioxidant, α -lipoic acid. This is an open-label, crossover study. 125 mg of IV SFG was administered during control (C) and intervention (I) visits. During the I visit, 600 mg of α -lipoic acid was given orally prior to IV SFG. Blood samples were collected at defined time periods for F2-isoprostane (FIP), lipid hydroperoxide (LHP), malondialdehyde (MDA), and iron indices. We recruited ten African-American ESRD subjects: 50% male; mean age 45 ± 9 years; mean hemoglobin 13 ± 1 g/dL; ferritin 449 ± 145 ng/mL; transferrin saturation 27 ± 4%. There were no significant differences in iron indices between the two visits after IV SFG. MDA, FIP, and LHP increased significantly for both C and I visits with a greater increase in the I group. Administration of IV SFG results in an acute rise in oxidative stress in ESRD patients. In contrast to previous studies, administration of α -lipoic acid was associated with a greater increase in oxidative stress.

Interleukin 8 promoter polymorphism predicts the initial response to bevacizumab treatment for exudative age-related macular degeneration

PURPOSE

To study the association of single-nucleotide polymorphisms of interleukin 8, vascular endothelial growth factor, erythropoietin, complement factor H, complement component C3, and LOC387715 genes with the response to bevacizumab treatment in exudative age-related macular degeneration.

METHODS

Clinical records, smoking history, optical coherence tomography, and angiographies of 96 bevacizumab-treated exudative age-related macular degeneration patients were analyzed retrospectively. Blood DNA was collected. Based on the disappearance of intra- or subretinal fluid in optical coherence tomography, patients were graded as responders, partial responders, or nonresponders after 3 initial treatment visits and a median time of 3.5 months.

RESULTS

Interleukin 8 promoter polymorphism -251A/T was significantly associated with persisting fluid in optical coherence tomography. The A allele was more frequent in nonresponders than in responders (P = 0.033). In multivariate modeling, the AA genotype of -251A/T (P = 0.043) and occult (P = 0.042) or predominantly classic (P = 0.040) lesions predicted poorer outcome. Visual acuity change was better in responders than in nonresponders (P = 0.006). Baseline lesion size (P = 0.006) and retinal cysts after the treatment (P < 0.001) correlated with less visual acuity gain.

CONCLUSION

The A allele and the homozygous AA genotype of interleukin 8 -251A/T were associated with anatomical nonresponse to bevacizumab treatment.

Effects of high-protein versus high-carbohydrate diets on markers of β-cell function, oxidative stress, lipid peroxidation, proinflammatory cytokines, and adipokines in obese, premenopausal women without diabetes: a randomized controlled trial

OBJECTIVE

To study the effects of high-protein versus high-carbohydrate diets on various metabolic end points (glucoregulation, oxidative stress [dichlorofluorescein], lipid peroxidation [malondialdehyde], proinflammatory cytokines [tumor necrosis factor-α and interleukin-6], adipokines, and resting energy expenditure [REE]) with high protein-low carbohydrate (HP) and high carbohydrate-low protein (HC) diets at baseline and after 6 months of dietary intervention.

RESEARCH DESIGN AND METHODS

We recruited obese, premenopausal women aged 20-50 years with no diabetes or prediabetes who were randomized to HC (55% carbohydrates, 30% fat, and 15% protein) or HP (40% carbohydrates, 30% fat, and 30% protein) diets for 6 months. The diets were provided in prepackaged food, which provided 500 kcal restrictions per day. The above metabolic end points were measured with HP and HC diet at baseline and after 6 months of dietary intervention.

RESULTS

After 6 months of the HP versus HC diet (12 in each group), the following changes were significantly different by Wilcoxon rank sum test for the following parameters: dichlorofluorescein (-0.8 vs. -0.3 µmol/L, P < 0.0001), malondialdehyde (-0.4 vs. -0.2 μmol/L, P = 0.0004), C-reactive protein (-2.1 vs. -0.8 mg/L, P = 0.0003), E-selectin (-8.6 vs. -3.7 ng/mL, P = 0.0007), adiponectin (1,284 vs. 504 ng/mL, P = 0.0011), tumor necrosis factor-α (-1.8 vs. -0.9 pg/mL, P < 0.0001), IL-6 (-1.3 vs. -0.4 pg/mL, P < 0.0001), free fatty acid (-0.12 vs. 0.16 mmol/L, P = 0.0002), REE (259 vs. 26 kcal, P < 0.0001), insulin sensitivity (4 vs. 0.9, P < 0.0001), and β-cell function (7.4 vs. 2.1, P < 0.0001).

