Obesity and extent of emphysema depicted at CT

Obesity Paradox in Lung Diseases: What Explains It?

BACKGROUND

Obesity is a globally increasing health problem that impacts multiple organ systems and a potentially modifiable risk factor for many diseases. Obesity has a significant impact on lung function and is strongly linked to the pathophysiology that contributes to lung diseases. On the other hand, reports have emerged that obesity is associated with a better prognosis than for normal weight individuals in some lung diseases, including pneumonia, acute lung injury/acute respiratory distress syndrome, chronic obstructive pulmonary disease, and lung cancer. The lesser mortality and better prognosis in patients with obesity is known as obesity paradox. While obesity paradox is both recognized and disputed in epidemiological studies, recent research has suggested possible mechanisms.

SUMMARY

In this review, we attempted to explain and summarize these factors and mechanisms, including immune response, pulmonary fibrosis, lung function, microbiota, fat and muscle reserves, which are significantly altered by obesity and may contribute to the obesity paradox in lung diseases. We also discuss contrary literature that attributes the "obesity paradox" to confounding.

KEY MESSAGES

The review will illustrate the possible role of obesity in the prognosis or course of lung diseases, leading to a better understanding of the obesity paradox and provide hints for further basic and clinical research in lung diseases.

Contemporary perspectives in COPD: Patient burden, the role of gender and trajectories of multimorbidity

An individual's experience of COPD is determined by many factors in addition to the pathological features of chronic bronchitis and emphysema and the symptoms that derive directly from them. Multimorbidity is the norm rather than the exception, so most people with COPD are living with a range of other medical problems which can decrease overall quality of life. COPD is caused by the inhalation of noxious particles or gases, in particular tobacco smoke, but also by early life disadvantage impairing lung development and by occupations where inhaled exposures are common (e.g. industrial, farming and cleaning work). Wealthy people are therefore relatively protected from developing COPD and people who do develop the condition may have reduced resources to cope. COPD is also no longer a condition that predominantly affects men. The prevalence of COPD among women has equalled that of men since 2008 in many high-income countries, due to increased exposure to tobacco, and in low-income countries due to biomass fuels. COPD is one of the leading causes of death in women in the USA, and death rates attributed to COPD in women in some countries are predicted to overtake those of men in the next decade. Many factors contribute to this phenomenon, but in addition to socioeconomic and occupational factors, there is increasing evidence of a higher susceptibility of females to smoking and pollutants. Quality of life is also more significantly impaired in women. Although most medications (bronchodilators and inhaled corticosteroids) used to treat COPD demonstrate similar trends for exacerbation prevention and lung function improvement in men and women, this is an understudied area and clinical trials frequently have a preponderance of males. A better understanding of gender-based predictors of efficacy of all therapeutic interventions is crucial for comprehensive patient care. There is an urgent need to recognize the increasing burden of COPD in women and to facilitate global improvements in disease prevention and management in this specific population. Many individuals with COPD follow a trajectory of both lung function decline and also multimorbidity. Unfavourable lung function trajectories throughout life have implications for later development of other chronic diseases. An enhanced understanding of the temporal associations underlying the development of coexisting diseases is a crucial first step in unravelling potential common disease pathways. Lessons can be learned from exploring disease trajectories of other NCD as well as multimorbidity development. Further research will be essential to explain how early life risk factors commonly influence trajectories of COPD and other diseases, how different diseases develop in relation to each other in a temporal way and how this ultimately leads to different multimorbidity patterns in COPD. This review integrates new knowledge and ideas pertaining to three broad themes (i) the overall burden of disease in COPD, (ii) an unappreciated high burden in women and (iii) the contrast of COPD trajectories and different multimorbidity patterns with trajectories of other NCD. The underlying pathology of COPD is largely irreversible, but many factors noted in the review are potentially amenable to intervention. Health and social care systems need to ensure that effective treatment is accessible to all people with the condition. Preventive strategies and treatments that alter the course of disease are crucial, particularly for patients with COPD as one of many problems.

