Low plasma tryptophan is associated with olfactory function in healthy elderly community dwellers in Japan.

BACKGROUND: Decreased circulating tryptophan (Trp) levels are frequently observed in elderly patients with neurodegenerative disease including Alzheimer's disease. Trp may serve as a potential biomarker for monitoring disease risk in elderly people. We aimed to investigate the association between low plasma Trp levels and olfactory function, which is known to predict age-related diseases including dementia in elderly people. METHODS: A total of 144 healthy elderly Japanese community (≥ 65 years old) dwellers from the Health, Aging and Nutritional Improvement study (HANI study) were the subjects of our analysis. Low Trp levels were classified using the lower limit values of the reference interval according to a previous report. Olfactory function was assessed using a card-type test called Open Essence, which includes 12 odour items that are familiar to Japanese people. The elderly subjects with low circulating Trp levels were compared to a control group with normal plasma Trp levels. RESULTS: We conducted the analyses using 144 people aged 65 years or older (mean age 73.7 ± 5.5 years; 36.1% men). The subjects showed normal serum albumin levels (4.4 ± 0.2 g/dL) and no daily living disabilities. Low plasma Trp levels (low Trp group) were found in 11.1% of the study population. The low Trp group showed a significantly lower correct-answer rate for the items india ink, perfume, curry and sweaty smelling socks than control group (P < 0.05). There was also a significant association between low Trp levels and low olfactory ability, after adjusting for age and sex. CONCLUSIONS: Lower plasma Trp levels were associated with a decrease in olfactory function in functionally competent older individuals. Because olfactory dysfunction predicts age-related diseases, low plasma Trp levels may represent a clinical sign of disease risk in elderly people.

Plasma amino acid profiles in healthy East Asian subpopulations living in Japan.

OBJECTIVES: Profiles of plasma free amino acids (PFAAs) have been utilized as biomarkers to detect various diseases. However, few studies have investigated whether ethnicity or specific subpopulations within East Asia influence PFAA concentrations. METHODS: A total of 95 healthy volunteers living in Japan, including 31 Japanese individuals, 36 Korean individuals and 28 Chinese individuals, were enrolled. Participants' PFAA levels were measured by high-performance liquid chromatography mass spectrometry, and the effects of factors such as sex, age, body mass index (BMI) and subpopulation on PFAA profiles were analyzed. RESULTS: With the exception of glutamine and α-aminobutyric acid, there were no significant differences among the three examined subpopulations with respect to either the means or the distributions of PFAA concentrations. A multiple regression analysis revealed that most of the PFAA concentrations were significantly related to sex. Ornithine concentrations, glutamate concentrations, and glutamine and α-aminobutyric acid concentrations were significantly associated with age, BMI, and Chinese subpopulation, respectively. CONCLUSION: The study results indicate that the contributions of subpopulation within East Asia to PFAA profiles are small, particularly relative to the contributions provided by sex.

Endogenous glutamine production in critically ill patients: the effect of exogenous glutamine supplementation.

INTRODUCTION: Glutamine rate of appearance (Ra) may be used as an estimate of endogenous glutamine production. Recently a technique employing a bolus injection of isotopically labeled glutamine was introduced, with the potential to allow for multiple assessments of the glutamine Ra over time in critically ill patients, who may not be as metabolically stable as healthy individuals. Here the technique was used to evaluate the endogenous glutamine production in critically ill patients in the fed state with and without exogenous glutamine supplementation intravenously. METHODS: Mechanically ventilated patients (n = 11) in the intensive care unit (ICU) were studied on two consecutive days during continuous parenteral feeding. To allow the patients to be used as their own controls, they were randomized for the reference measurement during basal feeding without supplementation, before or after the supplementation period. Glutamine Ra was determined by a bolus injection of 13C-glutamine followed by a period of frequent sampling to establish the decay-curve for the glutamine tracer. Exogenous glutamine supplementation was given by intravenous infusion of a glutamine containing dipeptide, L-alanyl-L-glutamine, 0.28 g/kg during 20 hours. RESULTS: A 14% increase of endogenous glutamine Ra was seen at the end of the intravenous supplementation period as compared to the basal measurements (P = 0.009). CONCLUSIONS: The bolus injection technique to measure glutamine Ra to estimate the endogenous production of glutamine in critically ill patients was demonstrated to be useful for repetitive measurements. The hypothesized attenuation of endogenous glutamine production during L-alanyl-L-glutamine infusion given as a part of full nutrition was not seen.

