Differential adipokine receptor expression on circulating leukocyte subsets in lean and obese children

Unravelling metabolic factors impacting iNKT cell biology in obesity

Obesity and related diseases have reached epidemic proportions and continue to rise. Beyond creating an economical burden, obesity and its co-morbidities are associated with shortened human life expectancy. Despite major advances, the underlying mechanisms of obesity remain not fully elucidated. Recently, several studies have highlighted that various immune cells are metabolically reprogrammed in obesity, thereby profoundly affecting the immune system. This sheds light on a new field of interest: the impact of obesity-related systemic metabolic changes affecting immune system that could lead to immunosurveillance loss. Among immune cells altered by obesity, invariant Natural Killer T (iNKT) cells have recently garnered intense focus due to their ability to recognize lipid antigen. While iNKT cells are well-described to be affected by obesity, how and to what extent immunometabolic factors (e.g., lipids, glucose, cytokines, adipokines, insulin and free fatty acids) can drive iNKT cells alterations remains unclear, but represent an emerging field of research. Here, we review the current knowledge on iNKT cells in obesity and discuss the immunometabolic factors that could modulate their phenotype and activity.

Impact of nutritional status on vaccine-induced immunity in children living in South Africa: Investigating the B-cell repertoire and metabolic hormones

OBJECTIVES

We explored the role of metabolic hormones and the B-cell repertoire in the association between nutritional status and vaccine responses.

METHODS

In this prospective cohort study, nested within a larger randomized open-label trial, 211 South African children received two doses of measles vaccine and two or three doses of pneumococcal conjugate vaccine (PCV). Metabolic markers (leptin, ghrelin and adiponectin) and distribution of B-cell subsets (n = 106) were assessed at 18 months of age.

RESULTS

Children with a weight-for-height z-score (WHZ) ≤ -1 standard deviation (SD) at booster vaccination had a decreased mean serotype-specific PCV IgG response compared with those with WHZ > -1 and <+1 SD or WHZ ≥ +1 SD at 9 months post-booster (18 months of age). (Naive) pre-germinal center B-cells were associated with pneumococcal antibody decay between one to nine months post-booster. Predictive performance of elastic net models for the combined effect of B-cell subsets, metabolic hormones and nutritional status (in addition to age, sex, and randomization group) on measles and PCV vaccine response had an average area under the receiver operating curve of 0.9 and 0.7, respectively.

CONCLUSIONS

The combined effect of B-cell subsets, metabolic hormones and nutritional status correlated well with the vaccination response for measles and most PCV serotypes.

CLINICALTRIALS

gov registration of parent studies: NCT02943902 and NCT03330171.

Short-term induced hyperinsulinaemia and dexamethasone challenge do not affect circulating total adiponectin concentrations in insulin-sensitive ponies

BACKGROUND

Hypoadiponectinaemia is a risk factor for endocrinopathic laminitis, but the directionality and nature of its association with insulin dysregulation is unclear.

OBJECTIVES

To investigate the effects of short-term induced hyperinsulinaemia and dexamethasone challenge on circulating [total adiponectin] and whole blood expression of adiponectin (AdipoR1 and AdipoR2), insulin, and insulin-like growth factor 1 (IGF-1) receptors in insulin-sensitive ponies.

STUDY DESIGN

In vivo experiment.

METHODS

Six never-laminitic, insulin-sensitive, native-breed UK ponies first underwent a dexamethasone challenge (0.08 mg/kg i.v.) with blood samples collected every 15 min over 3 h. After a 14-day washout period, hyperinsulinaemia was induced for 9 h via a euglycaemic-hyperinsulinaemic clamp (EHC), with blood samples collected every 30 min. Serum [insulin], plasma [total adiponectin], and plasma [IGF-1] were measured using validated assays and receptor gene expression was assessed via quantitative polymerase chain reaction (qPCR). Finally, whole blood was incubated with 10-1000 ng/mL dexamethasone for 3 h at 37°C to investigate its direct effects on gene expression.

RESULTS

There were no adverse effects observed during either protocol. Dexamethasone challenge did not alter circulating [insulin] or [total adiponectin] at any time-point, but significantly upregulated AdipoR1 and IGF-1R expression at 150 and 180 min. Ex vivo incubation of whole blood with dexamethasone did not alter expression of the genes examined. There was no change in [total adiponectin] or expression of the genes examined associated with EHC-induced hyperinsulinemia.

MAIN LIMITATIONS

This was a small sample size that included only native-breed ponies; total adiponectin was measured rather than high-molecular-weight adiponectin.

