Oncolytic Viruses Engineered to Enforce Leptin Expression Reprogram Tumor-Infiltrating T Cell Metabolism and Promote Tumor Clearance.

Immunotherapy can reinvigorate dormant responses to cancer, but response rates remain low. Oncolytic viruses, which replicate in cancer cells, induce tumor lysis and immune priming, but their immune consequences are unclear. We profiled the infiltrate of aggressive melanomas induced by oncolytic Vaccinia virus using RNA sequencing and found substantial remodeling of the tumor microenvironment, dominated by effector T cell influx. However, responses to oncolytic viruses were incomplete due to metabolic insufficiencies induced by the tumor microenvironment. We identified the adipokine leptin as a potent metabolic reprogramming agent that supported antitumor responses. Leptin metabolically reprogrammed T cells in vitro, and melanoma cells expressing leptin were immunologically controlled in mice. Engineering oncolytic viruses to express leptin in tumor cells induced complete responses in tumor-bearing mice and supported memory development in the tumor infiltrate. Thus, leptin can provide metabolic support to tumor immunity, and oncolytic viruses represent a platform to deliver metabolic therapy.

The Postnatal Leptin Surge Supports Immune Cell Function in Rats.

BACKGROUND: Leptin plays an important role in the regulation of the immune response. There is a physiological surge of leptin in rodents during the neonatal period, which has mainly been studied in the context of brain development. However, little is known about the effects of this neonatal leptin surge on immunity. Therefore, we investigated whether blocking this leptin surge could affect several immune functions. METHODS: Male and female rats were injected subcutaneously with 5 mg/Kg/day of rat pegylated super leptin antagonist during the neonatal period (PND5-9). On the peripubertal period, relevant functions as well as cytokine release by spleen leukocytes were studied in these animals. RESULTS: The results showed that the animals significantly display an impaired anti-tumor NK activity and chemotactic and proliferation capacity of lymphocytes in response to mitogens. In addition, several cytokine concentrations, released under mitogen-stimulated conditions, were also altered. CONCLUSION: In conclusion, the neonatal leptin surge seems to be involved in the establishment of an adequate immune response and cytokine profile, which are crucial for the maintenance of a healthy life.

An immunometabolic pathomechanism for chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is an inflammatory condition associated with abnormal immune responses, leading to airflow obstruction. Lungs of COPD subjects show accumulation of proinflammatory T helper (Th) 1 and Th17 cells resembling that of autoreactive immune responses. As regulatory T (Treg) cells play a central role in the control of autoimmune responses and their generation and function are controlled by the adipocytokine leptin, we herein investigated the association among systemic leptin overproduction, reduced engagement of glycolysis in T cells, and reduced peripheral frequency of Treg cells in different COPD stages. These phenomena were also associated with an impaired capacity to generate inducible Treg (iTreg) cells from conventional T (Tconv) cells. At the molecular level, we found that leptin inhibited the expression of forkhead-boxP3 (FoxP3) and its splicing variants containing the exon 2 (FoxP3-E2) that correlated inversely with inflammation and weakened lung function during COPD progression. Our data reveal that the immunometabolic pathomechanism leading to COPD progression is characterized by leptin overproduction, a decline in the expression of FoxP3 splicing forms, and an impairment in Treg cell generation and function. These results have potential implications for better understanding the autoimmune-like nature of COPD and the pathogenic events leading to lung damage.

Immunolocalization of leptin and leptin receptor in colorectal mucosa of ulcerative colitis, Crohn's disease and control subjects with no inflammatory bowel disease.

The expression of leptin and leptin receptor (Ob-R) has been partially elucidated in colon of patients with inflammatory bowel diseases (IBDs), even though leptin is involved in angiogenesis and inflammation. We previously reported overexpression of GLUT5 fructose transporter, in aberrant clusters of lymphatic vessels in lamina propria of IBD and controls. Here, we examine leptin and Ob-R expression in the same biopsies. Specimens were obtained from patients with ulcerative colitis (UC), Crohn's disease (CD) and controls who underwent screening for colorectal cancer, follow-up after polypectomy or with a history of lower gastrointestinal symptoms. Immunohistochemistry revealed leptin in apical and basolateral membranes of short epithelial portions, Ob-R on the apical pole of epithelial cells. Leptin and Ob-R were also identified in structures and cells scattered in the lamina propria. In UC, a significant correlation between leptin and Ob-R in the lamina propria was found in all inflamed samples, beyond non-inflamed samples of the proximal tract, while in CD, it was found in inflamed distal samples. Most of the leptin and Ob-R positive areas in the lamina propria were also GLUT5 immunoreactive in inflamed and non-inflamed mucosa. A significant correlation of leptin or Ob-R expression with GLUT5 was observed in the inflamed distal samples from UC. Our findings suggest that there are different sites of leptin and Ob-R expression in large intestine and those in lamina propria do not reflect the status of mucosal inflammation. The co-localization of leptin and/or Ob-R with GLUT5 may indicate concomitance effects in colorectal lamina propria areas.