A comparative study of chest CT findings regarding the effects of regional dust exposure on patients with COPD living in urban areas and rural areas near cement plants

Background

The clinical and radiological presentation of chronic obstructive pulmonary disease (COPD) is heterogenous depending on the characterized sources of inflammation. This study aimed to evaluate COPD phenotypes associated with specific dust exposure.

Methods

This study was designed to compare the characteristics, clinical outcomes and radiological findings between two prospective COPD cohorts representing two distinguishing regions in the Republic of Korea; COPD in Dusty Area (CODA) and the Korean Obstructive Lung Disease (KOLD) cohort. A total of 733 participants (n = 186 for CODA, and n = 547 for KOLD) were included finally. A multivariate analysis to compare lung function and computed tomography (CT) measurements of both cohort studies after adjusting for age, sex, education, body mass index, smoking status, and pack-year, Charlson comorbidity index, and frequency of exacerbation were performed by entering the level of FEV1(%), biomass exposure and COPD medication into the model in stepwise.

Results

The mean wall area (MWA, %) became significantly lower in COPD patients in KOLD from urban and metropolitan area than those in CODA cohort from cement dust area (mean ± standard deviation [SD]; 70.2 ± 1.21% in CODA vs. 66.8 ± 0.88% in KOLD, p = 0.028) after including FEV1 in the model. COPD subjects in KOLD cohort had higher CT-emphysema index (EI, 6.07 ± 3.06 in CODA vs. 20.0 ± 2.21 in KOLD, p < 0.001, respectively). The difference in the EI (%) was consistently significant even after further adjustment of FEV1 (6.12 ± 2.88% in CODA vs. 17.3 ± 2.10% in KOLD, p = 0.002, respectively). However, there was no difference in the ratio of mean lung density (MLD) between the two cohorts (p = 0.077). Additional adjustment for biomass parameters and medication for COPD did not alter the statistical significance after entering into the analysis with COPD medication.

Conclusions

Higher MWA and lower EI were observed in COPD patients from the region with dust exposure. These results suggest that the imaging phenotype of COPD is influenced by specific environmental exposure.

Impact of experimental obesity on diaphragm structure, function, and bioenergetics

Obesity is associated with bioenergetic dysfunction of peripheral muscles; however, little is known regarding the impact of obesity on the diaphragm. We hypothesized that obesity would be associated with diaphragm dysfunction attributable to mitochondrial oxygen consumption and structural and ultrastructural changes. Wistar rat litters were culled to 3 pups to induce early postnatal overfeeding and consequent obesity. Control animals were obtained from unculled litters. From postnatal day 150, diaphragm ultrasound, computed tomography, high-resolution respirometry, immunohistochemical, biomolecular, and ultrastructural histological analyses were performed. The diaphragms of obese animals, compared with those of controls, presented changes in morphology as increased thickening fraction, diaphragm excursion, and diaphragm dome height, as well as increased mitochondrial respiratory capacity coupled to ATP synthesis and maximal respiratory capacity. Fatty acid synthase gene expression was also higher in obese animals, suggesting a source of energy for the respiratory chain. Myosin heavy chain-IIA was increased, indicating shift from glycolytic toward oxidative muscle fiber profile. Diaphragm tissue also exhibited ultrastructural changes, such as compact, round, and swollen mitochondria with fainter cristae and more lysosomal bodies. Dynamin-1 expression in the diaphragm was reduced in obese rats, suggesting decreased mitochondrial fission. Furthermore, gene expressions of peroxisome γ proliferator-activated receptor coactivator-1α and superoxide dismutase-2 were lower in obese animals than in controls, which may indicate a predisposition to oxidative injury. In conclusion, in the obesity model used herein, muscle fiber phenotype was altered in a manner likely associated with increased mitochondrial respiratory capability, suggesting respiratory adaptation to increased metabolic demand.NEW & NOTEWORTHY Obesity has been associated with peripheral muscle dysfunction; however, little is known about its impact on the diaphragm. In the current study, we found high oxygen consumption in diaphragm tissue and changes in muscle fiber phenotypes toward a more oxidative profile in experimental obesity.

