Leptin as immune mediator: Interaction between neuroendocrine and immune system

The role of hyperleptinaemia and low values of interleukin 10 in de novo DSA production after kidney transplantation

BACKGROUND

White adipose tissue secretes a number of peptide hormones. The aim of this paper was to determine the role of leptin, adiponectin and interleukin-10 and interleukin-6 on the development of graft rejection in protocol biopsy after kidney transplantation.

METHODS

In a prospective analysis (n = 104), we monitored the values of leptin, adiponectin, IL-6, and IL-10 prior to the transplantation and in the 3rd month after the transplantation. The protocol biopsy of the graft was performed in the 3rd month after the transplantation. The group was divided into the following according to the biopsy result: negative result, IFTA 1, borderline, and DSA positive.

RESULTS

After adjusting for the differences in the baseline recipient and donor characteristics, we identified the hyperleptinaemia baseline (HR = 2.0444, P = 0.0341) and month 3 (HR = 49.8043, P < 0.0001) as independent risk factors for borderline changes in the protocol biopsy. The hyperleptinaemia baseline (HR = 7.4979, P = 0.0071) and month 3 (HR = 9.7432, P = 0.0057) are independent risk factors for de novo DSA positivity. A low value of IL-10 month 3 is a risk factor for de novo DSA positivity (HR = 3.0746, P = 0.0388).

CONCLUSIONS

Higher leptin levels and low values of IL-10 might play a role in rejection and de novo DSA production.

Minireview: Glucocorticoid-Leptin Crosstalk: Role of Glucocorticoid-Leptin Counterregulation in Metabolic Homeostasis and Normal Development

Glucocorticoids and leptin are two important hormones that regulate metabolic homeostasis by controlling appetite and energy expenditure in adult mammals. Also, glucocorticoids and leptin strongly counterregulate each other, such that chronic stress-induced glucocorticoids upregulate the production of leptin and leptin suppresses glucocorticoid production directly via action on endocrine organs and indirectly via action on food intake. Altered glucocorticoid or leptin levels during development can impair organ development and increase the risk of chronic diseases in adults, but there are limited studies depicting the significance of glucocorticoid-leptin interaction during development and its impact on developmental programming. In mammals, leptin-induced suppression of glucocorticoid production is critical during development, where leptin prevents stress-induced glucocorticoid production by inducing a period of short-hyporesponsiveness when the adrenal glands fail to respond to certain mild to moderate stressors. Conversely, reduced or absent leptin signaling increases glucocorticoid levels beyond what is appropriate for normal organogenesis. The counterregulatory interactions between leptin and glucocorticoids suggest the potential significant involvement of leptin in disorders that occur from stress during development.

Molecular Characterization and Expression Pattern of leptin in Yellow Cheek Carp (Elopichthys bambusa) and Its Transcriptional Changes in Response to Fasting and Refeeding

Leptin, a secretory protein encoded by obese genes, plays an important role in regulating feeding and energy metabolism in fish. To study the structure and function of the Leptin gene in yellow cheek carp (Elopichthys bambusa), the full-length cDNA sequence of leptin was cloned, named EbLep. The full-length cDNA of Eblep was 1140 bp, and the length of the open reading frame (ORF), which can encode a protein of 174 amino acids, was 525 bp. The signal peptide was predicted to contain 33 amino acids. Sequence alignment showed that the amino acid sequence of Leptin was conserved in cyprinid fish. Despite large differences between primary structures, the tertiary structure of the EbLep protein was similar to that of the human protein and had four α-helices. The EbLep mRNA transcript was detected in all tested tissues, with the highest expression in the liver and lowest expression in the spleen. In this study, short-term fasting significantly increased the mRNA expression of EbLep in the liver, which returned to a normal level after 6 days of refeeding and was significantly lower than the normal level after 28 days of refeeding. In the brain, the mRNA expression of EbLep significantly decreased during short-term fasting and significantly increased to a higher value than the control group after 1 h of refeeding. It then rapidly decreased to a lower value than the control group after 6 h of refeeding, returning to the normal level after 1 day of refeeding, and significantly decreasing to a lower value than the control group after 28 days of refeeding. To sum up, the change in the mRNA expression of EbLep in the brain and liver may be an adaptive strategy for different energy levels.

Obesity, gut microbiota, and multiple sclerosis: Unraveling the connection

Obesity is associated with chronic mild-grade systemic inflammation and neuroinflammation. Obesity in early childhood and adolescence is also a significant risk factor for multiple sclerosis (MS) development. However, the underlying mechanisms that explain the link between obesity and MS development are not fully explored. An increasing number of studies call attention to the importance of gut microbiota as a leading environmental risk factor mediating inflammatory central nervous system demyelination, particularly in MS. Obesity and high-calorie diet are also associated with disturbances in gut microbiota. Therefore, gut microbiota alteration is a plausible connection between obesity and the increased risk of MS development. A greater understanding of this connection could provide additional therapeutic opportunities, like dietary interventions, microbiota-derived products, and exogenous antibiotics and probiotics. This review summarizes the current evidence regarding the relationships between MS, obesity, and gut microbiota. We discuss gut microbiota as a potential link between obesity and increased risk for MS. Additional experimental studies and controlled clinical trials targeting gut microbiota are warranted to unravel the possible causal relationship between obesity and increased risk of MS.

The Role of Adipokines in the Pathogenesis of Psoriasis

Psoriasis is a chronic and immune-mediated skin condition characterized by pro-inflammatory cytokines and keratinocyte hyperproliferation. Dendritic cells, T lymphocytes, and keratinocytes represent the main cell subtypes involved in the pathogenesis of psoriasis, while the interleukin-23 (IL-23)/IL-17 pathway enhances the disease progression. Human adipose tissue is an endocrine organ, which secretes multiple proteins, known as adipokines, such as adiponectin, leptin, visfatin, or resistin. Current evidence highlights the immunomodulatory roles of adipokines, which may contribute to the progression or suppression of psoriasis. A better understanding of the complexity of psoriasis pathophysiology linked with adipokines could result in developing novel diagnostic or therapeutic strategies. This review aims to present the pathogenesis of psoriasis and the roles of adipokines in this process.

Drastic transformation of visceral adipose tissue and peripheral CD4 T cells in obesity

Obesity has a pronounced effect on the immune response in systemic organs that results in not only insulin resistance but also altered immune responses to infectious diseases and malignant tumors. Obesity-associated microenvironmental changes alter transcriptional expression and metabolism in T cells, leading to alterations in T-cell differentiation, proliferation, function, and survival. Adipokines, cytokines, and lipids derived from obese visceral adipose tissue (VAT) may also contribute to the systemic T-cell phenotype, resulting in obesity-specific pathogenesis. VAT T cells, which have multiple roles in regulating homeostasis and energy utilization and defending against pathogens, are most susceptible to obesity. In particular, many studies have shown that CD4 T cells are deeply involved in the homeostasis of VAT endocrine and metabolic functions and in obesity-related chronic inflammation. In obesity, macrophages and adipocytes in VAT function as antigen-presenting cells and contribute to the obesity-specific CD4 T-cell response by inducing CD4 T-cell proliferation and differentiation into inflammatory effectors via interactions between major histocompatibility complex class II and T-cell receptors. When obesity persists, prolonged stimulation by leptin and circulating free fatty acids, repetitive antigen stimulation, activating stress responses, and hypoxia induce exhaustion of CD4 T cells in VAT. T-cell exhaustion is characterized by restricted effector function, persistent expression of inhibitory receptors, and a transcriptional state distinct from functional effector and memory T cells. Moreover, obesity causes thymic regression, which may result in homeostatic proliferation of obesity-specific T-cell subsets due to changes in T-cell metabolism and gene expression in VAT. In addition to causing T-cell exhaustion, obesity also accelerates cellular senescence of CD4 T cells. Senescent CD4 T cells secrete osteopontin, which causes further VAT inflammation. The obesity-associated transformation of CD4 T cells remains a negative legacy even after weight loss, causing treatment resistance of obesity-related conditions. This review discusses the marked transformation of CD4 T cells in VAT and systemic organs as a consequence of obesity-related microenvironmental changes.

