B cells promote insulin resistance through modulation of T cells and production of pathogenic IgG antibodies

Depression in type 2 diabetes: A systematic review and meta-analysis of blood inflammatory markers

The prevalence of depression is higher among people with type 2 diabetes (T2DM). Individually, both conditions are associated with systemic inflammation. This study aimed to summarize the clinical data comparing peripheral inflammatory markers in blood between people with T2DM, with and without comorbid depression. From 2187 records, we identified 20 original peer-reviewed articles from which blood inflammatory marker concentrations could be combined and compared between people with T2DM and comorbid depression (D) vs. no depression (ND) as standardized mean differences (SMD) in random effects meta-analysis. Concentrations of C-reactive protein (CRP; ND/NND = 1742/15244, SMD = 0.31 95% confidence interval [0.16, 0.45], Z16 = 4.03, p < 0.01; I2 = 84.0%) and interleukin-6 (IL-6; ND/NND = 677/4349, SMD = 0.17 [0.04, 0.30], Z4 = 2.58, p = 0.01; I2 = 48.1%), were higher, and concentrations of brain derived neurotrophic factor (BDNF; ND/NND = 358/1512, SMD = -0.37 95% confidence interval [-0.64,-0.10], Z2 = -2.68, p = 0.01; I2 = 61.2%) were lower, among those with depression. Depression in T2DM was associated with systemic inflammation and lower peripheral blood BDNF concentrations. Inconsistency between studies suggests the need to explore further population heterogeneity and pathophysiological elements. PROSPERO (CRD42020188509).

The Emerging Role of B Cells in the Pathogenesis of NAFLD

NAFLD is one of the leading causes of abnormal liver function worldwide. NAFLD refers to a group of liver conditions ranging from nonalcoholic fatty liver to NASH, which involves inflammation, hepatocellular damage, and fibrosis. Triggering of inflammation in NASH is a key event in the progression of the disease, and identifying the factors that initiate or dysregulate this process is needed to develop strategies for its prevention or treatment. B cells have been implicated in several autoimmune and inflammatory diseases. However, their role in the pathogenesis of NAFLD and NASH is less clear. This review discusses the emerging evidence implicating intrahepatic B cells in the progression of NAFLD. We highlight the potential mechanisms of B-cell activation during NAFLD, such as increased hepatic expression of B-cell-activating factor, augmented oxidative stress, and translocation of gut-derived microbial products. We discuss the possible effector functions by which B cells promote NAFLD, including the production of proinflammatory cytokines and regulation of intrahepatic T cells and macrophages. Finally, we highlight the role of regulatory and IgA⁺ B cells in the pathogenesis of NASH-associated HCC. In this review, we make the case that future research is needed to investigate the potential of B-cell-targeting strategies for the treatment of NAFLD.

Biological Aspects of Inflamm-Aging in Childhood Cancer Survivors

Anti-cancer treatments improve survival in children with cancer. A total of 80% of children treated for childhood cancer achieve 5-year survival, becoming long-term survivors. However, they undergo several chronic late effects related to treatments. In childhood cancer survivors a chronic low-grade inflammation, known as inflamm-aging, is responsible for frailty, a condition characterized by vital organ failure and by premature aging processes. Inflamm-aging is closely related to chemotherapy and radiotherapy, which induce inflammation, accumulation of senescent cells, DNA mutations, and the production of reactive oxygen species. All these conditions are responsible for the onset of secondary diseases, such as osteoporosis, cardiovascular diseases, obesity, and infertility. Considering that the pathobiology of frailty among childhood cancer survivors is still unknown, investigations are needed to better understand frailty's biological and molecular processes and to identify inflamm-aging key biomarkers in order to facilitate the screening of comorbidities and to clarify whether treatments, normally used to modulate inflamm-aging, may be beneficial. This review offers an overview of the possible biological mechanisms involved in the development of inflamm-aging, focusing our attention on immune system alteration, oxidative stress, cellular senescence, and therapeutic strategies.

Targeting Inflammatory Cytokines to Improve Type 2 Diabetes Control

Type 2 diabetes (T2D) is one of the most common chronic metabolic disorders in adulthood worldwide, whose pathophysiology includes an abnormal immune response accompanied by cytokine dysregulation and inflammation. As the T2D-related inflammation and its progression were associated with the balance between pro and anti-inflammatory cytokines, anticytokine treatments might represent an additional therapeutic option for T2D patients. This review focuses on existing evidence for antihyperglycemic properties of disease-modifying antirheumatic drugs (DMARDs) and anticytokine agents (anti-TNF-α, anti-interleukin-(IL-) 6, -IL-1, -IL-17, -IL-23, etc.). Emphasis is placed on their molecular mechanisms and on the biological rationale for clinical use. Finally, we briefly summarize the results from experimental model studies and promising clinical trials about the potential of anticytokine therapies in T2D, discussing the effects of these drugs on systemic and islet inflammation, beta-cell function, insulin secretion, and insulin sensitivity.

Implications of Inflammatory States on Dysfunctional Immune Responses in Aging and Obesity

Aging and obesity are two conditions characterized by chronic, low-grade inflammation. While both conditions are also associated with dysfunctional immune responses, the shared and distinct underlying mechanisms are just starting to be uncovered. In fact, recent findings have suggested that the effects of obesity on the immune system can be thought of as a state of accelerated aging. Here we propose that chronic, low-grade inflammation seen in obesity and aging is complex, affects multiple cell types, and results in an altered basal immune state. In aging, part of this altered state is the emergence of regulatory immune populations that lead to further immune dysfunction in an attempt to reduce chronic inflammation. While in obesity, part of the altered state is the effect of expanding adipose tissue on immune cell function. Thus, in this review, we compare, and contrast altered immune states in aging and obesity and discuss their potential contribution to a shared clinical problem- decreased vaccine responsiveness.

T Cell Immunosenescence in Aging, Obesity, and Cardiovascular Disease

Although advances in preventive medicine have greatly improved prognosis, cardiovascular disease (CVD) remains the leading cause of death worldwide. This clearly indicates that there remain residual cardiovascular risks that have not been targeted by conventional therapies. The results of multiple animal studies and clinical trials clearly indicate that inflammation is the most important residual risk and a potential target for CVD prevention. The immune cell network is intricately regulated to maintain homeostasis. Ageing associated changes to the immune system occurs in both innate and adaptive immune cells, however T cells are most susceptible to this process. T-cell changes due to thymic degeneration and homeostatic proliferation, metabolic abnormalities, telomere length shortening, and epigenetic changes associated with aging and obesity may not only reduce normal immune function, but also induce inflammatory tendencies, a process referred to as immunosenescence. Since the disruption of biological homeostasis by T cell immunosenescence is closely related to the development and progression of CVD via inflammation, senescent T cells are attracting attention as a new therapeutic target. In this review, we discuss the relationship between CVD and T cell immunosenescence associated with aging and obesity.

The Sick Adipose Tissue: New Insights Into Defective Signaling and Crosstalk With the Myocardium

Adipose tissue (AT) biology is linked to cardiovascular health since obesity is associated with cardiovascular disease (CVD) and positively correlated with excessive visceral fat accumulation. AT signaling to myocardial cells through soluble factors known as adipokines, cardiokines, branched-chain amino acids and small molecules like microRNAs, undoubtedly influence myocardial cells and AT function via the endocrine-paracrine mechanisms of action. Unfortunately, abnormal total and visceral adiposity can alter this harmonious signaling network, resulting in tissue hypoxia and monocyte/macrophage adipose infiltration occurring alongside expanded intra-abdominal and epicardial fat depots seen in the human obese phenotype. These processes promote an abnormal adipocyte proteomic reprogramming, whereby these cells become a source of abnormal signals, affecting vascular and myocardial tissues, leading to meta-inflammation, atrial fibrillation, coronary artery disease, heart hypertrophy, heart failure and myocardial infarction. This review first discusses the pathophysiology and consequences of adipose tissue expansion, particularly their association with meta-inflammation and microbiota dysbiosis. We also explore the precise mechanisms involved in metabolic reprogramming in AT that represent plausible causative factors for CVD. Finally, we clarify how lifestyle changes could promote improvement in myocardiocyte function in the context of changes in AT proteomics and a better gut microbiome profile to develop effective, non-pharmacologic approaches to CVD.

