T-bet+ B cells accumulate in adipose tissue and exacerbate metabolic disorder during obesity

T-bet suppresses proliferation of malignant B cells in chronic lymphocytic leukemia

ABSTRACT

The T-box transcription factor T-bet is known as a master regulator of the T-cell response but its role in malignant B cells has not been sufficiently explored. Here, we conducted single-cell resolved multi-omics analyses of malignant B cells from patients with chronic lymphocytic leukemia (CLL) and studied a CLL mouse model with a genetic knockout of Tbx21. We found that T-bet acts as a tumor suppressor in malignant B cells by decreasing their proliferation rate. NF-κB activity, induced by inflammatory signals provided by the microenvironment, triggered T-bet expression, which affected promoter-proximal and distal chromatin coaccessibility and controlled a specific gene signature by mainly suppressing transcription. Gene set enrichment analysis identified a positive regulation of interferon signaling and negative control of proliferation by T-bet. In line, we showed that T-bet represses cell cycling and is associated with longer overall survival of patients with CLL. Our study uncovered a novel tumor suppressive role of T-bet in malignant B cells via its regulation of inflammatory processes and cell cycling, which has implications for the stratification and therapy of patients with CLL. Linking T-bet activity to inflammation explains the good prognostic role of genetic alterations in the inflammatory signaling pathways in CLL.

B-cell hub genes play a cardiovascular pathogenic role of in childhood obesity and Kawasaki disease as revealed by transcriptomics-based analyses

The study aims to explore the central genes that Kawasaki disease (KD) and Obesity (OB) may jointly contribute to coronary artery disease. Investigating single-cell datasets (GSE168732 and GSE163830) from a comprehensive gene expression database, we identified characteristic immune cell subpopulations in KD and OB. B cells emerged as the common immune cell characteristic subgroup in both conditions. Subsequently, we analyzed RNA sequencing datasets (GSE18606 and GSE87493) to identify genes associated with B-cell subpopulations in KD and OB. Lastly, a genome-wide association study and Mendelian randomization were conducted to substantiate the causal impact of these core genes on myocardial infarction. Quantitative real-time PCR (qRT-PCR) to validate the expression levels of hub genes in KD and OB. The overlapping characteristic genes of B cell clusters in both KD and OB yielded 70 shared characteristic genes. PPI analysis led to the discovery of eleven key genes that significantly contribute to the crosstalk. Employing receiver operating characteristic analysis, we evaluated the specificity and sensitivity of these core genes and scored them using Cytoscape software. The inverse variance weighting analysis suggested an association between TNFRSF17 and myocardial infarction risk, with an odds ratio of 0.9995 (95% CI = 0.9990-1.0000, p = 0.049). By employing a single-cell combined transcriptome data analysis, we successfully pinpointed central genes associated with both KD and OB. The implications of these findings extend to shedding light on the increased risk of coronary artery disease resulting from the co-occurrence of OB and KD.

Circulating B Cell-Derived Small RNA Delivered by Extracellular Vesicles: A Dialogue Mechanism for Long-Range Targeted Renal Mitochondrial Injury in Obesity

The intricate processes that govern the interactions between peripatetic immune cells and distal renal injury in obesity are not fully understood. Employing transcriptomic analysis of circulating extracellular vesicles (EVs), a marked amplification of small RNA (miR-3960) is discerned within CD3-CD19+ B cells. This RNA is found to be preferentially augmented in kidney tissues, contrasting with its subdued expression in other organs. By synthesizing dual-luciferase reporter assay with co-immunoprecipitation analysis, it is pinpointed that miR-3960 specifically targets the nuclear gene TRMT5, a pivotal actor in the methylation of mitochondrial tRNA. This liaison instigates aberrations in the post-transcriptional modifications of mitochondrial tRNA, engendering deficiencies within the electron respiratory chain, primarily attributable to the diminution of the mitochondrial bioenergetic compound (NDUFA7) complex I. Such perturbations lead to a compromised mitochondrial respiratory capacity in renal tubular cells, thereby exacerbating tubular injury. In contrast, EV blockade or miR-3960 depletion markedly alleviates renal tubular injury in obesity. This investigation unveils a hitherto unexplored pathway by which obesity-induced circulating immune cells remotely manipulate mitochondrial metabolism in target organs. The strategic targeting of obese EVs or infiltrative immune cells and their specifically secreted RNAs emerges as a promising therapeutic avenue to forestall obesity-related renal afflictions.

