Reference intervals for plasma-free amino acid in a Japanese population

Comprehensive GC-MS Measurement of Amino Acids, Metabolites, and Malondialdehyde in Metformin-Associated Lactic Acidosis at Admission and during Renal Replacement Treatment

Metformin is the most widely used drug in type 2 diabetes. Regular metformin use has been associated with changes in concentrations of amino acids. In the present study, we used valid stable-isotope labeled GC-MS methods to measure amino acids and metabolites, including creatinine as well as malondialdehyde (MDA), as an oxidative stress biomarker in plasma, urine, and dialysate samples in a patient at admission to the intensive care unit and during renal replacement treatment because of metformin-associated lactic acidosis (MALA, 21 mM lactate, 175 µM metformin). GC-MS revealed lower concentrations of amino acids in plasma, normal concentrations of the nitric oxide (NO) metabolites nitrite and nitrate, and normal concentrations of MDA. Renal tubular reabsorption rates were altered on admission. The patient received renal replacement therapy over 50 to 70 h of normalized plasma amino acid concentrations and their tubular reabsorption, as well as the tubular reabsorption of nitrite and nitrate. This study indicates that GC-MS is a versatile analytical tool to measure different classes of physiological inorganic and organic substances in complex biological samples in clinical settings such as MALA.

Differences in branched-chain amino acid to tyrosine ratio (BTR) among etiologies of chronic liver disease progression compared to healthy adults

BACKGROUND

The branched-chain amino acids (BCAAs) to tyrosine (Tyr) ratio (BTR) test is used to evaluate the progression of chronic liver disease (CLD). However, the differences across sex, age, body mass index (BMI) and etiologies are still unclear.

METHODS

We retrospectively reviewed data from 2,529 CLD cases with free amino acids (FAAs) in peripheral blood from four hospitals and 16,421 general adults with FAAs data from a biobank database. In total, 1,326 patients with CLD (covering seven etiologies) and 8,086 healthy controls (HCs) were analyzed after exclusion criteria. We investigated the change of BTR in HCs by sex, age and BMI and then compared these to patients divided by modified ALBI (mALBI) grade after propensity score matching.

RESULTS

BTR is significantly higher in males than females regardless of age or BMI and decreases with aging in HCs. In 20 types of FAAs, 7 FAAs including BCAAs were significantly decreased, and 11 FAAs including Tyr were significantly increased by mALBI grade in total CLD. The decreasing timings of BTR were at mALBI grade 2b in all CLD etiologies compared to HCs, however in chronic hepatitis C (CHC), chronic hepatitis B (CHB) and alcoholic liver disease (ALD), BTR started to decrease at 2a. There was a positive correlation between BCAAs and albumin among parameters in BTR and mALBI. The correlation coefficients in PBC, ALD and MASLD were higher than those of other etiologies.

CONCLUSIONS

BTR varies by sex and age even among healthy adults, and decreasing process and timing of BTR during disease progression is different among CLD etiologies.

Investigation of amino acid profile alterations in maternal serum for early diagnosis of anembryonic pregnancy with high performance liquid chromatography-mass spectrometry

BACKGROUND

Anembryonic pregnancy affects 12-15 % of clinically recognized pregnancies and a previous anembryonic pregnancy is an independent risk factor for future anembryonic pregnancy. This study aimed to investigate alternations in maternal amino acid profiles and analyze the diagnostic accuracy of amino acid biomarkers for anembryonic pregnancy in the early stage.

METHODS

Fasting serum from anembryonic pregnancy patients (n = 103) and healthy pregnancies (n = 97) was collected, and amino acid concentrations were determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). A receiver operating characteristic (ROC) curve was used to evaluate the diagnostic performance of each of the amino acid biomarkers and the amino acid profile index for anembryonic pregnancy screening.

RESULTS

The concentrations of 15 amino acids were significantly different between anembryonic pregnancy patients and healthy controls, and most of them were significantly higher at 7 weeks' gestational age in anembryonic pregnancy subjects. The area under the curve (AUC) based on an amino acid profile index combined with alanine, citrulline, aspartic acid, threonine, serine and isoleucine was 0.90 (sensitivity 82.76 %, specificity 83.64 %) for distinguishing early anembryonic pregnancy from healthy controls.

CONCLUSION

Maternal serum amino acid concentrations were significantly elevated in anembryonic pregnancy patients. The diagnostic potential of amino aicds for anembryonic pregnancy was verified, and the diagnostic efficiency was improved in the use of the amino acid profile index. The amino acid profile is expected to be applied for the risk screening of early-stage of anembryonic pregnancy in the future.

Sex-related differences in within-subject biological variation estimates for 22 essential and non-essential amino acids

BACKGROUND

Measurement of serum amino acid (AA) concentrations is important in particular for the diagnosis and monitoring of inborn errors of AA metabolism. To ensure optimal clinical interpretation of AAs, reliable biological variation (BV) data are essential. In the present study, we derived BV data for 22 non-essential, conditionally essential, and essential AAs and assessed differences in BV of AAs related to sex.

METHODS

Morning blood samples were drawn from 66 subjects (31 males and 35 females) once a week for 10 consecutive weeks. All samples were analyzed in duplicate using liquid chromatography-tandem mass-spectrometry. The data were assessed for outliers, trends, normality and variance homogeneity analysis prior to estimating within-subject (CVI) and between-subject (CVG) BV.

RESULTS

CVI estimates ranged from 9.0 % for histidine (male) to 33.0 % for taurine (male). CVI estimates in males and females were significantly different for all AAs except for aspartic acid, citrulline and phenylalanine, in most cases higher in females than in males. Apart from for arginine, CVG estimates in males and females were similar.

CONCLUSIONS

In this highly powered BV study, we provide updated BV estimates for 22 AAs and demonstrate that for most AAs, CVI estimates differ between males and females, with implications for interpretation and use of AAs in clinical practice.

Vitamin B and One-Carbon Metabolite Profiles Show Divergent Associations with Cardiometabolic Risk Markers but not Cognitive Function in Older New Zealand Adults: A Secondary Analysis of the REACH Study

BACKGROUND

Vitamin B inadequacies and elevated homocysteine status have been associated with impaired cognitive and cardiometabolic health with aging. There is, however, a scarcity of research investigating integrated profiles of one-carbon (1C) metabolites in this context, including metabolites of interconnected folate, methionine, choline oxidation, and transsulfuration pathways.

OBJECTIVES

The study aimed to examine associations between vitamins B and 1C metabolites with cardiometabolic health and cognitive function in healthy older adults, including the interactive effects of Apolipoprotein E-ε4 status.

METHODS

Three hundred and thirteen healthy participants (65-74 y, 65% female) were analyzed. Vitamins B were estimated according to dietary intake (4-d food records) and biochemical status (serum folate and vitamin B12). Fasting plasma 1C metabolites were quantified by liquid chromatography with tandem mass spectrometry. Measures of cardiometabolic health included biochemical (lipid panel, blood glucose) and anthropometric markers. Cognitive function was assessed by the Computerized Mental Performance Assessment System (COMPASS) and Montreal Cognitive Assessment (MoCA). Associations were analyzed using multivariate linear (COMPASS, cardiometabolic health) and Poisson (MoCA) regression modeling.