Adipose Tissue and Biological Factors. Possible Link between Lymphatic System Dysfunction and Obesity

The World Health Organization (WHO) has recognised obesity as one of the top ten threats to human health. Obesity is not only a state of abnormally increased adipose tissue in the body, but also of an increased release of biologically active metabolites. Moreover, obesity predisposes the development of metabolic syndrome and increases the incidence of type 2 diabetes (T2DM), increases the risk of developing insulin resistance, atherosclerosis, ischemic heart disease, polycystic ovary syndrome, hypertension and cancer. The lymphatic system is a one-directional network of thin-walled capillaries and larger vessels covered by a continuous layer of endothelial cells that provides a unidirectional conduit to return filtered arterial and tissue metabolites towards the venous circulation. Recent studies have shown that obesity can markedly impair lymphatic function. Conversely, dysfunction in the lymphatic system may also be involved in the pathogenesis of obesity. This review highlights the important findings regarding obesity related to lymphatic system dysfunction, including clinical implications and experimental studies. Moreover, we present the role of biological factors in the pathophysiology of the lymphatic system and we propose the possibility of a therapy supporting the function of the lymphatic system in the course of obesity.

Comparative Genomic Analysis of the DUF34 Protein Family Suggests Role as a Metal Ion Chaperone or Insertase

Members of the DUF34 (domain of unknown function 34) family, also known as the NIF3 protein superfamily, are ubiquitous across superkingdoms. Proteins of this family have been widely annotated as "GTP cyclohydrolase I type 2" through electronic propagation based on one study. Here, the annotation status of this protein family was examined through a comprehensive literature review and integrative bioinformatic analyses that revealed varied pleiotropic associations and phenotypes. This analysis combined with functional complementation studies strongly challenges the current annotation and suggests that DUF34 family members may serve as metal ion insertases, chaperones, or metallocofactor maturases. This general molecular function could explain how DUF34 subgroups participate in highly diversified pathways such as cell differentiation, metal ion homeostasis, pathogen virulence, redox, and universal stress responses.

B Cell Immunosenescence

Innate and adaptive immune responses decline with age, leading to greater susceptibility to infectious diseases and reduced responses to vaccines. Diseases are more severe in old than in young individuals and have a greater impact on health outcomes such as morbidity, disability, and mortality. Aging is characterized by increased low-grade chronic inflammation, so-called inflammaging, that represents a link between changes in immune cells and a number of diseases and syndromes typical of old age. In this review we summarize current knowledge on age-associated changes in immune cells with special emphasis on B cells, which are more inflammatory and less responsive to infections and vaccines in the elderly. We highlight recent findings on factors and pathways contributing to inflammaging and how these lead to dysfunctional immune responses. We summarize recent published studies showing that adipose tissue, which increases in size with aging, contributes to inflammaging and dysregulated B cell function.

White adipose tissue dysfunction in obesity and aging

Both obesity and aging are associated with the development of metabolic diseases such as type 2 diabetes and cardiovascular disease. Chronic low-grade inflammation of adipose tissue is one of the mechanisms implicated in the progression of these diseases. Obesity and aging trigger adipose tissue alterations that ultimately lead to a pro-inflammatory phenotype of the adipose tissue-resident immune cells. Obesity and aging also share other features such as a higher visceral vs. subcutaneous adipose tissue ratio and a decreased lifespan. Here, we review the common characteristics of obesity and aging and the alterations in white adipose tissue and resident immune cells. We focus on the adipose tissue metabolic derangements in obesity and aging such as inflammation and adipose tissue remodeling.

Microbiota-Driven Activation of Intrahepatic B Cells Aggravates NASH Through Innate and Adaptive Signaling

BACKGROUND AND AIMS

Nonalcoholic steatohepatitis is rapidly becoming the leading cause of liver failure and indication for liver transplantation. Hepatic inflammation is a key feature of NASH but the immune pathways involved in this process are poorly understood. B lymphocytes are cells of the adaptive immune system that are critical regulators of immune responses. However, the role of B cells in the pathogenesis of NASH and the potential mechanisms leading to their activation in the liver are unclear.

APPROACH AND RESULTS

In this study, we report that NASH livers accumulate B cells with elevated pro-inflammatory cytokine secretion and antigen-presentation ability. Single-cell and bulk RNA sequencing of intrahepatic B cells from mice with NASH unveiled a transcriptional landscape that reflects their pro-inflammatory function. Accordingly, B-cell deficiency ameliorated NASH progression, and adoptively transferring B cells from NASH livers recapitulates the disease. Mechanistically, B-cell activation during NASH involves signaling through the innate adaptor myeloid differentiation primary response protein 88 (MyD88) as B cell-specific deletion of MyD88 reduced hepatic T cell-mediated inflammation and fibrosis, but not steatosis. In addition, activation of intrahepatic B cells implicates B cell-receptor signaling, delineating a synergy between innate and adaptive mechanisms of antigen recognition. Furthermore, fecal microbiota transplantation of human NAFLD gut microbiotas into recipient mice promoted the progression of NASH by increasing the accumulation and activation of intrahepatic B cells, suggesting that gut microbial factors drive the pathogenic function of B cells during NASH.

CONCLUSION

Our findings reveal that a gut microbiota-driven activation of intrahepatic B cells leads to hepatic inflammation and fibrosis during the progression of NASH through innate and adaptive immune mechanisms.

Changes in abdominal subcutaneous adipose tissue phenotype following menopause is associated with increased visceral fat mass

Menopause is associated with a redistribution of adipose tissue towards central adiposity, known to cause insulin resistance. In this cross-sectional study of 33 women between 45 and 60 years, we assessed adipose tissue inflammation and morphology in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) across menopause and related this to menopausal differences in adipose tissue distribution and insulin resistance. We collected paired SAT and VAT biopsies from all women and combined this with anthropometric measurements and estimated whole-body insulin sensitivity. We found that menopause was associated with changes in adipose tissue phenotype related to metabolic dysfunction. In SAT, postmenopausal women showed adipocyte hypertrophy, increased inflammation, hypoxia and fibrosis. The postmenopausal changes in SAT was associated with increased visceral fat accumulation. In VAT, menopause was associated with adipocyte hypertrophy, immune cell infiltration and fibrosis. The postmenopausal changes in VAT phenotype was associated with decreased insulin sensitivity. Based on these findings we suggest, that menopause is associated with changes in adipose tissue phenotype related to metabolic dysfunction in both SAT and VAT. Whereas increased SAT inflammation in the context of menopause is associated with VAT accumulation, VAT morphology is related to insulin resistance.

PTIP Deficiency in B Lymphocytes Reduces Subcutaneous Fat Deposition in Mice

Recent studies have predominantly focused on the role of B cells in metabolic diseases, yet the function of B cells in adipose homeostasis remains unclear. Pax transactivation domain-interacting protein (PTIP), a licensing factor for humoral immunity, is necessary for B cell development and activation. Here, using mice that lack PTIP in B cells (PTIP^-/- mice), we explored the role of B cells in adipose homeostasis under physiological conditions. Fat deposition in 8-week-old mice was measured by micro-CT, and PTIP^-/- mice presented a marked decrease in the deposition of subcutaneous adipose tissue (SAT). Untargeted lipidomics revealed that the triglyceride composition in SAT was altered in PTIP^-/- mice. In addition, there was no difference in the number of adipocyte progenitor cells in the SAT of wild-type (WT) and PTIP^-/- mice as measured by flow cytometry. To study the effects of steady-state IgM and IgG antibody levels on fat deposition, PTIP^-/- mice were injected intraperitoneally with serum from WT mice once every 3-4 days for 4 weeks. The iSAT mass of the recipient mice showed no significant increase in comparison to the controls after 4 weeks of injections. Our findings reveal that PTIP plays an essential role in regulating subcutaneous adipocyte size, triglyceride composition, and fat deposition under physiological conditions by controlling B cells. The decreased subcutaneous fat deposition in PTIP^-/- mice does not appear to be related to the number of adipocyte progenitor cells. The steady-state levels of IgM and IgG antibodies in vivo are not associated with the subcutaneous fat deposition.