Mucosal CXCR4+ IgG plasma cells contribute to the pathogenesis of human ulcerative colitis through FcγR-mediated CD14 macrophage activation.

BACKGROUND: Chronic inflammation characterised by IgG-producing plasma cell infiltration of colonic mucosa is a histological hallmark of ulcerative colitis (UC); however, whether its function is pathogenic or protective remains unclear. OBJECTIVE: To explore the contribution of intestinal IgG plasma cells to UC pathogenesis. METHODS: We isolated lamina propria mononuclear cells (LPMCs) from intestinal mucosa of UC patients and analysed the characteristics of intestinal plasma cells (expression profiles of differentiation molecules and chemokine receptors). We investigated the involvement of IgG-immune complex (IC)-Fc gamma receptor (FcγR) signalling in intestinal inflammation by examining the cytokine production by LPMCs in response to IgG-IC stimulation. RESULTS: IgG plasma cells that were markedly increased in number in the inflamed mucosa of UC patients showed a distinct expression profile (CD19(+)CD27(low), CCR10(low)CXCR4(high)) compared with IgA plasma cells (CD19(+/-)CD27(high), CCR10(high)CXCR4(-/low)). In vitro IgG-IC stimulation activated intestinal CD14 macrophages that were increased in number in the inflamed mucosa of UC patients via FcγRI and FcγRII, and induced the extensive production of pro-inflammatory cytokines such as tumour necrosis factor (TNF) and interleukin-1ß (IL-1ß), comparable to the effect of commensal bacteria stimulation. Co-stimulation with IgG-IC and commensal bacteria increased TNF and IL-1ß production more than stimulation with the latter alone. Furthermore, IgG-IC notably up-regulated the expression of TL1A, whereas commensal bacteria specifically induced IL-23. CONCLUSIONS: Collectively, these results demonstrate a novel aspect of UC pathogenesis in which unique IgG plasma cells infiltrate the inflamed mucosa via CXCR4, and critically influence UC pathogenesis by exacerbating mucosal inflammation through the activation of 'pathogenic' intestinal CD14 macrophages via IgG-IC-FcγR signalling.

TGR5 signalling inhibits the production of pro-inflammatory cytokines by in vitro differentiated inflammatory and intestinal macrophages in Crohn's disease.

Bile acids (BAs) play important roles not only in lipid metabolism, but also in signal transduction. TGR5, a transmembrane receptor of BAs, is an immunomodulative factor, but its detailed mechanism remains unclear. Here, we aimed to delineate how BAs operate in immunological responses via the TGR5 pathway in human mononuclear cell lineages. We examined TGR5 expression in human peripheral blood monocytes, several types of in vitro differentiated macrophages (Mϕs) and dendritic cells. Mϕs differentiated with macrophage colony-stimulating factor and interferon-γ (Mγ-Mϕs), which are similar to the human intestinal lamina propria CD14(+) Mϕs that contribute to Crohn's disease (CD) pathogenesis by production of pro-inflammatory cytokines, highly expressed TGR5 compared with any other type of differentiated Mϕ and dendritic cells. We also showed that a TGR5 agonist and two types of BAs, deoxycholic acid and lithocholic acid, could inhibit tumour necrosis factor-α production in Mγ-Mϕs stimulated by commensal bacterial antigen or lipopolysaccharide. This inhibitory effect was mediated by the TGR5-cAMP pathway to induce phosphorylation of c-Fos that regulated nuclear factor-κB p65 activation. Next, we analysed TGR5 levels in lamina propria mononuclear cells (LPMCs) obtained from the intestinal mucosa of patients with CD. Compared with non-inflammatory bowel disease, inflamed CD LPMCs contained more TGR5 transcripts. Among LPMCs, isolated CD14(+) intestinal Mϕs from patients with CD expressed TGR5. In isolated intestinal CD14(+) Mϕs, a TGR5 agonist could inhibit tumour necrosis factor-α production. These results indicate that TGR5 signalling may have the potential to modulate immune responses in inflammatory bowel disease.

