Dietary fiber monosaccharide content alters gut microbiome composition and fermentation.

Members of the mammalian gut microbiota metabolize diverse complex carbohydrates that are not digested by the host, which are collectively labeled "dietary fiber." While the enzymes and transporters that each strain uses to establish a nutrient niche in the gut are often exquisitely specific, the relationship between carbohydrate structure and microbial ecology is imperfectly understood. The present study takes advantage of recent advances in complex carbohydrate structure determination to test the effects of fiber monosaccharide composition on microbial fermentation. Fifty-five fibers with varied monosaccharide composition were fermented by a pooled feline fecal inoculum in a modified MiniBioReactor array system over a period of 72 hours. The content of the monosaccharides glucose and xylose was significantly associated with the reduction of pH during fermentation, which was also predictable from the concentrations of the short-chain fatty acids lactic acid, propionic acid, and the signaling molecule indole-3-acetic acid. Microbiome diversity and composition were also predictable from monosaccharide content and SCFA concentration. In particular, the concentrations of lactic acid and propionic acid correlated with final alpha diversity and were significantly associated with the relative abundance of several of the genera, including Lactobacillus and Dubosiella. Our results suggest that monosaccharide composition offers a generalizable method to compare any dietary fiber of interest and uncover links between diet, gut microbiota, and metabolite production. IMPORTANCE: The survival of a microbial species in the gut depends on the availability of the nutrients necessary for that species to survive. Carbohydrates in the form of non-host digestible fiber are of particular importance, and the set of genes possessed by each species for carbohydrate consumption can vary considerably. Here, differences in the monosaccharides that are the building blocks of fiber are considered for their impact on both the survival of different species of microbes and on the levels of microbial fermentation products produced. This work demonstrates that foods with similar monosaccharide content will have consistent effects on the survival of microbial species and on the production of microbial fermentation products.

Differential Rates of Glycation Following Exposure to Unique Monosaccharides.

A complication of reducing sugars is that they can undergo Maillard chemical reactions, forming advanced glycation end-products (AGEs) that can induce oxidative stress and inflammation via engagements with the main receptor for AGEs (RAGE) in various tissues. Certain sugars, such as glucose and fructose, are well known to cause AGE formation. Recently, allulose has emerged as a rare natural sugar that is an epimer of fructose and which is of low caloric content that is minimally metabolized, leading to it being introduced as a low-calorie sugar alternative. However, the relative ability of allulose to generate AGEs compared to glucose and fructose is not known. Here we assess the accumulation of AGEs in cell-free, in vitro, and in vivo conditions in response to allulose and compare it to glycation mediated by glucose or fructose. AGEs were quantified in cell-free samples, cell culture media and lysates, and rat serum with glycation-specific ELISAs. In cell-free conditions, we observed concentration and time-dependent increases in AGEs when bovine serum albumin (BSA) was incubated with glucose or fructose and significantly less glycation when incubated with allulose. AGEs were significantly elevated when pulmonary alveolar type II-like cells were co-incubated with glucose or fructose; however, significantly less AGEs were detected when cells were exposed to allulose. AGE quantification in serum obtained from rats fed a high-fat, low-carb (HFLC) Western diet for 2 weeks revealed significantly less glycation in animals co-administered allulose compared to those exposed to stevia. These results suggest allulose is associated with less AGE formation compared to fructose or glucose, and support its safety as a low-calorie sugar alternative.

Probing altered receptor specificities of antigenically drifting human H3N2 viruses by chemoenzymatic synthesis, NMR, and modeling.

Prototypic receptors for human influenza viruses are N-glycans carrying α2,6-linked sialosides. Due to immune pressure, A/H3N2 influenza viruses have emerged with altered receptor specificities that bind α2,6-linked sialosides presented on extended N-acetyl-lactosamine (LacNAc) chains. Here, binding modes of such drifted hemagglutinin's (HAs) are examined by chemoenzymatic synthesis of N-glycans having 13C-labeled monosaccharides at strategic positions. The labeled glycans are employed in 2D STD-1H by 13C-HSQC NMR experiments to pinpoint which monosaccharides of the extended LacNAc chain engage with evolutionarily distinct HAs. The NMR data in combination with computation and mutagenesis demonstrate that mutations distal to the receptor binding domain of recent HAs create an extended binding site that accommodates with the extended LacNAc chain. A fluorine containing sialoside is used as NMR probe to derive relative binding affinities and confirms the contribution of the extended LacNAc chain for binding.