Instruction of Immunometabolism by Adipose Tissue: Implications for Cancer Progression

Simple Summary

Metabolism is the process by which living organisms and cells generate energy to sustain life. At the organismal level, metabolic homeostasis is a tightly controlled balance between energy consumption and energy expenditure. Many studies have shown that disruption of this homeostasis leads to an inflammatory phenotype within adipose tissue. The aim of this review is to provide an overview of the dynamic metabolic interplay within adipose tissue and its implications for cancer progression and metastasis.

Abstract

Disruption of metabolic homeostasis at the organismal level can cause metabolic syndrome associated with obesity. The role of adipose tissue in cancer has been investigated over the last several decades with many studies implicating obesity as a risk factor for the development of cancer. Adipose tissue contains a diverse array of immune cell populations that promote metabolic homeostasis through a tightly controlled balance of pro- and anti-inflammatory signals. During obesity, pro-inflammatory cell types infiltrate and expand within the adipose tissue, exacerbating metabolic dysfunction. Some studies have now shown that the intracellular metabolism of immune cells is also deregulated by the lipid-rich environment in obesity. What is not fully understood, is how this may influence cancer progression, metastasis, and anti-tumor immunity. This review seeks to highlight our current understanding of the effect of adipose tissue on immune cell function and discuss how recent results offer new insight into the role that adipose tissue plays in cancer progression and anti-tumor immunity.

Resident macrophages restrain pathological adipose tissue remodeling and protect vascular integrity in obese mice

Tissue‐resident macrophages in white adipose tissue (WAT) dynamically adapt to the metabolic changes of their microenvironment that are often induced by excess energy intake. Currently, the exact contribution of these macrophages in obesity‐driven WAT remodeling remains controversial. Here, using a transgenic CD169‐DTR mouse strain, we provide new insights into the interplay between CD169⁺ adipose tissue macrophages (ATMs) and their surrounding WAT microenvironment. Using targeted in vivo ATM ablation followed by transcriptional and metabolic WAT profiling, we found that ATMs protect WAT from the excessive pathological remodeling that occurs during obesity. As obesity progresses, ATMs control not only vascular integrity, adipocyte function, and lipid and metabolic derangements but also extracellular matrix accumulation and resultant fibrosis in the WAT. The protective role of ATMs during obesity‐driven WAT dysfunction supports the notion that ATMs represent friends, rather than foes, as has previously assumed.

A new way for punicalagin to alleviate insulin resistance: regulating gut microbiota and autophagy

Background

Insulin resistance, defined as a diminished ability to respond to the stimulation of insulin, is the main line for a variety of metabolic-related diseases. Punicalagin (PU), a hydrolyzable tannin of pomegranate juice, exhibits multiple biological properties, including anti-oxidant, anti-cancer and anti-inflammatory activities.

Objective

This research study aimed at determining the protective effect of PU on insulin resistance and to uncover the underlying mechanism based on the gut microbiota, IKKβ/NF-κB pathway, and autophagy.

Design

An insulin resistance animal model was established using C57BL/6 mice fed with a high-fat diet (HFD) for 8 weeks. The model included two groups continuing a HFD for 12 weeks with or without administering via gavage with PU 20 mg/kg/day. Changes in fasting plasma glucose levels, fasting serum insulin levels, glucose and insulin tolerance, glycolipid metabolism, gut microbiota composition (16S rRNA gene sequencing), inflammatory responses, and autophagy in the liver were evaluated. Body weight gain, glycolipid metabolic disorder, liver injury, as well as systemic and hepatic insulin sensitivity, were significantly attenuated after supplementing with PU.

Results

This research study revealed that PU alleviated HFD-induced glucose and lipid disorders, liver injury and insulin resistance; decreased the Firmicutes/Bacteroides ratio, decreased the abundance of Coprococcus and Anaerotruncus, and increased Rikenellaceae; and decreased serum and liver tumor necrosis factor-alpha and interleukin-1β levels, inhibited liver IKKβ and NF-κB phosphorylation; and increased liver autophagy-related proteins LC3-II, P62, and Beclin1, and increased the number of liver autophagosomes.

Conclusion

PU can improve HFD-induced insulin resistance, improved liver glucose and lipid metabolism disorder and liver injury, and the potential mechanism is that PU inhibited the IKKβ/NF-κB inflammatory pathway by regulating gut microbiota homeostasis and up-regulating liver autophagy activity.

Early Onset of SARS-COV-2 Antibodies after First Dose of BNT162b2: Correlation with Age, Gender and BMI

BACKGROUND

The first goal of the study was to analyse the antibody titre 21 days after the first dose of the BNT162b2 vaccine in a group of 252 healthcare workers (HCW). The second goal was to analyse how the antibody titre changes in correlation with age, gender and body mass index (BMI).

METHODS

Participants had a nasopharyngeal swab for SARS-CoV-2 and were assessed for the presence of SARS-CoV-2 antibodies at baseline and 21 days after the BNT162b2 priming dose.

RESULTS

First dose of BNT162b2 activated immune responses in 98% of the participants. Five HWC had no increase in antibody titre 21 days after the first dose. Antibody titre was greater in young (<38 years) vs. older participants (<38 vs. 47-56 p = 0.002; <38 vs. >56 p = 0.001). Higher antibody levels were detected in underweight vs. pre-obesity group (p = 0.026) and in normal-weight vs. pre-obesity group (p = 0.007). This association was confirmed after adjusting for age (p = 0.0001) and gender (p = 0.00001).

CONCLUSIONS

Our study demonstrates that a single dose of BNT162b2 activates the immune response, and being young and normal-weight correlate positively with this response. Larger specifically designed clinical trials are needed to validate these results.

Insulin resistance is linked to a specific profile of immune activation in human subjects

We tested the hypothesis that a particular immune activation profile might be correlated with insulin resistance in a general population. By measuring 43 markers of immune, endothelial, and coagulation activation, we have previously shown that five different immune activation profiles may be distinguished in 150 volunteers. One of these profiles, Profile 2, characterized by CD4+ T cell senescence, inflammation, monocyte, B cell, and endothelial activation, presented elevated insulinemia, glycemia, triglyceridemia, and γ-glutamyl transferase, a marker of liver injury, in comparison with other profiles. Our data are compatible with a model in which a particular immune activation profile might favor the development of insulin resistance and metabolic syndrome. In this hypothesis, identification of this profile, that is feasible with only 3 markers with an error rate of 5%, might allow to personalize the screening and prevention of metabolic syndrome-driven morbidities as liver steatosis.

