Bowel dysfunction in cystic fibrosis: importance of breath testing

A Gastroenterologist's Guide to Care Transitions in Cystic Fibrosis from Pediatrics to Adult Care

Cystic Fibrosis is a chronic disease affecting multiple systems, including the GI tract. Clinical manifestation in patients can start as early as infancy and vary across different age groups. With the advent of new, highly effective modulators, the life expectancy of PwCF has improved significantly. Various GI aspects of CF care, such as nutrition, are linked to an overall improvement in morbidity, lung function and the quality of life of PwCF. The variable clinical presentations and management of GI diseases in pediatrics and adults with CF should be recognized. Therefore, it is necessary to ensure efficient transfer of information between pediatric and adult providers for proper continuity of management and coordination of care at the time of transition. The transition of care is a challenging process for both patients and providers and currently there are no specific tools for GI providers to help ensure a smooth transition. In this review, we aim to highlight the crucial features of GI care at the time of transition and provide a checklist that can assist in ensuring an effective transition and ease the challenges associated with it.

Prevalence, risk factors, and treatment of small intestinal bacterial overgrowth in children

Small intestinal bacterial overgrowth (SIBO) is defined as the presence of an excessive number of bacteria within the small bowel. Pediatric SIBO is a heterogeneous disorder that manifests as various symptoms ranging from mild gastrointestinal symptoms to malabsorption or malnutrition. The carbohydrate breath test is a commonly used, safe, and noninvasive diagnostic test; however, a standardized methodology is lacking. Multiple factors, such as neuromuscular disorders, systemic diseases, chronic drug use, or altered intestinal anatomy that disturb intestinal motility or induce an abnormality in the body's defense systems against intestinal bacteria, predispose children to SIBO. The high prevalence and similar symptoms of SIBO in functional gastrointestinal disorders, including irritable bowel syndrome, suggest an association between them. The principles of treatment include managing predisposing conditions, nutritional support, symptom control, and antibacterial treatment. Rifaximin is the most commonly used drug. To date, studies of antibiotic treatment in pediatric populations with irritable bowel syndrome or SIBO are lacking and have shown mixed results. Here we review the prevalence, diagnostic tests, and treatment results in pediatric populations.

Association between Gut Dysbiosis and the Occurrence of SIBO, LIBO, SIFO and IMO

Gut microbiota is the aggregate of all microorganisms in the human digestive system. There are 1014 CFU/mL of such microorganisms in the human body, including bacteria, viruses, fungi, archaea and protozoa. The Firmicutes and Bacteroidetes bacteria phyla comprise 90% of the human gut microbiota. The microbiota support the healthy functioning of the human body by helping with digestion (mainly via short-chain fatty acids and amino acids) and producing short-chain fatty acids. In addition, it exhibits many physiological functions, such as forming the intestinal epithelium, intestinal integrity maintenance, the production of vitamins, and protection against pathogens. An altered composition or the number of microorganisms, known as dysbiosis, disrupts the body's homeostasis and can lead to the development of inflammatory bowel disease, irritable bowel syndrome, and metabolic diseases such as diabetes, obesity and allergies. Several types of disruptions to the gut microbiota have been identified: SIBO (Small Intestinal Bacterial Overgrowth), LIBO (Large Intestinal Bacterial Overgrowth), SIFO (Small Intestinal Fungal Overgrowth), and IMO (Intestinal Methanogen Overgrowth). General gastrointestinal problems such as abdominal pain, bloating, gas, diarrhoea and constipation are the main symptoms of dysbiosis. They lead to malabsorption, nutrient deficiencies, anaemia and hypoproteinaemia. Increased lipopolysaccharide (LPS) permeability, stimulating the inflammatory response and resulting in chronic inflammation, has been identified as the leading cause of microbial overgrowth in the gut. The subject literature is extensive but of limited quality. Despite the recent interest in the gut microbiome and its disorders, more clinical research is needed to determine the pathophysiology, effective treatments, and prevention of small and large intestinal microbiota overgrowth. This review was designed to provide an overview of the available literature on intestinal microbial dysbiosis (SIBO, LIBO, SIFO and IMO) and to determine whether it represents a real threat to human health.

Update in Advancing the Gastrointestinal Frontier in Cystic Fibrosis

Clinical complications of cystic fibrosis (CF) include a variety of gastrointestinal (GI) and hepatobiliary manifestations. Recent years have witnessed several advances in the understanding and management of these complications, in addition to opportunities for therapeutic innovations. Herein we review the current understanding of these disorders and also discuss the management of the GI and hepatobiliary complications experienced by persons with CF.

Changes in Glucose Breath Test in Cystic Fibrosis Patients Treated With 1 Month of Lumacaftor/Ivacaftor

BACKGROUND

Alteration of the airway microbiota is a hallmark of cystic fibrosis (CF) pulmonary disease. Dysfunction of cystic fibrosis transmembrane regulator (CFTR) in the intestine also promotes changes in local microbiota such as small intestinal bacterial overgrowth (SIBO), which is common in CF. We evaluated whether therapy with the CFTR modulator combination lumacaftor/ivacaftor (luma/iva) has a beneficial impact on SIBO as measured by breath testing (BT).

METHODS

A multicenter longitudinal study of CFTR-dependent disease profiling (NCT02477319) included a prospective evaluation for SIBO by BT. Tidal breath samples were collected after fasting and 15, 30, 45, 60, 90, and 120 minutes after ingestion of glucose, before and 1 month after subjects initiated luma + iva.

RESULTS

Forty-two subjects enrolled in the sub-study (mean age = 23.3 years; 51% female; 9.5% Latinx); 38 completed a hydrogen BT at both time points, of which 73.7% had a positive BT before luma/iva (baseline) and 65.8% had a positive test after luma/iva ( P = 0.44); shifts from negative to positive were also seen. Use of azithromycin (63.1%) and inhaled antibiotics (60.5%) were not associated with positive BT. Acid-blocking medications were taken by 73% of those with a negative BT at baseline and by 35% with a positive baseline BT ( P = 0.04).

