Application of branched-chain amino acids in human pathological states: renal failure

Transcriptomics and UHPLC-QQQ-MS analyses reveal the dysregulation of branched chain amino acids metabolism in renal fibrotic rats

The dysregulated levels of branched chain amino acids (BCAA) contribute to renal fibrosis in chronic kidney disease (CKD), yet specific analysis of BCAA contents and how they are regulated still remain unclear. It is therefore of great scientific interest to understand BCAA catabolism in CKD and develop a sensitive method for simultaneous determination of individual BCAA and their metabolites branched chain α-ketoacids (BCKA). In this work, the important role of BCAA metabolism that drives renal fibrosis in the process of CKD was first revealed by using transcriptomics. The key target genes controlling BCAA metabolism were then validated, that is, mRNA levels of BCKDHA and BCKDHB, the regulating rate-limiting enzymes during BCAA metabolism were abnormally reduced by quantitative PCR (qPCR), and a similar drop-off trend of protein expression of BCKDH, HIBCH and MCCC2 that are closely related to BCAA metabolism was also confirmed by western blotting. Furthermore, we established a novel strategy that simultaneously determines 6 individual BCAA and BCKA in serum and tissue. The method based on dansylhydrazine derivatization and ultra-high performance liquid chromatography-tandem triple quadrupole mass spectrometry (UHPLC-QQQ-MS) achieved to simultaneously determine the contents of BCAA and BCKA, which is efficient and stable. Compared with normal rats, levels of BCAA including leucine, isoleucine and valine in serum and kidney of CKD rats was decreased, while BCKA including α-ketoisocaproic acid, α-ketomethylvaleric acid and α-ketoisovaleric acid was increased. Together, these findings revealed the abnormality of BCAA metabolism in driving the course of kidney fibrosis and CKD. Our current study sheds new light on changes in BCAA metabolism during CKD, and may facilitate development of drugs to treat CKD and renal fibrosis.

Role of Gut Microbiota, Immune Imbalance, and Allostatic Load in the Occurrence and Development of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a prevailing complication arising from diabetes mellitus. Unfortunately, there are no trustworthy and efficacious treatment modalities currently available. In recent times, compelling evidence has emerged regarding the intricate correlation between the kidney and the gut microbiota, which is considered the largest immune organ within the human physique. Various investigations have demonstrated that the perturbation of the gut microbiota and its associated metabolites potentially underlie the etiology and progression of DKD. This phenomenon may transpire through perturbation of both the innate and the adaptive immunity, leading to a burdensome allostatic load on the body and ultimately culminating in the development of DKD. Within this literature review, we aim to delve into the intricate interplay between the gut microbiota, its metabolites, and the immune system in the context of DKD. Furthermore, we strive to explore and elucidate potential chemical interventions that could hold promise for the treatment of DKD, thereby offering invaluable insights and directions for future research endeavors.

Research progress on branched-chain amino acid aminotransferases

Branched-chain amino acid aminotransferases, widely present in natural organisms, catalyze bidirectional amino transfer between branched-chain amino acids and branched-chain α-ketoacids in cells. Branched-chain amino acid aminotransferases play an important role in the metabolism of branched-chain amino acids. In this paper, the interspecific evolution and biological characteristics of branched-chain amino acid aminotransferases are introduced, the related research of branched-chain amino acid aminotransferases in animals, plants, microorganisms and humans is summarized and the molecular mechanism of branched-chain amino acid aminotransferase is analyzed. It has been found that branched-chain amino acid metabolism disorders are closely related to various diseases in humans and animals and plants, such as diabetes, cardiovascular diseases, brain diseases, neurological diseases and cancer. In particular, branched-chain amino acid aminotransferases play an important role in the development of various tumors. Branched-chain amino acid aminotransferases have been used as potential targets for various cancers. This article reviews the research on branched-chain amino acid aminotransferases, aiming to provide a reference for clinical research on targeted therapy for various diseases and different cancers.

Amino acid metabolism in health and disease

Amino acids are the building blocks of protein synthesis. They are structural elements and energy sources of cells necessary for normal cell growth, differentiation and function. Amino acid metabolism disorders have been linked with a number of pathological conditions, including metabolic diseases, cardiovascular diseases, immune diseases, and cancer. In the case of tumors, alterations in amino acid metabolism can be used not only as clinical indicators of cancer progression but also as therapeutic strategies. Since the growth and development of tumors depend on the intake of foreign amino acids, more and more studies have targeted the metabolism of tumor-related amino acids to selectively kill tumor cells. Furthermore, immune-related studies have confirmed that amino acid metabolism regulates the function of effector T cells and regulatory T cells, affecting the function of immune cells. Therefore, studying amino acid metabolism associated with disease and identifying targets in amino acid metabolic pathways may be helpful for disease treatment. This article mainly focuses on the research of amino acid metabolism in tumor-oriented diseases, and reviews the research and clinical research progress of metabolic diseases, cardiovascular diseases and immune-related diseases related to amino acid metabolism, in order to provide theoretical basis for targeted therapy of amino acid metabolism.

Circulating Metabolites and Cardiovascular Disease in Asians with Chronic Kidney Disease

INTRODUCTION

Chronic kidney disease (CKD) is a growing public health problem, with significant burden of cardiovascular disease and mortality. The risk of cardiovascular disease in CKD is elevated beyond that predicted by traditional cardiovascular risk factors, suggesting that other factors may account for this increased risk. Through metabolic profiling, this study aimed to investigate the associations between serum metabolites and prevalent cardiovascular disease in Asian patients with CKD to provide insights into the complex interactions between metabolism, cardiovascular disease and CKD.

METHODS

This was a single-center cross-sectional study of 1,122 individuals from three ethnic cohorts in the population-based Singapore Epidemiology of Eye Disease (SEED) study (153 Chinese, 262 Indians, and 707 Malays) aged 40-80 years with CKD (estimated glomerular filtration rate <60 mL/min/1.73 m2). Nuclear magnetic resonance spectroscopy was used to quantify 228 metabolites from the participants' serum or plasma. Prevalent cardiovascular disease was defined as self-reported myocardial infarction, angina, or stroke. Multivariate logistic regression identified metabolites independently associated with cardiovascular disease in each ethnic cohort. Metabolites with the same direction of association with cardiovascular disease in all three cohorts were selected and subjected to meta-analysis.

RESULTS

Cardiovascular disease was present in 275 (24.5%). Participants with cardiovascular disease tend to be male; of older age; with hypertension, hyperlipidemia, and diabetes; with lower systolic and diastolic blood pressure (BP); lower high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol than those without cardiovascular disease. After adjusting for age, sex, systolic BP, diabetes, total cholesterol, and HDL cholesterol, 10 lipoprotein subclass ratios and 6 other metabolites were significantly associated with prevalent cardiovascular disease in at least one cohort. Meta-analysis with Bonferroni correction for multiple comparisons found that lower tyrosine, leucine, and valine concentrations and lower cholesteryl esters to total lipid ratio in intermediate-density lipoprotein (IDL) were associated with cardiovascular disease.

CONCLUSION

In Chinese, Indian, and Malay participants with CKD, prevalent cardiovascular disease was associated with tyrosine, leucine, valine, and cholesteryl esters to total lipid ratios in IDL. Increased cardiovascular risk in CKD patients may be contributed by altered amino acid and lipoprotein metabolism. The presence of CKD and ethnic differences may affect interactions between metabolites in health and disease, hence greater understanding will allow us to better risk stratify patients, and also individualize care with consideration of ethnic disparities.

