Disaccharide digestion: clinical and molecular aspects

Feeling gutted in chronic kidney disease (CKD): Gastrointestinal disorders and therapies to improve gastrointestinal health in individuals CKD, including those undergoing dialysis

Chronic kidney disease (CKD) affects 9.1% of the population worldwide. CKD may lead to structural and functional gastrointestinal alterations, including impairment in the intestinal barrier, digestion and absorption of nutrients, motility, and changes to the gut microbiome. These changes can lead to increased gastrointestinal symptoms in people with CKD, even in early grades of kidney dysfunction. Gastrointestinal symptoms have been associated with lower quality of life and reduced nutritional status. Therefore, there has been considerable interest in improving gastrointestinal health in this clinical population. Gastrointestinal health can be influenced by lifestyle and medications, particularly in advanced grades of kidney dysfunction. Therapies focused on gastrointestinal health have been studied, including the use of probiotics, prebiotics, and synbiotics, yielding limited and conflicting results. This review summarizes the alterations in the gastrointestinal tract structure and function and provides an overview of potential nutritional interventions that kidney disease professionals can provide to improve gastrointestinal health in individuals with CKD.

Approach to Congenital Diarrhea and Enteropathies (CODEs)

Congenital diarrhea and enteropathies (CODEs) constitute a group of rare genetic disorders characterized by severe diarrhea and malabsorption in the neonatal period or early infancy. Timely diagnosis and treatment is essential to prevent life-threatening complications, including dehydration, electrolyte imbalance, and malnutrition. This review offers a simplified approach to the diagnosis of CODEs, with a specific focus on microvillus inclusion disease (MVID), congenital tufting enteropathy (CTE), congenital chloride diarrhea (CLD), and congenital sodium diarrhea (CSD). Patients with CODEs typically present with severe watery or occasionally bloody diarrhea, steatorrhea, dehydration, poor growth, and developmental delay. Therefore, it is crucial to thoroughly evaluate infants with diarrhea to rule out infectious, allergic, or anatomical causes before considering CODEs as the underlying etiology. Diagnostic investigations for CODEs encompass various modalities, including stool tests, blood tests, immunological studies, endoscopy and biopsies for histology and electron microscopy, and next-generation sequencing (NGS). NGS plays a pivotal role in identifying the genetic mutations responsible for CODEs. Treatment options for CODEs are limited, often relying on total parenteral nutrition for hydration and nutritional support. In severe cases, intestinal transplantation may be considered. The long-term prognosis varies among specific CODEs, with some patients experiencing ongoing intestinal failure and associated complications. In conclusion, the early recognition and accurate diagnosis of CODEs are of paramount importance for implementing appropriate management strategies. Further research and advancements in genetic testing hold promise for enhancing diagnostic accuracy and exploring potential targeted therapies for these rare genetic disorders.

Antagonistic Effect of Zinc Oxide Nanoparticles Dietary Supplementation Against Chronic Copper Waterborne Exposure on Growth, Behavioral, Biochemical, and Gene Expression Alterations of African Catfish, Clarias gariepinus (Burchell, 1822)

The harmful impact of waterborne copper (Cu) as a common abiotic stressor in aquatic environments has gained much more interest. The present study aimed to investigate the utilization of zinc oxide nanoparticles (ZnONPs) dietary supplementation to mitigate the chronic toxicity of Cu in African catfish (Clarias gariepinus). Two hundred and forty fish (92.94 ± 0.13 g) were assigned into six groups for 60 days. Control (C), ZnONPs20, and ZnONPs30 groups were fed on basal diets fortified with 0, 20, and 30 mg kg-1 ZnONPs without Cu exposure. Cu, Cu + ZnONPs20, and Cu + ZnONPs30 groups were exposed to Cu at a dose of 10 mg L-1 and fed on basal diets fortified with 0, 20, and 30 mg kg-1 ZnONPs, respectively. The results revealed that the Cu-exposed fish experienced abnormal clinical signs and behavioral changes. The growth indices and acetylcholine esterase activity were significantly decreased (P < 0.05) in the Cu group. Meanwhile, hepatorenal and serum stress indices (P < 0.05) were significantly elevated with chronic Cu exposure. In addition, a higher expression of stress (P < 0.05) (heat shock protein 60 and hypoxia-inducible factor-1 alpha) and apoptotic-related genes (C/EBP homologous protein, caspase-3, and Bcl-2 Associated X-protein) with down-regulation (P < 0.05) of the anti-apoptotic-related genes (B-cell lymphoma 2 and proliferating cell nuclear antigen) was noticed in the Cu-exposed fish. Histopathological alterations in the gills, liver, kidney, and spleen were markedly reported in the Cu-exposed group. The dietary supplementation with ZnONPs significantly alleviated the negative impacts of chronic waterborne-Cu exposure on growth performance, physiological changes, gene expression, and tissue architecture, especially at 30 mg kg-1 diet level. In particular, the inclusion of ZnONPs at the 30 mg kg-1 diet level produced better outcomes than the 20 mg kg-1 diet. Overall, ZnONPs could be added as a feed supplement in the C. gariepinus diet to boost the fish's health and productivity and alleviate the stress condition brought on by Cu exposure.

Impaired digestive function of sucrase-isomaltase in a complex with the Greenlandic sucrase-isomaltase variant

Sucrase isomaltase (SI) is the most prominent disaccharidase in the small intestine. Congenital sucrase-isomaltase deficiency (CSID) is an autosomal recessive disorder caused by variants in the SI gene. A homozygous frameshift mutation, c.273_274delAG (p.Gly92Leufs*8), has been identified in CSID in the Greenlandic population. This variant eliminates the luminal domain of SI and results in loss of its digestive function. Surprisingly, the truncated mutant is transport-competent and localized at the cell surface; it interacts avidly with wild type SI and negatively impacts its enzymatic function. The data propose that heterozygote carriers of p.Gly92Leufs*8 may also present with CSID symptoms.

Glycosidic linkage of rare and new-to-nature disaccharides reshapes gut microbiota in vitro

The impact of glycosidic linkage of seven rare and new-to-nature disaccharides on gut bacteria was assessed in vitro. The community shift of the inocula from four donors in response to 1 % (w/v) disaccharide supplementation was captured by sequencing the 16S rRNA gene. A significant loss of bacterial alpha diversity, short lag time, low pH, and high total short-chain fatty acid displayed a faster fermentation of trehalose(Glc-α1,1α-Glc) and fibrulose(fructan, DP2-10). Bacteroides reduced in relative abundance under disaccharide supplementation suggesting a loss in complex carbohydrates metabolizing capacity. Fibrulose and l-arabinose glucoside(Glc-α1,3-l-Ara) significantly stimulated bifidobacteria but was suppressed with trehalose, ribose glucoside(Glc-α1,2-Rib), and 4'-epitrehalose(Glc-α1,1α-Gal) supplementation. Albeit insignificant, bifidobacteria increased with 4'-epikojibiose(Glc-α1,2-Gal), nigerose(Glc-α1,3-Glc), and kojibiose(Glc-α1,2-Glc). Prior conditioning of inoculum in kojibiose medium profoundly induced bifidobacteria by 44 % and 55 % upon reinoculation into kojibiose and fibrulose-supplemented media respectively. This study has demonstrated the importance of the disaccharide structure-function relationship in driving the gut bacterial community.