CONCLUSION

We found a high rate of positive hydrogen breath tests in individuals with CF, confirming that SIBO is common. One month of luma/iva did not significantly change the proportion of those with positive breath hydrogen measurements.

Understanding Cystic Fibrosis Comorbidities and Their Impact on Nutritional Management

Cystic fibrosis (CF) is a chronic, multisystem disease with multiple comorbidities that can significantly affect nutrition and quality of life. Maintaining nutritional adequacy can be challenging in people with cystic fibrosis and has been directly associated with suboptimal clinical outcomes. Comorbidities of CF can result in significantly decreased nutritional intake and intestinal absorption, as well as increased metabolic demands. It is crucial to utilize a multidisciplinary team with expertise in CF to optimize growth and nutrition, where patients with CF and their loved ones are placed in the center of the care model. Additionally, with the advent of highly effective modulators (HEMs), CF providers have begun to identify previously unrecognized nutritional issues, such as obesity. Here, we will review and summarize commonly encountered comorbidities and their nutritional impact on this unique population.

An ESPGHAN Position Paper on the Use of Breath Testing in Paediatric Gastroenterology

OBJECTIVES

Given a lack of a systematic approach to the use of breath testing in paediatric patients, the aim of this position paper is to provide expert guidance regarding the indications for its use and practical considerations to optimise its utility and safety.

METHODS

Nine clinical questions regarding methodology, interpretation, and specific indications of breath testing and treatment of carbohydrate malabsorption were addressed by members of the Gastroenterology Committee (GIC) of the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN).A systematic literature search was performed from 1983 to 2020 using PubMed, the MEDLINE and Cochrane Database of Systematic Reviews. Grading of Recommendations, Assessment, Development, and Evaluation was applied to evaluate the outcomes.During a consensus meeting, all recommendations were discussed and finalised. In the absence of evidence from randomised controlled trials, recommendations reflect the expert opinion of the authors.

RESULTS

A total of 22 recommendations were voted on using the nominal voting technique. At first, recommendations on prerequisites and preparation for as well as on interpretation of breath tests are given. Then, recommendations on the usefulness of H2-lactose breath testing, H2-fructose breath testing as well as of breath tests for other types of carbohydrate malabsorption are provided. Furthermore, breath testing is recommended to diagnose small intestinal bacterial overgrowth (SIBO), to control for success of Helicobacter pylori eradication therapy and to diagnose and monitor therapy of exocrine pancreatic insufficiency, but not to estimate oro-caecal transit time (OCTT) or to diagnose and follow-up on celiac disease.

CONCLUSIONS

Breath tests are frequently used in paediatric gastroenterology mainly assessing carbohydrate malabsorption, but also in the diagnosis of small intestinal overgrowth, fat malabsorption, H. pylori infection as well as for measuring gastrointestinal transit times. Interpretation of the results can be challenging and in addition, pertinent symptoms should be considered to evaluate clinical tolerance.

Nutrition in cystic fibrosis: From the past to the present and into the future

Nutritional management is an integral part of multidisciplinary care for persons with cystic fibrosis. This review will look at how nutrition care has evolved over time. In addition, we will look at how some newer therapies impact nutrition care.

The role of small intestinal bacterial overgrowth in cystic fibrosis: a randomized case-controlled clinical trial with rifaximin

BACKGROUND

Scientific literature shows a high prevalence of Small Intestinal Bacterial Overgrowth (SIBO) in patients with Cystic Fibrosis (CF). The role of SIBO in nutritional status and gastrointestinal symptoms in CF is not known. Our aim was to study epidemiology and clinical impact of SIBO while assessing the efficacy of rifaximin in eradicating SIBO in CF patients.

METHODS

Symptoms questionnaire and Glucose Breath Test (GBT) were given to 79 CF patients (median age 19.6 years; 9.2-36.9). Subjects with a positive GBT were enrolled in a randomized controlled trial and received rifaximin 1200 mg for 14 days or no treatment. Questionnaire and GBT were repeated 1 month after the end of treatment or 45 days after the first negative GBT.

RESULTS

Out of 79 patients, 25 were affected by SIBO (31.6%) with a significant correlation with lower BMI, SDS-BMI (p < 0.05) and serum albumin levels (p < 0.05), independently from pancreas insufficiency. Twenty-three patients took part in the randomized trial, 13 patients (56.5%) in rifaximin group and 10 patients (43.5%) in control group. Eradication rate of SIBO was 9/10 (90%) in rifaximin group and 2/6 (33.3%) in control group (p < 0.05). In the rifaximin group, gastrointestinal symptom improvement was observed in 4/5 patients aged ≤ 14 years and in 0/5 patients aged > 14 years (p < 0.05); in 2/6 patients in the control group.

CONCLUSIONS

CF patients show a high prevalence of SIBO, related to a poorer nutritional status. Rifaximin therapy is well tolerated and the results are promising in terms of efficacy in eradicating small intestinal bacterial overgrowth in CF.

Small Intestinal Bacterial Overgrowth in Children: A State-Of-The-Art Review

Small intestinal bacterial overgrowth (SIBO) is a heterogenous and poorly understood entity characterised by an excessive growth of select microorganisms within the small intestine. This excessive bacterial biomass, in turn, disrupts host physiology in a myriad of ways, leading to gastrointestinal and non-gastrointestinal symptoms and complications. SIBO is a common cause of non-specific gastrointestinal symptoms in children, such as chronic abdominal pain, abdominal distention, diarrhoea, and flatulence, amongst others. In addition, it has recently been implicated in the pathophysiology of stunting, a disease that affects millions of children worldwide. Risk factors such as acid-suppressive therapies, alterations in gastrointestinal motility and anatomy, as well as impoverished conditions, have been shown to predispose children to SIBO. SIBO can be diagnosed via culture-dependant or culture-independent approaches. SIBO's epidemiology is limited due to the lack of uniformity and consensus of its diagnostic criteria, as well as the paucity of literature available. Antibiotics remain the first-line treatment option for SIBO, although emerging modalities such as probiotics and diet manipulation could also have a role. Herein, we present a state-of-the-art-review which aims to comprehensively outline the most current information on SIBO in children, with particular emphasis on the gut microbiota.