The Peculiar Trialogue between Pediatric Obesity, Systemic Inflammatory Status, and Immunity

Pediatric obesity is not only an energetic imbalance, but also a chronic complex multisystem disorder that might impair both the life length and quality. Its pandemic status should increase worldwide awareness regarding the long-term life-threatening associated complications. Obesity related complications, such as cardiovascular, metabolic, or hepatic ones, affect both short and long-term wellbeing, and they do not spare pediatric subjects, defined as life-threatening consequences of the systemic inflammatory status triggered by the adipose tissue. The energetic imbalance of obesity clearly results in adipocytes hypertrophy and hyperplasia expressing different degrees of chronic inflammation. Adipose tissue might be considered an immune organ due to its rich content in a complex array of immune cells, among which the formerly mentioned macrophages, neutrophils, mast cells, but also eosinophils along with T and B cells, acting together to maintain the tissue homeostasis in normal weight individuals. Adipokines belong to the class of innate immunity humoral effectors, and they play a crucial role in amplifying the immune responses with a subsequent trigger effect on leukocyte activation. The usefulness of complete cellular blood count parameters, such as leukocytes, lymphocytes, neutrophils, erythrocytes, and platelets as predictors of obesity-triggered inflammation, was also proved in pediatric patients with overweight or obesity. The dogma that adipose tissue is a simple energy storage tissue is no longer accepted since it has been proved that it also has an incontestable multifunctional role acting like a true standalone organ resembling to endocrine or immune organs.

Unwrapping the mechanisms of ceramide and fatty acid-initiated signals leading to immune-inflammatory responses in obesity

Obesity is considered a global epidemic developed in part as a consequence of the overconsumption of high fat diets. One of the main negative outcomes of obesity is the development of low-grade chronic systemic inflammation, induced by dysregulated immune responses, which can lead to multiple obesity-related diseases. Ceramides are a group of bioactive lipids known to be elevated in obesity and obesity-associated conditions, including cardiovascular disease and type II diabetes. Ceramides may be key players in promoting an obesity-induced inflammatory environment due to their ability to activate key pathways such as Toll-like receptor 4 (TLR4) and NLR pyrin domain containing receptor 3 (Nlrp3), while studies have shown that inhibition of ceramide synthesis gives rise to an anti-inflammatory environment. N-3 polyunsaturated fatty acids (n-3 PUFA) have been of interest due to their anti-inflammatory actions and shown to have beneficial effects in obesity-related diseases. This review will highlight the impact of ceramides in promoting an obesity-induced inflammatory microenvironment and discuss how n-3 PUFA could potentially counteract these responses and have a regulatory effect promoting immune homeostasis.

Coronavirus Disease 2019 (COVID-19) and Nutritional Status: The Missing Link?

Coronavirus disease 2019 (COVID-19) is an emerging disease that has reached pandemic status by rapidly spreading worldwide. Elderly individuals and patients with comorbidities such as obesity, diabetes, and hypertension show a higher risk of hospitalization, severe disease, and mortality by acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. These patients frequently show exacerbated secretion of proinflammatory cytokines associated with an overreaction of the immune system, the so-called cytokine storm. Host nutritional status plays a pivotal role in the outcome of a variety of different infectious diseases. It is known that the immune system is highly affected by malnutrition, leading to decreased immune responses with consequent augmented risk of infection and disease severity. Body composition, especially low lean mass and high adiposity, has consistently been linked to worsened prognosis in many different diseases. In this review, evidence concerning the impact of nutritional status on viral infection outcomes is discussed.

Thermogenic Fat: Development, Physiological Function, and Therapeutic Potential

The concerning worldwide increase of obesity and chronic metabolic diseases, such as T2D, dyslipidemia, and cardiovascular disease, motivates further investigations into preventive and alternative therapeutic approaches. Over the past decade, there has been growing evidence that the formation and activation of thermogenic adipocytes (brown and beige) may serve as therapy to treat obesity and its associated diseases owing to its capacity to increase energy expenditure and to modulate circulating lipids and glucose levels. Thus, understanding the molecular mechanism of brown and beige adipocytes formation and activation will facilitate the development of strategies to combat metabolic disorders. Here, we provide a comprehensive overview of pathways and players involved in the development of brown and beige fat, as well as the role of thermogenic adipocytes in energy homeostasis and metabolism. Furthermore, we discuss the alterations in brown and beige adipose tissue function during obesity and explore the therapeutic potential of thermogenic activation to treat metabolic syndrome.

Emerging concepts in intestinal immune control of obesity-related metabolic disease

The intestinal immune system is an important modulator of glucose homeostasis and obesity-associated insulin resistance. Dietary factors, the intestinal microbiota and their metabolites shape intestinal immunity during obesity. The intestinal immune system in turn affects processes such as intestinal permeability, immune cell trafficking, and intestinal hormone availability, impacting systemic insulin resistance. Understanding these pathways might identify mechanisms underlying treatments for insulin resistance, such as metformin and bariatric surgery, or aid in developing new therapies and vaccination approaches. Here, we highlight evolving concepts centered on intestinal immunity, diet, and the microbiota to provide a working model of obesity-related metabolic disease.

Levels of Lymphocyte Subpopulations in Peripheral Blood among Patients with Diabetes

The aim of the study was to investigate the lymphocyte (lymph) subpopulations in peripheral blood as a part of the immune response among patients with diabetes mellitus type 1 (DMT1) and diabetes mellitus type 2 (DMT2).

Patients and methods: A prospective, cross-sectional, comparative, “case-control” study was conducted among 22 patients with DMT1 and 70 patients with DMT2. The levels of lymph subtypes [general nonspecific T-lymph (CD3+); T-helper lymph (CD4+); T-cytotoxic lymph (CD8+), natural killers [NK cells (CD3\ CD16+/CD56)] and B-lymph (CD19+)] in blood was measured and compared by flow-cytometric analisys (FAC Sort, BD).

Results were compared to those of 21 healthy persons. The data was processed using the statistics software. Results: Patients with DMT1 had longer duration of the disease, compared to patients with DMT2. No significant differences between arterial blood pressure, НвА1с levels and lipid profile among the patients with DMT1 and DMT2 were present. There were no differences in the total leukocyte count between the groups (DMT1-6,91 ± 1,32.109/l; DMT2-7,28 ± 1,85.109/l; controls-6,89 ± 1,07.109/l). The results from the flowcytometric investigation showed significantly higher absolute number of T-all lymph (CD3+), Th lymph (CD4+) and all NK (CD3\ CD16+/CD56), as well as a lower absolute number of Ts (CD8+) and B (CD19+) lymph among the diabetic patients compared to healthy subjects. The Th/Ts ratio in patients with DMT1 (2,02 ± 0,44) and DMT2 (2,36 ± 0,37) was also significantly higher compared to ratio of controls (1,02 ± 0,06). No significant differences were noted in the lymph subpopulations between the two groups with DM.

Conclusions: Changes of lymph types in peripheral blood in diabetic patients demonstrate immune activation and dysregulation among the two types of diabetes.

CD4+ T cells regulate glucose homeostasis independent of adipose tissue dysfunction in mice

Obesity is frequently associated with a chronic low-grade inflammation in the adipose tissue (AT) and impaired glucose homeostasis. Adipose tissue macrophages (ATMs) have been shown to accumulate in the inflamed AT either by means of recruitment from the blood or local proliferation. ATM proliferation and activation can be stimulated by TH2 cytokines, such as IL-4 and IL-13, suggesting involvement of CD4-positive T cells in ATM proliferation and activation. Furthermore, several studies have associated T cells to alterations in glucose metabolism. Therefore, we sought to examine a direct impact of CD4-positive T cells on ATM activation, ATM proliferation and glucose homeostasis using an in vivo depletion model. Surprisingly, CD4 depletion did not affect ATM activation, ATM proliferation, or insulin sensitivity. However, CD4 depletion led to a significant improvement of glucose tolerance. In line with this, we found moderate disturbances in pancreatic endocrine function following CD4 depletion. Hence, our data suggest that the effect on glucose metabolism observed after CD4 depletion might be mediated by organs other than AT and independent of AT inflammation.

Weight and organ specific immune cell profiling of sleeve gastrectomy in mice

OBJECTIVE

Sleeve gastrectomy (SG) has profound, immediate weight-loss independent effects on obesity related diabetes (T2D). Our prior studies have shown that immunologic remodeling may play a part in this metabolic improvement. However, to date, little is known about how the major immune cell populations change following SG and whether these are weight loss dependent.

