Early-onset obesity dysregulates pulmonary adipocytokine/insulin signaling and induces asthma-like disease in mice

Increased allergic inflammation and decreased lung insulin sensitivity in offspring of obese allergic mothers

Epidemiological studies demonstrate that maternal obesity and maternal allergy are major risk factors for asthma in offspring. However, the impact of maternal allergy and obesity on offspring lung insulin signaling and allergen responsiveness is not known. To evaluate this, allergic and nonallergic female mice were fed a high-fat diet or low-fat diet from 7 wk before pregnancy until weaning. Neonatal pups were allergen-sensitized and allergen-challenged and then were assessed for obesity, insulin signaling, and allergic inflammation. Compared with pups of nonobese nonallergic mothers, allergen-challenged pups of obese nonallergic mothers, nonobese allergic mothers, and obese allergic mothers had bronchoalveolar lavage (BAL) eosinophilia, with the pups of obese allergic mothers having the highest BAL eosinophilia. These pups also had lower insulin-induced lung AKT phosphorylation, indicating a decrease in lung parenchymal insulin sensitivity. In cross-fostering experiments, allergen-challenged pups exposed to both pre- and postnatal obese allergic mothers had the highest level of BAL eosinophilia. Maternal obesity or allergy increased offspring serum allergen-specific IgE and interleukin-5 that was highest when the mother was both obese and allergic. Also, allergen-challenged pups exposed to both pre- and postnatal obese allergic mothers had the highest level of interleukin-5. In summary, offspring born to obese allergic mothers have decreased lung insulin sensitivity and increased lung allergic inflammation. Interestingly, our data also demonstrate that there is both a pregnancy and postpregnancy aspect of maternal allergy and obesity that enhances allergen responsiveness in offspring.

CXCL10 deficiency limits macrophage infiltration, preserves lung matrix, and enables lung growth in bronchopulmonary dysplasia

Preterm infants with oxygen supplementation are at high risk for bronchopulmonary dysplasia (BPD), a neonatal chronic lung disease. Inflammation with macrophage activation is central to the pathogenesis of BPD. CXCL10, a chemotactic and pro-inflammatory chemokine, is elevated in the lungs of infants evolving BPD and in hyperoxia-based BPD in mice. Here, we tested if CXCL10 deficiency preserves lung growth after neonatal hyperoxia by preventing macrophage activation. To this end, we exposed Cxcl10 knockout (Cxcl10-/-) and wild-type mice to an experimental model of hyperoxia (85% O2)-induced neonatal lung injury and subsequent regeneration. In addition, cultured primary human macrophages and murine macrophages (J744A.1) were treated with CXCL10 and/or CXCR3 antagonist. Our transcriptomic analysis identified CXCL10 as a central hub in the inflammatory network of neonatal mouse lungs after hyperoxia. Quantitative histomorphometric analysis revealed that Cxcl10-/- mice are in part protected from reduced alveolar. These findings were related to the preserved spatial distribution of elastic fibers, reduced collagen deposition, and protection from macrophage recruitment/infiltration to the lungs in Cxcl10-/- mice during acute injury and regeneration. Complimentary, studies with cultured human and murine macrophages showed that hyperoxia induces Cxcl10 expression that in turn triggers M1-like activation and migration of macrophages through CXCR3. Finally, we demonstrated a temporal increase of macrophage-related CXCL10 in the lungs of infants with BPD. In conclusion, our data demonstrate macrophage-derived CXCL10 in experimental and clinical BPD that drives macrophage chemotaxis through CXCR3, causing pro-fibrotic lung remodeling and arrest of alveolarization. Thus, targeting the CXCL10-CXCR3 axis could offer a new therapeutic avenue for BPD.

Identification and analysis of lipid metabolism-related genes in allergic rhinitis

BACKGROUND

Studies have shown that the lipid metabolism mediator leukotriene and prostaglandins are associated with the pathogenesis of allergic rhinitis (AR). The aim of this study was to identify key lipid metabolism-related genes (LMRGs) related to the diagnosis and treatment of AR.

MATERIALS AND METHODS

AR-related expression datasets (GSE75011, GSE46171) were downloaded through the Gene Expression Omnibus (GEO) database. First, weighted gene co-expression network analysis (WGCNA) was used to get AR-related genes (ARRGs). Next, between control and AR groups in GSE75011, differentially expressed genes (DEGs) were screened, and DEGs were intersected with LMRGs to obtain lipid metabolism-related differentially expressed genes (LMR DEGs). Protein-protein interaction (PPI) networks were constructed for these LMR DEGs. Hub genes were then identified through stress, radiality, closeness and edge percolated component (EPC) analysis and intersected with the ARRGs to obtain candidate genes. Biomarkers with diagnostic value were screened via receiver operating characteristic (ROC) curves. Differential immune cells screened between control and AR groups were then assessed for correlation with the diagnostic genes, and clinical correlation analysis and enrichment analysis were performed. Finally, real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) was made on blood samples from control and AR patients to validate these identified diagnostic genes.

