Muscle oxygen utilization and ventilatory parameters during exercise in people with cystic fibrosis: Role of HbA1c.

INTRODUCTION: Glycated hemoglobin can interfere with oxygen delivery and CO2 removal during exercise. Additionally, pancreatic insufficiency increases oxidative stress and exacerbates exercise intolerance in people with cystic fibrosis (PwCF). This investigation sought to test the hypotheses that elevated Hemoglobin A1c (HbA1c) can negatively affect exercise parameters in PwCF and that reductions in oxidative stress can improve tissue oxygenation in individuals with elevated HbA1c. METHODS: Twenty four PwCF were divided into two groups; normal HbA1c <5.7% (N-HbA1c) and elevated HbA1c >5.7% (E-HbA1c). A maximal exercise test was conducted to obtain peak oxygen uptake (VO2peak), VO2 at ventilatory threshold (VT), ventilatory parameters (VE/VCO2 slope and end-tidal CO2 (petCO2)). Near-Infrared Spectroscopy (NIRS) was used to assess muscle oxygenated/deoxygenated hemoglobin during exercise. A subset of individuals with E-HbA1cwere given an antioxidant cocktail (AOC) for 4 weeks to determine the effects on tissue oxygenation during exercise. RESULTS: A negative relationship between HbA1c and VO2peak at VT was observed (r = -0.511; p = 0.018). In addition, a positive relationship between HbA1c and VE/VCO2 slope (r = 0.587;p = 0.005) and a negative relationship between HbA1c and petCO2 at maximal exercise (r = -0.472;p = 0.031) was observed. N-HbA1c had greater VO2peak (p = 0.021), VO2 at VT (p = 0.004), petCO2 (p = 0.002), and lower VE/VCO2 slope (p = 0.004) compared with E-HbA1c. Muscle deoxygenated hemoglobin at VT was higher in N-HbA1c vs. E-HbA1c and 4 weeks of AOC improved skeletal muscle utilization of oxygen. CONCLUSION: Findings demonstrate that glycated hemoglobin may lead to tissue oxygenation impairment and ventilation inefficiency during exercise in PwCF. In addition, antioxidant supplementation may lead to improved tissue oxygenation during exercise.

Exercise Intolerance in Cystic Fibrosis: Importance of Skeletal Muscle.

PURPOSE: Exercise intolerance, evaluated by O2 consumption, predicts mortality in cystic fibrosis (CF). People with CF exhibit skeletal muscle dysfunctions that may contribute to an imbalance between O2 delivery and utilization. Sildenafil, a phosphodiesterase type 5 inhibitor, increases blood flow and improves O2 consumption, although the exact mechanisms in CF have yet to be elucidated. Thus, we hypothesized that exercise intolerance in CF is limited primarily by an impaired skeletal muscle O2 utilization, and sildenafil improves exercise tolerance in CF by addressing this mismatch between O2 demand and extraction. METHODS: Fifteen individuals with mild to moderate CF and 18 healthy controls completed an incremental exercise test and measurements of gaseous exchange, chronotropic response, hemodynamics, and O2 extraction and utilization. People with CF also completed a 4-wk treatment with sildenafil with a subsequent follow-up evaluation after treatment. RESULTS: Skeletal muscle O2 extraction and utilization during exercise were reduced in people with CF when compared with controls. Exercise capacity in our CF population was minimally limited by hemodynamic or chronotopic responses, whereas peripheral O2 extraction was more closely associated with exercise capacity. The study also demonstrated that 4 wk of sildenafil improved skeletal muscle O2 utilization during exercise to similar values observed in healthy individuals. CONCLUSIONS: Individuals with mild to moderate CF exhibit exercise intolerance secondary to a reduction in O2 utilization by the exercising skeletal muscle. The present study demonstrated that 4 wk of sildenafil treatment improves the capacity of the skeletal muscle to use O2 more efficiently during exercise. Findings from the present study highlight the importance of targeting skeletal muscle O2 utilization to improve exercise tolerance in CF.

Sildenafil improves exercise capacity in patients with cystic fibrosis: a proof-of-concept clinical trial.