Symptoms of systemic lupus erythematosus are diagnosed in leptin transgenic pigs.

Leptin is a well-known adipokine that plays a critical role in immune responses. To further explore the immunological roles of leptin, we developed a transgenic leptin pig controlled by the pig leptin (pleptin) promoter to overexpress leptin. Symptoms typically associated with systemic lupus erythematosus (SLE) were evident in this transgenic pig strain, including anemia, leukopenia, and thrombocytopenia as well as kidney and liver impairment. Histologically, there were increased immunoglobulin G (IgG) levels, elevated antiplatelet antibody (APA) levels, and deposition of immune complexes in the kidney and liver. In addition, anti-double-stranded DNA antibodies (dsDNAs), antinuclear antibodies (ANAs), and antinucleosome antibodies (ANuAs) were all significantly increased in serum immunological examinations. These findings were also accompanied by repression of the regulatory T cell (Treg) ratio. Significantly, glucocorticoid experimental therapies partially relieved the autoimmune responses and bleeding symptoms observed in these transgenic leptin pigs. Together, these results indicate that leptin plays a critical role in the development of autoimmune disorders and demonstrate that our transgenic leptin pigs can act as a valuable model of SLE.

Leptin Promotes Monosodium Urate Crystal-Induced Inflammation in Human and Murine Models of Gout.

Gouty arthritis is an inflammatory disease that is triggered by abnormal uric acid metabolism, which is usually attributed to obesity, a risk factor of hyperuricemia and gout attack. A high level of leptin in plasma is a marker of individuals with obesity. Population studies show that leptin promotes obesity-related arthritis, such as osteoarthritis, but it is unknown whether leptin contributes to gouty arthritis, another form of obesity-related arthritis. Our present study showed that the levels of leptin and leptin receptor in patients with active gouty arthritis were elevated. Leptin facilitates the stimulation of human synoviocytes, mouse peritoneal macrophages, and HL-60 cells induced by monosodium urate, leading to higher levels of acute gout-related proinflammatory factors. Leptin obviously exacerbates the inflammation of monosodium urate-induced acute gouty arthritis in wild-type mice, whereas that in leptin-deficient C57BL6/Job/ob mice is markedly alleviated. The proinflammatory effect of leptin in acute gouty arthritis is partly mediated by mTORC1 signaling pathway. Our study reveals that leptin may serve as a novel prevention and treatment target in acute gouty arthritis.

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

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

Obesity, the most common comorbidity in SARS-CoV-2: is leptin the link?

Overweight and obesity are major risk factors for diabetes, cardiovascular disease, and lung disease. These diseases are the most commonly reported health conditions that predispose individuals with SARS-CoV-2 infection to require hospitalization including intensive care unit admissions. The innate immune response is the host's first line of defense against a human coronavirus infection. However, most coronaviruses are armed with one strategy or another to overcome host antiviral defense, and the pathogenicity of the virus is related to its capacity to suppress host immunity. The multifaceted nature of obesity including its effects on immunity can fundamentally alter the pathogenesis of acute respiratory distress syndrome and pneumonia, which are the major causes of death due to SARS-CoV-2 infection. Elevated circulating leptin concentrations are a hallmark of obesity, which is associated with a leptin-resistant state. Leptin is secreted by adipocytes in proportion to body fat and regulates appetite and metabolism through signaling in the hypothalamus. However, leptin also signals through the Jak/STAT and Akt pathways, among others, to modulate T cell number and function. Thus, leptin connects metabolism with the immune response. Therefore, it seems appropriate that its dysregulation would have serious consequences during an infection. We propose that leptin may be the link between obesity and its high prevalence as a comorbidity of the SARS-CoV-2 infection. In this article, we present a synthesis of the mechanisms underpinning susceptibility to respiratory viral infections and the contribution of the immunomodulatory effects of obesity to the outcome.

A novel leptin receptor antagonist uncouples leptin's metabolic and immune functions.