RESULTS

Over 90% of participants met dietary recommendations for riboflavin and vitamins B6 and B12, but only 78% of males and 67% of females achieved adequate folate intakes. Higher serum folate and plasma betaine and glycine concentrations were associated with favorable cardiometabolic markers, whereas higher plasma choline and homocysteine concentrations were associated with greater cardiometabolic risk based on body mass index and serum lipids concentration values (P< 0.05). Vitamins B and homocysteine were not associated with cognitive performance in this cohort, though higher glycine concentrations were associated with better global cognitive performance (P = 0.017), episodic memory (P = 0.016), and spatial memory (P = 0.027) scores. Apolipoprotein E-ε4 status did not modify the relationship between vitamins B or 1C metabolites with cognitive function in linear regression analyses.

CONCLUSIONS

Vitamin B and 1C metabolite profiles showed divergent associations with cardiometabolic risk markers and limited associations with cognitive performance in this cohort of healthy older adults.

Quality Control in Targeted GC-MS for Amino Acid-OMICS

Gas chromatography-mass spectrometry (GC-MS) is suitable for the analysis of non-polar analytes. Free amino acids (AA) are polar, zwitterionic, non-volatile and thermally labile analytes. Chemical derivatization of AA is indispensable for their measurement by GC-MS. Specific conversion of AA to their unlabeled methyl esters (d0Me) using 2 M HCl in methanol (CH3OH) is a suitable derivatization procedure (60 min, 80 °C). Performance of this reaction in 2 M HCl in tetradeutero-methanol (CD3OD) generates deuterated methyl esters (d3Me) of AA, which can be used as internal standards in GC-MS. d0Me-AA and d3Me-AA require subsequent conversion to their pentafluoropropionyl (PFP) derivatives for GC-MS analysis using pentafluoropropionic anhydride (PFPA) in ethyl acetate (30 min, 65 °C). d0Me-AA-PFP and d3Me-AA-PFP derivatives of AA are readily extractable into water-immiscible, GC-compatible organic solvents such as toluene. d0Me-AA-PFP and d3Me-AA-PFP derivatives are stable in toluene extracts for several weeks, thus enabling high throughput quantitative measurement of biological AA by GC-MS using in situ prepared d3Me-AA as internal standards in OMICS format. Here, we describe the development of a novel OMICS-compatible QC system and demonstrate its utility for the quality control of quantitative analysis of 21 free AA and metabolites in human plasma samples by GC-MS as Me-PFP derivatives. The QC system involves cross-standardization of the concentrations of the AA in their aqueous solutions at four concentration levels and a quantitative control of AA at the same four concentration levels in pooled human plasma samples. The retention time (tR)-based isotope effects (IE) and the difference (δ(H/D) of the retention times of the d0Me-AA-PFP derivatives (tR(H)) and the d3Me-AA-PFP derivatives (tR(D)) were determined in study human plasma samples of a nutritional study (n = 353) and in co-processed QC human plasma samples (n = 64). In total, more than 400 plasma samples were measured in eight runs in seven working days performed by a single person. The proposed QC system provides information about the quantitative performance of the GC-MS analysis of AA in human plasma. IE, δ(H/D) and a massive drop of the peak area values of the d3Me-AA-PFP derivatives may be suitable as additional parameters of qualitative analysis in targeted GC-MS amino acid-OMICS.

Plasma amino acid signature for sarcopenic phenotypes in community-dwelling octogenarians: Results from the Kawasaki Aging Wellbeing Project

Sarcopenia is one of the primary risk factors for various adverse health events in later life. However, its pathophysiology in the very old population remains unclear. Hence, this study aimed to examine whether plasma free amino acids (PFAAs) correlate with major sarcopenic phenotypes (i.e., muscle mass, muscle strength, and physical performance) in community-dwelling adults aged 85-89 years living in Japan. Cross-sectional data from the Kawasaki Aging Well-being Project were used. We included 133 adults aged 85-89 years. In this study, fasting blood was collected to measure 20 plasma PFAAs. Measures for the three major sarcopenic phenotypes included appendicular lean mass assessed by multifrequency bioimpedance, isometric handgrip strength, and gait speed from a 5 m walk at a usual pace. Furthermore, we used phenotype-specific elastic net regression models adjusted for age centered at 85 years, sex, body mass index, education level, smoking status, and drinking habit to identify significant PFAAs for each sarcopenic phenotype. Higher histidine and lower alanine levels were associated with poor gait speed, but no PFAAs correlated with muscle strength or mass. In conclusion, PFAAs such as plasma histidine and alanine are novel blood biomarkers associated with physical performance in community-dwelling adults aged 85 years or older.

Associations of sleep quality with the skeletal muscle strength in patients with type 2 diabetes with poor glycemic control

AIMS/INTRODUCTION

Patients with type 2 diabetes mellitus are reported to be at a high risk for sarcopenia, and are known to have a poorer sleep quality. However, the association between sleep quality and skeletal muscle in patients with type 2 diabetes mellitus is not yet precisely understood.

MATERIALS AND METHODS

A total of 110 inpatients with type 2 diabetes mellitus aged 40-90 years were enrolled. The sleep quality was assessed using the Pittsburgh sleep quality index (PSQI). Skeletal muscle mass was measured using bioelectrical impedance analysis. Muscle strength was evaluated by measuring the grip strength. We also performed dietary surveys and measurements of the plasma amino acid levels.

RESULTS

A high total score on the PSQI was significantly associated with reduced muscle strength, and the association persisted even after adjustments for confounders. On the other hand, adjusted analysis did not reveal any significant associations between the PSQI total score and the skeletal muscle mass. In regard to the associations with subscores of the PSQI, the scores for sleep latency, sleep efficiency, and daytime dysfunction were significantly negatively associated with the muscle strength. Although poor sleep quality was associated with a high confectionery intake and low plasma arginine, citrulline, and ornithine levels, neither confectionery intake levels nor the plasma levels of these amino acids was associated with the muscle strength.

CONCLUSIONS

Our study revealed a significant association between the sleep quality and muscle strength in patients with type 2 diabetes mellitus. These results suggest that poor sleep quality is an important risk factor for sarcopenia in patients with type 2 diabetes mellitus.

