The clinical consequences of sucrase-isomaltase deficiency

Genetic and acquired sucrase-isomaltase deficiency: A clinical review

Genetic sucrase-isomaltase deficiency (GSID) is an inherited deficiency in the ability to digest sucrose and potentially starch due to mutations in the sucrase-isomaltase (SI) gene. Congenital sucrase-isomaltase deficiency is historically considered to be a rare condition affecting infants with chronic diarrhea as exposure to dietary sucrose begins. Growing evidence suggests that individuals with SI variants may present later in life, with symptoms overlapping with those of irritable bowel syndrome. The presence of SI genetic variants may, either alone or in combination, affect enzyme activity and lead to symptoms of different severity. As such, a more appropriate term for this inherited condition is GSID, with a recognition of a spectrum of severity and onset of presentation. Currently, disaccharidase assay on duodenal mucosal tissue homogenates is the gold standard in diagnosing SI deficiency. A deficiency in the SI enzyme can be present at birth (genetic) or acquired later, often in association with damage to the enteric brush-border membrane. Other noninvasive diagnostic alternatives such as sucrose breath tests may be useful but require further validation. Management of GSID is based on sucrose and potentially starch restriction tailored to the individual patients' tolerance and symptoms. As this approach may be challenging, additional treatment with commercially available sacrosidase is available. However, some patients may require continued starch restriction. Further research is needed to clarify the true prevalence of SI deficiency, the pathobiology of single SI heterozygous mutations, and to define optimal diagnostic and treatment algorithms in the pediatric population.

Congenital Sucrase-Isomaltase Deficiency: Same Mutation with Different Clinical Presentations

BACKGROUND/AIMS

 Congenital sucrase-isomaltase deficiency is an autosomal recessive inherited disaccharidase deficiency characterized by chronic osmotic diarrhea. In this study, the genotype-phenotype relationships of close relatives of an index case with congenital sucrase-isomaltase deficiency were investigated.

MATERIALS AND METHODS

 A 23-month-old female patient with a sucrase-isomaltase gene c.317G>A (p.C106Y) homozygous mutation was diagnosed as an index case and her pedigree analysis was performed subsequently. The family members with and without sucrase- isomaltase gene mutations were compared in terms of clinical symptoms.

RESULTS

 The study included 109 cases [mean age ± SD: 22.6 ± 17.2 years (0.1-75 years), 61 males (56%)] of 130 family members of the index case. Sucrase-isomaltase gene c.317G>A (p.C106Y) heterozygous mutation was detected in 27 cases (24.7%); 14 (51.9%) were male and had a mean age of 23.2 ± 18.3 years. The most common complaints of 12 (44.4%) symptomatic patients with mutations were abdominal pain (37%), gas irritability (33.3%), bloating (22.2%), and foul-smelling stools (18.5%). Compared with the cases without mutation, a statistically significant difference was observed in the incidence of gas irritability, foul-smelling stool, ≥2 gastrointestinal symptoms, postprandial complaints, and food allergy (P = .005, P = .047, P = .049, P = .017, P = .021, respectively). Sacrosidase enzyme replacement was applied to 7 patients whose symptoms did not improve with dietary elimination. Clinical response was obtained after enzyme treatment.

CONCLUSION

 Despite its autosomal recessive inheritance, congenital sucrase-isomaltase deficiency can also be symptomatic in heterozygous individuals. Further studies are required to clarify the genotype-phenotype relationship and management of the disease.

Healthcare Burden in Greenland of Gastrointestinal Symptoms in Adults with Inherited Loss of Sucrase-Isomaltase Function

Background

Congenital sucrase isomaltase deficiency (CSID) is in general a very rare disease. However, 2-3% of the Greenlandic population are homozygous (HO) carriers of an Arctic-specific loss-of-function (LoF) variant in the sucrase-isomaltase (SI) encoding gene, causing CSID. The condition is characterized by gastrointestinal symptoms such as stomachache, diarrhea, and weight loss when consuming sucrose, the most common dietary sugar. However, the awareness of the condition in the population and the healthcare system seems to be limited, potentially leading to a higher healthcare burden. Hence, we aimed to investigate whether HO-carriers visit the healthcare system more with gastrointestinal symptoms compared to the control groups by using registry data.

