Exhaled nitric oxide in severe obesity: Effect of weight loss

Mediterranean Diet and Airway Inflammation in School-Aged Children

There seems to exist an intricate relationship between airway inflammation, body mass index (BMI), and diet. The intake of specific foods or food groups has been suggested to suppress the oxidative stress and inflammatory processes that characterize airway inflammation, but little is known about dietary patterns and their complex interplay with BMI and airway inflammation. Therefore, this cross-sectional study aimed to explore the association between adherence to the Mediterranean diet (MD), a characteristic European diet, and levels of airway inflammation in school-aged children, taking into account their BMI. This cross-sectional analysis comprised 660 children: 49.1% females, 7-12 years old. Adherence to the MD was assessed through the alternate Mediterranean score (aMED). Higher scores represent a healthier diet (0-8). Airway inflammation was assessed measuring exhaled fractional nitric oxide (eNO). Two categories of BMI were considered: non-overweight/non-obese (p < 85th) and overweight/obese (p ≥ 85th). The associations between diet and airway inflammation were estimated using logistic regression models. Higher scores of the aMED were associated with decreased odds of having eNO ≥ 35 ppb, but only in non-overweight/non-obese children (OR = 0.77; 95% CI, 0.61-0.97). For overweight/obese children, the previous association was not significant (OR = 1.57, 95% CI, 0.88-2.79). Our findings suggest that adherence to the MD is associated with lower levels of airway inflammation among non-overweight/non-obese children.

Fractional Exhaled Nitric Oxide (FeNO) in Patients with Stable Chronic Obstructive Pulmonary Disease: Short-Term Variability and Potential Clinical Implications

BACKGROUND

The use of fractional exhaled nitric oxide (FeNO) has been proposed for identifying and monitoring eosinophilic airway inflammation in chronic obstructive pulmonary disease (COPD). To explore the clinical utility of FeNO in COPD, we aimed to assess its short-term variability in a clinically stable COPD cohort.

METHODS

Consecutive COPD patients, formerly smokers, underwent FeNO assessment at the baseline and six time-points through serial sampling spaced 3 days apart.

RESULTS

A total of 41 patients (mean age 72.9, 87.8% males) showed a median baseline value of FeNO of 11.7 (8.0-16.8) ppb. A weak linear relationship was documented between baseline FeNO values and both eosinophil counts (r = 0.341, p = 0.029) and the percentage of eosinophils (r = 0.331, p = 0.034), confirmed in multiple linear regressions after adjusting for steroid use. The overall individual variability of FeNO between time-points was 3.90 (2.53-7.29) ppb, with no significant difference in the distribution of FeNO values measured at different time-points (p = 0.204). A total of 28 (68.3%) patients exhibited FeNO always below the 25 ppb cut-off at all determinations, while the remining 13 (31.7%) had at least one value above the established limit. Interestingly, none of these 13 participants had FeNO stably above 25 ppb, all showing at least one normal value during serial sampling. Compared to these patients with more fluctuating values, the 28 with stably normal FeNO only exhibited a significantly higher body weight (80.0 ± 18.2 kg vs. 69.0 ± 8.8 kg, p = 0.013) and body mass index (29.7 ± 6.5 kg/m2 vs. 25.9 ± 3.7 kg/m2, p = 0.026), confirmed in multiple logistic regressions after adjusting for major potential confounders.

CONCLUSIONS

A certain degree of FeNO variability, apparently unrelated to eosinophil counts but somehow influenced by body weight, must be considered in COPD patients. Further studies are needed to clarify whether this biomarker may be effectively used to plan more personalized pharmacological and rehabilitation strategies in this clinical setting.

School-Age Obese Asthmatic Children have Distinct Lung Function Measures From Lean Asthmatics and Obese Children

Background: The lung functions of children with obese asthma seem to be distinct from those of obese children or lean asthmatics.Aim: To measure baseline lung function, exercise-induced bronchoconstriction (EIB), and bronchial hyperreactivity (BHR) in school-age obese asthmatics (OA group) and to compare the data with obese children (O group), lean asthmatics (A group), and healthy controls (H group).Methods: One hundred seventy school-age children were enrolled in this prospective cross-sectional study. Baseline fractionated exhaled nitric oxide (FeNO), and baseline, post-exercise (post-E), and post-bronchodilation (post-BD) impulse oscillometry (IOS) and spirometry tests were performed. EIB and BHR were evaluated based on the difference (Δ) in post-E - baseline, and post-BD - baseline values.Results: The mean FeNO level was higher in the OA group than in the other groups (p = 0.002). Baseline zR5 and R5-20 were higher (p = 0.013 and p = 0.044), but zFEF25-75 was lower (p < 0.01), in the OA group. ΔPost-E - baseline zFEV1 was lower in the A group (p = 0.003) but was higher in the OA group (p = 0.014) than the other groups. ΔPost-BD - baseline zFEV1 was lower in the H group compared to the other three groups (p = 0.004), but no significant difference was observed among the O, A, and OA groups (p > 0.05).Conclusion: A higher airway inflammation (high FeNO), peripheral airway resistance (high zR5 and zR5-20) and a lower peripheral airway flow (low FEF25-75) were observed at baseline measurement in school-age obese asthmatics compared to lean asthmatics and obese children. Obese asthmatics had no EIB but exhibited a similar BHR to that of asthmatics.

