Adipokines and the control of mast cell functions: from obesity to inflammation?

Macrophages and Mast Cells in the Gastric Mucosa of Patients with Obesity Undergoing Sleeve Gastrectomy

Background. Adipose tissue macrophages (ATMs) and mast cells (MCs) play a role in immune responses. More recently, their involvement in tumor angiogenesis and chronic inflammatory conditions in patients with obesity has been discovered. Furthermore, a higher BMI (Body Mass Index) value corresponds to a higher inflammatory state. In particular, gastric tissue in obesity (GTO) is characterized by Macrophages, Mast Cells Positive to Triptase (MCPT), and neo-formed microvessels (MVD). Materials and Methods. We collected gastric tissue samples from December 2021 to December 2022. The patients selected had a BMI > 35 kg/m2 with different comorbidities. Regarding the surgery, surgeons executed a Laparoscopic Sleeve Gastrectomy (LapSG). Gastric tissue was analyzed by immunohistochemistry and morphometrical assay, comparing "obese-related" gastric tissue to normal gastric tissue. Furthermore, tissue parameters were correlated with important clinicopathological features. Results. We collected thirty gastric tissue samples from thirty patients with obesity. Blood tests, Electrocardiogram (ECG), esophagogastroduodenoscopy (EGDS) associated with a urea breath test, and chest X.R. were performed. A significant correlation between ATMs, MCPT, MVD, and BMI was found in GTO. Pearson t-test analysis was conducted (r ranged from 0.67 to 0.71; p-value < 0.05). Conclusions. These preliminary data suggest that ATMs, MCPT, and MVD related to BMI can play a role in both gastric tissue angiogenesis and inflammation inducing a tissue change that could lead to gastric inflammation or cancer diseases.

Prohibitions in the meta-inflammatory response: a review

Prohibitins are the central regulatory element of cellular homeostasis, especially by modulating the response at different levels: Nucleus, mitochondria and membranes. Their localization and interaction with various proteins, homons, transcription and nuclear factors, and mtDNA indicate the globality and complexity of their pleiotropic properties, which remain to be investigated. A more detailed deciphering of cellular metabolism in relation to prohibitins under normal conditions and in various metabolic diseases will allow us to understand the precise role of prohibitins in the signaling cascades of PI3K/Akt, Raf/MAP/ERK, STAT3, p53, and others and to fathom their mutual influence. A valuable research perspective is to investigate the role of prohibitins in the molecular and cellular interactions between the two major players in the pathogenesis of obesity-adipocytes and macrophages - that form the basis of the meta-inflammatory response. Investigating the subtle intercellular communication and molecular cascades triggered in these cells will allow us to propose new therapeutic strategies to eliminate persistent inflammation, taking into account novel molecular genetic approaches to activate/inactivate prohibitins.

Effect of Sprint Interval Training on Cardiometabolic Biomarkers and Adipokine Levels in Adolescent Boys with Obesity

This study investigated the effect of supervised sprint interval training (SIT) on different cardiometabolic risk factors and adipokines in adolescent boys with obesity. Thirty-seven boys were allocated to either a SIT group (13.1 ± 0.3 years; body mass index [BMI]: 30.3 ± 0.9 kg·m^-2) or a control group (CONT) (13.7 ± 0.4 years; BMI: 32.6 ± 1.6 kg·m^-2). The SIT group performed 4-6 × 30 s all-out cycling sprints, interspersed with 4 min rest, for 3 sessions/week, during a 12-week period, while the non-exercising CONT group maintained a habitual lifestyle. Anthropometric measurements, triglycerides, fasting insulin and glucose, total cholesterol (TC), high- (HDLc) and low-density (LDLc) cholesterol, leptin and adiponectin in blood, cardiorespiratory fitness (CRF), and a metabolic syndrome severity risk score (MSSS) were calculated before and after the 12-week period. Compared to baseline values, a significant reduction in MSSS was seen in the SIT group after intervention. LDLc showed favorable changes in SIT compared to CONT (-0.06 ± 0.1 vs. 0.19 ± 0.01 mmol·L^-1; p = 0.025). Additionally, CRF increased in the SIT group compared to the CONT group (5.2 ± 1.1 vs. -2.1 ± 1.1 mL·min^-1·kg^-1, p < 0.001). Moreover, a 12-week all-out SIT training effectively improves cardiometabolic health in adolescent boys with obesity.

