Dietary Gamma-Aminobutyric Acid (GABA) Induces Satiation by Enhancing the Postprandial Activation of Vagal Afferent Nerves

The use of an in vitro fecal fermentation model to uncover the beneficial role of omega-3 and punicic acid in gut microbiota alterations induced by a Western diet

The influence of gut microbiota in the onset and development of several metabolic diseases has gained attention over the last few years. Diet plays an essential role in gut microbiota modulation. Western diet (WD), characterized by high-sugar and high-fat consumption, alters gut microbiome composition, diversity index, microbial relative levels, and functional pathways. Despite the promising health effects demonstrated by polyunsaturated fatty acids, their impact on gut microbiota is still overlooked. The effect of Fish oil (omega-3 source) and Pomegranate oil (punicic acid source), and a mixture of both oils in gut microbiota modulation were determined by subjecting the oil samples to in vitro fecal fermentations. Cecal samples from rats from two different dietary groups: a control diet (CD) and a high-fat high-sugar diet (WD), were used as fecal inoculum. 16S amplicon metagenomics sequencing showed that Fish oil + Pomegranate oil from the WD group increased α-diversity. This sample can also increase the relative abundance of the Firmicutes and Bacteroidetes phylum as well as Akkermansia and Blautia, which were affected by the WD consumption. All samples were able to increase butyrate and acetate concentration in the WD group. Moreover, tyrosine concentrations, a precursor for dopamine and norepinephrine, increase in the Fish oil + Pomegranate oil WD sample. GABA, an important neurotransmitter, was also increased in WD samples. These results suggest a potential positive impact of these oils' mixture on gut-brain axis modulation. It was demonstrated, for the first time, the great potential of using a mixture of both Fish and Pomegranate oil to restore the gut microbiota changes associated with WD consumption.

Fermented foods and gastrointestinal health: underlying mechanisms

Although fermentation probably originally developed as a means of preserving food substrates, many fermented foods (FFs), and components therein, are thought to have a beneficial effect on various aspects of human health, and gastrointestinal health in particular. It is important that any such perceived benefits are underpinned by rigorous scientific research to understand the associated mechanisms of action. Here, we review in vitro, ex vivo and in vivo studies that have provided insights into the ways in which the specific food components, including FF microorganisms and a variety of bioactives, can contribute to health-promoting activities. More specifically, we draw on representative examples of FFs to discuss the mechanisms through which functional components are produced or enriched during fermentation (such as bioactive peptides and exopolysaccharides), potentially toxic or harmful compounds (such as phytic acid, mycotoxins and lactose) are removed from the food substrate, and how the introduction of fermentation-associated live or dead microorganisms, or components thereof, to the gut can convey health benefits. These studies, combined with a deeper understanding of the microbial composition of a wider variety of modern and traditional FFs, can facilitate the future optimization of FFs, and associated microorganisms, to retain and maximize beneficial effects in the gut.

Reducing the harms of alcohol: nutritional interventions and functional alcohol alternatives

The health risks and harm associated with regular alcohol consumption are well documented. In a recent WHO statement published in The Lancet Public Health alcohol consumption has been estimated to contribute worldwide to 3 million deaths in 2016 while also being responsible for 5·1% of the global burden of disease and injury. The total elimination of alcohol consumption, which has been long imbedded in human culture and society, is not practical and prohibition policies have proved historically ineffective. However, valuable strategies to reduce alcohol harms are already available and improved alternative approaches are currently being developed. Here, we will review and discuss recent advances on two main types of approaches, that is nutritional interventions and functional alcohol alternatives.

Simultaneous separation and identification of all structural isomers and enantiomers of aminobutyric acid using a highly sensitive chiral resolution labeling reagent

