Insulin resistance mediates high-fat diet-induced pulmonary fibrosis and airway hyperresponsiveness through the TGF-β1 pathway

Triglyceride-glucose index as an independent predictor of mortality in patients with chronic respiratory diseases

Objective

The consequences of chronic pulmonary illness are known to exacerbate in individuals with metabolic syndrome and insulin resistance. However, the relationship between triglyceride-glucose (TyG) index, a reliable alternative biomarker of metabolic dysfunction, and chronic respiratory diseases (CRDs) are inconclusive.

Research design and methods

Our research involved a total of 7,819 adult individuals diagnosed with CRDs who participated in the National Health and Nutrition Examination Survey (NHANES) from 2001 to 2018. To assess the correlation between the TyG index and survival rates, we employed multivariable weighted Cox regression analysis, smoothing curve fitting, survival curve analysis and subgroup analysis to investigate the relationship.

Results

Higher TyG index among CRDs shown a substantial positive correlation with all-cause mortality after controlling for relevant confounders. The restricted cubic spline analysis showed a nonlinear relationship between the TyG score and all-cause mortality in CRDs. Patients with higher TyG indexes had a greater risk of all-cause mortality according to Kaplan-Meier survival curves.

Conclusion

The clinical relevance of the TyG index in predicting the life expectancy of individuals with CRDs is highlighted by our research. The TyG index can serve as a substitute biomarker for monitoring the wellbeing of the individuals with CRDs.

The association between triglyceride glucose-body mass index and mortality in critically ill patients with respiratory failure: insights from ICU data

Respiratory failure (RF) lead to high mortality rates and extended hospital stays in intensive care unit (ICU). The Triglyceride-Glucose (TyG) index, a reliable surrogate marker for insulin resistance (IR), predicted adverse outcomes in various diseases. Combining weight-related indices like body mass index (BMI) with TyG to form the TyG-BMI enhanced the assessment of IR and its impact on patient outcomes. However, the association between TyG-BMI and outcomes in patients with RF remained underexplored. This study retrospectively analyzed data from the MIMIC-IV database, focusing on critically ill patients with RF. From an initial cohort of 19,429 patients, 2177 met the inclusion criteria and were divided into quartiles based on TyG-BMI values. Key clinical information was collected within the first 24 h of ICU admission, including demographics, lab results, vital signs, and scoring systems such as SAPS II and SOFA. Primary outcome was 28-day, secondary outcomes were 180-day and 1-year mortality. Data were analyzed using multivariable Cox regression models, Kaplan-Meier survival curves, and restricted cubic splines to assess the nonlinear relationship between TyG-BMI and mortality. The study found significant differences in baseline characteristics across TyG-BMI quartiles. Kaplan-Meier survival curves indicated a higher survival probability for patients in the lowest TyG-BMI quartile (Q1) compared to higher quartiles (Q2-Q4). Adjusted hazard ratios demonstrated a nonlinear association between higher TyG-BMI values and increased mortality risk at all three time points. The RCS-derived cut-off value of 269 for TyG-BMI was identified as a significant threshold, with higher TyG-BMI values correlating with lower mortality risks. Subgroup analyses reinforced these findings across different patient demographics and clinical profiles. Higher TyG-BMI was associated to lower short-term and long-term mortality, suggesting a potential protective effect. These findings highlighted the importance of the TyG-BMI as a robust prognostic marker, providing valuable insights for improving treatment strategies for patients with RF.

Differential effects of foodborne and waterborne micro(nano)plastics exposure on fish liver metabolism and gut microbiota community

Micro(nano)plastics (MNPs) primarily enter fish through two routes: directly ingestion via their diets and respiratory filtration through their gills. However, the specific impacts of these two routes on liver metabolism remain largely unknown. Here, we investigated the gene expression profiles of the liver of Nile tilapia Oreochromis niloticus following equivalent doses of foodborne and waterborne MNPs exposure. While the liver phenotypes of O. niloticus showed minimal differences between the two exposure routes, significant variations were observed in gene response patterns. Using WGCNA, we identified the key gene networks and KEGG pathways associated with each exposure type. The primary transcription factors regulating gene expression changes were thrb for foodborne exposure and fosl2 for waterborne exposure. The stimulus of foodborne MNPs primarily induced metabolic disorders through circadian rhythm, whereas waterborne MNPs induced inflammatory responses to affect host metabolism. By integrating gene expression alterations with gut microbiota enrichment data, we further found that Firmicutes, Fusobacteriota, Proteobacteria, and Chloroflexi jointly regulated the expression of mapk13 during foodborne exposure, whereas the expression of the most leading genes in waterborne exposure was predominantly influenced by Firmicutes. Collectively, our study demonstrated a distinct pattern in microbiota-gene gut-liver axis in O. niloticus in response to foodborne and waterborne MNPs exposure.

Mechanical stress contributes to ligamentum flavum hypertrophy by inducing local inflammation and myofibroblast transition in the innovative surgical rabbit model

Background

Lumbar spinal canal stenosis (LSCS) ranks as a prevalent spinal disorder in senior populations. Ligamentum flavum hypertrophy (LFH) is a significant feature of LSCS, yet its cause is unclear. The purpose of this study was to create a novel animal model for LFH and explore the pathological mechanisms involved.

Methods

A novel rabbit model for intervertebral mechanical stress concentration was established through posterolateral fusion using steel wire. Radiological analysis and biological validation were used to determine the crucial role of mechanical stress in LFH and explore the effect of this animal model.