Methods

We performed a case-control study identifying cases and controls using genotype information from the 1999-2001 and 2005-2010 Greenlandic health population cohorts. The cases were defined as HO LoF SI-carriers and controls were defined as non-carriers and were matched (1:1) on sex, age, place of residence, and European genetic admixture. We used electronic medical records to assess the number of electronic medical record contacts (EMRc) related to gastrointestinal symptoms and the number of gastrointestinal-related diagnostic procedures.

Results

A total of 80 HO-carriers and 80 non-carriers were included. The HO-carriers had 19% more EMRc related to gastrointestinal symptoms (IRR, 1.19, 95% CI [1.02;1.40], p=0.02) and had a 41% higher incidence of gastrointestinal related diagnostic procedures compared to controls (IRR, 1.41, 95% CI [1.05-1.92], p=0.02). Only one HO-carrier was aware of the condition according to the electronic medical records.

Conclusion

HO-carriers of the LoF SI-variant had both significantly more gastrointestinal-related EMRc and significantly more diagnostic procedures conducted due to gastrointestinal symptoms. Only one HO-carrier was aware of the condition. Given the high prevalence of HO-carriers in the Greenlandic population, we anticipate that diagnosing more patients with CSID and providing dietary advice could potentially reduce symptom burden and healthcare visits among HO-carriers.

Intestinal Disaccharidase Deficiency in Adults: Evaluation and Treatment

PURPOSE OF REVIEW

Disaccharidase deficiency in adults causes carbohydrate malabsorption, resulting in symptoms which significantly overlap with irritable bowel syndrome (IBS). This article discusses the diagnosis and treatment of disaccharidase deficiency within the context of recent literature.

RECENT FINDINGS

Disaccharidase deficiency in adults is more common than previously thought, which includes lactase, sucrase, maltase and isomaltase enzymes. Deficiency in disaccharidases, which are produced by the intestinal brush border, will interfere with the breakdown and absorption of carbohydrates and may result in abdominal pain, gas, bloating and diarrhea. Patients deficient in all 4 disaccharidases are known as having "pan-disaccharidase" deficiency, which has a distinct phenotype with more reported weight loss than patients deficient in one enzyme. IBS patients who do not respond to low FODMAP dietary restriction may have undiagnosed disaccharidase deficiency and may benefit from testing. Diagnostic testing methods are limited to duodenal biopsies, which is the gold standard, and breath testing. Dietary restriction and enzyme replacement therapy have been shown to be effective treatments in these patients. Disaccharidase deficiency is an underdiagnosed condition in adults with chronic GI symptoms. Patients who do not respond to traditional treatment strategies for DBGI may benefit from testing for disaccharidase deficiency. Further studies delineating the distinctions between disaccharidase deficient patients and those with other motility disorders are needed.

Mechanisms underlying food-related symptoms in disorders of gut-brain interaction: Course ahead in research and clinical practice

A subgroup of patients with a disorder of gut-brain interaction (DGBI) report symptoms such as abdominal pain, gas-related symptoms, dyspeptic symptoms and loose stool or urgency after meal intake. Therefore, the effect of several dietary therapies including fibre-rich or restrictive diets have already been studied in patients with irritable bowel syndrome, functional abdominal bloating or distention, and functional dyspepsia. However, there is a paucity of studies in the literature on the mechanisms underlying food-related symptoms. Therefore, this review focuses on these potential mechanisms and explains the role of nutrient sensing and tasting, physical considerations, malabsorption or allergy-like reaction to food and its interaction with microbiota. In addition, it emphasizes the importance of future research and clinical practice regarding food-related symptoms in patients with a DGBI.