How Maternal BMI Modifies the Impact of Personalized Asthma Management in Pregnancy

BACKGROUND

Maternal asthma is associated with perinatal complications and respiratory illness in offspring. Obesity increases asthma exacerbation risk in pregnancy and risk of wheeze in offspring.

OBJECTIVES

In this secondary analysis of a randomized controlled trial, we investigated the influence of maternal body mass index, gestational weight gain (GWG), and fractional exhaled nitric oxide (F_ENO)-based management on asthma exacerbations in pregnancy and offspring wheeze.

METHODS

A total of 220 women were randomized to asthma treatment adjustment according to symptoms (control group), or F_ENO and symptoms (F_ENO group). Exacerbations were recorded prospectively. Height and weight were measured at baseline, and in late pregnancy. GWG was categorized according to Institute of Medicine guidelines. A validated parent-completed questionnaire assessed infant wheeze-related outcomes.

RESULTS

F_ENO-based management was associated with a significantly lower incidence rate ratio for maternal exacerbations in nonobese mothers (0.52, 95% confidence interval [CI], 0.31-0.88, P = .015, n = 129), and women with GWG within recommendations (0.35, 95% CI, 0.12-0.96, P = .042, n = 43), but not for obese mothers (0.59, 95% CI, 0.32-1.08, P = .089, n = 88), or women with excess GWG (0.58, 95% CI, 0.32-1.04, P = .07, n = 104). Recurrent bronchiolitis occurred in 5.3% (n = 1) of infants born to non-overweight mothers, 16.7% (n = 3) of infants of overweight mothers, and 21.7% (n = 5) of infants of obese mothers in the control group. In the F_ENO group, 2 infants of obese mothers had recurrent bronchiolitis (7.1%, P = .031).

CONCLUSIONS

The benefits of F_ENO-based management are attenuated among obese mothers and those with excess GWG, indicating the importance of weight management in contributing to improved asthma management in pregnancy.

Obesity disproportionately impacts lung volumes, airflow and exhaled nitric oxide in children

Background

The current literature focusing on the effect of obesity and overweight on lung function and fraction of exhaled nitric oxide (FeNO) in children, particularly among healthy children of non-European descent, remains controversial. Furthermore, whether the relationship of obesity and overweight with lung function and FeNO in children is modified by atopy is unclear. The objective of this study was to examine the effect of excess weight on lung function parameters and FeNO among Asian children, with a particular focus on exploring the potential effect modification by atopy.

Methods

We investigated the effect of excess weight on lung function and FeNO in a population sample of 1,717 children aged 5 to 18 years and explored the potential modifying effect of atopy.

Results

There were positive associations of body mass index (BMI) z-score with forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁), peak expiratory flow (PEF), and forced expiratory flow at 25–75% (FEF_25-75) (all P<0.001), after controlling for confounders. The beta coefficient for FEV₁ (0.084) was smaller than that for FVC (0.111). In contrast, a negative association was found between BMI z-score and FEV₁/FVC ratio (P<0.001) and FeNO (P = 0.03). A consistent pattern of association for lung function variables was observed when stratifying by atopy. There was a negative association of BMI z-score with FeNO in atopic subjects (P = 0.006), but not in non-atopic subjects (P = 0.46).

Conclusions

Excess weight disproportionately impacts lung volumes and airflow in children from the general population, independent of atopic status. Excess weight inversely affects FeNO in atopic but not in non-atopic children.

The effect of body weight on distal airway function and airway inflammation

BACKGROUND/OBJECTIVES

Obesity is a global health problem that adversely influences the respiratory system. We assessed the effects of body mass index (BMI) on distal airway function and airway inflammation.

SUBJECTS/METHODS

Impulse oscillometry (IOS) as a measure of distal airway function, together with spirometry, were assessed in adults with a range of different BMIs. Airway inflammation was assessed with the fraction of exhaled nitric oxide (FeNO) and participants exhaled at various exhalation flows to determine alveolar and bronchial NO.

