Carbohydrate intolerance

Molecular characterization and nutritional regulation of sodium-dependent glucose cotransporter 1 (Sglt1) in blunt snout bream (Megalobrama amblycephala)

Fish has poor utilization capacity for glucose metabolism. The possible reasons are related to the core regulatory elements of glucose metabolism: transport proteins. Studies on the species and functions of Sglt1 in aquatic animals are scarce, therefore further studies are needed. In this study, the full length of blunt snout bream (Megalobrama amblycephala) sglt1 (Masglt1) was 2965 bp including 5′-UTR region of 168 bp and a 3′-UTR region of 820 bp. Masglt1 have a highest sequence homology in Cypriniformes fish. MaSglt1 protein was identified as a transmembrane protein with 14 α-helix structures locating plasma membrane by the methods of predicted tertiary structure and immunohistochemical staining. MaSglt1 protein has a hollow channel forms which could be specifically coupled with two Na⁺ ions to recognize glucose and carry out transmembrane transport. High sglt1 mRNA was found in the intestine and kidney. The mRNA levels of intestinal sglt1 had a positive correlation with dietary starch levels at 3 h after feeding, and the mRNA was significantly higher than that at 24 h, however, the mRNA levels of renal sglt1 presented results opposite to those of intestinal sglt1. The mRNA levels of renal sglt1 had a positive correlation with dietary starch levels at 24 h after feeding, and the expression was significantly higher than that at 3 h. These results confirmed that Masglt11 was mainly found in the intestine and kidney and was located in the cell membrane, playing a role in glucose homeostasis.

Prevalence of Disaccharidase Deficiency in Adults With Unexplained Gastrointestinal Symptoms

Background/Aims

Disaccharidase assay is used for assessing carbohydrate intolerance in children, but its usefulness in adults is not known. The aim of this study is to assess the prevalence of disaccharidase deficiency in patients with unexplained gastrointestinal symptoms.

Methods

A retrospective review of adults with chronic (> 1 year) abdominal symptoms and negative imaging and endoscopy/colonoscopy and who completed bowel symptom questionnaire and duodenal biopsy for lactase, maltase, sucrase, and palatinase was performed. A subset also underwent 25 g lactose breath test (LBT).

Results

One hundred twenty patients (females = 83) were evaluated, of whom 48 also underwent LBT. Fifty-six (46.7%) patients had enzyme deficiency; 44 (36.7%) had single (either lactase or maltase), 1 had 3 enzyme deficiencies, 11 (9.2 %) had all 4 disaccharidase enzyme (pan-disaccharidase) deficiency, and 64 (53.0%) had normal enzyme levels. Baseline prevalence and severity of 11 gastrointestinal symptoms were similar between normal and single enzyme deficiency groups. The sensitivity and specificity of LBT was 78.3% and 72.0%, respectively and overall agreement with lactase deficiency was 75.0%.

Conclusions

Isolated disaccharidase deficiency occurs in adults, usually lactase and rarely maltase, and pan-disaccharidase deficiency is rare. Baseline symptoms or its severity did not predict enzyme deficiency.

Infant Complementary Feeding of Prebiotics for theMicrobiome and Immunity

Complementary feeding transitions infants from a milk-based diet to solid foods, providing essential nutrients to the infant and the developing gut microbiome while influencing immune development. Some of the earliest microbial colonisers readily ferment select oligosaccharides, influencing the ongoing establishment of the microbiome. Non-digestible oligosaccharides in prebiotic-supplemented formula and human milk oligosaccharides promote commensal immune-modulating bacteria such as Bifidobacterium, which decrease in abundance during weaning. Incorporating complex, bifidogenic, non-digestible carbohydrates during the transition to solid foods may present an opportunity to feed commensal bacteria and promote balanced concentrations of beneficial short chain fatty acid concentrations and vitamins that support gut barrier maturation and immunity throughout the complementary feeding window.