Results

After 12 weeks, the LF subjected to mechanical stress concentration exhibited a disruption and reduction in elastic fibers, collagen accumulation, increased thickness of LF, elevated LF cells, and increased levels of certain factors related to fibrosis and inflammation. These findings were histologically consistent to those found in human LFH. Furthermore, in vitro, mechanical stretch was discovered to enhance the conversion of fibroblasts into myofibroblasts by boosting TGF-β1 secretion in LF fibroblasts. In addition, compared to conventional internal fixation, this new surgical model provided advantages such as minor damage, decreased bleeding, and reduced technical difficulty and molding costs.

Conclusion

This novel rabbit model is able to replicate the moderate pathological features of human LFH. Mechanical stress is an independent factor leading to LFH, which can promote the TGF-β1 secretion in LF cells and some inflammatory cells, subsequently induce the myofibroblast transition, and finally result in collagen accumulation and LF fibrosis.

Association between the triglyceride-glucose index and mortality in the asthma population

OBJECTIVE

To explore the relationship between the triglyceride-glucose (TyG) index and mortality in individuals with asthma, given the inconclusive evidence linking metabolic dysfunction to asthma outcomes.

RESEARCH DESIGN AND METHODS

We analyzed data from 5985 adults with asthma from the National Health and Nutrition Examination Survey (NHANES) 2001-2018. We used multivariable weighted Cox regression, smoothing curve fitting, survival curve analysis, and subgroup analysis to assess the correlation between the TyG index and survival rates.

RESULTS

A higher TyG index significantly correlated with increased all-cause mortality in asthmatics. Adjusted hazard ratios (HR) for higher TyG index categories (compared to TyG <8) were: 1.69 (95 % CI: 1.28, 2.24, p < 0.001) for 8 ≤ TyG <9, 2.04 (95 % CI: 1.51, 2.76, p < 0.001) for 9 ≤ TyG <10, and 2.94 (95 % CI: 2.03, 4.28, p < 0.001) for TyG ≥10. Restricted cubic spline analysis revealed a nonlinear relationship between the TyG score and mortality. Kaplan-Meier curves showed higher TyG indexes associated with greater mortality risk.

CONCLUSIONS

The TyG index is a significant predictor of mortality in asthma patients, highlighting its potential for risk stratification. Incorporating the TyG index into clinical assessments could improve monitoring and management. Future research should investigate interventions targeting the TyG index to enhance survival and quality of life in asthma patients.

Potential of the Advanced Lung Cancer Inflammation Index as a Risk Marker for Asthma-Chronic Obstructive Pulmonary Disease Overlap Syndrome and COPD: Evidence from NHANES 2007-2018

Background

The Advanced Lung Cancer Inflammation Index (ALI) is widely recognized as an emerging metric for assessing both inflammation and nutritional levels. However, it is unclear whether there is a correlation between ALI and Asthma-Chronic Obstructive Pulmonary Disease Overlap (ACO), Chronic Obstructive Pulmonary Disease (COPD), and asthma.

Materials and Methods

ALI was considered as a continuous and categorical variable (Q1, Q2, Q3, Q4), respectively, and the categories of its categorical variables were based on the quartiles of ALI. Logistic regression models were then developed to analyze the correlation between ALI and ACO, COPD, and asthma. Finally, correlations were further analyzed by propensity score matching (PSM) methods. In addition, we calculated the area under the curve (AUC) of the ROC curve to assess the predictive performance of the ALI.

Results

Results with ALI as a continuous variable: ALI was negatively associated with both ACO and COPD (ACO: OR=0.70; 95% CI: 0.58-0.86; P<0.001; COPD: OR=0.72; 95% CI: 0.65-0.79; P<0.001), whereas there was no association between ALI and asthma (OR=1.08; 95% CI: 0.97-1.20; P=0.140). Results of ALI as a categorical variable: the negative ALI-ACO association persisted in Q4 groups (Q4: OR=0.66; 95% CI: 0.49-0.88; P=0.006); the negative ALI-COPD association was maintained in all groups. After PSM, ALI remained negatively associated with ACO and COPD (ACO: OR=0.61; 95% CI: 0.45-0.83; P=0.002; COPD: OR=0.56; 95% CI: 0.48-0.64; P<0.001). The AUC was 0.69 for ALI-ACO and 0.73 for ALI-COPD.

Conclusion

High levels of ALI may be associated with a reduced risk of ACO and COPD.

Non-linear association of the metabolic score for insulin resistance with obstructive sleep apnea: a cross-sectional study from NHANES 2015-2018

Background

The relationship between the Metabolic Score for Insulin Resistance (METS-IR), a novel index integrating multiple metabolic parameters, and the risk of obstructive sleep apnea (OSA) remains under explored.

Methods

Analyses were conducted on data from 2,348 participants included in the National Health and Nutrition Examination Survey (NHANES) data from 2015 to 2018. Logistic regression, stratified analyses, curve-fitting analyses, and threshold effects analyses were employed to evaluate the association between METS-IR and the risk of OSA.

Results

Multifactorial logistic regression analyses revealed a significant positive correlation between METS-IR and the risk of OSA [OR: 1.05 (95% CI: 1.04-1.06)]. Stratified analyses showed consistent associations across various subgroups, including sex, race, age, marital status, education level, poverty income ratio, physical activity, alcohol use, smoking status, diabetes mellitus, hypertension, and cardiovascular disease. Nonlinear analysis identified an inflection point at METS-IR 46.65. On the left of the inflection point, the risk of OSA increased significantly, with each unit increase in METS-IR associated with a 7% increase in risk [OR: 1.07 (95% CI: 1.05-1.08)]. On the right side of the inflection point, however, the rate of risk increase slowed to 1% [OR: 1.01 (95% CI: 1.00-1.02)].