Leptin's Immune Action: A Review Beyond Satiety

The adipose tissue is an endocrine organ that secretes adipokines such as leptin, which is one of the most important hormones for controlling satiety, metabolism, and energy homeostasis. This hormone acts in the regulation of innate and adaptive immune responses since immune cells have leptin receptors from which this hormone initiates its biological action. These receptors have been identified in hematopoietic stem cells in the bone marrow and mature immune cells, inducing signaling pathways mediated by JAK/STAT, PI3K, and ERK 1/2. It is known that the bone marrow also contains leptin-producing adipocytes, which are crucial for regulating hematopoiesis through largely unknown mechanisms. Therefore, we have reviewed the roles of leptin inside and outside the bone marrow, going beyond its action in the control of satiety.

Obesity, leptin and host defence of Streptococcus pneumoniae: the case for more human research

Pneumococcal pneumonia is the leading cause of community-acquired pneumonia. Obesity is a risk factor for pneumonia. Host factors play a critical role in susceptibility to pulmonary pathogens and outcome from pulmonary infections. Obesity impairs innate and adaptive immune responses, important in the host defence against pneumococcal disease. One area of emerging interest in understanding the complex relationship between obesity and pulmonary infections is the role of the hormone leptin. There is a substantive evidence base supporting the associations between obesity, leptin, pulmonary infections and host defence mechanisms. Despite this, there is a paucity of research that specifically focuses on Streptococcus pneumoniae (pneumococcal) infections, which are the leading cause of community-acquired pneumonia hospitalisations and mortality worldwide. Much of the evidence examining the role of leptin in relation to S. pneumoniae infections has used genetically mutated mice. The purpose of this mini review is to explore the role leptin plays in the host defence of S. pneumoniae in subjects with obesity and posit an argument for the need for more human research.

Neuroendocrine-Immune Regulatory Network of Eucommia ulmoides Oliver

Eucommia ulmoides Oliver (E. ulmoides) is a popular medicinal herb and health supplement in China, Japan, and Korea, and has a variety of pharmaceutical properties. The neuroendocrine-immune (NEI) network is crucial in maintaining homeostasis and physical or psychological functions at a holistic level, consistent with the regulatory theory of natural medicine. This review aims to systematically summarize the chemical compositions, biological roles, and pharmacological properties of E. ulmoides to build a bridge between it and NEI-associated diseases and to provide a perspective for the development of its new clinical applications. After a review of the literature, we found that E. ulmoides has effects on NEI-related diseases including cancer, neurodegenerative disease, hyperlipidemia, osteoporosis, insomnia, hypertension, diabetes mellitus, and obesity. However, clinical studies on E. ulmoides were scarce. In addition, E. ulmoides derivatives are diverse in China, and they are mainly used to enhance immunity, improve hepatic damage, strengthen bones, and lower blood pressure. Through network pharmacological analysis, we uncovered the possibility that E. ulmoides is involved in functional interactions with cancer development, insulin resistance, NAFLD, and various inflammatory pathways associated with NEI diseases. Overall, this review suggests that E. ulmoides has a wide range of applications for NEI-related diseases and provides a direction for its future research and development.

Body size perceptions & diet modification in youth with multiple sclerosis

BACKGROUND

Investigate the perceptions of pediatric multiple sclerosis (MS) patients regarding their body size and assess the feasibility of recruitment for a study of diet modification in this unique population.

METHODS

This cross-sectional study surveyed a cohort of 43 consecutive youth with MS. The survey queried participant demographics, clinical disease characteristics, body size perception, and opinions of diet modification RESULTS: : While over three quarters of surveyed participants were overweight/obese, 58% of these participants did not self-identify as such. A single participant was attempting a diet at the time of survey, but 88% of participants indicated interest in pursuing diet modification. BMI category did not impact an individual's willingness to pursue diet intervention; however, obese participants were more willing to participate in diet intervention for longer durations.

CONCLUSION

A significant proportion of MS youth have an elevated BMI, yet the majority have the self-perception that they are not overweight or obese. Regardless of BMI, most youth with MS have an interest in pursuing diet modification in attempts to benefit their disease course.

Gallbladder Cancer Cell-Derived Exosome-Mediated Transfer of Leptin Promotes Cell Invasion and Migration by Modulating STAT3-Mediated M2 Macrophage Polarization

Tumor-associated macrophage (TAM) is a major component of tumor microenvironment (TME) and plays critical role in the progression of cancer metastasis. However, TAM-mediated regulation in gallbladder cancer (GBC) has not been fully characterized. Here, we found that exosomes derived from GBC cell polarized macrophage to M2 phenotype, which then facilitated the invasion and migration of GBC cells. We discovered that leptin was enriched in GBC cell-derived exosomes. Exosomal leptin levels promoted invasion and migration of GBC-SD cells. The inhibition of leptin not only attenuated M2 macrophage of polarization but also inhibited the invasive and migratory ability of GBC cell. In addition, GBC-SD cell-derived exosomal leptin induced M2 polarization of macrophage via activation of STAT3 signal pathway. Taken together, our results suggested that GBC cells secrete exosome-enclosed leptin facilitated cell invasion and migration via polarizing TAM.

Leptin hormone and its effectiveness in reproduction, metabolism, immunity, diabetes, hopes and ambitions

Leptin is a hormone derived from adipose tissue and the small intestine, mainly in enterocytes; it helps regulate the energy balance by suppressing hunger, resulting in decreased fat mass in adipocytes. Leptin has specific receptors in the ventromedial and arcuate nuclei and other parts of the hypothalamus and the feeding center in the ventral tegmental area. It also plays a role in regulatory aspects other than fat cells, such as obesity, which is linked to a loss of sensitivity of leptin receptors, resulting in an inability to produce satiety and an increase in food intake. Moreover, leptin plays a part in lactation, bone density, the immune system, diabetes treatments, and hypertriglyceridemia. The latest studies in leptin suggest that an analog of leptin may treat DM and hypertriglyceridemia. Further research should be conducted on the effectiveness of leptin on other related diseases.

Leptin in the Respiratory Tract: Is There a Role in SARS-CoV-2 Infection?

