Immunometabolism in obese asthmatics: are we there yet?

Research Progress of Metabolomics in Asthma

Asthma is a highly heterogeneous disease, but the pathogenesis of asthma is still unclear. It is well known that the airway inflammatory immune response is the pathological basis of asthma. Metabolomics is a systems biology method to analyze the difference of low molecular weight metabolites (<1.5 kDa) and explore the relationship between metabolic small molecules and pathophysiological changes of the organisms. The functional interdependence between immune response and metabolic regulation is one of the cores of the body's steady-state regulation, and its dysfunction will lead to a series of metabolic disorders. The signal transduction effect of specific metabolites may affect the occurrence of the airway inflammatory immune response, which may be closely related to the pathogenesis of asthma. Emerging metabolomic analysis may provide insights into the pathogenesis and diagnosis of asthma. The review aims to analyze the changes of metabolites in blood/serum/plasma, urine, lung tissue, and exhaled breath condensate (EBC) samples, and further reveals the potential pathogenesis of asthma according to the disordered metabolic pathways.

Potential Metabolic Biomarkers in Adult Asthmatics

Asthma is the most common chronic airway inflammation, with multiple phenotypes caused by complicated interactions of genetic, epigenetic, and environmental factors. To date, various determinants have been suggested for asthma pathogenesis by a new technology termed omics, including genomics, transcriptomics, proteomics, and metabolomics. In particular, the systematic analysis of all metabolites in a biological system, such as carbohydrates, amino acids, and lipids, has helped identify a novel pathway related to complex diseases. These metabolites are involved in the regulation of hypermethylation, response to hypoxia, and immune reactions in the pathogenesis of asthma. Among them, lipid metabolism has been suggested to be related to lung dysfunction in mild-to-moderate asthma. Sphingolipid metabolites are an important mediator contributing to airway inflammation in obese asthma and aspirin-exacerbated respiratory disease. Although how these molecular variants impact the disease has not been completely determined, identification of new causative factors may possibly lead to more-personalized and precise pathway-specific approaches for better diagnosis and treatment of asthma. In this review, perspectives of metabolites related to asthma and clinical implications have been highlighted according to various phenotypes.

ADIPOQ and LEP variants on asthma and atopy: Genetic association modified by overweight

BACKGROUND

Asthma and atopy are considered condition associated with obesity, being affected by genetic and environmental factors. The LEP and ADIPOQ genes, responsible for the expression and secretion of leptin and adiponectin, respectively, and polymorphisms in such genes have been linked to both diseases, independently, and also with the obesity-associated asthma phenotype in populations with high European ancestry and high-income countries. However, in mixed populations, there are few studies evaluating the impact of these variants in genes associated with the phenotype of asthma and obesity. Thus, the aim of this study was to investigate variants in LEP and ADIPOQ associated with asthma and atopy, and whether overweight modifies that effect.

METHODS

The study involved 203 asthmatics children and 813 control subjects (between 5 and 11 years old), with or without overweight, from the SCAALA (Asthma and Allergy Social Changes in Latin America) program. Among them, 831 had data for allergy markers, being 258 atopic and 573 non-atopic. Genotyping was performed using a commercial panel Omnium Illumina 2.5. Logistic regression was performed to identify associations expected by using PLINK 1.09 and three genetic models: additive, dominant and recessive adjusted for sex, age, helminth infection, BMI and Principal Components (PC) 1 and 2, for ancestry, in order to control the confounding factor by population structure.

RESULTS

For asthma, G allele of rs822396, in ADIPOQ, was positively associated in additive model (OR 1.4, 95% CI 1.08-1.83) and T allele of rs1063537 in dominant model (OR 1.52, 95% CI 1.01-2.30). In LEP, rs11763517 (C allele) and rs11760956 (A allele) were both negatively associated with asthma in the additive model (OR 0.70, 95% CI 0.54-0.91; OR 0.66, 95% CI 0.50-0.89) respectively, and the A allele of rs2167270 in dominant model (OR 0.71, 95% CI 0.51-0.98). The G allele of rs12706832 showed a positive association with asthma in the recessive model (OR 1.66, 95% CI 1.06-2.61). When the population was stratified by the BMI / Age Z-Score, the protection observed for asthma between the variants rs11760956, rs11763517 and rs2167270 was lost overweight individuals; The protection observed for atopy was lost in all variants (rs16861205, rs2167270 and rs17151919) in the overweight group.