Conclusion

This investigation reveals a significant and nonlinear relationship between METS-IR and OSA. Further investigation is needed to explore their association more comprehensively and to elucidate the underlying mechanisms.

Association Between Triglyceride-Glucose Index and Lung Function Parameters in the General Population Undergoing Health Examinations

Purpose

To investigate the relationship between the triglyceride-glucose (TyG) index and pulmonary function metrics among the general population undergoing health examinations.

Materials and Methods

The enrollment totaled 696 participants. Fasting triglycerides and glucose levels were used to calculate the TyG index. Participants were divided into two categories according to their median TyG: one with high TyG and the other with low TyG. A portable spirometer was used to assess lung function. Fundamental clinical features and lung function indicators were compared between the two groups, and the relationship between the TyG index and lung function parameters was explored.

Results

Compared with the low TyG group, the high TyG group exhibited significantly reduced levels of FEV1/FVC, FVC% pred, FEV1% pred, FEV3% pred, FEV3/FVC, FEF75, FEF75% pred, FEF25-75% pred, and MVV% pred, suggesting poor pulmonary function. The TyG index was significantly inversely correlated with multiple pulmonary function metrics, including FVC% pred, FEV1% pred, FEV3% pred, FEV1/FVC, FEV3/FVC, FEF75, FEF75% pred and FEF25-75% pred, which persisted even after accounting for confounding variables.

Conclusion

In summary, the present study establishes a correlation between the TyG index and some lung function indicators, offering a new indicator of metabolic abnormalities related to lung functionality.

Impact of obesity on airway remodeling in asthma: pathophysiological insights and clinical implications

The prevalence of obesity among asthma patients has surged in recent years, posing a significant risk factor for uncontrolled asthma. Beyond its impact on asthma severity and patients' quality of life, obesity is associated with reduced lung function, increased asthma exacerbations, hospitalizations, heightened airway hyperresponsiveness, and elevated asthma-related mortality. Obesity may lead to metabolic dysfunction and immune dysregulation, fostering chronic inflammation characterized by increased pro-inflammatory mediators and adipocytokines, elevated reactive oxygen species, and reduced antioxidant activity. This chronic inflammation holds the potential to induce airway remodeling in individuals with asthma and obesity. Airway remodeling encompasses structural and pathological changes, involving alterations in the airway's epithelial and subepithelial layers, hyperplasia and hypertrophy of airway smooth muscle, and changes in airway vascularity. In individuals with asthma and obesity, airway remodeling may underlie heightened airway hyperresponsiveness and increased asthma severity, ultimately contributing to the development of persistent airflow limitation, declining lung function, and a potential increase in asthma-related mortality. Despite efforts to address the impact of obesity on asthma outcomes, the intricate mechanisms linking obesity to asthma pathophysiology, particularly concerning airway remodeling, remain incompletely understood. This comprehensive review discusses current research investigating the influence of obesity on airway remodeling, to enhance our understanding of obesity's role in the context of asthma airway remodeling.

Genetic association analysis of dietary intake and idiopathic pulmonary fibrosis: a two-sample mendelian randomization study

BACKGROUND

IPF is a complex lung disease whose aetiology is not fully understood, but diet may have an impact on its development and progression. Therefore, we investigated the potential causal connection between dietary intake and IPF through TSMR to offer insights for early disease prevention recommendations.

METHODS

The study incorporated 29 dietary exposure factors, oily fish intake, bacon intake, processed meat intake, poultry intake, beef intake, pork intake, lamb/mutton intake, non-oily fish intake, fresh fruit intake, cooked vegetable intake, baked bean intake, fresh tomato intake, tinned tomato intake, salad/raw vegetable intake, Fresh fruit intake, coffee intake, tea intake, water intake, red wine intake, average weekly beer plus cider intake, alcoholic drinks per week, cereal intake, bread intake, whole-wheat intake, whole-wheat cereal intake, cheese intake, yogurt intake, salt added to food and whole egg intake. The study explored the causal link between diet and IPF using TSMR analysis, predominantly the IVW method, and performed sensitivity analyses to validate the results.

RESULT

The study revealed that consuming oily fish, yogurt, and dried fruits had a protective effect against IPF, whereas the consumption of alcoholic beverages and beef was linked to an increased risk of IPF.

CONCLUSION

In this MR study, it was discovered that the consumption of oily fish, yogurt, and dried fruits exhibited a protective effect against IPF, whereas the intake of alcoholic beverages and beef was associated with an elevated risk of IPF. These findings underscore the significance of making informed and timely dietary decisions in IPF prevention.

Effects of chitinase-1 inhibitor in obesity-induced and -aggravated asthma in a murine model

AIMS

Despite recent investigations on the role of chitinase in asthma, its role in obesity-induced asthma has not been evaluated. Therefore, we investigated the roles of chitin, chitinase-1, and a chitinase-1 inhibitor (compound X, CPX) in a murine model.

MAIN METHODS

We assigned C57BL/6 mice to the ovalbumin (OVA) model or obesity model group. In the OVA model, mice received intraperitoneal OVA twice within a 2-week interval and intranasal OVA for 3 consecutive days. Additionally, chitin was intranasally administered for 3 consecutive days, and CPX was intraperitoneally injected three times over 5 days. In the obesity model, a high-fat diet (HFD) was maintained for 13 weeks, and CPX was intraperitoneally injected eight times over 4 weeks.