Obesity and Morbidity Risk in the U.S. Veteran

The obesity epidemic in the United States has been well documented and serves as the basis for a number of health interventions across the nation. However, those who have served in the U.S. military (Veteran population) suffer from obesity in higher numbers and have an overall disproportionate poorer health status when compared to the health of the older non-Veteran population in the U.S. which may further compound their overall health risk. This study examined both the commonalities and the differences in obesity rates and the associated co-morbidities among the U.S. Veteran population, utilizing data from the 2018 Behavioral Risk Factor Surveillance System (BRFSS). These data are considered by the Centers for Disease Control and Prevention (CDC) to be the nation’s best source for health-related survey data, and the 2018 version includes 437,467 observations. Study findings show not only a significantly higher risk of obesity in the U.S. Veteran population, but also a significantly higher level (higher odds ratio) of the associated co-morbidities when compared to non-Veterans, including coronary heart disease (CHD) or angina (odds ratio (OR) = 2.63); stroke (OR = 1.86); skin cancer (OR = 2.18); other cancers (OR = 1.73); chronic obstructive pulmonary disease (COPD) (OR = 1.52), emphysema, or chronic bronchitis; arthritis (OR = 1.52), rheumatoid arthritis, gout, lupus, or fibromyalgia; depressive disorders (OR = 0.84), and diabetes (OR = 1.61) at the 0.95 confidence interval level.

Investigation of the Obesity Paradox in Chronic Obstructive Pulmonary Disease, According to Smoking Status, in the United States

An obesity paradox in chronic obstructive pulmonary disease (COPD), whereby overweight/obese individuals have improved survival, has been well-described. These studies have generally included smokers. It is unknown whether the paradox exists in individuals with COPD arising from factors other than smoking. Nonsmoking COPD is understudied yet represents some 25%-45% of the disease worldwide. To determine whether the obesity paradox differs between ever- and never-smokers with COPD, 1,723 adult participants with this condition were examined from 2 iterations of the National Health and Nutrition Examination Survey (1988-1994, 2007-2010), with mortality outcomes followed through December 2011. Using Cox proportional hazards models, adjusted for sociodemographic factors, lung function, and survey cycle, ever/never-smoking was found to modify the association between body mass index and hazard of death. Compared with normal-weight participants, overweight/obese participants had lower hazard of death among ever-smokers (for overweight, adjusted hazard ratio (aHR) = 0.56, 95% confidence interval (CI): 0.43, 0.74; for obesity, aHR = 0.66, 95% CI: 0.48, 0.92), but never-smokers did not (overweight, aHR = 1.41, 95% CI: 0.66, 3.03; obesity, aHR = 1.29, 95% CI: 0.48, 3.48). An obesity paradox appeared to be absent among never-smokers with COPD. This, to our knowledge, novel finding might be explained by pathophysiological differences between smoking-related and nonsmoking COPD or by smoking-associated methodological biases.

Using a spatial point process framework to characterize lung computed tomography scans

Pulmonary emphysema is a destructive disease of the lungs that is currently diagnosed via visual assessment of lung Computed Tomography (CT) scans by a radiologist. Visual assessment can have poor inter-rater reliability, is time consuming, and requires access to trained assessors. Quantitative methods that reliably summarize the biologically relevant characteristics of an image are needed to improve the way lung diseases are characterized. The goal of this work was to show how spatial point process models can be used to create a set of radiologically derived quantitative lung biomarkers of emphysema. We formalized a general framework for applying spatial point processes to lung CT scans, and developed a Shot Noise Cox Process to quantify how radiologically based emphysematous tissue clusters into larger structures. Bayesian estimation of model parameters was done using spatial Birth-Death MCMC (BD-MCMC). In simulations, we showed the BD-MCMC estimation algorithm is able to accurately recover model parameters. In an application to real lung CT scans from the COPDGene cohort, we showed variability in the clustering characteristics of emphysematous tissue across disease subtypes that were based on visual assessments of the CT scans.

Dietary ω-6 polyunsaturated fatty acid arachidonic acid increases inflammation, but inhibits ECM protein expression in COPD

Background

The obesity paradox in COPD describes protective effects of obesity on lung pathology and inflammation. However, the underlying relationships between obesity, diet and disease outcomes in COPD are not fully understood. In this study we measured the response to dietary fatty acids upon markers of inflammation and remodelling in human lung cells from people with and without COPD.

