Effects of intraduodenal fatty acids on appetite, antropyloroduodenal motility, and plasma CCK and GLP-1 in humans vary with their chain length

Inclusion of a spray-dried fat concentrate containing tributyrin and tricaproin in milk replacer enhanced increased feed intake, growth, and elicited metabolic and endocrine responses in ad libitum-fed calves

Fat composition of milk replacer (MR) for calves differs from that of bovine milk fat, resulting in lower levels of butyric (C4:0) and caproic acid (C6:0). These fatty acids play a critical role in the gastrointestinal and metabolic development of calves by supporting rumen epithelial growth, enhancing energy metabolism, and promoting overall gut health. The objective of this study was to evaluate the effects of inclusion of a spray-dried fat concentrate containing tributyrin (TB) and tricaproin (TC) in a high-fat MR on growth, feed intake, and metabolic profiles of ad libitum-fed calves. Forty-eight newborn Holstein calves were blocked based on arrival sequence. Within each block of 2 calves, calves were randomly assigned to a control MR (CON, n = 24) including vegetable fats from palm, coconut, and linseed fats, or to an experimental MR including the same fat blend, to which TB and TC (TRI, n = 24) was added to the same levels found in milk fat. Both MR contained 23.7% crude protein, 27.7% fat, and 35.6% lactose (DM basis) and were fed at 13.5% solids. Calves were group housed and fed ad libitum MR with automated feeders. Weaning was gradual and induced between wk 7-10, after which calves were only fed solid feeds. Starter feed, chopped straw, and water were offered ad libitum throughout the whole study period. Calves were weighed and blood was collected once weekly at 1300h. Calves fed TRI showed a ∼50% reduction in therapeutic intervention days compared with CON. In addition, calves fed TRI consumed significantly more MR and starter feed, resulting in a greater growth. Serum NEFA and plasma total cholesterol were lower, whereas the enzymatic activity of serum ALP was higher in calves fed TRI than in CON. In addition, calves fed TRI had lower serum ghrelin and higher insulin-like growth factor-I concentrations. Incorporating TB and TC is a suitable strategy to increase solid feed intake upon weaning, resulting in better growth performance in ad libitum systems, and to improve health of dairy rearing calves.

Dose-related effects of intraduodenal quinine on plasma glucose, glucoregulatory hormones and gastric emptying of a nutrient drink, and energy intake, in men with type 2 diabetes: a double-blind, randomised, crossover study

AIMS/HYPOTHESIS

Quinine, when administered intraduodenally to activate bitter-taste receptors, in a dose of 600 mg, stimulates glucagon-like peptide-1 (GLP-1) and insulin, slows gastric emptying and lowers postprandial glucose in healthy people, with consequent implications for the management of type 2 diabetes; the effect of quinine on energy intake is uncertain. We have investigated the dose-related effects of quinine on postprandial blood glucose levels and energy intake in people with type 2 diabetes.

METHODS

Male participants with type 2 diabetes (age: 68±5 years; HbA1c: 49.0±5.0 mmol/mol [6.7±0.4%], BMI: 30±1 kg/m2) received in two study parts (A and B, n=12 each), on three separate occasions each, in randomised, crossover fashion, control, or 300 mg (QHCl-300) or 600 mg (QHCl-600) quinine hydrochloride, intraduodenally 30 min before a nutrient drink (2092 kJ, 74 g carbohydrate) (part A) or a standardised buffet-lunch (part B). Both the participants and investigators performing the study procedures were blinded to the treatments. In part A, plasma glucose, GLP-1, C-peptide and glucagon were measured at baseline, for 30 min after quinine alone and for 3 h post drink. Gastric emptying of the drink was measured with a 13C-acetate breath test. In part B, energy intake from the buffet-lunch was quantified.

RESULTS

Quinine alone had no effect. Post drink, both quinine doses reduced peak plasma glucose markedly (QHCl-600 by 2.8±0.6 mmol/l) and slowed gastric emptying (all p<0.05; n=12, except for gastric emptying, n=11). QHCl-600, but not QHCl-300, stimulated plasma GLP-1 and C-peptide modestly (both p<0.05). Quinine did not affect energy intake.

CONCLUSIONS/INTERPRETATION

In type 2 diabetes, acute intraduodenal administration of quinine markedly reduces the plasma glucose response to oral carbohydrate, but does not affect energy intake. These findings support the potential use of quinine to reduce postprandial blood glucose levels in type 2 diabetes.

TRIAL REGISTRATION

anzctr.org.au ACTRN12620000972921/ACTRN12621000218897 FUNDING: The study was funded by a Diabetes Australia Research Project Grant.

Impact of fermented bamboo powder on the morphology and physiology of the gastrointestinal tract in yellow-feather broiler chickens

Bamboo powder, a novel ingredient, is gaining recognition for its potential as a dietary supplement in poultry feed. This study aimed to investigate the effects of fermented bamboo powder (FBP) on antioxidant status, gut hormone activities, intestinal digestive enzyme activities, gut morphological structure, gastrointestinal development, and the expression of nutritional transporter genes in dwarf yellow-feather broiler chickens. A total of 600 healthy 1-day-old chicks were allocated randomly into two groups, with 10 replicates per group and 30 chicks in each replicate. The control group was provided with a standard basal diet, whereas the experimental group received the same basal diet supplemented with 1.0, 2.0, 4.0, and 6.0 g/kg of fermented bamboo powder (FBP) in four phases: Phase I (days 1-22), Phase II (days 23-45), Phase III (days 46-60), and Phase IV (days 61-77). Phases I and II were categorized as the pretreatment period (days 0-45), while Phases III and IV represented the experimental period (days 46-77). Tissue samples were collected during Phase IV for further analysis. After 77 days of feeding, results revealed that FBP supplementation significantly enhanced the levels of gastrointestinal hormones (Glucagon-like peptide 1, Peptide YY, Cholecystokinin, and 5-hydroxytryptamine) in the duodenum, jejunum, and ileum. Similarly, the activities of digestive enzymes (protease, chymotrypsin, trypsin, and amylase) were significantly increased in the small intestine. It also improved gut morphology by increasing villus height, crypt depth, and goblet cell counts in the duodenum, jejunum, and ileum. Additionally, antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, and catalase) were significantly increased, while malondialdehyde content was significantly decreased in the jejunum. Additionally, FBP supplementation significantly enhanced gizzard development. Overall, FBP supplementation modulated gut hormones and enzymes, enhanced gut morphology and promoted antioxidant status and gene expression related to nutrient transport and antioxidant defenses in broiler chickens. These findings suggest that FBP has the potential as a beneficial dietary supplement in poultry feed.

Comparison of the effect of medium-chain fatty acids and long-chain fatty acids on postprandial appetite and lipemia: a randomised crossover trial

Background

Postprandial lipemia (PPL) has been recognised as a cardiovascular disease risk factor. Appetite and PPL can be influenced by the length of saturated fatty acids (FAs). Thus, this study aims to investigate if different FA chain lengths have different impacts on appetite and PPL in healthy volunteers.

Methods

This is a randomised crossover single-blinded intervention study of 20 healthy adults. Coconut oil and palm oil were consumed in the form of biscuits. Blood serum samples were withdrawn after an overnight fast and 1, 2, 4 and 6 hours after eating the test meals and examined for blood lipid profile (total cholesterol (TC), high-density lipoprotein (HDL) and triglycerides (TG)), while Friedewald's equation was used to calculate low-density lipoprotein (LDL). Visual analogue scales were used by participants to rate their appetites, and an ad libitum meal was weighed to determine the energy intake.

Results

The net area under the curve of TG and TC following the coconut oil were significantly lower than following the palm oil (P value ≤0.05). In the mean of the change in TC, LDL and HDL from the baseline, a significant difference was found after 6 hours of eating the biscuits (P value ≤0.05). The perceptions of hunger and fullness did not significantly differ between the two types of FAs. Also, the energy and macronutrient intakes were not significantly different after the two types of oil, neither at the ad libitum meal nor on the day following the treatments.

Conclusion

The selection of FA chain length may influence PPL, and thus cardiovascular disease risk in a way that is functionally significant. However, this study detected no influence of FA chain length on appetite up to 40 hours post-treatment.

Trial registration number

NCT05539742.

The role of nutrient sensing dysregulation in anorexia of ageing: The little we know and the much we don't

The age-related decline in appetite and food intake - termed "anorexia of ageing" - is implicated in undernutrition in later life and hence provides a public health challenge for our ageing population. Eating behaviour is controlled, in part, by homeostatic mechanisms which sense nutrient status and provide feedback to appetite control regions of the brain. Such feedback signals, propagated by episodic gut hormones, are dysregulated in some older adults. The secretory responses of appetite-related gut hormones to feeding are amplified, inducing a more anorexigenic signal which is associated with reduced appetite and food intake. Such an augmented response would indicate an increase in gut sensitivity to nutrients. Consequently, this review explores the role of gastrointestinal tract nutrient sensing in age-related appetite dysregulation. We review and synthesise evidence for age-related alterations in nutrient sensing which may explain the observed hormonal dysregulation. Drawing on what is known regarding elements of nutrient sensing pathways in animal models, in other tissues of the body, and in certain models of disease, we identify potential causal mechanisms including alterations in enteroendocrine cell number and distribution, dysregulation of cell signalling pathways, and changes in the gut milieu. From identified gaps in evidence, we highlight interesting and important avenues for future research.