Emerging role for branched-chain amino acids metabolism in fibrosis

Fibrosis is a common pathological feature of organ diseases resulting from excessive production of extracellular matrix, which accounts for significant morbidity and mortality. However, there is currently no effective treatment targeting fibrogenesis. Recently, metabolic alterations are increasingly considered as essential factors underlying fibrogenesis, and especially research on metabolic regulation of amino acids is flourishing. Among them, branched-chain amino acids (BCAAs) are the most abundant essential amino acids, including leucine, isoleucine and valine, which play significant roles in the substance and energy metabolism and their regulation. Dysregulation of BCAAs metabolism has been proven to contribute to numerous diseases. In this review, we summarize the metabolic regulation of fibrosis and the changes in BCAAs metabolism secondary to fibrosis. We also review the effects and mechanisms of the BCAAs intervention, and its therapeutic targeting in hepatic, renal and cardiac fibrosis, with a focus on the fibrosis in liver and associated hepatocellular carcinoma.

Metabolite, protein, and tissue dysfunction associated with COVID-19 disease severity

Proteins are direct products of the genome and metabolites are functional products of interactions between the host and other factors such as environment, disease state, clinical information, etc. Omics data, including proteins and metabolites, are useful in characterizing biological processes underlying COVID-19 along with patient data and clinical information, yet few methods are available to effectively analyze such diverse and unstructured data. Using an integrated approach that combines proteomics and metabolomics data, we investigated the changes in metabolites and proteins in relation to patient characteristics (e.g., age, gender, and health outcome) and clinical information (e.g., metabolic panel and complete blood count test results). We found significant enrichment of biological indicators of lung, liver, and gastrointestinal dysfunction associated with disease severity using publicly available metabolite and protein profiles. Our analyses specifically identified enriched proteins that play a critical role in responses to injury or infection within these anatomical sites, but may contribute to excessive systemic inflammation within the context of COVID-19. Furthermore, we have used this information in conjunction with machine learning algorithms to predict the health status of patients presenting symptoms of COVID-19. This work provides a roadmap for understanding the biochemical pathways and molecular mechanisms that drive disease severity, progression, and treatment of COVID-19.

The Critical Role of the Branched Chain Amino Acids (BCAAs) Catabolism-Regulating Enzymes, Branched-Chain Aminotransferase (BCAT) and Branched-Chain α-Keto Acid Dehydrogenase (BCKD), in Human Pathophysiology

Branched chain amino acids (BCAAs), leucine, isoleucine and valine, are essential amino acids widely studied for their crucial role in the regulation of protein synthesis mainly through the activation of the mTOR signaling pathway and their emerging recognition as players in the regulation of various physiological and metabolic processes, such as glucose homeostasis. BCAA supplementation is primarily used as a beneficial nutritional intervention in chronic liver and kidney disease as well as in muscle wasting disorders. However, downregulated/upregulated plasma BCAAs and their defective catabolism in various tissues, mainly due to altered enzymatic activity of the first two enzymes in their catabolic pathway, BCAA aminotransferase (BCAT) and branched-chain α-keto acid dehydrogenase (BCKD), have been investigated in many nutritional and disease states. The current review focused on the underlying mechanisms of altered BCAA catabolism and its contribution to the pathogenesis of a numerous pathological conditions such as diabetes, heart failure and cancer. In addition, we summarize findings that indicate that the recovery of the dysregulated BCAA catabolism may be associated with an improved outcome and the prevention of serious disease complications.

Analysis of plasma free amino acids in diabetic rat and the intervention of Ginkgo biloba leaves extract using hydrophilic interaction liquid chromatography coupled with tandem mass-spectrometry

Amino acids (AAs) are important metabolites that are related with diabetes. However, their roles in the initiation and development of diabetes mellitus (DM), especially in the treatment of Ginkgo biloba leaves extract (GBE) have not been fully explored. Thus, we investigated the roles that AAs played in the progression and GBE supplementation of DM rat induced by streptozotocin. The rats were randomly divided into a normal control group treated with drug-free solution, a normal control group treated with GBE, a DM group treated with drug-free solution, and DM group treated with GBE; and maintained on this protocol for 9 weeks. Rat plasma was collected from the sixth week to the ninth week and then analyzed with the optimized hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry method. A total of 17 AAs with differential levels were monitored to indicate dysfunction of AAs metabolism to confirm the occurrence and development of DM. Treatment with GBE partially reversed the changes seen in seven AAs including leucine, isoleucine, tyrosine, glutamic acid, asparagines, lysine and alanine in DM rats, indicating that GBE could prevent the occurrence and development of DM by acting on AAs metabolism. The improvement of those AAs metabolism disorders may play a considerable role in the treatment of GBE on the occurrence and development of DM. Those findings potentially promote the understanding of the pathogenic progression of DM and reveal the therapeutic mechanism of GBE against DM.

High L-Valine Concentrations Associate with Increased Oxidative Stress and Newly-Diagnosed Type 2 Diabetes Mellitus: A Cross-Sectional Study

OBJECTIVE

Branched-chain amino acids (BCAAs) are essential AAs which are widely used as antioxidants in patients with liver and kidney dysfunction. However, BCAAs are strongly correlated with insulin resistance (IR) and diabetes. This study aimed to evaluate the relationship among BCAAs, oxidative stress, and type 2 diabetes mellitus (T2DM) in a Chinese population.

METHODS

Anthropometric and biochemical examinations were performed in 816 individuals who participated in the Huai'an Diabetes Prevention Program. Serum BCAAs concentrations were measured by hydrophilic interaction chromatography-tandem mass spectrometric method. Oxidative stress was evaluated by malondialdehyde (MDA) as an index of lipid peroxidation and the superoxide dismutase (SOD) activity.

RESULTS

A total of 816 participants were divided into three groups: normal glucose metabolism (NGM), prediabetes, and newly-diagnosed diabetes mellitus (NDM). Subjects in NDM group show higher MDA and lower SOD levels than subjects in other groups. L-Val levels positively correlated with MDA levels and negatively with SOD in NDM groups. After adjusting for T2DM risk factors, high L-Val levels were significantly associated with higher BMI, WC, FPG, increased LnTG and decreased HDL-C. L-Val was also independently associated with NDM (OR 1.06, 95% CI 1.02-1.10; P = 0.005). Furthermore, the odds ratios for NDM among participants with high L-Val (≥35.25μg/mL) levels showed a 2.25-fold (95% CI 1.11-4.57; P = 0.024) increase compared to participants with low L-Val (<27.26 μg/mL) levels after adjusting for MDA and confounding factors.

CONCLUSION

High serum L-Val levels are independently associated with oxidative stress, thus promoting IR and NDM. Further study should be done to clarify the mechanism.

Aqueous Metabolite Trends for the Progression of Nonalcoholic Fatty Liver Disease in Female Bariatric Surgery Patients by Targeted 1H-NMR Metabolomics

Determining biomarkers and better characterizing the biochemical progression of nonalcoholic fatty liver disease (NAFLD) remains a clinical challenge. A targeted ¹H-NMR study of serum, combined with clinical variables, detected and localized biomarkers to stages of NAFLD in morbidly obese females. Pre-surgery serum samples from 100 middle-aged, morbidly obese female subjects, grouped on gold-standard liver wedge biopsies (non-NAFLD; steatosis; and fibrosis) were collected, extracted, and analyzed in aqueous (D₂O) buffer (¹H, 600 MHz). Profiled concentrations were subjected to exploratory statistical analysis. Metabolites varying significantly between the non-NAFLD and steatosis groups included the ketone bodies 3-hydroxybutyrate (↓; p = 0.035) and acetone (↓; p = 0.012), and also alanine (↑; p = 0.004) and a putative pyruvate signal (↑; p = 0.003). In contrast, the steatosis and fibrosis groups were characterized by 2-hydroxyisovalerate (↑; p = 0.023), betaine (↓; p = 0.008), hypoxanthine (↓; p = 0.003), taurine (↓; p = 0.001), 2-hydroxybutyrate (↑; p = 0.045), 3-hydroxyisobutyrate (↑; p = 0.046), and increasing medium chain fatty acids. Exploratory classification models with and without clinical variables exhibited overall success rates ca. 75–85%. In the study conditions, inhibition of fatty acid oxidation and disruption of the hepatic urea cycle are supported as early features of NAFLD that continue in fibrosis. In fibrosis, markers support inflammation, hepatocyte damage, and decreased liver function. Complementarity of NMR concentrations and clinical information in classification models is shown. A broader hypothesis that standard-of-care sera can yield metabolomic information is supported.