Leptin is a pleiotropic adipocytokine involved in several physiologic functions, with a known role in innate and adaptive immunity as well as in tissue homeostasis. Long- and short-isoforms of leptin receptors are widely expressed in many peripheral tissues and organs, such as the respiratory tract. Similar to leptin, microbiota affects the immune system and may interfere with lung health through the bidirectional crosstalk called the “gut-lung axis.” Obesity leads to impaired protective immunity and altered susceptibility to pulmonary infections, as those by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although it is known that leptin and microbiota link metabolism and lung health, their role within the SARS-CoV2 coronavirus disease 2019 (COVID-19) deserves further investigations. This review aimed to summarize the available evidence about: (i) the role of leptin in immune modulation; (ii) the role of gut microbiota within the gut-lung axis in modulating leptin sensitivity; and (iii) the role of leptin in the pathophysiology of COVID-19.

Evolutionary conservation of leptin effects on wound healing in vertebrates: Implications for veterinary medicine

In mammals, the cytokine hormone leptin promotes wound healing by increasing inflammation, cellular recruitment, angiogenic regrowth, and re-epithelialization; however, it is not known whether leptin has conserved actions on wound healing in other vertebrates. Here, we tested the hypothesis that leptin promotes both the quality and speed of wound healing in the South African clawed frog, Xenopus laevis. First, fluorescent immunohistochemistry using a polyclonal antibody specific to Xenopus leptin showed that in juvenile dorsal skin, leptin protein is expressed in the dorsal epidermal layer, as well in blood vessel endothelial cells and sensory nerves that run along the base of the dermis. Injection of recombinant Xenopus leptin (rXleptin) stimulates phosphorylated STAT3 (pSTAT3), indicative of leptin-activated JAK/STAT signaling in the epidermis. Similar to mammals, leptin protein expression increases at the wound site after injury of the epidermis. We then cultured "punch-in-a-punch" full-thickness dorsal skin explants in three doses of rXleptin (0, 10, and 100 ng/ml) and showed that leptin treatment doubled the rate of wound closure after 48 h relative to skin punches cultured without leptin. Food restriction prior to wound explant culture reduced the amount of wound closure, but leptin injection prior to euthanasia rescued closure to similar control levels. Leptin treatment also significantly reduced bacterial infection of these epidermal punches by 48 h in culture. This study shows that leptin is likely an endogenous promoter of wound healing in amphibians. Leptin-based therapies have the potential to expedite healing and reduce the incidence of secondary infections without toxicity issues, the threat of antibiotic resistance, or environmental antibiotic contamination. The conservation of leptin's actions on wound healing also suggests that it may have similar veterinary applications for other exotic species.

Infection and Immunometabolism in the Central Nervous System: A Possible Mechanistic Link Between Metabolic Imbalance and Dementia

Metabolic syndromes are frequently associated with dementia, suggesting that the dysregulation of energy metabolism can increase the risk of neurodegeneration and cognitive impairment. In addition, growing evidence suggests the link between infections and brain disorders, including Alzheimer's disease. The immune system and energy metabolism are in an intricate relationship. Infection triggers immune responses, which are accompanied by imbalance in cellular and organismal energy metabolism, while metabolic disorders can lead to immune dysregulation and higher infection susceptibility. In the brain, the activities of brain-resident immune cells, including microglia, are associated with their metabolic signatures, which may be affected by central nervous system (CNS) infection. Conversely, metabolic dysregulation can compromise innate immunity in the brain, leading to enhanced CNS infection susceptibility. Thus, infection and metabolic imbalance can be intertwined to each other in the etiology of brain disorders, including dementia. Insulin and leptin play pivotal roles in the regulation of immunometabolism in the CNS and periphery, and dysfunction of these signaling pathways are associated with cognitive impairment. Meanwhile, infectious complications are often comorbid with diabetes and obesity, which are characterized by insulin resistance and leptin signaling deficiency. Examples include human immunodeficiency virus (HIV) infection and periodontal disease caused by an oral pathogen Porphyromonas gingivalis. This review explores potential interactions between infectious agents and insulin and leptin signaling pathways, and discuss possible mechanisms underlying the relationship between infection, metabolic dysregulation, and brain disorders, particularly focusing on the roles of insulin and leptin.

Probiotic supplementation affects IGF-1 and leptin levels in Nile tilapia hepatopancreatic tissue

ABSTRACT This work aimed to assess the effect of the probiotic strain, Lactobacillus plantarum, on the levels of leptin, IGF-1 and their receptors on the hepatopancreatic tissues of Nile tilapia (Oreochromis niloticus) and then correlate fish growth performance and gut microbiological parameters. Fish juveniles (±23g) were reared in a recirculation system with constant aeration and temperature (25°C). They were distributed into six polyethylene tanks (45L) and fed twice a day at 5% of the tank biomass with the respective diets: control (commercial diet without probiotic) and supplemented with L. plantarum inoculum (1 x 108 CFU mL-1), both in triplicate. After 30 days of feeding, L. plantarum-fed fishes showed greater weekly growth rate, final weight, and feed conversion rate, in addition to higher count of lactic-acid bacteria and lower count of pathogenic bacteria in the intestinal tract, when compared to the control group. The immunostaining intensity for IGF-1 and leptin hormones was lower after L. plantarum supplementation than in the control group, with no change in the level for receptors. This reduction could implicate important changes in fish metabolism and homeostasis.

Leptin promotes glycolytic metabolism to induce dendritic cells activation via STAT3-HK2 pathway

Leptin is over-secreted in many autoimmune diseases, which can promote dendritic cells (DCs) maturation and up-regulate the expression of inflammatory cytokines, but the underlying mechanisms are not fully elucidated. Considering the major role of leptin in maintaining energy balance and the significant role of glycolysis in DCs activation, our study aims to investigate whether leptin promotes the activation of DCs via glycolysis and its underlying mechanisms. We demonstrated that leptin promoted the activation of DCs, including up-regulating the expression of co-stimulatory molecules and inflammatory cytokines, enhancing the proliferation and T helper 17 (Th17) cell ratio in peripheral blood mononuclear cells (PBMC) co-cultured with leptin-stimulated DCs. Leptin also enhanced DCs glycolysis with increased glucose consumption, lactate production, and the expression of hexokinase 2 (HK2). In addition, the activation of DCs stimulated by leptin could be inhibited by the glycolysis inhibitor 2-deoxy-d-glucose (2-DG). To explore the signaling pathways involved in leptin-induced HK2 expression, we observed that the inhibitors of STAT3 (NSC74859) could repress the enhancement of HK2 triggered by leptin stimulation. Therefore, our results indicated that leptin promoted glycolytic metabolism to induce DCs activation via STAT3-HK2 pathway.

Emerging role of leptin in joint inflammation and destruction

Rheumatoid arthritis (RA) is an autoimmune disease characterized by tumor-like hyperplasia and inflammation of the synovium, which causes synovial cell invasion into the bone and cartilage. In RA pathogenesis, various molecules in effector cells (i.e., immune cells and mesenchymal cells) are dysregulated by genetic and environmental factors. Consistent with the early stages of RA, these pathogenic cells cooperate and activate each other directly by cell-to-cell contact or indirectly via humoral factors. Recently, growing evidence has revealed essential role of adipokines, which are multifunctional signal transduction molecules, in the immune system. In this review, we summarize the current understanding of the cross-talk between leptin, one of the most well-known and best-characterized adipokines, and osteoimmunology. Furthermore, we discuss the contribution of leptin to the pathogenesis of RA and its potential mechanisms.

