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

Development of a plasma-free amino acid-based risk score for the incidence of cardiovascular diseases in a general population: The Nagahama study

BACKGROUND & AIMS

Levels of circulating amino acids (AAs) have been suggested to be associated with cardiovascular diseases (CVDs). This study aimed to develop a plasma-free amino acid (PFAA)-based CVD risk-prediction model in a general population.

METHODS

The study participants consisted of 9220 community residents (mean age, 53.2 years; standard deviation, 13.3 years). Circulating levels of 19 PFAAs were measured via high-performance liquid chromatography/electrospray ionization mass spectrometry. The incidence of CVDs was determined by reviewing participants' clinical records. The prediction model was developed using the Cox proportional hazards model with the brute force variable selection and then cross-validated.

RESULTS

During the 8.5-year follow-up, 220 CVD events were observed. Six AAs (alanine, citrulline, glycine, histidine, serine, and tyrosine) were identified as components of the prediction model, of which the C-index was 0.72. The association between the fourth quartile of the risk score calculated using the prediction model and the CVD events was independent of conventional risk factors (adjusted hazard ratio [HR], 1.9; 95 % confidence interval, 1.1-3.3). When examining crude relationships between conventional risk factors and the PFAA-based risk score by subgroup analyses, the association was significant for most subpopulations, men [crude HR = 6.4 (2.0-20.2)] and women [crude HR = 4.9 (2.6-9.3)], and individuals with [crude HR = 4.7 (2.5-8.9)] and without [crude HR = 7.2 (2.7-18.9)] lifestyle-related diseases, but not for older (≥70 years) participants [crude HR = 3.3 (0.8-13.5)]. The risk score successfully identified at-risk individuals [HR = 2.1 (1.2-3.5)] from participants who were classified as low risk by a conventional CVD risk score.

CONCLUSIONS

The PFAA-based risk score predicted CVD events independently of conventional risk factors.

No Evidence That Circulating GLP-1 or PYY Are Associated with Increased Satiety during Low Energy Diet-Induced Weight Loss: Modelling Biomarkers of Appetite

Bariatric surgery and pharmacology treatments increase circulating glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), in turn promoting satiety and body weight (BW) loss. However, the utility of GLP-1 and PYY in predicting appetite response during dietary interventions remains unsubstantiated. This study investigated whether the decrease in hunger observed following low energy diet (LED)-induced weight loss was associated with increased circulating 'satiety peptides', and/or associated changes in glucose, glucoregulatory peptides or amino acids (AAs). In total, 121 women with obesity underwent an 8-week LED intervention, of which 32 completed an appetite assessment via a preload challenge at both Week 0 and Week 8, and are reported here. Visual analogue scales (VAS) were administered to assess appetite-related responses, and blood samples were collected over 210 min post-preload. The area under the curve (AUC_0-210), incremental AUC (iAUC_0-210), and change from Week 0 to Week 8 (∆) were calculated. Multiple linear regression was used to test the association between VAS-appetite responses and blood biomarkers. Mean (±SEM) BW loss was 8.4 ± 0.5 kg (-8%). Unexpectedly, the decrease in ∆AUC_0-210 hunger was best associated with decreased ∆AUC_0-210 GLP-1, GIP, and valine (p < 0.05, all), and increased ∆AUC_0-210 glycine and proline (p < 0.05, both). The majority of associations remained significant after adjusting for BW and fat-free mass loss. There was no evidence that changes in circulating GLP-1 or PYY were predictive of changes in appetite-related responses. The modelling suggested that other putative blood biomarkers of appetite, such as AAs, should be further investigated in future larger longitudinal dietary studies.

