“A peripheral immune mechanism involving local mast cells stimulated by food-induced local IgE may underlie the symptoms associated with IBS and functional abdominal pain; these findings prompt consideration of new therapeutic strategies to target mast cells and allergies.”
The article reviews the experimental methods/results used in both mice and humans. Mice that were treated with agents that interfered with allergy “including anti-IgE, mast-cell stabilizers, and histamine H1 receptor antagonists, attenuated the pathologic and symptomatic responses…mice [that were] deficient in mast cells or in histamine H1 receptor were protected” as well.
The study shows that a “bacterial infection can break oral tolerance to a dietary antigen…which in turn can lead to increased gut permeability.”
The findings in human “showed no evidence of systemic IgE against common foods” but localized reactions were identified in every IBS patient after allergen injection into rectal mucosa.
My take: This study adds to the evidence that specific foods can lead to localized tissue-specific allergic responses. Nevetheless, it is still a futile effort to look for systemic allergic food reactions in patients with IBS and functional GI disorders.
Background: Up to ~30% of adults with IBS-D may have bile acid diarrhea (BAD); however, identification has been hampered by cumbersome testing. In the U.S., the most reliable test has been a 48-hr fecal bile acid (FBA) level of >2337 micromol/48 h. Alternatively, blood tests have been used:
7alpha-hydroxy-4-cholesten-3-one (C4)–a direct measure of BA production
Fibroblast growth factor-19 (FGF-19)–an indirect measure of ileal BA resorption
This prospective cross-sectional study of adolescents (n=26 and 56 healthy controls) examined these blood tests and 48-h FBA . Key findings:
20% of IBS-D patients had elevated C4 levels based on 90% of serum C4 in healthy controls (HC). Mean value in HC was 12 and mean value in IBS-D was 16; 90th% was 22 in HC.
28% had decreased fasting serum FGF-19 based on 10% of HC. Mean value in HC was 128 pg/mL compared with 93 in IBS-D; 10th% was 45 in HC.
There was good correlation between C4 and 48-h FBA and there was an inverse relationship between serum C4 and FGF-19. Mean value for 48-h FBA in HC was 490 micromol/48 h compared with 824 in IBS-D; 90th% was 972 in HC.
The authors argue that a definitive diagnosis of BAD is beneficial compared to empiric use of bile acid sequestrants. They point to studies showing that treatment is more effective in those with known BAD, up to 75% response rate. In addition, the use of empiric treatment “has not been validated as a diagnostic test for BAD.” Furthermore, definitive diagnosis would help with adherence to long-term treatment and avoid drug interactions/side effects in those who are unlikely to respond to treatment.
Using a prospective, population-based Swedish cohort (1994-1996) (BAMSE project), the authors analyzed data from 2455 children with complete follow-up evaluation at ages 1, 2, 12, and 16 years.
RAP was reported by 26.2% of children on at least 1 of 3 assessment points, of which 11.3% reported symptoms more than once
Children with RAP at 12 years had persistent symptoms at 16 years in 45% of cases and increased risks for RAP (relative risk, 2.2; 95% CI, 1.7–2.8), any AP-FGID (relative risk, 2.6; 95% CI, 1.9–3.6), and IBS (relative risk, 3.2; 95% CI, 2.0–5.1) at 16 years
Figure 3 summarizes the overlap of RAP at different time points:
**In early childhood (1-2 years of age), 149 (6%) had RAP per parental reports. Only 27 in this group, had RAP noted at 16 years of age which accounted for 7% of the total 16 year old cohort with RAP
**At 12 years of age, 98 (4%) had RAP. 44 (45%) of this group continued with pain at 16 years which accounted for 11% of the total 16 year old cohort with RAP
My take: Most children (84%) with RAP at 16 years of age did NOT report RAP at younger ages; however, in children with RAP at 12 years of age, 45% continued to have RAP at 16 years of age.
This study derived data from a longitudinal cohort; the sample for this study followed women with and without endometriosis who completed extensive surveys (n=323) and excluded women with celiac disease or inflammatory bowel disease. Cases of IBS were based on patient reports of Rome IV criteria, though 81% were confirmed via medical record review.
“More adolescents with endometriosis (54 of 224; 24%) had comorbid IBS compared with adolescents without endometriosis (7 of 99; 7.1%). The odds of IBS was 5.26-fold higher among participants with endometriosis than without (95% CI, 2.13–13.0).”
“For participants with endometriosis, each 1-point increase in acyclic pain severity increased the odds of IBS by 31% (adjusted odds ratio, 1.31; 95% CI, 1.18–1.47).”
The association of endometriosis with IBS was based on Rome IV criteria, as such, the authors assert that this is “not merely a diagnostic bias” However, some of the increase may be related to referral patterns.
“In the adult literature, pain in the pelvis, menstrual-related symptoms, symptoms related to sexual intercourse, ovarian cysts, and subfertility seem to distinguish women with endometriosis from other GI conditions.”
“Chronic pain syndromes were more prevalent in girls with endometriosis and IBS. Rates of migraine headaches, sleep disturbance, and urinary symptoms were higher…[and] had higher prevalence rates of mood disturbance.”
Why is there overlap between these disorders?
The authors speculate that “the inflammatory process likely plays a role…and central pain sensitization may play a crucial role in the two diseases”
My take: Adolescents with endometriosis have a higher likelihood of IBS. Acyclic pain is a strong predictor of IBS.
