Slow-reacting substances and their formation by a lipoxygenase pathway

The impact of a medical food containing gammalinolenic and eicosapentaenoic acids on asthma management and the quality of life of adult asthma patients

BACKGROUND

Leukotriene synthesis inhibitors and receptor antagonists are efficacious for the treatment of asthma. Diets containing the fatty acids gammalinolenic acid (GLA) and eicosapentaenoic acid (EPA) decrease leukotriene synthesis; however, their impact on asthma management and quality of life (QOL) has not been evaluated in asthmatic subjects.

OBJECTIVE

To evaluate asthma management and the QOL of asthmatic adult subjects consuming a medical food emulsion containing GLA and EPA.

RESEARCH DESIGN AND METHODS

Trial 1 was a randomized, prospective, double-blind, placebo-controlled, parallel group trial in atopic subjects with mild-to-moderate asthma (n = 35 evaluable) consuming a low dose (0.75 g GLA + 0.5 g EPA), high dose (1.13 g GLA + 0.75 g EPA) or placebo emulsion daily. Subjects were questioned about their asthma management using a non-validated questionnaire after 2 and 4 weeks. Blood leukotrienes were measured at baseline and after 4 weeks. Trial 2 was an open-label study (n = 65 evaluable) where subjects consumed the low-dose medical food emulsion, EFF1009, daily. QOL and asthma management were measured using the validated Mini Asthma Quality of Life (MiniAQLQ) and the Asthma Control (ACQ) questionnaires, respectively, administered at baseline and after 4 weeks.

RESULTS

In Trial 1, leukotriene biosynthesis decreased (p < 0.05). Self-reported asthma status and bronchodilator use improved in subjects consuming low- and high-dose emulsion between week 2 and week 4 (p < 0.01), but not compared to placebo (p > 0.1). In Trial 2, mean +/- standard error total MiniAQLQ and ACQ scores improved by 1.5 +/- 0.2 and 1.0 +/- 0.1, respectively (p < 0.001). Subdomain scores from MiniAQLQ improved and rescue bronchodilator use decreased (p < 0.001).

CONCLUSION

The inclusion of the medical food EFF1009 in asthma management regimens can improve patient quality of life and decrease reliance on rescue medication.

Inhibition of leukotriene biosynthesis by a novel dietary fatty acid formulation in patients with atopic asthma: a randomized, placebo-controlled, parallel-group, prospective trial

BACKGROUND

Leukotriene inhibitors and leukotriene-receptor antagonists are effective in the treatment of inflammatory diseases such as asthma. A search of the entirety of MEDLINE using the terms diet plus leukotrienes identified numerous studies that have explored dietary-management strategies to reduce leukotriene levels through supplementation with polyunsaturated fatty acids such as gamma-linolenic acid (GLA) and eicosapentaenoic acid (EPA). However, the search found no studies on the use of combinations of these fatty acids in patients with asthma.

OBJECTIVE

The goal of this study was to determine the effect of daily intake of an emulsion (PLT 3514) containing dietary GLA and EPA on ex vivo stimulated whole blood leukotriene biosynthesis in patients with atopic asthma.

METHODS

This was a randomized, double-blind, placebo-controlled, parallel-group, prospective trial in patients with mild to moderate atopic asthma. Patients consumed 10 g PLT 3514 emulsion (containing 0.75 g GLA + 0.5 g EPA), 15 g PLT 3514 emulsion (containing 1.13 g GLA + 0.75 g EPA), or placebo (olive oil) emulsion daily for 4 weeks. Plasma fatty acids were measured by gas chromatography, and stimulated whole blood leukotrienes were measured by reverse-phase high-performance liquid chromatography with ultraviolet detection using a diode array detector.

RESULTS

Forty-three patients (33 women, 10 men) participated in the study. Leukotriene biosynthesis was significantly decreased in patients consuming 10 or 15 g PLT 3514 compared with placebo (P < 0.05, analysis of covariance). No clinically significant changes in vital signs were observed throughout the study, and there were no significant between-group differences in treatment-emergent adverse events or mean clinical laboratory values.

CONCLUSION

Daily consumption of dietary GLA and EPA in a novel emulsion formulation inhibited leukotriene biosynthesis in this population of patients with atopic asthma and was well tolerated.