Evaluation of mango residues to produce hyaluronic acid by Streptococcus zooepidemicus.

Mango processing generates significant amounts of residues (35-65%) that may represent environmental problems owed to improper disposal. The use of mango byproducts as substrates to produce hyaluronic acid (HA) is an attractive alternative to reduce the cost of substrate. In this study, we evaluated the potential of hydrolyzates from mango peels and seeds to produce HA by Streptococcus equi. subsp. zooepidemicus. The physicochemical characterization of mango residues showed that the seeds contain a higher amount of holocellulose (cellulose and hemicellulose), which amounts 54.2% (w/w) whereas it only represents 15.5% (w/w) in the peels. Mango peels, however, are composed mainly of hot water-extractives (62% w/w, that include sucrose, fructose, glucose and organic acids). A higher concentration of monosaccharides (39.8 g/L) was obtained from the enzymatic hydrolysis (with Macerex) of peels as compared to seeds (24.8 g/L with Celuzyme). From mango peels, hydrolyzates were obtained 0.6 g/L HA, while 0.9 g/L HA were obtained with hydrolyzates from mango seeds. These results demonstrate that mango byproducts have the potential to be used for production of HA.

Low FODMAPs diet for functional abdominal pain disorders in children: critical review of current knowledge / Dieta com baixo teor de FODMAPs para distúrbios de dor abdominal funcional em crianças: revisão crítica do conhecimento atual

ABSTRACT Objective: This narrative review aimed to provide practitioners a synthesis of the current knowledge on the role of a low Fermentable Oligosaccharides Disaccharides Monosaccharides and Polyols diet in reducing symptoms associated with functional abdominal pain disorders in children. This review is focused on the pathophysiology, efficacy and criticism of low Fermentable Oligosaccharides Disaccharides Monosaccharides and Polyols diet in children. Sources: Cochrane Database, Pubmed and Embase were searched using specific terms for Fermentable Oligosaccharides Disaccharides Monosaccharides and Polyols diet interventions and functional abdominal pain disorders. Summary of the findings: In children, only one Randomized Control Trial and one open-label study reported positive results of low Fermentable Oligosaccharides Disaccharides Monosaccharides and Polyols diet; one Randomized Control Trial showed exacerbation of symptoms with fructans in children with Irritable Bowel Syndrome; no effect was found for the lactose-free diet whilst fructose-restricted diets were effective in 5/6 studies. Conclusions: In children there are few trials evaluating low Fermentable Oligosaccharides Disaccharides Monosaccharides and Polyols in functional abdominal pain disorders, with encouraging data on the therapeutic efficacy particularly of fructose-restricted diet. Additional efforts are still needed to fill this research gap and clarify the most efficient way for tailoring dietary restrictions based on the patient's tolerance and/or identification of potential biomarkers of low Fermentable Oligosaccharides Disaccharides Monosaccharides and Polyols efficacy, to maintain nutritional adequacy and to simplify the adherence to diet by labeling Fermentable Oligosaccharides Disaccharides Monosaccharides and Polyols content in commercial products.

