Unique metabolic activation of adipose tissue macrophages in obesity promotes inflammatory responses

Glycolytic metabolism: Food for immune cells, fuel for depression?

Inflammation is one biological pathway thought to impact the brain to contribute to major depressive disorder (MDD) and is reliably associated with resistance to standard antidepressant treatments. While peripheral immune cells, particularly monocytes, have been associated with aspects of increased inflammation in MDD and symptom severity, significant gaps in knowledge exist regarding the mechanisms by which these cells are activated to contribute to behavioral symptoms in MDD. One concept that has gained recent appreciation is that metabolic rewiring to glycolysis in activated myeloid cells plays a crucial role in facilitating these cells' pro-inflammatory functions, which may underlie myeloid contribution to systemic inflammation and its effects on the brain. Given emerging evidence from translational studies of depression that peripheral monocytes exhibit signs of glycolytic activation, better understanding the immunometabolic phenotypes of monocytes which are known to be elevated in MDD with high inflammation is a critical step toward comprehending and treating the impact of inflammation on the brain. This narrative review examines the extant literature on glycolytic metabolism of circulating monocytes in depression and discusses the functional implications of immunometabolic shifts at both cellular and systemic levels. Additionally, it proposes potential therapeutic applications of existing immunomodulators that target glycolysis and related metabolic pathways in order to reverse the impact of elevated inflammation on the brain and depressive symptoms.

Targeting Macrophage Phenotypes and Metabolism as Novel Therapeutic Approaches in Atherosclerosis and Related Cardiovascular Diseases

PURPOSE OF THE REVIEW

Macrophage accumulation and activation function as hallmarks of atherosclerosis and have complex and intricate dynamics throughout all components and stages of atherosclerotic plaques. In this review, we focus on the regulatory roles and underlying mechanisms of macrophage phenotypes and metabolism in atherosclerosis. We highlight the diverse range of macrophage phenotypes present in atherosclerosis and their potential roles in progression and regression of atherosclerotic plaque. Furthermore, we discuss the challenges and opportunities in developing therapeutic strategies for preventing and treating atherosclerotic cardiovascular disease.

RECENT FINDINGS

Dysregulation of macrophage polarization between the proinflammatory M1 and anti-inflammatory M2 phenotypealters the immuno-inflammatory response during atherosclerosis progression, leading to plaque initiation, growth, and ultimately rupture. Altered metabolism of macrophage is a key feature for their function and the subsequent progression of atherosclerotic cardiovascular disease. The immunometabolism of macrophage has been implicated to macrophage activation and metabolic rewiring of macrophages within atherosclerotic lesions, thereby shifting altered macrophage immune-effector and tissue-reparative function. Targeting macrophage phenotypes and metabolism are potential therapeutic strategies in the prevention and treatment of atherosclerosis and atherosclerotic cardiovascular diseases. Understanding the precise function and metabolism of specific macrophage subsets and their contributions to the composition and growth of atherosclerotic plaques could reveal novel strategies to delay or halt development of atherosclerotic cardiovascular diseases and their associated pathophysiological consequences. Identifying biological stimuli capable of modulating macrophage phenotypes and metabolism may lead to the development of innovative therapeutic approaches for treating patients with atherosclerosis and coronary artery diseases.

Obesity alters the macrophages' response to Leishmania major in C57BL/6 mice

Obesity is a global pandemic associated with several comorbidities, such as cardiovascular diseases and type 2 diabetes. It is also a predisposing factor for infectious diseases, increasing mortality rates. Moreover, diet-induced obesity can cause metabolic fluctuations that affect macrophage differentiation in various organs. In this sense, we investigated how bone marrow-derived macrophages and tissue-resident macrophages in the skin, which have been differentiated in a host with metabolic syndrome and with previous inflammatory burden, respond to Leishmania major infection. Our findings suggest that bone marrow-derived macrophages from obese C57BL/6 mice, even when cultivated in vitro with inflammatory stimuli, are more susceptible to L. major. These macrophages produce less tumor necrosing factor (TNF) and nitric oxide (NO) and show higher arginase activity. Furthermore, obese mice infected with an intermediate dose of L. major in the skin had more severe lesions when analyzed for ulceration, diameter, thickness, and parasite burden. The increase in lesion severity in obese mice was associated with a higher frequency of tissue-resident macrophages, which are less efficient in killing parasites. We also used CCR2-/- mice, which predominantly have tissue-resident macrophages, and found that lesion resolution was delayed in association with CCR2 deficiency. Additionally, obesity potentiated tissue damage, resulting in higher frequency of tissue-resident macrophages. Our results demonstrate that obesity can alter macrophage responses to infection, leading to increased susceptibility to L. major and more severe cutaneous leishmaniasis. These findings may have important implications for managing obesity-related infections and the development of new therapies for cutaneous leishmaniasis.

Macrophage energy metabolism in cardiometabolic disease

In a rapidly expanding body of literature, the major role of energy metabolism in determining the response and polarization status of macrophages has been examined, and it is currently a very active area of research. The metabolic flux through different metabolic pathways in the macrophage is interconnected and complex and could influence the polarization of macrophages. Earlier studies suggested glucose flux through cytosolic glycolysis is a prerequisite to trigger the pro-inflammatory phenotypes of macrophages while proposing that fatty acid oxidation is essential to support anti-inflammatory responses by macrophages. However, recent studies have shown that this understanding is oversimplified and that the metabolic control of macrophage polarization is highly complex and not fully defined yet. In this review, we systematically reviewed and summarized the literature regarding the role of energy metabolism in controlling macrophage activity and how that might be altered in cardiometabolic diseases, namely heart failure, obesity, and diabetes. We critically appraised the experimental studies and methodologies in the published studies. We also highlighted the challenging concepts in macrophage metabolism and identified several research questions yet to be addressed in future investigations.

The effects of exercise on microRNA expression profiling in adipose tissue macrophages of mice

Background

Exercise is recognized for its broad health benefits, influencing various physiological processes, including the behavior of adipose tissue macrophages (ATMs). While existing studies mainly associate ATM activity with obesity and metabolic syndrome, our study explores the impact of aerobic exercise on ATM microRNA expression profiling in a non-obese context, highlighting its general health-promoting mechanisms.

Methods

Sixty male C57BL/6 mice were randomly assigned to either a sedentary (S) or an exercise (E) group. The S group remained inactive, while the E group underwent a one-week treadmill adaptation, followed by an 8-week aerobic treadmill exercise protocol (60 min/day, 5 days/week, at 65%-75% VO2max). Post-training, glucose tolerance and the serum lipid levels were measured in mice subjected to both exercise and non-exercise conditions. ATMs harvested from visceral adipose tissues were analyzed and sorted using flow cytometer. To further investigate the effects of exercise in ATMs at the molecular level, miRNA microarray analysis was performed, followed by bioinformatic analysis.

Results

The 8-week regimen of moderate-intensity aerobic exercise ameliorated glucolipid metabolism and fostered a dynamic shift toward an M2 macrophage phenotype in the adipose tissue, independent of obesity. A total of 62 differentially expressed miRNAs were identified in ATMs of mice post-exercise. Notably, six miRNAs (miR-212-5p, miR-511-5p, miR-7b-5p, miR-142-3p, miR-1894-3p, and miR-31-5p) as well as their target gene were consistently altered and associated with macrophage polarization and metabolic regulation.

Conclusion

Our findings broaden the understanding of how exercise regulates ATM functions through significant changes in microRNA profiles, emphasizing its potential to enhance health and prevent chronic conditions. This study supports the application of aerobic exercise for its preventive effects on chronic diseases and underscores the importance of microRNA profiling in understanding the immune-modulatory impacts of exercise.

Obesity-induced chronic low-grade inflammation in adipose tissue: A pathway to Alzheimer's disease

Alzheimer's disease (AD) is a leading cause of cognitive impairment worldwide. Overweight and obesity are strongly associated with comorbidities, such as hypertension, diabetes, and insulin resistance (IR), which contribute substantially to the development of AD and subsequent morbidity and mortality. Adipose tissue (AT) is a highly dynamic organ composed of a diverse array of cell types, which can be classified based on their anatomic localization or cellular composition. The expansion and remodeling of AT in the context of obesity involves immunometabolic and functional shifts steered by the intertwined actions of multiple immune cells and cytokine signaling within AT, which contribute to the development of metabolic disorders, IR, and systemic markers of chronic low-grade inflammation. Chronic low-grade inflammation, a prolonged, low-dose stimulation by specific immunogens that can progress from localized sites and affect multiple organs throughout the body, leads to neurodystrophy, increased apoptosis, and disruption of homeostasis, manifesting as brain atrophy and AD-related pathology. In this review, we sought to elucidate the mechanisms by which AT contributes to the onset and progression of AD in obesity through the mediation of chronic low-grade inflammation, particularly focusing on the roles of adipokines and AT-resident immune cells.

Dysregulated cytokine and oxidative response in hyper-glycolytic monocytes in obesity

Introduction

Obesity is associated with a plethora of health complications, including increased susceptibility to infections or decreased vaccine efficacy, partly due to dysregulated immune responses. Monocytes play a crucial role in innate immunity, yet their functional alterations in obesity remain poorly understood.

