Routine disaccharidase testing: are we there yet?

PURPOSE OF REVIEW: Disaccharidase testing, as applied to the evaluation of gastrointestinal disturbances is available but it is not routinely considered in the diagnostic work-up. The purpose of this review was to determine if disaccharidase testing is clinically useful and to consider how the results could alter patient management. RECENT FINDINGS: Indicate that carbohydrate maldigestion could contribute functional bowel disorders and negatively impact the fecal microbiome. Diagnostic techniques include enzyme activity assays performed on random endoscopically obtained small intestinal biopsies, immunohistochemistry, stable isotope tracer and nonenriched substrate load breath testing, and genetic testing for mutations. More than 40 sucrase--isomaltase gene variants coding for defective or reduced enzymatic activity have been reported and deficiency conditions are more common than previously thought. SUMMARY: The rationale for disaccharidase activity testing relates to a need to fully assess unexplained recurrent abdominal discomfort and associated symptoms. All disaccharidases share the same basic mechanism of mucosal expression and deficiency has far reaching consequences. Testing for disaccharidase expression appears to have an important role in symptom evaluation, but there are accuracy and logistical issues that should be considered. It is likely that specific recommendations for patient management, dietary modification, and enzyme supplementation would come from better testing methods.

Clinical Characteristics of Disaccharidase Deficiencies Among Children Undergoing Upper Endoscopy.

OBJECTIVES: The epidemiology and clinical significance of disaccharidase deficiencies have not been thoroughly characterized. Recent work suggests at least genetic sucrase-isomaltase deficiency is more prevalent than previously believed. Because lactase deficiency (LD) is well described, the present study focuses on the clinical characteristics of children with disaccharidase deficiencies determined by esophagogastroduodenoscopy. METHODS: Endoscopic records were reviewed from patients undergoing esophagogastroduodenoscopies with biopsies assayed for disaccharidase activity performed by 13 pediatric gastroenterologists during 5 years (2010-2014). Presenting symptoms, clinical and histological diagnosis, treatment, disaccharidase results, and demographic variables were obtained from medical and endoscopic records of those with maltase and sucrase deficiency (SD). RESULTS: Among 963 patients undergoing intestinal disaccharidase testing, 73 (7.6%) had SD on biopsy (enzyme activity <25 µmol ·â€Šmin ·â€Šg). Thirty-four (34/73; 47%) had normal duodenal histology and are the focus of this report. Four patients had SD without LD. Pan-disaccharidase deficiency was observed in 24 patients when maltase and palatinase assays were obtained (n = 646), and 11 had SD + LD when just those 2 enzymes were analyzed (n = 317). Those with SD without LD were younger 4.6 ±â€Š6.1 versus 14.1 ±â€Š3.6 years and uniformly presented with diarrhea. Patients with pan-disaccharidase deficiency or SD + LD primarily reported abdominal pain (33/35; 94%), diarrhea (16/35; 46%), nausea (14/35; 40%); and poor weight gain/weight loss (10/35; 29%); constipation, flatulence, and bloating were also noted. Maltase deficiency is less common (8/963; 0.8%), presenting with similar symptoms. CONCLUSIONS: Genetic sucrase-isomaltase deficiency often occurs together with lactase or pan-disaccharide deficiency. Disaccharidase deficiency should be considered a potential cause of abdominal pain and/or diarrhea in children and adolescents.

Demographic and Clinical Correlates of Mucosal Disaccharidase Deficiencies in Children With Functional Dyspepsia.

