Intestinal fructose transport and malabsorption in humans

Intestinal fructose transporters GLUT5 and GLUT2 in children and adolescents with obesity and metabolic disorders

PURPOSE

The excessive fructose intake including high-fructose corn syrup (HFCS) may be responsible for increase of obesity occurrence. This study was designed to find potential differences in duodenal fructose transporters on mRNA and protein levels between obese and normal weight children and adolescents.

MATERIALS/METHODS

We performed a cross-sectional study on a group of 106 hospitalized patients aged 12 to 18. Glucose transporter 2 (GLUT2) and glucose transporter 5 (GLUT5) mRNA as well as protein levels (ELISA and Western blot methods) were assessed in duodenal mucosa biopsies of the patients categorized as obese or normal weight. Additionally, the expression of the aforementioned transporters was analyzed in patients based on the presence of insulin resistance (IR) and metabolic syndrome (MS).

RESULTS

In children with obesity, increased duodenal protein levels of GLUT5 (Relative protein GLUT5 expression/ACTB) (0.027 ​± ​0.009 vs. 0.011 ​± ​0.006, p ​< ​0.05) but not GLUT2 as compared with the normal weight group, were revealed. No significant differences in duodenal relative GLUT2 and GLUT5 genes expression between the studied groups were found. There was no relationship between the presence of IR or MS and intestinal mRNA GLUT2 and GLUT5 as well as GLUT2 protein expression.

CONCLUSION

The upregulation of the duodenal GLUT5 may contribute to obesity occurrence in children and adolescents.

Regulation of Fructose Metabolism in Nonalcoholic Fatty Liver Disease

Elevations in fructose consumption have been reported to contribute significantly to an increased incidence of obesity and metabolic diseases in industrial countries. Mechanistically, a high fructose intake leads to the dysregulation of glucose, triglyceride, and cholesterol metabolism in the liver, and causes elevations in inflammation and drives the progression of nonalcoholic fatty liver disease (NAFLD). A high fructose consumption is considered to be toxic to the body, and there are ongoing measures to develop pharmaceutical therapies targeting fructose metabolism. Although a large amount of work has summarized the effects fructose exposure within the intestine, liver, and kidney, there remains a gap in our knowledge regarding how fructose both indirectly and directly influences immune cell recruitment, activation, and function in metabolic tissues, which are essential to tissue and systemic inflammation. The most recent literature demonstrates that direct fructose exposure regulates oxidative metabolism in macrophages, leading to inflammation. The present review highlights (1) the mechanisms by which fructose metabolism impacts crosstalk between tissues, nonparenchymal cells, microbes, and immune cells; (2) the direct impact of fructose on immune cell metabolism and function; and (3) therapeutic targets of fructose metabolism to treat NAFLD. In addition, the review highlights how fructose disrupts liver tissue homeostasis and identifies new therapeutic targets for treating NAFLD and obesity.

Internalizing psychological symptoms in children and adolescents with fructose malabsorption

Introduction

Due to an inhibited tryptophan resorption, patients with fructose malabsorption are expected to experience decreased serotonin synthesis. A deficiency of serotonin may cause internalizing mental disorders like depression and anxiety, and a fructose-oriented eating behavior may affect these symptoms.

Methods

The parents of 24 children and adolescents with a currently diagnosed fructose malabsorption aged 4;00-13;02 years (M = 8.10, SD = 2.05), the parents of 12 patients with a currently confirmed combination of fructose and lactose malabsorption aged 4;00-12;11 years (M = 8.07, SD = 2.11) and the parents of a comparative sample of 19 healthy participants aged 5;00 to 17;07 years (M = 9.06, SD = 3.04) were interviewed. The interviews were conducted using a screening questionnaire of the German "Diagnostic System of Mental Disorders in children and adolescents based on the ICD-10 and DSM-5 DISYPS-III" and a self-developed questionnaire on eating, leisure and sleeping behavior.

Results

On standardized scales parents of children with fructose malabsorption reported higher levels of Depression compared to symptoms of Attention-Deficit/Hyperactivity Disorders (ADHD) and Oppositional Defiant and Conduct Disorders (ODD/CD). Compared to healthy controls, for patients with fructose malabsorption, higher symptom levels of Depression and Anxiety were reported. With regard to eating behavior, within the group with a combination of fructose and lactose malabsorption, a strong positive association between an increased fruit sugar consumption and higher levels of Anxiety and Obsessive-Compulsive Disorders/Tics were found.

Discussion

These results suggest a close association between fructose malabsorption and elevated internalizing psychological symptoms in children and adolescents.Clinical trial registration:https://drks.de/search/en/trial/DRKS00031047, DRKS-ID [DRKS00031047].

Western diet components that increase intestinal permeability with implications on health

Intestinal permeability is a physiological property that allows necessary molecules to enter the organism. This property is regulated by tight junction proteins located between intestinal epithelial cells. However, various factors can increase intestinal permeability (IIP), including diet. Specific components in the Western diet (WD), such as monosaccharides, fat, gluten, salt, alcohol, and additives, can affect the tight junctions between enterocytes, leading to increased permeability. This review explains how these components promote IIP and outlines their potential implications for health. In addition, we describe how a reduction in WD consumption may help improve dietary treatment of diseases associated with IIP. Research has shown that some of these components can cause changes in the gut microbiota, leading to dysbiosis, which can promote greater intestinal permeability and displacement of endotoxins into the bloodstream. These endotoxins include lipopolysaccharides derived from gram-negative bacteria, and their presence has been associated with various diseases, such as autoimmune, neurological, and metabolic diseases like diabetes and cardiovascular disease. Therefore, nutrition professionals should promote the reduction of WD consumption and consider the inclusion of healthy diet components as part of the nutritional treatment for diseases associated with increased intestinal permeability.

The low FODMAP diet in clinical practice: where are we and what are the long-term considerations?

A diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) improves functional bowel symptoms and is a second-line dietary management strategy for the treatment of irritable bowel syndrome (IBS). The diet is complex and involves three stages: restriction, reintroduction and personalisation and clinical effectiveness is achieved with dietitian-led education; however, this is not always available. The aim of this review is to provide an update on the evidence for using the low FODMAP diet, with a focus on the impact of FODMAP restriction and reintroduction considering long-term management of IBS in a clinical setting. Randomised controlled trials have assessed symptom response, quality of life, dietary intake and changes to the gut microbiota during FODMAP restriction. Systematic reviews and meta-analyses consistently report that FODMAP restriction has a better symptom response compared with control diets and a network analysis reports the low FODMAP diet is superior to other dietary treatments for IBS. Research focused on FODMAP reintroduction and personalisation is limited and of lower quality, however common dietary triggers include wheat, onion, garlic, pulses and milk. Dietitian-led delivery of the low FODMAP diet is not always available and alternative education delivery methods, e.g. webinars, apps and leaflets, are available but remove the personalised approach and may be less acceptable to patients and may introduce safety concerns in terms of nutritional adequacy. Predicting response to the low FODMAP diet using symptom severity or a biomarker is of great interest. More evidence on less restrictive approaches and non-dietitian-led education delivery methods are needed.

Getting the BS out of Irritable Bowel Syndrome with Diarrhea (IBS-D): Let's Make a Diagnosis

PURPOSE OF REVIEW

Irritable bowel syndrome with diarrhea (IBS-D) is diagnosed when chronic symptoms of abdominal pain accompany loose stools, and alarm features, such as fever, anemia, rectal bleeding, and weight loss are absent. This combination of symptoms makes structural disorders, such as inflammatory bowel disease or cancer, unlikely, but does not exclude other conditions that cause these symptoms. The question is whether making a "positive diagnosis" of IBS-D based on symptoms alone and instituting therapy based on that diagnosis still makes sense.

RECENT FINDINGS

Clinical observations suggest that at least two-thirds of cases of IBS-D can be explained by three mechanisms: a) food intolerances (~ 30-40%), b) bile acid diarrhea (~ 20-30%), and c) disturbed microbial flora (~ 15-20%). Other conditions that are less frequent but can cause IBS symptoms or be confused with IBS include: celiac disease, microscopic colitis, mastocytosis/mast cell activation, and drug side-effects. Many cases of IBS-D have a discoverable, underlying cause that can direct therapy more efficiently.

