CD11c expression in adipose tissue and blood and its role in diet-induced obesity

Identification of potential crucial genes and mechanisms associated with metabolically unhealthy obesity based on the gene expression profile

Background

Obesity is an epidemic and systemic metabolic disease that seriously endangers human health. This study aimed to understand the transcriptomic characteristics of the blood of metabolically unhealthy obesity (MUO) and provide insight into the target genes of differently expressed microRNAs in the occurrence and development of MUO.

Methods

The GSE146869, GSE145412, GSE23561, and GSE169290 datasets were analyzed to understand the transcriptome characteristics of the blood of MUO and provide insights into the target genes of differently expressed microRNAs (DEMs) in MUO. Functional and pathway enrichment analyses and gene interaction network analyses were performed to profile the function of differentially expressed genes (DEGs). In addition, miRNet 2.0, TransmiR v2.0, RNA22, TargetScan 7.2, miRDB, and miRWalk databases were used to predict the target genes of effective microRNAs.

Results

A total of 189 co-DEGs were identified in at least two datasets. The 156 co-upregulated genes were enriched into 29 biological process (BP) terms and 12 KEGG pathways. Among the 29 BP terms, the immune- and metabolism-related BP terms were enriched. The 33 co-downregulated genes were enriched into two BP terms, including apoptotic process and regulation of the apoptotic process, with no KEGG pathway. The hub genes EGF, STAT3, IL1B, PF4, SELP, and ITGA2B in the gene interaction network might play important roles in abnormal BP in MUO. Among the 19 DEMs identified in the blood of the MUO group by the GSE169290 dataset, 18 microRNAs targeted 85 genes as risk factors in MUO.

Conclusion

A network consisting of 18 microRNAs and 85 target genes might serve as a risk factor for metabolically unhealthy obesity.

Interplay Between Insulin Resistance and Immune Dysregulation in Type 2 Diabetes Mellitus: Implications for Therapeutic Interventions

Type 2 Diabetes Mellitus (T2DM) is a rapidly growing global health issue characterized by insulin resistance and chronic inflammation. Beyond regulating glucose homeostasis, insulin plays a pivotal role in modulating immune cell function, linking metabolic dysregulation with immune responses. This review examines the intricate relationship between insulin resistance and immune dysfunction in T2DM, focusing on how impaired insulin signaling pathways, particularly PI3K/Akt and MAPK, contribute to immune cell activation, proliferation, and chronic inflammation. Insulin resistance impacts immune cells such as T cells, B cells, macrophages, and neutrophils, leading to an imbalance between pro-inflammatory and anti-inflammatory responses. Elevated pro-inflammatory cytokines (eg, TNF-α, IL-6) and adipokines (eg, leptin, resistin) exacerbate insulin resistance, promoting a vicious cycle of metabolic and immune dysregulation. This interplay contributes to the chronic low-grade inflammation that underlies T2DM pathogenesis, further impairing insulin signaling and glucose metabolism. Restoration of insulin sensitivity is, therefore, a critical step toward correcting immune imbalance in insulin-resistant states like T2DM. Therapeutic approaches that reduce inflammation could also support improvements in insulin sensitivity, addressing both metabolic and immune disturbances simultaneously. The review also explores therapeutic strategies, including insulin therapy, targeting insulin signaling pathways, and lifestyle interventions. Insulin therapy can reduce pro-inflammatory cytokine production and enhance anti-inflammatory responses, although challenges such as potential immune suppression and hyperinsulinemia remain. Targeting key signaling pathways and transcription factors offers promising avenues for modulating immune responses, while lifestyle interventions, such as dietary modifications, physical activity, and weight management, can improve insulin sensitivity and reduce inflammation. By understanding the dual role of insulin in regulating both metabolic and immune functions, this review underscores the importance of addressing immune dysfunction as part of comprehensive T2DM management. Targeting the interconnected pathways of insulin signaling and immune regulation could lead to more effective therapeutic approaches, ultimately improving patient outcomes and reducing disease complications.

Siglec-E augments adipose tissue inflammation by modulating TRAF3 signaling and monocytic myeloid-derived suppressor cells during obesity

Background

Obesity is associated with dysregulated metabolism and low-grade chronic inflammation in adipose tissue (AT). Immune cells, including macrophages, T cells, and neutrophils, infiltrate the AT and secrete proinflammatory cytokines to exacerbate the AT inflammation. RNA-Seq analysis of AT immune cells isolated from mice fed a high-fat diet (HFD) versus normal fat diet (ND) identified a panel of genes that were markedly downregulated, including sialic acid-binding Ig-like lectin E (siglec-E), in HFD compared to ND mice.

Methods

A series of experiments in wild-type (WT) and siglec-E knockout (siglec-E KO) mice was designed to investigate the effect of HFD on the functional role of siglec-E in the regulation of AT inflammation and adipogenesis. We analyzed the changes in immune phenotypes, inflammatory response, adipogenesis, and levels of cytokines and chemokines after HFD and ND feeding.

Results

HFD consumption significantly increased the body weight and blood glucose levels in siglec-E KO mice relative to those of WT mice. This was associated with an increased infiltration of macrophages, CXCR3 expressing CD8 T cells, and monocytic myeloid-derived suppressor cells (M-MDSCs) with a concomitant decrease in numbers of dendritic cells (DCs), in the AT of siglec-E KO fed HFD versus the WT HFD counterparts. The HFD-fed siglec-E KO mice also exhibited elevated expression of intracellular Akt and TNF receptor-associated factor 3 (TRAF3) signaling, inducing C/EBPα, FASN, PPARγ, and resistin in suprascapular AT compared to WT HFD-fed mice. Taken together, these results suggest that a genetic deficiency of siglec-E plays a key role in inducing AT inflammation by differentially altering M-MDSCs and CD8+CXCR3+ T cell function and adipogenesis by TRAF3 and Akt signaling in AT.

Conclusion

Our findings strongly suggest that modulation of siglec-E pathways might have a protective effect at least in part against AT inflammation and metabolic disorders.

Protective Effects of Spirulina Against Lipid Micelles and Lipopolysaccharide-Induced Intestinal Epithelium Disruption in Caco-2 Cells: In Silico Molecular Docking Analysis of Phycocyanobilin

Damage to intestinal epithelial cells is present in obesity and other diseases because of inflammatory and oxidative processes. This damage compromises the gastrointestinal barrier, killing enterocytes, altering intestinal permeability, and eliciting abnormal immune responses that promote chronic inflammation. Recent evidence shows that spirulina is a potent natural agent with antioxidant and anti-inflammatory properties.

OBJECTIVES

This study was conducted to evaluate the effect of spirulina aqueous extract (SPAE) on the alterations of the intestinal epithelium induced by lipid micelles (LMs) and/or inflammation induced by lipopolysaccharides (LPSs) in the Caco-2 cell line.

METHODS

In the current research, we assessed the protective actions of SPAE against cytotoxicity, oxidative stress, inflammation, and epithelial barrier perturbation by using an in vitro model, the intestinal Caco-2 cells, treated with LPSs and/or LMs. We also performed an in silico molecular docking analysis with spirulina's bioactive compound, phycocyanobilin.

RESULTS

Our results showed that SPAE has no cytotoxic effect on Caco-2 cells. On the contrary, it improved cell viability and exhibited anti-inflammatory and antioxidant actions. SPAE also protected against endoplasmic reticulum stress and tight junction proteins, thus improving the epithelial barrier. The in silico study revealed a strong binding affinity of the phycocyanobilin compound with human SOD and NADPH oxidase and a good binding affinity towards COX-2 and iNOS.

CONCLUSIONS

Taken together, these findings demonstrate the beneficial actions of SPAE on Caco-2 cells, suggesting it may be useful in preserving the epithelial intestinal barrier in human conditions involving oxidative stress and inflammation such as obesity.

The multifaceted life of macrophages in white adipose tissue: Immune shift couples with metabolic switch

White adipose tissue (WAT) is a vital endocrine organ that regulates energy balance and metabolic homeostasis. In addition to fat cells, WAT harbors macrophages with distinct phenotypes that play crucial roles in immunity and metabolism. Nutrient demands cause macrophages to accumulate in WAT niches, where they remodel the microenvironment and produce beneficial or detrimental effects on systemic metabolism. Given the abundance of macrophages in WAT, this review summarizes the heterogeneity of WAT macrophages in physiological and pathological conditions, including their alterations in quantity, phenotypes, characteristics, and functions during WAT growth and development, as well as healthy or unhealthy expansion. We will discuss the interactions of macrophages with other cell partners in WAT including adipose stem cells, adipocytes, and T cells in the context of various microenvironment niches in lean or obese condition. Finally, we highlight how adipose tissue macrophages merge immunity and metabolic changes to govern energy balance for the organism.

Mouse vascularized adipose spheroids: an organotypic model for thermogenic adipocytes

Adipose tissues, particularly beige and brown adipose tissue, play crucial roles in energy metabolism. Brown adipose tissues' thermogenic capacity and the appearance of beige cells within white adipose tissue have spurred interest in their metabolic impact and therapeutic potential. Brown and beige fat cells, activated by environmental factors like cold exposure or by pharmacology, share metabolic mechanisms that drive non-shivering thermogenesis. Understanding these two cell types requires advanced, yet broadly applicable in vitro models that reflect the complex microenvironment and vasculature of adipose tissues. Here we present mouse vascularized adipose spheroids of the stromal vascular microenvironment from inguinal white adipose tissue, a tissue with 'beiging' capacity in mice and humans. We show that adding a scaffold improves vascular sprouting, enhances spheroid growth, and upregulates adipogenic markers, thus reflecting increased adipocyte maturity. Transcriptional profiling via RNA sequencing revealed distinct metabolic pathways upregulated in our vascularized adipose spheroids, with increased expression of genes involved in glucose metabolism, lipid metabolism, and thermogenesis. Functional assessment demonstrated increased oxygen consumption in vascularized adipose spheroids compared to classical 2D cultures, which was enhanced by β-adrenergic receptor stimulation correlating with elevated β-adrenergic receptor expression. Moreover, stimulation with the naturally occurring adipokine, FGF21, induced Ucp1 mRNA expression in the vascularized adipose spheroids. In conclusion, vascularized inguinal white adipose tissue spheroids provide a physiologically relevant platform to study how the stromal vascular microenvironment shapes adipocyte responses and influence activated thermogenesis in beige adipocytes.

Amino acid HPLC-FLD analysis of spirulina and its protective mechanism against the combination of obesity and colitis in wistar rats

Objective

The cafeteria diet (CD), designed as an experimental diet mimicking the obesogenic diet, may contribute to the pathogenesis of inflammatory bowel diseases (IBD). This study delves into the influence of spirulina (SP) on obesity associated with colitis in Wistar rats.

Methods

The amino acids composition of SP was analyzed using HPLC-FLD. Animals were equally separated into eight groups, each containing seven animals and treated daily for eight weeks as follows: Control diet (SD), cafeteria diet (CD) group, CD + SP (500 mg/kg) and SD + SP. Ulcerative colitis was provoked by rectal injection of acetic acid (AA) (3 % v/v, 5 ml/kg b.w.) on the last day of treatment in the following groups: SD + AA, SD + AA + SP, CD + AA, and CD + AA + SP.

Results

Findings revealed that UC and/or CD increased the abdominal fat, weights gain, and colons. Moreover, severe colonic alteration, perturbations in the serum metabolic parameters associated with an oxidative stress state in the colonic mucosa, defined by overproduction of reactive oxygen species (ROS) and increased levels of plasma scavenging activity (PSA). Additionally, obesity exacerbated the severity of AA-induced UC promoting inflammation marked by the overexpression of pro-inflammatory cytokines. Significantly, treatment with SP provided notable protection against inflammation severity, reduced histopathological alterations, attenuated lipid peroxidation (MDA), and enhanced antioxidant enzyme activities (CAT, SOD, and GPX) along with non-enzymatic antioxidants (GSH and SH-G).

Conclusions

Thus, the antioxidant effects and anti-inflammatory proprieties of SP could be attributed to its richness in amino acids, which could potentially mitigate inflammation severity in obese subjects suffering from ulcerative colitis. These results imply that SP hold promise as a therapeutic agent for managing of UC, particularly in individuals with concomitant obesity. Understanding SP's mechanisms of action may lead novel treatment strategies for inflammatory bowel diseases and hyperlipidemia in medical research.

Impact of Obesity and Age on Mouse Corneal Innervation at the Epithelial-Stromal Interface

Purpose

The corneal epithelium is the most highly innervated structure in the body. Previously, we reported a novel event whereby stromal axons fuse with basal epithelial cells, limiting nerve penetration into the epithelium. Although corneal-epithelial nerves undergo changes in sensitivity and distribution throughout life and in response to an obesogenic diet, it is unknown if neuronal-epithelial cell fusion is altered. Here, we sought to determine if neuronal-epithelial cell fusion frequency correlates with obesogenic diet consumption and age.

Methods

Corneas were collected from C57BL/6 mice and evaluated for neuronal-epithelial cell fusion frequency using serial block-face scanning electron microscopy. To assess the correlation between diet-induced obesity and fusion frequency, 6-week-old mice were fed either a normal diet or an obesogenic diet for 10 weeks. To assess changes in fusion frequency between young and adult mice under normal dietary conditions, 9- and 24-week-old mice were used.

Results

Mice fed a 10-week obesogenic diet showed 87% of central-cornea stromal nerves engaged in fusion compared with only 54% in age-matched controls (16 weeks old). In 9-week-old normal-diet animals, 48% of central-cornea stromal nerves contained fusing axons and increased to 81% at 24 weeks of age. Corneal sensitivity loss correlated with increased body weight and adiposity regardless of age and diet.

Conclusions

Neuronal-epithelial cell fusion positively correlates with age and obesogenic diet consumption, and corneal nerve sensitivity loss correlates with increased body weight and adiposity, regardless of age and diet. As such, neuronal-epithelial cell fusion may play a role in corneal nerve density and sensitivity regulation.

Obesity Is Associated with Immunometabolic Changes in Adipose Tissue That May Drive Treatment Resistance in Breast Cancer: Immune-Metabolic Reprogramming and Novel Therapeutic Strategies

White adipose tissue (WAT) represents an endocrinologically and immunologically active tissue whose primary role is energy storage and homeostasis. Breast WAT is involved in the secretion of hormones and proinflammatory molecules that are associated with breast cancer development and progression. The role of adiposity and systemic inflammation in immune responses and resistance to anti-cancer treatment in breast cancer (BC) patients is still not clear. Metformin has demonstrated antitumorigenic properties both in pre-clinical and clinical studies. Nevertheless, its immunomodulating properties in BC are largely unknown. This review aims to evaluate the emerging evidence on the crosstalk between adiposity and the immune-tumour microenvironment in BC, its progression and treatment resistance, and the immunometabolic role of metformin in BC. Adiposity, and by extension subclinical inflammation, are associated with metabolic dysfunction and changes in the immune-tumour microenvironment in BC. In oestrogen receptor positive (ER+) breast tumours, it is proposed that these changes are mediated via a paracrine interaction between macrophages and preadipocytes, leading to elevated aromatase expression and secretion of pro-inflammatory cytokines and adipokines in the breast tissue in patients who are obese or overweight. In HER2+ breast tumours, WAT inflammation has been shown to be associated with resistance to trastuzumab mediated via MAPK or PI3K pathways. Furthermore, adipose tissue in patients with obesity is associated with upregulation of immune checkpoints on T-cells that is partially mediated via immunomodulatory effects of leptin and has been paradoxically associated with improved responses to immunotherapy in several cancers. Metformin may play a role in the metabolic reprogramming of tumour-infiltrating immune cells that are dysregulated by systemic inflammation. In conclusion, evidence suggests that body composition and metabolic status are associated with patient outcomes. To optimise patient stratification and personalisation of treatment, prospective studies are required to evaluate the role of body composition and metabolic parameters in metabolic immune reprogramming with and without immunotherapy in patients with BC.

The link between immunity and hypertension in the kidney and heart

Hypertension is the primary cause of cardiovascular disease, which is a leading killer worldwide. Despite the prevalence of this non-communicable disease, still between 90% and 95% of cases are of unknown or multivariate cause ("essential hypertension"). Current therapeutic options focus primarily on lowering blood pressure through decreasing peripheral resistance or reducing fluid volume, but fewer than half of hypertensive patients can reach blood pressure control. Hence, identifying unknown mechanisms causing essential hypertension and designing new treatment accordingly are critically needed for improving public health. In recent years, the immune system has been increasingly implicated in contributing to a plethora of cardiovascular diseases. Many studies have demonstrated the critical role of the immune system in the pathogenesis of hypertension, particularly through pro-inflammatory mechanisms within the kidney and heart, which, eventually, drive a myriad of renal and cardiovascular diseases. However, the precise mechanisms and potential therapeutic targets remain largely unknown. Therefore, identifying which immune players are contributing to local inflammation and characterizing pro-inflammatory molecules and mechanisms involved will provide promising new therapeutic targets that could lower blood pressure and prevent progression from hypertension into renal or cardiac dysfunction.

A Low-Fat/Sucrose Diet Rich in Complex Carbohydrates Reverses High-Fat/Sucrose Diet-Induced Corneal Dysregulation

High-fat/sucrose diet feeding in mice causes loss of corneal nerve function and impairs corneal wound healing. While changing to a diet with a low fat/sugar composition and enrichments in complex carbohydrates mitigates the reduction in nerve function, it remains to be determined if it has an effect on corneal wound healing. In this study, 6-week-old C57BL/6 male mice were fed either a normal diet or a high-fat/sucrose diet for 20 weeks. A third group (diet reversal) was placed on a high-fat/sucrose diet for 10 weeks followed by a normal diet for an additional 10 weeks. A central corneal epithelial abrasion wound was created, and wound closure was monitored. Neutrophil and platelet recruitment was assessed by immunofluorescence microscopy. Mice fed the high-fat/sucrose diet-only had greater adiposity (p < 0.005) than normal diet-only fed mice; diet reversal markedly reduced adiposity. Following corneal abrasion, wound closure was delayed by ~6 h (p ≤ 0.01) and, at 30 h post-wounding, fewer neutrophils reached the wound center and fewer extravascular platelets were present at the limbus (p < 0.05). Diet restored normal wound closure and neutrophil and platelet influx in the injured cornea. These data suggest compositional changes to the diet may be an effective diet-based therapeutic strategy for maintaining or restoring corneal health.

