NK cells in childhood obesity are activated, metabolically stressed, and functionally deficient

Bariatric surgery reverses morbid obesity-induced changes in the composition of circulating immune cells-a prospective cohort study

BACKGROUND

Morbid obesity is associated with aging of the immune system, a phenomenon known as "inflammaging," characterized by increased numbers of various immune cell subsets.

OBJECTIVES

To evaluate the long-term effects of bariatric surgery on immune cell subsets in patients with obesity and to determine the impact of metabolic syndrome on these changes.

SETTING

High-volume bariatric center, Netherlands.

METHODS

This prospective cohort study included patients with obesity, with and without metabolic syndrome, as well as lean controls. Peripheral blood samples were collected preoperatively (T0) and at various time points up to 18 months postoperatively (T18). Flow cytometry was used to measure absolute numbers of T cells, B cells, natural killer (NK) cells, and monocyte subsets, with adjustments for age and cytomegalovirus (CMV) serostatus.

RESULTS

At T0, patients with obesity had elevated numbers of CD4+ CD31 naïve T cells, CD8+ terminally differentiated effector memory RA T cells, double-negative B cells, plasmablasts, NK cells, and monocytes compared with lean controls. CD8+ central memory T cells were decreased in patients with obesity. While most immune cell subsets gradually normalized by T18, some subsets, including T cells, B cells, and NK cells, that were initially elevated, decreased during follow-up and ultimately ended up lower than those in lean controls at T12 or T18. Metabolic syndrome did not affect these outcomes. COVID-19-related disruptions reduced the number of patients assessed over time.

CONCLUSIONS

Bariatric surgery restores the harmful effects of morbid obesity on the composition of innate and adaptive immune cell subsets in the long-term for patients with obesity, both with and without metabolic syndrome.

Obesity modulates NK cell activity via LDL and DUSP1 signaling for populations with adverse social determinants

African American (AA) women are disproportionately affected by obesity and hyperlipidemia, particularly in the setting of adverse social determinants of health (aSDoH) that contribute to health disparities. Obesity, hyperlipidemia, and aSDoH appear to impair NK cells. As potential common underlying mechanisms are largely unknown, we sought to investigate common signaling pathways involved in NK cell dysfunction related to obesity and hyperlipidemia in AA women from underresourced neighborhoods. We determined in freshly isolated NK cells that obesity and measures of aSDoH were associated with a shift in NK cell subsets away from CD56dim/CD16+ cytotoxic NK cells. Using ex vivo data, we identified LDL as a marker related to NK cell function in an AA population from underresourced neighborhoods. Additionally, NK cells from AA women with obesity and LDL-treated NK cells displayed a loss in NK cell function. Comparative unbiased RNA-sequencing analysis revealed DUSP1 as a common factor. Subsequently, chemical inhibition of Dusp1 and Dusp1 overexpression in NK cells highlighted its significance in NK cell function and lysosome biogenesis in a mTOR/TFEB-related fashion. Our data demonstrate a pathway by which obesity and hyperlipidemia in the setting of aSDoH may relate to NK cell dysfunction, making DUSP1 an important target for further investigation of health disparities.

Pilot Data Suggest That Obesity and Presence of Malignancy Are Associated with Altered Immune Cell Infiltration in Endometrial Biopsies

(1) Background: The worldwide endometrial cancer (EC) incidence is rising, amongst others linked to obesity, type 2 diabetes mellitus (T2DM), and metabolic syndrome, possibly due to low-grade adipose tissue inflammation. We studied immune cell infiltration in the endometrium in relation to diagnosis and obesity. (2) Methods: A cohort was created (n = 44) from postmenopausal women, lean (n = 15) and obese (n = 29), with bleeding complaints due to EC (n = 18) or benign pathology (n = 26). Endometrial biopsies were used to study the immune microenvironment and stained for macrophages (CD68 and CD163), T-cells (CD3 and CD8), and NK-cells (CD56). (3) Results: Malignant samples showed reduced intraepithelial CD3+ and CD8+ T-cells and increased stromal CD3+ T-cells. In obese patients, increased intraepithelial CD3+ and CD8+ T-cells were detected, especially in obese patients with T2DM. Epithelial CD56+ NK-cells were depleted in EC; however, no effect of obesity on NK-cell infiltration was observed. Stromal CD68+ cells were reduced in EC patients, whereas the CD163+ cells were increased. (4) Conclusions: Obesity and malignancy are associated with differences in immune cell presence. The alterations in immune cell infiltration seen in obese EC patients with and without diabetes suggest a complex interaction where obesity-related low-grade inflammation plays a central role.

Obesity, white adipose tissue and cancer

White adipose tissue (WAT) is crucial for whole-body energy homeostasis and plays an important role in metabolic and hormonal regulation. While healthy WAT undergoes controlled expansion and contraction to meet the body's requirements, dysfunctional WAT in conditions like obesity is characterized by excessive tissue expansion, alterations in lipid homeostasis, inflammation, hypoxia, and fibrosis. Obesity is strongly associated with an increased risk of numerous cancers, with obesity-induced WAT dysfunction influencing cancer development through various mechanisms involving both systemic and local interactions between adipose tissue and tumors. Unhealthy obese WAT affects circulating levels of free fatty acids and factors like leptin, adiponectin, and insulin, altering systemic lipid metabolism and inducing inflammation that supports tumor growth. Similar mechanisms are observed locally in an adipose-rich tumor microenvironment (TME), where WAT cells can also trigger extracellular matrix remodeling, thereby enhancing the TME's ability to promote tumor growth. Moreover, tumors reciprocally interact with WAT, creating a bidirectional communication that further enhances tumorigenesis. This review focuses on the complex interplay between obesity, WAT dysfunction, and primary tumor growth, highlighting potential targets for therapeutic intervention.

hPMSCs prevent erythrocytes dysfunction caused by graft versus host disease via promoting GSH synthesis

BACKGROUND

Oxidative stress is increased in allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients and leads to the development of graft versus host disease (GVHD). Mesenchymal stromal cells (MSCs) can ameliorate GVHD by regulating the function of T cells. However, whether MSCs can modulate erythrocyte antioxidant metabolism and thus reduce GVHD is not known.

METHODS

Forty female BALB/c mice were randomly assigned to four groups: the control, GVHDhigh, hPMSC, and PBS groups. A hypoxanthine/xanthine oxidase system was used to steadily and gradually produce superoxide in an in vitro experiment. A scanning microscope was used to examine the ultrastructure of erythrocytes. Laser diffraction analyses were used to analyze erythrocyte deformability. Western blotting was used to measure the expression of the erythrocyte membrane skeleton proteins Band 3 and β-Spectrin. Corresponding kits were used to assess the levels of oxidative damage and the activity of antioxidant enzymes.

RESULTS

Morphological and deformability defects were significantly increased in erythrocytes from GVHD patients. Band 3 and β-Spectrin expression was also reduced in GVHD patients and model mice. Furthermore, we observed significantly increased oxidative stress-induce injury and decreased antioxidant capability in erythrocytes from both GVHD patients and model mice. Subsequent research showed that human placenta-derived MSC (hPMSC) therapy decreased the GVHD-induced redox imbalance in erythrocytes. Furthermore, our findings suggested that upregulating glucose metabolism promoted both the de novo synthesis and recycling of GSH, which is the primary mechanism by which hPMSCs mediate the increase in antioxidant capacity in erythrocytes.

CONCLUSION

Together, our findings suggest that hPMSCs can increase antioxidant capacity by increasing erythrocyte GSH production and thus ameliorate GVHD.