Comprehensive Approach to Medical Nutrition Therapy in Patients with Type 2 Diabetes Mellitus: From Diet to Bioactive Compounds

In the pathogenesis of type 2 diabetes mellitus (T2DM), diet plays a key role. Individualized medical nutritional therapy, as part of lifestyle optimization, is one of the cornerstones for the management of T2DM and has been shown to improve metabolic outcomes. This paper discusses major aspects of the nutritional intervention (including macro- and micronutrients, nutraceuticals, and supplements), with key practical advice. Various eating patterns, such as the Mediterranean-style, low-carbohydrate, vegetarian or plant-based diets, as well as healthy eating plans with caloric deficits have been proven to have beneficial effects for patients with T2DM. So far, the evidence does not support a specific macronutrient distribution and meal plans should be individualized. Reducing the overall carbohydrate intake and replacing high glycemic index (GI) foods with low GI foods have been shown as valid options for patients with T2DM to improve glycemic control. Additionally, evidence supports the current recommendation to reduce the intake of free sugars to less than 10% of total energy intake, since their excessive intake promotes weight gain. The quality of fats seems to be rather important and the substitution of saturated and trans fatty acids with foods rich in monounsaturated and polyunsaturated fats lowers cardiovascular risk and improves glucose metabolism. There is no benefit of supplementation with antioxidants, such as carotene, vitamins E and C, or other micronutrients, due to the lack of consistent evidence showing efficacy and long-term safety. Some studies suggest possible beneficial metabolic effects of nutraceuticals in patients with T2DM, but more evidence about their efficacy and safety is still needed.

Stool biomarkers as measures of enteric pathogen infection in infants from Addis Ababa informal settlements

Frequent enteric infections in children may be an important cause of growth faltering; however, we do not fully understand the mechanisms by which pathogen infections and the physiological responses to these infections result in poorer growth. Commonly used protein fecal biomarkers (anti-alpha trypsin, neopterin, and myeloperoxidase) provide broad immunological information on an inflammatory response; however, they do not provide information on non-immune processes (e.g., gut integrity) that may be important indicators of chronic end states such as environmental enteric dysfunction (EED). To explore how additional biomarkers will better inform which physiological pathways (both immune and non-immune) are impacted by pathogen exposure we added to the traditional panel of 3 protein fecal biomarkers 4 novel fecal mRNA transcript biomarkers (sucrase isomaltase, caudal homeobox 1, S100A8, and mucin 12) and analyzed stool samples from infants living in informal settlements in Addis Ababa, Ethiopia. To test how this expanded biomarker panel captures distinct pathogen exposure processes we used two different scoring systems. First, we used a theory-based approach to assign each biomarker to specific physiological attributes based on prior understanding of each biomarker. Second, we used data reduction methods to categorize biomarkers and then assign physiological attributes to those categories. We used linear models to examine the association between the derived biomarker scores (based on mRNA and protein levels) and stool pathogen gene counts to determine pathogen specific effects on gut physiology and immune responses. Inflammation scores were positively associated with Shigella and enteropathogenic E.Coli (EPEC) infection, while gut integrity scores were negatively associated with Shigella, EPEC and, shigatoxigenic E.coli (STEC) infection. Our expanded panel of biomarkers hold promise as tools to measure systemic outcomes of enteric pathogen infection. mRNA biomarkers complement established protein biomarkers by providing important cell-specific physiological and immunological consequences of pathogen carriage that can lead to chronic end states such as EED.

Design, synthesis, in vitro, and in silico enzymatic evaluations of thieno[2,3-b]quinoline-hydrazones as novel inhibitors for α-glucosidase

In the development of novel anti-α-glucosidase agents, we synthesized novel thieno[2,3-b]quinoline-hydrazones 9a-n by facile and efficient conventional chemical reactions. These compounds were characterized by IR, ¹H NMR, ¹³C NMR, and elemental analysis. Inhibitory activities of the title compounds were evaluated against yeast α-glucosidase. In particular, compounds 9c, 9d, and 9h exhibited high anti-α-glucosidase activity. Representatively, compound 9c with IC₅₀ = 1.3 µM, was 576-times more potent than positive control acarbose. Molecular docking study of the most active compounds showed that these compounds formed important binding interactions at α-glucosidase active site. Molecular dynamics study of compound 9c was also performed and the obtained results were compared with acarbose. Compounds 9c, 9d, and 9h were also evaluated for in silico druglikeness properties and ADMET prediction. These studies showed that the title most potent compounds could be exploited as drug candidates.

Pediatric Aspects of Nutrition Interventions for Disorders of Gut-Brain Interaction

Dietary factors may play an important role in the generation of symptoms in children with disorders of gut-brain interaction (DGBIs). Although dietary modification may provide successful treatment, there is a relative paucity of controlled trials that have shown the effectiveness of dietary interventions. This study is a narrative review that explores the existing literature on food and pediatric DGBIs. The following have been shown to be beneficial: (i) in infants with colic, removing cow's milk from the infant's diet or from the maternal diet in those who are breastfed; (ii) in infants with regurgitation, adding thickeners to the formula or removing cow's milk protein from the infant's diet or the maternal diet in those who are breastfed; and (iii) in children with pain-predominant DGBIs, using soluble fiber supplementation or a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet. In children with functional constipation, there is no evidence that adding fiber is beneficial. Given that most dietary interventions include restriction of different foods in children, a thoughtful approach and close follow-up are needed.

Cellular adaptation of Clostridioides difficile to high salinity encompasses a compatible solute-responsive change in cell morphology

Infections by the pathogenic gut bacterium Clostridioides difficile cause severe diarrheas up to a toxic megacolon and are currently among the major causes of lethal bacterial infections. Successful bacterial propagation in the gut is strongly associated with the adaptation to changing nutrition-caused environmental conditions; e.g. environmental salt stresses. Concentrations of 350 mM NaCl, the prevailing salinity in the colon, led to significantly reduced growth of C. difficile. Metabolomics of salt- stressed bacteria revealed a major reduction of the central energy generation pathways, including the Stickland-fermentation reactions. No obvious synthesis of compatible solutes was observed up to 24 h of growth. The ensuing limited tolerance to high salinity and absence of compatible solute synthesis might result from an evolutionary adaptation to the exclusive life of C. difficile in the mammalian gut. Addition of the compatible solutes carnitine, glycine-betaine, γ-butyrobetaine, crotonobetaine, homobetaine, proline-betaine and dimethylsulfoniopropionate (DMSP) restored growth (choline and proline failed) under conditions of high salinity. A bioinformatically-identified OpuF-type ABC-transporter imported most of the used compatible solutes. A long-term adaptation after 48 h included a shift of the Stickland fermentation-based energy metabolism from the utilization to the accumulation of L-proline and resulted in restored growth. Surprisingly, salt stress resulted in the formation of coccoid C. difficile cells instead of the typical rod-shaped cells, a process reverted by the addition of several compatible solutes. Hence, compatible solute import via OpuF is the major immediate adaptation strategy of C. difficile to high salinity-incurred cellular stress. This article is protected by copyright. All rights reserved.

