Gut microbiota fermentation of prebiotics increases satietogenic and incretin gut peptide production with consequences for appetite sensation and glucose response after a meal

Physiological mechanisms behind Roux-en-Y gastric bypass surgery

Obesity and its related comorbidities can be detrimental for the affected individual and challenge public health systems worldwide. Currently, the only available treatment options leading to clinically significant and maintained body weight loss and reduction in obesity-related morbidity and mortality are based on surgical interventions. Apart from the 'gold standard' Roux-en-Y gastric bypass (RYGB), the vertical sleeve gastrectomy and gastric banding are two frequently performed procedures. This review will discuss animal experiments designed to understand the underlying mechanisms of body weight loss after bariatric surgery. While caloric malabsorption and mechanical restriction are no major factors in this respect, alterations in gut hormone levels are invariably found after RYGB. However, their causal role in RYGB effects on eating and body weight has recently been challenged. Other potential factors contributing to the RYGB effects include increased bile acid concentrations and an altered composition of gut microbiota. RYGB is further associated with remarkable changes in the preference for different dietary components such as a decrease in the preference for high fat or sugar; it is important to note that the contribution of altered food preferences to the RYGB effects on body weight is not clear.

Probiotics and prebiotics: prospects for public health and nutritional recommendations

Probiotics and prebiotics are useful interventions for improving human health through direct or indirect effects on the colonizing microbiota. However, translation of these research findings into nutritional recommendations and public health policy endorsements has not been achieved in a manner consistent with the strength of the evidence. More progress has been made with clinical recommendations. Conclusions include that beneficial cultures, including probiotics and live cultures in fermented foods, can contribute towards the health of the general population; prebiotics, in part due to their function as a special type of soluble fiber, can contribute to the health of the general population; and a number of challenges must be addressed in order to fully realize probiotic and prebiotic benefits, including the need for greater awareness of the accumulated evidence on probiotics and prebiotics among policy makers, strategies to cope with regulatory roadblocks to research, and high-quality human trials that address outstanding research questions in the field.

Impact of the gut microbiota on the development of obesity and type 2 diabetes mellitus

Obesity and its associated disorders are a major public health concern. Although obesity has been mainly related with perturbations of the balance between food intake and energy expenditure, other factors must nevertheless be considered. Recent insight suggests that an altered composition and diversity of gut microbiota could play an important role in the development of metabolic disorders. This review discusses research aimed at understanding the role of gut microbiota in the pathogenesis of obesity and type 2 diabetes mellitus (TDM2). The establishment of gut microbiota is dependent on the type of birth. With effect from this point, gut microbiota remain quite stable, although changes take place between birth and adulthood due to external influences, such as diet, disease and environment. Understand these changes is important to predict diseases and develop therapies. A new theory suggests that gut microbiota contribute to the regulation of energy homeostasis, provoking the development of an impairment in energy homeostasis and causing metabolic diseases, such as insulin resistance or TDM2. The metabolic endotoxemia, modifications in the secretion of incretins and butyrate production might explain the influence of the microbiota in these diseases.

The modulatory role of high fat feeding on gastrointestinal signals in obesity

The gastrointestinal (GI) tract is a specialized sensory system that detects and responds to constant changes in nutrient- and bacterial-derived intestinal signals, thus contributing to controls of food intake. Chronic exposure to dietary fat causes morphological, physiological and metabolic changes leading to disruptions in the regulatory feeding pathways promoting more efficient fat absorption and utilization, blunted satiation signals and excess adiposity. Accumulating evidence demonstrates that impaired gastrointestinal signals following long-term high fat consumption are, at least partially, responsible for increased caloric intake. This review focuses on the role of dietary fat in modulating oral and post-oral chemosensory signaling elements responsible for lipid detection and responses, including changes in sensitivity to satiation signals, such as GLP-1, PYY and CCK and their impact on food intake and weight gain. Furthermore, the influence of the gut microbiota on mechanisms controlling energy regulation in the face of excessive fat exposure will be explored. The profound influence of dietary fats on altering complex regulatory feeding pathways can result in dysregulation of body weight and development of obesity, while restoration or manipulation of satiation signaling may prove an effective tool in prevention and treatment of obesity.

Effects of whole grain rye crisp bread for breakfast on appetite and energy intake in a subsequent meal: two randomised controlled trails with different amounts of test foods and breakfast energy content

BACKGROUND

Fibre-rich rye products have been shown to have superior effects on self-reported appetite compared to white wheat bread and some studies have shown lower energy intake after subsequent meal. The aim of the present study was to evaluate the effects of whole grain rye crisp bread (RB) versus refined wheat bread (WB) on appetite in two studies using different portion sizes and total energy intakes.

METHODS

Two randomised cross-over pre-load studies were conducted in 20 and 21 subjects, respectively. Appetite was rated by visual analogue scale (VAS) for 4 h. In both studies, participants were 39 ± 14 years old and had BMI 23 ± 3. The studies differed in terms of energy content of the breakfasts and proportion of energy from the treatment product as well as amount of test products. Differences between treatments within the two studies were evaluated using mixed models with repeated measures appropriate for cross-over designs.

RESULTS

In Study one, hunger and desire to eat were significantly lower (P < 0.05) after RB compared with WB, but there were no difference for fullness or difference in energy intake at lunch served ad libitum. In Study two, the portion size was lower than in Study one and the test product constituted a larger proportion of the breakfast. Fullness was significantly higher after RB compared with WB (P < 0.05) and hunger, desire to eat as well as energy intake at lunch were significantly lower (P < 0.05).

CONCLUSIONS

Whole grain rye crisp bread caused lower self-reported hunger, higher fullness and less desire to eat compared to refined wheat bread. It also led to a lower energy intake after an ad libitum lunch. Results were stronger and/or more consistent when the test meal portion was smaller and accounted for a larger proportion of the total energy intake of the breakfast.

Diet effects in gut microbiome and obesity

The 100 trillion microbes in human gut coevolve with the host and exert significant influences on human health. The gut microbial composition presents dynamic changes correlated with various factors including host genotypes, age, and external environment. Effective manipulation of the gut microbiota through diets (both long-term and short-term diet patterns), probiotics and/or prebiotics, and antibiotics has been proved being potential to prevent from metabolic disorders such as obesity in many studies. The dietary regulation exerts influences on microbial metabolism and host immune functions through several pathways, of which may include selectively bacterial fermentation of nutrients, lower intestinal barrier function, overexpression of genes associated with disorders, and disruptions to both innate and adaptive immunity. Discoveries in the interrelationship between diet, intestinal microbiome, and body immune system provide us novel perceptions to the specific action mechanisms and will promote the development of therapeutic approaches for obesity.

