Antihypertensive effect of a gamma-aminobutyric acid rich tomato cultivar 'DG03-9' in spontaneously hypertensive rats

Contributions of Gamma-Aminobutyric Acid (GABA) Produced by Lactic Acid Bacteria on Food Quality and Human Health: Current Applications and Future Prospects

The need to increase food safety and improve human health has led to a worldwide increase in interest in gamma-aminobutyric acid (GABA), produced by lactic acid bacteria (LABs). GABA, produced from glutamic acid in a reaction catalyzed by glutamate decarboxylase (GAD), is a four-carbon, non-protein amino acid that is increasingly used in the food industry to improve the safety/quality of foods. In addition to the possible positive effects of GABA, called a postbiotic, on neuroprotection, improving sleep quality, alleviating depression and relieving pain, the various health benefits of GABA-enriched foods such as antidiabetic, antihypertension, and anti-inflammatory effects are also being investigated. For all these reasons, it is not surprising that efforts to identify LAB strains with a high GABA productivity and to increase GABA production from LABs through genetic engineering to increase GABA yield are accelerating. However, GABA's contributions to food safety/quality and human health have not yet been fully discussed in the literature. Therefore, this current review highlights the synthesis and food applications of GABA produced from LABs, discusses its health benefits such as, for example, alleviating drug withdrawal syndromes and regulating obesity and overeating. Still, other potential food and drug interactions (among others) remain unanswered questions to be elucidated in the future. Hence, this review paves the way toward further studies.

Ascertaining the Influence of Lacto-Fermentation on Changes in Bovine Colostrum Amino and Fatty Acid Profiles

The aim of this study was to collect samples of bovine colostrum (BCOL) from different sources (agricultural companies A, B, C, D and E) in Lithuania and to ascertain the influence of lacto-fermentation with Lactiplantibacillus plantarum strain 135 and Lacticaseibacillus paracasei strain 244 on the changes in bovine colostrum amino (AA), biogenic amine (BA), and fatty acid (FA) profiles. It was established that the source of the bovine colostrum, the used LAB, and their interaction had significant effects (p < 0.05) on AA contents; lactic acid bacteria (LAB) used for fermentation was a significant factor for aspartic acid, threonine, glycine, alanine, methionine, phenylalanine, lysine, histidine, and tyrosine; and these factor's interaction is significant on most of the detected AA concentrations. Total BA content showed significant correlations with glutamic acid, serine, aspartic acid, valine, methionine, phenylalanine, histidine, and gamma amino-butyric acid content in bovine colostrum. Despite the differences in individual FA contents in bovine colostrum, significant differences were not found in total saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids. Finally, the utilization of bovine colostrum proved to be challenging because of the variability on its composition. These results suggest that processing bovine colostrum into value-added formulations for human consumption requires the adjustment of its composition since the primary production stage. Consequently, animal rearing should be considered in the employed bovine colostrum processing technologies.

A Novel Method for γ-Aminobutyric Acid Biosynthesis Using Glutamate Decarboxylase Entrapped in Polyvinyl Alcohol-Sodium Alginate Capsules

γ-aminobutyric acid (GABA) has essential physiological functions in the human body. A novel method using glutamate decarboxylase (GAD) entrapped in polyvinyl alcohol (PVA)-sodium alginate (SA) capsules provides a green biological strategy for GABA synthesis. In this investigation, the stability range of immobilized GAD was effectively broadened, and immobilized GAD could be repeatedly used as a batch and fixed-bed column catalyst. The immobilized enzymes were stable and retained 89% of their activity in a pH range of 4.0-5.6, while there was an approximately 50% decrease in free GAD activity in the pH range of 4.8 ± 0.4. The immobilized GAD affinity to the substrate improved, and this was evidenced by the apparent decrease in Km to 13.3 mmol/L from the 30.9 mmol/L for free GAD. The immobilized GAD retained >90.6% activity after eight cycles and a near-100% enzyme activity retention after 120 h of a continuous fixed-bed column catalyst operation. This study has thus presented an effective PVA-SA-GAD immobilization method that could be used to continuously scale-up GABA biosynthesis.

Gamma-aminobutyric acid (GABA): a comprehensive review of dietary sources, enrichment technologies, processing effects, health benefits, and its applications

Gamma-aminobutyric acid (GABA) is a naturally occurring potential bioactive compound present in plants, microorganisms, animals, and humans. Especially, as a main inhibitory neurotransmitter in the central nervous system, GABA possesses a broad spectrum of promising bioactivities. Thus, functional foods enriched with GABA have been widely sought after by consumers. However, the GABA levels in natural foods are usually low, which cannot meet people's demand for health effects. With the increasing public awareness on the food securities and naturally occurring processes, using enrichment technologies to elevate the GABA contents in foods instead of exogenous addition can enhance the acceptability of health-conscious consumers. Herein, this review provides a comprehensive insight on the dietary sources, enrichment technologies, processing effects of GABA, and its applications in food industry. Furthermore, the various health benefits of GABA-enriched foods, mainly including neuroprotection, anti-insomnia, anti-depression, anti-hypertensive, anti-diabetes, and anti-inflammatory are also summarized. The main challenges for future research on GABA are related to exploring high GABA producing strains, enhancing the stability of GABA during storage, and developing emerging enrichment technologies without affecting food quality and other active ingredients. A better understanding of GABA may introduce new windows for its application in developing functional foods.

Microbial diversity and functional genes of red vinasse acid based on metagenome analysis

Red vinasse acid has a distinct flavor and a vivid red color that are directly tied to the intricate metabolic activities of microorganisms that produce it. In this study, metagenomic technology was used to mine its functional genes and examine the microbial diversity of red vinasse acid. The findings revealed the identification of 2,609 species, 782 genera, and 63 phyla of microorganisms, and the dominant genus was Lactobacillus. Amino acid metabolism and carbohydrate metabolism were significant activities among the 16,093 and 49,652 genes that were annotated in the evolutionary genealogy of genes: Non-supervised Orthologous Groups (eggNOG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, respectively. In gluconeogenesis, red vinasse acid encodes 194 genes controlling the transporter protein systems of different sugars and has key enzyme genes that catalyze the conversion of intracellular sugars into glycolytic intermediates. In amino acid flavor formation, red vinasse acid contains 32 control genes for branched-chain aminotransferase (BCAT), 27 control genes for aromatic-amino-acid transaminase (ArAT), 60 control genes for keto acid invertase, 123 control genes for alcohol/aldehyde dehydrogenase, and 27 control genes for acetyl esterase, which have the basis for the formation of strong flavor substances from amino acids.