Fat-associated lymphoid clusters: Supporting visceral adipose tissue B cell function in immunity and metabolism

It is now widely understood that visceral adipose tissue (VAT) is a highly active and dynamic organ, with many functions beyond lipid accumulation and storage. In this review, we discuss the immunological role of this tissue, underpinned by the presence of fat-associated lymphoid clusters (FALCs). FALC's distinctive structure and stromal cell composition support a very different immune cell mix to that found in classical secondary lymphoid organs, which underlies their unique functions of filtration, surveillance, innate-like immune responses, and adaptive immunity within the serous cavities. FALCs are important B cell hubs providing B1 cell-mediated frontline protection against infection and supporting B2 cell-adaptative immune responses. Beyond these beneficial immune responses orchestrated by FALCs, immune cells within VAT play important homeostatic role. Dysregulation of immune cells during obesity and aging leads to chronic pathological "metabolic inflammation", which contributes to the development of cardiometabolic diseases. Here, we examine the emerging and complex functions of B cells in VAT homeostasis and the metabolic complications of obesity, highlighting the potential role that FALCs play and emphasize the areas where further research is needed.

Therapeutic targeting of white adipose tissue metabolic dysfunction in obesity: mechanisms and opportunities

White adipose tissue is not only a highly heterogeneous organ containing various cells, such as adipocytes, adipose stem and progenitor cells, and immune cells, but also an endocrine organ that is highly important for regulating metabolic and immune homeostasis. In individuals with obesity, dynamic cellular changes in adipose tissue result in phenotypic switching and adipose tissue dysfunction, including pathological expansion, WAT fibrosis, immune cell infiltration, endoplasmic reticulum stress, and ectopic lipid accumulation, ultimately leading to chronic low-grade inflammation and insulin resistance. Recently, many distinct subpopulations of adipose tissue have been identified, providing new insights into the potential mechanisms of adipose dysfunction in individuals with obesity. Therefore, targeting white adipose tissue as a therapeutic agent for treating obesity and obesity-related metabolic diseases is of great scientific interest. Here, we provide an overview of white adipose tissue remodeling in individuals with obesity including cellular changes and discuss the underlying regulatory mechanisms of white adipose tissue metabolic dysfunction. Currently, various studies have uncovered promising targets and strategies for obesity treatment. We also outline the potential therapeutic signaling pathways of targeting adipose tissue and summarize existing therapeutic strategies for antiobesity treatment including pharmacological approaches, lifestyle interventions, and novel therapies.

Diet-induced obesity affects influenza disease severity and transmission dynamics in ferrets

Obesity, and the associated metabolic syndrome, is a risk factor for increased disease severity with a variety of infectious agents, including influenza virus. Yet, the mechanisms are only partially understood. As the number of people, particularly children, living with obesity continues to rise, it is critical to understand the role of host status on disease pathogenesis. In these studies, we use a diet-induced obese ferret model and tools to demonstrate that, like humans, obesity resulted in notable changes to the lung microenvironment, leading to increased clinical disease and viral spread to the lower respiratory tract. The decreased antiviral responses also resulted in obese animals shedding higher infectious virus for a longer period, making them more likely to transmit to contacts. These data suggest that the obese ferret model may be crucial to understanding obesity's impact on influenza disease severity and community transmission and a key tool for therapeutic and intervention development for this high-risk population.

