Does adiponectin play a role in pulmonary emphysema?

Chronic hypoxaemia and gender status modulate adiponectin plasmatic level and its multimer proportion in severe COPD patients: new endotypic presentation?

BACKGROUND

Disease progression in COPD patient is associated to lung function decline, leading to a higher risk of hypoxaemia and associated comorbidities, notably cardiovascular diseases (CVD). Adiponectin (Ad) is an adipokine with cardio-protective properties. In COPD patients, conflicting results were previously reported regarding Ad plasmatic (Adpl) level, probably because COPD is a heterogeneous disease with multifactorial influence. Among these factors, gender and hypoxaemia could interact in a variety of ways with Ad pathway. Therefore, we postulated that these components could influence Adpl level and its multimers in COPD patients and contribute to the appearance of a distinct endotype associated to an altered CVD risk.

METHODS

One hundred COPD patients were recruited: 61 were men and 39 were women. Patients who were not severely hypoxemic were allocated to non-hypoxemic group which included 46 patients: 27 men and 19 women. Hypoxemic group included 54 patients: 34 men and 20 women. For all patients, Adpl level and proportion of its different forms were measured. Differences between groups were evaluated by Rank-Sum tests. The relationship between these measures and BMI, blood gas analysis (PaO2, PaCO2), or lung function (FEV1, FEV1/FVC, TLCO, TLC, RV) were evaluated by Pearson correlation analysis.

RESULTS

Despite similar age, BMI and obstruction severity, women had a higher TLC and RV (median: TLC = 105%; RV = 166%) than men (median: TLC = 87%; RV = 132%). Adpl level was higher in women (median = 11,152 ng/ml) than in men (median = 10,239 ng/ml) and was negatively associated with hyperinflation (R = - 0,43) and hypercapnia (R = - 0,42). The proportion of the most active forms of Ad (HMW) was increased in hypoxemic women (median = 10%) compared with non-hypoxemic women (median = 8%) but was not modulated in men.

CONCLUSION

COPD pathophysiology seemed to be different in hypoxemic women and was associated to Ad modulations. Hyperinflation and air-trapping in association with hypercapnia and hypoxaemia, could contribute to a modulation of Adpl level and of its HMW forms. These results suggest the development of a distinct endotypic presentation, based on gender.

The burden of obesity in asthma and COPD: Role of adiponectin

The influence of obesity on development, severity and prognosis of both asthma and COPD is attracting growing interest. The impact of obesity on the respiratory system ranges from structural modifications (decline of total lung capacity) to humoral alterations. Adipose tissue strongly contributes to the establishment of an inflammatory state being an important source of adipokines. Amongst adipokines, adiponectin is an important component of organ cross talk with adipose tissue exerting protective effects on a variety of pathophysiological processes. Adiponectin is secreted in serum where it abundantly circulates as complexes of different molecular weight. Adiponectin properties are mediated by specific receptors that are widely expressed with AdipoR1, AdipoR2, and T-cadherin being present on epithelial and endothelial pulmonary cells indicating a functional role on lung physiology. In COPD, mild to moderate obesity has been shown to have protective effects on patient's survival, while a higher mortality rate has been observed in patients with low BMI. A specific cluster of obese patients has been identified; in this group, asthma features are particularly severe and difficult to treat. Better understanding of the molecular mechanisms at the base of cross talk among different tissues and organs will lead to identification of new targets for both diagnosis and treatment of asthma and COPD.

Different forms of adiponectin reduce the apoptotic and damaging effect of cigarette smoke extract on human bronchial epithelial cells

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease, in which adiponectin may serve an important role. The present study investigated the role of adiponectin in the apoptotic and damaging effect of cigarette smoke extract (CSE) on human bronchial epithelial cells (16HBECs). An MTT assay showed that CSE significantly inhibited the proliferation of 16HBECs (F=1808.88, P<0.01). The 16HBECs were treated with different concentrations of high molecular weight (HMW) adiponectin and globular domain (gAd) adiponectin and it was observed that HMW and gAd dose-dependently inhibited the expression of tumor necrosis factor (TNF)-α and interleukin (IL)-8, and the generation of 4-hydroxy-nonenal and reactive oxygen species (ROS) in 16HBECs, thereby blocking the upregulating effect of CSE on these factors. However, the inhibitory effect of gAd on TNF-α and IL-8 expression was stronger compared with that of HMW, but the suppressing effect of HMW on ROS production was superior compared with that of gAd. Further testing of apoptosis indicated that CSE and HMW promoted the apoptosis of 16HBECs. However, such effects of HMW declined with an increase in concentration. In contrast, gAd showed an inhibitory effect on apoptosis and inhibited the occurrence of CSE-induced apoptosis in a dose-dependent manner. Therefore, the present study demonstrated that different forms of adiponectin may have different mechanisms of action, suggesting that further exploration of their effects may open a new avenue for the treatment of COPD.