CONCLUSIONS

To our knowledge, this is the first report on the significant advantages of a 6-month hypocaloric HP diet versus hypocaloric HC diet on markers of β-cell function, oxidative stress, lipid peroxidation, proinflammatory cytokines, and adipokines in normal, obese females without diabetes.

The impact of obesity on the immune response to infection

There is strong evidence indicating that excess adiposity negatively impacts immune function and host defence in obese individuals. This is a review of research findings concerning the impact of obesity on the immune response to infection, including a discussion of possible mechanisms. Obesity is characterised by a state of low-grade, chronic inflammation in addition to disturbed levels of circulating nutrients and metabolic hormones. The impact of these metabolic abnormalities on obesity-related comorbidities has undergone intense scrutiny over the past decade. However, relatively little is known of how the immune system and host defence are influenced by the pro-inflammatory and excess energy milieu of the obese. Epidemiological data suggest obese human subjects are at greater risk for nosocomial infections, especially following surgery. Additionally, the significance of altered immunity in obese human subjects is emphasised by recent studies reporting obesity to be an independent risk factor for increased morbidity and mortality following infection with the 2009 pandemic influenza A (H1N1) virus. Rodent models offer important insight into how metabolic abnormalities associated with excess body weight can impair immunity. However, more research is necessary to understand the specific aspects of immunity that are impaired and what factors are contributing to reduced immunocompetence in the obese. Additionally, special consideration of how infection in this at-risk population is managed is required, given that this population may not respond optimally to antimicrobial drugs and vaccination. Obesity impacts millions globally, and greater understanding of its associated physiological disturbances is a key public health concern.

Saturated long-chain fatty acids activate inflammatory signaling in astrocytes

This study describes the effects of long-chain fatty acids on inflammatory signaling in cultured astrocytes. Data show that the saturated fatty acid palmitic acid, as well as lauric acid and stearic acid, trigger the release of TNFα and IL-6 from astrocytes. Unsaturated fatty acids were unable to induce cytokine release from cultured astrocytes. Furthermore, the effects of palmitic acid on cytokine release require Toll-like receptor 4 rather than CD36 or Toll-like receptor 2, and do not depend on palmitic acid metabolism to palmitoyl-CoA. Inhibitor studies revealed that pharmacologic inhibition of p38 or p42/44 MAPK pathways prevents the pro-inflammatory effects of palmitic acid, whereas JNK and PI3K inhibition does not affect cytokine release. Depletion of microglia from primary astrocyte cultures using the lysosomotropic agent l-leucine methyl ester revealed that the ability of palmitic acid to trigger cytokine release is not dependent on the presence of microglia. Finally, data show that the essential ω-3 fatty acid docosahexaenoic acid acts in a dose-dependent manner to prevent the actions of palmitic acid on inflammatory signaling in astrocytes. Collectively, these data demonstrate the ability of saturated fatty acids to induce astrocyte inflammation in vitro. These data thus raise the possibility that high levels of circulating saturated fatty acids could cause reactive gliosis and brain inflammation in vivo, and could potentially participate in the reported adverse neurologic consequences of obesity and metabolic syndrome.

Morbidly obese human subjects have increased peripheral blood CD4+ T cells with skewing toward a Treg- and Th2-dominated phenotype

Obesity is associated with local T-cell abnormalities in adipose tissue. Systemic obesity-related abnormalities in the peripheral blood T-cell compartment are not well defined. In this study, we investigated the peripheral blood T-cell compartment of morbidly obese and lean subjects. We determined all major T-cell subpopulations via six-color flow cytometry, including CD8+ and CD4+ T cells, CD4+ T-helper (Th) subpopulations, and natural CD4+CD25+FoxP3+ T-regulatory (Treg) cells. Moreover, molecular analyses to assess thymic output, T-cell proliferation (T-cell receptor excision circle analysis), and T-cell receptor-β (TCRB) repertoire (GeneScan analysis) were performed. In addition, we determined plasma levels of proinflammatory cytokines and cytokines associated with Th subpopulations and T-cell proliferation. Morbidly obese subjects had a selective increase in peripheral blood CD4+ naive, memory, natural CD4+CD25+FoxP3+ Treg, and Th2 T cells, whereas CD8+ T cells were normal. CD4+ and CD8+ T-cell proliferation was increased, whereas the TCRB repertoire was not significantly altered. Plasma levels of cytokines CCL5 and IL-7 were elevated. CD4+ T-cell numbers correlated positively with fasting insulin levels. The peripheral blood T-cell compartment of morbidly obese subjects is characterized by increased homeostatic T-cell proliferation to which cytokines IL-7 and CCL5, among others, might contribute. This is associated with increased CD4+ T cells, with skewing toward a Treg- and Th2-dominated phenotype, suggesting a more anti-inflammatory set point.

