Impact of Portulaca oleracea L. extract in patients with irritable bowel syndrome
Article information
Abstract
Background/Aims
Portulaca oleracea is known to have anti-inflammatory and immunoregulatory effects, and also showed positive effect on complete spontaneous bowel movement and bowel symptoms in patients with chronic constipation in a previous study. Thus, we aimed to investigate the impact of P. oleracea in patients with irritable bowel syndrome (IBS).
Methods
Patients with IBS defined by ROME IV criteria were enrolled between July 2022 and April 2023. Patients were randomly assigned to P. oleracea or placebo group and took drugs for 8 weeks. Clinical data including gastrointestinal and IBS symptoms, laboratory tests including inflammatory and immunologic laboratory markers, and stool tests including fecal calprotectin and stool microbial analysis were evaluated at the baseline, week 4, and week 8.
Results
A total of 108 patients were initially enrolled and 101 patients were finally included in the analysis. There was significant improvement during 8 weeks in P. oleracea group compared to placebo group in the aspect of gastrointestinal and IBS-related bowel symptoms (Gastrointestinal Symptom Rating Scale total score: from 44.1 to 31.7 vs. from 41.4 to 39.9; IBS-Symptom Severity Score total score: from 232.0 to 120.6 vs. from 202.7 to 178.2), especially in the aspect of abdominal pain. Interleukin-6 (IL-6) was significantly decreased during 8 weeks in P. oleracea group, although there was no significant difference between 2 groups. In addition, increase in IL-6 during study period was significantly associated with dysbiosis in stool microbial analysis. There was no significant adverse event.
Conclusions
P. oleracea has positive impact in patients with IBS showing improvement of immunologic cytokine and stool microbiome.
INTRODUCTION
Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders characterized by chronic abdominal pain accompanied by bowel habit change. The prevalence of IBS is increasing in Asian countries and IBS becomes a considerable burden on health-related quality of life [1,2]. Recently, IBS has been regarded as a multifactorial disorder of gut-brain interaction. Dietary therapy such as low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet, lifestyle modification such as regular exercise, and medical therapies including laxatives, antidiarrheals, and antispasmodics are main treatment options for IBS [2-5]. However, there are still unmet needs with conventional treatment, thus new medical treatments such as complementary and alternative medicines are gaining attention in the treatment of IBS [6].
Portulaca oleracea or purslane belongs to one of the annual grass and has been used as a traditional remedy for various diseases [7]. P. oleracea is known to have anti-inflammatory and immunoregulatory effects in previous animal studies [8-10], and also has a positive effect on fecal evacuation in an animal model [11]. Recently, our group reported the effect of P. oleracea on functional constipation which showed significant improvement of complete spontaneous bowel movement (CSBM) in P. oleracea group compared with the placebo group during an 8-week study period (P=0.003) [12].
Given these findings, we hypothesized that P. oleracea also could be effective in patients with IBS, which has not yet been evaluated. Therefore, in this study, we aimed to investigate the impact of P. oleracea in patients with IBS, including not only the constipation-predominant type but all subtypes.
METHODS
1. Patients
This study was a double-blinded, randomized controlled trial performed between July 2022 and April 2023 in a tertiary referral center. Eligible patients were adult subjects aged between 20 and 65 years who met ROME IV criteria of IBS and agreed to participate in this study. These include recurrent abdominal pain (on average, experienced for at least 1 day a week in the last 3 months with symptom onset at least 6 months before diagnosis) associated with 2 or more of the following criteria: (1) related to defecation; (2) associated with a change in a frequency of stool; or (3) associated with a change in form (appearance) of stool. Subtypes were based on stool consistency and included 4 subtypes: (1) constipation-predominant type (IBS-C); (2) diarrhea-predominant type (IBS-D); (3) mixed type (IBS-M); or (4) unclassified type (IBS-U). Patients aged 45 years and above were enrolled only if there were no advanced adenomas (high-grade dysplasia, villous adenoma, and size ≥ 1 cm) in a previous colonoscopy within the last 5 years to exclude significant organic colorectal disease [13-15].