RESULTS

73 LMR DEGs were obtained, which were involved in biological processes such as metabolism of lipids and lipid biosynthetic processes. 66 ARRGs and 22 hub genes were intersected to obtain four candidate genes. Three diagnostic genes (LPCAT1, SGPP1, SMARCD3) with diagnostic value were screened according to the AUC > 0.7, with markedly variant between control and AR groups. In addition, two immune cells, regulatory T cells (Treg) and T follicular helper cells (TFH), were marked variations between control and AR groups, and SMARCD3 was significantly associated with TFH. Moreover, SMARCD3 was relevant to immune-related pathways, and correlated significantly with clinical characteristics (age and sex). Finally, RT-qPCR results indicated that changes in the expression of LPCAT1 and SMARCD3 between control and AR groups were consistent with the GSE75011 and GSE46171.

CONCLUSION

LPCAT1, SGPP1 and SMARCD3 might be used as biomarkers for AR.

Application of Metabolomics in Obesity-Related Childhood Asthma Subtyping: A Narrative Scoping Review

Obesity-related asthma is a heterogeneous childhood asthma phenotype with rising prevalence. Observational studies identify early-life obesity or weight gain as risk factors for childhood asthma development. The reverse association is also described, children with asthma have a higher risk of being obese. Obese children with asthma have poor symptom control and an increased number of asthma attacks compared to non-obese children with asthma. Clinical trials have also identified that a proportion of obese children with asthma do not respond as well to usual treatment (e.g., inhaled corticosteroids). The heterogeneity of obesity-related asthma phenotypes may be attributable to different underlying pathogenetic mechanisms. Although few childhood obesity-related asthma endotypes have been described, our knowledge in this field is incomplete. An evolving analytical profiling technique, metabolomics, has the potential to link individuals' genetic backgrounds and environmental exposures (e.g., diet) to disease endotypes. This will ultimately help define clinically relevant obesity-related childhood asthma subtypes that respond better to targeted treatment. However, there are challenges related to this approach. The current narrative scoping review summarizes the evidence for metabolomics contributing to asthma subtyping in obese children, highlights the challenges associated with the implementation of this approach, and identifies gaps in research.

Increased serum cotinine and obesity negatively impact asthma exacerbations and hospitalizations: A cross-sectional analysis of NHANES

Background

Asthma is the most common non-communicable chronic airway disease worldwide. Obesity and cigarette use independently increase asthma morbidity and mortality. Current literature suggests that obesity and smoking synergistically increase asthma-related wheezing.

Objective

To assess whether increased serum cotinine and obesity act synergistically to increase the likelihood of having an asthma exacerbation, emergency department (ED) visit, or hospitalization.

Methods

A cross-sectional analysis of the 2011-2015 iterations of NHANES database was performed. Patients aged 18 years or greater with asthma were included. Serum cotinine was utilized as an accurate measurement of cigarette use. Logistic regression models were constructed to determine whether elevated serum cotinine and obesity were associated with self-reported asthma exacerbations, asthma-specific ED usage, and hospitalizations for any reason in the past year. Odds ratios were adjusted for age, gender, race, and ethnicity. Interactions were assessed by multiplying the adjusted effect sizes for elevated cotinine and obesity.

Results

We identified 2179 (N = 32,839,290) patients with asthma, of which 32.2% were active smokers and 42.7% were obese. Patients with an elevated cotinine and asthma were significantly more likely to have had an asthma-related ED visit in the past year (adjusted odds ratio [AOR] 1.82; 95% CI 1.19-2.79), have a physician-prescribed asthma medication (AOR 2.04; 95% CI 1.11-3.74), and have a hospitalization for any reason (AOR 3.65; 95% CI 1.88-7.07) compared to those with low cotinine. Patients with asthma and obesity were more likely to have an asthma-related ED visit (AOR 1.67; 95% CI 1.06-2.62) or hospitalization for any reason in the past year compared to non-obese patients (AOR 2.76; 95% CI 1.69-4.5). However, a statistically significant interaction between obesity and cotinine was only identified in patients who currently have asthma compared to a previous asthma diagnosis (AOR 1.76; 95% CI 1.10-2.82). There were no synergistic interactions among ED usage or asthma exacerbations.

Conclusion

Nearly one-third of patients with asthma were current smokers, and almost half were obese. This study identified elevated serum cotinine, a metabolite of cigarette use, and obesity as key risk factors for asthma exacerbations, asthma-related ED visits, and hospitalizations for any reason. Elevated serum cotinine and obesity were not found to act synergistically in increasing asthma exacerbations or ED visits. However, the presence of both risk factors increased the risk of currently having asthma (compared to a previous diagnosis) by 76%. Serum cotinine may be useful in predicting asthma outcomes.