RESUMO Objetivo: Nos últimos anos, foram feitos esforços consideráveis para esclarecer o papel da dieta com baixo teor de oligossacarídeos fermentáveis, dissacarídeos, monossacarídeos e polióis (FODMAPs) para o tratamento de distúrbios gastrintestinais funcionais (DGIFs). Esta revisão narrativa teve como objetivo fornecer aos profissionais uma síntese do conhecimento atual sobre o papel de uma dieta com baixo teor de FODMAPs (BFM) na redução dos sintomas associados a distúrbios funcionais de dor abdominal (DFDA) em crianças. Esta revisão está focada na fisiopatologia, eficácia e crítica da dieta BFM em crianças. Fontes: O banco de dados Cochrane, Pubmed e Embase foram pesquisados com o uso dos termos específicos para intervenções na dieta FODMAP e DFDA. Resumo dos achados: Em crianças, apenas um estudo controlado randomizado e um estudo aberto relataram resultados positivos da dieta BFM; um estudo controlado randomizado mostrou exacerbação dos sintomas com frutanos em crianças com síndrome do intestino irritável; nenhum efeito foi encontrado para a dieta livre de lactose, enquanto dietas com restrição de frutose foram eficazes em 5/6 estudos. Conclusões: Existem poucos estudos que avaliam BFM em DFDA em crianças, com dados encorajadores sobre a eficácia terapêutica, particularmente de dietas com restrição de frutose. Esforços adicionais ainda são necessários para preencher essa lacuna de pesquisa e esclarecer a maneira mais eficiente de adaptar as restrições dietéticas com base na tolerância do paciente e/ou identificação de biomarcadores potenciais de eficácia da BFM, para manter a adequação nutricional e simplificar a adesão à dieta, ao incluir informações sobre conteúdo de FODMAPs em rótulos de produtos comerciais.

Genotypic diversity of S. mutans in dental biofilm formed in situ under sugar stress exposure

In situ dental biofilm composition under sugar exposure is well known, but sugar effect on the genotypic diversity of S. mutans in dental biofilm has not been explored. This study evaluated S. mutans genotypic diversity in dental biofilm formed in situ under frequent exposure to sucrose and its monosaccharide constituents (glucose and fructose). Saliva of 7 volunteers was collected for isolation of S. mutans and the same volunteers wore intraoral palatal appliances, containing enamel slabs, which were submitted to the following treatments: distilled and deionized water (negative control), 10 percent glucose + 10 percent fructose (fermentable carbohydrates) solution or 20 percent sucrose (fermentable and EPS inductor) solution, 8x/day. After 3, 7 and 14 days, the biofilms were colleted and S. mutans colonies were isolated. Arbitrarily primed polymerase chain reaction (AP-PCR) of S. mutans showed that salivary genotypes were also detected in almost all biofilm samples, independently of the treatment, and seemed to reflect those genotypes present at higher proportion in biofilms. In addition to the salivary genotypes, others were found in biofilms but in lower proportions and were distinct among treatment. The data suggest that the in situ model seems to be useful to evaluate genotypic diversity of S. mutans, but, under the tested conditions, it was not possible to clearly show that specific genotypes were selected in the biofilm due to the stress induced by sucrose metabolism or simple fermentation of its monosaccharides.

A composição do biofilme dental in situ exposto a açúcares é bem conhecida, mas o efeito dos açúcares na diversidade genotípica de S. mutans no biofilme dental ainda não foi explorada. Este estudo avaliou a diversidade genotípica de S. mutans no biofilme dental formado in situ sob frequente exposição à sacarose e seus monossacarídeos constituintes (glicose e frutose). Primeiramente, saliva de voluntários foi coletada para isolamento de S. mutans e os mesmos voluntários usaram um dispositivo intraoral palatino, contendo blocos de esmalte, que foram submetidos 8x/dia aos seguintes tratamentos: água destilada e deionizada (controle negativo), solução de glicose 10 por cento + frutose 10 por cento (carboidratos fermentáveis) e solução de sacarose 20 por cento (fermentável e indutor de PEC). Após 3, 7 e 14 dias, os biofilmes foram coletados e colônias de S. mutans foram isoladas. A técnica de reação em cadeia de polimerase usando primers arbitrários (AP-PCR) demonstrou que o genótipo salivar foi detectado em quase todas as amostras de biofilme, independente do tratamento, e parece refletir aqueles genótipos presentes em maiores proporções no biofilme. Além do genótipo salivar, outros foram encontrados nos biofilmes, mas em uma menor proporção e foram distintos entre os tratamentos. Os dados sugerem que o modelo in situ é útil para a avaliação da diversidade genotípica de S. mutans. Porém, nas condições do presente estudo, não foi possível demonstrar que genótipos específicos foram detectados no biofilme devido ao estresse induzido pelo metabolismo da sacarose ou fermentação de seus monossacarídeos.