A randomized double-blind placebo-controlled crossover pilot study: Acute effects of the enzyme α-galactosidase on gastrointestinal symptoms in irritable bowel syndrome patients

BACKGROUND

Postprandial symptoms presumably related to intestinal gas production are common in patients with irritable bowel syndrome (IBS). The aim of the study was to assess if oral α-galactosidase is superior to placebo in reducing gastrointestinal (GI) symptoms and intestinal gas production after ingestion of carbohydrate-rich meals in adult patients with IBS.

METHODS

We studied the effect of 1200 GaIU/meal α-galactosidase (Nogasin^® ) or placebo capsules on GI symptoms in patients with IBS after three standardized, meals high in oligosaccharides, in a randomized, double-blind, crossover study. The intensity of eight GI symptoms was rated, and breath hydrogen and methane were measured every 30 min during 7.5 h. The severity of GI symptoms the following morning was assessed and compared with baseline.

S KEY RESULTS

Twenty adult patients with IBS (19 females), mean age 49 years (range 22-75 years), were included. All test meals were well tolerated but induced a gradual increase in GI symptom severity. Neither GI symptom ratings over time, nor hydrogen and methane concentrations differed between the days with α-galactosidase or placebo. The severity of abdominal pain and bloating was lower the following morning, but with no differences between α-galactosidase and placebo.

CONCLUSIONS & INFERENCES

The use of α-galactosidase together with meals high in oligosaccharides was in this pilot study not superior to placebo in reducing postprandial GI symptoms or the concentration of hydrogen and methane in expired air in IBS.

[Enteropathy with impaired membrane digestion and the prospects for cytoprotective therapy]

The article describes enteropathy with impaired membrane digestion (EIMD) as a new nosological form. The main clinical manifestation of EIMD is the poor tolerance of food products, in particular carbohydrates and a decrease in the activity of membrane enzymes, in particular, carbohydrates, in the mucous membrane of the small intestine. The cause of the disease can be acute intestinal infections, viruses, drugs and other agents that damage the small intestine. The pathophysiology, clinical picture and diagnosis of EIMD are described. The basis of therapy is rebamipide, which has the ability to reduce the symptoms of carbohydrate intolerance and increase the activity of disaccharidases.

Differential Effects of Sucrase-Isomaltase Mutants on Its Trafficking and Function in Irritable Bowel Syndrome: Similarities to Congenital Sucrase-Isomaltase Deficiency

Congenital sucrase-isomaltase deficiency (CSID) is a rare metabolic intestinal disorder with reduced or absent activity levels of sucrase-isomaltase (SI). Interestingly, the main symptoms of CSID overlap with those in irritable bowel syndrome (IBS), a common functional gastrointestinal disorder with unknown etiology. Recent advances in genetic screening of IBS patients have revealed rare SI gene variants that are associated with IBS. Here, we investigated the biochemical, cellular and functional phenotypes of several of these variants. The data demonstrate that the SI mutants can be categorized into three groups including immature, mature but slowly transported, and finally mature and properly transported but with reduced enzymatic activity. We also identified SI mutant phenotypes that are deficient but generally not as severe as those characterized in CSID patients. The variable effects on the trafficking and function of the mutations analyzed in this study support the view that both CSID and IBS are heterogeneous disorders, the severity of which is likely related to the biochemical phenotypes of the SI mutants as well as the environment and diet of patients. Our study underlines the necessity to screen for SI mutations in IBS patients and to consider enzyme replacement therapy as an appropriate therapy as in CSID.

An alternative pathway for sweet sensation: possible mechanisms and physiological relevance

Sweet substances are detected by taste-bud cells upon binding to the sweet-taste receptor, a T1R2/T1R3 heterodimeric G protein-coupled receptor. In addition, experiments with mouse models lacking the sweet-taste receptor or its downstream signaling components led to the proposal of a parallel "alternative pathway" that may serve as metabolic sensor and energy regulator. Indeed, these mice showed residual nerve responses and behavioral attraction to sugars and oligosaccharides but not to artificial sweeteners. In analogy to pancreatic β cells, such alternative mechanism, to sense glucose in sweet-sensitive taste cells, might involve glucose transporters and K_ATP channels. Their activation may induce depolarization-dependent Ca²⁺ signals and release of GLP-1, which binds to its receptors on intragemmal nerve fibers. Via unknown neuronal and/or endocrine mechanisms, this pathway may contribute to both, behavioral attraction and/or induction of cephalic-phase insulin release upon oral sweet stimulation. Here, we critically review the evidence for a parallel sweet-sensitive pathway, involved signaling mechanisms, neural processing, interactions with endocrine hormonal mechanisms, and its sensitivity to different stimuli. Finally, we propose its physiological role in detecting the energy content of food and preparing for digestion.

Alleviating the Hydrolysis of Carbohydrates, Tangzhiqing (TZQ) Decreased the Postprandial Glycemia in Healthy Volunteers: An Eight-Period Crossover Study

Tangzhiqing (TZQ), a Chinese herbal medicine, has been widely used to treat diabetes mellitus in China. TZQ works as a potential α-glucosidase inhibitor to reduce the absorption of glucose from dietary carbohydrates. The main aim of this study was to investigate the postprandial glucose-lowering effect of TZQ on the common carbohydrates in healthy humans. Meanwhile, the possible types of the inhibited α-glucosidase enzymes were predicted in this study. Glucose, sucrose, maltose, maltodextrin, and starch were chosen as investigated carbohydrates. The baseline incremental area under the curve (IAUC) and glycemic index (GI) values of the investigated carbohydrates were evaluated. Then, thirty-six subjects were randomly assigned to three groups to assess postprandial hypoglycemic effects of 3-, 6-, and 9-tablet TZQ. The subjects in each group were randomized to eight subgroups. An eight-period, eight-sequence, crossover design was performed to investigate the postprandial glucose-lowering effect of TZQ after drinking each carbohydrate. A significant decrease was observed on the postprandial glucose IAUCs (279.41 ± 111.31 vs. 203.86 ± 61.08) and GIs (124.91 ± 48.54 vs. 91.69 ± 27.47) of maltose after oral administration of 6-tablet TZQ, as well as IAUCs (145.05 ± 55.01 vs. 110.23 ± 57.03) and GIs (84.87 ± 33.40 vs. 65.50 ± 33.89) of sucrose after administration of 3-tablet TZQ. The glucose IAUCs (109.15 ± 55.92 vs. 57.68 ± 46.09) and GIs (49.09 ± 25.15 vs. 25.94 ± 20.73) of starch statistically reduced following the administration of 6-tablet TZQ. The lowering postprandial blood glucose effect of TZQ did not increase proportionally with increasing doses in humans. There were no significant changes in the glucose-lowering effect of glucose and maltodextrin after the administration of 3-, 6-, or 9-tablet TZQ, respectively. TZQ is a potential treatment for postprandial hyperglycemia, which can probably make α-glucosidases inhibit maltase, sucrase, and α-amylase in the digestive organs.