Targeting the Adipose Tissue-Liver-Gut Microbiota Crosstalk to Cure MASLD

The gut microbiota is a complex system, playing a peculiar role in regulating innate and systemic immunity. Increasing evidence links dysfunctional gut microbiota to metabolic dysfunction-associated steatotic liver disease (MASLD) due to the activation of multiple pathways in the gut and in the liver, including those mediated by Toll-like receptors (TLRs), that sustain hepatic inflammation. Thus, many efforts have been made to unravel the role of microbiota-associated dysfunction in MASLD, with the final aim of finding novel strategies to improve liver steatosis and function. Moreover, recent evidence underlines the role of adipose tissue in sustaining hepatic inflammation during MASLD development. In this review, we focus on the recently discovered strategies proposed to improve the alteration of gut microbiota observed in MASLD patients, with a particular insight into those known to modulate gut microbiota-associated dysfunction and to affect the complex crosstalk between the gut, the adipose tissue, and the liver.

Microbiome and Diet in Colon Cancer Development and Treatment

ABSTRACT

Diet plays critical roles in defining our immune responses, microbiome, and progression of human diseases. With recent progress in sequencing and bioinformatic techniques, increasing evidence indicates the importance of diet-microbial interactions in cancer development and therapeutic outcome. Here, we focus on the epidemiological studies on diet-bacterial interactions in the colon cancer. We also review the progress of mechanistic studies using the experimental models. Finally, we discuss the limits and future directions in the research of microbiome and diet in cancer development and therapeutic outcome. Now, it is clear that microbes can influence the efficacy of cancer therapies. These research results open new possibilities for the diagnosis, prevention, and treatment of cancer. However, there are still big gaps to apply these new findings to the clinical practice.

Fructose malabsorption in ChREBP-deficient mice disrupts the small intestine immune microenvironment and leads to diarrhea-dominant bowel habit changes

BACKGROUND

The mechanism by which incompletely absorbed fructose causes gastrointestinal symptoms is not fully understood. In this study, we investigated the immunological mechanisms of bowel habit changes associated with fructose malabsorption by examining Chrebp-knockout mice exhibiting defective fructose absorption.

METHODS

Mice were fed a high-fructose diet (HFrD), and stool parameters were monitored. The gene expression in the small intestine was analyzed by RNA sequencing. Intestinal immune responses were assessed. The microbiota composition was determined by 16S rRNA profiling. Antibiotics were used to assess the relevance of microbes for HFrD-induced bowel habit changes.

RESULTS

Chrebp-knockout (KO) mice fed HFrD showed diarrhea. Small-intestine samples from HFrD-fed Chrebp-KO mice revealed differentially expressed genes involved in the immune pathways, including IgA production. The number of IgA-producing cells in the small intestine decreased in HFrD-fed Chrebp-KO mice. These mice showed signs of increased intestinal permeability. Chrebp-KO mice fed a control diet showed intestinal bacterial imbalance, which the HFrD exaggerated. Bacterial reduction improved diarrhea-associated stool parameters and restored the decreased IgA synthesis induced in HFrD-fed Chrebp-KO mice.

CONCLUSIONS

The collective data indicate that gut microbiome imbalance and disrupting homeostatic intestinal immune responses account for the development of gastrointestinal symptoms induced by fructose malabsorption.

Short-term fructose feeding alters tissue metabolic pathways by modulating microRNAs expression both in young and adult rats

Dietary high fructose (HFrD) is known as a metabolic disruptor contributing to the development of obesity, diabetes, and dyslipidemia. Children are more sensitive to sugar than adults due to the distinct metabolic profile, therefore it is especially relevant to study the metabolic alterations induced by HFrD and the mechanisms underlying such changes in animal models of different ages. Emerging research suggests the fundamental role of epigenetic factors such as microRNAs (miRNAs) in metabolic tissue injury. In this perspective, the aim of the present study was to investigate the involvement of miR-122-5p, miR-34a-5p, and miR-125b-5p examining the effects induced by fructose overconsumption and to evaluate whether a differential miRNA regulation exists between young and adult animals. We used young rats (30 days) and adult rats (90 days) fed on HFrD for a short period (2 weeks) as animal models. The results indicate that both young and adult rats fed on HFrD exhibit an increase in systemic oxidative stress, the establishment of an inflammatory state, and metabolic perturbations involving the relevant miRNAs and their axes. In the skeletal muscle of adult rats, HFrD impair insulin sensitivity and triglyceride accumulation affecting the miR-122-5p/PTP1B/P-IRS-1(Tyr612) axis. In liver and skeletal muscle, HFrD acts on miR-34a-5p/SIRT-1: AMPK pathway resulting in a decrease of fat oxidation and an increase in fat synthesis. In addition, liver and skeletal muscle of young and adult rats exhibit an imbalance in antioxidant enzyme. Finally, HFrD modulates miR-125b-5p expression levels in liver and white adipose tissue determining modifications in de novo lipogenesis. Therefore, miRNA modulation displays a specific tissue trend indicative of a regulatory network that contributes in targeting genes of various pathways, subsequently yielding extensive effects on cell metabolism.

Plasma metabolomics for the assessment of the progression of non-small cell lung cancer

Objectives

Non-small cell lung cancer (NSCLC) is a leading type of lung cancer with a high mortality rate worldwide. Although many procedures for the diagnosis and prognosis assessment of lung cancer exist, they are often laborious, expensive, and invasive. This study aimed to develop an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC–MS/MS)-based analysis method for the plasma biomarkers of NSCLC with the potential to indicate the stages and progression of this malignancy conveniently and reliably.

Methods

A total of 53 patients with NSCLC in early stages (I–III) and advanced stage (IV) were classified into the early and advanced groups based on the tumor node metastasis staging system. A comprehensive metabolomic analysis of plasma from patients with NSCLC was performed via UPLC–MS/MS. Principal component analysis and partial least squares–discriminant analysis were conducted for statistical analysis. Potential biomarkers were evaluated and screened through receiver operating characteristic analyses and correlation analysis. Main differential metabolic pathways were also identified by utilizing metaboanalyst.

Results

A total of 129 differential metabolites were detected in accordance with the criteria of VIP ≥ 1 and a P-value of ≤ 0.05. The receiver operating characteristic curves indicated that 11 of these metabolites have the potential to be promising markers of disease progression. Apparent correlated metabolites were also filtered out. Furthermore, the 11 most predominant metabolic pathways with alterations involved in NSCLC were identified.

Conclusion

Our study focused on the plasma metabolomic changes in patients with NSCLC. These changes may be used for the prediction of the stage and progression of NSCLC. Moreover, we discussed the metabolic pathways wherein the altered metabolites were mainly enriched.

Allulose in human diet: the knowns and the unknowns

D-Allulose, also referred to as psicose, is a C3-epimer of D-fructose used as a sugar substitute in low energy products. It can be formed naturally during processing of food and drinks containing sucrose and fructose or is prepared by chemical synthesis or via enzymatic treatment with epimerases from fructose. Estimated intakes via Western style diets including sweetened beverages are below 500 mg per d but, when used as a sugar replacement, intake may reach 10 to 30 g per d depending on the food consumed. Due to its structural similarity with fructose, allulose uses the same transport and distribution pathways. But in contrast to fructose, the human genome does not encode for enzymes that are able to metabolise allulose leading to an almost complete renal excretion of the absorbed dose and near-to-zero energetic yield. However, in vitro studies have shown that certain bacteria such as Klebsiella pneumonia are able to utilise allulose as a substrate. This finding has been a subject of concern, since Klebsiella pneumoniae represents an opportunistic human pathogen. It therefore raised the question of whether a high dietary intake of allulose may cause an undesirable growth advantage for potentially harmful bacteria at mucosal sites such as the intestine or at systemic sites following invasive infection. In this brief review, we discuss the current state of science on these issues and define the research needs to better understand the fate of allulose and its metabolic and microbiological effects when ingested as a sugar substitute.