Glucagon-like peptide (GLP)-1 regulation of lipid and lipoprotein metabolism

Metabolic health is highly dependent on intestinal and hepatic handling of dietary and endogenous lipids and lipoproteins. Disorders of lipid and lipoprotein metabolism are commonly observed in patients with insulin resistant states such as obesity, metabolic syndrome, and type 2 diabetes. Evidence from both animal models and human studies indicates that a major underlying factor in metabolic or diabetic dyslipidemia is the overproduction of hepatic and intestinal apolipoprotein (apo)B-containing lipoprotein particles. These particles are catabolized down into highly proatherogenic remnants, which can be taken up into the arterial intima and promote plaque development. Several gut-derived peptides have been identified as key regulators of energy metabolism; one such peptide is the incretin hormone glucagon-like peptide (GLP)-1. Our laboratory has previously demonstrated that GLP-1 can signal both centrally and peripherally to reduce postprandial and fasting lipoprotein secretion. Moreover, we have demonstrated that GLP-1 receptor (GLP-1R) agonists can ameliorate diet-induced dyslipidemia. Recently, we published evidence for a novel vagal neuroendocrine signalling pathway by which native GLP-1 may exert its anti-lipemic effects. Furthermore, we demonstrated a novel role for other gut-derived peptides in regulating intestinal lipoprotein production. Overall, ample evidence supports a key role for GLP-1R on the portal vein afferent neurons and nodose ganglion in modulating intestinal fat absorption and lipoprotein production and identifies other gut-derived peptides as novel regulators of postprandial lipemia. Insights from these data may support identification of potential drug targets and the development of new therapeutics targeting treatment of diabetic dyslipidemia.

Fat composition of milk replacer influences growth performance, feeding behavior, and plasma fatty acid profile in ad libitum-fed calves

Fat composition in milk replacers (MR) for calves differs from bovine milk fat in multiple ways. The aim of the study was to investigate the impact of different approaches of formulating fat in MR on growth, ad libitum intakes of MR and solid feeds, as well as blood metabolites in dairy calves. Upon 24 to 96 h after birth, 63 calves were acquired from dairy farms and incorporated into the study. Calves were blocked based on arrival day and randomly assigned within each block to one of 3 treatments differing in MR fat composition (n = 21 per group): VG was based on vegetable fats including 80% rapeseed and 20% coconut fats; AN was formulated with animal fats including 65% lard and 35% dairy cream; and MX with a mixture of 80% lard and 20% coconut fats. All 3 MR contained 30% fat, 24% crude protein, and 36% lactose and were formulated to have a fatty acid profile resembling that of milk fat. From arrival onward (3.1 ± 0.84 d of age; means ± standard deviation), calves were group housed and were offered an ad libitum supply of MR at 135 g/L (13.5% solids). Weaning was gradual and induced between wk 7 and 10, after which calves were fed only solid feeds. Starter feed, chopped straw, and water were offered ad libitum throughout the study. Calves were weighed, and blood was collected weekly until d 84 after arrival. Preweaning average daily gain was greater in calves fed AN (915 g/d) than other treatments (783 g/d), whereas no differences were detected in the weaning and postweaning phases. Preweaning MR intake was greater in calves fed AN than MX from wk 2 to 6 and was also higher in calves fed AN than VG in wk 5 and 6. Consistently, the number of rewarded visits during the ad libitum phase was greater in calves fed AN than MX, whereas VG showed no differences. This led to a higher preweaning total metabolizable energy intake in calves fed AN than in calves fed VG and MX. Serum cholesterol was higher, and serum albumin was lower in calves fed VG than other treatments. The proportion of high-density lipoprotein cholesterol in total plasma cholesterol was lower and that of low-density lipoprotein (LDL) cholesterol was higher in calves fed VG compared with other treatments. Overall, the fatty acid profile of plasma largely mirrored the MR fat composition during the preweaning period. Feeding AN enhanced MR intake and improved preweaning growth compared with other treatments. Feeding VG resulted in a marked increase in plasma cholesterol, particularly in the form of LDL cholesterol, which could be linked to an excessive intake of polyunsaturated fatty acids. These findings underscore the importance of formulating the fat content of MR to be similar to bovine milk fat.

Fat composition of milk replacer influences postprandial and oxidative metabolisms in dairy calves fed twice daily

Milk replacers (MR) for calves contain alternative fat sources as substitute for milk fat. This substitution leads to differences in fat properties, such as the fatty acid profile and the triglyceride structure. This study evaluated how fat composition in MR affects gastrointestinal health, blood redox parameters, and postprandial metabolism in calves fed twice daily. Forty-five individually housed male Holstein-Friesian calves (2.3 ± 0.85 d of age) were assigned to 1 of 15 blocks based on the age and the day of arrival. Within each block, calves were randomly assigned to 1 of 3 experimental diets and received their respective diet from arrival until 35 d after arrival. The 3 experimental diets (n = 15 per treatment group) consisted of an MR with a blend of vegetable fats containing rapeseed and coconut (VG), an MR with only animal fats from lard and dairy cream (AN), and an MR containing a mixture of animal and vegetable fats including lard and coconut (MX). The fatty acid profile of each MR was formulated to resemble that of bovine milk fat while using only 2 fat sources. All MR were isoenergetic, with 30% fat (% DM), 24% crude protein, and 36% lactose. Chopped straw and water were available ad libitum from arrival onward but no starter feed was provided. Daily milk allowances were 6.0 L from d 1 to 5, 7.0 L from d 6 to 9, and 8.0 L from d 10 to 35, divided into 2 equal meals and prepared at 135 g/L (13.5% solids). Fecal appearance was scored daily; calves were weighed and blood was drawn on arrival and weekly thereafter. Urine and feces were collected over a 24-h period at wk 3 and 5 to determine apparent total-tract digestibility and assess gastrointestinal permeability using indigestible markers. Postprandial metabolism was evaluated at wk 4 by sequential blood sampling over 7.5 h, and the abomasal emptying rate was determined by acetaminophen appearance in blood. Fat composition in MR did not affect growth, MR intake, gastrointestinal permeability, nor nutrient digestibility. The percentage of calves with abnormal fecal scores was lower at wk 2 after arrival in calves fed VG than MX, whereas AN did not differ from the other treatments. Calves fed AN and MX had higher thiobarbituric acid reactive substances measured in serum than VG, whereas plasma ferric-reducing ability was greater in calves fed MX than VG. Postprandial acetaminophen concentrations did not differ across treatment groups, but the area under the curve was smaller in calves fed VG than in the other 2 treatments, which is indicative of a slower abomasal emptying. Postprandial serum triglyceride concentration was greater in calves fed AN than VG, whereas MX did not differ from the other treatments. Based on these outcomes, all 3 fat blends can be considered suitable for inclusion in MR for calves.

GPR84 in physiology-Many functions in many tissues

Members of the GPCR superfamily have a wide variety of physiological roles and are therefore valuable targets for developing effective medicines. However, within this superfamily are receptors that are less well characterized and remain orphans, including GPR84. This receptor is stimulated by ligands derived from dietary nutrients, specifically medium chain fatty acids (C9-14), and novel synthetic agonists. There are data demonstrating the role of GPR84 in inflammatory pathways, in addition to emerging data suggesting a key role for GPR84 as a nutrient-sensing GPCR involved in metabolism by sensing energy load via nutrient exposure and subsequent signalling leading to modulation of food intake. Exploring GPR84 pharmacology, its localization and what drives its expression has revealed multiple roles for this receptor. Here, we will reflect on these various roles of GRP84 demonstrated thus far, primarily by exploring data from pre-clinical and clinical studies in various physiological systems, with a specific focus on the gastrointestinal tract. LINKED ARTICLES: This article is part of a themed issue GPR84 Pharmacology. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.10/issuetoc.

Physiological Appetite Regulation and Bariatric Surgery

Obesity remains a common metabolic disorder and a threat to health as it is associated with numerous complications. Lifestyle modifications and caloric restriction can achieve limited weight loss. Bariatric surgery is an effective way of achieving substantial weight loss as well as glycemic control secondary to weight-related type 2 diabetes mellitus. It has been suggested that an anorexigenic gut hormone response following bariatric surgery contributes to weight loss. Understanding the changes in gut hormones and their contribution to weight loss physiology can lead to new therapeutic treatments for weight loss. Two distinct types of neurons in the arcuate hypothalamic nuclei control food intake: proopiomelanocortin neurons activated by the anorexigenic (satiety) hormones and neurons activated by the orexigenic peptides that release neuropeptide Y and agouti-related peptide (hunger centre). The arcuate nucleus of the hypothalamus integrates hormonal inputs from the gut and adipose tissue (the anorexigenic hormones cholecystokinin, polypeptide YY, glucagon-like peptide-1, oxyntomodulin, leptin, and others) and orexigeneic peptides (ghrelin). Replicating the endocrine response to bariatric surgery through pharmacological mimicry holds promise for medical treatment. Obesity has genetic and environmental factors. New advances in genetic testing have identified both monogenic and polygenic obesity-related genes. Understanding the function of genes contributing to obesity will increase insights into the biology of obesity. This review includes the physiology of appetite control, the influence of genetics on obesity, and the changes that occur following bariatric surgery. This has the potential to lead to the development of more subtle, individualised, treatments for obesity.

