Impaired alternative macrophage differentiation of peripheral blood mononuclear cells from obese subjects

Immunometabolic Signatures of Circulating Monocytes in Humans With Obesity and Insulin Resistance

Obesity is associated with chronic inflammation and metabolic complications, including insulin resistance (IR). Immune cells drive inflammation through the rewiring of intracellular metabolism. However, the impact of obesity-related IR on the metabolism and functionality of circulating immune cells, like monocytes, remains poorly understood. To increase insight into the interindividual variation of immunometabolic signatures among individuals and their role in the development of IR, we assessed systemic and tissue-specific IR and circulating immune markers, and we characterized metabolic signatures and cytokine secretion of circulating monocytes from 194 individuals with a BMI ≥25 kg/m2. Monocyte metabolic signatures were defined using extracellular acidification rates (ECARs) to estimate glycolysis and oxygen consumption rates (OCRs) for oxidative metabolism. Although monocyte metabolic signatures and function based on cytokine secretion varied greatly among study participants, they were strongly associated with each other. The ECAR-to-OCR ratio, representing the balance between glycolysis and oxidative metabolism, was negatively associated with fasting insulin levels, systemic IR, and liver-specific IR. These results indicate that monocytes from individuals with IR were relatively more dependent on oxidative metabolism, whereas monocytes from more insulin-sensitive individuals were more dependent on glycolysis. Additionally, circulating CXCL11 was negatively associated with the degree of systemic IR and positively with the ECAR-to-OCR ratio in monocytes, suggesting that individuals with high IR and a monocyte metabolic dependence on oxidative metabolism also have lower levels of circulating CXCL11. Our findings suggest that monocyte metabolism is related to obesity-associated IR progression and deepen insights into the interplay between innate immune cell metabolism and IR development in humans.

ARTICLE HIGHLIGHTS

Effects of HIIT training and HIIT combined with circuit resistance training on measures of physical fitness, miRNA expression, and metabolic risk factors in overweight/obese middle-aged women

OBJECTIVE

The purpose of this study was to examine the effects of 10 weeks of high-intensity interval training (HIIT) and HIIT combined with circuit resistance training (HCRT) on selected measures of physical fitness, the expression of miR-9, -15a, -34a, -145, and - 155 as well as metabolic risk factors including lipid profiles and insulin resistance in middle-aged overweight/obese women.

METHODS

Twenty-seven overweight/obese women aged 35-50 yrs. were randomized to HIIT (n = 14) or HCRT (n = 13) groups. The HIIT group performed running exercises (5 reps x 4 min per session) with active recovery between repetitions for 10 weeks with 5 weekly sessions. The HCRT group performed 10 weeks of HIIT and resistance training with 3 weekly HIIT sessions and 2 weekly HCRT sessions. Anthropometric measures (e.g., body mass), selected components of physical fitness (cardiovascular fitness, muscle strength), levels of miRNAs (miR-9, -15a, -34a, -145, and - 155), lipid profiles (total cholesterol; TC, Triglycerides; TG, low-density lipoprotein cholesterol; LDL-C and high-density lipoprotein cholesterol; HDL-C), and insulin resistance; HOMA-IR index, were measured at baseline and week 10.

RESULTS

An ANOVA analysis indicated no significant group by time interactions (p > 0.05) for all anthropometric measures, and maximum oxygen consumption (VO2max). A significant group by time interaction, however, was found for the one-repetition maximum (IRM; p < 0.001, ES= 0.751 , moderate). A post-hoc test indicated an increase in the pre-to-post mean 1RM for HCRT (p = 0.001, ES = 1.83, large). There was a significant group by time interaction for miR-155 (p = 0.05, ES = 0.014, trivial). Levels for miR-155 underwent pre-to-post HIIT increases (p = 0.045, ES = 1.232, large). Moreover, there were also significant group by time interactions for TC (p = 0.035, ES = 0.187, trivial), TG (p < 0.001, ES = 0.586, small), LDL-C (p = 0.029, ES = 0.200, small) and HDL-C (p = 0.009, ES = 0.273, small). Post-hoc tests indicated pre-post HCRT decreases for TC (p = 0.001, ES = 1.44, large) and HDL-C (p = 0.001, ES = 1.407, large). HIIT caused pre-to-post decreases in TG (p = 0.001, ES = 0.599, small), and LDL-C (p = 0.001, ES = 0.926, moderate).

CONCLUSIONS

Both training regimes did not improve cardiovascular fitness. But, HCRT improved lower/upper limb muscle strength, and HIIT resulted in an increase in miR-155 expression in peripheral blood mononuclear cells. Furthermore, HIIT and HCRT each improved selected metabolic risk factors including lipid profiles and glucose and insulin metabolism in overweight/obese middle-aged women.

TRIAL REGISTRATION

OSF, October, 4th 2023. Registration DOI: https://doi.org/10.17605/OSF.IO/UZ92E . osf.io/tc5ky . "Retrospectively registered".

An exploratory human study investigating the influence of type 2 diabetes on macrophage phenotype after myocardial infarction

Background

Myocardial infarction (MI) is the primary cause of death in subjects with type 2 diabetes (T2D) and their in-hospital mortality after MI is still elevated compared with those without T2D. Therefore, it is of crucial importance to identify possible mechanisms of worse clinical outcomes and mortality in T2D subjects. Monocyte/macrophage-mediated immune response plays an important role in heart remodelling to limit functional deterioration after MI. Indeed, first pro-inflammatory macrophages digest damaged tissue, then anti-inflammatory macrophages become prevalent and promote tissue repair. Here, we hypothesize that the worse clinical outcomes in patients with T2D could be the consequence of a defective or a delayed polarization of macrophages toward an anti-inflammatory phenotype.

Methods and results

In an exploratory human study, circulating monocytes from male patients with or without T2D at different time-points after MI were in vitro differentiated toward pro- or anti-inflammatory macrophages. The results of this pilot study suggest that the phenotype of circulating monocytes, as well as the pro- and anti-inflammatory macrophage polarization, or the kinetics of the pro- and anti-inflammatory polarization, is not influenced by T2D.

Conclusion

Further studies will be necessary to understand the real contribution of macrophages after MI in humans.

Stress induced proinflammatory adaptations: Plausible mechanisms for the link between stress and cardiovascular disease

Initiating from Hans Selye’s conceptualization of stress physiology, to our present understanding of allostatic load as the cumulative burden of chronic psychological stress and life events, investigators have sought to identify the physiological mechanisms that link stress to health and disease. Of particular interest has been the link between psychological stress and cardiovascular disease (CVD), the number one cause of death in the United States. In this regard, attention has been directed toward alterations in the immune system in response to stress that lead to increased levels of systemic inflammation as a potential pathway by which stress contributes to the development of CVD. More specifically, psychological stress is an independent risk factor for CVD, and as such, mechanisms that explain the connection of stress hormones to systemic inflammation have been examined to gain a greater understanding of the etiology of CVD. Research on proinflammatory cellular mechanisms that are activated in response to psychological stress demonstrates that the ensuing low-grade inflammation mediates pathways that contribute to the development of CVD. Interestingly, physical activity, along with its direct benefits to cardiovascular health, has been shown to buffer against the harmful consequences of psychological stress by “toughening” the SAM system, HPA axis, and immune system as “cross-stressor adaptations” that maintain allostasis and prevent allostatic load. Thus, physical activity training reduces psychological stress induced proinflammation and attenuates the activation of mechanisms associated with the development of cardiovascular disease. Finally, COVID-19 associated psychological stress and its associated health risks has provided another model for examining the stress-health relationship.