Methods

Here, we employed proteomic and metabolomic analyses to investigate monocyte characteristics in individuals with overweight, obesity, impaired glucose tolerance (IGT), and type 2 diabetes (T2D), compared to lean donors.

Results and discussion

Our results revealed distinct molecular signatures in monocytes from individuals with obesity, with significant alterations in pathways related to metabolism, cellular migration, and phagocytosis. Moreover, LPS-induced activation of monocytes unveiled heightened metabolic reprogramming towards glycolysis in subjects with obesity accompanied by dysregulated cytokine responses and elevated oxidative stress. Additionally, monocytes from donors with obesity exhibited increased lipid droplet accumulation. These findings shed light on the immunometabolic dysregulation underlying obesity-associated immune dysfunction, highlighting potential targets for therapeutic intervention.

Macrophage exosomes mediate palmitic acid-induced metainflammation by transferring miR-3064-5p to target IκBα and activate NF-κB signaling

INTRODUCTION

High palmitic acid (PA) levels trigger metainflammation, facilitating the onset and progression of chronic metabolic diseases. Recently, exosomes were identified as new inflammation mediators. However, the mechanism by which macrophage exosomes mediate PA-induced inflammation remains unclear.

OBJECTIVES

To explore how PA induces metainflammation through macrophage exosomes.

METHODS

Exosomes secreted by RAW264.7 mouse macrophages stimulated with PA (ExosPA) or not (Exos) were prepared by ultracentrifugation. The differential miRNAs between ExosPA and Exos were identified by high-throughput sequencing, and their targeted mRNAs and proteins were bioinformatically analyzed and verified by qPCR and western blot. Mouse macrophages and metabolic cells (AML-12 hepatocytes, C2C12 myocytes or 3T3-L1 adipocytes) were treated with ExosPA or Exos. The verified miRNAs and its targeted molecules related to inflammation were analyzed in recipient cells. Furthers, exosomes were prepared from primary peritoneal macrophages isolated from AIN93G diet-fed (Control PM-Exos) or HPD-fed (PA PM-Exos) mice. Control or PA PM-Exos were then tail vein injected (30 μg) into mice (n = 10), once a week for 2 weeks. The verified miRNA and its targets in blood, blood exosomes, and metabolic tissues were detected. Finally, measured the levels of miRNA, inflammatory factors, and fatty acids in the blood of 20 obese/overweight individuals and 20 healthy individuals.

RESULTS

ExoPA activate NF-κB signaling and enhance inflammatory enzyme/cytokine production in macrophages and metabolic cells. ExoPA enrich miR-3064-5p and target to inhibit IκBα as verified by exosome inhibitors and miR-3064-5p mimics and inhibitors. HPD elevates exosomal miR-3064-5p, macrophage exosomal miR-3064-5p, and inflammatory cytokine levels in mice circulation. PA PM-Exos from HPD-fed mice triggered inflammation in the circulation and metabolic tissues/organs of chow diet-fed mice. Overweight/obese individuals exhibit increased levels of circulating palmitoleic acid, exosomal miR-3064-5p, and high-sensitivity C-reactive proteins.

CONCLUSIONS

Macrophage exosomes transferring miR-3064-5p to target IκBα and activate NF-κB signaling in metabolic cells is a mechanism of PA-induced metainflammation.

Interrelation of adipose tissue macrophages and fibrosis in obesity

Obesity is characterized by adipose tissue expansion, extracellular matrix remodelling and unresolved inflammation that contribute to insulin resistance and fibrosis. Adipose tissue macrophages represent the most abundant class of immune cells in adipose tissue inflammation and could be key mediators of adipocyte dysfunction and fibrosis in obesity. Although macrophage activation states are classically defined by the M1/M2 polarization nomenclature, novel studies have revealed a more complex range of macrophage phenotypes in response to external condition or the surrounding microenvironment. Here, we discuss the plasticity of adipose tissue macrophages (ATMs) in response to their microenvironment in obesity, with special focus on macrophage infiltration and polarization, and their contribution to adipose tissue fibrosis. A better understanding of the role of ATMs as regulators of adipose tissue remodelling may provide novel therapeutic strategies against obesity and associated metabolic diseases.

Hippo-YAP/TAZ-ROS signaling axis regulates metaflammation induced by SelenoM deficiency in high-fat diet-derived obesity

INTRODUCTION

Metabolic inflammation (metaflammation) in obesity is primarily initiated by proinflammatory macrophage infiltration into adipose tissue. SelenoM contributes to the modulation of antioxidative stress and inflammation in multiple pathological processes; however, its roles in metaflammation and the proinflammatory macrophage (M1)-like state in adipose tissue have not been determined.

OBJECTIVES

We hypothesize that SelenoM could effectively regulate metaflammation via the Hippo-YAP/TAZ-ROS signaling axis in obesity derived from a high-fat diet.

METHODS

Morphological changes in adipose tissue were examined by hematoxylin-eosin (H&E) staining and fluorescence microscopy. The glucose tolerance test (GTT) and insulin tolerance test (ITT) were used to evaluate the impact of SelenoM deficiency on blood glucose levels. RNA-Seq analysis, LC-MS analysis, Mass spectrometry analysis and western blotting were performed to detect the levels of genes and proteins related to glycolipid metabolism in adipose tissue.

RESULTS

Herein, we evaluated the inflammatory features and metabolic microenvironment of mice with SelenoM-deficient adipose tissues by multi-omics analyses. The deletion of SelenoM resulted in glycolipid metabolic disturbances and insulin resistance, thereby accelerating weight gain, adiposity, and hyperglycemia. Mice lacking SelenoM in white adipocytes developed severe adipocyte hypertrophy via impaired lipolysis. SelenoM deficiency aggravated the generation of ROS by reducing equivalents (NADPH and glutathione) in adipocytes, thereby promoting inflammatory cytokine production and the M1-proinflammatory reaction, which was related to a change in nuclear factor kappa-B (NF-κB) levels in macrophages. Mechanistically, SelenoM deficiency promoted metaflammation via Hippo-YAP/TAZ-ROS-mediated transcriptional regulation by targeting large tumor suppressor 2 (LATS2). Moreover, supplementation with N-acetyl cysteine (NAC) to reduce excessive oxidative stress partially rescued adipocyte inflammatory responses and macrophage M1 activation.

CONCLUSION

Our data indicate that SelenoM ameliorates metaflammation mainly via the Hippo-YAP/TAZ-ROS signaling axis in obesity. The identification of SelenoM as a key regulator of metaflammation presents opportunities for the development of novel therapeutic interventions targeting adipose tissue dysfunction in obesity.

The causal associations of inflammatory cytokines with obesity and systemic lupus erythematosus: A Mendelian randomization study

OBJECTIVE

Previous studies have partly discussed the roles of inflammatory cytokines in obesity and systemic lupus erythematosus (SLE), but the causal relationship among inflammatory cytokines, obesity, and SLE is unclear. It is challenging to comprehensively evaluate the causal relationship between these variables. This study aimed to investigate the role of cytokines as intermediates between obesity and SLE.

METHODS

The inverse-variance weighted method (IVW) of mendelian randomization (MR) is mainly used to explore the causal relationship between exposure and outcome by using the genetic variation of the open large genome-wide association studies (GWAS), namely single-nucleotide polymorphisms (SNPs) related to obesity (more than 600 000 participants), inflammatory cytokines (8293 healthy participants) and SLE (7219 cases). Methods such as weighted median, MR-Egger are used to evaluate the reliability of causality. Reverse analysis is performed for each MR analysis to avoid reverse causality. Cochran's Q statistic and funnel chart are used to detect heterogeneity, MR-Egger intercept test and leave-one-out sensitivity analyses evaluated pleiotropy.

RESULTS

Obesity was associated with 25 cytokines, and 3 cytokines were associated with SLE, including CTACK (OR = 1.19, 95% CI: 1.06, 1.33, p = .002), IL-18 (OR = 1.13, 95% CI: 1.01, 1.26, p = .027), SCGFb (OR = 0.89, 95% CI: 0.79, 0.99, p = .044). In the opposite direction, SLE was associated with 18 cytokines, and 2 cytokines were associated with obesity, including IP-10 (βIVW = -.03, 95% CI: -0.05, -0.01, p = .002), MIP-1B (βIVW = -.03, 95% CI: -0.05, -0.01, p = .004).

CONCLUSION

Our MR study suggested that CTACK, IL-18 and SCGFb may play an intermediary role in obesity to SLE, while IP-10 and MIP-1B may play an intermediary role in SLE to obesity.

Causal association between type 2 diabetes mellitus and acute suppurative otitis media: insights from a univariate and multivariate Mendelian randomization study

Background

Type 2 diabetes mellitus (T2DM) and hearing loss (HL) constitute significant public health challenges worldwide. Recently, the association between T2DM and HL has aroused attention. However, possible residual confounding factors and other biases inherent to observational study designs make this association undetermined. In this study, we performed univariate and multivariable Mendelian Randomization (MR) analysis to elucidate the causal association between T2DM and common hearing disorders that lead to HL.