From Beneath the Skin to the Airway Wall: Understanding the Pathological Role of Adipose Tissue in Comorbid Asthma-Obesity

This article provides a contemporary report on the role of adipose tissue in respiratory dysfunction. Adipose tissue is distributed throughout the body, accumulating beneath the skin (subcutaneous), around organs (visceral), and importantly in the context of respiratory disease, has recently been shown to accumulate within the airway wall: "airway-associated adipose tissue." Excessive adipose tissue deposition compromises respiratory function and increases the severity of diseases such as asthma. The mechanisms of respiratory impairment are inflammatory, structural, and mechanical in nature, vary depending on the anatomical site of deposition and adipose tissue subtype, and likely contribute to different phenotypes of comorbid asthma-obesity. An understanding of adipose tissue-driven pathophysiology provides an opportunity for diagnostic advancement and patient-specific treatment. As an exemplar, the potential impact of airway-associated adipose tissue is highlighted, and how this may change the management of a patient with asthma who is also obese. © 2023 American Physiological Society. Compr Physiol 13:4321-4353, 2023.

Perinatal Obesity Sensitizes for Premature Kidney Aging Signaling

Chronic Kidney Disease (CKD), a global health burden, is strongly associated with age-related renal function decline, hypertension, and diabetes, which are all frequent consequences of obesity. Despite extensive studies, the mechanisms determining susceptibility to CKD remain insufficiently understood. Clinical evidence together with prior studies from our group showed that perinatal metabolic disorders after intrauterine growth restriction or maternal obesity adversely affect kidney structure and function throughout life. Since obesity and aging processes converge in similar pathways we tested if perinatal obesity caused by high-fat diet (HFD)-fed dams sensitizes aging-associated mechanisms in kidneys of newborn mice. The results showed a marked increase of γH2AX-positive cells with elevated 8-Oxo-dG (RNA/DNA damage), both indicative of DNA damage response and oxidative stress. Using unbiased comprehensive transcriptomics we identified compartment-specific differentially-regulated signaling pathways in kidneys after perinatal obesity. Comparison of these data to transcriptomic data of naturally aged kidneys and prematurely aged kidneys of genetic modified mice with a hypomorphic allele of Ercc1, revealed similar signatures, e.g., inflammatory signaling. In a biochemical approach we validated pathways of inflammaging in the kidneys after perinatal obesity. Collectively, our initial findings demonstrate premature aging-associated processes as a consequence of perinatal obesity that could determine the susceptibility for CKD early in life.

Airway immune response in the mouse models of obesity-related asthma

The prevalence rates of obesity and its complications have increased dramatically worldwide. Obesity can lead to low-grade chronic systemic inflammation, which predisposes individuals to an increased risk of morbidity and mortality. Although obesity has received considerable interest in recent years, the essential role of obesity in asthma development has not been explored. Asthma is a common chronic inflammatory airway disease caused by various environmental allergens. Obesity is a critical risk factor for asthma exacerbation due to systemic inflammation, and obesity-related asthma is listed as an asthma phenotype. A suitable model can contribute to the understanding of the in-depth mechanisms of obese asthma. However, stable models for simulating clinical phenotypes and the impact of modeling on immune response vary across studies. Given that inflammation is one of the central mechanisms in asthma pathogenesis, this review will discuss immune responses in the airways of obese asthmatic mice on the basis of diverse modeling protocols.

Maternal and perinatal obesity induce bronchial obstruction and pulmonary hypertension via IL-6-FoxO1-axis in later life

Obesity is a pre-disposing condition for chronic obstructive pulmonary disease, asthma, and pulmonary arterial hypertension. Accumulating evidence suggests that metabolic influences during development can determine chronic lung diseases (CLD). We demonstrate that maternal obesity causes early metabolic disorder in the offspring. Here, interleukin-6 induced bronchial and microvascular smooth muscle cell (SMC) hyperproliferation and increased airway and pulmonary vascular resistance. The key anti-proliferative transcription factor FoxO1 was inactivated via nuclear exclusion. These findings were confirmed using primary SMC treated with interleukin-6 and pharmacological FoxO1 inhibition as well as genetic FoxO1 ablation and constitutive activation. In vivo, we reproduced the structural and functional alterations in offspring of obese dams via the SMC-specific ablation of FoxO1. The reconstitution of FoxO1 using IL-6-deficient mice and pharmacological treatment did not protect against metabolic disorder but prevented SMC hyperproliferation. In human observational studies, childhood obesity was associated with reduced forced expiratory volume in 1 s/forced vital capacity ratio Z-score (used as proxy for lung function) and asthma. We conclude that the interleukin-6-FoxO1 pathway in SMC is a molecular mechanism by which perinatal obesity programs the bronchial and vascular structure and function, thereby driving CLD development. Thus, FoxO1 reconstitution provides a potential therapeutic option for preventing this metabolic programming of CLD.

