A double-blind, randomized, placebo-controlled trial of essential fatty acid supplementation in the maintenance of remission of ulcerative colitis

Authors


Correspondence to: Dr S. J. Middleton, Department of Gastroenterology, Unit E7, Box 201A, Addenbrooke's NHS Trust, Cambridge CB2 2QQ, UK. E-mail: stephen.middleton@addenbrookes.nhs.uk

Summary

Background : Essential fatty acid supplementation has been found to ameliorate certain chronic inflammatory diseases. This effect is thought to be mediated through the modulation of eicosanoid synthesis. Pro-inflammatory eicosanoids have been implicated in ulcerative colitis.

Aim : To investigate the possible therapeutic benefit of essential fatty acids in quiescent ulcerative colitis to reduce the frequency of disease relapse.

Methods : A randomized, double-blind, placebo-controlled study was performed with a treatment duration of 12 months. Patients with quiescent disease received either trial medication (gamma-linolenic acid, 1.6 g, eicosapentaenoic acid, 270 mg, and docosahexaenoic acid, 45 mg, per day) or placebo (sunflower oil, 500 mg/day). The primary end-point was disease activity, assessed by a previously validated clinical index, sigmoidoscopic appearance and histology.

Results : Sixty-three patients were randomized, 31 to receive essential fatty acid treatment and 32 to receive placebo. Disease relapse rates were similar at 12 months (placebo, 38%; essential fatty acids, 55%), as were changes in sigmoidoscopic grade from baseline.

Conclusions : The supplementation of the diet with this combination of essential fatty acids does not prolong the period of disease remission of ulcerative colitis.

Introduction

The observation that several chronic inflammatory diseases, such as rheumatoid arthritis and eczema, are less common in regions in which fish is a popular and frequent food1 has led to the investigation of certain essential fatty acids for potential anti-inflammatory properties. It has been reported that n-3 fatty acids reduce the synthesis of pro-inflammatory prostaglandins and leukotrienes.2–5 The anti-inflammatory effects of fish oils have been demonstrated in animal models6, 7 and, in clinical studies, they have been found to reduce inflammation in psoriasis,8 atopic dermatitis9 and rheumatoid arthritis.10 Belluzzi et al. found that n-3 fatty acid supplementation reduced the relapse rate of Crohn's disease,11 although others have found conflicting results.12 Anti-inflammatory effects of fish oils have been demonstrated in animal models,13, 14 and elevated arachidonic acid levels in the colonic mucosa of patients with ulcerative colitis have been found to fall during eicosapentaenoic acid (EPA) supplementation.15

EPA competes with arachidonic acid for cyclo-oxygenase and lipoxygenase, which favours the production of trienoic eicosanoids, such as prostaglandin I3 and thromboxane A3, and also increases leukotriene B5 synthesis, whilst suppressing pro-inflammatory prostaglandins and leukotriene B4.16–18 Furthermore, EPA reduces the synthesis of interleukin-1 and tumour necrosis factor by peripheral mononuclear cells.12 EPA is derived from dietary alpha-linolenic acid by a rate-limited delta-6-desaturase step. In order to increase tissue EPA levels, it is necessary to administer EPA. Gamma-linolenic acid (GLA) is converted to dihomogammalinolenic acid (DGLA) and again competes with arachidonic acid for the cyclo-oxygenase enzyme, suppressing pro-inflammatory prostaglandins and increasing prostaglandin E1, which subsequently inhibits the release of arachidonic acid from cell membranes, increasing this anti-inflammatory effect.16, 19, 20 Conversion of dietary linoleic acid to GLA is the rate-limiting step in DGLA synthesis. Therefore, the administration of GLA may considerably increase DGLA synthesis. DGLA is also metabolized to 15-OH-DGLA, which inhibits 5-lipoxygenase and 12-lipoxygenase enzymes22, 23 and reduces the production of leukotriene B4 and hydroxyeicosatetraenoic acid (12HETE), both powerful pro-inflammatory agents. Docosahexaenoic acid (DHA) is synthesized from EPA by a rate-limited step. DHA impairs arachidonic-derived eicosanoid formation, resulting in further anti-inflammatory effects.24

Previous studies of fish oil supplementation in ulcerative colitis have used EPA23–25 or GLA.16 The combination of EPA, GLA and DHA may have a more potent anti-inflammatory effect than any of the oils alone, and avoids the usual rate-limiting steps in the synthesis of these compounds from dietary precursors. We investigated the hypothesis that their combined administration to patients with quiescent colitis would reduce relapse frequency.