From Farm to Fork: Crickets as Alternative Source of Protein, Minerals, and Vitamins

Globally, there is growing interest to integrate cricket-based ingredients (flour) into food products to combat food and nutrition insecurity. However, there is lack of information on in-depth nutrient profile of the two cricket species (Scapsipedus icipe and Gryllus bimaculatus), which are the most widely consumed in Africa. Here we determined the nutrient composition of two cricket species and compared them with published records of key animal and plant sources. Our results revealed that the crude protein contents of S. icipe and G. bimaculatus were similar (56.8 and 56.9%, respectively) and comparable to those of animal protein sources. Both cricket species had balanced amino acid profiles that are superior to that of animal and plant sources, except for histidine and cysteine. The protein digestibility of S. icipe and G. bimaculatus ranged between 80 and 88%, which is comparable to that of common plant foods but slightly lower than that of animal proteins. The iron, Zinc, and potassium contents were considerably higher in both cricket species compared to that of plant and animal sources. The calcium contents of both crickets (S. icipe and G. bimaculatus) was superior to that of plant and animal origin except for kidney beans and eggs, respectively. Riboflavin, thiamine, and folic acid concentrations of S. icipe and G. bimaculatus were superior to that of the conventional sources. Vitamin A levels were significantly higher in S. icipe compared to G. bimaculatus. This implies that S. icipe and G. bimaculatus can adequately contribute to our daily required nutrient intake. Thus, integrating cricket flours into ready-to-eat food products would address some of the most pressing nutritional deficiency challenges that many developing countries have to grapple with, particularly high risk to serious health problems such as anemia, poor pregnancy outcomes, hypertension, increased risk of morbidity and mortality, stunted growth and impaired physical and cognitive development. We conclude that edible crickets present unique opportunities for improving food and nutritional insecurity status of both resource-poor and Western populations.

Effect of Branched-Chain Amino Acid Infusion on In-Hospital Mortality of Patients With Hepatic Encephalopathy and End-Stage Kidney Disease: A Retrospective Cohort Study Using a National Inpatient Database

OBJECTIVES

Renal failure and hepatic cirrhosis are mutually aggravating factors. However, no specific therapeutic strategies for hepatic encephalopathy (HE) and end-stage kidney disease have been established. The coexistence, with an extremely poor prognosis, makes randomized controlled trials unfeasible. We evaluated whether an infusion of branched-chain amino acids was associated with mortality in patients hospitalized for HE and end-stage kidney disease.

DESIGN AND METHODS

Using the Japanese Diagnosis Procedure Combination database, we retrospectively identified patients with HE and end-stage kidney disease who received hemodialysis within 2 days of admission from July 2011 to March 2017. We divided the patients into those who received branched-chain amino acid infusion within 2 days of admission and those who did not. We conducted analyses using overlap weights based on propensity scores to compare in-hospital mortality between the groups. Sub-group analysis was conducted by stratifying patients by Child-Pugh class.

RESULTS

We identified 553 eligible patients, including 503 patients who received branched-chain amino acid infusion and 50 who did not. The patients who received branched-chain amino acid infusion had lower mortality than those who did not (10.2% vs. 20.1%, relative risk 0.51, 95% confidence interval 0.27-0.95). Sub-group analysis showed that branched-chain amino acid infusion was associated with decreased in-hospital mortality in patients with Child-Pugh class C (16.2% vs. 39.0%, relative risk 0.41, 95% confidence interval 0.23-0.76).

CONCLUSIONS

Branched-chain amino acid infusion may improve the prognosis of HE in patients with end-stage kidney disease, particularly those with lower liver function. Further research is necessary to provide a suitable treatment for HE in patients with end-stage kidney disease.

Altered Amino Acid Metabolism in Patients with Cardiorenal Syndrome Type 2: Is It a Problem for Protein and Exercise Prescriptions?

The goal of this retrospective study was to document any alterations in plasma amino acids (AAs) in subjects with cardiorenal syndrome type 2 (CRS 2). We analyzed data from sixteen patients with CRS 2 and eight healthy subjects (control group, C), whose plasma arterial (A) and venous (V) AA concentrations had been measured. Compared to C, the group of CRS 2 patients showed significant reductions by more than 90% in A (p < 0.01) and V (p < 0.01) individual AAs, whereas negative A-V differences that indicated a net muscle AA release (muscle hypercatabolism) were found in 59% of CRS 2 patients (p < 0.03). No significant differences in plasma A and V AA concentrations nor in A-V differences were found between patients with mild kidney damage (N = 5; estimated glomerular filtration rate, eGFR ≥ 60 mL/min/1.73 m²) and patients with moderate-severe kidney damage (N = 11; eGFR < 60 mL/min/1.73 m²). Several plasma arterial AAs correlated with hemodynamic variables, but not with GFR. The study showed that patients with CRS 2 had very low concentrations of circulating AAs, independent of the degree of GFR damage.

Reading patterns of proteome damage by glycation, oxidation and nitration: quantitation by stable isotopic dilution analysis LC-MS/MS

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) provides a high sensitivity, high specificity multiplexed method for concurrent detection of adducts formed by protein glycation, oxidation and nitration, also called AGEomics. Combined with stable isotopic dilution analysis, it provides for robust quantitation of protein glycation, oxidation and nitration adduct analytes. It is the reference method for such measurements. LC-MS/MS has been used to measure glycated, oxidized and nitrated amino acids - also called glycation, oxidation and nitration free adducts, with a concurrent quantitation of the amino acid metabolome in physiological fluids. Similar adduct residues in proteins may be quantitated with prior exhaustive enzymatic hydrolysis. It has also been applied to quantitation of other post-translation modifications, such as citrullination and formation of Nε-(γ-glutamyl)lysine crosslink by transglutaminases. Application to cellular and extracellular proteins gives estimates of the steady-state levels of protein modification by glycation, oxidation and nitration, and measurement of the accumulation of glycation, oxidation and nitration adducts in cell culture medium and urinary excretion gives an indication of flux of adduct formation. Measurement of glycation, oxidation and nitration free adducts in plasma and urine provides for estimates of renal clearance of free adducts. Diagnostic potential in clinical studies has been enhanced by the combination of estimates of multiple adducts in optimized diagnostic algorithms by machine learning. Recent applications have been in early-stage detection of metabolic, vascular and renal disease, and arthritis, metabolic control and risk of developing vascular complication in diabetes, and a blood test for autism.

Sarcopenia in chronic kidney disease: what have we learned so far?