Methods

Our study employed univariate and multivariable MR analyses, with the Inverse Variance Weighted method as the primary approach to assessing the potential causal association between T2DM and hearing disorders. We selected 164 and 9 genetic variants representing T2DM from the NHGRI-EBI and DIAGRAM consortium, respectively. Summary-level data for 10 hearing disorders were obtained from over 500,000 participants in the FinnGen consortium and MRC-IEU. Sensitivity analysis revealed no significant heterogeneity of instrumental variables or pleiotropy was detected.

Results

In univariate MR analysis, genetically predicted T2DM from both sources was associated with an increased risk of acute suppurative otitis media (ASOM) (In NHGRI-EBI: OR = 1.07, 95% CI: 1.02-1.13, P = 0.012; In DIAGRAM: OR = 1.14, 95% CI: 1.02-1.26, P = 0.016). Multivariable MR analysis, adjusting for genetically predicted sleep duration, alcohol consumption, body mass index, and smoking, either individually or collectively, maintained these associations. Sensitivity analyses confirmed the robustness of the results.

Conclusion

T2DM was associated with an increased risk of ASOM. Strict glycemic control is essential for the minimization of the effects of T2DM on ASOM.

The molecular mechanism of macrophage-adipocyte crosstalk in maintaining energy homeostasis

Interactions between macrophages and adipocytes in adipose tissue are critical for the regulation of energy metabolism and obesity. Macrophage polarization induced by cold or other stimulations can drive metabolic reprogramming of adipocytes, browning, and thermogenesis. Accordingly, investigating the roles of macrophages and adipocytes in the maintenance of energy homeostasis is critical for the development of novel therapeutic approaches specifically targeting macrophages in metabolic disorders such as obesity. Current review outlines macrophage polarization not only regulates the release of central nervous system and inflammatory factors, but controls mitochondrial function, and other factor that induce metabolic reprogramming of adipocytes and maintain energy homeostasis. We also emphasized on how the adipocytes conversely motivate the polarization of macrophage. Exploring the interactions between adipocytes and macrophages may provide new therapeutic strategies for the management of obesity-related metabolic diseases.

Unraveling the complex roles of macrophages in obese adipose tissue: an overview

Macrophages, a heterogeneous population of innate immune cells, exhibit remarkable plasticity and play pivotal roles in coordinating immune responses and maintaining tissue homeostasis within the context of metabolic diseases. The activation of inflammatory macrophages in obese adipose tissue leads to detrimental effects, inducing insulin resistance through increased inflammation, impaired thermogenesis, and adipose tissue fibrosis. Meanwhile, adipose tissue macrophages also play a beneficial role in maintaining adipose tissue homeostasis by regulating angiogenesis, facilitating the clearance of dead adipocytes, and promoting mitochondrial transfer. Exploring the heterogeneity of macrophages in obese adipose tissue is crucial for unraveling the pathogenesis of obesity and holds significant potential for targeted therapeutic interventions. Recently, the dual effects and some potential regulatory mechanisms of macrophages in adipose tissue have been elucidated using single-cell technology. In this review, we present a comprehensive overview of the intricate activation mechanisms and diverse functions of macrophages in adipose tissue during obesity, as well as explore the potential of drug delivery systems targeting macrophages, aiming to enhance the understanding of current regulatory mechanisms that may be potentially targeted for treating obesity or metabolic diseases.

Polyphenols: immunonutrients tipping the balance of immunometabolism in chronic diseases

Mounting evidence progressively appreciates the vital interplay between immunity and metabolism in a wide array of immunometabolic chronic disorders, both autoimmune and non-autoimmune mediated. The immune system regulates the functioning of cellular metabolism within organs like the brain, pancreas and/or adipose tissue by sensing and adapting to fluctuations in the microenvironment's nutrients, thereby reshaping metabolic pathways that greatly impact a pro- or anti-inflammatory immunophenotype. While it is agreed that the immune system relies on an adequate nutritional status to function properly, we are only just starting to understand how the supply of single or combined nutrients, all of them termed immunonutrients, can steer immune cells towards a less inflamed, tolerogenic immunophenotype. Polyphenols, a class of secondary metabolites abundant in Mediterranean foods, are pharmacologically active natural products with outstanding immunomodulatory actions. Upon binding to a range of receptors highly expressed in immune cells (e.g. AhR, RAR, RLR), they act in immunometabolic pathways through a mitochondria-centered multi-modal approach. First, polyphenols activate nutrient sensing via stress-response pathways, essential for immune responses. Second, they regulate mammalian target of rapamycin (mTOR)/AMP-activated protein kinase (AMPK) balance in immune cells and are well-tolerated caloric restriction mimetics. Third, polyphenols interfere with the assembly of NLR family pyrin domain containing 3 (NLRP3) in endoplasmic reticulum-mitochondria contact sites, inhibiting its activation while improving mitochondrial biogenesis and autophagosome-lysosome fusion. Finally, polyphenols impact chromatin remodeling and coordinates both epigenetic and metabolic reprogramming. This work moves beyond the well-documented antioxidant properties of polyphenols, offering new insights into the multifaceted nature of these compounds. It proposes a mechanistical appraisal on the regulatory pathways through which polyphenols modulate the immune response, thereby alleviating chronic low-grade inflammation. Furthermore, it draws parallels between pharmacological interventions and polyphenol-based immunonutrition in their modes of immunomodulation across a wide spectrum of socioeconomically impactful immunometabolic diseases such as Multiple Sclerosis, Diabetes (type 1 and 2) or even Alzheimer's disease. Lastly, it discusses the existing challenges that thwart the translation of polyphenols-based immunonutritional interventions into long-term clinical studies. Overcoming these limitations will undoubtedly pave the way for improving precision nutrition protocols and provide personalized guidance on tailored polyphenol-based immunonutrition plans.

Pathogenesis of diabetic complications: Exploring hypoxic niche formation and HIF-1α activation

Hypoxia is a common feature of diabetic tissues, which highly correlates to the progression of diabetes. The formation of hypoxic context is induced by disrupted oxygen homeostasis that is predominantly driven by vascular remodeling in diabetes. While different types of vascular impairments have been reported, the specific features and underlying mechanisms are yet to be fully understood. Under hypoxic condition, cells upregulate hypoxia-inducible factor-1α (HIF-1α), an oxygen sensor that coordinates oxygen concentration and cell metabolism under hypoxic conditions. However, diabetic context exploits this machinery for pathogenic functions. Although HIF-1α protects cells from diabetic insult in multiple tissues, it also jeopardizes cell function in the retina. To gain a deeper understanding of hypoxia in diabetic complications, we focus on the formation of tissue hypoxia and the outcomes of HIF-1α dysregulation under diabetic context. Hopefully, this review can provide a better understanding on hypoxia biology in diabetes.

Real-time OXPHOS capacity analysis in wounded skin from diabetic mice: A pilot study

INTRODUCTION

Diabetes mellitus (DM) impairs wound healing. The aim was to determine whether DM influences mitochondrial respiration in wounded skin (WS) and non-wounded skin (NWS), in a pre-clinical wound healing model of streptozotocin (STZ)-induced diabetes.

METHODS

Six weeks after diabetes induction, two wounds were created in the back of C57BL/J6 mice. Using high-resolution respirometry (HRR), oxygen flux was measured, in WS and NWS, using two substrate-uncoupler-inhibitor titration protocols, at baseline (day 0), day 3 and 10 post-wounding, in STZ-DM and non-diabetic (NDM) mice. Flux control ratios for the oxidative phosphorylation (OXPHOS) capacity were calculated.

RESULTS

A significant increase in mitochondrial respiration was observed in STZ-DM skin compared to control skin at baseline. The OXPHOS capacity was decreased in WS under diabetes at day 3 post-wounding (inflammation phase). However, at day 10 post-wounding (remodeling phase), the OXPHOS capacity was higher in WS from STZ-DM compared to NDM mice, and compared to NWS from STZ-DM mice. A significant relative contribution of pyruvate, malate and glutamate (PMG) oxidation to the OXPHOS capacity was observed in WS compared to NWS from STZ-DM mice, at day 10, while the relative contribution of fatty acid oxidation to the OXPHOS capacity was higher in NWS. The OXPHOS capacity is altered in WS from STZ-DM compared to NDM mice across the healing process, and so is the substrate contribution in WS and NWS from STZ-DM mice, at each time point.

CONCLUSION

HRR may be a sensitive tool to evaluate the underlying mechanisms of tissue repair during wound healing.