Increased circulating obestatin in patients with chronic obstructive pulmonary disease

Background

Some peptides, which regulate the metabolic balance, are thought to play important roles in nutritional disorders and systemic inflammation in COPD. Treatment of rats with obestatin decreased body-weight gain. Obestatin was also found to be correlated with inflammation in rheumatoid arthritis. The aims of this study were to investigate the level of circulating obestatin in COPD and to analyze the relationship among obestatin and nutritional status, and systemic inflammation.

Methods

32 COPD patients with BMI less than 20 kg/m² and 22 normal controls were included. Body composition was estimated using “foot-to-foot” BIA technology. Circulating obestatin was determined with enzyme-linked immunosorbent assay. Pulmonary function, TNF-α and C reactive protein were also measured.

Results

The level of circulating obestatin was higher in COPD with underweight than that in normal control (5562.75 ± 3435.43 pg/ml in COPD, 3663.90 ± 2313.95 pg/ml in controls, p = 0.028). BMI, Waist circumference, hip circumference, bodyFAT and FAT% in COPD group were lower than those in normal control. Positive correlation was found among circulating C reactive protein, TNF-α and obestatin. There was no significant correlation among BMI, pulmonary function and obestatin.

Conclusions

This study shows that circulating obestatin is higher in underweight COPD patients, and positively correlated to systemic inflammation, but not to nutritional status.

Physical activity is the strongest predictor of all-cause mortality in patients with COPD: a prospective cohort study

BACKGROUND

Systemic effects of COPD are incompletely reflected by established prognostic assessments. We determined the prognostic value of objectively measured physical activity in comparison with established predictors of mortality and evaluated the prognostic value of noninvasive assessments of cardiovascular status, biomarkers of systemic inflammation, and adipokines.

METHODS

In a prospective cohort study of 170 outpatients with stable COPD (mean FEV(1), 56% predicted), we assessed lung function by spirometry and body plethysmography; physical activity level (PAL) by a multisensory armband; exercise capacity by 6-min walk distance test; cardiovascular status by echocardiography, vascular Doppler sonography (ankle-brachial index [ABI]), and N-terminal pro-B-type natriuretic peptide level; nutritional and muscular status by BMI and fat-free mass index; biomarkers by levels of high-sensitivity C-reactive protein, IL-6, fibrinogen, adiponectin, and leptin; and health status, dyspnea, and depressive symptoms by questionnaire. Established prognostic indices were calculated. The median follow-up was 48 months (range, 10-53 months).

RESULTS

All-cause mortality was 15.4%. After adjustments, each 0.14 increase in PAL was associated with a lower risk of death (hazard ratio [HR], 0.46; 95% CI, 0.33-0.64; P < .001). Compared with established predictors, PAL showed the best discriminative properties for 4-year survival (C statistic, 0.81) and was associated with the highest relative risk of death per standardized decrease. Novel predictors of mortality were adiponectin level (HR, 1.34; 95% CI, 1.06-1.71; P = .017), leptin level (HR, 0.81; 95% CI, 0.65-0.99; P = .042), right ventricular function (Tei-index) (HR, 1.26; 95% CI, 1.04-1.54; P = .020), and ABI < 1.00 (HR, 3.87; 95% CI, 1.44-10.40; P = .007). A stepwise Cox regression revealed that the best model of independent predictors was PAL, adiponectin level, and ABI. The composite of these factors further improved the discriminative properties (C statistic, 0.85).

CONCLUSIONS

We found that objectively measured physical activity is the strongest predictor of all-cause mortality in patients with COPD. In addition, adiponectin level and vascular status provide independent prognostic information in our cohort.

