Effects of L-arginine Supplementation in Adults With Moderate to Severe Asthma

University of California (UC) Davis

Status and phase: Completed; Phase 2

Conditions: Asthma

Treatments: Drug: Placebo; Drug: L-arginine

Study type: Interventional

Funder types: Other; NIH

Identifiers

NCT00280683

UL1RR024146 (U.S. NIH Grant/Contract)

K30-04-Z001 (Other Identifier)

200412788

Details and patient eligibility

About

Nitric oxide is an important marker of airway inflammation in asthma. Nitric oxide may have a protective role in patients with moderate to severe asthma. The investigators believe that a natural amino acid, L-arginine, that augments nitric oxide levels can decrease asthma exacerbations and improve the asthma care of moderate to severe asthma patients.

This study is a randomized, placebo controlled trial in which subjects will receive either 3 months of L-arginine supplementation or a placebo. The investigators will monitor subjects' symptoms, the number of asthma exacerbations, and lung function. In addition, we will draw blood, obtain induced sputum samples and measure exhaled breath nitric oxide levels at each monthly visit.

Full description

The primary objective of this 3 month clinical study is to determine if supplemental L-arginine can decrease the number of asthma exacerbations in patients with severe asthma. L-arginine, a natural amino acid, produces nitric oxide (NO) when it is converted to L-citrulline in the presence of the nitric oxide synthase enzymes. We and others have found that NO can protect against allergic airway inflammation, airway hyperresponsiveness and airway fibrosis in various animal models. In addition, we have found that arginase I expression correlates strongly with the lymphocyte and eosinophil influx into the lung and this enzyme may regulate the airway inflammatory response. Our central hypothesis is that L-arginine will increase NO levels in the lung and decrease the number of acute exacerbations of asthma. It may do this by either decreasing the number of Th2 lymphocytes or down-regulating arginase I expression or both.

Our specific aims are, therefore,

1. To test the hypothesis, in a randomized, double-blinded, placebo controlled trial, that 3 months of L-arginine supplementation will decrease the number of acute asthma exacerbations in severe asthmatic patients,
2. To determine whether L-arginine decreases the ratio of peripheral blood Th2 to Th1 lymphocytes and
3. To determine whether L-arginine will modulate serum arginase I/II levels and their downstream products.

Patients will be recruited primarily from the UC Davis Asthma Network (UCAN) clinics, which focus on the care of severe asthmatics, and the study will be performed at the UC Davis/VA General Clinical Research Center.

Enrollment: 20 patients

Sex: All

Ages: 18 to 90 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Moderate to severe persistent asthma
• Subject is stable on same asthma medications for at least one month
• If the subject is a woman of child-bearing age, a negative pregnancy test

Exclusion criteria

• Less than 18 yrs/ age
• Baseline Forced Expiratory Volume in 1 second (FEV1) <40% predicted
• Known or suspected allergy to L-arginine
• Pregnant women, nursing women, or women actively trying to achieve pregnancy
• Current smokers
• Subjects with more than a 15 pack-year history of smoking

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Quadruple Blind

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20 participants in 2 patient groups, including a placebo group

Arginine

Active Comparator group

Description:

Enrolled subjects will take L-arginine orally, at 0.1 g/kg/day. Subjects will take three to four 1 g capsules (based on weight) of L-arginine twice daily for three months. L-arginine capsules were obtained from Jarrow Pharmaceuticals.

Treatment:

Drug: L-arginine

Placebo

Placebo Comparator group

Description:

Enrolled subjects took three to four placebo capsules that matched color and size of the intervention twice daily for three months. Matching placebo capsules were obtained from Jarrow Pharmaceuticals.

Treatment:

Drug: Placebo