Hydrophobic Components in Light-Yellow Pulp Sweet Potato (Ipomoea batatas (L.) Lam.) Tubers Suppress LPS-Induced Inflammatory Responses in RAW264.7 Cells via Activation of the Nrf2 Pathway

Sweet potato is a crop that is widely consumed all over the world and is thought to contribute to health maintenance due to its abundant nutrients and phytochemicals. Previous studies on the functionality of sweet potatoes have focused on varieties that have colored pulp, such as purple and orange, which contain high levels of specific phytochemicals. Therefore, in the present study, we evaluated the anti-inflammatory effects of light-yellow-fleshed sweet potatoes, which have received little attention. After freeze-drying sweet potatoes harvested in 2020, extracts were prepared from the leaves, stems, roots, and tubers in 100% ethanol. Mouse macrophage-like cell line RAW264.7 cells were cultured with 10 µg/mL of the extracts and induced lipopolysaccharide (LPS)-stimulated inflammation. Of the extracts, the tuber extracts showed the highest suppression of LPS-induced interleukin-6 (IL-6) gene expression and production in RAW264.7, which was attributed to the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) oxidative stress response pathway. In addition, preparative high-performance liquid chromatography (HPLC) experiments suggested that hydrophobic components specific to the tuber were the main body of activity. In previous studies, it has been shown that the tubers and leaves of sweet potatoes with colored pulp exhibit anti-inflammatory effects due to their rich phytochemicals, and our results show that the tubers with light-yellow pulp also exhibit the effects. Furthermore, we were able to show a part of the mechanism, which may contribute to the fundamental understanding of the treatment and prevention of inflammation by food-derived components.

Smoking and BMI mediate the causal effect of education on lower back pain: observational and Mendelian randomization analyses

Objective

Low back pain (LBP) has been associated with education in previous observational studies, but the causality remains unclear. This study aims to assess the impact of education on LBP and to explore mediation by multiple lifestyle factors.

Design

Univariable Mendelian randomization (MR) was performed to examine the overall effect of education on LBP. Subsequently, multivariable MR was conducted to assess both the direct effect of education on LBP and the influence of potential mediators. Indirect effects were estimated using either the coefficient product method or the difference method, and the proportion of mediation was calculated by dividing the indirect effect by the total effect. The observational study utilized data from the NHANES database collected between 1999 and 2004, and included 15,580 participants aged 20 years and above.

Results

Increasing education by 4.2 years leads to a 48% reduction in the risk of LBP (OR=0.52; 95% CI: 0.46 to 0.59). Compared to individuals with less than a high school education, those with education beyond high school have a 28% lower risk of LBP (OR=0.72; 95% CI: 0.63 to 0.83). In the MR study, smoking accounts for 12.8% (95% CI: 1.04% to 20.8%) of the total effect, while BMI accounts for 5.9% (95% CI: 2.99% to 8.55%). The combined mediation effect of smoking and BMI is 27.6% (95% CI: 23.99% to 32.7%). In the NHANES study, only smoking exhibits a mediating effect, accounting for 34.3% (95% CI: 21.07% to 41.65%) of the effect, while BMI does not demonstrate a mediating role.

Conclusions

Higher levels of education provide a protective effect against the risk of LBP. Additionally, implementing interventions to reduce smoking and promote weight loss among individuals with lower levels of education can also decrease this risk.

Glycolytic Activation of CD14+ Intestinal Macrophages Contributes to the Inflammatory Responses via Exosomal Membrane Tumor Necrosis Factor in Crohn's Disease

BACKGROUND

Macrophage (Mφ) activation plays a critical role in the inflammatory response. Activated Mφ go through profound reprogramming of cellular metabolism. However, changes in their intracellular energy metabolism and its effect on inflammatory responses in Crohn's disease (CD) remain currently unclear. The aim of this study is to explore metabolic signatures of CD14+ Mφ and their potential role in CD pathogenesis as well as the underlying mechanisms.

METHODS

CD14+ Mφ were isolated from peripheral blood or intestinal tissues of CD patients and control subjects. Real-time flux measurements and enzyme-linked immunosorbent assay were used to determine the inflammatory states of Mφ and metabolic signatures. Multiple metabolic routes were suppressed to determine their relevance to cytokine production.

RESULTS

Intestinal CD14+ Mφ in CD patients exhibited activated glycolysis compared with those in control patients. Specifically, macrophagic glycolysis in CD largely induced inflammatory cytokine release. The intestinal inflammatory microenvironment in CD elicited abnormal glycolysis in Mφ. Mechanistically, CD14+ Mφ derived exosomes expressed membrane tumor necrosis factor (TNF), which engaged TNFR2 and triggered glycolytic activation via TNF/nuclear factor κB autocrine and paracrine signaling. Importantly, clinically applicable anti-TNF antibodies effectively prevented exosomal membrane TNF-induced glycolytic activation in CD14+ Mφ.

CONCLUSIONS

CD14+ Mφ take part in CD pathogenesis by inducing glycolytic activation via membrane TNF-mediated exosomal autocrine and paracrine signaling. These results provide novel insights into pathogenesis of CD and enhance understanding of the mechanisms of anti-TNF agents.

Improved identification of left atrial enlargement in patients with obesity

Accurate standardization of left atrium volume (LAV) in patients with obesity is challenging. The aim of this study was to investigate and to examine the relation between LAV indexed to height2 and left atrial function in patients with moderate to severe obesity. Echocardiograms of patients with moderate to severe obesity (body mass index (BMI) ≥ 35 kg/m2) without known cardiac disease were analyzed. LAV was indexed to body surface area (BSA) and height2, and patients were divided into those with or without left atrial enlargement (LAE) based on normalization using either BSA (LAEbsa) or height2 (LAEh2). Using speckle tracking echocardiography, LA reservoir strain (LASr), LA conduit strain (LAScd), and LA contractile strain (LASct) were assessed as a measure of LA function. LA dysfunction was defined as LASct < 14%. A total of 142 patients were included in the analysis of whom 54.2% had LAEh2 and 18.3% LAEBSA. The LAEh2 group had significantly lower LASct (12.2% ± 3.2% vs. 13.6% ± 4.5%, p = 0.019) as compared to the patients without LAEh2. Significantly more patients with LA dysfunction would be correctly identified by LAEh2 than by LAEBSA (41.5% vs. 15.0%, p < 0.001). In patients with moderate to severe obesity, the use of LAEh2 identified significantly more patients with decreased LA function. LAVh2 should be preferred over LAVBSA in patients with moderate to severe obesity.

Repeated social defeat stress leads to immunometabolic shifts in innate immune cells of the spleen

Psychosocial stress has been shown to prime peripheral innate immune cells, which take on hyper-inflammatory phenotypes and are implicated in depressive-like behavior in mouse models. However, the impact of stress on cellular metabolic states that are thought to fuel inflammatory phenotypes in immune cells are unknown. Using single cell RNA-sequencing, we investigated mRNA enrichment of immunometabolic pathways in innate immune cells of the spleen in mice subjected to repeated social defeat stress (RSDS) or no stress (NS). RSDS mice displayed a significant increase in the number of splenic macrophages and granulocytes (p < 0.05) compared to NS littermates. RSDS-upregulated genes in macrophages, monocytes, and granulocytes significantly enriched immunometabolic pathways thought to play a role in myeloid-driven inflammation (glycolysis, HIF-1 signaling, MTORC1 signaling) as well as pathways related to oxidative phosphorylation (OXPHOS) and oxidative stress (p < 0.05 and FDR<0.1). These results suggest that the metabolic enhancement reflected by upregulation of glycolytic and OXPHOS pathways may be important for cellular proliferation of splenic macrophages and granulocytes following repeated stress exposure. A better understanding of these intracellular metabolic mechanisms may ultimately help develop novel strategies to reverse the impact of stress and associated peripheral immune changes on the brain and behavior.

Central obesity is detrimental to anti-inflammatory, phenotype, and exhaustion markers in mononuclear cells - A cross-sectional study

OBJECTIVE

To investigate the role of central obesity on immunometabolic response in peripheral blood mononuclear cells (PBMCs) from normal weight and overweight/obese young men.

METHODS

Eighteen individuals were classified as normal weight (NW; n = 9 - age: 25 ± 5 and BMI: 21.4 ± 1.7) and overweight/obese (OW; n = 9 - age: 29 ± 7 and BMI: 29.2 ± 2.7). The body composition was evaluated by dual-energy x-ray absorptiometry (DXA), waist circumference, and visceral and subcutaneous fat depots by ultrasound. Physical activity levels, metabolic parameters, immune phenotypic characterization, cytokine production by lipopolysaccharide (LPS) -stimulated whole blood cells and LPS or phorbol 12-myristate 13-acetate (PMA)-stimulated PBMC, and mitochondrial respiration in PBMCs were evaluated. Expression of AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor gamma (PPAR-γ), nuclear factor-kappa B (NF-κB), toll-like receptor 4 (TLR-4), hypoxia-inducible factor-1 alpha (HIF-1α), and adrenergic receptor beta 1 and 2 (AR-β1 and β2) genes were evaluated in cultured PBMC using quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Individuals with overweight/obese (OW) presented higher glucose (P = 0.009) and leptin (P = 0.010) than individuals with normal weight (NW). PBMCs of OW under stimulation with LPS presented a lower production of interleukin-10 (IL-10) (P = 0.011) and macrophage inflammatory protein-1alpha (MIP-1α) (P = 0.048) than NW. Mitochondrial respiration rates were not different between NW and OW subjects. Cultured PBMCs in LPS-stimulated condition indicated higher gene expression of AR-β2 in OW, while PMA-stimulated PBMCs presented lower expression of AMPK (P = 0.002) and higher expression of NF-κB (P=<0.0001) than NW. OW presented higher numbers of CD3+CD4+ T cells (P = 0.009) and higher expression of programmed cell death protein 1 (PD-1) in CD8+ T cells (P = 0.001) than NW.