Carbohydrate Intolerance and Disaccharidase Measurement - a Mini-Review

Carbohydrate intolerance is one of several syndromes and diseases which together are known as malabsorption syndromes. These include small intestinal bacterial overgrowth (SIBO), coeliac disease, intestinal lymphangiectasia, short bowel syndrome, tropical sprue and some inherited metabolic disorders such as galactosaemia and pyruvate kinase deficiency. Specifically, the malabsorption of sugars affects morbidity for millions of sufferers across the world. Disaccharidase measurement is used in the investigation of disorders of the gastrointestinal tract. Diagnosis is by endoscopic small bowel biopsy of the duodenum or jejunum with subsequent biochemical and histopathological analysis. The diagnosis of bowel disorders presents several challenges with numerous overlapping presentations and symptoms such as bloating, diarrhoea, constipation, flatulence, borborygmus, weight loss and severe discomfort.

Heterozygotes Are a Potential New Entity among Homozygotes and Compound Heterozygotes in Congenital Sucrase-Isomaltase Deficiency

Congenital sucrase-isomaltase deficiency (CSID) is an autosomal recessive disorder of carbohydrate maldigestion and malabsorption caused by mutations in the sucrase-isomaltase (SI) gene. SI, together with maltase-glucoamylase (MGAM), belongs to the enzyme family of disaccharidases required for breakdown of α-glycosidic linkages in the small intestine. The effects of homozygote and compound heterozygote inheritance trait of SI mutations in CSID patients have been well described in former studies. Here we propose the inclusion of heterozygote mutation carriers as a new entity in CSID, possibly presenting with milder symptoms. The hypothesis is supported by recent observations of heterozygote mutation carriers among patients suffering from CSID or patients diagnosed with functional gastrointestinal disorders. Recent studies implicate significant phenotypic heterogeneity depending on the character of the mutation and call for more research regarding the correlation of genetics, function at the cellular and molecular level and clinical presentation. The increased importance of SI gene variants in irritable bowel syndrome (IBS) or other functional gastrointestinal disorders FGIDs and their available symptom relief diets like fermentable oligo-, di-, mono-saccharides and polyols FODMAPs suggest that the heterozygote mutants may affect the disease development and treatment.

MiR-26a and miR-26b downregulate the expression of sucrase-isomaltase enzyme: A new chapter in diabetes treatment

Type II diabetes is a metabolic disease that has affected 460 million people around the globe and become a heavy burden on health care system. Diabetic patients suffer from hyperglycemia and hyperinsulinemia which can damage vital organs in body like heart, kidneys, eyes and nervous system. Different strategies have been introduced to control or lessen these diabetic complications in which one of the most promising approaches is the inhibition of intestinal sucrase-isomaltase (SI). Inhibition of this enzyme will block the release of glucose into bloodstream and lead to reduced postprandial hyperglycemia. MicroRNAs are small regulatory molecules that play critical roles in different cellular pathways and molecular mechanisms. It is proved that microRNAs have significant effects on cellular mechanisms involved in diabetes and can be used as biomarkers for diagnosis of this metabolic disease. Based on bioinformatics analysis miR-26a and miR-26b can interact with a conserved 3'-UTR region of SI mRNA which lead to a hypothesis that these miRs may have negative regulatory effect on this enzyme. In this study, we investigated the impact of high glucose conditions on expression of sucrase-isomaltase, miR-26a and miR-26b in caco-2 cell line. It is proved that in a simulated diabetic condition there is a reverse correlation between the expression pattern of these miRs and SI. QRT-PCR method was used to evaluate the expression of our target molecules. Interestingly, transfection of miR-26a and miR-26b in caco-2 cell line reduced the transcription of SI mRNA and decreased the sucrase and maltase activity of its active sites. To sum up, our results demonstrate the first evidence of the significant effect of miR-26a and miR-26b on SI expression and activity. We proved that these microRNAs may directly inhibit this enzyme and can be used as a new scaffold in search of finding novel treatments for type II diabetes.

Acute Effects of Nutritive and Non-Nutritive Sweeteners on Postprandial Blood Pressure

Postprandial hypotension (PPH) is under-recognised, but common, particularly in the elderly, and is of clear clinical importance due to both the independent association between PPH and an increase in mortality and lack of effective management for this condition. Following health concerns surrounding excessive consumption of sugar, there has been a trend in the use of low- or non-nutritive sweeteners as an alternative. Due to the lack of literature in this area, we conducted a systematic search to identify studies relevant to the effects of different types of sweeteners on postprandial blood pressure (BP). The BP response to ingestion of sweeteners is generally unaffected in healthy young subjects, however in elderly subjects, glucose induces the greatest decrease in postprandial BP, while the response to sucrose is less pronounced. The limited studies investigating other nutritive and non-nutritive sweeteners have demonstrated minimal or no effect on postprandial BP. Dietary modification by replacing high nutritive sweeteners (glucose, fructose, and sucrose) with low nutritive (d-xylose, xylitol, erythritol, maltose, maltodextrin, and tagatose) and non-nutritive sweeteners may be a simple and effective management strategy for PPH.

Rebamipide increases the disaccharidases activity in patients with enteropathy with impaired membrane digestion. Pilot study

AIM

To evaluate the effectiveness of enteroprotector Rebamipide in the treatment of enteropathy with impaired membrane digestion (EIMD).

MATERIALS AND METHODS

We examined 102 patients aged 18 to 50 years (41 men and 61 women) with clinical signs of irritable bowel syndrome (n=65), functional diarrhea (n=33), and functional constipation (n=4) according to Rome IV criteria (2016). The activities of glucoamylase (GA), maltase, sucrase and lactase were determined by Dahlquist-Trinder method in duodenal biopsies obtained during esophagogastroduodenoscopy. The control group consisted of 20 healthy people aged 23-47. They showed following average enzyme activity: lactase - 42±13 ng glucose on 1 mg of tissue per minute, GA - 509±176, maltase - 1735±446, sucrase - 136±35 ng glucose on 1 mg of tissue per minute. These numbers were taken as the norm.

