Antibody level dynamics until after the third dose of COVID-19 vaccination.

The antibody titers of volunteers, including elderly people, were investigated after the second dose of the BNT162b2 vaccine (Pfizer-BioNTech) as an mRNA vaccine against the coronavirus disease 2019 (COVID-19). Serum samples were collected from 105 volunteers (44 healthcare workers and 61 elderly people) 7-14 days after the second vaccine dose, and antibody titers were measured. The antibody titers of study participants in their 20s were significantly higher than those of other age groups. Furthermore, the antibody titers of participants aged <60 years were significantly higher than those of participants aged ≥60 years. Serum samples were repeatedly collected from 44 healthcare workers until after the third vaccine dose. Eight months after the second round of vaccination, the antibody titer levels decreased to the same level as that before the second vaccine dose. After the third booster vaccination, the antibody titer recovered to the same level as that after the second dose. Neutralizing activities were also investigated at four time points before and after the second vaccine dose. The antibody titers and neutralizing activity were positively correlated. Therefore, neutralizing activity can be predicted by measuring the antibody titer. In conclusion, the antibody titers in the elderly population were significantly lower than those in the younger population. Although the antibody titers increased following vaccination, their levels showed a decline after several months, returning to the same level as that after a single dose of mRNA vaccination. The antibody titer levels recovered after the third dose of vaccination, which had already been administered in Japan. Routine administration of vaccine should be considered in the future.

Supplementing chicken broth with monosodium glutamate reduces energy intake from high fat and sweet snacks in middle-aged healthy women.

Monosodium L-glutamate (MSG) and inosine monophosphate-5 (IMP) are flavor enhancers for umami taste. However, their effects on appetite and food intake are not well-researched. The objective of the current study was to test their additions in a broth preload on subsequent appetite ratings, energy intake and food choice. Eighty-six healthy middle-aged women with normal body weight received three preload conditions on 3 test days 1 week apart - a low-energy chicken flavor broth (200 ml) as the control preload, and broths with added MSG alone (0.5 g/100 ml, MSG broth) or in combination with IMP (0.05 g/100 ml) (MSG+ broth) served as the experimental conditions. Fifteen minutes after preload administration subjects were provided an ad libitum testing meal which consisted of 16 snacks varying in taste and fat content. MSG and MSG+ enhanced savory taste and broth properties of liking and pleasantness. In comparison with control, the MSG preload resulted in less consumption of total energy, as well as energy from sweet and high-fat snacks. Furthermore, MSG broth preload reduced added sugar intake. These findings were not observed after MSG+ preload. Appetite ratings were not different across the three preloads. Results suggest a potential role of MSG addition to a low-energy broth preload in subsequent energy intake and food choice. This trial was registered at clinicaltrials.gov as NCT01761045.

Telmisartan activates endogenous peroxisome proliferator-activated receptor-δ and may have anti-fibrotic effects in human mesangial cells.

Telmisartan, an angiotensin II receptor type 1 blocker (ARB), was recently reported to promote lipolysis in mice by acting as a peroxisome proliferator-activated receptor (PPAR)-δ activator, although in clinical studies, it has also been recognized to activate PPAR-γ as a major cause of its pleiotropic actions. The aim of this study was to investigate whether telmisartan activates endogenous PPAR-δ and thereby exerts anti-fibrotic effects in human mesangial cells (HMC). Immunohistochemical analysis of human renal biopsy specimens revealed that PPAR-δ protein was detected in the HMC of glomeruli with moderately proliferative changes. In the HMC, both GW0742, an authentic PPAR-δ agonist, and telmisartan enhanced PPAR response element (PPRE)-luciferase activity dose dependently, and these increases were blunted by GSK0660, a specific PPAR-δ antagonist, but not by GW9662, a PPAR-γ antagonist. Telmisartan also upregulated the expression of PPAR-δ target genes related to fatty acid oxidation; that is, heart type-fatty acid-binding protein and uncoupling protein-2. These effects were inhibited by both PPAR-δ antagonism and PPAR-δ gene silencing. Transforming growth factor-ß1 (TGF-ß1) increased the expression of plasminogen activator inhibitor-1 (PAI-1), TGF-ß1 and collagen IV. The PAI-1 expression was mediated, at least in part by the phosphorylation of extracellular signal-regulated kinases (ERKs). Telmisartan suppressed TGF-ß1-stimulated PAI-1 and collagen IV expression and ERK phosphorylation, and these effects were weakened by PPAR-δ antagonism, whereas eprosartan, a non-PPAR activating ARB, did not affect TGF-ß1-stimulated PAI-1 expression. These results indicate that in HMC telmisartan activates endogenous PPAR-δ and may prevent TGF-ß1-induced fibrotic changes by reducing ERK phosphorylation in a PPAR-δ-dependent manner, and thus, might be useful for treating hypertensive patients with renal and metabolic disorders.