Bacterial overgrowth, dysbiosis, inflammation, and dysmotility in the Cystic Fibrosis intestine

Gastrointestinal disease in Cystic Fibrosis (CF) is caused by defective chloride and bicarbonate transport in intestinal cells leading to reduced intraluminal fluidity, increased mucous viscosity and consequently development of intestinal inflammation, dysbiosis and often times dysmotility. This triad is also referred to as the "CF gut". A diagnosis is mainly based on clinical observation and treatment is often times decided empirically. This review of the literature should provide CF caregivers with some tools to identify intestinal inflammation, dysbiosis and dysmotility as possible cause for their patient's gastrointestinal complaints and provide an overview of our current approach to its management.

Practical approach to the gastrointestinal manifestations of cystic fibrosis

Cystic fibrosis (CF) is the most common, life-shortening, genetic illness affecting children in Australia and New Zealand. The genetic abnormality results in abnormal anion transport across the apical membrane of epithelial cells in a number of organs, including the lungs, gastrointestinal tract, liver and genito-urinary tract. Thus, CF is a multi-system disorder that requires a multi-disciplinary approach. Respiratory disease is the predominant cause of both morbidity and mortality in patients with CF. However, there are significant and clinically relevant gastrointestinal, liver, pancreatic and nutritional manifestations that must be detected and managed in a timely and structured manner. The aim of this review is to provide evidence-based information and clinical algorithms to guide the nutritional and gastrointestinal management of patients with CF.

The gut-liver axis: impact of a mouse model of small-bowel bacterial overgrowth

BACKGROUND

The mechanisms by which intestinal bacteria impact liver diseases remain poorly understood. The aim of this study was to develop a mouse model of small-bowel bacterial overgrowth and to determine its impact on hepatobiliary injury.

MATERIALS AND METHODS

A jejunal self-filling blind loop (SFBL) was created in C57BL/6 mice. Three weeks after surgery, the mice were euthanized, and bacterial cultures of luminal content of the loop and extraintestinal tissues were performed. Liver and jejunum were collected for histological grading of inflammation and injury. Serum liver biochemistry assays were performed. Hepatobiliary transporter mRNA expression in liver was measured by quantitative real-time polymerase chain reaction. Bile and blood were collected for measurement of total bile acids, phospholipid, and cholesterol. Mice undergoing jejunal transection and reanastomosis and laparotomy only served as control groups.

RESULTS

SFBL induced a dramatic increase in intraluminal bacterial counts, mesenteric lymph node bacterial translocation, and evidence of jejunal and hepatobiliary injury. Significant reductions in hepatic expression of hepatobiliary transporters involved in biliary canalicular export and basolateral uptake were observed in SFBL mice. SFBL resulted in a significant increase in biliary total bile acid concentration, decreases in bile phospholipid and cholesterol output, and an increase in the bile acid/phospholipid ratio.

CONCLUSIONS

We have developed a reproducible mouse model of small-bowel bacterial overgrowth with evidence of liver inflammation, altered hepatobiliary transporter expression, and alterations in bile composition. This model may help to elucidate the mechanisms by which gut-derived bacterial factors impact the liver and contribute to the exacerbation of liver diseases and biliary injury.

Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus

OBJECTIVES

Breath tests (BTs) are important for the diagnosis of carbohydrate maldigestion syndromes and small intestinal bacterial overgrowth (SIBO). However, standardization is lacking regarding indications for testing, test methodology and interpretation of results. A consensus meeting of experts was convened to develop guidelines for clinicians and research.

METHODS

Pre-meeting survey questions encompassing five domains; indications, preparation, performance, interpretation of results, and knowledge gaps, were sent to 17 clinician-scientists, and 10 attended a live meeting. Using an evidence-based approach, 28 statements were finalized and voted on anonymously by a working group of specialists.

RESULTS

Consensus was reached on 26 statements encompassing all five domains. Consensus doses for lactulose, glucose, fructose and lactose BT were 10, 75, 25 and 25 g, respectively. Glucose and lactulose BTs remain the least invasive alternatives to diagnose SIBO. BT is useful in the diagnosis of carbohydrate maldigestion, methane-associated constipation, and evaluation of bloating/gas but not in the assessment of oro-cecal transit. A rise in hydrogen of ≥20 p.p.m. by 90 min during glucose or lactulose BT for SIBO was considered positive. Methane levels ≥10 p.p.m. was considered methane-positive. SIBO should be excluded prior to BT for carbohydrate malabsorption to avoid false positives. A rise in hydrogen of ≥20 p.p.m. from baseline during BT was considered positive for maldigestion.

CONCLUSIONS

BT is a useful, inexpensive, simple and safe diagnostic test in the evaluation of common gastroenterology problems. These consensus statements should help to standardize the indications, preparation, performance and interpretation of BT in clinical practice and research.

Beyond pancreatic insufficiency and liver disease in cystic fibrosis

Cystic fibrosis is a life shortening hereditary disease, primarily leading to progressive pulmonary infection and exocrine pancreatic dysfunction. Several gastrointestinal complications other than malabsorption can arise during the disease course and with the progressively increasing life span of patients with CF; new and more rare complications are being recognized. We review the literature on gastrointestinal manifestations in CF, excluding the liver and pancreas.

CONCLUSION

We describe the clinical presentation and treatment of more common conditions like gastroesophageal reflux, small intestinal bacterial overgrowth, intussusception, meconium ileus, distal intestinal obstruction syndrome, and constipation, and we also discuss what is known on celiac disease, appendicitis, fibrosing colonopathy, inflammation and inflammatory bowel disease and gastrointestinal cancer.

WHAT IS KNOWN

• Gastrointestinal complications arise early in the course of the disease and have a severe impact on the quality of life of the patients. What is New: • This review is a concise summary of the current literature on gastrointestinal complications of cystic fibrosis. • We focused on clinical presentation and diagnostic investigations and provide a comprehensive resume of the current treatment options.