Perinatal Obesity Induces Hepatic Growth Restriction with Increased DNA Damage Response, Senescence, and Dysregulated Igf-1-Akt-Foxo1 Signaling in Male Offspring of Obese Mice

Maternal obesity predisposes for hepato-metabolic disorders early in life. However, the underlying mechanisms causing early onset dysfunction of the liver and metabolism remain elusive. Since obesity is associated with subacute chronic inflammation and accelerated aging, we test the hypothesis whether maternal obesity induces aging processes in the developing liver and determines thereby hepatic growth. To this end, maternal obesity was induced with high-fat diet (HFD) in C57BL/6N mice and male offspring were studied at the end of the lactation [postnatal day 21 (P21)]. Maternal obesity induced an obese body composition with metabolic inflammation and a marked hepatic growth restriction in the male offspring at P21. Proteomic and molecular analyses revealed three interrelated mechanisms that might account for the impaired hepatic growth pattern, indicating prematurely induced aging processes: (1) Increased DNA damage response (γH2AX), (2) significant upregulation of hepatocellular senescence markers (Cdnk1a, Cdkn2a); and (3) inhibition of hepatic insulin/insulin-like growth factor (IGF)-1-AKT-p38-FoxO1 signaling with an insufficient proliferative growth response. In conclusion, our murine data demonstrate that perinatal obesity induces an obese body composition in male offspring with hepatic growth restriction through a possible premature hepatic aging that is indicated by a pathologic sequence of inflammation, DNA damage, senescence, and signs of a possibly insufficient regenerative capacity.

Perinatal Nutritional and Metabolic Pathways: Early Origins of Chronic Lung Diseases

Lung development is not completed at birth, but expands beyond infancy, rendering the lung highly susceptible to injury. Exposure to various influences during a critical window of organ growth can interfere with the finely-tuned process of development and induce pathological processes with aberrant alveolarization and long-term structural and functional sequelae. This concept of developmental origins of chronic disease has been coined as perinatal programming. Some adverse perinatal factors, including prematurity along with respiratory support, are well-recognized to induce bronchopulmonary dysplasia (BPD), a neonatal chronic lung disease that is characterized by arrest of alveolar and microvascular formation as well as lung matrix remodeling. While the pathogenesis of various experimental models focus on oxygen toxicity, mechanical ventilation and inflammation, the role of nutrition before and after birth remain poorly investigated. There is accumulating clinical and experimental evidence that intrauterine growth restriction (IUGR) as a consequence of limited nutritive supply due to placental insufficiency or maternal malnutrition is a major risk factor for BPD and impaired lung function later in life. In contrast, a surplus of nutrition with perinatal maternal obesity, accelerated postnatal weight gain and early childhood obesity is associated with wheezing and adverse clinical course of chronic lung diseases, such as asthma. While the link between perinatal nutrition and lung health has been described, the underlying mechanisms remain poorly understood. There are initial data showing that inflammatory and nutrient sensing processes are involved in programming of alveolarization, pulmonary angiogenesis, and composition of extracellular matrix. Here, we provide a comprehensive overview of the current knowledge regarding the impact of perinatal metabolism and nutrition on the lung and beyond the cardiopulmonary system as well as possible mechanisms determining the individual susceptibility to CLD early in life. We aim to emphasize the importance of unraveling the mechanisms of perinatal metabolic programming to develop novel preventive and therapeutic avenues.

Obesity and asthma

Obesity has been well recognized as an important comorbidity in patients with asthma, representing a unique phenotype and endotype. This association indicates a close relationship between metabolic and inflammatory dysregulation. However, the detailed organ-organ, cellular, and molecular interactions are not completely resolved. Because of that, the relationship between obesity and asthma remains unclear. In this article, clinical and epidemiological studies, as well as data from experimental animal work, are being summarized to provide a state of the art update on this important topic. Much more work is needed, particularly mechanistic, to fully understand the interaction between obesity and asthma and to develop novel preventive and therapeutic strategies.

Obesity Can Contribute to Severe Persistent Allergic Rhinitis in Children through Leptin and Interleukin-1β

BACKGROUND

Obesity/overweight is associated with a higher risk of allergic rhinitis (AR) in children.

OBJECTIVE

This study aimed at exploring the mechanisms by which obesity affects the severity of AR through leptin and interleukin (IL)-1β were investigated.

METHODS

In all, 210 subjects with AR and 82 subjects without AR were included in this study. The levels of leptin and inflammatory biomarkers were measured in the serum to investigate the correlation with the severity of AR. Additionally, we analyzed whether changes in BMI regulate the severity of AR through serial follow-up of obese children.

RESULTS

IL-1β, which is a biomarker of active inflammation in AR, was significantly higher in individuals with AR than in those without and higher in subjects in the obesity group than in those in the normal weight group. A regression analysis showed that the leptin level was associated with increased IL-1β expression in children with AR. In the multivariate analysis, only parental AR (9.2-fold increase in risk), elevated leptin (11.3-fold increase in risk), and high expression of IL-1β (5.8-fold increase in risk) emerged as significant risk factors of moderate to severe persistent allergic rhinitis. We also found that children with an increase or decrease in BMI showed changes in IL-1β and AR symptoms, which these changes were dependent on leptin and BMI.

CONCLUSIONS

These results suggest that obesity is an important risk factor for the exacerbation of symptoms and leptin can exacerbate inflammation as well as severe and persistent symptoms through IL-1β in AR.