γ-Aminobutyric acid (GABA) improves pesticide detoxification in plants

It is important to ensure food safety to study the technology and mechanism of pesticide residues degradation in crops. Though γ-aminobutyric acid (GABA) has been widely reported to involve in plant stress resistance, whether exogenous application or endogenous regulation of GABA by gene-editing technology can promote the pesticide detoxification is not clear in plants. Using tomato and chlorothalonil (CHT) as research models, we discovered that exogenous application of GABA or endogenous elevation of GABA by knockout of pyruvate-dependent GABA transaminase promoted both CHT metabolism and plant stress tolerance to CHT. This is closely related to the active adaptation of GABA to CHT stress by regulating the plant GABA shunt pathway and polyamine pathway. The transcriptome data revealed 17 target genes that may be closely related to the involvement of GABA in CHT metabolism, including 4 peroxidases, 5 glycosyltransferases, 4 glutathione S-transferases, and 4 ABC transporters. In addition, the glutathione detoxification pathway and antioxidative enzyme also actively participated in the GABA-induced CHT detoxification process, which played an important role in relieving CHT stress. As a result, GABA significantly increased the photosynthetic capacity of tomato leaves under CHT stress. While studying photosynthesis, we unexpectedly found that GABA promotes stomatal closure in terms of decreased stomatal conductance and stomatal diameter. This result implies that GABA can reduce CHT absorption by regulating stomatal movement in leaves. Together, we provided a novel viewpoint that foliar application of GABA or metabolic engineering of GABA is an effective approach to reduce the risk of pesticide contamination in crop production.

Tomatoes: An Extensive Review of the Associated Health Impacts of Tomatoes and Factors That Can Affect Their Cultivation

Simple Summary

The research outlined in this review paper discusses potential health benefits associated with a diet enriched with tomatoes and tomato products. This includes details of previous studies investigating the anticancer properties of tomatoes, protection against cardiovascular and neurodegenerative diseases and diabetes, maintenance of a healthy gut microbiome, and improved skin health, fertility, immune response, and exercise recovery. The specific parts of a tomato fruit that contribute these health benefits are also outlined. The potential disadvantages to a tomato-rich diet are detailed, especially the consumption of supplements that contain compounds found in tomatoes, such as lycopene. This review also discusses how the cultivation of tomato plants can affect the nutritional value of the fruit harvested. Different environmental growing conditions such as light intensity, growing media, and temperature are explained in terms of the impact they have on the quality of fruit, its nutrient content, and hence the potential health benefits acquired from eating the fruit.

Abstract

This review outlines the health benefits associated with the regular consumption of tomatoes and tomato products. The first section provides a detailed account of the horticultural techniques that can impact the quality of the fruit and its nutritional properties, including water availability, light intensity, temperature, and growing media. The next section provides information on the components of tomato that are likely to contribute to its health effects. The review then details some of the health benefits associated with tomato consumption, including anticancer properties, cardiovascular and neurodegenerative diseases and skin health. This review also discusses the impact tomatoes can have on the gut microbiome and associated health benefits, including reducing the risk of inflammatory bowel diseases. Other health benefits of eating tomatoes are also discussed in relation to effects on diabetes, the immune response, exercise recovery, and fertility. Finally, this review also addresses the negative effects that can occur as a result of overconsumption of tomato products and lycopene supplements.

Dietary gamma-aminobutyric acid ameliorates growth impairment and intestinal dysfunction in turbot (Scophthalmus maximus L.) fed a high soybean meal diet

Over-substitution of fishmeal with soybean meal (SBM) commonly induces inferior growth and intestinal dysfunction in fish. This study aims to evaluate whether dietary gamma-aminobutyric acid (GABA) could ameliorate the adverse effects in turbot fed a high-SBM diet (HSD). Two hundred and seventy turbots were randomly divided into three treatment groups including turbots fed on a control diet (CNT, containing 60% fishmeal), an HSD (with 45% fishmeal protein replaced by SBM), and an HSD supplemented with GABA (160 mg kg-1) for 53 days. The growth and feed utilization parameters were calculated and the intestinal antioxidant status, inflammation, apoptosis, and microbiota were evaluated using assay kits, histological analysis, qRT-PCR, high throughput sequencing, and bioinformatics analysis. The results showed that GABA ameliorated HSD-induced growth impairment and enhanced feed intake of turbot. GABA ameliorated HSD-induced intestinal oxidative stress and apoptosis by restoring the MDA content, CAT and T-AOC activities, and apoptosis-related gene (Bcl-2, Bax, Bid, and Caspase-3) expressions to similar levels to those in the CNT group. GABA also alleviated HSD-induced intestinal inflammation through down-regulating the expressions of TNF-α, IL-1β, and NF-κB p65 and up-regulating the expression of TGF-β1. Furthermore, GABA reversed HSD-induced microbiota dysbiosis through regulating the overall bacterial richness and dominative bacterial population. Spearman's correlation analysis indicated that the altered microbiota was closely associated with growth and intestinal function. Collectively, GABA could ameliorate HSD-induced intestinal dysfunction via relieving oxidative stress, inflammation, apoptosis and microbiota dysbiosis, and these findings would contribute to a better understanding of the function of GABA in the fish intestine.

From plant biology research to technology transfer and knowledge extension: improving food quality and mitigating environmental impacts

Academic scientists face an unpredictable path from plant biology research to real-life application. Fundamental studies of γ-aminobutyrate and carotenoid metabolism, control of Botrytis infection, and the uptake and distribution of mineral nutrients illustrate that most academic research in plant biology could lead to innovative solutions for food, agriculture, and the environment. The time to application depends on various factors such as the fundamental nature of the scientific questions, the development of enabling technologies, the research priorities of funding agencies, the existence of competitive research, the willingness of researchers to become engaged in commercial activities, and ultimately the insight and creativity of the researchers. Applied research is likely to be adopted more rapidly by industry than basic research, so academic scientists engaged in basic research are less likely to participate in science commercialization. It is argued that the merit of Discovery Grant applications to the Natural Sciences and Engineering Research Council (NSERC) of Canada should not be evaluated for their potential impact on policy and (or) technology. Matching industry funds in Canada rarely support the search for knowledge. Therefore, NSERC Discovery Grants should fund basic research in its entirety.

CRISPR/Cas9-Mediated Gene Editing Revolutionizes the Improvement of Horticulture Food Crops

Horticultural food crops are important sources of nutrients for humans. With the increase of the global population, enhanced horticulture food crop production has become a new challenge, and enriching their nutritional content has also been required. Gene editing systems, such as zinc finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9), have accelerated crop improvement through the modification of targeted genomes precisely. Here, we review the development of various gene editors and compare their advantages and shortcomings, especially the newly emerging CRISPR/Cas systems, such as base editing and prime editing. We also summarize their practical applications in crop trait improvement, including yield, nutritional quality, and other consumer traits.