CONCLUSION

Central obesity promoted reductions in interleukin 10 production response and increase in AR-β2 expressions in mitogen-stimulated PBMCs. Furthermore, central obesity altered the phenotype of PBMCs, also increasing the expression of PD-1 exhaustion markers in young adults.

A Newly Synbiotic Combination Alleviates Obesity by Modulating the Gut Microbiota-Fat Axis and Inhibiting the Hepatic TLR4/NF-κB Signaling Pathway

SCOPE

Obesity has been recognized as a worldwide public health crisis, this is accompanied by dysregulation of the intestinal microbiota and upregulation of liver steatosis and adipose inflammation. Synbiotic as a novel alternative therapy for obesity have recently gained much attention.

METHODS

This study innovatively research the anti-obesity properties of a newly synbiotic composed of Lactobacillus acidophilus, Bifidobacterium infantis and konjac glucomannan oligosaccharides.

RESULTS

The synbiotic treatment can reduce body weight, fat mass, blood sugar, liver steatosis and adipose inflammation in obesity mice fed by high-fat diet (HFD). Meanwhile, synbiotic treatment activated brown adipose tissue and improve energy, glucose and lipid metabolism. In addition, synbiotic treatment not solely enhanced the protection of intestinal barrier, but also ameliorated gut microbiota dysbiosis directly by enhancing beneficial microbes and reducing potentially harmful bacteria. Furthermore, the microbiome phenotype and functional prediction showed that synbiotic treatment can improve the gut microbiota functions involving inflammatory state, immune response, metabolism and pathopoiesia.

CONCLUSION

The synbiotic may be an effective candidate treatment strategy for the clinical prevention and treatment of obesity and other associated metabolic diseases such as hyperlipidemia, nonalcoholic fatty liver diseases by alleviating inflammatory response, regulating energy metabolism and maintaining the balance of intestinal microecology.

Metaflammation in obesity and its therapeutic targeting

Obesity-associated inflammation is a systemic process that affects all metabolic organs. Prominent among these is adipose tissue, where cells of the innate and adaptive immune system are markedly changed in obesity, implicating these cells in a range of processes linking immune memory to metabolic regulation. Furthermore, weight loss and weight cycling have unexpected effects on adipose tissue immune populations. Here, we review the current literature on the roles of various immune cells in lean and obese adipose tissue. Within this context, we discuss pharmacological and nonpharmacological approaches to obesity treatment and their impact on systemic inflammation.

Leptin-mediated meta-inflammation may provide survival benefit in patients receiving maintenance immunotherapy for extensive-stage small cell lung cancer (ES-SCLC)

BACKGROUND

Only few ES-SCLC patients experience long-term survival benefit by maintenance IT. Adipokines-induced metabolic meta-inflammation has been related to enhanced responsiveness to IT in obese patients; however, their prognostic role in SCLC is currently controversial.

METHODS

Pre-treatment CT scan was used for determining distribution of abdominal adiposity, and blood samples were collected at fasting for measuring glycemia, insulin, ghrelin, leptin and adipokines (TNF-α, IFN-γ, IL-6 and MCP-1). Patients with known history of DM type II or metabolic syndrome with HOMA index > 2.5 were considered insulin resistant (IR).

RESULTS

In ES-SCLC pts receiving maintenance IT, increased leptin concentration and higher leptin/visceral adipose tissue (VAT) ratio were significantly associated with prolonged PFS. By applying a hierarchical clustering algorithm, we identified a cluster of patients characterized by higher leptin values and lower pro-inflammatory cytokines (TNF-α, IFN-γ and IL-6) who experienced longer PFS (13.2 vs 8.05 months; HR: 0.42 [0.18-0.93] p = 0.02) and OS (18.04 vs 12.09 mo; HR: 0.53 [0.25-1.29] p = 0.07).

CONCLUSIONS

Adipokines can play a crucial role to determining effectiveness of anti-cancer immunotherapy. The role of metabolic immune dysfunctions needs further pre-clinical validation and is currently investigated in the larger prospective cohort.

Therapeutic targeting of adipose tissue macrophages ameliorates liver fibrosis in non-alcoholic fatty liver disease

Background & Aims

: The accumulation of adipose tissue macrophages (ATMs) in obesity has been associated with hepatic injury. However, the contribution of ATMs to hepatic fibrosis in non-alcoholic fatty liver disease (NAFLD) remains to be elucidated. Herein, we investigate the relationship between ATMs and liver fibrosis in patients with patients with NAFLD and evaluate the impact of modulation of ATMs over hepatic fibrosis in an experimental non-alcoholic steatohepatitis (NASH) model.

Methods

Adipose tissue and liver biopsies from 42 patients with NAFLD with different fibrosis stages were collected. ATMs were characterised by immunohistochemistry and flow cytometry and the correlation between ATMs and liver fibrosis stages was assessed. Selective modulation of the ATM phenotype was achieved by i.p. administration of dextran coupled with dexamethasone in diet-induced obesity and NASH murine models. Chronic administration effects were evaluated by histology and gene expression analysis in adipose tissue and liver samples. In vitro crosstalk between human ATMs and hepatic stellate cells (HSCs) and liver spheroids was performed.

Results

Patients with NAFLD presented an increased accumulation of pro-inflammatory ATMs that correlated with hepatic fibrosis. Long-term modulation of ATMs significantly reduced pro-inflammatory phenotype and ameliorated adipose tissue inflammation. Moreover, ATMs modulation was associated with an improvement in steatosis and hepatic inflammation and significantly reduced fibrosis progression in an experimental NASH model. In vitro, the reduction of the pro-inflammatory phenotype of human ATMs with dextran-dexamethasone treatment reduced the secretion of inflammatory chemokines and directly attenuated the pro-fibrogenic response in HSCs and liver spheroids.

Conclusions

Pro-inflammatory ATMs increase in parallel with fibrosis degree in patients with NAFLD and their modulation in an experimental NASH model improves liver fibrosis, uncovering the potential of ATMs as a therapeutic target to mitigate liver fibrosis in NAFLD.

Impact and implications

We report that human adipose tissue pro-inflammatory macrophages correlate with hepatic fibrosis in non-alcoholic fatty liver disease (NAFLD). Furthermore, the modulation of adipose tissue macrophages (ATMs) by dextran-nanocarrier conjugated with dexamethasone shifts the pro-inflammatory phenotype of ATMs to an anti-inflammatory phenotype in an experimental murine model of non-alcoholic steatohepatitis. This shift ameliorates adipose tissue inflammation, hepatic inflammation, and fibrosis. Our results highlight the relevance of adipose tissue in NAFLD pathophysiology and unveil ATMs as a potential target for NAFLD.

Impact of intestinal microenvironments in obesity and bariatric surgery on shaping macrophages

Obesity is associated with alterations in tissue composition, systemic cellular metabolism, and low-grade chronic inflammation. Macrophages are heterogenous innate immune cells ubiquitously localized throughout the body and are key components of tissue homeostasis, inflammation, wound healing, and various disease states. Macrophages are highly plastic and can switch their phenotypic polarization and change function in response to their local environments. Here, we discuss how obesity alters the intestinal microenvironment and potential key factors that can influence intestinal macrophages as well as macrophages in other organs, including adipose tissue and hematopoietic organs. As bariatric surgery can induce metabolic adaptation systemically, we discuss the potential mechanisms through which bariatric surgery reshapes macrophages in obesity.

Role of histone lactylation interference RNA m6A modification and immune microenvironment homeostasis in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a severe disease resulting from progressive increases in pulmonary vascular resistance and pulmonary vascular remodeling, ultimately leading to right ventricular failure and even death. Hypoxia, inflammation, immune reactions, and epigenetic modifications all play significant contributory roles in the mechanism of PAH. Increasingly, epigenetic changes and their modifying factors involved in reprogramming through regulation of methylation or the immune microenvironment have been identified. Among them, histone lactylation is a new post-translational modification (PTM), which provides a novel visual angle on the functional mechanism of lactate and provides a promising diagnosis and treatment method for PAH. This review detailed introduces the function of lactate as an important molecule in PAH, and the effects of lactylation on N6-methyladenosine (m6A) and immune cells. It provides a new perspective to further explore the development of lactate regulation of pulmonary hypertension through histone lactylation modification.