KEY FINDINGS

In the OVA model, chitin aggravated OVA-induced airway hyper-responsiveness (AHR), increased bronchoalveolar lavage fluid (BALF) cell proliferation, increased fibrosis, and increased the levels of various inflammatory cytokines (including chitinase-1, TGF-β, TNF-α, IL-1 β, IL-6, IL-4, and IL-13). CPX treatment significantly ameliorated these effects. In the obesity model, HFD significantly increased AHR, BALF cell proliferation, fibrosis, and the levels of various inflammatory cytokines. Particularly, compared to the control group, the mRNA expression of chitinase, chitinase-like molecules, and other molecules associated with inflammation and the immune system was significantly upregulated in the HFD and HFD/OVA groups. Immunofluorescence analysis also showed increased chitinase-1 expression in these groups. CPX significantly ameliorated all these effects in this model.

SIGNIFICANCE

This study showed that CPX can be an effective therapeutic agent in asthma, especially, obesity-induced and -aggravated asthma to protect against the progression to airway remodeling and fibrosis.

Ectopic and visceral fat deposition in aging, obesity, and idiopathic pulmonary fibrosis: an interconnected role

Idiopathic pulmonary fibrosis (IPF) is considered an age-related disease. Age-related changes, along with other factors such as obesity, hormonal imbalances, and various metabolic disorders, lead to ectopic fat deposition (EFD). This accumulation of fat outside of its normal storage sites is associated with detrimental effects such as lipotoxicity, oxidative stress, inflammation, and insulin resistance. This narrative review provides an overview of the connection between ectopic and visceral fat deposition in aging, obesity, and IPF. It also elucidates the mechanism by which ectopic fat deposition in the airways and lungs, pericardium, skeletal muscles, and pancreas contributes to lung injury and fibrosis in patients with IPF, directly or indirectly. Moreover, the review discusses the impact of EFD on the severity of the disease, quality of life, presence of comorbidities, and overall prognosis in IPF patients. The review provides detailed information on recent research regarding representative lipid-lowering drugs, hypoglycemic drugs, and lipid-targeting drugs in animal experiments and clinical studies. This may offer new therapeutic directions for patients with IPF.

Lifestyle, Genetic Susceptibility, and the Risk of Idiopathic Pulmonary Fibrosis: A Large Prospective Cohort Study

BACKGROUND

Lifestyle is an important contributor of age-related chronic disease, but the association between lifestyle and the risk of idiopathic pulmonary fibrosis (IPF) remains unknown. The extent to which genetic susceptibility modifies the effects of lifestyle on IPF also remains unclear.

RESEARCH QUESTION

Is there a joint effect or interaction of lifestyle and genetic susceptibility on the risk of developing IPF?

STUDY DESIGN AND METHODS

This study included 407,615 participants from the UK Biobank study. A lifestyle score and a polygenic risk score were constructed separately for each participant. Participants were then classified into three lifestyle categories and three genetic risk categories based on the corresponding score. Cox models were fitted to assess the association of lifestyle and genetic risk with the risk of incident IPF.

RESULTS

With favorable lifestyle as the reference group, intermediate lifestyle (hazard ratio, 1.384; 95% CI, 1.218-1.574) and unfavorable lifestyle (hazard ratio, 2.271; 95% CI, 1.852-2.785) were significantly associated with an increased risk of IPF. For the combined effect of lifestyle and polygenic risk score, participants with unfavorable lifestyle and high genetic risk had the highest risk of IPF (hazard ratio, 7.796; 95% CI, 5.482-11.086) compared with those with favorable lifestyle and low genetic risk. Moreover, approximately 32.7% (95% CI, 11.3-54.1) of IPF risk could be attributed to the interaction of an unfavorable lifestyle and high genetic risk.

INTERPRETATION

Exposure to unfavorable lifestyle significantly increased the risk of IPF, particularly in those with high genetic risk.

Utility of Hypoglycemic Agents to Treat Asthma with Comorbid Obesity

Adults with obesity may develop asthma that is ineffectively controlled by inhaled corticosteroids and long-acting beta-adrenoceptor agonists. Mechanistic and translational studies suggest that metabolic dysregulation that occurs with obesity, particularly hyperglycemia and insulin resistance, contributes to altered immune cell function and low-grade systemic inflammation. Importantly, in these cases, the same proinflammatory cytokines believed to contribute to insulin resistance may also be responsible for airway remodeling and hyperresponsiveness. In the past decade, new research has emerged assessing whether hypoglycemic therapies impact comorbid asthma as reflected by the incidence of asthma, asthma-related emergency department visits, asthma-related hospitalizations, and asthma-related exacerbations. The purpose of this review article is to discuss the mechanism of action, preclinical data, and existing clinical studies regarding the efficacy and safety of hypoglycemic therapies for adults with obesity and comorbid asthma.

The Impact of Insulin Resistance on Loss of Lung Function and Response to Treatment in Asthma

Rationale: The role of obesity-associated insulin resistance (IR) in airflow limitation in asthma is uncertain. Objectives: Using data in the Severe Asthma Research Program 3 (SARP-3), we evaluated relationships between homeostatic measure of IR (HOMA-IR), lung function (cross-sectional and longitudinal analyses), and treatment responses to bronchodilators and corticosteroids. Methods: HOMA-IR values were categorized as without (<3.0), moderate (3.0-5.0), or severe (>5.0). Lung function included FEV1 and FVC measured before and after treatment with inhaled albuterol and intramuscular triamcinolone acetonide and yearly for 5 years. Measurements and Main Results: Among 307 participants in SARP-3, 170 (55%) were obese and 140 (46%) had IR. Compared with patients without IR, those with IR had significantly lower values for FEV1 and FVC, and these lower values were not attributable to obesity effects. Compared with patients without IR, those with IR had lower FEV1 responses to β-adrenergic agonists and systemic corticosteroids. The annualized decline in FEV1 was significantly greater in patients with moderate IR (-41 ml/year) and severe IR (-32 ml/year,) than in patients without IR (-13 ml/year, P < 0.001 for both comparisons). Conclusions: IR is common in asthma and is associated with lower lung function, accelerated loss of lung function, and suboptimal lung function responses to bronchodilator and corticosteroid treatments. Clinical trials in patients with asthma and IR are needed to determine if improving IR might also improve lung function.