Plasma free amino acid profiles are associated with serum high molecular weight adiponectin levels in Japanese medical check-up population without type 2 diabetes mellitus

To prevent the progression of type 2 diabetes mellitus (T2DM), early detection and intervention are important. Several studies have already shown that the serum adiponectin level could be useful for evaluating the future risk of T2DM. Recently, plasma free amino acid (PFAA) concentrations have also emerged as potential biomarkers that predict the future onset of T2DM. In this study, we aimed to further characterise PFAA profiles by elucidating the association with the serum high molecular weight (HMW) adiponectin level in this cross-sectional study. A total of 1000 Japanese subjects who underwent medical check-ups were enrolled, and their plasma concentrations of 21 amino acids and clinical parameters were measured. The subjects without T2DM were divided into quartiles (Q1-4) by serum HMW adiponectin level, and the association with between PFAA concentrations was analysed. Concentrations of glutamate, alanine, proline, tyrosine, histidine, methionine, lysine, branched-chain amino acids (BCAAs) and tryptophan varied significantly according to the adiponectin quartile. Furthermore, serum adiponectin levels showed significant inverse correlations with these amino acids. The change in the PFAA profile in the group with the lowest adiponectin concentrations (Q1) was similar to that of T2DM patients. Although both adiponectin levels and PFAA concentrations are known to be altered by the accumulation of visceral fat and insulin resistance, the levels of glutamate, BCAA, lysine and tryptophan remain significantly associated with adiponectin level after adjustment for age, body mass index and homeostasis model assessment of insulin resistance, showing the direct association between PFAA concentrations and the serum HMW adiponectin level. Registration number: University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) UMIN000029920, registered on Nov 13th 2017 (prospectively registered).

Nutrients, Physical Activity, and Mitochondrial Dysfunction in the Setting of Metabolic Syndrome

Metabolic syndrome (MetS) is a cluster of metabolic risk factors for diabetes, coronary heart disease, non-alcoholic fatty liver disease, and some tumors. It includes insulin resistance, visceral adiposity, hypertension, and dyslipidemia. MetS is primarily linked to lipotoxicity, with ectopic fat deposition from fat storage exhaustion, more than obesity per se. Excessive intake of long-chain saturated fatty acid and sugar closely relates to lipotoxicity and MetS through several pathways, including toll-like receptor 4 activation, peroxisome proliferator-activated receptor-gamma regulation (PPARγ), sphingolipids remodeling, and protein kinase C activation. These mechanisms prompt mitochondrial dysfunction, which plays a key role in disrupting the metabolism of fatty acids and proteins and in developing insulin resistance. By contrast, the intake of monounsaturated, polyunsaturated, and medium-chain saturated (low-dose) fatty acids, as well as plant-based proteins and whey protein, favors an improvement in sphingolipid composition and metabolic profile. Along with dietary modification, regular exercises including aerobic, resistance, or combined training can target sphingolipid metabolism and improve mitochondrial function and MetS components. This review aimed to summarize the main dietary and biochemical aspects related to the physiopathology of MetS and its implications for mitochondrial machinery while discussing the potential role of diet and exercise in counteracting this complex clustering of metabolic dysfunctions.

Real-life impact of tenofovir disoproxil fumarate and entecavir therapy on lipid profile, glucose, and uric acid in chronic hepatitis B patients

The impact of long-term nucleos(t)ide analogs treatment on host metabolism is a concern. Hence, we conducted this study to compare the effect of entecavir (ETV) and tenofovir disoproxil fumarate (TDF) on metabolic parameters among chronic hepatitis B (CHB) patients. In this real-life retrospective study, 2030 CHB outpatients treated with ETV or TDF at Nanfang Hospital, China, were included. For treatment-naïve patients, pretreatment and semiannual metabolic parameters were collected. For treatment-experienced patients, metabolic parameters were collected at the first visit. Propensity score matching (PSM) was used to balance the effects of potential confounding factors. Among 122 treatment-naïve patients and 1908 treatment-experienced patients, ETV-treated patients were older with a higher percentage of metabolic syndrome. After PSM, the characteristics were comparable between the two groups. For treatment-naïve patients, four lipid parameters, including total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein, and triglyceride levels showed a decreasing trend during the 42-month TDF treatment, while they remained relatively stable or increased during ETV treatment. At Month 30, the levels of TC and LDL among TDF-treated patients were significantly lower than those among ETV-treated patients (TC: 4.7 mmol/L vs. 3.9 mmol/L, p = 0.004; LDL: 3.0 mmol/L vs. 2.4 mmol/L, p = 0.009). For treatment-experienced patients, we also observed lower levels of lipid parameters in patients with different durations of TDF treatment. The levels of glucose and uric acid were similar among ETV- and TDF-treated patients. TDF has a lipid-lowering effect in CHB patients, which provides a basis for the selection of antiviral drugs for aging CHB patients.

