Investigating Associations of Omega-3 Fatty Acids, Lung Function Decline, and Airway Obstruction

Mendelian randomisation studies for causal inference in chronic obstructive pulmonary disease: A narrative review

BACKGROUND AND OBJECTIVE

Most non-randomised controlled trials are unable to establish clear causal relationships in chronic obstructive pulmonary disease (COPD) due to the presence of confounding factors. This review summarises the evidence that the Mendelian randomisation method can be a powerful tool for performing causal inferences in COPD.

METHODS

A non-systematic search of English-language scientific literature was performed on PubMed using the following keywords: 'Mendelian randomisation', 'COPD', 'lung function', and 'GWAS'. No date restrictions were applied. The types of articles selected included randomised controlled trials, cohort studies, observational studies, and reviews.

RESULTS

Mendelian randomisation is becoming an increasingly popular method for identifying the risk factors of COPD. Recent Mendelian randomisation studies have revealed some risk factors for COPD, such as club cell secretory protein-16, impaired kidney function, air pollutants, asthma, and depression. In addition, Mendelian randomisation results suggest that genetically predicted factors such as PM2.5, inflammatory cytokines, growth differentiation factor 15, docosahexaenoic acid, and testosterone may have causal relationships with lung function.

CONCLUSION

Mendelian randomisation is a robust method for performing causal inferences in COPD research as it reduces the impact of confounding factors.

Chemical composition analysis of the proteins of leech extract with anti-pulmonary fibrosis and their effects on metabolomics based on chromatography-mass spectrometry

Idiopathic pulmonary fibrosis is a high-mortality chronic lung disease, and currently existing medications have limited therapeutic efficacy with noticeable adverse effects, urgently necessitating the exploration of more effective and safer treatment options. Our preliminary studies have demonstrated that the leech extract group with molecular weight greater than 10 kDa (>10 kDa group) exhibited superior anti-idiopathic pulmonary fibrosis efficacy. To trace the active components of > 10 kDa group, it was separated by gel electrophoresis and analyzed by Nano LC-MS/MS. To further analyze the effects of these active components on the regulation of metabolic pathways in fibrotic lung tissue, the metabolites of lung tissue were analyzed by UPLC/MS after administration of > 10 kDa group in bleomycin-induced pulmonary fibrosis (BML-induced PF) mice for 28 days at a 0.179 mg/g per day. A total of 17 proteins were identified in > 10 kDa group and 46 endogenous metabolites were identified in lung tissue, among which 18 significantly differential metabolites were screened as potential metabolomics biomarkers. Metabolic pathway analysis demonstrated that these identified differential metabolites mainly involved biosynthesis of unsaturated fatty acids, phenylalanine-tyrosine and tryptophan biosynthesis and tryptophan metabolism signaling pathway, indicating that the active components of > 10 kDa group mainly regulated the metabolic disorders of lung tissue in BLM-induced mice by up-regulating the biosynthesis of unsaturated fatty acids, down-regulating phenylalanine-tyrosine and tryptophan biosynthesis, and adjusting tryptophan metabolism signaling pathway.

The role of nutritional factors in exercise-induced bronchoconstriction: a narrative review

Exercise-induced bronchoconstriction (EIB) describes an acute narrowing of the airways that develops following vigorous physical activity. Clinical responses to current asthma therapy, such as leukotriene antagonists and corticosteroids, are heterogeneous, even with optimal treatment. Epidemiological studies indicate an increasing use of complementary and alternative medicine therapy in asthma patients due to the lack of efficacy of conventional treatment, concerns about potentially harmful side effects of pharmacological treatment, cost barriers to asthma care, and the accessibility of complementary and alternative medicine therapy. Plausible physiological mechanisms now exist for many nutrients as potential modifiers of EIB severity, primarily because of their role in inflammatory processes, airway smooth muscle function, and modulation of lung microvascular volume and pressure. Dietary supplementation as a treatment for EIB has generally shown evidence of significant yet incomplete inhibition of EIB with low-salt diets, omega-3 fatty acids, and vitamin C when supplemented for up to 3 weeks. However, larger, randomized, placebo-controlled, double-blinded trials are needed to clarify the effectiveness of nutritional intervention in individuals with EIB. Additionally, many studies have focused on nonathletes with EIB, and therefore, more studies are required to evaluate the efficacy of nutritional intervention on EIB in elite athletes. In conclusion, if dietary supplementation or restriction is prescribed, it should be seen as an option to lessen the reliance on pharmaceutical interventions and not as an alternative to established pharmacotherapies.