Targeted CFTR gene disruption with zinc-finger nucleases in human intestinal epithelial cells induces oxidative stress and inflammation

Cystic fibrosis (CF) is a multisystemic pathology caused by mutations of the CF transmembrane conductance regulator (CFTR) gene.

OBJECTIVES

As the intestine harbors the greatest number of CFTR transcripts after birth and since CFTR plays a role in glutathione transport, we hypothesized that CFTR deletion might produce oxidative stress (OxS) and inflammation in CF intestinal epithelial cell.

METHODS

CFTR gene was abrogated in Caco-2/15 enterocytes through the zinc-finger nuclease system. Their oxidative and inflammatory characteristics were appreciated under basal conditions and after the treatment with the pro-oxidant iron-ascorbate (Fe/Asc) complex and pro-inflammatory lipopolysaccharide (LPS).

RESULTS

Intestinal epithelial cells with CFTR knockout spontaneously exhibited an increased lipid peroxidation level, reflected by malondialdehyde overproduction and reduced antioxidant defense characterized by low enzymatic activities of glutathione peroxidase and catalase. CFTR silencing also resulted in elevated protein expression of pro-inflammatory tumor necrosis Factor-α, interleukin-6, cyclooxygenase-2, and the transcription factor nuclear factor-κB. Moreover, exaggerated OxS and inflammation processes occurred in CFTR(-/-) cells in response to the addition of Fe/Asc and LPS, respectively.

CONCLUSIONS

Intestinal Caco-2/15 cells with CFTR deletion, display innate oxidative and inflammatory features while being more sensitive to pro-oxidant and pro-inflammatory stimuli. These two pathophysiological processes could be implicated in CF-related intestinal disorders.

Cystic fibrosis

Cystic fibrosis is an autosomal recessive, monogenetic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The gene defect was first described 25 years ago and much progress has been made since then in our understanding of how CFTR mutations cause disease and how this can be addressed therapeutically. CFTR is a transmembrane protein that transports ions across the surface of epithelial cells. CFTR dysfunction affects many organs; however, lung disease is responsible for the vast majority of morbidity and mortality in patients with cystic fibrosis. Prenatal diagnostics, newborn screening and new treatment algorithms are changing the incidence and the prevalence of the disease. Until recently, the standard of care in cystic fibrosis treatment focused on preventing and treating complications of the disease; now, novel treatment strategies directly targeting the ion channel abnormality are becoming available and it will be important to evaluate how these treatments affect disease progression and the quality of life of patients. In this Primer, we summarize the current knowledge, and provide an outlook on how cystic fibrosis clinical care and research will be affected by new knowledge and therapeutic options in the near future. For an illustrated summary of this Primer, visit: http://go.nature.com/4VrefN.

Abdominal pain in adults with cystic fibrosis

Abdominal pain is a common symptom in individuals with cystic fibrosis (CF). As prognosis has improved, CF has changed from a pediatric disease to the current situation wherein most people with CF are adults. With improved survival, the spectrum of pathologies causing abdominal pain in CF has shifted. Despite this, there have been relatively few previous publications focusing on gastrointestinal disease in CF adults. The aim of this review was to examine the characteristics, differential diagnosis, investigation, and optimal management of adults with CF presenting with abdominal pain.

The cystic fibrosis intestine

The clinical manifestations of cystic fibrosis (CF) result from dysfunction of the cystic fibrosis transmembrane regulator protein (CFTR). The majority of people with CF have a limited life span as a consequence of CFTR dysfunction in the respiratory tract. However, CFTR dysfunction in the gastrointestinal (GI) tract occurs earlier in ontogeny and is present in all patients, regardless of genotype. The same pathophysiologic triad of obstruction, infection, and inflammation that causes disease in the airways also causes disease in the intestines. This article describes the effects of CFTR dysfunction on the intestinal tissues and the intraluminal environment. Mouse models of CF have greatly advanced our understanding of the GI manifestations of CF, which can be directly applied to understanding CF disease in humans.

Gastrointestinal complications of cystic fibrosis

The cystic fibrosis transmembrane regulator protein (CFTR) is an ion channel in the apical surface of epithelial membranes that regulates other ion channels. Dysfunction of CFTR leads to the clinical entity of CF when mutations in CFTR are inherited in an autosomal recessive fashion. Although airway obstruction, inflammation, and infection are usually the most serious consequences of CFTR dysfunction because they lead to respiratory failure, CFTR dysfunction affects the intestinal tract and the pancreatic and hepatobiliary ducts in a similar fashion, leading to significant morbidity. This review outlines pathophysiology and common gastrointestinal ailments in the CF population along with current medical and surgical management.

Translocated LPS might cause endotoxin tolerance in circulating monocytes of cystic fibrosis patients

Cystic Fibrosis (CF) is an inherited pleiotropic disease that results from abnormalities in the gene codes of a chloride channel. The lungs of CF patients are chronically infected by several pathogens but bacteraemia have rarely been reported in this pathology. Besides that, circulating monocytes in CF patients exhibit a patent Endotoxin Tolerance (ET) state since they show a significant reduction of the inflammatory response to bacterial stimulus. Despite a previous description of this phenomenon, the direct cause of ET in CF patients remains unknown. In this study we have researched the possible role of microbial/endotoxin translocation from a localized infection to the bloodstream as a potential cause of ET induction in CF patients. Plasma analysis of fourteen CF patients revealed high levels of LPS compared to healthy volunteers and patients who suffer from Chronic Obstructive Pulmonary Disease. Experiments in vitro showed that endotoxin concentrations found in plasma of CF patients were enough to induce an ET phenotype in monocytes from healthy controls. In agreement with clinical data, we failed to detect bacterial DNA in CF plasma. Our results suggest that soluble endotoxin present in bloodstream of CF patients causes endotoxin tolerance in their circulating monocytes.