Persistence of a Skewed Repertoire of NK Cells in People with HIV-1 on Long-Term Antiretroviral Therapy

HIV-1 infection greatly alters the NK cell phenotypic and functional repertoire. This is highlighted by the expansion of a rare population of FcRγ- NK cells exhibiting characteristics of traditional immunologic memory in people with HIV (PWH). Although current antiretroviral therapy (ART) effectively controls HIV-1 viremia and disease progression, its impact on HIV-1-associated NK cell abnormalities remains unclear. To address this, we performed a longitudinal analysis detailing conventional and memory-like NK cell characteristics in n = 60 PWH during the first 4 y of ART. Throughout this regimen, a skewed repertoire of cytokine unresponsive FcRγ- memory-like NK cells persisted and accompanied an overall increase in NK surface expression of CD57 and KLRG1, suggestive of progression toward immune senescence. These traits were linked to elevated serum inflammatory biomarkers and increasing Ab titers to human CMV, with human CMV viremia detected in approximately one-third of PWH at years 1-4 of ART. Interestingly, 40% of PWH displayed atypical NK cell subsets, representing intermediate stages of NK-poiesis based on single-cell multiomic trajectory analysis. Our findings indicate that NK cell irregularities persist in PWH despite long-term ART, underscoring the need to better understand the causative mechanisms that prevent full restoration of immune health in PWH.

Real-time ex vivo monitoring of NK cell migration toward obesity-associated oesophageal adenocarcinoma following modulation of CX3CR1

Oesophagogastric adenocarcinomas (OAC) are poor prognosis, obesity-associated cancers which may benefit from natural killer (NK) cell-based immunotherapies. Cellular immunotherapies encounter two key challenges to their success in OAC, namely recruitment to extratumoural tissues such as the omentum at the expense of the tumour and an immunosuppressive tumour microenvironment (TME) which can hamper NK cell function. Herein, we examined approaches to overcome the detrimental impact of obesity on NK cells and NK cell-based immunotherapies. We have demonstrated that NK cells migrate preferentially to the chemotactic signals of OAC patient-derived omentum over tumour in an ex vivo model of immune cell migration. We have identified CX3CR1 modulation and/or tumour chemokine profile remodelling as approaches to skew NK cell migration towards tumour. We also report targetable immunosuppressive facets of the obese OAC TME which dampen NK cell function, in particular cytotoxic capabilities. These data provide insights into approaches to therapeutically overcome key challenges presented by obesity and will inform superior design of NK cell-based immunotherapies for OAC.

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.

Gut microbiota, immunity, and bile acid metabolism: decoding metabolic disease interactions

In recent decades, the global prevalence of metabolic syndrome has surged, posing a significant public health challenge. Metabolic disorders, encompassing diabetes, obesity, nonalcoholic fatty liver disease, and polycystic ovarian syndrome, have been linked to alterations in the gut microbiota. Nonetheless, the connection between gut microbiota and host metabolic diseases warrants further investigation. In this review, we delve into the associations between various metabolic disorders and the gut microbiota, focusing on immune responses and bile acid (BA) metabolism. Notably, T helper cells, innate lymphoid cells, macrophages, and dendritic cells have been shown to modulate host metabolism through interactions with intestinal microorganisms and the release of cytokines. Furthermore, secondary BA metabolites, derived from the microbiota, are involved in the pathogenesis of metabolic diseases via the farnesoid X receptor and Takeda G protein-coupled receptor 5. By covering both aspects of this immune system-microorganism axis, we present a comprehensive overview of the roles played by the gut microbiota, microbiota-derived BA metabolites, and immune responses in metabolic diseases, as well as the interplay between these systems.

The placental vasculature is affected by changes in gene expression and glycogen-rich cells in a diet-induced obesity mouse model

Maternal obesity is a risk factor for pregnancy complications. Obesity caused by a high-fat diet (HFD) may alter maternal glucose/glycogen metabolism. Here, our objective was to investigate whether the placental vasculature is altered via changes in gene expression and glycogen-rich cells using a preclinical mouse model of diet-induced obesity. We subjected female FVB/N mice to one of three feeding regimens: regular chow (RC) given at preconception and during pregnancy (Control); RC given at preconception and then a HFD during pregnancy (HFD-P); or HFD initiated 4 weeks preconception and during pregnancy (HFD-PreCP). Daily food consumption and weekly maternal weights were recorded. Maternal blood glucose levels were measured at preconception and 4 gestational epochs (E6.5-E9.5, E10.5-E12.5, E13.5-E15.5, E16.5-E19.5). At E8.5-E16.5, total RNA in placentas were isolated for gene expression analyses. Placentas were also collected for HE and periodic acid Schiff's (PAS) staining and glycogen content assays. Dams in the HFD-P and HFD-PreCP groups gained significantly more weight than controls. Pre- and antenatal glucose levels were also significantly higher (15%-30%) in HFD-PreCP dams. Expression of several placental genes were also altered in HFD dams compared with controls. Consumption of the HFD also led to phenotypic and morphologic changes in glycogen trophoblasts (GlyTs) and uterine natural killer (uNK) cells. Alterations in vascularity were also observed in the labyrinth of HFD-PreCP placentas, which correlated with decreased placental efficiency. Overall, we observed that a HFD induces gestational obesity in mice, alters expression of placental genes, affects glucose homeostasis, and alters glycogen-positive GlyTs and uNK cells. All these changes may lead to impaired placental vascular development, and thus heighten the risk for pregnancy complications.

Lipid accumulation-mediated histone hypoacetylation drives persistent NK cell dysfunction in anti-tumor immunity

Hyperlipidemia impairs anti-tumor immune responses and is closely associated with increased human cancer incidence and mortality. However, the underlying mechanisms are not well understood. In the present study, we show that natural killer (NK) cells isolated from high-fat-diet mice or treated with oleic acid (OA) in vitro exhibit sustainable functional defects even after removal from hyperlipidemic milieu. This is accompanied by reduced chromatin accessibility in the promoter region of NK cell effector molecules. Mechanistically, OA exposure blunts P300-mediated c-Myc acetylation and shortens its protein half-life in NK cells, which in turn reduces P300 accumulation and H3K27 acetylation and leads to persistent NK cell dysfunction. NK cells engineered with hyperacetylated c-Myc mutants surmount the suppressive effect of hyperlipidemia and display superior anti-tumor activity. Our findings reveal the persistent dysfunction of NK cells in dyslipidemia milieu and extend engineered NK cells as a promising strategy for tumor immunotherapy.

NK cells vs. obesity: A tale of dysfunction & redemption

Natural killer (NK) cells are critical in protecting the body against infection and cancer. NK cells can rapidly respond to these threats by directly targeting the infected or transformed cell using their cytotoxic machinery or by initiating and amplifying the immune response via their production of cytokines. Additionally, NK cells are resident across many tissues including adipose, were their role extends from host protection to tissue homeostasis. Adipose resident NK cells can control macrophage polarization via cytokine production, whilst also regulating stressed adipocyte fate using their cytotoxic machinery. Obesity is strongly associated with increased rates of cancer and a heightened susceptibility to severe infections. This is in part due to significant obesity-related immune dysregulation, including defects in both peripheral and adipose tissue NK cells. In this review, we detail the literature to date on NK cells in the setting of obesity - outlining the consequences, mechanisms and therapeutic interventions.

Social Determinants modulate NK cell activity via obesity, LDL, and DUSP1 signaling

Adverse social determinants of health (aSDoH) are associated with obesity and related comorbidities like diabetes, cardiovascular disease, and cancer. Obesity is also associated with natural killer cell (NK) dysregulation, suggesting a potential mechanistic link. Therefore, we measured NK phenotypes and function in a cohort of African-American (AA) women from resource-limited neighborhoods. Obesity was associated with reduced NK cytotoxicity and a shift towards a regulatory phenotype. In vitro, LDL promoted NK dysfunction, implicating hyperlipidemia as a mediator of obesity-related immune dysregulation. Dual specific phosphatase 1 (DUSP1) was induced by LDL and was upregulated in NK cells from subjects with obesity, implicating DUSP1 in obesity-mediated NK dysfunction. In vitro, DUSP1 repressed LAMP1/CD107a, depleting NK cells of functional lysosomes to prevent degranulation and cytokine secretion. Together, these data provide novel mechanistic links between aSDoH, obesity, and immune dysregulation that could be leveraged to improve outcomes in marginalized populations.