Macrophages, Chronic Inflammation, and Insulin Resistance

The prevalence of obesity has reached alarming levels, which is considered a major risk factor for several metabolic diseases, including type 2 diabetes (T2D), non-alcoholic fatty liver, atherosclerosis, and ischemic cardiovascular disease. Obesity-induced chronic, low-grade inflammation may lead to insulin resistance, and it is well-recognized that macrophages play a major role in such inflammation. In the current review, the molecular mechanisms underlying macrophages, low-grade tissue inflammation, insulin resistance, and T2D are described. Also, the role of macrophages in obesity-induced insulin resistance is presented, and therapeutic drugs and recent advances targeting macrophages for the treatment of T2D are introduced.

Very Low-Carbohydrate High-Fat Diet Improves Risk Markers for Cardiometabolic Health More Than Exercise in Men and Women With Overfat Constitution: Secondary Analysis of a Randomized Controlled Clinical Trial

Purpose

This randomized controlled parallel-group study examined the effects of a very low-carbohydrate high-fat (VLCHF) diet and high-intensity interval training (HIIT) program over 12-weeks on cardiometabolic risk factors in individuals with overfat constitution.

Methods

Ninety-one participants out of 109 completed the study. The participants were randomly allocated to the HIIT (N = 22), VLCHF (N = 25), VLCHF+HIIT (N = 25), or control (N = 19) groups for 12 weeks. Fasting plasma samples were collected before the intervention and after 4 and 12 weeks. The analyzed outcomes included complete blood count, glucose, insulin, glycated hemoglobin, triglycerides (TG), cholesterol, high- and low-density lipoprotein (HDL-C and LDL-C), lipoprotein(a), adiponectin (Adpn), leptin (Lep), tumor necrosis factor α (TNF-α), other interleukins (hs-IL-6, IL-1β, and IL-10), and IL-1RA. The homeostasis model assessment of insulin resistance (HOMA-IR), Adpn/Lep ratio, TG/HDL-C ratio, and TyG index were calculated and analyzed. Blood pressure was measured before the intervention, after 4, 8, and 12 weeks (ClinicalTrials.gov: NCT03934476).

Results

Absolute changes in HOMA-IR, Adpn/Lep ratio, LDL-C, and diastolic blood pressure after 12 weeks differed by study groups (p < 0.05). The most pronounced changes were revealed in the VLCHF (ΔM [95% CI]; HOMA-IR: -0.75 [-1.13; -0.55]; Adpn/Lep: 9.34 [6.33; 37.39]; LDL-C: 0.06 [-0.12; 0.50] mmol/l) and VLCHF+HIIT (HOMA-IR: -0.44 [-1.14; 0.12]; Adpn/Lep: 4.26 [2.24; 13.16]; LDL-C: 0.25 [-0.04; 0.50] mmol/l) groups.

Conclusions

A 12-week VLCHF diet intervention in individuals with overfat constitution is effective for favorable changes in HOMA-IR (compared to HIIT), Adpn/Lep ratio, and diastolic blood pressure. HIIT, or HIIT combined with the VLCHF diet, had no additional benefits for the analyzed variables. No adverse side effects were observed.

Evaluating Possible Mechanisms Linking Obesity to COVID-19: a Narrative Review

Currently, pneumonia caused by the coronavirus disease 2019 (COVID-19) is a pandemic. To date, there is no specific antiviral treatment for the disease, and universal access to the vaccine is a serious challenge. Some observational studies have shown that COVID-19 is more common in countries with a high prevalence of obesity and that people with COVID-19 have a higher body mass index. In these studies, obesity increased the risk of disease, as well as its severity and mortality. This study aimed to review the mechanisms that link obesity to COVID-19.