Insights into associations between Life's essential 8 and lung function from NHANES data

The Life's Essential 8 (LE8) is a novel indicator of cardiovascular health proposed by the American Heart Association. While numerous studies have demonstrated its guiding value in chronic diseases, research on its role in lung function remains limited. This study utilized data from the National Health and Nutrition Examination Surveys (NHANES 2007-2012), which included comprehensive measurements of lung function, diet, physical activity, nicotine exposure, sleep patterns, body mass index (BMI), blood glucose, blood pressure, blood lipids, and relevant covariates. We calculated lung function Z-score and LE8 scores, employing multiple linear regression, multivariable logistic regression, and restricted cubic spline models to evaluate their correlations. In this study of 10,400 participants (mean age 44 years; 48.75% male), participants were classified into threeforcedexpiratory volume in one second (FEV1) Z-score groups: Z1 (normal lung function, n = 9,600), Z2 (mild impairment, n = 618), and Z3 (moderate to severe impairment, n = 182). Significant differences in demographic characteristics and health parameters were observed among the groups. Notably, variations in the Healthy Eating Index 2015 (HEI-2015), physical activity, nicotine exposure, and sleep patterns were identified within the LE8 health behavior domain. Higher LE8 scores were found to be positively associated with lung function, even after adjusting for demographic and health factors. Further analysis revealed positive correlations between lung function and favorable dietary habits, higher physical activity levels, reduced nicotine exposure, and improved sleep quality. Conversely, BMI, blood lipids, blood glucose, and blood pressure exhibited variable effects. Subgroup and sensitivity analyses consistently supported findings, confirming a positive correlation between LE8 and lung function. Our study highlights significant associations between LE8 scores and lung function, demonstrating that higher LE8 scores, which reflect better cardiovascular health behaviors, are positively correlated with improved lung function.

Nutrition, Lifestyle, and Environmental Factors in Lung Homeostasis and Respiratory Health

The lungs play a vital role in maintaining homeostasis by facilitating gas exchange and serving as a structural and immune barrier. External factors, including nutrition, lifestyle, and environmental exposures, profoundly influence normal lung function and contribute to the development, progression, and prognosis of various respiratory diseases. Deficiencies in key micronutrients, such as vitamins A, D, and C, as well as omega-3 fatty acids, can impair the integrity of the epithelial lining, compromising the lungs' defense mechanisms and increasing susceptibility to injury and disease. Obesity and physical inactivity further disrupt respiratory function by inducing structural changes in the chest wall and promoting a pro-inflammatory state. Environmental pollutants further worsen oxidative damage and activate inflammatory pathways. Addressing these modifiable factors through interventions such as dietary optimization, physical activity programs, and strategies to reduce environmental exposure offers promising avenues for preserving lung function and preventing disease progression. This review examines the molecular pathways through which nutrition, lifestyle, and environmental influences impact lung homeostasis.

Food for thought: optimal diet in patients with asthma and chronic obstructive pulmonary disease

PURPOSE OF REVIEW

Nutritional intake plays a major role in the management of lung health. This review provides the latest perspective on how dietary choices can modulate lung function in patients with chronic obstructive pulmonary disease (COPD) and asthma.

RECENT FINDINGS

The pathophysiology of COPD and asthma is driven by oxidative stress and inflammation of the airways, which is exacerbated by modifiable risk factors such as cigarette smoking and diet. Various foods can influence patient symptoms; highly processed foods increase the production of reactive oxygen species that augment airway inflammation, whereas foods rich in antioxidants, fiber and protein combat oxidative stress and muscle wastage. Patients with COPD or asthma are at increased risk of developing metabolic comorbidities, including cachexia and obesity that complicate disease phenotypes, leading to greater symptom severity. While clinical findings suggest a role for antioxidant and macronutrient support of lung function, comprehensive translational and clinical studies are necessary to better understand the mechanisms underlying nutrient interaction and lung structure-function.

SUMMARY

Understanding the nutritional requirements that protect lung health and support weight management in COPD and asthma is imperative to providing personalized dietary recommendations and reducing patient morbidity.

Omega-3 polyunsaturated fatty acids and pulmonary arterial hypertension: Insights and perspectives

Pulmonary arterial hypertension (PAH) is a rare and progressive disorder that affects the pulmonary vasculature. Although recent developments in pharmacotherapy have extended the life expectancy of PAH patients, their 5-year survival remains unacceptably low, underscoring the need for multitarget and more comprehensive approaches to managing the disease. This should incorporate not only medical, but also lifestyle interventions, including dietary changes and the use of nutraceutical support. Among these strategies, n-3 polyunsaturated fatty acids (n-3 PUFAs) are emerging as promising agents able to counteract the inflammatory component of PAH. In this narrative review, we aim at analysing the preclinical evidence for the impact of n-3 PUFAs on the pathogenesis and the course of PAH. Although evidence for the role of n-3 PUFAs deficiencies in the development and progression of PAH in humans is limited, preclinical studies suggest that these dietary components may influence several aspects of the pathobiology of PAH. Further clinical research should test the efficacy of n-3 PUFAs on top of approved clinical management. These studies will provide evidence on whether n-3 PUFAs can genuinely serve as a valuable tool to enhance the efficacy of pharmacotherapy in the treatment of PAH.