RESULTS

The activity of the disaccharidases was reduced in 89.2% out of 102 patients, and they were diagnosed with EIMD. Thirteen patients with EIMD were recommended to maintain the FODMAP diet and take enteroprotector Rebamipide 100 mg 3 times a day for 12 weeks. After 3 months 11 patients reported decreased or no flatulence, abdominal pain, stool disorder; 2 patients reported no change. The activity of GA increased to an average of 149±82 (by 78%, p=0.016), maltase - to 864±472 (by 131%, p=0.0019), sucrase - 63±35 (by 95%, p=0.0041) and lactase - 10±8 ng glucose on 1 mg of tissue per minute. The activity of lactase did not change.

CONCLUSION

We discovered a previously unknown phenomenon of the disaccharidases activity increase in duodenal mucosa and improved carbohydrates tolerance in the patients with EIMD taking Rebamipide in the dose 300 mg/day for 12 weeks.

Phylogenetic analysis reveals key residues in substrate hydrolysis in the isomaltase domain of sucrase-isomaltase and its role in starch digestion

BACKGROUND

Starch constitutes one of the main sources of nutrition in the human diet and is broken down through a number of stages of digestion. Small intestinal breakdown of starch-derived substrates occurs through the mechanisms of small intestinal brush border enzymes, maltase-glucoamylase and sucrase-isomaltase. These enzymes each contain two functional enzymatic domains, and though they share sequence and structural similarities due to their evolutionary conservation, they demonstrate distinct substrate preferences and catalytic efficiency. The N-terminal isomaltase domain of sucrase-isomaltase has a unique ability to actively hydrolyze isomaltose substrates in contrast to the sucrase, maltase and glucoamylase enzymes.

METHODS

Through phylogenetic analysis, structural comparisons and mutagenesis, we were able to identify specific residues that play a role in the distinct substrate preference. Mutational analysis and comparison with wild-type activity provide evidence that this role is mediated in part by affecting interactions between the sucrase and isomaltase domains in the intact molecule.

RESULTS

The sequence analysis revealed three residues proposed to play key roles in isomaltase specificity. Mutational analysis provided evidence that these residues in isomaltase can also affect activity in the partner sucrase domain, suggesting a close interaction between the domains.

MAJOR CONCLUSIONS

The sucrase and isomaltase domains are closely interacting in the mature protein. The activity of each is affected by the presence of the other.

GENERAL SIGNIFICANCE

There has been little experimental evidence previously of the effects on activity of interactions between the sucrase-isomaltase enzyme domains. By extension, similar interactions might be expected in the other intestinal α-glucosidase, maltase-glucoamylase.

Investigation on the Enzymatic Profile of Mulberry Alkaloids by Enzymatic Study and Molecular Docking

α-glucosidase inhibitors (AGIs) have been an important category of oral antidiabetic drugs being widely exploited for the effective management of type 2 diabetes mellitus. However, the marketed AGIs not only inhibited the disaccharidases, but also exhibited an excessive inhibitory effect on α-amylase, resulting in undesirable gastrointestinal side effects. Compared to these agents, Ramulus Mori alkaloids (SZ-A), was a group of effective alkaloids from natural Morus alba L., and showed excellent hypoglycemic effect and fewer side effects in the Phase II/III clinical trials. Thus, this paper aims to investigate the selective inhibitory effect and mechanism of SZ-A and its major active ingredients (1-DNJ, FA and DAB) on different α-glucosidases (α-amylase and disaccharidases) by using a combination of kinetic analysis and molecular docking approaches. From the results, SZ-A displayed a strong inhibitory effect on maltase and sucrase with an IC₅₀ of 0.06 μg/mL and 0.03 μg/mL, respectively, which was similar to the positive control of acarbose with an IC₅₀ of 0.07 μg/mL and 0.68 μg/mL. With regard to α-amylase, SZ-A exhibited no inhibitory activity at 100 μg/mL, while acarbose showed an obvious inhibitory effect with an IC₅₀ of 1.74 μg/mL. The above analysis demonstrated that SZ-A could selectively inhibit disaccharidase to reduce hyperglycemia with a reversible competitive inhibition, which was primarily attributed to the three major active ingredients of SZ-A, especially 1-DNJ molecule. In the light of these findings, molecular docking study was utilized to analyze their inhibition mechanisms at molecular level. It pointed out that acarbose with a four-ring structure could perform desirable interactions with various α-glucosidases, while the three active ingredients of SZ-A, belonging to monocyclic compounds, had a high affinity to the active site of disaccharidases through forming a wide range of hydrogen bonds, whose affinity and consensus score with α-amylase was significantly lower than that of acarbose. Our study illustrates the selective inhibition mechanism of SZ-A on α-glucosidase for the first time, which is of great importance for the treatment of type 2 diabetes mellitus.

Achieving protein targets without energy overfeeding in critically ill patients: A prospective feasibility study

BACKGROUND & AIMS

High protein delivery during early critical illness is associated with lower mortality, while energy overfeeding is associated with higher mortality. Protein-to-energy ratios of traditional enteral formulae are sometimes too low to reach protein targets without energy overfeeding. This prospective feasibility study aimed to evaluate the ability of a new enteral formula with a high protein-to-energy ratio to achieve the desired protein target while avoiding energy overfeeding.

METHODS

Mechanically ventilated non-septic patients received the high protein-to-energy ratio nutrition during the first 4 days of ICU stay (n = 20). Nutritional prescription was 90% of measured energy expenditure. Primary endpoint was the percentage of patients reaching a protein target of ≥1.2 g/kg ideal body weight on day 4. Other endpoints included a comparison of nutritional intake to matched historic controls and the response of plasma amino acid concentrations. Safety endpoints were gastro-intestinal tolerance and plasma urea concentrations.

RESULTS

Nineteen (95%) patients reached the protein intake target of ≥1.2 g/kg ideal body weight on day 4, compared to 65% in historic controls (p = 0.024). Mean plasma concentrations of all essential amino acids increased significantly from baseline to day 4. Predefined gastro-intestinal tolerance was good, but unexplained foul smelling diarrhoea occurred in two patients. In one patient plasma urea increased unrelated to acute kidney injury.

CONCLUSIONS

In selected non-septic patients tolerating enteral nutrition, recommended protein targets can be achieved without energy overfeeding using a new high protein-to-energy ratio enteral nutrition.

Update on Dietary Management of Childhood Functional Abdominal Pain Disorders

Diet plays a significant role for children with functional abdominal pain disorders. A large majority of these children identify at least 1 food that exacerbates their symptoms. Malabsorbed carbohydrates may have both direct and microbiome-mediated physiologic effects. There are several factors associated with carbohydrate symptom generation, including (1) the amount ingested, (2) ingestion with a meal, (3) small intestinal enzymatic activity, (4) consuming the carbohydrate with microorganisms capable of breaking down the carbohydrate, (5) the gut microbiome, and (6) host factors. Therapies include carbohydrate (single and/or comprehensive) restriction, selective prebiotic and/or enzyme supplementation. Fiber supplementation may also be beneficial.

