ABSTRACT
BACKGROUNDThe airways of obese asthmatics have been shown to be NO deficient, and this contributes to airway dysfunction and reduced response to inhaled corticosteroids. In cultured airway epithelial cells, L-citrulline, a precursor of L-arginine recycling and NO formation, has been shown to prevent asymmetric dimethyl arginine-mediated (ADMA-mediated) NO synthase (NOS2) uncoupling, restoring NO and reducing oxidative stress.METHODSIn a proof-of-concept, open-label pilot study in which participants were analyzed before and after treatment, we hypothesized that 15 g/d L-citrulline for 2 weeks would (a) increase the fractional excretion of NO (FeNO), (b) improve asthma control, and (c) improve lung function. To this end, we recruited obese (BMI >30) asthmatics on controller therapy, with a baseline FeNO of ≤30 ppb from the University of Colorado Medical Center and Duke University Health System.RESULTSA total of 41 subjects with an average FeNO of 17 ppb (95% CI, 15-19) and poorly controlled asthma (average asthma control questionnaire [ACQ] 1.5 [95% CI, 1.2-1.8]) completed the study. Compared with baseline, L-citrulline increased whereas ADMA and arginase concentration did not (values represent the mean Δ and 95% CI): plasma L-citrulline (190 µM, 84-297), plasma L-arginine (67 µM, 38-95), and plasma L-arginine/ADMA (ratio 117, 67-167). FeNO increased by 4.2 ppb (1.7-6.7 ppb); ACQ decreased by -0.46 (-0.67 to 0.27 points); the forced vital capacity and forced exhalation volume in 1 second, respectively, changed by 86 ml (10-161 ml) and 52 ml (-11 to 132 ml). In a secondary analysis, the greatest FEV1 increments occurred in those subjects with late-onset asthma (>12 years) (63 ml [95% CI, 1-137]), in females (80 ml [95% CI, 5-154]), with a greater change seen in late-onset females (100 ml, [95% CI, 2-177]). The changes in lung function or asthma control were not significantly associated with the changes before and after treatment in L-arginine/ADMA or FeNO.CONCLUSIONShort-term L-citrulline treatment improved asthma control and FeNO levels in obese asthmatics with low or normal FeNO. Larger FEV1 increments were observed in those with late-onset asthma and in females.TRIAL REGISTRATIONClinicalTrials.gov NCT01715844.FUNDINGNIH NHLBI R01 HL146542-01.
Subject(s)
Asthma/diet therapy , Citrulline/administration & dosage , Dietary Supplements , Nitric Oxide/metabolism , Obesity/diet therapy , Adult , Aged , Arginine/analogs & derivatives , Arginine/blood , Asthma/blood , Asthma/complications , Asthma/diagnosis , Citrulline/blood , Female , Forced Expiratory Volume , Humans , Male , Middle Aged , Nitric Oxide/blood , Nitric Oxide Synthase Type II/metabolism , Obesity/blood , Obesity/complications , Oxidative Stress/drug effects , Pilot Projects , Proof of Concept Study , Severity of Illness Index , Treatment Outcome , Young AdultABSTRACT
IMPORTANCE: In asthma and other diseases, vitamin D insufficiency is associated with adverse outcomes. It is not known if supplementing inhaled corticosteroids with oral vitamin D3 improves outcomes in patients with asthma and vitamin D insufficiency. OBJECTIVE: To evaluate if vitamin D supplementation would improve the clinical efficacy of inhaled corticosteroids in patients with symptomatic asthma and lower vitamin D levels. DESIGN, SETTING, AND PARTICIPANTS: The VIDA (Vitamin D Add-on Therapy Enhances Corticosteroid Responsiveness in Asthma) randomized, double-blind, parallel, placebo-controlled trial studying adult patients with symptomatic asthma and a serum 25-hydroxyvitamin D level of less than 30 ng/mL was conducted across 9 academic US medical centers in the National Heart, Lung, and Blood Institute's AsthmaNet network, with enrollment starting in April 2011 and follow-up complete by January 2014. After a run-in period that included treatment with an inhaled corticosteroid, 408 patients were randomized. INTERVENTIONS: Oral vitamin D3 (100,000 IU once, then 4000 IU/d for 28 weeks; n = 201) or placebo (n = 207) was added to inhaled ciclesonide (320 µg/d). If asthma control was achieved after 12 weeks, ciclesonide was tapered to 160 µg/d for 8 weeks, then to 80 µg/d for 8 weeks if asthma control was maintained. MAIN OUTCOMES AND MEASURES: The primary outcome was time to first asthma treatment failure (a composite outcome of decline in lung function and increases in use of ß-agonists, systemic corticosteroids, and health care). RESULTS: Treatment with vitamin D3 did not alter the rate of first treatment failure during 28 weeks (28% [95% CI, 21%-34%] with vitamin D3 vs 29% [95% CI, 23%-35%] with placebo; adjusted hazard ratio, 0.9 [95% CI, 0.6-1.3]). Of 14 prespecified secondary outcomes, 9 were analyzed, including asthma exacerbation; of those 9, the only statistically significant outcome was a small difference in the overall dose of ciclesonide required to maintain asthma control (111.3 µg/d [95% CI, 102.2-120.4 µg/d] in the vitamin D3 group vs 126.2 µg/d [95% CI, 117.2-135.3 µg/d] in the placebo group; difference of 14.9 µg/d [95% CI, 2.1-27.7 µg/d]). CONCLUSIONS AND RELEVANCE: Vitamin D3 did not reduce the rate of first treatment failure or exacerbation in adults with persistent asthma and vitamin D insufficiency. These findings do not support a strategy of therapeutic vitamin D3 supplementation in patients with symptomatic asthma. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01248065.
Subject(s)
Adrenal Cortex Hormones/administration & dosage , Asthma/drug therapy , Cholecalciferol/therapeutic use , Glucocorticoids/administration & dosage , Pregnenediones/administration & dosage , Vitamin D Deficiency/drug therapy , Vitamins/therapeutic use , Administration, Inhalation , Administration, Oral , Adult , Anti-Asthmatic Agents/administration & dosage , Asthma/complications , Asthma/physiopathology , Dose-Response Relationship, Drug , Double-Blind Method , Female , Humans , Lung/drug effects , Lung/physiopathology , Male , Middle Aged , Treatment Failure , Vitamin D Deficiency/complicationsABSTRACT
Both arginase isoforms (AI and AII) regulate high-level NO production by the inducible NOS, but whether the arginase isoforms also regulate low-level NO production by neuronal NOS (nNOS) is not known. In this study, 293 cells that stably overexpress nNOS gene (293nNOS cells) were transfected with rat AI (pEGFP-AI) or AII (pcDNA-AII) plasmids, and nitrite production was measured with or without supplemental L-arginine. Transfection with pEGFP-AI increased AI expression and activity 10-fold and decreased intracellular l-arginine by 50%. Nitrite production was inhibited by >80% when no l-arginine was supplemented but not when 1 mM L-arginine was present. The inhibition was reversed by an arginase inhibitor, N(omega)-hydroxy-L-arginine. Transfection with pcDNA-AII increased AII expression and activity but had little effect on nitrite production even if no l-arginine was added. These results suggest that, in 293nNOS cells, AI was more effective in regulating NO production by nNOS, most likely by competing for L-arginine.