Crosstalk between AdipoR1/AdipoR2 and Nrf2/HO-1 signal pathways activated by β-caryophyllene suppressed the compound 48/80 induced pseudo-allergic reactions

Mast cell activation is initiated by two signalling pathways: immunoglobulin E (IgE)-dependent and IgE-independent pathway. It is reported that the IgE-independent type or pseudo-allergy pathway gets activated by G-protein-dependent activation of the mast cell. Recently, adiponectin (APN) receptors, AdipoR1, and AdipoR2 have been identified as G-protein-coupled receptors (GPCRs). Interestingly, APN replenishment is reported to activate the Nrf2/HO-1 signalling axis. However, no study has been performed interlinking the role of APN and the Nrf2/HO-1 signalling axis in pseudo-allergic reaction. In the present study, we evaluated the anti-pseudo-allergic effects of β-caryophyllene, an FDA-approved food additive, in activating AdipoR1/AdipoR2 and Nrf2/HO-1 axis signalling pathway. Compound 48/80 (C48/80)-induced systemic and cutaneous anaphylaxis-like shock in BALB/c mice was performed to assess the efficacy of β-caryophyllene (BCP). To assess the effect of BCP in anaphylactic hypotension, mean arterial pressure was measured in Wistar rats. Inhibitory properties of BCP in mast cell degranulation were estimated in rat peritoneal mast cells (RPMCs). ELISA was performed to estimate interleukin (IL)-6, tumour necrosis factor (TNF), IL-1β, IgE, ovalbumin (OVA)-IgE and APN and western blotting for protein expression of Nrf2/HO-1 and AdipoR1-AdipoR2. BCP dose-dependently inhibited systemic and cutaneous anaphylaxis-like shock induced by C48/80. BCP dose-dependently inhibited the mast cell degranulation followed by inhibition of histamine release. Also BCP dose-dependently activated the Nrf2/HO-1 and AdipoR1-AdipoR2 signalling axis pathway. Moreover, BCP reversed the drop in blood pressure when the haemodynamic parameters were accessed. Our findings suggest that BCP is a potent AdipoR1/AdipoR2-Nrf2/HO-1 axis pathway agonist that may suppress the IgE-independent pathway towards allergic response to secretagogues.

Association of Single Nucleotide Polymorphism LEP-R c.668A>G (p.Gln223Arg, rs1137101) of leptin receptor gene with endometrial cancer

Background

The aim of this study was to analyze the frequencies of genotypes and alleles of Single Nucleotide Polymorphism (SNP) LEP-R c.668A>G (p.Gln223Arg, rs1137101) of leptin receptor gene and to assess the influence this DNA marker has on endometrial cancer (EC) with respect to total body fat content.

Methods

The study comprised 120 patients treated for endometrial cancer and 90 controls treated for uterine fibroids. In total, 210 patients were included in this research. DNA was isolated from archival post-operative specimens. Polymerase Chain Reaction – Restriction Fragment Length Polymorphism was employed to analyze the SNP.

Results

In this paper we have demonstrated that heterozygous genotype AG of SNP LEP-R c.668A>G (p.Gln223Arg, rs1137101) is statistically less frequent in women with endometrial cancer (EC) than in controls: 33 versus 57%, respectively. Similarly, this heterozygous genotype is statistically significantly less frequent in obese (BMI > 30) women with EC than in lean controls (BMI < 25): 30 versus 63%, respectively.

Conclusions

AG polymorphic variant of SNP LEP-R c.668A>G (p.Gln223Arg, rs1137101) in LEP-R may be considered a protective factor in the development of endometrial cancer.