Novel XBP1s-independent function of IRE1 RNase in HIF-1α-mediated glycolysis upregulation in human macrophages upon stimulation with LPS or saturated fatty acid

In obesity, adipose tissue infiltrating macrophages acquire a unique pro-inflammatory polarization, thereby playing a key role in the development of chronic inflammation and Type 2 diabetes. Increased saturated fatty acids (SFAs) levels have been proposed to drive this specific polarization. Accordingly, we investigated the immunometabolic reprogramming in SFA-treated human macrophages. As expected, RNA sequencing highlighted a pro-inflammatory profile but also metabolic signatures including glycolysis and hypoxia as well as a strong unfolded protein response. Glycolysis upregulation was confirmed in SFA-treated macrophages by measuring glycolytic gene expression, glucose uptake, lactate production and extracellular acidification rate. Like in LPS-stimulated macrophages, glycolysis activation in SFA-treated macrophages was dependent on HIF-1α activation and fueled the production of pro-inflammatory cytokines. SFAs and LPS both induced IRE1α endoribonuclease activity, as demonstrated by XBP1 mRNA splicing, but with different kinetics matching HIF-1α activation and the glycolytic gene expression. Interestingly, the knockdown of IRE1α and/or the pharmacological inhibition of its RNase activity prevented HIF-1α activation and significantly decreased glycolysis upregulation. Surprisingly, XBP1s appeared to be dispensable, as demonstrated by the lack of inhibiting effect of XBP1s knockdown on glycolytic genes expression, glucose uptake, lactate production and HIF-1α activation. These experiments demonstrate for the first time a key role of IRE1α in HIF-1α-mediated glycolysis upregulation in macrophages stimulated with pro-inflammatory triggers like LPS or SFAs through XBP1s-independent mechanism. IRE1 could mediate this novel function by targeting other transcripts (mRNA or pre-miRNA) through a mechanism called regulated IRE1-dependent decay or RIDD. Deciphering the underlying mechanisms of this novel IRE1 function might lead to novel therapeutic targets to curtail sterile obesity- or infection-linked inflammation.

Insulin resistance and adipose tissue interactions as the cornerstone of metabolic (dysfunction)-associated fatty liver disease pathogenesis

The relationship between metabolic derangements and fatty liver development are undeniable, since more than 75% of patients with type 2 diabetes mellitus present with fatty liver. There is also significant epidemiological association between insulin resistance (IR) and metabolic (dysfunction)-associated fatty liver disease (MAFLD). For little more than 2 years, the nomenclature of fatty liver of non-alcoholic origin has been intended to change to MAFLD by multiple groups. While a myriad of reasons for which MAFLD is thought to be of metabolic origin could be exposed, the bottom line relies on the role of IR as an initiator and perpetuator of this disease. There is a reciprocal role in MAFLD development and IR as well as serum glucose concentrations, where increased circulating glucose and insulin result in increased de novo lipogenesis by sterol regulatory element-binding protein-1c induced lipogenic enzyme stimulation; therefore, increased endogenous production of triglycerides. The same effect is achieved through impaired suppression of adipose tissue (AT) lipolysis in insulin-resistant states, increasing fatty acid influx into the liver. The complementary reciprocal situation occurs when liver steatosis alters hepatokine secretion, modifying fatty acid metabolism as well as IR in a variety of tissues, including skeletal muscle, AT, and the liver. The aim of this review is to discuss the importance of IR and AT interactions in metabolic altered states as perhaps the most important factor in MAFLD pathogenesis.

An Exploration of the Relationship Between Atrial Fibrillation and Obesity

In the past 40 years, the prevalence of atrial fibrillation and obesity have skyrocketed. It has long been established that obesity can lead to adverse cardiovascular outcomes due to its myriad of effects on cardiovascular architecture, cardiovascular hemodynamics, and electrical conduction interference. The goal of this article is to explore the pathogenesis of atrial fibrillation in obese patients and examine the role of atrial enlargement, increased adipose deposits surrounding the pericardium, interstitial fibrosis, and inflammation in the development and worsening of atrial fibrillation in obese patients.

Molecular Mechanisms for the Vicious Cycle between Insulin Resistance and the Inflammatory Response in Obesity

The comprehensive anabolic effects of insulin throughout the body, in addition to the control of glycemia, include ensuring lipid homeostasis and anti-inflammatory modulation, especially in adipose tissue (AT). The prevalence of obesity, defined as a body mass index (BMI) ≥ 30 kg/m², has been increasing worldwide on a pandemic scale with accompanying syndemic health problems, including glucose intolerance, insulin resistance (IR), and diabetes. Impaired tissue sensitivity to insulin or IR paradoxically leads to diseases with an inflammatory component despite hyperinsulinemia. Therefore, an excess of visceral AT in obesity initiates chronic low-grade inflammatory conditions that interfere with insulin signaling via insulin receptors (INSRs). Moreover, in response to IR, hyperglycemia itself stimulates a primarily defensive inflammatory response associated with the subsequent release of numerous inflammatory cytokines and a real threat of organ function deterioration. In this review, all components of this vicious cycle are characterized with particular emphasis on the interplay between insulin signaling and both the innate and adaptive immune responses related to obesity. Increased visceral AT accumulation in obesity should be considered the main environmental factor responsible for the disruption in the epigenetic regulatory mechanisms in the immune system, resulting in autoimmunity and inflammation.

Hypoxia inducible factor-1α is an important regulator of macrophage biology

Hypoxia-inducible factor-1 (HIF-1), a heterodimeric transcription factor composed of the α and β subunits, regulates cellular adaptive responses to hypoxia. Macrophages, which are derived from monocytes, function as antigen-presenting cells that activate various immune responses. HIF-1α regulates the immune response, viability, migration, phenotypic plasticity, and metabolism of macrophages. Specifically, macrophage-derived HIF-1α can prevent excessive pro-inflammatory responses by attenuating the transcriptional activity of nuclear factor-kappa B in vivo and in vitro. HIF-1α modulates macrophage migration by inducing the release of various chemokines and providing necessary energy. HIF-1α promotes macrophage M1 polarization by targeting glucose metabolism. Additionally, HIF-1α induces the upregulation of glycolysis-related enzymes and intermediates of the tricarboxylic acid cycle and pentose phosphate pathway. HIF-1α promotes macrophage apoptosis, necroptosis and reduces autophagy. The current review highlights the mechanisms associated with the regulation of HIF-1α stabilization in macrophages as well as the role of HIF-1α in modulating the physiological functions of macrophages.

Adipose Tissue Macrophage-Mediated Inflammation in Obesity: A Link to Posttranslational Modification

Adipose tissue macrophages (ATM) are an essential type of immune cells in adipose tissue. Obesity induces the inflammation of adipose tissues, as expressed by ATM accumulation, that is more likely to become a source of systemic metabolic diseases, including insulin resistance. The process is characterized by the transcriptional regulation of inflammatory pathways by virtue of signaling molecules such as cytokines and free fatty acids. Notably, posttranslational modification (PTM) is a key link for these signaling molecules to trigger the proinflammatory or anti-inflammatory phenotype of ATMs. This review focuses on summarizing the functions and molecular mechanisms of ATMs regulating inflammation in obese adipose tissue. Furthermore, the role of PTM is elaborated, hoping to identify new horizons of treatment and prevention for obesity-mediated metabolic disease.

Macrophage function in adipose tissue homeostasis and metabolic inflammation

Obesity-related metabolic organ inflammation contributes to cardiometabolic disorders. In obese individuals, changes in lipid fluxes and storage elicit immune responses in the adipose tissue (AT), including expansion of immune cell populations and qualitative changes in the function of these cells. Although traditional models of metabolic inflammation posit that these immune responses disturb metabolic organ function, studies now suggest that immune cells, especially AT macrophages (ATMs), also have important adaptive functions in lipid homeostasis in states in which the metabolic function of adipocytes is taxed. Adverse consequences of AT metabolic inflammation might result from failure to maintain local lipid homeostasis and long-term effects on immune cells beyond the AT. Here we review the complex function of ATMs in AT homeostasis and metabolic inflammation. Additionally, we hypothesize that trained immunity, which involves long-term functional adaptations of myeloid cells and their bone marrow progenitors, can provide a model by which metabolic perturbations trigger chronic systemic inflammation.

Glucocorticoid activation of anti-inflammatory macrophages protects against insulin resistance

Insulin resistance (IR) during obesity is linked to adipose tissue macrophage (ATM)-driven inflammation of adipose tissue. Whether anti-inflammatory glucocorticoids (GCs) at physiological levels modulate IR is unclear. Here, we report that deletion of the GC receptor (GR) in myeloid cells, including macrophages in mice, aggravates obesity-related IR by enhancing adipose tissue inflammation due to decreased anti-inflammatory ATM leading to exaggerated adipose tissue lipolysis and severe hepatic steatosis. In contrast, GR deletion in Kupffer cells alone does not alter IR. Co-culture experiments show that the absence of GR in macrophages directly causes reduced phospho-AKT and glucose uptake in adipocytes, suggesting an important function of GR in ATM. GR-deficient macrophages are refractory to alternative ATM-inducing IL-4 signaling, due to reduced STAT6 chromatin loading and diminished anti-inflammatory enhancer activation. We demonstrate that GR has an important function in macrophages during obesity by limiting adipose tissue inflammation and lipolysis to promote insulin sensitivity.