CONCLUSIONS

Short-term induced hyperinsulinaemia and dexamethasone challenge did not affect circulating [total adiponectin] in insulin-sensitive ponies. However, dexamethasone administration was associated with upregulation of two receptors linked to adiponectin signalling, suggesting that a physiological response occurred possibly to counteract dexamethasone-associated changes in tissue insulin sensitivity.

Adolescent intermittent ethanol (AIE) produces lasting, sex-specific changes in rat body fat independent of changes in white blood cell composition

Early initiation of alcohol use during adolescence, and adolescent binge drinking are risk factors for the development of alcohol use disorder later in life. Adolescence is a time of rapid sex-dependent neural, physiological, and behavioral changes as well as a period of heightened vulnerability to many effects of alcohol. The goal of the present studies was to determine age-related changes in blood (leukocyte populations) and body composition across adolescence and early adulthood, and to investigate whether adolescent intermittent ethanol (AIE) exposure would alter the trajectory of adolescent development on these broad physiological parameters. We observed significant ontogenetic changes in leukocyte populations that were mirrored by an age-related increase in cytokine expression among mixed populations of circulating leukocytes. Despite these developmental changes, AIE did not significantly alter overall leukocyte numbers or cytokine gene expression. However, AIE led to sex-specific changes in body fat mass and fat percentage, with AIE-exposed male rats showing significantly decreased fat levels and female rats showing significantly increased fat levels relative to controls. These changes suggest that while AIE may not alter overall leukocyte levels, more complex phenotypic changes in leukocyte populations could underlie previously reported differences in cytokine expression. Coupled with long-term shifts in adipocyte levels, this could have long-lasting effects on innate immunity and the capacity of individuals to respond to later immunological and physiological threats.

Impact of body mass index on peripheral and uterine immune status in the window of implantation in patients with recurrent reproductive failure

This study aimed to investigate whether maternal obesity affects the immune status of peripheral blood and endometrium in patients with recurrent reproductive failure classified according to their body mass index (BMI). A total of 228 repeated implantation failure (RIF) and 266 recurrent miscarriage (RM) patients were enrolled in the study and further subdivided into three groups according to their BMI: (i) normal weight (18.5≤ BMI <23); (ii) overweight (23≤ BMI <25); and (iii) obese (BMI ≥25). Peripheral blood and endometrium samples were collected in the mid-luteal phase before IVF treatment or natural pregnancy. Peripheral immunocytes were analyzed by flow cytometry, while uterine immune cells were subjected to immunohistochemistry. In RM patients, significantly increased peripheral helper T cells and decreased cytotoxic T cells, NK cells were observed in the obese group compared with the normal-weight group. Meanwhile, in the endometrium, the percentage of NK cell, macrophage cell, M2 macrophage cell, and Treg cell significantly reduced with increased BMI in RIF patients, and the percentage of NK cell and M2 macrophage cell significantly decreased with increased BMI in RM patients. In conclusion, obesity may cause endometrial immune disorder in recurrent reproductive failure women, but was only associated with the peripheral immune change in RM patients.

Leptin, Adiponectin, and Melatonin Modulate Colostrum Lymphocytes in Mothers with Obesity

Pregnancy complicated by obesity is associated with adverse triggered gestational and neonatal outcomes, with reductions in the subtypes of CD4+ T-lymphocytes representing the modulators of inflammation. It needs to be better established how maternal nutritional statuses impact the neuroendocrine-immune system's action and affect the immunological mechanisms of the maternal-infant relationship via breastfeeding. This study examined the effects of maternal obesity on human colostrum lymphocytes and the intracellular mechanisms of lymphocyte modulation in the presence of leptin, adiponectin, and melatonin via cell proliferation; the release of intracellular calcium; and apoptosis induction. This cross-sectional study analyzed colostrum samples from 52 puerperal splits and divided them into overweight and eutrophic groups. Colostrum lymphocytes underwent immunophenotyping and cell proliferation by flow cytometry and intracellular calcium release and apoptosis assays by immunofluorescence in the presence or absence of hormones. Significant differences were considered when p < 0.05 by the chi-square or t-test. Maternal obesity reduced the population of T-lymphocytes and TCD4+ in human colostrum and proliferative activities (p < 0.05). These hormones restore lymphocyte proliferation to a level similar to the eutrophic group (p < 0.05). Leptin, adiponectin, melatonin hormones, and biological actions consolidated in the scientific literature also represent maternal and infant protection mechanisms via colostrum and the modulation of human colostrum lymphocytes.