Inverted U-Shaped relationship Between Systemic Immune-Inflammation Index and Pulmonary Function: A Large Population-Based Study in US Adults

Background

Systemic immune-inflammation index (SII) is a novel comprehensive inflammatory marker. Inflammation is associated with impaired lung function. We aimed to explore the possible relationship between SII and lung function to examine the potential of SII in predicting lung function decline.

Methods

A cross-sectional survey was conducted using the data of the NHANES from 2007 to 2012. Multiple linear regression models were used to analyze the linear relationship between SII and pulmonary functions. Sensitivity analyses, subgroup analyses, and interaction tests were used to examine the robustness of this relationship across populations. Fitted smooth curves and threshold effect analysis were used to describe the nonlinear relationships.

Results

A total of 10,125 patients were included in this study. After adjusting for all covariates, multiple linear regression model analysis showed that high Log2-SII level was significantly associated with decreased FVC(β, -23.4061; 95% CI, -42.2805- -4.5317), FEV1(β, -46.7730; 95% CI, -63.3371- -30.2089), FEV1%(β, -0.7923; 95% CI, -1.1635- -0.4211), FEV1/FVC(β, -0.6366; 95% CI, -0.8328- -0.4404) and PEF(β, -121.4468; 95% CI,-164.1939- -78.6998). The negative correlation between Log2-SII and pulmonary function indexes remained stable in trend test and stratified analysis. Inverted U-shaped relationships between Log2-SII and FVC, FEV1, FEV1%, and PEF were observed, while a negative linear correlation existed between FEV1/FVC and Log2-SII. The cutoff values of the nonlinear relationship between Log2-SII and FVC, FEV1, FEV1%, PEF were 8.3736, 8.0688, 8.3745, and 8.5255, respectively. When SII exceeded the critical value, the lung function decreased significantly.

Conclusion

This study found a close correlation between SII and pulmonary function indicators. This study investigated the SII threshold when lung functions began to decline in the overall population. SII may become a promising serological indicator for predicting lung function decline. However, prospective studies were needed further to establish the causal relationship between these two factors.

Genetically Determined Circulating Saturated and Unsaturated Fatty Acids and the Occurrence and Exacerbation of Chronic Obstructive Pulmonary Disease-A Two-Sample Mendelian Randomization Study

Research on dietary fatty acids (FAs) and lung health has reported skeptical findings. This study aims to examine the causal relationship between circulating FAs and Chronic Obstructive Pulmonary Disease (COPD) onset and exacerbation, using a two-sample Mendelian Randomization (MR) analysis. Strong and independent genetic variants of FAs were obtained from the UK Biobank of European ancestry. The exposure traits included saturated FA (SFA), poly- and mono-unsaturated FA (PUFA and MUFA), omega-3 and omega-6 PUFA, docosahexaenoic acid (DHA), and linoleic acid (LA), all expressed as total FA (TFA) percentages. Summary statistics for COPD outcomes were obtained from the FinnGen consortium including COPD, COPD hospitalization, COPD/asthma-related infections, COPD-related respiratory insufficiency, and COPD/asthma/interstitial lung disease (ILD)-related pneumonia. The inverse-variance weighted (IVW) was the primary MR approach. MR-Egger regression and MR-PRESSO were utilized to evaluate heterogeneity and pleiotropy. MR-PRESSO tests suggested no obvious horizontal pleiotropy. MR results by the IVW approach indicated that the genetically high SFA/TFA levels were associated with an increased risk of COPD/asthma/ILD-related pneumonia (OR: 1.275, 95%CI: 1.103-1.474, p for FDR = 0.002). No significant relationship was observed between other types of FAs and COPD outcomes. Our MR analysis suggests that there is weak evidence that the genetically predicted high SFA/TFA was associated with an increased risk of pneumonia.

Associations of Plasma Omega-3 Fatty Acids With Progression and Survival in Pulmonary Fibrosis

BACKGROUND

Preclinical experiments suggest protective effects of omega-3 fatty acids and their metabolites in lung injury and fibrosis. Whether higher intake of omega-3 fatty acids is associated with disease progression and survival in humans with pulmonary fibrosis is unknown.