CONCLUSION

These results suggest that SNPs on the LEP and ADIPOQ genes may have an impact on atopy and asthma. Furthermore, we also show that the asthma and atopy protection attributed to variants on LEP and ADIPOQ genes is lost in individuals exposed to overweight.

Immunometabolism and Pulmonary Infections: Implications for Protective Immune Responses and Host-Directed Therapies

The biology and clinical efficacy of immune cells from patients with infectious diseases or cancer are associated with metabolic programming. Host immune- and stromal-cell genetic and epigenetic signatures in response to the invading pathogen shape disease pathophysiology and disease outcomes. Directly linked to the immunometabolic axis is the role of the host microbiome, which is also discussed here in the context of productive immune responses to lung infections. We also present host-directed therapies (HDT) as a clinically viable strategy to refocus dysregulated immunometabolism in patients with infectious diseases, which requires validation in early phase clinical trials as adjuncts to conventional antimicrobial therapy. These efforts are expected to be continuously supported by newly generated basic and translational research data to gain a better understanding of disease pathology while devising new molecularly defined platforms and therapeutic options to improve the treatment of patients with pulmonary infections, particularly in relation to multidrug-resistant pathogens.

Caloric restriction prevents the development of airway hyperresponsiveness in mice on a high fat diet

We have previously shown that high fat diet (HFD) for 2 weeks increases airway hyperresponsiveness (AHR) to methacholine challenge in C57BL/6J mice in association with an increase in IL-1β levels in lung tissue. We hypothesize that obesity increases AHR via the IL-1β mechanism, which can be prevented by caloric restriction and IL-1β blockade. In this study, we fed C57BL/6J mice for 8 weeks with several hypercaloric diets, including HFD, HFD supplemented with fructose, high trans-fat diet (HTFD) supplemented with fructose, either ad libitum or restricting their food intake to match body weight to the mice on a chow diet (CD). We also assessed the effect of the IL-1β receptor blocker anakinra. All mice showed the same total respiratory resistance at baseline. All obese mice showed higher AHR at 30 mg/ml of methacholine compared to CD and food restricted groups, regardless of the diet. Obese mice showed significant increases in lung IL-1 β mRNA expression, but not the protein, compared to CD and food restricted mice. Anakinra abolished an increase in AHR. We conclude that obesity leads to the airway hyperresponsiveness preventable by caloric restriction and IL-1β blockade.

Immunometabolism features of metabolic deregulation and cancer

Immunometabolism is a branch dealing at the interface of immune functionalities and metabolic regulations. Considered as a bidirectional trafficking, metabolic contents and their precursors bring a considerable change in immune cells signal transductions which as a result affect the metabolic organs and states as an implication. Lipid metabolic ingredients form a major chunk of daily diet and have a proven contribution in immune cells induction, which then undergo metabolic pathway shuffling inside their ownself. Lipid metabolic states activate relevant metabolic pathways inside immune cells that in turn prime appropriate responses to outside environment in various states including lipid metabolic disorders itself and cancers as an extension. Although data on Immunometabolism are still growing, but scientific community need to adjust and readjust according to recent data on given subject. This review attempts to provide current important data on Immunometabolism and consequently its metabolic ramifications. Incumbent data on various lipid metabolic deregulations like obesity, metabolic syndrome, obese asthma and atherosclerosis are analysed. Further, metabolic repercussions on cancers and its immune modalities are also analysed.

Obesity-Associated Metabolic Signatures Correlate to Clinical and Inflammatory Profiles of Asthma: A Pilot Study

PURPOSE

Obesity is associated with metabolic dysregulation, but the underlying metabolic signatures involving clinical and inflammatory profiles of obese asthma are largely unexplored. We aimed at identifying the metabolic signatures of obese asthma.