Distinguishing the differences in β-glycosylceramidase folds, dynamics, and actions informs therapeutic uses

Glycosyl hydrolases (GHs) are carbohydrate-active enzymes that hydrolyze a specific β-glycosidic bond in glycoconjugate substrates; β-glucosidases degrade glucosylceramide, a ubiquitous glycosphingolipid. GHs are grouped into structurally similar families that themselves can be grouped into clans. GH1, GH5, and GH30 glycosidases belong to clan A hydrolases with a catalytic (β/α)8 TIM barrel domain, whereas GH116 belongs to clan O with a catalytic (α/α)6 domain. In humans, GH abnormalities underlie metabolic diseases. The lysosomal enzyme glucocerebrosidase (family GH30), deficient in Gaucher disease and implicated in Parkinson disease etiology, and the cytosol-facing membrane-bound glucosylceramidase (family GH116) remove the terminal glucose from the ceramide lipid moiety. Here, we compare enzyme differences in fold, action, dynamics, and catalytic domain stabilization by binding site occupancy. We also explore other glycosidases with reported glycosylceramidase activity, including human cytosolic β-glucosidase, intestinal lactase-phlorizin hydrolase, and lysosomal galactosylceramidase. Last, we describe the successful translation of research to practice: recombinant glycosidases and glucosylceramide metabolism modulators are approved drug products (enzyme replacement therapies). Activity-based probes now facilitate the diagnosis of enzyme deficiency and screening for compounds that interact with the catalytic pocket of glycosidases. Future research may deepen the understanding of the functional variety of these enzymes and their therapeutic potential.

Ingestão de cálcio e densidade mineral óssea em mulheres adultas intolerantes à lactose

OBJETIVO: Comparar a ingestão de cálcio e a densidade mineral óssea entre mulheres adultas portadoras de intolerância à lactose e suas congêneres não portadoras da doença. MÉTODOS: A amostra foi composta por 60 mulheres jovens adultas (de 20 a 40 anos), separadas em dois grupos: 30 diagnosticadas com intolerância à lactose e 30 saudáveis. A ingestão de cálcio foi avaliada por três autorregistros alimentares, e a densidade mineral óssea do colo do fêmur por absortometria radiológica de dupla energia. RESULTADOS: As densidades minerais ósseas do colo do fêmur (M=0,86, DP=0,13g/cm² versus M=0,77, DP=0,12g/cm²) e do fêmur total (M=1,14, DP=0,14g/cm² versus M=1,06, DP=0,12g/cm²) foram menores (p<0,05) para as portadoras de intolerância à lactose do que para o grupo-controle, mas não houve diferença significativa na densidade mineral óssea para corpo inteiro (M=1,14, DP=0,15g/cm² versus M=1,08, DP=0,09g/cm², p>0,05). Além disso, a ingestão de cálcio foi menor para intolerantes à lactose do que para o grupo-controle (M=250,5, DP=111,7mg/dia¹ vs M=659,7, DP=316,1mg/dia¹, p<0,05). CONCLUSÃO: Os Resultados do presente estudo sugerem que o aparecimento de sintomas de intolerância pode influenciar a massa óssea devido a uma redução da ingestão de cálcio.

Clinical impact of identifying lactose maldigestion or fructose malabsorption in irritable bowel syndrome or other conditions

BACKGROUND

The role of carbohydrate maldigestion or malabsorption remains unclear in patients with irritable bowel syndrome (IBS). The purpose of this study was to examine the impact of identifying lactose maldigestion (LM) and fructose malabsorption (FM) on patients with and without IBS.

METHODS

Patients who received lactose and fructose challenge testing formed the study group. Carbohydrate challenge testing was performed with 50 g lactose and 25 g fructose. Breath samples were collected and analyzed for hydrogen, methane, and CO2 (for correction) using a MicroLyzer Model SC (QuinTron Instrument Company, Milwaukee, WI). Questionnaires were used to assess Rome III IBS criteria, compliance with carbohydrate dietary modifications, and changes in symptoms.

RESULTS

One hundred and twenty-one of the 181 (67%) study subjects were able to be contacted 8 months to 4 years after carbohydrate testing. LM (21) and FM (2) were seen in 33% of the 66 IBS subjects. LM (12) and FM (9) were seen in 33% of the 55 subjects without IBS. Seventy-seven percent of IBS and 72% of those without IBS reported compliance with dietary advice. Of the subjects who reported compliance, 47% of IBS and 77% of those without IBS reported that, after identifying LM or FM, their symptoms resolved or improved.