Lean adipose tissue macrophage derived exosome confers immunoregulation to improve wound healing in diabetes

Chronic non-healing wounds, a prevalent complication of diabetes, are associated with increased mortality in diabetic patients. Excessive accumulation of M1 macrophages in diabetic wounds promotes inflammation and results in dysregulated tissue repair. Adipose tissue macrophages (ATMs) derived from healthy lean donors have the ability to improve glucose tolerance and insulin sensitivity, as well as modulate inflammation. MicroRNAs (miRs), which can be packaged into exosomes (Exos) and secreted from cells, serve as essential regulators of macrophage polarization. Here, we revealed that ATMs isolated from lean mice secrete miRs-containing Exos, which modulate macrophage polarization and promote rapid diabetic wound healing when administered to diabetes-prone db/db mice. The miRs sequence of tissue samples from wounds treated with Exos secreted by lean ATMs (Exos^Lean) revealed that miR-222-3p was up-regulated. Further analyses showed that inhibiting miR-222-3p using a miR inhibitor impaired the macrophage-reprogramming effect of Exos^Lean. In the excisional skin wound mouse model, locally inhibiting miR-222-3p disrupted healing dynamics and failed to modulate macrophage polarization. Mechanistic studies revealed a connection between miR-222-3p, Bcl2l11/Bim, an inflammatory response effector, macrophage polarization, and diabetic wound healing. In summary, Exos^Lean act as positive regulators of macrophage polarization by regulating miR levels in wounds and accelerating wound healing, and thus have important implications for wound management in diabetes.

Dysregulated glycolysis underpins high-fat-associated endometrial decidualization impairment during early pregnancy in mice

Pregnancy complications are more likely to occur in obese women because of defective decidualization. However, the specific mechanism of glycolysis in decidual modulation associated with obesity remains unknown. Therefore, we explored the role of glycolysis in the endometrium of obese pregnant mice during decidualization. C57BL/6J mice were fed a high-fat diet (HFD) to induce obesity. All obesity related parameters were significantly higher in the HFD mice than control. Furthermore, the HFD mice had fewer implantation sites, a smaller decidual area growth, and decreased decidualization marker protein expression than control. The HFD mice also had significantly decreased lactate production and glycolytic enzyme expression. To confirm the functional role of glycolysis during the decidual period in obese pregnant mice, we extracted endometrial stromal cells (ESCs) and treated them with oleic acid (OA) and palmitic acid (PA) to mimic a high-fat environment. Decidualization and glycolysis were significantly restricted in the OA-and PA-treated groups. Moreover, we administered a glycolytic inhibitor, 2-DG, and an agonist, pioglitazone. 2-DG treatment considerably decreased the cells' glycolysis and decidualization. However, pioglitazone treatment improved glycolysis and alleviated defective decidualization. In conclusion, obesity-induced endometrial glycolysis modifications and key glycolytic enzyme downregulation during early pregnancy might cause abnormal decidualization, leading to an unsustainable pregnancy.

Metaflammation in glucolipid metabolic disorders: Pathogenesis and treatment

The public health issue of glucolipid metabolic disorders (GLMD) has grown significantly, posing a grave threat to human wellness. Its prevalence is rising yearly and tends to affect younger people. Metaflammation is an important mechanism regulating body metabolism. Through a complicated multi-organ crosstalk network involving numerous signaling pathways such as NLRP3/caspase-1/IL-1, NF-B, p38 MAPK, IL-6/STAT3, and PI3K/AKT, it influences systemic metabolic regulation. Numerous inflammatory mediators are essential for preserving metabolic balance, but more research is needed to determine how they contribute to the co-morbidities of numerous metabolic diseases. Whether controlling the inflammatory response can influence the progression of GLMD determines the therapeutic strategy for such diseases. This review thoroughly examines the role of metaflammation in GLMD and combs the research progress of related therapeutic approaches, including inflammatory factor-targeting drugs, traditional Chinese medicine (TCM), and exercise therapy. Multiple metabolic diseases, including diabetes, non-alcoholic fatty liver disease (NAFLD), cardiovascular disease, and others, respond therapeutically to anti-inflammatory therapy on the whole. Moreover, we emphasize the value and open question of anti-inflammatory-based means for treating GLMD.

Oxidative phosphorylation selectively orchestrates tissue macrophage homeostasis

In vitro studies have associated oxidative phosphorylation (OXPHOS) with anti-inflammatory macrophages, whereas pro-inflammatory macrophages rely on glycolysis. However, the metabolic needs of macrophages in tissues (TMFs) to fulfill their homeostatic activities are incompletely understood. Here, we identified OXPHOS as the highest discriminating process among TMFs from different organs in homeostasis by analysis of RNA-seq data in both humans and mice. Impairing OXPHOS in TMFs via Tfam deletion differentially affected TMF populations. Tfam deletion resulted in reduction of alveolar macrophages (AMs) due to impaired lipid-handling capacity, leading to increased cholesterol content and cellular stress, causing cell-cycle arrest in vivo. In obesity, Tfam depletion selectively ablated pro-inflammatory lipid-handling white adipose tissue macrophages (WAT-MFs), thus preventing insulin resistance and hepatosteatosis. Hence, OXPHOS, rather than glycolysis, distinguishes TMF populations and is critical for the maintenance of TMFs with a high lipid-handling activity, including pro-inflammatory WAT-MFs. This could provide a selective therapeutic targeting tool.

Knowledge mapping of autophagy in osteoarthritis from 2004 to 2022: A bibliometric analysis

Background

Autophagy in osteoarthritis (OA) has become an active area of research with substantial value and potential. Nevertheless, few bibliometric studies have systematically analyzed the available research in the field. The main goal of this study was to map the available literature on the role of autophagy in OA and identify global research hotspots and trends.

Methods

The Web of Science Core Collection and Scopus databases were interrogated for studies of autophagy in OA published between 2004 and 2022. Microsoft Excel, VOSviewer and CiteSpace software were used to analyze and visualize the number of publications and associated citations, and reveal global research hotspots and trends in the autophagy in OA field.

Results

732 outputs published by 329 institutions from 55 countries/regions were included in this study. From 2004 to 2022, the number of publications increased. China produced the most publications (n=456), prior to the USA (n=115), South Korea (n=33), and Japan (n=27). Scripps Research Institute (n=26) was the most productive institution. Martin Lotz (n=30) was the highest output author, while Caramés B (n=302) was the highest output author. Osteoarthritis and Cartilage was the most prolific and most co-cited journal. Currently, the autophagy in OA research hotspots include chondrocyte, transforming growth factor beta 1 (TGF-β1), inflammatory response, stress, and mitophagy. The emerging research trends in this field are AMPK, macrophage, senescence, apoptosis, tougu xiaotong capsule (TXC), green tea extract, rapamycin, and dexamethasone. Novel drugs targeting specific molecule such as TGF-β and AMPK have shown therapeutic potential but are still in the preclinical stage of development.

Conclusions

Research on the role of autophagy in OA is flourishing. Martin Lotz, Beatriz Caramés, and Osteoarthritis and Cartilage have made outstanding contributions to the field. Prior studies of OA autophagy mainly focused on mechanisms underlying OA and autophagy, including AMPK, macrophages, TGF-β1, inflammatory response, stress, and mitophagy. Emerging research trends, however, are centered around the relationship between autophagy, apoptosis, and senescence, as well as drug candidates such as TXC and green tea extract. The development of new targeted drugs that enhance or restore autophagic activity is a promising strategy for the treatment of OA.

Caspase-11 promotes high-fat diet-induced NAFLD by increasing glycolysis, OXPHOS, and pyroptosis in macrophages

Introduction

Non-alcoholic fatty liver disease (NAFLD) has a global prevalence of 25% of the population and is a leading cause of cirrhosis and hepatocellular carcinoma. NAFLD ranges from simple steatosis (non-alcoholic fatty liver) to non-alcoholic steatohepatitis (NASH). Hepatic macrophages, specifically Kupffer cells (KCs) and monocyte-derived macrophages, act as key players in the progression of NAFLD. Caspases are a family of endoproteases that provide critical connections to cell regulatory networks that sense disease risk factors, control inflammation, and mediate inflammatory cell death (pyroptosis). Caspase-11 can cleave gasdermin D (GSDMD) to induce pyroptosis and specifically defends against bacterial pathogens that invade the cytosol. However, it's still unknown whether high fat diet (HFD)-facilitated gut microbiota-generated cytoplasmic lipopolysaccharides (LPS) activate caspase-11 and promote NAFLD.

Methods

To examine this hypothesis, we performed liver pathological analysis, RNA-seq, FACS, Western blots, Seahorse mitochondrial stress analyses of macrophages and bone marrow transplantation on HFD-induced NAFLD in WT and Casp11-/- mice.