The term sarcopenia was first introduced in 1988 by Irwin Rosenberg to define a condition of muscle loss that occurs in the elderly. Since then, a broader definition comprising not only loss of muscle mass, but also loss of muscle strength and low physical performance due to ageing or other conditions, was developed and published in consensus papers from geriatric societies. Sarcopenia was proposed to be diagnosed based on operational criteria using two components of muscle abnormalities, low muscle mass and low muscle function. This brought awareness of an important nutritional derangement with adverse outcomes for the overall health. In parallel, many studies in patients with chronic kidney disease (CKD) have shown that sarcopenia is a prevalent condition, mainly among patients with end stage kidney disease (ESKD) on hemodialysis (HD). In CKD, sarcopenia is not necessarily age-related as it occurs as a result of the accelerated protein catabolism from the disease and from the dialysis procedure per se combined with low energy and protein intakes. Observational studies showed that sarcopenia and especially low muscle strength is associated with worse clinical outcomes, including worse quality of life (QoL) and higher hospitalization and mortality rates. This review aims to discuss the differences in conceptual definition of sarcopenia in the elderly and in CKD, as well as to describe etiology of sarcopenia, prevalence, outcome, and interventions that attempted to reverse the loss of muscle mass, strength and mobility in CKD and ESKD patients.

High Plasma Branched-Chain Amino Acids Are Associated with Higher Risk of Post-Transplant Diabetes Mellitus in Renal Transplant Recipients

Post-transplant diabetes mellitus (PTDM) is a serious complication in renal transplant recipients. Branched-chain amino acids (BCAAs) are involved in the pathogenesis of insulin resistance. We determined the association of plasma BCAAs with PTDM and included adult renal transplant recipients (≥18 y) with a functioning graft for ≥1 year in this cross-sectional cohort study with prospective follow-up. Plasma BCAAs were measured in 518 subjects using nuclear magnetic resonance spectroscopy. We excluded subjects with a history of diabetes, leaving 368 non-diabetic renal transplant recipients eligible for analyses. Cox proportional hazards analyses were used to assess the association of BCAAs with the development of PTDM. Mean age was 51.1 ± 13.6 y (53.6% men) and plasma BCAA was 377.6 ± 82.5 µM. During median follow-up of 5.3 (IQR, 4.2–6.0) y, 38 (9.8%) patients developed PTDM. BCAAs were associated with a higher risk of developing PTDM (HR: 1.43, 95% CI 1.08–1.89) per SD change (p = 0.01), independent of age and sex. Adjustment for other potential confounders did not significantly change this association, although adjustment for HbA1c eliminated it. The association was mediated to a considerable extent (53%) by HbA1c. The association was also modified by HbA1c; BCAAs were only associated with renal transplant recipients without prediabetes (HbA1c < 5.7%). In conclusion, high concentrations of plasma BCAAs are associated with developing PTDM in renal transplant recipients. Alterations in BCAAs may represent an early predictive biomarker for PTDM.

Urinary Metabolomic Markers of Protein Glycation, Oxidation, and Nitration in Early-Stage Decline in Metabolic, Vascular, and Renal Health

Glycation, oxidation, nitration, and crosslinking of proteins are implicated in the pathogenic mechanisms of type 2 diabetes, cardiovascular disease, and chronic kidney disease. Related modified amino acids formed by proteolysis are excreted in urine. We quantified urinary levels of these metabolites and branched-chain amino acids (BCAAs) in healthy subjects and assessed changes in early-stage decline in metabolic, vascular, and renal health and explored their diagnostic utility for a noninvasive health screen. We recruited 200 human subjects with early-stage health decline and healthy controls. Urinary amino acid metabolites were determined by stable isotopic dilution analysis liquid chromatography-tandem mass spectrometry. Machine learning was applied to optimise and validate algorithms to discriminate between study groups for potential diagnostic utility. Urinary analyte changes were as follows: impaired metabolic health-increased N _ε -carboxymethyl-lysine, glucosepane, glutamic semialdehyde, and pyrraline; impaired vascular health-increased glucosepane; and impaired renal health-increased BCAAs and decreased N _ε -(γ-glutamyl)lysine. Algorithms combining subject age, BMI, and BCAAs discriminated between healthy controls and impaired metabolic, vascular, and renal health study groups with accuracy of 84%, 72%, and 90%, respectively. In 2-step analysis, algorithms combining subject age, BMI, and urinary N _ε -fructosyl-lysine and valine discriminated between healthy controls and impaired health (any type), accuracy of 78%, and then between types of health impairment with accuracy of 69%-78% (cf. random selection 33%). From likelihood ratios, this provided small, moderate, and conclusive evidence of early-stage cardiovascular, metabolic, and renal disease with diagnostic odds ratios of 6 - 7, 26 - 28, and 34 - 79, respectively. We conclude that measurement of urinary glycated, oxidized, crosslinked, and branched-chain amino acids provides the basis for a noninvasive health screen for early-stage health decline in metabolic, vascular, and renal health.

Concentration of Branched-Chain Amino Acids Is a Strong Risk Marker for Incident Hypertension

The potential role of branched-chain amino acids (BCAAs) in the pathogenesis of cardiometabolic diseases is increasingly recognized, but the association of BCAAs with incident hypertension remains unknown. The aim of the present study was to explore the association of BCAAs with incident hypertension in a prospective population-based cohort study. We measured plasma concentrations of BCAAs by means of nuclear magnetic resonance spectroscopy in 4169 participants from the PREVEND (Prevention of Renal and Vascular End-stage Disease) study. We estimated the risk of incident hypertension using multivariable-adjusted Cox regression models. After a median follow-up of 8.6 years, incident hypertension was ascertained in 924 subjects. Cox regression analyses revealed a significant association between BCAAs and incident hypertension. The hazard ratio per one SD of BCAAs was 1.11 (95% CI, 1.02-1.20; P=0.01) after full adjustment for multiple clinical variables. Likewise, the fully adjusted association remained significant when evaluated as categorical variable (hazard ratio for upper quartile with lowest quartile as reference category, 1.36; 95% CI, 1.11-1.68; P=0.003). Furthermore, the net reclassification improvement assessment improved after addition of BCAAs to a traditional risk model (P<0.001). This prospective study revealed that high plasma concentrations of BCAAs are associated with an increased risk of newly developed hypertension. The association remained after adjusting for age, sex, body mass index, and lipid profile.

Effect of renal tubule-specific knockdown of the Na+/H+ exchanger NHE3 in Akita diabetic mice

Na+/H+ exchanger isoform 3 (NHE3) contributes to Na+/bicarbonate reabsorption and ammonium secretion in early proximal tubules. To determine its role in the diabetic kidney, type 1 diabetic Akita mice with tubular NHE3 knockdown [Pax8-Cre; NHE3-knockout (KO) mice] were generated. NHE3-KO mice had higher urine pH, more bicarbonaturia, and compensating increases in renal mRNA expression for genes associated with generation of ammonium, bicarbonate, and glucose (phosphoenolpyruvate carboxykinase) in proximal tubules and H+ and ammonia secretion and glycolysis in distal tubules. This left blood pH and bicarbonate unaffected in nondiabetic and diabetic NHE3-KO versus wild-type mice but was associated with renal upregulation of proinflammatory markers. Higher renal phosphoenolpyruvate carboxykinase expression in NHE3-KO mice was associated with lower Na+-glucose cotransporter (SGLT)2 and higher SGLT1 expression, indicating a downward tubular shift in Na+ and glucose reabsorption. NHE3-KO was associated with lesser kidney weight and glomerular filtration rate (GFR) independent of diabetes and prevented diabetes-associated albuminuria. NHE3-KO, however, did not attenuate hyperglycemia or prevent diabetes from increasing kidney weight and GFR. Higher renal gluconeogenesis may explain similar hyperglycemia despite lower SGLT2 expression and higher glucosuria in diabetic NHE3-KO versus wild-type mice; stronger SGLT1 engagement could have affected kidney weight and GFR responses. Chronic kidney disease in humans is associated with reduced urinary excretion of metabolites of branched-chain amino acids and the tricarboxylic acid cycle, a pattern mimicked in diabetic wild-type mice. This pattern was reversed in nondiabetic NHE3-KO mice, possibly reflecting branched-chain amino acids use for ammoniagenesis and tricarboxylic acid cycle upregulation to support formation of ammonia, bicarbonate, and glucose in proximal tubule. NHE3-KO, however, did not prevent the diabetes-induced urinary downregulation in these metabolites.