RESULTS

In total 34 subjects were enrolled in the study; 19 subjects had a normal BMI (18.50-24.99), whilst 15 subjects were overweight (BMI 25.00-29.99), or obese (BMI ≥30). All subjects had normal spirometry. However, IOS measures of airway resistance (R) at 5Hz, 20Hz and frequency dependence (R_5-20) were elevated in overweight/obese individuals, compared to subjects with a normal BMI (median (interquartile range)); 5Hz: 0.41 (0.37, 0.45) vs. 0.32 (0.30, 0.37)kPa/l/s; 20Hz: 0.34 (0.30, 0.37) vs. 0.30 (0.26, 0.33)kPa/l/s; R_5-20: 0.06 (0.04, 0.11) vs. 0.03 (0.01, 0.05)kPa/l/s; p<0.05), whereas airway reactance at 20Hz was decreased in overweight/obese individuals (20Hz: 0.07 (0.03, 0.09) vs. 0.10 (0.07, 0.13)kPa/l/s, p=0.009; 5Hz: -0.12 (-0.15, -0.10) vs. -0.10 (-0.13, -0.09)kPa/l/s, p=0.07). In contrast, within-breath IOS measures (a sign of expiratory flow limitation) and FeNO inflammatory measures, did not differ between groups (p>0.05).

CONCLUSIONS

Being overweight has significant effects on distal and central airway function as determined by IOS, which is not detected by spirometry. Obesity does not influence airway inflammation as measured by FeNO. IOS is a reliable technique to identify airway abnormalities in the presence of normal spirometry in overweight people.

Low alveolar and bronchial nitric oxide in severe uncomplicated obesity

BACKGROUND

Fractional concentration of exhaled nitric oxide (FeNO) is a recognized biomarker of the lower respiratory tract, where it is produced by the proximal conducting airways and the expansible peripheral bronchoalveolar compartment. We have previously shown that large increase in body mass decreases FeNO. Here we evaluated bronchial and alveolar components of the NO output of the lower respiratory tract in subjects with severe uncomplicated obesity (OB).

METHODS

Fifteen OB subjects (BMI 45.3 ± 5.6 kg/m(2)), 15 healthy controls (HC) (BMI 22.4 ± 2.4 kg/m(2)) and 10 obese subjects who experienced weight loss after bariatric surgery (OBS) (BMI 31.2 ± 3.4 kg/m(2)), were examined. Anthropometry and respiratory lung tests were performed. Exhaled NO was assessed using multiple single-breath NO analysis at different constant expiratory flow rates. From the fractional NO concentration measured at each flow-rate, the total NO flux between tissue and gas phase in the bronchial lumen (J'awNO), and the alveolar NO concentration (CANO) were extrapolated.

RESULTS

Measured FeNO levels at 50 mL/s were lower in OB compared with HC and OBS (11.6 ± 2.8 ppb, 18.0 ± 4.1 ppb and 17.6 ± 2.9 ppb, respectively, p < 0.05). In OB, both J'awNO and CANO resulted significantly lower than OBS and HC values.

CONCLUSIONS

Respiratory NO output is decreased in severe uncomplicated obesity for the reduction of both large/central airway maximal NO flux and alveolar NO concentration. The pathophysiological relevance of airway NO abnormalities in severe obese phenotype remains to be investigated.

Nitric oxide, oxidant status and antioxidant response in morbidly obese patients: the impact of 1-year surgical weight loss

BACKGROUND

The aims of this study were to evaluate nitric oxide (NO) metabolites (nitrite/nitrate NO x ) as proinflammatory parameter and total oxidant status (TOS) as well as total antioxidant response (TAR) as oxidative stress (OS) markers in morbidly obese (MO) patients in comparison with normal-weight healthy (NWH) subjects and to determine the post-bariatric surgery changes of NO x and OS indicators in relation with weight loss.

METHODS

We examined serum NO x , TOS, and TAR in a bariatric group of MO patients and a NWH control group (n = 23 each group). In the NWH group, serum was examined once, while in the MO group, serum was examined before and at 3, 6, and 12 months after silastic ring vertical gastroplasty (SRVG).

RESULTS

Serum NO x and TOS values were higher (p < 0.001), while TAR level was lower (p < 0.001) in MO patients as compared to the NWH group. No significant changes occurred at 12 months after surgery in the MO group as far as the NO x (p = 0.93), TOS (p = 0.11), and TAR (p = 0.15) levels were concerned as compared to baseline values. However, NO x increased at 6 months after surgery (p < 0.008) and then decreased by the 12th month after SRVG (p < 0.008), reaching almost baseline values.

CONCLUSIONS

At baseline, there was a high production of proinflammatory and OS markers in MO patients. SRVG surgical weight loss was not accompanied by significant changes of these parameters at 1 year after surgery.

Association of serum paraoxonase enzyme activity and oxidative stress markers with dyslipidemia in obese adolescents

OBJECTIVES

The aim of the present study was to investigate the serum paraoxonase 1 (PON1) concentration and oxidative stress markers and assess its relations with the biochemical parameters in obese adolescents.