Nutrient Combinations Sensed by L-Cell Receptors Potentiate GLP-1 Secretion

Obesity is a risk factor for cardiometabolic diseases. Nutrients stimulate GLP-1 release; however, GLP-1 has a short half-life (<2 min), and only <10-15% reaches the systemic circulation. Human L-cells are localized in the distal ileum and colon, while most nutrients are absorbed in the proximal intestine. We hypothesized that combinations of amino acids and fatty acids potentiate GLP-1 release via different L-cell receptors. GLP-1 secretion was studied in the mouse enteroendocrine STC-1 cells. Cells were pre-incubated with buffer for 1 h and treated with nutrients: alpha-linolenic acid (αLA), phenylalanine (Phe), tryptophan (Trp), and their combinations αLA+Phe and αLA+Trp with dipeptidyl peptidase-4 (DPP4) inhibitor. After 1 h GLP-1 in supernatants was measured and cell lysates taken for qPCR. αLA (12.5 µM) significantly stimulated GLP-1 secretion compared with the control. Phe (6.25-25 mM) and Trp (2.5-10 mM) showed a clear dose response for GLP-1 secretion. The combination of αLA (6.25 µM) and either Phe (12.5 mM) or Trp (5 mM) significantly increased GLP-1 secretion compared with αLA, Phe, or Trp individually. The combination of αLA and Trp upregulated GPR120 expression and potentiated GLP-1 secretion. These nutrient combinations could be used in sustained-delivery formulations to the colon to prolong GLP-1 release for diminishing appetite and preventing obesity.

The impacts and mechanisms of dietary proteins on glucose homeostasis and food intake: a pivotal role of gut hormones

Glucose and energy metabolism disorders are the main reasons induced type 2 diabetes (T2D) and obesity. Besides providing energy, dietary nutrients could regulate glucose homeostasis and food intake via intestinal nutrient sensing induced gut hormone secretion. However, reviews regarding intestinal protein sensing are very limited, and no accurate information is available on their underlying mechanisms. Through intestinal protein sensing, dietary proteins regulate glucose homeostasis and food intake by secreting gut hormones, such as glucagon-like peptide 1 (GLP-1), cholecystokinin (CCK), peptide YY (PYY) and glucose-dependent insulinotropic polypeptide (GIP). After activating the sensory receptors, such as calcium-sensing receptor (CaSR), peptide transporter-1 (PepT1), and taste 1 receptors (T1Rs), protein digests induced Ca2+ influx and thus triggered gut hormone release. Additionally, research models used to study intestinal protein sensing have been emphasized, especially several innovative models with excellent physiological relevance, such as co-culture cell models, intestinal organoids, and gut-on-a-chips. Lastly, protein-based dietary strategies that stimulate gut hormone secretion and inhibit gut hormone degradation are proposed for regulating glucose homeostasis and food intake.

Effects of omega fatty acids on the short-term postprandial satiety related peptides in rats

We aimed to assess the effects of omega fatty acids on time depending on responses of satiety hormones. Sixty adult rats were randomly divided into 4 groups; linoleic acid (LA), α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) groups. For each fatty acid, the dose of 400 mg/kg was applied by oral gavage. Blood samples were taken after the 15, 30, 60 and 120 minutes. Ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), peptide YY (PYY), leptin and insulin hormones were analyzed by ELISA. We observed the significant increases (p<0.05) of the levels of CCK between n-3 (ALA, at 60th min; EPA, at 30th and 60th min and DHA, at 60 min) and n-6 (LA) supplemented rats. The highest GLP-1 levels were in ALA (0.70 ng/mL) and DHA (0.67 ng/mL) supplemented groups at 60th and 120th min indicating n-3 fatty acids efficiency on satiety compared to LA. It seems that ALA at 60th min and EPA at 120th min could provide the highest satiety effect with the highest insulin response, while the efficiency of LA supplementation on insulin-induced satiety diminished. The only significant change in AUC values among all hormones was in the CCK of the ALA group (p=0.004). The level of leptin increased in DHA and EPA supplemented rats (p=0.140). Our results showed that dietary omega fatty acids influenced the releasing of hormones in different ways possibly depending on chain length or saturation degree. Comprehensive studies need to be addressed for each fatty acid on satiety-related peptide hormones.

Effects of Quinine on the Glycaemic Response to, and Gastric Emptying of, a Mixed-Nutrient Drink in Females and Males

Intraduodenal quinine, in the dose of 600 mg, stimulates glucagon-like peptide-1 (GLP-1), cholecystokinin and insulin; slows gastric emptying (GE); and lowers post-meal glucose in men. Oral sensitivity to bitter substances may be greater in women than men. We, accordingly, evaluated the dose-related effects of quinine on GE, and the glycaemic responses to, a mixed-nutrient drink in females, and compared the effects of the higher dose with those in males. A total of 13 female and 13 male healthy volunteers received quinine-hydrochloride (600 mg ('QHCl-600') or 300 mg ('QHCl-300', females only) or control ('C'), intraduodenally (10 mL bolus) 30 min before a drink (500 kcal, 74 g carbohydrates). Plasma glucose, insulin, C-peptide, GLP-1, glucose-dependent insulinotropic polypeptide (GIP) and cholecystokinin were measured at baseline, for 30 min after quinine alone, and then for 2 h post-drink. GE was measured by 13C-acetate breath-test. QHCl-600 alone stimulated insulin, C-peptide and GLP-1 secretion compared to C. Post-drink, QHCl-600 reduced plasma glucose, stimulated C-peptide and GLP-1, and increased the C-peptide/glucose ratio and oral disposition index, while cholecystokinin and GIP were less, in females and males. QHCl-600 also slowed GE compared to C in males and compared to QHCl-300 in females (p < 0.05). QHCl-300 reduced post-meal glucose concentrations and increased the C-peptide/glucose ratio, compared to C (p < 0.05). Magnitudes of glucose lowering and increase in C-peptide/glucose ratio by QHCl-600 were greater in females than males (p < 0.05). We conclude that quinine modulates glucoregulatory functions, associated with glucose lowering in healthy males and females. However, glucose lowering appears to be greater in females than males, without apparent differential effects on GI functions.

Effects of intraduodenal or intragastric administration of a bitter hop extract (Humulus lupulus L.), on upper gut motility, gut hormone secretion and energy intake in healthy-weight men

Gastrointestinal functions, particularly pyloric motility and the gut hormones, cholecystokinin and peptide YY, contribute to the regulation of acute energy intake. Bitter tastants modulate these functions, but may, in higher doses, induce GI symptoms. The aim of this study was to evaluate the effects of both dose and delivery location of a bitter hop extract (BHE) on antropyloroduodenal pressures, plasma cholecystokinin and peptide YY, appetite perceptions, gastrointestinal symptoms and energy intake in healthy-weight men. The study consisted of two consecutive parts, with part A including n = 15, and part B n = 11, healthy, lean men (BMI 22.6 ± 1.1 kg/m², aged 25 ± 3 years). In randomised, double-blind fashion, participants received in part A, BHE in doses of either 100 mg ("ID-BHE-100") or 250 mg ("ID-BHE-250"), or vehicle (canola oil; "ID-control") intraduodenally, or in part B, 250 mg BHE ("IG-BHE-250") or vehicle ("IG-control") intragastrically. Antropyloroduodenal pressures, hormones, appetite and symptoms were measured for 180 min, energy intake from a standardised buffet-meal was quantified subsequently. ID-BHE-250, but not ID-BHE-100, had modest, and transient, effects to stimulate pyloric pressures during the first 90 min (P < 0.05), and peptide YY from t = 60 min (P < 0.05), but did not affect antral or duodenal pressures, cholecystokinin, appetite, gastrointestinal symptoms or energy intake. IG-BHE-250 had no detectable effects. In conclusion, BHE, when administered intraduodenally, in the selected higher dose, modestly affected some appetite-related gastrointestinal functions, but had no detectable effects when given in the lower dose or intragastrically. Thus, BHE, at none of the doses or routes of administration tested, has appetite- or energy intake-suppressant effects.

Colonic Delivery of Nutrients for Sustained and Prolonged Release of Gut Peptides: A Novel Strategy for Appetite Management

Obesity is one of the major global threats to human health and risk factors for cardiometabolic diseases and certain cancers. Glucagon-like peptide-1 (GLP-1) plays a major role in appetite and glucose homeostasis and recently the USFDA approved GLP-1 agonists for the treatment of obesity and type 2 diabetes. GLP-1 is secreted from enteroendocrine L-cells in the distal part of the gastrointestinal (GI) tract in response to nutrient ingestion. Endogenously released GLP-1 has a very short half-life of <2 min and most of the nutrients are absorbed before reaching the distal GI tract and colon, which hinders the use of nutritional compounds for appetite regulation. The review article focuses on nutrients that endogenously stimulate GLP-1 and peptide YY (PYY) secretion via their receptors in order to decrease appetite as preventive action. In addition, various delivery technologies such as pH-sensitive, mucoadhesive, time-dependent, and enzyme-sensitive systems for colonic targeting of nutrients delivery are described. Sustained colonic delivery of nutritional compounds could be one of the most promising approaches to prevent obesity and associated metabolic diseases by, e.g., sustained GLP-1 release.