Amino acid status in dogs with protein-losing nephropathy

BACKGROUND

Proteinuria in dogs with kidney disease can contribute to protein-energy wasting and malnutrition. Little is known about amino acid (AA) status in dogs with protein-losing nephropathy (PLN).

OBJECTIVES

The purpose of our study was to further elucidate AA status in PLN dogs, with the hypothesis that PLN dogs would have altered AA status as compared to healthy dogs.

ANIMALS

Thirty client-owned PLN dogs were compared to 10 healthy control dogs.

METHODS

Prospective observational study. Dogs with PLN that were presented to the teaching hospital were enrolled. Plasma AA profiles were measured using an automated high-performance liquid chromatography AA analyzer.

RESULTS

Compared to control dogs, PLN dogs had significantly lower concentrations of leucine, threonine, histidine, glycine, proline, asparagine, tyrosine, o-hydroxyproline, and serine, as well as sums of both essential and nonessential AA (P < .05). Dogs with PLN had significantly lower ratios of tyrosine-to-phenylalanine and glycine-to-serine (P < .05), and a significantly greater ratio of valine-to-glycine (P < .05).

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with PLN have altered AA status compared to healthy dogs. These findings could have therapeutic implications in determining optimal management of PLN dogs, such as providing AA supplementation along with other standard treatment.

The aldose reductase inhibitor epalrestat exerts nephritic protection on diabetic nephropathy in db/db mice through metabolic modulation

Epalrestat is an inhibitor of aldose reductase in the polyol pathway and is used for the management of diabetic neuropathy clinically. Our pilot experiments and accumulated evidences showed that epalrestat inhibited polyol pathway and reduced sorbitol production, and suggested the potential renal protection effects of epalrestat on diabetic nephropathy (DN). To evaluate the protective effect of epalrestat, the db/db mice were used and exposed to epalrestat for 8 weeks, both the physiopathological condition and function of kidney were examined. For the first time, we showed that epalrestat markedly reduced albuminuria and alleviated the podocyte foot process fusion and interstitial fibrosis of db/db mice. Metabolomics was employed, and metabolites in the plasma, renal cortex, and urine were profiled using a gas chromatography-mass spectrometry (GC/MS)-based metabolomic platform. We observed an elevation of sorbitol and fructose, and a decrease of myo-inositol in the renal cortex of db/db mice. Epalrestat reversed the renal accumulation of the polyol pathway metabolites of sorbitol and fructose, and increased myo-inositol level. Moreover, the upregulation of aldose reductase, fibronectin, collagen III, and TGF-β1 in renal cortex of db/db mice was downregulated by epalrestat. The data suggested that epalrestat has protective effects on DN, and the inhibition of aldose reductase and the modulation of polyol pathway in nephritic cells be a potentially therapeutic strategy for DN.

Differences in Amino Acid Loss Between High-Efficiency Hemodialysis and Postdilution and Predilution Hemodiafiltration Using High Convection Volume Exchange-A New Metabolic Scenario? A Pilot Study

OBJECTIVE

The objective of the study was to quantify the loss of total amino acids (TAAs), nonessential amino acids, essential amino acids, and branched chain amino acids (BCAAs) produced by high-efficiency hemodialysis (HEHD), postdilution hemodiafiltration (HDFpost), and predilution hemodiafiltration (HDFpre) using high ultrafiltration volumes; and to define the specific AA losses registered in HEHD, HDFpost, and HDFpre; to identify a potential metabolic and nutritional decline into protein energy wasting; to compare AA analysis of arterial blood samples taken from healthy controls and patients with end-stage renal disease undergoing hemodialysis.

DESIGN AND METHODS

Identical dialysis monitors, membranes, and dialysate/infusate were used to homogenize extracorporeal body influence. Ten patients were recruited and randomized to receive treatment with HEHD, HDFpost, and HDFpre it was used on-line dialytic water methodologies (OL); patients' AA arterial concentrations were measured at the start and on completion of dialysis; TAA from the dialyzer filter was calculated, and baseline levels were subsequently compared with findings obtained 1 year later. Finally, the results obtained were compared with the data from a study of 8 healthy volunteers conducted using bioimpedance analysis and laboratory blood tests to assess nutritional status.

RESULTS

A higher convective dose results in a higher weekly loss of TAA, nonessential AAs, essential AAs, and BCAAs (HEHD: 15.7 g; HDFpost-OL: 16.1 g; HDFpre-OL: 16.3 g, P < .01). After 12 months, the same hemodialys patients showed a reduced body and water intracellular mass and reduced phase angle. Arterial concentrations of TAAs and BCAAs were lower than those detected in healthy subjects (P < .01).

CONCLUSION

The study shows that the AA losses in dialytic liquid are greater after high exchange volume HDF techniques, especially HDFpre. The AA losses are not metabolically compensated, so these increase the derangements of predialytic arterial plasma AA levels. Both AA losses and arterial AA perturbations further worsened body composition already after 12 months of additional dialysis.

Diagnostic value of plasma tryptophan and symmetric dimethylarginine levels for acute kidney injury among tacrolimus-treated kidney transplant patients by targeted metabolomics analysis

Few literatures have evaluated the exact role of metabolomics in the identification process of potential biomarkers for acute kidney injury among the patients receiving renal transplantation. On top of this, the success of metabolomics in biomarker translation seems to lie in the robust quantitative method. As such, a single-center retrospective observational study was conducted enrolling 42 patients underwent renal transplantation with/without acute kidney injury, as well as 24 healthy volunteers, in Shanghai Changzheng Hospital. Plasma amino acid metabolic patterns for the participants were investigated by targeted UHPLC-MS/MS metabolic profiling. The most significant changes of the explored metabolites were related to the disturbance of tryptophan metabolism and arginine metabolism. Abnormal circulating tryptophan and symmetric dimethylarginine were identified to be potential biomarkers of acute kidney injury, combination of which showed a higher area under receiver-operator curve value (AUC = 0.901), improved sensitivity (0.889) and specificity (0.831) compared with creatinine only. Overall, these results revealed that targeted metabolomics analysis would be a potent and promising strategy for identification and pre-validation of biomarkers of acute kidney injury in renal transplantation patients.

Metabolic Profiling of Multiorgan Samples: Evaluation of MODY5/RCAD Mutant Mice

In the present study, we performed a metabolomics analysis to evaluate a MODY5/RCAD mouse mutant line as a potential model for HNF1B-associated diseases. Gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) of gut, kidney, liver, muscle, pancreas, and plasma samples uncovered the tissue specific metabolite distribution. Orthogonal projections to latent structures discriminant analysis (OPLS-DA) was used to identify the differences between MODY5/RCAD and wild-type mice in each of the tissues. The differences included, for example, increased levels of amino acids in the kidneys and reduced levels of fatty acids in the muscles of the MODY5/RCAD mice. Interestingly, campesterol was found in higher concentrations in the MODY5/RCAD mice, with a four-fold and three-fold increase in kidneys and pancreas, respectively. As expected, the MODY5/RCAD mice displayed signs of impaired renal function in addition to disturbed liver lipid metabolism, with increased lipid and fatty acid accumulation in the liver. From a metabolomics perspective, the MODY5/RCAD model was proven to display a metabolic pattern similar to what would be suspected in HNF1B-associated diseases. These findings were in line with the presumed outcome of the mutation based on the different anatomy and function of the tissues as well as the effect of the mutation on development.