Maternal high-fat diet induces long-term obesity with sex-dependent metabolic programming of adipocyte differentiation, hypertrophy and dysfunction in the offspring

Maternal obesity determines obesity and metabolic diseases in the offspring. The white adipose tissue (WAT) orchestrates metabolic pathways, and its dysfunction contributes to metabolic disorders in a sex-dependent manner. Here, we tested if sex differences influence the molecular mechanisms of metabolic programming of WAT in offspring of obese dams. To this end, maternal obesity was induced with high-fat diet (HFD) and the offspring were studied at an early phase [postnatal day 21 (P21)], a late phase (P70) and finally P120. In the early phase we found a sex-independent increase in WAT in offspring of obese dams using magnetic resonance imaging (MRI), which was more pronounced in females than males. While the adipocyte size increased in both sexes, the distribution of WAT differed in males and females. As mechanistic hints, we identified an inflammatory response in females and a senescence-associated reduction in the preadipocyte factor DLK in males. In the late phase, the obese body composition persisted in both sexes, with a partial reversal in females. Moreover, female offspring recovered completely from both the adipocyte hypertrophy and the inflammatory response. These findings were linked to a dysregulation of lipolytic, adipogenic and stemness-related markers as well as AMPKα and Akt signaling. Finally, the sex-dependent metabolic programming persisted with sex-specific differences in adipocyte size until P120. In conclusion, we do not only provide new insights into the molecular mechanisms of sex-dependent metabolic programming of WAT dysfunction, but also highlight the sex-dependent development of low- and high-grade pathogenic obesity.

Identification of Critical Windows of Metabolic Programming of Metabolism and Lung Function in Male Offspring of Obese Dams

Perinatal nutritional determinants known as metabolic programming could be either detrimental or protective. Maternal obesity in the perinatal period determines susceptibility for diseases, such as obesity, metabolic disorders, and lung disease. Although this adverse metabolic programming is well‐recognized, the critical developmental window for susceptibility risk remains elusive. Thus, we aimed to define the vulnerable window for impaired lung function after maternal obesity; and to test if dietary intervention protects. First, we studied the impact of high‐fat diet (HFD)‐induced maternal obesity during intrauterine (HFD^iu), postnatal (HFD^post), or perinatal (i.e., intrauterine and postnatal (HFD^peri) phase on body weight, white adipose tissue (WAT), glucose tolerance, and airway resistance. Although HFD^iu, HFD^post, and HFD^peri induced overweight in the offspring, only HFD^peri and HFD^iu led to increased WAT in the offspring early in life. This early‐onset adiposity was linked to impaired glucose tolerance in HFD^peri‐offspring. Interestingly, these metabolic findings in HFD^peri‐offspring, but not in HFD^iu‐offspring and HFD^post‐offspring, were linked to persistent adiposity and increased airway resistance later in life. Second, we tested if the withdrawal of a HFD immediately after conception protects from early‐onset metabolic changes by maternal obesity. Indeed, we found a protection from early‐onset overweight, but not from impaired glucose tolerance and increased airway resistance. Our study identified critical windows for metabolic programming of susceptibility to impaired lung function, highlighting thereby windows of opportunity for prevention.

Potential Role of Cellular Senescence in Asthma

Cellular senescence is a complicated process featured by irreversible cell cycle arrest and senescence-associated secreted phenotype (SASP), resulting in accumulation of senescent cells, and low-grade inflammation. Cellular senescence not only occurs during the natural aging of normal cells, but also can be accelerated by various pathological factors. Cumulative studies have shown the role of cellular senescence in the pathogenesis of chronic lung diseases including chronic obstructive pulmonary diseases (COPD) and idiopathic pulmonary fibrosis (IPF) by promoting airway inflammation and airway remodeling. Recently, great interest has been raised in the involvement of cellular senescence in asthma. Limited but valuable data has indicated accelerating cellular senescence in asthma. This review will compile current findings regarding the underlying relationship between cellular senescence and asthma, mainly through discussing the potential mechanisms of cellular senescence in asthma, the impact of senescent cells on the pathobiology of asthma, and the efficiency and feasibility of using anti-aging therapies in asthmatic patients.

Maternal Obesity in Mice Exacerbates the Allergic Inflammatory Response in the Airways of Male Offspring

It was previously demonstrated that non-allergen-sensitized rodents born to mothers exposed to a high-fat diet (HFD) spontaneously develop lower respiratory compliance and higher respiratory resistance. In the present study, we sought to determine if mice born to mothers consuming HFD would exhibit changes in inflammatory response and lung remodeling when subjected to ovalbumin (OVA) sensitization/challenge in adult life. Mice born to dams consuming either HFD or standard chow had increased bronchoalveolar lavage (BAL) levels of IL-1β, IL-4, IL-5, IL-10, IL-13, TNF-α and TGF-β1 after challenge with OVA. IL-4, IL-13, TNF-α and TGF-β1 levels were further increased in the offspring of HFD-fed mothers. Mice born to obese dams also had exacerbated values of leukocyte infiltration in lung parenchyma, eosinophil and neutrophil counts in BAL, mucus overproduction and collagen deposition. The programming induced by maternal obesity was accompanied by increased expression of miR-155 in peripheral-blood mononuclear cells and reduced miR-133b in trachea and lung tissue in adult life. Altogether, the present data support the unprecedented notion that the progeny of obese mice display exacerbated responses to sensitization/challenge with OVA, leading to the intensification of the morphological changes of lung remodeling. Such changes are likely to result from long-lasting changes in miR-155 and miR-133b expression.