Serum amino acid profile in chronic sinusitis

Objective: Serum amino acid profile is known to vary in many diseases. The changes in the serum amino acid profile provide important information about diagnosis and prognosis of related diseases and the effectiveness of treatment. The aim of this study is to investigate whether serum amino acids are effective in the development of CRS. Methods: A total of 23 healthy volunteers between the ages of 20 and 40 years were allocated to the control group (Group 1) and 27 patients with chronic rhinosinusitis were allocated to the study group (Group 2). The patients whose history, symptom, and examination findings were consistent with chronic sinusitis and who also who had sinusitis findings on a paranasal sinus tomography and were diagnosed with chronic sinusitis for at least one year were included in Group 2. A total of 32 serum-free amino acid levels were measured in both group using the LC-MS/MS system. Results: The serum taurine level was found to be statistically significantly lower in Group 2 compared to Group 1 (p:0.002). A significant alteration was not observed in the serum levels of remaining 31 amino acids. Conclusion: According to the data we obtained from the study, decreased serum taurine level may be a factor in the etiopathogenesis of chronic rhinosinusitis and therefore taurine supplementation may be considered as a new therapeutic target in the treatment of chronic rhinosinusitis.

The serum amino acid profile in COVID-19

The pandemic of the coronavirus disease (COVID-19) caused by SARS-CoV-2 affects millions of people worldwide. There are still many unknown aspects to this infection which affects the whole world. In addition, the potential impacts caused by this infection are still unclear. Amino acid metabolism, in particular, contains significant clues in terms of the development and prevention of many diseases. Therefore, this study aimed to compare amino acid profile of COVID-19 and healthy subject. In this study, the amino acid profiles of patients with asymptomatic, mild, moderate, and severe/critical SARS-CoV-2 infection were scanned with LC–MS/MS. The amino acid profile encompassing 30 amino acids in 142 people including 30 control and 112 COVID-19 patients was examined. 20 amino acids showed significant differences when compared to the control group in COVID-19 patient groups with different levels of severity in the statistical analyses conducted. It was detected that the branched-chain amino acids (BCAAs) changed in correlation with one another, and l-2-aminobutyric acid and l-phenylalanine had biomarker potential for COVID-19. Moreover, it was concluded that l-2-aminobutyric acid could provide prognostic information about the course of the disease. We believe that a new viewpoint will develop regarding the diagnosis, treatment, and prognosis as a result of the evaluation of the serum amino acid profiles of COVID-19 patients. Determining l-phenylalanine and l-2-aminobutyric levels can be used in laboratories as a COVID-19-biomarker. Also, supplementing COVID patients with taurine and BCAAs can be beneficial for treatment protocols.

A Metabolomic Analysis of the Sex-Dependent Hispanic Paradox

In Mexican Americans, metabolic conditions, such as obesity and type 2 diabetes (T2DM), are not necessarily associated with an increase in mortality; this is the so-called Hispanic paradox. In this cross-sectional analysis, we used a metabolomic analysis to look at the mechanisms behind the Hispanic paradox. To do this, we examined dietary intake and body mass index (BMI; kg/m²) in men and women and their effects on serum metabolomic fingerprints in 70 Mexican Americans (26 men, 44 women). Although having different BMI values, the participants had many similar anthropometric and biochemical parameters, such as systolic and diastolic blood pressure, total cholesterol, and LDL cholesterol, which supported the paradox in these subjects. Plasma metabolomic phenotypes were measured using liquid chromatography tandem mass spectrometry (LC-MS/MS). A two-way ANOVA assessing sex, BMI, and the metabolome revealed 23 significant metabolites, such as 2-pyrrolidinone (p = 0.007), TMAO (p = 0.014), 2-aminoadipic acid (p = 0.019), and kynurenine (p = 0.032). Pathway and enrichment analyses discovered several significant metabolic pathways between men and women, including lysine degradation, tyrosine metabolism, and branch-chained amino acid (BCAA) degradation and biosynthesis. A log-transformed OPLS-DA model was employed and demonstrated a difference due to BMI in the metabolomes of both sexes. When stratified for caloric intake (<2200 kcal/d vs. >2200 kcal/d), a separate OPLS-DA model showed clear separation in men, while females remained relatively unchanged. After accounting for caloric intake and BMI status, the female metabolome showed substantial resistance to alteration. Therefore, we provide a better understanding of the Mexican-American metabolome, which may help demonstrate how this population—particularly women—possesses a longer life expectancy despite several comorbidities, and reveal the underlying mechanisms of the Hispanic paradox.