United States Pharmacopeia (USP) Safety Review of Gamma-Aminobutyric Acid (GABA)

Gamma-amino butyric acid (GABA) is marketed in the U.S. as a dietary supplement. USP conducted a comprehensive safety evaluation of GABA by assessing clinical studies, adverse event information, and toxicology data. Clinical studies investigated the effect of pure GABA as a dietary supplement or as a natural constituent of fermented milk or soy matrices. Data showed no serious adverse events associated with GABA at intakes up to 18 g/d for 4 days and in longer studies at intakes of 120 mg/d for 12 weeks. Some studies showed that GABA was associated with a transient and moderate drop in blood pressure (<10% change). No studies were available on effects of GABA during pregnancy and lactation, and no case reports or spontaneous adverse events associated with GABA were found. Chronic administration of GABA to rats and dogs at doses up to 1 g/kg/day showed no signs of toxicity. Because some studies showed that GABA was associated with decreases in blood pressure, it is conceivable that concurrent use of GABA with anti-hypertensive medications could increase risk of hypotension. Caution is advised for pregnant and lactating women since GABA can affect neurotransmitters and the endocrine system, i.e., increases in growth hormone and prolactin levels.

Phytotherapy of Hypertension: An Updated Overview

BACKGROUND

Cardiovascular disorders are the leading cause of morbidity and mortality throughout the globe. Hypertension is the main risk factor that contributes to the development of many diseases. The use of herbal therapies, medicinal plants and their derivatives for the remedy and management of hypertension is well-recognized and popular among a wide part of the world population.

METHODS

The aim of the current review was to collect, treat, and critically analyze the published research studies relative to experimental and clinical investigations which have studied the blood pressure lowering abilities of medicinal plant derivatives in the last decade. This review was organized into three principal axes; the first axis was attributed to the in vivo and in vitro experimental studies; the second treated the clinical trials; while, the last one is devoted to analyze the mechanisms of action underlying the therapeutic antihypertensive effectiveness of phytochemicals.

RESULTS

Different types of extracts and isolated molecules obtained from a large variety of species demonstrated their efficiency in improving the increase of blood pressure either experimentally or clinically. Medicinal species such as garlic (Allium sativum), celery (Apium graveolens), Black Cumin (Nigella sativa) and Ginseng (Panax) are among the most common and therapeutically used plant derivatives for controlling hypertension while Asteraceae, Apiaceae and Rosaceae are among the botanical families which were frequently studied in the last decade. Isolated compounds such as allicin and apigenin have received more interest in this field. Recent evidence from clinical trials suggests that a wide variety of herbal preparations and plant extracts or natural isolated compounds have a favorable therapeutic impact on blood flow. Interestingly, phytochemicals can either act directly on blood vessels via a vasorelaxant effect involving a variety of signaling cascades or indirectly through inhibiting or stimulating diversity of systems such as angiotensin-converting enzyme (ACE), renin-angiotensin system (RAS) or the diuretic activity. Hence, based on the findings of the present review medicinal plant derivatives could be used as preventive and curative agents in the case of cardiovascular disorders, particularly hypertension and could play a promoting function for the discovery of new antihypertensive agents.

CONCLUSION

The analysis of the published data shows that a great effort remains to be done to investigate the medicinal plants cited as antihypertensive through published ethnopharmacological surveys. The analysis of the literature in this field shows the lack of standardization at the level of experimental study methods as well as the need to study purified molecules. Moreover, the mechanistic studies when they exist remain in the whole partial. On the other hand, few advanced clinical studies have been conducted. Finally, the determination of the efficacy/safety ratio remains absent in almost all studies.

GABA enhancement by simple carbohydrates in yoghurt fermented using novel, self-cloned Lactobacillus plantarum Taj-Apis362 and metabolomics profiling

This study aimed to enhance natural gamma aminobutyric acid (GABA) production in yoghurt by the addition of simple sugars and commercial prebiotics without the need for pyridoxal 5′-phosphate (PLP) cofactor. The simple sugars induced more GABA production (42.83–58.56 mg/100 g) compared to the prebiotics (34.19–40.51 mg/100 g), with glucose promoting the most GABA production in yoghurt (58.56 mg/100 g) surpassing the control sample with added PLP (48.01 mg/100 g). The yoghurt prepared with glucose also had the highest probiotic count (9.31 log CFU/g). Simulated gastrointestinal digestion of this GABA-rich yoghurt showed a non-significant reduction in GABA content and probiotic viability, demonstrating the resistance towards a highly acidic environment (pH 1.2). Refrigerated storage up to 28 days improved GABA production (83.65 mg/100 g) compared to fresh GABA-rich yoghurt prepared on day 1. In conclusion, the addition of glucose successfully mitigates the over-use of glutamate and omits the use of PLP for increased production of GABA in yoghurt, offering an economical approach to produce a probiotic-rich dairy food with potential anti-hypertensive effects.

Effect of Different Drying Methods on the Nutritional Value of Hibiscus sabdariffa Calyces as Revealed by NMR Metabolomics

Red mature calyces of Hibiscus sabdariffa were collected from 16 different locations in Meghalaya, India. Samples were processed using shade drying (SD) and tray drying (TD). NMR spectroscopy was used to assess the metabolic composition of the calyces. In this study, 18 polar metabolites were assigned using 1D and 2D NMR spectra, and 10 of them were quantified. Proximate analysis showed that the TD method is more efficient at reducing moisture and maintaining the ash content of the Hibiscus biomass. NMR metabolomics indicates that the metabolite composition significantly differs between SD and TD samples and is more stable in TD plant processing. The differences in post-harvest drying has a greater impact on the metabolite composition of Hibiscus than the plant location.

Impact of functional foods and nutraceuticals on high blood pressure with a special focus on meta-analysis: review from a public health perspective

In recent times many researchers are expressing immense interest in nutraceuticals and functional foods for combating various diseases or abnormal conditions, especially against hypertension (HT). Persistent HT is medically referred to as chronic high blood pressure (BP) and considered to be one of the major risk factors for the deadliest diseases including cardiovascular disease (CVD) and cerebrovascular diseases. Hence HT poses a serious socio-economic burden worldwide, particularly to developing countries. The current treatment strategy for HT includes standard anti-hypertensive drugs, which are associated with many adverse effects and lower drug adherence rates. Therefore, an alternative or complementary natural therapy (functional foods or nutraceuticals or dietary supplements) would be the alternate choice along with a modified lifestyle pattern that might help to manage or combat HT and its related complications. During this review, the author would like to shed light on the basic science behind HT including pathophysiology and the impact of dietary salt on HT and the impact of various functional foods or nutraceuticals against HT in humans (meta-analysis and systemic review). This contribution gives a better idea (public health perspective) for choosing the best functional foods/nutraceuticals for the prevention, management or delaying the onset of HT and its associated conditions along with modified lifestyle patterns and standard anti-hypertensive drugs.