The Sensory Mechanisms of Nutrient-Induced GLP-1 Secretion

The enteroendocrine system of the gut regulates energy homeostasis through the release of hormones. Of the gut-derived hormones, GLP-1 is particularly interesting, as analogs of the hormone have proven to be highly effective for the treatment of type 2 diabetes mellitus and obesity. Observations on increased levels of GLP-1 following gastric bypass surgery have enhanced the interest in endogenous hormone secretion and highlighted the potential of endogenous secretion in therapy. The macronutrients and their digestive products stimulate the secretion of GLP-1 through various mechanisms that we have only begun to understand. From findings obtained from different experimental models, we now have strong indications for a role for both Sodium-Glucose Transporter 1 (SGLT1) and the K⁺_ATP channel in carbohydrate-induced GLP-1 secretion. For fat, the free fatty acid receptor FFA1 and the G-protein-coupled receptor GPR119 have been linked to GLP-1 secretion. For proteins, Peptide Transporter 1 (Pept1) and the Calcium-Sensing Receptor (CaSR) are thought to mediate the secretion. However, attempts at clinical application of these mechanisms have been unsuccessful, and more work is needed before we fully understand the mechanisms of nutrient-induced GLP-1 secretion.

Effects of intraduodenal infusion of lauric acid and L-tryptophan, alone and combined, on glucoregulatory hormones, gastric emptying and glycaemia in healthy men

BACKGROUND AND AIM

In healthy men, intraduodenal administration of the fatty acid, lauric acid ('C12') and the amino acid, L-tryptophan ('TRP'), at loads that individually do not affect energy intake, reduce energy intake substantially when combined. C12 and TRP may also stimulate cholecystokinin and glucagon-like peptide-1 (GLP-1), which both slow gastric emptying, a key determinant of postprandial blood glucose. Accordingly, combination of C12 and TRP has the potential to reduce post-meal glycaemia more than either nutrient alone.

METHODS

Twelve healthy, lean men (age (mean ± SD): 28 ± 7 years) received, on 4 separate occasions, 45-min intraduodenal infusions of C12 (0.3 kcal/min), TRP (0.1 kcal/min), C12 + TRP (0.4 kcal/min), or 0.9% saline (control), in a randomised, double-blind fashion. 30 min after commencement of the infusion a mixed-nutrient drink was consumed and gastric emptying measured (13C breath-test) for 3 h. Blood samples were obtained at baseline, in response to treatments alone, and for 2 h post-drink for measurements of plasma glucose, cholecystokinin, GLP-1, C-peptide, insulin and glucagon. 'Early' (first 30 min) and 'overall' glycaemic and hormone responses were evaluated.

RESULTS

C12 + TRP and C12 delayed the rise in, but did not affect the overall glycaemic response to the drink, compared with control and TRP (all P < 0.05). C12 + TRP slowed gastric emptying compared with control and TRP (both P < 0.005), and C12 non-significantly slowed gastric emptying compared with control (P = 0.090). C12 + TRP and C12 delayed the rise in C-peptide and insulin, and also stimulated CCK and glucagon, compared with control and TRP (all P < 0.05). Only C12 + TRP stimulated early and overall GLP-1 compared with control (P < 0.05).

CONCLUSIONS

In healthy men, C12 + TRP and C12, in the loads administered, had comparable effects to delay the rise in glucose following a nutrient drink, probably primarily by slowing of gastric emptying, as a result of CCK and GLP-1 stimulation, while TRP had no effect.

A systematic review and meta-analysis of dietary fat effects on reproductive performance of sows and growth performance of piglets

Effects of added fat in sow diets on the sows’ reproductive performance and offspring growth performance are influenced by multiple factors such as genetics, nutrition, parity, ambient temperatures, and farm management. Individual studies cannot cover all these factors. With the view to address this challenge, we searched all studies that were published from 1986 to 2020, and performed a systematic review and meta-analysis on the fat effect. In total, 19 papers were collected and analyzed. Fat supplementation in sow diets during late gestation and lactation decreased average daily feed intake (ADFI, P < 0.05) and tended to increase average daily energy intake (ADEI, P = 0.11). It had no impact on litter weights at birth (P = 0.40) or weaning (P = 0.46). It increased total numbers of piglets at birth (P = 0.07), but had no effect on liveborn per litter (P = 0.90) or survival rate (P = 0.48) of piglets to weaning. Fat supplementation had no significant effect on sow body weight loss (P = 0.67) or backfat thickness changes (P = 0.66), but sows fed diets with added fat had increased milk fat concentration (P = 0.03) and shorter wean to estrus intervals (WEI, P = 0.01). In specific circumstances, fat supplementation tended to improve growth performance of piglets with low litter weights at birth (P = 0.14), or when the sows lost large amounts of body weight during lactation (P = 0.11). The level of supplemented fat was 10% and higher would decrease liveborn per litter at neutral temperature (P = 0.10). The meta-analysis revealed that fat supplementation to sows diet during late gestation and lactation can be beneficial for sow reproductive performance and litter growth performance.

2-Arachidonoyl glycerol potently induces cholecystokinin secretion in murine enteroendocrine STC-1 cells via cannabinoid receptor CB1

Cholecystokinin (CCK) is a peptide hormone secreted from enteroendocrine cells and regulates the exocrine pancreas, gastric motility, and appetite. Dietary triacylglycerols are hydrolyzed to fatty acids (FA) and 2-monoacylglycerols (2-MAG) in the small intestine. Although it is well known that FA stimulate CCK secretion, whether 2-MAG have the CCK-releasing activity remains unclear. We examined the CCK-releasing activity of four commercially available 2-MAG in a murine CCK-producing cell line, STC-1, and the molecular mechanism underlying 2-MAG-induced CCK secretion. CCK released from the cells was measured using ELISA. Among four 2-MAG (2-palmitoyl, 2-oleoyl, 2-linoleoyl, and 2-arachidonoyl monoacylglycerols) examined, 2-arachidonoyl glycerol (2-AG) potently stimulated CCK secretion in a dose-dependent manner. Structurally related compounds, such as 2-arachidonoyl glycerol ether and 1-arachidonoyl glycerol, did not stimulate CCK secretion. Both arachidonic acid and 2-AG stimulated CCK secretion at 100 μM, but only 2-AG did at 50 μM. 2-AG-induced CCK secretion but not arachidonic acid-induced CCK secretion was attenuated by treatment with a cannabinoid receptor 1 (CB1) antagonist. These results indicate that a specific 2-MAG, 2-AG, directly stimulates CCK secretion via CB1.

25 Years of Research in Human Lactation: From Discovery to Translation

Researchers have recently called for human lactation research to be conceptualized as a biological framework where maternal and infant factors impacting human milk, in terms of composition, volume and energy content are studied along with relationships to infant growth, development and health. This approach allows for the development of evidence-based interventions that are more likely to support breastfeeding and lactation in pursuit of global breastfeeding goals. Here we summarize the seminal findings of our research programme using a biological systems approach traversing breast anatomy, milk secretion, physiology of milk removal with respect to breastfeeding and expression, milk composition and infant intake, and infant gastric emptying, culminating in the exploration of relationships with infant growth, development of body composition, and health. This approach has allowed the translation of the findings with respect to education, and clinical practice. It also sets a foundation for improved study design for future investigations in human lactation.

Dietary Fat Chain Length, Saturation, and PUFA Source Acutely Affect Diet-Induced Thermogenesis but Not Satiety in Adults in a Randomized, Crossover Trial

Structural differences in dietary fatty acids modify their rate of oxidation and effect on satiety, endpoints that may influence the development of obesity. This study tests the hypothesis that meals containing fat sources with elevated unsaturated fats will result in greater postprandial energy expenditure, fat oxidation, and satiety than meals containing fats with greater saturation. In a randomized, 5-way crossover design, healthy men and women (n = 23; age: 25.7 ± 6.6 years; BMI: 27.7 ± 3.8 kg/m²) consumed liquid meals containing 30 g of fat from heavy cream (HC), olive oil (OO), sunflower oil (SFO), flaxseed oil (FSO), and fish oil (FO). Energy expenditure and diet-induced thermogenesis (DIT) were determined by metabolic rate over a 240 min postprandial period. Serum concentrations of ghrelin, glucose, insulin, and triacylglycerol (TAG) were assessed. DIT induced by SFO was 5% lower than HC and FO (p = 0.04). Energy expenditure and substrate oxidation did not differ between fat sources. Postprandial TAG concentrations were significantly affected by fat source (p = 0.0001). Varying fat sources by the degree of saturation and PUFA type modified DIT but not satiety responses in normal to obese adult men and women.

Reappraising the role of the vagus nerve in GLP-1-mediated regulation of eating

Here, we provide a focused review of the evidence for the roles of the vagus nerve in mediating the regulatory effects of peripherally and centrally produced GLP-1 on eating behaviour and energy balance. We particularly focus on recent studies which have used selective genetic, viral, and transcriptomic approaches to provide important insights into the anatomical and functional organisation of GLP-1-mediated gut-brain signalling pathways. A number of these studies have challenged canonical ideas of how GLP-1 acts in the periphery and the brain to regulate eating behaviour, with important implications for the development of pharmacological treatments for obesity.