The Efficacy of Short-Term Weight Loss Programs and Consumption of Natural Probiotic Bryndza Cheese on Gut Microbiota Composition in Women

Weight loss interventions with probiotics have favourable effects on gut microbiota composition and derived metabolites. However, little is known about whether the consumption of natural probiotics, such as Bryndza cheeses, brings similar benefits. The purpose of the study was to find the effect of short-term weight loss programs and Bryndza cheese consumption on the structure of the gut microbiota, microbiota-derived metabolites and body composition in middle-aged women. We conducted a randomised controlled intervention study. Twenty-two female participants with a body fat percentage ≥25% underwent a short weight loss program (4 weeks). Subjects were randomised to either the control or intervention group according to diet. The intervention group comprised 13 participants, whose diet contained 30 g of “Bryndza” cheese daily (WLPB). The control group comprised nine participants without the regular consumption of Bryndza cheese (WLP) in their diet. Both interventions lead to a significant and favourable change of BMI, body fat, waist circumference and muscle mass. Moreover, the relative abundance of Erysipelotrichales significantly increased in both groups. However, the relative abundance of lactic acid bacteria (Lactobacillales, Streptococcaceae, Lactococcus and Streptococcus) significantly increased only in the WLPB group. Furthermore, short-chain fatty acid producers Phascolarctobacterium and Butyricimonas increased significantly in the WLPB group. A short-term weight loss program combined with Bryndza cheese consumption improves body composition and increases the abundance of lactic acid bacteria and short-chain fatty acid producers in middle-aged women.

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.

The effect of circuit resistance training on plasma levels of amino acids, alpha-hydroxybutyrate, mannose, and urinary levels of glycine conjugated adducts in obese adolescent boys

Few studies have examined the improving effects of exercise on the association between metabolites of impaired protein metabolism and insulin resistance in obese children. Therefore, this study aims to investigate the effect of circuit resistance training (CRT) on plasma levels of amino acids, alpha-hydroxybutyrate (α-HB), mannose, and urinary levels of glycine conjugated adducts in obese adolescent boys. Forty obese adolescent boys (body mass index above the 95th percentile) with an age range of 14-17 years were randomly divided into the CRT group (n = 20) and control group (n = 20). The CRT program (3 times/week, 70%-80% of 1-repetition maximum) was performed for 8 weeks. The results indicated that the body composition and plasma levels of glucose, insulin resistance, valine, mannose, lysine, and the sum of branched-chain amino acids (BCAA) were decreased because of CRT. The plasma levels of asparagine, glycine, serine, and urinary levels of glycine conjugated adduct also increased in the CRT group. Although α-HB level decreased during CRT, it had no significant difference from that of the control group. It can be concluded that the improvement in obesity complications including insulin resistance in obese adolescent boys after CRT may be due to decrease in plasma levels of mannose and BCAA and increase urinary metabolites. Novelty: CRT improves glucose metabolism and insulin resistance in obese adolescent boys. CRT decreases plasma levels of mannose and BCAA and normalizes other amino acids. CRT increases urinary levels of glycine conjugated adducts.

Does high dietary protein intake contribute to the increased risk of developing prediabetes and type 2 diabetes?