METHODS

Eligible subjects with obese (n = 11) and lean (n = 22) asthma underwent body composition and clinical assessment, sputum induction, and blood sampling. Sputum supernatant was assessed for interleukin (IL)-1β, -4, -5, -6, -13, and tumor necrosis factor (TNF)-α, and serum was detected for leptin, adiponectin and C-reactive protein. Untargeted gas chromatography time-of-flight mass spectrometry (GC-TOF-MS)-based metabolic profiles in sputum, serum and peripheral blood monocular cells (PBMCs) were analyzed by orthogonal projections to latent structures-discriminate analysis (OPLS-DA) and pathway topology enrichment analysis. The differential metabolites were further validated by correlation analysis with body composition, and clinical and inflammatory profiles.

RESULTS

Body composition, asthma control, and the levels of IL-1β, -4, -13, leptin and adiponectin in obese asthmatics were significantly different from those in lean asthmatics. OPLS-DA analysis revealed 28 differential metabolites that distinguished obese from lean asthmatic subjects. The validation analysis identified 18 potential metabolic signatures (11 in sputum, 4 in serum and 2 in PBMCs) of obese asthmatics. Pathway topology enrichment analysis revealed that cyanoamino acid metabolism, caffeine metabolism, alanine, aspartate and glutamate metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, pentose phosphate pathway in sputum, and glyoxylate and dicarboxylate metabolism, glycerolipid metabolism and pentose phosphate pathway in serum are suggested to be significant pathways related to obese asthma.

CONCLUSIONS

GC-TOF-MS-based metabolomics indicates obese asthma is characterized by a metabolic profile different from lean asthma. The potential metabolic signatures indicated novel immune-metabolic mechanisms in obese asthma with providing more phenotypic and therapeutic implications, which needs further replication and validation.

A novel nutritional intervention improves lung function in overweight/obese adolescents with poorly controlled asthma: the Supplemental Nutrition in Asthma Control (SNAC) pilot study

Asthma in the obese is often severe, difficult to treat, and characterized by less eosinophilic inflammation than asthma in the nonobese. Obesity-associated metabolic dysregulation may be a causal factor. We previously reported that a nutrient- and fiber-dense bar [Children's Hospital Oakland Research Institute (CHORI)-bar], which was designed to fill gaps in poor diets, improved metabolism in healthy overweight/obese (OW/OB) adults. In this pilot trial, OW/OB adolescents with poorly controlled asthma were randomized to weekly nutrition/exercise classes with or without twice-daily CHORI-bar consumption. Intent-to-treat analysis did not indicate CHORI-bar-specific effects. However, restricting the analysis to participants with acceptable compliance and a relatively low fraction of exhaled nitric oxide (FENO; <50/ ppb, a surrogate for noneosinophilic asthma; study participants: CHORI-bar, n = 16; controls, n = 15) indicated that CHORI-bar-specific, significant improvements in lung function (forced vital capacity, percent-predicted forced expiratory volume in 1 s, and percent-predicted forced expiratory flow between 25 and 75% of forced vital capacity), primarily in participants with low chronic inflammation (high-sensitivity C-reactive protein <1.5 mg/L). (We previously observed that chronic inflammation blunted CHORI-bar-induced metabolic improvements in healthy OW/OB adults.) Lung function improvement occurred without weight loss and was independent of improvements in metabolic and anthropometric end points and questionnaire-based measures of asthma control and quality of life. This study suggests that a nutritional intervention can improve lung function in OW/OB adolescents with asthma and relatively low FENO without requiring major changes in dietary habits, lifestyle, or weight loss and that this effect is blunted by chronic inflammation.-Bseikri, M., McCann, J. C., Lal, A., Fong, E., Graves, K., Goldrich, A., Block, D., Gildengoren, G. L., Mietus-Snyder, M., Shigenaga, M., Suh, J., Hardy, K., Ames, B. N. A novel nutritional intervention improves lung function in overweight/obese adolescents with poorly controlled asthma: the Supplemental Nutrition in Asthma Control (SNAC) pilot study.