Improvement of Glucose Tolerance by Food Factors Having Glucagon-Like Peptide-1 Releasing Activity

Glucagon-like peptide-1 (GLP-1) is a gastrointestinal hormone released from enteroendocrine L cells in response to meal ingestion. GLP-1 receptor agonists and GLP-1 enhancers have been clinically employed to treat diabetes owing to their glucose-dependent insulin-releasing activity. The release of GLP-1 is primarily stimulated by macronutrients such as glucose and fatty acids, which are nutritionally indispensable; however, excessive intake of sugar and fat is responsible for the development of obesity and diabetes. Therefore, GLP-1 releasing food factors, such as dietary peptides and non-nutrients, are deemed desirable for improving glucose tolerance. Human and animal studies have revealed that dietary proteins/peptides have a potent effect on stimulating GLP-1 secretion. Studies in enteroendocrine cell models have shown that dietary peptides, amino acids, and phytochemicals, such as quercetin, can directly stimulate GLP-1 secretion. In our animal experiments, these food factors improved glucose metabolism and increased GLP-1 secretion. Furthermore, some dietary peptides not only stimulated GLP-1 secretion but also reduced plasma peptidase activity, which is responsible for GLP-1 inactivation. Herein, we review the relationship between GLP-1 and food factors, especially dietary peptides and flavonoids. Accordingly, utilization of food factors with GLP-1-releasing/enhancing activity is a promising strategy for preventing and treating obesity and diabetes.

Comparative Effects of Intragastric and Intraduodenal Administration of Quinine on the Plasma Glucose Response to a Mixed-Nutrient Drink in Healthy Men: Relations with Glucoregulatory Hormones and Gastric Emptying

BACKGROUND

In preclinical studies, bitter compounds, including quinine, stimulate secretion of glucoregulatory hormones [e.g., glucagon-like peptide-1 (GLP-1)] and slow gastric emptying, both key determinants of postprandial glycemia. A greater density of bitter-taste receptors has been reported in the duodenum than the stomach. Thus, intraduodenal (ID) delivery may be more effective in stimulating GI functions to lower postprandial glucose.

OBJECTIVE

We compared effects of intragastric (IG) and ID quinine [as quinine hydrochloride (QHCl)] administration on the plasma glucose response to a mixed-nutrient drink and relations with gastric emptying, plasma C-peptide (reflecting insulin secretion), and GLP-1.

METHODS

Fourteen healthy men [mean ± SD age: 25 ± 3 y; BMI (in kg/m2): 22.5 ± 0.5] received, on 4 separate occasions, in double-blind, randomly assigned order, 600 mg QHCl or control, IG or ID, 60 min (IG conditions) or 30 min (IG conditions) before a mixed-nutrient drink. Plasma glucose (primary outcome) and hormones were measured before, and for 2 h following, the drink. Gastric emptying of the drink was measured using a 13C-acetate breath test. Data were analyzed using repeated-measures 2-way ANOVAs (factors: treatment and route of administration) to evaluate effects of QHCl alone and 3-way ANOVAs (factors: treatment, route-of-administration, and time) for responses to the drink.

RESULTS

After QHCl alone, there were effects of treatment, but not route of administration, on C-peptide, GLP-1, and glucose (P < 0.05); QHCl stimulated C-peptide and GLP-1 and lowered glucose concentrations (IG control: 4.5 ± 0.1; IG-QHCl: 3.9 ± 0.1; ID-control: 4.6 ± 0.1; ID-QHCl: 4.2 ± 0.1 mmol/L) compared with control. Postdrink, there were treatment × time interactions for glucose, C-peptide, and gastric emptying, and a treatment effect for GLP-1 (all P < 0.05), but no route-of-administration effects. QHCl stimulated C-peptide and GLP-1, slowed gastric emptying, and reduced glucose (IG control: 7.2 ± 0.3; IG-QHCl: 6.2 ± 0.3; ID-control: 7.2 ± 0.3; ID-QHCl: 6.4 ± 0.4 mmol/L)  compared with control.

CONCLUSIONS

In healthy men, IG and ID quinine administration similarly lowered plasma glucose, increased plasma insulin and GLP-1, and slowed gastric emptying. These findings have potential implications for lowering blood glucose in type 2 diabetes. This study was registered as a clinical trial with the Australian New Zealand Clinical Trials at www.anzctr.org.au as ACTRN12619001269123.

Review on the Regional Effects of Gastrointestinal Luminal Stimulation on Appetite and Energy Intake: (Pre)clinical Observations

Macronutrients in the gastrointestinal (GI) lumen are able to activate “intestinal brakes”, feedback mechanisms on proximal GI motility and secretion including appetite and energy intake. In this review, we provide a detailed overview of the current evidence with respect to four questions: (1) are regional differences (duodenum, jejunum, ileum) present in the intestinal luminal nutrient modulation of appetite and energy intake? (2) is this “intestinal brake” effect macronutrient specific? (3) is this “intestinal brake” effect maintained during repetitive activation? (4) can the “intestinal brake” effect be activated via non-caloric tastants? Recent evidence indicates that: (1) regional differences exist in the intestinal modulation of appetite and energy intake with a proximal to distal gradient for inhibition of energy intake: ileum and jejunum > duodenum at low but not at high caloric infusion rates. (2) the “intestinal brake” effect on appetite and energy appears not to be macronutrient specific. At equi-caloric amounts, the inhibition on energy intake and appetite is in the same range for fat, protein and carbohydrate. (3) data on repetitive ileal brake activation are scarce because of the need for prolonged intestinal intubation. During repetitive activation of the ileal brake for up to 4 days, no adaptation was observed but overall the inhibitory effect on energy intake was small. (4) the concept of influencing energy intake by intra-intestinal delivery of non-caloric tastants is intriguing. Among tastants, the bitter compounds appear to be more effective in influencing energy intake. Energy intake decreases modestly after post-oral delivery of bitter tastants or a combination of tastants (bitter, sweet and umami). Intestinal brake activation provides an interesting concept for preventive and therapeutic approaches in weight management strategies.

Nutrient-Induced Cellular Mechanisms of Gut Hormone Secretion

The gastrointestinal tract can assess the nutrient composition of ingested food. The nutrient-sensing mechanisms in specialised epithelial cells lining the gastrointestinal tract, the enteroendocrine cells, trigger the release of gut hormones that provide important local and central feedback signals to regulate nutrient utilisation and feeding behaviour. The evidence for nutrient-stimulated secretion of two of the most studied gut hormones, glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), along with the known cellular mechanisms in enteroendocrine cells recruited by nutrients, will be the focus of this review. The mechanisms involved range from electrogenic transporters, ion channel modulation and nutrient-activated G-protein coupled receptors that converge on the release machinery controlling hormone secretion. Elucidation of these mechanisms will provide much needed insight into postprandial physiology and identify tractable dietary approaches to potentially manage nutrition and satiety by altering the secreted gut hormone profile.

Cholecystokinin and the hormone concept

The birth certificate for endocrinology was Bayliss' and Starling's demonstration in 1902 that regulation of bodily functions is not only neuronal but also due to blood-borne messengers. Starling named these messengers hormones. Since then transport via blood has defined hormones. This definition, however, may be too narrow. Thus, today we know that several peptide hormones are not only produced and released to blood from endocrine cells but also released from neurons, myocytes, immune cells, endothelial cells, spermatogenic cells, fat cells, etc. And they are often secreted in cell-specific molecular forms with more or less different spectra of activity. The present review depicts this development with the story about cholecystokinin which was discovered in 1928 as a hormone and still in 1976 was conceived as a single blood-borne peptide. Today's multifaceted picture of cholecystokinin suggests that time may be ripe for expansion of the hormone concept to all messenger molecules, which activate their target cells - irrespective of their road to the target (endocrine, neurocrine, neuronal, paracrine, autocrine, etc.) and irrespective of their kind of activity as classical hormone, growth factor, neurotransmitter, adipokine, cytokine, myokine, or fertility factor.

Macronutrient Sensing in the Oral Cavity and Gastrointestinal Tract: Alimentary Tastes

There are numerous and diverse factors enabling the overconsumption of foods, with the sense of taste being one of these factors. There are four well established basic tastes: sweet, sour, salty, and bitter; all with perceptual independence, salience, and hedonic responses to encourage or discourage consumption. More recently, additional tastes have been added to the basic taste list including umami and fat, but they lack the perceptual independence and salience of the basics. There is also emerging evidence of taste responses to kokumi and carbohydrate. One interesting aspect is the link with the new and emerging tastes to macronutrients, with each macronutrient having two distinct perceptual qualities that, perhaps in combination, provide a holistic perception for each macronutrient: fat has fat taste and mouthfeel; protein has umami and kokumi; carbohydrate has sweet and carbohydrate tastes. These new tastes can be sensed in the oral cavity, but they have more influence post- than pre-ingestion. Umami, fat, kokumi, and carbohydrate tastes have been suggested as an independent category named alimentary. This narrative review will present and discuss evidence for macronutrient sensing throughout the alimentary canal and evidence of how each of the alimentary tastes may influence the consumption of foods.

A comparison of the satiating properties of medium-chain triglycerides and conjugated linoleic acid in participants with healthy weight and overweight or obesity

PURPOSE

Inconsistent evidence exists for greater satiety after medium-chain triglycerides (MCT) or conjugated linoleic acid (CLA) compared to long-chain triglycerides (LCT). Furthermore, the mechanisms are poorly understood and effects in people with a healthy weight and those with overweight/obesity have not been compared. This study aimed to compare appetite responses in these groups and examine the mechanisms behind any differences.