Immunometabolic factors in adolescent chronic disease are associated with Th1 skewing of invariant Natural Killer T cells

Invariant Natural Killer T (iNKT) cells respond to the ligation of lipid antigen-CD1d complexes via their T-cell receptor and are implicated in various immunometabolic diseases. We considered that immunometabolic factors might affect iNKT cell function. To this end, we investigated iNKT cell phenotype and function in a cohort of adolescents with chronic disease and immunometabolic abnormalities. We analyzed peripheral blood iNKT cells of adolescents with cystic fibrosis (CF, n = 24), corrected coarctation of the aorta (CoA, n = 25), juvenile idiopathic arthritis (JIA, n = 20), obesity (OB, n = 20), and corrected atrial septal defect (ASD, n = 25) as controls. To study transcriptional differences, we performed RNA sequencing on a subset of obese patients and controls. Finally, we performed standardized co-culture experiments using patient plasma, to investigate the effect of plasma factors on iNKT cell function. We found comparable iNKT cell numbers across patient groups, except for reduced iNKT cell numbers in JIA patients. Upon ex-vivo activation, we observed enhanced IFN-γ/IL-4 cytokine ratios in iNKT cells of obese adolescents versus controls. The Th1-skewed iNKT cell cytokine profile of obese adolescents was not explained by a distinct transcriptional profile of the iNKT cells. Co-culture experiments with patient plasma revealed that across all patient groups, obesity-associated plasma factors including LDL-cholesterol, leptin, and fatty-acid binding protein 4 (FABP4) coincided with higher IFN-γ production, whereas high HDL-cholesterol and insulin sensitivity (QUICKI) coincided with higher IL-4 production. LDL and HDL supplementation in co-culture studies confirmed the effects of lipoproteins on iNKT cell cytokine production. These results suggest that circulating immunometabolic factors such as lipoproteins may be involved in Th1 skewing of the iNKT cell cytokine response in immunometabolic disease.

Neuroimmune Interactions and Rhythmic Regulation of Innate Lymphoid Cells

The Earth’s rotation around its axis, is one of the parameters that never changed since life emerged. Therefore, most of the organisms from the cyanobacteria to humans have conserved natural oscillations to regulate their physiology. These daily oscillations define the circadian rhythms that set the biological clock for almost all physiological processes of an organism. They allow the organisms to anticipate and respond behaviorally and physiologically to changes imposed by the day/night cycle. As other physiological systems, the immune system is also regulated by circadian rhythms and while diurnal variation in host immune responses to lethal infection have been observed for many decades, the underlying mechanisms that affect immune function and health have only just started to emerge. These oscillations are generated by the central clock in our brain, but neuroendocrine signals allow the synchronization of the clocks in peripheral tissues. In this review, we discuss how the neuroimmune interactions create a rhythmic activity of the innate lymphoid cells. We highlight how the disruption of these rhythmic regulations of immune cells can disturb homeostasis and lead to the development of chronic inflammation in murine models.

The transcriptome-wide association search for genes and genetic variants which associate with BMI and gestational weight gain in women with type 1 diabetes

BACKGROUND

Clinical data suggest that BMI and gestational weight gain (GWG) are strongly interconnected phenotypes; however, the genetic basis of the latter is rather unclear. Here we aim to find genes and genetic variants which influence BMI and/or GWG.

METHODS

We have genotyped 316 type 1 diabetics using Illumina Infinium Omni Express Exome-8 v1.4 arrays. The GIANT, ARIC and T2D-GENES summary statistics were used for TWAS (performed with PrediXcan) in adipose tissue. Next, the analysis of association of imputed expression with BMI in the general and diabetic cohorts (Analysis 1 and 2) or GWG (Analysis 3 and 4) was performed, followed by variant association analysis (1 Mb around identified loci) with the mentioned phenotypes.

RESULTS

In Analysis 1 we have found 175 BMI associated genes and 19 variants (p < 10-4) which influenced GWG, with the strongest association for rs11465293 in CCL24 (p = 3.18E-06). Analysis 2, with diabetes included in the model, led to discovery of 1812 BMI associated loci and 207 variants (p < 10-4) influencing GWG, with the strongest association for rs9690213 in PODXL (p = 9.86E-07). In Analysis 3, among 648 GWG associated loci, 2091 variants were associated with BMI (FDR < 0.05). In Analysis 4, 7 variants in GWG associated loci influenced BMI in the ARIC cohort.