A spectrophotometric method for the determination of tryptophan following oxidation by the addition of sodium hypochlorite pentahydrate

Tryptophan (Trp) is an essential amino acid that functions in various biological processes and human daily health. As the significant functions of Trp become more apparent, its measurement is becoming increasingly important in various situations. Herein, we improved the Trp color reaction based on the Hopkins-Cole reaction and established a simple colorimetric method for Trp determination using several different reagents, including sodium hypochlorite pentahydrate and monosodium glutamate. The detection method can be performed using safe materials, rather than conventional toxic substances, and induces a crimson color change with an absorption peak at 525 nm, enabling the quantification of Trp by simple spectrophotometry in just 10 min. This assay exhibited a linear detection range from 10 to 100 mg/L (R2 = 0.9996). The average recoveries in the spiked cerebrospinal fluid ranged from 90.5% to 104.3%, with a relative standard deviation of 0.27% (n = 3, 29.40 mg/L Trp) to 1.19% (n = 3, 72.90 mg/L Trp). This novel spectrophotometric method may enable many researchers and laboratory technicians to detect Trp in various sample solutions without expensive analytical instruments or complicated operations.

Arginine concentration in arterial vs venous blood in a bleomycin-induced lung inflammation model in mice

Pneumonia, always a major malady, became the main public health and economic disaster of historical proportions with the COVID-19 pandemic. This study was based on a premise that pathology of lung metabolism in inflammation may have features invariant to the nature of the underlying cause. Amino acid uptake by the lungs was measured from plasma samples collected pre-terminally from a carotid artery and vena cava in mice with bleomycin-induced lung inflammation (N = 10) and compared to controls treated with saline instillation (N = 6). In the control group, the difference in concentrations between the arterial and venous blood of the 19 amino acids measured reached the level of statistical significance only for arginine (-10.7%, p = 0.0372) and phenylalanine (+5.5%, p = 0.0266). In the bleomycin group, 11 amino acids had significantly lower concentrations in the arterial blood. Arginine concentration was decreased by 21.1% (p<0.0001) and only that of citrulline was significantly increased (by 20.1%, p = 0.0002). Global Arginine Bioavailability Ratio was decreased in arterial blood by 19.5% (p = 0.0305) in the saline group and by 30.4% (p<0.0001) in the bleomycin group. Production of nitric oxide (NO) and citrulline from arginine by the inducible nitric oxide synthase (iNOS) is greatly increased in the immune system's response to lung injury. Deprived of arginine, the endothelial cells downstream may fail to provide enough NO to prevent the activation of thrombocytes. Thrombotic-related vascular dysfunction is a defining characteristic of pneumonia, including COVID-19. This experiment lends further support to arginine replacement as adjuvant therapy in pneumonia.

Decreased circulating branched-chain amino acids are associated with development of Alzheimer's disease in elderly individuals with mild cognitive impairment

Background

Nutritional epidemiology has shown that inadequate dietary protein intake is associated with poor brain function in the elderly population. The plasma free amino acid (PFAA) profile reflects nutritional status and may have the potential to predict future changes in cognitive function. Here, we report the results of a 2-year interim analysis of a 3-year longitudinal study following mild cognitive impairment (MCI) participants.

Method

In a multicenter prospective cohort design, MCI participants were recruited, and fasting plasma samples were collected. Based on clinical assessment of cognitive function up to 2 years after blood collection, MCI participants were divided into two groups: remained with MCI or reverted to cognitively normal ("MCI-stable," N = 87) and converted to Alzheimer's disease (AD) ("AD-convert," N = 68). The baseline PFAA profile was compared between the two groups. Stratified analysis based on apolipoprotein E ε4 (APOE ε4) allele possession was also conducted.

Results

Plasma concentrations of all nine essential amino acids (EAAs) were lower in the AD-convert group. Among EAAs, three branched-chain amino acids (BCAAs), valine, leucine and isoleucine, and histidine (His) exhibited significant differences even in the logistic regression model adjusted for potential confounding factors such as age, sex, body mass index (BMI), and APOE ε4 possession (p < 0.05). In the stratified analysis, differences in plasma concentrations of these four EAAs were more pronounced in the APOE ε4-negative group.

Conclusion

The PFAA profile, especially decreases in BCAAs and His, is associated with development of AD in MCI participants, and the difference was larger in the APOE ε4-negative population, suggesting that the PFAA profile is an independent risk indicator for AD development. Measuring the PFAA profile may have importance in assessing the risk of AD conversion in the MCI population, possibly reflecting nutritional status.

Clinical trial registration

[https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000025322], identifier [UMIN000021965].

Essential amino acids as diagnostic biomarkers of hepatocellular carcinoma based on metabolic analysis

Metabolomics, defined as the comprehensive identification of all small metabolites in a biological sample, has the power to shed light on phenotypic changes associated with various diseases, including cancer. To discover potential metabolomic biomarkers of hepatocellular carcinoma (HCC), we investigated the metabolomes of tumor and non-tumor tissue in 20 patients with primary HCC using capillary electrophoresis-time-of-flight mass spectrometry. We also analyzed blood samples taken immediately before and 14 days after hepatectomy to identify associated changes in the serum metabolome. Marked changes were detected in the different quantity of 61 metabolites that could discriminate between HCC tumor and paired non-tumor tissue and additionally between HCC primary tumors and colorectal liver metastases. Among the 30 metabolites significantly upregulated in HCC tumors compared with non-tumor tissues, 10 were amino acids, and 7 were essential amino acids (leucine, valine, tryptophan, isoleucine, methionine, lysine, and phenylalanine). Similarly, the serum metabolomes of HCC patients before hepatectomy revealed a significant increase in 16 metabolites, including leucine, valine, and tryptophan. Our results reveal striking differences in the metabolomes of HCC tumor tissue compared with non-tumor tissue, and identify the essential amino acids leucine, valine, and tryptophan as potential metabolic biomarkers for HCC.

Amino acid availability enhanced through glucose coadministration of amino acid supplementation during hemodiafiltration: two case reports

Background

Intravenous administration of amino acid (AA) formulation (IVAA) as intradialytic parenteral nutrition is widely used for malnourished patients with end-stage kidney disease (ESKD) treated with hemodialysis (HD) or hemodiafiltration (HDF). Although various therapy recipes such as AA compositions or simultaneous administration of glucose and/or lipids have been attempted, the specific effects of each recipe on AA behaviors and metabolic consequences have not been well investigated. To clarify the effect of simultaneous glucose administration with IVAA, we investigated the behavior of AAs, insulin as a metabolic hormone, and energy-related metabolites during an HDF session in two patients.

Case presentation

We aimed to determine the effect of IVAA with or without simultaneous glucose administration. The plasma levels of AAs, branched-chain AAs (leucine, isoleucine, and valine), major nonessential AAs (alanine and glutamine with glutamate), insulin, glucose, and ketone bodies were measured before HDF and at the second hour (prior to the meal in the HDF session). Lost AAs in the spent dialysate were also measured for the first two hours during the HDF session.

Conclusion

In the absence of glucose administration, plasma AA levels and the loss of AAs in the dialysate increased owing to IVAA, with the increase in plasma levels in ketone bodies occurring because of scarce secretion of plasma insulin. In the presence of glucose administration, plasma levels and the loss of AA decreased even when the same amount of AAs was injected, possibly because of the profound secretion of insulin with a decrease in ketone bodies. The present findings suggest that the metabolic effects of simultaneous glucose administration on IVAAs enhanced AA uptake into the body during HDF sessions, which might increase the effectiveness of IVAAs.