Insulin resistance is a complex metabolic disorder implicated in the development of many chronic diseases. While it is generally accepted that body mass loss should be the primary approach for the management of insulin resistance-related disorders in overweight and obese individuals, there is no consensus among researchers regarding optimal protein intake during dietary restriction. Recently, it has been suggested that increased plasma branched-chain amino acids concentrations are associated with the development of insulin resistance and type 2 diabetes. The exact mechanism by which excessive amino acid availability may contribute to insulin resistance has not been fully investigated. However, it has been hypothesised that mammalian target of rapamycin (mTOR) complex 1 hyperactivation in the presence of amino acid overload contributes to reduced insulin-stimulated glucose uptake because of insulin receptor substrate (IRS) degradation and reduced Akt-AS160 activity. In addition, the long-term effects of high-protein diets on insulin sensitivity during both weight-stable and weight-loss conditions require more research. This review focusses on the effects of high-protein diets on insulin sensitivity and discusses the potential mechanisms by which dietary amino acids can affect insulin signalling. Novelty: Excess amino acids may over-activate mTOR, resulting in desensitisation of IRS-1 and reduced insulin-mediated glucose uptake.

The effect of eight-week walking program on plasma levels of amino acids in early/mid pubertal obese girls

Background: Altered circulating amino acids levels have been observed in metabolic disorders, like obesity, type-2 diabetes, and other insulin-resistant states. This study aimed to investigate the effect of 8-week walking on plasma amino acids (PAAs) in obese girls. Methods: This clinical trial study (IRCT20180928041160N1) was conducted on 32 early/mid pubertal obese girls which they divided into interval-walking (IWG, n=12), continuous-walking (CWG, n=11) and control (CG, n=9) groups. The walking program (3- sessions/week for 8-weeks) consists of 30-min walking with 70-85%HRmax and 60-75%HRmax, respectively in the IWG (2-min walking and 1-min active rest) and CWG. The concentration of PAAs was measured at baseline and 72-hours after the last session in fasting state, using high-performance liquid chromatography. A repeated measures ANCOVA (group (3) * time (2)) with post hoc Bonferroni was used to analyze the data. Results: More the PAAs were not affected by interval or continuous walking training. A significant increase in lysine (p=0.003, 95%CI 24.08, 108.97) was observed only in the CG, and there was a significant difference between the CG and CWG (p=0.032). Global arginine bioavailability (GABA) significantly decreased in the CG (P<0.001, 95%CI -0.65, -0.21) and the IWG (p=0.004, 95%CI -0.60, -0.21). A significant increase in weight (p=0.043, 95%CI 0.27, 1.46), insulin (p=0.046, 95%CI -0.91, 9.01), and HOMA-IR (p=0.007, 95%CI 0.26, 2.63) were found only in the CG, and both insulin and HOMA-IR tended to decline in the CWG. Conclusion: Except for lysine and GABA, all groups roughly showed similar changes in more amino acids. Continuous-walking could improve the plasma level of lysine and GABA, which along with an improvement of fasting insulin levels and HOMA-IR.

Distinct Gut Microbiota and Serum Metabolites in Response to Weight Loss Induced by Either Dairy or Exercise in a Rodent Model of Obesity

Energy imbalance is a primary cause of obesity. While the classical approach to attenuate weight gain includes an increase in energy expenditure through exercise, dietary manipulation such as the inclusion of dairy products has also been proven effective. In the present study, we explored the potential mechanisms by which dairy and exercise attenuate weight gain in diet-induced obese rats. Male Sprague-Dawley rats were fed a high fat, high-sugar (HFHS) diet to induce obesity for 8 weeks. Rats were then further grouped into either control (HFHS + casein) or dairy diet (HFHS + nonfat skim milk) with and without treadmill exercise for 6 weeks. Serum and fresh fecal samples were collected for gut microbiota, serum metabolomics, and metallomics analysis. Diet and exercise resulted in distinct separation in both gut microbiota and serum metabolite profiles. Most intriguingly, obesogenic bacteria including Desulfovibrio and Oribacterium were reduced, and bioactive molecules such as mannose and arginine were significantly increased in the dairy group. Correlations of at least six bacterial genera with serum metal ions and metabolites were also found. Results reveal distinct impacts of dairy and exercise on the gut microbiota and in the modulation of circulating metabolites with the former primarily responsible for driving microbial alterations known to attenuate weight gain.