An evaluation of the impact of the implementation of the Tele-ICU: a retrospective observational study.

BACKGROUND: The telemedicine intensive care unit (Tele-ICU) is defined as a system in which intensive care professionals remotely provide care to critically ill patients and support the on-site staff in the intensive care unit (ICU) using secured audio-video and electronic links. Although the Tele-ICU is expected to resolve the shortage of intensivists and reduce the regional disparities in intensive care resources, the efficacy has not yet been evaluated in Japan because of a lack of clinically available system. METHODS: This was a single-center, historical comparison study in which the impact of the Tele-ICU on ICU performance and changes in workload of the on-site staff were evaluated. The Tele-ICU system developed in the United States was used. Data for 893 adult ICU patients before the Tele-ICU implementation and for all adult patients registered in the Tele-ICU system from April 2018 to March 2020 were abstracted and included. We investigated ICU and hospital mortality and length of stay and ventilation duration after the Tele-ICU implementation in each ICU, and compared between pre and post implementation and changes over time. We also assessed physician workload as defined by the frequency and duration of access to the electronic medical record (EMR) of the targeted ICU patients. RESULTS: After the Tele-ICU implementation 5438 patients were included. In unadjusted data pre/post study showed significant decreases in ICU (8.5-3.8%) and hospital (12.4-7.7%) mortality and ICU length of stay (p < 0.001), and those values were maintained for 2 years. In data stratified by predicted hospital mortality, ICU and hospital actual mortality in high and medium risk patients decreased significantly after the implementation. Ventilation duration was shortened (p < 0.007). Access frequency of the on-site physicians decreased by 25%, and the decrease occurred in the daytime shift and in the physicians with 3-15 years of work experience. CONCLUSIONS: Our study showed the Tele-ICU implementation was associated with lower mortality, especially in medium and high risk patients, and decreased EMR-related tasks of on-site physicians. These results suggest that the Tele-ICU could be a solution of the shortage of intensivists and regional disparities for intensive care.

Protein metabolism and gene expression in skeletal muscle of critically ill patients with sepsis.

Muscle wasting negatively affects morbidity and mortality in critically ill patients. This progressive wasting is accompanied by, in general, a normal muscle PS (protein synthesis) rate. In the present study, we investigated whether muscle protein degradation is increased in critically ill patients with sepsis and which proteolytic enzyme systems are involved in this degradation. Eight patients and seven healthy volunteers were studied. In vivo muscle protein kinetics was measured using arteriovenous balance techniques with stable isotope tracers. The activities of the major proteolytic enzyme systems were analysed in combination with mRNA expression of genes related to these proteolytic systems. Results show that critically ill patients with sepsis have a variable but normal muscle PS rate, whereas protein degradation rates are dramatically increased (up to 160%). Of the major proteolytic enzyme systems both the proteasome and the lysosomal systems had higher activities in the patients, whereas calpain and caspase activities were not changed. Gene expression of several genes related to the proteasome system was increased in the patients. mRNA levels of the two main lysosomal enzymes (cathepsin B and L) were not changed but, conversely, genes related to calpain and caspase had a higher expression in the muscles of the patients. In conclusion, the dramatic muscle wasting seen in critically ill patients with sepsis is due to increased protein degradation. This is facilitated by increased activities of both the proteasome and lysosomal proteolytic systems.