METHODS

Fifteen participants with healthy weight (BMI: 22.7 ± 1.9 kg·m-2) and fourteen participants with overweight/obesity (BMI: 30.9 ± 3.9 kg·m-2) consumed a breakfast containing either 23.06 g vegetable oil (CON), 25.00 g MCT oil (MCT), or 6.25 g CLA and 16.80 g vegetable oil (CLA). Appetite, peptide YY (PYY), total ghrelin (TG), β-hydroxybutyrate, and gastric emptying (GE) were measured throughout. Energy intake was assessed at an ad libitum lunch and throughout the following ~ 36 h.

RESULTS

Neither MCT nor CLA decreased ad libitum intake; however MCT decreased day 1 energy intake (P = 0.031) and the 48-h period (P = 0.005) compared to CON. MCT delayed GE (P ≤ 0.01) compared to CON, whereas CLA did not. PYY and TG concentrations were not different (P = 0.743 and P = 0.188, respectively), but MCT increased β-hydroxybutyrate concentrations compared to CON (P = 0.005) and CLA (P < 0.001). β-hydroxybutyrate concentrations were higher in participants with overweight/obesity (P = 0.009).

CONCLUSION

Consumption of MCT reduces energy intake in the subsequent 48 h, whereas CLA does not. Delayed gastric emptying or increased β-hydroxybutyrate concentrations may mediate this.

A review on differential effects of dietary fatty acids on weight, appetite and energy expenditure

The association between weight and chronic diseases is well defined. The quality and quantity of dietary fatty acids is an important external factor and appetite and energy expenditure, are important internal factors in determining body weight. On the other hand, dietary fatty acids composition can modulate appetite and energy metabolism, but not all fats are equal in producing metabolic responses.Given the accumulating evidence for differential effects of various dietary fatty acids, one important area of investigation is to scrutinize their roles in weight, appetite and energy expenditure modulation. There is substantial evidence to suggest that saturated fatty acids have a greater effect on appetite control, although in the long run may result in more weight gain than unsaturated fatty acids due to a weaker stimulation of energy expenditure. In contrast, mono-unsaturated fats do not have much effects on appetite control, but they can be beneficial in weight control over the long term due to stimulatory effects on energy expenditure. Interestingly, in case of poly unsaturated fats, including n-3 and n-6, their effect on increasing energy expenditure is aligned, but they act differently in controlling weight and appetite.

Emulsion Droplet Crystallinity Attenuates Short-Term Satiety in Healthy Adult Males: A Randomized, Double-Blinded, Crossover, Acute Meal Study

BACKGROUND

The influence of triacylglycerol (TAG) physical properties on satiety remains poorly understood.

OBJECTIVES

The objective was to investigate if and how TAG digestion and absorption, modulated only by differences in TAG crystallinity, would differentially affect short-term satiety in healthy men.

METHODS

We tempered 500 mL 10% palm stearin oil-in-water emulsions such that the lipid droplets were either undercooled liquid (LE) or partially crystalline solid (SE). Fifteen healthy men (mean ± SD age: 27.5 ± 5.7 y; BMI: 24.1 ± 2.5 kg/m2; fasting TAG: 0.9 ± 0.3 mmol/L) consumed each beverage at two 6-h study visits separated by ≥6 d after an overnight fast, along with 1500 mg acetaminophen suspended in water. The participants characterized the emulsion sensory properties, completed satiety visual analog scale ratings, and had serial blood samples collected for 6-h analysis of plasma peptide YY (PYY), glucagon-like peptide-1 (GLP-1), ghrelin, leptin, glucose-dependent insulinotropic polypeptide (GIP), insulin, and acetaminophen (for assessing gastric emptying). Repeated-measures ANOVAs and 2-tailed paired t tests were used to analyze the changes from baseline and incremental area under the curve (iAUC) values, respectively.

RESULTS

With consumption of LE compared with SE, there was a 358% higher fullness (P = 0.015) and a 103% lower average appetite (P = 0.041) score, along with higher iAUC values for PYY (P = 0.011) and GLP-1 (P = 0.028) (103% and 66% higher, respectively), but not for ghrelin (P = 0.39), based on change from baseline values. Acetaminophen response trended toward significance (P = 0.08) and was 15% higher with LE. SE was rated as 44% thicker (P = 0.034) and 24% creamier (P = 0.05) than LE.

CONCLUSIONS

The suppression of TAG digestion by the presence of partially crystalline lipid droplets blunted the appetite-suppressing effects of an oil-in-water emulsion.This trial was registered at clinicaltrials.gov as NCT03990246.

Effects of intraduodenal coadministration of lauric acid and leucine on gut motility, plasma cholecystokinin, and energy intake in healthy men

The fatty acid, lauric acid (C12), and the amino acid, leucine (Leu) stimulate gut hormones, including CCK, associated with suppression of energy intake. In our recent study, intraduodenal infusion of a combination of C12 and l-tryptophan, at loads that individually did not affect energy intake, reduced energy intake substantially, associated with much greater stimulation of CCK. We have now investigated whether combined administration of C12 and Leu would enhance the intake-suppressant effects of each nutrient, when given at loads that each suppress energy intake individually. Sixteen healthy, lean males (age: 23 ± 2 yr) received, in randomized, double-blind fashion, 90-min intraduodenal infusions of control (saline), C12 (0.4 kcal/min), Leu (0.45 kcal/min), or C12+Leu (0.85 kcal/min). Antropyloroduodenal pressures were measured continuously and plasma CCK at 15-min intervals, and energy intake from a standardized buffet-meal, consumed immediately postinfusion, was quantified. All nutrient infusions stimulated plasma CCK compared with control (P < 0.05). Moreover, C12 and C12+Leu stimulated CCK compared with Leu (P < 0.05) (mean concentration, pmol/L; control: 2.3 ± 0.3, C12: 3.8 ± 0.3, Leu: 2.7 ± 0.3, and C12+Leu: 4.0 ± 0.4). C12+Leu, but not C12 or Leu, stimulated pyloric pressures (P < 0.05). C12+Leu and C12 reduced energy intake (P < 0.05), and there was a trend for Leu to reduce (P = 0.06) energy intake compared with control, with no differences between the three nutrient treatments (kcal; control: 1398 ± 84, C12: 1226 ± 80, Leu: 1260 ± 92, and C12+Leu: 1208 ± 83). In conclusion, combination of C12 and Leu, at the loads given, did not reduce energy intake beyond their individual effects, possibly because maximal effects had been evoked.

A systematic review and meta-analysis of medium-chain triglycerides effects on acute satiety and food intake

Research has indicated that consuming medium-chain triglycerides (MCT) may be more satiating than consuming long-chain triglycerides (LCT) potentially causing a reduction in energy intake. However not all studies have demonstrated this acute reduction in energy intake and it has yet to be systematically reviewed. Our main objective was to examine how ingestion of MCT influences energy intake, subjective appetite ratings and appetite-related hormones compared to LCT. Web of Science, MEDLINE, CINHAL, and Embase were searched for publications comparing the effect of MCT on appetite (commonly hunger, fullness, desire to eat, and prospective food consumption), appetite-related hormones (pancreatic polypeptide (PP), gastric inhibitory polypeptide (GIP), peptide YY (PYY), glucagon-like peptide-1 (GLP-1), neurotensin, leptin, total ghrelin and active ghrelin) and energy intake to LCT. A random-effects meta-analysis was conducted on studies which examined energy intake. Seventeen studies (291 participants) were included in the systematic review, of which 11 were included in the energy intake meta-analysis. Synthesis of combined data showed evidence of a statistically significant moderate decrease in ad libitum energy intake after both acute and chronic ingestion of MCT compared to LCT when assessed under laboratory conditions (mean effect size: -0.444, 95% CI -0.808, -0.080, p < 0.017), despite little evidence of any effect of MCT on subjective appetite ratings or circulating hormones. The current evidence supports the notion that MCT decreases subsequent energy intake, but does not appear to affect appetite. Further research is warranted to elucidate the mechanisms by which MCT reduce energy intake.

What Is GLP-1 Really Doing in Obesity?

Glucagon-like peptide-1 (GLP-1) is a gastrointestinal hormone released in response to meal ingestion and enhances insulin secretion from pancreatic β cells. In several human studies, GLP-1 secretory responses to oral glucose load or a meal were decreased in subjects with obesity, glucose intolerance, or diabetes compared with those in healthy subjects. However, the results of meta-analysis and cohort studies do not necessarily support this concept. Results from animal studies are also inconsistent; in multiple studies, GLP-1 secretory responses to a meal were repeatedly higher in diet-induced obese rats than in control rats. Thus, the postprandial GLP-1 response is not necessarily decreased but rather enhanced during obesity development, which is likely to play a protective role against glucose intolerance.

Intestinal sensing and handling of dietary lipids in gastric bypass-operated patients and matched controls

BACKGROUND

Altered meal-related gut hormone secretion seems important for weight loss and diabetes remission after Roux-en-Y gastric bypass (RYGB). Elucidating the responsible meal components and receptors could aid discovery of new treatments of obesity and diabetes. Enteroendocrine cells respond to digestion products of dietary triacylglycerol, especially long-chain fatty acids (LCFAs) and 2-oleoyl-glycerol (2-OG), but not medium-chain fatty acids (MCFAs).

OBJECTIVE

We examined the impact of olive oil (20 mL) and its derivates, LCFAs and 2-OG, on enteroendocrine secretions [glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), cholecystokinin (CCK), peptide YY (PYY), and neurotensin (NT)] and on glucose, lipid, and bile acid metabolism in RYGB-operated and unoperated individuals.