The Presence of Psoriasis, Metabolic Syndrome and Their Combination Increases the Serum Levels of CRP and CD5L but Not sCD200R1 and sTLR2 in Participants

Psoriasis and metabolic syndrome (MetS) are chronic inflammatory conditions associated with the dysregulation of immune system reactivity. The inflammatory processes of both diseases have not yet been fully characterized, and the evaluation of proteins/markers that could be involved in their pathogenesis is of great importance. We selected four markers: CRP, sCD200R1, CD5L, and sTLR2; in particular, sCDR2001 has not yet been measured in the context of psoriasis and metabolic syndrome. Material and methods: In the study, 64 controls and 43 patients with psoriasis with or without a metabolic syndrome were enrolled. The levels of selected markers were measured using ELISA kits. Results: CRP levels were significantly higher in psoriasis patients, especially in the subgroup of patients with MetS compared to nonMetS patients (p < 0.01). sCD200R1 and sTLR2 were not significantly different between groups and subgroups; however, CD200R1 levels were slightly higher in both control groups compared to both groups of patients. CD5L levels were significantly higher in patients with MetS compared to nonMets patients (p < 0.02). We also evaluated the correlations between parameters in controls and patients’ groups, as well as in subgroups. Correlations between BMI and CRP were found in all groups and subgroups. Other correlations were group- and subgroup-specific. For example, in the patients’ group, CD5L correlated with sCD200R1 (p < 0.05) and in MetS controls, with age (p < 0.03). Conclusion: The results show that the presence of systemic inflammation associated with psoriasis and metabolic syndrome and their combination alters the expression of specific molecules, especially CRP and CD5L, which were significantly increased in patients with psoriasis and a metabolic syndrome compared to controls without metabolic syndromes. Correlations between CRP and BMI in all groups suggest that overweight and obesity increase the intensity of inflammation and potentiate CD5L expression. In contrast, levels of molecules that may limit inflammation were not increased in psoriasis and metabolic syndrome subjects (they were non-significantly lower compared with healthy controls), which may reflect the chronic nature of both diseases and the exhaustion of inhibitory mechanisms.

Nitazoxanide Exerts Immunomodulatory Effects on Peripheral Blood Mononuclear Cells from Type 2 Diabetes Patients

BACKGROUND

Type 2 diabetes (T2D) is a low-grade inflammatory condition with abnormalities in the immune response mediated by T lymphocytes and macrophages. Drug repositioning for immunomodulatory molecules is an attractive proposal for treating T2D. Nitazoxanide (NTZ) is a broad-spectrum drug with promising immunomodulatory effects. Thus, we investigated the immunomodulatory effect of NTZ on peripheral blood mononuclear cells (PBMCs) from patients with T2D.

METHODS

Fifty patients with T2D were selected, and the proliferative response of T lymphocytes and the M1/M2 ratio of macrophages post cell culture were evaluated by flow cytometry, as well as measuring the concentration of cytokines by ELISA and the relative expression of microRNAs (miRNAs) related to the immune response by real-time PCR.

RESULTS

NTZ exerts an inhibitory effect on the cell proliferation of T lymphocytes stimulated with anti-CD3 and anti-CD28 antibodies without modifying cell viability, and significant decreases in the supernatant concentrations of interleukin (IL)-1β, IL-2, IL-6, IL-10, and IL-12. Furthermore, NTZ negatively regulates the relative expression of miR-155-5p without changes in miR-146a-5p. The M1/M2 ratio of monocytes/macrophages decreased the M1 and increased the M2 subpopulation by NTZ.

CONCLUSIONS

Our results suggest that NTZ exerts immunomodulatory effects on PBMCs from T2D patients, and shows potential alternative therapeutic benefits.

Does iron overload in metabolic syndrome affect macrophage profile? A case control study

AIMS

Dysmetabolic iron overload syndrome (DIOS) is common but the clinical relevance of iron overload is not understood. Macrophages are central cells in iron homeostasis and inflammation. We hypothesized that iron overload in DIOS could affect the phenotype of monocytes and impair macrophage gene expression.

METHODS

This study compared 20 subjects with DIOS to 20 subjects with metabolic syndrome (MetS) without iron overload, and 20 healthy controls. Monocytes were phenotyped by Fluorescence-Activated Cell Sorting (FACS) and differentiated into anti-inflammatory M2 macrophages in the presence of IL-4. The expression of 38 genes related to inflammation, iron metabolism and M2 phenotype was assessed by real-time PCR.

RESULTS

FACS showed no difference between monocytes across the three groups. The macrophagic response to IL-4-driven differentiation was altered in four of the five genes of M2 phenotype (MRC1, F13A1, ABCA1, TGM2 but not FABP4), in DIOS vs Mets and controls demonstrating an impaired M2 polarization. The expression profile of inflammatory genes was not different in DIOS vs MetS. Several genes of iron metabolism presented a higher expression in DIOS vs MetS: SCL11A2 (a free iron transporter, +76 %, p = 0.04), SOD1 (an antioxidant enzyme, +27 %, p = 0.02), and TFRC (the receptor 1 of transferrin, +59 %, p = 0.003).

CONCLUSIONS

In DIOS, macrophage polarization toward the M2 alternative phenotype is impaired but not associated with a pro-inflammatory profile. The up regulation of transferrin receptor 1 (TFRC) in DIOS macrophages suggests an adaptive role that may limit iron toxicity in DIOS.

Nature versus Number: Monocytes in Cardiovascular Disease

Monocytes play a key role in cardiovascular disease (CVD) as their influx into the vessel wall is necessary for the development of an atherosclerotic plaque. Monocytes are, however, heterogeneous differentiating from classical monocytes through the intermediate subset to the nonclassical subset. While it is recognized that the percentage of intermediate and nonclassical monocytes are higher in individuals with CVD, accompanying changes in inflammatory markers suggest a functional impact on disease development that goes beyond the increased proportion of these ‘inflammatory’ monocyte subsets. Furthermore, emerging evidence indicates that changes in monocyte proportion and function arise in dyslipidemia, with lipid lowering medication having some effect on reversing these changes. This review explores the nature and number of monocyte subsets in CVD addressing what they are, when they arise, the effect of lipid lowering treatment, and the possible implications for plaque development. Understanding these associations will deepen our understanding of the clinical significance of monocytes in CVD.

Monocyte M1/M2 profile is altered in paediatric burn patients with hypertrophic scarring

Hypertrophic scars (HTS) remain a common outcome of burn injury, particularly in children. They can arise from variations in the wound healing stages, such as an excessive inflammatory response or inefficient remodelling. Of the cells contributing to these healing stages, macrophages and fibrocytes are crucial. Specifically, the inflammatory phase is dominated by M1 macrophages, the proliferation/remodelling stages by M2 macrophages, and scar tissue contains numerous fibrocytes. As the progenitors to these cells, monocytes, can also exhibit M1- and M2-skewing, we proposed that their profile, or circulating fibrocyte counts, could be used to predict poor healing outcomes. To investigate this, we obtained blood samples from paediatric controls and burns patients, which were then divided into HTS and NoHTS groups upon scar assessment at 12 months. The samples were assessed by whole blood flow cytometry to quantify fibrocytes and monocyte subset proportions and to determine monocyte levels of M1 (CD86, CD120b, CD319) and M2 (CD93, CD163, CD200R) markers. Both burns groups had higher proportions of classical monocytes compared to controls, indicating increased cell turnover and/or entry of other subsets into the wound. In burns patients who took more than 21 days to heal, the HTS group had lower M2 (CD200R) expression with the ratio of M1/M2 (CD86/CD200R) being significantly higher. These results suggest an elevated early inflammatory monocyte response contributes to development of HTS. Correlations of marker expression with remaining healing time revealed a significant positive correlation with M1 (CD120b) and M1/M2 (CD120b/CD200R), suggesting a potential role for CD120b as an indicator of healing delay. Fibrocytes did not significantly differ between the groups. In conclusion, increased monocyte inflammation likely contributes to slower healing and development of scarring, but further studies are needed to determine the predictive power of monocyte inflammatory profile.

Peripheral Blood Mononuclear Cells Oxidative Stress and Plasma Inflammatory Biomarkers in Adults with Normal Weight, Overweight and Obesity

Background: Obesity is an important pathology in public health worldwide. Obese patients are characterized by higher cardiovascular risk and a pro-inflammatory profile. Objective: To assess the oxidative stress in peripheral blood mononuclear cells (PBMCs) and inflammatory biomarkers in plasma in adults with normal weight, overweight and obesity. Methods: One hundred and fifty adults (55-80-years-old; 60% women) from the Balearic Islands, Spain, were recruited and classified according to body mass index (BMI). Anthropometric measurements were carried out, fasting blood samples were collected and plasma and PBMCs were obtained. Biochemical parameters, hemogram, antioxidant enzyme activities and protein levels, reactive oxygen species production (ROS), malondialdehyde (MDA), and cytokine (tumour necrosis factor, TNFα, and interleukin 6, IL-6) levels were measured. Results: Glycaemia, triglyceridemia, abdominal obesity, and waist-to-height ratio (WHtR) were higher, and HDL-cholesterol was lower in obese patients. MDA and TNFα plasma levels were higher in the obese compared to normal-weight group, while the levels of IL-6 were higher in both obese and overweight subjects with respect to normal-weight peers. The activities of all antioxidant enzymes in PBMCs as well as the production ROS progressively increased with BMI. The protein levels of catalase in PBMCs were higher in obese and glutathione reductase in obese and overweight subjects compared to normal-weight peers. No other differences were observed. Conclusion: The current results show that overweight and obesity are related to an increase in pro-oxidant and proinflammatory status in plasma and PBMCs. The studied biomarkers may be useful for monitoring the progression/reversal of obesity.