In The Shawshank Redemption, Andy Dufresne (Tim Robbins) manages to escape prison by crawling through 500 yards of a filthy sewage pipe. It seems like a similar effort will be needed to find out how to benefit from fecal transplantation when given for problems like irritable bowel syndrome and metabolic disease/obesity. Some recent studies and associated editorials are noted below.
This editorial stresses that trials of FMT in IBS have had inconsistent results and risks are unclear. “How many clinicians inform patients receiving FMT that the donor microbiota might include components that increase (or decrease) one’s risk of colorectal cancer?” Part of the problem is “due, in part, because a normal microbiome has not been defined.”
In this randomized controlled trial with 90 participants, autologous FMT (aFMT) significantly attenuated weight regain in the green-Mediterranean group (aFMT, 17.1%, vs placebo, 50%; P = .02) and improved insulin resistance: insulin rebound (aFMT, –1.46 ± 3.6 μIU/mL vs placebo, 1.64 ± 4.7 μIU/mL; P = .04) (Graphical abstract below)
In mice, Mankai-modulated aFMT in the weight-loss phase compared with control diet aFMT, significantly prevented weight regain and resulted in better glucose tolerance during a high-fat diet–induced regain phase (all, P < .05).
“These findings add support to the current body of evidence that the gut microbiota have a role in weight gain and metabolism. However, many questions remain. Indeed, although studies have shown varying degrees of effectiveness of FMT in the improvement of metabolic parameters in human participants, there has been no evidence yet that FMT can induce weight loss in obese patients.”
“The finding that maintenance of weight loss was only seen in the one dietary group consuming the Mediterranean diet plus green tea and Mankai supplement who received autologous FMT, would suggest that specific microbial profiles may be involved and that weight loss per se may not result in the required microbial profiles.”
My take: Both of these studies show that modulation of the fecal microbiome may be helpful under the right set of circumstances to help with both irritable bowel syndrome and metabolic syndrome. However, ‘hundreds of yards’ of more research is needed to determine if this is really feasible and to assure that the benefits outweigh the potential risks.
Background: “Up to 20% of people worldwide develop gastrointestinal symptoms following a meal, leading to decreased quality of life, substantial morbidity and high medical costs”
“Here we show that a bacterial infection and bacterial toxins can trigger an immune response that leads to the production of dietary-antigen-specific IgE antibodies in mice, which are limited to the intestine. Following subsequent oral ingestion of the respective dietary antigen, an IgE- and mast-cell-dependent mechanism induced increased visceral pain. This aberrant pain signaling resulted from histamine receptor H1-mediated sensitization of visceral afferents. Moreover, injection of food antigens (gluten, wheat, soy and milk) into the rectosigmoid mucosa of patients with irritable bowel syndrome induced local oedema and mast cell activation.”
My take: This study shows how innocuous food can trigger pain after an intestinal infection.
The IB-Stim group (n=27, median age 15 years) had a ≥30% reduction in abdominal pain in 59% compared to 26% of the sham group (n=23)
A symptom response scale score of 2 or more was observed in 82% of patients who received IB-Stim vs 26% of patients in the sham group ( P ≤ .001)
The authors indicate that the NNT for IB-Stim is 3 compared to 6-14 for other medical therapies (lubiprostone, linaclotide, and rifaximin)
The effects of IB-Stim were NOT sustained at follow-up 8-12 weeks and there was no significant improvment in functional disability or anxiety. “The lack of long-term effect…likely reflects insufficient statistical power.” The authors indicate that longer or repeated courses could be needed
My take: This study indicates that IB-Stim can be helpful, at least in the short term, for adolescents with IBS. More studies showing long-term benefit would be helpful.
According to a recent study (RJ Shulman et al. J Pediatri 2020; 222: 134-40), the prevalence of joint hypermobility does NOT differ in children with irritable bowel syndrome, functional abdominal pain, or healthy control children.
Methods (to reach this conclusion):
Children (median age ~9.5 years) with irritable bowel syndrome (n=109), functional abdominal pain (n=31), and healthy controls (n=69) completed a prospective 2-week pain and stooling diaries. In addition, children and parents reported on measures of anxiety, depression, and somatization. Children were recruited from both primary care and tertiary care settings
Joint hypermobility was determined using Beighton criteria using a goniometer and examined cutoffs at both ≥4 or ≥6).
Beighton scores were similar between the groups, as was the proportion with joint hypermobility. Beighton scores were not related to abdominal pain or stooling characteristics.
Children reported depression more frequently in those with Beighton scores ≥6 and somatization was greater in those with a score ≥4.
“It is well-recognized that patients with joint hypermobility syndromes (eg, Ehlers-Danlos syndrome, Marfan) commonly have GI symptoms.” However, joint hypermobility is common —in this study’s healthy control group 36% had a score ≥4 and 9% had a score ≥6.
This study is in agreement with a school-based study (n=136) (M Saps et al. JPGN 2018; 66: 387-90).
Limitations: This study population had a median age of ~9.5 years; thus, these findings need to be determined in an older children
My take: There does not appear to be an increased risk of functional GI disorders in children with joint hypermobility. Thus, looking for joint laxity/hypermobility in children with abdominal pain is not needed.