Aberrant pulmonary immune response of obese mice to periodontal infection

Obesity and periodontitis constitute mutual risk factors in respiratory disorders; this study aimed to explore the pulmonary immune response to periodontal infection using combined animal models with diet-induced obesity (DIO). Thirty-two C57 BL/6J mice were randomly divided into low-fat (LF) or high-fat (HF) diet groups and fed an LF diet as a control or an HF diet to induce obesity. The 30-week mice in the diet group were divided into periodontal ligation group (10 days using Porphyromonas gingivalis ATCC 33277) or sham-ligation group. The expressions of the macrophage-specific maker (F4/80), macrophage chemotactic protein1 (MCP1), and inflammatory cytokines in lung tissues were analyzed. The mRNA and protein levels of F4/80, MCP1, interleukin (IL)-1β, and IL-6 expressions were significantly upregulated by obesity in lung tissues. However, the mRNA and protein levels of F4/80, MCP1, and IL-6 were downregulated by periodontitis in DIO mice relative to that of the HF control group. Periodontitis increased tumor necrosis factor-α level of lung tissues under LF, while IL-10 was not affected by obesity regardless of periodontitis. Periodontitis may aggravate pulmonary immune response in obese rodents. This may relate to the imbalance of the pro- and anti-inflammatory cytokine status of lung lesions, which tends to attenuate the infiltration of alveolar macrophages.

Differences in Inflammatory Cytokine Profile in Obesity-Associated Asthma: Effects of Weight Loss

Obesity and asthma are associated with systemic inflammation maintained by mediators released by adipose tissue and lung. This study investigated the inflammatory serum mediator profile in obese subjects (O) (n = 35), non-obese asthma (NOA) patients (n = 14), obese asthmatics (OA) (n = 21) and healthy controls (HC) (n = 33). The effect of weight loss after bariatric surgery (BS) was examined in 10 OA and 31 O subjects. We analyzed serum markers including leptin, adiponectin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, ST2, IL-5, IL-9, and IL-18. Compared with HC subjects, the O group showed increased levels of leptin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, and ST2; the OA group presented increased levels of MCP-1, ezrin, YKL-40, and IL-18, and the NOA group had increased levels of ezrin, YKL-40, IL-5, and IL-18. The higher adiponectin/leptin ratio in NOA with respect to OA subjects was the only significant difference between the two groups. IL-9 was the only cytokine with significantly higher levels in OA with respect to O subjects. TNFR2, ezrin, MCP-1, and IL-18 concentrations significantly decreased in O subjects after BS. O, OA, and NOA showed distinct patterns of systemic inflammation. Leptin and adiponectin are regulated in asthma by obesity-dependent and -independent mechanisms. Combination of asthma and obesity does not result in significant additive effects on circulating cytokine levels.

Neutrophils and Asthma

Although eosinophilic inflammation is characteristic of asthma pathogenesis, neutrophilic inflammation is also marked, and eosinophils and neutrophils can coexist in some cases. Based on the proportion of sputum cell differentiation, asthma is classified into eosinophilic asthma, neutrophilic asthma, neutrophilic and eosinophilic asthma, and paucigranulocytic asthma. Classification by bronchoalveolar lavage is also performed. Eosinophilic asthma accounts for most severe asthma cases, but neutrophilic asthma or a mixture of the two types can also present a severe phenotype. Biomarkers for the diagnosis of neutrophilic asthma include sputum neutrophils, blood neutrophils, chitinase-3-like protein, and hydrogen sulfide in sputum and serum. Thymic stromal lymphoprotein (TSLP)/T-helper 17 pathways, bacterial colonization/microbiome, neutrophil extracellular traps, and activation of nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 pathways are involved in the pathophysiology of neutrophilic asthma and coexistence of obesity, gastroesophageal reflux disease, and habitual cigarette smoking have been associated with its pathogenesis. Thus, targeting neutrophilic asthma is important. Smoking cessation, neutrophil-targeting treatments, and biologics have been tested as treatments for severe asthma, but most clinical studies have not focused on neutrophilic asthma. Phosphodiesterase inhibitors, anti-TSLP antibodies, azithromycin, and anti-cholinergic agents are promising drugs for neutrophilic asthma. However, clinical research targeting neutrophilic inflammation is required to elucidate the optimal treatment.

Obesity and the Development of Lung Fibrosis

Obesity is an epidemic worldwide and the obese people suffer from a range of respiratory complications including fibrotic changes in the lung. The influence of obesity on the lung is multi-factorial, which is related to both mechanical injury and various inflammatory mediators produced by excessive adipose tissues, and infiltrated immune cells. Adiposity causes increased production of inflammatory mediators, for example, cytokines, chemokines, and adipokines, both locally and in the systemic circulation, thereby rendering susceptibility to respiratory diseases, and altered responses. Lung fibrosis is closely related to chronic inflammation in the lung. Current data suggest a link between lung fibrosis and diet-induced obesity, although the mechanism remains incomplete understood. This review summarizes findings on the association of lung fibrosis with obesity, highlights the role of several critical inflammatory mediators (e.g., TNF-α, TGF-β, and MCP-1) in obesity related lung fibrosis and the implication of obesity in the outcomes of idiopathic pulmonary fibrosis patients.