Methods

Pulmonary fibroblasts were challenged with ω-3 polyunsaturated fatty acids (PUFAs), ω-6 PUFAs, saturated fatty acids (SFAs) or the obesity-associated cytokine TNFα. After 48–72 h release of the pro-inflammatory cytokines interleukin (IL)-6 and CXCL8 was measured using ELISA and mRNA expression and deposition of the extracellular matrix (ECM) proteins fibronectin, type I collagen, tenascin and perlecan were measured using qPCR or ECM ELISA, respectively.

Results

Challenge with the ω-6 PUFA arachidonic acid (AA), but not ω-3 PUFAs or SFAs, resulted in increased IL-6 and CXCL8 release from fibroblasts, however IL-6 and CXCL8 release was reduced in COPD (n = 19) compared to non-COPD (n = 36). AA-induced cytokine release was partially mediated by downstream mediators of cyclooxygenase (COX)-2 in both COPD and non-COPD. In comparison, TNFα-induced IL-6 and CXCL8 release was similar in COPD and non-COPD, indicating a specific interaction of AA in COPD. In patients with or without COPD, regression analysis revealed no relationship between BMI and cytokine release. In addition, AA, but not SFAs or ω-3 PUFAs reduced the basal deposition of fibronectin, type I collagen, tenascin and perlecan into the ECM in COPD fibroblasts. In non-COPD fibroblasts, AA-challenge decreased basal deposition of type I collagen and perlecan, but not fibronectin and tenascin.

Conclusions

This study shows that AA has disease-specific effects on inflammation and ECM protein deposition. The impaired response to AA in COPD might in part explain why obesity appears to have less detrimental effects in COPD, compared to other lung diseases.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0919-4) contains supplementary material, which is available to authorized users.

What do polymorphisms tell us about the mechanisms of COPD?

COPD (chronic obstructive pulmonary disease) is characterized by irreversible lung airflow obstruction. Cigarette smoke is the major risk factor for COPD development. However, only a minority number of smokers develop COPD, and there are substantial variations in lung function among smokers, suggesting that genetic determinants in COPD susceptibility. During the past decade, genome-wide association studies and exome sequencing have been instrumental to identify the genetic determinants of complex traits, including COPD. Focused studies have revealed mechanisms by which genetic variants contribute to COPD and have led to novel insights in COPD pathogenesis. Through functional investigations of causal variants in COPD, from the proteinase-antiproteinase theory to emerging roles of developmental pathways (such as Hedgehog and Wnt pathways) in COPD, we have greatly expanded our understanding on this complex pulmonary disease. In this review, we critically review functional investigations on roles of genetic polymorphisms in COPD, and discuss future challenges and opportunities in discovering novel mechanisms of functional variants.

Urinary desmosine is associated with emphysema severity and frequent exacerbation in patients with COPD

BACKGROUND AND OBJECTIVE

Matrix degradation is a key feature of chronic obstructive pulmonary disease (COPD). Desmosine and isodesmosine (desmosines) are excreted in urine following matrix degradation. The main purpose of this study was to investigate the association between computed tomography (CT) emphysema indices and urinary desmosines in patients with COPD.

METHODS

A total of 152 subjects were selected from the Korean Obstructive Lung Disease cohort. Their urine samples were assayed for desmosines using liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. The cohort was divided into emphysema-dominant (n = 80) and non-emphysema dominant- (n = 72) groups according to the CT emphysema index.

RESULTS

The level of urinary desmosines was significantly higher in the emphysema-dominant group. Significant differences were also observed between the two groups for body mass index and lung function. Multivariate analysis indicated that a high level of urinary desmosines was a significant independent predictor of emphysema (relative risk: 2.6; 95% CI: 1.11-6.09; P = 0.028). The percentage of frequent exacerbators was significantly higher in the high urinary desmosine group in the first year of follow-up (P = 0.041). The mean number of exacerbations was higher in the high urinary desmosine group, although this difference was not statistically significant (P = 0.067). The changes in emphysema index did not differ between the two urinary desmosine groups over 3 years of follow-up.