γ-Aminobutyric acid found in fermented foods and beverages: current trends

γ-aminobutyric acid (GABA) is synthesised by glutamic acid decarboxylase which catalyses the decarboxylation of L-glutamic acid. L-glutamic acid is formed by α-ketoglutarate in the TCA cycle by glutamic acid dehydrogenase (GDH). GABA is found in the human brain, plants, animals and microorganisms. GABA functions as an antidepressant, antihypertensive, antidiabetic and immune system enhancer and has a good effect on neural disease. As GABA have pharmaceutical properties, conditions for GABA production need to be established. Microbiological GABA production is more safe and eco-friendly rather than chemical methods. Moreover, it is easier to control conditions of production using microorganisms compared to production in plants and animals. GABA production in fermented foods and beverages has the potential to be optimised to increase the functional effect of fermented foods and beverages.

Challenges and Prospects of New Plant Breeding Techniques for GABA Improvement in Crops: Tomato as an Example

Over the last seven decades, γ-aminobutyric acid (GABA) has attracted great attention from scientists for its ubiquity in plants, animals and microorganisms and for its physiological implications as a signaling molecule involved in multiple pathways and processes. Recently, the food and pharmaceutical industries have also shown significantly increased interest in GABA, because of its great potential benefits for human health and the consumer demand for health-promoting functional compounds, resulting in the release of a plethora of GABA-enriched products. Nevertheless, many crop species accumulate appreciable GABA levels in their edible parts and could help to meet the daily recommended intake of GABA for promoting positive health effects. Therefore, plant breeders are devoting much effort into breeding elite varieties with improved GABA contents. In this regard, tomato (Solanum lycopersicum), the most produced and consumed vegetable worldwide and a fruit-bearing model crop, has received much consideration for its accumulation of remarkable GABA levels. Although many different strategies have been implemented, from classical crossbreeding to induced mutagenesis, new plant breeding techniques (NPBTs) have achieved the best GABA accumulation results in red ripe tomato fruits along with shedding light on GABA metabolism and gene functions. In this review, we summarize, analyze and compare all the studies that have substantially contributed to tomato GABA breeding with further discussion and proposals regarding the most recent NPBTs that could bring this process to the next level of precision and efficiency. This document also provides guidelines with which researchers of other crops might take advantage of the progress achieved in tomato for more efficient GABA breeding programs.

Effects of regular-fat and low-fat dairy consumption on daytime ambulatory blood pressure and other cardiometabolic risk factors: a randomized controlled feeding trial

BACKGROUND

The extent to which dairy products and their fat content influence cardiovascular health remains uncertain.

OBJECTIVE

This study aimed to assess how consumption of low-fat milk and regular-fat cheese enriched in γ-aminobutyric acid (GABA) influences daytime ambulatory blood pressure (BP) and other cardiometabolic risk factors.

METHODS

In this crossover controlled feeding study, 55 healthy men and women with high-normal daytime BP were randomly assigned to sequences of three 6-wk isoenergetic diets, each comprising 1) no dairy (control diet), 2) 3 daily servings of 1% fat milk, and 3) 1 daily serving of 31% fat cheddar cheese naturally enriched in GABA. Total proteins, carbohydrates, and fats were matched across all 3 diets. The additional 2% of energy from SFAs in the cheese diet was replaced by n-6 PUFAs in the other diets.

RESULTS

Comparison of postdiet ambulatory systolic BP revealed no difference (P = 0.34), which was also the case for ambulatory diastolic BP (P = 0.45). The cheese diet increased serum LDL-cholesterol concentrations compared with the control and milk diets (+5.8%, P = 0.006 and +7.0%, P = 0.0008, respectively) and increased LDL particle size compared with the milk diet (P = 0.02). HDL-cholesterol concentrations after the milk diet were lower than after the control diet (-4.1%; P = 0.009). The milk and cheese diets increased triglycerides compared with the control diet (+9.9%, P = 0.01 and +10.5%, P = 0.007, respectively). There was no significant difference between all diets for C-reactive protein concentrations and markers of glucose/insulin homeostasis.

CONCLUSIONS

These results suggest that short-term consumption of dairy products, whether low or regular in fat, has no overall effect on daytime ambulatory BP compared with a dairy-free diet. Other cardiometabolic risk factors may be differently modified according to the fat content of the dairy product. This trial was registered at clinicaltrials.gov as NCT02763930.

Production of GABA-enriched idli with ACE inhibitory and antioxidant properties using Aspergillus oryzae: the antihypertensive effects in spontaneously hypertensive rats

The present study aimed to develop a fermented food (idli) with enhanced γ-aminobutyric acid (GABA) and angiotensin I-converting enzyme (ACE) inhibitory properties using a GABA-producing fungus.

Role of Gamma Amino Butyric Acid (GABA) against abiotic stress tolerance in legumes: a review

Legumes are well known for their nutritional and health benefits as well as for their impact in the sustainability of agricultural systems. Under current scenarios threatened by climate change highlights the necessity for concerted research approaches in order to develop crops that are able to cope up with environmental challenges. Various abiotic stresses such as cold, heat, drought, salt, and heavy metal induce a variety of negative effects in plant growth, development and significantly decline yield and quality. Plant growth regulators or natural products of plants are reported to be effective to improve plant tolerance to several abiotic stresses. Gamma Amino Butyric Acid (GABA) is a non-protein amino acid involved in various metabolic processes, and partially protects plants from abiotic stress. GABA appears to impart partial protection to various abiotic stresses in most plants by increasing leaf turgor, increased osmolytes and reduced oxidative damage by stimulation of antioxidants. We have compiled various scientific reports on the role and mechanism of GABA in plants against coping with various environmental stresses. We have also described the emerging information about the metabolic and signaling roles of GABA which is being used to improve legume crop against abiotic stress.

Neuroactive compounds in foods: Occurrence, mechanism and potential health effects

Neuroactive compounds are synthesized by certain plants and microorganisms by undertaking different tasks, especially as a stress response. Most common neuroactive compounds in foods are gamma-aminobutyric acid (GABA), serotonin, melatonin, kynurenine, kynurenic acid, dopamine, norepinephrine, histamine, tryptamine, tyramine and β-phenylethylamine. Fermented foods contain some of these compounds, which can affect human health and mood. Moreover, food processing such as roasting and malting alter amount and profile of neuroactive compounds in foods. In addition to plant-origin and microbially-formed neuroactive compounds in foods, these substances are also formed by gut microbiota, which is the most attractive subject to assess the interaction between gut microbiota and mental health. The discovery of microbiota-gut-brain axis calls for the investigation of the effects of diet on the formation of neuroactive compounds in the gut. Furthermore, probiotics and prebiotics are indispensable elements for the understanding of the food-mood relationship. The focus of this comprehensive review is to investigate the neuroactive compounds found naturally in foods or formed during fermentation. Their formation pathways in humans, plants and microorganisms, potential health effects, effects of diet on the formation of microbial metabolites including neuroactive compounds in the gut are discussed throughout this review. Furthermore, the importance of gut-brain axis, probiotics and prebiotics are discussed.