Specific amino acids regulate Sestrin2 mRNA and protein levels in an ATF4-dependent manner in C2C12 myocytes

BACKGROUND

Sestrin2 is a conserved protein in several species, and its expression is upregulated in cells under various environmental stresses. Sestrin2 content is involved in the function of mechanistic target of rapamycin complex 1 (mTORC1) in mouse embryonic fibroblasts and C2C12 cells.

METHODS

C2C12 cells were treated with amino acid-free DMEM (AF-DMEM) for 5 h. The effects of the addition of specific amino acids to AF-DMEM on Sestrin2 mRNA and protein expression were examined using RT-qPCR and western blotting, respectively. The mechanism by which amino acids regulate Sestrin2 mRNA expression was examined using blocking and siRNA experiments.

RESULTS

AF-DMEM increased the mRNA and protein levels of both Sestrin2 and activating transcription factor 4 (ATF4). The addition of a specific amino acid changed Sestrin2 mRNA and protein levels. The response pattern of Sestrin2 to specific amino acids was similar to that of ATF4. ATF4 siRNA reduced Sestrin2 mRNA levels. AF-DMEM increased eukaryotic initiation factor 2α (eIF2α) phosphorylation as early as 10 min after the treatment; however, ATF4 and Sestrin2 were increased 300 min after the treatment. Nuclear factor erythroid 2-related factor 2 and pancreatic and duodenal homeobox 1 siRNA did not affect ATF4 and Sestrin2 mRNA expression.

CONCLUSIONS

Specific Amino acids regulate Sestrin2 levels in an ATF4-dependent manner in C2C12 cells.

GENERAL SIGNIFICANCE

The results of the present study indicate that amino acids regulate levels of Sestrin2, which might cause phenotypic alterations, including mTORC1 activity, in C2C12 cells.

Circulatory amino acid responses to milk consumption in dairy and lactose intolerant individuals

Background/objectives

Self-reported digestive intolerance to dairy foods is common. As dairy can be an important source of dietary protein, this study aimed to identify whether milk protein digestion is compromised in individuals with digestive intolerance.

Subjects/methods

Adult women (n = 40) were enroled in this double-blinded, randomised cross-over trial, with digestive symptoms characterised using a lactose challenge and self-reported digestive symptom questionnaire. Participants were classified as either lactose intolerant (LI, n = 10), non-lactose dairy intolerant (NLDI, n = 20) or dairy tolerant (DT, n = 10). In a randomised sequence, participants consumed three different kinds of milk (750 ml); conventional milk (CON), a2 Milk™ (A2M), and lactose-free conventional milk (LF-CON). Circulatory plasma amino acid (AA) concentrations were measured at baseline and every 30 min until 3 h post-ingestion.

Results

In all participants across all milk types, plasma AA concentrations (AUC_0-180) increased after milk ingestion with no significant differences in responses observed between milk types or participants (P > 0.05), with the exception of the suppressed lysine response in the DT group following A2M ingestion, relative to the other two groups and milk types (P < 0.05).

Conclusion

Milk protein digestion, as determined by circulatory AAs, is largely unaffected by dairy- and lactose- intolerances.

Lysine and homoarginine are closely interrelated metabolites in the rat

L-Lysine (Lys) and L-arginine (Arg), but not L-homoarginine (hArg), are proteinogenic amino acids. In healthy humans, oral administration of hArg increased the plasma concentration of Lys, suggesting Lys as a metabolite of hArg. In humans and animals, hArg is biosynthesized from Arg and Lys by arginine:glycine amidinotransferase (AGAT). In vitro, recombinant human arginase and bovine liver arginase I hydrolyzed hArg to Lys, suggesting Lys as a metabolite of hArg. The aim of the present study was to investigate whether changes in blood concentrations of hArg and Lys in old rats fed for 4 months with varied controlled experimental diets could suggest interconversion of these amino acids. Blood samples (n = 253) were taken before (T0) and after 2 months (T2) and 4 months (T4) of the experiment. Plasma concentrations of Lys and hArg were determined by gas chromatography-mass spectrometry. The plasma hArg concentration markedly correlated with the plasma Lys concentration at all timepoints (r ≥ 0.7, P < 0.0001). Further analysis demonstrated that hArg and Lys are closely and specifically associated independently of experimental time/rat age and diet, suggesting that hArg and Lys are mutual metabolites in old rats. Based on the plasma concentration changes, the median yield of hArg from Lys was determined to be 0.17% at T0 and each 0.27% at T2 and T4. With a circulating concentration of about 3 µM, hArg a major metabolite of Lys in healthy humans. hArg supplementation is currently investigated as a cardioprotective means to improve impaired hArg synthesis. Present knowledge suggests that Lys rather than hArg supplementation may be even more favorable.

Development of a Novel Nutrition-Related Multivariate Biomarker for Mild Cognitive Impairment Based on the Plasma Free Amino Acid Profile

Nutritional epidemiology has shown the importance of protein intake for maintaining brain function in the elderly population. Mild cognitive impairment (MCI) may be associated with malnutrition, especially protein intake. We explored blood-based biomarkers linking protein nutritional status with MCI in a multicenter study. In total, 219 individuals with MCI (79.5 ± 5.7 year) from 10 institutions and 220 individuals who were cognitively normal (CN, 76.3 ± 6.6 year) in four different cities in Japan were recruited. They were divided into the training (120 MCI and 120 CN) and validation (99 MCI and 100 CN) groups. A model involving concentrations of PFAAs and albumin to discriminate MCI from CN individuals was constructed by multivariate logistic regression analysis in the training dataset, and the performance was evaluated in the validation dataset. The concentrations of some essential amino acids and albumin were significantly lower in MCI group than CN group. An index incorporating albumin and PFAA discriminated MCI from CN participants with the AUC of 0.705 (95% CI: 0.632–0.778), and the sensitivities at specificities of 90% and 60% were 25.3% and 76.8%, respectively. No significant association with BMI or APOE status was observed. This cross-sectional study suggests that the biomarker changes in MCI group may be associated with protein nutrition.

An increase in circulating levels of branched-chain amino acids during hemodialysis with regard to protein breakdown: three case reports

Background

Hemodialysis (HD) is a protein catabolic event. However, the amino acid (AA) kinetics during HD sessions involved in protein breakdown have not been well investigated in patients with and without diabetes mellitus (DM).

Case presentation

Three patients (two patients with DM and one patient without DM) underwent fasting HD. Plasma levels of branched-chain AAs (BCAA; leucine, isoleucine, and valine), major non-essential AAs (alanine and glutamine, including glutamate), insulin, and ketone bodies were measured every hour during each HD session. After the start of the HD session, the plasma levels of insulin and all BCAAs dropped simultaneously. There was a significant subsequent increase in the plasma level of leucine and isoleucine levels, while valine levels remained constant. However, the recovery in levels of BCAAs during HD indicated a profound amount of BCAAs entering the blood from body tissues such as muscles. BCAAs may have surpassed their removal by HD. Ketone body levels increased continuously from the start of the sessions and reached high values in patients with DM. Synchronous changes in insulin depletion and an increase in the levels of ketone bodies may indicate disruption of energy metabolism.