Aerobic Exercise Improves Pulmonary Fibrosis by Improving Insulin Resistance and Inflammation in Obese Mice

Background

Previous studies have demonstrated that obesity is associated with pulmonary fibrosis. We attempted to identify whether regular aerobic exercise (AE) can protect against high-fat diet (HFD)-associated pulmonary fibrosis.

Methods

Forty-eight C57BL/6 mice were randomly assigned to four groups: chow group (Ch), chow plus exercise group (CE), obesity group (Ob), and obesity plus exercise group (OE). The mice were fed either an HFD or a chow diet for 16 weeks, and low-intensity aerobic exercise (AE) was performed in the last 8 weeks. We measured the degree of pulmonary fibrosis; pulmonary inflammation; oxidative stress parameters; insulin resistance-related indicators; the number of inflammatory cells in bronchoalveolar lavage fluid (BALF); the mRNA expression levels of IL-10, IL-1β, TGF-β, TNF-α, CXCL-1, IL-17, MMP-9, MPO, NE, and sirt-1; and the BALF levels of CXCL-1, IL-17, TGF-β, IL-10, IL-1β, and TNF-α in lung tissue.

Results

AE in obese mice protected against obesity-associated pulmonary fibrosis, chronic inflammation, pro-oxidative/antioxidative imbalance, and insulin resistance. AE ameliorated the HFD-induced inflammatory response and neutrophil infiltration in the lung. AE downregulated BALF levels of CXCL-1, IL-1β, TNF-α IL-17, and TGF-β but upregulated BALF levels of IL-10. AE decreased IL-1β, TGF-β, TNF-α, CXCL-1, IL-17, MMP-9, MPO, and NE mRNA expression levels but upregulated IL-10 and sirt-1 mRNA expression levels in the lung.

Conclusions

AE protects against HFD-induced pulmonary fibrosis by improving obesity-associated insulin resistance, chronic low-grade inflammation, and pro-oxidative/antioxidative imbalance. AE improved HFD-induced pulmonary fibrosis by suppressing IL-17, TGF-β, NE, and MMP-9 expression and activating IL-10 and sirt-1 expression.

Asthma Phenotype with Metabolic Dysfunction

Asthma is chronic eosinophilic bronchitis with the dominancy of T helper 2 (Th2) inflammation. However, patients with asthma and metabolic dysfunction have pathogenic and pathological differences from those with Th2 inflammation. Metabolic dysfunction, typically presented as metabolic syndrome, has several important clinical components including central obesity, insulin resistance or glucose intolerance, dyslipidemia, and vitamin D deficiency. Data from large epidemiological studies support the significance of these components in the control of asthma and their contribution to airway remodeling, suggesting the presence of an asthma phenotype with metabolic dysfunction. These components are quite interactive with each other, so it is difficult to reveal the individual role of each. It is well known that asthma is difficult to treat in patients with obesity, due in part to inadequate response to inhaled corticosteroids. Additionally, vitamin D deficiency and insulin resistance have been regarded as aggravating factors of asthma control and airway remodeling. Recent clinical and in vivo studies have revealed the specific mechanisms of these components, which may aggravate asthma control and airway remodeling. In this review article, I summarize the recent studies and unmet needs for patients with asthma and metabolic dysfunction.

Association between Lung Function and New-Onset Diabetes Mellitus in Healthy Individuals after a 6-Year Follow-up

BACKGROUND

We analyzed hemoglobin A1c (HbA1c) levels and various lung function test results in healthy individuals after a 6-year follow-up period to explore the influence of lung function changes on glycemic control.

METHODS

Subjects whose HbA1c levels did not qualify as diabetes mellitus (DM) and who had at least two consecutive lung function tests were selected among the people who visited a health promotion center. Lung function parameters, including forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV/FVC ratio, and forced expiratory flow 25% to 75% (FEF25%-75%), were divided into four groups based on their baseline quantiles. To evaluate future DM onset risk in relation to lung function changes, the correlation between baseline HbA1c levels and changes in lung function parameters after a 6-year follow-up period was analyzed.

RESULTS

Overall, 17,568 individuals were included; 0.9% of the subjects were diagnosed with DM. The individuals included in the quartile with FEV1/FVC ratio values of 78% to 82% had lower risk of DM than those in the quartile with FEV1/FVC ratio values of ≥86% after adjusting for age, sex, and body mass index (P=0.04). Baseline percent predicted FEV1, FVC, FEV1/FVC ratio, and FEF25%-75%, and differences in the FEV1/FVC ratio or FEF25%-75%, showed negative linear correlations with baseline HbA1c levels.

CONCLUSION

Healthy subjects with FEV1/FVC ratio values between 78% and 82% had 40% lower risk for future DM. Smaller differences and lower baseline FEV1/FVC ratio or FEF25%-75% values were associated with higher baseline HbA1c levels. These findings suggest that airflow limitation affects systemic glucose control and that the FEV1/FVC ratio could be one of the factors predicting future DM risk in healthy individuals.

β-caryophyllene ameliorated obesity-associated airway hyperresponsiveness through some non-conventional targets

BACKGROUND

Obesity worsens airway hyperresponsiveness (AHR) in asthmatic subjects by up-regulating macrophage polarization that leads to excessive secretion of pro-inflammatory adipokines from white adipose tissue followed by generation of oxidative stress in the respiratory system. Treatment through conventional signaling pathways proved to be inadequate in obese asthmatics, so a therapeutical approach through a non-conventional pathway may prove to be effective.