Posttranslational Processing and Function of Mucosal Maltases

The final step of carbohydrate digestion in the intestine is performed by 2 major α-glucosidases of the intestinal mucosa, sucrase-isomaltase (SI) and maltase-glucoamylase. Both of these enzymes are type II membrane glycoproteins, which share a significant level of homology in gene and protein structures and yet have differences in the posttranslational processing, substrate specificity and functional capacity. Insufficient activity of these disaccharidases particularly SI as a result of genetic mutations or secondary intestinal pathologies is associated with carbohydrate maldigestion and gastrointestinal intolerances. This review will discuss the maturation profiles of SI and maltase-glucoamylase relative to their functional capacities and deficiencies.

Characterization of Mucosal Disaccharidases from Human Intestine

In this study, we used a brush border membrane (BBM) preparation from human small intestine to analyze the proportion and the activity of major intestinal disaccharidases, including sucrase-isomaltase (SI), maltase-glucoamylase (MGAM) and lactase-phlorizin hydrolase (LPH). SI, MGAM and LPH respectively constituted 8.2%, 2.7% and 1.4% of total BBM protein. The activity of SI and LPH decreased threefold after purification from the brush border membrane, which highlights the effect of membrane microdomains on the functional capacity of these enzymes. All of the disaccharidases showed optimal activity at pH 6, over 50% residual activity between pH 5 to pH 7, and increasing activity with rising temperatures up to 45 °C, along with a stable functional structure. Therefore the enzymes can withstand mild intraluminal pH alterations with adequate function, and are able to increase their activity with elevated core body temperature. Our data provide a functional measure for characterization of intestinal disaccharidases under different physiological and pathological conditions.

Starch Polysaccharides in the Human Diet: Effect of the Different Source and Processing on its Absorption

Starch is the main source of carbohydrates in human diet. It is widely used in food processing and non-food industrial applications. The effects on starch digestion and absorption in humans are reviewed in relation to the starch composition, sources, plant genetic variation, food processing and cooking. The impact of food industrial processing and starch modification on the digestibility of starch containing foods and on gut microbiota are discussed. Considering that the resistant starch (RS) fraction escaped from the small intestine is fermented in large intestine, all the variables that influence starch digestibility and absorption must be taken into account when discussing about healthy properties of fibers. Future trends in food industries are aimed to increase the RS fraction in processed foods in order to improve nutritional quality as well as to clarify the influence of RS3 and RS4 on gut microbiota.

蔗糖酶-异麦芽糖酶缺乏与腹泻的研究进展

蔗糖酶-异麦芽糖酶(sucrase-isomaltase, SI)是蔗糖酶在肠道内最主要的存在形式, 是最丰富的肠道二糖酶, 其包含了所有的蔗糖酶活性, 大部分的异麦芽糖酶活性及60%-80%的麦芽糖酶活性. 蔗糖酶-异麦芽糖酶缺乏症(sucrase-isomaltase deficiency, SID)是由于该二糖酶缺乏导致二糖吸收不良, 肠道正常生理功能受损, 机体营养不良, 生长发育落后, 甚至产生危及生命的胃肠道症状. 其最主要的临床表现是腹泻. 临床上通过调整肠道SI活性来治疗腹泻, 并将SI活性用于临床诊断. 本文主要阐述SID与腹泻的关系、研究进程以及诊疗手段, 促进SI在药理方面的研究.

Contribution of the Individual Small Intestinal α-Glucosidases to Digestion of Unusual α-Linked Glycemic Disaccharides

The mammalian mucosal α-glucosidase complexes, maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI), have two catalytic subunits (N- and C-termini). Concurrent with the desire to modulate glycemic response, there has been a focus on di-/oligosaccharides with unusual α-linkages that are digested to glucose slowly by these enzymes. Here, we look at disaccharides with various possible α-linkages and their hydrolysis. Hydrolytic properties of the maltose and sucrose isomers were determined using rat intestinal and individual recombinant α-glucosidases. The individual α-glucosidases had moderate to low hydrolytic activities on all α-linked disaccharides, except trehalose. Maltase (N-terminal MGAM) showed a higher ability to digest α-1,2 and α-1,3 disaccharides, as well as α-1,4, making it the most versatile in α-hydrolytic activity. These findings apply to the development of new glycemic oligosaccharides based on unusual α-linkages for extended glycemic response. It also emphasizes that mammalian mucosal α-glucosidases must be used in in vitro assessment of digestion of such carbohydrates.

Dietary Carbohydrates and Childhood Functional Abdominal Pain

Childhood functional gastrointestinal disorders (FGIDs) affect a large number of children throughout the world. Carbohydrates (which provide the majority of calories consumed in the Western diet) have been implicated both as culprits for the etiology of symptoms and as potential therapeutic agents (e.g., fiber) in childhood FGIDs. In this review, we detail how carbohydrate malabsorption may cause gastrointestinal symptoms (e.g., bloating) via the physiologic effects of both increased osmotic activity and increased gas production from bacterial fermentation. Several factors may play a role, including: (1) the amount of carbohydrate ingested; (2) whether ingestion is accompanied by a meal or other food; (3) the rate of gastric emptying (how quickly the meal enters the small intestine); (4) small intestinal transit time (the time it takes for a meal to enter the large intestine after first entering the small intestine); (5) whether the meal contains bacteria with enzymes capable of breaking down the carbohydrate; (6) colonic bacterial adaptation to one's diet, and (7) host factors such as the presence or absence of visceral hypersensitivity. By detailing controlled and uncontrolled trials, we describe how there is a general lack of strong evidence supporting restriction of individual carbohydrates (e.g., lactose, fructose) for childhood FGIDs. We review emerging evidence suggesting that a more comprehensive restriction of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) may be effective. Finally, we review how soluble fiber (a complex carbohydrate) supplementation via randomized controlled intervention trials in childhood functional gastrointestinal disorders has demonstrated efficacy.