Carbohydrate Maldigestion and Intolerance

This review summarizes dietary carbohydrate intolerance conditions and recent advances on the possible role of carbohydrate maldigestion and dietary outcomes in patients with functional bowel disease. When malabsorbed carbohydrates reach the colon, they are fermented by colonic bacteria, with the production of short-chain fatty acids and gas lowering colonic pH. The appearance of diarrhoea or symptoms of flatulence depends in part on the balance between the production and elimination of these fermentation products. Different studies have shown that there are no differences in the frequency of sugar malabsorption between patients with irritable bowel disease (IBS) and healthy controls; however, the severity of symptoms after a sugar challenge is higher in patients than in controls. A diet low in 'Fermentable, Oligo-Di- and Monosaccharides and Polyols' (FODMAPs) is an effective treatment for global symptoms and abdominal pain in IBS, but its implementation should be supervised by a trained dietitian. A 'bottom-up' approach to the low-FODMAP diet has been suggested to avoid an alteration of gut microbiota and nutritional status. Two approaches have been suggested in this regard: starting with only certain subgroups of the low-FODMAP diet based on dietary history or with a gluten-free diet.

Gene variants of the SLC2A5 gene encoding GLUT5, the major fructose transporter, do not contribute to clinical presentation of acquired fructose malabsorption

Background

While role of ALDOB-related gene variants for hereditary fructose intolerance is well established, contribution of gene variants for acquired fructose malabsorption (e.g. SLC2A5, GLUT5) is not well understood.

Methods

Patients referred to fructose breath test were further selected to identify those having acquired fructose malabsorption. Molecular analysis of genomic DNA included (I) exclusion of 3 main ALDOB gene variants causing hereditary fructose intolerance and (II) sequencing analysis of SLC2A5 gene comprising complete coding region, at least 20 bp of adjacent intronic regions and 700 bp of proximal promoter.

Results

Among 494 patients, 35 individuals with acquired fructose malabsorption were identified based on pathological fructose-breath test and normal lactose-breath test. Thirty four of them (97%) had negative tissue anti-transglutaminase and/or deamidated gliadin antibodies in their medical records. Molecular analysis of SLC2A5 gene of all 35 subjects identified 5 frequent and 5 singular gene variants mostly in noncoding regions (promoter and intron). Allele frequencies of gene variants were similar to those reported in public databases strongly implying that none of them was associated with acquired fructose malabsorption.

Conclusions

Gene variants of coding exons, adjacent intronic regions and proximal promoter region of SLC2A5 gene are unlikely to contribute to genetic predisposition of acquired fructose malabsorption.

A review on the fruit components affecting uric acid level and their underlying mechanisms

Uric acid (UA) is produced in the liver and excreted through the kidneys and intestines. If UA is overproduced or its excretion reduces, the concentration of UA increases, leading to hyperuricemia and gout. The high concentration of UA is also related to cardiovascular disease, hypertension, obesity, and other diseases. Fruits are healthy foods. However, fruits contain fructose and small amounts of purine, and the product of their metabolism is UA. Therefore, theoretically, eating fruits will increase the concentration of serum UA. Fruit components are numerous, and their effects on serum UA are complex. According to the current research, fructose, purine, polyphenols, vitamin C, dietary fiber, and minerals present in fruits influence serum UA concentrations. In addition to the UA synthesized by fructose and purine metabolism, the mechanisms by which other components affect the concentration of serum UA can be summarized as follows: (a) inhibiting xanthine oxidase; (b) reducing reabsorption of UA; and (c) improving the excretion of UA. In this review, we comprehensively discussed the fruit components that affect serum UA concentrations, and explained their mechanisms for the first time, which references for patients with hyperuricemia to take fruits. PRACTICAL APPLICATIONS: With the rising prevalence, hyperuricemia and gout have become public health problems that endanger our daily life. The key to the treatment of hyperuricemia is to control the level of serum UA within the normal range. Fruits are healthy foods. However, fruit components are numerous, and their effects on serum UA are complex. According to the current research, fructose, purine, polyphenols, vitamin C, dietary fiber, and minerals present in fruits influence serum UA concentrations. In this review, we comprehensively discussed the fruit components that affect serum UA concentrations. We also explained their mechanisms, which references for patients with hyperuricemia to take fruits.

Excess dietary fructose does not alter gut microbiota or permeability in humans: A pilot randomized controlled study

Introduction:

Non-alcoholic fatty liver disease (NAFLD) is an increasing cause of chronic liver disease that accompanies obesity and the metabolic syndrome. Excess fructose consumption can initiate or exacerbate NAFLD in part due to a consequence of impaired hepatic fructose metabolism. Preclinical data emphasized that fructose-induced altered gut microbiome, increased gut permeability, and endotoxemia play an important role in NAFLD, but human studies are sparse. The present study aimed to determine if two weeks of excess fructose consumption significantly alters gut microbiota or permeability in humans.

Methods:

We performed a pilot double-blind, cross-over, metabolic unit study in 10 subjects with obesity (body mass index [BMI] 30–40 mg/kg/m²). Each arm provided 75 grams of either fructose or glucose added to subjects’ individual diets for 14 days, substituted isocalorically for complex carbohydrates, with a 19-day wash-out period between arms. Total fructose intake provided in the fructose arm of the study totaled a mean of 20.1% of calories. Outcome measures included fecal microbiota distribution, fecal metabolites, intestinal permeability, markers of endotoxemia, and plasma metabolites.

Results:

Routine blood, uric acid, liver function, and lipid measurements were unaffected by the fructose intervention. The fecal microbiome (including Akkermansia muciniphilia), fecal metabolites, gut permeability, indices of endotoxemia, gut damage or inflammation, and plasma metabolites were essentially unchanged by either intervention.

Conclusions:

In contrast to rodent preclinical findings, excess fructose did not cause changes in the gut microbiome, metabolome, and permeability as well as endotoxemia in humans with obesity fed fructose for 14 days in amounts known to enhance NAFLD.

Fructose and the Liver

Chronic diseases represent a major challenge in world health. Metabolic syndrome is a constellation of disturbances affecting several organs, and it has been proposed to be a liver-centered condition. Fructose overconsumption may result in insulin resistance, oxidative stress, inflammation, elevated uric acid levels, increased blood pressure, and increased triglyceride concentrations in both the blood and liver. Non-alcoholic fatty liver disease (NAFLD) is a term widely used to describe excessive fatty infiltration in the liver in the absence of alcohol, autoimmune disorders, or viral hepatitis; it is attributed to obesity, high sugar and fat consumption, and sedentarism. If untreated, NAFLD can progress to nonalcoholic steatohepatitis (NASH), characterized by inflammation and mild fibrosis in addition to fat infiltration and, eventually, advanced scar tissue deposition, cirrhosis, and finally liver cancer, which constitutes the culmination of the disease. Notably, fructose is recognized as a major mediator of NAFLD, as a significant correlation between fructose intake and the degree of inflammation and fibrosis has been found in preclinical and clinical studies. Moreover, fructose is a risk factor for liver cancer development. Interestingly, fructose induces a number of proinflammatory, fibrogenic, and oncogenic signaling pathways that explain its deleterious effects in the body, especially in the liver.

Fructose and metabolic diseases: too much to be good

ABSTRACT

Excessive consumption of fructose, the sweetest of all naturally occurring carbohydrates, has been linked to worldwide epidemics of metabolic diseases in humans, and it is considered an independent risk factor for cardiovascular diseases. We provide an overview about the features of fructose metabolism, as well as potential mechanisms by which excessive fructose intake is associated with the pathogenesis of metabolic diseases both in humans and rodents. To accomplish this aim, we focus on illuminating the cellular and molecular mechanisms of fructose metabolism as well as its signaling effects on metabolic and cardiovascular homeostasis in health and disease, highlighting the role of carbohydrate-responsive element-binding protein in regulating fructose metabolism.

Dietary fructose as a model to explore the influence of peripheral metabolism on brain function and plasticity

High consumption of fructose has paralleled an explosion in metabolic disorders including obesity and type 2 diabetes. Even more problematic, sustained consumption of fructose is perceived as a threat for brain function and development of neurological disorders. The action of fructose on peripheral organs is an excellent model to understand how systemic physiology impacts the brain. Given the recognized action of fructose on liver metabolism, here we discuss mechanisms by which fructose can impact the brain by interacting with liver and other organs. The interaction between peripheral and central mechanisms is a suitable target to reduce the pathophysiological consequences of neurological disorders.