Low Muscle and High Fat Percentages Are Associated with Low Natural Killer Cell Activity: A Cross-Sectional Study

This study aimed to investigate whether body fat and muscle percentages are associated with natural killer cell activity (NKA). This was a cross-sectional study, conducted on 8058 subjects in a medical center in Korea. The association between the muscle and fat percentage tertiles and a low NKA, defined as an interferon-gamma level lower than 500 pg/mL, was assessed. In both men and women, the muscle mass and muscle percentage were significantly low in participants with a low NKA, whereas the fat percentage, white blood cell count, and C-reactive protein (CRP) level were significantly high in those with a low NKA. Compared with the lowest muscle percentage tertile as a reference, the fully adjusted odd ratios (ORs) (95% confidence intervals (CIs)) for a low NKA were significantly lower in T2 (OR: 0.69; 95% CI: 0.55-0.86) and T3 (OR: 0.74; 95% CI: 0.57-0.95) of men, and T3 (OR: 0.76; 95% CI: 0.59-0.99) of women. Compared with the lowest fat percentage tertile as a reference, the fully adjusted OR was significantly higher in T3 of men (OR: 1.31; 95% CI: 1.01-1.69). A high muscle percentage was significantly inversely associated with a low NKA in men and women, whereas a high fat percentage was significantly associated with a low NKA in men.

Immunometabolism: a new dimension in immunotherapy resistance

Immune checkpoint inhibitors (ICIs) have demonstrated unparalleled clinical responses and revolutionized the paradigm of tumor treatment, while substantial patients remain unresponsive or develop resistance to ICIs as a single agent, which is traceable to cellular metabolic dysfunction. Although dysregulated metabolism has long been adjudged as a hallmark of tumor, it is now increasingly accepted that metabolic reprogramming is not exclusive to tumor cells but is also characteristic of immunocytes. Correspondingly, people used to pay more attention to the effect of tumor cell metabolism on immunocytes, but in practice immunocytes interact intimately with their own metabolic function in a way that has never been realized before during their activation and differentiation, which opens up a whole new frontier called immunometabolism. The metabolic intervention for tumor-infiltrating immunocytes could offer fresh opportunities to break the resistance and ameliorate existing ICI immunotherapy, whose crux might be to ascertain synergistic combinations of metabolic intervention with ICIs to reap synergic benefits and facilitate an adjusted anti-tumor immune response. Herein, we elaborate potential mechanisms underlying immunotherapy resistance from a novel dimension of metabolic reprogramming in diverse tumor-infiltrating immunocytes, and related metabolic intervention in the hope of offering a reference for targeting metabolic vulnerabilities to circumvent immunotherapeutic resistance.

The Impact of Obesity on T and NK Cells after LVAD Implantation

INTRODUCTION

Infections are a major problem after left ventricular assist device (LVAD) implantation that affects morbidity, mortality, and the quality of life. Obesity often increases the risk for infection. In the cohort of LVAD patients, it is unknown if obesity affects the immunological parameters involved in viral defense. Therefore, this study investigated whether overweight or obesity affects immunological parameters such as CD8+ T cells and natural killer (NK) cells.

METHODS

Immune cell subsets of CD8+ T cells and NK cells were compared between normal-weight (BMI 18.5-24.9 kg/m2, n = 17), pre-obese (BMI 25.0-29.9 kg/m2, n = 24), and obese (BMI ≥30 kg/m2, n = 27) patients. Cell subsets and cytokine serum levels were quantified prior to LVAD implantation and at 3, 6, and 12 months after LVAD implantation.

RESULTS

At the end of the first postoperative year, obese patients (31.8% ± 2.1%) had a lower proportion of CD8+ T cells than normal-weight patients (42.4% ± 4.1%; p = 0.04), and the percentage of CD8+ T cells was negatively correlated with BMI (p = 0.03; r = -0.329). The proportion of circulating NK cells increased after LVAD implantation patients in normal-weight (p = 0.01) and obese patients (p < 0.01). Patients with pre-obesity showed a delayed increase (p < 0.01) 12 months after LVAD implantation. Further, obese patients showed an increase in the percentage of CD57+ NK cells after 6 and 12 months (p = 0.01) of treatment, higher proportions of CD56bright NK cells (p = 0.01), and lower proportions of CD56dim/neg NK cells (p = 0.03) 3 months after LVAD implantation than normal-weight patients. The proportion of CD56bright NK cells positively correlated with BMI (p < 0.01, r = 0.403) 1 year after LVAD implantation.

CONCLUSIONS

This study documented that obesity affects CD8+ T cells and subsets of NK cells in patients with LVAD in the first year after LVAD implantation. Lower proportions of CD8+ T cells and CD56dim/neg NK cells and higher proportion of CD56bright NK cells were detected in obese but not in pre-obese and normal-weight LVAD patients during the first year after LVAD implantation. The induced immunological imbalance and phenotypic changes of T and NK cells may influence viral and bacterial immunoreactivity.

Glucagon-like peptide-1 therapy in people with obesity restores natural killer cell metabolism and effector function

OBJECTIVE

People with obesity (PWO) have functionally defective natural killer (NK) cells, with a decreased capacity to produce cytokines and kill target cells, underpinned by defective cellular metabolism. It is plausible that the changes in peripheral NK cell activity are contributing to the multimorbidity in PWO, which includes an increased risk of cancer. This study investigated whether therapy with long-acting glucagon-like peptide-1 (GLP-1) analogues, which are an effective treatment for obesity, could restore NK cell functionality in PWO.

METHODS

In a cohort of 20 PWO, this study investigated whether 6 months of once weekly GLP-1 therapy (semaglutide) could restore human NK cell function and metabolism using multicolor flow cytometry, enzyme-linked immunosorbent assays, and cytotoxicity assays.

RESULTS

These data demonstrate that PWO who received GLP-1 therapy have improved NK cell function, as measured by cytotoxicity and interferon-γ/granzyme B production. In addition, the study demonstrates increases in a CD98-mTOR-glycolysis metabolic axis, which is critical for NK cell cytokine production. Finally, it shows that the reported improvements in NK cell function appear to be independent of weight loss.

CONCLUSIONS

The restoration, by GLP-1 therapy, of NK cell functionality in PWO may be contributing to the overall benefits being seen with this class of medication.

The proliferation of human mucosal-associated invariant T cells requires a MYC-SLC7A5-glycolysis metabolic axis

Mucosal-associated invariant T (MAIT) cells are an abundant population of innate T cells that recognize bacterial ligands and play a key role in host protection against bacterial and viral pathogens. Upon activation, MAIT cells undergo proliferative expansion and increase their production of effector molecules such as cytokines. In this study, we found that both mRNA and protein abundance of the key metabolism regulator and transcription factor MYC was increased in stimulated MAIT cells. Using quantitative mass spectrometry, we identified the activation of two MYC-controlled metabolic pathways, amino acid transport and glycolysis, both of which were necessary for MAIT cell proliferation. Last, we showed that MAIT cells isolated from people with obesity showed decreased MYC mRNA abundance upon activation, which was associated with defective MAIT cell proliferation and functional responses. Collectively, our data uncover the importance of MYC-regulated metabolism for MAIT cell proliferation and provide additional insight into the molecular basis for the functional defects of MAIT cells in obesity.