Short-term high-fat diet feeding protects from the development of experimental allergic asthma in mice

BACKGROUND

A close association between obesity and asthma has been described. The nature of this association remains elusive, especially with respect to allergic asthma. Controversial findings exist regarding the impact of short-term high-fat diet (HFD) feeding on the development of allergic asthma.

OBJECTIVE

To delineate the impact of short-term HFD feeding on the development of experimental allergic asthma.

METHODS

Female C57BL/6JRJ mice were fed with a short-term HFD or chow diet (CD) for 12 weeks. Allergic asthma was induced by intraperitoneal OVA/alum sensitization followed by repeated OVA airway challenges. We determined airway hyperresponsiveness (AHR) and pulmonary inflammation by histologic and flow cytometric analysis of immune cells. Furthermore, we assessed the impact of HFD on dendritic cell (DC)-mediated activation of T cells.

RESULTS

Female mice showed a mild increase in body weight accompanied by mild metabolic alterations. Upon OVA challenge, CD-fed mice developed strong AHR and airway inflammation, which were markedly reduced in HFD-fed mice. Mucus production was similar in both treatment groups. OVA-induced increases in DC and CD4⁺ T-cell recruitment to the lungs were significantly attenuated in HFD-fed mice. MHC-II expression and CD40 expression in pulmonary CD11b⁺ DCs were markedly lower in HFD-fed compared to CD-fed mice, which was associated in vivo with a decreased T helper (Th) 1/17 differentiation and Treg formation without impacting Th2 differentiation.

CONCLUSIONS/CLINICAL RELEVANCE

These findings suggest that short-term HFD feeding attenuates the development of AHR, airway inflammation, pulmonary DC recruitment and MHC-II/CD40 expression leading to diminished Th1/17 but unchanged Th2 differentiation. Thus, short-term HFD feeding and associated metabolic alterations may have protective effects in allergic asthma development.

Maternal high fat diet compromises survival and modulates lung development of offspring, and impairs lung function of dams (female mice)

Background

Epidemiological studies have identified strong relationships between maternal obesity and offspring respiratory dysfunction; however, the causal direction is not known. We tested whether maternal obesity alters respiratory function of offspring in early life.

Methods

Female C57Bl/6 J mice were fed a high or low fat diet prior to and during two rounds of mating and resulting pregnancies with offspring lung function assessed at 2 weeks of age. The lung function of dams was measured at 33 weeks of age.

Results

A high fat diet caused significant weight gain prior to conception with dams exhibiting elevated fasting glucose, and glucose intolerance. The number of surviving litters was significantly less for dams fed a high fat diet, and surviving offspring weighed more, were longer and had larger lung volumes than those born to dams fed a low fat diet. The larger lung volumes significantly correlated in a linear fashion with body length. Pups born from the second pregnancy had reduced tissue elastance compared to pups born from the first pregnancy, regardless of the dam’s diet. As there was reduced offspring survival born to dams fed a high fat diet, the statistical power of lung function measures of offspring was limited. There were signs of increased inflammation in the bronchoalveolar lavage fluid of dams (but not offspring) fed a high fat diet, with more tumour necrosis factor-α, interleukin(IL)-5, IL-33 and leptin detected. Dams that were fed a high fat diet and became pregnant twice had reduced fasting glucose immediately prior to the second mating, and lower levels of IL-33 and leptin in bronchoalveolar lavage fluid.

Conclusions

While maternal high fat diet compromised litter survival, it also promoted somatic and lung growth (increased lung volume) in the offspring. Further studies are required to examine downstream effects of this enhanced lung volume on respiratory function in disease settings.

Opposing Actions of Developmental Trichloroethylene and High-Fat Diet Coexposure on Markers of Lipogenesis and Inflammation in Autoimmune-Prone Mice

Trichloroethylene (TCE) is a widespread environmental pollutant associated with immunotoxicity and autoimmune disease. Previous studies showed that mice exposed from gestation through early life demonstrated CD4+ T cell alterations and autoimmune hepatitis. Determining the role of one environmental risk factor for any disease is complicated by the presence of other stressors. Based on its known effects, we hypothesized that developmental overnutrition in the form of a moderately high-fat diet (HFD) consisting of 40% kcal fat would exacerbate the immunotoxicity and autoimmune-promoting effects of low-level (<10 μg/kg/day) TCE in autoimmune-prone MRL+/+ mice over either stressor alone. When female offspring were evaluated at 27 weeks of age we found that a continuous exposure beginning at 4 weeks preconception in the dams until 10 weeks of age in offspring that TCE and HFD promoted unique effects that were often antagonistic. For a number of adiposity endpoints, TCE significantly reversed the expected effects of HFD on expression of genes involved in fatty acid synthesis/insulin resistance, as well as mean pathology scores of steatosis. Although none of the animals developed pathological signs of autoimmune hepatitis, the mice generated unique patterns of antiliver antibodies detected by western blotting attributable to TCE exposure. A majority of cytokines in liver, gut, and splenic CD4+ T cells were significantly altered by TCE, but not HFD. Levels of bacterial populations in the intestinal ileum were also altered by TCE exposure rather than HFD. Thus, in contrast to our expectations this coexposure did not promote synergistic effects.