BACKGROUND: A subset of children with functional gastrointestinal disorders (FGIDs), which includes functional dyspepsia, may have duodenal disaccharidase deficiencies. OBJECTIVES: To determine the frequency, demographics, and clinical characteristics associated with duodenal disaccharidase deficiencies in children with functional dyspepsia. METHODS: Children ages 4 to 18 years undergoing esophagogastroduodenoscopy (EGD) evaluation for dyspepsia were enrolled in either a retrospective (study 1) or prospective (study 2) evaluation. Those with histologic abnormalities were excluded. Duodenal biopsies were obtained for disaccharidase enzyme analysis. In the retrospective study, both demographic and clinical characteristics were obtained via chart review. In the prospective study, parents completed the Rome II Questionnaire on Gastrointestinal Symptoms before the EGD. RESULTS: One hundred and twenty-nine children (n = 101, study 1; n = 28, study 2) were included. Mean age was 11.2 ±â€Š3.8 (SD) years in study 1 and 10.6 ±â€Š3.2 years in study 2. Forty-eight (47.5%) of subjects in study 1 and 13 (46.4%) of subjects in study 2 had at least 1 disaccharidase deficiency identified. All of those with a disaccharidase deficiency in both studies had lactase deficiency with 8 (7.9%) and 5 (17.9%) of those in studies 1 and 2, respectively, having an additional disaccharidase deficiency. The second most common disaccharidase deficiency pattern was that of pan-disaccharidase deficiency (PDD) in both studies. In study 1 (where both race and ethnicity were captured), self-identified Hispanic (vs non-Hispanic, P < 0.05) and non-white (vs white, P < 0.01) children were more likely to have lactase deficiency. Age, sex, and type of gastrointestinal symptom were not associated with presence or absence of a disaccharidase deficiency. CONCLUSIONS: Approximately half of children with functional dyspepsia undergoing EGD were identified as having a disaccharidase deficiency (predominantly lactase deficiency). Race/ethnicity may be associated with the likelihood of identifying a disaccharidase deficiency. Other clinical characteristics were not able to distinguish those with versus without a disaccharidase deficiency.

[Disaccharidase deficiency and functional bowel diseases]. / Disakharidaznaia nedostatochnost' i funktsional'nye zabolevaniia kishechnika.

AIM: To elucidate the role of intestinal carbohydrases (glucoamylase, maltase, sucrose, and lactase) in the etiology and pathogenesis of functional bowel diseases (FBD). SUBJECTS AND METHODS: 74 patients (36 men and 38 women) aged 18 to 50 years with FBD were examined. According to Rome IV criteria (2016), there was diarrhea-predominant irritable bowel syndrome (IBS) in 21 patients, functional diarrhea (FD) in 33, constipation-predominant IBS in 6, functional constipation (FC) in 4, and mixed IBS in 10. The activity of carbohydrases in the small intestine mucosa (SIM) was investigated by the Dahlquist method modified by Trinder in the duodenal biopsy specimens obtained during esophagogastroduodenoscopy. RESULTS: Lactase deficiency was identified in 87.8% of the patients; maltase deficiency in 48.6%; sucrose deficiency in 51.3%; and glucoamylase deficiency in 85.1%. The activity of all the investigated enzymes was reduced in 23 (31.1%) patients with FBD; deficiency of 1-3 carbohydrases was found in 47 (63.5%). Normal enzymatic activity was established in 4 (5.4%) patients. CONCLUSION: In the majority of patients with FBD, the intestinal symptoms are caused by the decreased activity of SIM carbohydrases. Therefore, disaccharidase deficiency associated with an established damaging agent (nonsteroidal anti-inflammatory drugs, antibiotics, acute intestinal infections, etc.) should be considered to be a more precise diagnosis.

Tinospora cordifolia, a novel source of extracellular disaccharidases, useful for human disaccharidase deficiency therapy.

Disaccharide intolerance is the inability to digest certain carbohydrates due to a lack of one or more intestinal disaccharidases (e.g., lactase, maltase, isomaltase and sucrase). Symptoms include diarrhea, abdominal distention and flatulence. Management of the disorder by external enzymes supplementation has not yet been attempted. We report that the medicinal plant Tinospora cordifolia contains substantial amounts of all disaccharidases required for intestinal digestion of carbohydrates. The plant is also a rich source of saccharifying amylase. We recovered (units/100 g fresh stem) amylase: 49,000+500, maltase: 400+50, isomaltase: 130+50, sucrase: 4500+500, acid lactase: 350+30, cellobiase: 35+10 and trehalase: 40+10 by buffer extraction of the blended stem. Crude enzymes in the forms of stem powder, lyophilized aqueous extract and ethanol precipitated protein were found to be stable. Disaccharidases were optimally active at 50 (0) C in the pH range of 4-5. Lactase was an acid lactase similar to the type linked with human lactose intolerance. Enzymes were catalytically stable in the pH range of 2-7 and temperature range of up to 40 (0) C. T. cordifolia enzyme was non-toxic up to a dose of 200 mg protein/kg body weight.

Increased thermal and osmotic stress resistance in Listeria monocytogenes 568 grown in the presence of trehalose due to inactivation of the phosphotrehalase-encoding gene treA.