Inulin-grown Faecalibacterium prausnitzii cross-feeds fructose to the human intestinal epithelium

Many chronic diseases are associated with decreased abundance of the gut commensal Faecalibacterium prausnitzii. This strict anaerobe can grow on dietary fibers, e.g., prebiotics, and produce high levels of butyrate, often associated to epithelial metabolism and health. However, little is known about other F. prausnitzii metabolites that may affect the colonic epithelium. Here, we analyzed prebiotic cross-feeding between F. prausnitzii and intestinal epithelial (Caco-2) cells in a "Human-oxygen Bacteria-anaerobic" coculture system. Inulin-grown F. prausnitzii enhanced Caco-2 viability and suppressed inflammation- and oxidative stress-marker expression. Inulin-grown F. prausnitzii produced excess butyrate and fructose, but only fructose efficiently promoted Caco-2 growth. Finally, fecal microbial taxonomy analysis (16S sequencing) from healthy volunteers (n = 255) showed the strongest positive correlation for F. prausnitzii abundance and stool fructose levels. We show that fructose, produced and accumulated in a fiber-rich colonic environment, supports colonic epithelium growth, while butyrate does not.

Role of Diet in Diarrhea-predominant Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a chronic condition characterized by abdominal pain associated with altered bowel habits. Patients with IBS often complain of food-related gastrointestinal symptoms. Specifically, those with diarrhea-predominant IBS report a significantly higher effect on quality on life because of food avoidance compared with those with other IBS subtypes. Physicians and patients often use dietary therapies to mitigate IBS symptoms. In the last 10 years, several dietary interventions such as a gluten-free diet, a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diets have been studied in several studies. This review summarizes the current literature on the role of diets such as gluten-free diet, low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet, and other carbohydrate malabsorption in the pathophysiology and symptom management in patients with diarrhea-predominant IBS.

Sweet but Bitter: Focus on Fructose Impact on Brain Function in Rodent Models

Fructose consumption has drastically increased during the last decades due to the extensive commercial use of high-fructose corn syrup as a sweetener for beverages, snacks and baked goods. Fructose overconsumption is known to induce obesity, dyslipidemia, insulin resistance and inflammation, and its metabolism is considered partially responsible for its role in several metabolic diseases. Indeed, the primary metabolites and by-products of gut and hepatic fructolysis may impair the functions of extrahepatic tissues and organs. However, fructose itself causes an adenosine triphosphate (ATP) depletion that triggers inflammation and oxidative stress. Many studies have dealt with the effects of this sugar on various organs, while the impact of fructose on brain function is, to date, less explored, despite the relevance of this issue. Notably, fructose transporters and fructose metabolizing enzymes are present in brain cells. In addition, it has emerged that fructose consumption, even in the short term, can adversely influence brain health by promoting neuroinflammation, brain mitochondrial dysfunction and oxidative stress, as well as insulin resistance. Fructose influence on synaptic plasticity and cognition, with a major impact on critical regions for learning and memory, was also reported. In this review, we discuss emerging data about fructose effects on brain health in rodent models, with special reference to the regulation of food intake, inflammation, mitochondrial function and oxidative stress, insulin signaling and cognitive function.

Effect of chlorogenic acid on alleviating inflammation and apoptosis of IPEC-J2 cells induced by deoxyniyalenol

Deoxynivalenol (DON) is extensively detected in many kinds of foods and feeds to harm human and animal health. This research aims to investigate the effect of chlorogenic acid (CGA) on alleviating inflammation and apoptosis of swine jejunal epithelial cells (IPEC-J2) triggered by DON. The results demonstrated that cell viability was decreased when DON concentrations increased or incubation time expanded. The pretreatment with CGA (40 μg/mL) for 1 h increased cell viability, decreased lactate dehydrogenase (LDH) release and apoptosis in cells triggered by DON at 0.5 μg/mL for 6 h, compared with the DON alone-treated cells. Moreover, the mRNA abundances of IL-8, IL-6, TNF-α, COX-2, caspase-3, Bax and ASCT2 genes, and protein expressions of COX-2, Bax and ASCT2 were significantly down-regulated; while the mRNA abundances of ZO-1, claudin-1, occludin, PePT1 and GLUT2 genes, and protein expressions of ZO-1, claudin-1 and PePT1 were significantly up-regulated in the CGA + DON group, compared with the DON alone group. This study indicated that CGA pretreatment alleviated cytotoxicity, inflammation and apoptosis in DON-triggered IPEC-J2 cells, and protected intestinal cell integrity from DON damages.

Dietary Carbohydrates and Lipids in the Pathogenesis of Leaky Gut Syndrome: An Overview

This review summarizes the recent knowledge on the effects of dietary carbohydrates and lipids on the pathophysiology of leaky gut syndrome (LGS). Alterations in intestinal barrier permeability may lead to serious gastrointestinal (GI) disorders. LGS is caused by intestinal hyperpermeability due to changes in the expression levels and functioning of tight junctions. The influence of dietary habits on intestinal physiology is clearly visible in incidence rates of intestinal diseases in industrial and developing countries. Diseases which are linked to intestinal hyperpermeability tend to localize to Westernized countries, where a diet rich in fats and refined carbohydrates predominates. Several studies suggest that fructose is one of the key carbohydrates involved in the regulation of the intestinal permeability and its overuse may cause harmful effects, such as tight junction protein dysfunction. On the other hand, short chain fatty acids (mainly butyrate) at appropriate concentrations may lead to the reduction of intestinal permeability, which is beneficial in LGS. However, long chain fatty acids, including n-3 and n-6 polyunsaturated fatty acids have unclear properties. Some of those behave as components untightening and tightening the intestinal membrane.

Triose Kinase Controls the Lipogenic Potential of Fructose and Dietary Tolerance

The surge in fructose consumption is a major factor behind the rapid rise of nonalcoholic fatty liver disease in modern society. Through flux and genetic analyses, we demonstrate that fructose is catabolized at a much higher rate than glucose, and triose kinase (TK) couples fructolysis with lipogenesis metabolically and transcriptionally. In the absence of TK, fructose oxidation is accelerated through the activation of aldehyde dehydrogenase (ALDH) and serine biosynthesis, accompanied by increased oxidative stress and fructose aversion. TK is also required by the endogenous fructolysis pathway to drive lipogenesis and hepatic triglyceride accumulation under high-fat diet and leptin-deficient conditions. Intriguingly, a nonsynonymous TK allele (rs2260655_A) segregated during human migration out of Africa behaves as TK null for its inability to rescue fructose toxicity and increase hepatic triglyceride accumulation. Therefore, we posit TK as a metabolic switch controlling the lipogenic potential of fructose and its dietary tolerance.

Transporter-Targeted Nano-Sized Vehicles for Enhanced and Site-Specific Drug Delivery

Nano-devices are recognized as increasingly attractive to deliver therapeutics to target cells. The specificity of this approach can be improved by modifying the surface of the delivery vehicles such that they are recognized by the target cells. In the past, cell-surface receptors were exploited for this purpose, but plasma membrane transporters also hold similar potential. Selective transporters are often highly expressed in biological barriers (e.g., intestinal barrier, blood-brain barrier, and blood-retinal barrier) in a site-specific manner, and play a key role in the vectorial transfer of nutrients. Similarly, selective transporters are also overexpressed in the plasma membrane of specific cell types under pathological states to meet the biological needs demanded by such conditions. Nano-drug delivery systems could be strategically modified to make them recognizable by these transporters to enhance the transfer of drugs across the biological barriers or to selectively expose specific cell types to therapeutic drugs. Here, we provide a comprehensive review and detailed evaluation of the recent advances in the field of transporter-targeted nano-drug delivery systems. We specifically focus on areas related to intestinal absorption, transfer across blood-brain barrier, tumor-cell selective targeting, ocular drug delivery, identification of the transporters appropriate for this purpose, and details of the rationale for the approach.