The Exercise Training Modulatory Effects on the Obesity-Induced Immunometabolic Dysfunctions

Reduced physical activity rate in people's lifestyle is a global concern associated with the prevalence of health disorders such as obesity and metabolic disturbance. Ample evidence has indicated a critical role of the immune system in the aggravation of obesity. The type, duration, and production of adipose tissue-released mediators may change subsequent inactive lifestyle-induced obesity, leading to the chronic systematic inflammation and monocyte/macrophage (MON/MФ) phenotype polarization. Preliminary adipose tissue expansion can be inhibited by changing the lifestyle. In this context, exercise training is widely recommended due to a definite improvement of energy balance and the potential impacts on the inflammatory signaling cascades. How exercise training affects the immune system has not yet been fully elucidated, because its anti-inflammatory, pro-inflammatory, or even immunosuppressive impacts have been indicated in the literature. A thorough understanding of the mechanisms triggered by exercise can suggest a new approach to combat meta-inflammation-induced metabolic diseases. In this review, we summarized the obesity-induced inflammatory pathways, the roles of MON/MФ polarization in adipose tissue and systemic inflammation, and the underlying inflammatory mechanisms triggered by exercise during obesity.

Macrophage-Derived microRNA-155 Increases in Obesity and Influences Adipocyte Metabolism by Targeting Peroxisome Proliferator-Activated Receptor Gamma

OBJECTIVE

This study aimed to investigate cellular sources of microRNAs (miRNA) within adipose tissue and the impact of obesity on miRNA expression, as well as to examine targets of miRNAs.

METHODS

miRNA expression by quantitative polymerase chain reaction was examined in adipocytes, adipose tissue macrophages (ATM), and peripheral blood mononuclear cells from and individuals with normal weight and with obesity. Differentiated 3T3-L1 adipocytes were cocultured with macrophages, and 3T3-L1 and differentiated human mesenchymal stem cells were transfected with miR-155, with peroxisome proliferator-activated receptor gamma (PPAR-γ) and solute carrier family 2 member 4 (GLUT4) abundance measured via Western blot analysis.

RESULTS

Abundance of miR-155 and miR-210 was increased in ATM of participants with obesity by 6.7-fold and 2.9-fold (P = 0.002 and P = 0.013, respectively). miR-130b expression was increased 1.8-fold in ATM and 4.3-fold in adipocytes from participants with obesity (P = 0.007 and P = 0.02, respectively). PPARG mRNA expression decreased 32% (P = 0.044) in adipocytes from individuals with obesity. In 3T3-L1 cells exposed to macrophages, PPARG expression decreased 99.4% (P = 0.02). PPAR-γ protein content declined 75% (P = 0.001) in 3T3-L1 cells transfected with miR-155. GLUT4 protein levels were reduced by 55% (P = 0.021) in differentiated human mesenchymal stem cells exposed to miR-155.

CONCLUSIONS

Adipose tissue miRNAs are influenced in a cell type-specific fashion by obesity, with macrophage miR-155 potentially impacting neighboring adipocytes.

Inflamm-Aging Is Associated with Lower Plasma PTX3 Concentrations and an Impaired Capacity of PBMCs to Express hTERT following LPS Stimulation

Age-related elevations in proinflammatory cytokines, known as inflamm-aging, are associated with shorter immune cell telomere lengths. Purpose. This study examined the relationship of plasma PTX3 concentrations, a biomarker of appropriate immune function, with telomere length in 15 middle-aged (40-64 years) and 15 young adults (20-31 years). In addition, PBMCs were isolated from middle-aged and young adults to examine their capacity to express a key mechanistic component of telomere length maintenance, human telomerase reverse transcriptase (hTERT), following ex vivo cellular stimulation. Methods. Plasma PTX3 and inflammatory cytokines (i.e., IL-6, IL-10, TGF-β, and TNF-α), PBMC telomere lengths, and PBMC hTERT gene expression and inflammatory protein secretion following exposure to LPS, PTX3, and PTX3+LPS were measured. Results. Aging was accompanied by the accumulation of centrally located visceral adipose tissue, without changes in body weight and BMI, and alterations in the systemic inflammatory milieu (decreased plasma PTX3 and TGF-β; increased TNF-α (p ≤ 0.050)). In addition, shorter telomere lengths in middle-aged compared to young adults (p = 0.011) were negatively associated with age, body fat percentages, and plasma TNF-α (r = -0.404, p = 0.027; r = -0.427, p = 0.019; and r = -0.323, p = 0.041, respectively). Finally, the capacity of PBMCs to increase hTERT gene expression following ex vivo stimulation was impaired in middle-aged compared to young adults (p = 0.033) and negatively associated with telomere lengths (r = 0.353, p = 0.028). Conclusions. Proinflammation and the impaired hTERT gene expression capacity of PBMCs may contribute to age-related telomere attrition and disease.

Trauma-Induced Nanohydroxyapatite Deposition in Skeletal Muscle is Sufficient to Drive Heterotopic Ossification

Heterotopic ossification (HO), or the pathologic formation of bone within soft tissues, is a significant complication following severe injuries as it impairs joint motion and function leading to loss of the ability to perform activities of daily living and pain. While soft tissue injury is a prerequisite of developing HO, the exact molecular pathology leading to trauma-induced HO remains unknown. Through prior investigations aimed at identifying the causative factors of HO, it has been suggested that additional predisposing factors that favor ossification within the injured soft tissues environment are required. Considering that chondrocytes and osteoblasts initiate physiologic bone formation by depositing nanohydroxyapatite crystal into their extracellular environment, we investigated the hypothesis that deposition of nanohydroxyapatite within damaged skeletal muscle is likewise sufficient to predispose skeletal muscle to HO. Using a murine model genetically predisposed to nanohydroxyapatite deposition (ABCC6-deficient mice), we observed that following a focal muscle injury, nanohydroxyapatite was robustly deposited in a gene-dependent manner, yet resolved via macrophage-mediated regression over 28 days post injury. However, if macrophage-mediated regression was inhibited, we observed persistent nanohydroxyapatite that was sufficient to drive the formation of HO in 4/5 mice examined. Together, these results revealed a new paradigm by suggesting the persistent nanohydroxyapatite, referred to clinically as dystrophic calcification, and HO may be stages of a pathologic continuum, and not discrete events. As such, if confirmed clinically, these findings support the use of early therapeutic interventions aimed at preventing nanohydroxyapatite as a strategy to evade HO formation.

Maximal Exercise Alters the Inflammatory Phenotype and Response of Mononuclear Cells

PURPOSE

Monocytes express the CD14 receptor that facilitates lipopolysaccharide (LPS) ligation to toll-like receptor 4 (TLR4) to elicit production of interleukin (IL)-6, IL-10, and tumor necrosis factor alpha (TNF-α). However, proinflammatory conditions, such as strenuous exercise, increase the percentage of monocytes expressing CD16, a receptor that enhances LPS stimulated TNF-α production. Therefore, we examined whether maximal treadmill exercise would alter the inflammatory phenotype of classical (CD14/CD16) and proinflammatory monocytes (intermediate [CD14/CD16] and nonclassical [CD14/CD16]), evidenced by changes in TLR4, CD14, and CD16 receptor expression, and their inflammatory response to ex vivo LPS stimulation.

METHODS

Human mononuclear cells from 25 male participants (age, 24.2 ± 4.0 yr) were isolated before and after exercise to assess TLR4, CD14, and CD16 expression by flow cytometry and ex vivo production of LPS-stimulated inflammatory cytokines (IL-6, IL-10, and TNF-α).

RESULTS

Exercise reduced the percentage of classical monocytes and increased the percentage of intermediate and nonclassical monocytes. In addition, TLR4 expression decreased on classical and intermediate monocytes, but not the nonclassical monocyte subset. Furthermore, although CD14 expression decreased on all monocyte subsets, CD16 expression increased on intermediate monocytes only. In parallel with these phenotypic changes, the inflammatory milieu shifted toward a proinflammatory response after LPS stimulation (decreased IL-6 and IL-10 and increased IL-6 to IL-10 ratio and TNF-α production).