Prenatal Exposure to Lipopolysaccharide Induces PTX3 Expression and Results in Obesity in Mouse Offspring

This study tested the hypothesis whether inflammation will directly lead to obesity. This study was designed to investigate the relationship between inflammation and obesity by intraperitoneally injecting pregnant mice with lipopolysaccharide (LPS) (75 μg kg^-1). The results showed that inflammation during pregnancy could lead to a significant increase in the levels of the inflammatory factor PTX3. The offspring of the LPS-treated mice displayed abnormal levels of fat development, blood lipids, and glucose metabolism, and fat differentiation markers were significantly increased. Our study also confirmed that PTX3 can increase the susceptibility to obesity by regulating the expression of adipogenic markers; this regulatory role of PTX3 is most likely caused by MAPK pathway hyperactivation. Our study is the first to find strong evidence of inflammation as a cause of obesity. We determined that PTX3 was an important moderator of obesity, and we elucidated its mechanism, thus providing new targets and theories for obesity therapy. Moreover, our study provides new ideas and directions for the early intervention of anti-inflammation in pregnancy.

Association of Childhood Obesity and the Immune System: A Systematic Review of Reviews

The growing prevalence of childhood obesity has become a serious health problem over the past decades. As the immune system is greatly affected by excess weight, in this review of reviews, we discuss the findings of review articles about the relationship between childhood/maternal obesity and children's immune system. We searched English-language articles in PubMed, Scopus, ISI Thomson Reuters, and Google Scholar databases. All relevant reviews, either systematic or narrative, were retrieved. Then their quality was assessed by using the Assessment of Multiple Systematic Reviews and International Narrative Systematic Assessment tools, respectively. In the final step, 26 reviews were included. Our review suggests that childhood obesity is associated with extensive changes in the serum levels of inflammatory and anti-inflammatory cytokines and proteins, as well as the number of immune cells and their behavior. Therefore, it might cause or exacerbate diseases such as asthma, allergy, atopic dermatitis (AD), and obstructive sleep apnea syndrome. Moreover, childhood obesity may reduce the immune system responsiveness to vaccines and microorganisms. Furthermore, studies suggest that maternal obesity increases the risk of asthma in offspring. Future studies are needed to determine different associations of childhood obesity with allergy, atophic dermatitis, and autoimmune diseases.

Treadmill walking exercise modulates bone mineral status and inflammatory cytokines in obese asthmatic patients with long term intake of corticosteroids

BACKGROUND

Obesity and asthma are an important public health problem in Saudi Arabia. An increasing body of data supports the hypothesis that obesity is a risk factor for asthma. Asthma appears to be associated with low bone mineral density (BMD) due to long-term use of corticosteroids. Studies recently showed that weight bearing exercise training can increase mineral bone density, reduce weight and improve metabolic control.

OBJECTIVE

The present study aimed to measure the effects of treadmill walking exercises on bone mineral status and inflammatory cytokines in obese asthmatic patients treated with long term intake of corticosteroids.

METHODS

Eighty obese asthmatic patients of both sexes, their age ranged from 41 to 53 years. Subjects were divided into two equal groups: training group (group A) received aerobic exercise training on treadmill for six months in addition to the medical treatment where, the control group (group B) received only the medical treatment.

RESULTS

The results of this study indicated a significant increase in BMD of the lumbar spine & the radius, serum calcium and high density lipoprotein cholesterol (HDL-c) & significant reduction in parathyroid hormone, leptin, tumor necrosis factor- alpha(TNF-α), interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-6 (IL-6), low density lipoprotein cholesterol (LDL-c), triglycerides (TG) and body mass index (BMI) in group (A), while these changes were not significant in group (B).Also; there was a significant difference between both groups at the end of the study.

CONCLUSION

Treadmill walking exercise training is an effective treatment policy to improve bone mineral status and modulates inflammatory cytokines and blood lipids profile in obese asthmatic patients with long term intake of corticosteroids.

Pediatric Obesity-Related Asthma: The Role of Metabolic Dysregulation

The burden of obesity-related asthma among children, particularly among ethnic minorities, necessitates an improved understanding of the underlying disease mechanisms. Although obesity is an independent risk factor for asthma, not all obese children develop asthma. Several recent studies have elucidated mechanisms, including the role of diet, sedentary lifestyle, mechanical fat load, and adiposity-mediated inflammation that may underlie the obese asthma pathophysiology. Here, we review these recent studies and emerging scientific evidence that suggest metabolic dysregulation may play a role in pediatric obesity-related asthma. We also review the genetic and epigenetic factors that may underlie susceptibility to metabolic dysregulation and associated pulmonary morbidity among children. Lastly, we identify knowledge gaps that need further exploration to better define pathways that will allow development of primary preventive strategies for obesity-related asthma in children.