Exclusion criteria were as follows: (1) subjects who took antibiotics or probiotics within the 2 weeks before enrollment; (2) subjects who have a history of suggesting organic gastrointestinal disease; (3) subjects who had undergone abdominal surgery (excluding appendectomy); (4) subjects who take medications affecting gastrointestinal motility such as antispasmodics or prokinetics within the 2 weeks before enrollment; (5) subjects with liver cirrhosis, severe congestive heart failure (New York Heart Association grade III or IV), severe renal dysfunction (creatinine clearance <30 mL/min), uncontrolled hypertension, endocrine disorders, metabolic disorders, malignant tumors, or immunodeficiency; (6) subjects who had a history of clinically significant hypersensitivity reactions; (7) subjects who have engaged in abnormal dietary practices within 30 days before the first day of administration; (8) subjects with a history of drug abuse; (9) subjects with excessive alcohol consumption (alcohol >21 units/week; 1 unit=10 mL of pure alcohol); (10) subjects who were pregnant or lactating women; (11) subjects who have taken other investigational food/drugs within 3 months before the first day of administration of the investigational food; and (12) any other reason which is unsuitable for participation in the clinical trial. This study was approved by the Institutional Review Board of Dankook University Hospital (IRB No. DKUH 2021-12-010) and written informed consent was obtained.
Eligible participants were randomly assigned to either the investigation group, which received KDC16-2, a 70% ethanol extract of P. oleracea (480 mg) [8,11], or the control group, which received a placebo consisting of a 1:1 mixture of maltodextrin and mannitol (480 mg). To maintain the blinding during the study period, the investigation and the placebo drug were designed to be indistinguishable in terms of shape, color, flavor, and scent. Random allocations were carried out using a specific program available at http://randomization.com. Patients took 1 tablet of each medication once daily for 8 weeks, and visited the hospital at baseline, week 4, and week 8. Vital signs, physical exam, and gastrointestinal and bowel symptoms were evaluated at baseline, week 4, and week 8. Laboratory tests including inflammatory and immunologic markers, and stool tests including fecal calprotectin and stool microbial analysis were evaluated at baseline and week 8.
2. Stool Microbial Analysis
Microbial genomic DNA was extracted from stool samples using Qiagen’s QIAamp Power Fecal Pro DNA Kit (Qiagen, Hilden, Germany). Subsequently, the 16S ribosomal RNA V3-V4 hypervariable region was amplified by polymerase chain reaction using 341F/805R library, and microbial genomic data were obtained through Illumina MiSeq sequencing (Illumina, San Diego, CA, USA).
3. Outcome Measurement
Patients were requested to report their gastrointestinal symptoms using Gastrointestinal Symptom Rating Scale (GSRS) [16], bowel symptoms using IBS-Severity Scoring System (IBS-SSS) [17], Bristol Stool Form Scale (BSFS), spontaneous bowel movement (SBM), CSBM at each visit (baseline, week 4, and week 8). Laboratory tests including inflammatory and immunologic biomarkers (tumor necrosis factor-α, interferon-γ, interleukin [IL]-1β, IL-6, IL-8, IL-10, immunoglobulin G, immunoglobulin A, high-sensitivity C-reactive protein, erythrocyte sedimentation rate, prostaglandin E2, myeloperoxidase, and leukotriene B4), and stool tests including fecal calprotectin and stool microbial analyses were performed at the baseline and week 8. Primary outcomes were the improvement of gastrointestinal and bowel symptoms after 4 weeks and 8 weeks compared to the baseline. Secondary outcomes were the improvement of inflammatory and immunologic laboratory findings and the change of microbiome after 8 weeks compared to the baseline.
4. Sample Size
Until now, there was no relevant data about the efficacy of P. oleracea on IBS. It was assumed that statistical power was 80%, dropout rate was 20%, effect size was 0.14, correlation coefficient between repeated measurements was 0.5, and two-sided significance was 5%. Using G-power 3.1.9.7. [18], effective sample size was calculated as 90 patients (45 patients for each group), and considering 20% of dropout rate, the final sample size was assumed as 108 patients (54 patients for each group).
5. Statistical Analysis
Categorical variables were presented as the number and percentages, and evaluated by chi-square test or Fisher exact test. Continuous variables were presented as mean±standard deviation, and evaluated by t-test or Wilcoxon signed rank test. Baseline demographics and safety analysis were performed based on intention-to-treat analysis. Gastrointestinal and bowel symptom, stool consistency and frequency, laboratory data and stool microbial analysis were performed based on per-protocol analysis. To evaluate the effect of P. oleracea during the study period, repeated measure analysis of variance and paired t-test were used for continuous variables, and linear mixed effect model and McNemar test were used for categorical variables. Two-sided P-values <0.05 were considered statistically significant. Statistical analyses were conducted using R software (version 4.1.3, R Foundation for Statistical Computing, Vienna, Austria).