Methods

Patient selection

Patients were recruited from a single teaching hospital in the UK. Patients gave written informed consent and local research ethical committee approval was obtained. Adults aged between 18 and 70 years were included if they had established ulcerative colitis in remission (confirmed histologically to have minimal or no acute inflammatory infiltrate as assessed by an independent histopathologist). Patients were excluded if they had serious renal or liver impairment, malignancy or epilepsy, were anticoagulated or on lithium or phenothiazine medications. Females were excluded if they were lactating, pregnant or at significant risk of conception.

Study design

This was a randomized, double-blind, placebo-controlled study of the efficacy of fatty acid supplementation in maintaining remission of ulcerative colitis. Study medication was taken as six capsules per day containing a daily dose of 1.62 g GLA as free fatty acid and lithium salt, 270 mg EPA and 45 mg DHA (HGA group). The placebo consisted of sunflower oil, 500 mg, in enteric-coated gelatine capsules. Patients were screened for eligibility and randomized after a 2-week run-in period to receive either placebo or study medication. The study was conducted over a 12-month period and patients were assessed at regular intervals (1, 3, 4, 6, 9 and 12 months) and also in the event of an adverse effect or possible disease relapse.

At the scheduled visits, symptoms were assessed using a clinical index derived from a previously published index.26 This produced a numerical clinical index by scoring symptoms for severity: urgency (0–4), abdominal pain (0–3), frequency of loose motions per 24 h and general well-being (0–4). The clinical index was used on the preceding 3 days and taken as an average daily score. Sigmoidoscopy was undertaken to further evaluate disease activity. At sigmoidoscopy, the grade of inflammation was assessed according to a standard grading system.27 Blood tests included standard, haematological and biochemical tests, and dietary analysis was conducted by an experienced dietician. Rectal biopsies were routinely taken at baseline and at 6 and 12 months. Remission was defined as a clinical index below 7, the appearance of normal rectal mucosa or minimal erythema, and the absence of active inflammation at histological analysis. Evidence of active disease at sigmoidoscopy or a clinical index greater than 6 was defined as disease activity.

Statistical analysis

A sample size of 50 patients was calculated to have 95% power to detect a reduction in relapse rate of 15% at the 5% significance level. The SAS system (version 6.1) was used to analyse the intention-to-treat populations, and randomized patients were included in the population if they had provided at least one measure of efficacy whilst on medication. Statistical tests were two-sided. Significance was indicated by a P value of less than 0.05. The demographic and clinical characteristics were compared by Student's t-test, Wilcoxon's signed rank test or chi-squared test as appropriate.28, 29 Statistical comparison of treatment efficacy was undertaken using proportional Cox hazard regression. There was no significant difference between treatments by disease site at the 10% level, and so all data, regardless of site, were combined prior to analysis. Data were analysed by a third party before breaking the treatment code.

Results

Patients

Sixty-three patients with quiescent ulcerative colitis were randomized to treatment over a 33-month period: 31 were randomized to the HGA group and 32 to the placebo group. Two patients in the HGA group and two in the placebo group withdrew due to adverse events prior to 1 month and one patient in the placebo group failed to return after day 1. As these patients did not undergo an assessment of treatment, they were excluded from the study population as per protocol, which therefore consisted of 58 patients, 29 in each group, upon whom the efficacy analyses were performed. The age and gender distribution of the HGA group (male/ female = 15/12; age (mean ± s.d.), 41 ± 9 years; range, 26–66 years) was similar to that of the placebo group (male/female = 14/15; age, 43 ± 12 years; range, 18–65 years). One patient in the HGA group smoked, as did three in the placebo group. Concurrent medication taken during the study was similar in the two groups. All patients took a 5-aminosalicylic acid preparation (range, 400–800 mg t.d.s.) throughout the study. Prednisolone was taken at the onset of the study period by 10 (34%) patients in the placebo group and eight (28%) patients in the HGA group (N.S.). Prednisolone was taken in reducing doses (5 mg/week) and stopped within 4 weeks of commencing the study in all but two patients in each group, who were on long-term maintenance treatment at 10 mg once daily. One patient in the placebo group took replacement hydrocortisone throughout the study. There were no major protocol violations. Other demographic details are given in Table 1. Figure 1 shows the disposition of all patients and the stages at which patient withdrawal occurred.