Leptin links body energy stores to high energy demanding processes like reproduction and immunity. Based on leptin's role in autoimmune diseases and cancer, several leptin and leptin receptor (LR) antagonists have been developed, but these intrinsically lead to unwanted weight gain. Here, we report on the uncoupling of leptin's metabolic and immune functions based on the cross talk with the epidermal growth factor receptor (EGFR). We show that both receptors spontaneously interact and, remarkably, that this complex can partially overrule the lack of LR activation by a leptin antagonistic mutein. Moreover, this leptin mutant induces EGFR phosphorylation comparable to wild-type leptin. Exploiting this non-canonical leptin signalling pathway, we identified a camelid single-domain antibody that selectively inhibits this LR-EGFR cross talk without interfering with homotypic LR signalling. Administration in vivo showed that this single-domain antibody did not interfere with leptin's metabolic functions, but could reverse the leptin-driven protection against starvation-induced thymic and splenic atrophy. These findings offer new opportunities for the design and clinical application of selective leptin and LR antagonists that avoid unwanted metabolic side effects.

Correlation between leptin and IFN-γ involved in granulosa cell apoptosis in PCOS.

OBJECTIVES: Our study aimed to explore the relationship between leptin and IFN-γ in PCOS patients, and confirmed the effect of leptin-induced IFN-γ on granulosa cells furtherly. METHODS: 29 patients with PCOS and 36 healthy controls were enrolled. Leptin level and the proportion of Th1 cells were detected and association between them were analyzed. Meanwhile, peripheral blood mononuclear cells (PBMCs) isolated from PCOS patients were treated with leptin and then the proportion of Th1 was analyzed. Besides that, the apoptotic level of KGN cells was monitored after IFN-γ treatment. RESULTS: In the circulation of PCOS patients, leptin level dramatically increased compared with controls. And, this was associated with upregulated Th1 cells proportion and IFN-γ level. In vitro, Th1 cells proportion increased after leptin treated PBMCs from PCOS patients. Furthermore, for KGN cells, the percentage of live cells decreased and later apoptosis cells increased after IFN-γ treatment. CONCLUSIONS: Our results indicated that leptin takes part in process of PCOS via inducing expression of IFN-γ. Our findings highlight the importance of the connection between leptin and inflammation in PCOS and provide new insights therapeutic strategy for this disease.

An oscillatory switch in mTOR kinase activity sets regulatory T cell responsiveness.

There is a discrepancy between the in vitro anergic state of CD4(+)CD25(hi)FoxP3(+) regulatory T (Treg) cells and their in vivo proliferative capability. The underlying mechanism of this paradox is unknown. Here we show that the anergic state of Treg cells depends on the elevated activity of the mammalian target of rapamycin (mTOR) pathway induced by leptin: a transient inhibition of mTOR with rapamycin, before T cell receptor (TCR) stimulation, made Treg cells highly proliferative in the absence of exogenous interleukin-2 (IL-2). This was a dynamic and oscillatory phenomenon characterized by an early downregulation of the leptin-mTOR pathway followed by an increase in mTOR activation necessary for Treg cell expansion to occur. These data suggest that energy metabolism, through the leptin-mTOR-axis, sets responsiveness of Treg cells that use this information to control immune tolerance and autoimmunity.

Innate Immune Dysregulation in the Development of Cardiovascular Disease in Lupus.

PURPOSE OF REVIEW: The systemic inflammatory nature of systemic lupus erythematosus (SLE) is patent not only in the diverse clinical manifestations of the disease but also in the increased risk of premature cardiovascular diseases (CVD). In this review, we discuss the latest findings on the key factors of the innate immune system known to play critical roles in the pathogenesis of accelerated CVD in patients with SLE and discuss the potential that immunometabolism may play a key role in this respect. RECENT FINDINGS: Recent studies exploring the association between SLE and premature CVD clearly showed that alterations of specific immune functions play a pivotal role in the increased cardiovascular morbidity and mortality in the SLE patients. Novel molecular factors such as type I interferons (IFN), dysregulated neutrophil function, and changes to cellular metabolism and metabolites are emerging as important regulators of systemic immune dysfunction and as strong risk factors for premature CVD in SLE. Although corticosteroids and cytotoxic agents can be used to effectively manage and control various lupus-related complications, to date, no drug has been proven to prevent the development of premature atherosclerosis in SLE. However, as new mechanisms underlying this complication of SLE are uncovered, such as the role of metabolism and neutrophil-driven inflammation, new avenues for therapeutic intervention are being discovered.