MATERIALS AND METHODS

One hundred and fifty obese adolescents (range 16-18 years) and 150 healthy age- and sex-matched controls were enrolled in the study. The data were extracted from a project entitled "Obesity among Youth: Lifestyle and Genetic Factors" funded by the Science and Technology Development Fund, Egypt. Serum paraoxonase 1 (PON1), nitric oxide (NO), and malonaldehyde were measured. Anthropometry, fasting glucose, insulin concentrations, total cholesterol, high density lipoprotein-cholesterol, low density lipoprotein-cholesterol, triglycerides, systolic and diastolic blood pressure (BP) were measured. Insulin resistance was determined by Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). Diagnostic accuracy of oxidative markers to identify dyslipidemia was calculated with ROC analysis.

RESULTS

The study showed that PON1 activity was significantly lower in obese adolescents than controls. Obese adolescents had significant lower NO level and significant increased MA values as compared to controls. PON1 was negatively correlated with MAD and body mass index in obese subjects. Obese adolescents showed dyslipidemia and increased blood pressure and HOMA-IR values. PON1 had high area under the curve in ROC analysis for identifying dyslipidemia in obese subjects.

CONCLUSIONS

Our results indicate that obese subjects have increased oxidative stress and decreased PON1 activity. The lower paraoxonase level might contribute to the greater risk of dyslipidemia, insulin resistance, high blood pressure that are considered as important components in the pathogenesis of the metabolic syndrome in obese adolescents.

The effect of obesity on the level of fractional exhaled nitric oxide in children with asthma

BACKGROUND

Several studies have demonstrated a relationship between asthma and obesity. However, the results have been conflicting with regard to the relationship between fractional exhaled nitric oxide (FeNO), used as a marker of airway inflammation in asthmatic patients, and obesity. We aimed to evaluate the association of FeNO with obesity and obesity-related metabolic complications in asthmatic and nonasthmatic children.

METHODS

The study population included children aged between 6 and 17 years and consisted of 4 groups: obese asthmatics (n = 52), normal-weight asthmatics (n = 49), obese nonasthmatics (n = 51) and normal-weight nonasthmatics (n = 42). FeNO measurement and spirometry were performed for all patients. To evaluate the metabolic complications, serum lipids, glucose and insulin levels were measured. Insulin resistance (IR) was estimated by the homeostasis model assessment, HOMA-IR. All participants were evaluated for the presence of metabolic syndrome (MS).

RESULTS

The mean age for the 194 subjects participating in the study was 11.6 ± 2.5 years. The FeNO level of asthma patients with MS was not different from those without MS (14.5 ± 8.0 and 16.7 ± 8.7, respectively, p = 0.449). In the nonasthmatic group, subjects with MS had a higher FeNO level than subjects without MS (12.5 ± 5.1 and 17.3 ± 8.3, respectively, p = 0.014). Spearman's rank correlation coefficients revealed a positive correlation between FeNO and body mass index (BMI; p = 0.049, r(2): 0.204) in the nonasthmatic group and after multivariate regression analysis, BMI still persisted as an independent risk factor for FeNO.

CONCLUSION

We found a positive correlation between BMI and FeNO level which suggests a link between obesity and increased airway inflammation in nonasthmatic children.

Exhaled nitric oxide in asthma: progress since the introduction of standardized methodology

The measurement of nitric oxide (NO) in exhaled breath has given us the ability to learn about and monitor the inflammatory status of the airway through a non-invasive method that is easy to perform and repeat. This has been most useful in the diagnosis and management of asthma and has promised a seemingly unlimited potential for evaluating the airways and how clinical decisions are made (Grob N M and Dweik R A 2008 Chest133 837-9). The exhaled NO field was initially limited, however, due to the absence of standardized methodology. The ATS and ERS jointly released recommendations for standardized methods of measuring and reporting exhaled NO in 1999 that were revised in 2005 (1999 Am. J. Respir. Crit. Care. Med. 160 2104-17; 2005 Am. J. Respir. Crit. Care. Med. 171 912-30). In this paper, we summarize the literature that followed this standardization. We searched the literature for all papers that included the term 'exhaled nitric oxide' and selected those that followed ATS guidelines for online measurement for further review. We also reviewed cut-off values suggested by groups studying exhaled nitric oxide. We found a wide range of NO values reported for normal and asthma populations. The geometric mean for FE(NO) ranged from 10 ppb to 33 ppb in healthy adult control populations. For asthma, the FE(NO) geometric mean ranged from 6 ppb to 98 ppb. This considerable variation likely reflects the different clinical settings and purposes of measurement. Exhaled NO has been used for a multitude of reasons that range from screening, to diagnosis, to monitoring the effect of therapy. The field of exhaled NO has made undeniable progress since the standardization of the measurement methods. Our challenge now is to have guidelines to interpret exhaled NO levels in the appropriate context. As the utility of exhaled NO continues to evolve, it can serve as a good example of the crucial role of the standardization of collection and measurement methods to propel any new test in the right direction as it makes its way from a research tool to a clinically useful test.