Taste cell-expressed α-glucosidase enzymes contribute to gustatory responses to disaccharides

The primary sweet sensor in mammalian taste cells for sugars and noncaloric sweeteners is the heteromeric combination of type 1 taste receptors 2 and 3 (T1R2+T1R3, encoded by Tas1r2 and Tas1r3 genes). However, in the absence of T1R2+T1R3 (e.g., in Tas1r3 KO mice), animals still respond to sugars, arguing for the presence of T1R-independent detection mechanism(s). Our previous findings that several glucose transporters (GLUTs), sodium glucose cotransporter 1 (SGLT1), and the ATP-gated K(+) (KATP) metabolic sensor are preferentially expressed in the same taste cells with T1R3 provides a potential explanation for the T1R-independent detection of sugars: sweet-responsive taste cells that respond to sugars and sweeteners may contain a T1R-dependent (T1R2+T1R3) sweet-sensing pathway for detecting sugars and noncaloric sweeteners, as well as a T1R-independent (GLUTs, SGLT1, KATP) pathway for detecting monosaccharides. However, the T1R-independent pathway would not explain responses to disaccharide and oligomeric sugars, such as sucrose, maltose, and maltotriose, which are not substrates for GLUTs or SGLT1. Using RT-PCR, quantitative PCR, in situ hybridization, and immunohistochemistry, we found that taste cells express multiple α-glycosidases (e.g., amylase and neutral α glucosidase C) and so-called intestinal "brush border" disaccharide-hydrolyzing enzymes (e.g., maltase-glucoamylase and sucrase-isomaltase). Treating the tongue with inhibitors of disaccharidases specifically decreased gustatory nerve responses to disaccharides, but not to monosaccharides or noncaloric sweeteners, indicating that lingual disaccharidases are functional. These taste cell-expressed enzymes may locally break down dietary disaccharides and starch hydrolysis products into monosaccharides that could serve as substrates for the T1R-independent sugar sensing pathways.

Disaccharidase activity in children undergoing esophagogastroduodenoscopy: A systematic review

AIM: To investigate the utility of intestinal disaccharide analysis during esophagogastroduodenoscopy (EGD) in children, we performed a systematic review of studies examining disaccharide activity.

METHODS: All full-length articles published in English during 1966-2014 were included if: (1) participants had small intestinal biopsy evaluation of disaccharide activity; (2) levels of lactase, sucrase, maltase or palatinase were reported; and (3) age of participants was under 18 years.

RESULTS: Thirty articles examining 34753 disaccharide assays fulfilled the specific search, inclusion, and exclusion criteria. All of the studies were observational in design and 57% (17) were prospective. Sixteen studies were conducted in the United States and 9 European studies were identified. The biggest study enrolled about 30, 314 procedures and 13 studies investigated fewer than 50 procedures. Eleven studies examined Caucasian subjects, 3 studies examined Asian subjects, and 6 examined African subjects. Only one Hispanic subject was included. In studies reporting disaccharide deficiency, the overall proportion of lactase deficiency was 39.2%, sucrase deficiency was 9.0%, maltase deficiency was 12.6% and palatinase deficiency was 9.1%. The prevalence of duodenal inflammatory changes ranged from 6% to 24% for non-specific histological lesions (e.g., duodenitis). Sixteen studies examined the association of histologic findings with disaccharide activities, and 12 studies reported an inverse association between degree of histologic inflammation and disaccharide levels.

CONCLUSION: We reviewed 30 studies including 34753 biopsy specimens with disaccharide analysis from children undergoing EGD. Our findings advocate a large study is to further illuminate the importance of EGD with disaccharide analysis in children.

The multiple roles of sucrase-isomaltase in the intestinal physiology

Osmotic diarrhea and abdominal pain in humans are oftentimes associated with carbohydrate malabsorption in the small intestine due to loss of function of microvillar disaccharidases. Disaccharidases are crucial for the digestion and the subsequent absorption of carbohydrates. This review focuses on sucrase-isomaltase as the most abundant intestinal disaccharidase and the primary or induced pathological conditions that affect its physiological function. Congenital defects are primary factors which directly influence the transport and function of sucrase-isomaltase in a healthy epithelium. Based on the mutation type and the pattern of inheritance, a mutation in the sucrase-isomaltase gene may exert a variety of symptoms ranging from mild to severe. However, structure and function of wild type sucrase-isomaltase can be also affected by secondary factors which influence its structure and function either specifically via certain inhibitors and therapeutic agents or generally as a part of intestinal pathogenesis, for example in the inflammatory responses. Diagnosis of sucrase-isomaltase deficiency and discriminating it from other gastrointestinal intolerances can be latent in the patients because of common symptoms observed in all of these cases.

Here, we summarize the disorders that implicate the digestive function of sucrase-isomaltase as well as the diagnostic and therapeutic strategies utilized to restore normal intestinal function.

Carbohydrate malabsorption in acutely malnourished children and infants: a systematic review

CONTEXT

Severe acute malnutrition (SAM) accounts for approximately 1 million child deaths per year. High mortality is linked with comorbidities, such as diarrhea and pneumonia.

OBJECTIVE

The aim of this systematic review was to determine the extent to which carbohydrate malabsorption occurs in children with SAM.

DATA SOURCES

The PubMed and Embase databases were searched. Reference lists of selected articles were checked.

DATA EXTRACTION

All observational and controlled intervention studies involving children with SAM in which direct or indirect measures of carbohydrate absorption were analyzed were eligible for inclusion. A total of 20 articles were selected for this review.

DATA SYNTHESIS

Most studies reported carbohydrate malabsorption, particularly lactose malabsorption, and suggested an increase in diarrhea and reduced weight gain in children on a lactose-containing diet. As most studies reviewed were observational, there was no conclusive scientific evidence of a causal relationship between lactose malabsorption and a worse clinical outcome among malnourished children.

CONCLUSION

The combined data indicate that carbohydrate malabsorption is prevalent in children with SAM. Additional well-designed intervention studies are needed to determine whether outcomes of SAM complicated by carbohydrate malabsorption could be improved by altering the carbohydrate/lactose content of therapeutic feeds and to elucidate the precise mechanisms involved.

Modeling of cooked starch digestion process using recombinant human pancreatic α-amylase and maltase-glucoamylase for in vitro evaluation of α-glucosidase inhibitors

In human, digestion of cooked starch mainly involves breaking down of α-amylase to α-limit dextrins and small linear malto-oligosaccharides, which are in turn hydrolyzed to glucose by the gut mucosal maltase-glucoamylase (MGAM). Human pancreatic α-amylase (HPA), amino- and carboxyl-terminal portions of MGAM (ntMGAM and ctMGAM) catalyze the hydrolysis of α-D-(1,4) glycosidic linkages in starch, playing a crucial role in the production of glucose in the human lumen. Accordingly, these enzymes are effective drug targets for the treatments of type 2 diabetes and obesity. In this study, a Plackett-Burman based statistical screening procedure was adopted to determine the most critical factors affecting cooked starch digestion by the combination of HPA, ctMGAM and ntMGAM. Six factors were tested and experimental results showed that pH and temperature were the major influencing factors, with optimal pH and temperature at 6.0 and 50 °C, respectively. Surprisingly, ntMGAM had no significant contribution to the glucose production from starch digestion compared to the HPA and ctMGAM. The optimal proportion of HPA and ctMGAM in a starch digestion system was further determined by response surface methodology. Results showed a maximum starch digestion (88.05%) within 0.5 h when used HPA:ctMGAM=1:9 (U). The inhibitory effects of various inhibitors on the cooked starch digestion by HPA1/ctMGAM9 were evaluated by determining their half maximal inhibitory concentration (IC50) values. Acarviostatin II03 showed the highest inhibitory activity, with 67 times higher potency than acarbose. Moreover, acarviostatin II03 could significantly depress postprandial blood glucose levels in mice, better than that by acarbose. These findings suggest that our in vitro enzymatic system can simulate in vivo starch digestion process, and thus can be used to screen and evaluate α-glucosidase inhibitors.