Adipocytes, mast cells and angiogenesis

Healthy adipose tissue contains a wide variety of innate and adaptive immune cells, including macrophages, dendritic cells, mast cells, eosinophils, neutrophils, and lymphocytes. Numerous signaling molecules in the adipose microenvironment can positively or negatively modulate angiogenic processes, regulate the interaction between the vascular system and adipocytes, and participate in tumor progression. Mast cells are involved in the new formation or metabolism of fat, are present in abundant quantities in fatty tissue, among fat cells, and a number of mediators released from mast cells play a role in adipogenesis. Moreover, mast cells produce several pro-angiogenic factors and are involved in tumor angiogenesis. In this context, the angiogenic effect might be amplified when the adipocytes and mast cells act in concert, and treatment of adipose tissue- and mast cell-associated cancers with anti-angiogenic drugs may represent an alternative or adjuvant strategy for the treatment of these tumors.

Leptin, Both Bad and Good Actor in Cancer

Leptin is an important regulator of basal metabolism and food intake, with a pivotal role in obesity. Leptin exerts many different actions on various tissues and systems, including cancer, and is considered as a linkage between metabolism and the immune system. During the last decades, obesity and leptin have been associated with the initiation, proliferation and progression of many types of cancer. Obesity is also linked with complications and mortality, irrespective of the therapy used, affecting clinical outcomes. However, some evidence has suggested its beneficial role, called the "obesity paradox", and the possible antitumoral role of leptin. Recent data regarding the immunotherapy of cancer have revealed that overweight leads to a more effective response and leptin may probably be involved in this beneficial process. Since leptin is a positive modulator of both the innate and the adaptive immune system, it may contribute to the increased immune response stimulated by immunotherapy in cancer patients and may be proposed as a good actor in cancer. Our purpose is to review this dual role of leptin in cancer, as well as trying to clarify the future perspectives of this adipokine, which further highlights its importance as a cornerstone of the immunometabolism in oncology.

Adiponectin/leptin ratio increases after a 12-week very low-carbohydrate, high-fat diet, and exercise training in healthy individuals: A non-randomized, parallel design study

This study aimed to investigate the effect of a 12-week very low-carbohydrate, high-fat (VLCHF) diet and exercise on biomarkers of inflammation in healthy individuals. Since the anti-inflammatory effects of a ketogenic diet have been established, we hypothesized that the VLCHF diet, along with exercise, would have an additional favorable effect on biomarkers of inflammation. Twenty-four healthy individuals were allocated to the VLCHF diet (VLCHF: N = 12, age 25.3 ± 2.0 years, body mass 66.7 ± 9.8 kg, fat mass 21.5% ± 4.9%), or habitual diet (HD: N = 12, age 23.9 ± 3.8 years, body mass 72.7 ± 15.0 kg, fat mass 23.4 ± 8.4 %) group. Biomarkers of inflammation (adiponectin, leptin, and high-sensitive interleukin-6 [hs-IL-6]) and substrate metabolism (glycated hemoglobin, fasting glucose, triacylglycerides, and cholesterol) were analyzed from blood at baseline and after 12 weeks. The adiponectin-leptin ratio significantly increased in the VLCHF group after the intervention period (ES [95% CL]: -0.90 [-0.96, -0.77], P ≤ .001, BF₁₀ = 22.15). The adiponectin-leptin ratio changes were associated with both a significant increase in adiponectin (-0.79 [-0.91, -0.54], P ≤ .001, BF₁₀ = 9.43) and a significant decrease in leptin (0.58 [0.19, 0.81], P = .014, BF₁₀ = 2.70). There was moderate evidence of changes in total cholesterol (-1.15 [-2.01, -0.27], P = .010, BF₁₀ = 5.20), and LDL cholesterol (-1.12 [-2.01, -0.21], P = .016, BF₁₀ = 4.56) in the VLCHF group. Body weight (kg) and fat mass (%) decreased in the VLCHF group by 5.4% and 14.9%, respectively. We found that in healthy young individuals, consuming a VLCHF diet while performing regular exercise over a 12-week period produced favorable changes in body weight and fat mass along with beneficial changes in serum adiponectin and leptin concentrations. These data support the use of a VLCHF diet strategy for the primary prevention of chronic diseases associated with systemic low-grade inflammation.