CONCLUSIONS

These findings demonstrate that acute maximal exercise elicits a proinflammatory phenotype of isolated monocytes exposed to LPS and highlight potential mechanisms that will help elucidate the role of acute and chronic exercise on the innate immune response of circulating monocytes.

Characterization of Human Monocyte Subsets by Whole Blood Flow Cytometry Analysis

Monocytes are key contributors in various inflammatory disorders and alterations to these cells, including their subset proportions and functions, can have pathological significance. An ideal method for examining alterations to monocytes is whole blood flow cytometry as the minimal handling of samples by this method limits artifactual cell activation. However, many different approaches are taken to gate the monocyte subsets leading to inconsistent identification of the subsets between studies. Here we demonstrate a method using whole blood flow cytometry to identify and characterize human monocyte subsets (classical, intermediate, and non-classical). We outline how to prepare the blood samples for flow cytometry, gate the subsets (ensure contaminating cells have been removed), and determine monocyte subset expression of surface markers - in this example M1 and M2 markers. This protocol can be extended to other studies that require a standard gating method for assessing monocyte subset proportions and monocyte subset expression of other functional markers.

ADSC-conditioned media elicit an ex vivo anti-inflammatory macrophage response

Obesity-associated inflammatory mechanisms play a key role in the pathogenesis of metabolic-related diseases. Failure of anti-inflammatory control mechanisms within adipose tissue and peripheral blood mononuclear cells (PBMCs) have been implicated in disease progression. This study investigated the efficacy of allogeneic adipose tissue-derived mesenchymal stem cells conditioned media (ADSC-CM) to counteract persistent inflammation by inducing an anti-inflammatory phenotype and cytokine response within PBMCs derived from patients with and without metabolic syndrome. Forty six (n=46) mixed ancestry females (18 - 45 years) were subdivided into a) healthy lean (HL) (n=10) (BMI < 25 kg/m2), b) overweight/obese (OW/OB) (BMI ≥ 25 kg/m2, < 3 metabolic risk factors) (n=22) and c) metabolic syndrome (MetS) (visceral adiposity , ≥ 3 metabolic risk factors) (n=14) groups. Body composition (DXA scan), metabolic (cholesterol, HDL, LDL, triglycerides, blood glucose) and inflammatory profiles (38-Plex cytokine panel) were determined. PBMCs were isolated from whole blood and treated ex vivo with either i) autologous participant-derived serum ii) ADSCs-CM or iii) a successive treatment regime. The activation status (CD11b+) and intracellular cytokine (IL6, IL10, TNFa) expression were determined in M1 (CD68+CD206-CD163-) and M2 (CD68+CD163+ CD206+) macrophage populations using flow cytometry. ADSC-CM treatment, promoted a M2 macrophage phenotype and induced IL10 expression, this was most pronounced in the OW/OB group. This response is likely mediated by multiple complementing factors within ADSC-CM, yet to be identified. This study is the first to demonstrate the therapeutic potential of ADSC-CM to restore the inflammatory balance in immune compromised obese individuals.

Smokers Display Reduced Glucocorticoid Sensitivity Prior to Symptomatic Chronic Disease Development

Background

Chronic stress plays a critical role in many of today's diseases and causes of death. Tobacco use reliably increases the likelihood of chronic disease development and premature death. In addition, habitual tobacco use elevates risk of chronic inflammatory diseases, and glucocorticoid therapy is often less effective in smokers compared with nonsmokers. Taken together, smokers may develop glucocorticoid insensitivity, thereby removing the body's greatest anti-inflammatory mechanism.

Purpose

The purpose of this study was to examine glucocorticoid sensitivity among 24 smokers and 24 age-, sex-, and body mass index-matched never smokers who were clinically healthy individuals (i.e., no diagnosis or medication use for chronic diseases and normotensive).

Method

Participants visited the lab after a 12 hr fast, provided a blood sample, and completed a series of psychosocial questionnaires. Smokers continued smoking ad libitum before the lab visit. Group differences in glucocorticoid sensitivity were examined using ANCOVA and repeated with linear mixed model to account for possible dependence among immune outcomes that matching participants on age, sex, and body mass index may have introduced.

Results

Prior to clinical disease onset, smokers' peripheral blood mononuclear cells (PBMCs) exhibited reduced glucocorticoid sensitivity as well as a diminished inflammatory response to lipopolysaccharide compared with never smokers' PBMCs; results were identical regardless of statistical modeling used.

Conclusions

Cigarette smoking, a self-initiated pharmacological chronic stressor, may provide a unique opportunity to examine early wear and tear on physiological functioning that may lead to chronic disease development. Additional research into PBMCs' intracellular changes must be examined as well as repeating this study in a larger, more heterogeneous population.

Infrequent Feeding of Restricted Amounts of Food Induces Stress and Adipose Tissue Inflammation, Contributing to Impaired Glucose Metabolism

Food restriction has been recommended as an effective strategy for body weight loss. However, food restriction can alter biological rhythms and leads to physiological stress. However, relatively little is known about the physiological impact of different methods of food restriction. Therefore, we investigated whether different schedules of restricted food intake induce physiological stress and then contribute to glucose metabolism disorder. C57BL/6 mice were fed a high fat diet (60% fat) for 8 weeks and then randomly divided into three groups: the control group was continuously fed the high fat diet; the two food restriction groups were fed 50% of food consumed by the control mice with one group (FR1) being fed the full amount once a day and the other group (FR2) being fed the same total amount as FR1 twice a day for 3 days. We found increased body weight loss, the serum triglyceride levels, the expression of lipolysis-related genes, and serum corticosterone levels in the FR1 group compared with the FR2 group. The immune cell population infiltrating the adipose tissue and the expression of monocyte chemoattractant protein (MCP-1) and toll-like receptor (TLR-4) mRNA were increased in the FR1 group compared with the control. To determine whether long-term dietary manipulation is associated with metabolic disorders, mice were fed a restricted diet for 3 days alternating with an unrestricted diet for the following 4 days and this was repeated for 8 weeks. The alternating FR1 group showed impaired glucose tolerance compared with the alternating FR2 group. These results indicate that infrequent feeding of restricted amounts of food could induce stress hormones, lipolysis, adipose tissue immune cell infiltration and inflammation, which in turn may promote glucose metabolism disorder.

Human Alternative Macrophages Populate Calcified Areas of Atherosclerotic Lesions and Display Impaired RANKL-Induced Osteoclastic Bone Resorption Activity

Rationale:

Vascular calcification is a process similar to bone formation leading to an inappropriate deposition of calcium phosphate minerals in advanced atherosclerotic plaques. Monocyte-derived macrophages, located in atherosclerotic lesions and presenting heterogeneous phenotypes, from classical proinflammatory M1 to alternative anti-inflammatory M2 macrophages, could potentially display osteoclast-like functions.

Objective:

To characterize the phenotype of macrophages located in areas surrounding the calcium deposits in human atherosclerotic plaques.

Methods and Results:

Macrophages near calcium deposits display an alternative phenotype being both CD68 and mannose receptor–positive, expressing carbonic anhydrase type II, but relatively low levels of cathepsin K. In vitro interleukin-4-polarization of human primary monocytes into macrophages results in lower expression and activity of cathepsin K compared with resting unpolarized macrophages. Moreover, interleukin-4 polarization lowers expression levels of the osteoclast transcriptional activator nuclear factor of activated T cells type c-1, associated with increased gene promoter levels of the transcriptional repression mark H3K27me3 (histone 3 lysine 27 trimethylation). Despite higher expression of the receptor activator of nuclear factor κB receptor, receptor activator of nuclear factor κB ligand/macrophage colony-stimulating factor induction of nuclear factor of activated T cells type c-1 and cathepsin K expression is defective in these macrophages because of reduced Erk/c-fos–mediated downstream signaling resulting in impaired bone resorption capacity.

Conclusions:

These results indicate that macrophages surrounding calcium deposits in human atherosclerotic plaques are phenotypically defective being unable to resorb calcification.