The food-borne pathogen Listeria monocytogenes is a problem for food processors and consumers alike, as the organism is resistant to harsh environmental conditions and inimical barriers implemented to prevent the survival and/or growth of harmful bacteria. One mechanism by which listeriae mediate survival is through the accumulation of compatible solutes, such as proline, betaine and carnitine. In other bacteria, including Escherichia coli, the synthesis and accumulation of another compatible solute, trehalose, are known to aid in the survival of stressed cells. The objective of this research was to investigate trehalose metabolism in L. monocytogenes, where the sugar is thought to be transferred across the cytoplasmic membrane via a specific phosphoenolpyruvate phosphotransferase system and phosphorylation to trehalose-6-phosphate (T6P). The latter is subsequently broken down into glucose and glucose-6-phosphate by α,α-(1,1) phosphotrehalase, the putative product of the treA gene. Here we report on an isogenic treA mutant of L. monocytogenes 568 (568:ΔTreA) which, relative to the wild-type strain, displays increased tolerances to multiple stressors, including heat, high osmolarity, and desiccation. This is the first study to examine the putative trehalose operon in L. monocytogenes, and we demonstrate that lmo1254 (treA) in L. monocytogenes 568 indeed encodes a phosphotrehalase required for the hydrolysis of T6P. Disruption of the treA gene results in the accumulation of T6P which is subsequently dephosphorylated to trehalose in the cytosol, thereby contributing to the stress hardiness observed in the treA mutant. This study highlights the importance of compatible solutes for microbial survival in adverse environments.

Disaccharidase deficiency in pediatric patients with celiac disease and intact villi.

BACKGROUND AND AIMS: The "gold standard" for the diagnosis of celiac disease (CD) is the small intestinal biopsy. A significant number of biopsies are inadequate for interpretation. Furthermore, the labeling of a biopsy as a Marsh I or II is somewhat subjective and may vary with the experience of the pathologist. Our hypothesis is that patients with intact villi undergoing biopsies frequently have associated disaccharidase deficiencies (DSD). METHODS: We reviewed 220 charts of pediatric patients with CD and selected those with a duodenal biopsy Marsh score of I/II. The disaccharidase (DS) levels of these patients were compared with a randomly selected, age-matched control group. DSD is defined as levels below the lower limits of normal. RESULTS: Lactase (mean lactase = 18.8 in the control group vs. 4.2 in the diseased group, p = 0.004); sucrase (mean sucrase = 46.4 in the control group vs. 21.4 in the diseased group, p = 0.001); maltase (mean maltase = 138 in the control group vs. 52.5 in the diseased group, p = 0.001); palatinase (mean palatinase = 9.6 in the control group vs. 3.3 in the diseased group, p < 0.001). CONCLUSION: There is a profound deficiency of DS levels in pediatric patients with CD who have intact villi.

Relationships between disaccharidase deficiencies, duodenal inflammation and symptom profile in children with abdominal pain.

Abdominal pain has been associated with disaccharidase deficiencies. While relationships with individual symptoms have been assessed, relationships between disaccharidase deficiencies and symptom complexes or inflammation have not been evaluated in this group. The primary aims of the current study were to assess relationships between disaccharidase deficiency and symptoms or symptom complexes and duodenal inflammation, respectively. Patients with abdominal pain who underwent endoscopy with evaluation of disaccharidase activity levels were identified. After excluding all patients with inflammatory bowel disease, celiac disease, H. pylori, or gross endoscopic lesions, patients were evaluated for disaccharidase deficiency frequency. Disaccharidase were compared between patients with and without histologic duodenitis. Lastly, relationships between individual gastrointestinal symptoms or symptom complexes were evaluated. Lactase deficiency was found in 34.3% of patients and disaccharidase pan-deficiency in 7.6%. No individual symptoms or symptom complexes predicted disaccharidase deficiency. While duodenitis was not associated with disaccharidase deficiency, it was only present in 5.9% of patients. Disaccharidase deficiency, particularly lactase deficiency, is common in youth with abdominal pain and multiple deficiencies are not uncommon. Disaccharidase deficiency cannot be predicted by symptoms in this population. Further studies are needed to assess the clinical significance of disaccharidase deficiency.

Stool Reducing Sugars and Stool pH Are Poor Screening Tests for Intestinal Disaccharidase Deficiencies in Children.