Antihypertensive effect of giant embryo brown rice and pre-germinated giant embryo brown rice on spontaneously hypertensive rats

"Shangshida NO.5" is a giant embryo mutant resulting from giant embryo gene (GE) dysfunction in "Chao2-10" rice. Here, we compared the antihypertensive effects of "Chao2-10" brown rice (C2-10), "Shangshida NO.5" brown rice (GER), and pre-germinated "Shangshida NO.5" brown rice (PGER) in spontaneously hypertensive rats (SHR). Male SHR at 6 weeks of age were divided into four groups and were fed with (a) a control diet (control), (b) a 40% C2-10-supplemented diet (C2-10), (c) a 40% GER-supplemented diet (GER), or (d) a 40% PGER-supplemented diet (PGER) for 8 weeks, and their physiological and biochemical parameters were measured. The results showed that the C2-10-, GER-, and PGER-supplemented diets significantly decreased systolic blood pressure (SBP) and diastolic blood pressure (DBP) during the experiment. At the end of the experimental period, the SBP and DBP of the C2-10, GER, and PGER groups were 7.6, 23.3, and 31.1 mmHg and 9.8, 21.1, and 29 mmHg lower than those in the control group, respectively, suggesting the GER and PGER diets were better able to inhibit blood pressure elevation than the C2-10 diet. The serum creatinine levels in the C2-10, GER, and PGER groups and the blood urea nitrogen content in the PGER group were significantly lower than those of the control group, indicating that C2-10-, GER-, and especially PGER-supplemented diets improved renal function. In addition, the antioxidant activity of the C2-10 group and especially of the GER and PGER groups also improved. The above results suggest that "Shangshida NO.5" rice, particularly pre-germinated rice, is a good dietary supplement for preventing the development of hypertension.

An Updated Review on Pharmaceutical Properties of Gamma-Aminobutyric Acid

Gamma-aminobutyric acid (Gaba) is a non-proteinogenic amino acid that is widely present in microorganisms, plants, and vertebrates. So far, Gaba is well known as a main inhibitory neurotransmitter in the central nervous system. Its physiological roles are related to the modulation of synaptic transmission, the promotion of neuronal development and relaxation, and the prevention of sleeplessness and depression. Besides, various pharmaceutical properties of Gaba on non-neuronal peripheral tissues and organs were also reported due to anti-hypertension, anti-diabetes, anti-cancer, antioxidant, anti-inflammation, anti-microbial, anti-allergy, hepato-protection, reno-protection, and intestinal protection. Therefore, Gaba may be considered as potential alternative therapeutics for prevention and treatment of various diseases. Accordingly, this updated review was mainly focused to describe the pharmaceutical properties of Gaba as well as emphasize its important role regarding human health.

Versatile and multifaceted CRISPR/Cas gene editing tool for plant research

The ability to create desirable gene variants through targeted changes offers tremendous opportunities for the advancement of basic and applied plant research. Gene editing technologies have opened new avenues to perform such precise gene modifications in diverse biological systems. These technologies use sequence-specific nucleases, such as homing endonucleases, zinc-finger nucleases, transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein (CRISPR/Cas) complexes to enable targeted genetic manipulations. Among these, the CRISPR/Cas system has emerged as a broadly applicable and valued gene editing system for its ease of use and versatility. The adaptability of the CRISPR/Cas system has facilitated rapid and continuous innovative developments to the precision and applications of this technology, since its introduction less than a decade ago. Although developed in animal systems, the simple and elegant CRISPR/Cas gene editing technology has quickly been embraced by plant researchers. From early demonstration in model plants, the CRISPR/Cas system has been successfully adapted for various crop species and enabled targeting of agronomically important traits. Although the approach faces several efficiency and delivery related challenges, especially in recalcitrant crop species, continuous advances in the CRISPR/Cas system to address these limitations are being made. In this review, we discuss the CRISPR/Cas technology, its myriad applications and their prospects for crop improvement.

Amino acids and biogenic amines as food quality factors

The importance of amino acids and biogenic amines is widely recognised in various fields, particularly in the fields of food science and nutrition. This mini-review contains a summary of my main research field that centres on aspects of Food Quality and Food Safety, with a particular emphasis on amino acids and biogenic amines. It also gives an overview of the recent developments on the related areas.

Metabolic Alternations of Amino Acids, γ-Aminobutyric Acid, and Salicylic Acid in Solanum lycopersicum (L.) Following Preplanting Seedling Spray with Salicylic Acid

Preplanting foliar spray of salicylic acid (SA) (0.0, 5.0, and 10.0 μg/mL) to Solanum lycopersicum (L.) altered the metabolite profile of amino acids, γ-aminobutyric acid (GABA), and SA in leaf, root, and fruits. Free amino acid pools increased; bound amino acid pools reduced. In vegetative tissues, amino acid biosyntheses linked to osmo-compatibility (Pro, Leu, Val and GABA); N (Arg, Asn, Asp, Gln, and Glu); C (Pro, Ser, and Tyr); S (Cys) assimilation; stress tolerance (Ala, Gly, Hyp, His, Lys, Met, and Thr); and central metabolism (Phe, Trp, and Tyr) enhanced for 60-120 days. Concentrations of Ala, Arg, Gln, Gly, Leu, and Ser in leaf and of Asp, Cys, Glu, His, Hyp, Lys, Met, Pro, and Val in root predominated. In planta SA and GABA biosynthesis increased concurrently. SA affected GABA biosynthesis via Glu, Pro, and Arg metabolism. SA, GABA, Glu, and Pro were key canonical variables. This study first reported SA-induced metabolites promoting health (SA/GABA; Cys/Met) and palatability (Glu/Asp; Gln) in table tomato.

Antihypertensive effects of orally administered eggplant (Solanum melongena) rich in acetylcholine on spontaneously hypertensive rats

Our previous results (Nakamura et al., 2013, 2016) indicated that acetylcholine (ACh) in orally administered foods exerts antihypertensive effects. Eggplants (Solanum melongena) contain abundant ACh (Horiuchi et al., 2003), and their food functionality was discovered, using spontaneously hypertensive rats, by measuring blood pressure after oral administration of a suspension of lyophilized eggplant powder. We found that lyophilized eggplant powder induced significantly lowered acute and chronic blood pressure levels at very low doses of 0.0650 mg/kg body weight (b.w.) and 0.821 mg/(kg b.w.·day), respectively. Chronic administration suppressed adrenaline and noradrenaline excretion in the urine, and aorta assays showed that eggplant acted on the M3 muscarinic ACh receptor (M3 mAChR). ACh was conclusively shown to function as the main component of eggplant contributing to antihypertensive activity by suppressing sympathetic nervous activity via M3 mAChR. This report reveals a new food functionality of eggplant and its potential as a novel antihypertensive food.