Trajectory of leptin and leptin receptor in vertebrates: Structure, function and their regulation

The present review provides a comparative insight into structure, function and control of leptin system in fishes, herptiles, birds and mammals. In general, leptin acts as an anorexigenic hormone since its administration results in decrease of food intake in vertebrates. Nonetheless, functional paradox arises in fishes from contradictory observations on level of leptin during fasting and re-feeding. In addition, leptin is shown to modulate metabolic functions in fishes, reptiles, birds and mammals. Leptin also regulates reproductive and immune functions though more studies are warranted in non-mammalian vertebrates. The expression of leptin and its receptor is influenced by numerous factors including sex steroids, stress and stress-induced catecholamines and glucocorticoids though their effect in non-mammalian vertebrates is hard to be generalized due to limited studies.

Circulating leptin, soluble leptin receptor and free leptin index in critically ill patients with sepsis: a prospective observational study

BACKGROUND

Leptin, the prototype adipokine, exerts immunomodulatory actions being implicated in inflammatory responses during sepsis. Clinical evidence regarding its role in sepsis has been contradictory, while free leptin has not been studied. Our aim was to jointly investigate circulating total leptin, its soluble receptor (sOBR), and free leptin, as well as their kinetics in critically ill patients with sepsis regarding their diagnostic and prognostic value.

METHODS

In a prospective study, serum total leptin, sOBR and free leptin index (FLI) were determined in 102 critically ill patients with sepsis within 48 hours from sepsis onset and one week after enrollment, and in 102 age and gender-matched healthy controls.

RESULTS

Upon enrollment, total leptin, sOB-R and FLI were significantly higher in septic patients compared to controls and they were positively correlated with sepsis severity scores, while they presented a significant decrease during the first week (p<0.001). The decrease in total leptin and sOB-R was significantly higher in patients with sepsis compared to septic shock and in survivors compared to nonsurvivors at 28 days (p<0.001). Higher serum total leptin was independently associated with survival at 28 days (enrollment: HR 0.86, p=0.03; one week after: HR 0.77, p<0.001). Higher kinetics of total leptin (but not FLI) was independently associated with survival after adjustment (HR: 0.48, p=0.001).

CONCLUSIONS

Higher circulating total leptin and its higher kinetics during the first week from sepsis onset independently predict 28 day survival in critically ill patients. Free leptin did not present any additional diagnostic and prognostic value in sepsis.

Changes in leptin, serotonin, and cortisol after eight weeks of aerobic exercise with probiotic intake in a cuprizone-induced demyelination mouse model of multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is the most common non-traumatic neurological cause of disability in young adults. Physical activity, particularly exercise training, is an evidence-based approach to managing symptoms, restoring function, and improving overall wellness in people with MS. As well, the use of probiotics can be effective in reducing the damage from inflammation in MS patients.

OBJECTIVE

The study aimed to address changes in leptin, serotonin, and cortisol following eight weeks of aerobic exercise along with probiotic intake in a cuprizone-induced demyelination mouse model of MS.

METHODS

Mice were exposed to cuprizone for 12 weeks. After 5 weeks, beam and performance tests were performed on them. The mice (n = 5 per group) were randomly divided into five groups: control (C), MS, MS with exercise (MS + Exe), MS with probiotic (MS + Prob), and MS with probiotic and exercise (MS + Prob + Exe). Exercise groups performed aerobic exercises 5 days a week, 10 min in the first week, 20 min in the second week, and 30 min daily in the third week until the eighth week. In the probiotic groups, the mice received probiotic by gavage. They were sacrificed after 3 months. Biochemical and molecular biology analyses were performed.

RESULTS

The results showed that leptin gene expression values in the MS + Prob + Exe, MS + Prob, and MS + Exe groups showed a decrease compared to the MS group, but the reduction was not significant (p > 0.05). Also, the leptin Elisa test in these intervention groups showed a significant decrease (P < 0.05). The serotonin gene expression values in the MS + Prob + Exe, MS + Prob, and MS + Exe groups were increased compared to the MS group, but the increase was not significant (p > 0.05). Furthermore, the serotonin Elisa test in these intervention groups showed a significant increase (P < 0.05). The cortisol Elisa test values in the MS + Exe and MS + Prob groups exhibited a decrease compared to the MS group, but the reduction was not significant (p > 0.05).

CONCLUSION

Overall, these results suggest that lifestyle interventions can be effective in improving pathological factors in patients with MS.

Rat Milk and Plasma Immunological Profile throughout Lactation

The composition of bioactive factors with immune activity in human breast milk is widely studied. However, the knowledge on rat milk immune factors during the whole lactation period is still scarce. This study aimed to analyze rat breast milk’s immunoglobulin (Ig) content and some critical adipokines and growth factors throughout the lactation period, and to assess relationships with corresponding plasma levels. During lactation, milk concentration of the transforming growth factor (TGF)-β2 and -β3 showed a punctual increase in the first week, whereas adiponectin and leptin remained stable. In the second period of lactation (d14–21), despite the increase in the milk epidermal growth factor (EGF), a decrease in fibroblast growth factor 21 (FGF21) was detected at day 21. Milk IgA concentration had a progressive increase during lactation, while no significant changes were found in IgM and IgG. Regarding plasma levels, a decrease in all studied adipokines was observed in the second period of lactation, with the exception of IgA and TGF-β1, which reached their highest values at the end of the study. A positive correlation in IgM, IgG, and adipokine concentration was detected between milk and plasma compartments. In summary, the changes in the pattern of these bioactive compounds in rat milk and plasma and their relationships during lactation are established.

Immune cells lacking Y chromosome show dysregulation of autosomal gene expression

Epidemiological investigations show that mosaic loss of chromosome Y (LOY) in leukocytes is associated with earlier mortality and morbidity from many diseases in men. LOY is the most common acquired mutation and is associated with aberrant clonal expansion of cells, yet it remains unclear whether this mosaicism exerts a direct physiological effect. We studied DNA and RNA from leukocytes in sorted- and single-cells in vivo and in vitro. DNA analyses of sorted cells showed that men diagnosed with Alzheimer's disease was primarily affected with LOY in NK cells whereas prostate cancer patients more frequently displayed LOY in CD4 + T cells and granulocytes. Moreover, bulk and single-cell RNA sequencing in leukocytes allowed scoring of LOY from mRNA data and confirmed considerable variation in the rate of LOY across individuals and cell types. LOY-associated transcriptional effect (LATE) was observed in ~ 500 autosomal genes showing dysregulation in leukocytes with LOY. The fraction of LATE genes within specific cell types was substantially larger than the fraction of LATE genes shared between different subsets of leukocytes, suggesting that LOY might have pleiotropic effects. LATE genes are involved in immune functions but also encode proteins with roles in other diverse biological processes. Our findings highlight a surprisingly broad role for chromosome Y, challenging the view of it as a "genetic wasteland", and support the hypothesis that altered immune function in leukocytes could be a mechanism linking LOY to increased risk for disease.