Optimising experimental research in respiratory diseases: an ERS statement

Experimental models are critical for the understanding of lung health and disease and are indispensable for drug development. However, the pathogenetic and clinical relevance of the models is often unclear. Further, the use of animals in biomedical research is controversial from an ethical perspective.The objective of this task force was to issue a statement with research recommendations about lung disease models by facilitating in-depth discussions between respiratory scientists, and to provide an overview of the literature on the available models. Focus was put on their specific benefits and limitations. This will result in more efficient use of resources and greater reduction in the numbers of animals employed, thereby enhancing the ethical standards and translational capacity of experimental research.The task force statement addresses general issues of experimental research (ethics, species, sex, age, ex vivo and in vitro models, gene editing). The statement also includes research recommendations on modelling asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, lung infections, acute lung injury and pulmonary hypertension.The task force stressed the importance of using multiple models to strengthen validity of results, the need to increase the availability of human tissues and the importance of standard operating procedures and data quality.

High-fat-diet induces airway hyperresponsiveness partly through activating CD38 signaling pathway

CD38 is a plasma membrane bound multifunctional enzyme. It can be activated by inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-13, inducing calcium responses to agonist in airway smooth muscle cells (ASMC). Previous studies have found that high-fat-diet (HFD) induced obesity exhibited innate airway hyperresponsiveness (AHR). This study aimed to detect the effect of CD38 signaling pathway on the AHR of overweight/obese mice. The HFD-fed mice exhibited a significantly higher baseline airway resistance (Rn), and the increasing rates of Rn responded to increasing doses of methacholine compared with the LFD-fed mice. High-fat-diet increased CD38 expressions both in lung tissues and primary cultured ASMCs. Besides, preincubation with TNF-α led to a higher expression of CD38 protein and increased intracellular calcium in ASMC of the HFD-fed mice. Furthermore, CD38 gene knockdown through transfection of CD38 siRNA decreased the concentration of intracellular calcium. Additionally, the upregulations of CD38 protein and CD38 mRNA were also found in the lung tissues of HFD-fed mice challenged by ovalbumin (OVA). Collectively, our findings demonstrated a role of CD38 signaling pathway on the AHR of obesity and might be a potential therapeutic target for treating difficult-to-control obese asthma phenotype.

Obesogenic diets alter metabolism in mice

Obesity and accompanying metabolic disease is negatively correlated with lung health yet the exact mechanisms by which obesity affects the lung are not well characterized. Since obesity is associated with lung diseases as chronic bronchitis and asthma, we designed a series of experiments to measure changes in lung metabolism in mice fed obesogenic diets. Mice were fed either control or high fat/sugar diet (45%kcal fat/17%kcal sucrose), or very high fat diet (60%kcal fat/7% sucrose) for 150 days. We performed untargeted metabolomics by GC-TOFMS and HILIC-QTOFMS and lipidomics by RPLC-QTOFMS to reveal global changes in lung metabolism resulting from obesity and diet composition. From a total of 447 detected metabolites, we found 91 metabolite and lipid species significantly altered in mouse lung tissues upon dietary treatments. Significantly altered metabolites included complex lipids, free fatty acids, energy metabolites, amino acids and adenosine and NAD pathway members. While some metabolites were altered in both obese groups compared to control, others were different between obesogenic diet groups. Furthermore, a comparison of changes between lung, kidney and liver tissues indicated few metabolic changes were shared across organs, suggesting the lung is an independent metabolic organ. These results indicate obesity and diet composition have direct mechanistic effects on composition of the lung metabolome, which may contribute to disease progression by lung-specific pathways.

Epigenetic underpinnings of developmental immunotoxicity and autoimmune disease

The concordance rate for developing autoimmune disease in identical twins is around 50% demonstrating that gene and environmental interactions contribute to disease etiology. The environmental contribution to autoimmune disease is a wide-ranging concept including exposure to immunotoxic environmental chemicals. Because the immune system is immature during development suggests that adult-onset autoimmunity may originate when the immune system is particularly sensitive. Among the pollutants most closely associated with inflammation and/or autoimmunity include Bisphenol-A, mercury, TCDD, and trichloroethylene. These toxicants have been shown to impart epigenetic changes (e.g., DNA methylation) that may alter immune function and promote autoreactivity. Here we review these autoimmune-promoting toxicants and their relation to immune cell epigenetics both in terms of adult and developmental exposure.