Regulation of adipose tissue energy availability through blood flow control in the metabolic syndrome

Maintenance of blood flow rate is a critical factor for tissue oxygen and substrate supply. The potentially large mass of adipose tissue deeply influences the body distribution of blood flow. This is due to increased peripheral resistance in obesity and the role of this tissue as the ultimate destination of unused excess of dietary energy. However, adipose tissue cannot grow indefinitely, and the tissue must defend itself against the avalanche of nutrients provoking inordinate growth and inflammation. In the obese, large adipose tissue masses show lower blood flow, limiting the access of excess circulating substrates. Blood flow restriction is achieved by vasoconstriction, despite increased production of nitric oxide, the vasodilatation effects of which are overridden by catecholamines (and probably also by angiotensin II and endothelin). Decreased blood flow reduces the availability of oxygen, provoking massive glycolysis (hyperglycemic conditions), which results in the production of lactate, exported to the liver for processing. However, this produces local acidosis, which elicits the rapid dissociation of oxyhemoglobin, freeing bursts of oxygen in localized zones of the tissue. The excess of oxygen (and of nitric oxide) induces the production of reactive oxygen species, which deeply affect the endothelial, blood, and adipose cells, inducing oxidative and nitrosative damage and eliciting an increased immune response, which translates into inflammation. The result of the defense mechanism for adipose tissue, localized vasoconstriction, may thus help develop a more generalized pathologic response within the metabolic syndrome parameters, extending its effects to the whole body.

The problem of nitrogen disposal in the obese

Amino-N is preserved because of the scarcity and nutritional importance of protein. Excretion requires its conversion to ammonia, later incorporated into urea. Under conditions of excess dietary energy, the body cannot easily dispose of the excess amino-N against the evolutively adapted schemes that prevent its wastage; thus ammonia and glutamine formation (and urea excretion) are decreased. High lipid (and energy) availability limits the utilisation of glucose, and high glucose spares the production of ammonium from amino acids, limiting the synthesis of glutamine and its utilisation by the intestine and kidney. The amino acid composition of the diet affects the production of ammonium depending on its composition and the individual amino acid catabolic pathways. Surplus amino acids enhance protein synthesis and growth, and the synthesis of non-protein-N-containing compounds. But these outlets are not enough; consequently, less-conventional mechanisms are activated, such as increased synthesis of NO∙ followed by higher nitrite (and nitrate) excretion and changes in the microbiota. There is also a significant production of N(2) gas, through unknown mechanisms. Health consequences of amino-N surplus are difficult to fathom because of the sparse data available, but it can be speculated that the effects may be negative, largely because the fundamental N homeostasis is stretched out of normalcy, forcing the N removal through pathways unprepared for that task. The unreliable results of hyperproteic diets, and part of the dysregulation found in the metabolic syndrome may be an unwanted consequence of this N disposal conflict.

Airway responsiveness measured by forced oscillation technique in severely obese patients, before and after bariatric surgery

BACKGROUND

The influence of obesity on airway responsiveness remains controversial.

OBJECTIVE

This study was designed to investigate airway responsiveness, airway inflammation, and the influence of sleep apnea syndrome (SAS), in severely obese subjects, before and after bariatric surgery.

METHODS

A total of 120 non-asthmatic obese patients were referred consecutively for pre-bariatric surgery evaluation. Lung function, airway responsiveness to methacholine, exhaled nitric oxide measurement, and sleep studies were performed. Airway hyperresponsiveness (AHR) was defined as a 50% or greater increase in respiratory resistance measured using the forced oscillation technique in response to a methacholine dose ≤ 2000 μg. Forced expiratory volume in 1 second (FEV₁) was measured after the last methacholine dose. Airway responsiveness was reevaluated after weight loss in patients with a pre-surgery AHR.

RESULTS

AHR was found in 16 patients. The percent FEV₁ decrease or percent respiratory resistance increase in response to methacholine was related to baseline expiratory airflow (forced expiratory flow at 50%) (r = 0.26, p < .006 and r = 0.315, p = .0005, respectively) but not to body mass index (BMI) or exhaled nitric oxide. Both airway responsiveness parameters were significantly related to forced expiratory flow at 25-75%/forced vital capacity, a measure of airway size relative to lung size (r = 0.27, p < .005 and r = 0.25, p < .007, respectively). Sleep apnea was not significantly associated with AHR or airway inflammation. About 11 patients with AHR were reevaluated 18 months to 2 years after surgery, with no change in AHR associated with weight loss.