Prepubertal gonad investment modulates thymus function: evidence in a teleost fish

Thymus plasticity following gonadectomy or sex hormone replacement has long since exemplified sex hormone effects on the immune system in mammals and, to a lesser extent, in 'lower vertebrates', including amphibians and fish. Nevertheless, the underlying physiological significances as well as the ontogenetic establishment of this crosstalk remain largely unknown. Here, we used a teleost fish, the European sea bass, Dicentrarchus labrax, to investigate: (1) whether the regulation of thymus plasticity relies on resource trade-off with somatic growth and reproductive investment and (2) if the gonad-thymus interaction takes place during gonadal differentiation and development. Because gonadal development and, supposedly, thymus function in sea bass depend on environmental changes associated with the winter season, we evaluated thymus changes (foxn1 expression, and thymocyte and T cell content) in juvenile D. labrax raised for 1 year under either constant or fluctuating photoperiod and temperature. Importantly, in both conditions, intensive gonadal development following sex differentiation coincided with a halt of thymus growth, while somatic growth continued. To the best of our knowledge, this is the first study showing that gonadal development during prepuberty regulates thymus plasticity. This finding may provide an explanation for the initiation of the thymus involution related to ageing in mammals. Comparing fixed and variable environmental conditions, our work also demonstrates that the extent of the effects on the thymus, which are related to reproduction, depend on ecophysiological conditions, rather than being directly related to sexual maturity and sex hormone levels.

Association of Leptin Levels and Disease Activity in Patients with Early Rheumatoid Arthritis

OBJECTIVE

Previous studies have reported a link between metabolic parameters and disease activity in rheumatoid arthritis (RA), although the evidence is limited in early RA. We aimed to investigate the relationship between disease activity and adipocytokine levels in subjects with early RA.

METHODS

Forty-seven patients with early RA (symptom duration ≤12 months) were enrolled. Disease activity was determined by DAS28-CRP. Patients were treated with DMARDs according to the EULAR recommendations. Subjects were tested before and five months after treatment.

RESULTS

Early RA patients with high disease activity (DAS28-CRP > 4.9) had greater BMI (31.2 ± 6.8 kg/m² vs. 26.7 ± 4.1 kg/m²; p = 0.006) and higher leptin levels (14.62 ± 15.60 ng/mL vs. 7.82 ± 8.00 ng/mL; p = 0.048). Levels of other adipocytokines were not significantly different. Leptin levels were similar in subjects with mild/moderate disease activity and controls. DAS28-CRP was correlated with leptin (r = 0.303, p = 0.039). Leptin levels decreased significantly after treatment (from 10.86 ± 12.34 ng/mL to 9.22 ± 9.29 ng/mL; p = 0.047) along with insulin levels (from 13.68 ± 21.90 mU/L to 7.09 ± 4.72 mU/L; p = 0.010) and HOMA-IR (from 4.39 ± 9.53 to 1.70 ± 1.38; p = 0.012). HDL cholesterol levels increased (from 41 ± 10 mg/dL48 ± 10 mg/dL; p <0.001).

CONCLUSION

Leptin levels were associated with disease activity in patients with early RA and these levels decreased after treatment with DMARDs. Further research is needed to elicit leptin's role to regulate disease activity in early RA.

Research and prospect of peptides for use in obesity treatment (Review)

Obesity and its related diseases, such as type 2 diabetes, hypertension and cardiovascular disease, are steadily increasing worldwide. Over the past few decades, numerous studies have focused on the differentiation and function of brown and beige fat, providing evidence for their therapeutic potential in treating obesity. However, no specific novel drug has been developed to treat obesity in this way. Peptides are a class of chemically active substances, which are linked together by amino acids using peptide bonds. They have specific physiological activities, including browning of white fat. As signal molecules regulated by the neuroendocrine system, the role of polypeptides, such as neuropeptide Y, brain-gut peptide and glucagon-like peptide in obesity and its related complications has been revealed. Notably, with the rapid development of peptidomics, peptide drugs have been widely used in the prevention and treatment of metabolic diseases, due to their short half-life, small apparent distribution volume, low toxicity and low side effects. The present review summarizes the progress and the new trend of peptide research, which may provide novel targets for the prevention and treatment of obesity.

Emerging Role of Adipocyte Dysfunction in Inducing Heart Failure Among Obese Patients With Prediabetes and Known Diabetes Mellitus

Adipose tissue dysfunction is a predictor for cardiovascular (CV) events and heart failure (HF) in patient population with obesity, metabolic syndrome, and known type 2 diabetes mellitus. Previous preclinical and clinical studies have yielded controversial findings regarding the role of accumulation of adipose tissue various types in CV risk and HF-related clinical outcomes in obese patients. There is evidence for direct impact of infiltration of epicardial adipocytes into the underlying myocardium to induce adverse cardiac remodeling and mediate HF development and atrial fibrillation. Additionally, perivascular adipocytes accumulation is responsible for release of proinflammatory adipocytokines (adiponectin, leptin, resistin), stimulation of oxidative stress, macrophage phenotype switching, and worsening vascular reparation, which all lead to microvascular inflammation, endothelial dysfunction, atherosclerosis acceleration, and finally to increase in CV mortality. However, systemic effects of white and brown adipose tissue can be different, and adipogenesis including browning of adipose tissue and deficiency of anti-inflammatory adipocytokines (visfatin, omentin, zinc-α2-glycoprotein, glypican-4) was frequently associated with adipose triglyceride lipase augmentation, altered glucose homeostasis, resistance to insulin of skeletal muscles, increased cardiomyocyte apoptosis, lowered survival, and weak function of progenitor endothelial cells, which could significantly influence on HF development, as well as end-organ fibrosis and multiple comorbidities. The exact underlying mechanisms for these effects are not fully understood, while they are essential to help develop improved treatment strategies. The aim of the review is to summarize the evidence showing that adipocyte dysfunction may induce the onset of HF and support advance of HF through different biological mechanisms involving inflammation, pericardial, and perivascular adipose tissue accumulation, adverse and electrical cardiac remodeling, and skeletal muscle dysfunction. The unbalancing effects of natriuretic peptides, neprilysin, and components of renin–angiotensin system, as exacerbating cause of altered adipocytokine signaling on myocardium and vasculature, in obesity patients at high risk of HF are disputed. The profile of proinflammatory and anti-inflammatory adipocytokines as promising biomarker for HF risk stratification is discussed in the review.

Cytokine profiling of extracellular vesicles isolated from plasma in myalgic encephalomyelitis/chronic fatigue syndrome: a pilot study

BACKGROUND

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating disease of unknown etiology lasting for a minimum of 6 months but usually for many years, with features including fatigue, cognitive impairment, myalgias, post-exertional malaise, and immune system dysfunction. Dysregulation of cytokine signaling could give rise to many of these symptoms. Cytokines are present in both plasma and extracellular vesicles, but little investigation of EVs in ME/CFS has been reported. Therefore, we aimed to characterize the content of extracellular vesicles (EVs) isolated from plasma (including circulating cytokine/chemokine profiling) from individuals with ME/CFS and healthy controls.

METHODS

We included 35 ME/CFS patients and 35 controls matched for age, sex and BMI. EVs were enriched from plasma by using a polymer-based precipitation method and characterized by Nanoparticle Tracking Analysis (NTA), Transmission Electron Microscopy (TEM) and immunoblotting. A 45-plex immunoassay was used to determine cytokine levels in both plasma and isolated EVs from a subset of 19 patients and controls. Linear regression, principal component analysis and inter-cytokine correlations were analyzed.