Aminobutyric acid has structural isomers (α-, β-, and γ-aminobutyric acids) and enantiomers (D/L-forms) with various unique functions. Therefore, a quantitative method for determining the content of each aminobutyric acid must be developed. In general, quantitative simultaneous analysis of multiple compounds is conducted via high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). However, simultaneous separation and highly sensitive detection of all aminobutyric acids are complicated, so highly sensitive analytical methods for the separation and identification of each compound have not yet been established. We previously developed highly sensitive chiral resolution labeling reagents. Herein, we propose a highly sensitive analytical method for the simultaneous separation and identification of all aminobutyric acids via LC-MS and labeling with our original highly sensitive chiral resolution labeling reagent, 1-fluoro-2,4-dinitrophenyl-5-L-valine-N,N-dimethylethylenediamine amide (L-FDVDA). The labeling reagent was completely bound to all aminobutyric acids through incubation overnight (>15 h) at 50 °C. Additionally, the labeled aminobutyric acids could be stored for at least 1 week at 4 °C. Furthermore, we demonstrated simultaneous separation and identification of aminobutyric acids in biological samples and foods through LC-MS using a C18 column after labeling with L-FDVDA. Our method is expected to be adopted for the analysis of the contents of all aminobutyric acids in biological and clinical samples as well as various foods.

Designing poly(gamma-aminobutyric acid)-based nanoparticles for the treatment of major depressive disorders

Major depressive disorder (MDD) is a worldwide concern owing to its negative impact on the quality of life. Gamma-aminobutyric acid (GABA), an essential neurotransmitter in the brain, is important for regulating the enteric nervous system and gut-brain dual communication (gut-brain axis), thus providing gastrointestinal GABA and GABA-related pathways with possible targets for MDD treatment. However, the use of GABA for this disease remains limited due to its poor pharmacokinetic properties, including the low permeability through the blood-brain barrier, and the rapid clearance from the gastrointestinal tract. Since poly(amino acid)s are advantageous for improving the beneficial bioactivities of conventional amino acids, poly(gamma-aminobutyric acid) (poly(GABA)) is a potential candidate for MDD therapy. Nevertheless, the non-water-soluble and non-dispersible characteristics of poly(GABA) render difficulty in administering its conventional forms in vitro/in vivo, thereby hindering its therapeutic applications. Therefore, this study proposes a new design for poly(GABA) in nanoparticle form, which is composed of the amphiphilic diblock copolymers of poly(GABA) and poly(ethylene glycol), providing a suitable formulation for medication applications. Herein, we report on a new orally deliverable poly(GABA)-based nanoparticles (NanoGABA) in aqueous media and their efficacy on mouse depression models. NanoGABA treatment efficiently attenuated depression-like symptoms as evidenced by behavioral tests (forced swimming tests and tail suspension tests) and stress biomarkers (corticosterone). These findings suggest that the newly designed poly(GABA)-based nanoparticles are a promising candidate for the treatment of depression. STATEMENT OF SIGNIFICANCE: This research is the first to report the preparation of poly(GABA)-based nanoparticles in aqueous conditions with beneficial physical properties to open the gate for medical and pharmaceutical applications of poly (GABA). It is also a pioneer in using poly(GABA)-based materials for major depressive disorder therapeutics in vivo. Oral administration of NanoGABA attenuates depressive-like symptoms by targeting the enteric nervous system possibly through modulation of the gut-brain axis pathways with negligible toxicity, suggesting that NanoGABA is a promising therapeutic agent for major depressive disorders.

Disturbed rhythmicity of intestinal hydrogen peroxide alters gut microbial oscillations in BMAL1-deficient monkeys

Circadian oscillation of gut microbiota exerts significant influence on host physiology, but the host factors that sustain microbial oscillations are rarely reported. We compared the gut microbiome and metabolome of wild-type and BMAL1-deficient cynomolgus monkeys during a diurnal cycle by performing 16S rRNA sequencing and untargeted fecal metabolomics and uncovered the influence of intestinal H₂O₂ on microbial compositions. Ablation of BMAL1 induced expansion of Bacteroidota at midnight and altered microbial oscillations. Some important fecal metabolites changed significantly, and we investigated their correlations with microbes. Further analyses revealed that disturbed rhythmicity of NOX1-derived intestinal H₂O₂ was responsible for the altered microbial oscillations in BMAL1-deficient monkeys. Mechanistic studies showed that BMAL1 transactivated NOX1 via binding to the E1-E2 site in its promoter. Notably, BMAL1-dependent activation of NOX1 was conserved in cynomolgus monkeys and humans. Our study demonstrates the importance of intestine clock-controlled H₂O₂ rhythmicity on the rhythmic oscillation of gut microbiota.