Conclusions

This is the first report to demonstrate the time course of the changes in circulating levels of BCAAs and related metabolites in energy homeostasis during HD. An increase in BCAA levels during HD was found to be due to their transfer from the body tissue which suggested protein breakdown.

Changes in plasma-concentration ratios of branched-chain amino acids in acute and convalescent phases of bacterial pneumonia

Branched-chain amino acids (BCAAs) have different immunity-related functions. Thus, BCAAs require evaluation in terms of their plasma concentration ratio. Eighty healthy participants and 57 patients with community-acquired pneumonia were enrolled. Samples from the healthy participants were collected after 12-h fasting; samples from the community-acquired pneumonia group were collected 2–3 h after lunch, during the acute (day 0) and convalescent (day 7) phases. The coefficient “a” of the regression line (Y = aX + b) of each BCAA plasma concentration was calculated from healthy participants and fixed, and each intercept “b” was calculated from the plasma concentration of each BCAA pair. Isoleucine levels increased; no significant changes in leucine concentrations were observed between healthy participants and pneumonia patients on days 0 and 7. In female participants in the pneumonia group, valine concentrations decreased on day 0. The isoleucine concentration was relatively higher than the leucine concentration on day 7 when evaluated with “b”. Changes in “b” on days 0 and 7 differed between men and women. There were sex-related differences in the plasma concentration ratios of BCAAs evaluated by “b”, which indicates a possible sex-related difference in the metabolic response to bacterial infection.

Capillary Electrophoresis Mass Spectrometry-Based Metabolomics of Plasma Samples from Healthy Subjects in a Cross-Sectional Japanese Population Study

For large-scale metabolomics, such as in cohort studies, normalization protocols using quality control (QC) samples have been established when using data from gas chromatography and liquid chromatography coupled to mass spectrometry. However, normalization protocols have not been established for capillary electrophoresis-mass spectrometry metabolomics. In this study, we performed metabolome analysis of 314 human plasma samples using capillary electrophoresis-mass spectrometry. QC samples were analyzed every 10 samples. The results of principal component analysis for the metabolome data from only the QC samples showed variations caused by capillary replacement in the first principal component score and linear variation with continuous measurement in the second principal component score. Correlation analysis between diagnostic blood tests and plasma metabolites normalized by the QC samples was performed for samples from 188 healthy subjects who participated in a Japanese population study. Five highly correlated pairs were identified, including two previously unidentified pairs in normal healthy subjects of blood urea nitrogen and guanidinosuccinic acid, and gamma-glutamyl transferase and cysteine glutathione disulfide. These results confirmed the validity of normalization protocols in capillary electrophoresis-mass spectrometry using large-scale metabolomics and comprehensive analysis.

Population epidemiology and concordance for plasma amino acids and precursors in 11-12-year-old children and their parents

Amino acid (AA) concentrations are influenced by both exogenous (e.g. diet, lifestyle) and endogenous factors (e.g. genetic, transcriptomic, epigenetic, and metabolomic). Fasting plasma AA profiles in adulthood are predictive of diabetes risk over periods of up to 12 years. Data on AA profiles in cross-generational cohorts, including individuals from shared gene-environment settings are scarce, but would allow the identification of the contribution of heritable and environmental factors characterising the levels of circulating AAs. This study aimed to investigate parent–child (familial dyad) concordance, absolute differences between generations- (children versus adults), age- (in adults: 28–71 years), and sex-dependent differences in plasma AA concentrations. Plasma AA concentrations were measured by UHPLC/MS–MS in 1166 children [mean (SD) age 11 (0.5) years, 51% female] and 1324 of their parents [44 (5.1) years, 87% female]. AA concentrations were variably concordant between parents and their children (5–41% of variability explained). Most AA concentrations were higher in adults than children, except for the non-essential AAs arginine, aspartic acid, glutamine, hydroxy-proline, proline, and serine. Male adults and children typically had higher AA concentrations than females. The exceptions were alanine, glutamine, glycine, hydroxy-proline, serine, and threonine in girls; and glycine and serine in women. Age, sex, and shared familial factors are important determinants of plasma AA concentrations.

Branched-chain amino acids are linked with iron metabolism

Background

The branched-chain amino acids (BCAAs) valine, leucine and isoleucine are reported to influence erythropoiesis and the human iron status. Large study cohorts encompassing biomarkers of iron metabolism and BCAAs are still lacking.

Methods

We investigated potential interactions between blood concentrations of all three BCAAs valine, leucine and isoleucine and biomarkers of iron metabolism [i.e., hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), iron, transferrin, ferritin, transferrin saturation, soluble transferrin receptor (sTfR)] in 430 outpatients referred for a medical health check-up. Linear regression models were performed to assess possible associations between variables.

Results

All three BCAAs were positively correlated with Hb, ferritin and the sTfR (r-values: 0.145–0.382; P values: <0.001–0.003). The strongest correlation was observed between valine and Hb (r=0.382; P value <0.001). Linear regression models showed a statistically significant influence of all three BCAAs on Hb and ferritin (β-coefficients: 0.173–0.351; all P values: <0.001). Seventeen patients with anemia (4%) were found with significantly lower serum BCAA concentrations compared to 413 non-anemic individuals (P<0.05).

Conclusions

These data indicate a pathophysiological link between the three BCAAs valine, leucine and isoleucine and the human iron indicators Hb and ferritin. Further studies are needed to clarify the exact causal mechanisms of these findings.

A chemical-specific adjustment factor for human interindividual differences in kinetics for glutamates (E620-625)

Use of a default methodology for establishment of a health-based guidance value (HBGV) resulted in a group acceptable daily intake (ADI) for glutamates (E620-625) below the normal dietary glutamate intake, and also lower than the intake of free glutamate by breast fed babies. Use of a chemical-specific adjustment factor (CSAF) may overcome this problem. The present study investigates the interindividual human variability in glutamate plasma and brain levels in order to define a CSAF for the interindividual variation in kinetics, a HK_AF, for glutamates. Human clinical data on plasma glutamate levels available from different groups of subjects at Mitsui Memorial Hospital as well as literature data on plasma and brain-related glutamate levels were collected and analysed. The median HK_AF value obtained amounted to 2.62-2.74 to 2.33-2.52 for plasma derived values and to 1.68-1.81 for brain derived values. Combining these values with the CSAF for the interspecies differences in kinetics of 1 and the default factors for interspecies and interindividual differences in dynamics of 2.5 and 3.16 results in an overall CSAF of 16-20. Using this CSAF will result in a HBGV for glutamate that is no longer below the acceptable range of oral intake (AROI).