RESULTS
A total of 108 patients were initially enrolled and randomized equally to 54 patients for each group. Mean age was 45.1 years and 49 patients (45.4%) were male. There was no significant difference in demographic data between the 2 groups except mean diastolic blood pressure and mean pulse rate in intention-to-treat analysis (P=0.044) (Table 1). During the study period, 7 patients (1 patient in P. oleracea group and 6 patients in placebo group) were dropped out due to withdrawal of consent for this study. Finally, 53 patients in P. oleracea group and 48 patients in placebo group were analyzed based on per-protocol analysis (Supplementary Table 1). Among them, IBS-D was the most common subtype in both groups, followed by IBS-C (Fig. 1).
Demographic Characteristics of Enrolled Patients
Study overview. IBS, irritable bowel syndrome; P. oleracea, Portulaca oleracea; IBS-C, constipation-dominant IBS; IBS-D, diarrheadominant IBS; IBS-M, mixed-type IBS; IBS-U, unclassified IBS.
1. Impact of P. oleracea on Gastrointestinal Symptoms
During the study period, there was significant improvement of total GSRS in P. oleracea group at week 8 compared with placebo group (from 44.1 at baseline to 31.7 at week 8 in P. oleracea group vs. from 41.4 at baseline to 39.9 at week 8 in placebo group; P<0.001), although no significant difference at week 4 (37.6 at week 4 in P. oleracea group vs. 40.2 at week 4 in placebo group; P=0.261). In detail, abdominal pain, indigestion syndrome, and diarrhea syndrome were significantly improved at week 8 in P. oleracea group compared with placebo group (all P<0.05) (Table 2).
Changes of Gastrointestinal Symptoms during the Study Period
2. Impact of P. oleracea on Bowel Symptoms
During the study period, there was a significant improvement of total IBS-SSS score in P. oleracea group at week 8 compared with placebo group (from 232.0 at baseline to 120.6 at week 8 in P. oleracea group vs. from 202.7 at baseline to 178.2 at week 8 in placebo group; P=0.001). In detail, abdominal pain, abdominal bloating, bowel habit satisfaction, and symptom severity were significantly improved at week 8 in P. oleracea group compared with placebo group (all P<0.05) (Table 3). In addition, P. oleracea group exhibited a higher number of patients who experienced significant improvement (≥ 50) in total IBS-SSS scores compared with placebo group (79.3% in P. oleracea group vs. 25.0% in placebo group) (Table 4).
Changes of Bowel Symptoms during the Study Period
Changes of Total IBS-SSS Score during the Study Period
3. Impact of P. oleracea on Stool Consistency and Frequency
At baseline, the number of patients of BSFS type 3–5 in P. oleracea group was relatively lower than that in placebo group (11.3% vs. 31.3%; P=0.047). During 8-week study period, there were significant increase in the number of patients of BSFS type 3–5 at week 4 and week 8 in both groups (all P<0.05), however no significant difference between the 2 groups at week 4 and week 8 (Table 5). There was no significant difference of SBM and CSBM per week at baseline, week 4, and week 8 in each group, however there were significant improvements of CSBM at week 4 and week 8 compared with baseline in P. oleracea group (Table 6).
Changes of Stool Consistency during the Study Period
Changes of Stool Frequency during the Study Period
4. Impact of P. oleracea on Immunologic and Inflammatory Markers
During the study period, there was no significant difference of immunologic markers in placebo group. In contrast, IL-6 significantly decreased (from 1.70 to 1.25; P=0.034) and IL-8 significantly increased (from 12.31 to 13.72; P=0.003) in P. oleracea group (Supplementary Table 2). In addition, there was no significant difference of inflammatory markers including fecal calprotectin in both groups except myeloperoxidase (from 163.12 to 149.37 in P. oleracea group vs. from 189.80 to 216.04 in placebo group) (Supplementary Table 3).
5. Impact of P. oleracea on Stool Microbiota
During the study period, 52 patients in P. oleracea group and 48 patients in placebo group were evaluated for stool microbiome at baseline and week 8. One patient in P. oleracea group was excluded from the final analysis due to poor data quality. Compared to baseline, there were significant improvements of alpha-diversity indices (observed features, Chao1 index, Shannon index, Simpson index, and Pielou evenness) at week 8, indicating an increase in richness during the study period, in both group (P<0.05) (Fig. 2). For beta-diversity, there were no significant differences in Bray-Curtis dissimilarity, however there were significant differences in unweighted UniFrac in both groups by PERMANOVA test (P=0.028 for P. oleracea group, P=0.027 for placebo group) (Fig. 3).
Changes in alpha diversity in subjects before and after the intervention. (A) Placebo group and (B) Portulaca oleracea group. *P<0.05, **P<0.01, ***P<0.001. NS, not significant.
Change in beta diversity in subjects before and after the intervention, Bray-Curtis and unweighted UniFrac dissimilarity. (A) Placebo group and (B) Portulaca oleracea group.