Elevated exosome-transferrable lncRNA EPB41L4A-AS1 in CD56bright NK cells is responsible for the impaired NK function in neuroblastoma patients by suppressing cell glycolysis

NK cells are one of key immune components in neuroblastoma (NB) surveillance and eradication. Glucose metabolism as a major source of fuel for NK activation is exquisitely regulated. Our data revealed a diminished NK activation and a disproportionally augmented CD56^bright subset in NB. Further study showed that NK cells in NB presented with an arrested glycolysis accompanied by an elevated expression of the long noncoding RNA (lncRNA) EPB41L4A-AS1, a known crucial participant in glycolysis regulation, in the CD56^bright NK subset. The inhibitory function of lncRNA EPB41L4A-AS1 was recapitulated. Interestingly, our study demonstrated that exosomal lncRNA EPB41L4A-AS1 was transferrable from CD56^bright NK to CD56^dim NK and was able to quench the glycolysis of target NK. Our data demonstrated that an arrested glycolysis in patient NK cells was associated with an elevated lncRNA in CD56^bright NK subset and a cross-talk between heterogeneous NK subsets was achieved by transferring metabolic inhibitory lncRNA through exosomes.

Natural killer cells and type 1 innate lymphoid cells in cancer

Innate lymphoid cells (ILCs) are a group of innate lymphocytes that do not express RAG-dependent rearranged antigen-specific cell surface receptors. ILCs are classified into five groups according to their developmental trajectory and cytokine production profile. They encompass NK cells, which are cytotoxic, helper-like ILCs 1-3, which functionally mirror CD4⁺ T helper (Th) type 1, Th2 and Th17 cells respectively, and lymphoid tissue inducer (LTi) cells. NK cell development depends on Eomes (eomesodermin), whereas the ILC1 program is regulated principally by the transcription factor T-bet (T-box transcription factor Tbx21), that of ILC2 is regulated by GATA3 (GATA-binding protein 3) and that of ILC3 is regulated by RORγt (RAR-related orphan receptor γ). NK cells were discovered close to fifty years ago, but ILC1s were first described only about fifteen years ago. Within the ILC family, NK and ILC1s share many similarities, as witnessed by their cell surface phenotype which largely overlap. NK cells and ILC1s have been reported to respond to tissue inflammation and intracellular pathogens. Several studies have reported an antitumorigenic role for NK cells in both humans and mice, but data for ILC1s are both scarce and contradictory. In this review, we will first describe the different NK cell and ILC1 subsets, their effector functions and development. We will then discuss their role in cancer and the effects of the tumor microenvironment on their metabolism.

Child and adult adiposity and subtype-specific endometrial cancer risk: a multivariable Mendelian randomisation study

Increased adiposity is a known risk factor for endometrial cancer (EC). This study aimed to disentangle the separate causal roles of child and adult adiposity on EC risk in adults, including endometrioid and non-endometrioid histological subtypes using multivariable Mendelian randomisation. These analyses employed genetic associations derived from UK Biobank as proxies for child and adult body size in 12,906 cases and 108,979 controls that participated in the Endometrial Cancer Association Consortium. In multivariable analyses, adult body size increased overall EC (OR 2.30, 95% CI 1.73-3.06) and endometrioid EC risk (OR 2.28, 95% CI 1.65-3.16), while child body size had minimal effect. In contrast, child body size (OR 2.26, 95% CI 1.03-4.99) but not adult body size increased non-endometrioid EC risk. As such, child adiposity has an indirect effect on endometrioid EC risk that is mediated by adult adiposity but has a direct effect on non-endometrioid EC risk that is independent of adult adiposity. These novel findings indicate that interventions targeting adiposity during distinct periods in life have a critical role in preventing subtype-specific EC.

Functionality of natural killer cells in obese asthma phenotypes

BACKGROUND

Obesity-associated asthma (OA) is a difficult to treat asthma phenotype due to its severity and poor response to inhaled steroids. Early-onset allergic (EoOA) and late-onset non-allergic (LoOA) OA are suggested subtypes of this phenotype. Natural Killer (NK) cells are key elements of innate immunity involved in cytotoxicity and immune regulation, with uncertain role in OA pathogenesis.

METHODS

Early-onset allergic and LoOA patients together with obese non-asthmatic (ONA) controls have been enrolled in the study. Peripheral blood samples have been collected for analysis. Percentages of total NK cells, CD3^- CD56^dim and CD3^- CD56^bright NK cell subsets, cytotoxic activity, intracellular interferon-γ, interleukin (IL)-10, IL-13, IL-17 secretion and activatory receptors (NKG2D, NKp46i and NKp44) have been investigated by flow cytometry. The effect of IL-12 and IL-23 stimulation on NK cells and intracellular cytokines in different groups have also been analysed and compared with unstimulated conditions.

RESULTS

Results of ONA (n = 5, age 42 ± 8), EoOA (n = 5, age 42 ± 10) and LoOA (n = 8, age 46 ± 8) patients have analysed. Body Mass Index has been found to be negatively correlated with CD69 (p = .022, r = -0.534). NKG2D receptor has been significantly low in CD56^dim cells of asthma population (p = .046). NKp44 receptor expression has increased after IL-12 stimulation in EoOA and control group (p = .02). Intracellular IL-10 content has increased in LoOA and control subjects (p = .018, p = .03) but not in the EoOA group. Intracellular IL-17 level has found be higher in allergic OA group. LoOA patients showed a decreased NK cytotoxicity compared with the early-onset asthma group (p = .05).

CONCLUSION

Our study suggests an impaired NK receptor expression, activation and reduced cytotoxicity in OA patients together with variances between different subtypes of this phenotype. This data would be beneficial for tailoring a more personalized treatment strategy combatting steroid resistance and frequent exacerbations in this group of patients.

Identification of key genes and their association with immune infiltration in adipose tissue of obese patients: a bioinformatic analysis

Immune cell-mediated adipose tissue (AT) inflammation contributes to obesity-related metabolic disorders, but the precise underlying mechanisms remain largely elusive. In this study, we used the R software to screen key differentially expressed genes (DEGs) in AT from lean and obese individuals and conducted function enrichment analysis. We then analysed their PPI network by using the STRING database. Hub genes were screened by cytohubba plugin. Subsequently, CIBERSORTx was used to predict the proportion of immune cells in AT from lean and obese subjects. Finally, the correlation between hub genes and immune cell proportions was analysed. These studies identified 290 DEGs in the AT between lean and obese subjects. Among them, IL6, CCL19, CXCL8, CXCL12, CCL2, CCL3, CCL4, CXCL2, IL1B, and CXCL1 were proved to be hub genes in regulating the protein-protein interaction (PPI) network. We also found that CXCL8 is positively correlated with resting NK cells, monocytes, activated mast cells, and eosinophils, but negatively correlated with CD8⁺ T cells and activated NK cells in obese individuals. Taken together, our study identified key genes in AT that are correlated with immune cell infiltration, uncovering potential new targets for the prevention and treatment of obesity and its related complications via regulating the immune microenvironment.

Immune response to arbovirus infection in obesity

Obesity is a global health problem that affects 650 million people worldwide and leads to diverse changes in host immunity. Individuals with obesity experience an increase in the size and the number of adipocytes, which function as an endocrine organ and release various adipocytokines such as leptin and adiponectin that exert wide ranging effects on other cells. In individuals with obesity, macrophages account for up to 40% of adipose tissue (AT) cells, three times more than in adipose tissue (10%) of healthy weight individuals and secrete several cytokines and chemokines such as interleukin (IL)-1β, chemokine C-C ligand (CCL)-2, IL-6, CCL5, and tumor necrosis factor (TNF)-α, leading to the development of inflammation. Overall, obesity-derived cytokines strongly affect immune responses and make patients with obesity more prone to severe symptoms than patients with a healthy weight. Several epidemiological studies reported a strong association between obesity and severe arthropod-borne virus (arbovirus) infections such as dengue virus (DENV), chikungunya virus (CHIKV), West Nile virus (WNV), and Sindbis virus (SINV). Recently, experimental investigations found that DENV, WNV, CHIKV and Mayaro virus (MAYV) infections cause worsened disease outcomes in infected diet induced obese (DIO) mice groups compared to infected healthy-weight animals. The mechanisms leading to higher susceptibility to severe infections in individuals with obesity remain unknown, though a better understanding of the causes will help scientists and clinicians develop host directed therapies to treat severe disease. In this review article, we summarize the effects of obesity on the host immune response in the context of arboviral infections. We have outlined that obesity makes the host more susceptible to infectious agents, likely by disrupting the functions of innate and adaptive immune cells. We have also discussed the immune response of DIO mouse models against some important arboviruses such as CHIKV, MAYV, DENV, and WNV. We can speculate that obesity-induced disruption of innate and adaptive immune cell function in arboviral infections ultimately affects the course of arboviral disease. Therefore, further studies are needed to explore the cellular and molecular aspects of immunity that are compromised in obesity during arboviral infections or vaccination, which will be helpful in developing specific therapeutic/prophylactic interventions to prevent immunopathology and disease progression in individuals with obesity.