CONCLUSION

Airway responsiveness is not related to BMI or to SAS. AHR in severely obese patients might be related to distal airway obstruction or low relative airway size.

Implications for kidney disease in obese children and adolescents

Increasing attention has been focused on the implications of obesity in adults on the development of kidney disease, but data on the obese pediatric population are lacking. The aim of this study was to investigate whether changes in various renal function indexes/markers, as expressed by the glomerular filtration rate [GFR, as estimated by the Schwartz formula (eGFR)], serum cystatin C (CysC) level, albumin excretion rate (AER), and modifications in nitric oxide (NO; an important modulator of renal function and morphology), urinary isoprostanes (markers of oxidative stress), and blood pressure (BP), can be detected in obese children and adolescents when compared to normal weight controls. Blood and urinary samples were collected to evaluate markers of renal function, serum and urinary NO, and urinary isoprostanes in 107 obese Caucasian subjects and 50 controls. Ambulatory BP monitoring (ABPM) was performed in all cases. Obesity was expressed by the body mass index standard deviation score (SDS-BMI), and insulin resistance by the homeostasis model assessment of insulin resistance (HOMA-IR). CysC and eGFR did not significantly differ between the two groups; AER was increased in obese children. CysC and GFR were related to HOMA-IR, and AER was related to HOMA-IR and SDS-BMI. Obese subjects had reduced NO levels and increased urinary isoprostanes and BP measurements; all three parameters were related to SDS-BMI and insulin resistance. ABPM showed an increased incidence of hypertension and non-dipping in the obese group. Based on our comparison of obese and nonobese children, we conclude that renal involvement is not an early clinically evident manifestation of adiposity in childhood, since no overt changes in eGFR and only a mild albuminuria were detected. A longer exposure to obesity is probably needed before renal function impairment appears.

Adiposity, adipokines, and exhaled nitric oxide in healthy adults without asthma

BACKGROUND

Epidemiological studies have shown that obesity/adiposity is closely associated with asthma in terms of development, severity, and control of asthma. However, effects of obesity/adiposity on airway inflammation are not well known in subjects without asthma. We assessed whether fractional exhaled nitric oxide (FeNO), a marker of eosinophilic airway inflammation, was associated with obesity/adiposity in nonasthmatic healthy adults.

METHODS

We measured FeNO and serum levels of adipose-derived hormones and adipokines in 117 adult subjects without a previous diagnosis of asthma or current asthmatic symptoms. Associations between FeNO and measures of obesity/adiposity [body mass index (BMI), body fat mass, and body fat percentages] were examined by correlation analyses and uni- and multivariate linear regression analyses.

RESULTS

FeNO was not significantly associated with BMI, body fat mass, or body fat percentage by a multivariate linear regression model, adjusting for age, gender, chronic rhinitis, atopy, and lung function. No significant association of FeNO with serum levels of leptin, adiponectin, tumor necrosis factor (TNF)-α, or interleukin (IL)-6 was observed.

CONCLUSIONS

These findings suggest that in healthy subjects without asthma, obesity/adiposity has no significant effect on eosinophilic airway inflammation and that hormones and systemic inflammation derived from adipose tissue do not affect eosinophilic airway inflammation.

Decreased fraction of exhaled nitric oxide in obese subjects with asthma symptoms: data from the population study INTERGENE/ADONIX

BACKGROUND

Several studies have demonstrated an association between obesity and asthma. However, it is uncertain if fraction of exhaled nitric oxide (Feno), which is used as a marker of airway inflammation, and atopy are associated with BMI. The aim of this study was to examine if obese subjects with asthma symptoms have a different phenotype of asthma than nonobese subjects as indicated by Feno.

METHODS

The subjects (N = 2,187) consisted of women and men, aged 25 to 74, living in Gothenburg, Sweden, who participated in the randomly selected INTERGENE study cohort. Measurements included anthropometric measures, bioelectric impedance, Feno, pulmonary function, and blood samples for IgE; questionnaires included items on respiratory symptoms. Obesity was defined as BMI ≥ 30 kg/m(2). In this cross-sectional analysis, general linear models were used to analyze how Feno was associated with anthropometry, body composition, wheezing, and atopy.

RESULTS

In nonobese subjects, wheezing was associated with raised Feno and atopy, whereas in contrast, obese subjects who reported wheezing had lower Feno than obese subjects without wheezing (16.1 vs 19.1 parts per billion, P < .01). The prevalence of atopy was similar in both of those subgroups (25.0% vs 20.7%, P = .4). Similarly, in 395 subjects (19%) who reported wheezing, Feno was negatively associated with BMI, waist-to-hip ratio, and percentage of body fat, whereas no significant relationships were observed in those without respiratory symptoms.

CONCLUSIONS

Wheezing was significantly associated with reduced Feno in obese subjects, whereas there was a positive association between wheezing and Feno among the nonobese subjects, indicating a possible difference in asthma phenotype, based on body weight.