Adiponectin-deficient mice are protected against tobacco-induced inflammation and increased emphysema

Adiponectin is a cytokine with both proinflammatory and anti-inflammatory properties that is expressed in epithelial cells in the airway in chronic obstructive pulmonary disease-emphysema (COPD-E). To determine whether adiponectin modulates levels of lung inflammation in tobacco smoke-induced COPD-E, we used a mouse model of COPD-E in which either adiponectin-deficient or wild-type (WT) mice were exposed to tobacco smoke for 6 mo. Outcomes associated with tobacco smoke-induced COPD-E were quantitated including lung inflammation [bronchoalveolar lavage (BAL) and total and differential cell count], lung mediators of inflammation (cytokines and chemokines), air space enlargement (i.e., linear intercept), and lung function (tissue elastance) in the different groups of mice. Whereas exposure of WT mice to tobacco smoke for 6 mo induced significant lung inflammation (increased total BAL cells, neutrophils, and macrophages), adiponectin-deficient mice had minimal BAL inflammation when exposed to tobacco smoke for 6 mo. In addition, whereas chronic tobacco-exposed WT mice had significantly increased levels of lung mediators of inflammation [i.e., TNF-α, keratinocyte-derived chemokine (KC), and adiponectin] as well as significantly increased air space enlargement (increased linear intercept) and decreased tissue elastance, exposure of adiponectin-deficient mice to chronic tobacco smoke resulted in no further increase in lung mediators, air space enlargement, or tissue elastance. In vitro studies demonstrated that BAL macrophages derived from adiponectin-deficient mice incubated in media containing tobacco smoke expressed minimal TNF-α or KC compared with BAL macrophages from WT mice. These studies suggest that adiponectin plays an important proinflammatory role in tobacco smoke-induced COPD-E.

Impact of adiponectin deficiency on pulmonary responses to acute ozone exposure in mice

Obese mice have increased responses to acute ozone (O(3)) exposure. T-cadherin is a binding protein for the high-molecular weight isoforms of adiponectin, an anti-inflammatory hormone that declines in obesity. The objective of the present study was to determine whether adiponectin affects pulmonary responses to O(3), and whether these effects are mediated through T-cadherin. We performed bronchoalveolar lavage (BAL) and measured pulmonary responsiveness to methacholine after acute air or O(3) exposure (2 ppm for 3 h) in adiponectin-deficient (Adipo(-/-)) or T-cadherin-deficient (T-Cad(-/-)) mice. O(3) increased pulmonary responses to methacholine and increased BAL neutrophils and protein to a greater extent in wild-type than in Adipo(-/-) mice, whereas T-cadherin deficiency had no effect. O(3)-induced increases in BAL IL-6 and keratinocyte-derived chemokine (KC), which contribute to O(3)-induced pulmonary neutrophilia, were also greater in wild-type than in Adipo(-/-) mice. In contrast, responses to O(3) were not altered by transgenic overexpression of adiponectin. To determine which adiponectin isoforms are present in the lung, Western blotting was performed. The hexameric isoform of adiponectin dominated in serum, whereas BAL was dominated by the high-molecular weight isoform of adiponectin. Interestingly, serum adiponectin was greater in T-Cad(-/-) versus wild-type mice, whereas BAL adiponectin was lower in T-Cad(-/-) versus wild-type mice, suggesting that T-cadherin may be important for transit of high-molecular weight adiponectin from the blood to the lung. Our results indicate that adiponectin deficiency inhibits pulmonary inflammation induced by acute O(3) exposure, and that T-cadherin does not mediate the effects of adiponectin responsible for these events.

Adiponectin deficiency increases allergic airway inflammation and pulmonary vascular remodeling

Obesity is associated with an increased incidence and severity of asthma, as well as other lung disorders, such as pulmonary hypertension. Adiponectin (APN), an antiinflammatory adipocytokine, circulates at lower levels in the obese, which is thought to contribute to obesity-related inflammatory diseases. We sought to determine the effects of APN deficiency in a murine model of chronic asthma. Allergic airway inflammation was induced in APN-deficient mice (APN(-/-)) using sensitization without adjuvant followed by airway challenge with ovalbumin. The mice were then analyzed for changes in inflammation and lung remodeling. APN(-/-) mice in this model develop increased allergic airway inflammation compared with wild-type mice, with greater accumulation of eosinophils and monocytes in the airways associated with elevated lung chemokine levels. Surprisingly, APN(-/-) mice developed severe pulmonary arterial muscularization and pulmonary arterial hypertension in this model, whereas wild-type mice had only mild vascular remodeling and comparatively less pulmonary arterial hypertension. Our findings demonstrate that APN modulates allergic inflammation and pulmonary vascular remodeling in a model of chronic asthma. These data provide a possible mechanism for the association between obesity and asthma, and suggest a potential novel link between obesity, inflammatory lung disease, and pulmonary hypertension.