RESULTS

ME/CFS individuals had significantly higher levels of EVs that ranged from 30 to 130 nm in size as compared to controls, but the mean size for total extracellular vesicles did not differ between groups. The enrichment of typical EV markers CD63, CD81, TSG101 and HSP70 was confirmed by Western blot analysis and the morphology assessed by TEM showed a homogeneous population of vesicles in both groups. Comparison of cytokine concentrations in plasma and isolated EVs of cases and controls yielded no significant differences. Cytokine-cytokine correlations in plasma revealed a significant higher number of interactions in ME/CFS cases along with 13 inverse correlations that were mainly driven by the Interferon gamma-induced protein 10 (IP-10), whereas in the plasma of controls, no inverse relationships were found across any of the cytokines. Network analysis in EVs from controls showed 2.5 times more significant inter-cytokine interactions than in the ME/CFS group, and both groups presented a unique negative association.

CONCLUSIONS

Elevated levels of 30-130 nm EVs were found in plasma from ME/CFS patients and inter-cytokine correlations revealed unusual regulatory relationships among cytokines in the ME/CFS group that were different from the control group in both plasma and EVs. These disturbances in cytokine networks are further evidence of immune dysregulation in ME/CFS.

Role of Neuroendocrine, Immune, and Autonomic Nervous System in Anorexia Nervosa-Linked Cardiovascular Diseases

Anorexia nervosa represents a severe mental disorder associated with food avoidance and malnutrition. In patients suffering from anorexia nervosa, cardiovascular complications are the main reason leading to morbidity and mortality. However, the origin and pathological mechanisms leading to higher cardiovascular risk in anorexia nervosa are still unclear. In this aspect, the issue of exact pathological mechanisms as well as sensitive biomarkers for detection of anorexia nervosa-linked cardiovascular risk are discussed. Therefore, this review synthesised recent evidence of dysfunction in multiple neuroendocrine axes and alterations in the immune system that may represent anorexia nervosa-linked pathological mechanisms contributing to complex cardiovascular dysregulation. Further, this review is focused on identification of non-invasive biomarkers for the assessment of increased cardiovascular risk in anorexia nervosa that can be linked to a clinical application. Complex non-invasive assessment of cardiovascular autonomic regulation—cardiac vagal control (heart rate variability), sympathetic vascular activity (blood pressure variability), and cardiovascular reflex control (baroreflex sensitivity)—could represent a promising tool for early diagnosis, personalized therapy, and monitoring of therapeutic interventions in anorexia nervosa particularly at a vulnerable adolescent age.

Altered structural connectivity and cytokine levels in Schizophrenia and Genetic high-risk individuals: Associations with disease states and vulnerability

BACKGROUND

Alterations of white matter (WM) integrity have been observed in both schizophrenia (SZ) and individuals at genetic high risk for SZ (GHR-SZ); however, the molecular mechanisms underlying WM disruption remain unclear. Cytokines are chemical messengers of the immune system that are closely related to inflammation and neurogenesis in the brain. This study aimed to identify abnormalities in WM integrity, cytokine levels, and their association in SZ and GHR-SZ.

METHODS

A total of 355 participants (126 with SZ, 99 GHR-SZ, and 130 healthy controls [HCs]) were recruited. All participants underwent diffusion tensor imaging and blood samples were obtained from 113 participants within 24 h of imaging.

RESULTS

In SZ, there was decreased fractional anisotropy(FA) in the genu and body of the corpus callosum (GCC/BCC), anterior corona radiata, anterior and posterior limbs of the internal capsule (ALIC/PLIC), superior fronto-occipital fasciculus, external capsule, and fornix, and elevated IL-6 levels. In both SZ and GHR-SZ, decreased FA in the splenium of the corpus callosum (SCC), posterior corona radiate (PCR), and posterior thalamic radiation (PTR) was observed, and elevated leptin levels were present. Additionally, the IL-6 levels were negatively correlated with FA in the GCC and ALIC in SZ, and leptin levels were negatively correlated with the SCC, PCR, and PTR in SZ and GHR-SZ.

CONCLUSIONS

Abnormal WM integrity in SZ may reflect the state of disease and is associated with increased IL-6 levels. In addition, these leptin-associated WM integrity abnormalities in both SZ and GHR-SZ may reflect a genetic vulnerability to SZ.

The Teleost Thymus in Health and Disease: New Insights from Transcriptomic and Histopathological Analyses of Turbot, Scophthalmus maximus

The thymus is a primary lymphoid organ that plays a pivotal role in the adaptive immune system. The immunobiology of the thymus in fish is considered to be similar to that of mammals, but it is actually poorly characterized in several cultured teleost species. In particular, while investigations in human and veterinary medicine have highlighted that the thymus can be affected by different pathological conditions, little is known about its response during disease in fish. To better understand the role of the thymus under physiological and pathological conditions, we conducted a study in turbot (Scophthalmus maximus), a commercially valuable flatfish species, combining transcriptomic and histopathological analyses. The myxozoan parasite Enteromyxum scophthalmi, which represents a major challenge to turbot production, was used as a model of infection. The thymus tissues of healthy fish showed overrepresented functions related to its immunological role in T-cell development and maturation. Large differences were observed between the transcriptomes of control and severely infected fish. Evidence of inflammatory response, apoptosis modulation, and declined thymic function associated with loss of cellularity was revealed by both genomic and morphopathological analyses. This study presents the first description of the turbot thymus transcriptome and provides novel insights into the role of this organ in teleosts’ immune responses.

Modulation of Leptin and Leptin Receptor Expression in Mice Acutely Infected with Neospora caninum

Neospora caninum is an apicomplexan parasite that in cattle assumes particular importance, as it is responsible for abortions reported worldwide. Leptin is an adipokine mainly secreted by adipocytes, which beside its role in maintaining metabolic homeostasis also has important effects in both innate and adaptive immunity. In previous work, we showed that mice chronically infected with N. caninum had elevated serum leptin levels. Here, we sought to assess whether acute infection with N. caninum infection influenced the production of this adipokine as well as leptin receptor mRNA levels. Our results show that acute infection with N. caninum led to decreased leptin serum levels and mRNA expression in adipose tissue. A decrease in leptin receptor transcript variant 1 mRNA (long isoform) and leptin receptor transcript variant 3 mRNA (one of the short isoforms) expression was also observed. An increase in the number of cells staining positive for leptin in the liver of infected mice was observed, although this increase was less marked in Interleukin (IL)-12/IL-23 p40-deficient mice. Overall, our results show that N. caninum infection also influences leptin production during acute infection.