Dietary Advanced Glycation Endproducts and the Gastrointestinal Tract

The prevalence of inflammatory bowel diseases (IBD) is increasing in the world. The introduction of the Western diet has been suggested as a potential explanation of increased prevalence. The Western diet includes highly processed food products, and often include thermal treatment. During thermal treatment, the Maillard reaction can occur, leading to the formation of dietary advanced glycation endproducts (dAGEs). In this review, different biological effects of dAGEs are discussed, including their digestion, absorption, formation, and degradation in the gastrointestinal tract, with an emphasis on their pro-inflammatory effects. In addition, potential mechanisms in the inflammatory effects of dAGEs are discussed. This review also specifically elaborates on the involvement of the effects of dAGEs in IBD and focuses on evidence regarding the involvement of dAGEs in the symptoms of IBD. Finally, knowledge gaps that still need to be filled are identified.

Considering histamine in functional gastrointestinal disorders

In westernized countries, adverse reactions to ingested foods are reported to affect up to 20% of the population. Functional, nonspecific, non-allergic gastrointestinal complaints are mainly due to the intolerance/malabsorption of carbohydrates (lactose and fructose), proteins (gluten), and biogenic amines (histamine). Food intolerance/malabsorption is defined by one or several of the above mentioned food components not being degraded and/or absorbed properly within the gastrointestinal tract. Food intolerance/malabsorption causes variable, functional, nonspecific, non-allergic gastrointestinal and extra-intestinal complaints, and a detailed diagnostic workup for all possible etiologic factors in individual patients is essential. Usually, evaluation for histamine intolerance is not included in differential diagnoses of patients with functional, nonspecific, non-allergic gastrointestinal complaints. A targeted dietary intervention for single or possibly combined intolerance/malabsorption is required. In this article, we review currently discussed differential diagnoses and available tests for intolerance/malabsorption. Accordingly, we aim to outline why including histamine and, histamine intolerance, should be considered in differential diagnoses of patients with functional, nonspecific, non-allergic gastrointestinal complaints.

Evidence-based and mechanistic insights into exclusion diets for IBS

Exclusion diets are becoming increasingly popular in the management of irritable bowel syndrome (IBS). Several mechanisms exist by which food items might cause gastrointestinal symptoms, such as direct osmotic effects of food in the gut lumen, changes to the gut microbiota and immune activation. These effects have been demonstrated in animal models and in human studies, particularly in the case of gluten-free diets and diets low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs). Indeed, randomized controlled trials (RCTs) suggest that gluten-free diets and low-FODMAP diets improve IBS symptoms, and guidelines recommend the latter approach for treating symptoms in some patients with IBS. Designing such RCTs is challenging as participants need to eat so an 'inert' placebo is not an option. Blinding is also an issue with these studies; in the future, new exclusion diets should not advertise what the diet consists of until it is proved to reduce symptoms. In this Review, we outline the advantages and disadvantages of each choice of control group and emphasize the importance of collecting mechanistic data (regarding direct effects of food on the gut lumen, changes in gut microbiota and intestinal inflammation) as well as symptom data in RCTs of exclusion diets in IBS.

Adaptation of the Gut Microbiota to Modern Dietary Sugars and Sweeteners

The consumption of sugar has become central to the Western diet. Cost and health concerns associated with sucrose spurred the development and consumption of other sugars and sweeteners, with the average American consuming 10 times more sugar than 100 y ago. In this review, we discuss how gut microbes are affected by changes in the consumption of sugars and other sweeteners through transcriptional, abundance, and genetic adaptations. We propose that these adaptations result in microbes taking on different metabolic, ecological, and genetic profiles along the intestinal tract. We suggest novel approaches to assess the consequences of these changes on host-microbe interactions to determine the safety of novel sugars and sweeteners.

Fructose and irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic disorder characterised by recurrent abdominal pain or discomfort and transit disturbances with heterogeneous pathophysiological mechanisms. The link between food and gastrointestinal (GI) symptoms is often reported by patients with IBS and the role of fructose has recently been highlighted. Fructose malabsorption can easily be assessed by hydrogen and/or methane breath test in response to 25 g fructose; and its prevalence is about 22 % in patients with IBS. The mechanism of fructose-related symptoms is incompletely understood. Osmotic load, fermentation and visceral hypersensitivity are likely to participate in GI symptoms in the IBS population and may be triggered or worsened by fructose. A low-fructose diet could be integrated in the overall treatment strategy, but its role and implication in the improvement of IBS symptoms should be evaluated. In the present review, we discuss fructose malabsorption in adult patients with IBS and the interest of a low-fructose diet in order to underline the important role of fructose in IBS.

Routine disaccharidase testing: are we there yet?

PURPOSE OF REVIEW

Disaccharidase testing, as applied to the evaluation of gastrointestinal disturbances is available but it is not routinely considered in the diagnostic work-up. The purpose of this review was to determine if disaccharidase testing is clinically useful and to consider how the results could alter patient management.

RECENT FINDINGS

Indicate that carbohydrate maldigestion could contribute functional bowel disorders and negatively impact the fecal microbiome. Diagnostic techniques include enzyme activity assays performed on random endoscopically obtained small intestinal biopsies, immunohistochemistry, stable isotope tracer and nonenriched substrate load breath testing, and genetic testing for mutations. More than 40 sucrase--isomaltase gene variants coding for defective or reduced enzymatic activity have been reported and deficiency conditions are more common than previously thought.

SUMMARY

The rationale for disaccharidase activity testing relates to a need to fully assess unexplained recurrent abdominal discomfort and associated symptoms. All disaccharidases share the same basic mechanism of mucosal expression and deficiency has far reaching consequences. Testing for disaccharidase expression appears to have an important role in symptom evaluation, but there are accuracy and logistical issues that should be considered. It is likely that specific recommendations for patient management, dietary modification, and enzyme supplementation would come from better testing methods.

Consumption of Lactose, Other FODMAPs and Diarrhoea during Adjuvant 5-Fluorouracil Chemotherapy for Colorectal Cancer

Chemotherapy-induced mucosal injury of the small intestine may interfere with the enzymes and transporters responsible for the hydrolysis and absorption of dietary carbohydrates causing diarrhoea, abdominal discomfort and pain. The aim of this study was to investigate the association between the consumption of foods rich in FODMAPs (fermentable oligo-, di- and monosaccharides and polyols) and gastrointestinal symptoms in patients receiving adjuvant therapy for colorectal cancer. The patients (n = 52) filled in a 4-day food diary at baseline and during therapy and kept a symptom diary. The intakes of FODMAP-rich foods were calculated as portions and the intakes were divided into two consumption categories. Patients with high consumption of FODMAP-rich foods had diarrhoea more frequently than those with low consumption (for lactose-rich foods the odds ratio (OR) was 2.63, P = 0.03; and for other FODMAP-rich foods 1.82, P = 0.20). Patients with high consumption of both lactose-rich and other FODMAP-rich foods had an over 4-fold risk of developing diarrhoea as compared to those with low consumption of both (OR, 4.18; P = 0.02). These results were confirmed in multivariate models. Conclusion: Consumption of lactose-rich foods results in an increased risk of diarrhoea during adjuvant therapy for colorectal cancer, especially when the consumption of other FODMAP-rich foods is also high.

Intestinal Fructose and Glucose Metabolism in Health and Disease

The worldwide epidemics of obesity and diabetes have been linked to increased sugar consumption in humans. Here, we review fructose and glucose metabolism, as well as potential molecular mechanisms by which excessive sugar consumption is associated to metabolic diseases and insulin resistance in humans. To this end, we focus on understanding molecular and cellular mechanisms of fructose and glucose transport and sensing in the intestine, the intracellular signaling effects of dietary sugar metabolism, and its impact on glucose homeostasis in health and disease. Finally, the peripheral and central effects of dietary sugars on the gut-brain axis will be reviewed.

Review article: biological mechanisms for symptom causation by individual FODMAP subgroups - the case for a more personalised approach to dietary restriction

BACKGROUND

Due to the paucity of targeted therapy for irritable bowel syndrome (IBS), many patients turn to dietary modifications for symptom management. The combination of five subgroups of poorly absorbed and rapidly fermented carbohydrates-fructans, galacto-oligosaccharides, lactose, excess fructose and polyols-are thought to trigger gastrointestinal symptoms and are referred to collectively as "FODMAPs".