Production of free glutamate in milk requires the leucine transporter LAT1.

The concentration of free glutamate (Glu) in rat's milk is ∼10 times higher than that in plasma. Previous work has shown that mammary tissue actively transports circulatory leucine (Leu), which is transaminated to synthesize other amino acids such as Glu and aspartate (Asp). To investigate the molecular basis of Leu transport and its conversion into Glu in the mammary gland, we characterized the expression of Leu transporters and [(3)H]Leu uptake in rat mammary cells. Gene expression analysis indicated that mammary cells express two Leu transporters, LAT1 and LAT2, with LAT1 being more abundant than LAT2. This transport system is sodium independent and transports large neutral amino acids. The Leu transport system in isolated rat mammary cells could be specifically blocked by the LAT1 inhibitors 2-aminobicyclo-[2.2.1]-heptane-2-carboxylic acid (BCH) and triiodothyronine (T3). In organ cultures, Glu secretion was markedly inhibited by these LAT1 inhibitors. Furthermore, the profiles of Leu uptake inhibition by amino acids in mammary cells were similar to those reported for LAT1. In vivo, concentrations of free Glu and Asp increased in milk by oral gavage with Leu at 6, 12, and 18 days of lactation. These results indicate that the main Leu transporter in mammary tissue is LAT1 and the transport of Leu is a limiting factor for the synthesis and release of Glu and Asp into milk. Our studies provide the bases for the molecular mechanism of Leu transport in mammary tissue by LAT1 and its active role on free Glu secretion in milk, which confer umami taste in suckling pups.

Physiological roles of dietary glutamate signaling via gut-brain axis due to efficient digestion and absorption.

Dietary glutamate (Glu) stimulates to evoke the umami taste, one of the five basic tastes, enhancing food palatability. But it is also the main gut energy source for the absorption and metabolism for each nutrient, thus, only a trace amount of Glu reaches the general circulation. Recently, we demonstrated a unique gut sensing system for free Glu (glutamate signaling). Glu is the only nutrient among amino acids, sugars and electrolytes that activates rat gastric vagal afferents from the luminal side specifically via metabotropic Glu receptors type 1 on mucosal cells releasing mucin and nitrite mono-oxide (NO), then NO stimulates serotonin (5HT) release at the enterochromaffin cell. Finally released 5HT stimulates 5HT3 receptor at the nerve end of the vagal afferent fiber. Functional magnetic resonance imaging (f-MRI, 4.7 T) analysis revealed that luminal sensing with 1 % (w/v) monosodium L-glutamate (MSG) in rat stomach activates both the medial preoptic area (body temperature controller) and the dorsomedial hypothalamus (basic metabolic regulator), resulting in diet-induced thermogenesis during mealing without changes of appetite for food. Interestingly, rats were forced to eat a high fat and high sugar diet with free access to 1 % (w/w) MSG and water in a choice paradigm and showed the strong preference for the MSG solution and subsequently, they displayed lower fat deposition, weight gain and blood leptin. On the other hand, these brain functional changes by the f-MRI signal after 60 mM MSG intubation into the stomach was abolished in the case of total vagotomized rats, suggesting that luminal glutamate signaling contributes to control digestion and thermogenesis without obesity.