Multiplexed CRISPR/Cas9-mediated metabolic engineering of γ-aminobutyric acid levels in Solanum lycopersicum

In recent years, the type II CRISPR system has become a widely used and robust technique to implement site-directed mutagenesis in a variety of species including model and crop plants. However, few studies manipulated metabolic pathways in plants using the CRISPR system. Here, we introduced the pYLCRISPR/Cas9 system with one or two single-site guide RNAs to target the tomato phytoene desaturase gene. An obvious albino phenotype was observed in T0 regenerated plants, and more than 61% of the desired target sites were edited. Furthermore, we manipulated the γ-aminobutyric acid (GABA) shunt in tomatoes using a multiplex pYLCRISPR/Cas9 system that targeted five key genes. Fifty-three genome-edited plants were obtained following single plant transformation, and these samples represented single to quadruple mutants. The GABA accumulation in both the leaves and fruits of genomically edited lines was significantly enhanced, and the GABA content in the leaves of quadruple mutants was 19-fold higher than that in wild-type plants. Our data demonstrate that the multiplex CRISPR/Cas9 system can be exploited to precisely edit tomato genomic sequences and effectively create multisite knockout mutations, which could shed new light on plant metabolic engineering regulations.

Utilization of a Genome-Edited Tomato (Solanum lycopersicum) with High Gamma Aminobutyric Acid Content in Hybrid Breeding

γ-Aminobutyric acid (GABA) is a nonproteogenic amino acid with health-promoting functions. Although tomato fruits have a relatively high GABA content compared with other crops, levels must be further increased to effectively confer the health-promoting functions. In this study, we evaluated the potential of the genome-edited tomato as a breeding material for producing high-GABA hybrid tomatoes. Hybrid lines were produced by crossing the genome-edited tomato with a pure line tomato cultivar, "Aichi First", and were evaluated for GABA accumulation and other fruit traits. The hybrid lines showed high GABA accumulation in the fruits, which was sufficiently high for expecting health-promoting functions and had minimal effects on other fruit traits, suggesting that the high GABA is a dominant trait and that the genome-edited tomato would be useful as a parental line of hybrid cultivars. These results also indicate that genome editing technology is useful for the rapid breeding of high-GABA hybrid tomato cultivars.

High γ-aminobutyric acid production from lactic acid bacteria: Emphasis on Lactobacillus brevis as a functional dairy starter

γ-Aminobutyric acid (GABA) and GABA-rich foods have shown anti-hypertensive and anti-depressant activities as the major functions in humans and animals. Hence, high GABA-producing lactic acid bacteria (LAB) could be used as functional starters for manufacturing novel fermented dairy foods. Glutamic acid decarboxylases (GADs) from LAB are highly conserved at the species level based on the phylogenetic tree of GADs from LAB. Moreover, two functionally distinct GADs and one intact gad operon were observed in all the completely sequenced Lactobacillus brevis strains suggesting its common capability to synthesize GABA. Difficulties and strategies for the manufacture of GABA-rich fermented dairy foods have been discussed and proposed, respectively. In addition, a genetic survey on the sequenced LAB strains demonstrated the absence of cell envelope proteinases in the majority of LAB including Lb. brevis, which diminishes their cell viabilities in milk environments due to their non-proteolytic nature. Thus, several strategies have been proposed to overcome the non-proteolytic nature of Lb. brevis in order to produce GABA-rich dairy foods.

Effects of Vegetables on Cardiovascular Diseases and Related Mechanisms

Epidemiological studies have shown that vegetable consumption is inversely related to the risk of cardiovascular diseases. Moreover, research has indicated that many vegetables like potatoes, soybeans, sesame, tomatoes, dioscorea, onions, celery, broccoli, lettuce and asparagus showed great potential in preventing and treating cardiovascular diseases, and vitamins, essential elements, dietary fibers, botanic proteins and phytochemicals were bioactive components. The cardioprotective effects of vegetables might involve antioxidation; anti-inflammation; anti-platelet; regulating blood pressure, blood glucose, and lipid profile; attenuating myocardial damage; and modulating relevant enzyme activities, gene expression, and signaling pathways as well as some other biomarkers associated to cardiovascular diseases. In addition, several vegetables and their bioactive components have been proven to protect against cardiovascular diseases in clinical trials. In this review, we analyze and summarize the effects of vegetables on cardiovascular diseases based on epidemiological studies, experimental research, and clinical trials, which are significant to the application of vegetables in prevention and treatment of cardiovascular diseases.

Recent advances in γ-aminobutyric acid (GABA) properties in pulses: an overview

Beans, peas, and lentils are all types of pulses that are extensively used as foods around the world due to their beneficial effects on human health including their low glycaemic index, cholesterol lowering effects, ability to decrease the risk of heart diseases and their protective effects against some cancers. These health benefits are a result of their components such as bioactive proteins, dietary fibre, slowly digested starches, minerals and vitamins, and bioactive compounds. Among these bioactive compounds, γ-aminobutyric acid (GABA), a non-proteinogenic amino acid with numerous reported health benefits (e.g. anti-diabetic and hypotensive effects, depression and anxiety reduction) is of particular interest. GABA is primarily synthesised in plant tissues by the decarboxylation of l-glutamic acid in the presence of glutamate decarboxylase (GAD). It is widely reported that during various processes including enzymatic treatment, gaseous treatment (e.g. with carbon dioxide), and fermentation (with lactic acid bacteria), GABA content increases in the plant matrix. The objective of this review paper is to highlight the current state of knowledge on the occurrence of GABA in pulses with special focus on mechanisms by which GABA levels are increased and the analytical extraction and estimation methods for this bioactive phytochemical. © 2017 Society of Chemical Industry.

Impact of Precooling and Controlled-Atmosphere Storage on γ-Aminobutyric Acid (GABA) Accumulation in Longan (Dimocarpus longan Lour.) Fruit

Longan (Dimocarpus longan Lour.) fruit cultivars 'Chuliang' and 'Shixia' were analyzed for γ-aminobutyric acid (GABA) accumulation after precooling and in controlled-atmosphere storage. Fruit were exposed to 5% O2 plus 3%, 5%, or 10% CO2 at 4 °C, and GABA and associated enzymes, aril firmness, and pericarp color were measured. Aril softening and pericarp browning were delayed by 5% CO2 + 5% O2. GABA concentrations and glutamate decarboxylase (GAD; EC 4.1.1.15) activities declined during storage at the higher-CO2 treatments. However, GABA aminotransferase (GABA-T; EC 2.6.1.19) activities in elevated CO2-treated fruit fluctuated during storage. GABA concentrations increased after precooling treatments. GAD activity and GABA-T activity were different between cultivars after precooling. GABA concentrations in fruit increased after 3 days of 10% CO2 + 5% O2 treatment and then declined as storage time increased. GABA accumulation was associated with stimulation of GAD activity rather than inhibition of GABA-T activity.