Impaired mucosal barrier function in the small intestine of the cystic fibrosis mouse

OBJECTIVES

The intestinal mucosal barrier protects the body from the large numbers of microbes that inhabit the intestines and the molecules they release. Intestinal barrier function is impaired in humans with cystic fibrosis (CF), including reduced activity of the lipopolysaccharide-detoxifying enzyme intestinal alkaline phosphatase (IAP) and increased permeability. The objective of this study was to determine the suitability of using the CF mouse to investigate intestinal barrier function, and whether interventions that are beneficial for the CF mouse intestinal phenotype (antibiotics or laxative), would improve barrier function. Also tested were the effects of exogenous IAP administration.

MATERIALS AND METHODS

The Cftr(tm1UNC) mouse was used. IAP expression (encoded by the murine Akp3 gene) was measured by quantitative reverse transcription-polymerase chain reaction and enzyme activity. Intestinal permeability was assessed by measuring rhodamine-dextran plasma levels following gavage.

RESULTS

CF mice had 40% Akp3 mRNA expression and 30% IAP enzyme activity, as compared with wild-type mice. Oral antibiotics and laxative treatments normalized Akp3 expression and IAP enzyme activity in the CF intestine. CF mice had a 5-fold greater transfer of rhodamine-dextran from gut lumen to blood. Antibiotic and laxative treatments reduced intestinal permeability in CF mice. Administration of exogenous purified IAP to CF mice reduced intestinal permeability to wild-type levels and reduced small intestinal bacterial overgrowth by >80%.

CONCLUSIONS

The CF mouse intestine has impaired mucosal barrier function, similar to human CF. Interventions that improve other aspects of the CF intestinal phenotype (antibiotics and laxative) also increase IAP activity and decrease intestinal permeability in CF mice. Exogenous IAP improve permeability and strongly reduce bacterial overgrowth in CF mice, suggesting this may be a useful therapy for CF.

Persistent fat malabsorption in cystic fibrosis; lessons from patients and mice

Fat malabsorption in pancreatic insufficient cystic fibrosis (CF) patients is classically treated with pancreatic enzyme replacement therapy (PERT). Despite PERT, intestinal fat absorption remains insufficient in most CF patients. Several factors have been suggested to contribute to the persistent fat malabsorption in CF (CFPFM). We reviewed the current insights concerning the proposed causes of CFPFM and the corresponding intervention studies. Most data are obtained from studies in CF patients and CF mice. Based on the reviewed literature, we conclude that alterations in intestinal pH and intestinal mucosal abnormalities are most likely to contribute to CFPFM. The presently available data indicate that acid suppressive drugs and broad spectrum antibiotics could be helpful in individual CF patients for optimizing fat absorption and/or nutritional status.

Mild CFTR mutations and genetic predisposition to lactase persistence in cystic fibrosis

Taking into account the reported incidence of hypolactasia in cystic fibrosis (CF) and the possible impact of milk products on nutritional status we aimed to assess the genetic predisposition to adult-type hypolactasia (ATH) and its incidence in CF. Single nucleotide polymorphism upstream of the lactase gene (LCT) was assessed in 289 CF patients. In subject with -13910C/C genotype (C/C) predisposing to ATH, hydrogen-methane breath test (BT) with lactose loading was conducted and clinical symptoms typical for lactose malabsorption were assessed. The percentage of CF patients with C/C was similar to that observed in healthy subjects (HS) (31.5 vs 32.5% ). Eleven out of 52 (24.5%) CF C/C patients had abnormal BT results. The recalculated frequency of lactose malabsorption was similar for the entire CF and HS populations (6.9 vs 7.2%). Similarly as in the control group, few CF patients have identified and linked to lactose consumption clinical symptoms. The frequency of LCT polymorphic variants in CF patients having and not having severe mutations of CFTR gene showed significant differences. The C allele was more frequent in homozygotes of the severe mutations than in patients carrying at least one mild/unknown mutation (P<0.0028) and in patients with at least one mild mutation (P < 0.0377). In conclusion, CF patients carrying mild CFTR mutations seem to have lower genetic predisposition to ATH. Lactose malabsorption due to ATH in CF is not more frequent than in the general population. Symptomatic assessment of lactose malabsorption in CF is not reliable.

Enteric circular muscle dysfunction in the cystic fibrosis mouse small intestine

BACKGROUND Cystic fibrosis (CF) has multiple effects on the gastrointestinal system, including altered motility. The Cftr knockout mouse model of CF has impaired small intestinal transit but the mechanism is unknown. METHODS Behaviour of circular smooth muscle was studied in an organ bath. Expression levels of prostaglandin (PG) degradative genes were measured by quantitative RT-PCR, and PGE(2) levels were measured by enzyme immunoassay. KEY RESULTS Cystic fibrosis circular muscle activity was erratic and had variable frequency of contractions, as compared to WT. The CF tissue was non-responsive to cholinergic stimulation or direct KCl depolarization. PGE(2) and PGF(2alpha) are significantly elevated in the CF mouse small intestine, and we hypothesized these contribute to impaired smooth muscle activity. After inhibition of PG synthesis, the CF circular muscle exhibited greater cholinergic responsiveness, which was reversed by exogenous PGE(2). PGF(2alpha) enhanced activity of CF tissue only after inhibition of PG synthesis. The enteric microbiota was implicated in PGE(2)-mediated dysmotility because broad spectrum antibiotic treated WT mice, which have slowed transit, exhibit impaired circular muscle activity. This was accompanied by decreased expression of PG degradative genes and increased intestinal PGE(2) levels. Furthermore, administration of oral laxative, which eradicates bacterial overgrowth and improves transit in CF mice, increased expression of PG degradative genes, decreased PGE(2) levels, and improved CF muscle activity. CONCLUSIONS & INFERENCES These results suggest that the enteric microbiota modulates PGE(2) levels in a complex manner, which affects enteric smooth muscle activity and contributes to slower small intestinal transit in CF.

Application of the glucose hydrogen breath test for the detection of bacterial overgrowth in patients with cystic fibrosis--a reliable method?