Nitrogen in dietary glutamate is utilized exclusively for the synthesis of amino acids in the rat intestine.

Although previous studies have shown that virtually the entire carbon skeleton of dietary glutamate (glutamate-C) is metabolized in the gut for energy production and amino acid synthesis, little is known regarding the fate of dietary glutamate nitrogen (glutamate-N). In this study, we hypothesized that dietary glutamate-N is an effective nitrogen source for amino acid synthesis and investigated the fate of dietary glutamate-N using [(15)N]glutamate. Fischer male rats were given hourly meals containing [U-(13)C]- or [(15)N]glutamate. The concentration and isotopic enrichment of several amino acids were measured after 0-9 h of feeding, and the net release of each amino acid into the portal vein was calculated. Most of the dietary glutamate-C was metabolized into CO(2), lactate, or alanine (56, 13, and 12% of the dietary input, respectively) in the portal drained viscera (PDV). Most of the glutamate-N was utilized for the synthesis of other amino acids such as alanine and citrulline (75 and 3% of dietary input, respectively) in the PDV, and only minor amounts were released into the portal vein in the form of ammonia and glutamate (2 and 3% of the dietary input, respectively). Substantial incorporation of (15)N into systemic amino acids such as alanine, glutamine, and proline, amino acids of the urea cycle, and branched-chain amino acids was also evident. These results provide quantitative evidence that dietary glutamate-N distributes extensively to amino acids synthesized in the PDV and, consequently, to circulating amino acids.

Reversible brain response to an intragastric load of L-lysine under L-lysine depletion in conscious rats.

L-Lysine (Lys) is an essential amino acid and plays an important role in anxiogenic behaviour in both human subjects and rodents. Previous studies have shown the existence of neural plasticity between the Lys-deficient state and the normal state. Lys deficiency causes an increase in noradrenaline release from the hypothalamus and serotonin release from the amygdala in rats. However, no studies have used functional MRI (fMRI) to compare the brain response to ingested Lys in normal, Lys-deficient and Lys-recovered states. Therefore, in the present study, using acclimation training, we performed fMRI on conscious rats to investigate the brain response to an intragastric load of Lys. The brain responses to intragastric administration of Lys (3 mmol/kg body weight) were investigated in six rats intermittently in three states: normal, Lys-deficient and recovered state. First, in the normal state, an intragastric load of Lys activated several brain regions, including the raphe pallidus nucleus, prelimbic cortex and the ventral/lateral orbital cortex. Then, after 6 d of Lys deprivation from the normal state, an intragastric load of Lys activated the ventral tegmental area, raphe pallidus nucleus and hippocampus, as well as several hypothalamic areas. After recovering from the Lys-deficient state, brain activation was similar to that in the normal state. These results indicate that neural plasticity in the prefrontal cortex, hypothalamic area and limbic system is related to the internal Lys state and that this plasticity could have important roles in the control of Lys intake.

Functional brain mapping of conscious rats during reward anticipation.

Functional magnetic resonance imaging (fMRI) in humans and non-primates has been useful to clarify the brain regions involved in the psychological process such as the reward anticipation. However, there is still no report of the fMRI study on the reward prediction in rodents. This is mainly because of the problem of anesthesia in rodent fMRI. In this study, we first developed awake fMRI method to investigate the brain region involved in reward anticipation in rats. After fMRI adaptation training, rats received light stimulation 1min before intraperitoneal infusion of ethanol solution (4g/kg body weight) in the MRI bore. Five or six days after the start of the experiment, the caudate-putamen, anterior insular cortex, hippocampus, ventral pallidum, nucleus accumbens and medial preoptic area were activated during light presentation. In contrast, no activation was observed in the control group. These results indicate the availability of awake fMRI method to investigate neural plasticity in the psychological process, learning, and memory such as the reward anticipation.

New therapeutic strategy for amino acid medicine: effects of dietary glutamate on gut and brain function.