Early Palliative Care Improves Overall Survival in Patients With Lymphoma: A Single-institution Retrospective Study.

BACKGROUND/AIM: Early palliative care (EPC) intervention in patients with solid tumors can provide many benefits. However, studies on patients with hematological malignancies are limited, and there is no data on patients with lymphoma. We conducted a preliminary retrospective survey of palliative care (PC) intervention in patients with lymphoma to clarify the effect of EPC on overall survival (OS). PATIENTS AND METHODS: The first palliative care consultation (PC1) was retrospectively reviewed from medical records in Japan. Patients with lymphoma requiring inpatient PC at our institution from January 2012 to December 2018 were recruited. We conducted receiver operating characteristic (ROC) analysis; patients were divided into two groups (early and delayed), and the survival periods and palliative care team (PCT) referral details were compared. RESULTS: The analysis included 77 patients with lymphoma [median age, 71 (64-79)] years. The median period to PC1 from the initial diagnosis was 395 (180-1,086) days. ROC analysis revealed an optimal PC intervention timing of 140 days. OS was significantly longer in the early group than that in the delayed group. The most common counseling details for the PCT were symptom relief and palliative care transfer (36.8% and 35.2%, respectively). CONCLUSION: This real-world evaluation of PC intervention for inpatients with lymphoma revealed that PC intervention was provided at approximately 13 months following initial diagnosis. EPC intervention from diagnosis to 140 days may improve OS in patients with lymphoma; however further large-scale studies are required to verify this finding.

Correlation between serum albumin and serum zinc in malignant lymphoma.

Objectives: Zinc (Zn) is a cofactor for more than 200 enzymes within the human body. Zn deficiency can result in cell-mediated immune dysfunction. Furthermore, serum Zn levels have been reported to be associated with nutritional status, but this association has not been clarified in malignant lymphoma. This study aimed to examine the deficiency of serum Zn levels and clarify the factors that are correlated with serum Zn in malignant lymphoma. Methods: Initial malignant lymphoma was diagnosed in patients at Fujita Health University Hospital between April 2011 and March 2019. Based on the serum Zn levels, the study population was divided into "deficient" and "low or normal". For the serum Zn levels of patients undergoing pre-chemotherapy, laboratory parameters and nutritional factors were included. We compared these factors between the abovementioned two groups, and the serum Zn levels with its correlation factors were investigated. Results: A total of 77 patients (Deficient group, n=20 and Low or Normal group, n=57) were enrolled. Histology, hemoglobin, serum albumin levels, Glasgow Prognostic Score (GPS), neutrophile-lymphocyte ratio (NLR), prognostic nutrition index (PNI) and Controlling Nutritional Status (CONUT) were significantly different between the two groups. Of these parameters, only serum albumin level was significantly associated with serum Zn level (p=0.0024; estimated regression coefficient, 9.51; adjusted coefficient of determination, 0.28). Conclusions: Poor nutritional status at the initial diagnosis may have affected Zn deficiency in initial malignant lymphoma.

Roles of Early Mobilization Program in Preventing Muscle Weakness and Decreasing Psychiatric Disorders in Patients with Coronavirus Disease 2019 Pneumonia: A Retrospective Observational Cohort Study.

Although many coronavirus 2019 patients have experienced persistent symptoms and a long-term decline in quality of life after discharge, the details of these persistent symptoms and the effect of early rehabilitation are still unclear. We conducted a single-center, retrospective observational study to investigate the prevalence of persistent symptoms three months after discharge from the intensive care unit by checking the medical records. All patients received an early mobilization program. Four out of 13 patients (31%) had postintensive care syndrome. No patients had muscle weakness, and 11 patients (85%) returned to their previous work. However, psychiatric disorder, such as anxiety (23%) and posttraumatic stress disorder (15%), were observed. Eleven patients claimed persistent symptoms, including fatigue and numbness in the extremities. Our results suggest that the implementation of an early rehabilitation program plays some role in preventing muscle weakness and that decreasing psychiatric disorders should be a next target of patient care in the intensive care unit.