METHODS

Using mass cytometry with time of flight analysis (CyTOF), we broadly quantified the organ-specific immune cell repertoire induced by SG from splenic, jejunal, ileal, colonic, and hepatic lymphocyte fractions. Surgeries were performed in both diet-induced obese (DIO), insulin resistant mice and lean mice, which leads to sustained and non-sustained weight loss in SG animals compared to shams, respectively. Intergroup comparisons allow understanding of the relative contribution of diet, weight-loss, and surgery on immune profiling. Conserved immune changes represent surgery-specific, weight-independent, and diet-independent phenotypic changes.

RESULTS

Initial analysis by way of visualization of t-distributed stochastic neighbor embedding analysis revealed changes in the B cell compartment following SG in both DIO and lean mice compared to Sham animals. In depth, traditional gating showed a shift within the splenic B cell compartment toward innate-like phenotype. There was a 1.3-fold reduction in follicular B cells within DIO SG (14% absolute reduction; p = 0.009) and lean SG (15% absolute reduction; p = 0.031) animals with a significant increase in innate-like B cell subsets in DIO SG mice(2.2 to 4.3-fold increase; p < 0.05). There was a similar trend toward increased innate B cell subsets in lean SG mice. There was a concomitant increase in multiple circulating immunoglobulin classes in both models. Further, lean (p = 0.009) and DIO SG animals (p = 0.015) had a conserved 5.5-fold and 5.7-fold increase, respectively, in splenic neutrophils and tendency toward M2 macrophage polarization.

CONCLUSIONS

SG induces surgery-specific, weight-loss independent immune cells changes that have been previously linked to improved glucose metabolism. This immune phenotype may be a major contributor to post SG physiology. Characterizing the complex immune milieu following SG is an important step toward understanding the physiology of SG and the potential therapies therein.

Exercise and Adipose Tissue Immunity: Outrunning Inflammation

Chronic inflammation is considered a precipitating factor and possibly an underlying cause of many noncommunicable diseases, including cardiovascular disease, metabolic diseases, and some cancers. Obesity, which manifests in more than 650 million people worldwide, is the most common chronic inflammatory condition, with visceral adiposity thought to be the major inflammatory hub that links obesity and chronic disease. Adipose tissue (AT) inflammation is triggered or heightened in large part by (1) accelerated immune cell recruitment, (2) reshaping of the AT stromal-immuno landscape (e.g., immune cells, endothelial cells, fibroblasts, adipocyte progenitors), and (3) perturbed AT immune cell function. Exercise, along with diet management, is a cornerstone in promoting weight loss and preventing weight regain. This review focuses on evidence that increased physical activity reduces AT inflammation caused by hypercaloric diets or genetic obesity. The precise cell types and mechanisms responsible for the therapeutic effects of exercise on AT inflammation remain poorly understood. This review summarizes what is known about obesity-induced AT inflammation and immunomodulation and highlights mechanisms by which aerobic exercise combats inflammation by remodeling the AT immune landscape. Furthermore, key areas are highlighted that require future exploration and novel discoveries into the burgeoning field of how the biology of exercise affects AT immunity.

Xylo-Oligosaccharides in Prevention of Hepatic Steatosis and Adipose Tissue Inflammation: Associating Taxonomic and Metabolomic Patterns in Fecal Microbiomes with Biclustering

We have shown that prebiotic xylo-oligosaccharides (XOS) increased beneficial gut microbiota (GM) and prevented high fat diet-induced hepatic steatosis, but the mechanisms associated with these effects are not clear. We studied whether XOS affects adipose tissue inflammation and insulin signaling, and whether the GM and fecal metabolome explain associated patterns. XOS was supplemented or not with high (HFD) or low (LFD) fat diet for 12 weeks in male Wistar rats (n = 10/group). Previously analyzed GM and fecal metabolites were biclustered to reduce data dimensionality and identify interpretable groups of co-occurring genera and metabolites. Based on our findings, biclustering provides a useful algorithmic method for capturing such joint signatures. On the HFD, XOS-supplemented rats showed lower number of adipose tissue crown-like structures, increased phosphorylation of AKT in liver and adipose tissue as well as lower expression of hepatic miRNAs. XOS-supplemented rats had more fecal glycine and less hypoxanthine, isovalerate, branched chain amino acids and aromatic amino acids. Several bacterial genera were associated with the metabolic signatures. In conclusion, the beneficial effects of XOS on hepatic steatosis involved decreased adipose tissue inflammation and likely improved insulin signaling, which were further associated with fecal metabolites and GM.

Modulatory Effect of Intermittent Fasting on Adipose Tissue Inflammation: Amelioration of Cardiovascular Dysfunction in Early Metabolic Impairment

Cardiometabolic syndrome (CMS) is a cluster of maladaptive cardiovascular, renal, thrombotic, inflammatory, and metabolic disorders. It confers a high risk of cardiovascular mortality and morbidity. CMS is triggered by major shifts in lifestyle and dietary habits with increased consumption of refined, calorie-dense diets. Evidence indicates that diet-induced CMS is linked to Adipose tissue (AT) inflammation. This led to the proposal that adipose inflammation may be involved in metabolic derangements, such as insulin resistance and poor glycemic control, as well as the contribution to the inflammatory process predisposing patients to increased cardiovascular risk. Therefore, in the absence of direct pharmacological interventions for the subclinical phase of CMS, time restricted feeding regimens were anticipated to alleviate early metabolic damage and subsequent comorbidities. These regimens, referred to as intermittent fasting (IF), showed a strong positive impact on the metabolic state of obese and non-obese human subjects and animal models, positive AT remodeling in face of overnutrition and high fat diet (HFD) consumption, and improved CV outcomes. Here, we summarize the available evidence on the role of adipose inflammation in triggering cardiovascular impairment in the context of diet induced CMS with an emphasis on the involvement of perivascular adipose tissue. As well, we propose some possible molecular pathways linking intermittent fasting to the ameliorative effect on adipose inflammation and cardiovascular dysfunction under such circumstances. We highlight a number of targets, whose function changes in perivascular adipose tissue inflammation and could be modified by intermittent fasting acting as a novel approach to ameliorate the inflammatory status.

Interaction between IgA and gut microbiota and its role in controlling metabolic syndrome

Immunoglobulin A (IgA) is the most abundant immunoglobulin isotype secreted into the mucosal tissues, mainly intestinal mucus. Humans can produce several grams of IgA every day, accounting for three quarters of the body's total immunoglobulin content. IgA, together with mucus and antimicrobial peptides, forms the first line of defence for intestinal epithelial cells, protecting them from a significant number of intestinal antigens. IgA also plays a principal role in controlling the gut microbiota (GM), and disruption in IgA can result in dysbiosis, such as the enrichment of Proteobacteria, which are generally bound by IgA. Proteobacteria overexpansion is also usually seen in obesity and colitis. Consistent with this, IgA dysfunction frequently results in metabolic syndrome (MetS), including conditions such as obesity, adiposity, insulin resistance, and inflammation. In contrast, enhanced IgA function can improve, and even prevent, MetS. Interactions among IgA, GM, and metabolism provide a promising avenue to combat MetS.

The role of immune dysfunction in obesity-associated cancer risk, progression, and metastasis

Obesity has been linked to an increased risk of and a worse prognosis for several types of cancer. A number of interrelated mediators contribute to obesity's pro-tumor effects, including chronic adipose inflammation and other perturbations of immune cell development and function. Here, we review studies examining the impact of obesity-induced immune dysfunction on cancer risk and progression. While the role of adipose tissue inflammation in obesity-associated cancer risk has been well characterized, the effects of obesity on immune cell infiltration and activity within the tumor microenvironment are not well studied. In this review, we aim to highlight the impact of both adipose-mediated inflammatory signaling and intratumoral immunosuppressive signaling in obesity-induced cancer risk, progression, and metastasis.