Use of plasma-free amino acids as biomarkers for detecting and predicting disease risk

This paper reviews developments regarding the use of plasma-free amino acid (PFAA) profiles as biomarkers for detecting and predicting disease risk. This work was initiated and first published in 2006 and was subsequently developed by Ajinomoto Co., Inc. After commercialization in 2011, PFAA-based tests were adopted in over 1500 clinics and hospitals in Japan, and numerous clinician-led studies have been performed to validate these tests. Evidence is accumulating that PFAA profiles can be used for diabetes prediction and evaluation of frailty; in particular, decreased plasma essential amino acids could contribute to the pathophysiology of severe frailty. Integration of PFAA evaluation as a biomarker and effective essential amino acid supplementation, which improves physical and mental functions in the elderly, could facilitate the development of precision nutrition, including personalized solutions. This present review provides the background for the technology as well as more recent clinical findings, and offers future possibilities regarding the implementation of precision nutrition.

Reactions of kynurenic acid with hypobromous acid and hypochlorous acid

Kynurenic acid, a tryptophan metabolite, acts as antagonist or agonist of several receptors. Hypobromous acid (HOBr) and hypochlorous acid (HOCl) are generated by eosinophils and neutrophils. At inflammation sites, kynurenic acid may encounter HOBr and HOCl to generate products. When kynurenic acid was incubated with HOBr under neutral conditions, kynurenic acid generated a single product almost exclusively. This was identified as 3-bromokynurenic acid. Kynurenic acid reacted with HOCl, generating two products. The major product was identified as 3-chlorokynurenic acid with its oxidative decarboxylation product, 3-chloro-4-hydroxy-2(1H)-quinolinone as a by-product. Free amino acids suppressed the reactions of kynurenic acid with HOBr and HOCl. Taurine suppressed the HOCl reaction but not the HOBr reaction. An eosinophil peroxidase system containing H₂O₂, NaCl, and NaBr reacted with kynurenic acid, generating 3-bromokynurenic acid under mildly acidic conditions. Although a myeloperoxidase system containing H₂O₂ and NaCl reacted with kynurenic acid to generate 3-chlorokynurenic acid under mildly acidic conditions, the product was altered to 3-bromokynurenic acid by addition of NaBr to the system. These results suggest that 3-bromokynurenic acid and 3-chlorokynurenic acid may be generated from kynurenic acid at inflammation sites in humans, although their formation will be suppressed by coexistent amino acids.

Cross-correlation of plasma concentrations of branched-chain amino acids: A comparison between healthy participants and patients with chronic kidney disease

BACKGROUND & AIMS

Plasma concentrations of branched-chain amino acids (BCAAs) are known to exhibit strong intercorrelations; however, the associated regulatory mechanism is not sufficiently understood. Furthermore, the mechanisms underlying the intercorrelation changes in metabolic disorders with the disease are unclear. Therefore, plasma BCAAs in patients with chronic kidney disease (CKD) were examined.

METHODS

This study included a healthy group of older participants (Group C; n = 87, 46 males, 41 females) who had undergone health examinations at Sanyudo Hospital and a group of CKD patients (Group CKD; n = 71, 49 males, 22 females) receiving maintenance hemodialysis at the same hospital. Samples from Group C were collected 12 h after fasting. CKD samples were collected before and after hemodialysis (pre-HD and post-HD, respectively), without 12 h fasting. The samples were analyzed for 38 amino acids by SRL Inc., using liquid chromatography-mass spectrometry (LC-MS).

RESULTS

Differences between the plasma BCAA concentrations of Group C and pre-HD were determined. Dialysis-induced BCAA losses were different for each BCAA. However, strong intercorrelations between the plasma concentrations of each BCAA were maintained. In addition, the regression lines did not converge at the origin and were in different positions for groups C, pre-HD, and post-HD. A different distribution of the constant (b) for each group was observed for each BCAA correlation when a in the regression line (Y = aX + b) was fixed at the value for Group C, and b was calculated.

CONCLUSION

Strong intercorrelations among plasma concentrations of BCAAs were maintained in CKD patients both pre- and post-dialysis, whereas the changes in the plasma concentrations of each BCAA were different. We speculate that there is a novel mechanism that selectively regulates each BCAA and suggest that changes in the constant of the regression formula for correlation may have a novel function as an index for renal contribution to BCAA metabolism.

Reactions of Methotrexate with Hypobromous Acid and Hypochlorous Acid

Methotrexate is a folate antagonist cytotoxic drug employed in the therapy of cancers and rheumatoid arthritis. Hypobromous acid (HOBr) and hypochlorous acid (HOCl) are generated by eosinophils and neutrophils at inflammation sites. The administered methotrexate may encounter HOBr and HOCl, and react with them to generate products. When methotrexate was incubated with HOBr or HOCl at pH 7.4 and 37°C for 30 min, a single product was generated almost exclusively in each case, identified as 3'-bromomethotrexate for HOBr and 3'-chloromethotrexate for HOCl. When methotrexate was incubated with HOCl in the presence of NaBr, the concentration of 3'-bromomethotrexate increased with decreasing concentration of 3'-chloromethotrexate in a dose-dependent manner with NaBr, probably due to the formation of HOBr. Free amino acids suppressed the reactions of methotrexate with HOBr and HOCl. Taurine suppressed the HOCl reaction but not the HOBr reaction. These results suggest that 3'-bromomethotrexate and 3'-chloromethotrexate may be generated from methotrexate at inflammation sites in humans, although their formation will be suppressed by coexistent amino acids.

Development of a rapid and simple glycine analysis method using a stable glycine oxidase mutant

Glycine analysis is important in research fields such as physiology and healthcare because the concentration of glycine in human plasma has been reported to change with various disorders. Glycine oxidase from Bacillus subtilis (GlyOX) is useful for quantitative analysis of glycine. However, GlyOX is not sufficiently stable for use in physiology-based research or clinical settings. In this report, site-directed mutagenesis was used to engineer a GlyOX mutant suitable for glycine analysis. The GlyOX triple-mutant (T42 A/C245 S/L301V) retained most of its enzymatic activity during storage for over a year at 4 °C. A colorimetric enzyme analysis protocol was established using the GlyOX triple-mutant to determine glycine concentrations in human plasma. The analysis showed high accuracy (-5.4 to 3.5% relative errors when compared with the results from an amino acid analyzer, and 96.0-98.7% recoveries) and high precision (<4% between-run variation). Sample pretreatments of deproteinization and derivatization were not required. Therefore, this novel enzymatic analysis offers an effective and useful method for determining glycine concentrations in physiology related research and the healthcare field.

Reactions of Rebamipide with Hypobromous Acid

Rebamipide is a therapeutic agent for gastric ulcers and chronic gastritis. Hypobromous acid (HOBr) is generated not only by eosinophils but also by neutrophils in the presence of bromide ions in the plasma. At inflammation sites, rebamipide may encounter and react with HOBr to generated various products. When rebamipide was incubated with reagent HOBr in potassium phosphate buffer at pH 4.7 and 37°C for 4 h, several products were generated. A major product was identified as 3-bromorebamipide, a novel compound. Rebamipide does not react with hypochlorous acid (HOCl). However, when rebamipide was incubated with HOCl in the presence of NaBr, 3-bromorebamipide was generated in a dose-dependent manner, probably because of formation of HOBr. These results suggest that 3-bromorebamipide may generate from rebamipide at inflammation sites in humans.