AIMS

To examine the biological plausibility and mechanisms by which foods high in specific FODMAP subgroups cause symptoms, and to use this information to explore the possibility of targeting select dietary components to allow for a more personalised approach to dietary adjustment METHODS: Recent literature was analysed via search databases including Medline, PubMed and Scopus.

RESULTS

Lactose, fructans and galacto-oligosaccharides have strong biologic plausibility for symptom generation due to lack of hydrolases resulting in distention from osmosis and rapid fermentation. However, excess fructose and polyols may only cause symptoms in specific individuals when consumed in high doses, but this remains to be established. There is evidence to suggest that certain patient characteristics such as ethnicity may predict response to lactose, but differentiation of other subgroups is difficult prior to dietary manipulation.

CONCLUSIONS

While some clear mechanisms of action for symptom generation have been established, further research is needed to understand which patients will respond to specific FODMAP subgroup restriction. We suggest that clinicians consider in some patients a tailored, personalised "bottom-up" approach to the low-FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile and usual dietary intake.

Effects of Dietary Aged Maize with Oxidized Fish Oil on Growth Performance, Antioxidant Capacity and Intestinal Health in Weaned Piglets

Simple Summary

In China, large quantities of maize are stored in grain depots for two years or more to mitigate the risk of natural disasters impacting feed supplies. However, it is unknown whether the use of long-term stored maize in diets will impair growth performance of piglets, and whether additional dietary oxidants would further exacerbate the effects. This study investigates the effects of dietary aged maize with the supplementation of different levels of oxidized fish oil on growth performance, nutrient digestibility, serum antioxidant activity and gut health in piglets and tries to provide a theoretical foundation for the better use of aged maize in swine production. The results of this study showed that aged maize had no significant effect on growth performance, diarrhea and nutrient digestibility of the piglets, but it did reduce serum antioxidant capacity. When oxidized fish oil was added, aged maize reduced serum antioxidant capacity further, inhibited the expressions of genes related to intestinal nutrient transport, promoted intestinal inflammation, and also reduced the apparent total tract digestibility (ATTD) of nutrients, increased diarrhea and finally reduced the growth performance of piglets. Thus, the use of aged maize in the diet of the piglets may be not feasible, especially when other oxidation-inducing factors existed, which would exacerbate the negative effects of the aged maize.

Abstract

This study aimed to determine the effects of dietary aged maize with supplementation of different levels of oxidized fish oil on growth performance, nutrient digestibility, serum antioxidant activity and gut health in piglets. Forty-two piglets were arranged in 2 × 3 factorial treatments in a complete randomized block design with seven replicates per treatment and one pig per replicate for 28 d. Diets included twp types of maize (normal maize or aged maize) and three levels of oxidized fish oil (OFO) (3% non-oxidized fish oil (0% OFO), 1.5% OFO and 1.5% non-oxidized fish oil (1.5% OFO), and 3% OFO (3% OFO). Results showed that dietary aged maize did not affect growth performance, diarrhea, and the apparent total tract digestibility (ATTD) of nutrients in piglets (p > 0.05). However, aged maize increased malonaldehyde (MDA) content and decreased total antioxidant capacity (T-AOC) in serum on both 14th and 28th days (p < 0.05) compared to the normal maize groups. Meanwhile, compared with normal maize, dietary aged maize showed a slight, but not significant (p > 0.10) decrease in total superoxide dismutase (T-SOD) activity and VE content in serum on the 14th day. In addition, aged maize significantly decreased GLUT2 mRNA expression (p < 0.05) and tended to increase (p < 0.10) TNF-α and IL-6 mRNA expression in jejunal mucosa. Compared with non-oxidized fish oil, oxidized fish oil resulted in the decrease of the 14–28 d and 0–28 d ADG, as well as the ATTD of dry matter (DM), ether extract (EE), organic matter (OM) (p < 0.05), whereas the increase in diarrhea index (p < 0.05) and F/G of the whole period (p < 0.05). Oxidized fish oil decreased serum T-AOC on both the 14th and the 28th days (p < 0.05), and decreased serum T-SOD activity and VE content on the 28th day (p < 0.05), whereas increased serum MDA content on the 28th day (p < 0.05) and 14th day (p < 0.10) compared with fresh fish oil. Meanwhile, MUC2 (p < 0.05) and SGLT1 (p < 0.10) mRNA expression in jejunal mucosa were decreased compared with non-oxidized fish oil. In addition, dietary oxidized fish oil tended to decrease 14–28 d ADFI and the ATTD of CP (p < 0.10), and piglets fed oxidized fish oil significantly decreased 14–28 d ADFI, the ATTD of CP, GLUT2 and SGLT1 mRNA expressions in jejunal mucosa when piglet also fed with aged maize (p < 0.05). Collectively, these results indicated that dietary oxidized fish oil decreased growth performance and nutrients digestibility of piglets fed with aged maize. This nutrient interaction may be mediated by inhibiting intestinal nutrient transporter, inducing intestinal inflammation, and reducing antioxidant capacity.

High Fructose Intake and Adipogenesis

In modern societies, high fructose intake from sugar-sweetened beverages has contributed to obesity development. In the diet, sucrose and high fructose corn syrup are the main sources of fructose and can be metabolized in the intestine and transported into the systemic circulation. The liver can metabolize around 70% of fructose intake, while the remaining is metabolized by other tissues. Several tissues including adipose tissue express the main fructose transporter GLUT5. In vivo, chronic fructose intake promotes white adipose tissue accumulation through activating adipogenesis. In vitro experiments have also demonstrated that fructose alone induces adipogenesis by several mechanisms, including (1) triglycerides and very-low-density lipoprotein (VLDL) production by fructose metabolism, (2) the stimulation of glucocorticoid activation by increasing 11β-HSD1 activity, and (3) the promotion of reactive oxygen species (ROS) production through uric acid, NOX and XOR expression, mTORC1 signaling and Ang II induction. Moreover, it has been observed that fructose induces adipogenesis through increased ACE2 expression, which promotes high Ang-(1-7) levels, and through the inhibition of the thermogenic program by regulating Sirt1 and UCP1. Finally, microRNAs may also be involved in regulating adipogenesis in high fructose intake conditions. In this paper, we propose further directions for research in fructose participation in adipogenesis.

Fructose malabsorption induces cholecystokinin expression in the ileum and cecum by changing microbiota composition and metabolism

Current fructose consumption levels often overwhelm the intestinal capacity to absorb fructose. We investigated the impact of fructose malabsorption on intestinal endocrine function and addressed the role of the microbiota in this process. To answer this question, a mouse model of moderate fructose malabsorption [ketohexokinase mutant (KHK)^-/-] and wild-type (WT) littermate mice were used and received a 20%-fructose (KHK-F and WT-F) or 20%-glucose diet. Cholecystokinin (Cck) mRNA and protein expression in the ileum and cecum, as well as preproglucagon (Gcg) and neurotensin (Nts) mRNA expression in the cecum, increased in KHK-F mice. In KHK-F mice, triple-label immunohistochemistry showed major up-regulation of CCK in enteroendocrine cells (EECs) that were glucagon-like peptide-1 (GLP-1)⁺/Peptide YY (PYY^-) in the ileum and colon and GLP-1^-/PYY^- in the cecum. The cecal microbiota composition was drastically modified in the KHK-F in association with an increase in glucose, propionate, succinate, and lactate concentrations. Antibiotic treatment abolished fructose malabsorption-dependent induction of cecal Cck mRNA expression and, in mouse GLUTag and human NCI-H716 cells, Cck mRNA expression levels increased in response to propionate, both suggesting a microbiota-dependent process. Fructose reaching the lower intestine can modify the composition and metabolism of the microbiota, thereby stimulating the production of CCK from the EECs possibly in response to propionate.-Zhang, X., Grosfeld, A., Williams, E., Vasiliauskas, D., Barretto, S., Smith, L., Mariadassou, M., Philippe, C., Devime, F., Melchior, C., Gourcerol, G., Dourmap, N., Lapaque, N., Larraufie, P., Blottière, H. M., Herberden, C., Gerard, P., Rehfeld, J. F., Ferraris, R. P., Fritton, J. C., Ellero-Simatos, S., Douard, V. Fructose malabsorption induces cholecystokinin expression in the ileum and cecum by changing microbiota composition and metabolism.