Impact of the cardiovascular system-associated adipose tissue on atherosclerotic pathology

Cardiac obesity makes an important contribution to the pathogenesis of cardiovascular disease. One of the important pathways of this contribution is the inflammatory process that takes place in the adipose tissue. In this review, we consider the role of the cardiovascular system-associated fat in atherosclerotic cardiovascular pathology and a non-atherosclerotic cause of coronary artery disease, such as atrial fibrillation. Cardiovascular system-associated fat not only serves as the energy store, but also releases adipokines that control local and systemic metabolism, heart/vascular function and vessel tone, and a number of vasodilating and anti-inflammatory substances. Adipokine appears to play an important protective role in cardiovascular system. Under chronic inflammation conditions, the repertoire of signaling molecules secreted by cardiac fat can be altered, leading to a higher amount of pro-inflammatory messengers, vasoconstrictors, profibrotic modulators. This further aggravates cardiovascular inflammation and leads to hypertension, induction of the pathological tissue remodeling and cardiac fibrosis. Contemporary imaging techniques showed that epicardial fat thickness correlates with the visceral fat mass, which is an established risk factor and predictor of cardiovascular disease in obese subjects. However, this correlation is no longer present after adjustment for other covariates. Nevertheless, recent studies showed that pericardial fat volume and epicardial fat thickness can probably serve as a better indicator for atrial fibrillation.

IL-10 expression in macrophages from neonates born from obese mothers is suppressed by IL-4 and LPS/INFγ

Obese women offspring have a higher risk of developing chronic diseases associated with an altered immune function. We aim to determine, in neonatal monocyte-derived macrophages, whether maternal obesity is associated with an altered expression and DNA methylation of pro- and anti-inflammatory genes, along with a higher pro-inflammatory response. Cord blood from newborns of obese (Ob) and lean (control) women were obtained at delivery. Monocytes were isolated and differentiated into macrophages, in which M1 (LPS/IFNγ) and M2 (IL-4) polarization were assayed. The mRNA levels for TNFα, IL-1β, IL-12A, IL-12B, IL-10, and IL-4R were quantified by qPCR and the DNA methylation of candidate genes determined by pyrosequencing.

RESULTS

Ob-monocytes had decreased levels of mRNA for pro-inflammatory cytokines IL-1β, IL-10, and IL-12B compared with controls. Conversely, Ob-macrophages showed increased levels of mRNA for TNFα, IL-4R, and IL-10 compared with controls. M1 response was comparable between both groups, characterized by an important induction of TNFα and IL-1β. In response to an M2 stimulus, control macrophages showed a decreased expression of inflammatory mediators while Ob-macrophages had an additional suppression of the anti-inflammatory mediator IL-10. Changes in IL-1β (monocytes) and IL-10 (macrophages) in Ob-monocytes were paralleled by changes in their promoter DNA methylation in fetal monocytes. These results suggest that monocyte-derived macrophages from obese newborns show a basal anti-inflammatory phenotype with an unbalanced response to M1 and M2 polarization stimuli. The presence of changes in DNA methylation of key inflammatory genes in neonatal monocytes suggests an intrauterine programing of immune function by maternal obesity.

The Potential Role of Aerobic Exercise-Induced Pentraxin 3 on Obesity-Related Inflammation and Metabolic Dysregulation

Obesity is defined as the excess accumulation of intra-abdominal body fat, resulting in a state of chronic, low-grade proinflammation that can directly contribute to the development of insulin resistance. Pentraxin 3 (PTX3) is an acute-phase protein that is expressed by a variety of tissue and cell sources and provides an anti-inflammatory property to downregulate the production of proinflammatory cytokines, in particular interleukin-1 beta and tumor necrosis factor alpha. Although PTX3 may therapeutically aid in altering the proinflammatory milieu in obese individuals, and despite elevated expression of PTX3 mRNA observed in adipose tissue, the circulating level of PTX3 is reduced with obesity. Interestingly, aerobic activity has been demonstrated to elevate PTX3 levels. Therefore, the purpose of this review is to discuss the therapeutic potential of PTX3 to positively regulate obesity-related inflammation and discuss the proposition for utilizing aerobic exercise as a nonpharmacological anti-inflammatory treatment strategy to enhance circulating PTX3 concentrations in obese individuals.

β2 Adrenoceptors are underexpressed in peripheral blood mononuclear cells and associated with a better metabolic profile in central obesity

Background: Central obesity (CO) is an inflammatory disease. Because immune cells and adipocytes are catecholamines(CA)-producing cells, we studied the expression of adrenoceptors (AR) in peripheral blood mononuclear cells (PBMCs) hypothesizing a distinct adrenergic pattern in inflammatory obesity. Methods: AR expression was assessed in blood donors categorized by waist circumference (WC) (CO: WC≥0.80 m in women and ≥0.94 m in men). Following a pilot study for all AR subtypes, we measured β₂AR expression in fifty-seven individuals and correlated this result with anthropometric, metabolic and inflammatory parameters. A ratio (R) between AR mRNA of CO and non-CO<0.5 was considered under and >2.0 over expression. Results: The pilot study revealed no differences between groups, except for β₂AR mRNA. CO individuals showed underexpression of β₂AR relatively to those without CO (R=0.08; p=0.009). β₂AR expression inversely correlated with triacylglycerol (r=-0.271; p=0.041), very low-density lipoprotein-cholesterol (r=-0.313; p=0.018) and leptin (r=-0.392; p=0.012) and positively with high-density lipoprotein-cholesterol (r=0.310: p=0.045) plasma levels. Multiple logistic regression analysis showed a protective effect of β₂AR expression (≥2x10-6) [odds ratio (OR) 0.177 with respective confidence interval of 95% (95% CI) (0.040- 0.796)] for the occurrence of CO. A higher association was found for women as compared to men (Ξ9:1) [OR 8.972 (95% CI) (1.679-47.949)]. Conclusion: PBMCs β₂AR, underexpressed in centrally obese, are associated with a better metabolic profile and showed a protective role for the development of CO. The discovery of β₂AR as a new molecular marker of obesity subphenotypes in PBMCs might contribute to clarify the adrenergic immunomodulation of inflammatory obesity.

Differences in metabolic biomarkers in the blood and gene expression profiles of peripheral blood mononuclear cells among normal weight, mildly obese and moderately obese subjects

We compared metabolic biomarkers in the blood and peripheral blood mononuclear cell (PBMC) gene expression profiles among normal weight (BMI, 18·5–23 kg/m2), mildly obese (BMI, 25–27·5 kg/m2) and moderately obese Korean adult men (BMI, 27·5–30 kg/m2). High leptin, lipids (except LDL- and HDL-cholesterol) and apoB levels and low adiponectin and HDL-cholesterol levels were present in the plasma of both mildly and moderately obese subjects. Circulating levels of inflammatory cytokines and markers of insulin resistance, oxidative stress and liver damage were altered in moderately obese subjects but not in mildly obese subjects. PBMC transcriptome data showed enrichment of pathways involved in energy metabolism, insulin resistance, bone metabolism, cancer, inflammation and fibrosis in both mildly and moderately obese subjects. Signalling pathways involved in oxidative phosphorylation, TAG synthesis, carbohydrate metabolism and insulin production; mammalian target of rapamycin, forkhead box O, ras-proximate-1, RAS and transforming growth factor-β signalling; as well as extracellular matrix–receptor interaction were enriched only in moderately obese subjects, indicating that changes in PBMC gene expression profiles, according to metabolic disturbances, were associated with the development and/or aggravation of obesity. In particular, fourteen and fifteen genes differentially expressed only in mildly obese subjects and in both mildly and moderately obese subjects, respectively, could be used as early or stable biomarkers for diagnosing and treating obesity-associated metabolic disturbance. We characterised BMI-associated metabolic and molecular biomarkers in the blood and provided clues about potential blood-based targets for preventing or treating obesity-related complications.

Pentraxin 3 is an anti-inflammatory protein associated with lipid-induced interleukin 10 in vitro

Pentraxin 3 (PTX3) is an acute phase protein expressed in response to pro-inflammatory stimuli during atherosclerosis. However, recent findings suggest that PTX3 is a counter-regulatory protein which enhances the anti-inflammatory response.

OBJECTIVE

Therefore, the capacity of PTX3 to alter the inflammatory milieu following in vitro stimulation of PBMCs with the pro-inflammatory lipid, palmitate, was examined.

METHODS

PBMCs from 17 healthy male donors were isolated and cultured under four separate conditions; 200μmol/L palmitate, a physiologically relevant concentration of PTX3, in combination (pal+PTX3), and an unstimulated time-course control.