CONCLUSIONS

Carbohydrate maldigestion has a similar incidence in patients with and without IBS and both populations have similar compliance with therapeutic diets. However, patients without IBS are more likely to have improvement in symptoms when dietary changes are instituted when compared to IBS patients.

The role of colonic metabolism in lactose intolerance

Lactose maldigestion and intolerance affect a large part of the world population. The underlying factors of lactose intolerance are not fully understood. In this review, the role of colonic metabolism is discussed, i.e. fermentation of lactose by the colonic microbiota, colonic processing of the fermentation metabolites and how these processes would play a role in the pathophysiology of lactose intolerance. We suggest that the balance between the removal and production rate of osmotic-active components (lactose, and intermediate metabolites, e.g. lactate, succinate, etc.) in the colon is a key factor in the development of symptoms. The involvement of the colon may provide the basis for designing new targeted strategies for dietary and clinical management of lactose intolerance.

Nutritional genomics: food industry applications from farm to fork

Nutritional genomics is a new and promising science area which can broadly be defined as the application of high throughput genomics (transcriptomics, proteomics, metabolomics/metabonomics) and functional genomic technologies to the study of nutritional sciences and food technology. First utilised in the food industry by plant biotechnologists to manipulate plant biosynthetic pathways, the use of genomic technologies has now spread within the agriculture sector, unleashing a host of new applications (e.g. approaches for producing novel, non-transgenic plant varietals; identification of genetic markers to guide plant and animal breeding programmes; exploration of diet-gene interactions for enhancing product quality and plant/animal health). Beyond agriculture, genomic technologies are also contributing to the improvement of food processing, food safety and quality assurance as well as the development of functional food products and the evolution of new health management concepts such as 'personalised nutrition', an emerging paradigm in which the diet of an individual is customised, based on their own genomic information, to optimise health and prevent disease. In this review the relevance of nutritional genomics to the food industry will be considered and examples given on how this science area is starting to be leveraged for economic benefits and to improve human nutrition and health.

Effect of lactose on oro-cecal transit in lactose digesters and maldigesters

BACKGROUND

The transit time of the small intestine, in addition to lactase activity, may influence lactose digestion and thus play a role in the occurrence of lactose intolerance. The objectives of this study were to investigate the effect of lactose on the oro-cecal transit time (OCTT) in lactose digesters and maldigesters as well as the possible mechanisms underlying these effects.

MATERIALS AND METHODS

Twenty-eight Chinese subjects and 16 Dutch subjects underwent one glucose and one lactose challenge in two single-blinded tests. Twenty of the Chinese subjects without complaints after the challenge then underwent another lactose challenge. A 6-h symptom score (SSC) was recorded, breath-hydrogen concentration was measured and OCTT after consumption of glucose and lactose was determined with the lactose-[13C] ureide breath test. The lactose digestion index (LDI) was determined in both the Dutch and 20 Chinese subjects with the 13C/2H-glucose test.

RESULTS

Lactose digesters (n = 13) and maldigesters (n = 20) were classified based on the results of the LDI and the breath-hydrogen test. The OCTT after the lactose and glucose challenges did not differ in the digesters, whereas in the maldigesters the OCTT, after the lactose challenge, was shorter than that after glucose. There was no difference in OCTT after the glucose challenge between the maldigesters and the digesters. However, the OCTT after the lactose challenge in the maldigesters was shorter than that in the digesters. The LDI of the digesters was significantly higher than that of the maldigesters. The OCTT after the lactose challenge was not correlated to the LDI in the maldigesters nor in the digesters. Based on the SSC after the one glucose and two lactose challenges, a tolerant (n = 7) and an intolerant (n = 5) group were classified in the Chinese subjects. The two groups did not differ in their LDI or OCTT after the lactose challenge. The OCTT after the lactose challenge was not correlated to the SSC or the LDI.

CONCLUSIONS

Lactose triggers a faster oro-cecal transit in lactose maldigesters, but not in digesters. However, this could not be explained by intestinal distension resulting from the osmotic load posed by maldigested lactose, and thus suggests a direct effect of lactose on intrinsic factors regulating intestinal motility.