Role of the renal nerves in γ-aminobutyric acid-induced antihypertensive effect in spontaneously hypertensive rats

Influence of fresh-cut process on γ-aminobutyric acid (GABA) metabolism and sensory properties in carrot

Effect of fresh-cut procedure on the accumulation of GABA in carrots via γ-aminobutyric acid (GABA) shunt and polyamines degradation pathway was investigated. Results showed that fresh-cut processing enhanced glutamate decarboxylase (GAD) activity and expression levels of DcGAD1 and DcGAD2, while reduced GABA transaminase (GABA-T) activity and DcGABA-T1 expression level, which induced the more glutamate (Glu) conversion to GABA. Polyamines (PAs) in shredded carrots were significantly lower than the whole, due to the elevated activities of diamine oxidase (DAO), polyamine oxidase (PAO) and aminoaldehyde dehydrogenase (AMADH) and DcPAO expression level, which indicated that the polyamines degradation pathway was activated and more PAs were converted to GABA. These results suggested that fresh-cut procedure can induce the accumulation of GABA through activating GABA shunt and polyamines degradation pathway. Besides, fresh-cut processing treatment did not have much adverse effect on the organoleptic quality of carrots.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at (10.1007/s13197-021-05039-y).

A Review of Red Yeast Rice, a Traditional Fermented Food in Japan and East Asia: Its Characteristic Ingredients and Application in the Maintenance and Improvement of Health in Lipid Metabolism and the Circulatory System

Red yeast rice has been used to produce alcoholic beverages and various fermented foods in China and Korea since ancient times; it has also been used to produce tofuyo (Okinawan-style fermented tofu) in Japan since the 18th century. Recently, monacolin K (lovastatin) which has cholesterol-lowering effects, was found in some strains of Monascus fungi. Since statins have been used world-wide as a cholesterol-lowering agent, processed foods containing natural statins are drawing attention as materials for primary prevention of life-style related diseases. In recent years, large-scale commercial production of red yeast rice using traditional solid-state fermentation has become possible, and various useful materials, including a variety of monascus pigments (polyketides) that spread as natural pigments, in addition to statins, are produced in the fermentation process. Red yeast rice has a lot of potential as a medicinal food. In this paper, we describe the history of red yeast rice as food, especially in Japan and East Asia, its production methods, use, and the ingredients with pharmacological activity. We then review evidence of the beneficial effects of red yeast rice in improving lipid metabolism and the circulatory system and its safety as a functional food.

Evaluation of GABA Production and Probiotic Activities of Enterococcus faecium BS5

Gamma-aminobutyric acid (GABA) is a principal inhibitory neurotransmitter in the central nervous system and is produced by irreversible decarboxylation of glutamate. It possesses several physiological functions such as neurotransmission, diuretic, and tranquilizer effects and also regulates cardiovascular functions such as blood pressure and heart rate in addition to playing a role in the reduction of pain and anxiety. The objective of this study was to evaluate the GABA producing ability and probiotic capability of certain lactic acid bacteria strains isolated from dairy products. Around sixty-four bacterial isolates were collected and screened for their ability to produce GABA from monosodium glutamate, among which nine isolates were able to produce GABA. The most efficient GABA producer was Enterococcus faecium BS5. Further, assessment of several important and desirable probiotic properties showed that Ent. faecium BS5 was resistant to acid stress, bile salt, and antibiotics. Ent. faecium BS5 may potentially be used for large-scale industrial production of GABA and also for functional fermented product development.

Improving nutritional quality of rice for human health

This review surveys rice nutritional value, mainly focusing on breeding achievements via adoption of both genetic engineering and non-transgenic strategies to improve key nutrients associated with human health. Rice (Oryza sativa) is an essential component of the diets and livelihoods of over 3.5 billion people. Polished rice is mostly consumed as staple food, fulfilling daily energy demands and part of the protein requirement. Brown rice is comparatively more nutritious, containing more lipids, minerals, vitamins, dietary fiber, micronutrients, and bioactive compounds. In this article, we review the nutritional facts about rice including the level of γ-aminobutyric acid, resistant starch, lysine, iron, zinc, β-carotene, folate, anthocyanin, various carotenoids, and flavonoids, focusing on their synthesis and metabolism and the advances in their biofortification via adoption of both conventional and genetic engineering strategies. We conclude that besides representing a staple food, rice has the potential to become a source of various essential nutrients or bioactive compounds through appropriate genetic improvements to benefit human health and prevent certain chronic diseases. Finally, we discuss the available, non-genetically engineering strategies for the nutritional improvement of rice, including their main strengths and constraints.