Plasma-Free Amino Acid Profiling of Nasal Polyposis Patients

AIM AND OBJECTIVE

To determine the mechanisms present in the etiopathogenesis of nasal polyposis. It is not clear whether amino acids contribute in a causal way to the development of the disease. Therefore, the aim of this study was to determine the plasma-free amino acid profile in patients with nasal polyposis and to compare the results with a healthy control group.

MATERIALS AND METHODS

This was a prospective controlled study that took place in the Otolaryngology Department at the Harran University Faculty of Medicine between April 2017 and April 2018. Plasmafree amino acid profile levels were studied in serum samples taken from a patient group and a healthy control group. Patients who were diagnosed with bilateral diffuse nasal polyposis and were scheduled for surgical interventions were included in this study. Individuals whose age, gender, and body mass index values were compatible with that of the patient group and who did not have any health problems were included in the control group. All the participants whose levels of plasma-free amino acid were thought to be affected by one or more of the following factors were excluded from the study: smoking and alcohol use, allergic rhinitis presence, the presence of acute or chronic sinusitis, a history of endoscopic sinus surgery, unilateral nasal masses, a history of chronic drug use, systemic or topical steroid use in the last three months for any reason, and liver, kidney, hematological, cardiovascular, metabolic, neurological, or psychiatric disorders or malignancies.

RESULTS

In patients with nasal polyposis, 3-methyl histidine (3-MHIS: nasal polyposis group (ng) = 3.22 (1.92 - 6.07); control group (cg) = 1.21 (0.77 - 1.68); p = 0.001); arginine (arg: ng = 98.95 (70.81 - 117.75); cg = 75.10 (54.49 - 79.88); p = 0.005); asparagine (asn: ng = 79.84 (57.50 - 101.44); cg = 60.66 (46.39 - 74.62); p = 0.021); citrulline (cit: ng = 51.83 (43.81 - 59.78); cg = 38.33 (27.81 - 53.73); p = 0.038); cystine (cys: ng = 4.29 (2.43 - 6.66); cg = 2.41 (1.51 - 4.16); p = 0.019); glutamic acid (glu: ng = 234.86 (128.75 - 286.66); cg = 152.37 (122.51 - 188.34); p = 0.045); histidine (his: ng = 94.19 (79.34 - 113.99); cg = 74.80 (62.76 - 98.91); p = 0.018); lysine (lys: ng = 297.22 (206.55 - 371.25); cg = 179.50 (151.58 - 238.02); p = 0.001); ornithine (ng = 160.62 (128.36 - 189.32); cg = 115.91 (97.03 - 159.91); p = 0.019); serine (ser: ng = 195.15 (151.58 - 253.07); cg = 83.07 (67.44 - 92.44); p = 0.001); taurine (tau: ng = 74.69 (47.00 - 112.13); cg = 53.14 (33.57 - 67.31); p = 0.006); tryptophan (trp: ng = 52.31 (33.81 - 80.11); cg = 34.44 (25.94 - 43.07); p = 0.005), homocitrulline (ng = 1.75 (1.27 - 2.59); cg = 0.00 (0.00 - 0.53); p = 0.001); norvaline (ng = 6.90 (5.61 - 9.18); cg = 4.93 (3.74 - 7.13); p = 0.021); argininosuccinic acid (ng = 14.33 (10.06 - 25.65); cg = 12.22 (5.77 - 16.87) p = 0.046); and plasma concentrations were significantly higher than in the healthy control group (p <0.05). However, the gamma-aminobutyric acid (gaba: ng = 0.16 (0.10 - 0.24); cg = 0.21 (0.19 - 0.29); p = 0.010) plasma concentration was significantly lower in the nasal polyposis group than in the healthy control group.

CONCLUSION

In this study, plasma levels of 15 free amino acids were significantly higher in the nasal polyposis group than in the healthy control group. A plasma level of 1 free amino acid was found to be significantly lower in the nasal polyposis group compared to the healthy control group. Therefore, it is important to determine the possibility of using the information obtained to prevent the recurrence of the condition and to develop effective treatment strategies. This study may be a milestone for studies of this subject. However, this study needs to be confirmed by further studies conducted in a larger series.