Emerging Comorbidities in Adult Asthma: Risks, Clinical Associations, and Mechanisms

Asthma is a heterogeneous disease with many phenotypes, and age at disease onset is an important factor in separating the phenotypes. Most studies with asthma have been performed in patients being otherwise healthy. However, in real life, comorbid diseases are very common in adult patients. We review here the emerging comorbid conditions to asthma such as obesity, metabolic syndrome, diabetes mellitus type 2 (DM2), and cardiac and psychiatric diseases. Their role as risk factors for incident asthma and whether they affect clinical asthma are evaluated. Obesity, independently or as a part of metabolic syndrome, DM2, and depression are risk factors for incident asthma. In contrast, the effects of comorbidities on clinical asthma are less well-known and mostly studies are lacking. Cross-sectional studies in obese asthmatics suggest that they may have less well controlled asthma and worse lung function. However, no long-term clinical follow-up studies with these comorbidities and asthma were identified. These emerging comorbidities often occur in the same multimorbid adult patient and may have in common metabolic pathways and inflammatory or other alterations such as early life exposures, systemic inflammation, inflammasome, adipokines, hyperglycemia, hyperinsulinemia, lung mechanics, mitochondrial dysfunction, disturbed nitric oxide metabolism, and leukotrienes.

Increased asthma and adipose tissue inflammatory gene expression with obesity and Inuit migration to a western country

BACKGROUND

An overlap between obesity and asthma exists, and inflammatory cells in adipose tissue could drive the development of asthma. Comparison of adipose tissue gene expression among Inuit living in Greenland to those in Denmark provides an opportunity to assess how changes in adipose tissue inflammation can be modified by migration and diet.

OBJECTIVE

To examine mast cell and inflammatory markers in adipose tissue and the association with asthma.

METHODS

Two Inuit populations were recruited, one living in Greenland and another in Denmark. All underwent adipose subcutaneous biopsy, followed by clinical assessment of asthma, and measurement of AHR. Adipose tissue biopsies were homogenised, RNA extracted, and PCR was performed to determine the relative gene expression of mast cell (tryptase, chymase, CPA3) and inflammatory markers (IL-6, IL-1β, and CD163).

RESULTS

Of the 1059 Greenlandic Inuit participants, 556 were living in Greenland and 6.4% had asthma. Asthma was increased in Denmark (9%) compared to Greenland (3.6%, p < 0.0001) and associated with increased adipose tissue IL-6 gene expression and increased BMI. There was no association between asthma and adipose tissue mast cell gene expression. Pro-inflammatory gene expression (IL-6, IL-1β) was higher in those living in Denmark, and with increasing BMI and dietary changes. The anti-inflammatory (M2) macrophage marker, CD163, was higher in Greenland-dwelling Inuit (p < 0.01).

CONCLUSIONS

No association was found between gene expression of mast cell markers in adipose tissue and asthma. Among Greenlandic Inuit, adipose tissue inflammation is also increased in those who migrate to Denmark, possibly as a result of dietary changes.

Phenotypes, Risk Factors, and Mechanisms of Adult-Onset Asthma

Asthma is a heterogeneous disease with many phenotypes, and age at disease onset is an important factor in separating the phenotypes. Genetic factors, atopy, and early respiratory tract infections are well-recognized factors predisposing to childhood-onset asthma. Adult-onset asthma is more often associated with obesity, smoking, depression, or other life-style or environmental factors, even though genetic factors and respiratory tract infections may also play a role in adult-onset disease. Adult-onset asthma is characterized by absence of atopy and is often severe requiring treatment with high dose of inhaled and/or oral steroids. Variety of risk factors and nonatopic nature of adult-onset disease suggest that variety of mechanisms is involved in the disease pathogenesis and that these mechanisms differ from the pathobiology of childhood-onset asthma with prevailing Th2 airway inflammation. Recognition of the mechanisms and mediators that drive the adult-onset disease helps to develop novel strategies for the treatment. The aim of this review was to summarize the current knowledge on the pathogenesis of adult-onset asthma and to concentrate on the mechanisms and mediators involved in establishing adult-onset asthma in response to specific risk factors. We also discuss the involvement of these mechanisms in the currently recognized phenotypes of adult-onset asthma.