METHODS

In an exploratory randomized crossover design, 10 RYGB-operated patients and 10 matched controls ingested 3 equimolar triacylglycerol formulations on separate days: olive oil (digested to 2-OG + LCFAs), C8-dietary oil (2-OG + MCFAs), and tricaprylin (MCFAs; negative control). Hormone responses were calculated as area under the curve (AUC).

RESULTS

Independent of group status, olive oil had greater effects than C8-dietary oil on AUCs of plasma GLP-1 (+32%; 95% CI: 23%, 43%; P < 0.01), CCK (+53%, P < 0.01), and NT (+71%, P < 0.01), whereas the effect on GIP differed between groups (+90% in controls, P < 0.01; +24% in RYGB, P = 0.10). Independent of group status, C8-dietary oil had greater effects than tricaprylin on AUCs of plasma CCK (+40%, P < 0.01) and NT (+32%, P < 0.01), but not GLP-1 (+5%; 95% CI: -2.9%, 13%; P = 0.22), whereas the effect on GIP again differed between groups (+78% in controls, P < 0.01; +39% in RYGB, P = 0.01). Distal (GLP-1/PYY/NT), but not proximal (CCK/GIP), enteroendocrine responses were generally greater in RYGB patients than in controls.

CONCLUSIONS

The combination of LCFAs plus 2-OG was substantially more effective than 2-OG plus MCFAs in stimulating enteroendocrine secretion in RYGB-operated and matched control individuals. Distal lipid-induced gut hormone release was greater after RYGB.This trial was registered at clinicaltrials.gov as NCT03223389.

Effect of medium-chain TAG and exercise on satiety, energy intake and energy balance

The present study examined whether the combination of medium-chain TAG (MCT) along with exercise suppresses energy intake to a greater extent compared with either intervention alone. Twelve participants consumed a porridge breakfast containing 692·9 kJ of either vegetable or MCT oil on two separate occasions: one followed by rest for 240 min and another followed by rest broken up with 1 h of cycling at 65 % $\dot V$O2peak starting at 120 min. At 240 min, participants consumed a buffet lunch to satiation and recorded their food intake for the rest of the day. Expired air samples (for calculation of energy expenditure (EE)) and subjective ratings of appetite on visual analogue scales were taken every 30 min, and gastric emptying (GE) breath samples were taken every 15 min. No effect of either breakfast or exercise condition was observed on energy intake at any time point (P > 0·05) or no effect was observed on subjective appetite ratings (P > 0·05). Exercise trials resulted in significantly higher EE compared with resting trials (2960·6 kJ, 95 % CI 2528·9, 3392·2; P < 0·001), and MCT increased resting EE over 4 h compared with long-chain TAG (LCT) (124·8 kJ, 95 % CI 13·5, 236·0; P = 0·031). GE was accelerated by exercise, regardless of the breakfast consumed, but delayed by MCT in both resting and exercise trials. The results show that exercise causes energy deficits via increased EE without promoting dietary compensation. MCT has no effect on energy intake or satiety but increases EE under resting conditions. There is no additive effect of MCT and exercise on EE, intake or appetite ratings.

GutSelf: Interindividual Variability in the Processing of Dietary Compounds by the Human Gastrointestinal Tract

Nutritional research is currently entering the field of personalized nutrition, to a large extent driven by major technological breakthroughs in analytical sciences and biocomputing. An efficient launching of the personalized approach depends on the ability of researchers to comprehensively monitor and characterize interindividual variability in the activity of the human gastrointestinal tract. This information is currently not available in such a form. This review therefore aims at identifying and discussing published data, providing evidence on interindividual variability in the processing of the major nutrients, i.e., protein, fat, carbohydrates, vitamins, and minerals, along the gastrointestinal tract, including oral processing, intestinal digestion, and absorption. Although interindividual variability is not a primary endpoint of most studies identified, a significant number of publications provides a wealth of information on this topic for each category of nutrients. This knowledge remains fragmented, however, and understanding the clinical relevance of most of the interindividual responses to food ingestion described in this review remains unclear. In that regard, this review has identified a gap and sets the base for future research addressing the issue of the interindividual variability in the response of the human organism to the ingestion of foods.

Influence of subliminal intragastric fatty acid infusion on subjective and physiological responses to positive emotion induction in healthy women: A randomized trial

BACKGROUND

Subliminal intragastric fatty acid infusion attenuates subjective and brain responses to negative emotion induction. However, the underlying gut-brain signaling mechanisms remain unclear, and it is unknown whether such effect equally applies to positive emotion.

OBJECTIVE

We aimed to investigate the interaction between fatty acid-induced gut-brain signaling and subjective responses to positive emotion, and the potential mediational role of gastrointestinal (GI) hormones.

DESIGN

Twelve fasting healthy women underwent intragastric infusion of 2.5 g lauric acid or saline, after which either positive or neutral emotion was induced for 30 min, in 4 separate visits. Appetite-related sensations, subjective emotional state, and GI hormones were measured at baseline and every 10 min after infusion. Heart rate variability was measured at baseline and at t = 20-30 min to quantify vagal tone (root mean square of successive differences, RMSSD), and sympathovagal balance (low frequency to high frequency ratio, LF/HF).

RESULTS

Fatty acid infusion did not influence appetite-related sensations (as expected), nor emotional state ratings (contrary to expectations). As anticipated, fatty acid stimulated release of CCK at t = 20-40 min (p < 0.001), and GLP1 at t = 30-40 min (p < 0.001), but not PYY. Interestingly, positive emotion induction suppressed plasma octanoylated ghrelin at t = 20-40 min (p = 0.020). Further, both positive emotion and fatty acid attenuated RMSSD (p = 0.012 & 0.0073, respectively). Positive emotion attenuated LF/HF after fatty acid (p = 0.0006), but raised LF/HF after saline (p = 0.004).

CONCLUSIONS

Subliminal fatty acid did not influence subjective responses to positive emotion induction. However, positive emotion induction suppressed octanoylated ghrelin release. Moreover, both positive emotion and subliminal fatty acid decreased cardiac vagal tone. Further, the fatty acid reversed the effect of positive emotion on sympathovagal balance.

Dietary fatty acid content influences the expression of genes involved in the lipid turnover and inflammation in mouse colon and spleen

BACKGROUND

Dietary interventions can improve gastrointestinal (GI) symptoms. We determined the effects of fatty acids (FAs) supplementation with medium- and long-chain saturated FAs on mouse GI motility and correlated them with the expression of genes for free FA receptors (FFAR)1-4, FA binding protein 4 (FABP4) and inflammation.

METHODS

Forty-eight BalbC were assigned to: standard diet (STD), diet rich in medium-chain saturated FAs (COCO) and long-chain saturated FAs (HF) (7% by weight). Body weight (BW) and food intake (FI) were monitored for 8-weeks. GI motility was determined by fecal pellet output (FPO) and colon bead expulsion tests. FABP4 inhibitor, BMS309403 (1mg/kg, ip) was injected to half of each group 2 days/week. mRNA expression of FABP4, (FFAR)1-4, and pro-inflammatory cytokines were measured in colonic and splenic tissues using real-time PCR.

RESULTS

COCO and HF decreased FI. COCO accelerated overall GI transit (p<0.05). COCO increased the mRNA expression of FFAR2 (p<0.001) and TNFα (p<0.01); HF increased the expression of FABP4 and FFAR4 (p<0.05), and FFAR2 (p<0.001) in the colon, and decreased FFAR1 and FFAR4 (p<0.001), TNFα (p<0.01) and IL-1β (p<0.05) in splenic tissues. BMS309403 decreased the FI and delayed colonic transit in STD+BMS and COCO+BMS vs. STD (p<0.05). HF+BMS increased colonic expression of FFAR3 (p<0.01), TNFα (p<0.01), IL-6 (p<0.01), and reduced FFAR4 (p<0.05); COCO+BMS decreased TNFα (p<0.01).

CONCLUSION

Diversification in the dietary lipid content affected GI motility in mice and the expression of FFARs and pro-inflammatory cytokines in vivo.

Chain length of dietary fatty acids determines gastrointestinal motility and visceromotor function in mice in a fatty acid binding protein 4-dependent manner

Purpose

We hypothesize that different types of dietary fatty acids (FAs) affect gastrointestinal (GI) motility and visceromotor function and that this effect can be regulated by the fatty acid binding protein 4 (FABP4).

Methods

Mice were fed for 60 days with standard diet (STD), STD with 7% (by weight) coconut oil, rich in medium-chain FAs (MCFAs) (COCO), or with 7% evening primrose oil, rich in long-chain FAs (LCFAs) (EPO). In each group, half of the mice received FABP4 inhibitor, BMS309403 (1 mg/kg; i.p.) twice a week. Body weight (BW) and food intake were measured; well-established tests were performed to characterize the changes in GI motility and visceral pain. White adipose tissue and colonic samples were collected for cell culturing and molecular studies.

Results

COCO significantly increased GI transit, but not colonic motility. COCO and EPO delayed the onset of diarrhea, but none affected the effect of loperamide. EPO reduced BW and increased the visceromotor response (VMR) to colorectal distension (CRD). COCO and EPO reduced differentiation of preadipocytes. Treatment with BMS309403: (1) reversed the effects induced by COCO in physiological conditions and in mouse models of diarrhea; (2) prevented the effects of EPO on BW, VMR to CRD and castor oil-induced diarrhea; (3) affected proliferation of preadipocytes; (4) changed the expression of Fabp4 in colonic and adipocyte samples from COCO and EPO.