Development of Biomarkers for Inhibition of SLC6A19 (B⁰AT1)-A Potential Target to Treat Metabolic Disorders

Recent studies have established that dietary protein restriction improves metabolic health and glucose homeostasis. SLC6A19 (B⁰AT1) is the major neutral amino acid transporter in the intestine and carries out the bulk of amino acid absorption from the diet. Mice lacking SLC6A19 show signs of protein restriction, have improved glucose tolerance, and are protected from diet-induced obesity. Pharmacological blockage of this transporter could be used to induce protein restriction and to treat metabolic diseases such as type 2 diabetes. A few novel inhibitors of SLC6A19 have recently been identified using in vitro compound screening, but it remains unclear whether these compounds block the transporter in vivo. To evaluate the efficacy of SLC6A19 inhibitors biomarkers are required that can reliably detect successful inhibition of the transporter in mice. A gas chromatography mass spectrometry (GC-MS)-based untargeted metabolomics approach was used to discriminate global metabolite profiles in plasma, urine and faecal samples from SLC6A19ko and wt mice. Due to inefficient absorption in the intestine and lack of reabsorption in the kidney, significantly elevated amino acids levels were observed in urine and faecal samples. By contrast, a few neutral amino acids were reduced in the plasma of male SLC6A19ko mice as compared to other biological samples. Metabolites of bacterial protein fermentation such as p-cresol glucuronide and 3-indole-propionic acid were more abundant in SLC6A19ko mice, indicating protein malabsorption of dietary amino acids. Consistently, plasma appearance rates of [¹⁴C]-labelled neutral amino acids were delayed in SLC6A19ko mice as compared to wt after intra-gastric administration of a mixture of amino acids. Receiver operating characteristic (ROC) curve analysis was used to validate the potential use of these metabolites as biomarkers. These findings provide putative metabolite biomarkers that can be used to detect protein malabsorption and the inhibition of this transporter in intestine and kidney.

Impact of predicting health-guidance candidates using massive health check-up data: A data-driven analysis

INTRODUCTION

Starting in 2008, specific health checkups and health guidance to prevent non-communicable diseases have been provided in Japan, which has the highest proportion of elderly citizens in the world. The attendance rate for health guidance appointments is 17.7%, which is far from the national goal of the system (45%). To improve the attendance rate, we present a model for predicting whether an examinee is a candidate for health guidance; this model was based on a machine learning method and a restricted but massive amount of health checkup information.

MATERIALS AND METHODS

Using machine learning methods, we developed the following five prediction models for identifying health-guidance candidates: baseline: this model included sex and age; model 1: this model included variables that can be measured in person+information on whether the examinee was a candidate in the past year; model 2: model 1+systolic blood pressure+diastolic blood pressure; model 3: model 2+all health checkup results from the past year; and model 4: model 3 using the training dataset excluding cases with missing data.

RESULTS

The performance levels of the five prediction models (the AUC values of the models for the test dataset) were as follows: 0.592 [95% CI: 0.586-0.596] for the baseline model, 0.855 [95% CI: 0.851-0.858] for model 1, 0.985 [95% CI: 0.984-0.985] for model 2, 0.993 [95% CI: 0.993-0.993] for model 3, and 0.943 [95% CI: 0.941-0.945] for model 4.

CONCLUSIONS

We studied five models for identifying health-guidance candidates. The model that used all health checkup results from the past year had the highest predictive power. Application of the prediction model developed in the present study to the selection of health-guidance candidates could reduce the cost of guidance.

Metabolite profiling of obese individuals before and after a one year weight loss program

OBJECTIVE

We and others have previously characterized changes in circulating metabolite levels following diet-induced weight loss. Our aim was to investigate whether baseline metabolite levels and weight-loss-induced changes in these are predictive of or associated with changes in body mass index (BMI) and metabolic risk traits.