Patients with cystic fibrosis (CF) have recently been deemed highly susceptible for bacterial intestinal overgrowth (BIO). We aimed to define the prevalence of BIO in children with CF by applying the H(2)-glucose breath test. Forty children with CF and ten healthy children received 1 g/kg D-glucose orally. Breath samples for H(2) content (ppm) were collected for 3 h. BIO was suspected if the breath hydrogen content increased by more than 20 ppm or if baseline concentrations topped 20 ppm. In 27 of 40 CF children (68%), breath hydrogen content exceeded 20 ppm. Whereas the breath hydrogen exhalation persisted above 20 ppm in almost all these children throughout the sampling period, none of the remaining children increased above this threshold. The high rate of CF children with elevated fasting hydrogen breath concentrations indicates that this phenomenon is less a sign of BIO rather than a consequence of global malabsorption and intestinal dysmotility.

Mast cells and gastrointestinal dysmotility in the cystic fibrosis mouse

BACKGROUND

Cystic fibrosis (CF) has many effects on the gastrointestinal tract and a common problem in this disease is poor nutrition. In the CF mouse there is an innate immune response with a large influx of mast cells into the muscularis externa of the small intestine and gastrointestinal dysmotility. The aim of this study was to evaluate the potential role of mast cells in gastrointestinal dysmotility using the CF mouse (Cftr(tm1UNC), Cftr knockout).

METHODOLOGY

Wild type (WT) and CF mice were treated for 3 weeks with mast cell stabilizing drugs (ketotifen, cromolyn, doxantrazole) or were treated acutely with a mast cell activator (compound 48/80). Gastrointestinal transit was measured using gavage of a fluorescent tracer.

RESULTS

In CF mice gastric emptying at 20 min post-gavage did not differ from WT, but was significantly less than in WT at 90 min post-gavage. Gastric emptying was significantly increased in WT mice by doxantrazole, but none of the mast cell stabilizers had any significant effect on gastric emptying in CF mice. Mast cell activation significantly enhanced gastric emptying in WT mice but not in CF mice. Small intestinal transit was significantly less in CF mice as compared to WT. Of the mast cell stabilizers, only doxantrazole significantly affected small intestinal transit in WT mice and none had any effect in CF mice. Mast cell activation resulted in a small but significant increase in small intestinal transit in CF mice but not WT mice.

CONCLUSIONS

The results indicate that mast cells are not involved in gastrointestinal dysmotility but their activation can stimulate small intestinal transit in cystic fibrosis.

Altered eicosanoid metabolism in the cystic fibrosis mouse small intestine

OBJECTIVES

Imbalances in essential fatty acid levels have been reported in cystic fibrosis (CF), which may relate to elevated proinflammatory eicosanoid generation. The aim of this work was to better define eicosanoid metabolism in the CF intestine.

MATERIALS AND METHODS

We used the small intestine of the cystic fibrosis transmembrane conductance regulator knockout mouse (CF mouse) to measure eicosanoid metabolic gene expression by quantitative reverse transcription polymerase chain reaction and Western blot, and eicosanoid levels by enzyme immunoassay, as compared with wild-type (WT) littermates.

RESULTS

In the CF small intestine, expression of the secretory phospholipase A2 Pla2g5 mRNA was upregulated to 980% of WT levels. The following were downregulated: leukotriene C4 synthase Ltc4s (mRNA 55% of WT); omega-hydroxylase cytochrome P450s Cyp2c40 (mRNA 54% of WT), and Cyp4a10 (mRNA 4% of WT); and the major prostaglandin degradative enzymes prostaglandin dehydrogenase Hpgd (mRNA 27% of WT) and leukotriene B4 12-hydroxydehydrogenase/15-oxo-prostaglandin 13-reductase Ltb4dh (mRNA 64% and protein 30% of WT). The prostaglandins PGE2 and PGF2alpha were increased to 400% to 600% of WT levels in the CF mouse intestine, and the hydroxyeicosatetraenoic acids (HETEs) 12-, 15-, and 20-HETE were decreased to 3% to 20% of WT levels.

CONCLUSIONS

There are changes in eicosanoid metabolic gene expression that are accompanied by significant changes in specific eicosanoid levels. These changes are expected to play important roles in the pathophysiology of CF in the intestine.

A systematic review of diagnostic tests for small intestinal bacterial overgrowth

BACKGROUND

A growing number of studies seem to suggest that small intestinal bacterial overgrowth (SIBO) is a common clinical problem. Although various techniques are available to make this diagnosis, tradition has accepted small bowel aspirate (>10(5) cfu/ml) as a gold standard. In this systematic review, the validity of culture and other diagnostic testing for SIBO is evaluated.

METHODS

We performed a systematic review of the literature from 1966 to present using electronic databases (PubMed and OVID). Full paper review of those abstracts that fulfilled preset criteria was carried out to evaluate the validity of various tests in diagnosing SIBO. Finally, all papers were evaluated against published standards for studies on diagnostic testing.

RESULTS

Seventy-one papers met the criteria for detailed review. Studies were very heterogeneous with regards to patient populations, test definitions, sample size, and methods in general. Small bowel colony counts appeared elevated in most gastrointestinal diseases compared to controls. The traditional definition of >10(5) cfu/ml was usually indicative of stagnant loop conditions. Although, numerous diagnostic tests were studied, not even culture papers met the quality standards described by Reid et al. Breath testing and other diagnostic testing suffered therefore from the lack of a gold standard against which to validate in addition to the poor quality.

CONCLUSIONS

There is no validated diagnostic test or gold standard for SIBO. In this context, the most practical method to evaluate SIBO in studies at this time would be a test, treat, and outcome technique.