Cow milk protein allergy and other common food allergies and intolerances

The prevalence of food allergy and food intolerance is increasing and it is an important public health problem affecting children. Food allergy results from an immunological reaction to certain food(s) and affects numerous organs in the body. Food intolerances are non-immunological reactions including metabolic, toxic, pharmacological and undefined mechanisms. Cow milk is the most common cause of food allergy and food intolerance, especially in young children. Food intolerance can present with similar symptoms to those of food allergy. Health-care personnel, patients and their caregivers often confuse food intolerance with food allergy. This review focuses on the clinical manifestations, diagnostic evaluation, treatment and prevention of food allergy and food intolerance.

Effect of a short-term low fermentable oligiosaccharide, disaccharide, monosaccharide and polyol (FODMAP) diet on exercise-related gastrointestinal symptoms

BACKGROUND

Research has demonstrated that low fermentable oligiosaccharide, disaccharide, monosaccharide and polyol (FODMAP) diets improve gastrointestinal (GI) symptoms in irritable bowel syndrome sufferers. Exercise-related GI issues are a common cause of underperformance, with current evidence focusing on the use of FODMAP approaches with recreationally competitive or highly trained athletes. However, there is a paucity of research exploring the potential benefit of FODMAP strategies to support healthy, recreational athletes who experience GI  issues during training. This study therefore aimed to assess whether a short-term LOWFODMAP diet improved exercise-related GI symptoms and the perceived ability to exercise in recreational runners.

METHODS

Sixteen healthy volunteers were randomly assigned in a crossover design manner to either a LOWFODMAP (16.06 ± 1.79 g·d- 1) or HIGHFODMAP (38.65 ± 6.66 g·d- 1) diet for 7 days, with a one week washout period followed by a further 7 days on the alternate diet. Participants rated their gastrointestinal symptoms on an adapted version of the Irritable Bowel Syndrome-Severity Scoring System (IBS-SSS) questionnaire before and at the end of each dietary period. Perceived ability to exercise (frequency, intensity and duration) in relation to each dietary period was also rated using a visual analogue scale. Resting blood samples were collected prior to and on completion of each diet to determine plasma intestinal fatty acid binding protein (I-FABP) as a marker of acute GI injury.

RESULTS

Overall IBS-SSS score significantly reduced in the LOWFODMAP condition from 81.1 ± 16.4 to 31.3 ± 9.2 (arbitrary units; P = 0.004). Perceived exercise frequency (z = 2.309, P = 0.02) and intensity (z = 2.687, P = 0.007) was significantly improved following a short-term LOWFODMAP approach compared to HIGHFODMAP. No significant differences were reported between dietary conditions for plasma I-FABP (P > 0.05).

CONCLUSIONS

A short-term LOWFODMAP diet under free-living conditions reduced exercise-related GI symptoms and improved the perceived ability to exercise in otherwise healthy, recreational runners. These findings may be explained by a reduction in indigestible carbohydrates available for fermentation in the gut. The therapeutic benefits of LOWFODMAP diets in recreational and trained athletes during sustained training periods warrants further investigation.

A high‑fructose diet induces epithelial barrier dysfunction and exacerbates the severity of dextran sulfate sodium‑induced colitis

Excessive fructose intake is a risk factor for gut symptoms in patients with inflammatory bowel disease, however, its effect on the intestinal tract has not been evaluated previously. The present study investigated the impact of a high‑fructose diet (HFD) on intestinal barrier function in mice with experimental colitis. C57/BL6 mice were provided with either a HFD or control diet and either plain drinking water or water containing 1% dextran sulfate sodium (DSS) for 2 weeks. The disease activity index (DAI), pathological scores and expression of inflammatory cytokines were compared among the groups, and the proportions of fecal bacteria in the colon were analyzed. The body weight and colon length were significantly decreased, and the DAI and pathological scores were significantly increased in the DSS/HFD‑treated mice compared with the non‑DSS‑treated and control diet mice. Regarding the expression of inflammatory cytokines, the levels of interleukin (IL)‑6, IL‑1β and tumor necrosis factor‑α were significantly increased, and the expression of the tight junction protein occludin was significantly decreased in the DSS/HFD‑treated mice. The total bacterial count was increased in the HFD mice. Taken together, these results indicate that an HFD resulted in the deterioration of intestinal barrier function and increased susceptibility to DSS‑induced colitis.

Recent insights into the role of ChREBP in intestinal fructose absorption and metabolism

Fructose in the form of sucrose and high fructose corn syrup is absorbed by the intestinal transporter and mainly metabolized in the small intestine. However, excess intake of fructose overwhelms the absorptive capacity of the small intestine, leading to fructose malabsorption. Carbohydrate response element-binding protein (ChREBP) is a basic helix-loop-helix leucine zipper transcription factor that plays a key role in glycolytic and lipogenic gene expression in response to carbohydrate consumption. While ChREBP was initially identified as a glucose-responsive factor in the liver, recent evidence suggests that ChREBP is essential for fructoseinduced lipogenesis and gluconeogenesis in the small intestine as well as in the liver. We recently identified that the loss of ChREBP leads to fructose intolerance via insufficient induction of genes involved in fructose transport and metabolism in the intestine. As fructose consumption is increasing and closely associated with metabolic and gastrointestinal diseases, a comprehensive understanding of cellular fructose sensing and metabolism via ChREBP may uncover new therapeutic opportunities. In this mini review, we briefly summarize recent progress in intestinal fructose metabolism, regulation and function of ChREBP by fructose, and delineate the potential mechanisms by which excessive fructose consumption may lead to irritable bowel syndrome.

The Microbiotic Highway to Health-New Perspective on Food Structure, Gut Microbiota, and Host Inflammation

This review provides evidence that not only the content of nutrients but indeed the structural organization of nutrients is a major determinant of human health. The gut microbiota provides nutrients for the host by digesting food structures otherwise indigestible by human enzymes, thereby simultaneously harvesting energy and delivering nutrients and metabolites for the nutritional and biological benefit of the host. Microbiota-derived nutrients, metabolites, and antigens promote the development and function of the host immune system both directly by activating cells of the adaptive and innate immune system and indirectly by sustaining release of monosaccharides, stimulating intestinal receptors and secreting gut hormones. Multiple indirect microbiota-dependent biological responses contribute to glucose homeostasis, which prevents hyperglycemia-induced inflammatory conditions. The composition and function of the gut microbiota vary between individuals and whereas dietary habits influence the gut microbiota, the gut microbiota influences both the nutritional and biological homeostasis of the host. A healthy gut microbiota requires the presence of beneficial microbiotic species as well as vital food structures to ensure appropriate feeding of the microbiota. This review focuses on the impact of plant-based food structures, the "fiber-encapsulated nutrient formulation", and on the direct and indirect mechanisms by which the gut microbiota participate in host immune function.

Dietary chlorogenic acid improves growth performance of weaned pigs through maintaining antioxidant capacity and intestinal digestion and absorption function

Chlorogenic acid (CGA) is a natural phenolic acid, which is an important component of biologically active dietary phenols isolated from various species. Two experiments were conducted to investigate the effects of CGA on growth performance, antioxidant capacity, nutrient digestibility, diarrhea incidence, intestinal digestion and absorption function, and the expression levels of intestinal digestion and absorption-related genes in weaned pigs. In Exp. 1, 200 weaned pigs were randomly allotted to four dietary treatments and fed with a basal diet or a basal diet supplemented with 250, 500, or 1,000 mg/kg CGA, respectively, in a 14-d trial. Pigs on the 1,000 mg/kg CGA-supplemented group had greater (P < 0.05) G:F compared with those on the control (CON) group. In Exp. 2, 24 weaned pigs were randomly allotted to two groups and fed with a basal diet (CON group) or a basal diet supplemented with 1,000 mg/kg CGA (the optimum does from Exp. 1; CGA group). After a 14-d trial, 8 pigs per treatment were randomly selected to collect serum and intestinal samples. Compared with the CON group, the ADG, G:F, as well as the apparent total tract digestibility of CP, crude fat, and ash were increased (P < 0.05), whereas the diarrhea incidence was decreased (P < 0.05) in the CGA group. Pigs on the CGA group had greater (P < 0.05) serum albumin and IGF-1, and lower (P < 0.05) serum urea nitrogen than pigs on the CON group. Furthermore, dietary CGA supplementation enhanced (P < 0.05) the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in the serum, the activity of maltase in the jejunum and ileum, as well as the activities of sucrase and alkaline phosphatase (AKP) in the jejunum. The mRNA levels of sodium glucose transport protein-1 (SGLT1) and zinc transporter-1 (ZNT1) in the duodenum and the mRNA levels of SGLT1, glucose transporter-2 (GLUT2), and divalent metal transporter-1 (DMT1) in the jejunum were upregulated (P < 0.05) in pigs fed the CGA diet. These results suggested that dietary CGA supplementation has the potentials to improve the growth performance and decrease the diarrhea incidence of the weaned pigs, possibly through improving the antioxidant capacity and enhancing the intestinal digestion and absorption function.