Identification of the key genes and characterizations of Tumor Immune Microenvironment in Lung Adenocarcinoma (LUAD) and Lung Squamous Cell Carcinoma (LUSC)

This study aimed to investigate the key genes and immune microenvironment involved in different TNM stages of lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). The gene expression and clinical characteristics data were downloaded from the genomic data commons (GDC) database. After initial data processing, the characteristics of the immune microenvironment were analyzed. The differentially expressed genes (DEGs) in tumor vs. normal, and in early vs. advanced stages were screened, followed by Spearman correlation test for tumor infiltrating immune cells (TIICs) to identify immune-related genes. Finally, functional enrichment, protein-protein interaction, and survival analyses were performed. In LUAD, early stage was with higher immune scores, greater number of memory B cells and M0 macrophages compared to advanced stage. M0 and M2 macrophages, and resting memory CD4+ T cells accounted for a large proportion of TIICs in LUAD. The abundance of M0 macrophage infiltration was significantly correlated with the TNM stage and survival. In LUSC, early stage was with higher cytolytic activity and neoantigen burden compared to advanced stage. M0 and M2 macrophages, and plasma cells accounted for a large proportion of TIICs in LUSC. The abundance of resting and activated mast cells was significantly correlated with TNM stage, while resting dendritic cells, eosinophils, activated memory CD4 T cells, and mast cells were significantly correlated with prognosis. Tumor mutation burden analysis revealed that the median of variants per sample decreased from stage I to IV in LUAD, while it increased in LUSC. Further, 83 and 9 immune-related DEGs were identified in LUAD and LUSC, respectively, of which 23 genes in LUAD and 2 genes in LUSC correlated with survival. In conclusion, we identified the key genes, and characterized the tumor immune microenvironment in LUAD and LUSC which may provide therapeutic targets for the treatment of NSCLC.

Analysis of the percentages of monocyte subsets and ILC2s, their relationships with metabolic variables and response to hypocaloric restriction in obesity

PURPOSE

Obesity results from excess energy intake over expenditure and is characterized by chronic low-grade inflammation involving circulating monocytes (Mo) and group 2 innate lymphoid cells (ILC2s) imbalance. We analyzed circulating Mo subsets and ILC2s percentages and β2-adrenergic receptor (β2AR) expression in lean and obese subjects, and the possible effect of hypocaloric restriction on these innate immune cells.

METHODS

In 139 individuals aged 45 to 57 years, classified in 74 lean individuals (>18.9kg/m2 BMI <24.9kg/m2) and 65 with obesity (n = 65), we collected fasting blood samples to detect Mo subsets, ILC2s number, and β2AR expression by flow cytometry. Lipids, insulin, leptin, and acylated-ghrelin concentrations were quantified. Resting energy expenditure (REE) was estimated by indirect calorimetry. These measurements were repeated in obese subjects after 7-weeks of hypocaloric restriction.

RESULTS

Non-classical monocytes (NCM) and β2AR expression on intermediate Mo (IM) were increased in obese individuals (p<0.001, in both cases), whereas the percent of ILC2s was decreased (p<0.0001). Stepwise regression analysis showed significantly negative associations of ILC2s with caloric intake, β2AR expression on IM with REE, but a positive relationship between NCM and HOMA-IR. Caloric restriction allowed a significant diminution of NCM and the β2AR expression on IM, as well as, an increase in the percent of classical Mo (CM), and ILC2s. ΔREE was related to ΔCD16+/CD16- ratio.

CONCLUSIONS

These findings show that in obesity occur changes in NCM, ILC2s and β2AR expression, which contribute to the low-grade inflammation linked to obesity and might revert with caloric restriction.