BACKGROUND: Tests for stool reducing sugars and stool pH are ordered for children with osmotic diarrhea to screen for carbohydrate malabsorption. METHODS: We compared the results of the two screening tests, stool reducing sugars and stool pH, with a more definitive result from an intestinal tissue disaccharidase activity assay ordered for pediatric patients (<18 years old). Overall, 159 patients had results for tissue disaccharidase and stool reducing sugars, but only 115 had additional results of stool pH. Forty-six of the 159 patients had mild, moderate, or severe disaccharidase deficiencies. The sensitivity and specificity of the screening tests were calculated for individual disaccharidase deficiencies. In addition, trends of abnormal tissue disaccharidase, stool reducing sugars, and stool pH results were examined in different age groups. RESULTS: The sensitivities for stool reducing sugars and stool pH were 9% to 28% and specificities were 74% to 81% for individual disaccharidase deficiencies. Infants (0 years of age) had the highest percentage of abnormal results across all three tests; however, the positive predicative values were 54% and 50% for stool reducing sugars and stool pH, respectively. CONCLUSIONS: The screening tests, stool reducing sugars and stool pH, had low sensitivity compared with results of measured tissue disaccharidase activity in pediatric patients. Infants had the highest percentage of abnormal results for all three tests, but the screening tests still performed poorly in that age group. This study suggests that stool reducing sugars and stool pH should not be used as screening tests for carbohydrate malabsorption due to disaccharidase deficiencies in pediatric patients.

Clinical and Histopathologic Predictors of Disaccharidase Deficiency in Duodenal Biopsy Specimens.

OBJECTIVES: Disaccharidase (DS) activity in duodenal biopsy specimens is the gold standard for diagnosing DS deficiency. We investigated strategies to reduce the need for DS testing and whether clinical or histopathologic factors predict DS deficiency. METHODS: A retrospective chart review analyzed 1,678 DS results in children, biopsy indication(s), and duodenal histopathology. RESULTS: One or more DSs were abnormal in 42.8%. Sufficient lactase predicted sucrase, palatinase, and maltase sufficiency (negative predictive value 97.7%). Three patients had sucrase-isomaltase deficiency (0.2%). DS deficiency was more common in biopsy specimens for positive celiac serology (78.0%). Villous blunting, intraepithelial lymphocytosis, and active inflammation predicted DS deficiency; a combination of any two had an 81.4% positive predictive value. CONCLUSIONS: Utilization could be reduced by only testing cases with normal duodenal histopathology and ongoing clinical suspicion for DS deficiency after reviewing pathology. In cases with suspected celiac disease and/or mucosal injury, DS deficiency is common and likely secondary, limiting test utility.

Personalized medicine in functional gastrointestinal disorders: Understanding pathogenesis to increase diagnostic and treatment efficacy.

There is overwhelming evidence that functional gastrointestinal disorders (FGIDs) are associated with specific mechanisms that constitute important targets for personalized treatment. There are specific mechanisms in patients presenting with functional upper gastrointestinal symptoms (UGI Sx). Among patients with UGI Sx, approximately equal proportions (25%) of patients have delayed gastric emptying (GE), reduced gastric accommodation (GA), both impaired GE and GA, or neither, presumably due to increased gastric or duodenal sensitivity. Treatments targeted to the underlying pathophysiology utilize prokinetics, gastric relaxants, or central neuromodulators. Similarly, specific mechanisms in patients presenting with functional lower gastrointestinal symptoms, especially with diarrhea or constipation, are recognized, including at least 30% of patients with functional constipation pelvic floor dyssynergia and 5% has colonic inertia (with neural or interstitial cells of Cajal loss in myenteric plexus); 25% of patients with diarrhea-predominant irritable bowel syndrome (IBSD) has evidence of bile acid diarrhea; and, depending on ethnicity, a varying proportion of patients has disaccharidase deficiency, and less often sucrose-isomaltase deficiency. Among patients with predominant pain or bloating, the role of fermentable oligosaccharides, disaccharides, monosaccharides and polyols should be considered. Personalization is applied through pharmacogenomics related to drug pharmacokinetics, specifically the role of CYP2D6, 2C19 and 3A4 in the use of drugs for treatment of patients with FGIDs. Single mutations or multiple genetic variants are relatively rare, with limited impact to date on the understanding or treatment of FGIDs. The role of mucosal gene expression in FGIDs, particularly in IBS-D, is the subject of ongoing research. In summary, the time for personalization of FGIDs, based on deep phenotyping, is here; pharmacogenomics is relevant in the use of central neuromodulators. There is still unclear impact of the role of genetics in the management of FGIDs.

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.

Glycopeptide storage in skin fibroblasts cultured from a patient with alpha-mannosidase deficiency.