Mechanisms Underlying Food-Triggered Symptoms in Disorders of Gut-Brain Interactions

There has been a dramatic increase in clinical studies examining the relationship between disorders of gut-brain interactions and symptoms evoked by food ingestion in the upper and lower gastrointestinal tract, but study design is challenging to verify valid endpoints. Consequently, mechanistic studies demonstrating biological relevance, biomarkers and novel therapeutic targets are greatly needed. This review highlights emerging mechanisms related to nutrient sensing and tasting, maldigestion, physical effects with underlying visceral hypersensitivity, allergy and immune mechanisms, food-microbiota interactions and gut-brain signaling, with a focus on patients with functional dyspepsia and irritable bowel syndrome. Many patients suffering from disorders of gut-brain interactions exhibit these mechanism(s) but which ones and which specific properties may vary widely from patient to patient. Thus, in addition to identifying these mechanisms and the need for further studies, biomarkers and novel therapeutic targets are identified that could enable enriched patient groups to be studied in future clinical trials examining the role of food in the generation of gut and non-gut symptoms.

Chronic Diarrhea in an Infant With Malrotation: A Diagnostic Dilemma

In children, diarrhea has a global incidence of 2.7 episodes per child-year and contributes to significant disease burden and mortality in children under 5 years of age. Chronic diarrhea, defined as diarrhea lasting for more than 2 weeks, may be particularly challenging to evaluate and manage in children under 2 years of age. While most have infectious enteritis or cow milk protein intolerance, others have conditions such as malnutrition, anatomic abnormalities, or congenital enteropathies that can be challenging to diagnose and treat. We present here a complex case of chronic diarrhea in an infant and highlight such diagnostic and therapeutic challenges.

Food intolerances and the small intestine

The article presents an analysis of the literature on food intolerance (FS) associated with the presence in the diet of fermentable oligodimosaccharides and polyols FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols), histamine and food additives. The relationship between FS and insufficient activity of enzymes of the small intestine mucosa, in particular, in patients with irritable bowel syndrome, is discussed. FS often noted in them forces them to strictly adhere to the elimination diet and significantly impair the quality of life due to dissatisfaction with the results of treatment. Analysis of the literature has confirmed in many patients with irritable bowel syndrome an etiotropic relationship with poor food tolerance and dictates the need for randomized studies to further study the pathogenetic mechanisms of increasing food tolerance under the influence of cytoprotective therapy.

All layers matter: Innovative three-dimensional epithelium-stroma-endothelium intestinal model for reliable permeability outcomes

Drug development is an ever-growing field, increasingly requesting reliable in vitro tools to speed up early screening phases, reducing the need for animal experiments. In oral delivery, understanding the absorption pattern of a new drug in the small intestine is paramount. Classical two-dimensional (2D) in vitro models are generally too simplistic and do not accurately represent native tissues. The main goal of this work was to develop an advanced three-dimensional (3D) in vitro intestinal model to test absorption in a more reliable manner, by better mimicking the native environment. The 3D model is composed of a collagen-based stromal layer with embedded fibroblasts mimicking the intestinal lamina propria and providing support for the epithelium, composed of enterocytes and mucus-secreting cells. An endothelial layer, surrogating the absorptive capillary network, is also present. The cellular crosstalk between the different cells present in the model is unveiled, disclosing key players, namely those involved in the contraction of collagen by fibroblasts. The developed 3D model presents lower levels of P-glycoprotein (P-gp) and Multidrug Resistance Protein 2 (MRP2) efflux transporters, which are normally overexpressed in traditional Caco-2 models, and are paramount in the absorption of many compounds. This, allied with transepithelial electrical resistance (TEER) values closer to physiological ranges, leads to improved and more reliable permeability outcomes, which are observed when comparing our results with in vivo data.