ABCs begin with ZEB2

Age-associated B cells (ABCs) are a stable subset of memory B lymphocytes that develop during microbial infections and in autoimmune diseases. Despite growing appreciation of their phenotypic and functional characteristics, the transcriptional networks involved in ABC fate commitment and maintenance have remained elusive. In their recent publication, Dai et al. tackle this problem, leveraging both mouse models and human diseases to reveal zinc finger E-box-binding homeobox 2 (ZEB2) as a key transcriptional regulator of ABC lineage specification. In aggregate, their results show that ZEB2, a member of the zinc finger E homeobox binding family, promotes ABC differentiation by repressing alternative differentiative fates and targeting genes important for ABC character and function. Moreover, their results strengthen the case for causal links between ABC fate and function in autoimmune pathologies.

Age-associated accumulation of B cells promotes macrophage inflammation and inhibits lipolysis in adipose tissue during sepsis

Non-canonical lipolysis induced by inflammatory cytokines or Toll-like receptor ligands is required for the regulation of inflammation during endotoxemia and sepsis. Canonical lipolysis induced by catecholamines declines during aging due to factors including an expansion of lymphocytes, pro-inflammatory macrophage polarization, and an increase in chronic low-grade inflammation; however, the extent to which the non-canonical pathway of lipolysis is active and impacted by immune cells during aging remains unclear. Therefore, we aimed to define the extent to which immune cells from old mice influence non-canonical lipolysis during sepsis. We identified age-associated impairments of non-canonical lipolysis and an accumulation of dysfunctional B1 B cells in the visceral white adipose tissue (vWAT) of old mice. Lifelong deficiency of B cells results in restored non-canonical lipolysis and reductions in pro-inflammatory macrophage populations. Our study suggests that targeting the B cell-macrophage signaling axis may resolve metabolic dysfunction in aged vWAT and attenuate septic severity in older individuals.

Single-cell analysis of age-related changes in leukocytes of diabetic mouse hindpaws

Complications associated with Type 1 and Type 2 diabetes, such as diabetic peripheral neuropathy and diabetic foot ulcers, are a growing health-care concern. In addition, this concern increases as diabetic patients age due to their increased susceptibility to complications. To address this growing problem, it is important to understand fluctuations in physiology which lead to pathological changes associated with the metabolic disturbances of diabetes. Our study explores dysregulation of immune cell populations in the hindpaws of healthy and diabetic mice at 12 and 21 weeks of age using single-cell RNA sequencing to provide insight into immune disruptions occurring in the distal limb during chronic diabetes. In 21-week-old Leprdb/db mice, increases were seen in mast cells/basophils, dermal γδ T cells, heterogeneous T cells, and Type 2 innate lymphoid cells. In addition, macrophages represented the largest cluster of immune cells and showed the greatest increase in genes associated with immune-specific pathways. Sub-clustering of macrophages revealed a bias toward angiogenic Lyve1+MHCIIlo macrophages in the hindpaws of 21-week-old diabetic mice, which corresponded to an increase in Lyve1+ macrophages in the hindpaws of 21-week-old diabetic mice on histology. Our results show that in Type 2 diabetes, the immunological function and phenotype of multiple immune cell types shift not only with metabolic disturbance, but also with duration of disease, which may explain the increased susceptibility to pathologies of the distal limb in patients with more chronic diabetes.

Diabetes Mellitus, Energy Metabolism, and COVID-19

Obesity, diabetes mellitus (mostly type 2), and COVID-19 show mutual interactions because they are not only risk factors for both acute and chronic COVID-19 manifestations, but also because COVID-19 alters energy metabolism. Such metabolic alterations can lead to dysglycemia and long-lasting effects. Thus, the COVID-19 pandemic has the potential for a further rise of the diabetes pandemic. This review outlines how preexisting metabolic alterations spanning from excess visceral adipose tissue to hyperglycemia and overt diabetes may exacerbate COVID-19 severity. We also summarize the different effects of SARS-CoV-2 infection on the key organs and tissues orchestrating energy metabolism, including adipose tissue, liver, skeletal muscle, and pancreas. Last, we provide an integrative view of the metabolic derangements that occur during COVID-19. Altogether, this review allows for better understanding of the metabolic derangements occurring when a fire starts from a small flame, and thereby help reducing the impact of the COVID-19 pandemic.