Chronic exposure to high fatty acids impedes receptor agonist-induced nitric oxide production and increments of cytosolic Ca2+ levels in endothelial cells

Dyslipidemia is a common metabolic disorder in diabetes. Nitric oxide (NO) production from endothelium plays the primary role in endothelium-mediated vascular relaxation and other endothelial functions. Therefore, we investigated the effects of elevated free fatty acids (FFA) on the stimulation of NO production by phospholipase C (PLC)-activating receptor agonists (potent physiological endothelium-dependent vasodilators) and defined the possible alterations of signaling pathways implicated in this scenario. Exposure of bovine aortic endothelial cells (BAECs) to high concentrations of a mixture of fatty acids (oleate and palmitate) for 5 or 10 days significantly reduced NO production evoked by receptor agonists (bradykinin or ATP) in a time- and dose-dependent manner. Such defects were not associated with alterations of either endothelial NO synthase mass or inositol phospholipid contents but were probably due to reduced elevations of intracellular free Ca(2)(+) levels ([Ca(2)(+)](i)) under these conditions. Exposure of BAECs to FFA significantly attenuated agonist-induced [Ca(2)(+)](i) increases by up to 54% in a dose- and time-dependent manner. Moreover, bradykinin receptor affinity on the cell surface was significantly decreased by high concentrations of FFA. The morphology of BAECs was altered after 10-day culture with high FFA. Co-culture with protein kinase C (PKC) inhibitors or antioxidants was able to reverse the impairments of receptor agonist-induced NO production and [Ca(2)(+)](i) rises as well as the alteration of receptor affinity in BAECs exposed to FFA. These data indicate that chronic exposure to high FFA reduces NO generation in endothelial cells probably by impairing PLC-mediated Ca(2)(+) signaling pathway through activation of PKC and excess generation of oxidants.

Endothelial lipase (EL) and EL-generated lysophosphatidylcholines promote IL-8 expression in endothelial cells

OBJECTIVE

Previously we identified palmitoyl-lysophosphatidylcholine (LPC 16:0), as well as linoleoyl-, arachidonoyl- and oleoyl-LPC (LPC 18:2, 20:4 and 18:1) as the most prominent LPC species generated by the action of endothelial lipase (EL) on high-density lipoprotein (HDL). In the present study, the impact of EL and EL-generated LPC on interleukin-8 (IL-8) synthesis was examined in vitro in primary human aortic endothelial cells (HAEC) and in mice.

METHODS AND RESULTS

Adenovirus-mediated overexpression of the catalytically active EL, but not its inactive mutant, increased endothelial synthesis of IL-8 mRNA and protein in a time- and HDL-concentration-dependent manner. While LPC 18:2 was inactive, LPC 16:0, 18:1 and 20:4 promoted IL-8 mRNA- and protein-synthesis, differing in potencies and kinetics. The effects of all tested LPC on IL-8 synthesis were completely abrogated by addition of BSA and chelation of intracellular Ca(2+). Underlying signaling pathways also included NFkB, p38-MAPK, ERK, PKC and PKA. In mice, adenovirus-mediated overexpression of EL caused an elevation in the plasma levels of MIP-2 (murine IL-8 analogue) accompanied by a markedly increased plasma LPC/PC ratio. Intravenously injected LPC also raised MIP-2 plasma concentration, however to a lesser extent than EL overexpression.

CONCLUSION

Our results indicate that EL and EL-generated LPC, except of LPC 18:2, promote endothelial IL-8 synthesis, with different efficacy and kinetics, related to acyl-chain length and degree of saturation. Accordingly, due to its capacity to modulate the availability of the pro-inflammatory and pro-adhesive chemokine IL-8, EL should be considered an important player in the development of atherosclerosis.