CONCLUSIONS

Here, we have shown that loci influencing BMI might have an impact on GWG and GWG associated loci might influence BMI, both in the general and T1DM cohorts. The results suggest that both phenotypes are related to insulin signaling, glucose homeostasis, mitochondrial metabolism, ubiquitinoylation and inflammatory responses.

Obesity and immune status in children

PURPOSE OF REVIEW

Childhood obesity, with persistent chronic inflammation, is a worldwide epidemic. Obesity causes dysregulation throughout the immune system, affecting the balance and levels of cytokines, adipokines, and innate and adaptive immune cells. The present review focuses on the impact of obesity on immune function in children: altering the baseline activation state of immune cells and affecting the ability of the host to combat pathogens and malignancy and respond appropriately to vaccination.

RECENT FINDINGS

Obesity causes dysregulation of the immune system. Single-cell RNA-sequencing of adipose tissue and resident immune cells is quantifying the impact of obesity on the frequency of immune cell subsets and their states. The system-wide alterations in immune function in obesity are most evident upon perturbation, including the response to infection (e.g. increased risk of severe COVID-19 in the ongoing pandemic), vaccination, and malignancy. However, mechanistic research in pediatric obesity is limited and this impacts our ability to care for these children.

SUMMARY

We must better understand baseline and perturbed immune health in obese children to determine how to account for altered frequency and function of humoral and cellular immune components in acute infection, during vaccine design and when considering therapeutic options for this complex, medically vulnerable group.

The role of adipokines in the modulation of lymphoid lineage cell development and activity: An overview

Adipokines are predominantly known to play a vital role in the control of food intake, energy homeostasis and regulation of glucose and lipid metabolism. However, evidence supporting the concept of their extensive involvement in immune system defence mechanisms and inflammatory processes continues to grow. Some of the adipokines, that is, leptin and resistin, have been recognized to exhibit mainly pro-inflammatory properties, whereas others such as visfatin, chemerin, apelin and vaspin have been found to exert regulatory effects. In contrast, adiponectin or omentin are known for their anti-inflammatory activities. Hence, adipokines influence the activity of various cells engaged in innate immune response and inflammatory processes mainly by affecting adhesion molecule expression, chemotaxis, apoptosis and phagocytosis, as well as mediators production and release. However, much less is known about the role of adipokines in processes involving lymphoid lineage cells. This review summarizes the current knowledge regarding the importance of different adipokines in the lymphopoiesis, recirculation, differentiation and polarization of lymphoid lineage cells. It also provides insight into the influence of selected adipokines on the activity of those cells in tissues.

Mesenchymal stromal cells in bone marrow express adiponectin and are efficiently targeted by an adiponectin promoter-driven Cre transgene

Stromal cells in bone marrow (BM) constitute a specific microenvironment supporting the development and maintenance of hematopoietic cells. Adiponectin is a cytokine secreted by adipocytes. Besides its anti-diabetic and anti-atherogenic roles, adiponectin reportedly regulates the development and function of hematopoietic cells in BM. However, it remains unclear whether mesenchymal stromal cells in BM express adiponectin. Here, we show that PDGFRβ+VCAM-1+ stromal cells express adiponectin. Lineage tracing revealed that a majority of PDGFRβ+VCAM-1+ cells were targeted by an adiponectin promoter-driven Cre (Adipoq-Cre) transgene. Additionally, the Adipoq-Cre transgene targets a minority of osteoblasts at a younger age but larger populations are targeted at an older age. Furthermore, the Adipoq-Cre transgene targets almost all CXCL12-abundant reticular (CAR) cells and most of the stromal cells targeted by the Adipoq-Cre transgene are CAR cells. Finally, deletion of interleukin-7 (IL-7) by the Adipoq-Cre transgene resulted in severe impairment of B lymphopoiesis in BM. These results demonstrate that PDGFRβ+VCAM-1+ stromal cells in BM express adiponectin and are targeted by the Adipoq-Cre transgene, suggesting a broader specificity of the Adipoq-Cre transgene.

Obesity-Associated Alterations of Natural Killer Cells and Immunosurveillance of Cancer

Obesity is accompanied by a systemic chronic low-grade inflammation as well as dysfunctions of several innate and adaptive immune cells. Recent findings emphasize an impaired functionality and phenotype of natural killer (NK) cells under obese conditions. This review provides a detailed overview on research related to overweight and obesity with a particular focus on NK cells. We discuss obesity-associated alterations in subsets, distribution, phenotype, cytotoxicity, cytokine secretion, and signaling cascades of NK cells investigated in vitro as well as in animal and human studies. In addition, we provide recent insights into the effects of physical activity and obesity-associated nutritional factors as well as the reduction of body weight and fat mass on NK cell functions of obese individuals. Finally, we highlight the impact of impaired NK cell physiology on obesity-associated diseases, focusing on the elevated susceptibility for viral infections and increased risk for cancer development and impaired treatment response.