Tryptophan as a surrogate prognostic marker for diabetic nephropathy

AIMS/INTRODUCTION

Diabetic nephropathy is one of the leading causes of end-stage renal disease. Unfortunately, reliable surrogate markers for predicting the prognostic outcome of diabetic nephropathy are as yet absent. In order to find new markers in predicting the progression of diabetic nephropathy, we carried out a prospective study by investigating the correlation between serum metabolites and the annual change of estimated glomerular filtration rate (eGFR).

MATERIALS AND METHODS

From September 2013 to September 2015, 52 diabetes patients at various stages of chronic kidney disease were enrolled. While serum levels of 175 metabolites were measured by AbsoluteIDQ™ p180 kit, only those with a significant difference in advancing chronic kidney disease stages were selected. After then, serial renal function change of these patients was followed up for 12 months, the outcome of renal function with each selected metabolite was compared according to the occurrence of a rapid decline (sustained annual decrement rate ≥5%) of eGFR.

RESULTS

A total of 26 metabolites were found to be significantly associated with the severity of chronic kidney disease. Tryptophan (Trp) showed a significant association with the event of rapid decline in eGFR (P = 0.036). Serum concentration of Trp <44.20 μmol/L showed the most valuable predictive value with 55.6% sensitivity and 87% specificity.

CONCLUSIONS

A lower level of Trp, especially <44.20 μmol/L, was related to a rapid decline in eGFR. Accordingly, Trp might be regarded as a potential prognostic marker for diabetic nephropathy.

NAD+/NADH homeostasis affects metabolic adaptation to hypoxia and secondary metabolite production in filamentous fungi

Filamentous fungi are used to produce fermented foods, organic acids, beneficial secondary metabolites and various enzymes. During such processes, these fungi balance cellular NAD⁺:NADH ratios to adapt to environmental redox stimuli. Cellular NAD(H) status in fungal cells is a trigger of changes in metabolic pathways including those of glycolysis, fermentation, and the production of organic acids, amino acids and secondary metabolites. Under hypoxic conditions, high NADH:NAD⁺ ratios lead to the inactivation of various dehydrogenases, and the metabolic flow involving NAD⁺ is down-regulated compared with normoxic conditions. This review provides an overview of the metabolic mechanisms of filamentous fungi under hypoxic conditions that alter the cellular NADH:NAD⁺ balance. We also discuss the relationship between the intracellular redox balance (NAD/NADH ratio) and the production of beneficial secondary metabolites that arise from repressing the HDAC activity of sirtuin A via Nudix hydrolase A (NdxA)-dependent NAD⁺ degradation.

Amino acid supplements and metabolic health: a potential interplay between intestinal microbiota and systems control

Dietary supplementation of essential amino acids (EAAs) has been shown to promote healthspan. EAAs regulate, in fact, glucose and lipid metabolism and energy balance, increase mitochondrial biogenesis, and maintain immune homeostasis. Basic science and epidemiological results indicate that dietary macronutrient composition affects healthspan through multiple and integrated mechanisms, and their effects are closely related to the metabolic status to which they act. In particular, EAA supplementation can trigger different and even opposite effects depending on the catabolic and anabolic states of the organisms. Among others, gut-associated microbial communities (referred to as gut microbiota) emerged as a major regulator of the host metabolism. Diet and host health influence gut microbiota, and composition of gut microbiota, in turn, controls many aspects of host health, including nutrient metabolism, resistance to infection, and immune signals. Altered communication between the innate immune system and the gut microbiota might contribute to complex diseases. Furthermore, gut microbiota and its impact to host health change largely during different life phases such as lactation, weaning, and aging. Here we will review the accumulating body of knowledge on the impact of dietary EAA supplementation on the host metabolic health and healthspan from a holistic perspective. Moreover, we will focus on the current efforts to establish causal relationships among dietary EAAs, gut microbiota, and health during human development.

Novel consortium of Klebsiella variicola and Lactobacillus species enhances the functional potential of fermented dairy products by increasing the availability of branched-chain amino acids and the amount of distinctive volatiles

AIMS

Identify novel bacterial taxa that could increase the availability of branched-chain amino acids and the amount of distinctive volatiles during skim milk fermentation.

METHODS AND RESULTS

We recovered 344 bacterial isolates from stool samples of healthy and breastfed infants. Five were selected based on their ability to produce branched-chain amino acids. Three strains were identified as Escherichia coli, one as Klebsiella pneumoniae and other as Klebsiella variicola by molecular and biochemical methods. HPLC and solid-phase microextraction with GC-MS were used for the determination of free amino acids and volatile compounds respectively. The consortium formed by K. variicola and four Lactobacillus species showed the highest production of Leu and Ile in skim milk fermentation. In addition, the production of volatile compounds, such as acetoin, ethanol, 2-nonanone, and acetic, hexanoic and octanoic acids, increased in comparison to commercial yogurt, Emmental and Gouda cheese. Also, distinctive volatiles, such as 2,3-butanediol, 4-methyl-2- hexanone and octanol, were identified.

CONCLUSION

The use of K. variicola in combination with probiotic Lactobacillus species enhances the availability of Leu and Ile and the amount of distinctive volatiles during skim milk fermentation.

SIGNIFICANCE AND IMPACT OF THE STUDY

The identified consortium increases the functional potential of fermented dairy products.

The construction of a panel of serum amino acids for the identification of early chronic kidney disease patients

BACKGROUND

Serum creatinine, urea, and cystatin-c are standardly used for the evaluation of renal function in the clinic. However, some patients have chronic kidney disease but still retain kidney function; a conventional serum index in these patients can be completely normal. Serum amino acid levels can reflect subtle changes in metabolism and are closely related to renal function. Here, we investigated how amino acids change as renal impairment increases.

METHODS

Subjects were divided into three groups by renal function glomerular filtration rate: healthy controls, patients with chronic kidney disease with normal kidney function, and patients with chronic kidney disease with decreased kidney function group. We identified 11 amino acids of interest using LC-MS/MS on MRM (+) mode.

RESULTS

Statistical analysis indicated that alanine (ALA), valine (VAL), and tyrosine (TYR) decrease with renal function impairment, whereas phenylalanine (PHE) and citrulline (CIT) increase. We tried to construct a diagnostic model utilizing a combination of amino acids capable of identifying early chronic kidney disease patients. The accuracy, specificity, and sensitivity of the combining predictors were 86.9%, 84.6%, and 90.9%, respectively, which is superior to the reported values for serum creatinine, urea, and cystatin-c.

CONCLUSION

Our data suggest that serum amino acid levels may supply important information for the early detection of chronic kidney disease. We are the first to establish a diagnostic model utilizing serum levels of multiple amino acids for the diagnosis of patients with early-stage chronic kidney disease.