Apolipoprotein A-IV reduced metabolic inflammation in white adipose tissue by inhibiting IKK and JNK signaling in adipocytes

Apolipoprotein A-IV (ApoA-IV) plays a role in satiation and serum lipid transport. In diet-induced obesity (DIO) C57BL/6J mice, ApoA-IV deficiency induced in ApoA-IV-/-knock-out (KO mice) resulted in increased bodyweight, insulin resistance (IR) and plasma free fatty acid (FFA), which was partially reversed by stable ApoA-IV-green fluorescent protein (KO-A4-GFP) transfection in KO mice. DIO KO mice exhibited increased M1 macrophages in epididymal white adipose tissue (eWAT) as well as in the blood. Based on RNA-sequencing analyses, cytokine-cytokine receptor interactions, T cell and B cell receptors, and especially IL-17 and TNF-α, were up-regulated in eWAT of DIO ApoA-IV KO compared with WT mice. Supplemented ApoA-IV suppressed lipopolysaccharide (LPS)-induced IKK and JNK phosphorylation in Raw264.7 macrophage cell culture assays. When the culture medium was supplemented to 3T3-L1 adipocytes they exhibited an increased sensitivity to insulin. ApoA-IV protects against obesity-associated metabolic inflammation mainly through suppression in M1 macrophages of eWAT, IL17-IKK and IL17-JNK activity.

Lipedema: Insights into Morphology, Pathophysiology, and Challenges

Lipedema is an adipofascial disorder that almost exclusively affects women. Lipedema leads to chronic pain, swelling, and other discomforts due to the bilateral and asymmetrical expansion of subcutaneous adipose tissue. Although various distinctive morphological characteristics, such as the hyperproliferation of fat cells, fibrosis, and inflammation, have been characterized in the progression of lipedema, the mechanisms underlying these changes have not yet been fully investigated. In addition, it is challenging to reduce the excessive fat in lipedema patients using conventional weight-loss techniques, such as lifestyle (diet and exercise) changes, bariatric surgery, and pharmacological interventions. Therefore, lipedema patients also go through additional psychosocial distress in the absence of permanent treatment. Research to understand the pathology of lipedema is still in its infancy, but promising markers derived from exosome, cytokine, lipidomic, and metabolomic profiling studies suggest a condition distinct from obesity and lymphedema. Although genetics seems to be a substantial cause of lipedema, due to the small number of patients involved in such studies, the extrapolation of data at a broader scale is challenging. With the current lack of etiology-guided treatments for lipedema, the discovery of new promising biomarkers could provide potential solutions to combat this complex disease. This review aims to address the morphological phenotype of lipedema fat, as well as its unclear pathophysiology, with a primary emphasis on excessive interstitial fluid, extracellular matrix remodeling, and lymphatic and vasculature dysfunction. The potential mechanisms, genetic implications, and proposed biomarkers for lipedema are further discussed in detail. Finally, we mention the challenges related to lipedema and emphasize the prospects of technological interventions to benefit the lipedema community in the future.

The Roles of Adipose Tissue Macrophages in Human Disease

Macrophages are a population of immune cells functioning in antigen presentation and inflammatory response. Research has demonstrated that macrophages belong to a cell lineage with strong plasticity and heterogeneity and can be polarized into different phenotypes under different microenvironments or stimuli. Many macrophages can be recruited by various cytokines secreted by adipose tissue. The recruited macrophages further secrete various inflammatory factors to act on adipocytes, and the interaction between the two leads to chronic inflammation. Previous studies have indicated that adipose tissue macrophages (ATMs) are closely related to metabolic diseases like obesity and diabetes. Here, we will not only conclude the current progress of factors affecting the polarization of adipose tissue macrophages but also elucidate the relationship between ATMs and human diseases. Furthermore, we will highlight its potential in preventing and treating metabolic diseases as immunotherapy targets.

Inflammatory Links Between Hypertriglyceridemia and Atherogenesis

PURPOSE OF REVIEW

Recent studies indicate an association between hypertriglyceridemia (HTG) and atherosclerotic cardiovascular disease (ASCVD). The purpose of this review is to discuss the potential mechanism connecting HTG and ASCVD risk and the potential efficacy of HTG-targeting therapies in ASCVD prevention.

RECENT FINDINGS

HTG, with elevations in triglyceride-rich lipoproteins (TGRL) and their remnants, are causal ASCVD risk factors. The mechanisms whereby HTG increases ASCVD risk are not well understood but may include multiple factors. Inflammation plays a crucial role in atherosclerosis. TGRL compared to low-density lipoproteins (LDL) correlate better with inflammation. TGRL remnants can penetrate endothelium and interact with macrophages leading to foam cell formation and inflammation in arterial walls, thereby contributing to atherogenesis. In addition, circulating monocytes can take up TGRL and become lipid-laden foamy monocytes, which infiltrate the arterial wall and may also contribute to atherogenesis. Novel therapies targeting HTG or inflammation are in development and have potential of reducing residual ASCVD risk associated with HTG. Clinical and preclinical studies show a causal role of HTG in promoting ASCVD, in which inflammation plays a vital role. Novel therapies targeting HTG or inflammation have potential of reducing residual ASCVD risk.

The Role of T Cells in Obesity-Associated Inflammation and Metabolic Disease

Chronic inflammation plays a critical role in the development of obesity-associated metabolic disorders such as insulin resistance. Obesity alters the microenvironment of adipose tissue and the intestines from anti-inflammatory to pro-inflammatory, which promotes low grade systemic inflammation and insulin resistance in obese mice. Various T cell subsets either help maintain metabolic homeostasis in healthy states or contribute to obesity-associated metabolic syndromes. In this review, we will discuss the T cell subsets that reside in adipose tissue and intestines and their role in the development of obesity-induced systemic inflammation.

Myeloid Cell-Specific IL-4 Receptor Knockout Partially Protects from Adipose Tissue Inflammation

IL-4 receptor signaling is supposed to play a major role in anti-inflammatory polarization and proliferation of adipose tissue macrophages. In this study, we examined the metabolic and inflammatory phenotype of C57BL/6J mice (IIl4ra) with LysM-dependent knockout (IIl4ra ^Δmyel) of the IL-4 receptor α-chain (IL-4Rα), the mandatory signaling component of IL-4 and IL-13, on chow and high-fat diet. Lean IIl4ra ^Δmyel mice showed decreased insulin sensitivity, no divergent adipose tissue macrophage polarization, but an increased percentage of CD8⁺ T cells in visceral adipose tissue. After 20 wk of a high-fat diet, IIl4ra ^Δmyel mice exhibited higher glucose tolerance, no changes in the lymphocyte compartment and fewer M1 macrophages in visceral adipose tissue. In vivo adipose tissue macrophage proliferation measured by BrdU incorporation was unaffected by Il4ra knockout. Interestingly, we show that IL-4Rα signaling directly augmented Itgax (Cd11c) gene expression in bone marrow-derived macrophages and increased the amount of CD11c⁺ macrophages in adipose tissue explants. Myeloid cell-specific knockout of Il4ra deteriorated insulin sensitivity in lean mice but improved parameters of glucose homeostasis and partially protected from adipose tissue inflammation in obese mice. Hence, IL-4Rα signaling probably plays a minor role in maintaining the macrophage M2 population and proliferation rates in vivo. Moreover, our data indicate that IL-4 signaling plays a proinflammatory role in adipose tissue inflammation by directly upregulating CD11c on adipose tissue macrophages.

The effects of dietary vitamin D supplementation and in vitro 1,25 dihydroxyvitamin D3 treatment on autophagy in bone marrow-derived dendritic cells from high-fat diet-induced obese mice

Obesity is associated with the dysregulation of vitamin D metabolism and altered immune responses in bone marrow-derived dendritic cells (BMDCs). Vitamin D can affect the differentiation, maturation, and activation of dendritic cells (DCs) and regulate autophagy via vitamin D receptor signaling. Autophagy was shown to be involved in the functions of DCs. We investigated the effects of dietary vitamin D supplementation and in vitro 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) treatment on autophagy in BMDCs from control diet (CON)-fed lean and high-fat diet (HFD)-induced obese mice. C57BL/6 male mice were fed CON or HFD with 10% or 45% kcal fat, respectively, supplemented with 1,000 or 10,000 IU vitamin D/kg diet (vDC or vDS) for 12 weeks. BMDCs were generated by culturing bone marrow cells from the mice with 20 ng/mL rmGM-CSF and treated with 1 nM 1,25(OH)₂D₃. Maturation of BMDCs was induced by lipopolysaccharide (50 ng/mL) stimulation. Treatment with 1,25(OH)₂D₃ inhibited the expression of phenotypes related to DC function (MHC class Ⅱ, CD86, CD80) and production of IL-12p70 by BMDCs from control and obese mice, regardless of dietary vitamin D supplementation. LC3Ⅱ/Ⅰ and VPS34 protein levels increased, and p62 expression decreased, after 1,25(OH)₂D₃ treatment of the BMDCs in CON-vDC only. Vdr mRNA levels decreased following 1,25(OH)₂D₃ treatment of BMDCs in the HFD-vDC. In conclusion, autophagy flux was increased by 1,25(OH)₂D₃ treatment of the BMDCs in CON-vDC but not in the HFD-vDC group. This suggests that the decreased expression of Vdr following 1,25(OH)₂D₃ treatment might have affected autophagy flux in BMDCs from obese mice.

