Regulation of α-Transducin and α-Gustducin Expression by a High Protein Diet in the Pig Gastrointestinal Tract

Discovery of bitter masking compounds from Allspice (Pimenta dioica) using sensory guided isolation

Bitter substances in functional foods and beverages can act as nutraceuticals, offering potential health benefits. However, their unpleasant sensory impact reduces the consumption of these foods. Consequently, the discovery of bitter masking compounds is crucial for enhancing the intake of bioactive compounds in functional foods and beverages. Bitter taste is mediated by TAS2Rs, a sub-family of G-protein-coupled receptors. TAS2R14 is especially pivotal in the perception of bitterness, as it is one of the most broadly tuned bitter receptors. In this study, allspice was extracted and purified to yield five single compounds based on sensory guided fractionation. The structures of each compound were determined based on nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HR-MS). In a sensory evaluation, compound 1 exhibited bitter masking activity against quinine. Molecular docking analysis revealed that compound 1 could act as an antagonist of the TAS2R14 bitter receptor.

Dietary Verbascoside Influences Gut Morphology and the Expression of α-Transducin and α-Gustducin in the Small Intestine of Weaned Piglets Exposed to n-6 Polyunsaturated Fatty Acids-Induced Oxidative Stress

Simple Summary

In recent years, feed interventions with natural antioxidants have grown because oxidative stress is linked to the development of several diseases in pigs. Weaning is one of the most stressful events in pig breeding, inducing physiological, environmental, and social changes. These cause intestinal disorder, inflammation and oxidative stress that result in reduced pig health and growth. Previous data reported that dietary supplementation with a natural extract containing verbascoside positively affects piglets’ health and welfare by reducing oxidative stress parameters. This study shows that verbascoside protects the gastrointestinal tract from oxidative stress and may have an appetite-stimulatory effect by modulating gastrointestinal taste receptors’ related protein expression.

Abstract

Reducing oxidative stress is an important goal in post-weaning piglets; previous studies have reported that verbascoside decreases oxidative stress in piglets. The effect of verbascoside on gut morphology and α-transducin and α-gustducin expression in weaned piglets fed high dosages of sunflower oil, inducing oxidative stress, was evaluated. A diet with 9% sunflower oil (T1), the same diet supplemented with 5 mg of verbascoside/kg feed (T2) and a diet containing starch (control—CTR) were employed. Histology, histometry, histochemistry, immunofluorescence and Western blot analyses were performed on the piglets’ small intestine. In the T1 group, apical erosion was observed and villi height was lower than in other groups. The mucin profile was acidic in goblet cells of both the T1 and T2 groups. However, it was both neutral and acidic in the CTR group. Dietary treatments did not affect α-gustducin expression. Otherwise, the expression of α-transducin in the duodenum was lower (p < 0.01) in the T1 groups than in the other groups. The colocalization of α-transducin with chromogranin A and ghrelin revealed that the endocrine cells were immunopositive for both ghrelin and α-transducin. Overall, these results provide new insights into gut sensory perception in piglets and contribute to understanding how feed ingredients such as fat and polyphenols may be involved in gustatory signal transduction.

Intestinal Signaling of Proteins and Digestion-Derived Products Relevant to Satiety

Luminal nutrients stimulate enteroendocrine cells through the activation of specific receptors to release hormones that inhibit appetite and promote glucose homeostasis. While food protein is the macronutrient with the highest effect on satiety, the signaling on the protein digestion products at the gut is poorly understood. This perspective aims to highlight the existing gaps in the study of protein digestion products as signaling molecules in gastrointestinal enteroendocrine cells. Because dietary protein digestion can be modulated by the technological processes applied to food, it is possible to target gut receptors to control food intake by formulating specific food ingredients or protein preloads.

Essential oils as alternatives to antibiotics in swine production

This review article summarizes the efficacy, feasibility and potential mechanisms of the application of essential oils as antibiotic alternatives in swine production. Although there are numerous studies demonstrating that essential oils have several properties, such as antimicrobial, antioxidative and anti-inflammatory effects, feed palatability enhancement and improvement in gut growth and health, there is still a need of further investigations to elucidate the mechanisms underlying their functions. In the past, the results has been inconsistent in both laboratory and field studies because of the varied product compositions, dosages, purities and growing stages and conditions of animals. The minimal inhibitory concentration (MIC) of essential oils needed for killing enteric pathogens may not ensure the optimal feed intake and the essential oils inclusion cost may be too high in swine production. With the lipophilic and volatile nature of essential oils, there is a challenge in effective delivery of essential oils within pig gut and this challenge can partially be resolved by microencapsulation and nanotechnology. The effects of essential oils on inflammation, oxidative stress, microbiome, gut chemosensing and bacterial quorum sensing (QS) have led to better production performance of animals fed essential oils in a number of studies. It has been demonstrated that essential oils have good potential as antibiotic alternatives in feeds for swine production. The combination of different essential oils and other compounds (synergistic effect) such as organic acids seems to be a promising approach to improve the efficacy and safety of essential oils in applications. High-throughput systems technologies have been developed recently, which will allow us to dissect the mechanisms underlying the functions of essential oils and facilitate the use of essential oils in swine production.

Taste receptors in the gut - A new target for health promoting properties in diet

In this review we describe a new target for food functionality, the taste receptors in the gastrointestinal tract. These receptors are involved in an intricate signalling network for monitoring of taste and nutrient intake, homeostasis and energy metabolism, and they are also an early warning system for toxic substances in our diet. Especially the receptors for bitter taste provide a new possibility to activate a number of health related signalling pathways, already at low concentrations of the active substance, without requiring uptake into the body and transport via the circulation. When ligands bind to these receptors, signalling is induced either via peptide hormones into the circulation to other organs in the body, or via nerve fibers directly to the brain.

Gut chemosensing: implications for disease pathogenesis

The ability of humans to sense chemical signals in ingested substances is implicit in the ability to detect the five basic tastes; sweet, sour, bitter, salty, and umami. Of these, sweet, bitter, and umami tastes are detected by lingual G-protein-coupled receptors (GPCRs). Recently, these receptors were also localized to the gut mucosa. In this review, we will emphasize recent advances in the understanding of the mechanisms and consequences of foregut luminal chemosensing, with special emphasis on cell surface GPCRs such as the sweet and proteinaceous taste receptors (TASRs), short- and long-chain fatty acid (FA) receptors, and bile acid receptors. The majority of these luminal chemosensors are expressed on enteroendocrine cells (EECs), which are specialized endocrine cells in the intestine and pancreas that release gut hormones with ligand activation. These gut hormones are responsible for a wide variety of physiologic and homeostatic mechanisms, including glycemic control, appetite stimulation and suppression, regulation of gastric emptying, and trophic effects on the intestinal epithelium. Released from the EECs, the gut peptides have paracrine, autocrine, and endocrine effects. Additionally, EECs have unique direct connections to the enteric nervous system enabling precise transmission of sensory data to and communication with the central nervous system. We will also describe how gut sensors are implicated in gut hormone release, followed by examples of how altered gut chemosensing has been implicated in pathological conditions such as metabolic diseases including diabetes and obesity, functional dyspepsia, helminthic infections, colitis, gastric bypass surgery, and gastric inflammation and cancer.