Modifiable Host Factors in Melanoma: Emerging Evidence for Obesity, Diet, Exercise, and the Microbiome.

PURPOSE OF REVIEW: We discuss how potentially modifiable factors including obesity, the microbiome, diet, and exercise may impact melanoma development, progression, and therapeutic response. RECENT FINDINGS: Obesity is unexpectedly associated with improved outcomes with immune and targeted therapy in melanoma, with early mechanistic data suggesting leptin as one mediator. The gut microbiome is both a biomarker of response to immunotherapy and a potential target. As diet is a major determinant of the gut microbiome, ongoing studies are examining the interaction between diet, the gut microbiome, and immunity. Data are emerging for a potential role of exercise in reducing hypoxia and enhancing anti-tumor immunity, though this has not yet been well-studied in the context of contemporary therapies. Recent data suggests energy balance may play a role in the outcomes of metastatic melanoma. Further studies are needed to demonstrate mechanism and causality as well as the feasibility of targeting these factors.

New insights into different adipokines in linking the pathophysiology of obesity and psoriasis.

Psoriasis is a chronic, systemic, hyper-proliferative immune-mediated inflammatory skin disease. The results of epidemiological investigations have shown that psoriasis affects around 2% of the general population worldwide, and the total number of psoriasis patients is more than 6 million in China. Apart from the skin manifestations, psoriasis has been verified to associate with several metabolic comorbidities, such as insulin resistance, diabetes and obesity. However, the underlying mechanism is still not elucidated. Adipocytes, considered as the active endocrine cells, are dysfunctional in obesity which displays increased synthesis and secretion of adipokines with other modified metabolic properties. Currently, growing evidence has pointed to the central role of adipokines in adipose tissue and the immune system, providing new insights into the effect of adipokines in linking the pathophysiology of obesity and psoriasis. In this review, we summarize the current understanding of the pathological role of adipokines and the potential mechanisms whereby different adipokines link obesity and psoriasis. Furthermore, we also provide evidence which identifies a potential therapeutic target aiming at adipokines for the management of these two diseases.

Molecular Links between Central Obesity and Breast Cancer.

: Worldwide, breast cancer (BC) is the most common malignancy in women, in regard to incidence and mortality. In recent years, the negative role of obesity during BC development and progression has been made abundantly clear in several studies. However, the distribution of body fat may be more important to analyze than the overall body weight. In our review of literature, we reported some key findings regarding the role of obesity in BC development, but focused more on central adiposity. Firstly, the adipose microenvironment in obese people bears many similarities with the tumor microenvironment, in respect to associated cellular composition, chronic low-grade inflammation, and high ratio of reactive oxygen species to antioxidants. Secondly, the adipose tissue functions as an endocrine organ, which in obese people produces a high level of tumor-promoting hormones, such as leptin and estrogen, and a low level of the tumor suppressor hormone, adiponectin. As follows, in BC this leads to the activation of oncogenic signaling pathways: NFκB, JAK, STAT3, AKT. Moreover, overall obesity, but especially central obesity, promotes a systemic and local low grade chronic inflammation that further stimulates the increase of tumor-promoting oxidative stress. Lastly, there is a constant exchange of information between BC cells and adipocytes, mediated especially by extracellular vesicles, and which changes the transcription profile of both cell types to an oncogenic one with the help of regulatory non-coding RNAs.

E74-Like Factor (ELF3) and Leptin, a Novel Loop Between Obesity and Inflammation Perpetuating a Pro-Catabolic State in Cartilage.

BACKGROUND/AIMS: The E74-like factor 3 (ELF3) is an inflammatory mediator that participates in cartilage destruction in osteoarthritis. Leptin and other adipokines negatively impact articular cartilage, triggering catabolic and inflammatory responses in chondrocytes. Here, we investigated whether leptin induces ELF3 expression in chondrocytes and the signaling pathway involved in this process. METHODS: We determined mRNA and protein levels of ELF3 by RT-qPCR and Western blotting using cultured human primary chondrocytes and the human T/C-28a2 chondrocyte cell line. Further, we measured luciferase activities of different reporter constructs, and we assessed the contribution of leptin to the induction of ELF3 mRNA by knocking down hLEPR gene expression using siRNA technology. RESULTS: Leptin synergizes with IL-1ß in inducing ELF3 expression in chondrocytes. We also found that PI3K, p38, and JAK2 signaling pathways are at play in the leptin-driven induction of ELF3. Moreover, we confirm the participation of NFΚB in the leptin/IL-1ß synergistic induction of ELF3. CONCLUSION: Here we show, for the first time, the regulation of ELF3 expression by leptin, suggesting that this transcription factor likely mediates the inflammatory responses triggered by leptin in articular chondrocytes.