Partitioning of exhaled NO in ventilated patients undergoing cardiac surgery

The change in exhaled NO after cardio-pulmonary bypass remains controversial. The aims were to determine whether exhaled NO sources (alveolar or bronchial) are modified after bypass, and whether mechanical ventilation (MV) settings during bypass modify exhaled NO changes. Thirty-two patients were divided into three groups: without MV during bypass and positive end-expiratory pressure (PEEP) (n=12), dead space MV without PEEP (n=10) and dead space MV with PEEP (n=10). Alveolar NO concentration and bronchial NO flux were calculated before and 1h after surgery using a two-compartment model of NO exchange developed in spontaneous breathing patients. Whereas a significant decrease in bronchial NO was found after bypass in the two groups without PEEP during bypass, this decrease was not observed in patients with dead space ventilation with PEEP. Alveolar NO was not significantly modified whatever the ventilation settings. In conclusion, the impairment of bronchial NO seemed related to airway closure since dead space mechanical ventilation with PEEP prevented its decrease.

Increased serum nitric oxide concentration after bariatric surgery--a potential mechanism for cardiovascular benefit

BACKGROUND

It is believed that endothelial dysfunction associated with obesity contributes to reduced vascular production of nitric oxide (NO). Weight reduction after bariatric surgery is known to decrease the risk of cardiovascular disease. The purpose of this study was to determine whether bariatric surgery leads to improvement of metabolic markers of endothelial function: serum NO and its precursor (arginine) concentrations in obese patients.

METHODS

Serum NO and L-arginine concentrations were measured in 25 morbidly obese patients directly before and 6 months after bariatric surgery. Moreover, selected parameters that may be involved in development of endothelial dysfunction were also studied. Control group consisted of ten healthy individuals with normal body weight.

RESULTS

Six months after bariatric surgery, serum NO concentration was approximately 40% higher than before surgery. Surprisingly, serum NO concentration in nonobese controls was essentially similar to obese patients before surgery. In contrast, serum L-arginine concentration was higher in obese patients than in controls and decreased significantly after surgery. The body weight, blood pressure, triacylglycerols, LDL/HDL-cholesterol ratio, insulin, homeostasis model assessment score (HOMA-index), C-reactive protein, and white blood cell count were higher in obese patients as compared with controls and decreased significantly after surgery.

CONCLUSIONS

Our results indicate that improvement of insulin resistance, lipidemia, and blood pressure as well as reduction of systemic inflammation after bariatric surgery were associated with the increase of serum NO concentration. We propose that the increase in serum NO concentration contribute to diverse beneficial effects of weight loss after bariatric surgery especially in the context of risk of atherosclerosis.

Exhaled nitric oxide in pediatric asthma

Exhaled nitric oxide can now be measured in a clinical setting as a noninvasive, reproducible, facile, point-of-service test to measure airway inflammation, a central component of asthma that had not been assessed previously. An excellent surrogate marker of steroid-responsive eosinophilic airway inflammation, it serves to identify steroid-sensitive asthmatic patients and enables clinical monitoring of the response to steroid therapy and titration of the dose. Standardization of methodology and technological advances, such as the recent availability of handheld analyzers, individualized patient cards to store serial test measurements, and the assignment of coding procedural terminology, make this a necessary adjunct to clinical and functional assessment of airway obstruction and hyperresponsiveness in ambulatory pediatric and adult asthma practices.

Exhaled nitric oxide and other major exhaled compounds for the diagnosis of metabolic diseases

BACKGROUND

Many metabolic diseases including obesity, cardiovascular disease and diabetes share common pathogenetic pathways, which may involve chronic oxidative stress and inflammation. There is increasing evidence that assessment of biomarkers on exhaled gases or exhaled breath condensate may serve as a non-invasive tool to detect abnormalities in metabolic diseases mirroring increased in oxidative stress, systemic inflammation and endothelial dysfunction.

METHODS

Among commonly used exhaled biomarkers, nitric oxide (NO) on exhaled air and some constituents of exhaled breath condensate in volatile or non-volatile form may represent suitable markers. Nasal, bronchial and alveolar NO could be analyzed separately, with implications in the assessment of systemic disease and endothelial dysfunction. Moreover, the profiles of several exhaled gases have a place in phenotyping diabetic patients and their risk of complications. Accordingly, metabolomics of the airway fluid using exhaled breath condensate has recently confirmed the value of this biological matrix for the evaluation of both volatile and non-volatile biomarkers.

CONCLUSION

Normative studies for reference values are, however, lacking, and the influence of preanalytical variables on the methodology warrants further studies.