Kale supplementation during high fat feeding improves metabolic health in a mouse model of obesity and insulin resistance

Cruciferous vegetables have been widely studied for cancer prevention and cardiovascular health. Broccoli is the cruciferous vegetable whose phytochemistry and physiological effects have been most extensively studied. Kale (Brassica oleracea var. acephala) appears on lists of 'healthiest, nutrient dense foods' but, there is paucity of data on kale as a functional food. In a 12-week study, we tested the effect of curly green kale on high fat diet (HFD) induced obesity and insulin resistance, lipid metabolism, endotoxemia and inflammation in C57BL/6J mice fed isocaloric diets. Kale supplementation did not attenuate HFD diet induced fat accumulation and insulin resistance (P = ns; n = 9) but, it lowered serum triglycerides, low density lipoprotein (LPL) cholesterol and prevented HFD induced increases in systemic endotoxemia and inflammation (serum LPS and Ccl2) (P<0.01; n = 9). In adipose tissue, kale enhanced the expression of genes involved in adipogenesis (P<0.01; n = 9), reduced the appearance of histologic markers of inflammation, downregulated both the gene expression and protein expression of the adipose tissue specific inflammation markers CD11c and F4/80 (P<0.001; n = 9) and reduced the gene expression of a battery of chemokine C-C motif ligands (Ccl2, Ccl6, Ccl7, Ccl8, Ccl9) and chemokine C-C motif receptors (Ccr2, Ccr3, Ccr5). We conclude that kale vegetable protects against HFD diet induced dysfunction through mechanisms involving lipid metabolism, endotoxemia and inflammation.

CD11c participates in triggering acute graft-versus-host disease during bone marrow transplantation

CD11c is a canonical dendritic cell (DC) marker with poorly defined functions in the immune system. Here, we found that blocking CD11c on human peripheral blood mononuclear cell‐derived DCs (MoDCs) inhibited the proliferation of CD4⁺ T cells and the differentiation into IFN‐γ‐producing T helper 1 (Th1) cells, which were critical in acute graft‐versus‐host disease (aGVHD) pathogenesis. Using allogeneic bone marrow transplantation (allo‐BMT) murine models, we consistently found that CD11c‐deficient recipient mice had alleviated aGVHD symptoms for the decreased IFN‐γ‐expressing CD4⁺ Th1 cells and CD8⁺ T cells. Transcriptional analysis showed that CD11c participated in several immune regulation functions including maintaining antigen presentation of APCs. CD11c‐deficient bone marrow‐derived DCs (BMDCs) impaired the antigen presentation function in coculture assay. Mechanistically, CD11c interacted with MHCII and Hsp90 and participated in the phosphorylation of Akt and Erk1/2 in DCs after multiple inflammatory stimulations. Therefore, CD11c played crucial roles in triggering aGVHD and might serve as a potential target for the prevention and treatment of aGVHD.

Effects of three different mannans on obesity and gut microbiota in high-fat diet-fed C57BL/6J mice

To compare the effects of three mannans, Konjac glucomannan (KGM), guar gum (GG) and locust bean gum (LBG), on obesity and obesity-related metabolic disorders in mice fed with high-fat diet (HFD), and to investigate the potential modulation of gut microbiota, we performed a 14 week study on C57BL/6J mice fed a HFD with/without mannan supplementation. The results showed that supplementing 8% KGM, GG, and LBG to a HFD dramatically reduced the body weight gain and adipose accumulation, attenuated liver injury, and antagonized glycolipid metabolism and inflammation-related parameters of HFD-fed mice in different degrees. However, only LBG had such roles when the supplement dose was reduced to 2%. In addition, it was found that LBG required more time to exert its impacts on weight control and lipid metabolism. Furthermore, 16S rRNA gene sequencing of gut microbiota indicated that mannans with different structures and supplement doses affected the overall structure of the gut microbiota to a varying extent and specifically changed the abundance of some OTUs. Moreover, several OTUs belonging to the genera Muribaculum, Staphylococcus, [Eubacterium] fissicatena group, and Christensenella had a high correlation with obesity and obesity-related metabolic disorders of the host. In summary, all the three mannans had the potential to be used as alternative dietary supplements or functional foods to prevent obesity and obesity-related metabolic disorders induced by a HFD, but the effects of the dose and time varied, and the functions of the mannans were associated with their ability to regulate the gut microbiota.

Ceramide kinase regulates TNF-α-induced immune responses in human monocytic cells

Ceramide kinase (CERK) phosphorylates ceramide to produce ceramide-1-phosphate (C1P), which is involved in the development of metabolic inflammation. TNF-α modulates inflammatory responses in monocytes associated with various inflammatory disorders; however, the underlying mechanisms remain not fully understood. Here, we investigated the role of CERK in TNF-α-induced inflammatory responses in monocytes. Our results show that disruption of CERK activity in monocytes, either by chemical inhibitor NVP-231 or by small interfering RNA (siRNA), results in the defective expression of inflammatory markers including CD11c, CD11b and HLA-DR in response to TNF-α. Our data show that TNF-α upregulates ceramide phosphorylation. Inhibition of CERK in monocytes significantly reduced the secretion of IL-1β and MCP-1. Similar results were observed in CERK-downregulated cells. TNF-α-induced phosphorylation of JNK, p38 and NF-κB was reduced by inhibition of CERK. Additionally, NF-κB/AP-1 activity was suppressed by the inhibition of CERK. Clinically, obese individuals had higher levels of CERK expression in PBMCs compared to lean individuals, which correlated with their TNF-α levels. Taken together, these results suggest that CERK plays a key role in regulating inflammatory responses in human monocytes during TNF-α stimulation. CERK may be a relevant target for developing novel therapies for chronic inflammatory diseases.

Deficiency of Stat1 in CD11c+ Cells Alters Adipose Tissue Inflammation and Improves Metabolic Dysfunctions in Mice Fed a High-Fat Diet

CD11c⁺ macrophages/dendritic cells (MDCs) are increased and display the classically activated M1-like phenotype in obese adipose tissue (AT) and may contribute to AT inflammation and insulin resistance. Stat1 is a key transcription factor for MDC polarization into the M1-like phenotype. Here, we examined the role of Stat1 in obesity-induced AT MDC polarization and inflammation and insulin resistance using mice with specific knockout of Stat1 in MDCs (cKO). Stat1 was upregulated and phosphorylated, indicating activation, early and persistently in AT and AT MDCs of wild-type mice fed a high-fat diet (HFD). Compared with littermate controls, cKO mice fed an HFD (16 weeks) had reductions in MDC (mainly CD11c⁺ macrophage) M1-like polarization and interferon-γ-expressing T-helper type 1 (Th1) cells but increases in interleukin 5-expressing Th2 cells and eosinophils in perigonadal and inguinal AT, and enhanced inguinal AT browning, with increased energy expenditure. cKO mice compared with controls also had significant reductions in triglyceride content in the liver and skeletal muscle and exhibited improved insulin sensitivity and glucose tolerance. Taken together, our results demonstrate that Stat1 in MDCs plays an important role in obesity-induced MDC M1-like polarization and AT inflammation and contributes to insulin resistance and metabolic dysfunctions in obese mice.

Nanocarriers targeting adipose macrophages increase glucocorticoid anti-inflammatory potency to ameliorate metabolic dysfunction

Obesity is associated with systemic inflammation due to macrophage accumulation in adipose tissue (AT). AT macrophages are, therefore, a target for therapeutics to modulate inflammation and prevent comorbidities. Because inflammatory processes have pleiotropic effects throughout the body and are intertwined with metabolic axes, systemic anti-inflammatory therapies are often harmful. We report that targeting AT macrophages using dextran nanocarriers radically alters the pharmacology of anti-inflammatory glucocorticoids, uncoupling the metabolic axis in obese mice. Following a single treatment, expression of inflammatory mediators and markers of inflammatory macrophages decreased with a nearly 20-fold higher potency compared with free drug. As a result, long-term treatment resulted in potent fat mobilization, AT reduction, weight loss, improved glucose tolerance, and altered AT gene expression profiles that led to elevated liver stress. Two weeks after treatment ceased, gene expression of inflammatory mediators in AT remained lower than obese controls, while gene expression related to metabolic function improved. These data demonstrate that nanocarriers show potential for amelioration of obesity-related AT inflammation and metabolic dysfunction, highlighting an important opportunity for nanomedicine to impact chronic metabolic disorders with complex and poorly understood etiology.