Clinical - pathological significance of leptin receptor (LEPR) expression in squamous cell carcinoma of the skin

Adipokine leptin functions through its transmembrane receptors (LEPR). In many malignant tumors it stimulates the growth, migration and invasion of malignant cells. The aim of our work is to examine the effect of LEPR expression on the clinical-morphological properties of squamous cell carcinoma of the skin (cSCC). The biopsy material obtained by excision of squamous cell skin cancer was used. The test group consisted of excision biopsies of squamous cell carcinoma of the skin (n = 62), and the control group (n = 62) consisted of excision biopsies of non-tumor tissue of the skin (from the tumor environment) from an operative preparation delivered to the Pathohistology Department. After routine processing and paraffin molding, histochemical Hematoxylin-Eosin and immunohistochemical ABC method with anti LEPR and Ki67 antibodies were applied at 4 μm sections. The statistical software package SPSS for Windows (26.0) was used to analyze obtained results. Intracytoplasmic and intramembranous LEPR expression was found in 100 % of examined cSCCs. LEPR expression was statistically significantly associated with proliferation index and histologic grade of tumors. Pronounced LEPR expression was associated with a high proliferation index in 66.7 % of cases and with poorly differentiated cSCC in 94.4 %. Multivariate regression analysis showed that cSCCs with pronounced LEPR expression were seven times more often poorly differentiated than tumors with moderate or LEPR expression in trace. Our results indicate that LEPR expression is a predictor of the malignant potential of cSCC, so that based on LEPR expression, it is possible to identify an aggressive cSCC phenotype, which provides the possibility of individualizing anti-tumor treatment using LEPR antagonists.

The Adipokines in Cancer Cachexia

Cachexia is a devastating pathology induced by several kinds of diseases, including cancer. The hallmark of cancer cachexia is an extended weight loss mainly due to skeletal muscle wasting and fat storage depletion from adipose tissue. The latter exerts key functions for the health of the whole organism, also through the secretion of several adipokines. These hormones induce a plethora of effects in target tissues, ranging from metabolic to differentiating ones. Conversely, the decrease of the circulating level of several adipokines positively correlates with insulin resistance, metabolic syndrome, diabetes, and cardiovascular disease. A lot of findings suggest that cancer cachexia is associated with changed secretion of adipokines by adipose tissue. In agreement, cachectic patients show often altered circulating levels of adipokines. This review reported the findings of adipokines (leptin, adiponectin, resistin, apelin, and visfatin) in cancer cachexia, highlighting that to study in-depth the involvement of these hormones in this pathology could lead to the development of new therapeutic strategies.

Obesity Expands a Distinct Population of T Cells in Adipose Tissue and Increases Vulnerability to Infection

Obesity in humans is associated with poorer health outcomes after infections compared with non-obese individuals. Here, we examined the effects of white adipose tissue and obesity on T cell responses to viral infection in mice. We show that lymphocytic choriomeningitis virus (LCMV) grows to high titer in adipose tissue. Virus-specific T cells enter the adipose tissue to resolve infection but then remain as a memory population distinct from memory T cells in lymphoid tissues. Memory T cells in adipose tissue are abundant in lean mice, and diet-induced obesity further increases memory T cell number in adipose tissue and spleen. Upon re-challenge infection, memory T cells rapidly cause severe pathogenesis, leading to increases in lipase levels, calcification of adipose tissue, pancreatitis, and reduced survival in obese mice but not lean mice. Thus, obesity leads to a unique form of viral pathogenesis involving memory T cell-dependent adipocyte destruction and damage to other tissues.

Obesity is associated with increased morbidity and mortality after viral infections. Using a mouse model of obesity, Misumi et al. identify a distinct population of memory T cells in white adipose tissue and a memory cell-dependent pathogenic response to infection that leads to acute fat necrosis, pancreatitis, and lethality.

Dietary fibre intake and its association with inflammatory markers in adolescents

A high dietary fibre intake has been associated with improvements in inflammatory conditions in adults. However, little is known on whether associations between dietary fibre and inflammation are evident during adolescence. We examined the relationship between dietary fibre intake measured by FFQ and the inflammatory marker high-sensitivity C-reactive protein (hs-CRP) and the adipokines leptin and adiponectin cross-sectionally in 17-year-olds participating in the Raine Study (n 621). In weighted analysis using tobit and linear regression, and after excluding participants with hs-CRP > 10 mg/l, higher total dietary fibre intake (per 5 g/d) was significantly associated with lower leptin (β = -0·13, 95 % CI -0·17, -0·09) and adiponectin (β = -0·28, 95 % CI -0·49, -0·07), but not hs-CRP, in unadjusted analyses. These associations were no longer significant after adjustment for sex, anthropometry and a number of lifestyle factors. However, higher cereal and grain fibre intake was significantly associated with lower leptin (β = -0·06, 95 % CI -0·10, -0·01) in fully adjusted analysis. Our findings suggest that a higher intake of cereal and grain fibre may contribute to lower leptin in adolescents. This may contribute to reductions in low-grade chronic inflammation and improved health outcomes.

Multiple Sclerosis: Lipids, Lymphocytes, and Vitamin D

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. We review the two core MS features, myelin instability, fragmentation, and remyelination failure, and dominance of pathogenic CD4⁺ Th17 cells over protective CD4⁺ Treg cells. To better understand myelin pathology, we describe myelin biosynthesis, structure, and function, then highlight stearoyl-CoA desaturase (SCD) in nervonic acid biosynthesis and nervonic acid's contribution to myelin stability. Noting that vitamin D deficiency decreases SCD in the periphery, we propose it also decreases SCD in oligodendrocytes, disrupting the nervonic acid supply and causing myelin instability and fragmentation. To better understand the distorted Th17/Treg cell balance, we summarize Th17 cell contributions to MS pathogenesis, then highlight how 1,25-dihydroxyvitamin D₃ signaling from microglia to CD4⁺ T cells restores Treg cell dominance. This signaling rapidly increases flux through the methionine cycle, removing homocysteine, replenishing S-adenosyl-methionine, and improving epigenetic marking. Noting that DNA hypomethylation and inappropriate DRB1*1501 expression were observed in MS patient CD4⁺ T cells, we propose that vitamin D deficiency thwarts epigenetic downregulation of DRB1*1501 and Th17 cell signature genes, and upregulation of Treg cell signature genes, causing dysregulation within the CD4⁺ T cell compartment. We explain how obesity reduces vitamin D status, and how estrogen and vitamin D collaborate to promote Treg cell dominance in females. Finally, we discuss the implications of this new knowledge concerning myelin and the Th17/Treg cell balance, and advocate for efforts to address the global epidemics of obesity and vitamin D deficiency in the expectation of reducing the impact of MS.

Reproductive phase-dependent variation, sexually dimorphic expression and sex steroids-mediated transcriptional regulation of lep and lepr in lymphoid organs of Channa punctata

The reproductive phase-dependent and sex-related differential expression of leptin (lep) and its receptor (lepr) in primary and secondary lymphoid organs of a highly nutritive economically important Channa punctata preempts the involvement of sex steroids in modulating intra-immuno-leptin system. This hypothesis was strengthened when plasma testosterone (T) and estradiol (E₂) levels in male and female fish of reproductively active spawning and quiescent phases were correlated with lep and lepr expression in their immune organs. Splenic lep and lepr showed a negative correlation with T in both male and female, while with E₂ there was a positive correlation in male and negative in female C. punctata. In head kidney, a contrasting correlation was observed as compared to spleen. To validate the implication of sex steroids in regulating leptin system in immune organs, in vivo and in vitro experiments were performed with DHT and E₂. Upon administration, lep and lepr expression in tissues of either sex was downregulated. In addition, in vitro results with either of the sex steroids exemplified their direct involvement. Overall, this study, for the first time, reports correlation between sex steroids and transcript expression of leptin system in immune organs of a seasonally breeding vertebrate.