Branched-chain amino acids differently modulate catabolic and anabolic states in mammals: a pharmacological point of view

Substantial evidence has been accumulated suggesting that branched-chain amino acid (BCAA) supplementation or BCAA-rich diets have a positive effect on the regulation of body weight, muscle protein synthesis, glucose homeostasis, the ageing process and extend healthspan. Despite these beneficial effects, epidemiological studies have shown that BCAA plasma concentrations and BCAA metabolism are altered in several metabolic disorders, including type 2 diabetes mellitus and cardiovascular diseases. In this review article, we present an overview of the current literature on the different effects of BCAAs in health and disease. We also highlight the results showing the most promising therapeutic effects of dietary BCAA supplementation and discuss how BCAAs can trigger different and even opposite effects, depending on the catabolic and anabolic states of the organisms. Moreover, we consider the effects of BCAAs when metabolism is abnormal, in the presence of a mixture of different anabolic and catabolic signals. These unique pharmacodynamic properties may partially explain some of the markedly different effects found in BCAA supplementation studies. To predict accurately these effects, the overall catabolic/anabolic status of patients should be carefully considered. In wider terms, a correct modulation of metabolic disorders would make nutraceutical interventions with BCAAs more effective.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Branched-chain amino acids attenuate early kidney injury in diabetic rats

Diabetic nephropathy (DN) is the most severe diabetic microvascular complication. The pathogenesis of diabetic nephropathy is complex, and oxidative stress plays an important role in the development of diabetic nephropathy. Elevated reactive oxygen species (ROS) levels activate various signaling pathways and influence the activities of transforming growth factor-β (TGF-β) and matrix metalloproteinase-9 (MMP-9), which contributes to glomerular hypertrophy. Branched-chain amino acids (BCAAs) are widely used in clinical treatment, and BCAAs can reduce the oxidative stress associated with the diabetic pancreas and some liver diseases. Thus, the aim of the present study was to determine whether BCAAs could attenuate oxidative stress in the kidneys of streptozotocin (STZ)-induced diabetic rats to prevent early diabetic kidney injury. Male Wistar rats were fed for two weeks with a normal chow diet or a high-fat diet in which 40% of calories were derived from fat. After this two-week period, the mice fed normal chow were injected with vehicle, while the high-fat diet group was injected intraperitoneally (i.p.) with 40 mg/kg STZ. The STZ-treated group was randomly divided into four subgroups that were treated with different doses of BCAAs or vehicle for two months by oral gavage. Plasma glucose, plasma creatinine, urinary protein and JNK, TGF-β, and MMP-9 mRNA and protein expression levels were measured in the rats. The ROS levels and proteinuria in the STZ-induced diabetic rats were significantly higher than those in the control groups. Moreover, early kidney injury occurred in the STZ-induced diabetic rats. However, BCAAs treatment decreased ROS levels, proteinuria and kidney injury. Moreover, JNK, TGF-β and MMP-9 mRNA and protein levels were significantly increased in the diabetic rats when compared with the control rats, and BCAAs treatment reversed these changes. Our results suggest that BCAAs counter oxidative stress in the kidneys of diabetic rats and alleviate diabetic kidney injury via the JNK/TGF-β/MMP-9 pathway.

Nutrition habits in 24-hour mountain bike racers

We investigated seventy-four ultra-mountain bikers (MTBers) competing in the solo category in the first descriptive field study to detail nutrition habits and the most common food before during and after the 24 hour race using questionnaires. During the race, bananas (86.5%), energy bars (50.0%), apples (43.2%) and cheese (43.2%) were the most commonly consumed food, followed by bread (44.6%), rice (33.8%) and bananas (33.8%) after the race. Average fluid intake was 0.5 ± 0.2 l/h. The main beverage was isotonic sports drink (82.4%) during and pure water (66.2%) after the race. The most preferred four supplements in the four weeks before, the day before, during and after the race were vitamin C (35.1%), magnesium (44.6%), magnesium (43.2%) and branched-chain amino acids (24.3%), respectively. Total frequency of food intake (30.6 ± 10.5 times/24 hrs) was associated with fluid intake (r = 0.43, P = 0.04) and both were highest at the beginning of the race and lower during the night hours and the last race segment in a subgroup of twenty-three ultra-MTBers. Supplement intake frequency (6.8 ± 8.4 times/24 hrs) was highest during the night hours and lower at the beginning and end of the race. Elevated food and fluid intake among participants tracked across all race segments (P < 0.001). In conclusion, the nutrition strategy employed by ultra-MTBers was similar to those demonstrated in previous studies of ultra-cyclists with some exceptions among selected individuals.

Dietary supplementation with essential amino acids boosts the beneficial effects of rosuvastatin on mouse kidney

The effects of high-potency statins on renal function are controversial. To address the impact of statins on renal morpho-functional aspects, normotensive young mice were treated with rosuvastatin (Rvs). Moreover, because statins may impair mitochondrial function, mice received either dietary supplementation with an amino acid mixture enriched in essential amino acids (EAAm), which we previously demonstrated to increase mitochondrial biogenesis in muscle or an unsupplemented control diet for 1 month. Mitochondrial biogenesis and function, apoptosis, and insulin signaling pathway events were studied, primarily in cortical proximal tubules. By electron microscopy analysis, mitochondria were more abundant and more heterogeneous in size, with dense granules in the inner matrix, in Rvs- and Rvs plus EAAm-treated animals. Rvs administration increased protein kinase B and endothelial nitric oxide synthase phosphorylation, but the mammalian target of rapamycin signaling pathway was not affected. Rvs increased the expression of sirtuin 1, peroxisome proliferator-activated receptor γ coactivator-1α, cytochrome oxidase type IV, cytochrome c, and mitochondrial biogenesis markers. Levels of glucose-regulated protein 75 (Grp75), B-cell lymphoma 2, and cyclin-dependent kinase inhibitor 1 were increased in cortical proximal tubules, and expression of the endoplasmic reticulum-mitochondrial chaperone Grp78 was decreased. EAAm supplementation maintained or enhanced these changes. Rvs promotes mitochondrial biogenesis, with a probable anti-apoptotic effect. EAAm boosts these processes and may contribute to the efficient control of cellular energetics and survival in the mouse kidney. This suggests that appropriate nutritional interventions may enhance the beneficial actions of Rvs, and could potentially prevent chronic renal side effects.

The importance and dosage of amino acids in nutritional support of various pathological conditions in ICU patients

BACKGROUND

Normal adults require twenty L-amino acids (AA) for protein synthesis. Functional AA regulate key metabolic pathways that are necessary for maintenance, growth, reproduction and immunity. Dietary supplementation with one or a mixture of these AA may be beneficial for ameliorating health problems at various stages of the life cycle and for optimizing of the efficiency of metabolic transformations. During disease, other amino acids also become essential. The principal goal of protein/amino acid administration in various pathological conditions in intensive care unit (ICU) patients is to provide the precursors of protein synthesis in tissues with high turnover and to protect skeletal muscle mass and function. Amino acid requirements in parenteral nutrition (PN) are higher when the patient is stressed/traumatized/infected than in the unstressed state. In severely ill ICU patients a higher provision of protein and amino acids has been associated with a lower mortality.

METHODS AND RESULTS

An overview of the effects and dosage of amino acids in nutritional support of various pathological conditions in ICU patients is presented.

CONCLUSION

It was demonstrated that 2.0-2.5 g protein substrate/kg normal body weight/day is safe and could be optimal for the most critically ill adults to decrease the risk of morbidity and mortality in some pathological conditions.

Uremic solutes and risk of end-stage renal disease in type 2 diabetes: metabolomic study

Here we studied plasma metabolomic profiles as determinants of progression to ESRD in patients with Type 2 diabetes (T2D). This nested case-control study evaluated 40 cases who progressed to ESRD during 8-12 years of follow-up and 40 controls who remained alive without ESRD from the Joslin Kidney Study cohort. Controls were matched with cases for baseline clinical characteristics; although controls had slightly higher eGFR and lower levels of urinary albumin excretion than T2D cases. Plasma metabolites at baseline were measured by mass spectrometry-based global metabolomic profiling. Of the named metabolites in the library, 262 were detected in at least 80% of the study patients. The metabolomic platform recognized 78 metabolites previously reported to be elevated in ESRD (uremic solutes). Sixteen were already elevated in the baseline plasma of our cases years before ESRD developed. Other uremic solutes were either not different or not commonly detectable. Essential amino acids and their derivatives were significantly depleted in the cases, whereas certain amino acid-derived acylcarnitines were increased. All findings remained statistically significant after adjustment for differences between study groups in albumin excretion rate, eGFR or HbA1c. Uremic solute differences were confirmed by quantitative measurements. Thus, abnormal plasma concentrations of putative uremic solutes and essential amino acids either contribute to progression to ESRD or are a manifestation of an early stage(s) of the disease process that leads to ESRD in T2D.