High-Fat Diet and Feeding Regime Impairs Number, Phenotype, and Cytotoxicity of Natural Killer Cells in C57BL/6 Mice

Overweight and obesity are major public health challenges worldwide. Obesity is associated with a higher risk for the development of several cancer types, but specific mechanisms underlying the link of obesity and cancer are still unclear. Natural killer (NK) cells are circulating lymphoid cells promoting the elimination of virus-infected and tumor cells. Previous investigations demonstrated conflicting results concerning the influence of obesity on functional NK cell parameters in small animal models. The aim of the present study was to clarify potential obesity-associated alterations of murine NK cells in vivo, implementing different feeding regimes. Therefore, C57BL/6 mice were fed a normal-fat diet (NFD) or high-fat diet (HFD) under restrictive and ad libitum feeding regimes. Results showed diet and feeding-regime dependent differences in body weight, visceral fat mass and plasma cytokine concentrations. Flow cytometry analyses demonstrated significant changes in total cell counts as well as frequencies of immune cell populations in peripheral blood comparing mice fed NFD or HFD in an ad libitum or restrictive manner. Mice fed the HFD showed significantly decreased frequencies of total NK cells and the mature CD11b⁺CD27⁺ NK cell subset compared to mice fed the NFD. Feeding HFD resulted in significant changes in the expression of the maturation markers KLRG1 and CD127 in NK cells. Furthermore, real-time PCR analyses of NK-cell related functional parameters in adipose tissue revealed significant diet and feeding-regime dependent differences. Most notable, real-time cytotoxicity assays demonstrated an impaired cytolytic activity of splenic NK cells toward murine colon cancer cells in HFD-fed mice compared to NFD-fed mice. In conclusion, our data demonstrate that feeding a high-fat diet influences the frequency, phenotype and function of NK cells in C57BL/6 mice. Interestingly, restricted feeding of HFD compared to ad libitum feeding resulted in a partial prevention of the obesity-associated alterations on immune cells and especially on NK cells, nicely fitting with the current concept of an advantage for interval fasting for improved health.

Corneal dysfunction precedes the onset of hyperglycemia in a mouse model of diet-induced obesity

PURPOSE

The purpose of this study was to use a mouse model of diet-induced obesity to determine if corneal dysfunction begins prior to the onset of sustained hyperglycemia and if the dysfunction is ameliorated by diet reversal.

METHODS

Six-week-old male C57BL/6 mice were fed a high fat diet (HFD) or a normal diet (ND) for 5-15 weeks. Diet reversal (DiR) mice were fed a HFD for 5 weeks, followed by a ND for 5 or 10 weeks. Corneal sensitivity was determined using aesthesiometry. Corneal cytokine expression was analyzed using a 32-plex Luminex assay. Excised corneas were prepared for immunofluorescence microscopy to evaluate diet-induced changes and wound healing. For wounding studies, mice were fed a HFD or a ND for 10 days prior to receiving a central 2mm corneal abrasion.

RESULTS

After 10 days of HFD consumption, corneal sensitivity declined. By 10 weeks, expression of corneal inflammatory mediators increased and nerve density declined. While diet reversal restored nerve density and sensitivity, the corneas remained in a heightened inflammatory state. After 10 days on the HFD, corneal circadian rhythms (limbal neutrophil accumulation, epithelial cell division and Rev-erbα expression) were blunted. Similarly, leukocyte recruitment after wounding was dysregulated and accompanied by delays in wound closure and nerve recovery.

CONCLUSION

In the mouse, obesogenic diet consumption results in corneal dysfunction that precedes the onset of sustained hyperglycemia. Diet reversal only partially ameliorated this dysfunction, suggesting a HFD diet may have a lasting negative impact on corneal health that is resistant to dietary therapeutic intervention.

Immunogenetics of Atherosclerosis-Link between Lipids, Immunity, and Genes

PURPOSE OF REVIEW

Atherosclerosis is a complex disease process with lipid as a traditional modifiable risk factor and therapeutic target in treating atherosclerotic cardiovascular disease (ACVD). Recent evidence indicates that genetic influence and host immune response also are vital in this process. How these elements interact and modify each other and if immune response may emerge as a novel modifiable target remain poorly understood.

RECENT FINDINGS

Numerous preclinical studies have clearly demonstrated that hypercholesterolemia is essential for atherogenesis, but genetic variations and host immune-inflammatory responses can modulate the pro-atherogenic effect of elevated LDL-C. Clinical studies also suggest that a similar paradigm may also be operational in atherogenesis in humans. More importantly each element modifies the biological behavior of the other two elements, forming a triangular relationship among the three. Modulating any one of them will have downstream impact on atherosclerosis. This brief review summarizes the relationship among lipids, genes, and immunity in atherogenesis and presents evidence to show how these elements affect each other. Modulation of immune response, though in its infancy, has a potential to emerge as a novel clinical strategy in treating ACVD.

Maternal Obesity and the Uterine Immune Cell Landscape: The Shaping Role of Inflammation

Inflammation is often equated to the physiological response to injury or infection. Inflammatory responses defined by cytokine storms control cellular mechanisms that can either resolve quickly (i.e., acute inflammation) or remain prolonged and unabated (i.e., chronic inflammation). Perhaps less well-appreciated is the importance of inflammatory processes central to healthy pregnancy, including implantation, early stages of placentation, and parturition. Pregnancy juxtaposed with disease can lead to the perpetuation of aberrant inflammation that likely contributes to or potentiates maternal morbidity and poor fetal outcome. Maternal obesity, a prevalent condition within women of reproductive age, associates with increased risk of developing multiple pregnancy disorders. Importantly, chronic low-grade inflammation is thought to underlie the development of obesity-related obstetric and perinatal complications. While diverse subsets of uterine immune cells play central roles in initiating and maintaining healthy pregnancy, uterine leukocyte dysfunction as a result of maternal obesity may underpin the development of pregnancy disorders. In this review we discuss the current knowledge related to the impact of maternal obesity and obesity-associated inflammation on uterine immune cell function, utero-placental establishment, and pregnancy health.

Metabolic Inflammation and Insulin Resistance in Obesity

Obesity is becoming an epidemic in the United States and worldwide and increases risk for many diseases, particularly insulin resistance, type 2 diabetes mellitus, and cardiovascular disease. The mechanisms linking obesity with these diseases remain incompletely understood. Over the past 2 to 3 decades, it has been recognized that in obesity, inflammation, with increased accumulation and inflammatory polarization of immune cells, takes place in various tissues, including adipose tissue, skeletal muscle, liver, gut, pancreatic islet, and brain and may contribute to obesity-linked metabolic dysfunctions, leading to insulin resistance and type 2 diabetes mellitus. Therapies targeting inflammation have shed light on certain obesity-linked diseases, including type 2 diabetes mellitus and atherosclerotic cardiovascular disease, but remain to be tested further and confirmed in clinical trials. This review focuses on inflammation in adipose tissue and its potential role in insulin resistance associated with obesity.

Urtica dioica Whole Vegetable as a Functional Food Targeting Fat Accumulation and Insulin Resistance-a Preliminary Study in a Mouse Pre-Diabetic Model

The shoot of Urtica dioica is used in several cultures as a vegetable or herb. However, not much has been studied about the potential of this plant when consumed as a whole food/vegetable rather than an extract for dietary supplements. In a 12-week dietary intervention study, we tested the effect of U. dioica vegetable on high fat diet induced obesity and insulin resistance in C57BL/6J mice. Mice were fed ad libitum with isocaloric diets containing 10% fat or 45% fat with or without U. dioica. The diet supplemented with U. dioica attenuated high fat diet induced weight gain (p < 0.005; n = 9), fat accumulation in adipose tissue (p < 0.005; n = 9), and whole-body insulin resistance (HOMA-IR index) (p < 0.001; n = 9). Analysis of gene expression in skeletal muscle showed no effect on the constituents of the insulin signaling pathway (AKT, IRS proteins, PI3K, GLUT4, and insulin receptor). Notable genes that impact lipid or glucose metabolism and whose expression was changed by U. dioica include fasting induced adipocyte factor (FIAF) in adipose and skeletal muscle, peroxisome proliferator-activated receptor-α (Ppar-α) and forkhead box protein (FOXO1) in muscle and liver, and Carnitine palmitoyltransferase I (Cpt1) in liver (p < 0.01). We conclude that U. dioica vegetable protects against diet induced obesity through mechanisms involving lipid accumulation and glucose metabolism in skeletal muscle, liver, and adipose tissue.

Hematopoiesis and Cardiovascular Disease

A central feature of atherosclerosis, the most prevalent chronic vascular disease and root cause of myocardial infarction and stroke, is leukocyte accumulation in the arterial wall. These crucial immune cells are produced in specialized niches in the bone marrow, where a complex cell network orchestrates their production and release. A growing body of clinical studies has documented a correlation between leukocyte numbers and cardiovascular disease risk. Understanding how leukocytes are produced and how they contribute to atherosclerosis and its complications is, therefore, critical to understanding and treating the disease. In this review, we focus on the key cells and products that regulate hematopoiesis under homeostatic conditions, during atherosclerosis and after myocardial infarction.

Deep Phenotyping by Mass Cytometry and Single-Cell RNA-Sequencing Reveals LYN-Regulated Signaling Profiles Underlying Monocyte Subset Heterogeneity and Lifespan

RATIONALE

Monocytes are key effectors of the mononuclear phagocyte system, playing critical roles in regulating tissue homeostasis and coordinating inflammatory reactions, including those involved in chronic inflammatory diseases such as atherosclerosis. Monocytes have traditionally been divided into 2 major subsets termed conventional monocytes and patrolling monocytes (pMo) but recent systems immunology approaches have identified marked heterogeneity within these cells, and much of what regulates monocyte population homeostasis remains unknown. We and others have previously identified LYN tyrosine kinase as a key negative regulator of myeloid cell biology; however, LYN's role in regulating specific monocyte subset homeostasis has not been investigated.

OBJECTIVE

We sought to comprehensively profile monocytes to elucidate the underlying heterogeneity within monocytes and dissect how Lyn deficiency affects monocyte subset composition, signaling, and gene expression. We further tested the biological significance of these findings in a model of atherosclerosis.