Two Distinct C-Type Lysozymes in Goldfish: Molecular Characterization, Antimicrobial Potential, and Transcriptional Regulation in Response to Opposing Effects of Bacteria/Lipopolysaccharide and Dexamethasone/Leptin

Lysozymes are key antimicrobial peptides in the host innate immune system that protect against pathogen infection. In this study, the full-length cDNAs of two c-type lysozymes (gfLyz-C1 and gfLyz-C2) were cloned from goldfish (Carassius auratus). The structural domains, three-dimensional structures, and amino acid sequences of gfLyz-C1 and gfLyz-C2 were highly comparable, as the two proteins shared 89.7% sequence identity. The gfLyz-C1 and gfLyz-C2 recombinant proteins were generated in the insoluble fractions of an Escherichia coli system. Based on the results of lysoplate and turbidimetric assays, gfLyz-C1 and gfLyz-C2 showed broad-spectrum antimicrobial properties with high levels of activity against Micrococcus lysodeikticus, Vibrio parahemolyticus, and Edwardsiella tarda, and relatively low activity against E. coli. Both gfLyz-C1 and gfLyz-C2 mRNAs were mainly expressed in the trunk kidney and head kidney, and gfLyz-C1 was expressed at much higher levels than gfLyz-C2 in the corresponding tissues. The expression of the gfLyz-C1 and gfLyz-C2 transcripts in the trunk kidney and head kidney was induced in these tissues by challenge with heat-inactivated E. coli and lipopolysaccharides (LPS), and the transcriptional responses of gfLyz-C1 were more intense. In goldfish primary trunk kidney cells, the levels of the gfLyz-C1 and gfLyz-C2 transcripts were upregulated by heat-inactivated E. coli, V. parahemolyticus, and E. tarda, as well as LPS, and downregulated by treatment with dexamethasone and leptins. Overall, this study may provide new insights that will improve our understanding of the roles of c-type lysozymes in the innate immunity of cyprinid fish, including the structural and phylogenetic characteristics, antimicrobial effects, and regulatory mechanism.

The Association of Obesity with Autoimmune Thyroiditis and Thyroid Function-Possible Mechanisms of Bilateral Interaction

A growing number of patients suffer from autoimmune diseases, including autoimmune thyroid disease. There has simultaneously been a significant increase in the prevalence of obesity worldwide. It is still an open question whether adiposity can directly influence activation of inflammatory processes affecting the thyroid in genetically predisposed individuals. Adipokines, biologically active substances derived from the adipocytes, belong to a heterogenic group of compounds involved in numerous physiological functions, including the maintenance of metabolism, hormonal balance, and immune response. Notably, the presence of obesity worsens the course of selected autoimmune diseases and impairs response to treatment. Moreover, the excess of body fat may result in the progression of autoimmune diseases. Nutritional status, body weight, and energy expenditure may influence thyroid hormone secretion. Interestingly, thyroid hormones might influence the activity of adipose tissue as metabolic alterations related to fat tissue are observed under pathological conditions in which there are deficits or overproduction of thyroid hormones. Functioning TSH receptors are expressed on adipocytes. Thermogenesis may presumably be stimulated by TSH binding to its receptor on brown adipocytes. There could be a bilateral interaction between the thyroid and adipose. Obesity may influence the onset and course of autoimmune disease.

Role of Leptin in Cardiovascular Diseases

The adipocyte-derived adipokine leptin exerts pleiotropic effects, which are essential for the regulation of energy balance and cell metabolism, for controlling inflammatory and immune responses, and for the maintenance of homeostasis of the cardiovascular system. Leptin resistance in obese or type 2 diabetes mellitus (T2DM) patients is defined as a decrease in tissue response to leptin. In the cardiovascular system, leptin resistance exhibits the adverse effect on the heart's response to stress conditions and promoting cardiac remodeling due to impaired cardiac metabolism, increased fibrosis, vascular dysfunction, and enhanced inflammation. Leptin resistance or leptin signaling deficiency results in the risk increase of cardiac dysfunction and heart failure, which is a leading cause of obesity- and T2DM-related morbidity and mortality. Animal studies using leptin- and leptin receptor- (Lepr) deficient rodents have provided many useful insights into the underlying molecular and pathophysiological mechanisms of obese- and T2DM-associated metabolic and cardiovascular diseases. However, none of the animal models used so far can fully recapitulate the phenotypes of patients with obese or T2DM. Therefore, the role of leptin in the human cardiovascular system, and whether leptin affects cardiac function directly or acts through a leptin-regulated neurohumoral pathway, remain elusive. As the prevalence of obesity and diabetes is continuously increasing, strategies are needed to develop and apply human cell-based models to better understand the precise role of leptin directly in different cardiac cell types and to overcome the existing translational barriers. The purpose of this review is to discuss the mechanisms associated with leptin signaling deficiency or leptin resistance in the development of metabolic and cardiovascular diseases. We analyzed and comprehensively addressed substantial findings in pathophysiological mechanisms in commonly used leptin- or Lepr-deficient rodent models and highlighted the differences between rodents and humans. This may open up new strategies to develop directly and reliably applicable models, which resemble the human pathophysiology in order to advance health care management of obesity- and T2DM-related cardiovascular complications.

Leptin: an unappreciated key player in SLE

Leptin is the forerunner of the adipokine superfamily and plays a key role in regulating energy expenditure and neuroendocrine function. Researches into leptin put emphasize not only on the metabolic role but also its immunoregulatory effect on immune response through immunocyte activation and cytokine secretion. Leptin acts on receptors that are widespread throughout the body and that are expressed across many tissue types. As a consequence, the abnormal expression of leptin has been found to correlate with a number of diseases, including cancers, autoimmune diseases, and cardiovascular diseases. The significance of leptin in the development of autoimmune diseases is becoming increasingly prominent. Systemic lupus erythematosus (SLE) is a severe atypical autoimmune disease that causes damage to multiple organ systems. It is characterised by the following: impaired clearance of apoptotic cells, loss of tolerance to self-antigens, aberrant activation of T cells and B cells, and chronic inflammation. The heightened immunocyte response in SLE means that these physiological systems are particularly vulnerable to regulation by leptin in addition to being of great significance to the research field. Our current review provides insight into the regulatory roles that leptin plays on immune effector cells in SLE.

Anorexia Nervosa and the Immune System-A Narrative Review

The pathogenesis of an increasing number of chronic diseases is being attributed to effects of the immune system. However, its role in the development and maintenance of anorexia nervosa is seemingly under-appreciated. Yet, in examining the available research on the immune system and genetic studies in anorexia nervosa, one becomes increasingly suspicious of the immune system’s potential role in the pathophysiology of anorexia nervosa. Specifically, research is suggestive of increased levels of various pro-inflammatory cytokines as well as the spontaneous production of tumor necrosis factor in anorexia nervosa; genetic studies further support a dysregulated immune system in this disorder. Potential contributors to this dysregulated immune system are discussed including increased oxidative stress, chronic physiological/psychological stress, changes in the intestinal microbiota, and an abnormal bone marrow microenvironment, all of which are present in anorexia nervosa.

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.