Keto Acids Research Articles

Biosynthetic Incorporation of Non-native Aryl Acid Building Blocks into Peptide Products Using Engineered Adenylation Domains.

Nonribosomal peptides (NRPs), one of the most widespread secondary metabolites in nature, with therapeutically significant activities, are biosynthesized by modular nonribosomal peptide synthetases (NRPSs). Aryl acids contribute to the structural diversity of NRPs as well as nonproteinogenic amino acids and keto acids. We previously confirmed that a single Asn-to-Gly substitution in the 2,3-dihydroxybenzoic acid-activating adenylation (A) domain EntE involved in enterobactin biosynthesis accepts monosubstituted benzoic acid derivatives with nitro, cyano, bromo, and iodo functionalities at the 2 or 3 positions. Here, we showed that the mutant EntE (N235G) accommodates various disubstituted benzoic acid derivatives with halogen, methyl, methoxy, nitro, and cyano functionalities at the 2 and 3 positions and monosubstituted benzoic acid with an alkyne at the 3 position. Structural analysis of the mutant EntE (N235G) with nonhydrolyzable aryl-AMP analogues using 3-chloro-2-methylbenzoic acid and 3-prop-2-ynoxybenzoic acid revealed how bulky 3-chloro-2-methylbenzoic acid and clickable 3-prop-2-ynoxybenzoic acid are recognized by enlarging the substrate-binding pocket of the enzyme. When engineered EntE mutants were coupled with enterobactin and vibriobactin biosynthetic enzymes, 3-hydroxybenzoic acid-, salicylic acid-, and 3-bromo-2-fluorobenzoic acid-containing peptides were produced as early stage intermediates, highlighting the potential of NRP biosynthetic pathway engineering for constructing diverse aryl acid-containing metabolites.

Ketonization of Valeric Acid to 5‐Nonanone over Metal Oxides catalysts

Valeric acid (VA), readily obtainable in the biorefinery from sugary biomass, can be upgraded to 5‐nonanone, a versatile chemical with numerous applications. This study investigates the performance of nine metal oxide catalysts (SnO2, SiO2, Y2O3, CeO2, ZrO2, TiO2, La2O3, Cr2O3, and Al2O3) in the gas‐phase ketonization of VA to 5‐nonanone in the 350‐450°C range. The screening reveals a correlation between the metal oxides lattice energy and their catalytic activity for valeric acid ketonization.ZrO2, TiO2, and La2O3, characterized by high lattice energy, demonstrate the highest catalytic activity. Y2O3, SnO2, SiO2, showing low lattice energy, are barely active. However, exceptions to this trend were observed: Cr2O3 and Al2O3 displayed poor catalytic performance despite their elevated lattice energy. A comprehensive characterization of the catalysts, encompassing XRD, N2‐physisorption, NH3‐TPD, and CO2‐TPD analyses, unveiled the role of important parameters including acid‐base properties in addition to lattice energy. Only oxides showing amphoteric properties can catalyse the reaction effectively. Low‐lattice energy and amphoteric oxides such as SnO2 (showing poor performance) become significantly active at higher temperature (500°C). Analysis of by‐products by online GC‐MS and spent catalyst characterization indicated that in this case the ketonization mechanism changed from the so‐called surface mechanism to the so‐called bulk mechanism.

Aerobic exercise attenuates insulin resistance via restoring branched chain amino acids homeostasis in obese mice.