Adipocytokines in Rheumatoid Arthritis: The Hidden Link between Inflammation and Cardiometabolic Comorbidities

Rheumatoid arthritis is a chronic autoimmune disease affecting typically synovial joints and leading to progressive articular damage, disability, and reduced quality of life. Despite better recent therapeutic strategies improving long-term outcomes, RA is associated with a high rate of comorbidities, infections, malignancies, and cardiovascular disease (CVD). Remarkably, some well-known pathogenic proinflammatory mediators in RA, such as interleukin-1β (IL-1β) and tumor necrosis factor (TNF), may play a pivotal role in the development of CVD. Interestingly, different preclinical and clinical studies have suggested that biologic agents commonly used to treat RA patients may be effective in improving CVD. In this context, the contribution of adipocytokines has been suggested. Adipocytokines are pleiotropic molecules, mainly released by white adipose tissue and immune cells. Adipocytokines modulate the function of different tissues and cells, and in addition to energy homeostasis and metabolism, amplify inflammation, immune response, and tissue damage. Adipocytokines may contribute to the proinflammatory state in RA patients and development of bone damage. Furthermore, they could be associated with the occurrence of CVD. In this study, we reviewed available evidence about adipocytokines in RA, because of their involvement in disease activity, associated CVD, and possible biomarkers of prognosis and treatment outcome and because of their potential as a possible new therapeutic target.

Impaired natural killer cell subset phenotypes in human obesity

Obesity is associated with alterations in functionality of immune cells, like macrophages and natural killer (NK) cells, leading to an increased risk for severe infections and several cancer types. This study aimed to examine immune cell populations and functional NK cell parameters focusing on NK cell subset phenotypes in normal-weight and obese humans. Therefore, peripheral blood mononuclear cells (PBMCs) were isolated from normal-weight and obese individuals and analyzed by flow cytometry. Results show no significant changes in the frequency of monocytes, B lymphocytes, or NKT cells but a significantly increased frequency of T lymphocytes in obesity. The frequency of total NK cells was unaltered, whereas the number of low cytotoxic CD56bright NK cell subset was increased, and the number of high cytotoxic CD56dim NK cell subset was decreased in obese subjects. In addition, the frequency of CD56bright NK cells expressing the activating NK cell receptor NKG2D as well as intracellular interferon (IFN)-γ was elevated in the obese study group. In contrast, the frequency of NKG2D- and IFN-γ-positive CD56dim NK cells was lower in obesity compared to normal-weight individuals. Moreover, the expression of the activation marker CD69 was decreased in NK cells, which can be attributed to a reduction of CD69-positive CD56dim NK cells in obese subjects. In conclusion, data reveal an impaired NK cell phenotype and NK cell subset alterations in obese individuals. This NK cell dysfunction might be one link to the higher cancer risk and the elevated susceptibility for viral infections in obesity.

Endogenous lipid antigens for invariant natural killer T cells hold the reins in adipose tissue homeostasis

The global obesity epidemic and its associated co-morbidities, including type 2 diabetes, cardiovascular disease and certain types of cancers, have drawn attention to the pivotal role of adipocytes in health and disease. Besides their 'classical' function in energy storage and release, adipocytes interact with adipose-tissue-resident immune cells, among which are lipid-responsive invariant natural killer T (iNKT) cells. The iNKT cells are activated by lipid antigens presented by antigen-presenting cells as CD1d/lipid complexes. Upon activation, iNKT cells can rapidly secrete soluble mediators that either promote or oppose inflammation. In lean adipose tissue, iNKT cells elicit a predominantly anti-inflammatory immune response, whereas obesity is associated with declining iNKT cell numbers. Recent work showed that adipocytes act as non-professional antigen-presenting cells for lipid antigens. Here, we discuss endogenous lipid antigen processing and presentation by adipocytes, and speculate on how these lipid antigens, together with 'environmental factors' such as tissue/organ environment and co-stimulatory signals, are able to influence the fate of adipose-tissue-resident iNKT cells, and thereby the role of these cells in obesity and its associated pathologies.