The gustatory and visceral stimulation from food regulates digestion and nutrient utilization, and free glutamate (Glu) release from food is responsible for the umami taste perception that increases food palatability. The results of recent studies reveal a variety of physiological roles for Glu. For example, luminal applications of Glu into the mouth, stomach, and intestine increase the afferent nerve activities of the glossopharyngeal nerve, the gastric branch of the vagus nerve, and the celiac branch of the vagus nerve, respectively. Additionally, luminal Glu evokes efferent nerve activation of each branch of the abdominal vagus nerve. The intragastric administration of Glu activates several brain areas (e.g., insular cortex, limbic system, and hypothalamus) and has been shown to induce flavor-preference learning in rats. Functional magnetic resonance imaging of rats has shown that the intragastric administration of Glu activates the nucleus tractus solitarius, amygdala, and lateral hypothalamus. In addition, Glu may increase flavor preference as a result of its postingestive effect. Considering these results, we propose that dietary Glu functions as a signal for the regulation of the gastrointestinal tract via the gut-brain axis and contributes to the maintenance of a healthy life.

Peripheral chemosensing system for tastants and nutrients.

PURPOSE OF REVIEW: The purpose of this review is to discuss the presence and possible roles of peripheral taste/nutrient sensors, particularly taste receptors. RECENT FINDINGS: Recent studies have demonstrated that taste signaling molecules are distributed not only in the gustatory epithelium, but also in other tissues, including the gastrointestinal tract, airways, testes and brain. Taste signaling mechanisms in the gastrointestinal tract were reported to participate in detecting sweet, umami and bitter compounds. Several research groups have suggested that tastant/nutrient detection by other systems contributes to the behavioral responses to food intake. SUMMARY: Taste-like cells expressing taste signaling components are distributed in multiple tissues. Investigation of their potential roles in chemosensing has just begun. Researchers have identified at least two chemosensory pathways in the gastrointestinal tract for detecting tastants/nutrients. One is the taste receptor signaling pathway and the other is the currently unknown nutrient-sensing pathway that elicits postingestive effects. The former system utilizes a mechanism similar to taste sensing in the oral cavity. By understanding how tastants/nutrients are sensed and regulated through both systems, we may be able to more effectively control food intake in the future.

Umami taste in mice uses multiple receptors and transduction pathways.

The distinctive umami taste elicited by l-glutamate and some other amino acids is thought to be initiated by G-protein-coupled receptors. Proposed umami receptors include heteromers of taste receptor type 1, members 1 and 3 (T1R1+T1R3), and metabotropic glutamate receptors 1 and 4 (mGluR1 and mGluR4). Multiple lines of evidence support the involvement of T1R1+T1R3 in umami responses of mice. Although several studies suggest the involvement of receptors other than T1R1+T1R3 in umami, the identity of those receptors remains unclear. Here, we examined taste responsiveness of umami-sensitive chorda tympani nerve fibres from wild-type mice and mice genetically lacking T1R3 or its downstream transduction molecule, the ion channel TRPM5. Our results indicate that single umami-sensitive fibres in wild-type mice fall into two major groups: sucrose-best (S-type) and monopotassium glutamate (MPG)-best (M-type). Each fibre type has two subtypes; one shows synergism between MPG and inosine monophosphate (S1, M1) and the other shows no synergism (S2, M2). In both T1R3 and TRPM5 null mice, S1-type fibres were absent, whereas S2-, M1- and M2-types remained. Lingual application of mGluR antagonists selectively suppressed MPG responses of M1- and M2-type fibres. These data suggest the existence of multiple receptors and transduction pathways for umami responses in mice. Information initiated from T1R3-containing receptors may be mediated by a transduction pathway including TRPM5 and conveyed by sweet-best fibres, whereas umami information from mGluRs may be mediated by TRPM5-independent pathway(s) and conveyed by glutamate-best fibres.

Dietary free glutamate prevents diarrhoea during intra-gastric tube feeding in a rat model.