Effects of a honeybee sting on the serum free amino acid profile in humans

The aim of this study was to assess the response to a honeybee venom by analyzing serum levels of 34 free amino acids. Another goal of this study was to apply complex analytic-bioinformatic-clinical strategy based on up-to-date achievements of mass spectrometry in metabolomic profiling. The amino acid profiles were determined using hybrid triple quadrupole/linear ion trap mass spectrometer coupled with a liquid chromatography instrument. Serum samples were collected from 27 beekeepers within 3 hours after they were stung and after a minimum of 6 weeks following the last sting. The differences in amino acid profiles were evaluated using MetaboAnalyst and ROCCET web portals. Chemometric tests showed statistically significant differences in the levels of L-glutamine (Gln), L-glutamic acid (Glu), L-methionine (Met) and 3-methyl-L-histidine (3MHis) between the two analyzed groups of serum samples. Gln and Glu appeared to be the most important metabolites for distinguishing the beekeepers tested shortly after a bee sting from those tested at least 6 weeks later. The role of some amino acids in the response of an organism to the honeybee sting was also discussed. This study indicated that proposed methodology may allow to identify the individuals just after the sting and those who were stung at least 6 weeks earlier. The results we obtained will contribute to better understanding of the human body response to the honeybee sting.

Effects of a new mixture of essential amino acids (Aminotrofic(®)) in malnourished haemodialysis patients

The aim of this study was to verify the clinical efficacy of a diet associated with already commercially available oral amino acid functional cluster (AFC) compared to the administration of a diet associated with a nitrogen protein-based supplement (casein) in antagonizing malnutrition in patients with Chronic renal failure (CRF) undergoing haemodialysis. The secondary aim was to assess the changes in protein levels during the acute phase such as the expression of inflammatory cytokines. Twenty patients in haemodialysis aged between 18 and 85 of both genders (13 m, 7f) were recruited, randomized and divided into two groups and treated for 4 months respectively with: (1) oral AFC supplement (*)8 g/die: group A, and (2) oral supplementation of a protein nitrogenous mixture compared to AFC with a casein protein source) of 6.6 g: group P. During the initial assessment and thereafter on a monthly basis all patients underwent the following: Dietary recall 24 h; Anthropometric: Weight, height, BMI, expected dry weight, actual weight; Biochemical: Albumin, transferrin, Na, K, Cl, Ca, P, Mg, long-interval creatinine (Aminotrofic(®): Errekappa Euroterapici, Milano) pre-albumin, α1 acid glycoprotein, C reactive protein (CRP), protein nitrogen appearance (PNA); Instrumental: Handgrip strength evaluation, Calorimetry by means of Armband, Bio-impedance analysis (BIA), Spitzer Index (quality of life), Subjective Global Assessment Generated by the patient (PG SGA). Considering the nutritional parameters, no significant differences concerning dry weight emerged between the beginning (T0) and the end (T4) (weight A to T0: kg 64.41 ± 6.34; weight A to T4: kg 64.51 ± 7.05: P = NS; weight P to T0: kg 60.17 ± 11.94; weight P to T4: kg 59.86 ± 11.43: P = NS); biochemical parameters, significant differences were observed only for two parameters: pre-albumin (Pre-albumin A to T0 30.12 ± 7.23; Pre-albumin A to T4: 28.91 ± 5.8; Pre-albumin P to T0 22.51 ± 6.04; Pre-albumin P to T4: 26.10 ± 9.82), and Transferrin (Transferrin A to T0 171.77 ± 28.87 mg/dL, Transferrin A to T4: 181.44 ± 38.83 mg/dL: P < 0.005; Transferrin P to T0 160.29 ± 27.46 mg/dL, Transferrin P to T4: 146.57 ± 24.96 mg/dL: P < 0.005), but not in other parameters. From a nutritional perspective, after 4 months of treatment an increase in protein synthesis was noted in group A compared to group P which was proved by the significant increase of transferrin. This pilot study suggests the AFC oral supplementation may represent a valid alternative to intradialytic parenteral treatment and may also allow for an improvement in blood chemical values and nutritional status.

Leucine-stimulated mTOR signaling is partly attenuated in skeletal muscle of chronically uremic rats

The branched-chain amino acid leucine stimulates muscle protein synthesis in part by directly activating the mTOR signaling pathway. Furthermore, leucine, if given in conjunction with resistance exercise, enhances the exercise-induced mTOR signaling and protein synthesis. Here we tested whether leucine can activate the mTOR anabolic signaling pathway in uremia and whether it can enhance work overload (WO)-induced signaling through this pathway. Chronic kidney disease (CKD) and control rats were studied after 7 days of surgically induced unilateral plantaris muscle WO and a single leucine or saline load. In the basal state, 4E-BP1 phosphorylation was modestly depressed in non-WO muscle of CKD rats, whereas rpS6 phosphorylation was nearly completely suppressed. After oral leucine mTOR, S6K1 and rpS6 phosphorylation increased similarly in both groups, whereas the phospho-4E-BP1 response was modestly attenuated in CKD. WO alone activated the mTOR signaling pathway in control and CKD rats. In WO CKD, muscle leucine augmented mTOR and 4E-BP1 phosphorylation, but its effect on S6K1 phosphorylation was attenuated. Taken together, this study has established that the chronic uremic state impairs basal signaling through the mTOR anabolic pathway, an abnormality that may contribute to muscle wasting. However, despite this abnormality, leucine can stimulate this signaling pathway in CKD, although its effectiveness is partially attenuated, including in skeletal muscle undergoing sustained WO. Thus, although there is some resistance to leucine in CKD, the data suggest a potential role for leucine-rich supplements in the management of uremic muscle wasting.

Mechanism of de novo branched-chain amino acid synthesis as an alternative electron sink in hypoxic Aspergillus nidulans cells

Although branched-chain amino acids are synthesized as building blocks of proteins, we found that the fungus Aspergillus nidulans excretes them into the culture medium under hypoxia. The transcription of predicted genes for synthesizing branched-chain amino acids was upregulated by hypoxia. A knockout strain of the gene encoding the large subunit of acetohydroxy acid synthase (AHAS), which catalyzes the initial reaction of the synthesis, required branched-chain amino acids for growth and excreted very little of them. Pyruvate, a substrate for AHAS, increased the amount of hypoxic excretion in the wild-type strain. These results indicated that the fungus responds to hypoxia by synthesizing branched-chain amino acids via a de novo mechanism. We also found that the small subunit of AHAS regulated hypoxic branched-chain amino acid production as well as cellular AHAS activity. The AHAS knockout resulted in higher ratios of NADH/NAD(+) and NADPH/NADP(+) under hypoxia, indicating that the branched-chain amino acid synthesis contributed to NAD(+) and NADP(+) regeneration. The production of branched-chain amino acids and the hypoxic induction of involved genes were partly repressed in the presence of glucose, where cells produced ethanol and lactate and increased levels of lactate dehydrogenase activity. These indicated that hypoxic branched-chain amino acid synthesis is a unique alternative mechanism that functions in the absence of glucose-to-ethanol/lactate fermentation and oxygen respiration.