RESULTS

Palmitate-induced production of the counter-regulatory protein PTX3 was positively associated with the production of the anti-inflammatory cytokine interleukin 10 (IL-10) following in vitro stimulation of human PBMCs. Furthermore, stimulation of PBMCs in vitro with 500pg/mL PTX3 elicited a significantly greater increase in IL-10 production compared to the palmitate stimulated conditions. However, PTX3 stimulation did not result in the production of the pro-inflammatory cytokines IL-1β, IL-6, and tumor necrosis factor alpha, and when combined with palmitate, did not alter the pro-inflammatory milieu from PBMCs in this study.

CONCLUSION

These findings provide evidence supporting the role of PTX3 as a mediator of the anti-inflammatory response in physiologically relevant conditions, and suggests that PTX3 counter regulates the development of atherosclerosis by enhancing the production of IL-10.

Transcriptome-Wide Analysis Reveals Modulation of Human Macrophage Inflammatory Phenotype Through Alternative Splicing

OBJECTIVE

Human macrophages can shift phenotype across the inflammatory M1 and reparative M2 spectrum in response to environmental challenges, but the mechanisms promoting inflammatory and cardiometabolic disease-associated M1 phenotypes remain incompletely understood. Alternative splicing (AS) is emerging as an important regulator of cellular function, yet its role in macrophage activation is largely unknown. We investigated the extent to which AS occurs in M1 activation within the cardiometabolic disease context and validated a functional genomic cell model for studying human macrophage-related AS events.

APPROACH AND RESULTS

From deep RNA-sequencing of resting, M1, and M2 primary human monocyte-derived macrophages, we found 3860 differentially expressed genes in M1 activation and detected 233 M1-induced AS events; the majority of AS events were cell- and M1-specific with enrichment for pathways relevant to macrophage inflammation. Using genetic variant data for 10 cardiometabolic traits, we identified 28 trait-associated variants within the genomic loci of 21 alternatively spliced genes and 15 variants within 7 differentially expressed regulatory splicing factors in M1 activation. Knockdown of 1 such splicing factor, CELF1, in primary human macrophages led to increased inflammatory response to M1 stimulation, demonstrating CELF1's potential modulation of the M1 phenotype. Finally, we demonstrated that an induced pluripotent stem cell-derived macrophage system recapitulates M1-associated AS events and provides a high-fidelity macrophage AS model.

CONCLUSIONS

AS plays a role in defining macrophage phenotype in a cell- and stimulus-specific fashion. Alternatively spliced genes and splicing factors with trait-associated variants may reveal novel pathways and targets in cardiometabolic diseases.

Transducin-like enhancer of split-1 is expressed and functional in human macrophages

Macrophages display heterogeneous phenotypes, including the classical M1 proinflammatory and the alternative M2 anti-inflammatory polarization states. The transducin-like enhancer of split-1 (TLE1) is a transcriptional corepressor whose functions in macrophages have not been studied yet. We report that TLE1 is highly expressed in human alternative macrophages in vitro and in atherosclerotic plaques as well as in adipose tissue M1/M2 mixed macrophages. TLE1 silencing in alternative macrophages decreases the expression of the M2 markers IL-1Ra and IL-10, while it exacerbates TNFα and CCL3 induction by lipopolysaccharide. Hence, TLE1 is expressed in human macrophages where it has potential anti-inflammatory and alternative phenotype promoting properties.

M1 and M2 macrophage proteolytic and angiogenic profile analysis in atherosclerotic patients reveals a distinctive profile in type 2 diabetes

This study aimed to investigate atherosclerotic mediators' expression levels in M1 and M2 macrophages and to focus on the influence of diabetes on M1/M2 profiles. Macrophages from 36 atherosclerotic patients (19 diabetics and 17 non-diabetics) were cultured with interleukin-1β (IL-1β) or IL-4 to induce M1 or M2 phenotype, respectively. The atherosclerotic mediators' expression was evaluated by quantitative reverse transcription-polymerase chain reaction (RT-PCR). The results showed that M1 and M2 macrophages differentially expressed mediators involved in proteolysis and angiogenesis processes. The proteolytic balance (matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of metalloproteinase-1 (TIMP-1), MMP-9/plasminogen activator inhibitor-1 (PAI-1) and MMP-9/tissue factor pathway inhibitor-2 (TFPI-2) ratios) was higher in M1 versus M2, whereas M2 macrophages presented higher angiogenesis properties (increased vascular endothelial growth factor/TFPI-2 and tissue factor/TFPI-2 ratios). Moreover, M1 macrophages from diabetics displayed more important proangiogenic and proteolytic activities than non-diabetics. This study reveals that M1 and M2 macrophages could differentially modulate major atherosclerosis-related pathological processes. Moreover, M1 macrophages from diabetics display a deleterious phenotype that could explain the higher plaque vulnerability observed in these subjects.

Peripheral blood mononuclear cells as in vivo model for dietary intervention induced systemic oxidative stress

Our aim was to assess the use of peripheral blood mononuclear cells (PBMC) as an in vivo cellular model to evaluate diet-induced changes in the oxidative stress status by analyzing the gene expression pattern of NADPH-oxidase subunits and antioxidant genes. A randomized, controlled trial assigned metabolic syndrome patients to 4 diets for 12 weeks each: (i) high-saturated fatty acid (HSFA), (ii) high-monounsaturated fatty acid, and (iii), (iv) two low-fat, high-complex carbohydrate diets supplemented with n-3 polyunsaturated fatty acids or placebo. A fat challenge reflecting the fatty acid composition as the original diets was conducted post-intervention. The mRNA levels of gp91(phox) (P<0.001), p22(phox) (P=0.005), p47(phox) (P=0.001) and p40(phox) (P<0.001) increased at 2h after the intake of the HSFA meal. The expression of SOD1, SOD2, GSR, GPx1, GPX4, TXN, TXNRD1 and Nrf2 increased after the HSFA meal (p<0.05). In contrast, the expression of these genes remained unaltered in response to the other dietary interventions. Our results suggest that the increased expression of antioxidant genes in PBMC seems to be due to the response to the postprandial oxidative stress generated mainly in adipose tissue after the consumption of an HSFA diet.

Myeloid cell dysfunction and the pathogenesis of the diabetic chronic wound

Diabetes can promote a state of chronic inflammation associated with serious complications that are difficult to treat, including ulceration of the lower extremities and chronic wounds. Chronic wounds are often incurable and contribute to both a reduced quality of life for patients and an enormous burden for healthcare services. In diabetes, the inflammatory response early in wound healing is inappropriately amplified and prolonged, leading to the persistent presence in the wound of vastly elevated numbers of dysfunctional, hyperpolarised macrophages that fail to transition to a pro-healing phenotype. Recent evidence suggests that systemic chronic inflammation induces intrinsic defects in monocytes via chromatin modifications that may pre-programme monocytes to a pro-inflammatory phenotype, while the local wound environment inhibits differentiation to a pro-healing phenotype. Current understanding remains incomplete, and careful dissection of how local and systemic inflammation combine to negatively influence myeloid cell development will be key to developing effective therapies aimed at healing the diabetic wound.

Obesity and lifespan health--importance of the fetal environment

A marked increase in the frequency of obesity at the population level has resulted in an increasing number of obese women entering pregnancy. The increasing realization of the importance of the fetal environment in relation to chronic disease across the lifespan has focused attention on the role of maternal obesity in fetal development. Previous studies have demonstrated that obesity during adolescence and adulthood can be traced back to fetal and early childhood exposures. This review focuses on factors that contribute to early developmental events, such as epigenetic modifications, the potential for an increase in inflammatory burden, early developmental programming changes such as the variable development of white versus brown adipose tissue, and alterations in organ ontogeny. We hypothesize that these mechanisms promote an unfavorable fetal environment and can have a long-standing impact, with early manifestations of chronic disease that can result in an increased demand for future health care. In order to identify appropriate preventive measures, attention needs to be placed both on reducing maternal obesity as well as understanding the molecular, cellular, and epigenetic mechanisms that may be responsible for the prenatal onset of chronic disease.