Inhibition of leukotriene synthesis, pharmacokinetics, and tolerability of a novel dietary fatty acid formulation in healthy adult subjects

BACKGROUND

Numerous studies have explored dietary-management strategies for decreasing leukotriene synthesis by inflammatory cells through supplementation with polyunsaturated fatty acids such as gamma-linolenic acid (GLA) and eicosapentaenoic acid (EPA).

OBJECTIVES

This study sought to determine the optimal daily intake, ratios, and formulation of dietary GLA and EPA required to safely reduce leukotriene biosynthesis in healthy individuals, and to evaluate the pharmacokinetics and safety profile of such a formulation.

METHODS

Two preliminary trials were conducted to determine the minimum effective levels of GLA and EPA intake needed to reduce leukotriene biosynthesis and prevent increases in plasma arachidonic acid (AA) concentrations. These preliminary trials were followed by a single-center, randomized, double-blind, placebo-controlled, parallel-group, escalating-intake inpatient trial of a dietary GLA/EPA emulsion (PLT 3514) in healthy adult subjects. Subjects consumed either 10, 20, or 100 g of the PLT 3514 emulsion (respectively containing 0.75 g GLA + 0.5 g EPA, 1.5 g GLA + 1 g EPA, and 7.5 g GLA + 5 g EPA), or a placebo emulsion containing olive oil daily for 14 days. Plasma fatty acids were measured by gas chromatography Stimulated whole blood leukotrienes were measured by high-performance liquid chromatography with ultraviolet detection.

RESULTS

Thirty subjects were included in the preliminary trials; 47 subjects were enrolled in the escalating-intake trial, of whom 42 completed the study. In the preliminary trials, intake of GLA 1.5 g/d in gelatin capsules decreased the capacity to synthesize leukotrienes but increased plasma levels of AA (both, P < 0.05). Inclusion of 0.25 or 1 g of dietary EPA prevented the increase in plasma AA concentrations. Dietary GLA and EPA showed significantly enhanced bioavailability when consumed in 20 g PLT 3514 emulsion compared with consumption in gelatin capsules (P < 0.05), resulting in a reduction in the amount of intake required to block leukotriene biosynthesis. Pharmacokinetic analyses indicated that fasting plasma GLA and EPA levels plateaued within 7 days' daily consumption at all levels of intake, whereas the time to maximum plasma concentration (Tmax) was shorter for GLA than for EPA. The Tmax was similar on days 1 and 14 for both GLA and EPA. There were no clinically significant between-group differences in changes in vital signs, mean clinical laboratory values, or abbreviated hematology laboratory tests, or significant differences in the occurrence of treatment-emergent adverse events between the group consuming up to 20 g/d of the GLA/EPA emulsion and the group consuming placebo.

CONCLUSION

Consumption of specific proportions and intake levels of dietary GLA and EPA in a novel emulsion formulation inhibited leukotriene biosynthesis and appeared to be well tolerated in this population of healthy adult subjects.

Thromboxane A2 mediated bronchoconstriction in the anesthetized guinea pig

Arachidonic acid-induced platelet aggregation has been shown to be selectively antagonized by the thromboxane A2 synthetase inhibitor SQ 80,338 or by the thromboxane A2 receptor antagonist SQ 24,775. Experiments were done to see what effect these two compounds would have on the bronchoconstrictor response to various agents in the anesthetized guinea pig. Increases in pulmonary resistance and decreases in dynamic compliance were taken as an index of bronchoconstriction. Both SQ 80,338 (0.3-10.0 mg/kg) and SQ 24,775 (0.1-1.0 mg/kg) administered i.v. caused dose-related inhibitions of arachidonate-induced bronchoconstriction. SQ 80,338 (3.0 and 10.0 mg/kg) also inhibited bradykinin-induced bronchoconstriction in the presence of beta-adrenergic blockade. These same doses of SQ 80,338 and SQ 24,775 did not alter either histamine- or antigen-induced bronchoconstriction. SQ 80,338 (10.0 micrograms/ml) prevented arachidonate-induced release of TXA2 from the isolated perfused guinea pig lung while SQ 24,775 (1.0 microgram/ml) antagonized the contraction of the isolated rat aorta induced by 9,11,AZO-PGH2. These results suggest that both arachidonate and bradykinin-induced bronchoconstriction are mediated through the generation of TXA2, while histamine- and antigen-induced bronchoconstriction are not.