Sucrase-Isomaltase Deficiency Causing Persistent Bloating and Diarrhea in an Adult Female

Congenital sucrase isomaltase deficiency (CSID) is an autosomal recessive disorder which leads to chronic intestinal malabsorption of nutrients from ingested starch and sucrose. Symptoms usually present after consumption of fruits, juices, grains, and starches, leading to failure to thrive and malnutrition. Diagnosis is suspected on detailed patient history and confirmed by a disaccharidase assay using small intestinal biopsies or sucrose hydrogen breath test. Treatment of CSID consists of limiting sucrose in diet and replacement therapy with sacrosidase. Due to its nonspecific symptoms, CSID may be undiagnosed in many patients for several years. We present a case of a 50-year-old woman with persistent symptoms of bloating in spite of extensive evaluation and treatment.

The patient journey to diagnosis and treatment of congenital sucrase-isomaltase deficiency

Purpose

Congenital sucrase-isomaltase deficiency (CSID) is a rare genetic disorder characterized by a deficiency of the sucrase-isomaltase (SI) enzyme complex within the brush border membrane of the small intestine. Mutations in the SI gene result in abnormal synthesis and/or incorrect transport of the SI enzyme. Patients with CSID generally have reduced sucrase activity, but levels of isomaltase activity range from absent to almost normal. This study sought to better understand the experience of patients with CSID prior to, during, and after their diagnosis and its subsequent treatment with sacrosidase.

Methods

This was a cross-sectional interview study conducted in conjunction with a longitudinal, observational study of US patients prescribed and taking sacrosidase for at least three consecutive months as treatment for CSID. The observational study included both children and adults.

Results

This qualitative interview study explored the experiences of 43 adult and pediatric patients (n = 8 adults and n = 35 children/adolescents) with CSID pre-, during, and post-diagnosis. Findings suggest that a CSID diagnosis is particularly problematic given the disparate range of more commonly understood gastrointestinal (GI) disorders. After diagnosis and treatment with sacrosidase, participants reported considerable improvement in symptoms and health-related quality of life (HRQL), yet symptoms persist that continue to affect daily life, indicating areas of potential unmet need.

Conclusion

Educating clinicians about CSID may help improve the overall diagnosis experience. As this research is the first of its kind in CSID, additional research, qualitative and quantitative, will be important to furthering the understanding of HRQL impact and unmet need experienced by this population and identifying ways to best meet those needs.

NGS Gene Panel Analysis Revealed Novel Mutations in Patients with Rare Congenital Diarrheal Disorders

Congenital diarrheal disorders (CDDs) are early-onset enteropathies generally inherited as autosomal recessive traits. Most patients with CDDs require rapid diagnosis as they need immediate and specific therapy to avoid a poor prognosis, but their clinical picture is often overlapping with a myriad of nongenetic diarrheal diseases. We developed a next-generation sequencing (NGS) panel for the analysis of 92 CDD-related genes, by which we analyzed patients suspect for CDD, among which were (i) three patients with sucrose-isomaltase deficiency; (ii) four patients with microvillous inclusion disease; (iii) five patients with congenital tufting enteropathy; (iv) eight patients with glucose-galactose malabsorption; (v) five patients with congenital chloride diarrhea. In all cases, we identified the mutations in the disease-gene, among which were several novel mutations for which we defined pathogenicity using a combination of bioinformatic tools. Although CDDs are rare, all together, they have an incidence of about 1%. Considering that the clinical picture of these disorders is often confusing, a CDD-related multigene NGS panel contributes to unequivocal and rapid diagnosis, which also reduces the need for invasive procedures.

Sucrase-isomaltase Gene Variants in Patients With Abnormal Sucrase Activity and Functional Gastrointestinal Disorders

OBJECTIVES

The aim of the study was to determine prevalence and characterize sucrase-isomaltase (SI) gene variants of congenital sucrase-isomaltase deficiency in non-Hispanic white pediatric and young adult patients with functional gastrointestinal disorders (FGIDs), and abnormal sucrase activity on histologically normal duodenal biopsy.