Susceptibility and Severity of Viral Infections in Obesity: Lessons from Influenza to COVID-19. Does Leptin Play a Role?

The recent pandemic Sars-CoV2 infection and studies on previous influenza epidemic have drawn attention to the association between the obesity and infectious diseases susceptibility and worse outcome. Metabolic complications, nutritional aspects, physical inactivity, and a chronic unbalance in the hormonal and adipocytokine microenvironment are major determinants in the severity of viral infections in obesity. By these pleiotropic mechanisms obesity impairs immune surveillance and the higher leptin concentrations produced by adipose tissue and that characterize obesity substantially contribute to such immune response dysregulation. Indeed, leptin not only controls energy balance and body weight, but also plays a regulatory role in the interplay between energy metabolism and immune system. Since leptin receptor is expressed throughout the immune system, leptin may exert effects on cells of both innate and adaptive immune system. Chronic inflammatory states due to metabolic (i.e., obesity) as well as infectious diseases increase leptin concentrations and consequently lead to leptin resistance further fueling inflammation. Multiple factors, including inflammation and ER stress, contribute to leptin resistance. Thus, if leptin is recognized as one of the adipokines responsible for the low grade inflammation found in obesity, on the other hand, impairments of leptin signaling due to leptin resistance appear to blunt the immunologic effects of leptin and possibly contribute to impaired vaccine-induced immune responses. However, many aspects concerning leptin interactions with inflammation and immune system as well as the therapeutical approaches to overcome leptin resistance and reduced vaccine effectiveness in obesity remain a challenge for future research.

Activation of Bone Marrow Adaptive Immunity in Type 2 Diabetes: Rescue by Co-stimulation Modulator Abatacept

Background: Chronic low-grade inflammation and alterations in innate and adaptive immunity were reported in Type 2 diabetes (T2D). Here, we investigated the abundance and activation of T cells in the bone marrow (BM) of patients with T2D. We then verified the human data in a murine model and tested if the activation of T cells can be rescued by treating mice with abatacept, an immunomodulatory drug employed for the treatment of rheumatoid arthritis. Clinical evidence indicated abatacept can slow the decline in beta-cell function.

Methods: A cohort of 24 patients (12 with T2D) undergoing hip replacement surgery was enrolled in the study. Flow cytometry and cytokine analyses were performed on BM leftovers from surgery. We next compared the immune profile of db/db and control wt/db mice. In an additional study, db/db mice were randomized to receive abatacept or vehicle for 4 weeks, with endpoints being immune cell profile, indices of insulin sensitivity, and heart performance.

Results: Patients with T2D showed increased frequencies of BM CD4⁺ (2.8-fold, p = 0.001) and CD8⁺ T cells (1.8-fold, p = 0.01), with the upregulation of the activation marker CD69 and the homing receptor CCR7 in CD4⁺ (1.64-fold, p = 0.003 and 2.27-fold, p = 0.01, respectively) and CD8⁺ fractions (1.79-fold, p = 0.05 and 1.69-fold, p = 0.02, respectively). These differences were confirmed in a multivariable regression model. CCL19 (CCR7 receptor ligand) and CXCL10/11 (CXCR3 receptor ligands), implicated in T-cell migration and activation, were the most differentially modulated chemokines. Studies in mice confirmed the activation of adaptive immunity in T2D. Abatacept reduced the activation of T cells and the levels of proinflammatory cytokines and improved cardiac function but not insulin sensitivity.

Conclusions: Results provide proof-of-concept evidence for the activation of BM adaptive immunity in T2D. In mice, treatment with abatacept dampens the activation of adaptive immunity and protects from cardiac damage.

Role of obesity-induced inflammation in the development of insulin resistance and type 2 diabetes: history of the research and remaining questions

The prevalence of obesity has increased alarmingly both worldwide and in Korea. This has also dramatically increased the prevalence of chronic obesity-associated diseases, including type 2 diabetes (T2D). Extensive studies on the molecular etiology of T2D have revealed several potential mechanisms by which obesity induces the development of insulin resistance and T2D. One of these is low-grade chronic inflammation. Studies hinting at the existence of this phenomenon were first published about 30 years ago. Ten years later, several seminal papers confirmed its existence, which then led to a rapid and massive escalation of research in this field. Today, the notion that obesity-induced inflammation mediates T2D is now well-accepted. This paper will review the key developments in this field, including the discovery that obesity-induced inflammation and insulin resistance is mainly regulated by adipose tissue-resident immune cells, particularly those in visceral adipose tissue. This review further details the research areas, including (1) the obesity-related factors that induce adipose tissue macrophage (ATM) inflammation, (2) the precise effector functions by which adipose tissue immune cells promote insulin resistance, (3) whether there are early immunological events that have an outsize effect on later events and could be targeted to arrest the development of insulin resistance, (4) the roles played by nonimmunological functions of ATMs and other immune cells, and (5) whether there are noncanonical immune responses to obesity (i.e., immune responses that are unique to obesity and cannot be detected by following the discoveries in the classical immunity field).

TFEB-GDF15 axis protects against obesity and insulin resistance as a lysosomal stress response

TFEB, a key regulator of lysosomal biogenesis and autophagy, is induced not only by nutritional deficiency but also by organelle stress. Here, we find that Tfeb and its downstream genes are upregulated together with lipofuscin accumulation in adipose tissue macrophages (ATMs) of obese mice or humans, suggestive of obesity-associated lysosomal dysfunction/stress in ATMs. Macrophage-specific TFEB-overexpressing mice display complete abrogation of diet-induced obesity, adipose tissue inflammation and insulin resistance, which is independent of autophagy, but dependent on TFEB-induced GDF15 expression. Palmitic acid induces Gdf15 expression through lysosomal Ca²⁺-mediated TFEB nuclear translocation in response to lysosomal stress. In contrast, mice fed a high-fat diet with macrophage-specific Tfeb deletion show aggravated adipose tissue inflammation and insulin resistance, accompanied by reduced GDF15 level. Finally, we observe activation of TFEB-GDF15 in ATMs of obese humans as a consequence of lysosomal stress. These findings highlight the importance of the TFEB-GDF15 axis as a lysosomal stress response in obesity or metabolic syndrome and as a promising therapeutic target for treatment of these conditions.

COVID-19 severity in obese patients: Potential mechanisms and molecular targets for clinical intervention

With the global spread of SARS-CoV-2, millions of people have been affected leading to the declaration of coronavirus disease 2019 (COVID-19) as a pandemic by the WHO. Several studies have linked the severity of COVID-19 cases and increased fatality in patients with obesity and other comorbid conditions such as diabetes, cardiovascular diseases, hypertension, and kidney disease. Obesity, a metabolically deranged condition, establishes a low-grade chronic inflammation in the body, which affects different organs and promotes the development of several other diseases. The ways in which SARS-CoV-2 infection aggravates the already overloaded body organs with inflammation or vice versa has perplexed the researchers. As a result, there is an intensified search for the clear-cut mechanism to understand the link of obesity with the increased severity of COVID-19 in obese patients. In this article we have discussed various mechanisms linking obesity, inflammation, and COVID-19 to enhance the understanding of the disease process and help the clinicians and scientists develop potential cellular, molecular and metabolic targets for clinical intervention and management of COVID-19 severity in obese patients.

Hyper-metabolic B cells in the spleens of old mice make antibodies with autoimmune specificities

BACKGROUND

Aging is associated with increased intrinsic B cell inflammation, decreased protective antibody responses and increased autoimmune antibody responses. The effects of aging on the metabolic phenotype of B cells and on the metabolic programs that lead to the secretion of protective versus autoimmune antibodies are not known.