Orchestration of the Adipose Tissue Immune Landscape by Adipocytes

Obesity is epidemic and of great concern because of its comorbid and costly inflammatory-driven complications. Extensive investigations in mice have elucidated highly coordinated, well-balanced interactions between adipocytes and immune cells in adipose tissue that maintain normal systemic metabolism in the lean state, while in obesity, proinflammatory changes occur in nearly all adipose tissue immune cells. Many of these changes are instigated by adipocytes. However, less is known about obesity-induced adipose-tissue immune cell alterations in humans. Upon high-fat diet feeding, the adipocyte changes its well-known function as a metabolic cell to assume the role of an immune cell, orchestrating proinflammatory changes that escalate inflammation and progress during obesity. This transformation is particularly prominent in humans. In this review, we (a) highlight a leading and early role for adipocytes in promulgating inflammation, (b) discuss immune cell changes and the time course of these changes (comparing humans and mice when possible), and (c) note how reversing proinflammatory changes in most types of immune cells, including adipocytes, rescues adipose tissue from inflammation and obese mice from insulin resistance.

Contribution of Nucleotide-Binding Oligomerization Domain-like (NOD) Receptors to the Immune and Metabolic Health

Nucleotide-binding oligomerization domain-like (NOD) receptors rely on the interface between immunity and metabolism. Dietary factors constitute critical players in the activation of innate immunity and modulation of the gut microbiota. The latter have been involved in worsening or improving the control and promotion of diseases such as obesity, type 2 diabetes, metabolic syndrome, diseases known as non-communicable metabolic diseases (NCDs), and the risk of developing cancer. Intracellular NODs play key coordinated actions with innate immune 'Toll-like' receptors leading to a diverse array of gene expressions that initiate inflammatory and immune responses. There has been an improvement in the understanding of the molecular and genetic implications of these receptors in, among others, such aspects as resting energy expenditure, insulin resistance, and cell proliferation. Genetic factors and polymorphisms of the receptors are determinants of the risk and severity of NCDs and cancer, and it is conceivable that dietary factors may have significant differential consequences depending on them. Host factors are difficult to influence, while environmental factors are predominant and approachable with a preventive and/or therapeutic intention in obesity, T2D, and cancer. However, beyond the recognition of the activation of NODs by peptidoglycan as its prototypical agonist, the underlying molecular response(s) and its consequences on these diseases remain ill-defined. Metabolic (re)programming is a hallmark of NCDs and cancer in which nutritional strategies might play a key role in preventing the unprecedented expansion of these diseases. A better understanding of the participation and effects of immunonutritional dietary ingredients can boost integrative knowledge fostering interdisciplinary science between nutritional precision and personalized medicine against cancer. This review summarizes the current evidence concerning the relationship(s) and consequences of NODs on immune and metabolic health.

Adipose tissue lymphocytes and obesity

Obesity is associated with chronic inflammation in adipose tissue (AT), mainly evidenced by infiltration and phenotypic changes of various types of immune cells. Macrophages are the major innate immune cells and represent the predominant immune cell population within AT. Lymphocytes, including T cells and B cells, are adaptive immune cells and constitute another important immune cell population in AT. In obesity, CD8+ effector memory T cells, CD4+ Th1 cells, and B2 cells are increased in AT and promote AT inflammation, while regulatory T cells and Th2 cells, which usually function as immune regulatory or type 2 inflammatory cells, are reduced in AT. Immune cells may regulate the metabolism of adipocytes and other cells through various mechanisms, contributing to the development of metabolic diseases, including insulin resistance and type 2 diabetes. Efforts targeting immune cells and inflammation to prevent and treat obesity-linked metabolic disease have been explored, but have not yielded significant success in clinical studies. This review provides a concise overview of the changes in lymphocyte populations within AT and their potential role in AT inflammation and the regulation of metabolic functions in the context of obesity.