BACKGROUND: Exercise intolerance is a common phenotype observed in patients with cystic fibrosis (CF). Treatment with sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, has previously been shown to improve exercise capacity (VO2 peak) in other patient populations. Thus, the present study sought to determine the acute and subacute effects of sildenafil on exercise capacity in patients with CF. METHODS: The present investigation utilized a randomized, double-blind, placebo-controlled, crossover study with an acute dose of either sildenafil (50 mg) or placebo (n = 13, age 25 ± 10), followed by a 4 week open-label extension with sildenafil (20 mg, TID; n = 15, age 23 ± 11). A comprehensive evaluation of pulmonary function and a maximal exercise test were each performed at every visit. RESULTS: A significant increase in VO2 peak was observed after the acute sildenafil dose with no changes following placebo (77 ± 13 versus 72 ± 13% predicted; p = 0.033). In addition, after 4 weeks of treatment, patients showed a significant increase in exercise capacity (72 ± 12 versus 75 ± 12% predicted; p = 0.028) and exercise duration (409 ± 98 versus 427 ± 101 s; p = 0.014). A robust correlation (r = 0.656; p = 0.008) between baseline FEV1 (% predicted) and the change in exercise capacity following 4 weeks of treatment was identified. CONCLUSIONS: This proof-of-concept clinical trial demonstrates that sildenafil treatment can improve exercise capacity in patients with CF and that pulmonary function may play an important role in the effectiveness of treatment. Future investigations of sildenafil treatment in patients with CF are certainly warranted.

Endothelial Dysfunction in Cystic Fibrosis: Role of Oxidative Stress.

Oxidative stress and vascular endothelial dysfunction are established characteristics of cystic fibrosis (CF). Oxidative stress may contribute to vascular dysfunction via inhibition of nitric oxide (NO) bioavailability. Purpose. To determine if ingestion of a single antioxidant cocktail (AOC) improves vascular endothelial function in patients with CF. Methods. In 18 patients with CF (age 8-39 y), brachial artery flow-mediated dilation (FMD) was assessed using a Doppler ultrasound prior to and two hours following either an AOC (n = 18; 1,000 mg vitamin C, 600 IU vitamin E, and 600 mg α-lipoic acid) or a placebo (n = 9). In a subgroup of patients (n = 9), changes in serum concentrations of α-tocopherol and lipid hydroperoxide (LOOH) were assessed following AOC and placebo. Results. A significant (p = 0.032) increase in FMD was observed following AOC (Δ1.9 ± 3.3%), compared to no change following placebo (Δ - 0.8 ± 1.9%). Moreover, compared with placebo, AOC prevented the decrease in α-tocopherol (Δ0.48 ± 2.91 vs. -1.98 ± 2.32 µM, p = 0.024) and tended to decrease LOOH (Δ - 0.2 ± 0.1 vs. 0.1 ± 0.1 µM, p = 0.063). Conclusions. These data demonstrate that ingestion of an antioxidant cocktail can improve vascular endothelial function and improve oxidative stress in patients with CF, providing evidence that oxidative stress is a key contributor to vascular endothelial dysfunction in CF.

Tetrahydrobiopterin improves endothelial function in patients with cystic fibrosis.

Cystic fibrosis (CF) is a genetic disorder associated with vascular endothelial dysfunction. Nitric oxide (NO) plays a major role in maintaining vascular function, and tetrahydrobiopterin (BH4) is a critical determinant of NO bioavailability. Thus the purpose of this study was to investigate the effects of oral administration of BH4 on endothelial function in patients with CF. Twenty-nine patients with CF (18 ± 8 yr old) and 29 healthy matched controls were recruited. Patients with CF participated in a randomized trial where they received a 5 mg/kg dose of oral BH4 (BH4-5; n = 17) or a 20 mg/kg dose of oral BH4 (BH4-20; n = 12). On a separate visit, a subset of patients from each group was retested following a placebo (PLC; n = 9). Brachial artery flow-mediated dilation (FMD) was used to evaluate vascular endothelial function, and a plasma sample was obtained before and 3 h after treatment. Cultured endothelial cells were treated with plasma to assess NO bioavailability. Baseline FMD was lower in patients compared with controls (5.7 ± 3.4 vs. 8.4 ± 3.5%, respectively, P = 0.005). No change in FMD was observed following PLC or BH4-5 (∆FMD: -0.8 ± 1.9% and -0.5 ± 2.5%; P = 0.273 and 0.132, respectively). Treatment with BH4-20, however, resulted in significant improvements in FMD (∆FMD: 1.1 ± 1.4%) compared with BH4-5 ( P = 0.023) and PLC ( P = 0.017). Moreover, BH4-20 significantly decreased endothelial cell superoxide production and increased NO production. These data suggest that a single oral dose of BH4 at 20 mg/kg improves vascular endothelial function in patients with CF, likely via increased endothelial NO synthase coupling. These findings support the hypothesis that loss of BH4 bioactivity contributes, in part, to endothelial dysfunction in patients with CF. NEW & NOTEWORTHY For the first time, the present study documents that a single dose of oral BH4 can improve vascular endothelial function in patients with cystic fibrosis (CF), and our in vitro data suggest this is via decreasing uncoupled nitric oxide. These data provide insight into the important role of BH4 bioactivity in vascular dysfunction and provide the foundation for further investigation into the chronic effects of BH4 treatment in patients with CF.