Metabolic regulation of immune responses to cancer

The tumor microenvironment is an ecosystem composed of multiple types of cells, such as tumor cells, immune cells, and cancer-associated fibroblasts. Cancer cells grow faster than non-cancerous cells and consume larger amounts of nutrients. The rapid growth characteristic of cancer cells fundamentally alters nutrient availability in the tumor microenvironment and results in reprogramming of immune cell metabolic pathways. Accumulating evidence suggests that cellular metabolism of nutrients, such as lipids and amino acids, beyond being essential to meet the bioenergetic and biosynthetic demands of immune cells, also regulates a broad spectrum of cellular signal transduction, and influences immune cell survival, differentiation, and anti-tumor effector function. The cancer immunometabolism research field is rapidly evolving, and exciting new discoveries are reported in high-profile journals nearly weekly. Therefore, all new findings in this field cannot be summarized within this short review. Instead, this review is intended to provide a brief introduction to this rapidly developing research field, with a focus on the metabolism of two classes of important nutrients-lipids and amino acids-in immune cells. We highlight recent research on the roles of lipids and amino acids in regulating the metabolic fitness and immunological functions of T cells, macrophages, and natural killer cells in the tumor microenvironment. Furthermore, we discuss the possibility of "editing" metabolic pathways in immune cells to act synergistically with currently available immunotherapies in enhancing anti-tumor immune responses.

Several areas of overlap between obesity and aging indicate obesity as a biomarker of accelerated aging of human B cell function and antibody responses

Aging and obesity are high risk factors for several conditions and diseases. They are both associated with systemic inflammation and they are both ameliorated by a healthy life style, suggesting that they may share cellular and molecular pathways and underlying mechanisms. A close relationship between aging and obesity is also supported by the observation that the aging overweight/obese population is increasing worldwide, and mechanisms involved will be presented here. A focus of our work is to evaluate if obesity may be considered a good biomarker of accelerated aging of human antibody responses. We will summarize our published results showing the effects of obesity in accelerating age defects in the peripheral B cell pool and how these lead to dysfunctional humoral immunity.

Obesity and Adipose Tissue Dysfunction: From Pediatrics to Adults

Obesity is a growing health problem that affects both children and adults. The increasing prevalence of childhood obesity is associated with comorbidities such as cardiovascular disease, type 2 diabetes and metabolic syndrome due to chronic low-grade inflammation present at early stages of the disease. In pediatric patients suffering from obesity, the role of epigenetics, the gut microbiome and intrauterine environment have emerged as causative factors Interestingly, pediatric obesity is strongly associated with low birth weight. Accelerated weight gain oftentimes occurs in these individuals during the post-natal period, which can lead to increased risk of adiposity and metabolic disease. The pathophysiology of obesity is complex and involves biological and physiological factors compounded by societal factors such as family and community. On a cellular level, adipocytes contained within adipose tissue become dysregulated and further contribute to development of comorbidities similar to those present in adults with obesity. This review provides an overview of the current understanding of adipose tissue immune, inflammatory and metabolic adaptation of the adipose tissue in obesity. Early cellular changes as well as the role of immune cells and inflammation on the progression of disease in pivotal pediatric clinical trials, adult studies and mouse models are emphasized. Understanding the initial molecular and cellular changes that occur during obesity can facilitate new and improved treatments aimed at early intervention and subsequent prevention of adulthood comorbidities.

Heightened metabolic responses in NK cells from patients with neuroblastoma suggests increased potential for immunotherapy

High risk neuroblastoma is responsible for 15% of deaths in pediatric cancer patients. The introduction of anti-GD2 immunotherapy has significantly improved outcomes but there is still only approximately a 50% 5 year event-free-survival for these children and improvements in treatments are urgently required. Anti-GD2 immunotherapy uses the patients’ own immune system to kill cancer cells. In particular, Natural Killer (NK) cells kill antibody coated tumor cells by a process called antibody dependent cellular cytotoxicity (ADCC). However, our previous work has highlighted metabolic exhaustion of NK cells in circulating blood of adult cancer patients, identifying this as a potential therapeutic target. In this study, we investigated circulating NK cells in patients newly diagnosed with neuroblastoma. We found evidence of activation of NK cells in vivo by the cancer itself. While some evidence of NK cell dysfunction was observed in terms of IFNγ production, most results indicated that the NK cell compartment remained relatively intact. In fact, some aspects of metabolic and functional activities were actually increased in patients compared to controls. Glycolytic responses, which we show are crucial for ADCC, were actually enhanced in patients and CD16, the NK cell receptor that mediates ADCC, was also expressed at high levels in some patients. Overall, the data suggest that patient NK cells could be harvested at diagnosis for subsequent beneficial autologous use during immunotherapy. Enhancing glycolytic capacity of cell therapies could also be a strategic goal of future cell therapies for patients with neuroblastoma and indeed other cancers.

Immune mechanisms linking metabolic injury to inflammation and fibrosis in fatty liver disease - novel insights into cellular communication circuits

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease and is emerging as the leading cause of cirrhosis, liver transplantation and hepatocellular carcinoma (HCC). NAFLD is a metabolic disease that is considered the hepatic manifestation of the metabolic syndrome; however, during the evolution of NAFLD from steatosis to non-alcoholic steatohepatitis (NASH), to more advanced stages of NASH with liver fibrosis, the immune system plays an integral role. Triggers for inflammation are rooted in hepatic (lipid overload, lipotoxicity, oxidative stress) and extrahepatic (gut-liver axis, adipose tissue, skeletal muscle) systems, resulting in unique immune-mediated pathomechanisms in NAFLD. In recent years, the implementation of single-cell RNA-sequencing and high dimensional multi-omics (proteogenomics, lipidomics) and spatial transcriptomics have tremendously advanced our understanding of the complex heterogeneity of various liver immune cell subsets in health and disease. In NAFLD, several emerging inflammatory mechanisms have been uncovered, including profound macrophage heterogeneity, auto-aggressive T cells, the role of unconventional T cells and platelet-immune cell interactions, potentially yielding novel therapeutics. In this review, we will highlight the recent discoveries related to inflammation in NAFLD, discuss the role of immune cell subsets during the different stages of the disease (including disease regression) and integrate the multiple systems driving inflammation. We propose a refined concept by which the immune system contributes to all stages of NAFLD and discuss open scientific questions arising from this paradigm shift that need to be unravelled in the coming years. Finally, we discuss novel therapeutic approaches to target the multiple triggers of inflammation, including combination therapy via nuclear receptors (FXR agonists, PPAR agonists).