Emerging insights into atypical B cells in pediatric chronic infectious diseases and immune system disorders: T(o)-bet on control of B-cell immune activation

Repetitive or persistent cellular stimulation in vivo has been associated with the development of a heterogeneous B-cell population that exhibits a distinctive phenotype and, in addition to classical B-cell markers, often expresses the transcription factor T-bet and myeloid marker CD11c. Research suggests that this atypical population consists of B cells with distinct B-cell receptor specificities capable of binding the antigens responsible for their development. The expansion of this population occurs in the presence of chronic inflammatory conditions and autoimmune diseases where different nomenclatures have been used to describe them. However, as a result of the diverse contexts in which they have been investigated, these cells have remained largely enigmatic, with much ambiguity remaining regarding their phenotype and function in humoral immune response as well as their role in autoimmunity. Atypical B cells have garnered considerable interest because of their ability to produce specific antibodies and/or autoantibodies and because of their association with key disease manifestations. Although they have been widely described in the context of adults, little information is present for children. Therefore, the aim of this narrative review is to describe the characteristics of this population, suggest their function in pediatric immune-related diseases and chronic infections, and explore their potential therapeutic avenues.

High Fat Diet-Induced Obesity Dysregulates Splenic B Cell Mitochondrial Activity

Diet-induced obesity impairs mitochondrial respiratory responses in tissues that are highly metabolically active, such as the heart. However, less is known about the impact of obesity on the respiratory activity of specific cell types, such as splenic B cells. B cells are of relevance, as they play functional roles in obesity-induced insulin resistance, inflammation, and responses to infection. Here, we tested the hypothesis that high-fat-diet (HFD)-induced obesity could impair the mitochondrial respiration of intact and permeabilized splenic CD19+ B cells isolated from C57BL/6J mice and activated ex vivo with lipopolysaccharide (LPS). High-resolution respirometry was used with intact and permeabilized cells. To reveal potential mechanistic targets by which HFD-induced obesity dysregulates B cell mitochondria, we conducted proteomic analyses and 3D serial block face scanning electron microscopy (SBFEM). High-resolution respirometry revealed that intact LPS-stimulated B cells of obese mice, relative to controls, displayed lower ATP-linked, as well as maximal uncoupled, respiration. To directly investigate mitochondrial function, we used permeabilized LPS-stimulated B cells, which displayed increased H2O2 emission and production with obesity. We also examined oxidative phosphorylation efficiency simultaneously, which revealed that oxygen consumption and ATP production were decreased in LPS-stimulated B cells with obesity relative to controls. Despite minimal changes in total respiratory complex abundance, in LPS-stimulated B cells of obese mice, three of the top ten most downregulated proteins were all accessory subunits of respiratory complex I. SBFEM showed that B cells of obese mice, compared to controls, underwent no change in mitochondrial cristae integrity but displayed increased mitochondrial volume that was linked to bioenergetic function. Collectively, these results establish a proof of concept that HFD-induced obesity dysregulates the mitochondrial bioenergetic metabolism of activated splenic B cells.

Diet-induced obesity impacts influenza disease severity and transmission dynamics in ferrets

Obesity, and the associated metabolic syndrome, is a risk factor for increased disease severity with a variety of infectious agents, including influenza virus. Yet the mechanisms are only partially understood. As the number of people, particularly children, living with obesity continues to rise, it is critical to understand the role of host status on disease pathogenesis. In these studies, we use a novel diet-induced obese ferret model and new tools to demonstrate that like humans, obesity resulted in significant changes to the lung microenvironment leading to increased clinical disease and viral spread to the lower respiratory tract. The decreased antiviral responses also resulted in obese animals shedding higher infectious virus for longer making them more likely to transmit to contacts. These data suggest the obese ferret model may be crucial to understanding obesity's impact on influenza disease severity and community transmission, and a key tool for therapeutic and intervention development for this high-risk population.

Teaser

A new ferret model and tools to explore obesity's impact on respiratory virus infection, susceptibility, and community transmission.