Exercise testing in patients with cystic fibrosis-importance of ventilatory parameters.

BACKGROUND: Ventilatory parameters obtained during exercise predict survival in several chronic diseases; however, long-term changes in exercise ventilatory parameters in patients with cystic fibrosis (CF) have yet to be examined and potential differences between sexes in CF are unknown. PURPOSE: We sought to examine the change in exercise ventilatory parameters over time in patients with CF and determine if the change is different between sexes. METHODS: Exercise capacity (VO2 peak) and exercise ventilatory parameters (VE/VO2 peak, VE/VCO2 peak, and VE/VCO2 slope) were determined from a maximal cardio-pulmonary test on a cycle ergometer on two visits separated by 39 ± 16 months in 20 patients with CF (10 female, 10 male). RESULTS: No differences between sexes were observed at visit 1 (all p > 0.05). Overall, exercise ventilatory parameters significantly (p < 0.05) deteriorated between visits, with no change (p > 0.05) in VO2 peak. Moreover, compared to males, female patients exhibited greater deteriorations in VE/VO2 peak (p = 0.001), VE/VCO2 peak (p = 0.002), and VE/VCO2 slope (p = 0.016) between visits. CONCLUSIONS: These data in patients with CF indicate that exercise ventilatory parameters decline over time despite no change in VO2 peak, and female patients exhibit a more rapid deterioration compared to males.

Sildenafil improves vascular endothelial function in patients with cystic fibrosis.

Cystic fibrosis (CF), characterized by defective CFTR function, is associated with multiple systemic complications, including vascular dysfunction. Sildenafil, a phosphodiesterase type 5 inhibitor, not only enhances nitric oxide (NO) metabolism but has been shown to improve CFTR functionality as well. Thus, sildenafil has been proposed as a therapy to improve vascular health in CF; however, its potential therapeutic role has yet to be determined. We sought to investigate the effect of sildenafil on endothelial function in patients with CF. Patients with CF completed a randomized, double-blind, placebo-controlled, crossover study with an acute dose of sildenafil (50 mg) or placebo followed by a 4-wk open-label extension with sildenafil (20 mg/day). Flow-mediated dilation (FMD) was used to evaluate endothelial function before and after treatments. In addition, phosphorylated endothelial NO synthase (pNOS3) and total NOS3 protein expression was determined from endothelial cells that were exposed to plasma from the patients before and after 4 wk of sildenafil treatment. No changes ( P ≥ 0.110) in endothelial function were observed after the acute dose of sildenafil. However, FMD significantly ( P = 0.029) increased after 4 wk of treatment (∆FMD: 1.5 ± 2.2%). Moreover, pNOS3 protein expression significantly ( P = 0.013) increased after 4 wk of treatment (∆pNOS3: 0.31 ± 0.39 arbitrary units) and was associated ( r = 0.593, P = 0.033) with the change in FMD. These data suggest that 4 wk of sildenafil treatment can improve vascular endothelial function in patients with CF, likely through an increase in NOS3 phosphorylation. NEW & NOTEWORTHY Findings from the present study demonstrate, for the first time, significant improvement of endothelial function in patients with cystic fibrosis treated with sildenafil that is associated with greater phosphorylation of endothelial nitric oxide synthase. These results support the use of sildenafil as a potential novel therapy for this patient population.

A single bout of maximal exercise improves lung function in patients with cystic fibrosis.

BACKGROUND: Responses to a single bout of exercise may provide critical information for maximizing improvements in pulmonary function following exercise training in cystic fibrosis (CF). We sought to determine if acute maximal exercise improves pulmonary function in patients with CF. METHODS: Thirty-three patients with CF completed a comprehensive assessment of pulmonary function to determine forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and lung clearance index (LCI) prior to and immediately following maximal aerobic exercise on a cycle ergometer. RESULTS: Following exercise, FVC (∆0.08±0.14L) and FEV1 (∆0.06±0.15L) increased, while LCI decreased (∆-0.71±0.93) (all p<0.05). Changes in FEV1 (%predicted) were associated with peak work (r=0.40, p=0.02) and peak pulmonary ventilation (r=0.45, p=0.01). CONCLUSIONS: A single bout of maximal exercise acutely improves pulmonary function in patients with CF and improvements may be related to peak work and peak pulmonary ventilation.