Targeting Strategies for Aberrant Lipid Metabolism Reprogramming and the Immune Microenvironment in Esophageal Cancer: A Review

Esophageal cancer is of high importance to occurrence, development, and treatment resistance. As evidenced by recent studies, pathways (e.g., Wnt/β-catenin, AMPK, and Hippo) are critical to the proliferation, differentiation, and self-renewal of esophageal cancer. In addition, the above pathways play a certain role in regulating esophageal cancer and act as potential therapeutic targets. Over the past few years, the function of lipid metabolism in controlling tumor cells and immune cells has aroused extensive attention. It has been reported that there are intricate interactions between lipid metabolism reprogramming between immune and esophageal cancer cells, whereas molecular mechanisms should be studied in depth. Immune cells have been commonly recognized as a vital player in the esophageal cancer microenvironment, having complex crosstalk with cancer cells. It is increasingly evidenced that the function of immune cells in the tumor microenvironment (TME) is significantly correlated with abnormal lipid metabolism. In this review, the latest findings in lipid metabolism reprogramming in TME are summarized, and the above findings are linked to esophageal cancer progression. Aberrant lipid metabolism and associated signaling pathways are likely to serve as a novel strategy to treat esophageal cancer through lipid metabolism reprogramming.

Translating MSC Therapy in the Age of Obesity

Mesenchymal stromal cell (MSC) therapy has seen increased attention as a possible option to treat a number of inflammatory conditions including COVID-19 acute respiratory distress syndrome (ARDS). As rates of obesity and metabolic disease continue to rise worldwide, increasing proportions of patients treated with MSC therapy will be living with obesity. The obese environment poses critical challenges for immunomodulatory therapies that should be accounted for during development and testing of MSCs. In this review, we look to cancer immunotherapy as a model for the challenges MSCs may face in obese environments. We then outline current evidence that obesity alters MSC immunomodulatory function, drastically modifies the host immune system, and therefore reshapes interactions between MSCs and immune cells. Finally, we argue that obese environments may alter essential features of allogeneic MSCs and offer potential strategies for licensing of MSCs to enhance their efficacy in the obese microenvironment. Our aim is to combine insights from basic research in MSC biology and clinical trials to inform new strategies to ensure MSC therapy is effective for a broad range of patients.

Obesity-Mediated Immune Modulation: One Step Forward, (Th)2 Steps Back

Over the past decades, the relationship between the immune system and metabolism has become a major research focus. In this arena of immunometabolism the capacity of adipose tissue to secrete immunomodulatory molecules, including adipokines, within the underlying low-grade inflammation during obesity brought attention to the impact obesity has on the immune system. Adipokines, such as leptin and adiponectin, influence T cell differentiation into different T helper subsets and their activation during immune responses. Furthermore, within the cellular milieu of adipose tissue nutrient availability regulates differentiation and activation of T cells and changes in cellular metabolic pathways. Upon activation, T cells shift from oxidative phosphorylation to oxidative glycolysis, while the differential signaling of the kinase mammalian target of rapamycin (mTOR) and the nuclear receptor PPARγ, amongst others, drive the subsequent T cell differentiation. While the mechanisms leading to a shift from the typical type 2-dominated milieu in lean people to a Th1-biased pro-inflammatory environment during obesity are the subject of extensive research, insights on its impact on peripheral Th2-dominated immune responses become more evident. In this review, we will summarize recent findings of how Th2 cells are metabolically regulated during obesity and malnutrition, and how these states affect local and systemic Th2-biased immune responses.

Influence of adipose tissue immune dysfunction on childhood obesity

In recent decades, a dramatic rise has been observed in the prevalence of obesity in childhood and adolescence, along with an increase in fetal microsomia rates. The increased risk of obesity during this key period in development negatively affects the health of the individual later in life. Immune cells residing and recruited to white adipose tissue have been highlighted as important factors contributing to the pathogenesis of childhood obesity. Immune dysfunction in the context of obesity begins early in childhood, which is different from the pathological characteristics and influencing factors of adipose immunity in adults. Here, we explore the current understanding of the roles of childhood and early life events that result in high risks for obesity by influencing adipose tissue immune dysfunction under the pathological condition of obesity. Such knowledge will help in determining the mechanisms of childhood and early life obesity in efforts to ameliorate chronic inflammation-related metabolic diseases.

Natural killer cell therapy: A new frontier for obesity-associated cancer

Natural killer (NK) cell infiltration of solid tumours is associated with better outcomes, placing augmentation of NK cell abundance in tumours as an attractive immunotherapeutic approach. The unique ability of NK cells to target cancer cells without antigen specificity increases their versatility and applicability as an immunotherapeutic tool. However, successful utilisation of NK cell-based therapies in solid tumours is still at an early stage. Obesity has become a global health epidemic, and the prevalence of obesity-associated cancers has significantly increased. Obesity-associated malignancies provide a unique challenge for the successful application of cell-based immunotherapies including NK cell-based therapies because significant numbers of NK and T cells are recruited to the visceral adipose tissue at the expense of successful tumour infiltration and eradication. As such, immunotherapy efficacy has been disappointing for obesity-associated malignancies such as oesophageal and gastric adenocarcinoma. Therefore, immunotherapies for obesity-associated cancers warrant our further attention. Indeed, it is becoming ever more obvious that more innovative approaches are needed to re-invigorate anti-tumour immunity and overcome immune exclusion in such tumours. In this review, we briefly summarise the dysfunctionality of NK cells in obesity-associated cancer. We outline the NK cell-based immunotherapeutic approaches which hold promise as effective treatments in this disease space, including CAR-NK cells. Furthermore, we suggest future avenues which possess the potential to transform immunotherapy and specifically NK cell therapy efficacy for obesity-associated cancer.

No association of natural killer cell number and function in peripheral blood with overweight/obesity and metabolic syndrome in a cohort of young women

AIM

To reexamine the associations of NK cell number and function in the peripheral blood with overweight/obesity and the metabolic syndrome in a large, well-phenotyped human cohort.

METHODS

Cross-sectional analysis of 273 women in the PPSDiab Study; measurement of absolute and relative number of NK cells in peripheral blood, and of functional parameters CD69 positivity and cytotoxicity against K562 cells; group comparison of NK cell characteristics between lean, overweight, and obese participants, as well as metabolic syndrome scores of 0, 1, 2, and ≥3; Spearman correlation analyses to clinical parameters related to the metabolic syndrome.

RESULTS

We found no differences in NK cell number and function between lean, overweight, and obese women (relative NK cell number (median (Q1-Q3), [%]) 5.1(2.6-9.4) vs. 4.8 (2.9-8.4) vs. 3.8 (1.7-7.8), p = 0.187; absolute NK cell number [106 /L]: 86.9 (44.6-188.8) vs. 92.6 (52.5-154.6) vs. 85.9 (44-153.8), p = 0.632; CD69+ [%]: 27.2 (12.9-44.3) vs. 37.6 (13.2-52.8) vs. 33.6 (16.3-45), p = 0.136; cytotoxicity [%]: 11.0 (7.1-14.5) vs. 8.5 (6.4-13.2) vs. 11.3 (8.7-14.2), p = 0.094), as well as between different metabolic syndrome scores. Nonesterified fatty acids correlated with absolute and relative NK cell number and cytotoxicity (ρ [p-value]: 0.142 [0.021], 0.119 [0.049], and 0.131 [0.035], respectively). Relative NK cell number further correlated with high-density lipoprotein cholesterol (0.144 [0.018]) and cytotoxicity with 2 h glucose in oral glucose tolerance testing (0.132 [0.034]). CD69 positivity correlated with body fat (0.141 [0.021]), triglycerides (0.129 [0.033]), and plasma leptin (0.155 [0.010]). After correction for multiple testing, none of the associations remained significant.

CONCLUSION

In the present study, we observed no associations of NK cell number and function in the peripheral blood with overweight/obesity and the metabolic syndrome. Extreme phenotypes of obesity and the metabolic syndrome might have caused differing results in previous studies. Further analyses with a focus on compartments other than peripheral blood may help to clarify the relation between NK cells and metabolic diseases.