RESEARCH QUESTION

What are the associations of plasma omega-3 fatty acid levels (a validated marker of omega-3 nutritional intake) with disease progression and transplant-free survival in pulmonary fibrosis?

STUDY DESIGN AND METHODS

Omega-3 fatty acid levels were measured from plasma samples of patients with clinically diagnosed pulmonary fibrosis from the Pulmonary Fibrosis Foundation Patient Registry (n = 150), University of Virginia (n = 58), and University of Chicago (n = 101) cohorts. The N-3 index (docosahexaenoic acid + eicosapentaenoic acid) was the primary exposure variable of interest. Linear-mixed effects models with random intercept and slope were used to examine associations of plasma omega-3 fatty acid levels with changes in FVC and diffusing capacity for carbon monoxide over a period of 12 months. Cox proportional hazards models were used to examine transplant-free survival. Stratified analyses by telomere length were performed in the University of Chicago cohort.

RESULTS

Most of the cohort were patients with idiopathic pulmonary fibrosis (88%) and male patients (74%). One-unit increment in log-transformed N-3 index plasma level was associated with a change in diffusing capacity for carbon monoxide of 1.43 mL/min/mm Hg per 12 months (95% CI, 0.46-2.41) and a hazard ratio for transplant-free survival of 0.44 (95% CI, 0.24-0.83). Cardiovascular disease history, smoking, and antifibrotic usage did not significantly modify associations. Omega-3 fatty acid levels were not significantly associated with changes in FVC. Higher eicosapentaenoic acid plasma levels were associated with longer transplant-free survival among University of Chicago participants with shorter telomere length (P value for interaction = .02).

INTERPRETATION

Further research is needed to investigate underlying biological mechanisms and whether omega-3 fatty acids are a potential disease-modifying therapy.

Clinical data mining: challenges, opportunities, and recommendations for translational applications

Clinical data mining of predictive models offers significant advantages for re-evaluating and leveraging large amounts of complex clinical real-world data and experimental comparison data for tasks such as risk stratification, diagnosis, classification, and survival prediction. However, its translational application is still limited. One challenge is that the proposed clinical requirements and data mining are not synchronized. Additionally, the exotic predictions of data mining are difficult to apply directly in local medical institutions. Hence, it is necessary to incisively review the translational application of clinical data mining, providing an analytical workflow for developing and validating prediction models to ensure the scientific validity of analytic workflows in response to clinical questions. This review systematically revisits the purpose, process, and principles of clinical data mining and discusses the key causes contributing to the detachment from practice and the misuse of model verification in developing predictive models for research. Based on this, we propose a niche-targeting framework of four principles: Clinical Contextual, Subgroup-Oriented, Confounder- and False Positive-Controlled (CSCF), to provide guidance for clinical data mining prior to the model's development in clinical settings. Eventually, it is hoped that this review can help guide future research and develop personalized predictive models to achieve the goal of discovering subgroups with varied remedial benefits or risks and ensuring that precision medicine can deliver its full potential.

Inhaled toxicants and pulmonary lipid metabolism: biological consequences and therapeutic interventions

Inhaled toxicants drive the onset of and exacerbate preexisting chronic pulmonary diseases, however, the biological mechanisms by which this occurs are largely unknown. Exposure to inhaled toxicants, both environmental and occupational, drives pulmonary inflammation and injury. Upon activation of the inflammatory response, polyunsaturated fatty acids (PUFAs) are metabolized into predominately proinflammatory lipid mediators termed eicosanoids which recruit immune cells to the site of injury, perpetuating inflammation to clear the exposed toxicants. Following inflammation, lipid mediator class-switching occurs, a process that leads to increased metabolism of hydroxylated derivates of PUFAs. These mediators, which include mono-hydroxylated PUFA derivatives and specialized proresolving lipid mediators, initiate an active process of inflammation resolution by inhibiting the inflammatory response and activating resolution pathways to return the tissue to homeostasis. Exposure to inhaled toxicants leads to alterations in the synthesis of these proinflammatory and proresolving lipid mediator pathways, resulting in greater pulmonary inflammation and injury, and increasing the risk for the onset of chronic lung diseases. Recent studies have begun utilizing supplementation of PUFAs and their metabolites as potential therapeutics for toxicant-induced pulmonary inflammation and injury. Here we will review the current understanding of the lipid mediators in pulmonary inflammation and resolution as well as the impact of dietary fatty acid supplementation on lipid mediator-driven inflammation following air pollution exposure.