Leptin Elicits In Vivo Eosinophil Migration and Activation: Key Role of Mast Cell-Derived PGD2

Eosinophils are key regulators of adipose tissue homeostasis, thus characterization of adipose tissue-related molecular factors capable of regulating eosinophil activity is of great interest. Leptin is known to directly activate eosinophils in vitro, but leptin ability of inducing in vivo eosinophilic inflammatory response remains elusive. Here, we show that leptin elicits eosinophil influx as well as its activation, characterized by increased lipid body biogenesis and LTC₄ synthesis. Such leptin-triggered eosinophilic inflammatory response was shown to be dependent on activation of the mTOR signaling pathway, since it was (i) inhibited by rapamycin pre-treatment and (ii) reduced in PI3K-deficient mice. Local infiltration of activated eosinophils within leptin-driven inflammatory site was preceded by increased levels of classical mast cell-derived molecules, including TNFα, CCL5 (RANTES), and PGD₂. Thus, mice were pre-treated with a mast cell degranulating agent compound 48/80 which was capable to impair leptin-induced PGD₂ release, as well as eosinophil recruitment and activation. In agreement with an indirect mast cell-driven phenomenon, eosinophil accumulation induced by leptin was abolished in TNFR-1 deficient and also in HQL-79-pretreated mice, but not in mice pretreated with neutralizing antibodies against CCL5, indicating that both typical mast cell-driven signals TNFα and PGD₂, but not CCL5, contribute to leptin-induced eosinophil influx. Distinctly, leptin-induced eosinophil lipid body (lipid droplet) assembly and LTC₄ synthesis appears to depend on both PGD₂ and CCL5, since both HQL-79 and anti-CCL5 treatments were able to inhibit these eosinophil activation markers. Altogether, our data show that leptin triggers eosinophilic inflammation in vivo via an indirect mechanism dependent on activation of resident mast cell secretory activity and mediation by TNFα, CCL5, and specially PGD₂.

Candidate Gene and Genome-Wide Association Studies for Circulating Leptin Levels Reveal Population and Sex-Specific Associations in High Cardiovascular Risk Mediterranean Subjects

Leptin is a hormone crucial in the regulation of food intake and body-weight maintenance. However, the genes and gene variants that influence its plasma levels are still not well known. Results of studies investigating polymorphisms in candidate genes have been inconsistent, and, in addition, very few genome-wide association studies (GWAS) have been undertaken. Our aim was to investigate the genes and gene variants most associated with plasma leptin concentrations in a high-cardiovascular-risk Mediterranean population. We measured plasma leptin in 1011 men and women, and analyzed the genetic factors associated using three approaches: (1) Analyzing the single nucleotide polymorphisms (SNPs) reported in a GWAS meta-analysis in other populations (including an SNP in/near each of these LEP, SLC32A1, GCKR, CCNL, COBLL1, and FTO genes); (2) Investigating additional SNPs in/near those genes, also including the RLEP gene; and (3) Undertaking a GWAS to discover new genes. We did not find any statistically significant associations between the previously published SNPs and plasma leptin (Ln) in the whole population adjusting for sex and age. However, on undertaking an extensive screening of other gene variants in those genes to capture a more complete set of SNPs, we found more associations. Outstanding among the findings was the heterogeneity per sex. We detected several statistically significant interaction terms with sex for these SNPs in the candidate genes. The gene most associated with plasma leptin levels was the FTO gene in men (specifically the rs1075440 SNP) and the LEPR in women (specifically the rs12145690 SNP). In the GWAS on the whole population, we found several new associations at the p < 1 × 10^-5 level, among them with the rs245908-CHN2 SNP (p = 1.6 × 10^-6). We also detected a SNP*sex interaction at the GWAS significance level (p < 5 × 10^-8), involving the SLIT3 gene, a gene regulated by estrogens. In conclusion, our study shows that the SNPs selected as relevant for plasma leptin levels in other populations, are not good markers for this Mediterranean population, so supporting those studies claiming a bias when generalizing GWAS results to different populations. These population-specific differences may include not only genetic characteristics, but also age, health status, and the influence of other environmental variables. In addition, we have detected several sex-specific effects. These results suggest that genomic analyses, involving leptin, should be estimated by sex and consider population-specificity for more precise estimations.