Recent studies indicate that l-glutamate (l-Glu), abundant in many foods, is a stimulator of gastric vagal afferent nerves. The aim of the present study was to examine the possibility that l-Glu supplementation of a protein-rich liquid diet may prevent the incidence of diarrhoea during repetitive intra-gastric tube feeding. The gastric vagal afferent nerve recording of rats indicated that intra-gastric administration of a protein-rich liquid diet supplemented with 0·5 % monosodium glutamate enhanced the basal afferent activities seen with the protein-rich diet alone. The examination of the faeces showed that the addition of monosodium glutamate to the liquid diet significantly prevented the incidence of diarrhoea induced by repetitive gastric feeding. In conclusion, supplementation of an enteral liquid diet with free l-Glu may ameliorate diarrhoea during intra-gastric tube feeding by sending visceral glutamate information from the stomach to the brain.

Clinical utility of the neutrophil distribution pattern obtained using the CELL-DYN SAPPHIRE hematology analyzer for the diagnosis of myelodysplastic syndrome.

We evaluated the diagnostic utility of peripheral blood neutrophil distribution patterns obtained using the CELL-DYN SAPPHIRE hematology analyzer in patients with myelodysplastic syndrome (MDS). Peripheral blood was obtained from 467 individuals including 32 patients with MDS, and the respective neutrophil distribution patterns were observed using two light scatters [7-degree complexity (7D) and 90-degree lobularity (90D)]. These scattering intensities are shown as median (median neutrophil distribution: MND) and coefficient of variation (neutrophil distribution width: NDW). Generally, MDS patients showed lower 7D MND, higher 7D NDW, lower 90D MND and higher 90D NDW than other comparable groups. Whereas 90D parameters were more diagnostically efficient than 7D ones in patients with MDS. The sensitivity and specificity of 90D MND for MDS patients became 78.1 and 78.9%, respectively (cut-off value = 14,514). 90D NDW was most diagnostically effective with 87.5% sensitivity and 91.0% specificity (cut-off value = 21.2%). Both 90D parameters showed no evident correlation with the degree of either leukocytopenia or peripheral blood dysgranulopoiesis. In conclusion, neutrophil distribution parameters, especially 90D NDW, appear to provide convenient and objective markers for the screening of patients with MDS in routine laboratory hematology.

Dietary glutamate signal evokes gastric juice excretion in dogs.

BACKGROUND: Dietary-free L-glutamate (Glu) in the stomach interacts with specific Glu receptors (T1R1/T1R3 and mGluR1-8) expressed on surface epithelial and gastric gland cells. Furthermore, luminal Glu activates the vagal afferents in the stomach through the paracrine cascade including nitric oxide and serotonin (5-HT). AIM: To elucidate the role of dietary Glu in neuroendocrine control of the gastrointestinal phase of gastric secretion. METHODS: In Pavlov or Heidenhain gastric pouch dogs, secretion was measured in the pouch while monosodium glutamate (MSG) was intubated into the main stomach alone or in combination with liquid diets. RESULTS: In both experimental models, supplementation of the amino acid-rich diet with MSG (100 mmol/l) enhanced secretions of acid, pepsinogen and fluid, and elevated plasma gastrin-17. However, MSG did not affect secretion stimulated by the carbohydrate-rich diet and had no effect on basal secretion when applied in aqueous solution. Effects of MSG were abolished by denervation of the stomach and proximal small intestine with intragastrically applied lidocaine and partially suppressed with the 5-HT(3) receptor blocker granisetron. CONCLUSIONS: Supplementation of amino acid-rich liquid diets with MSG enhances gastrointestinal phase secretion through neuroendocrine pathways which are partially mediated by 5-HT. Possible mechanisms are discussed.

Luminal amino acid-sensing cells in gastric mucosa.