Association between plasma essential amino acids and atherogenic lipid profile in a Chinese population: A cross-sectional study

BACKGROUND AND AIMS

The association between amino acids and small dense low-density lipoprotein cholesterol (sdLDL-C) and remnant-like particle cholesterol (RLP-C) remains poorly understood. This study aims to investigate the association between plasma essential amino acids (EAAs) and atherogenic lipid profiles.

METHODS

Plasma amino acid levels of 475 individuals were measured using liquid chromatography-mass spectrometry. SdLDL-C, RLP-C, and other lipid components were evaluated. Associations between EAAs and lipid components or dyslipidemia were determined using correlation analysis and multivariate logistic regression.

RESULTS

Concentrations of plasma branched-chain amino acid (BCAA) were positively correlated with sdLDL-C, RLP-C, and triglycerides (TG) levels, but inversely correlated with high-density lipoprotein cholesterol (HDL-C). In contrast, threonine concentration was inversely correlated with sdLDL-C, RLP-C, and TG. Compared with the lowest tertile, individuals in the highest tertile of plasma total BCAAs level had an odds ratio (OR) of 2.33 (95% confidence interval [CI]: 1.35, 4.03) for the risk of high sdLDL-C, 3.63 (95%CI: 1.69, 7.80) for the risk of high RLP-C, 3.10 (95%CI: 1.66, 5.80) for the risk of high TG, and 3.67 (95%CI: 2.00, 6.73) for atherogenic lipid triad (all p < 0.01). In contrast, compared with the lowest tertile, individuals in the highest plasma threonine tertile had a 43% lower OR for high sdLDL-C, 56% lower OR for high TG, and 55% lower OR for lipid triad risk (all p < 0.05).

CONCLUSIONS

Among the EAAs evaluated, elevated plasma BCAAs were significantly associated with increased risk of atherogenic lipid profile. In contrast, elevated threonine was associated with reduced risk of atherogenic lipid profile.

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.

Methods for Absolute Quantification of Human Plasma Free Amino Acids by High-Performance Liquid Chromatography/Electrospray Ionization Mass Spectrometry Using Precolumn Derivatization

Plasma free amino acid (PFAA) concentrations in humans are affected by various diseases. However, the variations caused are not dramatic, so a high accurate and precise method for analyzing PFAAs is required. The PFAA analysis protocol described in this chapter covers blood sampling, sample pretreatment, amino acid derivatization, and LC-MS analysis. Each procedure is important for accurate and precise quantification.In the protocol, a human blood sample is collected using an EDTA-2Na or 2K vacuum collection tube and then immediately cooled in water mixed with crushed ice. The sample is then centrifuged on cooling to allow a plasma sample to be removed. A stable-isotope-labeled internal standard solution is added to the plasma, and then the plasma is deproteinized with acetonitrile. The amino acids in the plasma are then derivatized using 3-aminopyridyl-N-hydroxysuccinimidyl carbamate (APDS) reagent which is designed for LC-MS analysis. The derivatized amino acids are separated by reverse-phase HPLC and detected by electrospray ionization mass spectrometry. Using this method, 21 amino acids in human plasma can be analyzed with a 12 min cycle. The accuracy and precision are both better than the required criteria given by the US Food and Drug Administration in guidance of Bioanalytical Method Validation.

Age-dependent Changes in Plasma Amino Acids Contribute to Alterations in Glycoxidation Products

BACKGROUND

Glycative stress is involved in the pathogenesis of various degenerative disorders. This study sought to determine the effect of age-related changes in amino acids on serum levels of pentosidine and carboxymethyl-lysine (CML) in healthy individuals.

METHODS

The subjects were 78 healthy individuals categorized into three age groups. The ages of the groups were as follows: 26 young adults (20-30 y, 25.2±3.03), 26 middle-aged adults (35-50 y, 39.46±6.97) and 26 older adults (60 y or older, 69.80±10.01). Serum levels of pentosidine and CML were measured by ELISA and levels of plasma amino acids were determined using HPLC.

RESULTS

Serum levels of pentosidine and CML in the youngest group were higher than in the oldest group (p=0.026, 0.029, respectively). There was a positive correlation between the serum levels of pentosidine and CML and the levels of plasmaTyrosine (p=0.032, r=0.211 and p=0.037, r=0.224), Valine (p=0.037, r=0.224 and p=0.021, r=0.247) and Isoleucine (p=0.041, r=0.203 and p=0.021, r=0.247), respectively. Serum levels of pentosidine and CML may be modulated by the plasma levels of selected amino acids.

CONCLUSIONS

Better understanding of the role of these selective amino acids might provide new perception of how glycation pathways may be altered and pave the way for new therapeutic principles.

Age-Related Reference Intervals for Blood Amino Acids in Thai Pediatric Population Measured by Liquid Chromatography Tandem Mass Spectrometry

Background

Age, race, and analytic method influence levels of blood amino acids, of which reference intervals are required for the diagnosis and management of inherited metabolic disorders.

Objectives

To establish age-specific reference intervals for blood amino acids in Thai pediatric population measured by liquid chromatography tandem mass spectrometry (LC-MS/MS).

Methods

A cross-sectional study of 277 healthy children from birth to 12 years was conducted. Anthropometric, clinical, and dietary information were recorded. Dried blood spots on a filtered paper were used for measurement by derivatized LC-MS/MS. Factors that might affect amino acids such as fasting time and dietary intake were analyzed using quantile regression analysis.

Results

Levels of thirteen blood amino acids were reported as median and interval from 2.5th–97.5th percentiles. Compared with those of Caucasian, most blood amino acid levels of Thai children were higher. Compared with a previous study using HPLC in Thai children, many amino acid levels are different. Glycine, alanine, leucine/isoleucine, and glutamic acid sharply decreased after birth. Citrulline, arginine, and methionine stayed low from birth throughout childhood, whereas phenylalanine was at middle level and slightly increased during preadolescence.

Conclusion

Reference intervals of age-specific blood amino acids using LC-MS/MS were established in the Thai pediatric population. They diverge from previous studies, substantiating the recommendation that, for the optimal clinical practice, age-specific reference intervals of amino acids should be designated for the particular population and analysis method.

Investigating the changes in amino acid values in premature infants: a pilot study

BACKGROUND

The objective of the study was to investigate the changes in amino acid (AAs) values in premature infants.

METHODS

A total of 2159 premature and/or low birth weight infants were recruited for this study. They were divided into three groups: premature infants with normal birth weight (G1), simple low birth weight infants (G2) and premature combined with low birth weight infants (G3). The tandem mass spectrometry technique was used to detect the levels of 11 AAs in neonatal blood.