Patients with mannosidosis, an inherited deficiency of lysosomal alpha-mannosidase, accumulate large amounts of mannose-rich oligosaccharides (the "core" of the carbohydrate units of many glocoproteins) in brain and liver and excrete these partial degradation products in their urine. A profound alpha-mannosidase deficiency was demonstrated in fibroblasts cultured from a skin biopsy obtained from a child with mannosidosis. Further, abnormal glycopeptides rich in mannose and similar to oligosaccharides found in the patient's urine were isolated from fibroblast extracts by a variety of chromatographic procedures and by virtue of their binding to a concanavalin A-Sepharose 4B affinity column. This storage material contained mannose, N-acetylglucosamine, and asparagine in the ratio 3 : 1 : 1 together with a few toher amino acids and had a molecular weight of approximately 1,100. There was no evidence for excretion of storage material by mannosidosis fibroblasts or for any abnormality in cell surface glycoprotein composition. The glycopeptide nature of the storage material isolated from cultured skin fibroblasts may be attributed to the low level of N-aspartyl-beta-glucosamindase (EC 3.5.1.-) activity in these cells.

Disaccharidase Deficiencies in Children With Chronic Abdominal Pain.

OBJECTIVES: Carbohydrate intolerance or malabsorption has been suggested as a cause of chronic abdominal pain (CAP) in a subset of patients. We aimed to evaluate disaccharidase deficiencies in children with functional CAP and to correlate deficiencies with clinical features. METHOD: Patients presenting to the gastroenterology clinic at Children's Hospital of Wisconsin with abdominal pain prospectively completed a detailed demographic, history, and symptom questionnaire. The CAP cohort included those with at least 1 month of symptoms. Data on disaccharidase activity and histology of endoscopic biopsies were collected retrospectively. Only patients with normal histology were included in the study. The association between groups with low disaccharidases and clinical features was examined. RESULTS: A total of 203 pediatric patients with CAP were included. The mean (SD) age was 11.5 (3.1) years, and 32.5% were male. The percentages of abnormally low disaccharidase levels using the standard laboratory cutoffs were lactase, 37%; sucrase, 21%; glucoamylase, 25%; and palatinase, 8%. Thirty-nine percent of the patients with low lactase also had low sucrase, and 67% of the patients with low sucrase had low lactase. There was no significant difference in the activities of any of the disaccharidases or sucrase/lactase ratio in relation to age. Also, no association was found between stool consistency, stool frequency, or location of pain and low disaccharidase activity. CONCLUSIONS: A large proportion of patients with CAP have deficiencies in disaccharidases. Bowel frequency, vomiting, or location of pain was no different between groups, suggesting that these clinical features cannot be used to predict disaccharidase deficiencies.

Human alpha-fucosidase. Single residual enzymatic form in fucosidosis.

Four major forms of alpha-fucosidase (EC 3.2.1.51) activity were separated by isoelectrofocusing from sera of normal control individuals. All forms shifted towards less acidic pI values after neuraminidase treatment. In two patients affected with fucosidosis, only a single major acidic peak was observed and this was affected to a lesser degree by neuraminidase treatment. The kinetics of heat inactivation of the residual activity found in these two patients showed two decay rates while the controls showed only one rate. These data are considered in relation to the hypothesis of the existence of interconvertible thermolabile and thermostable forms of the enzyme which has been discussed in the preceeding paper. The residual alpha-fucosidase found in patients could be structurally altered so that its ability to form the thermostable higher molecular weight aggregates is impaired.

Mannosidosis: pathology of the nervous system.

In a girl with mannosidosis, who died at 3 1/2 years of age, histopathological and ultrastructural changes in the nervous system are described. A widespread neuronal storage evidenced by ballooning of the neuronal perikarya is the salient histological feature and the occurrence of electron-lucent storage vacuoloes in neurons, astrocytes, endothelial cells and pericytes is the most striking ultrastructural feature of mannosidosis in the nervous system. By virtue of the deficiency of acidic alpha-mannosidases A and B, the accumulation of mannose-containing oligosaccharides in tissues and the occurrence of storage vacuoles in various cells, mannoisidosis is similar to various neuronal storage diseases associated with lysosomal enzyme deficiencies. In mannosidosis, the storage vacuoles in the neural and visceral tissues are alike with little variation in details and contain chiefly loosely dispersed, finely reticulogranular material. The storage vacuoles in neurons in mannosidosis are, therefore, distinct from those in neurons in other lysosomal storage disease such as Pompe's disease, various lipidoses and mucopolysaccharidoses. However, they resemble closely the storage vacuoles in neurons in fucosidosis and those in liver cells in various mucopolysaccharidoses.