Results and Discussion

Our results showed that 1) HFD increases body wight, liver wight, plasma cholesterol levels, liver fat deposition, and NAFLD activity score (NAS score) in wild-type (WT) mice; 2) HFD increases the expression of caspase-11, GSDMD, interleukin-1β, and guanylate-binding proteins in WT mice; 3) Caspase-11 deficiency decreases fat liver deposition and NAS score; 4) Caspase-11 deficiency decreases bone marrow monocyte-derived macrophage (MDM) pyroptosis (inflammatory cell death) and inflammatory monocyte (IM) surface GSDMD expression; 5) Caspase-11 deficiency re-programs liver transcriptomes and reduces HFD-induced NAFLD; 6) Caspase-11 deficiency decreases extracellular acidification rates (glycolysis) and oxidative phosphorylation (OXPHOS) in inflammatory fatty acid palmitic acid-stimulated macrophages, indicating that caspase-11 significantly contributes to maintain dual fuel bioenergetics-glycolysis and OXPHOS for promoting pyroptosis in macrophages. These results provide novel insights on the roles of the caspase-11-GSDMD pathway in promoting hepatic macrophage inflammation and pyroptosis and novel targets for future therapeutic interventions involving the transition of NAFLD to NASH, hyperlipidemia, type II diabetes, metabolic syndrome, metabolically healthy obesity, atherosclerotic cardiovascular diseases, autoimmune diseases, liver transplantation, and hepatic cancers.

The markers to delineate different phenotypes of macrophages related to metabolic disorders

Macrophages have a wide variety of roles in physiological and pathological conditions, making them promising diagnostic and therapeutic targets in diseases, especially metabolic disorders, which have attracted considerable attention in recent years. Owing to their heterogeneity and polarization, the phenotypes and functions of macrophages related to metabolic disorders are diverse and complicated. In the past three decades, the rapid progress of macrophage research has benefited from the emergence of specific molecular markers to delineate different phenotypes of macrophages and elucidate their role in metabolic disorders. In this review, we analyze the functions and applications of commonly used and novel markers of macrophages related to metabolic disorders, facilitating the better use of these macrophage markers in metabolic disorder research.

The crucial role and mechanism of insulin resistance in metabolic disease

Insulin resistance (IR) plays a crucial role in the development and progression of metabolism-related diseases such as diabetes, hypertension, tumors, and nonalcoholic fatty liver disease, and provides the basis for a common understanding of these chronic diseases. In this study, we provide a systematic review of the causes, mechanisms, and treatments of IR. The pathogenesis of IR depends on genetics, obesity, age, disease, and drug effects. Mechanistically, any factor leading to abnormalities in the insulin signaling pathway leads to the development of IR in the host, including insulin receptor abnormalities, disturbances in the internal environment (regarding inflammation, hypoxia, lipotoxicity, and immunity), metabolic function of the liver and organelles, and other abnormalities. The available therapeutic strategies for IR are mainly exercise and dietary habit improvement, and chemotherapy based on biguanides and glucagon-like peptide-1, and traditional Chinese medicine treatments (e.g., herbs and acupuncture) can also be helpful. Based on the current understanding of IR mechanisms, there are still some vacancies to follow up and consider, and there is also a need to define more precise biomarkers for different chronic diseases and lifestyle interventions, and to explore natural or synthetic drugs targeting IR treatment. This could enable the treatment of patients with multiple combined metabolic diseases, with the aim of treating the disease holistically to reduce healthcare expenditures and to improve the quality of life of patients to some extent.

Improved Regularized Multi-class Logistic Regression for Gene Classification with Optimal Kernel PCA and HC Algorithm

A significant challenge in high-dimensional and big data analysis is related to the classification and prediction of the variables of interest. The massive genetic datasets are complex. Gene expression datasets are enriched with useful genes that are associated with specific diseases such as cancer. In this study, we used two gene expression datasets from the Gene Expression Omnibus and preprocessed them before classification. We used optimal kernel principal component analysis in which the optimal kernel function was chosen for dataset dimensionality reduction and extraction of the most important features. The gene sets with a high validity index were collected using a combined hieratical clustering and optimal kernel principal component analysis (KHC-RLR) algorithm. Logistic regression is one of the most common methods for classification, and it has been shown to be a useful classification approach for gene expression data analysis. In this study, we used multi-class logistic regression to classify the collected gene sets. We found that ordinary logistic regression caused a major overfitting problem; therefore, we used regularized multi-class logistic regression to classify the gene sets. The proposed KHC-RLR algorithm showed a high performance and satisfied accuracy measures.

Decreased left atrial function in obesity patients without known cardiovascular disease

Obesity is a risk factor for heart failure with preserved ejection fraction (HFpEF). We hypothesized that assessment of left atrial (LA) strain may be useful to reveal precursors of HFpEF in obesity patients. Echocardiograms of obesity patients without known cardiovascular disease who underwent bariatric surgery, and echocardiograms of age- and gender matched controls were analyzed. The echocardiogram was repeated 1 year after bariatric surgery. LA reservoir strain (LASr), LA conduit strain (LAScd), and LA contractile strain (LASct) were measured. 77 Obesity patients were compared with 46 non-obese controls. Obesity patients showed a significantly decreased LA function compared with non-obese individuals (LASr 32.2% ± 8.8% vs. 39.6% ± 10.8%, p < 0.001; LAScd 20.1% ± 7.5% vs. 24.9% ± 8.3%, p = 0.001; LASct 12.1% ± 3.6% vs. 14.5% ± 5.5%, p = 0.005). There was no difference in prevalence of diastolic dysfunction between the obesity group and controls (9.1% vs. 2.2%, p = 0.139). One year after bariatric surgery, LASr improved (32.1% ± 8.9% vs. 34.2% ± 8.7%, p = 0.048). In the multivariable linear regression analysis, BMI was associated with LASr, LAScd, and LASct (β =  - 0.34, CI - 0.54 to - 0.13; β =  - 0.22, CI - 0.38 to - 0.06; β =  - 0.10, CI - 0.20 to - 0.004). Obesity patients without known cardiovascular disease have impairment in all phases of LA function. LA dysfunction in obesity may be an early sign of cardiac disease and may be a predictor for developing HFpEF. LASr improved 1 year after bariatric surgery, indicating potential reversibility of LA function in obesity.

Obese visceral fat tissue inflammation: from protective to detrimental?

Obesity usually is accompanied by inflammation of fat tissue, with a prominent role of visceral fat. Chronic inflammation in obese fat tissue is of a lower grade than acute immune activation for clearing the tissue from an infectious agent. It is the loss of adipocyte metabolic homeostasis that causes activation of resident immune cells for supporting tissue functions and regaining homeostasis. Initially, the excess influx of lipids and glucose in the context of overnutrition is met by adipocyte growth and proliferation. Eventual lipid overload of hypertrophic adipocytes leads to endoplasmic reticulum stress and the secretion of a variety of signals causing increased sympathetic tone, lipolysis by adipocytes, lipid uptake by macrophages, matrix remodeling, angiogenesis, and immune cell activation. Pro-inflammatory signaling of adipocytes causes the resident immune system to release increased amounts of pro-inflammatory and other mediators resulting in enhanced tissue-protective responses. With chronic overnutrition, these protective actions are insufficient, and death of adipocytes as well as senescence of several tissue cell types is seen. This structural damage causes the expression or release of immunostimulatory cell components resulting in influx and activation of monocytes and many other immune cell types, with a contribution of stromal cells. Matrix remodeling and angiogenesis is further intensified as well as possibly detrimental fibrosis. The accumulation of senescent cells also may be detrimental via eventual spread of senescence state from affected to neighboring cells by the release of microRNA-containing vesicles. Obese visceral fat inflammation can be viewed as an initially protective response in order to cope with excess ambient nutrients and restore tissue homeostasis but may contribute to tissue damage at a later stage.

Mitochondrial Stress in Metabolic Inflammation: Modest Benefits and Full Losses

Energy intake and metabolic balance are the pillars of health preservation. Overnutrition causes nonspecific, persistently low inflammatory state known as metabolic inflammation. This condition contributes to the pathophysiology of various metabolic disorders, such as atherosclerosis, obesity, diabetes mellitus, and metabolic syndrome. The mitochondria maintain the balance of energy metabolism. Excessive energy stress can lead to mitochondrial dysfunction, which promotes metabolic inflammation. The inflammatory environment further impairs mitochondrial function. Accordingly, excellent organism design keeps the body metabolically healthy in the context of mitochondrial dysfunction, and moderate mitochondrial stress can have a beneficial effect. This review summarises the research progress on the multifaceted characterisation of mitochondrial dysfunction and its role in metabolic inflammation.

Adipose tissue macrophages: Regulators of adipose tissue immunometabolism during obesity

BACKGROUND

Adipose tissue macrophages (ATMs) are a well characterized regulator of adipose tissue inflammatory tone. Previously defined by the M1 vs M2 classification, we now have a better understanding of ATM diversity that departs from the old paradigm and reports a spectrum of ATM function and phenotypes in both brown and white adipose tissue.

SCOPE OF REVIEW

This review provides an updated overview of ATM activation and function, ATM diversity in humans and rodents, and novel ATM functions that contribute to metabolic homeostasis and disease.

MAJOR CONCLUSIONS

While the paradigm that resident ATMs predominate in the lean state and obesity leads to the accumulation of lipid-associated and inflammatory ATMs still broadly remains rigorously supported, the details of this model continue to be refined and single cell data provide new insight into ATM subtypes and states.