Genetic basis for plasma amino acid concentrations based on absolute quantification: a genome-wide association study in the Japanese population.

To assess the use of plasma free amino acids (PFAAs) as biomarkers for metabolic disorders, it is essential to identify genetic factors that influence PFAA concentrations. PFAA concentrations were absolutely quantified by liquid chromatography-mass spectrometry using plasma samples from 1338 Japanese individuals, and genome-wide quantitative trait locus (QTL) analysis was performed for the concentrations of 21 PFAAs. We next conducted a conditional QTL analysis using the concentration of each PFAA adjusted by the other 20 PFAAs as covariates to elucidate genetic determinants that influence PFAA concentrations. We identified eight genes that showed a significant association with PFAA concentrations, of which two, SLC7A2 and PKD1L2, were identified. SLC7A2 was associated with the plasma levels of arginine and ornithine, and PKD1L2 with the level of glycine. The significant associations of these two genes were revealed in the conditional QTL analysis, but a significant association between serine and the CPS1 gene disappeared when glycine was used as a covariate. We demonstrated that conditional QTL analysis is useful for determining the metabolic pathways predominantly used for PFAA metabolism. Our findings will help elucidate the physiological roles of genetic components that control the metabolism of amino acids.

Serial changes in expression of functionally clustered genes in progression of liver fibrosis in hepatitis C patients.

AIM: To investigate the relationship of changes in expression of marker genes in functional categories or molecular networks comprising one functional category or multiple categories in progression of hepatic fibrosis in hepatitis C (HCV) patients. METHODS: Marker genes were initially identified using DNA microarray data from a rat liver fibrosis model. The expression level of each fibrosis associated marker gene was analyzed using reverse transcription-polymerase chain reaction (RT-PCR) in clinical biopsy specimens from HCV-positive patients (n = 61). Analysis of changes in expression patterns and interactions of marker genes in functional categories was used to assess the biological mechanism of fibrosis. RESULTS: The profile data showed several biological changes associated with progression of hepatic fibrosis. Clustered genes in functional categories showed sequential changes in expression. Several sets of clustered genes, including those related to the extracellular matrix (ECM), inflammation, lipid metabolism, steroid metabolism, and some transcription factors important for hepatic biology showed expression changes in the immediate early phase (F1/F2) of fibrosis. Genes associated with aromatic amino acid (AA) metabolism, sulfur-containing AA metabolism and insulin/ Wnt signaling showed expression changes in the middle phase (F2/F3), and some genes related to glucose metabolism showed altered expression in the late phase of fibrosis (F3/F4). Therefore, molecular networks showing serial changes in gene expression are present in liver fibrosis progression in hepatitis C patients. CONCLUSION: Analysis of gene expression profiles from a perspective of functional categories or molecular networks provides an understanding of disease and suggests new diagnostic methods. Selected marker genes have potential utility for biological identification of advanced fibrosis.

Classification of acute pain trajectory after breast cancer surgery identifies patients at risk for persistent pain: a prospective observational study.