Exploring flavour-producing core microbiota in multispecies solid-state fermentation of traditional Chinese vinegar

Multispecies solid-state fermentation (MSSF), a natural fermentation process driven by reproducible microbiota, is an important technique to produce traditional fermented foods. Flavours, skeleton of fermented foods, was mostly produced by microbiota in food ecosystem. However, the association between microbiota and flavours and flavour-producing core microbiota are still poorly understood. Here, acetic acid fermentation (AAF) of Zhenjiang aromatic vinegar was taken as a typical case of MSSF. The structural and functional dynamics of microbiota during AAF process was determined by metagenomics and favour analyses. The dominant bacteria and fungi were identified as Acetobacter, Lactobacillus, Aspergillus, and Alternaria, respectively. Total 88 flavours including 2 sugars, 9 organic acids, 18 amino acids, and 59 volatile flavours were detected during AAF process. O2PLS-based correlation analysis between microbiota succession and flavours dynamics showed bacteria made more contribution to flavour formation than fungi. Seven genera including Acetobacter, Lactobacillus, Enhydrobacter, Lactococcus, Gluconacetobacer, Bacillus and Staphylococcus were determined as functional core microbiota for production of flavours in Zhenjiang aromatic vinegar, based on their dominance and functionality in microbial community. This study provides a perspective for bridging the gap between the phenotype and genotype of ecological system, and advances our understanding of MSSF mechanisms in Zhenjiang aromatic vinegar.

Efficient bioconversion of L-glutamate to γ-aminobutyric acid by Lactobacillus brevis resting cells

This work investigated the efficient bioconversion process of L-glutamate to GABA by Lactobacillus brevis TCCC 13007 resting cells. The optimal bioconversion system was composed of 50 g/L 48 h cultivated wet resting cells, 0.1 mM pyridoxal phosphate in glutamate-containing 0.6 M citrate buffer (pH 4.5) and performed at 45 °C and 180 rpm. By 10 h bioconversion at the ratio of 80 g/L L-glutamic acid to 240 g/L monosodium glutamate, the final titer of GABA reached 201.18 g/L at the molar bioconversion ratio of 99.4 %. This process presents a potential for industrial and commercial applications and also offers a promising feasibility of continuous GABA production coupled with fermentation. Besides, the built kinetics model revealed that the optimum operating conditions were 45 °C and pH 4.5, and the bioconversion kinetics at low ranges of substrate concentration (0 < S < 80 g/L) was assumed to follow the classical Michaelis-Menten equation.

Pharmacological characteristics of Artemisia vulgaris L. in isolated porcine basilar artery

ETHNOPHARMACOLOGICAL RELEVANCE

In Vietnamese traditional herbalism, there are conflicting opinions about the effect of Artemisia vulgaris L. (AVL, English name: mugwort) on hypertension. Some ethnic doctors recommend the use of AVL for treatment of hypertension, whereas others advise against it. The purpose of this study was to clarify the pharmacological characteristics of AVL in isolated arteries to explain the conflicts surrounding the use of AVL for treatment of hypertension.

MATERIALS AND METHODS

We initially performed a functional study using an organ bath system to investigate the effect of AVL extract on isolated porcine basilar artery. We then measured the change in intracellular free Ca(2+) concentration elicited by AVL using cultured smooth muscle cells loaded with the Ca(2+) indicator fluo-4. Finally, using HPLC, we determined the active components in AVL.

RESULTS AND DISCUSSION

AVL induced vasoconstriction at resting tension, and endothelial removal enhanced this effect significantly. Pretreatment with PD123319 (an AT2 receptor antagonist), Nω-nitro-L-arginine (a nitric oxide synthase inhibitor), or both, also enhanced this effect. AVL-induced contraction was competitively inhibited by methiothepin (a 5-HT1 and 5-HT2 receptor antagonist) in the presence of ketanserin (a 5-HT2 receptor antagonist). Removal of extracellular calcium with nifedipine (an L-type Ca(2+) channel blocker) or ruthenium red (a ryanodine receptor blocker) significantly reduced AVL-induced contraction, whereas losartan (an AT1 receptor antagonist) and diphenhydramine (a H1 receptor antagonist) had no effect on this contraction. AVL increased the intracellular free Ca(2+) concentration in cultured cells, and this increment was inhibited by methiothepin. HPLC analysis revealed that the retention time of the first peak in the AVL profile was similar to that of the 5-HT standard, and that addition of 5-HT to the AVL sample enhanced this peak. On the other hand, AVL induced endothelium-independent relaxation under precontracted conditions with 60mM KCl. Captopril (an angiotensin converting enzyme inhibitor), atenolol (a β1 receptor antagonist) and cimetidine (a H2 receptor antagonist) had no effect on this relaxation. In Ca(2+)-free 60mM KCl-containing solution, pretreatment with AVL significantly inhibited CaCl2-induced contraction.

CONCLUSION

For the first time, the present study has demonstrated that AVL has two opposite effects, contraction and relaxation, on isolated artery, which may help to explain the conflicting indications for AVL in traditional herbalism. 5-HT is a significant factor affecting artery contraction in the presence of AVL.

Enhancing Contents of γ-Aminobutyric Acid (GABA) and Other Micronutrients in Dehulled Rice during Germination under Normoxic and Hypoxic Conditions

Biofortification of staple grains with high contents of essential micronutrients is an important strategy to overcome micronutrient malnutrition. However, few attempts have targeted at γ-aminobutyric acid (GABA), a functional nutrient for aging populations. In this study, two rice cultivars, Heinuo and Xianhui 207, were used to investigate changes in GABA and other nutritional compounds of dehulled rice after germination under normoxic and hypoxic conditions. Forty-one metabolites were identified in both cultivars treated by normoxic germination, whereas the germinated dehulled rice of Heinuo and Xianhui 207 under hypoxic treatment had 43 and 41 metabolites identified, respectively. GABA increased in dehulled rice after germination, especially under hypoxia. Meanwhile, a number of other health-beneficial and/or flavor-related compounds such as lysine and d-mannose increased after the hypoxic treatment. The accumulation of GABA exhibited genotype-specific modes in both normoxic and hypoxic treatments. With regard to GABA production, Xianhui 207 was more responsive to the germination process than Heinuo, whereas Heinuo was more responsive to hypoxia than Xianhui 207. This study provides a promising approach to biofortify dehulled rice with increased GABA and other nutrients through metabolomic-based regulation.