Effects of laxative and N-acetylcysteine on mucus accumulation, bacterial load, transit, and inflammation in the cystic fibrosis mouse small intestine

The accumulation of mucus in affected organs is characteristic of cystic fibrosis (CF). The CF mouse small intestine has dramatic mucus accumulation and exhibits slower interdigestive intestinal transit. These factors are proposed to play cooperative roles that foster small intestinal bacterial overgrowth (SIBO) and contribute to the innate immune response of the CF intestine. It was hypothesized that decreasing the mucus accumulation would reduce SIBO and might improve other aspects of the CF intestinal phenotype. To test this, solid chow-fed CF mice were treated with an osmotic laxative to improve gut hydration or liquid-fed mice were treated orally with N-acetylcysteine (NAC) to break mucin disulfide bonds. Treatment with laxative or NAC reduced mucus accumulation by 43% and 50%, respectively, as measured histologically as dilation of the intestinal crypts. Laxative and NAC also reduced bacterial overgrowth in the CF intestine by 92% and 63%, respectively. Treatment with laxative normalized small intestinal transit in CF mice, whereas NAC did not. The expression of innate immune response-related genes was significantly reduced in laxative-treated CF mice, whereas there was no significant effect in NAC-treated CF mice. In summary, laxative and NAC treatments of CF mice reduced mucus accumulation to a similar extent, but laxative was more effective than NAC at reducing bacterial load. Eradication of bacterial overgrowth by laxative treatment was associated with normalized intestinal transit and a reduction in the innate immune response. These results suggest that both mucus accumulation and slowed interdigestive small intestinal transit contribute to SIBO in the CF intestine.

Altered transit and bacterial overgrowth in the cystic fibrosis mouse small intestine

Small intestinal bacterial overgrowth (SIBO) may play an important role in the gastrointestinal complications of cystic fibrosis (CF). This work explored two potential factors in development of SIBO in the CF (cftr(tm1UNC)) mouse: impaired Paneth cell innate defenses and altered gastrointestinal motility. Postnatal differentiation of Paneth cells was followed by Defcr, Lyzs, and Ang4 gene expression, and SIBO was measured by quantitative PCR of the bacterial 16S rRNA gene. Paneth cell gene expression was low in 4-day-old CF and wild-type (WT) mice and increased similarly in both groups of mice between 12 and 16 days. Peak Paneth cell gene expression was reached by 40 days of age and was less for Defcr and Lyzs in CF mice compared with WT, whereas Ang4 levels were greater in CF mice. SIBO occurred by postnatal day 8 in CF mice, which is before Paneth cell development. With the use of gavaged rhodamine-dextran to follow motility, gastric emptying in CF mice was slightly decreased compared with WT, and small intestinal transit was dramatically less. Since antibiotics improve weight gain in CF mice, their effects on gastric emptying and small intestinal transit were determined. Antibiotics did not affect gastric emptying or transit in CF mice but did significantly slow intestinal transit in WT mice, suggesting a potential role of normal microflora in regulating transit. In conclusion, small intestinal transit was significantly slower in CF mice, and this is likely a major factor in SIBO in CF.

Risk factors for small bowel bacterial overgrowth in cystic fibrosis

OBJECTIVES

The purpose of this study was to determine the prevalence of small bowel bacterial overgrowth in patients with pancreatic-insufficient cystic fibrosis (CF) compared with age-matched controls and to identify potential risk factors for small bowel bacterial overgrowth.

PATIENTS AND METHODS

Fifty patients, 25 pancreatic-insufficient CF study patients (mean age, 17 y) and 25 gastrointestinal clinic control patients (mean age, 15 y), completed a glucose-hydrogen breath test after an overnight fast. Study patients completed a quality-of-life questionnaire modified from the Cystic Fibrosis Questionnaire. The medical history of each patient was compared with breath test results. A positive breath test was defined as a fasting hydrogen > or =15 ppm or a rise of > or =10 ppm hydrogen over baseline during the test.

RESULTS

The prevalence of positive breath tests was higher in the CF study group (56%) than in the control group (20%) (P = 0.02). The mean fasting hydrogen levels of patients in the study and control groups were 22 and 5 ppm (P = 0.0001). The mean questionnaire scores were not significantly different between breath test-positive and -negative study patients. The use of azithromycin was associated with an increased risk of a positive breath test. Use of laxatives and inhaled ipratropium was associated with a decreased risk of a positive breath test.

CONCLUSIONS

Patients with CF were more likely to have elevated fasting hydrogen levels compared with controls. This suggests a high prevalence of small bowel bacterial overgrowth in CF patients. Medications commonly used by CF patients may influence intestinal health.

Eradication of small intestinal bacterial overgrowth in the cystic fibrosis mouse reduces mucus accumulation

OBJECTIVES

Mucus accumulation in cystic fibrosis (CF) is involved in blockage of the distal small intestine. Because expression of mucin genes and mucus secretion can be increased by infection and previous work indicated that small intestinal bacterial overgrowth occurs in CF, we tested whether reduction of bacterial load by antibiotic treatment would reduce mucin gene expression and mucus accumulation in the CF mouse small intestine.

METHODS

CF transmembrane conductance regulator null (cftr (tm1UNC)) and wild type littermates were treated with ciprofloxacin and metronidazole for 3 weeks. Muc2 and Muc3 gene expression were measured by quantitative reverse-transcriptase polymerase chain reaction. Periodic acid Schiff (PAS) staining and morphometry were used to measure the size of mucus droplets within goblet cells and dilation of the intestinal crypt lumen, as estimates of mucus secretion and accumulation.

RESULTS

Antibiotic treatment did not significantly affect Muc2 and Muc3 gene expression in CF mice. In untreated CF mice, the crypt lumen was almost sevenfold wider than wild type. Antibiotic treatment of CF mice reduced the intensity of PAS crypt lumen staining, and the lumen width was decreased by approximately 25%. The area occupied by PAS-positive material in goblet cells was significantly greater in tissues from antibiotic treated mice.

CONCLUSIONS

Eradication of bacterial overgrowth in CF mice significantly decreased mucus secretion and accumulation in intestinal crypts without an effect on mucin gene expression. It is proposed that bacterial overgrowth stimulates mucus secretion, which contributes to its accumulation in the small intestine. Control of bacterial overgrowth is expected to reduce mucus accumulation and may improve intestinal function and overall health in CF.