When a Friend Becomes Your Enemy: Natural Killer Cells in Atherosclerosis and Atherosclerosis-Associated Risk Factors

Atherosclerosis (ATS), the change in structure and function of arteries with associated lesion formation and altered blood flow, is the leading cause of cardiovascular disease, the number one killer worldwide. Beyond dyslipidemia, chronic inflammation, together with aberrant phenotype and function of cells of both the innate and adaptive immune system, are now recognized as relevant contributors to atherosclerosis onset and progression. While the role of macrophages and T cells in atherosclerosis has been addressed in several studies, Natural Killer cells (NKs) represent a poorly explored immune cell type, that deserves attention, due to NKs’ emerging contribution to vascular homeostasis. Furthermore, the possibility to re-polarize the immune system has emerged as a relevant tool to design new therapies, with some succesfull exmples in the field of cancer immunotherapy. Thus, a deeper knowledge of NK cell pathophysiology in the context of atherosclerosis and atherosclerosis-associated risk factors could help developing new preventive and treatment strategies, and decipher the complex scenario/history from “the risk factors for atherosclerosis” Here, we review the current knowledge about NK cell phenotype and activities in atherosclerosis and selected atherosclerosis risk factors, namely type-2 diabetes and obesity, and discuss the related NK-cell oriented environmental signals.

Role of Innate lymphoid Cells in Obesity and Insulin Resistance

Obesity, a growing chronic metabolic disease, greatly increases the risk of metabolic syndrome which includes type 2 diabetes, fatty liver and cardiovascular diseases. Obesity-associated metabolic diseases significantly contribute to mortality and reduce life expectancy. Recently, innate lymphoid cells (ILCs) have emerged as crucial regulators of metabolic homeostasis and tissue inflammation. This review focuses on the roles of ILCs in different metabolic tissues, including adipose tissue, liver, pancreas, and intestine. We briefly outline the relationship between obesity, inflammation, and insulin resistance. We then discuss how ILCs in distinct metabolic organs may function to maintain metabolic homeostasis and contribute to obesity and its associated metabolic diseases. The potential of ILCs as the therapeutic target for obesity and insulin resistance is also addressed.

Cytokine-induced natural killer cell training is dependent on cellular metabolism and is defective in obesity

NK cell cytokine training is dependent on glycolysis, oxidative phosphorylation, and the metabolic regulator Srebp.

NK cell cytokine training is defective in PWO.

Natural killer (NK) cells are a population of innate immune cells that can rapidly kill cancer cells and produce cytokines such as interferon-γ. A key feature of NK cells is their ability to respond without prior sensitization; however, it is now well established that NK cells can possess memory-like features. After activation with cytokines, NK cells demonstrate enhanced effector functions upon restimulation days or weeks later. This demonstrates that NK cells may be trained to be more effective killers and harnessed as more potent cancer immunotherapy agents. We have previously demonstrated that cellular metabolism is essential for NK cell responses, with NK cells upregulating both glycolysis and oxidative phosphorylation upon cytokine stimulation. Limiting NK cell metabolism results in reduced cytotoxicity and cytokine production. We have also demonstrated that defective NK cell responses in obesity are linked to defective cellular metabolism. In the current study, we investigated if cellular metabolism is required during the initial period of NK cell cytokine training and if NK cells from people with obesity (PWO) can be effectively trained. We show that increased flux through glycolysis and oxidative phosphorylation during the initial cytokine activation period is essential for NK cell training, as is the metabolic signaling factor Srebp. We show that NK cells from PWO, which are metabolically defective, display impaired NK cell training, which may have implications for immunotherapy in this particularly vulnerable group.

A Forgotten Corner in Cancer Immunotherapy: The Role of Lipids

In the past decade, cancer immunotherapy has achieved great success owing to the unravelling of unknown molecular forces in cancer immunity. However, it is critical that we address the limitations of current immunotherapy, including immune-related adverse events and drug resistance, and further enhance current immunotherapy. Lipids are reported to play important roles in modulating immune responses in cancer. Cancer cells use lipids to support their aggressive behaviour and allow immune evasion. Metabolic reprogramming of cancer cells destroys the equilibrium between lipid anabolism and catabolism, resulting in lipid accumulation within the tumour microenvironment (TME). Consequently, ubiquitous lipids, mainly fatty acids, within the TME can impact the function and phenotype of infiltrating immune cells. Determining the complex roles of lipids and their interactions with the TME will provide new insight for improving anti-tumour immune responses by targeting lipids. Herein, we present a review of recent literature that has demonstrated how lipid metabolism reprogramming occurs in cancer cells and influences cancer immunity. We also summarise the potential for lipid-based clinical translation to modify immune treatment.

Innate Immune System Orchestrates Metabolic Homeostasis and Dysfunction in Visceral Adipose Tissue During Obesity

Arising incidence of metabolic disorders and related diseases caused by obesity is a global health concern. Elucidating the role of the immune system in this process will help to understand the related mechanisms and develop treatment strategies. Here, we have focused on innate immune cells in visceral adipose tissue (VAT) and summarized the roles of these cells in maintaining the homeostasis of VAT. Furthermore, this review reveals the importance of quantitative and functional changes of innate immune cells when the metabolic microenvironment changes due to obesity or excess lipids, and confirms that these changes eventually lead to the occurrence of chronic inflammation and metabolic diseases of VAT. Two perspectives are reviewed, which include sequential changes in various innate immune cells in the steady state of VAT and its imbalance during obesity. Cross-sectional interactions between various innate immune cells at the same time point are also reviewed. Through delineation of a comprehensive perspective of VAT homeostasis in obesity-induced chronic inflammation, and ultimately metabolic dysfunction and disease, we expect to clarify the complex interactive networks among distinct cell populations and propose that these interactions should be taken into account in the development of biotherapeutic strategies.

Peptide Adjuvant to Invigorate Cytolytic Activity of NK Cells in an Obese Mouse Cancer Model

Cancer patients who are overweight compared to those with normal body weight have obesity-associated alterations of natural killer (NK) cells, characterized by poor cytotoxicity, slow proliferation, and inadequate anti-cancer activity. Concomitantly, prohibitin overexpressed by cancer cells elevates glucose metabolism, rendering the tumor microenvironment (TME) more tumor-favorable, and leading to malfunction of immune cells present in the TME. These changes cause vicious cycles of tumor growth. Adoptive immunotherapy has emerged as a promising option for cancer patients; however, obesity-related alterations in the TME allow the tumor to bypass immune surveillance and to down-regulate the activity of adoptively transferred NK cells. We hypothesized that inhibiting the prohibitin signaling pathway in an obese model would reduce glucose metabolism of cancer cells, thereby changing the TME to a pro-immune microenvironment and restoring the cytolytic activity of NK cells. Priming tumor cells with an inhibitory the prohibitin-binding peptide (PBP) enhances cytokine secretion and augments the cytolytic activity of adoptively transferred NK cells. NK cells harvested from the PBP-primed tumors exhibit multiple markers associated with the effector function of active NK cells. Our findings suggest that PBP has the potential as an adjuvant to enhance the cytolytic activity of adoptively transferred NK cells in cancer patients with obesity.

Dysregulation of Metabolic Pathways in Circulating Natural Killer Cells Isolated from Inflammatory Bowel Disease Patients

BACKGROUND AND AIMS

Inflammatory bowel diseases [IBD], comprising Crohn's disease [CD] and ulcerative colitis [UC], are chronic conditions characterized by severe dysregulation of innate and adaptive immunity resulting in the destruction of the intestinal mucosa. Natural killer [NK] cells play a pivotal role in the dynamic interaction between the innate and adaptive immune response. There is an increasing appreciation for the key role immunometabolism plays in the regulation of NK cell function, yet little remains known about the metabolic profile, cytokine secretion, and killing capacity of human NK cells during active IBD.

METHODS

Peripheral blood mononuclear cells were isolated from peripheral blood of patients with moderate to severely active IBD and healthy controls. NK cells were stained with a combination of cell surface receptors, intracellular cytokines, and proteins and analyzed by flow cytometry. For measurements of NK cell cytotoxicity, the calcein-AM release assay was performed. The metabolic profile was analyzed by an extracellular flux analyzer.