Considering the impact of P. oleracea on the change of IL-6 in this study, we performed additional stool microbial analysis according to the change of IL-6. In the respect of alpha-diversity, there was a significant decrease in IL-6 increase group (P=0.048 for Shannon index, P<0.01 for Simpson index), whereas no significant change in IL-6 decrease group. In addition, diversity (P=0.04 for Simpson index) and evenness (P=0.02 for Pielou evenness) at week 8 were significantly lower in IL-6 increase group compared to IL-6 decrease group (Fig. 4). In terms of beta-diversity, there was a significant difference in Bray-Curtis dissimilarity between IL-6 increase group and IL-6 decrease group (P=0.05; PERMANOVA test) (Fig. 5). In taxonomic analysis, the relative abundance of beneficial genera such as Blautia, Faecalibacterium, and Weissella decreased in the IL-6 increase group. This inverse relationship suggests that a reduction in these strains may be associated with the aggravation of inflammation (increase in IL-6).
Change in alpha diversity in relation to interleukin-6 (IL-6) alteration in subjects before and after the intervention. Change in alpha diversity in subject with decreased IL-6 (A), increased IL-6 (B), IL-6 change (C). *P<0.05, **P<0.01. NS, not significant.
Change in beta diversity in subject with IL-6 change before and after the intervention, Bray-Curtis and unweighted UniFrac dissimilarity.
6. Safety Issues
During the study period, there was no serious adverse event but 2 moderate adverse events were reported (urinary stone in P. oleracea group and diarrhea in placebo group). Urinary stone was regarded not to be related to investigation drug. Laboratory tests showed no significant difference between the 2 groups. In terms of vital sign and physical examination, mean diastolic blood pressure at baseline and mean pulse rate at baseline and 4 weeks were significantly higher in P. oleracea group than placebo group (P<0.05), however there was no significant differences in other variables.
DISCUSSION
In this study, clinical impact of P. oleracea in patients with IBS was evaluated by prospective randomized placebo-controlled study. The use of P. oleracea in patients with IBS was associated with significant improvement in gastrointestinal and IBS symptoms, especially in the aspect of abdominal pain and CSBM, which are important clinical aspects in IBS. Proinflammatory markers such as IL-6 were significantly decreased in P. oleracea group during the study period, and increase in IL-6 was associated with stool microbial dysbiosis, suggesting the positive effect of P. oleracea in the intestinal microbiota.
Although IBS is not a life-threatening condition, it puts significant health-related and socioeconomic burden in worldwide. The prevalence of IBS varies according to the studied regions, and recent study reported 12.6% as the prevalence of IBS in East Asia, which was higher than that in North America and Europe, and lower than in Latin America [19], although relatively higher prevalence was reported using ROME III criteria compared to ROME IV criteria [6]. Traditionally, IBS was regarded as a functional bowel disorder. However, more recently, researchers have proposed that low-grade intestinal inflammation and immune system activation as well as the brain-gut axis may play a crucial role in its mechanism [20,21]. Thus anti-inflammatory and immunoregulatory agent could be beneficial to control the IBS-related symptoms [22], and we focused on the clinical impact of P. oleracea in patients with all subtypes of IBS.
In previous study, P. oleracea showed the significant improvement in CSBM (2.1/week in P. oleracea group vs. 1.2/week in placebo group) and CTT (–10.8 hours in P. oleracea group vs. +5.2 hours in placebo group) in patients with functional constipation during 8-week study period [12]. P. oleracea had been used as a laxative in traditional medicine, and animal study also showed that P. oleracea increases fecal volume and improves bowel movement. These anti-constipation effects might be associated with both biochemical and fiber component of P. oleracea. In addition, significant improvement of constipation-related symptoms and quality of life were noted in previous study, which suggested the analgesic and anti-inflammatory effect of P. oleracea [12]. Thus, we hypothesized that P. oleracea could be beneficial for the improvement of clinical symptoms in patients with IBS, not only IBS-C with delayed bowel movement but also other subtypes such as IBS-D and IBS-M.