CONCLUSION

This study indicates that the level of urinary desmosines measured by LC-MS/MS methods is associated with the CT emphysema index. Urinary desmosine can be a useful predictor in identifying frequent exacerbators.

Differences in chronic obstructive pulmonary disease phenotypes between non-smokers and smokers

INTRODUCTION AND OBJECTIVES

Although tobacco smoking is a major risk factor for chronic obstructive pulmonary disease (COPD), more than one-fourth of COPD patients are non-smokers. In this cross-sectional study, the differences in COPD phenotypes between non-smokers and smokers in male subjects were investigated and were focused on structural lung changes using a quantitative assessment of computed tomography (CT) images.

METHODS

They divided male participants with COPD, from a Korean cohort near a cement plant, into non-smokers and smokers by a cutoff of a 5 pack-year smoking history. Clinical characteristics, including age, body mass index (BMI), spirometry results, history of biomass smoke exposure, and CT measurements, were compared between the two groups. Emphysema index (EI) and mean wall area percentage (MWA %) were used to evaluate the structural lung changes on volumetric CT scans.

RESULTS

The non-smoker group (n = 49) had younger patients and had a greater BMI than the smoker group (n = 113) (P < .05). Spirometry results, including post-bronchodilator forced expiratory volume in 1 s, were comparable between the two groups. More smokers had emphysema than non-smokers (EI 10.0 vs. 6.5, P < .001), but after accounting the potential confounders in model analysis, the difference was borderline significance (P = .051). In the subgroup of biomass smoke-exposed subjects, MWA% was significantly greater in smokers than in non-smokers (MWA 69.1 vs. 65.3, P = .03), while EI was not statistically different (EI 7.1 vs. 10.4, P = .52).

CONCLUSIONS

Non-smoker males with COPD were younger and had a greater BMI than the smokers. Tobacco smoke exposure seemed to be associated with an emphysema-predominant phenotype, while biomass smoke exposure exhibited a significant interaction with tobacco smoking in an airway-predominant phenotype.

Clinical Characterization and Treatment Patterns for the Frequent Exacerbator Phenotype in Chronic Obstructive Pulmonary Disease with Severe or Very Severe Airflow Limitation

Chronic obstructive pulmonary disease (COPD) patients experiencing several episodes of acute clinical derangement suffer from increased morbidity, mortality, and accelerated decline in lung function. Nevertheless, the relationship between co-morbidity profile and exacerbation rates in the frequent exacerbator phenotype is poorly characterized, and evidence-based management guidelines are lacking. We sought to evaluate the co-morbidity profile and treatment patterns of "frequent exacerbators" with severe or very severe airflow limitation. We conducted a cross-sectional, multicenter study in 50 Italian hospitals. Pulmonologists abstracted clinical information from medical charts of 743 COPD frequent exacerbators. We evaluated the exacerbation risk and center-related variations in diagnostic testing. One-third of patients (n = 210) underwent a bronchodilator response test, and 163 (22%) received a computerized tomography (CT) scan; 35 had a partial response to bronchodilators, while 119 had a diagnosis of emphysema; 584 (79%) lacked sufficient diagnostic testing for classification. Only 17% of patients did not have any coexistent disease. Cardiovascular conditions were the most frequent co-morbidities. A history of heart failure [odds ratio (OR): 1.89; 95% confidence interval (CI) 1.48-2.3] and affective disorders (OR: 1.66; 95% CI 1.24-2.1) was associated with the frequency of exacerbations. Center membership was strongly associated with exacerbation risk, independent of casemix (variance partition coefficient = 29.6%). Examining the regional variation in health outcomes and health care behavior may help identify the best practices, especially when evidence-based recommendations are lacking and uncertainties surround clinical decision-making.

Sex differences of COPD phenotypes in nonsmoking patients

BACKGROUND

There is growing evidence about sex-related phenotypes of COPD. However, the sex differences in COPD mainly result from smokers. This study evaluated the sex differences in nonsmoking patients with COPD, focusing on structural changes in the lungs in airway diseases and emphysema.

METHODS

Ninety-seven nonsmoking patients, defined as having <1 pack-year of lifetime cigarette smoking, diagnosed with COPD were selected from a Korean COPD cohort. Emphysema extent and mean wall area percentage (WA%) on computed tomography were compared between the male and female groups.