METHODS

Clinical symptoms and disaccharidase activities data were collected for an abnormal (low) sucrase (≤25.8 U, n = 125) activity group, and 2 normal sucrase activity groups with moderate (≥25.8-≤55 U, n = 250) and high (>55 U, n = 250) sucrase activities. SI gene variants were detected by next-generation sequencing of DNA from formalin-fixed paraffin-embedded tissues of these patients. FGIDs symptoms based on Rome IV criteria and subsequent clinical management of abnormal sucrase activity cases with pathogenic SI gene variants were analyzed.

RESULTS

Thirteen SI gene variants were found to be significantly higher in abnormal sucrase cases with FGIDs symptoms (36/125, 29%; 71% did not have a pathogenic variant) compared to moderate normal (16/250, 6.4%, P < 0.001) or high normal (5/250, 2.0%, P < 0.001) sucrase groups. Clinical management data were available in 26 of abnormal sucrase cases, and only 10 (38%) were correctly diagnosed and managed by the clinicians. Concomitant lactase deficiency (24%; 23/97) and pan-disaccharidase deficiency (25%; 13/51) were found in the abnormal sucrase group.

CONCLUSIONS

Heterozygous and compound heterozygous mutations in the SI gene were more prevalent in cases with abnormal sucrase activity presenting with FGIDs, and normal histopathology. This suggests heterozygous pathogenic variants of congenital sucrase-isomaltase deficiency may present as FGIDs. Concomitant lactase or pan-disaccharidase deficiencies were common in abnormal sucrase cases with SI gene variants.

Sucrase-Isomaltase Deficiency as a Potential Masquerader in Irritable Bowel Syndrome

BACKGROUND

Patients with irritable bowel syndrome (IBS) frequently have meal-related symptoms and can recognize specific trigger foods. Lactose intolerance is a well-established carbohydrate malabsorption syndrome that causes symptoms similar to IBS such as bloating, abdominal pain, and diarrhea. However, the prevalence of sucrase-isomaltase deficiency (SID) in this population is poorly defined. SID is a condition in which sucrase-isomaltase, an enzyme produced by brush border of small intestine to metabolize sucrose, is deficient. Just like lactase deficiency, SID causes symptoms of maldigestion syndromes including abdominal pain, bloating, gas, and diarrhea. In this study, we aim to determine the prevalence of SID in patients with presumed IBS-D/M and characterize its clinical presentation.

METHODS

Patients with a presumed diagnosis of IBS-D/M based on symptoms of abdominal pain, diarrhea, and/or bloating who underwent esophagogastroduodenoscopy with duodenal biopsies and testing for disaccharidase deficiency were included. Patients with a history of inflammatory bowel disease, gastrointestinal malignancy, or celiac disease were excluded. Odds ratio was calculated for abdominal pain, diarrhea, and bloating in patients with versus without SID.

RESULTS

A total of 31 patients with clinical suspicion for IBS-D/M were included with a median age of 46 years (IQR 30.5-60) and with 61% females. SID was present in 35% of patients. Among patients with SID, 63.6% had diarrhea, 45.4% had abdominal pain, and 36.4% had bloating. Patients with SID were less likely than controls to have abdominal pain (OR 0.16, 95% CI 0.03-0.81, p = 0.04) although no difference in diarrhea or bloating was found. Only two patients with SID underwent sucrose breath testing of which only one had a positive result. However, this patient also had a positive glucose breath test and may have had small intestinal bacterial overgrowth as a confounder.

CONCLUSION

SID was found in 35% of patients with presumed IBS-D/M and should be considered in the differential diagnosis of patients presenting with abdominal pain, diarrhea, or bloating. Further studies should better characterize the clinical features of SID and investigate the effects of dietary modification in this group of patients.

Synthesis of montbretin A analogues yields potent competitive inhibitors of human pancreatic α-amylase

Simplified analogues of the potent human amylase inhibitor montbretin A were synthesised and shown to bind tightly, K I = 60 and 70 nM, with improved specificity over medically relevant glycosidases, making them promising candidates for controlling blood glucose. Crystallographic analysis confirmed similar binding modes and identified new active site interactions.