PURPOSE: Predictive value and accuracy of the acute pain trajectory were compared with those of pain intensity at 1 day after the surgery for pain prevalence at 6 months after the surgery. MATERIALS AND METHODS: Female patients scheduled for breast cancer surgery were eligible for this study. Patients were questioned about pain intensity daily during the 7 days after surgery. Presence of pain, its location, and intensity as well as the Japanese version of the quality of the recovery-40 (QOR-40) were determined in an interview prior to and at 6 months after the surgery. Acute pain trajectory was determined by a group-based trajectory modeling analysis that was based on the pain intensity at 1-7 days after surgery. Predictive value of the acute pain trajectory for the presence of pain at 6 months after the surgery was assessed by a logistic regression model. The predictive value was compared with pain intensity at 1 day after the surgery. RESULTS: A total of 123 participants completed the 6-month follow-up. The three-cluster model (mild, moderate, and severe pain) was considered to be the most statistically appropriate model for the acute pain trajectory. After 6 months, 51.2% and 8.9% of participants reported pain and severe pain, respectively. Presence of pain at 6 months after the surgery was associated with poor recovery. The severe pain cluster was significantly associated with the presence of pain at 6 months after the surgery (adjusted odds ratio, 9.40; P<0.001 vs mild pain cluster). CONCLUSION: Classification of patients according to the acute pain trajectory, when compared with the classification according to pain intensity at 1 day after the surgery, made it possible to predict with better precision those patients who will develop persistent postsurgical pain.

Relationship between regional population and healthcare delivery in Japan.

In order to address regional inequality in healthcare delivery in Japan, healthcare districts were established in 1985. However, regional healthcare delivery has now become a national issue because of population migration and the aging population. In this study, the state of healthcare delivery at the district level is examined by analyzing population, the number of physicians, and the number of hospital beds. The results indicate a continuing disparity in healthcare delivery among districts. We find that the rate of change in population has a strong positive correlation with that in the number of physicians and a weak positive correlation with that in the number of hospital beds. In addition, principal component analysis is performed on three variables: the rate of change in population, the number of physicians per capita, and the number of hospital beds per capita. This analysis suggests that the two principal components contribute 90.1% of the information. The first principal component is thought to show the effect of the regulations on hospital beds. The second principal component is thought to show the capacity to recruit physicians. This study indicates that an adjustment to the regulations on hospital beds as well as physician allocation by public funds may be key to resolving the impending issue of regionally disproportionate healthcare delivery.

Decreased Plasma Histidine Level Predicts Risk of Relapse in Patients with Ulcerative Colitis in Remission.

Ulcerative colitis (UC) is characterized by chronic intestinal inflammation. Patients with UC have repeated remission and relapse. Clinical biomarkers that can predict relapse in UC patients in remission have not been identified. To facilitate the prediction of relapse of UC, we investigated the potential of novel multivariate indexes using statistical modeling of plasma free amino acid (PFAA) concentrations. We measured fasting PFAA concentrations in 369 UC patients in clinical remission, and 355 were observed prospectively for up to 1 year. Relapse rate within 1 year was 23% (82 of 355 patients). The age- and gender-adjusted hazard ratio for the lowest quartile compared with the highest quartile of plasma histidine concentration was 2.55 (95% confidence interval: 1.41-4.62; p = 0.0020 (log-rank), p for trend = 0.0005). We demonstrated that plasma amino acid profiles in UC patients in clinical remission can predict the risk of relapse within 1 year. Decreased histidine level in PFAAs was associated with increased risk of relapse. Metabolomics could be promising for the establishment of a non-invasive predictive marker in inflammatory bowel disease.

Food antigen-induced immune responses in Crohn's disease patients and experimental colitis mice.