RESULTS

NK cells from IBD patients produce large quantities of pro-inflammatory cytokines, IL-17A and TNF-α ex vivo, but have limited killing capability. Furthermore, patient NK cells have reduced mitochondrial mass and oxidative phosphorylation. mTORC1, an important cell and metabolic regulator, demonstrated limited activity in both freshly isolated cells and cytokine-stimulated cells.

CONCLUSIONS

Our results demonstrate that circulating NK cells of IBD patients have an unbalanced metabolic profile, with faulty mitochondria and reduced capacity to kill. These aberrations in NK cell metabolism may contribute to defective killing and thus the secondary infections and increased risk of cancer observed in IBD patients.

Effects of Morbid Obesity and Metabolic Syndrome on the Composition of Circulating Immune Subsets

Morbid obesity is characterized by chronic, low-grade inflammation, which is associated with ‘inflamm-aging’. The presence of metabolic syndrome (MetS) might accelerate this phenomenon of metaflammation. In this study, we assessed the effects of morbid obesity and MetS on the composition of a broad spectrum of immune cells present within the circulation. A total of 117 morbidly obese patients (MOP) without MetS (MetS-), 127 MOP with MetS (MetS+) and 55 lean controls (LC) were included in this study. Absolute numbers of T cell, B cell, NK cell and monocyte subsets were assessed within peripheral blood using flow cytometry. Both absolute cell numbers and proportion of cells were evaluated correcting for covariates age, body mass index and cytomegalovirus serostatus. Although the absolute number of circulating CD4+ T cells was increased in the MetS+ group, the CD4+ T cell composition was not influenced by MetS. The CD8+ T cell and B cell compartment contained more differentiated cells in the MOP, but was not affected by MetS. Even though the absolute numbers of NK cells and monocytes were increased in the MOP as compared to LC, there was no difference in proportions of NK and monocyte subsets between the three study groups. In conclusion, although absolute numbers of CD4+ and CD8+ T cells, B cells, NK cells and monocytes are increased in MOP, obesity-induced effects of the composition of the immune system are confined to a more differentiated phenotype of CD8+ T cells and B cells. These results were not affected by MetS.

Natural Killer Cell Dysfunction in Obese Patients with Breast Cancer: A Review of a Triad and Its Implications

Natural killer cells (NK cells) are a crucial constituent of the innate immune system as they mediate immunity against viruses, bacteria, parasites, and most importantly, tumor cells. The exact mechanism of how the innate immune system and specifically NK cells interact with cancer cells is complex and is yet to be understood. Several factors that constitute the tumor microenvironment (TME) such as hypoxia and TGF-β are believed to play a role in the complex physiological reaction of NK cells to tumor cells. On the other hand, several risk factors are implicated in the development and progression of breast cancer, most importantly: obesity. Cytokines released from adipose tissue such as adipokines, leptin, and resistin, among others, are also believed to facilitate tumor progression. In this study, we aimed to build a triad of breast cancer, obesity, and NK cell dysfunction to elucidate a link between these pillars on a cellular level. Directing efforts towards solidifying the link between these factors will help in designing a targeted immunotherapy with a low side-effect profile that can revolutionize breast cancer treatment and improve survival in obese patients.

Optimising NK cell metabolism to increase the efficacy of cancer immunotherapy

Immunotherapy has ushered in an exciting new era for cancer treatment. The recent discovery and success of immune checkpoint blockade and chimeric antigen receptor (CAR) T cell adoptive cell transfer has raised interest in using other immune cells, including Natural Killer (NK) cells, which might overcome some limitations with CAR T cell therapy. In this review article, we discuss the evidence that cellular metabolism is crucial for NK cell effector function. Additionally, potential strategies to optimise the metabolism of therapeutic NK cells for improved function within the metabolically adverse tumour microenvironment will be explored.

Metabolic dysfunction and immunometabolism in COVID-19 pathophysiology and therapeutics

The COVID-19 pandemic has emerged as a public health crisis and has placed a significant burden on healthcare systems. Patients with underlying metabolic dysfunction, such as type 2 diabetes mellitus and obesity, are at a higher risk for COVID-19 complications, including multi-organ dysfunction, secondary to a deranged immune response, and cellular energy deprivation. These patients are at a baseline state of chronic inflammation associated with increased susceptibility to the severe immune manifestations of COVID-19, which are triggered by the cellular hypoxic environment and cytokine storm. The altered metabolic profile and energy generation of immune cells affect their activation, exacerbating the imbalanced immune response. Key immunometabolic interactions may inform the development of an efficacious treatment for COVID-19. Novel therapeutic approaches with repurposed drugs, such as PPAR agonists, or newly developed molecules such as the antagomirs, which block microRNA function, have shown promising results. Those treatments, alone or in combination, target both immune and metabolic pathways and are ideal for septic COVID-19 patients with an underlying metabolic condition.

Immunosurveillance of Cancer and Viral Infections with Regard to Alterations of Human NK Cells Originating from Lifestyle and Aging

Natural killer (NK) cells are cytotoxic immune cells with an innate capacity for eliminating cancer cells and virus- infected cells. NK cells are critical effector cells in the immunosurveillance of cancer and viral infections. Patients with low NK cell activity or NK cell deficiencies are predisposed to increased risks of cancer and severe viral infections. However, functional alterations of human NK cells are associated with lifestyles and aging. Personal lifestyles, such as cigarette smoking, alcohol consumption, stress, obesity, and aging are correlated with NK cell dysfunction, whereas adequate sleep, moderate exercise, forest bathing, and listening to music are associated with functional healthy NK cells. Therefore, adherence to a healthy lifestyle is essential and will be favorable for immunosurveillance of cancer and viral infections with healthy NK cells.

Natural Killer Cells: Friend or Foe in Metabolic Diseases?

The worldwide epidemic of metabolic diseases, especially obesity and other diseases caused by it, has shown a dramatic increase in incidence. A great deal of attention has been focused on the underlying mechanisms of these pathological processes and potential strategies to solve these problems. Chronic inflammation initiated by abdominal adipose tissues and immune cell activation in obesity is the major cause of the consequent development of complications. In addition to adipocytes, macrophages and monocytes, natural killer (NK) cells have been verified to be vital components involved in shaping the inflammatory microenvironment, thereby leading to various obesity-related metabolic diseases. Here, we provide an overview of the roles of NK cells and the interactions of these cells with other immune and nonimmune cells in the pathological processes of metabolic diseases. Finally, we also discuss potential therapeutic strategies targeting NK cells to treat metabolic diseases.

Revisiting the Role of Natural Killer Cells in Non-Alcoholic Fatty Liver Disease

Non-Alcoholic Fatty Liver Disease (NAFLD) is the most common form of chronic liver disease. The histological spectrum of NAFLD ranges from simple steatosis to chronic inflammation and liver fibrosis during Non-Alcoholic Steatohepatitis (NASH). The current view is that innate immune mechanisms represent a key element in supporting hepatic inflammation in NASH. Natural Killer (NK) cells are lymphoid cells and a component of the innate immune system known to be involved in NASH progression. Increasing evidence has shed light on the differential function of circulating and tissue-resident NK cells, as well as on the relevance of metabolism and the microenvironment in regulating their activity. Here, we revisit the complex role of NK cells as regulators of NASH progression as well as potential therapeutic approaches based on their modulation.

Cancer-associated adipocytes as immunomodulators in cancer

Cancer-associated adipocytes (CAAs), as a main component of the tumor-adipose microenvironment (TAME), have various functions, including remodeling the extracellular matrix and interacting with tumor cells or infiltrated leukocytes through a variety of mutual signals. Here, we summarize the primary interplay among CAAs, the immune response and cancer with a focus on the mechanistic aspects of these relationships. Finally, unifying our understanding of CAAs with the immune cell function may be an effective method to enhance the efficacy of immunotherapeutic and conventional treatments.