Inflammation, metabolic dysregulation, and pulmonary function among obese urban adolescents with asthma

RATIONALE

Insulin resistance and low high-density lipoprotein (HDL) are associated with pulmonary morbidity, including asthma, but the underlying mechanisms are not well elucidated.

OBJECTIVES

To investigate whether systemic inflammation underlies the association of metabolic abnormalities with pulmonary function among urban adolescents.

METHODS

Th-cell responses and monocyte subsets, and their association with serum homeostatic model assessment of insulin resistance (HOMA-IR) and HDL, and pulmonary function were quantified in 168 adolescents, including 42 obese subjects with asthma, 42 normal-weight subjects with asthma, 40 obese subjects without asthma, and 44 healthy control subjects. Th-cell responses (Th1 [CD4(+)IFNγ(+)] and Th2 [CD4(+)IL4(+)] cells) to stimulation with phytohemagglutinin, leptin, and dust mite, and classical (CD14(+)CD16(-)), resident (CD14(+)CD16(+)), and patrolling (CD14dimCD16(+)) monocytes, and their C-C chemokine receptor type-2 (CCR2) expression were quantified by flow cytometry.

MEASUREMENTS AND MAIN RESULTS

Th1/Th2 ratio to all three stimuli was higher in obese subjects with asthma than normal-weight subjects with asthma and directly correlated with HOMA-IR. Classical monocytes inversely associated with Th1/Th2 ratio to phytohemagglutinin (r = -0.43; P = 0.01) and directly with Asthma Control Test score (β = 1.09; P = 0.04), while patrolling monocytes correlated with Composite Asthma Severity Index score (β = 1.11; P = 0.04) only among obese subjects with asthma. HDL was inversely associated with patrolling monocytes and directly associated with CCR2 expression on resident monocytes. CCR2 expression on patrolling monocytes predicted residual volume (RV), RV/TLC ratio, and FRC, after adjusting for HDL, but not after adjusting for body mass index. Association of Th1/Th2 ratio with RV, FRC, and inspiratory capacity was attenuated after adjusting for HOMA-IR.

CONCLUSIONS

Th1 polarization and monocyte activation among obese subjects with asthma correlates with metabolic abnormalities. Association of monocyte activation with pulmonary function is mediated by body mass index, whereas that of Th1 polarization is mediated by insulin resistance.

Nutrition and respiratory health--feature review

Diet and nutrition may be important modifiable risk factors for the development, progression and management of obstructive lung diseases such as asthma and chronic obstructive pulmonary disease (COPD). This review examines the relationship between dietary patterns, nutrient intake and weight status in obstructive lung diseases, at different life stages, from in-utero influences through childhood and into adulthood. In vitro and animal studies suggest important roles for various nutrients, some of which are supported by epidemiological studies. However, few well-designed human intervention trials are available to definitively assess the efficacy of different approaches to nutritional management of respiratory diseases. Evidence for the impact of higher intakes of fruit and vegetables is amongst the strongest, yet other dietary nutrients and dietary patterns require evidence from human clinical studies before conclusions can be made about their effectiveness.

Defining severe asthma - an approach to find new therapies

Asthma is a chronic inflammatory disease that has reached epidemic proportions worldwide. It is treatable in the majority of patients, but there is no cure. Moreover, a proportion of patients suffer from severe, difficult-to-control disease with daily symptoms and high morbidity, making it imperative that we continue to improve our understanding of the underlying mechanisms of this disease. Severe asthma is a heterogeneous condition. A systematic approach to identify specific asthma phenotypes, including clinical characteristics and inflammatory processes, is the first step toward individualized, logical therapy. This review focuses on the need to characterize severe asthma phenotypes and on novel, targeted molecular treatment options currently under development.