RESULTS

Compared with normal babies, there were eight and five AAs that significantly changed in G1 and G2, respectively. It was worth noting that the changes greatly exacerbated when the babies were both premature and of low birth weight. All the levels of AAs demonstrated significant changes in G3 compared with the normal control group (G4). With the increase in gestational age, the AAs in premature infants tended to the levels in normal newborns. Meanwhile, there was a correlation between AAs and birth weight. Four AAs significantly changed with the increase in body weight. Among normal newborns, the levels of AAs in girls were significantly higher than in boys. However, if the newborns were premature or had low birth weight, the differences between AA values and sexual distinction would decrease. In the end, we established the specific reference ranges of AAs for premature and/or low birth weight infants.

CONCLUSIONS

There were significant differences in AAs in the premature and/or low birth weight infants. Gestational age and birth weight were two important factors inflecting the AAs metabolism.

Plasma Amino Acid Concentrations Are Associated with Muscle Function in Older Japanese Women

BACKGROUND

Although several previous studies have found benefits for amino acid supplementation in terms of muscle function, the role of plasma amino acid concentrations on sarcopenia are not well addressed yet.

OBJECTIVE

The aim of this study was to compare the amino acid concentrations at each stage of sarcopenia (normal, pre-sarcopenia, dynapenia, and sarcopenia) in community-dwelling older Japanese adults.

SETTING AND SUBJECTS

Community-dwelling older Japanese women (n=232, 79.4±7.0 years) participated in this study.

MEASUREMENTS

We measured plasma amino acid concentrations, 5-m walking speed, grip strength, and skeletal muscle mass using a bioelectrical impedance data acquisition system and compared them among participants at each stage of sarcopenia.

RESULTS

The proportions of normal, pre-sarcopenia, dynapenia, and sarcopenia patients were 40.5% (n=94), 12.1% (n=28), 26.3% (n=61), and 21.1% (n=49), respectively. Significant differences were observed for concentrations of leucine, branched-chain amino acid (BCAAs), and essential amino acid (EAAs) among the four groups (p<0.05), and the dynapenia and sarcopenia groups showed significantly lower concentrations of leucine than the normal group (p<0.05).

CONCLUSIONS

This study indicated a positive relationship between plasma leucine, BCAA and EAA concentrations and muscle function. A longitudinal study is needed to determine the causal relationship between leucine/BCAA concentrations and muscle function.

Plasma amino acid profile associated with fatty liver disease and co-occurrence of metabolic risk factors

Fatty liver disease (FLD) increases the risk of diabetes, cardiovascular disease, and steatohepatitis, which leads to fibrosis, cirrhosis, and hepatocellular carcinoma. Thus, the early detection of FLD is necessary. We aimed to find a quantitative and feasible model for discriminating the FLD, based on plasma free amino acid (PFAA) profiles. We constructed models of the relationship between PFAA levels in 2,000 generally healthy Japanese subjects and the diagnosis of FLD by abdominal ultrasound scan by multiple logistic regression analysis with variable selection. The performance of these models for FLD discrimination was validated using an independent data set of 2,160 subjects. The generated PFAA-based model was able to identify FLD patients. The area under the receiver operating characteristic curve for the model was 0.83, which was higher than those of other existing liver function-associated markers ranging from 0.53 to 0.80. The value of the linear discriminant in the model yielded the adjusted odds ratio (with 95% confidence intervals) for a 1 standard deviation increase of 2.63 (2.14–3.25) in the multiple logistic regression analysis with known liver function-associated covariates. Interestingly, the linear discriminant values were significantly associated with the progression of FLD, and patients with nonalcoholic steatohepatitis also exhibited higher values.

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.

Electronic supplementary material

The online version of this article (10.1186/s12877-017-0639-5) contains supplementary material, which is available to authorized users.

The role of amino acid profiles in diabetes risk assessment

PURPOSE OF REVIEW

The concentrations of plasma-free amino acids, such as branched-chain amino acids and aromatic amino acids, are associated with visceral obesity, insulin resistance, and the future development of diabetes and cardiovascular diseases. This review discusses recent progress in the early assessment of the risk of developing diabetes and the reversal of altered plasma-free amino acids through interventions. Additionally, recent developments that have increased the utility of amino acid profiling technology are also described.

RECENT FINDINGS

Plasma-free amino acid alterations in the early stage of lifestyle-related diseases are because of obesity and insulin resistance-related inflammation, and these alterations are reversed by appropriate (nutritional, drug, or surgical) interventions that improve insulin sensitivity. For clinical applications, procedures for measuring amino acids are being standardized and automated.

SUMMARY

Plasma-free amino acid profiles have potential as biomarkers for both assessing diabetes risk and monitoring the effects of strategies designed to lower that risk. In addition, the methodology for measuring amino acids has been refined, with the goal of routine clinical application.

Weight loss is associated with plasma free amino acid alterations in subjects with metabolic syndrome

OBJECTIVES

The prevalence of metabolic syndrome is increasing worldwide, especially in Asian populations. Early detection and effective intervention are vital. Plasma free amino acid profile is a potential biomarker for the early detection for lifestyle-related diseases. However, little is known about whether the altered plasma free amino acid profiles in subjects with metabolic syndrome are related to the effectiveness of dietary and exercise interventions.

METHODS

Eighty-five Japanese subjects who fulfilled the Japanese diagnostic criteria for metabolic syndrome were enrolled in a 3-month diet and exercise intervention. The plasma free amino acid concentrations and metabolic variables were measured, and the relationships between plasma free amino acid profiles, metabolic variables and the extent of body weight reduction were investigated. Those who lost more than 3% of body weight were compared with those who lost less than 3%.

RESULTS

Baseline levels of most amino acids in the subset that went on to lose <3% body weight were markedly lower compared with the counterpart, although both groups showed similar proportional pattern of plasma amino acid profiles. The weight loss induced by the diet and exercise intervention normalized plasma free amino acid profiles. For those with a high degree of weight loss, those changes were also associated with improvement in blood pressure, triglyceride and hemoglobin A1c levels.

CONCLUSIONS

These data suggest that among Japanese adults meeting the criteria for metabolic syndrome, baseline plasma free amino acid profiles may differ in ways that predict who will be more vs less beneficially responsive to a standard diet and exercise program. Plasma free amino acid profiles may also be useful as markers for monitoring the risks of developing lifestyle-related diseases and measuring improvement in physiological states.

Application of Pre-Column Labeling Liquid Chromatography for Canine Plasma-Free Amino Acid Analysis

Plasma-free amino acid (PFAA) levels are a useful metric for diagnosing cancer and providing a prognosis. However, the use of analysis of PFAA levels has been limited in the veterinary medicine field. We addressed the application of liquid chromatography (LC) using a pre-column labeling technique for analysis of canine PFAA levels. This method significantly shortened the analysis time relative to conventional methods. No diurnal fluctuations were detected at 9:00 AM in most PFAA levels, and food intake increased the levels of some PFAAs, including valine, leucine, tyrosine, phenylalanine, and proline. These results indicate that LC with pre-column labeling is useful for measuring canine PFAA levels, for which time of day and interval after food intake must be taken into consideration.

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.