Functional human antibody CDR fusions as long-acting therapeutic endocrine agonists.

On the basis of the 3D structure of a bovine antibody with a well-folded, ultralong complementarity-determining region (CDR), we have developed a versatile approach for generating human or humanized antibody agonists with excellent pharmacological properties. Using human growth hormone (hGH) and human leptin (hLeptin) as model proteins, we have demonstrated that functional human antibody CDR fusions can be efficiently engineered by grafting the native hormones into different CDRs of the humanized antibody Herceptin. The resulting Herceptin CDR fusion proteins were expressed in good yields in mammalian cells and retain comparable in vitro biological activity to the native hormones. Pharmacological studies in rodents indicated a 20- to 100-fold increase in plasma circulating half-life for these antibody agonists and significantly extended in vivo activities in the GH-deficient rat model and leptin-deficient obese mouse model for the hGH and hLeptin antibody fusions, respectively. These results illustrate the utility of antibody CDR fusions as a general and versatile strategy for generating long-acting protein therapeutics.

Leptin Enhances TH2 and ILC2 Responses in Allergic Airway Disease.

Allergic asthma and obesity are the leading health problems in the world. Many studies have shown that obesity is a risk factor of development of asthma. However, the underlying mechanism has not been well established. In this study, we demonstrate that leptin, an adipokine elevated in obese individuals, promoted proliferation and survival of pro-allergic type 2 helper T cells and group 2 innate lymphoid cells and production of type 2 cytokines, which together contribute to allergic responses. Leptin activates mTORC1, MAPK, and STAT3 pathways in TH2 cells. The effects of leptin on TH2 cell proliferation, survival, and cytokine production are dependent on the mTORC1 and MAPK pathways as revealed by specific inhibitors. In vivo, leptin-deficiency led to attenuated experimental allergic airway inflammation. Our results thus support that obesity-associated elevation of leptin contributes to the increased susceptibility of asthma via modulation of pro-allergic lymphocyte responses.

Leptin positively regulates MUC5AC production and secretion induced by interleukin-13 in human bronchial epithelial cells.

Mucus hypersecretion and plugging of lower respiratory tract airways due to mucus plugs have long been recognized as the leading cause of the morbidity and mortality in asthma. MUC5AC protein is a major component of airway mucus. Here, we showed that interleukin (IL)-13 induced MUC5AC production and secretion, and leptin expression in the human bronchial epithelial cell line-16 (HBE16) cells in a concentration-dependent manner. Leptin knockdown suppressed MUC5AC production and secretion induced by IL-13. We further investigated the molecular mechanism by which leptin functioned, and found that leptin regulated IL-13-induced MUC5AC production and secretion via the JAK2-STAT3 pathway. Subsequently, Munc18b, a limiting component of the exocytic machinery of airway epithelial and mast cells, was found that when knockdown, MUC5AC secretion was significantly inhibited. SABiosciences ChIP search tool identified three STAT3 binding sites with Munc18b promoter. Chromatin immunoprecipitation analysis further confirmed that Stat3 upregulated Munc18b expression by directly binding to its promoter. These data suggested that leptin promotes MUC5AC secretion via JAK2-STAT3-MUNC18b regulatory network. Taken together, our data highlight a positive feedback role and molecular mechanism for leptin in the control of MUC5AC production and secretion from airway epithelial cells stimulated by IL-13, which encourage further exploration of the therapeutic potentials of manipulating leptin in the treatment of mucus hypersecretion in chronic inflammation lung diseases.

Long term persistence of inflammation in children vaccinated with Salmonella conjugate vaccine is associated with augmented Th9-Th17 cytokine.

Vaccine induced serum cytokines not only serves as a biomarker of immunity but also serves as a reliable measure of inflammation. Long term persistence of inflammation can lead to metabolic derangement. Towards this end, in the present study, we measured levels of cytokines along with hormones (insulin, leptin and adiponectin) in children who have been vaccinated with Salmonella typhi Vi conjugate vaccine, 30months after vaccination. Vaccinated children showed a unique cytokine profile with suppressed Th1-Th2 and increased Th9-Th17 cytokines indicating immune polarization which was associated with decreased serum adiponectin (but not insulin or leptin) levels. The study gains major importance since it is a longitudinal study which reports vaccine induced long term persistence of inflammation for the first time in the high risk ethnic population.