Modulation of gut microbiota in the management of metabolic disorders: the prospects and challenges

The gut microbiota plays a number of important roles including digestion, metabolism, extraction of nutrients, synthesis of vitamins, prevention against pathogen colonization, and modulation of the immune system. Alterations or changes in composition and biodiversity of the gut microbiota have been associated with many gastrointestinal tract (GIT) disorders such as inflammatory bowel disease and colon cancer. Recent evidence suggests that altered composition and diversity of gut microbiota may play a role in the increased prevalence of metabolic diseases. This review article has two main objectives. First, it underscores approaches (such as probiotics, prebiotics, antimicrobial agents, bariatric surgery, and weight loss strategies) and their prospects in modulating the gut microbiota in the management of metabolic diseases. Second, it highlights some of the current challenges and discusses areas of future research as it relates to the gut microbiota and metabolic diseases. The prospect of modulating the gut microbiota seems promising. However, considering that research investigating the role of gut microbiota in metabolic diseases is still in its infancy, more rigorous and well-designed in vitro, animal and clinical studies are needed.

Obesity as a consequence of gut bacteria and diet interactions

Obesity is a major public health concern, caused by a combination of increased consumption of energy-dense foods and reduced physical activity, with contributions from host genetics, environment, and adipose tissue inflammation. In recent years, the gut microbiome has also been found to be implicated and augmented research in mice and humans have attributed to it both the manifestation and/or exacerbation of this major epidemic and vice versa. At the experimental level, analysis of fecal samples revealed a potential link between obesity and alterations in the gut flora (drop in Bacteroidetes and increase in Firmicutes), the specific gut microbiome being associated with the obese phenotype. Conventionally raised mice were found to have over 40% more total body fat compared with those raised under germ-free conditions, while conventionalization of germ-free mice resulted in a significant increase in total body fat. Similarly, the sparse data in humans supports the fact that fat storage is favoured by the presence of the gut microbiota, through a multifaceted mechanism. Efforts to identify new therapeutic strategies to modulate gut microbiota would be of high priority for public health, and to date, probiotics and/or prebiotics seem to be the most effective tools.

Influence of diet on gut microbiota, inflammation and type 2 diabetes mellitus. First experience with macrobiotic Ma-Pi 2 diet

Type 2 diabetes mellitus (T2DM) is a complex disorder influenced by both genetic and environmental factors. Recent studies have suggested that an imbalance of the intestinal microbiota may be involved in the development of several human diseases, including obesity and T2DM. The main regulators of the intestinal microbiota are age, ethnicity, the immune system and diet. A high-fat diet may induce dysbiosis, which can result in a low-grade inflammatory state, obesity and other metabolic disorders. Adding prebiotics to the diet may reduce inflammation, endotoxaemia and cytokine levels as well as improving insulin resistance and glucose tolerance. The administration of prebiotics such as fermentable dietary fibres, promotes glucagon-like peptide 1 and peptide YY (anorexigenic) and decreases ghrelin (orexigenic). In a recent 21-day, intervention study in patients with T2DM, the effect of using the macrobiotic Ma-Pi 2 diet was investigated. Results suggested that it could induce a significant improvement in fasting blood glucose, plasma lipid fractions, plasma insulin and homeostasis. It is therefore possible that a diet rich in prebiotics and probiotics can play a role in T2DM management, probably due to positive intestinal microbiota modulation. However, this must be demonstrated by larger studies including randomized controlled trials that measure indicators of inflammation.

Neuropeptides and the microbiota-gut-brain axis

Neuropeptides are important mediators both within the nervous system and between neurons and other cell types. Neuropeptides such as substance P, calcitonin gene-related peptide and neuropeptide Y (NPY), vasoactive intestinal polypeptide, somatostatin and corticotropin-releasing factor are also likely to play a role in the bidirectional gut-brain communication. In this capacity they may influence the activity of the gastrointestinal microbiota and its interaction with the gut-brain axis. Current efforts in elucidating the implication of neuropeptides in the microbiota-gut-brain axis address four information carriers from the gut to the brain (vagal and spinal afferent neurons; immune mediators such as cytokines; gut hormones; gut microbiota-derived signalling molecules) and four information carriers from the central nervous system to the gut (sympathetic efferent neurons; parasympathetic efferent neurons; neuroendocrine factors involving the adrenal medulla; neuroendocrine factors involving the adrenal cortex). Apart from operating as neurotransmitters, many biologically active peptides also function as gut hormones. Given that neuropeptides and gut hormones target the same cell membrane receptors (typically G protein-coupled receptors), the two messenger roles often converge in the same or similar biological implications. This is exemplified by NPY and peptide YY (PYY), two members of the PP-fold peptide family. While PYY is almost exclusively expressed by enteroendocrine cells, NPY is found at all levels of the gut-brain and brain-gut axis. The function of PYY-releasing enteroendocrine cells is directly influenced by short chain fatty acids generated by the intestinal microbiota from indigestible fibre, while NPY may control the impact of the gut microbiota on inflammatory processes, pain, brain function and behaviour. Although the impact of neuropeptides on the interaction between the gut microbiota and brain awaits to be analysed, biologically active peptides are likely to emerge as neural and endocrine messengers in orchestrating the microbiota-gut-brain axis in health and disease.

Gut microbiota-based translational biomarkers to prevent metabolic syndrome via nutritional modulation

In the face of the global epidemic of metabolic syndrome (MetS) and its strong association with the increasing rate of cardiovascular morbidity and mortality, it is critical to detect MetS at an early stage in the clinical setting to implement preventive intervention long before the complications arise. Lipopolysaccharide, the cell wall component of Gram-negative bacteria produced from diet-disrupted gut microbiota, has been shown to induce metabolic endotoxemia, chronic low-grade inflammation, and ultimately insulin resistance. Therefore, ameliorating the inflammation and insulin resistance underlying MetS by gut microbiota-targeted, dietary intervention has gained increasing attention. In this review, we propose using dynamic monitoring of a set of translational biomarkers related with the etiological role of gut microbiota, including lipopolysaccharide binding protein (LBP), C-reactive protein (CRP), fasting insulin, and homeostasis model assessment of insulin resistance (HOMA-IR), for early detection and prevention of MetS via nutritional modulation. LBP initiates the recognition and monomerization of lipopolysaccharide and amplifies host immune responses, linking the gut-derived antigen load and inflammation indicated by the plasma levels of CRP. Fasting plasma insulin and HOMA-IR are measured to evaluate insulin sensitivity that is damaged by pro-inflammatory cytokines. The dynamic monitoring of these biomarkers in high-risk populations may provide translational methods for the quantitative and dynamic evaluation of dysbiosis-induced insulin resistance and the effectiveness of dietary treatment for MetS.