Evidence of microvascular dysfunction in patients with cystic fibrosis.

Cystic fibrosis (CF) is a genetic, multisystemic disorder with broad clinical manifestations apart from the well-characterized pulmonary dysfunction. Recent findings have described impairment in conduit vessel function in patients with CF; however, whether microvascular function is affected in this population has yet to be elucidated. Using laser-Doppler imaging, we evaluated microvascular function through postocclusive reactive hyperemia (PORH), local thermal hyperemia (LTH), and iontophoresis with acetylcholine (ACh). PORH [518 ± 174% (CF) and 801 ± 125% (control), P = 0.039], LTH [1,338 ± 436% (CF) and 1,574 ± 620% (control), P = 0.045], and iontophoresis with ACh [416 ± 140% (CF) and 617 ± 143% (control), P = 0.032] were significantly lower in patients with CF than control subjects. In addition, the ratio of PORH to LTH was significantly (P = 0.043) lower in patients with CF (55.3 ± 5.1%) than control subjects (68.8 ± 3.1%). Significant positive correlations between LTH and forced expiratory volume in 1 s (%predicted) (r = 0.441, P = 0.013) and between the PORH-to-LTH ratio and exercise capacity (r = 0.350, P = 0.049) were observed. These data provide evidence of microvascular dysfunction in patients with CF compared with control subjects. In addition, our data demonstrate a complex relationship between microvascular function and classical markers of disease severity (i.e., pulmonary function and exercise capacity) in CF.

An unusual cause of massive pleural effusion.

Pleural effusions in ovarian hyperstimulation syndrome, whether transudative or exudative, can occur in up to 30% of cases. This disorder is always reversible but may have various clinical presentations and degrees of severity. Although assessing for risk factors to predict clinical severity is helpful, it is rare for ovarian hyperstimulation syndrome to present as a massive pleural effusion requiring emergent intervention. In this study, such a case is reported.

Predictive role of HER-2/neu overexpression and clinical features at initial presentation in patients with extensive stage small cell lung carcinoma.

Although recent advances in therapy have improved the quality of life in patients with extensive stage small cell lung cancer (ESSCLC), prolonged survival is still uncommon. To determine the role of HER-2/neu overexpression and other clinical predictors (symptoms at presentation) of adverse outcome in ESSCLC, we performed a retrospective study on subjects with a biopsy-proven diagnosis of ESSCLC. HER-2/neu overexpression was evaluated using immunohistochemistry (IHC) performed on paraffin-embedded specimens. An IHC score of > or = 2+ was considered positive for overexpression. Between 1991 and 2000, 223 patients with ESSCLC were identified, of whom 193 patients (84 females, 109 males) with a mean age of 68.5 years (range: 42-90 years) had adequate tissue specimens for HER-2/neu testing. The symptoms at initial presentation and proportionate number of patients were: weight loss 61 (31.6%), cough 53 (27.5%), dyspnea 33 (17.1%), mass on chest radiograph 18 (9.3%), chest pain 15 (7.7%), asymptomatic 14 (7.2%) and others (weakness, lymphadenopathy, hoarseness and paraneoplastic syndromes) 29 (15.0%). Of the 193 specimens, 57 (29.5%) revealed HER-2/neu overexpression. The median survival for patients with ESSCLC who were HER-2/neu positive was 8 months (range: 1-25.5 months) while that in the HER-2/neu negative group was 16 months (range: 2-34 months). Interestingly, after adjusting for age, performance status and type of therapy, subset analysis revealed that the survival was significantly lower in HER-2/neu positive individuals (P<0.001; Mann-Whitney U-test). In our study, weight loss and cough were the two most common (59%) presenting complaints in patients with ESSCLC. Also, since HER-2/neu positivity was a marker for poor prognosis in ESSCLC, testing for overexpression may play a role in identifying patients at risk for shortened survival. Further studies would delineate whether HER-2/neu overexpression renders SCLC chemoresistant and thus, adversely affects outcome. There exists a need for randomized controlled trials to assess the role of Herceptin (alone or in combination with standard chemotherapy) in patients with ESSCLC.