Emerging evidences suggests that the disrupted branched-chain amino acids (BCAAs) homeostasis and elevated BCAAs promote obesity-related insulin resistance (IR). Exercise improves insulin sensitivity. However, whether BCAAs plays a role in the exercise-attenuated IR remains to be fully investigated. In this study, male C57BL/6J mice were induced to become diet-induced obese (DIO) and served as subjects. The initial investigation focused on the impact of exercise on IR and BCAAs. The DIO mice were randomly assigned to either a sedentary group (CON, n = 16) or an exercise group (EX, n = 16). The EX group underwent a 12-week aerobic exercise regimen on a treadmill. After 12-week, plasma BCAAs and branched-chain keto acids (BCKAs) were measured by liquid chromatography-mass spectrometry, glucose tolerance test (GTT) and insulin tolerance test (ITT) were performed, and the expression and phosphorylation of BCAAs catabolic proteins, as well as AKT T308 in gastrocnemius muscle and liver tissues, were evaluated using western blotting. Subsequently, the study explored the role of BCAAs in enhancing IR through exercise. Mice were randomly allocated into 4 groups: sedentary group (CON, n = 8), sedentary with BCAAs supplementation group (CON+BCAA, n = 8), exercise group (EX, n = 16), and exercise with BCAAs supplementation group (EX+BCAA, n = 16). The exercise protocol was as above. Mice in the BCAAs supplemented groups received drinking water containing 2% BCAAs. After 12-week, plasma BCAAs and BCKAs were measured, GTT and ITT tests were performed, and the phosphorylation of AKT T308, as well as p70S6K T389 in gastrocnemius muscle and liver, were compared between the EX group and the EX+BCAA group. Additionally, the phosphorylation of AMPKα T172 in both tissues was measured across all four groups. 12-week aerobic exercise improved insulin sensitivity in DIO mice while inducing BCAAs catabolic protein expression in skeletal muscle and liver, and reducing the plasma BCAAs level. Importantly, BCAAs supplementation elevated the plasma level of BCAAs and counteracted the exercise-attenuated IR. In skeletal muscle and liver tissues, BCAAs supplementation impaired the exercise-improved insulin signaling without enhancing mammalian target of rapamycin activity. AMPK activity was enhanced by aerobic exercise, which was abolished by BCAAs supplementation. Aerobic exercise attenuated insulin resistance via restoring BCAAs homeostasis and AMPK activity. The impacts of BCAAs intake on the metabolic effects of exercise sheds light on the combined exercise and nutrition intervention strategy for diabetes management.

A Catalytic Version of the Knorr Pyrrole Synthesis Permits Access to Pyrroles and Pyridines.

Aromatic N-heterocycles, such as pyrroles and pyridines, are important natural products and bulk and fine chemicals with numerous applications as active ingredients of pharmaceuticals and agrochemicals, as catalysts, and in materials sciences. We report here a catalytic version of the Knorr pyrrole synthesis in which simple and diversely available starting materials, such as 1,2-amino alcohols or 1,3-amino alcohols and keto esters, undergo a dehydrogenative coupling to form pyrroles and pyridines, respectively. Our reaction forms hydrogen as a collectible (and usable) byproduct and is mediated by a well-defined Mn catalyst. The synthesis of highly functionalized heterocycles and applications was demonstrated, and 35 compounds, not yet reported in the literature, were introduced.

Expression profile of tsRNAs in white adipose tissue of vitamin D deficiency young male mice with or without obesity

The expression of tsRNA in white adipose tissue (WAT) of VD deficiency male mice with obesity has not been reported. The healthy male C57BL/6J mice aged 4-6 weeks were divided into 4 groups according to the VD3 and fat energy supplement in daily diets. The qPCR verification further demonstrated that tRF5-20-HisGTG-3 were significantly up-regulated and mt-tRF3a-ProTGG was significantly down-regulated not only in HFVDD vs HFVDS, but aslo in HFVDD vs ConVDS. tRF5-22-CysGCA-27 were significantly up-regulated and mt-5'tiRNA-32-SerTGA, mt-5'tiRNA-33-SerTGA and mt-5'tiRNA-33-AlaTGC was significantly down-regulated only in HFVDD vs ConVDS. Enrichment analysis of the qPCR verified DE tsRNAs showed that the 3 up-regulated tsRNAs seemed to be associated with FoxO signaling pathway, GnRH secretion, 2−Oxocarboxylic acid metabolism, Autophagy-animal, Glucagon and insulin signaling pathway, while 4 down-regulated tsRNA seemed to be associated with cell communication, primary metabolic process, metabolic process, response to stimulus, multicellular organismal process, cellular metabolic process, cellular process and biological regulation. The tsRNAs were differentially expressed in VD deficiency with obesity, especially tRF5-20-HisGTG-3, tRF5-22-CysGCA-27, tRF3a-GlyGCC-1, mt-5'tiRNA-33-AlaTGC, mt-5'tiRNA-33-SerTGA, mt-5'tiRNA-32-SerTGA and mt-tRF3a-ProTGG. These tsRNAs seemed to be associated with FoxO signaling pathway, GnRH secretion, 2−oxocarboxylic acid metabolism, autophagy, glucagon and insulin signaling pathway, metabolic process and biological regulation.