METHODS AND RESULTS

Mass cytometric analysis of monocyte subsets and signaling pathway activation patterns in conventional monocytes and pMos revealed distinct baseline signaling profiles and far greater heterogeneity than previously described. Lyn deficiency led to a selective expansion of pMos and alterations in specific signaling pathways within these cells, revealing a critical role for LYN in pMo physiology. LYN's role in regulating pMos was cell-intrinsic and correlated with an increased circulating half-life of Lyn-deficient pMos. Furthermore, single-cell RNA sequencing revealed marked perturbations in the gene expression profiles of Lyn^-/- monocytes with upregulation of genes involved in pMo development, survival, and function. Lyn deficiency also led to a significant increase in aorta-associated pMos and protected Ldlr^-/- mice from high-fat diet-induced atherosclerosis.

CONCLUSIONS

Together our data identify LYN as a key regulator of pMo development and a potential therapeutic target in inflammatory diseases regulated by pMos.

Transcriptome analysis reveals the difference between "healthy" and "common" aging and their connection with age-related diseases

A key goal of aging research was to understand mechanisms underlying healthy aging and develop methods to promote the human healthspan. One approach is to identify gene regulations unique to healthy aging compared with aging in the general population (i.e., "common" aging). Here, we leveraged Genotype-Tissue Expression (GTEx) project data to investigate "healthy" and "common" aging gene expression regulations at a tissue level in humans and their interconnection with diseases. Using GTEx donors' disease annotations, we defined a "healthy" aging cohort for each tissue. We then compared the age-associated genes derived from this cohort with age-associated genes from the "common" aging cohort which included all GTEx donors; we also compared the "healthy" and "common" aging gene expressions with various disease-associated gene expressions to elucidate the relationships among "healthy," "common" aging and disease. Our analyses showed that 1. GTEx "healthy" and "common" aging shared a large number of gene regulations; 2. Despite the substantial commonality, "healthy" and "common" aging genes also showed distinct function enrichment, and "common" aging genes had a higher enrichment for disease genes; 3. Disease-associated gene regulations were overall different from aging gene regulations. However, for genes regulated by both, their regulation directions were largely consistent, implying some aging processes could increase the susceptibility to disease development; and 4. Possible protective mechanisms were associated with some "healthy" aging gene regulations. In summary, our work highlights several unique features of GTEx "healthy" aging program. This new knowledge could potentially be used to develop interventions to promote the human healthspan.

Deficiency in AIM2 induces inflammation and adipogenesis in white adipose tissue leading to obesity and insulin resistance

AIMS/HYPOTHESIS

Absent in melanoma 2 (AIM2) is a cytosolic sensor for double-stranded DNA and a tumour suppressor. Binding of double-stranded DNA to AIM2 forms the AIM2 inflammasome, leading to activation of caspase-1 and production of IL-1β and IL-18. Although inflammasome-independent effects of AIM2 have been reported, its role in energy metabolism is unknown. We aimed to evaluate the effect of AIM2 in energy metabolism and glucose homeostasis.

METHODS

Male and female whole body Aim2 knockout (Aim2^-/-) mice were used in the current study. Body weight, food intake, body composition, energy expenditure, fasting blood glucose levels, GTT and body temperature were measured at indicated time points. RNA sequencing was carried out on gonadal white adipose tissue (gWAT) in 14-month-old female mice. mRNA and protein levels in tissues were analysed by quantitative real-time PCR and immunoblot. Immune cell infiltration in gWAT was examined by flow cytometry. Stromal vascular fractions isolated from gWAT were used to investigate adipocyte differentiation.

RESULTS

Male and female Aim2^-/- mice were obese compared with wild-type controls from 7 weeks of age until 51 weeks of age, with increased adiposity in both subcutaneous and visceral fat depots. While there were no differences in food intake, Aim2^-/- mice demonstrated decreased energy expenditure and impaired brown adipose tissue function compared with wild-type controls. Fasting glucose and insulin levels were elevated, and Aim2^-/- mice were glucose intolerant on intraperitoneal GTT. RNA sequencing revealed marked upregulation of the IFN-inducible gene Ifi202b, which encodes protein 202 (p202) and elevated inflammatory signalling in gWAT of Aim2^-/- mice. Increased infiltration of total and Ly6C^low monocytes was noted at 8 weeks of age in gWAT, before the onset of obesity and insulin resistance. Ifi202b knockdown blocked adipogenesis in stromal vascular fractions and reduced inflammation in bone marrow-derived macrophages, demonstrating a key role of p202 in mediating the increased adipogenesis and inflammation in Aim2^-/- mice.

CONCLUSIONS/INTERPRETATION

These results demonstrate a fundamental role for AIM2 in energy metabolism, inflammation and insulin resistance. Our studies establish a novel link between the innate immunity proteins, AIM2 and p202, and metabolism.

Clcn3 deficiency ameliorates high-fat diet-induced obesity and adipose tissue macrophage inflammation in mice

Obesity induces accumulation of adipose tissue macrophages (ATMs) and ATM-driven inflammatory responses that promote the development of glucose and lipid metabolism disorders. ClC-3 chloride channel/antiporter, encoded by the Clcn3, is critical for some basic cellular functions. Our previous work has shown significant alleviation of type 2 diabetes in Clcn3 knockout (Clcn3^−/−) mice. In the present study we investigated the role of Clcn3 in high-fat diet (HFD)-induced obesity and ATM inflammation. To establish the mouse obesity model, both Clcn3^−/− mice and wild-type mice were fed a HFD for 4 or 16 weeks. The metabolic parameters were assessed and the abdominal total adipose tissue was scanned using computed tomography. Their epididymal fat pad tissue and adipose tissue stromal vascular fraction (SVF) cells were isolated for analyses. We found that the HFD-fed Clcn3^−/− mice displayed a significant decrease in obesity-induced body weight gain and abdominal visceral fat accumulation as well as an improvement of glucose and lipid metabolism as compared with HFD-fed wild-type mice. Furthermore, the Clcn3 deficiency significantly attenuated HFD-induced ATM accumulation, HFD-increased F4/80⁺ CD11c⁺ CD206⁻ SVF cells as well as HFD-activated TLR-4/NF-κB signaling in epididymal fat tissue. In cultured human THP-1 macrophages, adenovirus-mediated transfer of Clcn3 specific shRNA inhibited, whereas adenovirus-mediated cDNA overexpression of Clcn3 enhanced lipopolysaccharide-induced activation of NF-κB and TLR-4. These results demonstrate a novel role for Clcn3 in HFD-induced obesity and ATM inflammation.

A Single 48 mg Sucralose Sip Unbalances Monocyte Subpopulations and Stimulates Insulin Secretion in Healthy Young Adults

Sucralose is a noncaloric artificial sweetener that is widely consumed worldwide and has been associated with alteration in glucose and insulin homeostasis. Unbalance in monocyte subpopulations expressing CD11c and CD206 hallmarks metabolic dysfunction but has not yet been studied in response to sucralose. Our goal was to examine the effect of a single sucralose sip on serum insulin and blood glucose and the percentages of classical, intermediate, and nonclassical monocytes in healthy young adults subjected to an oral glucose tolerance test (OGTT). This study was a randomized, placebo-controlled clinical trial. Volunteers randomly received 60 mL water as placebo (n = 20) or 48 mg sucralose dissolved in 60 mL water (n = 25), fifteen minutes prior to an OGTT. Blood samples were individually drawn every 15 minutes for 180 minutes for quantifying glucose and insulin concentrations. Monocyte subsets expressing CD11c and CD206 were measured at -15 and 180 minutes by flow cytometry. As compared to controls, volunteers receiving sucralose exhibited significant increases in serum insulin at 30, 45, and 180 minutes, whereas blood glucose values showed no significant differences. Sucralose consumption caused a significant 7% increase in classical monocytes and 63% decrease in nonclassical monocytes with respect to placebo controls. Pearson's correlation models revealed a strong association of insulin with sucralose-induced monocyte subpopulation unbalance whereas glucose values did not show significant correlations. Sucralose ingestion decreased CD11c expression in all monocyte subsets and reduced CD206 expression in nonclassical monocytes suggesting that sucralose does not only unbalance monocyte subpopulations but also alter their expression pattern of cell surface molecules. This work demonstrates for the first time that a 48 mg sucralose sip increases serum insulin and unbalances monocyte subpopulations expressing CD11c and CD206 in noninsulin-resistant healthy young adults subjected to an OGTT. The apparently innocuous consumption of sucralose should be reexamined in light of these results.

T Cells in Adipose Tissue in Aging

Similar to obesity, aging is associated with visceral adiposity and insulin resistance. Inflammation in adipose tissue, mainly evidenced by increased accumulation and proinflammatory polarization of T cells and macrophages, has been well-documented in obesity and may contribute to the associated metabolic dysfunctions including insulin resistance. Studies show that increased inflammation, including inflammation in adipose tissue, also occurs in aging, so-called "inflamm-aging." Aging-associated inflammation in adipose tissue has some similarities but also differences compared to obesity-related inflammation. In particular, conventional T cells are elevated in adipose tissue in both obesity and aging and have been implicated in metabolic functions in obesity. However, the changes and also possibly functions of regulatory T cells (Treg) in adipose tissue are different in aging and obesity. In this review, we will summarize recent advances in research on the changes of these immune cells in adipose tissue with aging and obesity and discuss their possible contributions to metabolism and the potential of these immune cells as novel therapeutic targets for prevention and treatment of metabolic diseases associated with aging or obesity.