Table 1.  Summary of patient characteristics and reasons for withdrawal from the study
 PlaceboHGA
  1. HGA, eicosapentaenoic acid, gamma-linolenic acid and docosahexaenoic acid.

  2. Data are patient numbers and percentages in parentheses.

  3. There were no statistically significant differences between the groups for any of the above parameters.

Number of patients2929
Duration of disease (months)75 ± 8986 ± 76
Distribution of disease (%)
 Total 3 (10) 5 (18)
 Left13 (45)12 (41)
 Rectal13 (45)12 (41)
Reasons for withdrawal from study (%)
 Death 1 (3.5) 0
 Adverse event 0 3 (10)
 Failure to return 0 1 (3.5)
 Other 0 2 (7)
Figure 1.

Flow diagram illustrating the disposition of patients during the study and the stages at which patient withdrawals occurred. Reasons for patient withdrawal are given in Table 1. HGA, eicosapentaenoic acid, gamma-linolenic acid and docosahexaenoic acid.

Clinical efficacy

There was no statistically significant difference in relapse rate between the groups (Figure 2), and no significant difference in the intake of dietary constituents or adverse events between the groups. Sigmoidoscopic evaluation of disease activity was also similar between the groups, as were the haematological and biochemical parameters. The reasons for patient withdrawal from the study are given in Table 1.

Figure 2.

Time of disease relapse for patients randomized to HGA (eicosapentaenoic acid, gamma-linolenic acid and docosahexaenoic acid) or placebo (sunflower oil) groups. Differences between study groups did not achieve statistical significance. On relapse of disease, patients were withdrawn from the study.

Discussion

In this study, supplementation of the diet with a combination of EPA, DHA and GLA did not reduce the relapse rate of quiescent ulcerative colitis.

Two small open studies of dietary supplementation with essential fatty acids30, 31 noted a fall in pro-inflammatory leukotriene B4 levels and prompted larger studies. Hawthorne et al. studied 69 patients with quiescent ulcerative colitis for a 1-year period and, in concordance with our results, found that EPA did not have a beneficial effect.23 Greenfield et al. administered EPA in a double-blind manner to 343 patients with quiescent colitis over a 6-month period and found that the disease process was not significantly altered in either group.16 In contrast, Loeschke et al. noted a delay in early relapse frequency in a study of 164 patients with quiescent colitis who were randomized to receive either supplementary n-3 fatty acids or maize oil placebo for 2 years.32 Fewer patients relapsed in the first 3 months on n-3 fatty acids than placebo but, at 2 years, a similar proportion of patients had relapsed.

Patients with active ulcerative colitis were not included in our study, although others have found fish oils to be of modest benefit in this condition. Stenson et al. found that histological improvement occurred in patients who received a combination of EPA and DHA for 4 months, and also noted an increase in body weight and reduced rectal dialysate leukotriene B4 level, although symptoms and sigmoidoscopic scores did not significantly improve.33 Aslan & Triadafilopoulos found that EPA and DHA in combination allowed a reduction in the medication taken for ulcerative colitis.34

The use of DHA and GLA in addition to EPA might theoretically have an advantage over EPA alone. However, in our study, this combination did not reduce the relapse rate of quiescent ulcerative colitis. The low dose regime used in our study did not cause any adverse events. It is possible that larger doses of these agents in combination might have a therapeutic effect.

Acknowledgement

We would like to acknowledge Mrs K. Ball for her kind help in the preparation of the manuscript, and Scotia Pharmaceuticals for provision of study medication.

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