Pharmacological agents for nonalcoholic steatohepatitis

The rationale for specific pharmacologic therapy in nonalcoholic steatohepatitis (NASH) is determined by the potential for disease progression and the difficulties, in many patients, to successfully implement diet and lifestyle changes in the long term. Because they correct insulin resistance, insulin-sensitizing agents are attractive candidates for the treatment of NASH. However, two randomized studies have shown that vitamin E, despite having no effect on insulin sensitivity, achieves interesting histological and biochemical efficacy. This review provides an insight into the therapeutic efficacy and safety issues of different pharmacological agents tested in human NASH.

Metabolic benefits of dietary prebiotics in human subjects: a systematic review of randomised controlled trials

Complex relationships exist between the gut microflora and their human hosts. Emerging evidence suggests that bacterial dysbiosis within the colon may be involved in the pathogenesis of the metabolic syndrome, type 2 diabetes and CVD. The use of dietary prebiotic supplements to restore an optimal balance of intestinal flora may positively affect host metabolism, representing a potential treatment strategy for individuals with cardiometabolic disorders. The present review aimed to examine the current evidence supporting that dietary prebiotic supplementation in adults has beneficial effects on biochemical parameters associated with the development of metabolic abnormalities including obesity, glucose intolerance, dyslipidaemia, hepatic steatosis and low-grade chronic inflammation. Between January 2000 and September 2013, eight computer databases were searched for randomised controlled trials published in English. Human trials were included if at least one group received a dietary prebiotic intervention. In the present review, twenty-six randomised controlled trials involving 831 participants were included. Evidence indicated that dietary prebiotic supplementation increased self-reported feelings of satiety in healthy adults (standardised mean difference -0.57, 95% CI -1.13, -0.01). Prebiotic supplementation also significantly reduced postprandial glucose (-0.76, 95% CI -1.41, -0.12) and insulin (-0.77, 95% CI -1.50, -0.04) concentrations. The effects of dietary prebiotics on total energy intake, body weight, peptide YY and glucagon-like peptide-1 concentrations, gastric emptying times, insulin sensitivity, lipids, inflammatory markers and immune function were contradictory. Dietary prebiotic consumption was found to be associated with subjective improvements in satiety and reductions in postprandial glucose and insulin concentrations. Additional evidence is required before recommending prebiotic supplements to individuals with metabolic abnormalities. Large-scale trials of longer duration evaluating gut microbial growth and activity are required.

Gut microbiome and metabolic diseases

The prevalence of obesity and obesity-related disorders is increasing worldwide. In the last decade, the gut microbiota has emerged as an important factor in the development of obesity and metabolic syndrome, through its interactions with dietary, environmental, and host genetic factors. Various studies have shown that alteration of the gut microbiota, shifting it toward increased energy harvest, is associated with an obese phenotype. However, the molecular mechanisms by which the gut microbiota affects host metabolism are still obscure. In this review, we discuss the complexity of the gut microbiota and its relationship to obesity and obesity-related diseases. Furthermore, we discuss the anti-obesity potential of probiotics and prebiotics.

Effects of dietary nutrients on volatile breath metabolites

Breath analysis is becoming increasingly established as a means of assessing metabolic, biochemical and physiological function in health and disease. The methods available for these analyses exploit a variety of complex physicochemical principles, but are becoming more easily utilised in the clinical setting. Whilst some of the factors accounting for the biological variation in breath metabolite concentrations have been clarified, there has been relatively little work on the dietary factors that may influence them. In applying breath analysis to the clinical setting, it will be important to consider how these factors may affect the interpretation of endogenous breath composition. Diet may have complex effects on the generation of breath compounds. These effects may either be due to a direct impact on metabolism, or because they alter the gastrointestinal flora. Bacteria are a major source of compounds in breath, and their generation of H₂, hydrogen cyanide, aldehydes and alkanes may be an indicator of the health of their host.

In vitro fermentation of NUTRIOSE(®) FB06, a wheat dextrin soluble fibre, in a continuous culture human colonic model system

Wheat dextrin soluble fibre may have metabolic and health benefits, potentially acting via mechanisms governed by the selective modulation of the human gut microbiota. Our aim was to examine the impact of wheat dextrin on the composition and metabolic activity of the gut microbiota. We used a validated in vitro three-stage continuous culture human colonic model (gut model) system comprised of vessels simulating anatomical regions of the human colon. To mimic human ingestion, 7 g of wheat dextrin (NUTRIOSE^® FB06) was administered to three gut models, twice daily at 10.00 and 15.00, for a total of 18 days. Samples were collected and analysed for microbial composition and organic acid concentrations by 16S rRNA-based fluorescence in situ hybridisation and gas chromatography approaches, respectively. Wheat dextrin mediated a significant increase in total bacteria in vessels simulating the transverse and distal colon, and a significant increase in key butyrate-producing bacteria Clostridium cluster XIVa and Roseburia genus in all vessels of the gut model. The production of principal short-chain fatty acids, acetate, propionate and butyrate, which have been purported to have protective, trophic and metabolic host benefits, were increased. Specifically, wheat dextrin fermentation had a significant butyrogenic effect in all vessels of the gut model and significantly increased production of acetate (vessels 2 and 3) and propionate (vessel 3), simulating the transverse and distal regions of the human colon, respectively. In conclusion, wheat dextrin NUTRIOSE^® FB06 is selectively fermented in vitro by Clostridium cluster XIVa and Roseburia genus and beneficially alters the metabolic profile of the human gut microbiota.

Designing future prebiotic fiber to target metabolic syndrome

The metabolic syndrome (MetS), characterized by obesity, hyperlipidemia, hypertension, and insulin resistance, is a growing epidemic worldwide, requiring new prevention strategies and therapeutics. The concept of prebiotics refers to selective stimulation of growth and/or activity(ies) of one or a limited number of microbial genus(era)/species in the gut microbiota that confer(s) health benefits to the host. Sequencing the gut microbiome and performing metagenomics has provided new knowledge of the significance of the composition and activity of the gut microbiota in metabolic disease. As knowledge of how a healthy gut microbiota is composed and which bacterial metabolites are beneficial increases, tailor-made dietary interventions using prebiotic fibers could be developed for individuals with MetS. In this review, we describe how dietary fibers alter short-chain fatty acid (SCFA) profiles and the intrinsic and extrinsic effects of prebiotics on host metabolism. We focus on several key aspects in prebiotic research in relation to MetS and provide mechanistic data that support the use of prebiotic fibers in order to alter the gut microbiota composition and SCFA profiles. Further studies in the field should provide reliable mechanistic and clinical evidence for how prebiotics can be used to alleviate MetS and its complications. Additionally, it will be important to clarify the effect of individual differences in the gut microbiome on responsiveness to prebiotic interventions.

Satiety and energy intake after single and repeated exposure to gel-forming dietary fiber: post-ingestive effects

BACKGROUND

Viscous or gel-forming dietary fibers can increase satiety by a more firm texture and increased eating time. Effects of viscous or gel-forming fibers on satiety by post-ingestive mechanisms such as gastric emptying, hormonal signals, nutrient absorption or fermentation are unclear. Moreover, it is unclear whether the effects persist after repeated exposure.

OBJECTIVE

To investigate satiety and energy intake after single and repeated exposure to gelled fiber by post-ingestive mechanisms.

DESIGN

In a two-arm crossover design, 32 subjects (24 female subjects, 21±2 y, BMI 21.8±1.9 kg m(-2)) consumed test foods once daily for 15 consecutive days, with 2 weeks of washout. Test foods were isocaloric (0.5 MJ, 200 g) with either 10 g gel-forming pectin or 3 g gelatin and 2 g starch, matched for texture and eating time. Hourly satiety ratings, ad libitum energy intake and body weight were measured on days 1 (single exposure) and 15 (repeated exposure). In addition, hourly breath hydrogen, fasting glucose, insulin, leptin and short-chain fatty acids were measured.

RESULTS

Subjects rated hunger, desire to eat and prospective intake about 2% lower (P<0.015) and fullness higher (+1.4%; P=0.041) when they received pectin compared with control. This difference was similar after single and repeated exposure (P>0.64). After receiving pectin, energy intake was lower (-5.6%, P=0.012) and breath hydrogen was elevated (+12.6%, P=0.008) after single exposure, but not after repeated exposure. Fasting glucose concentrations were higher both after single and repeated exposure to pectin (+2.1%, P=0.019). Body weight and concentrations of insulin, leptin and short-chain fatty acids did not change during the study.

CONCLUSIONS

Gelled pectin can increase satiety and reduce energy intake by post-ingestive mechanisms. Although the effects were small, the effects on satiety were consistent over time, whereas the effects on energy intake reduction were not.

Microbiota in health and irritable bowel syndrome: current knowledge, perspectives and therapeutic options

The gastrointestinal tract is a natural reservoir of microbiota. The gut is germ-free at birth, but rapidly becomes host to various bacteria establishing a progressively mutual relationship. The composition of gut microbiota is individual-specific and depends on the genotype of the host and environmental factors. Novel techniques have been used to characterize gastrointestinal microbiota, including genomic approaches. The bacterial profile shows that dominant and minor phyla are present in the gastrointestinal tract. From the proximal to the distal segments of the gut the bacterial density gradually increases, reaching an estimated 10(11) to 10(12) bacteria per gram of colonic content. Dynamic interactions between gut and microbiota play a physiological role in metabolic, protective and structural functions, while dysbiosis contributes to several diseases. Microbiota appear to play a role in IBS, where qualitative and quantitative changes of bacteriaoccur in IBS subtypes. Initial therapeutic approaches in IBS have focused on microbiota. The relationship between perturbations of the microbiota, mucosal inflammation and IBS remains to be further investigated.

Insight into the prebiotic concept: lessons from an exploratory, double blind intervention study with inulin-type fructans in obese women

OBJECTIVE

To highlight the contribution of the gut microbiota to the modulation of host metabolism by dietary inulin-type fructans (ITF prebiotics) in obese women.

METHODS

A double blind, placebo controlled, intervention study was performed with 30 obese women treated with ITF prebiotics (inulin/oligofructose 50/50 mix; n=15) or placebo (maltodextrin; n=15) for 3 months (16 g/day). Blood, faeces and urine sampling, oral glucose tolerance test, homeostasis model assessment and impedancemetry were performed before and after treatment. The gut microbial composition in faeces was analysed by phylogenetic microarray and qPCR analysis of 16S rDNA. Plasma and urine metabolic profiles were analysed by 1H-NMR spectroscopy.

RESULTS

Treatment with ITF prebiotics, but not the placebo, led to an increase in Bifidobacterium and Faecalibacterium prausnitzii; both bacteria negatively correlated with serum lipopolysaccharide levels. ITF prebiotics also decreased Bacteroides intestinalis, Bacteroides vulgatus and Propionibacterium, an effect associated with a slight decrease in fat mass and with plasma lactate and phosphatidylcholine levels. No clear treatment clustering could be detected for gut microbial analysis or plasma and urine metabolomic profile analyses. However, ITF prebiotics led to subtle changes in the gut microbiota that may importantly impact on several key metabolites implicated in obesity and/or diabetes.

CONCLUSIONS

ITF prebiotics selectively changed the gut microbiota composition in obese women, leading to modest changes in host metabolism, as suggested by the correlation between some bacterial species and metabolic endotoxaemia or metabolomic signatures.

Adiposity and insulin resistance in humans: the role of the different tissue and cellular lipid depots

Human adiposity has long been associated with insulin resistance and increased cardiovascular risk, and abdominal adiposity is considered particularly adverse. Intra-abdominal fat is associated with insulin resistance, possibly mediated by greater lipolytic activity, lower adiponectin levels, resistance to leptin, and increased inflammatory cytokines, although the latter contribution is less clear. Liver lipid is also closely associated with, and likely to be an important contributor to, insulin resistance, but it may also be in part the consequence of the lipogenic pathway of insulin action being up-regulated by hyperinsulinemia and unimpaired signaling. Again, intramyocellular triglyceride is associated with muscle insulin resistance, but anomalies include higher intramyocellular triglyceride in insulin-sensitive athletes and women (vs men). Such issues could be explained if the "culprits" were active lipid moieties such as diacylglycerol and ceramide species, dependent more on lipid metabolism and partitioning than triglyceride amount. Subcutaneous fat, especially gluteofemoral, appears metabolically protective, illustrated by insulin resistance and dyslipidemia in patients with lipodystrophy. However, some studies suggest that deep sc abdominal fat may have adverse properties. Pericardial and perivascular fat relate to atheromatous disease, but not clearly to insulin resistance. There has been recent interest in recognizable brown adipose tissue in adult humans and its possible augmentation by a hormone, irisin, from exercising muscle. Brown adipose tissue is metabolically active, oxidizes fatty acids, and generates heat but, because of its small and variable quantities, its metabolic importance in humans under usual living conditions is still unclear. Further understanding of specific roles of different lipid depots may help new approaches to control obesity and its metabolic sequelae.

Feeding spinach thylakoids to rats modulates the gut microbiota, decreases food intake and affects the insulin response

Thylakoid membranes derived from green leaf chloroplasts affect appetite-regulating hormones, suppress food intake, reduce blood lipids and lead to a decreased body weight in animals and human subjects. Thylakoids also decrease the intestinal in vitro uptake of methyl-glucose in the rat. The aim of this study was to investigate the effect of dietary thylakoids on the gut microbiota composition, mainly the taxa of lactobacilli and bifidobacteria, in rats fed either a thylakoid-enriched diet or a control diet for 10 d. At the same time, a glucose-tolerance test in the same rats was also performed. Food intake was significantly decreased in the thylakoid-fed rats compared with the control-fed rats over the 10-d study. An oral glucose tolerance test after 10 d of thylakoid- or control-food intake resulted in significantly reduced plasma insulin levels in the thylakoid-fed rats compared with the control-fed rats, while no difference was observed for blood glucose levels. Analysis of gut bacteria showed a significant increase of lactobacilli on the ileal mucosa, specifically Lactobacillus reuteri, in the rats fed the thylakoid diet compared with rats fed the control diet, while faecal lactobacilli decreased. No difference in bifidobacteria between the thylakoid and control groups was found. Analyses with terminal restriction fragment length polymorphism and principal component analysis of faeces demonstrated different microbial populations in the thylakoid- and control-fed animals. These findings indicate that thylakoids modulate the gut microbial composition, which might be important for the regulation of body weight and energy metabolism.

Effect of supplementary calcium phosphate on plasma gastrointestinal hormones in a double-blind, placebo-controlled, cross-over human study

Gastrointestinal hormones and Ca are associated with bone metabolism. The objective of the present human study was to determine the effect of calcium phosphate on the postprandial circulation of gastrointestinal hormones. A total of ten men participated in the present double-blind, placebo-controlled, cross-over study. The participants were divided into two groups. Of these, one group consumed bread enriched with 1 g Ca (pentacalcium hydroxy-triphosphate, CaP) daily for 3 weeks. The other group consumed placebo bread. After 2 weeks of washout, the intervention was changed between the groups for another 3 weeks. The subjects consumed a defined diet at the beginning (single administration) and at the end (repeated administration) of the intervention periods, and blood samples were drawn at 0, 30, 60, 120, 180 and 240 min. Between 0 and 30 min, the participants consumed a test meal, with or without CaP. The concentrations of gastrointestinal hormones (glucose-dependent insulinotropic polypeptide, glucagon-like peptide (GLP) 1 and GLP2), insulin and glucose were determined. The AUC of GLP1 (total and active) and GLP2 increased significantly after the repeated CaP administrations compared with that after placebo administration. The AUC of insulin and glucose showed no differences between the CaP and placebo administrations. CaP affects the postprandial plasma concentrations of gastrointestinal hormones through the modulation of the intestinal environment, e.g. bile acids and microbiota.

Beneficial metabolic effects of a probiotic via butyrate-induced GLP-1 hormone secretion

Obesity and diabetes are associated with excess caloric intake and reduced energy expenditure resulting in a negative energy balance. The incidence of diabetes has reached epidemic proportions, and childhood diabetes and obesity are increasing alarmingly. Therefore, it is important to develop safe, easily deliverable, and economically viable treatment alternatives for these diseases. Here, we provide data supporting the candidacy of probiotics as such a therapeutic modality against obesity and diabetes. Probiotics are live bacteria that colonize the gastrointestinal tract and impart beneficial effects for health. However, their widespread prescription as medical therapies is limited primarily because of the paucity of our understanding of their mechanism of action. Here, we demonstrate that the administration of a probiotic, VSL#3, prevented and treated obesity and diabetes in several mouse models. VSL#3 suppressed body weight gain and insulin resistance via modulation of the gut flora composition. VSL#3 promoted the release of the hormone GLP-1, resulting in reduced food intake and improved glucose tolerance. The VSL#3-induced changes were associated with an increase in the levels of a short chain fatty acid (SCFA), butyrate. Using a cell culture system, we demonstrate that butyrate stimulated the release of GLP-1 from intestinal L-cells, thereby providing a plausible mechanism for VSL#3 action. These findings suggest that probiotics such as VSL#3 can modulate the gut microbiota-SCFA-hormone axis. Moreover, our results indicate that probiotics are of potential therapeutic utility to counter obesity and diabetes.

Consumption of buckwheat modulates the post-prandial response of selected gastrointestinal satiety hormones in individuals with type 2 diabetes mellitus

PURPOSE

In healthy participants and those with diet-controlled type 2 diabetes (T2DM), to (1) compare the acute 3-hour post-prandial response of glucose, insulin and other gastrointestinal hormones known to influence food intake and glucose metabolism after consumption of a food product made from whole grain buckwheat flour versus rice flour; (2) determine the effect of daily consumption of a food product made from whole grain buckwheat flour on fasting glucose, lipids and apolipoproteins.

METHODS

Healthy participants or those with T2DM consumed either buckwheat or rice crackers. Blood samples were collected at baseline and 15, 30, 45, 60, 120 and 180minutes after consumption. In a second phase of the study, participants consumed one serving of buckwheat crackers daily for 1week; fasting blood samples from day 1 and day 7 were analyzed.

RESULTS

Post-prandial plasma glucagon-like peptide-1, glucose-dependent insulinotropic peptide and pancreatic polypeptide were altered after consuming buckwheat versus rice crackers. Interestingly, changes in these hormones did not lead to changes in post-prandial glucose, insulin or C-peptide concentrations. Significant correlations were observed between both fasting concentrations and post-prandial responses of several of the hormones examined. Interestingly, certain correlations were present only in the healthy participant group or the T2DM group. There was no effect of consuming buckwheat for one week on fasting glucose, lipids or apolipoproteins in either the healthy participants or those with T2DM.

CONCLUSIONS

Although the buckwheat cracker did not modify acute glycemia or insulinemia, it was sufficient to modulate gastrointestinal satiety hormones.

Daily consumption of a synbiotic yogurt decreases energy intake but does not improve gastrointestinal transit time: a double-blind, randomized, crossover study in healthy adults

Objective

Probiotic and synbiotic products are widely marketed to healthy individuals, although potential benefits for these individuals are rarely studied. This study investigated the effect of daily consumption of a synbiotic yogurt on gastrointestinal (GI) function in a sample of healthy adults.

Subjects/Methods

In a randomized crossover double-blind study, 65 healthy adults consumed 200 g/day of yogurt with (synbiotic) or without (control) added probiotics (Bifidobacterium lactis Bb12, Lactobacillus acidophilus La5, Lactobacillus casei CRL431) and 4 g inulin for two 15-day treatment periods, each preceded by a 6-week washout period. GI transit time (GTT), duration of colour (DOC), GI symptoms and dietary intake were assessed and analyzed using repeated measures ANOVA, including PRE-treatment GTT as a covariate. Participants were grouped as short GTT (STT, n = 50, ≤32.7 h) or long GTT (LTT, n = 15, >32.7 h) based on their PRE-treatment GTT assessment.

Results

POST-treatment GTT and DOC were not different between synbiotic and control, and did not change from PRE-treatment, within the STT or LTT groups. There were no changes in GI symptom ratings, indicating that both yogurts were well tolerated. In STT, energy, fat and protein intakes were decreased from baseline with synbiotic (p = 0.055, p = 0.059 and p = 0.005, respectively) and dietary fibre intake was higher POST-treatment with synbiotic versus control (p = 0.0002). In LTT, decreases in energy and fat intakes with synbiotic were not significant (p = 0.14 and p = 0.18, respectively) and there were no differences in dietary fibre intake.

Conclusion

Consuming 200 g/day of synbiotic yogurt did not significantly alter GTT in healthy adults, but was well tolerated and helped to reduce overall energy intake.

Fiber and prebiotics: mechanisms and health benefits

The health benefits of dietary fiber have long been appreciated. Higher intakes of dietary fiber are linked to less cardiovascular disease and fiber plays a role in gut health, with many effective laxatives actually isolated fiber sources. Higher intakes of fiber are linked to lower body weights. Only polysaccharides were included in dietary fiber originally, but more recent definitions have included oligosaccharides as dietary fiber, not based on their chemical measurement as dietary fiber by the accepted total dietary fiber (TDF) method, but on their physiological effects. Inulin, fructo-oligosaccharides, and other oligosaccharides are included as fiber in food labels in the US. Additionally, oligosaccharides are the best known "prebiotics", "a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well-bring and health." To date, all known and suspected prebiotics are carbohydrate compounds, primarily oligosaccharides, known to resist digestion in the human small intestine and reach the colon where they are fermented by the gut microflora. Studies have provided evidence that inulin and oligofructose (OF), lactulose, and resistant starch (RS) meet all aspects of the definition, including the stimulation of Bifidobacterium, a beneficial bacterial genus. Other isolated carbohydrates and carbohydrate-containing foods, including galactooligosaccharides (GOS), transgalactooligosaccharides (TOS), polydextrose, wheat dextrin, acacia gum, psyllium, banana, whole grain wheat, and whole grain corn also have prebiotic effects.

Effects of indigestible carbohydrates in barley on glucose metabolism, appetite and voluntary food intake over 16 h in healthy adults

Background

Recent knowledge in animals suggests that gut microbial metabolism may affect host metabolism, including appetite regulating hormones. The aim of the present study was to evaluate the potential effects of a whole grain barley kernel product, rich in intrinsic indigestible carbohydrates (dietary fibre and resistant starch), on markers of metabolism and appetite regulation in healthy subjects.

Methods

Boiled barley kernels (BK) or white wheat bread (WWB; reference) were provided as late evening meals to 19 young adults in random order using a cross-over design. During subsequent ad libitum standardized breakfast and lunch meals (10.5-16 h), blood was collected for analysis of glucose, plasma insulin, adiponectin, ghrelin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), serum free fatty acids (FFA) and interleukin (IL)-6. In addition, appetite sensations, voluntary energy intake and breath H₂ were determined.

Results

BK as evening meal increased plasma GLP-1 at fasting (P < 0.05) and during the experimental day (P < 0.01) compared with WWB. In addition the BK evening meal decreased fasting serum FFA (P < 0.05) and tended to decrease fasting serum IL-6 (P = 0.06). At lunch, preceded by BK evening meal, voluntary energy intake was decreased (P < 0.05) when compared to WWB evening meal. The BK evening meal decreased incremental blood glucose area (P < 0.01), promoted higher breath H₂ (P < 0.001), maintained adiponectin concentrations (P < 0.05) and reduced perceived hunger (P < 0.05) during 10.5-16 h after the meal.

Conclusions

The results indicate that the BK evening meal, facilitate glucose regulation, increase the release of GLP-1, reduce subsequent energy intake while at the same time decreasing hunger over 2 subsequent meals, and reduce fasting FFA the subsequent morning, possibly mediated through gut microbial fermentation of the indigestible carbohydrates.

Effects of a brown beans evening meal on metabolic risk markers and appetite regulating hormones at a subsequent standardized breakfast: a randomized cross-over study

BACKGROUND

Dietary prevention strategies are increasingly recognized as essential to combat the current epidemic of obesity and related metabolic disorders. The purpose of the present study was to evaluate the potential prebiotic effects of indigestible carbohydrates in Swedish brown beans (Phaseolus vulgaris var. nanus) in relation to cardiometabolic risk markers and appetite regulating hormones.

METHODS

Brown beans, or white wheat bread (WWB, reference product) were provided as evening meals to 16 healthy young adults in a randomised crossover design. Glucose, insulin, appetite regulatory hormones, GLP-1, GLP-2, appetite sensations, and markers of inflammation were measured at a following standardised breakfast, that is at 11 to 14 h post the evening meals. Additionally, colonic fermentation activity was estimated from measurement of plasma short chain fatty acids (SCFA, including also branched chain fatty acids) and breath hydrogen (H2) excretion.

RESULTS

An evening meal of brown beans, in comparison with WWB, lowered blood glucose (-15%, p<0.01)- and insulin (-16%, p<0.05) responses, increased satiety hormones (PYY 51%, p<0.001), suppressed hunger hormones (ghrelin -14%, p<0.05), and hunger sensations (-15%, p = 0.05), increased GLP-2 concentrations (8.4%, p<0.05) and suppressed inflammatory markers (IL-6 -35%, and IL-18 -8.3%, p<0.05) at a subsequent standardised breakfast. Breath H2 (141%, p<0.01), propionate (16%, p<0.05), and isobutyrate (18%, P<0.001) were significantly increased after brown beans compared to after WWB, indicating a higher colonic fermentative activity after brown beans.

CONCLUSIONS

An evening meal with brown beans beneficially affected important measures of cardiometabolic risk and appetite regulatory hormones, within a time frame of 11-14 h, in comparison to a WWB evening meal. Concentrations of plasma SCFA and H2 were increased, indicating involvement of colonic fermentation. Indigestible colonic substrates from brown beans may provide a preventive tool in relation to obesity and the metabolic syndrome.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01706042.

Gut microbiota and metabolic disorders: How prebiotic can work?

Experimental data in animals, but also observational studies in obese patients, suggest that the composition of the gut microbiota differs in obese v. lean individuals, in diabetic v. non-diabetic patients or in patients presenting other diseases associated with obesity or nutritional dysbalance, such as non-alcoholic steatohepatitis. In the present review, we will describe how changes in the gut microbiota composition and/or activity by dietary fibres with prebiotic properties, can modulate host gene expression and metabolism. We will evaluate their potential relevance in the management of obesity and related metabolic disturbances, in view of the experimental data and intervention studies published up to date.

Methane and hydrogen positivity on breath test is associated with greater body mass index and body fat

CONTEXT

Colonization of the gastrointestinal tract with methanogenic archaea (methanogens) significantly affects host metabolism and weight gain in animal models, and breath methane is associated with a greater body mass index (BMI) among obese human subjects.

OBJECTIVE

The objective of the study was to characterize the relationship between methane and hydrogen on breath test (as a surrogate for colonization with the hydrogen requiring methanogen, Methanobrevibacter smithii), body weight, and percent body fat in a general population cohort.

DESIGN AND SUBJECTS

This was a prospective study (n = 792) of consecutive subjects presenting for breath testing.

SETTING

The study was conducted at a tertiary care center.

OUTCOME MEASUREMENTS

BMI and percent body fat were measured.

RESULTS

Subjects were classified into 4 groups based on breath testing: normal (N) (methane <3 ppm and hydrogen <20 ppm at or before 90 minutes); hydrogen positive only (H+) [methane <3 ppm and hydrogen ≥20 ppm); methane positive only (M+) (methane ≥3 ppm and hydrogen <20 ppm), or methane and hydrogen positive (M+/H+) (methane ≥3 ppm and hydrogen ≥20 ppm]. There were significant differences in age but not in gender across the groups. After controlling for age as a confounding variable, M+/H+ subjects had significantly higher BMI than other groups (N: 24.1 ± 5.2 kg/m(2); H+: 24.2 ± 4.5 kg/m(2); M+: 24.0 ± 3.75 kg/m(2); M+/H+: 26.5 ± 7.1 kg/m(2), P < .02) and also had significantly higher percent body fat (N: 28.3 ± 10.0%; H+: 27.5 ± 9.0%; M+: 28.0 ± 8.9%; M+/H+; 34.1 ± 10.9%, P < .001).

CONCLUSIONS

The presence of both methane and hydrogen on breath testing is associated with increased BMI and percent body fat in humans. We hypothesize that this is due to colonization with the hydrogen-requiring M smithii, which affects nutrient availability for the host and may contribute to weight gain.

Gut microbiota and metabolic syndrome

Symbiosis is the result of the relationship between gut microbiota and human surfaces; in fact, it regulates many functions such as metabolic and protective ones. It is widely known that any changes in the microbes in gut microbiota (dysbiosis) and the regulation of mucosal and systemic host's immunity have been linked to different diseases such as metabolic syndromes and associated disorders. Recent studies report an aberrant gut microbiota and an alteration of gut microbial metabolic activities in obese subjects, with an important influence of a number of human physiological functions. Most studies suggest that diet, especially the high-fat low-fiber western-style diet, dramatically impacts on gut microbiota composition and functions in those patients with metabolic syndrome. A deeper knowledge of a specific microbiota profile associated with increased risk of metabolic disease and its subsequent modification induced by prebiotics, probiotics or targeted antibiotics will be necessary for the development of new therapeutic approaches in the treatment of metabolic disease.

Diet, microbiome, and the intestinal epithelium: an essential triumvirate?

The intestinal epithelium represents a critical barrier protecting the host against diverse luminal noxious agents, as well as preventing the uncontrolled uptake of bacteria that could activate an immune response in a susceptible host. The epithelial monolayer that constitutes this barrier is regulated by a meshwork of proteins that orchestrate complex biological function such as permeability, transepithelial electrical resistance, and movement of various macromolecules. Because of its key role in maintaining host homeostasis, factors regulating barrier function have attracted sustained attention from the research community. This paper will address the role of bacteria, bacterial-derived metabolism, and the interplay of dietary factors in controlling intestinal barrier function.

Gut hormone release and appetite regulation in healthy non-obese participants following oligofructose intake. A dose-escalation study

Prevention of weight gain in adults is a major public health target. Animal experiments have consistently demonstrated a relationship between fermentable carbohydrate intake, such as oligofructose, anorectic gut hormones, and appetite suppression and body weight control. This study was designed to determine the dose of oligofructose which would augment the release of anorectic gut hormones and reduce appetite consistently in non-obese humans. Twelve non-obese participants were recruited for a 5-week dose-escalation study. Following a 9-14-day run-in, participants increased their daily oligofructose intake every week from 15, 25, 35, 45, to 55 g daily. Subjective appetite and side effects were monitored daily. Three-day food diaries were completed every week. Appetite study sessions explored the acute effects of 0, 15, 35, and 55 g oligofructose on appetite-related hormones, glycaemia, subjective appetite, and energy intake. In the home environment, oligofructose suppressed hunger, but did not affect energy intake. Oligofructose dose-dependently increased peptide YY, decreased pancreatic polypeptide and tended to decrease ghrelin, but did not significantly affect appetite profile, energy intake, glucose, insulin, or glucagon-like peptide 1 concentrations during appetite study sessions. In conclusion, oligofructose supplementation at ≥ 35 g/day increased peptide YY and suppressed pancreatic polypeptide and hunger; however, energy intake did not change significantly.

Nutrients related to GLP1 secretory responses

The hormone glucagon-like peptide (GLP-1) is secreted from gut endocrine L cells in response to ingested nutrients. The activities of GLP-1 include stimulating insulin gene expression and biosynthesis, improving β-cell proliferation, exogenesis, and survival. Additionally, it prevents β-cell apoptosis induced by a variety of cytotoxic agents. In extrapancreatic tissues, GLP-1 suppresses hunger, delays gastric emptying, acts as an ileal brake, and increases glucose uptake. The pleiotropic actions of GLP-1, especially its glucose-lowering effect, gave rise to the suggestion that it is a novel approach to insulin resistance treatment. Hormones secreted from the gut including GLP-1, which are involved in the regulation of insulin sensitivity and secretions, have been found to be affected by nutrient intake. In recent years, there has been a growing interest in the effect nutrients may have on GLP-1 secretion; some frequently studied dietary constituents include monounsaturated fatty acids, fructooligosaccharides, and glutamine. This review focuses on the influence that the carbohydrate, fat, and protein components of a meal may have on the GLP-1 postprandial responses.

Dietary fibre fermentability but not viscosity elicited the ‘second-meal effect’ in healthy adult dogs

The present study evaluated the effects of fibre fermentability and viscosity in a morning meal on glucose, insulin and glucagon-like peptide-1 (GLP-1) responses to a glucose challenge later in the day in six healthy female dogs. For this purpose, two Latin square design experiments were performed. In Expt 1, dogs were fed a low-fibre (LF; 1 % Solka-Floc (International Fiber Corporation) and 1 % soya hulls) diet, a low-fermentable fibre (LFF; 5 % Solka-Floc (International Fiber Corporation) and 3 % soya hulls) diet or a high-fermentable fibre (HFF; 5 % pectin and 3 % short-chain fructo-oligosaccharides) diet. In Expt 2, dogs were fed a low-viscosity fibre (5 % Solka-Floc (International Fiber Corporation) and 3 % soya hulls) diet, a moderate-viscosity fibre (MVF; 2 % Solka-Floc (International Fiber Corporation), 2 % soya hulls, 2 % psyllium and 2 % pectin) diet or a high-viscosity fibre (HVF; 4 % psyllium and 4 % pectin) diet. Dogs were fed at 08.00, 12.00 and 16.00 hours on days 1–6 of each period. On day 7, dogs were fed at 08.00 hours and then dosed with maltodextrin at 12.00 hours. Data were analysed to identify baseline and incremental AUC (IAUC) changes among the treatments. In Expt 1, glucose IAUC0–180min was lower (P< 0·05) in dogs fed the HFF v. LF and LFF diets. Insulin and GLP-1 IAUC0–180min were not affected. In Expt 2, baseline GLP-1 was greater (P< 0·005) and baseline insulin was lower (P< 0·05) in dogs fed the HVF v. MVF diet, but glucose, insulin and GLP-1 IAUC0–180min were not affected. In summary, HFF in a morning meal has the potential to decrease blood glucose response in a consequent meal.

Probiotics as potential biotherapeutics in the management of type 2 diabetes - prospects and perspectives

Diabetes mellitus is a looming epidemic worldwide, affecting almost all major sections of society, creating burdens on global health and economy. A large number of studies have identified a series of multiple risk factors such as genetic predisposition, epigenetic changes, unhealthy lifestyle, and altered gut microbiota that cause increased adiposity, β-cell dysfunction, hyperglycemia, hypercholesterolemia, adiposity, dyslipidaemia, metabolic endotoxemia, systemic inflammation, intestinal permeability (leaky gut), defective secretion of incretins and oxidative stress associated with type 2 diabetes (T2D). Recent studies have proposed multifactorial interventions including dietary manipulation in the management of T2D. The same interventions have also been recommended by many national and international diabetes associations. These studies are aimed at deciphering the gut microbial influence on health and disease. Interestingly, results from several genomic, metagenomic and metabolomic studies have provided substantial information to target gut microbiota by dietary interventions for the management of T2D. Probiotics particularly lactobacilli and bifidobacteria have recently emerged as the prospective biotherapeutics with proven efficacy demonstrated in various in vitro and in vivo animal models adequately supported with their established multifunctional roles and mechanism of action for the prevention and disease treatment. The dietary interventions in conjunction with probiotics - a novel multifactorial strategy to abrogate progression and development of diabetes - hold considerable promise through improving the altered gut microbial composition and by targeting all the possible risk factors. This review will highlight the new developments in probiotic interventions and future prospects for exploring probiotic therapy in the prevention and control of lifestyle diseases like T2D.

Nutrition, the gut microbiome and the metabolic syndrome

Metabolic syndrome is a lifestyle disease, determined by the interplay of genetic and environmental factors. Obesity is a significant risk factor for development of the metabolic syndrome, and the prevalence of obesity is increasing due to changes in lifestyle and diet. Recently, the gut microbiota has emerged as an important contributor to the development of obesity and metabolic disorders, through its interactions with environmental (e.g. diet) and genetic factors. Human and animal studies have shown that alterations in intestinal microbiota composition and shifts in the gut microbiome towards increased energy harvest are associated with an obese phenotype. However, the underlying mechanisms by which gut microbiota affects host metabolism still need to be defined. In this review we discuss the complexity surrounding the interactions between diet and the gut microbiota, and their connection to obesity. Furthermore, we review the literature on the effects of probiotics and prebiotics on the gut microbiota and host metabolism, focussing primarily on their anti-obesity potential.

Diabetes, obesity and gut microbiota

The gut microbiota composition has been associated with several hallmarks of metabolic syndrome (e.g., obesity, type 2 diabetes, cardiovascular diseases, and non-alcoholic steatohepatitis). Growing evidence suggests that gut microbes contribute to the onset of the low-grade inflammation characterising these metabolic disorders via mechanisms associated with gut barrier dysfunctions. Recently, enteroendocrine cells and the endocannabinoid system have been shown to control gut permeability and metabolic endotoxaemia. Moreover, targeted nutritional interventions using non-digestible carbohydrates with prebiotic properties have shown promising results in pre-clinical studies in this context, although human intervention studies warrant further investigations. Thus, in this review, we discuss putative mechanisms linking gut microbiota and type 2 diabetes. These data underline the advantage of investigating and changing the gut microbiota as a therapeutic target in the context of obesity and type 2 diabetes.

Effects of dietary fibers with different fermentation characteristics on feeding motivation in adult female pigs

Dietary fibers can be fermented in the colon, resulting in production of short-chain fatty acids (SCFA) and secretion of satiety-related peptides. Fermentation characteristics (fermentation kinetics and SCFA-profile) differ between fibers and could impact their satiating potential. We investigated the effects of fibers with varying fermentation characteristics on feeding motivation in adult female pigs. Sixteen pair-housed pigs received four diets in four periods in a Latin square design. Starch from a control (C) diet was exchanged, based on gross energy, for inulin (INU), guar gum (GG), or retrograded tapioca starch (RS), each at a low (L) and a high (H) inclusion level. This resulted in a decreased metabolizable energy intake when feeding fiber diets as compared with the C diet. According to in vitro fermentation measurements, INU is rapidly fermentable and yields relatively high amounts of propionate, GG is moderately rapidly fermentable and yields relatively high amounts of acetate, and RS is slowly fermentable and yields relatively high amounts of butyrate. Feeding motivation was assessed using behavioral tests at 1h, 3h and 7h after the morning meal, and home pen behavioral observations throughout the day. The number of wheel turns paid for a food reward in an operant test was unaffected by diet. Pigs on H-diets ran 25% slower for a food reward in a runway test than pigs on L-diets, and showed less spontaneous physical activity and less stereotypic behavior in the hours before the afternoon meal, reflecting increased interprandial satiety. Reduced feeding motivation with increasing inclusion level was most pronounced for RS, as pigs decreased speed in the runway test and tended to have a lower voluntary food intake in an ad libitum food intake test when fed RS-H. In conclusion, increasing levels of fermentable fibers in the diet seemed to enhance satiety in adult pigs, despite a reduction in metabolizable energy supply. RS was the most satiating fiber, possibly due to its slow rate of fermentation and high production of butyrate.

Antimicrobials: Strategies for targeting obesity and metabolic health?

Obesity is associated with a number of serious health consequences, including type 2 diabetes, cardiovascular disease and a variety of cancers among others and has been repeatedly shown to be associated with a higher risk of mortality. The relatively recent discovery that the composition and metabolic activity of the gut microbiota may affect the risk of developing obesity and related disorders has led to an explosion of interest in this distinct research field. A corollary of these findings would suggest that modulation of gut microbial populations can have beneficial effects with respect to controlling obesity. In this addendum, we summarize our recent data, showing that therapeutic manipulation of the microbiota using different antimicrobial strategies may be a useful approach for the management of obesity and metabolic conditions. In addition, we will explore some of the mechanisms that may contribute to microbiota-induced susceptibility to obesity and metabolic diseases.