Food Intolerances

Food intolerances are estimated to affect up to 20% of the population but complete understanding of diagnosis and management is complicated, given presentation and non-immunological mechanisms associated vary greatly. This review aims to provide a scientific update on common food intolerances resulting in gastrointestinal and/or extra-intestinal symptoms. FODMAP sensitivity has strong evidence supporting its mechanisms of increased osmotic activity and fermentation with the resulting distention leading to symptoms in those with visceral hypersensitivity. For many of the other food intolerances reviewed including non-coeliac gluten/wheat sensitivity, food additives and bioactive food chemicals, the findings show that there is a shortage of reproducible well-designed double-blind, placebo-controlled studies, making understanding of the mechanisms, diagnosis and management difficult. Enzyme deficiencies have been proposed to result in other food sensitivities including low amine oxidase activity resulting in histamine intolerance and sucrase-isomaltase deficiency resulting in reduced tolerance to sugars and starch. Lack of reliable diagnostic biomarkers for all food intolerances result in an inability to target specific foods in the individual. As such, a trial-and-error approach is used, whereby suspected food constituents are reduced for a short-period and then re-challenged to assess response. Future studies should aim to identify biomarkers to predict response to dietary therapies.

[Saccharomyces boulardii CNCM I-745 - the medicinal yeast improves intestinal enzyme function]

BACKGROUND

Saccharomyces boulardii CNCM I-745 is a probiotic medicinal yeast used in the prevention and treatment of diarrhea. It has numerous effects, i. a. immunological and antitoxin effects, it binds pathogens and has a beneficial effect on the intestinal microbiota. In addition, pronounced trophic effects were detected.

METHOD

The focus of this review is on the effects of S. boulardii CNCM I-745 on digestive enzymes located in the brush border membrane. An important role in this context is attributed to polyamines which are synthesized and secreted by S. boulardii CNCM I-745.

RESULTS AND CONCLUSIONS

Polyamines are essential for cell proliferation and differentiation. They enhance the expression of intestinal enzymes as well as nutrient transport systems and directly influence the nucleic acid binding capacity. S. boulardii CNCM I-745 induces signals via mitogen-activated protein kinase cascades (MAP kinase pathway) and influences the PI3 kinase signaling pathway. Furthermore, S. boulardii CNCM I-745 secretes certain enzymes that promote nutrient delivery to both the yeast itself and the host organism. The increased presence of digestive enzymes obviously contributes significantly to the clinical effect of S. boulardii CNCM I-745.

The Role of Disaccharidase Deficiencies in Functional Abdominal Pain Disorders-A Narrative Review

Disaccharidase deficiencies are reportedly underdiagnosed in pediatric populations. Though typically thought to cause diarrheal disease, they can also be a cause of abdominal pain and dyspepsia, and patients diagnosed with these functional disorders may actually have associated enzyme deficiencies. While the effects of lactose deficiency have been widely studied, sucrase, maltase, and isomaltase are less frequently considered when approaching a patient with an apparent functional abdominal pain disorder. This review seeks to provide an up-to-date narrative on the current scientific literature on the possible role of sucrase, maltase, and isomaltase deficiency in pediatric functional gastrointestinal disorders.