METHODS

Splenic B cells and the major splenic B cell subsets, Follicular (FO) and Age-associated B cells (ABCs), were isolated from the spleens of young and old mice and left unstimulated. The RNA was collected to measure the expression of markers associated with intrinsic inflammation and autoimmune antibody production by qPCR. B cells and B cell subsets were also stimulated with CpG and supernatants collected after 7 days to measure autoimmune IgG secretion by ELISA. Metabolic measures (oxygen consumption rate, extracellular acidification rate and glucose uptake) were performed using a Seahorse XFp extracellular flux analyzer.

RESULTS

Results have identified the subset of ABCs, whose frequencies and numbers increase with age and represent the most pro-inflammatory B cell subset, as the cell type mainly if not exclusively responsible for the expression of inflammatory markers and for the secretion of autoimmune antibodies in the spleen of old mice. Hyper-inflammatory ABCs from old mice are also hyper-metabolic, as compared to those from young mice and to the subset of FO B cells, a feature needed not only to support their higher expression of RNA for inflammatory markers but also their higher autoimmune antibody secretion.

CONCLUSIONS

These results identify a relationship between intrinsic inflammation, metabolism and autoimmune B cells and suggest possible ways to understand cellular mechanisms that lead to the generation of pathogenic B cells, that are hyper-inflammatory and hyper-metabolic, and secrete IgG antibodies with autoimmune specificities.

T cells accumulate in non-diabetic islets during ageing

Background

The resident immune population of pancreatic islets has roles in islet development, beta cell physiology, and the pathology of diabetes. These roles have largely been attributed to islet macrophages, comprising 90% of islet immune cells (in the absence of islet autoimmunity), and, in the case of type 1 diabetes, to infiltrating autoreactive T cells. In adipose, tissue-resident and recruited T and B cells have been implicated in the development of insulin resistance during diet-induced obesity and ageing, but whether this is paralleled in the pancreatic islets is not known. Here, we investigated the non-macrophage component of resident islet immune cells in islets isolated from C57BL/6 J male mice during ageing (3 to 24 months of age) and following similar weight gain achieved by 12 weeks of 60% high fat diet. Immune cells were also examined by flow cytometry in cadaveric non-diabetic human islets.

Results

Immune cells comprised 2.7 ± 1.3% of total islet cells in non-diabetic mouse islets, and 2.3 ± 1.7% of total islet cells in non-diabetic human islets. In 3-month old mice on standard diet, B and T cells each comprised approximately 2–4% of the total islet immune cell compartment, and approximately 0.1% of total islet cells. A similar amount of T cells were present in non-diabetic human islets. The majority of islet T cells expressed the αβ T cell receptor, and were comprised of CD8-positive, CD4-positive, and regulatory T cells, with a minor population of γδ T cells. Interestingly, the number of islet T cells increased linearly (R² = 0.9902) with age from 0.10 ± 0.05% (3 months) to 0.38 ± 0.11% (24 months) of islet cells. This increase was uncoupled from body weight, and was not phenocopied by a degree similar weight gain induced by high fat diet in mice.

Conclusions

This study reveals that T cells are a part of the normal islet immune population in mouse and human islets, and accumulate in islets during ageing in a body weight-independent manner. Though comprising only a small subset of the immune cells within islets, islet T cells may play a role in the physiology of islet ageing.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-021-00221-4.

Dysregulation of Leukocyte Trafficking in Type 2 Diabetes: Mechanisms and Potential Therapeutic Avenues

Type 2 Diabetes Mellitus (T2DM) is a chronic inflammatory disorder that is characterized by chronic hyperglycemia and impaired insulin signaling which in addition to be caused by common metabolic dysregulations, have also been associated to changes in various immune cell number, function and activation phenotype. Obesity plays a central role in the development of T2DM. The inflammation originating from obese adipose tissue develops systemically and contributes to insulin resistance, beta cell dysfunction and hyperglycemia. Hyperglycemia can also contribute to chronic, low-grade inflammation resulting in compromised immune function. In this review, we explore how the trafficking of innate and adaptive immune cells under inflammatory condition is dysregulated in T2DM. We particularly highlight the obesity-related accumulation of leukocytes in the adipose tissue leading to insulin resistance and beta-cell dysfunction and resulting in hyperglycemia and consequent changes of adhesion and migratory behavior of leukocytes in different vascular beds. Thus, here we discuss how potential therapeutic targeting of leukocyte trafficking could be an efficient way to control inflammation as well as diabetes and its vascular complications.

Deep Learning for Integrated Analysis of Insulin Resistance with Multi-Omics Data

Technological advances in next-generation sequencing (NGS) have made it possible to uncover extensive and dynamic alterations in diverse molecular components and biological pathways across healthy and diseased conditions. Large amounts of multi-omics data originating from emerging NGS experiments require feature engineering, which is a crucial step in the process of predictive modeling. The underlying relationship among multi-omics features in terms of insulin resistance is not well understood. In this study, using the multi-omics data of type II diabetes from the Integrative Human Microbiome Project, from 10,783 features, we conducted a data analytic approach to elucidate the relationship between insulin resistance and multi-omics features, including microbiome data. To better explain the impact of microbiome features on insulin classification, we used a developed deep neural network interpretation algorithm for each microbiome feature’s contribution to the discriminative model output in the samples.

B Cells with a Senescent-Associated Secretory Phenotype Accumulate in the Adipose Tissue of Individuals with Obesity

Senescent cells accumulate in the adipose tissue (AT) of individuals with obesity and secrete multiple factors that constitute the senescence-associated secretory phenotype (SASP). This paper aimed at the identification of B cells with a SASP phenotype in the AT, as compared to the peripheral blood, of individuals with obesity. Our results show increased expression of SASP markers in AT versus blood B cells, a phenotype associated with a hyper-metabolic profile necessary to support the increased immune activation of AT-derived B cells as compared to blood-derived B cells. This hyper-metabolic profile is needed for the secretion of the pro-inflammatory mediators (cytokines, chemokines, micro-RNAs) that fuel local and systemic inflammation.

Helix-Loop-Helix Factor Id3 (Inhibitor of Differentiation 3): A Novel Regulator of Hyaluronan-Mediated Adipose Tissue Inflammation

OBJECTIVE

The aim of this study was to unravel mechanisms whereby deficiency of the transcription factor Id3 (inhibitor of differentiation 3) leads to metabolic dysfunction in visceral obesity. We investigated the impact of loss of Id3 on hyaluronic acid (HA) production by the 3 HAS isoenzymes (HA synthases; -1, -2, and -3) and on obesity-induced adipose tissue (AT) accumulation of proinflammatory B cells. Approach and Results: Male Id3-/- mice and respective wild-type littermate controls were fed a 60% high-fat diet for 4 weeks. An increase in inflammatory B2 cells was detected in Id3-/- epididymal AT. HA accumulated in epididymal AT of high-fat diet-fed Id3-/- mice and circulating levels of HA were elevated. Has2 mRNA expression was increased in epididymal AT of Id3-/- mice. Luciferase promoter assays showed that Id3 suppressed Has2 promoter activity, while loss of Id3 stimulated Has2 promoter activity. Functionally, HA strongly promoted B2 cell adhesion in the AT and on cultured vascular smooth muscle cells of Id3-/- mice, an effect sensitive to hyaluronidase.

CONCLUSIONS

Our data demonstrate that loss of Id3 increases Has2 expression in the epididymal AT, thereby promoting HA accumulation. In turn, elevated HA content promotes HA-dependent binding of B2 cells and an increase in the B2 cells in the AT, which contributes to AT inflammation.