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.

Nutritional content and health benefits of sun-dried and salt-aged radish (takuan-zuke)

We investigated the nutritional characteristics of salted radish roots (takuan-zuke) prepared using different methods: takuan-zuke based on sun-drying (hoshi) or salt-pressing (shio-oshi) dehydration, different salt-aging temperatures, and salting with rice bran. We examined differences in nutritional substances in salted radish using chromatographic analysis, bioassay methods, and multivariate analysis. We previously reported that the amount of γ-aminobutyrate in takuan-zuke was increased by both dehydration treatments. In the present study, we observed that sucrose and proline were increased by sun-drying treatment, while little change occurred with salt-pressing treatment. Branched-chain amino acids were increased by both treatments. Interestingly, free fatty acids increased with salt-aging duration, irrespective of the dehydration method. Addition of rice bran to long salt-aging treatment increased the levels of niacin, glutamate, and acetate. Metabolite concentrations were higher in hoshi takuan-zuke than shio-oshi takuan-zuke. Our comprehensive analysis reveals effects of specific manufacturing conditions on beneficial components of takuan-zuke.

Renal Denervation Improves the Baroreflex and GABA System in Chronic Kidney Disease-induced Hypertension

Hypertensive rats with chronic kidney disease (CKD) exhibit enhanced gamma-aminobutyric acid (GABA)_B receptor function and regulation within the nucleus tractus solitarii (NTS). For CKD with hypertension, renal denervation (RD) interrupts the afferent renal sympathetic nerves, which are connecting to the NTS. The objective of the present study was to investigate how RD improves CKD-induced hypertension. Rats underwent 5/6 nephrectomy for 8 weeks, which induced CKD and hypertension. RD was induced by applying phenol to surround the renal artery in CKD. RD improved blood pressure (BP) by lowering sympathetic nerve activity and markedly restored the baroreflex response in CKD. The GABA_B receptor expression was increased in the NTS of CKD; moreover, the central GABA levels were reduced in the cerebrospinal fluid, and the peripheral GABA levels were increased in the serum. RD restored the glutamic acid decarboxylase activity in the NTS in CKD, similar to the effect observed for central treatment with baclofen, and the systemic administration of gabapentin reduced BP. RD slightly improved renal function and cardiac load in CKD. RD may improve CKD-induced hypertension by modulating the baroreflex response, improving GABA system dysfunction and preventing the development and reducing the severity of cardiorenal syndrome type 4 in CKD rats.

Antihypertensive and Natriuretic Effects of Less-Sodium Soy Sauce Containing γ-Aminobutyric Acid in Spontaneously Hypertensive Rats

We investigated the mechanism of the antihypertensive effect of less-sodium soy sauce containing gamma-aminobutyric acid (GABA) in spontaneously hypertensive rats (SHRs). When SHRs were given a diet with less-sodium soy sauce containing GABA (GABA-rich soy sauce group) for 6 weeks, the systolic blood pressure decreased as compared with that in rats fed diets with less-sodium soy sauce or a solution of salt. Renal sympathetic nerve activity (RSNA) and positive Na balance were reduced, and the urinary Na excretion tended to increase in the GABA-rich soy sauce group. Vascular hypertrophy of the thoracic aorta and the coronary and renal interlobular arteries tended to reduce in the GABA-rich soy sauce group. These results suggest that inhibition of Na retention by natriuresis, as a result of inhibition of RSNA by the GABA in the soy sauce contributed to the antihypertensive effect of GABA in the SHRs. Intake of less-sodium soy sauce containing GABA might help to reduce overall cardiovascular risk.

Bio-functional pickles that reduce blood pressure of rats

Addition of γ-aminobutyric acid (GABA) and angiotensin converting enzyme (ACE)-inhibitory peptides to the pickles was studied in order to develop a new type of pickles that reduce blood pressure. Based on the outcome of these studies, a new type of fermentation bed composed of rice bran and white miso has been successfully developed. The advantage of such pickles is that they not only contain both GABA and ACE-inhibitory peptides, but also that their taste and flavor are excellent, with colors close to the original ones. The new type of pickles could temporarily reduce blood pressure in two types of rats, spontaneously hypertensive rats and NaCl-sensitive model rats. Thus, the newly developed pickles appear to be beneficial for pickle business.

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

This study aimed to investigate the effects of a gamma-aminobutyric acid (GABA) rich tomato (Solanum lycopersicum L.) cultivar 'DG03-9' in comparison with 'Momotaro', a commonly consumed tomato cultivar in Japan, on systolic blood pressure (SBP) in spontaneously hypertensive rats (SHR). In a single administration study, treatment with the GABA-rich cultivar elicited a significant decrease in SBP compared to the control group. In a chronic administration study, SHR were fed diets containing one of the tomato cultivars for 4 weeks. Both cultivars significantly reduced the increase in SBP compared to the control. The antihypertensive effect of the GABA-rich cultivar was higher than that of the commonly consumed cultivar in both the single- and chronic-administration studies. Treatment with a comparable amount of GABA elicited a similar response to treatment with the GABA-rich cultivar. These results suggest that the GABA-rich cultivar 'DG03-9' is a potent antihypertensive food and may be useful for treating hypertension effectively.

Development of a method for the determination of gamma-aminobutyric acid in foodstuffs

A method for the determination of gamma-aminobutyric acid (GABA) in foodstuffs has been developed by combination of its dinitrophenylation and high-performance liquid chromatography (HPLC) using norleucine as an internal standard. GABA was converted to its stable derivative with 1-fluoro-2,4-dinitrobenzene and the derivative was extracted with ether. After evaporation of the extract, the residue was dissolved in 0.1 M NaOH and the solution was subjected to reversed-phase HPLC with an elution system of a linear gradient of methanol in 10 mM Tris-HCl buffer (pH 6.0) and a detection system monitoring the absorbance of the effluent at 400 nm. The present method was shown to be utilized as a satisfactory method for the determination of gamma-aminobutyric acid in foodstuffs.

The Effects of gamma-Aminobutyric Acid, Vinegar, and Dried Bonito on Blood Pressure in Normotensive and Mildly or Moderately Hypertensive Volunteers

The purpose of this study was to examine the effects of γ-aminobutyric acid (GABA) in fermented drinking water prepared from sodium glutamate, vinegar, and dried bonito (FDWG) compared with placebo [vinegar and dried bonito without GABA (FDW)] and its safety in normotensive and mildly or moderately hypertensive volunteers. A double-blind, placebo-controlled, randomized study was conducted involving volunteers with normal (group-N) and mildly or moderately high (group-H) blood pressure (BP). After a pretreatment period of 2 weeks (weeks –2), the subjects received FDWG or FDW for 12 weeks followed by 4 weeks of no intake (weeks 16). In group-H, both FDWG and FDW significantly decreased systolic (SBP, −7.6 ± 4.0 and −5.5 ± 1.5 mmHg, p<0.05, respectively) and diastolic (DBP, −10.6 ± 4.0 and −7.6 ± 1.7 mmHg, p<0.01, respectively) BP compared to the baseline (0-week) value at 12 weeks, respectively. There were no abnormal changes in hematological or blood chemistry variables, urinalysis, heart rate, or body weight in the study groups. These findings indicated that vinegar and dried bonito with or without GABA might have an effect on BP in mildly or moderately hypertensive patients.

GAMMA.-Aminobutyric Acid Specifically Inhibits Progression of Tubular Fibrosis and Atrophy in Nephrectomized Rats

Gamma-aminobutyric acid (GABA) was administered orally to rats for 60 d after excision of five-sixths of their kidney volume. A decrease in renal function parameters was observed in these nephrectomized rats. However, the administration of GABA ameliorated renal dysfunction, and a longer administration period of GABA increased its protective effect. In addition, tubular fibrosis was markedly increased at 10 and 60 d in nephrectomized control rats, while GABA administration for 10 d reduced tubular fibrosis to the normal level. Tubular atrophy was markedly induced by nephrectomy, and was significantly reduced by the administration of GABA at 60 d. Furthermore, the nephrectomized control rats exhibited an increased expression level of transforming growth factor-beta1, where GABA significantly decreased it after administration for 10 d. The expression of fibronectin in the tubuli of rats administrated GABA for 60 d was completely and dose-dependently reduced as compared with nephrectomized control rats. However, the improvement effects in glomeruli were less. We also found that GABAA and GABAB receptors were specifically localized in tubuli. Specific agonists for GABAA and GABAB receptors improved renal function. These results suggest that GABA may have a beneficial effect on renal function in nephrectomized rats by inhibiting fibrosis and atrophy primarily in tubuli, and that it ameliorates losses of renal function in renal failure.