Effect of Functional Bread Rich in Potassium, γ-Aminobutyric Acid and Angiotensin-Converting Enzyme Inhibitors on Blood Pressure, Glucose Metabolism and Endothelial Function: A Double-blind Randomized Crossover Clinical Trial

Because it has been suggested that food rich in γ-aminobutyric acid (GABA) or angiotensin-converting enzyme inhibitor (ACEI) peptides have beneficial effects on blood pressure (BP) and other cardiovascular risk factors, we tested the effects of low-sodium bread, but rich in potassium, GABA, and ACEI peptides on 24-hour BP, glucose metabolism, and endothelial function.A randomized, double-blind, crossover trial was conducted in 30 patients with pre or mild-to-moderate hypertension, comparing three 4-week nutritional interventions separated by 2-week washout periods. Patients were randomly assigned to consume 120 g/day of 1 of the 3 types of bread for each nutritional intervention: conventional wheat bread (CB), low-sodium wheat bread enriched in potassium (LSB), and low-sodium wheat bread rich in potassium, GABA, and ACEI peptides (LSB + G). For each period, 24-hour BP measurements, in vivo endothelial function, and biochemical samples were obtained.After LSB + G consumption, 24-hour ambulatory BP underwent a nonsignificant greater reduction than after the consumption of CB and LSB (0.26 mm Hg in systolic BP and -0.63 mm Hg in diastolic BP for CB; -0.71 mm Hg in systolic BP and -1.08 mm Hg in diastolic BP for LSB; and -0.75 mm Hg in systolic BP and -2.12 mm Hg in diastolic BP for LSB + G, respectively). Diastolic BP at rest decreased significantly during the LSB + G intervention, although there were no significant differences in changes between interventions. There were no significant differences between interventions in terms of changes in in vivo endothelial function, glucose metabolism, and peripheral inflammatory parameters.Compared with the consumption of CB or LSB, no greater beneficial effects on 24-hour BP, endothelial function, or glucose metabolism were demonstrated after the consumption of LSB + G in a population with pre or mild-to-moderate hypertension. Further studies are warranted to clarify the effect of GABA on BP, preferably using a specific design for noninferiority trials and ambulatory BP monitoring as a measure of BP.This study was registered at Current Controlled Trials as ISRCTN31436822.

Two-step production of gamma-aminobutyric acid from cassava powder using Corynebacterium glutamicum and Lactobacillus plantarum

Production of gamma-aminobutyric acid (GABA) from crop biomass such as cassava in high concentration is desirable, but difficult to achieve. A safe biotechnological route was investigated to produce GABA from cassava powder by C. glutamicum G01 and L. plantarum GB01-21. Liquefied cassava powder was first transformed to glutamic acid by simultaneous saccharification and fermentation with C. glutamicum G01, followed by biotransformation of glutamic acid to GABA with resting cells of L. plantarum GB01-21 in the reaction medium. After optimizing the reaction conditions, the maximum concentration of GABA reached 80.5 g/L with a GABA productivity of 2.68 g/L/h. This is the highest yield ever reported of GABA production from cassava-derived glucose. The bioprocess provides the added advantage of employing nonpathogenic microorganisms, C. glutamicum and L. plantarum, in microbial production of GABA from cassava biomass, which can be used in the food and pharmaceutical industries.

Field trial of GABA-fortified rice plants and oral administration of milled rice in spontaneously hypertensive rats

Hypertension is one of the most critical risk factors accompanying cardiovascular diseases. γ-Aminobutyric acid (GABA) is a non-protein amino acid that functions as a major neurotransmitter in mammals and also as a blood-pressure lowering agent. We previously produced GABA-fortified rice lines of a popular Japonica rice cultivar 'Koshihikari' by genetic manipulation of GABA shunt-related genes. In the study reported here, we grew these same novel rice lines in a field trial and administered the milled rice orally to rats. The yield parameters of the transgenic rice plants were almost unchanged compared to those of untransformed cv. 'Koshihikari' plants, while the rice grains of the transgenic plants contained a high GABA content (3.5 g GABA/kg brown rice; 0.75-0.85 GABA g/kg milled rice) in a greenhouse trial. Oral administration of a diet containing 2.5% GABA-fortified rice, with a daily intake for 8 weeks, had an approximately 20 mmHg anti-hypertensive effect in spontaneous hypertensive rats but not in normotensive Wistar-Kyoto rats. These results suggest that GABA-fortified rice may be applicable as a staple food to control or prevent hypertension.

Gas release-based prescreening combined with reversed-phase HPLC quantitation for efficient selection of high-γ-aminobutyric acid (GABA)-producing lactic acid bacteria

High γ-aminobutyric acid (GABA)-producing lactobacilli are promising for the manufacture of GABA-rich foods and to synthesize GRAS (generally recognized as safe)-grade GABA. However, common chromatography-based screening is time-consuming and inefficient. In the present study, Korean kimchi was used as a model of lactic acid-based fermented foods, and a gas release-based prescreening of potential GABA producers was developed. The ability to produce GABA by potential GABA producers in de Man, Rogosa, and Sharpe medium supplemented with or without monosodium glutamate was further determined by HPLC. Based on the results, 9 isolates were regarded as high GABA producers, and were further genetically identified as Lactobacillus brevis based on the sequences of 16S rRNA gene. Gas release-based prescreening combined with reversed-phase HPLC confirmation was an efficient and cost-effective method to identify high-GABA-producing LAB, which could be good candidates for probiotics. The GABA that is naturally produced by these high-GABA-producing LAB could be used as a food additive.

Evolution and expression analysis of the soybean glutamate decarboxylase gene family

Glutamate decarboxylase (GAD) is an enzyme that catalyses the conversion of L-glutamate into gamma-aminobutyric acid (GABA), which is a four-carbon non-protein amino acid present in all organisms. Although plant GAD plays important roles in GABA biosynthesis, our knowledge concerning GAD gene family members and their evolutionary relationship remains limited. Therefore, in this study, we have analysed the evolutionary mechanisms of soybean GAD genes and suggested that these genes expanded in the soybean genome partly due to segmental duplication events. The approximate dates of duplication events were calculated using the synonymous substitution rate, and we suggested that the segmental duplication of GAD genes in soybean originated 9.47 to 11.84 million years ago (Mya). In addition, all segmental duplication pairs (GmGAD1/3 and GmGAD2/4) are subject to purifying selection. Furthermore, GmGAD genes displayed differential expression either in their transcript abundance or in their expression patterns under abiotic stress conditions like salt, drought, and cold. The expression pattern of paralogous pairs suggested that they might have undergone neofunctionalization during the subsequent evolution process. Taken together, our results provide valuable information for the evolution of the GAD gene family and represent the basis for future research on the functional characterization of GAD genes in higher plants.