Peripheral blood leucocyte subclasses as potential biomarkers of adipose tissue inflammation and obesity subphenotypes in humans

While obesity is clearly accepted as a major risk factor for cardio-metabolic morbidity, it is also apparent that some obese patients largely escape this association, forming a unique obese subphenotype(s). Current approaches to define such subphenotypes include clinical biomarkers that largely reflect already manifested comorbidities, such as markers of dyslipidaemia, hyperglycaemia and impaired regulation of vascular tone, and anthropometric or imaging-based assessment of adipose tissue distribution. Low-grade inflammation, evident both systemically and within adipose tissue (particularly intra-abdominal fat depots), seems to characterize the more cardio-metabolically morbid forms of obesity. Indeed, several systemic inflammatory markers (C-reactive protein), adipokines (retinol-binding protein 4, adiponectin) and cytokines have been shown to correlate in humans with adipose tissue inflammation and with obesity-associated health risks. Circulating leucocytes constitute a diverse group of cells that form a major arm of the immune system. They are both major sources of cytokines and likely also of infiltrating adipose tissue immune cells in obesity. In the present review, we summarize currently available literature on 'classical' blood white cell classes and on more specific leucocyte subclasses present in the circulation in human obesity. We critically raise the possibility that leucocytes may constitute clinically available markers for the more morbidity-associated obesity subphenotype(s), and when available, for intra-abdominal adipose tissue inflammation.

HDL does not influence the polarization of human monocytes toward an alternative phenotype

BACKGROUND

Macrophages are crucial cells in the pathogenesis of atherosclerosis. Macrophages are plastic cells which can switch from a classical pro-inflammatory M1 to an alternative anti-inflammatory M2 macrophage phenotype, depending on the environmental stimuli. Because high-density lipoprotein (HDL) cholesterol levels are inversely correlated to cardiovascular disease and since HDL displays anti-inflammatory properties, we investigated whether HDL can affect alternative macrophage differentiation of primary human monocytes in the presence of interleukin (IL)-4, a M2 macrophage polarization driver, in vitro and ex vivo.

METHODS AND RESULTS

M2 macrophages are highly responsive to HDL stimulation, since the expression of pentraxin 3 (PTX3), a well known HDL target gene, is induced by HDL more strongly in M2 macrophages than in control unpolarized resting macrophages (RM). As expected, the expression of M2 markers, such as Mannose Receptor (MR), CD200 Receptor (CD200R), Coagulation factor XIII A1 (F13A1), IL-1 receptor antagonist (IL-1RA) and IL10, was induced in IL-4 polarized M2 macrophages compared to RM. However, incubation with HDL added in vitro did not modulate the gene expression of M2 macrophage polarization markers. Moreover, monocytes isolated from subjects with genetically low HDL levels, carrying ABCA1 or LCAT mutations, differentiated ex vivo into M2 macrophages without any difference in the alternative macrophage marker expression profile.

CONCLUSIONS

These in vitro and ex vivo results indicate that, contrary to mouse macrophages, HDL does not influence macrophage M2 polarization of human monocyte-derived macrophages. Thus, the anti-inflammatory properties of HDL in humans are probably not related to the enhancement of the M2 macrophage phenotype.

Immune system and glucose metabolism interaction in schizophrenia: a chicken-egg dilemma

Impaired glucose metabolism and the development of metabolic syndrome contribute to a reduction in the average life expectancy of individuals with schizophrenia. It is unclear whether this association simply reflects an unhealthy lifestyle or whether weight gain and impaired glucose tolerance in patients with schizophrenia are directly attributable to the side effects of atypical antipsychotic medications or disease-inherent derangements. In addition, numerous previous studies have highlighted alterations in the immune system of patients with schizophrenia. Increased concentrations of interleukin (IL)-1, IL-6, and transforming growth factor-beta (TGF-β) appear to be state markers, whereas IL-12, interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and soluble IL-2 receptor (sIL-2R) appear to be trait markers of schizophrenia. Moreover, the mononuclear phagocyte system (MPS) and microglial activation are involved in the early course of the disease. This review illustrates a "chicken-egg dilemma", as it is currently unclear whether impaired cerebral glucose utilization leads to secondary disturbances in peripheral glucose metabolism, an increased risk of cardiovascular complications, and accompanying pro-inflammatory changes in patients with schizophrenia or whether immune mechanisms may be involved in the initial pathogenesis of schizophrenia, which leads to disturbances in glucose metabolism such as metabolic syndrome. Alternatively, shared underlying factors may be responsible for the co-occurrence of immune system and glucose metabolism disturbances in schizophrenia.

A reappraisal of the role of circulating (progenitor) cells in the pathobiology of diabetic complications

Traditionally, the development of diabetic complications has been attributed to the biochemical pathways driving hyperglycaemic cell damage, while reparatory mechanisms have been long overlooked. A more comprehensive view of the balance between damage and repair suggests that an impaired regenerative capacity of bone marrow (BM)-derived cells strongly contributes to defective re-endothelisation and neoangiogenesis in diabetes. Although recent technological advances have redefined the biology and function of endothelial progenitor cells (EPCs), interest in BM-derived vasculotropic cells in the setting of diabetes and its complications remains high. Several circulating cell types of haematopoietic and non-haematopoietic origin are affected by diabetes and are potentially involved in the pathobiology of chronic complications. In addition to classical EPCs, these include circulating (pro-)angiogenic cells, polarised monocytes/macrophages (M1 and M2), myeloid calcifying cells and smooth muscle progenitor cells, having disparate roles in vascular biology. In parallel with the study of elusive progenitor cell phenotypes, it has been recognised that diabetes induces a profound remodelling of the BM stem cell niche. The alteration of circulating (progenitor) cells in the BM is now believed to be the link among distant end-organ complications. The field is rapidly evolving and interest is shifting from specific cell populations to the complex network of interactions that orchestrate trafficking of circulating vasculotropic cells.

Modulation of adipose tissue inflammation by FOXP3+ Treg cells, IL-10, and TGF-β in metabolically healthy class III obese individuals

OBJECTIVE

The objective of this study was to compare the profiles of proinflammatory (interleukin [IL]-6 and tumor necrosis factor [TNF]) and anti-inflammatory (IL-10 and transforming growth factor [TGF]-β) adipokines in the blood, subcutaneous adipose tissue (SAT), and visceral adipose tissue (VAT) of metabolically healthy class III obese individuals and normal-weight controls.

METHODS

The serum concentrations (enzyme-linked immunosorbent assay [ELISA]), mRNA expression levels (reverse transcriptase polymerase chain reaction), and adipose tissue secretion (ELISA) of IL-6, TNF, IL-10, and TGF-β were analyzed, as were the mRNA expression of FOXP3 (present in regulatory T cells) and the secretion (Western blotting) of matrix metalloproteinases in the adipose tissue.

RESULTS

There were no differences in the circulating levels, expression, or secretion of IL-6 and TNF between the groups or tissues. The expression and circulating levels of IL-10 were higher in obese individuals, especially in the SAT. Although the blood concentration of TGF-β was similar between the groups, its expression and secretion levels were higher in the adipose tissues of obese individuals compared with controls. FOXP3 and MMP expression levels were higher in the SAT and VAT of obese individuals, respectively, compared with the controls.

CONCLUSION

Metabolically healthy, extremely obese individuals have effective immunoregulation to counter chronic obesity-related inflammation through the increased production of the anti-inflammatory cytokines IL-10 and TGF-β in adipose tissue, especially SAT; the increased presence of FOXP3-positive regulatory T cells; and increases in angiogenesis and adipogenesis induced by TGF-β and MMPs. These regulatory mechanisms could be important in the delayed onset of metabolic complications, even in extremely obese individuals.

Ixmyelocel-T, an expanded multicellular therapy, contains a unique population of M2-like macrophages

INTRODUCTION

M2 macrophages promote tissue repair and regeneration through various mechanisms including immunomodulation and scavenging of tissue debris. Delivering increased numbers of these cells to ischemic tissues may limit tissue injury and promote repair. Ixmyelocel-T is an expanded, autologous multicellular therapy cultured from bone-marrow mononuclear cells (BMMNCs). The purpose of this study was to characterize further a unique expanded population of M2-like macrophages, generated in ixmyelocel-T therapy.