Bacterial overgrowth in the cystic fibrosis transmembrane conductance regulator null mouse small intestine

We recently reported the inflammation of the cystic fibrosis (CF) mouse small intestine, and we hypothesized bacterial overgrowth as a possible cause. Quantitative PCR of bacterial 16S genomic DNA in the CF mouse small intestine revealed an increase of greater than 40-fold compared to controls. Sequencing of 16S PCR products and Gram staining showed that the majority of bacteria in the CF mouse intestine were gram negative. Bacteria were observed to colonize the mucus that accumulates in the intestinal lumen of mice with CF. Impaired Paneth cell defenses were suggested by observation of partially dispersed Paneth granules in the mucus plugs of CF mouse intestinal crypts, and this mucus was strongly immunoreactive for Paneth cell bactericidal products. The role of bacterial overgrowth in intestinal inflammation in CF was tested by treating mice with oral antibiotics (ciprofloxacin and metronidazole) for 3 weeks, which reduced bacterial load in the CF mouse small intestine over 400-fold. Antibiotic treatment decreased the expression of the inflammation-related genes mast cell protease 2, leucine-rich alpha2 glycoprotein/leucine-rich high endothelial venule glycoprotein, suppressor of cytokine signaling 3, hematopoietic cell transcript 1, and resistin-like molecule beta/found in inflammatory zone 2, all of which were no longer expressed at levels significantly different from control levels. The reduction of intestinal bacteria also significantly improved the growth of CF mice but had no effect on the growth of wild-type mice. These data suggest that bacterial overgrowth in the CF mouse small intestine has a role in inflammation and contributes to the failure to thrive in this mouse model of CF.

Treatment of Gastrointestinal Problems in Cystic Fibrosis

The gastrointestinal (GI) manifestations of cystic fibrosis (CF) are varied and include pancreatic insufficiency, meconium ileus, distal intestinal obstruction syndrome (DIOS), liver disease, and other less common manifestations. Treatment of pancreatic insufficiency consists of providing appropriate pancreatic enzyme replacement therapy and may include raising duodenal pH to allow for optimal action of these enzymes. Despite a number of pancreatic enzyme replacement products, malabsorption cannot be normalized. Management of DIOS depends on the severity of the symptoms; adequate hydration is very important. Polyethylene glycol solutions are being increasingly used. The precipitating cause of the episode of DIOS should be looked for so future episodes can be prevented. Liver disease is relatively silent and annual monitoring of liver function and status is recommended. Treatment is mainly supportive and the role of ursodeoxycholic acid in the prevention of cirrhosis needs to be better defined. Nutritional status is an important part of management of all GI and liver manifestations of CF. A team approach and the assistance of a registered dietitian are extremely valuable in managing the GI and liver manifestations of CF.

Using breath tests wisely in a gastroenterology practice: an evidence-based review of indications and pitfalls in interpretation

Breath tests are a simple and safe alternative to more invasive investigation strategies for many gastroenterological conditions. Both the hydrogen breath tests and the new 13C stable radioisotope breath tests are nonradioactive and safe in children and pregnancy. The range of diseases that can be identified include Helicobacter pylori infection, lactose and fructose intolerance, bacterial overgrowth, bile salt wastage, pancreatic insufficiency, liver dysfunction, and abnormal small bowel transit. In this review, the physiology supporting these tests and the principles of normal gas dynamics in the gut are briefly reviewed and then related to the test preparation and interpretation in two parts: 1) detection of H. pylori and 2) small bowel, pancreatic, and hepatobiliary disorders. A MEDLINE search reviewing all English language abstracts from 1966 to March, 2001 was performed, with an additional review of abstracts from major national meetings from 1997 to 2001. Using the information from this review, the performance characteristics of the various tests were detailed, and an attempt is made to provide some literature-based guidance regarding their indications and limitations. The interpretation of "flat" breath tests and the selective use of methane collection and colonic alkalinization are discussed. Breath tests are valuable tools that are, in general, underutilized in evaluating dyspepsia and functional bloating and diarrhea, as well as suspected malabsorption, including lactose intolerance.

Lactose-[13C]ureide breath test: a new, noninvasive technique to determine orocecal transit time in children

BACKGROUND

The lactose-[13C]ureide breath test (LUBT) is a novel, noninvasive test to determine orocecal transit time. Lactose ureide resists the action of brush border enzymes and is metabolized by colonic bacteria. The purpose of the present study was to adapt this breath test for children of various age groups and to determine whether it can be applied in infants, newborns, and preterms to study the development of small intestinal motility.

METHODS

In a group of 20 children (3-17 years) in vitro stool analysis and in vivo LUBT results were compared. From each subject a blank stool sample and a sample produced after induction with unlabeled lactose ureide were incubated with 10 mg lactose-[13C]ureide in small, closed bottles. Ten-milliliter CO2 samples were aspirated from the bottles using a needle and a syringe every 30 minutes for 24 hours. All children performed the breath test after induction of 500 mg unlabeled lactose ureide three times the prior day. A liquid test meal (chocolate milk) with 250 mg lactose-[13C]ureide was ingested. Breath samples were collected every 15 minutes for 10 hours. In a second group of 32 children (age range, 0-3 years) consisting of 6 children between 1 and 3 years of age, 6 infants between 6 and 12 months, 13 infants between 0 and 6 months, and 7 preterm infants, only the in vitro stool analysis was performed. Stools were collected for stool incubation, as described.

RESULTS

The mean orocecal transit time in the group of 20 children aged 3 to 17 years was 255 minutes (range, 165-390 minutes). Stool incubations demonstrated a clear 13CO2 peak in all infants aged more than 8 months, indicating that their colonic bacterial enzymic activity hydrolyses lactose ureide. However, in all infants aged less than 6 months and in preterm infants, the 13CO2 signal was absent, indicating that those subjects were unable to hydrolyze lactose ureide.

CONCLUSION

Infants aged less than 6 months do not host the appropriate bacterial enzymic activity for splitting lactose ureide. The authors conclude that the LUBT can be applied in infants aged more than 8 months, after weaning to solid foods, to determine orocecal transit time.