Association between body fat distribution and B-lymphocyte subsets in peripheral blood

BACKGROUND

Obesity is associated with chronic low-grade inflammation, which is underpinned by the presence of elevated levels of circulating proinflammatory cytokines in obese individuals. Due to the close relationship between adipose tissue and the immune system, it can be speculated that the accumulation of fat may influence the frequency and phenotype of lymphocyte populations. The aim of our study was to investigate whether body fat distribution is associated with B lymphocyte composition in peripheral blood. We examined the association between visceral (VAT) and total body fat (TBF) and the frequencies of B-cell subsets in 238 subjects over a period of up to one year using random intercept models. B lymphocyte subsets were determined by fluorescence-based flow cytometry.

RESULTS

Inverse associations were found between body fat measurements and plasma blasts, memory B cells, and IgM-IgD- cells. VAT, but not TBF, was positively associated with naive CD19 cells. In our analyses, both VAT and TBF showed positive associations with IgD only B cells.

CONCLUSIONS

In conclusion, body fat accumulation seems to be associated with a lower proportion of antibody-secreting plasma blasts and memory cells and an increasing amount of partially anergic, naive CD19 cells.

Phenotypic and functional characteristics of murine CD11c+ B cells which is suppressed by metformin

Since the description of age-associated or autoimmune-associated B cells (ABCs), there has been a growing interest in the role of these cells in autoimmunity. ABCs are differently defined depending on the research group and are heterogenous subsets. Here, we sought to characterize ABCs in Sle1/2/3 triple congenic (TC) mice, which is a well accepted mouse model of lupus. Compared to follicular (FO) B cells, ABCs have many distinct functional properties, including antigen presentation. They express key costimulatory molecules for T cell activation and a distinct profile of cytokines. Moreover, they exhibit an increased capacity for antigen uptake. ABCs were also compared with germinal center (GC) B cells, which are antigen activated B cell population. There are several phenotypic similarities between ABCs and GC B cells, but GC B cells do not produce proinflammatory cytokines or take up antigen. While T cell proliferation and activation is induced by both FO B and ABCs in an antigen-dependent manner, ABCs induce stronger T cell receptor signaling in naïve CD4+ T cells and preferentially induce differentiation of T follicular helper (Tfh) cells. We found that ABCs exhibit a distinct transcriptomic profile which is focused on metabolism, cytokine signaling and antigen uptake and processing. ABCs exhibit an increase in both glycolysis and oxidative phosphorylation compared to FO B cells. Treatment of ABCs with metformin suppresses antigen presentation by decreasing antigen uptake, resulting in decreased Tfh differentiation. Taken together, these findings define a fundamental connection between metabolism and function within ABCs.

Adipose Tissue and Metabolic Health

In this review, we provide a brief synopsis of the connections between adipose tissue and metabolic health and highlight some recent developments in understanding and exploiting adipocyte biology. Adipose tissue plays critical roles in the regulation of systemic glucose and lipid metabolism and secretes bioactive molecules possessing endocrine, paracrine, and autocrine functions. Dysfunctional adipose tissue has a detrimental impact on metabolic health and is intimately involved in key aspects of metabolic diseases such as insulin resistance, lipid overload, inflammation, and organelle stress. Differences in the distribution of fat depots and adipose characteristics relate to divergent degrees of metabolic dysfunction found in metabolically healthy and unhealthy obese individuals. Thermogenic adipocytes increase energy expenditure via mitochondrial uncoupling or adenosine triphosphate-consuming futile substrate cycles, while functioning as a metabolic sink and participating in crosstalk with other metabolic organs. Manipulation of adipose tissue provides a wealth of opportunities to intervene and combat the progression of associated metabolic diseases. We discuss current treatment modalities for obesity including incretin hormone analogs and touch upon emerging strategies with therapeutic potential including exosome-based therapy, pharmacological activation of brown and beige adipocyte thermogenesis, and administration or inhibition of adipocyte-derived factors.