PURPOSE

This study aimed to investigate the efficacy of a FDA-approved food additive, β-caryophyllene (BCP) in obesity-associated AHR.

METHOD

A repertoire of protein expression, cytokine and adiponectin estimation, oxidative stress assays, histopathology, and fluorescence immune-histochemistry were performed to assess the efficacy of BCP in C57BL/6 mice model of obesity-associated AHR. Additionally, human adipocyte was utilized to study the effect of BCP on macrophage polarization in Boyden chamber cell culture inserts.

RESULTS

Obesity-associated AHR is ameliorated by administration of BCP by inhibition of the macrophage polarization by activation of AMPKα, Nrf2/HO-1 and AdipoR1 and AdipoR2 signaling pathway, up-regulation of adiponectin, GLP-1, IFN-γ, SOD, catalase and down-regulation of NF-κB, leptin, IL-4, TNF, and IL-1β. Browning of eWAT by induction of thermogenesis and activation of melanocortin pathway also contributed to the amelioration of obesity-associated AHR. We conclude that BCP ameliorated the obesity-associated AHR via inhibition of macrophage polarization, activation of AMPKα, Nrf2/HO-1, and up-regulation of AdipoR1 and AdipoR2 expression and down-regulation of NFκB expression in lung of animal.

CONCLUSION

Being an FDA-approved food additive, BCP may prove to be a safe and potential agent against obesity-associated AHR.

Dysregulated Metabolism in the Pathophysiology of Non-Allergic Obese Asthma

Asthma is an obstructive airway disease that is characterized by reversible airway obstruction and is classically associated with atopic, T_H2 driven inflammation. Landmark studies in the second half of the twentieth century identified eosinophils as a key mediator of inflammation and steroids, both inhaled and systemic, as a cornerstone of therapy. However, more recently other phenotypes of asthma have emerged that do not respond as well to traditional therapies. In particular, obese patients who develop asthma as adults are less likely to have eosinophilic airway inflammation and do not respond to traditional therapies. Obese patients often have metabolic comorbidities such as impaired glucose tolerance and dyslipidemias, also known as metabolic syndrome (MetS). The unified pathophysiology of metabolic syndrome is not known, however, several signaling pathways, such as the neuropeptide glucagon-like peptide-1 (GLP-1) and nitric oxide (NO) signaling have been shown to be dysregulated in MetS. These pathways are targeted by commercially available medications. This review discusses the potential roles that dysregulation of the GLP-1 and NO signaling pathways, along with arginine metabolism, play in the development of asthma in obese patients. GLP-1 receptors are found in high density in the lung and are also detectable in bronchoalveolar lavage fluid. NO has long been associated with asthma. We hypothesize that these derangements in metabolic signaling pathways underpin the asthmatic phenotype seen in obese patients with non-eosinophilic airway inflammation and poor response to established therapies. While still an active area of research, novel interventions are needed for this subset of patient who respond poorly to available asthma therapies.

Impact of diet and the bacterial microbiome on the mucous barrier and immune disorders

The prevalence of chronic immune and metabolic disorders is increasing rapidly. In particular, inflammatory bowel diseases, obesity, diabetes, asthma and chronic obstructive pulmonary disease have become major healthcare and economic burdens worldwide. Recent advances in microbiome research have led to significant discoveries of associative links between alterations in the microbiome and health, as well as these chronic supposedly noncommunicable, immune/metabolic disorders. Importantly, the interplay between diet, microbiome and the mucous barrier in these diseases has gained significant attention. Diet modulates the mucous barrier via alterations in gut microbiota, resulting in either disease onset/exacerbation due to a "poor" diet or protection against disease with a "healthy" diet. In addition, many mucosa-associated disorders possess a specific gut microbiome fingerprint associated with the composition of the mucous barrier, which is further influenced by host-microbiome and inter-microbial interactions, dietary choices, microbe immigration and antimicrobials. Our review focuses on the interactions of diet (macronutrients and micronutrients), gut microbiota and mucous barriers (gastrointestinal and respiratory tract) and their importance in the onset and/or progression of major immune/metabolic disorders. We also highlight the key mechanisms that could be targeted therapeutically to prevent and/or treat these disorders.

Obesity-induced Vitamin D Deficiency Contributes to Lung Fibrosis and Airway Hyperresponsiveness

Vitamin D (VitD) has pleiotropic effects. VitD deficiency is closely involved with obesity and may contribute to the development of lung fibrosis and aggravation of airway hyperresponsiveness (AHR). We evaluated the causal relationship between VitD deficiency and the lung pathologies associated with obesity. In vivo effects of VitD supplementation were analyzed using high-fat diet (HFD)-induced obese mice and TGF-β1 (transforming growth factor-β1) triple transgenic mice. Effects of VitD supplementation were also evaluated in both BEAS-2B and primary lung cells from the transgenic mice. Obese mice had decreased 25-OH VitD and VitD receptor expressions with increases of insulin resistance, renin and angiotensin-2 system (RAS) activity, and leptin. In addition, lung pathologies such as a modest increase in macrophages, enhanced TGF-β1, IL-1β, and IL-6 expression, lung fibrosis, and AHR were found. VitD supplementation to HFD-induced obese mice recovered these findings. TGF-β1-overexpressing transgenic mice enhanced macrophages in BAL fluid, lung expression of RAS, epithelial-mesenchymal transition markers, AHR, and lung fibrosis. VitD supplementation also attenuated these findings in addition to the attenuation of the expressions of TGF-β1, and phosphorylated Smad-2/3 in lung. Supplementing in vitro-stimulated BEAS-2B and primary lung cells with VitD inhibited TGF-β1 expression, supporting the suppressive effect of VitD for TGF-β1 expression. These results suggest that obesity leads to VitD deficiency and worsens insulin resistance while enhancing the expression of leptin, RAS, TGF-β1, and proinflammatory cytokines. These changes may contribute to the development of lung fibrosis and AHR. VitD supplementation rescues these changes and may have therapeutic potential for asthma with obesity.