Enzyme therapy for functional bowel disease-like post-prandial distress

Post-prandial gastrointestinal symptoms such as diarrhea, abdominal distension, flatulence, bloating and a feeling of fullness are common complaints of often unknown etiology and pathogenesis. There is a long history of trials reporting the successful use of products containing a variety of combinations of digestive enzymes including a number of randomized placebo-controlled trials. We provide a narrative review of studies describing the use of multi-digestive enzymes for symptoms consistent with irritable bowel syndrome. We describe clinical trials reported over the past 60 years including double-blinded randomized, placebo-controlled studies and recent trials that focused on post-prandial diarrhea consistent with diarrhea-predominant irritable bowel syndrome. Disaccharidase deficiencies or deficiencies of other carbohydrate digesting enzymes were excluded. Worldwide studies have generally reported success with multi-enzyme preparations although none used a factorial design to identify subgroups or attempted to link specific symptom responses to specific components of therapy. Although there is a long history of the successful use of multi-enzyme preparations for post-prandial symptoms consistent with irritable bowel syndrome, long-term studies using validated scoring systems and factorial designs are needed to confirm the results for specific symptoms and the components of the combination drugs received.

Saccharomyces boulardii CNCM I-745 Improves Intestinal Enzyme Function: A Trophic Effects Review

Several properties of the probiotic medicinal yeast Saccharomyces boulardii CNCM I-745 contribute to its efficacy to prevent or treat diarrhoea. Besides immunologic effects, pathogen-binding and anti-toxin effects, as well as positive effects on the microbiota, S boulardii CNCM I-745 also has pronounced effects on digestive enzymes of the brush border membrane, known as trophic effects. The latter are the focus of this review. Literature has been reviewed after searching Medline and PMC databases. All relevant non-clinical and clinical studies are summarized. S. boulardii CNCM I-745 synthesizes and secretes polyamines, which have a role in cell proliferation and differentiation. The administration of polyamines or S. boulardii CNCM I-745 enhances the expression of intestinal digestive enzymes as well as nutrient uptake transporters. The signalling mechanisms leading to enzyme activation are not fully understood. However, polyamines have direct nucleic acid–binding capacity with regulatory impact. S. boulardii CNCM I-745 induces signalling via the mitogen-activated protein kinase pathway. In addition, effects on the phosphatidylinositol-3 kinase (PI3K) pathway have been reported. As an additional direct effect, S. boulardii CNCM I-745 secretes certain enzymes, which enhance nutrient acquisition for the yeast and the host. The increased availability of digestive enzymes seems to be one of the mechanisms by which S. boulardii CNCM I-745 counteracts diarrhoea; however, also people with certain enzyme deficiencies may profit from its administration. More studies are needed to fully understand the mechanisms of trophic activation by the probiotic yeast.

Relationships among Dietary Intakes and Persistent Gastrointestinal Symptoms in Patients Receiving Enzyme Treatment for Genetic Sucrase-Isomaltase Deficiency

BACKGROUND

Sucrose-isomaltase deficiency (SID) remains underdiagnosed. Absent or reduced enzyme activity promotes diarrhea, abdominal bloating, and flatulence from undigested and malabsorbed disaccharides. Frequency and severity of gastrointestinal symptoms may be associated with the type of carbohydrates consumed.

OBJECTIVE

To characterize the dietary intakes of patients treated with sacrosidase (Sucraid; QOL Medical) for SID and determine relationships between type of carbohydrates, sacrosidase dose, and gastrointestinal symptoms.

DESIGN

A prospective 30-day observational study.

PARTICIPANTS/SETTING

Forty-nine patients treated with sacrosidase for ≥3 months were recruited from the enzyme manufacturer's nationwide clinical database between November 2014 and August 2015.

MAIN OUTCOME MEASURES

Dietary energy and nutrient intakes reported during 24-hour diet recall interviews, frequency and severity of gastrointestinal (GI) symptoms, and sacrosidase dose.

STATISTICAL ANALYSES PERFORMED

Relationships between nutrient intakes, sacrosidase dose, and GI symptoms were evaluated using Spearman ρ correlation coefficients.

RESULTS

Sacrosidase dose averaged 5.2±3.1 mL/day. Participants reported 1.3±0.9 bowel movements daily. Having less frequent GI symptoms was associated with higher sacrosidase intake. Energy intakes averaged 1,562.5±411.5 kcal/day in children, 1,964.7±823.6 kcal/day in adolescents, and 1,952.6±546.5 kcal/day in adults. Macronutrient composition averaged 44% carbohydrate, 39% fat, and 17% protein. Average carbohydrate composition was 35% starch, 8% fiber, and 59% sugars. Sucrose and fructose intakes were not associated with GI symptoms. Lactose intake was associated with diarrhea. Maltose intake was associated with nausea, distension, and reflux.