Renal Metabolic Programming Is Linked to the Dynamic Regulation of a Leptin-Klf15 Axis and Akt/AMPKα Signaling in Male Offspring of Obese Dams

Childhood obesity is associated with renal diseases. Maternal obesity is a risk factor linked to increased adipocytokines and metabolic disorders in the offspring. Therefore, we studied the impact of maternal obesity on renal-intrinsic insulin and adipocytokine signaling and on renal function and structure. To induce maternal obesity, female mice were fed a high-fat diet (HFD) or a standard diet (SD; control group) prior to mating, during gestation, and throughout lactation. A third group of dams was fed HFD only during lactation (HFD-Lac). After weaning at postnatal day (P)21, offspring of all groups received SD. Clinically, HFD offspring were overweight and insulin resistant at P21. Although no metabolic changes were detected at P70, renal sodium excretion was reduced by 40%, and renal matrix deposition increased in the HFD group. Mechanistically, two stages were differentiated. In the early stage (P21), compared with the control group, HFD showed threefold increased white adipose tissue, impaired glucose tolerance, hyperleptinemia, and hyperinsulinemia. Renal leptin/Stat3-signaling was activated. In contrast, the Akt/ AMPKα cascade and Krüppel-like factor 15 expression were decreased. In the late stage (P70), although no metabolic differences were detected in HFD when compared with the control group, leptin/Stat3-signaling was reduced, and Akt/AMPKα was activated in the kidneys. This effect was linked to an increase of proliferative (cyclinD1/D2) and profibrotic (ctgf/collagen IIIα1) markers, similar to leptin-deficient mice. HFD-Lac mice exhibited metabolic changes at P21 similar to HFD, but no other persistent changes. This study shows a link between maternal obesity and metabolic programming of renal structure and function and intrinsic-renal Stat3/Akt/AMPKα signaling in the offspring.

Novel role of NPY in neuroimmune interaction and lung growth after intrauterine growth restriction

Individuals with intrauterine growth restriction (IUGR) are at risk for chronic lung disease. Using a rat model, we showed in our previous studies that altered lung structure is related to IL-6/STAT3 signaling. As neuropeptide Y (NPY), a coneurotransmitter of the sympathetic nervous system, regulates proliferation and immune response, we hypothesized that dysregulated NPY after IUGR is linked to IL-6, impaired myofibroblast function, and alveolar growth. IUGR was induced in rats by isocaloric low-protein diet; lungs were analyzed on embryonic day (E) 21, postnatal day (P) 3, P12, and P23. Finally, primary neonatal lung myofibroblasts (pnF) and murine embryonic fibroblasts (MEF) were used to assess proliferation, apoptosis, migration, and IL-6 expression. At E21, NPY and IL-6 expression was decreased, and AKT/PKC and STAT3/AMPKα signaling was reduced. Early reduction of NPY/IL-6 was associated with increased chord length in lungs after IUGR at P3, indicating reduced alveolar formation. At P23, however, IUGR rats exhibited a catch-up of body weight and alveolar growth coupled with more proliferating myofibroblasts. These structural findings after IUGR were linked to activated NPY/PKC, IL-6/AMPKα signaling. Complementary, IUGR-pnF showed increased survival, impaired migration, and reduced IL-6 compared with control-pnF (Co-pnF). In contrast, NPY induced proliferation, migration, and increased IL-6 synthesis in fibroblasts. Additionally, NPY^-/- mice showed reduced IL-6 signaling and less proliferation of lung fibroblasts. Our study presents a novel role of NPY during alveolarization: NPY regulates 1) IL-6 and lung STAT3/AMPKα signaling, and 2) proliferation and migration of myofibroblasts. These new insights in pulmonary neuroimmune interaction offer potential strategies to enable lung growth.

Maternal high-fat diet in mice leads to innate airway hyperresponsiveness in the adult offspring

Maternal obesity prior to and during pregnancy has been associated with an increased incidence of childhood asthma. As diets rich in saturated fat are linked to obesity and inflammation, we created a murine model to investigate the effect of maternal high-fat diet (HFD) on adult offspring airway hyperreactivity (AHR), a cardinal feature of asthma. Balb/cByJ dams were fed a HFD (60% fat Calories) or normal-fat diet (NFD) (10% fat Calories) from 8 weeks prior to first breeding through their pregnancies. Pups were weaned to either a HFD or NFD (at 4 weeks of age). AHR was measured in the 10-week-old offspring following inhaled methacholine challenge by end-inflation technique. Bronchial alveolar lavage fluid (BALF) was analyzed for cell count, total protein, and IL-6. Offspring of HFD dams weaned to NFD had increased AHR compared to offspring of NFD dams weaned to NFD Offspring of HFD dams that remained on HFDs had increased AHR compared to offspring of NFD dams weaned to HFDs. Offspring of HFD dams had higher BALF cell counts, higher neutrophil percentage, greater total protein, and IL-6 in the BALF These results demonstrate that a maternal diet high in saturated fat through pregnancy and lactation plays a key role in programming adult offspring AHR.