Neutrophils in asthma: the good, the bad and the bacteria

Airway inflammation plays a key role in asthma pathogenesis but is heterogeneous in nature. There has been significant scientific discovery with regard to type 2-driven, eosinophil-dominated asthma, with effective therapies ranging from inhaled corticosteroids to novel biologics. However, studies suggest that approximately 1 in 5 adults with asthma have an increased proportion of neutrophils in their airways. These patients tend to be older, have potentially pathogenic airway bacteria and do not respond well to classical therapies. Currently, there are no specific therapeutic options for these patients, such as neutrophil-targeting biologics.Neutrophils comprise 70% of the total circulatory white cells and play a critical defence role during inflammatory and infective challenges. This makes them a problematic target for therapeutics. Furthermore, neutrophil functions change with age, with reduced microbial killing, increased reactive oxygen species release and reduced production of extracellular traps with advancing age. Therefore, different therapeutic strategies may be required for different age groups of patients.The pathogenesis of neutrophil-dominated airway inflammation in adults with asthma may reflect a counterproductive response to the defective neutrophil microbial killing seen with age, resulting in bystander damage to host airway cells and subsequent mucus hypersecretion and airway remodelling. However, in children with asthma, neutrophils are less associated with adverse features of disease, and it is possible that in children, neutrophils are less pathogenic.In this review, we explore the mechanisms of neutrophil recruitment, changes in cellular function across the life course and the implications this may have for asthma management now and in the future. We also describe the prevalence of neutrophilic asthma globally, with a focus on First Nations people of Australia, New Zealand and North America.

Amylin deposition activates HIF1α and 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3) signaling in failing hearts of non-human primates

Hyperamylinemia induces amylin aggregation and toxicity in the pancreas and contributes to the development of type-2 diabetes (T2D). Cardiac amylin deposition in patients with obesity and T2D was found to accelerate heart dysfunction. Non-human primates (NHPs) have similar genetic, metabolic, and cardiovascular processes as humans. However, the underlying mechanisms of cardiac amylin in NHPs, particularly related to the hypoxia inducible factor (HIF)1α and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) signaling pathways, are unknown. Here, we demonstrate that in NHPs, amylin deposition in heart failure (HF) contributes to cardiac dysfunction via activation of HIF1α and PFKFB3 signaling. This was confirmed in two in vitro cardiomyocyte models. Furthermore, alterations of intracellular Ca2+, reactive oxygen species, mitochondrial function, and lactate levels were observed in amylin-treated cells. Our study demonstrates a pathological role for amylin in the activation of HIF1α and PFKFB3 signaling in NHPs with HF, establishing amylin as a promising target for heart disease patients.

TGF-β: The missing link in obesity-associated airway diseases?

Obesity is emerging as a global public health epidemic. The co-morbidities associated with obesity significantly contribute to reduced quality of life, mortality, and global healthcare burden. Compared to other asthma comorbidities, obesity prominently engenders susceptibility to inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease (COPD), contributes to greater disease severity and evokes insensitivity to current therapies. Unlike in other metabolic diseases associated with obesity, the mechanistic link between obesity and airway diseases is only poorly defined. Transforming growth factor-β (TGF-β) is a pleiotropic inflammatory cytokine belonging to a family of growth factors with pivotal roles in asthma. In this review, we summarize the role of TGF-β in major obesity-associated co-morbidities to shed light on mechanisms of the diseases. Literature evidence shows that TGF-β mechanistically links many co-morbidities with obesity through its profibrotic, remodeling, and proinflammatory functions. We posit that TGF-β plays a similar mechanistic role in obesity-associated inflammatory airway diseases such as asthma and COPD. Concerning the role of TGF-β on metabolic effects of obesity, we posit that TGF-β has a similar mechanistic role in obesity-associated inflammatory airway diseases in interplay with different comorbidities such as hypertension, metabolic diseases like type 2 diabetes, and cardiomyopathies. Future studies in TGF-β-dependent mechanisms in obesity-associated inflammatory airway diseases will advance our understanding of obesity-induced asthma and help find novel therapeutic targets for prevention and treatment.

Insights into the Role of Bioactive Food Ingredients and the Microbiome in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic disease mainly associated with aging and, to date, its causes are still largely unknown. It has been shown that dietary habits can accelerate or delay the occurrence of aging-related diseases; however, their potential role in IPF development has been underestimated so far. The present review summarizes the evidence regarding the relationship between diet and IPF in humans, and in animal models of pulmonary fibrosis, in which we discuss the bioactivity of specific dietary food ingredients, including fatty acids, peptides, amino acids, carbohydrates, vitamins, minerals and phytochemicals. Interestingly, many animal studies reveal preventive and therapeutic effects of particular compounds. Furthermore, it has been recently suggested that the lung and gut microbiota could be involved in IPF, a relationship which may be linked to changes in immunological and inflammatory factors. Thus, all the evidence so far puts forward the idea that the gut-lung axis could be modulated by dietary factors, which in turn have an influence on IPF development. Overall, the data reviewed here support the notion of identifying food ingredients with potential benefits in IPF, with the ultimate aim of designing nutritional approaches as an adjuvant therapeutic strategy.