Mechanism of immune attack in the progression of obesity-related type 2 diabetes

Obesity and overweight are widespread issues in adults, children, and adolescents globally, and have caused a noticeable rise in obesity-related complications such as type 2 diabetes mellitus (T2DM). Chronic low-grade inflammation is an important promotor of the pathogenesis of obesity-related T2DM. This proinflammatory activation occurs in multiple organs and tissues. Immune cell-mediated systemic attack is considered to contribute strongly to impaired insulin secretion, insulin resistance, and other metabolic disorders. This review focused on highlighting recent advances and underlying mechanisms of immune cell infiltration and inflammatory responses in the gut, islet, and insulin-targeting organs (adipose tissue, liver, skeletal muscle) in obesity-related T2DM. There is current evidence that both the innate and adaptive immune systems contribute to the development of obesity and T2DM.

T-bethighCD21low B cells: the need to unify our understanding of a distinct B cell population in health and disease

After many years of a niche research in a few laboratories of the world, T-bet^highCD21^low B cells have entered the limelight during the last years after the discovery of T-bet as common transcription factor of this unconventional B cell population and the increasing awareness of the expansion of these cells in autoimmune and infectious diseases. This population consists of different subsets which share large parts of their transcriptome, essential phenotypic markers, and reduced B cell receptor (BCR) signaling capacity. Inborn errors of immunity have helped to delineate essential signals for their differentiation. While our comprehension of their origin has improved, future research will hopefully profit from a common definition of the different T-bet^highCD21^low subpopulations in order to better define their specific roles during normal and aberrant immune responses.

Adipose tissue in communication: within and without

Single-cell mapping of human and mouse white adipose tissue across different depots and body masses revealed cellular heterogeneity, and identified distinct subpopulations of adipocytes, adipose progenitors and immune cells across species and types of diet2 . In obesity, T-bet+ B cells, which express the T helper 1-lineage transcription factor T-bet, accumulated in the adipose tissue of humans and mice, and activated T-bet+ B cells secreted the proinflammatory chemokine CXCL10 to exacerbate obesity-associated metabolic abnormalities5 . Extracellular vesicles (EVs) produced by dysfunctional adipose tissue could deliver microRNAs to the brain and cause synaptic damage in the hippocampus and cognitive impairments; targeting adipose tissue-derived EVs or microRNAs prevented cognitive defects in mice7 . Cold exposure inhibited tumour growth in mice carrying various xenografted solid tumours, an effect mediated via the activation of brown adipose tissue, leading to decreased circulating levels of glucose and attenuated glycolytic and lipid metabolism in tumours8 . SARS-CoV-2 directly infected human adipocytes and altered cell metabolism in a depot-specific and viral lineage-dependent fashion; visceral adipocytes were more susceptible to SARS-CoV-2 infection than subcutaneous adipocytes10 .

Environmental endocrine disruptor Bisphenol A induces metabolic derailment and obesity via upregulating IL-17A in adipocytes

BACKGROUND

Bisphenol A (BPA), a ubiquitous environmental endocrine disruptor, has been extensively demonstrated to be associated with metabolic disorders, including obesity and type 2 diabetes mellitus. However, the underlying mechanism underpinning the environmental etiology of chronic metabolic disorders has not been sufficiently elucidated.

OBJECTIVES

This study is designed to explore the toxicological pathogenesis of chronic inflammation in BPA exposure during obesity.

METHODS

We investigated the role of IL-17A in the association of BPA exposure and obesity from human cross-sectional study to animal models, including genetically modified IL-17A^-/- mice.

RESULTS

Here, our work started from case-control observation that BPA exposure was significantly associated with risk of obesity (odds ratio = 4.72, 95%CI: 3.18 - 11.18, P < 0.01), metabolic disorder and levels of interleukin-17A (IL-17A) in human adipose (estimated changes β = 0.46, 95%CI: 0.15 - 1.01, P < 0.01) with bariatric surgery. Animal model fed with high-fat diet (HFD) confirmed that BPA exposure aggravated body weight gain and insulin resistance, concurrent with much heightened inflammatory responses in the adipose tissue including increase in IL-17A and macrophage polarization towards M1 stage. Genetically modified IL-17A ablated mice (IL-17A^-/-) showed reversed adipose tissue inflammation response, improved macrophage polarization homeostasis, along with insulin sensitivity in both HFD group alone or much more significantly the HFD + BPA group. Moreover, mediation analysis in human epidemiological investigation demonstrated that plasma IL-17A attributed up to 30.01% mediating role in the associations between BPA exposure and obesity risk.