Management of asthma based on exhaled nitric oxide in addition to guideline-based treatment for inner-city adolescents and young adults: a randomised controlled trial

BACKGROUND

Preliminary evidence is equivocal about the role of exhaled nitric oxide (NO) in clinical asthma management. We aimed to assess whether measurement of exhaled NO, as a biomarker of airway inflammation, could increase the effectiveness of asthma treatment, when used as an adjunct to clinical care based on asthma guidelines for inner-city adolescents and young adults.

METHODS

We did a randomised, double-blind, parallel-group trial at ten centres in the USA. We screened 780 inner-city patients, aged 12-20 years, who had persistent asthma. All patients completed a run-in period of 3 weeks on a regimen based on standard treatment. 546 eligible participants who adhered to treatment during this run-in period were then randomly assigned to 46 weeks of either standard treatment, based on the guidelines of the National Asthma Education and Prevention Program (NAEPP), or standard treatment modified on the basis of measurements of fraction of exhaled NO. The primary outcome was the number of days with asthma symptoms. We analysed patients on an intention-to-treat basis. This trial is registered with clinicaltrials.gov, number NCT00114413.

FINDINGS

During the 46-week treatment period, the mean number of days with asthma symptoms did not differ between the treatment groups (1.93 [95% CI 1.74 to 2.11] in the NO monitoring group vs 1.89 [1.71 to 2.07] in the control group; difference 0.04 [-0.22 to 0.29], p=0.780). Other symptoms, pulmonary function, and asthma exacerbations did not differ between groups. Patients in the NO monitoring group received higher doses of inhaled corticosteroids (difference 119 mug per day, 95% CI 49 to 189, p=0.001) than controls. Adverse events did not differ between treatment groups (p>0.1 for all adverse events).

INTERPRETATION

Conventional asthma management resulted in good control of symptoms in most participants. The addition of fraction of exhaled NO as an indicator of control of asthma resulted in higher doses of inhaled corticosteroids, without clinically important improvements in symptomatic asthma control.

Obesity reduces the bioavailability of nitric oxide in juveniles

OBJECTIVE

There is growing evidence that nitric oxide (NO) is critically involved in obesity and its clinical consequences like cardiovascular disease, hypertension and diabetes. We hypothesize that NO is already involved in the pathophysiology of juvenile obesity. We here determined the role of NO, its metabolites arginine and citrulline in obese and normal weight children.

DESIGN

We investigated 57 obese and 57 normal weight age- and gender-matched juveniles. Various clinical parameters as well as body measurements and intima media thickness were determined.

RESULTS

Obese juveniles revealed highly significant alterations in the NO pathway. NOX and citrulline were decreased in obese compared to normal weight juveniles and negatively correlated with body weight. Arginine was increased in obese juveniles and positively correlated with body weight. We found a significant negative correlation between NOX and oxidized low-density lipoprotein. Analysis of gamma-aminobutyric acid (GABA) revealed correlations with the NO pathway as NOX and citrulline were negatively correlated with GABA and arginine showed a positive correlation.

CONCLUSION

We show here that NO and its metabolites arginine and citrulline are already involved in juvenile obesity that may contribute to atherogenesis via reduced bioavailability of NO. Moreover, we identify GABA as a new parameter in the mechanism of obesity-related NO reduction.

Weight loss and asthma control in severely obese asthmatic females

BACKGROUND

Obesity is proposed to represent an important predisposing condition to serious respiratory disturbances including asthma. The effects of consistent weight loss on asthma control are not well known. We investigated the effect of weight reduction induced by bariatric surgery on asthma control in severely obese asthmatic patients.

PATIENTS AND METHODS

A consecutive series of 12 asthmatic obese females who had laparoscopic adjustable gastric banding (OB group) and 10 non-operated asthmatic obese females as control group (CG). Body mass index (BMI), Asthma Control Test (ACT), pulmonary function test (PFT), exhaled nitric oxide (NO) were evaluated at baseline and after 1 year.

RESULTS

Mean BMI (kg/m(2)) of OB group decreased from 45.2+/-4.7 before surgery to 34.8+/-4.2 post-operatively. After surgery the overall ACT score in OB group significantly improved from 18.7 to 22.2 (p<0.001), while it remained unchanged in CG (from 18.8 to 18.6, p=0.73). In particular, in OB group the parameters of shortness of breath and rescue medication use were significantly improved respectively from 3.2 and 3.9 before surgery to 4.2 and 4.6 after surgery (always p<0.05). Accordingly, none of the CG who did not experience any weight loss was able to obtain a full asthma control. In the OB group after the surgery PFT significantly improved as compared to CG. No significant difference in exhaled NO was found both in OB group after surgery as compared to before surgery.

CONCLUSION

Consistent weight loss in severely obese patients with asthma is associated to improvement in respiratory symptoms and lung function. However, the mechanisms underlying the effect of large body mass changes on asthma would require further studies.