A mathematical analysis of adaptations to the metabolic fate of fructose in essential fructosuria subjects

Fructose is a major component of Western diets and is implicated in the pathogenesis of obesity and type 2 diabetes. In response to an oral challenge, the majority of fructose is cleared during "first-pass" liver metabolism, primarily via phosphorylation by ketohexokinase (KHK). A rare benign genetic deficiency in KHK, called essential fructosuria (EF), leads to altered fructose metabolism. The only reported symptom of EF is the appearance of fructose in the urine following either oral or intravenous fructose administration. Here we develop and use a mathematical model to investigate the adaptations to altered fructose metabolism in people with EF. First, the model is calibrated to fit available data in normal healthy subjects. Then, to mathematically represent EF subjects, we systematically implement metabolic adaptations such that model simulations match available data for this phenotype. We hypothesize that these modifications represent the major metabolic adaptations present in these subjects. This modeling approach suggests that several other aspects of fructose metabolism, beyond hepatic KHK deficiency, are altered and contribute to the etiology of this benign condition. Specifically, we predict that fructose absorption into the portal vein is altered, peripheral metabolism is slowed, renal reabsorption of fructose is mostly ablated, and alternate pathways for hepatic metabolism of fructose are upregulated. Moreover, these findings have implications for drug discovery and development, suggesting that the therapeutic targeting of fructose metabolism could lead to unexpected metabolic adaptations, potentially due to a physiological response to high-fructose conditions.

ChREBP deficiency leads to diarrhea-predominant irritable bowel syndrome

OBJECTIVE

Fructose malabsorption is a common digestive disorder in which absorption of fructose in the small intestine is impaired. An abnormality of the main intestinal fructose transporter proteins has been proposed as a cause for fructose malabsorption. However the underlying molecular mechanism for this remains unclear. In this study, we investigated whether carbohydrate response element-binding protein (ChREBP) plays a role in intestinal fructose absorption through the regulation of genes involved in fructose transport and metabolism and ion transport.

METHODS

Wild type (WT) and Chrebp knockout (KO) mice (6 or 8 weeks old) were fed a control diet (55% starch, 15% maltodextrin 10) or high-fructose diet (HFrD, 60% fructose, 10% starch) for 3-12 days. Body weight and food intake were measured, signs of fructose malabsorption were monitored, and the expression of genes involved in fructose transport/metabolism and ion transport was evaluated. Furthermore, transient transfection and chromatin immunoprecipitation were performed to show the direct interaction between ChREBP and carbohydrate response elements in the promoter of Slc2A5, which encodes the fructose transporter GLUT5.

RESULTS

Chrebp KO mice fed the control diet maintained a constant body weight, whereas those fed a HFrD showed significant weight loss within 3-5 days. In addition, Chrebp KO mice fed the HFrD exhibited a markedly distended cecum and proximal colon containing both fluid and gas, suggesting incomplete fructose absorption. Fructose-induced increases of genes involved in fructose transport (GLUT5), fructose metabolism (fructokinase, aldolase B, triokinase, and lactate dehydrogenase), and gluconeogenesis (glucose-6-phosphatase and fructose-1,6-bisphosphatase) were observed in the intestine of WT but not of Chrebp KO mice. Moreover the Na⁺/H⁺ exchanger NHE3, which is involved in Na⁺ and water absorption in the intestine, was significantly decreased in HFrD-fed Chrebp KO mice. Consistent with this finding, the high-fructose diet-fed Chrebp KO mice developed severe diarrhea. Results of chromatin immunoprecipitation assays showed a direct interaction of ChREBP with the Glut5 promoter, but not the Nhe3 promoter, in the small intestine. Ectopic co-expression of ChREBP and its heterodimer partner Max-like protein X activated the Glut5 promoter in Caco-2BBE cells.

CONCLUSIONS

ChREBP plays a key role in the dietary fructose transport as well as conversion into lactate and glucose through direct transcriptional control of genes involved in fructose transport, fructolysis, and gluconeogenesis. Moreover, ablation of Chrebp results in a severe diarrhea in mice fed a high-fructose diet, which is associated with the insufficient induction of GLUT5 in the intestine.

Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology, 3rd edition

Chronic diarrhoea is a common problem, hence clear guidance on investigations is required. This is an updated guideline from 2003 for the investigations of chronic diarrhoea commissioned by the Clinical Services and Standards Committee of the British Society of Gastroenterology (BSG). This document has undergone significant revision in content through input by 13 members of the Guideline Development Group (GDG) representing various institutions. The GRADE system was used to appraise the quality of evidence and grading of recommendations.

Intestinal Microbial and Metabolic Profiling of Mice Fed with High-Glucose and High-Fructose Diets

Increased sugar intake is implicated in Type-2 diabetes and fatty liver disease; however, the mechanisms through which glucose and fructose promote these conditions are unclear. We hypothesize that alterations in intestinal metabolite and microbiota profiles specific to each monosaccharide are involved. Two groups of six adult C57BL/6 mice were fed for 10-weeks with diets with glucose (G) or fructose (F) as sole carbohydrates, and a third group was fed with a normal chow carbohydrate mixture (N). Fecal metabolites were profiled by nuclear magnetic resonance (NMR) and microbial composition by real-time polymerase chain reaction (qPCR). Although N, G and F mice exhibited similar weight gains (with slight slower gains for F) and glucose tolerance, multivariate analysis of NMR data indicated that F mice were separated from N and G, with decreased butyrate and glutamate and increased fructose, succinate, taurine, tyrosine, and xylose. The different sugar diets also resulted in distinct intestinal microbiota profiles. That associated with fructose seemed to hold more potential to induce host metabolic disturbances compared to glucose, mainly by promoting bile acid deconjugation and taurine release and compromising intestinal barrier integrity. This may reflect the noted nonquantitative intestinal fructose absorption hence increasing its availability for microbial metabolism, a subject for further investigation.

Hypertension in Children: Role of Obesity, Simple Carbohydrates, and Uric Acid

Over the past 60 years there has been a dramatic increase in the prevalence of overweight in children and adolescents, ranging from 4% in 1975 to 18% in 2016. Recent estimates indicate that overweight or obese children and adolescents are more than 340 million. Obesity is often associated with hypertension, which is an important cardiovascular risk factor. Recent studies show that the presence of hypertension is a frequent finding in the pediatric age. Hypertensive children easily become hypertensive adults. This phenomenon contributes to increasing cardiovascular risk in adulthood. Primary hypertension is a growing problem especially in children and adolescents of western countries, largely because of its association with the ongoing obesity epidemic. Recently, it has been hypothesized that a dietary link between obesity and elevated blood pressure (BP) values could be simple carbohydrate consumption, particularly fructose, both in adults and in children. Excessive intake of fructose leads to increased serum uric acid (SUA) and high SUA values are independently associated with the presence of hypertension and weaken the efficacy of lifestyle modifications in children. The present review intends to provide an update of existing data regarding the relationship between BP, simple carbohydrates (particularly fructose), and uric acid in pediatric age. In addition, we analyze the national policies that have been carried out over the last few years, in order to identify the best practices to limit the socio-economic impact of the effects of excessive sugar consumption in children.