DISCUSSION

This research paradigm from human to animal provides strong evidence for the elucidation of IL-17A moderating inflammation and insulin resistance in obesity. Such findings reiterate the obesogenic role of environmental endocrine disruptor BPA in metabolic disorders and unveils the potential toxicological mechanisms underpinning such effect.

Mechanic Insight into the Distinct and Common Roles of Ovariectomy Versus Adrenalectomy on Adipose Tissue Remodeling in Female Mice

Dysfunctions of the ovaries and adrenal glands are both evidenced to cause aberrant adipose tissue (AT) remodeling and resultant metabolic disorders, but their distinct and common roles are poorly understood. In this study, through biochemical, histological and RNA-seq analyses, we comprehensively explored the mechanisms underpinning subcutaneous (SAT) and visceral adipose tissue (VAT) remodeling, in response to ovariectomy (OVX) versus adrenalectomy (ADX) in female mice. OVX promoted adipocyte differentiation and fat accumulation in both SAT and VAT, by potentiating the Pparg signaling, while ADX universally prevented the cell proliferation and extracellular matrix organization in both SAT and VAT, likely by inactivating the Nr3c1 signaling, thus causing lipoatrophy in females. ADX, but not OVX, exerted great effects on the intrinsic difference between SAT and VAT. Specifically, ADX reversed a large cluster of genes differentially expressed between SAT and VAT, by activating 12 key transcription factors, and thereby caused senescent cell accumulation, massive B cell infiltration and the development of selective inflammatory response in SAT. Commonly, both OVX and ADX enhance circadian rhythmicity in VAT, and impair cell proliferation, neurogenesis, tissue morphogenesis, as well as extracellular matrix organization in SAT, thus causing dysfunction of adipose tissues and concomitant metabolic disorders.

Age/autoimmunity-associated B cells in inflammatory arthritis: An emerging therapeutic target

Age/autoimmunity-associated B cells (ABCs) are a novel B cell subpopulation with a unique transcriptional signature and cell surface phenotype. They are not sensitive to BCR but rely on TLR7 or TLR9 in the context of T cell-derived cytokines for the differentiation. It has been established that aberrant expansion of ABCs is linked to the pathogenesis of systemic autoimmune diseases such as systemic lupus erythematosus. Recently, we and other groups have shown that increased ABCs is associated with rheumatoid arthritis (RA) disease activity and have demonstrated their pathogenic role in RA, indicating that targeting specific B cell subsets is a promising strategy for the treatment of inflammatory arthritis. In this review, we summarize the current knowledge of ABCs, focusing on their emerging role in the pathogenesis of inflammatory arthritis. A deep understanding of the biology of ABCs in the context of inflammatory settings in vivo will ultimately contribute to the development of novel targeted therapies for the treatment of inflammatory arthritis.

T-bet+ B cells exacerbate obesity-related metabolic disease

B cells are associated with the development of obesity-associated metabolic disease. Recently, Hägglöf, Vanz, et al. identified a novel obesity-related subset of B cells that are demarcated by the transcription factor T-bet and their pathogenic ability to worsen metabolic disease outcomes.

T-bet B or not T-bet B, is that the question in obesity-related metabolic disease?

Obesity is linked to inflammation and downstream metabolic dysregulation. In this issue of Cell Metabolism, Hägglöf et al. show that iNKT cells enable the accumulation of T-bet⁺ B cells in white adipose tissue, which in turn produce chemokine and antibody mediators that exacerbate the onset and severity of metabolic disease.