RESULTS

The 97 patients with COPD included 62 females and 35 males. Emphysema index was significantly lower (3.5±4.2 vs 6.2±5.7, P<0.01) and mean WA% on computed tomography was significantly higher (71.8%±5% vs 69.4%±5%, P<0.01) in females than in males, after adjusting for age, body mass index, history of biomass exposure, and postbronchodilator forced expiratory volume in 1 second (% of predicted).

CONCLUSION

WA% was higher and emphysema extent was lower in nonsmoking females with COPD than in nonsmoking males with COPD. These findings suggest that males may be predisposed to an emphysema phenotype and females may be predisposed to an airway phenotype of COPD.

Emphysema prevalence related air pollution caused by a cement plant

Background

To identify adverse pulmonary health effects due to air pollution derived from a cement plant in Korea. The emphysema prevalence in residents around a cement plant was compared to that in the group who live far away from the plant by chest films (PA and lateral view) and high-resolution computed tomography (HRCT) lung images.

Methods

From June to August in 2013 and from August to November in 2014, chest films and HRCT scan were conducted on residents over the age of 40 who lived around a cement plant. The residents were divided into two groups; a “more exposed group (MEG)” which consisted of 1,046 people who lived within a 1 km radius and a “less exposed group (LEG)” which consisted of 317 people who lived more than 5 km away from the same plant. We compared the emphysema prevalence and estimated the OR of this between the MEG and the LEG by using a chi-square and logistic regression on chest films and HRCT.

Results

The emphysema prevalence was 9.1 % in the LEG, 14.3 % in the MEG on chest films and 11.4 %, 17.8 % on the HRCT, respectively. The OR of the emphysema prevalence in MEG was 2.92 (95 % CI 1.77-4.83) on the chest films, 2.56 (95 % CI 1.64–3.99) on the HRCT after sex, age, body mass index (BMI), smoking history, residency period and firewood used history were adjusted. The OR in the less than 29 pack-years smoking history was 1.66 (95 % CI 0.92–3.06) and in the more than 30 pack-years was 3.05 (95 % CI 1.68–5.52) on the chest films, and was 1.68 (95 % CI 0.98–2.90), 2.93 (95 % CI 1.72–4.98) on the HRCT, respectively.

Conclusion

The emphysema prevalence seems to be affected by the level of exposure to air pollution derived from the cement plant as well as sex, age, BMI, and smoking history in this study. Moreover, the OR of the case of the more exposed to the air pollution was similar to that of the case in smoking.

Gender and asthma-chronic obstructive pulmonary disease overlap syndrome

OBJECTIVE

To assess relationships between obstructive lung diseases, respiratory symptoms, and comorbidities by gender.

METHODS

Data from 12 594 adult respondents to the 2012 South Carolina Behavioral Risk Factor Surveillance System telephone survey were used. Five categories of chronic obstructive airway disease (OAD) were defined: former asthma only, current asthma only, chronic obstructive pulmonary disease (COPD) only, asthma-COPD overlap syndrome (ACOS), and none. Associations of these categories with respiratory symptoms (frequent productive cough, shortness of breath, and impaired physical activities due to breathing problems), overall health, and comorbidities were assessed using multivariable logistic regression for men and women.

RESULTS

Overall, 16.2% of men and 18.7% of women reported a physician diagnosis of COPD and/or asthma. Former asthma only was higher among men than women (4.9% vs. 3.2%, t-test p = 0.008). Current asthma only was more prevalent among women than men (7.2% vs. 4.7%, p < 0.001), as was ACOS (4.0% vs. 2.2%, p < 0.001). Having COPD only did not differ between women (4.3%) and men (4.4%). Adults with ACOS were most likely to report the 3 respiratory symptoms. COPD only and ACOS were associated with higher likelihoods of poor health and most comorbidities for men and women. Current asthma only was also associated with these outcomes among women, but not among men.

CONCLUSIONS

In this large population-based sample, women were more likely than men to report ACOS and current asthma, but not COPD alone. Gender differences were evident between the OAD groups in sociodemographic characteristics, respiratory symptoms, and comorbidities, as well as overall health.