Association between Trp48Arg polymorphism of the CD11c gene and risk for obesity among Iranian population

BACKGROUND

Despite assessing the expression of CD11c gene in macrophages in adipose tissues and suggesting association between the gene expressions and predisposing to obesity, the relationship of the changes in CD11c gene and its variants with obesity has not been exclusively evaluated. The present study aimed to assess the relationship between rs2230424 gene polymorphism leading a single amino acid Arginine 48 to Tryptophan interchange in CD11c gene protein chain and obesity in a sample of Iranian population.

METHODS

This case-control association study was performed on 247 subjects including obese individuals and a sex- and age-matched healthy non-obese individuals. After DNA extraction, the DNA sequence containing the relevant polymorphic site was amplified by polymerase chain reaction (PCR). Determining different genotypic patterns of the SNP was carried out by restriction fragment length polymorphism (RFLP) analysis. To final draft the suspected genotypes of the SNP, DNA sequencing was performed.

RESULTS

The frequency of wild genotype (TT) of Trp48Arg polymorphism of the CD11c gene in obese and non-obese groups was 97.9% and 94.6% and the frequency of heterozygous genotype (TC) was 2.1% and 5.4%, respectively with no significant difference (p = 0.230,). None of the participants had mutant genotypic pattern of the polymorphism. There was no association of the genotypic pattern of Trp48Arg polymorphism with different underlying risk factors as well as mean laboratory parameters.

CONCLUSION

The presence of Trp48Arg polymorphism of the CD11c gene is not associated with increased risk for obesity among Iranian population.

T Cells in Adipose Tissue: Critical Players in Immunometabolism

Adipose tissue performs immunoregulatory functions in addition to fat storage. Various T cells in different fat depots either help maintain metabolic homeostasis under healthy conditions or contribute to metabolic disorders in pathological conditions such as obesity, diabetes, cardiovascular diseases, or even cancer. These T cells play critical roles in immunometabolism, which refers to the intersection of immunity and metabolism. Numerous studies have examined the presence and changes of different T cell subsets, including helper T cells, regulatory T cells, cytotoxic T cells, and natural killer T cells, in adipose depots in health and diseases. In this review, we will discuss the adipose tissue niches that influence the patterns and functions of T cell subsets and in turn the impact of these T cells on cell- or body-based immunometabolism accounting for health and obesity.

Properties and functions of adipose tissue macrophages in obesity

The expansion of adipose tissue (AT) in obesity is accompanied by the accumulation of immune cells that contribute to a state of low-grade, chronic inflammation and dysregulated metabolism. Adipose tissue macrophages (ATMs) represent the most abundant class of leukocytes in AT and are involved in the regulation of several regulatory physiological processes, such as tissue remodeling and insulin sensitivity. With progressive obesity, ATMs are key mediators of meta-inflammation, insulin resistance and impairment of adipocyte function. While macrophage recruitment from blood monocytes is a critical component of the generation of AT inflammation, new studies have revealed a role for ATM proliferation in the early stages of obesity and in sustaining AT inflammation. In addition, studies have revealed a more complex range of macrophage activation states than the previous M1/M2 model, and the existence of different macrophage profiles between human and animal models. This review will summarize the current understanding of the regulatory mechanisms of ATM function in relation to obesity, type 2 diabetes, depot of origin, and to other leukocytes such as AT dendritic cells, with hopes of emphasizing the regulatory nodes that can potentially be targeted to prevent and treat obesity-related metabolic disorders.

Murine models of sleep apnea: functional implications of altered macrophage polarity and epigenetic modifications in adipose and vascular tissues

Obstructive sleep apnea (OSA) is a highly prevalent disease across the lifespan, is characterized by chronic intermittent hypoxia and sleep fragmentation, and has been independently associated with substantial cardiometabolic morbidity. However, the reversibility of end-organ morbidity with treatment is not always apparent, suggesting that both tissue remodeling and epigenetic mechanisms may be operationally involved. Here, we review the cumulative evidence focused around murine models of OSA to illustrate the temporal dependencies of cardiometabolic dysfunction and its reversibility, and more particularly to discuss the critical contributions of tissue macrophages to adipose tissue insulin resistance and vascular atherogenesis. In addition, we describe initial findings potentially implicating epigenetic alterations in both the emergence of the cardiometabolic morbidity of OSA, and in its reversibility with treatment. We anticipate that improved understanding of macrophage biology and epigenetics in the context of intermittent hypoxia and sleep fragmentation will lead to discovery of novel therapeutic targets and improved cardiovascular and metabolic outcomes in OSA.

Impaired insulin signaling upon loss of ovarian function is associated with a reduction of tristetraprolin and an increased stabilization of chemokine in adipose tissue

Loss of ovarian function can activate inflammation and lead to insulin resistance (IR). IR is also a core feature of obesity and obesity-associated metabolic dysfunction. Tristetraprolin/zinc finger protein 36 (TTP) interferes with TNF-α production by destabilizing TNF-α mRNA, and mice deficient in TTP develop a complex syndrome of inflammatory disease (Carballo et al., 1998; Taylor et al., 1999). We hypothesized that ovariectomy (OVX) might also prime inflammation by reducing tristetraprolin/zinc finger protein 36 (TTP) levels. We used a mouse OVX model to study impaired insulin signaling due to loss of ovarian function by evaluating Akt activity upon insulin stimulus. Impaired insulin signaling was initially detected in adipose tissue (AT) at 4 weeks after OVX, and then spread to liver and muscle, finally resulting in systemic IR at 12 weeks after OVX. OVX decreased TTP protein levels and increased adipocyte size, oxidative stress, chemokine expression and fat mass in AT by 4 weeks after surgery. TTP deficiency due to TTP gene deletion induced aberrant insulin signaling and increased chemokine expression and macrophage numbers in AT but did not increase adipocyte size, oxidative stress, or fat mass, suggesting that it promotes insulin signaling by decreasing AT inflammation independent of oxidative stress and adiposity. OVX, like TTP deficiency, increased the stability of chemokine transcripts as assessed from their half-lives. Our data indicate that the impaired insulin signaling resulting from OVX is due to an OVX-induced reduction of TTP and the resulting stabilization of inflammatory chemokines.

Protective effects of polyphenol-rich infusions from carob (Ceratonia siliqua) leaves and cladodes of Opuntia ficus-indica against inflammation associated with diet-induced obesity and DSS-induced colitis in Swiss mice

In the present study, we have investigated the effects of polyphenol-rich infusions from carob leaves and OFI-cladodes on inflammation associated with obesity and dextran sulfate sodium (DSS)-induced ulcerative colitis in Swiss mice. In vitro studies revealed that aqueous extracts of carob leaves and OFI-cladodes exhibited anti-inflammatory properties marked by the inhibition of IL-6, TNF-α and nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells concomitant with NF-κβ nucleus translocation inhibition. For in vivo investigations, Swiss male mice were subjected to control or high fat diet (HFD). At the 8th week after the start of study, animals received or not 1% infusion of either carob leaves or OFI-cladode for 4 weeks and were subjected to 2% DSS administration in drinking water over last 7 days. After sacrifice, pro-inflammatory cytokines levels in plasma and their mRNA expression in different organs were determined. Results showed that carob leaf and OFI-cladode infusions reduced inflammation severity associated with HFD-induced obesity and DSS-induced acute colitis indicated by decrease in pro-inflammatory cytokines expression (as such TNF-α, IL1b and IL-6) in colon, adipose tissue and spleen. In addition, plasma levels of IL-6 and TNF-α were also curtailed in response to infusions treatment. Thus, carob leaf and OFI-cladode infusions prevented intestinal permeability through the restoration of tight junction proteins (Zo1, occludins) and immune homeostasis. Hence, the anti-inflammatory effect of carob leaves and OFI-cladodes could be attributed to their polyphenols which might alleviate inflammation severity associated with obesity and colitis.

Integrated Immunomodulatory Mechanisms through which Long-Chain n-3 Polyunsaturated Fatty Acids Attenuate Obese Adipose Tissue Dysfunction

Obesity is a global health concern with rising prevalence that increases the risk of developing other chronic diseases. A causal link connecting overnutrition, the development of obesity and obesity-associated co-morbidities is visceral adipose tissue (AT) dysfunction, characterized by changes in the cellularity of various immune cell populations, altered production of inflammatory adipokines that sustain a chronic state of low-grade inflammation and, ultimately, dysregulated AT metabolic function. Therefore, dietary intervention strategies aimed to halt the progression of obese AT dysfunction through any of the aforementioned processes represent an important active area of research. In this connection, fish oil-derived dietary long-chain n-3 polyunsaturated fatty acids (PUFA) in the form of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been demonstrated to attenuate obese AT dysfunction through multiple mechanisms, ultimately affecting AT immune cellularity and function, adipokine production, and metabolic signaling pathways, all of which will be discussed herein.

Effects of n-3 fatty acid treatment on monocyte phenotypes in humans with hypertriglyceridemia

BACKGROUND

Hypertriglyceridemia increases risk for atherosclerotic cardiovascular disease and may contribute to atherosclerosis by changing circulating monocyte phenotypes. High-dose n-3 polyunsaturated fatty acids reduce blood triglyceride levels. Effects of triglyceride-lowering therapy on monocyte phenotypes are not well known.