BACKGROUND: In Crohn's disease (CD), the involvement of food antigens in immune responses remains unclear. The objective of this study was to detect immune responses against food antigens in CD patients and examine the mechanism in a mouse model of colitis. METHODS: We enrolled 98 CD patients, 50 ulcerative colitis patients, and 52 healthy controls (HCs) to compare the levels of serum immunoglobulin (Ig)Gs against 88 foods. The presence of serum IgGs against foods was also examined in interleukin (IL)-10 knockout (KO) mice in which CD4(+) T cell activation by antigenic food protein was assessed. Mice transferred with IL-10 KO cells received diets with or without food antigens, and the development of colitis was evaluated. RESULTS: The prevalence of IgGs against various foods, especially vegetables, grains, and nuts, was significantly higher in CD patients than in HCs. Similarly, the prevalence of IgGs against food proteins was higher in IL-10 KO mice than in BALB/c mice. Beta-conglycinin, identified as an antigenic food proteins in IL-10 KO mice, induced CD4(+) T cell production of interferon-γ and IL-17 through dendritic cell antigen presentation. Elimination of the food antigens ameliorated the development of colitis in mice without altering the composition of their intestinal microbiota. CONCLUSIONS: In CD colitis mice, intestinal inflammation via CD4(+) T cell hyperactivation was induced by food antigens associated with high serum IgG levels and was ameliorated by the elimination of food antigens. This disrupted immunological tolerance to food antigen, which might act as an exacerbating factor, remains to be elucidated in CD patients.

The performance of a novel amino acid multivariate index for detecting lung cancer: A case control study in Korea.

INTRODUCTION: Previous studies have shown that plasma free amino acid (PFAA) profiles are altered in cancer patients compared with healthy controls. A multivariate index based on PFAAs was generated from a Japanese dataset and has been previously demonstrated to be clinically valuable for discriminating patients in the early stages of lung cancer. However, it remains unclear whether similar PFAA profile changes occur in cancer patients from other populations. Therefore, this study aimed to validate the performance of this index in discriminating lung cancer patients from controls in the Korean population. METHODS: Samples were collected from a total of 142 Korean subjects (72 lung cancer/70 controls) for this study. PFAAs were quantified by high-performance liquid chromatography-electrospray ionization-mass spectrometry, and the clinical performance characteristics of the amino acid multivariate index were evaluated across cancer stages and histological types. RESULTS: The concentrations of several PFAAs were significantly decreased in the Korean lung cancer patients compared with the controls. Significant decreases in threonine, citrulline, histidine and tryptophan and increases in proline, isoleucine, phenylalanine and ornithine were observed, which are similar to the PFAA changes reported by a previous Japanese study. The area under the receiver-operator characteristic curve (AUC of the ROC) for the index was 0.80, and similar performances were demonstrated for the different histological types. CONCLUSIONS: These results suggest that the amino acid multivariate index previously developed from a Japanese dataset has the potential to aid in the early detection of lung cancers of different histological types in Korean patients.

A tracer bolus method for investigating glutamine kinetics in humans.

Glutamine transport between tissues is important for the outcome of critically ill patients. Investigation of glutamine kinetics is, therefore, necessary to understand glutamine metabolism in these patients in order to improve future intervention studies. Endogenous glutamine production can be measured by continuous infusion of a glutamine tracer, which necessitates a minimum measurement time period. In order to reduce this problem, we used and validated a tracer bolus injection method. Furthermore, this method was used to measure the glutamine production in healthy volunteers in the post-absorptive state, with extra alanine and with glutamine supplementation and parenteral nutrition. Healthy volunteers received a bolus injection of [1-13C] glutamine, and blood was collected from the radial artery to measure tracer enrichment over 90 minutes. Endogenous rate of appearance (endoRa) of glutamine was calculated from the enrichment decay curve and corrected for the extra glutamine supplementation. The glutamine endoRa of healthy volunteers was 6.1±0.9 µmol/kg/min in the post-absorptive state, 6.9±1.0 µmol/kg/min with extra alanyl-glutamine (p = 0.29 versus control), 6.1±0.4 µmol/kg/min with extra alanine only (p = 0.32 versus control), and 7.5±0.9 µmol/kg/min with extra alanyl-glutamine and parenteral nutrition (p = 0.049 versus control). In conclusion, a tracer bolus injection method to measure glutamine endoRa showed good reproducibility and small variation at baseline as well as during parenteral nutrition. Additionally, we showed that parenteral nutrition including alanyl-glutamine increased glutamine endoRa in healthy volunteers, which was not attributable to the alanine part of the dipeptide.