METHODS

Serum metabolites were analyzed with gas and liquid chromatography/mass spectrometry in 91 obese individuals at baseline and after participating in a 1 year non-surgical weight loss program.ResultsA total of 137 metabolites were identified and semi-quantified at baseline (BMI 42.7±5.8, mean±s.d.) and at follow-up (BMI 36.3±6.6). Weight-loss-induced modification was observed for levels of 57 metabolites in individuals with ⩾10% weight loss. Lower baseline levels of xylitol was predictive of a greater decrease in BMI (β=0.06, P<0.01) and ⩾10% weight loss (odds ratio (OR)=0.2, confidence interval (CI)=0.07-0.7, P=0.01). Decreases in levels of isoleucine, leucine, valine and tyrosine were associated with decrease in BMI (β>0.1, P<0.05) and ⩾10% weight loss (isoleucine: OR=0.08, CI=0.01-0.3, leucine: OR=0.1, CI=0.01-0.6, valine: OR=0.1, CI=0.02-0.5, tyrosine: OR=0.1, CI=0.03-0.6, P<0.02).

CONCLUSIONS

Diet-induced weight loss leads to mainly reduced levels of metabolites that are elevated in obese insulin resistant individuals. We identified multiple new associations with metabolic risk factors and validated several previous findings related to weight loss-mediated metabolite changes. Levels of specific metabolites, such as xylitol, may be predictive of the response to non-surgical weight loss already at baseline.

Alteration in plasma free amino acid levels and its association with gout

Background

Studies on the association of plasma-free amino acids with gout are very limited and produced conflicting results. Therefore, we sought to explore and characterize the plasma-free amino acid (PFAA) profile in patients with gout and evaluate its association with the latter.

Methods

Data from a total of 819 subjects (including 34 patients with gout) undergoing an annual health examination program in Shimane, Japan were considered for this study. Venous blood samples were collected from the subjects and concentrations of 19 plasma amino acids were determined by high-performance liquid chromatography–electrospray ionization–mass spectrometry. Student’s t-test was applied for comparison of variables between patient and control groups. The relationships between the presence or absence of gout and individual amino acids were investigated by logistic regression analysis controlling for the effects of potential demographic confounders.

Results

Among 19 amino acids, the levels of 10 amino acids (alanine, glycine, isoleucine, leucine, methionine, phenylalanine, proline, serine, tryptophan, valine) differed significantly (P < .001 to .05) between the patient and control groups. Univariate logistic regression analysis revealed that plasma levels of alanine, isoleucine, leucine, phenylalanine, tryptophan and valine had significant positive associations (P < .005 to .05) whereas glycine and serine had significant inverse association (P < .05) with gout.

Conclusions

The observed significant changes in PFAA profiles may have important implications for improving our understanding of pathophysiology, diagnosis and prevention of gout. The findings of this study need further confirmation in future large-scale studies involving a larger number of patients with gout.

Amino Acid Signatures to Evaluate the Beneficial Effects of Weight Loss

Aims. We investigated the relationship between circulating amino acid levels and obesity; to what extent weight loss followed by weight maintenance can correct amino acid abnormalities; and whether amino acids are related to weight loss. Methods. Amino acids associated with waist circumference (WC) and BMI were studied in 804 participants from the Malmö Diet and Cancer Cardiovascular Cohort (MDC-CC). Changes in amino acid levels were analyzed after weight loss and weight maintenance in 12 obese subjects and evaluated in a replication cohort (n = 83). Results. Out of the eight identified BMI-associated amino acids from the MDC-CC, alanine, isoleucine, tyrosine, phenylalanine, and glutamate decreased after weight loss, while asparagine increased after weight maintenance. These changes were validated in the replication cohort. Scores that were constructed based on obesity-associated amino acids and known risk factors decreased in the ≥10% weight loss group with an associated change in BMI (R² = 0.16-0.22, p < 0.002), whereas the scores increased in the <10% weight loss group (p < 0.0004). Conclusions. Weight loss followed by weight maintenance leads to differential changes in amino acid levels associated with obesity. Treatment modifiable scores based on epidemiological and interventional data may be used to evaluate the potential metabolic benefit of weight loss.

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.