Mechanistic and Therapeutic Implications of Protein and Lipid Sialylation in Human Diseases.

Glycan structures of glycoproteins and glycolipids on the surface glycocalyx and luminal sugar layers of intracellular membrane compartments in human cells constitute a key interface between intracellular biological processes and external environments. Sialic acids, a class of alpha-keto acid sugars with a nine-carbon backbone, are frequently found as the terminal residues of these glycoconjugates, forming the critical components of these sugar layers. Changes in the status and content of cellular sialic acids are closely linked to many human diseases such as cancer, cardiovascular, neurological, inflammatory, infectious, and lysosomal storage diseases. The molecular machineries responsible for the biosynthesis of the sialylated glycans, along with their biological interacting partners, are important therapeutic strategies and targets for drug development. The purpose of this article is to comprehensively review the recent literature and provide new scientific insights into the mechanisms and therapeutic implications of sialylation in glycoproteins and glycolipids across various human diseases. Recent advances in the clinical developments of sialic acid-related therapies are also summarized and discussed.

BCAA was more closely associated with visceral fat area than subcutaneous fat area in patients of type 2 diabetes mellitus: a cross-sectional study

BackgroundBranched-chain amino acid (BCAA) has been reported to be associated with obesity, the association of BCAA with visceral fat area (VFA) and subcutaneous fat area (SFA) remained unclear in patients with type 2 diabetes.MethodsThis cross-sectional study was conducted in 284 patients with type 2 diabetes mellitus. Enzyme-linked immunospecific assay was used to measure levels of serum BCAA and branched-chain keto acid (BCKA). VFA and SFA were measured with bio-impedance analysis method. The association between BCAA and VFA was calculated using Pearson correlation and multivariable linear regression analysis.ResultsThere were significant differences in the means of body mass index, waist circumstance, SFA and VFA among the three groups divided by total BCAA tertiles (all p < 0.05). Compared to patients with lower levels of serum BCAA (the lower tertile group), the means of VFA and SFA were significantly larger in the middle and upper tertile groups (all p < 0.05). However, the differences in above obesity parameters were nonsignificant according to various BCKA tertiles. Pearson correlation analysis also demonstrated that BCAA levels were positive associated with each obesity parameter (p < 0.05). Nevertheless, multivariable linear regression analysis showed that levels of serum BCAA were correlated with VFA, BMI and WC (all p < 0.05) rather than SFA after adjusted for other confounders.Conclusionslevels of serum BCAA were more closely correlated with VFA than SFA, prospective studies should be warranted to further explore the mechanism mediating BCAA and visceral fat accumulation in Human beings.Clinical trial numberNot applicable.

Branched-chain amino acids and their metabolites decrease human and rat hepatic stellate cell activation

BackgroundEnd-stage liver diseases (ESLDs) are a significant global health challenge due to their high prevalence and severe health impacts. Despite the severe outcomes associated with ESLDs, therapeutic options remain limited. Targeting the activation of hepatic stellate cells (HSCs), key drivers of extracellular matrix accumulation during liver injury presents a novel therapeutic approach. In ESLDs patients, branched-chain amino acids (BCAAs, leucine, isoleucine and valine) levels are decreased, and supplementation has been proposed to attenuate liver fibrosis and improve regeneration. However, their effects on HSCs require further investigation.ObjectiveTo evaluate the efficacy of BCAAs and their metabolites, branched-chain α-keto acids (BCKAs), in modulating HSCs activation in human and rat models.MethodsPrimary HSCs from rats and cirrhotic and non-cirrhotic human livers, were cultured and treated with BCAAs or BCKAs to assess their effects on both preventing (from day 1 of isolation) and reversing (from day 7 of isolation) HSCs activation.ResultsIn rat HSCs, leucine and BCKAs significantly reduced fibrotic markers and cell proliferation. In human HSCs, the metabolite of isoleucine decreased cell proliferation around 85% and increased the expression of branched-chain ketoacid dehydrogenase. The other metabolites also showed antifibrotic effects in HSCs from non-cirrhotic human livers.ConclusionBCAAs and their respective metabolites inhibit HSC activation with species-specific responses. Further research is needed to understand how BCAAs influence liver fibrogenesis. BCKAs supplementation could be a strategic approach for managing ESLDs, considering the nutritional status and amino acid profiles of patients.Graphical abstractThe antifibrotic effects of BCAAs and BCKAs in various conditions are depicted for human HSCs (left) and rat HSCs (right) The symbol ‘↓’ indicates a downregulation or a decrease. α-SMA alpha-smooth muscle actin, BCAAs branched-chain amino acids, BCKAs branched-chain keto acids, HSCs hepatic stellate cells, KMV α-keto-β-methylvalerate. Figure created with Biorender.com

Mitochondrial redox signals upon insulin secretion stimulated by branched-chain keto acids

Mitochondrial redox signals upon insulin secretion stimulated by branched-chain keto acids

Electrosynthesis of Amino Acids from Biomass and Nitrate at Industrial Current Densities Using Porous PbBi Electrodes.

Electrosynthesis is a rising and attractive method for efficient amino acid production. However, industrial-grade electrosynthesis of high-value amino acids from simple carbon and nitrogen substrates is confronted with a great challenge. Herein, we design a dual-site PbBi alloy catalyst for various amino acids' electrosynthesis from keto acids and nitrate. An alanine Faradaic efficiency of 59.7% is delivered at -1.5 V vs SCE, reaching the industrial current density of 570 mA cm-2 with high catalytic durability of the porous Pb1Bi0.1 catalyst. In the tandem reaction process, nitrate is first converted to NH2OH via electrochemical reduction mainly over the Bi site. Then the obtained NH2OH integrates with the α-keto acid to form the oxime intermediate. Lastly, the Pb site facilitates the electroreduction of oxime to the final amino acids. More importantly, over 10 kinds of α-amino acids can be successfully synthesized in excellent FE and high yield at high current density, indicating the superior catalytic activity and wide universality of our strategy. In short, this work opens up a novel approach to realize the one-pot electrosynthesis of various amino acids from renewable biomass feedstocks and nitrate waste industrially.

Liquid chromatography-mass spectrometric method for the simultaneous analysis of branched-chain amino acids and their ketoacids from dried blood spot as secondary analytes for the detection of maple syrup urine disease

BackgroundMaple syrup urine disease (MSUD) is an aminoacidopathy caused by a defective branched-chain alpha-ketoacid dehydrogenase complex, leading to the accumulation of branched-chain amino acids (BCAAs) and their respective keto acids (BCKAs). A comprehensive test was developed to measure BCAAs and BCKAs using LC-MS from dried blood spot (DBS) samples for the diagnosis and prevention of MSUD in newborns and infants. MethodsAnalytes were extracted from DBS using a methanol:0.1 % v/v formic acid solution (75:25) containing internal standards and analyzed on a Luna PFP column (150 mm × 4.6 mm, 3 µm) at a flow rate of 0.3 mL/min. The method was validated for linearity, accuracy, precision, recovery, carry-over, matrix effect, hematocrit, blood volume, and punch position effects. Biomarker stability in the matrix and stock solution was assessed. Correlation with the plasma method was determined using Pearson’s correlation coefficient and Bland-Altman analysis. The method established reference ranges for the Udupi district population in South India. ResultsThe method demonstrated linearity (r2 > 0.99), with a lower limit of detection at 2 µM (BCAA) and 1 µM (BCKA), and acceptable recovery of QC samples. Hematocrit, blood volume, punch position, and storage condition effects were within acceptable limits. Correlation and Bland-Altman analysis showed strong interconvertibility between plasma and DBS assays. Reference ranges for leucine, isoleucine, valine, KIC, KIV, and KMV were established. ConclusionThe developed DBS method, requiring no derivatization and involving simple sample preparation with short run times, is a cost-effective and reliable approach for the confirmatory diagnosis of MSUD.

12248 Leptin Signaling Deficiency At The Central Nervous System Reduces Hepatic Glucagon Sensibility Disturbing Liver Amino Acid Metabolism Leading To Hyperaminoacidemia And Hyperglucagonemia In Male Adult Rats

Abstract Disclosure: C. Pintado Losa: None. L. Mazuecos Fernández-Pacheco: None. