Ileal short-chain fatty acids inhibit gastric motility by a humoral pathway

Effect of sorghum flour-containing pasta on postprandial glycemia, appetite and energy intake in healthy individuals

BACKGROUND/OBJECTIVES

In vitro studies suggest that incorporating sorghum flour into staple foods including pasta reduces their starch digestibility and hence may suppress postprandial blood glucose levels, appetite and energy intake; however, these effects in humans have yet to be reported. Therefore, this study investigated the effect of red and white sorghum-containing pasta on blood glucose response, appetite and energy intake in humans.

SUBJECTS/METHODS

In a randomised crossover design, healthy individuals (n = 20) consumed the following three iso-caloric test meals (each providing 50 g available carbohydrates) as breakfast: control pasta (CP) made from100% durum wheat; 30% red sorghum pasta (RSP) and; 30% white sorghum pasta (WSP). Blood glucose and subjective appetite were measured postprandially for 2 and 3 h, respectively. Energy intakes from ad libitum lunch consumed 3 h after breakfast and for the remainder of the day were also measured. Incremental areas under or over the curves (iAUCs/iAOCs) for blood glucose and appetite parameters were calculated.

RESULTS

The RSP meal resulted in significantly lower blood glucose response (-0.35 ± 0.09 mmol/l; 95% CI: -0.61 ~ -0.09; P = 0.005) and glucose iAUC over 120 min (-36.11 ± 10.53 mmol/l × min; 95% CI: -67.11 ~ -5.11; P = 0.017) compared to CP meal. Compared to CP meal, the RSP meal resulted in significantly higher satiety iAUC (1219.46 ± 383.26 mm × min; 95% 91.18 ~ 2347.75; P = 0.029), lower hunger iAOC (-1410.47 ± 349.14 mm x min; 95% CI: -2438.30 ~ -382.63; P = 0.004) and lower prospective food intake iAOC (-1645.73 ± 324.14 mm x min; 95% CI: -2599.97 ~ -691.49; P < 0.001). Energy intake at ad libitum lunch was significantly lower after the RSP meal than after the CP meal (-794.17 ± 163.25 kJ; 95% CI: -1274.77 ~ -313.57; P = 0.001).

CONCLUSION

The results indicate that red sorghum addition into pasta provides a product inducing reduced glycemia, favourably changed appetite parameters and decreased subsequent energy intake.

Resistant starch and type 2 diabetes mellitus: Clinical perspective

The immediate and well-documented benefits of carbohydrate restriction include improved glycemic control in individuals with diabetes mellitus. Starch, a significant source of carbohydrates, is categorized as rapidly digestible, slowly digestible, or resistant starch (RS). RS, which is a non-viscous fermentable fiber, has shown promise in animal studies for antidiabetic effects by improving glucose metabolism. Although the exact mechanism by which RS affects glucose metabolism remains unclear, it is expected to positively impact glucose tolerance and insulin sensitivity. The fermentation of RS by colonic microbiota in the large bowel produces short-chain fatty acids, which exert multiple metabolic effects on glucose regulation and homeostasis. Moreover, RS may influence glucose metabolism via bile acid modulation, independent of its fermentation. Diets rich in RS could aid in blood glucose homeostasis. However, it is uncertain whether they can alter the metabolic pathology associated with glucose regulation. In essence, RS has the potential to lower postprandial glucose levels similarly to a low-glycemic index diet. Yet, its efficacy as a medical nutrition therapy for type 2 diabetes needs further investigation. To confirm the role of RS in glycemic control and to possibly recommend it as an additional dietary approach for people with type 2 diabetes mellitus, a well-designed, large-scale intervention is required.

Pectin mediates the mechanism of host blood glucose regulation through intestinal flora

Pectin is a complex polysaccharide found in plant cell walls and interlayers. As a food component, pectin is benefit for regulating intestinal flora. Metabolites of intestinal flora, including short-chain fatty acids (SCFAs), bile acids (BAs) and lipopolysaccharides (LPS), are involved in blood glucose regulation. SCFAs promote insulin synthesis through the intestine-GPCRs-derived pathway and hepatic adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway to promote hepatic glycogen synthesis. On the one hand, BAs stimulate intestinal L cells and pancreatic α cells to secrete Glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) through receptors G protein-coupled receptor (TGR5) and farnesoid X receptor (FXR). On the other hand, BAs promote hepatic glycogen synthesis through AMPK pathway. LPS inhibits the release of inflammatory cytokines through Toll-like receptors (TLRs)-myeloid differentiation factor 88 (MYD88) pathway and mitogen-activated protein kinase (MAPK) pathway, thereby alleviating insulin resistance (IR). In brief, both SCFAs and BAs promote GLP-1 secretion through different pathways, employing strategies of increasing glucose consumption and decreasing glucose production to maintain normal glucose levels. Notably, pectin can also directly inhibit the release of inflammatory cytokines through the -TLRs-MYD88 pathway. These data provide valuable information for further elucidating the relationship between pectin-intestinal flora-glucose metabolism.

The Molecular Determinants of Glucagon-like Peptide Secretion by the Intestinal L cell

The intestinal L cell secretes a diversity of biologically active hormones, most notably the glucagon-like peptides, GLP-1 and GLP-2. The highly successful introduction of GLP-1-based drugs into the clinic for the treatment of patients with type 2 diabetes and obesity, and of a GLP-2 analog for patients with short bowel syndrome, has led to the suggestion that stimulation of the endogenous secretion of these peptides may serve as a novel therapeutic approach in these conditions. Situated in the intestinal epithelium, the L cell demonstrates complex relationships with not only circulating, paracrine, and neural regulators, but also ingested nutrients and other factors in the lumen, most notably the microbiota. The integrated input from these numerous secretagogues results in a variety of temporal patterns in L cell secretion, ranging from minutes to 24 hours. This review combines the findings of traditional, physiological studies with those using newer molecular approaches to describe what is known and what remains to be elucidated after 5 decades of research on the intestinal L cell and its secreted peptides, GLP-1 and GLP-2.

The role of dietary fibers in regulating appetite, an overview of mechanisms and weight consequences

Dietary fibers prevent obesity through reduction of hunger and prolongation of satiety. A number of mechanical and endocrine signals from gastrointestinal tract are stimulated by fibers and their fermentation products, reach regions of brain involved in the regulation of appetite, and ultimately reduce food intake. Gastric distention, delayed gastric emptying, prevention of hypoglycemic, increased amounts of unabsorbed nutrients reaching to the ileum, and stimulation of enteroendocrine cells for secretion of cholecystokinin, glucagon-like peptide-1 (GLP-1), and peptide YY are among mechanisms of fibers in decreasing hunger and prolongation of satiety. Fermentation of fibers produces short-chain fatty acids that also stimulates enteroendocrine cells to secrete GLP-1 and PYY. Randomized controlled trials have shown reductions in energy intake and body weight along with increased satiation and reduced hunger following consumption of fibers. Prospective cohort studies have confirmed these results but the extent of weight loss in some studies has been small. Controversies exist between studies particularly for the effect of fibers on the gastrointestinal hormones, subsequent food intake, and the resultant weight loss. More studies are needed before a clear conclusion can be drawn especially for the effect of fibers on appetite-related hormones and weight loss.

Influence of the Gut Microbiome on Feed Intake of Farm Animals

With the advancement of microbiome research, the requirement to consider the intestinal microbiome as the “last organ” of an animal emerged. Through the production of metabolites and/or the stimulation of the host’s hormone and neurotransmitter synthesis, the gut microbiota can potentially affect the host’s eating behavior both long and short-term. Based on current evidence, the major mediators appear to be short-chain fatty acids (SCFA), peptide hormones such as peptide YY (PYY) and glucagon-like peptide-1 (GLP-1), as well as the amino acid tryptophan with the associated neurotransmitter serotonin, dopamine and γ-Aminobutyrate (GABA). The influence appears to extend into central neuronal networks and the expression of taste receptors. An interconnection of metabolic processes with mechanisms of taste sensation suggests that the gut microbiota may even influence the sensations of their host. This review provides a summary of the current status of microbiome research in farm animals with respect to general appetite regulation and microbiota-related observations made on the influence on feed intake. This is briefly contrasted with the existing findings from research with rodent models in order to identify future research needs. Increasing our understanding of appetite regulation could improve the management of feed intake, feed frustration and anorexia related to unhealthy conditions in farm animals.

Gastrin and Nitric Oxide Production in Cultured Gastric Antral Mucosa Are Altered in Response to a Gastric Digest of a Dietary Supplement

In vitro organ culture can provide insight into isolated mucosal responses to particular environmental stimuli. The objective of the present study was to investigate the impact of a prolonged culturing time as well as the addition of acidic gastric fluid into the in vitro environment of cultured gastric antral tissue to evaluate how altering the commonly used neutral environment impacted tissue. Furthermore, we aimed to investigate the impact of G's Formula, a dietary supplement for horses, on the secretion of gastrin, interleukin1-beta (IL-1β), and nitric oxide (NO). These biomarkers are of interest due to their effects on gastric motility and mucosal activity. Gastric mucosal tissue explants from porcine stomachs were cultured in the presence of a simulated gastric fluid (BL, n = 14), simulated gastric fluid containing the dietary supplement G's Formula (DF, n = 12), or an equal volume of phosphate buffered saline (CO, n = 14). At 48 and 60 h, 10⁻⁵ M carbachol was used to stimulate gastrin secretion. Cell viability was assessed at 72 h using calcein and ethidium-homodimer 1 staining. Media was analyzed for gastrin, IL-1β, and NO at 48, 60, and 72 h. There were no effects of treatment or carbachol stimulation on explant cell viability. Carbachol resulted in a significant increase in gastrin concentration in CO and DF treatments, but not in BL. NO was higher in CO than in BL, and NO increased in the CO and DF treatments but not in BL. In conclusion, the addition of carbachol and gastric digests to culture media did not impact cell viability. The use of an acidic gastric digest (BL) reduced the effect of cholinergic stimulation with carbachol at a concentration of 10⁻⁵ M and reduced NO secretion. The addition of the dietary supplement to the gastric digest (DF) appeared to mediate these effects within this model. Further research is required to evaluate the specific effects of this dietary supplement on direct markers of mucosal activity and the functional relevance of these results in vivo.

Effect of Total Starch and Resistant Starch in Commercial Extruded Dog Foods on Gastric Emptying in Siberian Huskies

Simple Summary

Gastric emptying is the release of nutrients from the stomach into the small intestine. The rate at which gastric emptying occurs may be associated with diabetes and obesity risk in humans and could help prevent weight gain in dogs. The largest portion of carbohydrates in pet diets is provided by various starches that are digested and absorbed at different rates. This study investigated the effects of common starch ingredients found in commercial dog foods on the gastric emptying rate in dogs. Dogs received each test diet once (4 total) and a glucose control twice in a randomized order, along with acetaminophen. Blood samples were taken once prior to meal consumption and at multiple time points after to determine acetaminophen concentrations. A mathematical model was used to estimate the rate of gastric emptying using postprandial acetaminophen concentrations. Overall, more gastric emptying occurred at a faster rate in dogs when fed the diet containing the highest fraction of starch ingredients resistant to canine digestion. These findings suggest that the inclusion of different starch sources may be associated with altered digestion and absorption of nutrients, which consequently affects gastric emptying rate. The link between carbohydrate sources and gastric emptying may provide a mechanism to prevent weight gain in dogs.

Abstract

Gastric emptying rate (GER) may impact diabetes and obesity in humans and could provide a method to reduce canine weight gain. Starch, the most common source of carbohydrates (CHOs) in pet food, is classified as rapidly or slowly digestible, or resistant to digestion. This study investigated starch source effects in commercial extruded dog foods on the GER of 11 healthy adult Siberian Huskies. Test diets were classified as traditional, grain-free, whole-grain, and vegan. Dogs received each diet once, a glucose control twice, and acetaminophen (Ac) as a marker for GER in a randomized, partially replicated, 6 × 6 Latin square design. Pre- and post-prandial blood samples were collected at 16 timepoints from −15 to 480 min. Serum Ac concentrations were assessed via standard spectrophotometric assays and fitted with a mathematical model to estimate parameters of GER. Parameter values were subjected to ANOVA, with period and treatment as fixed effects and dog as a random effect. More total emptying (p = 0.074) occurred at a faster rate (p = 0.028) in dogs fed the grain-free diet, which contained the lowest total starch (34.03 ± 0.23%) and highest resistant starch (0.52 ± 0.007%). This research may benefit future diet formulations to reduce the prevalence of canine weight gain.

The Gut-Liver Axis in the Control of Energy Metabolism and Food Intake in Animals

Recent research has convincingly demonstrated a bidirectional communication axis between the gut and liver that enables the gut microbiota to strongly affect animals' feeding behavior and energy metabolism. As such, the gut-liver axis enables the host to control and shape the gut microbiota and to protect the intestinal barrier. Gut microbiota-host communication is based on several gut-derived compounds, such as short-chain fatty acids, bile acids, methylamines, amino acid-derived metabolites, and microbial-associated molecular patterns, which act as communication signals, and multiple host receptors, which sense the signals, thereby stimulating signaling and metabolic pathways in all key tissues of energy metabolism and food intake regulation. Disturbance in the microbial ecosystem balance, or microbial dysbiosis, causes profound derangements in the regulation of appetite and satiety in the hypothalamic centers of the brain and in key metabolic pathways in peripheral tissues owing to intestinal barrier disruption and subsequent induction of hepatic and hypothalamic inflammation.

Review: Effects of fibre, grain starch digestion rate and the ileal brake on voluntary feed intake in pigs

Grains rich in starch constitute the primary source of energy for both pigs and humans, but there is incomplete understanding of physiological mechanisms that determine the extent of digestion of grain starch in monogastric animals including pigs and humans. Slow digestion of starch to produce glucose in the small intestine (SI) leads to undigested starch escaping to the large intestine where it is fermented to produce short-chain fatty acids. Glucose generated from starch provides more energy than short-chain fatty acids for normal metabolism and growth in monogastrics. While incomplete digestion of starch leads to underutilised feed in pigs and economic losses, it is desirable in human nutrition to maintain consistent body weight in adults. Undigested nutrients reaching the ileum may trigger the ileal brake, and fermentation of undigested nutrients or fibre in the large intestine triggers the colonic brake. These intestinal brakes reduce the passage rate in an attempt to maximise nutrient utilisation, and lead to increased satiety that may reduce feed intake. The three physiological mechanisms that control grain digestion and feed intake are: (1) gastric emptying rate; (2) interplay of grain digestion and passage rate in the SI controlling the activation of the ileal brake; and (3) fermentation of undigested nutrients or fibre in the large intestine activating the colonic brake. Fibre plays an important role in influencing these mechanisms and the extent of their effects. In this review, an account of the physiological mechanisms controlling the passage rate, feed intake and enzymatic digestion of grains is presented: (1) to evaluate the merits of recently developed methods of grain/starch digestion for application purposes; and (2) to identify opportunities for future research to advance our understanding of how the combination of controlled grain digestion and fibre content can be manipulated to physiologically influence satiety and food intake.

Pigs Ferment Enzymatically Digestible Starch when it Is Substituted for Resistant Starch

BACKGROUND

Feeding behavior is controlled by satiety mechanisms, which are affected by the extent of starch digestion, and thus resistant starch (RS) intake. Alterations in feeding behavior to changes in RS intake may depend on the adaptation of processes involved when shifting from starch digestion to fermentation or vice versa.

OBJECTIVES

The aim of this study was to investigate how growing pigs adapt their feeding behavior in response to increasing and decreasing dietary RS concentrations.

METHODS

Thirty-six groups of 6 pigs (25.4 ± 2.8 kg; Hypor Libra × Hypor Maxter; male:female, 1:1) were fed diets containing 50% high-amylose maize starch (high RS; HRS) or waxy maize starch (low RS; LRS). Over 28 d, diets were exchanged following a 5-step titration (25% per step) that was executed in the upward (LH) or downward direction (HL). Twelve groups received a control diet to correct for changes over time. Individual feeding behavior and total tract starch digestion and fermentation were evaluated. The response in each parameter to increasing dietary HRS inclusion was estimated through the use of linear regression procedures, and tested for titration direction and sex effects.

RESULTS

Complete substitution of LRS with HRS increased the proportion of starch fermented, which was greater in LH pigs than in HL pigs (17.6% compared with 8.18%; P < 0.001), and decreased the feed intake (106 g/d; P = 0.021) and meal size (12.6 g; P < 0.001) of LH pigs, but not of HL pigs. In LH pigs, the size of the starch fermentation response positively correlated with the size of the feed intake response (r = 0.90, P < 0.001).

CONCLUSIONS

The attenuated response in starch fermentation in HL pigs indicates that pigs adapt more slowly to dietary supply of digestible starch than to RS, consequently resulting in fermentation of enzymatically digestible starch. Feed intake and feeding behavior only changed in pigs poorly adapting to RS, indicating that adequacy of adaptation, rather than RS itself, drives feed intake. These findings stress the importance of diet history for nutrient digestion and feeding behavior.

Effect of arabinoxylo-oligosaccharides and arabinoxylans on net energy and nutrient utilization in broilers

Arabinoxylo-oligosaccharides (AXOS) are hydrolytic degradation products of arabinoxylans (AX) that can be fermented by the gut microbiota, thus potentially displaying prebiotic properties. This study examined the effects of AX and AXOS on net energy (NE) and nutrient utilization in broilers. Ross 308 broilers (n = 90, 30 birds per treatment) were fed wheat-soybean diets supplemented with pure AX, AXOS produced by exposing the AX to xylanase in vitro (AXOS), or AX with xylanase (AX + E) from d 10 to 21. Performance parameters were measured from d 10 to 21. On d 15, 10 birds per treatment were allocated to closed-circuit net energy chambers to assess the impact of AX and AXOS on dietary energy utilization, through assessment of both metabolisable energy (ME) and NE. Ileal and caecal digesta samples were collected on d 21 to determine the effect of AX and AXOS on ileal and total tract dry matter digestibility, ileal digestible energy, digesta pH, short chain fatty acids (SCFA) and microbiota concentration. Feed conversion ratio was numerically the lowest in birds fed the diet supplemented with AXOS, which is 1.26 compared to 1.37 and 1.30 for AX and AX + E, respectively. Ileal dry matter digestibility was higher in birds fed AXOS than those fed AX (P = 0.047). Ileal digestible energy and total tract dry matter digestibility were higher in birds fed AXOS than those fed AX or AX + E (P = 0.004 and P = 0.001, respectively). Birds fed AXOS had higher ME intake (P = 0.049) and nitrogen retention (P = 0.001) and a strong trend of higher NE (P = 0.056), NE intake (P = 0.057) and retained energy (P = 0.054) compared to those fed AX. Ileal total SCFA, lactic and formic acid concentrations were higher in birds fed AXOS than those fed AX (P = 0.011, P = 0.012 and P = 0.023, respectively). Birds fed AXOS or AX + E had higher caecal total SCFA, acetic, butyric and isovaleric acid concentrations compared to those fed AX (P = 0.001, P = 0.004, P = 0.016 and P = 0.008, respectively), and caecal propionic acid concentration was higher in birds fed AX + E than those fed AX (P = 0.050). Ileal and caecal microbiota concentrations were numerically higher and pH was lower in birds fed AXOS and AX + E than those fed AX. Results from this study indicate that feeding AXOS directly is more efficient than AXOS generation in the gastrointestinal tract, and suggest that AXOS has a potential to be an efficacious prebiotic in broiler diets.

Is It Time to Use Probiotics to Prevent or Treat Obesity?

In recent years, attention has been given to the role potentially played by gut microbiota in the development of obesity. Several studies have shown that in individuals with obesity, the gut microbiota composition can be significantly different from that of lean individuals, that faecal bacteria can exert a fundamental role in modulating energy metabolism, and that modifications of gut microbiota composition can be associated with increases or reductions of body weight and body mass index. Based on this evidence, manipulation of the gut microbiota with probiotics has been considered a possible method to prevent and treat obesity. However, despite a great amount of data, the use of probiotics to prevent and treat obesity and related problems remains debated. Studies have found that the probiotic effect on body weight and metabolism is strain specific and that only some of the species included in the Lactobacillus and Bifidobacterium genera are effective, whereas the use of other strains can be deleterious. However, the dosage, duration of administration, and long-term effects of probiotics administration to prevent overweight and obesity are not known. Further studies are needed before probiotics can be rationally prescribed for the prevention or treatment of obesity. Control of the diet and environmental and life-style factors that favour obesity development remain the best solution to problems related to weight gain.

Nutrient and fiber utilization responses of supplemental xylanase in broiler chickens fed wheat based diets are independent of the adaptation period to test diets

The effects of adaptation (AD) to xylanase-supplemented diets on nutrient and fiber utilization in 21-d-old broilers were investigated. Six treatments, arranged in two levels of AD (starting at d 0 or d 14 of age) and three levels of xylanase (0 or 2,500 or 5,000 xylanase units/kg feed) were used. All diets had 500 phytase U/kg and 0.3% TiO2 as indigestible marker. A total of 384 d old male broiler (Ross 308) chicks were divided into two groups. The first group was assigned on weight basis to 24 cages (8 chicks per cage) and randomly allocated to the diets from d 0. Birds in the second group were reared on a commercial starter diet in the same room for 13 d. On d 14, the birds were individually weighed, assigned on weight basis to 24 cages (8 chicks per cage), and randomly allocated to the diets. Birds had free access to experimental diets and water. Excreta samples were collected from d 18 to 21. On d 21, all birds were euthanized to access ileal digesta. There was no interaction (P > 0.05) between AD and xylanase on the apparent ileal digestibility (AID) and apparent retention (AR) of components. The main effect of AD was such that the birds exposed to diets for 7 d (d 14 to 21) had higher (P < 0.01) AID of energy than those exposed for 21 d (d 0 to 21). In contrast, birds exposed to diets for 21 d had higher (P < 0.05) AMEn and AR of neutral detergent fiber. Xylanase improvements (P < 0.01) in the AID of energy and AMEn were dose dependent and coincided with linear improvements (P < 0.05) in the AID of nitrogen, fat, and starch. In conclusion, xylanase improvements on retention of fiber and nutrients were independent of AD (7 or 21 d) suggesting that the xylanase effects are not transitional. Greater retention of fiber with longer AD is suggestive of possible microbial adaptation.

The effects of xylanase on grower pig performance, concentrations of volatile fatty acids and peptide YY in portal and peripheral blood

Non-starch polysaccharides (NSP) present in wheat and barley can act as anti-nutrients leading to an increase in digesta viscosity and a reduction in nutrient digestibility. Xylanase, an NSP-degrading enzyme, has been shown to increase nutrient digestibility in pigs. The objectives of this study were: (1) to identify the optimum inclusion level of xylanase in grower pig diets by measuring the effect of increasing enzyme levels on growth performance, the concentration of volatile fatty acids (VFA) and peptide YY concentration in portal and peripheral blood of grower pigs and (2) to increase our understanding of the interrelationships between xylanase inclusion, VFA production and peptide YY secretion. A total of 512 grower pigs ((Large White×Landrace)×MAXGRO) were allocated to pens creating 32 replicates of four pigs per pen per treatment. Pigs were allocated to trial weighing 14.2±0.31 kg and remained on trial until ~41.5±3.31 kg. The experiment was a dose response design with four inclusion levels (0, 8000, 16 000 or 32 000 BXU/kg) of xylanase (Econase XT). Diets were cereal-based wheat, barley mix formulated to meet or exceed the nutrient requirements of grower pigs. Body weight and feed intake were recorded to calculate growth performance. Pen faecal samples were collected to estimate DM, organic matter (OM) and crude fibre (CF) apparent total-tract digestibility. At the end of the trial 16 pigs per treatment were euthanised by schedule 1 procedures. Peripheral and portal blood samples were collected for peptide YY and VFA analysis. The addition of xylanase to the diet had no effect on growth performance, DM, OM or CF total-tract digestibility; however, xylanase tended to have a quadratic effect on ileum pH with higher pH values recorded for pigs fed a diet supplemented with 8000 and 16 000 BXU/kg xylanase (P<0.1). Xylanase had no effect on peptide YY levels or VFA concentration. Total VFA concentration was higher in portal compared with peripheral blood (P<0.05). In conclusion, the addition of xylanase had no effect on grower pig performance, nutrient digestibility, VFA concentration or peptide YY concentration when fed up to 32 000 BXU/kg over a 35-day period. Pig performance was good for all treatments throughout the trial suggesting that diet quality was sufficient thus there were no beneficial effects of adding xylanase.

Effects of the Artificial Sweetener Neotame on the Gut Microbiome and Fecal Metabolites in Mice

Although artificial sweeteners are widely used in food industry, their effects on human health remain a controversy. It is known that the gut microbiota plays a key role in human metabolism and recent studies indicated that some artificial sweeteners such as saccharin could perturb gut microbiome and further affect host health, such as inducing glucose intolerance. Neotame is a relatively new low-caloric and high-intensity artificial sweetener, approved by FDA in 2002. However, the specific effects of neotame on gut bacteria are still unknown. In this study, we combined high-throughput sequencing and gas chromatography-mass spectrometry (GC-MS) metabolomics to investigate the effects of neotame on the gut microbiome and fecal metabolite profiles of CD-1 mice. We found that a four-week neotame consumption reduced the alpha-diversity and altered the beta-diversity of the gut microbiome. Firmicutes was largely decreased while Bacteroidetes was significantly increased. The Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis also indicated that the control mice and neotame-treated mice have different metabolic patterns and some key genes such as butyrate synthetic genes were decreased. Moreover, neotame consumption also changed the fecal metabolite profiles. Dramatically, the concentrations of multiple fatty acids, lipids as well as cholesterol in the feces of neotame-treated mice were consistently higher than controls. Other metabolites, such as malic acid and glyceric acid, however, were largely decreased. In conclusion, our study first explored the specific effects of neotame on mouse gut microbiota and the results may improve our understanding of the interaction between gut microbiome and neotame and how this interaction could influence the normal metabolism of host bodies.

Postprandial PYY increase by resistant starch supplementation is independent of net portal appearance of short-chain fatty acids in pigs

Increased dietary fiber (DF) fermentation and short-chain fatty acid (SCFA) production may stimulate peptide tyrosine-tyrosine (PYY) secretion. In this study, the effects of hindgut SCFA production on postprandial PYY plasma levels were assessed using different experimental diets in a porto-arterial catheterized pig model. The pigs were fed experimental diets varying in source and levels of DF for one week in 3×3 Latin square designs. The DF sources were whole-wheat grain, wheat aleurone, rye aleurone-rich flour, rye flakes, and resistant starch. Postprandial blood samples were collected from the catheters and analyzed for PYY levels and net portal appearance (NPA) of PYY was correlated to NPA of SCFA. No significant effects of diets on NPA of PYY were observed (P > 0.05), however, resistant starch supplementation increased postprandial NPA of PYY levels by 37 to 54% compared with rye-based and Western-style control diets (P = 0.19). This increase was caused by higher mesenteric artery and portal vein PYY plasma levels (P < 0.001) and was independent of SCFA absorption (P > 0.05). The PYY levels were higher in response to the second daily meal compared with the first daily meal (P < 0.001), but similar among diets (P > 0.10). In conclusion, the increased postprandial PYY responses in pigs fed with different levels and sources of DF are not caused by an increased SCFA absorption and suggest that other mechanisms such as neural reflexes and possibly an increased flow of digesta in the small intestine may be involved. The content of DF and SCFA production did not affect PYY levels.

Effect of exogenous xylanase, amylase, and protease as single or combined activities on nutrient digestibility and growth performance of broilers fed corn/soy diets

Two trials (a 42-d performance and a 21-d cohort digestibility) were conducted to evaluate the performance and nutrient digestibility of broilers fed corn diets supplemented with exogenous xylanase, amylase, and protease as single or combined activities. A nutritionally adequate, positive control (PC) diet was formulated. The negative control (NC) diet was formulated to be lower in metabolizable energy (∼86 kcal/kg diet) and digestible amino acids (1 to 2%) compared to PC. The other 4 treatments were based on the NC and they were either supplemented with xylanase (X), amylase (A), protease (P), or a combination of X, A, and P (XAP; to provide 2,000 U of X, 200 U of A, and 4,000 U of P/kg diet). All diets were marginal in AvP and Ca and contained a background of phytase (1,000 FTU/kg). In each trial, male broiler (Ross 308) chicks were allocated to the 5 treatments (10 replicates of 20 birds/pen and 9 replicates of 8 birds/cage for the performance and digestibility trials, respectively). In the digestibility trial, ileal digesta was collected on d21 for the determination of nutrient utilization. Data were subjected to one-way ANOVA and means were separated by Tukey's HSD test. Only the XAP improved (P < 0.05) AMEn compared to NC. X, A or XAP improved (P < 0.05) N digestibility and apparent ileal digestible energy (AIDE). Both P and XAP improved N retention. The relative improvement in energy digestibility due to enzyme supplementation was greater at the ileal level than that measured in the excreta. The measured changes on AIDE due to supplemental enzymes were much higher than the sum of calculated contributions from starch, fat, and protein. Supplementation of all enzymes reduced (P < 0.05) ileal flow of soluble rhamnose and mannose relative to NC. In the performance trial, both X and XAP improved (P < 0.05) weight gain (WG) and only XAP improved (P < 0.05) FCR compared to NC during the starter phase (1-21d). Over the entire period (1–42d), WG and FI were not influenced (P > 0.05) by dietary treatments. Both X and XAP had lower (P < 0.05) FCR compared to NC (1.540 and 1.509 vs 1.567, respectively). However, birds fed diet supplemented with XAP had an improved (P < 0.05) FCR compared to birds fed single activities and had similar (P > 0.05) FCR compared to PC. In conclusion, these results suggest a synergistic effect between X, A and P on broiler performance and nutrient digestibility. In the current study, AIDE measurements appeared to overestimate the enzyme response. Calculation of the energy contribution by supplemental enzymes using the improvements in the digestibility of the undigested fraction of starch, fat and protein may be a more accurate measurement for the enzyme response than the absolute response in AIDE.

Short-chain fatty acids augment rat duodenal mucosal barrier function

NEW FINDINGS

What is the central question of this study? Small intestinal epithelium is exposed to high concentrations of short-chain fatty acids (SCFAs), but their role in regulating intestinal mucosal barrier function and motility is not fully understood. What is the main finding and its importance? By perfusing the duodenal segment in anaesthetized rats, we show that acetate and propionate significantly decrease mucosal paracellular permeability and transepithelial net fluid flux and increase mucosal bicarbonate secretion. Likewise, SCFAs administered i.v. decrease mucosal permeability but decrease bicarbonate secretion. Altered luminal chemosensing or aberrant signalling in response to SCFAs might contribute to symptoms observed in patients with suppressed mucosal barrier function. Short-chain fatty acids (SCFAs) are produced by bacterial fermentation in the large intestine, particularly from diets containing fibres and carbohydrates. The small intestinal epithelium is exposed to SCFAs derived mainly from oral bacteria or food supplementation. Although luminal nutrients are important in regulation of intestinal functions, the role of SCFAs in regulation of small intestinal mucosal barrier function and motility has not been fully described. The aim of the present study was to elucidate the effects of acetate and propionate on duodenal mucosal barrier function and motility. Rats were anaesthetized with thiobarbiturate, and a 30 mm segment of proximal duodenum with an intact blood supply was perfused. The effects on duodenal bicarbonate secretion, blood-to-lumen clearance of ⁵¹ Cr-EDTA, motility and transepithelial net fluid flux were investigated. Perfusion of the duodenum with acetate or propionate significantly decreased mucosal paracellular permeability and transepithelial net fluid flux and significantly increased bicarbonate secretion. Acetate or propionate administered as an i.v. infusion decreased the mucosal paracellular permeability, but significantly decreased bicarbonate secretion. Luminal SCFAs changed the duodenal motility pattern from migrating motor complexes to fed patterns. Systemic administration of glucagon-like peptide-2 induced increases in both bicarbonate secretion and net fluid absorption, but did not change motility. Glucagon-like peptide-2 infusion during luminal perfusion of SCFAs significantly reduced the motility. In conclusion, SCFAs decreased duodenal paracellular permeability and net fluid flux. Short-chain fatty acids induced opposite effects on bicarbonate secretion after luminal and i.v. administration. Presence of SCFAs in the lumen induces fed motility patterns. Altered luminal chemosensing and aberrant signalling in response to SCFAs might contribute to symptoms observed in patients with suppressed barrier function.

Does the Ileal Brake Contribute to Delayed Gastric Emptying After Pancreatoduodenectomy?

Delayed gastric emptying (DGE) represents a significant cause for morbidity following pancreatoduodenectomy (PD). At a time when no specific and universally effective therapy exists to treat these patients, elucidating other potential (preventable or treatable) mechanisms for DGE is important. The aim of the manuscript was to test the hypothesis that ileal brake contributes to DGE in PD patients receiving jejunal tube feeding by systematically reviewing experimental and clinical literature. A series of clinically relevant questions were framed related to the potential role of the ileal brake in development of DGE post-PD and formed the basis of targeted literature searches. A comprehensive search of major reference databases from January 1980 to June 2015 was carried out which included human and animal studies. The ileal brake is a feedback loop neurally mediated by the vagus and sympatho-adrenergic pathways and hormonally by gut peptides including glucagon-like peptide-1, peptide YY (PYY), and neurotensin. The most potent stimulus for this inhibitory reflex is intra-ileal fat. There is evidence to indicate the role of an inhibitory reflex (on gastric emptying) mediated by PYY and CCK which, in turn, are stimulated by nutrient delivery into the distal small intestine providing indirect support to the role of ileal brake in post-PD DGE. The ileal brake is a likely factor contributing to DGE post-PD. While there has been no study to directly test this hypothesis, there is compelling indirect evidence to support it. Designing a trial that would answer such a question appears to be the most appropriate way forward.

Body fat mobilization in early lactation influences methane production of dairy cows

Long-chain fatty acids mobilized during early lactation of dairy cows are increasingly used as energy substrate at the expense of acetate. As the synthesis of acetate in the rumen is closely linked to methane (CH4) production, we hypothesized that decreased acetate utilization would result in lower ruminal acetate levels and thus CH4 production. Twenty heifers were sampled for blood, rumen fluid and milk, and CH4 production was measured in respiration chambers in week -4, +5, +13 and +42 relative to first parturition. Based on plasma non-esterified fatty acid (NEFA) concentration determined in week +5, animals were grouped to the ten highest (HM; NEFA > 580 μmol) and ten lowest (LM; NEFA < 580 μmol) mobilizing cows. Dry matter intake (DMI), milk yield and ruminal short-chain fatty acids did not differ between groups, but CH4/DMI was lower in HM cows in week +5. There was a negative regression between plasma NEFA and plasma acetate, between plasma NEFA and CH4/DMI and between plasma cholecystokinin and CH4/DMI in week +5. Our data show for the first time that fat mobilization of the host in early lactation is inversely related with ruminal CH4 production and that this effect is not attributed to different DMI.

Effects of a viscous-fibre supplemented evening meal and the following un-supplemented breakfast on post-prandial satiety responses in healthy women

The post-prandial satiety response and "second-meal effect" of a viscous fibre supplement PolyGlycopleX(®) (PGX(®)) was evaluated in a single-blind, randomised controlled crossover study of 14 healthy adult women. The two hour post-prandial satiety response, expressed as the area under the curve (AUC) of perceived hunger/fullness score versus post-prandial time, of a standardised evening meal with concurrent intake of either PGX softgel or rice flour softgel (control) was determined. On the following morning, after an overnight fast, the four hour satiety response to a standardised breakfast with no softgel supplementation was assessed. A significantly higher satiety response (AUC) to the standard dinner for the PGX-supplemented dinner compared with the control dinner (p=0.001) was found. No significant difference (p=0.09) was observed in the satiety response (AUC) of the breakfast regardless of which supplemented-dinner had been consumed prior, however the p value indicated a trend towards a higher response to the breakfast following the PGX-supplemented dinner. The fullness scores of the breakfast following the PGX-supplemented dinner at 15, 30, 90, 120, 150, 180, 210 and 240min post-prandial were significantly higher than those for the breakfast following the control dinner (p=<0.001, 0.007, 0.009, 0.009, 0.049, 0.03, 0.003 and <0.001 respectively). PGX supplementation at dinner increased the satiety effects of both the dinner itself and the subsequent un-supplemented breakfast; a "second meal effect" indicting the potential for this fibre supplement to induce extended satiety.

The Influence of the Gut Microbiome on Obesity, Metabolic Syndrome and Gastrointestinal Disease

There is a fine balance in the mutual relationship between the intestinal microbiota and its mammalian host. It is thought that disruptions in this fine balance contribute/account for the pathogenesis of many diseases. Recently, the significance of the relationship between gut microbiota and its mammalian host in the pathogenesis of obesity and the metabolic syndrome has been demonstrated. Emerging data has linked intestinal dysbiosis to several gastrointestinal diseases including inflammatory bowel disease, irritable bowel syndrome, nonalcoholic fatty liver disease, and gastrointestinal malignancy. This article is intended to review the role of gut microbiota maintenance/alterations of gut microbiota as a significant factor as a significant factor discriminating between health and common diseases. Based on current available data, the role of microbial manipulation in disease management remains to be further defined and a focus for further clinical investigation.

Post-meal perceivable satiety and subsequent energy intake with intake of partially hydrolysed guar gum

Partially hydrolysed guar gum (PHGG), a soluble dietary fibre, has been shown to provide many health benefits. Previous studies had suggested that the combination of PHGG with protein provided a significant satiation effect on visual analogue scales (VAS). What was lacking was only the effect of administration of small doses of PHGG on post-meal satiation and subsequent energy intake. The objectives of the present investigations were to find the subjective perception of post-meal satiety with acute and long term administration of small amounts of PHGG alone with food, its effects on subsequent energy intake and the comparative effects among different types of soluble fibres. The following three separate studies were conducted: in study 1, healthy subjects (n 12) consumed PHGG along with breakfast, lunch and an evening snack; in study 2, healthy subjects (n 24) consumed 2 g of PHGG or dextrin along with yogurt as breakfast for 2 weeks; in study 3, healthy subjects (n 6) took 6 g each of either PHGG or indigestible dextrin or inulin along with lunch. In all the studies, various satiety parameters were measured on VAS before and after consumption of PHGG. The addition of PHGG showed significant (P < 0.05) acute (studies 1 and 3) and long-term (studies 1 and 2) satiety effects compared to the control and/or an equal amount of carbohydrate or other types of soluble fibre. Study 2 also indicated that the prolonged consumption of PHGG may significantly (P < 0.05) reduce energy intake from whole-day snacking. PHGG could be an ideal natural soluble fibre for delivering acute and long term satiety effects for comfortable appetite control.

Growth performance, nutrient utilization, and digesta characteristics in broiler chickens fed corn or wheat diets without or with supplemental xylanase

Efficacy of supplemental xylanase on growth performance, nutrient utilization, and digesta characteristics in broiler chickens fed corn- or wheat-based diets was investigated. In experiment 1, 192 male broilers (8 birds/pen; n = 6) were fed 4 diets (corn or wheat without or with 1,250 xylanase units/kg) in 2 phases (starter, d 0-21 and grower, d 22-42). There was no interaction (P > 0.05) between diet and xylanase on performance (d 0-42). Wheat diets resulted (P < 0.01) in better performance than corn diets, whereas xylanase-fed birds had improved (P < 0.01) BW gain (2,457 vs. 2,275 g) and feed per gain (1.677 vs. 1.762) relative to birds not fed xylanase. In experiment 2, TiO2 (0.3%) was added in starter diets used in experiment 1, allocated to 13-d-old broiler chicks (n = 6) housed in cages (6 birds/cage) and fed up to d 21. Excreta samples were obtained from d 17 to 20 and birds were euthanized on d 21 for digesta. Corn diets had a greater concentration (10.7 vs. 9.8%) of insoluble nonstarch polysaccharides (NSP) than wheat diets, which in turn had more than twice the concentration of soluble NSP. There was an interaction (P < 0.03) between diet type and xylanase on jejunal digesta viscosity but not (P > 0.10) on apparent ileal digestibilities of nutrients, cecal volatile fatty acids, and AMEn. In this context, diet type influenced (P < 0.05) cecal volatile fatty acids and retention of nutrients and fiber but did not affect (P = 0.45) AMEn. In contrast, xylanase-fed birds showed higher (P < 0.05) ceca digesta acetic acid, apparent ileal digestibilities of nutrients, and retention of components. As a result, birds fed xylanase had higher AMEn (3,059 vs. 2,995 kcal/kg; P < 0.01) compared with birds not fed xylanase. Although wheat diets had superior growth performance, the AMEn was similar in both diets. Xylanase improved growth performance and AMEn independent of diet type, suggesting hydrolysis of both soluble and insoluble NSP.

The role and influence of gut microbiota in pathogenesis and management of obesity and metabolic syndrome

The obesity epidemic has drastically impacted the state of health care in the United States. Aside from poor diet hygiene and genetics, there are many other factors thought to play a role in the emergence of obesity and the metabolic syndrome. There has been a paradigm shift toward further investigating the gut microbiota and its implications in the pathogenesis of a variety of disease states, including inflammatory bowel disease, Clostridium difficile, and most recently obesity and the metabolic syndrome. This article is intended to evaluate the role of gut microbiota in the pathogenesis of obesity and metabolic syndrome and its influence in future management.

Contributions of colonic short-chain Fatty Acid receptors in energy homeostasis

The gastrointestinal (GI) tract is separated from the body's internal environment by a single layer of epithelial cells, through which nutrients must pass for their absorption into the bloodstream. Besides food and drink, the GI lumen is also exposed to bioactive chemicals and bacterial products including short-chain fatty acids (SCFAs). Therefore, the GI tract has to monitor the composition of its contents continuously to discriminate between necessary and unnecessary compounds. Recent molecular identification of epithelial membrane receptor proteins has revealed the sensory roles of intestinal epithelial cells in the gut chemosensory system. Malfunctioning of these receptors may be responsible for a variety of metabolic dysfunctions associated with obesity and related disorders. Recent studies suggest that SCFAs produced by microbiota fermentation act as signaling molecules and influence the host's metabolism; uncovering the sensory mechanisms of such bacterial metabolites would help us understand the interactions between the host and microbiota in host energy homeostasis. In this review, the contribution of colonic SCFA receptors in energy metabolism and our recent findings concerning the possible link between SCFA receptors and host energy homeostasis are discussed.

Lipids, CHOs, proteins: can all macronutrients put a 'brake' on eating?

The gastrointestinal (GI) tract and specifically the most distal part of the small intestine, the ileum, has become a renewed focus of interest for mechanisms targeting appetite suppression. The 'ileal brake' is stimulated when energy-containing nutrients are delivered beyond the duodenum and jejunum and into the ileum, and is named for the feedback loop which slows or 'brakes' gastric emptying and duodeno-jejunal motility. More recently it has been hypothesized that the ileal brake also promotes secretion of satiety-enhancing GI peptides and suppresses hunger, placing a 'brake' on food intake. Postprandial delivery of macronutrients to the ileum, other than unavailable carbohydrates (CHO) which bypass absorption in the small intestine en route to fermentation in the large bowel, is an uncommon event and hence this brake mechanism is rarely activated following a meal. However the ability to place a 'brake' on food intake through delivery of protected nutrients to the ileum is both intriguing and challenging. This review summarizes the current clinical and experimental evidence for activation of the ileal brake by the three food macronutrients, with emphasis on eating behavior and satiety as well as GI function. While clinical studies have shown that exposure of the ileum to lipids, CHOs and proteins may activate GI components of the ileal brake, such as decreased gut motility, gastric emptying and secretion of GI peptides, there is less evidence as yet to support a causal relationship between activation of the GI brake by these macronutrients and the suppression of food intake. The predominance of evidence for an ileal brake on eating comes from lipid studies, where direct lipid infusion into the ileum suppresses both hunger and food intake. Outcomes from oral feeding studies are less conclusive with no evidence that 'protected' lipids have been successfully delivered into the ileum in order to trigger the brake. Whether CHO or protein may induce the ileal brake and suppress food intake has to date been little investigated, although both clearly have GI mediated effects. This review provides an overview of the mechanisms and mediators of activation of the ileal brake and assesses whether it may play an important role in appetite suppression.

The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism

Short-chain fatty acids (SCFAs), the end products of fermentation of dietary fibers by the anaerobic intestinal microbiota, have been shown to exert multiple beneficial effects on mammalian energy metabolism. The mechanisms underlying these effects are the subject of intensive research and encompass the complex interplay between diet, gut microbiota, and host energy metabolism. This review summarizes the role of SCFAs in host energy metabolism, starting from the production by the gut microbiota to the uptake by the host and ending with the effects on host metabolism. There are interesting leads on the underlying molecular mechanisms, but there are also many apparently contradictory results. A coherent understanding of the multilevel network in which SCFAs exert their effects is hampered by the lack of quantitative data on actual fluxes of SCFAs and metabolic processes regulated by SCFAs. In this review we address questions that, when answered, will bring us a great step forward in elucidating the role of SCFAs in mammalian energy metabolism.

Plasma concentrations and effects of glucagon-like peptide-1 (7-36) amide in calves before and after weaning

Glucagon-like peptide-1 (7-36) amide (GLP-1), secreted by the small intestine, has insulinotropic and glucose-lowering action. Basal plasma GLP-1 concentrations were measured in calves around the weaning period, the effect of short-chain fatty acids (SCFA) on plasma GLP-1 concentrations was examined, and the effects of GLP-1 administration on plasma insulin, glucagon, and glucose concentrations were measured. Thirteen Holstein bull calves were fed whole milk and solid feed and weaned at 7 wk of age. Preprandial plasma samples were obtained from 5 calves once a week from week 0 to 13 to measure basal concentrations of plasma GLP-1 and insulin (experiment 1). Four calves were intravenously administered with a mixed solution of SCFA (2.4 mmol/kg body weight [BW]) in week 2 and 11 to measure plasma GLP-1 concentrations (experiment 2). Another 4 calves were intravenously injected with GLP-1 (1.0 μg/kg BW) to elucidate the response of plasma insulin, glucagon, and glucose concentrations in week 1, 2, 4, 6, 7, 9, 11, and 13 (experiment 3). In experiment 1, age and weaning did not affect preprandial basal concentrations of plasma GLP-1 throughout the experimental period. Preprandial insulin concentrations increased after weaning (P < 0.05), and GLP-1 and insulin were more strongly correlated postweaning than preweaning. In experiment 2, intravenous treatment with SCFA increased plasma GLP-1 concentrations in both week 2 and 11 (P < 0.05.) In experiment 3, intravenous GLP-1 treatment decreased plasma glucose concentrations throughout the experiment (P < 0.05), but increased plasma insulin concentrations only after weaning (P < 0.05). Treatment with GLP-1 did not affect plasma glucagon concentrations, regardless of age. These results indicate that preprandial basal concentrations of plasma GLP-1 in calves are not changed by weaning, but SCFA stimulate GLP-1 secretion. The insulinotropic action of GLP-1 is detected only after weaning, but the glucose-lowering action of GLP-1 is not affected by weaning.

Effects of long- and short-chain fatty acids on the release of gastrointestinal hormones using an ex vivo porcine intestinal tissue model

Gastrointestinal (GI) peptide hormones play an important role in short-term regulation of food intake and blood glucose levels. Modulating their release is of potential relevance for weight management and possibly diabetes. As currently available models are hard to extrapolate to the human situation, the use of porcine intestinal tissue, collected from slaughter pigs, was investigated for this purpose. Intestinal tissue disks showed a predicted regional release pattern of GI peptides. Various long-chain fatty acids differentially stimulated release of glucagon-like peptide 1 (GLP-1) (up to 500%) and glucagon-like peptide 2 (GLP-2) (up to 200%) from ileal tissue disks, but effects on peptide YY (PYY) did not reach significance. Short-chain fatty acids had no effects on the release of GLP-1, GLP-2, and PYY in either the ileum or colon. In conclusion, this porcine tissue model shows to be of advantageous use in a tiered approach to study the potential of satiety-inducing compounds to be selected for studies in humans.

Modulatory role of PYY in transport and metabolism of cholesterol in intestinal epithelial cells

Background

Gastrointestinal peptides are involved in modulating appetite. Other biological functions attributed to them include the regulation of lipid homeostasis. However, data concerning PYY remain fragmentary. The objectives of the study were: (i) To determine the effect of PYY on intestinal transport and synthesis of cholesterol, the biogenesis of apolipoproteins (apos) and assembly of lipoproteins and (ii) To analyze whether the effects of PYY are similar according to whether cells are exposed to PYY on apical or basolateral surface.

Methodology/Principal Findings

Caco-2/15 cells were incubated with PYY (1–36) administered either to the apical or basolateral medium, at concentrations of 50 or 200 nM for 24 hours. De novo synthesis of cholesterol, cholesterol uptake, and assembly of lipoproteins were evaluated through the incorporation of [¹⁴C]-acetate, [¹⁴C]-cholesterol, and [¹⁴C]-oleate, respectively. Biogenesis of apos (A-I, A-IV, E, B-48 and B-100) was examined by the incorporation of [³⁵S]-methionine. The influence of PYY on protein and mRNA levels of many key mediators of lipid metabolism was analyzed by Western blot and PCR, respectively. Our results show that PYY influenced cholesterol metabolism in Caco-2/15 cells depending on the site of PYY delivery. Apical addition of PYY significantly lowered the incorporation of [¹⁴C]-cholesterol likely via the reduction of NPC1L1, stimulated intracellular cholesterol synthesis probably through an increase in SREBP-2 expression, whereas it concomitantly increased apo A-I synthesis and decreased LDL secretion. In contrast, basolateral PYY reduced the production of chylomicrons (CM) as well as the biogenesis of apos B-48 and B-100, while lowering the expression of the transcription factors RXRα and PPAR(α,β).

Conclusions/Significance

PYY is capable of influencing cholesterol homeostasis in intestinal Caco-2/15 cells depending on the site delivery. Apical PYY was able to decrease cholesterol uptake via NPC1L1 downregulation, whereas basolateral PYY diminished CM output through the biogenesis decline of apos B-48 and B-100.

Butyrate and propionate protect against diet-induced obesity and regulate gut hormones via free fatty acid receptor 3-independent mechanisms

Short-chain fatty acids (SCFAs), primarily acetate, propionate, and butyrate, are metabolites formed by gut microbiota from complex dietary carbohydrates. Butyrate and acetate were reported to protect against diet-induced obesity without causing hypophagia, while propionate was shown to reduce food intake. However, the underlying mechanisms for these effects are unclear. It was suggested that SCFAs may regulate gut hormones via their endogenous receptors Free fatty acid receptors 2 (FFAR2) and 3 (FFAR3), but direct evidence is lacking. We examined the effects of SCFA administration in mice, and show that butyrate, propionate, and acetate all protected against diet-induced obesity and insulin resistance. Butyrate and propionate, but not acetate, induce gut hormones and reduce food intake. As FFAR3 is the common receptor activated by butyrate and propionate, we examined these effects in FFAR3-deficient mice. The effects of butyrate and propionate on body weight and food intake are independent of FFAR3. In addition, FFAR3 plays a minor role in butyrate stimulation of Glucagon-like peptide-1, and is not required for butyrate- and propionate-dependent induction of Glucose-dependent insulinotropic peptide. Finally, FFAR3-deficient mice show normal body weight and glucose homeostasis. Stimulation of gut hormones and food intake inhibition by butyrate and propionate may represent a novel mechanism by which gut microbiota regulates host metabolism. These effects are largely intact in FFAR3-deficient mice, indicating additional mediators are required for these beneficial effects.

Role of Y(2) receptors in the regulation of gastric tone in rats

We set out to determine the effect of peptide YY(3-36) (PYY(3-36)) on the gastric muscle tone in conscious rats by measuring intragastric pressure (IGP) during intragastric nutrient drink infusion. After an overnight fast, a chronically implanted gastric fistula was connected to a custom-made nutrient drink infusion system and a catheter to measure IGP. IGP was measured before and during the infusion of a nutrient drink (Nutridrink; 0.5 ml/min) until 10 ml was infused. Rats were treated with PYY(3-36) (0, 33, and 100 pmol·kg(-1)·min(-1)) in combination with a subcutaneous injection of the Y(2) receptor antagonists JNJ31020028 (10 mg/kg) or BIIE0246 (2 mg/kg). Experiments were also performed after subdiaphragmatic vagotomy and after pretreatment with 3 ml of nutrient drink (to mimic a fed state). IGP was compared as the average IGP during nutrient infusion, represented as means ± SE and compared using ANOVA. PYY(3-36) dose dependently increased the IGP during nutrient infusion (4.7 ± 0.3, 5.7 ± 0.5 and 7.3 ± 0.7 mmHg; P < 0.01) while JNJ31020028 and BIIE0246 could block this increase [4.4 ± 0.5 (P < 0.001) and 4.8 ± 0.4 (P < 0.05) mmHg, respectively]. Also in vagotomized rats, PYY(3-36) was able to significantly increase the IGP during, an effect attenuated by JNJ31020028. BIIE0246 and JNJ31020028 were not able to decrease the IGP when no PYY(3-36) was administered. PYY(3-36) increased gastric tone through an Y(2) receptor-mediated mechanism that does not involve the vagus nerve. Y(2) receptor antagonists were not able to decrease gastric tone without exogenous administration of PYY(3-36), indicating that Y(2) receptors do not play a crucial role in the determination of gastric tone in physiological conditions.

Effects of gut microbes on nutrient absorption and energy regulation

Malnutrition may manifest as either obesity or undernutrition. Accumulating evidence suggests that the gut microbiota plays an important role in the harvest, storage, and expenditure of energy obtained from the diet. The composition of the gut microbiota has been shown to differ between lean and obese humans and mice; however, the specific roles that individual gut microbes play in energy harvest remain uncertain. The gut microbiota may also influence the development of conditions characterized by chronic low-level inflammation, such as obesity, through systemic exposure to bacterial lipopolysaccharide derived from the gut microbiota. In this review, the role of the gut microbiota in energy harvest and fat storage is explored, as well as differences in the microbiota in obesity and undernutrition.

Gastroplastia como tratamento do diabete melito tipo 2

RACIONAL: O diabete melito tipo 2 está, com certa frequência, associado à obesidade mórbida e pode ser prevenido, melhorado e até mesmo revertido com as diversas modalidades de operações bariátricas. OBJETIVOS: Comparar as glicemias séricas pré e pós-operatórias dos pacientes submetidos à gastroplastia com as técnicas de Capella e sleeve gástrico. MÉTODO: Estudo descritivo e prospectivo com análises das glicemias séricas pré e pós-operatórias de pacientes submetidos à gastroplastia. RESULTADOS: Dos 83 pacientes analisados, 76 (91,5%) eram do sexo feminino. A idade variou de 21 a 64 anos, sendo 44 anos a idade média. Setenta e sete (92,7%) foram submetidos à gastroplastia (Capella) e seis (7,3%) à sleeve gástrico. A glicemia pré-operatória variou de 125 a 500 mg/dL caindo para a variação de 76 a 120 mg/dL no pós-operatório de três meses. Dos 77 pacientes que usavam tratamento medicamentoso para a diabete, 57 tomavam metformina de 850 a 3500 mg por dia, 18 glibenclamida de 5 a 10 mg por dia e 17 insulina. Após 3 meses da operação, 92,2% cessaram o uso de medicamentos para diabete e em 100% dos que permaneceram medicados houve redução de mais de 65% na dose do fármaco, sendo que nenhum permaneceu dependente de insulina no tratamento. CONCLUSÃO: A cirurgia bariátrica constitui-se em método eficaz para a melhora e até mesmo reversão do diabete melito tipo 2.

Propionate absorbed from the colon acts as gluconeogenic substrate in a strict carnivore, the domestic cat (Felis catus)

In six normal-weight and six obese cats, the metabolic effect of propionate absorbed from the colon was assessed. Two colonic infusions were tested in a crossover design with intervals of 4 weeks. The test solution contained 4 mmol sodium propionate per kg ideal body weight in a 0.2% NaCl solution. Normal saline was given as control solution. Solutions were infused into the hindgut over 30 min. Blood samples were obtained prior to and at various time points after starting the infusion. As body condition did not affect evaluated parameters, all data were pooled. Plasma glucose concentrations showed differences neither over time nor during or after infusion with propionate or control. Plasma amino acid concentrations rose over time (p < 0.001), but were similar for both infusions. Plasma propionylcarnitine rose markedly towards the end of the propionate infusion and decreased afterwards (p < 0.001), whereas 3-hydroxy-3-methylglutarylcarnitine was lower 30 (p = 0.005) and 60 min (p = 0.032) after ending propionate infusions and acetylcarnitine tended to fall at the same time points (p = 0.079; p = 0.080), suggesting inhibition of gluconeogenesis from pyruvate and amino acids, but initiation of propionate-induced gluconeogenesis. In conclusion, propionate absorbed from the colon is hypothesized to act as gluconeogenic substrate, regardless of the cat's body condition.

Obesity and the gut microbiota: does up-regulating colonic fermentation protect against obesity and metabolic disease?

Obesity is now considered a major public health concern globally as it predisposes to a number of chronic human diseases. Most developed countries have experienced a dramatic and significant rise in obesity since the 1980s, with obesity apparently accompanying, hand in hand, the adoption of "Western"-style diets and low-energy expenditure lifestyles around the world. Recent studies report an aberrant gut microbiota in obese subjects and that gut microbial metabolic activities, especially carbohydrate fermentation and bile acid metabolism, can impact on a number of mammalian physiological functions linked to obesity. The aim of this review is to present the evidence for a characteristic "obese-type" gut microbiota and to discuss studies linking microbial metabolic activities with mammalian regulation of lipid and glucose metabolism, thermogenesis, satiety, and chronic systemic inflammation. We focus in particular on short-chain fatty acids (SCFA) produced upon fiber fermentation in the colon. Although SCFA are reported to be elevated in the feces of obese individuals, they are also, in contradiction, identified as key metabolic regulators of the physiological checks and controls mammals rely upon to regulate energy metabolism. Most studies suggest that the gut microbiota differs in composition between lean and obese individuals and that diet, especially the high-fat low-fiber Western-style diet, dramatically impacts on the gut microbiota. There is currently no consensus as to whether the gut microbiota plays a causative role in obesity or is modulated in response to the obese state itself or the diet in obesity. Further studies, especially on the regulatory role of SCFA in human energy homeostasis, are needed to clarify the physiological consequences of an "obese-style" microbiota and any putative dietary modulation of associated disease risk.

Effects of a diet with inulin-enriched pasta on gut peptides and gastric emptying rates in healthy young volunteers

AIM

Our group has previously shown that the administration of pasta enriched along with the prebiotic inulin induces a significant reduction in triglyceride and glucose levels with a significant delay in gastric emptying (GE) rates. This protective effect may occur by affecting the release of a number of gut peptides involved in the control of gastrointestinal motility. The aim of the present study was to evaluate the effects of inulin-enriched pasta on the circulating levels of neurotensin (NT), somatostatin (SS), and corticotropin-releasing factor (CRF) in relation to the GE time in young healthy subjects.

METHODS

Twenty healthy young male volunteers completed a randomized double-blind crossover study consisting of a 2-week run-in period and two 5-week study periods (11% inulin-enriched/control pasta), with an 8-week wash-out period in between. Gut peptide concentrations were evaluated by radioimmunoassay. GE time was evaluated by ultrasonography.

RESULTS

The prebiotic treatment significantly increased the area under the curve (AUC) values of both NT and SS (p < 0.05 Dunn's post-test). With regard to gastric motility, along with a significant delay in both the final time and T (1/2) gastric emptying time, a positive correlation was found between T (1/2) and SS AUC values (r = 0.57, p = 0.009) in the inulin-enriched pasta group.

CONCLUSION

These results support the hypothesis that inulin plays an active role in mechanisms affecting the release of these gut peptides, which may modulate the gastric emptying of digesta.

Butyrylated starch increases large bowel butyrate levels and lowers colonic smooth muscle contractility in rats

The short-chain fatty acids acetate, propionate, and butyrate are produced by colonic bacterial fermentation of carbohydrates. Butyrate is important in the regulation of the colonocyte cell cycle and gut motility and may also reduce the risk of large bowel cancer. We have shown that dietary butyrylated starch can deliver butyrate to the large bowel in a sustained manner. We hypothesized that ingestion of butyrylated starch increases large bowel butyrate levels and decreases colonic contractility. Groups of male Sprague-Dawley rats (n = 8) were fed AIN-93G-based diet containing a highly digestible low-amylose maize starch (LAMS) control or 5% or 10% butyrylated LAMS (LAMSB) for 10 days. We found that cecal but not colonic tissue weight as well as cecal and distal colonic digesta weights and fecal output were higher in LAMSB fed rats. Butyrylated LAMS lowered digesta pH throughout the large bowel. Cecal, proximal, and distal colonic butyrate pools and portal venous butyrate concentrations were higher in rats fed LAMSB. Electrically stimulated and receptor-dependent carbachol and prostaglandin E(2)-induced isotonic contractions were lower in isolated intact sections of proximal colon (P < .05) but not the terminal ileum after 10% LAMSB ingestion. These results demonstrated that elevation of butyrate levels in the large bowel of the rat correlated with reduction of contractile activity of the colonic musculature, which may assist in the reabsorption of water and minerals.