CONCLUSIONS

Intakes were lower in carbohydrates and higher in fat compared with the Acceptable Macronutrient Distribution Ranges. Sucrose and fructose intakes were not associated with GI symptoms. Higher maltose and lactose intakes were associated with GI symptom frequency and severity. These findings provide evidence to guide nutrition counseling for patients treated for SID.

Variable Use of Disaccharidase Assays When Evaluating Abdominal Pain

Background and Aims: Patients with a disaccharidase deficiency typically present with abdominal discomfort and often with diarrhea. However, disaccharidase deficiency is often overlooked as a cause of these complaints. Therefore, we sought to determine the prevalence of lactase and sucrase deficiencies in a pediatric population undergoing diagnostic esophagogastroduodenoscopy (EGD) and to describe disaccharidase testing practices among pediatric gastroenterologists. Methods: Endoscopic records from patients undergoing diagnostic EGD and disaccharidase analysis (DA) were retrospectively reviewed. Diagnostic EGDs performed over a 5-year period (2010 through 2014) at a freestanding endoscopy center serving 13 pediatric gastroenterologists were assessed. Demographic and clinical data on patients were collected and grouped; patients with primary sucrase-isomaltase deficiency (SID) were the main focus. The data were stratified by the physician performing the procedures. Results: Over the 5-year study period, 5368 EGDs were performed, with abdominal pain as the primary indication in 3235 cases (60.2%). DAs were performed on 963 patients (17.9% of the total cohort; 29.8% of those with abdominal pain). Lactase deficiencies, sucrase deficiencies, and primary SID were found in 44.7%, 7.6%, and 3.5% of DAs, respectively. The number of DAs performed varied widely among physicians, ranging from 1.6% to 64.5% of EGDs evaluating patients with abdominal pain. Univariate regression analysis revealed significant correlations between the number of DAs performed and the number of SID and lactase deficiencies found (P<.001 for both). Conclusion: Rates of DAs vary widely among pediatric gastroenterologists performing diagnostic EGDs in children with abdominal pain. Physician education and clinical practice guidelines regarding the use of DAs are warranted.

Structure-function analysis of human sucrase-isomaltase identifies key residues required for catalytic activity

Sucrase-isomaltase (SI) is an intestinal membrane-associated α-glucosidase that breaks down di- and oligosaccharides to absorbable monosaccharides. SI has two homologous functional subunits (sucrase and isomaltase) that both belong to the glycoside hydrolase family 31 (GH31) and differ in substrate specificity. All GH31 enzymes share a consensus sequence harboring an aspartic acid residue as a catalytic nucleophile. Moreover, crystallographic structural analysis of isomaltase predicts that another aspartic acid residue functions as a proton donor in hydrolysis. Here, we mutagenized the predicted proton donor residues and the nucleophilic catalyst residues in each SI subunit. We expressed these SI variants in COS-1 cells and analyzed their structural, transport, and functional characteristics. All of the mutants revealed expression levels and maturation rates comparable with those of the wild-type species and the corresponding nonmutated subunits were functionally active. Thereby we determined rate and substrate specificity for each single subunit without influence from the other subunit. This approach provides a model for functional analysis of the single subunits within a multidomain protein, achieved without the necessity to express the individual subunits separately. Of note, we also found that glucose product inhibition regulates the activities of both SI subunits. We experimentally confirmed the catalytic function of the predicted proton donor residues, and sequence analysis suggested that these residues are located in a consensus region in many GH31 family members. In summary, these findings reveal the kinetic features specific for each human SI subunit and demonstrate that the activities of these subunits are regulated via product inhibition.