Chemosensing of nutrients in the gastrointestinal tract plays physiologically important roles in the regulation of food intake behaviors, including digestion, absorption, metabolism and other subsequently occurring body functions via brain activation. Free amino acids, liberated from ingested foods, are of course essential nutrients which compose the body proteins and sometimes determine the taste of the food. Glutamate, one of the most abundant amino acids in the foods and the liberated free form, critically contributes to the 'umami' taste perception. Recently, it has been revealed that dietary glutamate has many beneficial functions in the gastrointestinal tract. However, the precise mechanism of glutamate sensing still remains unclear. Using primary rat gastric mucosal cell cultures, we demonstrated that somatostatin-secreting D cells are candidate cells for glutamate sensing in the stomach through inhibition of somatostatin release. Considering that somatostatin is one of the major negative regulators of gastric functions, it is suggested that some parts of glutamate's beneficial effects could be explained by suppression of the inhibitory somatostatin effects, i.e. stimulation, by glutamate.

Biological significance of glutamate signaling during digestion of food through the gut-brain axis.

Monosodium L-glutamate (MSG) elicits a unique taste termed umami and is widely used as a flavor enhancer in various cuisines. In addition, recent studies suggest the existence of sensors for L-glutamate (Glu) and transduction molecules in the gut mucosa as well as in the oral cavity. The vagal gastric afferent responds specifically to the luminal stimulation of Glu in the stomach and regulates the autonomic reflexes. The intragastric infusion of Glu also activates several brain areas (insular cortex, limbic system, and hypothalamus) and is able to induce flavor-preference learning in rats. These results suggest that umami signaling via gustatory and visceral pathways plays an important role in the processes of digestion, absorption, metabolism, and other physiological functions via activation of the brain.

Evaluation of the 'liking' and 'wanting' properties of umami compound in rats.

Food reward is neurologically and psychologically divided into at least two properties; 'liking' and 'wanting'. Although umami taste enhances food palatability, the liking and wanting properties of umami taste, and the underlying neural mechanisms for these properties are not clear. Here, we compared sucrose (0, 10, 30, 120 and 480 mM) and monosodium l-glutamate (MSG; 0, 10, 30, 60 and 120 mM) solutions using a taste reactivity test to evaluate liking, and fixed/progressive-ratio operant licking tasks to evaluate wanting. To determine the underlying neural mechanisms, we also conducted systemic blockade of opioid receptors in both tests. In the taste reactivity test, the hedonic reactions to 30, 60 and 120 mM MSG were greater than those to water (0mM) but lower than those to 480 mM sucrose. In the operant task, the intake, number of licks, and breakpoint to MSG reached peaks at around 60mM but they were lower than those to 30-480 mM sucrose. The systemic naloxone treatment decreased the hedonic responses to MSG and sucrose, and reduced the incentive salience of MSG but not sucrose. These findings indicate that the hedonic response and incentive salience of MSG is lower than those of sucrose when compared at the maximum response and that the incentive salience of MSG is lower than sucrose even where the hedonic response is similar. The present study also suggest that the hedonic response and incentive salience of umami compound is modulated by brain opioid signaling.

Effects of oral monosodium glutamate in mouse models of asthma.

The available evidence from numerous clinical studies has failed to demonstrate a clear and consistent relationship between monosodium glutamate (MSG) and asthma. The objective of this study was to investigate the effects of MSG on bronchial inflammation by measuring cytological, histological and functional changes in an ovalbumin-induced asthma mouse model. BALB/c mice with experimentally induced asthma were fed a diet containing 0.5% or 5% MSG the week before the first ovalbumin injection and for the subsequent 3-week period. MSG feeding did not affect pulmonary eosinophil infiltration, production of Th2 cytokines, circulating IgE concentrations or airway hyperresponsiveness (induced by methacholine). Histological observations did not reveal pulmonary inflammation, including secondary changes, in the asthmatic mice. An oral gavage challenge with an MSG solution (0.5% or 5%, w/w) did not exert any acute effects on lung inflammation or airway hyperresponsiveness in the asthmatic mice. The results of this study suggest that MSG is not involved in the development of asthma or in acute asthmatic responses, and they support previous observations from well-designed clinical studies.