Dietary phenolic compounds selectively inhibit the individual subunits of maltase-glucoamylase and sucrase-isomaltase with the potential of modulating glucose release

In this study, it was hypothesized that dietary phenolic compounds selectively inhibit the individual C- and N-terminal (Ct, Nt) subunits of the two small intestinal α-glucosidases, maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI), for a modulated glycemic carbohydrate digestion. The inhibition by chlorogenic acid, caffeic acid, gallic acid, (+)-catechin, and (-)-epigallocatechin gallate (EGCG) on individual recombinant human Nt-MGAM and Nt-SI and on mouse Ct-MGAM and Ct-SI was assayed using maltose as the substrate. Inhibition constants, inhibition mechanisms, and IC50 values for each combination of phenolic compound and enzymatic subunit were determined. EGCG and chlorogenic acid were found to be more potent inhibitors for selectively inhibiting the two subunits with highest activity, Ct-MGAM and Ct-SI. All compounds displayed noncompetitive type inhibition. Inhibition of fast-digesting Ct-MGAM and Ct-SI by EGCG and chlorogenic acid could lead to a slow, but complete, digestion of starch for improved glycemic response of starchy foods with potential health benefit.

Ehealth monitoring in irritable bowel syndrome patients treated with low fermentable oligo-, di-, mono-saccharides and polyols diet

In the present study we report on changes in irritable bowel syndrome-severity scoring system (IBS-SSS) and irritable bowel syndrome-quality of life (IBS-QoL) in 19 IBS patients, aged 18 to 74 years (F/M: 14/5), during 12 wk registering their symptoms on the web-application (www.ibs.constant-care.dk). During a control period of the first 6-wk patients were asked to register their IBS-SSS and IBS-QoL on the web-application weekly without receiving any intervention. Thereafter, low fermentable oligo-, di-, mono-saccharides and polyols (FODMAP) diet (LFD) was introduced for the next 6 wk while continuing the registration. Though a small sample size a significant improvement in disease activity (IBS-SSS) was observed during both the control period, median: 278 (range: 122-377), P = 0.02, and subsequently during the LFD period, median: 151 (range: 29-334), P < 0.01. The IBS-QoL solely changed significantly during the LFD period, median: 67 (37-120), P < 0.01. The significant reduction in disease activity during the control period shows a positive effect of the web-application on IBS symptoms when presented as a “traffic light”. However adding the diet reduced IBS-SSS to < 150, inactive to mild symptoms. In the future results from larger scale trials are awaited.

Different sucrose-isomaltase response of Caco-2 cells to glucose and maltose suggests dietary maltose sensing

Using the small intestine enterocyte Caco-2 cell model, sucrase-isomaltase (SI, the mucosal α-glucosidase complex) expression and modification were examined relative to exposure to different mono- and disaccharide glycemic carbohydrates. Caco-2/TC7 cells were grown on porous supports to post-confluence for complete differentiation, and dietary carbohydrate molecules of glucose, sucrose (disaccharide of glucose and fructose), maltose (disaccharide of two glucoses α-1,4 linked), and isomaltose (disaccharide of two glucoses α-1,6 linked) were used to treat the cells. qRT-PCR results showed that all the carbohydrate molecules induced the expression of the SI gene, though maltose (and isomaltose) showed an incremental increase in mRNA levels over time that glucose did not. Western blot analysis of the SI protein revealed that only maltose treatment induced a higher molecular weight band (Mw ~245 kDa), also at higher expression level, suggesting post-translational processing of SI, and more importantly a sensing of maltose. Further work is warranted regarding this putative sensing response as a potential control point for starch digestion and glucose generation in the small intestine.

Enzyme-synthesized highly branched maltodextrins have slow glucose generation at the mucosal α-glucosidase level and are slowly digestible in vivo

For digestion of starch in humans, α-amylase first hydrolyzes starch molecules to produce α-limit dextrins, followed by complete hydrolysis to glucose by the mucosal α-glucosidases in the small intestine. It is known that α-1,6 linkages in starch are hydrolyzed at a lower rate than are α-1,4 linkages. Here, to create designed slowly digestible carbohydrates, the structure of waxy corn starch (WCS) was modified using a known branching enzyme alone (BE) and an in combination with β-amylase (BA) to increase further the α-1,6 branching ratio. The digestibility of the enzymatically synthesized products was investigated using α-amylase and four recombinant mammalian mucosal α-glucosidases. Enzyme-modified products (BE-WCS and BEBA-WCS) had increased percentage of α-1,6 linkages (WCS: 5.3%, BE-WCS: 7.1%, and BEBA-WCS: 12.9%), decreased weight-average molecular weight (WCS: 1.73×10⁸ Da, BE-WCS: 2.76×10⁵ Da, and BEBA-WCS 1.62×10⁵ Da), and changes in linear chain distributions (WCS: 21.6, BE-WCS: 16.9, BEBA-WCS: 12.2 DP_w). Hydrolysis by human pancreatic α-amylase resulted in an increase in the amount of branched α-limit dextrin from 26.8% (WCS) to 56.8% (BEBA-WCS). The α-amylolyzed samples were hydrolyzed by the individual α-glucosidases (100 U) and glucogenesis decreased with all as the branching ratio increased. This is the first report showing that hydrolysis rate of the mammalian mucosal α-glucosidases is limited by the amount of branched α-limit dextrin. When enzyme-treated materials were gavaged to rats, the level of postprandial blood glucose at 60 min from BEBA-WCS was significantly higher than for WCS or BE-WCS. Thus, highly branched glucan structures modified by BE and BA had a comparably slow digesting property both in vitro and in vivo. Such highly branched α-glucans show promise as a food ingredient to control postprandial glucose levels and to attain extended glucose release.

Miglustat-induced intestinal carbohydrate malabsorption is due to the inhibition of α-glucosidases, but not β-galactosidases

Miglustat is an oral medication that has approved indication for type I Gaucher disease and Niemann pick disease type C. Usually treatment with Miglustat is associated with occurrence of gastrointestinal side effects similar to carbohydrate maldigestion symptoms. Here, we studied the direct influence of Miglustat on the enzymatic function of the major disaccharidases of the intestinal epithelium. Our findings show that an immediate effect of Miglustat is its interference with carbohydrate digestion in the intestinal lumen via reversible inhibition of disaccharidases that cleave α-glycosidically linked carbohydrates. Higher non physiological concentrations of Miglustat can partly affect lactase activity. We further show that the inhibition of the disaccharidases function by Miglustat is mainly competitive and does not occur via alteration of the enzyme folding.