METHODS

Approximately 50 ml of whole bone marrow was obtained from healthy donors and shipped overnight. BMMNCs were produced by using density-gradient separation and cultured for approximately 12 days to generate ixmyelocel-T. CD14+ cells were isolated from ixmyelocel-T with positive selection for analysis. Cell-surface phenotype was examined with flow cytometry and immunofluorescence, and expression of cytokines and chemokines was analyzed with enzyme-linked immunosorbent assay (ELISA). Quantitative real-time PCR was used to analyze expression of genes in BMMNCs, ixmyelocel-T, the CD14+ population from ixmyelocel-T, and M1 and M2 macrophages. Ixmyelocel-T was cultured with apoptotic BMMNCs, and then visualized under fluorescence microscopy to assess efferocytosis.

RESULTS

Macrophages in ixmyelocel-T therapy expressed surface markers of M2 macrophages, CD206, and CD163. These cells were also found to express several M2 markers, and few to no M1 markers. After stimulation with lipopolysaccharide (LPS), they showed minimal secretion of the proinflammatory cytokines interleukin-12 (IL-12) and tumor necrosis factor alpha (TNF-α) compared with M1 and M2 macrophages. Ixmyelocel-T macrophages efficiently ingested apoptotic BMMNCs.

CONCLUSIONS

Ixmyelocel-T therapy contains a unique population of M2-like macrophages that are characterized by expression of M2 markers, decreased secretion of proinflammatory cytokines after inflammatory stimuli, and efficient removal of apoptotic cells. This subpopulation of cells may have a potential role in tissue repair and regeneration.

Changes in human dendritic cell number and function in severe obesity may contribute to increased susceptibility to viral infection

Dendritic cells (DCs) are key immune sentinels linking the innate and adaptive immune systems. DCs recognise danger signals and initiate T-cell tolerance, memory and polarisation. They are critical cells in responding to a viral illness. Obese individuals have been shown to have an impaired response to vaccinations against virally mediated conditions and to have an increased susceptibility to multi-organ failure in response to viral illness. We investigated if DCs are altered in an obese cohort (mean body mass index 51.7±7.3 kg m(-2)), ultimately resulting in differential T-cell responses. Circulating DCs were found to be significantly decreased in the obese compared with the lean cohort (0.82% vs 2.53%). Following Toll-like receptor stimulation, compared with lean controls, DCs generated from the obese cohort upregulated significantly less CD83 (40% vs 17% mean fluorescence intensity), a molecule implicated in the elicitation of T-cell responses, particularly viral responses. Obese DCs produced twofold more of the immunosuppressive cytokine interleukin (IL)-10 than lean controls, and in turn stimulated fourfold more IL-4-production from allogenic naive T cells. We conclude that obesity negatively impacts the ability of DCs to mature and elicit appropriate T-cell responses to a general stimulus. This may contribute to the increased susceptibility to viral infection observed in severe obesity.

An unbalanced monocyte polarisation in peripheral blood and bone marrow of patients with type 2 diabetes has an impact on microangiopathy

AIM/HYPOTHESIS

Monocytes/macrophages play important roles in adipose and vascular tissues and can be polarised as inflammatory M1 or anti-inflammatory M2. We sought to analyse monocyte polarisation status in type 2 diabetes, which is characterised by chronic inflammation.

METHODS

We enrolled 60 individuals without diabetes and 53 patients with type 2 diabetes. We quantified standard monocyte subsets defined by cluster of differentiation (CD)14 and CD16. In addition, based on the phenotype of polarised macrophages in vitro, we characterised and quantified more definite M1 (CD68(+)CCR2(+)) and M2 (CX3CR1(+)CD206(+)/CD163(+)) monocytes. We also analysed bone marrow (BM) samples and the effects of granulocyte-colony stimulating factor (G-CSF) stimulation in diabetic and control individuals.

RESULTS

We found no alterations in standard monocyte subsets (classical, intermediate and non-classical) when comparing groups. For validation of M1 and M2 phenotypes, we observed that M2 were enriched in non-classical monocytes and had lower TNF-α content, higher LDL scavenging and lower transendothelial migratory capacity than M1. Diabetic patients displayed an imbalanced M1/M2 ratio compared with the control group, attributable to a reduction in M2. The M1/M2 ratio was directly correlated with waist circumference and HbA1c and, among diabetic patients, M2 reduction and M1/M2 increase were associated with microangiopathy. A decrease in M2 was also found in the BM from diabetic patients, with a relative M2 excess compared with the bloodstream. BM stimulation with G-CSF mobilised M2 macrophages in diabetic but not in healthy individuals.

CONCLUSIONS/INTERPRETATION

We show that type 2 diabetes markedly reduces anti-inflammatory M2 monocytes through a dysregulation in bone-marrow function. This defect may have a negative impact on microangiopathy.

Vitamin D deficiency induces high blood pressure and accelerates atherosclerosis in mice

Multiple epidemiological studies link vitamin D deficiency to increased cardiovascular disease (CVD), but causality and possible mechanisms underlying these associations are not established. To clarify the role of vitamin D-deficiency in CVD in vivo, we generated mouse models of diet-induced vitamin D deficiency in two backgrounds (LDL receptor- and ApoE-null mice) that resemble humans with diet-induced hypertension and atherosclerosis. Mice were fed vitamin D-deficient or -sufficient chow for 6 weeks and then switched to high fat (HF) vitamin D-deficient or -sufficient diet for 8-10 weeks. Mice with diet-induced vitamin D deficiency showed increased systolic and diastolic blood pressure, high plasma renin, and decreased urinary sodium excretion. Hypertension was reversed and renin was suppressed by returning chow-fed vitamin D-deficient mice to vitamin D-sufficient chow diet for 6 weeks. On a HF diet, vitamin D-deficient mice had ~2-fold greater atherosclerosis in the aortic arch and ~2-8-fold greater atherosclerosis in the thoracic and abdominal aorta compared to vitamin D-sufficient mice. In the aortic root, HF-fed vitamin D-deficient mice had increased macrophage infiltration with increased fat accumulation and endoplasmic reticulum (ER) stress activation, but a lower prevalence of the M1 macrophage phenotype within atherosclerotic plaques. Similarly, peritoneal macrophages from vitamin D-deficient mice displayed an M2-predominant phenotype with increased foam cell formation and ER stress. Treatment of vitamin D-deficient mice with the ER stress reliever PBA during HF feeding suppressed atherosclerosis, decreased peritoneal macrophage foam cell formation, and downregulated ER stress proteins without changing blood pressure. Thus, we suggest that vitamin D deficiency activates both the renin angiotensin system and macrophage ER stress to contribute to the development of hypertension and accelerated atherosclerosis, highlighting vitamin D replacement as a potential therapy to reduce blood pressure and atherosclerosis.

Vitamin D suppression of endoplasmic reticulum stress promotes an antiatherogenic monocyte/macrophage phenotype in type 2 diabetic patients

Cardiovascular disease is the leading cause of morbidity/mortality in patients with type 2 diabetes mellitus (T2DM), but there is a lack of knowledge about the mechanism(s) of increased atherosclerosis in these patients. In patients with T2DM, the prevalence of 25-hydroxy vitamin D (25(OH)D) deficiency is almost twice that for nondiabetics and doubles the relative risk of developing cardiovascular disease compared with diabetic patients with normal 25(OH)D. We tested the hypothesis that monocytes from vitamin D-deficient subjects will have a proatherogenic phenotype compared with vitamin D-sufficient subjects in 43 patients with T2DM. Serum 25(OH)D level inversely correlated with monocyte adhesion to endothelial cells even after adjustment for demographic and comorbidity characteristics. Vitamin D-sufficient patients (≥30 ng/ml 25(OH)D) had lower monocyte endoplasmic reticulum (ER) stress, a predominance of M1 over M2 macrophage membrane receptors, and decreased mRNA expression of monocyte adhesion molecules PSGL-1, β(1)-integrin, and β(2)-integrin compared with patients with 25(OH)D levels of <30 ng/ml. In vitamin D-deficient macrophages, activation of ER stress increased adhesion and adhesion molecule expression and induced an M2-predominant phenotype. Moreover, adding 1,25(OH)(2)D(3) to vitamin D-deficient macrophages shifted their phenotype toward an M1-predominant phenotype with suppressed adhesion. Conversely, deletion of the vitamin D receptor in macrophages from diabetic patients activated ER stress, accelerated adhesion, and increased adhesion molecule expression. The absence of ER stress protein CCAAT enhancer-binding protein homologous protein suppressed monocyte adhesion, adhesion molecule expression, and the M2-predominant phenotype induced by vitamin D deficiency. Thus, vitamin D is a natural ER stress reliever that induced an antiatherogenic monocyte/macrophage phenotype.