Immune Response to SARS-CoV-2 Infection in Obesity and T2D: Literature Review

In December 2019, a novel coronavirus known as SARS-CoV-2 was first detected in Wuhan, China, causing outbreaks of the coronavirus disease COVID-19 that has now spread globally. For this reason, The World Health Organization (WHO) declared COVID-19 a public health emergency in March 2020. People living with pre-existing conditions such as obesity, cardiovascular diseases, type 2 diabetes (T2D), and chronic kidney and lung diseases, are prone to develop severe forms of disease with fatal outcomes. Metabolic diseases such as obesity and T2D alter the balance of innate and adaptive responses. Both diseases share common features characterized by augmented adiposity associated with a chronic systemic low-grade inflammation, senescence, immunoglobulin glycation, and abnormalities in the number and function of adaptive immune cells. In obese and T2D patients infected by SARS-CoV-2, where immune cells are already hampered, this response appears to be stronger. In this review, we describe the abnormalities of the immune system, and summarize clinical findings of COVID-19 patients with pre-existing conditions such as obesity and T2D as this group is at greater risk of suffering severe and fatal clinical outcomes.

Impact of obesity and SARS-CoV-2 infection: implications for host defence - a living review

The role of obesity in the pathophysiology of respiratory virus infections has become particularly apparent during the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, where obese patients are twice as likely to suffer from severe coronavirus disease 2019 (COVID-19) than healthy weight individuals. Obesity results in disruption of systemic lipid metabolism promoting a state of chronic low-grade inflammation. However, it remains unclear how these underlying metabolic and cellular processes promote severe SARS-CoV-2 infection. Emerging data in SARS-CoV-2 and Influenza A virus (IAV) infections show that viruses can further subvert the host's altered lipid metabolism and exploit obesity-induced alterations in immune cell metabolism and function to promote chronic inflammation and viral propagation. In this review, we outline the systemic metabolic and immune alterations underlying obesity and discuss how these baseline alterations impact the immune response and disease pathophysiology. A better understanding of the immunometabolic landscape of obese patients may aid better therapies and future vaccine design.

Epigenetic Regulation of Adipogenesis in Development of Metabolic Syndrome

Obesity is one of the biggest public health concerns identified by an increase in adipose tissue mass as a result of adipocyte hypertrophy and hyperplasia. Pertaining to the importance of adipose tissue in various biological processes, any alteration in its function results in impaired metabolic health. In this review, we discuss how adipose tissue maintains the metabolic health through secretion of various adipokines and inflammatory mediators and how its dysfunction leads to the development of severe metabolic disorders and influences cancer progression. Impairment in the adipocyte function occurs due to individuals' genetics and/or environmental factor(s) that largely affect the epigenetic profile leading to altered gene expression and onset of obesity in adults. Moreover, several crucial aspects of adipose biology, including the regulation of different transcription factors, are controlled by epigenetic events. Therefore, understanding the intricacies of adipogenesis is crucial for recognizing its relevance in underlying disease conditions and identifying the therapeutic interventions for obesity and metabolic syndrome.

Chlorogenic Acid-Induced Gut Microbiota Improves Metabolic Endotoxemia

BACKGROUND

Coffee can regulate glucose homeostasis but the underlying mechanism is unclear. This study investigated the preventive and therapeutic effects of chlorogenic acid (CGA), a polyphenol that is found in coffee, on obesity and obesity-related metabolic endotoxemia.

METHOD

Male 4-week-old C57BL/6 mice were fed either normal chow or a high-fat diet or 20 weeks and half the mice in each group were gavaged with CGA. Oral glucose tolerance tests (OGTTs) and insulin tolerance tests (ITTs) were performed. Markers of inflammation and intestinal barrier function were assayed. The composition of the gut microbiota was analyzed by 16S rRNA high-throughput pyrosequencing. The role of CGA-altered microbiota in metabolic endotoxemia was verified by fecal microbiota transplantation.

RESULTS

CGA protected against HFD-induced weight gain, decreased the relative weight of subcutaneous and visceral adipose, improved intestinal barrier integrity, and prevented glucose metabolic disorders and endotoxemia (P <0.05). CGA significantly changed the composition of the gut microbiota and increased the abundance of short chain fatty acid (SCFA)-producers (e.g., Dubosiella, Romboutsia, Mucispirillum, and Faecalibaculum) and Akkermansia, which can protect the intestinal barrier. In addition, mice with the CGA-altered microbiota had decreased body weight and fat content and inhibited metabolic endotoxemia.

CONCLUSION

CGA-induced changes in the gut microbiota played an important role in the inhibition of metabolic endotoxemia in HFD-fed mice.

Protein Glycosylation in Diabetes

Diabetes mellitus is a group of metabolic disorders characterized by the presence of hyperglycaemia. Due to its high prevalence and substantial heterogeneity, many studies have been investigating markers that could identify predisposition for the disease development, differentiate between the various subtypes, establish early diagnosis, predict complications or represent novel therapeutic targets. N-glycans, complex oligosaccharide molecules covalently linked to proteins, emerged as potential markers and functional effectors of various diabetes subtypes, appearing to have the capacity to meet these requirements. For instance, it has been shown that N-glycome changes in patients with type 2 diabetes and that N-glycans can even identify individuals with an increased risk for its development. Moreover, genome-wide association studies identified glycosyltransferase genes as candidate causal genes for both type 1 and type 2 diabetes. N-glycans have also been suggested to have a major role in preventing the impairment of glucose-stimulated insulin secretion by modulating cell surface expression of glucose transporters. In this chapter we aimed to describe four major diabetes subtypes: type 1, type 2, gestational and monogenic diabetes, giving an overview of suggested role for N-glycosylation in their development, diagnosis and management.

Insulin Resistance Adversely Affect IVF Outcomes in Lean Women Without PCOS

OBJECTIVE

To investigate the effects of insulin resistance (IR) on IVF outcomes and a potential underlying mechanism in lean women without PCOS.

DESIGN

A prospective cohort study at the University Clinic.

SETTING

IVF center at the University setting.

PATIENTS

A total of 155 lean women (body mass index <25) without PCOS undergoing IVF cycle.

INTERVENTION

Patients were allocated to IR and non-IR groups based on HOMA-M₁₂₀.

MAIN OUTCOME MEASURES

IVF outcomes, including egg quality, the percentage of mature oocytes, fertilization rate, blastocyst formation rate, advanced embryo rate, and cumulative live birth rate were investigated. Auto-immune parameters, peripheral blood immunophenotypes, thyroid hormone, homocysteine, and 25-OH-vitamin D₃ (25-OH-VD₃) levels were analyzed.

RESULTS

The percentage of mature oocytes and blastocyst formation rate were significantly lower in the IR group as compared with those of the non-IR group (p<0.05, respectively). The proportion of peripheral blood CD19⁺ B cells was significantly higher in the IR group than those of the non-IR group (p<0.05). Homocysteine, 25-OH-VD_3, and auto-immune parameters were the same between the two groups.

CONCLUSION

In lean infertile women without PCOS, IR is associated with the decreased percentage of mature eggs and poor embryo quality in which B cell immunity may play a role.

B cell depletion therapies in autoimmune disease: advances and mechanistic insights

In the past 15 years, B cells have been rediscovered to be not merely bystanders but rather active participants in autoimmune aetiology. This has been fuelled in part by the clinical success of B cell depletion therapies (BCDTs). Originally conceived as a method of eliminating cancerous B cells, BCDTs such as those targeting CD20, CD19 and BAFF are now used to treat autoimmune diseases, including systemic lupus erythematosus and multiple sclerosis. The use of BCDTs in autoimmune disease has led to some surprises. For example, although antibody-secreting plasma cells are thought to have a negative pathogenic role in autoimmune disease, BCDT, even when it controls the disease, has limited impact on these cells and on antibody levels. In this Review, we update our understanding of B cell biology, review the results of clinical trials using BCDT in autoimmune indications, discuss hypotheses for the mechanism of action of BCDT and speculate on evolving strategies for targeting B cells beyond depletion.