OBJECTIVE

We examined effects of n-3 polyunsaturated fatty acid treatments (eicosapentaenoic acid [EPA] plus docosapentaenoic acid [MAT9001] vs EPA ethyl esters [EPA-EE]) on monocyte phenotypes in individuals with hypertriglyceridemia.

METHODS

Individuals with triglycerides 200 to 400 mg/dL were recruited. Subjects received 2 treatments in randomized order for 14 days each: MAT9001 and EPA-EE, at 4 g/d. At 2 days before the start of, and on the last day of, each treatment, nile red staining for lipids and phenotypes of each monocyte subset were examined by flow cytometry after an overnight fast and postprandially after a high-fat meal.

RESULTS

Treatment with MAT9001 or EPA-EE reduced fasting triglyceride levels and decreased proportions of intermediate monocytes. Only MAT9001 decreased postprandial blood triglyceride levels, lowered fasting nile red levels, indicating less lipid in classical and intermediate monocytes, and reduced postprandial CD11c levels on nonclassical monocytes. MAT9001 and EPA-EE each reduced fasting and postprandial CD11c and CD36 levels on classical and intermediate monocytes and postprandial CCR5 levels on intermediate and nonclassical monocytes, with no significant differences between the 2 treatments.

CONCLUSIONS

Treatment with MAT9001 in individuals with hypertriglyceridemia reduced fasting nile red staining for lipids in classical and intermediate monocytes. MAT9001 and EPA-EE each improved fasting and postprandial monocyte phenotypes, which could potentially help to protect against atherosclerosis.

OX40 promotes obesity-induced adipose inflammation and insulin resistance

Adaptive immunity plays a critical role in IR and T2DM development; however, the biological mechanisms linking T cell costimulation and glucose metabolism have not been fully elucidated. In this study, we demonstrated that the costimulatory molecule OX40 controls T cell activation and IR development. Inflammatory cell accumulation and enhanced proinflammatory gene expression, as well as high OX40 expression levels on CD4+ T cells, were observed in the adipose tissues of mice with diet-induced obesity. OX40-KO mice exhibited significantly less weight gain and lower fasting glucose levels than those of WT mice, without obvious adipose tissue inflammation. The effects of OX40 on IR are mechanistically linked to the promotion of T cell activation, Th1 cell differentiation and proliferation-as well as the attenuation of Treg suppressive activity and the enhancement of proinflammatory cytokine production-in adipose tissues. Furthermore, OX40 expression on T cells was positively associated with obesity in humans, suggesting that our findings are clinically relevant. In summary, our study revealed that OX40 in CD4+ T cells is crucial for adipose tissue inflammation and IR development. Therefore, the OX40 signaling pathway may be a new target for preventing or treating obesity-related IR and T2DM.

Modulation of Gr1low monocyte subset impacts insulin sensitivity and weight gain upon high-fat diet in female mice

Background/Objectives:

Blood monocytes are expanded during obesity. However, the differential contribution of monocyte subsets in obesity-related metabolic disorders remains unknown. The aim of the study was to define the role of the Gr1^low monocyte subset upon high-fat diet (HFD).

Methods:

We used transgenic female mouse models allowing the modulation of circulating Gr1^low monocyte number (decreased number in CX3CR1^−/− mice and increased number in CD11c-hBcl2 mice) and studied obesity upon HFD.

Results:

We reported here that HFD induced monocytosis in mice, preferentially due to Gr1^low monocyte expansion, and was associated with a specific upregulation of CD11c on that subset. Using mice models with altered Gr1^low monocyte number, we found a striking correlation between Gr1^low monocytes, bodyweight (BW) and insulin resistance (RT) status. Indeed, CX3CR1^−/− female mice, with reduced Gr1^low monocytes upon HFD, showed increased RT and a pro-inflammatory profile of the adipose tissue (AT) despite a lower BW. Conversely, mice expressing the anti-apoptotic gene hBcl2 in CD11c-expressing cells have increased Gr1^low monocytes, higher insulin sensitivity upon HFD and an anti-inflammatory profile of the AT. Finally, increasing Gr1^low monocytes in Gr1^low-defective CX3CR1^−/− mice rescued BW loss in these mice.

Conclusions:

By using transgenic female mice and adoptive transfer experiments, we established the evidence for a correlation between Gr1^low monocyte subset and weight gain and RT. Hence, this specific Gr1^low monocyte subset could be used as a target for acting on AT inflammation and RT.

Diet-induced obesity causes visceral, but not subcutaneous, lymph node hyperplasia via increases in specific immune cell populations

OBJECTIVES

The spatial proximity of adipose depots to secondary lymph nodes allows a unique relation between the two systems. Obesity, predominately visceral adiposity, links to numerous diseases; hence, we postulate that secondary lymphatics within this region contributes to disease risk.

MATERIAL AND METHODS

Male C57BL/6 mice were fed standard CHOW (18% kcal fat) or Western diet (45% kcal fat) for 7 weeks. Visceral and subcutaneous lymph nodes and associated adipose depots they occupy were excised. Lymph node morphology and resident immune cell populations were characterized via histopathology, immunofluorescence and flow cytometry. Adipose tissue immune cell populations were also characterized.

RESULTS

Obesity caused lymph node expansion, increased viable cell number and deviations in immune cell populations. These alterations were exclusive to visceral lymph nodes. Notably, pro-inflammatory antigen presenting cells and regulatory T cells increased in number in the visceral lymph node. Obesity, however, reduced T regulatory cells in visceral lymph nodes. The visceral adipose depot also had greater reactivity towards HFD than subcutaneous, with a greater percent of macrophages, dendritic and CD8⁺ T cells. Immune cell number, in both the visceral and subcutaneous, however decreased as adipose depots enlarged.

CONCLUSION

Overall, HFD has a greater influence on visceral cavity than the subcutaneous. In the visceral lymph node, but not subcutaneous, HFD-induced obesity decreased cell populations that suppressed immune function while increasing those that regulate/activate immune response.

Thrombin promotes diet-induced obesity through fibrin-driven inflammation

Obesity promotes a chronic inflammatory and hypercoagulable state that drives cardiovascular disease, type 2 diabetes, fatty liver disease, and several cancers. Elevated thrombin activity underlies obesity-linked thromboembolic events, but the mechanistic links between the thrombin/fibrin(ogen) axis and obesity-associated pathologies are incompletely understood. In this work, immunohistochemical studies identified extravascular fibrin deposits within white adipose tissue and liver as distinct features of mice fed a high-fat diet (HFD) as well as obese patients. Fibγ390-396A mice carrying a mutant form of fibrinogen incapable of binding leukocyte αMβ2-integrin were protected from HFD-induced weight gain and elevated adiposity. Fibγ390-396A mice had markedly diminished systemic, adipose, and hepatic inflammation with reduced macrophage counts within white adipose tissue, as well as near-complete protection from development of fatty liver disease and glucose dysmetabolism. Homozygous thrombomodulin-mutant ThbdPro mice, which have elevated thrombin procoagulant function, gained more weight and developed exacerbated fatty liver disease when fed a HFD compared with WT mice. In contrast, treatment with dabigatran, a direct thrombin inhibitor, limited HFD-induced obesity development and suppressed progression of sequelae in mice with established obesity. Collectively, these data provide proof of concept that targeting thrombin or fibrin(ogen) may limit pathologies in obese patients.

Hepatocyte MyD88 affects bile acids, gut microbiota and metabolome contributing to regulate glucose and lipid metabolism

OBJECTIVE

To examine the role of hepatocyte myeloid differentiation primary-response gene 88 (MyD88) on glucose and lipid metabolism.

DESIGN

To study the impact of the innate immune system at the level of the hepatocyte and metabolism, we generated mice harbouring hepatocyte-specific deletion of MyD88. We investigated the impact of the deletion on metabolism by feeding mice with a normal control diet or a high-fat diet for 8 weeks. We evaluated body weight, fat mass gain (using time-domain nuclear magnetic resonance), glucose metabolism and energy homeostasis (using metabolic chambers). We performed microarrays and quantitative PCRs in the liver. In addition, we investigated the gut microbiota composition, bile acid profile and both liver and plasma metabolome. We analysed the expression pattern of genes in the liver of obese humans developing non-alcoholic steatohepatitis (NASH).

RESULTS

Hepatocyte-specific deletion of MyD88 predisposes to glucose intolerance, inflammation and hepatic insulin resistance independently of body weight and adiposity. These phenotypic differences were partially attributed to differences in gene expression, transcriptional factor activity (ie, peroxisome proliferator activator receptor-α, farnesoid X receptor (FXR), liver X receptors and STAT3) and bile acid profiles involved in glucose, lipid metabolism and inflammation. In addition to these alterations, the genetic deletion of MyD88 in hepatocytes changes the gut microbiota composition and their metabolomes, resembling those observed during diet-induced obesity. Finally, obese humans with NASH displayed a decreased expression of different cytochromes P450 involved in bioactive lipid synthesis.

CONCLUSIONS

Our study identifies a new link between innate immunity and hepatic synthesis of bile acids and bioactive lipids. This dialogue appears to be involved in the susceptibility to alterations associated with obesity such as type 2 diabetes and NASH, both in mice and humans.