In this study, P. oleracea group showed significant improvement in gastrointestinal symptoms compared with placebo group, especially in the aspect of abdominal pain. Abdominal pain associated with bowel movements is the most characteristic symptoms of IBS. However, it is challenging to control abdominal pain in IBS rather than constipation or diarrhea, and medical treatment for abdominal pain is more difficult compared with those for bowel movement. Usually, medications such as antispasmodics, antidepressants, and anxiolytics are frequently used in daily practice. However, there are concerns about the decreased effect and adverse events with long-term use of these medications [23,24]. The safety profile of P. oleracea is one of the advantages of its long-term use. In addition, P. oleracea was also effective to improve IBS-related bowel symptoms such as bowel habit satisfaction and effect of IBS symptom, and CSBM was significantly increased during the study period, like the laxative effect of P. oleracea in previous study [12]. Although there was no significant difference between the 2 groups, increased number of the patients with BSFS type 3–5 was seen in P. oleracea group during the study period, suggesting the effect of normalizing bowel movement in patients with IBS. Thus P. oleracea could be alternative option to control abdominal pain in patients with IBS without significant adverse event.
Low-grade inflammation is considered as one of the pathogenic factors in IBS [22,25]. Elevation of proinflammatory cytokines (e.g., tumor necrosis factor-α, IL-1β, IL-6, and IL-8) in the blood or stool has been reported, however data was not consistent between the studies [20,21,26]. In P. oleracea group, IL-6 was significantly decreased, whereas IL-8 was significantly increased during the study period. These results may be attributable to low-grade inflammation that does not influence systemic inflammatory response enough to alter serum cytokine levels. Other inflammatory markers and cytokines showed no significant change during the study period. Although it was not statistically significant, fecal calprotectin showed decreasing tendency during the study period. Considering these anti-inflammatory effects, we supposed that P. oleracea is beneficial for the patients with IBS.
Dysbiosis is an emerging important pathogenetic factor and treatment target in the management of IBS. High level of dysbiosis was associated with poor response to low FODMAP diet in patients with IBS [27], and rifaximin is suggested as the treatment option in patients with IBS-D [3]. In this study, increase in IL-6 was significantly related with decrease in diversity, and intake of P. oleracea was significantly associated with increase in diversity, suggesting beneficial effect of P. oleracea on dysbiosis. Decrease of Blautia, Faecalibacterium, and Weissella after P. oleracea intake is only seen in IL-6 increase group, suggesting beneficial effect of P. oleracea in intestinal dysbiosis. Further studies are needed to prove the impact of P. oleracea on the intestinal dysbiosis.
This study has some limitations. First, relatively small number of patients was enrolled and mean patient age was relatively young, which has limitations to generalize our findings. This study was conducted in a single tertiary referral center and mean age of enrolled patients was 45 years; thus, patient population could be different from those in a daily practice and it is difficult to generalize our results in this study. Second, strict diet control was not applied which can influence IBS symptoms [2]. In addition, 8-week study period was relatively short to distinguish the effect of P. oleracea in a usual clinical setting. Third, subgroup analysis for IBS-D and/or IBS-M was not performed due to the lack of relevant information. To evaluate the net effect of P. oleracea in all subtypes of IBS, further studies are needed including large IBS population and long-term study duration.
In conclusion, this study showed that P. oleracea might have positive impact in patients with IBS. This effect was prominent in the aspect of abdominal pain and immunologic cytokine, and improvement of dysbiosis, without significant adverse effect. Further studies are warranted to validate the application of P. oleracea as an alternative option for the patients with IBS.
Notes
Funding Source
The present research was conducted by a grant from the High-value Food Technology Development Program funded by the Ministry of Agriculture, Food and Rural Affairs through Korea Pharmaceutical Co., Ltd. (Grant No. 821054031SB010).
Conflict of Interest
Choi J, Park JH, Kim H, Lee S, and Lee Y are employees of Korea Drug Co., Ltd. The remaining authors declare no conflicts of interest.
Data Availability Statement
Data analyzed in this study are available from the corresponding author upon reasonable request.
Author Contributions
Conceptualization: Nam K, Choi JH, Shin JE. Data curation: Nam K, Lee D, Ryou S, Shin JE. Formal analysis: Nam K, Choi JH, Kim YS, Lee S, Shin JE. Investigation: Nam K, Choi JH, Kim YS, Lee S, Park JH, Kim H, Lee S, Lee Y, Shin JE. Methodology: Nam K, Choi JH, Lee S, Shin JE. Project administration: Lee S, Shin JE. Supervision: Shin JE. Writing–original draft: Nam K, Choi JH, Shin JE. Writing–review & editing: all authors. Approval of final manuscript: all authors.
Additional Contributions
The authors thank Yongju Ahn of HuNBiome for support with microbiota analysis and interpretation.
Supplementary Material
Supplementary materials are available at the Intestinal Research website (https://www.irjournal.org).
Supplementary Table 1.
Demographic Characteristics of Enrolled Patients (Per-Protocol Analysis)
Supplementary Table 2.
Changes of Immunologic Cytokines during the Study Period
Supplementary Table 3.
Changes of Immunologic Cytokines during the Study Period