Conclusion

Modifying dietary intake of MCFAs and LCFAs may be used to control GI motility or visceral pain and thus modulate the symptoms of functional GI disorders. The effect is dependent on the expression of FABP4.

Electronic supplementary material

The online version of this article (10.1007/s00394-019-02094-2) contains supplementary material, which is available to authorized users.

Relationship between diet/exercise and pharmacotherapy to enhance the GLP-1 levels in type 2 diabetes

The rapid rise in the prevalence of type 2 diabetes mellitus (T2DM) poses a huge healthcare burden across the world. Although there are several antihyperglycaemic agents (AHAs) available including addition of new drug classes to the treatment algorithm, more than 50% of patients with T2DM do not achieve glycaemic targets, suggesting an urgent need for treatment strategies focusing on prevention and progression of T2DM and its long-term complications. Lifestyle changes including implementation of healthy diet and physical activity are cornerstones for the management of T2DM. The positive effects of diet and exercise on incretin hormones such as glucagon-like peptide-1 (GLP-1) have been reported. We hypothesize an IDEP concept (Interaction between Diet/Exercise and Pharmacotherapy) aimed at modifying the diet and lifestyle, along with pharmacotherapy to enhance the GLP-1 levels, would result in good glycaemic control in patients with T2DM. Consuming protein-rich food, avoiding saturated fatty acids and making small changes in eating habits such as eating slowly with longer mastication time can have a positive impact on the GLP-1 secretion and insulin levels. Further the type of physical activity (aerobic/resistance training), intensity of exercise, duration, time and frequency of exercise have shown to improve GLP-1 levels. Apart from AHAs, a few antihypertensive drugs and lipid-lowering drugs have also shown to increase endogenous GLP-1 levels, however, due to quick degradation of GLP-1 by dipeptidyl peptidase-4 (DPP-4) enzyme, treatment with DPP-4 inhibitors would protect GLP-1 from degradation and prolong its activity. Thus, IDEP concept can be a promising treatment strategy, which positively influences the GLP-1 levels and provide additive benefits in terms of improving metabolic parameters in patients with T2DM and slowing the progression of T2DM and its associated complications.

Medium-chain triglyceride diet stimulates less GIP secretion and suppresses body weight and fat mass gain compared with long-chain triglyceride diet

Gastric inhibitory polypeptide (GIP) is an incretin secreted from enteroendocrine K cells and potentiates insulin secretion from pancreatic β-cells. GIP also enhances long-chain triglyceride (LCT) diet-induced obesity and insulin resistance. Long-term intake of medium-chain triglyceride (MCT) diet is known to induce less body weight and fat mass gain than that of LCT diet. However, the effect of MCT diet feeding on GIP secretion and the effect of GIP on body weight and fat mass under MCT diet-feeding condition are unknown. In this study, we evaluated the effect of single MCT oil administration on GIP secretion and compared the effect of long-term MCT and LCT diet on body weight and fat mass gain in wild-type (WT) and GIP-knockout (GIP KO) mice. Single administration of LCT oil induced GIP secretion but that of MCT oil did not in WT mice. Long-term intake of LCT diet induced GIP hypersecretion and significant body weight and fat mass gain compared with that of control fat (CF) diet in WT mice. In contrast, MCT diet did not induce GIP hypersecretion, and MCT diet-fed mice showed smaller increase in body weight and fat mass gain compared with CF diet-fed mice. In GIP KO mice, body weight and fat mass were markedly attenuated in LCT diet-fed mice but not in MCT diet-fed mice. Our results suggest that long-term intake of MCT diet stimulates less GIP secretion and suppresses body weight and fat mass gain compared with that of LCT diet.

The Effect of Canola Oil on Body Weight and Composition: A Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials

A number of clinical trials have examined the effect of canola oil (CO) on body composition in recent years; however, the results have been inconsistent. The present investigation aims to examine the effect of CO on body weight (BW) and body composition using a systematic review and meta-analysis of controlled clinical trials. Online databases including PubMed, Scopus, and Google Scholar were searched up to February, 2018 for randomized controlled clinical trials that examined the effect of CO on anthropometric measures and body composition indexes in adults. The Cochrane Collaboration's tool was used to assess the risk of bias in individual studies. A random-effects model was used to evaluate the effect of CO consumption on several outcomes: BW, body mass index, waist circumference, hip circumference, waist-to-hip ratio, android-to-gynoid ratio, and body lean and fat mass. In total, 25 studies were included in the systematic review. The meta-analysis revealed that CO consumption reduces BW [weighted mean difference (WMD) = -0.30 kg; 95% CI: -0.52, -0.08 kg, P = 0.007; n = 23 effect sizes], particularly in participants with type 2 diabetes (WMD = -0.63 kg; 95% CI: -1.09, -0.17 kg, P = 0.007), in studies with a parallel design (WMD = -0.49 kg; 95% CI: -0.85, -0.14 kg, P = 0.006), in nonfeeding trials (WMD = -0.32 kg; 95% CI: -0.55, -0.09 kg, P = 0.006), and when compared with saturated fat (WMD = -0.40 kg; 95% CI: -0.74, -0.06 kg, P = 0.019). CO consumption did not significantly affect any other anthropometric measures or body fat markers (P > 0.05). Although CO consumption results in a modest decrease in BW, no significant effect was observed on other adiposity indexes. Further well-constructed clinical trials that target BW and body composition as their primary outcomes are needed.

Effects of intraduodenal administration of lauric acid and L-tryptophan, alone and combined, on gut hormones, pyloric pressures, and energy intake in healthy men

BACKGROUND

The fatty acid, lauric acid ('C12'), and the amino acid, L-tryptophan ('Trp'), modulate gastrointestinal functions including gut hormones and pyloric pressures, which are important for the regulation of energy intake, and both potently suppress energy intake.

OBJECTIVE

We hypothesized that the intraduodenal administration of C12 and Trp, at loads that do not affect energy intake individually, when combined will reduce energy intake, which is associated with greater modulation of gut hormones and pyloric pressures.

DESIGN

Sixteen healthy, lean males (age: 24 ± 1.5 y) received 90-min intraduodenal infusions of saline (control), C12 (0.3 kcal/min), Trp (0.1 kcal/min), or C12 + Trp (0.4 kcal/min), in a randomized, double-blind, cross-over study. Antropyloroduodenal pressures were measured continuously, and plasma cholecystokinin (CCK), ghrelin, and glucagon-like peptide-1 (GLP-1) concentrations, appetite perceptions, and gastrointestinal symptoms at 15-min intervals. Immediately after the infusions, energy intake from a standardized buffet meal was quantified.

RESULTS

C12 + Trp markedly reduced energy intake (kcal; control: 1,232 ± 72, C12: 1,180 ± 82, Trp: 1,269 ± 73, C12 + Trp: 1,056 ± 106), stimulated plasma CCK (AUC(area under the curve)0-90 min, pmol/L*min; control: 21 ± 8; C12: 129 ± 15; Trp: 97 ± 16; C12 + Trp: 229 ± 22) and GLP-1 (AUC0-90 min, pmol/L*min; control: 102 ± 41; C12: 522 ± 102; Trp: 198 ± 63; C12 + Trp: 545 ± 138), and suppressed ghrelin (AUC0-90 min, pg/mL*min; control: -3,433 ± 2,647; C12: -11,825 ± 3,521; Trp: -8,417 ± 3,734; C12 + Trp: -18,188 ± 4,165) concentrations, but did not stimulate tonic, or phasic, pyloric pressures, compared with the control (all P < 0.05), or have adverse effects. C12 and Trp each stimulated CCK (P < 0.05), but to a lesser degree than C12 + Trp, and did not suppress energy intake or ghrelin. C12, but not Trp, stimulated GLP-1 (P < 0.05) and phasic pyloric pressures (P < 0.05), compared with the control.

CONCLUSION

The combined intraduodenal administration of C12 and Trp, at loads that individually do not affect energy intake, substantially reduces energy intake, which is associated with a marked stimulation of CCK and suppression of ghrelin. The study was registered as a clinical trial at the Australian and New Zealand Clinical Trial Registry (www.anzctr.org.au,) as 12613000899741.

Glucagon Receptor Signaling and Lipid Metabolism

Glucagon is secreted from the pancreatic alpha cells upon hypoglycemia and stimulates hepatic glucose production. Type 2 diabetes is associated with dysregulated glucagon secretion, and increased glucagon concentrations contribute to the diabetic hyperglycemia. Antagonists of the glucagon receptor have been considered as glucose-lowering therapy in type 2 diabetes patients, but their clinical applicability has been questioned because of reports of therapy-induced increments in liver fat content and increased plasma concentrations of low-density lipoprotein. Conversely, in animal models, increased glucagon receptor signaling has been linked to improved lipid metabolism. Glucagon acts primarily on the liver and by regulating hepatic lipid metabolism glucagon may reduce hepatic lipid accumulation and decrease hepatic lipid secretion. Regarding whole-body lipid metabolism, it is controversial to what extent glucagon influences lipolysis in adipose tissue, particularly in humans. Glucagon receptor agonists combined with glucagon-like peptide 1 receptor agonists (dual agonists) improve dyslipidemia and reduce hepatic steatosis. Collectively, emerging data support an essential role of glucagon for lipid metabolism.