Chronic lactose intake modifies the gastric emptying of monosaccharides but not of disaccharides in weanling rats

Ninety-six weanling male Wistar rats were fed for four weeks one of two different chows: a normal rat chow containing 55.5 percent (w/w) starch (control group, N = 48) or a rat chow in which starch was partially replacced by lactose, in such a way that the experimental group (N = 48) received 35.3 per cent (w/w) starch and 20 percent (w/w) lactose. The gastric emptying of fluid was then studied by measuring the gastric retention of four test meals containing lactose (5 percent or 10 percent, w/v) or glucose + galactose (5 percent or 10 percent, w/v). Homogenates of the small intestine were assayed for lactase activity. The gastric retention values were obtained 15 min after orogastric infusion of the liquid meals. The median values for gastric retention of the 5 percent lactose solutions were 37.7 percent for the control group and 37.0 percent for the experimental group (P>0.02) For the 10 percent lactose solution the median values were 51.2 percent and 47.9 percent (P>0.02) for the control and experimental groups, respectively. However, for the 2.5 percent glucose + 2.5 percent galactose meal the median gastric retention was lower (P<0.02) in the group fed a lactose-enriched chow (38.5 percent) than in the control group (41.6 percent). For the 5 percent glucose + 5 percent galactose solution the median values were not statistically different between groups, 65.0 percent for the control group and 58.8 percent for the experimental group. The median values of the specific lactase activity in the small intestine homogenate was 0.74 U/g in the control group and 0.91 U/g in the experimental group. These values were not statistically different (P>0.05). These results suggest that the prolonged ingestion of lactose by young adult rats changes the gastric emptying of a solution containing 5 percent monosaccharides. This adaptation may reflect the desensitization of intestinal nutrient receptors, possibly by an osmotic effect of lactose present in the chow.

Estudo comparativo do esvaziamento gástrico de dissacarídios e de seus respectivos monossacarídios em ratos com deficiência ontogênica de lactase / Comparative study of the gastric emptying of disaccharides and their respective monosaccharides in rats with ontogenic lactase deficiency

Com a finalidade de avaliar o esvaziamento gástrico de dissacarídios e monossacarídios, foram empregados no estudo 64 ratos Wistar, machos, pesando, em média, 180g. com idade de 8-10 semanas de vida, divididos em grupos de oito animais cada. Os grupos foram assim constituídos: grupo maltose, grupo sacarose, grupo lactose e grupo lactulose e os correspondentes grupos de monossacarídios: grupos glicose, grupo frutose + glicose, grupo galactose + glicose e grupo galactose + frutose. Cada animal de cada grupo recebeu, por via orogástrica, após jejum alimentar de 20h, refeiçäo de prova constituída de uma soluçäo a 10% (p/v) de açucar, acrescida de fenol vermelho na concentraçäo de 6mg/dl, como marcador. O volume empregado foi de 2ml/100g de peso do animal. A retençäo gástrica foi determinada aos 10 min após infusäo da refeiçäo de prova, e expressa em porcentagem. Os resultados (X ñ SE) das retençöes gástricas (%) da sacarose (35,0ñ 1,8), lactose (30,4 ñ 1,5) e lactulose (29,5 ñ 1,6 foram significativamente menores (teste t, alfa = 0,05) que os observados com os respectivos monossacarídios, ou seja, glicose + frutose (46,9 ñ 2,6), glicose + galactose (48,3 ñ 2,4), galactose + frutose (43,5 ñ 1,5). Näo foi observada diferença da retençäo gástrica de maltose (49,0 ñ 4,7), quando comparada com a glicose (53,0 ñ 3,0). Entre os dissacarídios, a análise estatístoca (análise de variância seguida do teste de Tukey, alfa = 0,05) dos resultados näo mostrou diferenças na retençäo gástrica de sacarose, lactose e lactulose. A retençäo gástrica da maltose foi significativamente maior em relaçäo aos outros dissacarídios. Näo foram observadas diferenças significativas na retençäo gástrica dos monossacarídios. Estas observaçöes indicam que a menor concentraçäo de dissacaridases (sacarase, lactase) ou aausência de uma enzima específica (lactulase), na mucosa do intestino delgado, induz um esvaziamento gástrico mais rápido dos respectivos dissacarídios. O fenômeno pode ser explicado pela falta de estímulo dos receptores que modulam o esvaziamento gástrico, lcoalizados mais profundamente em relaçäo às enzimas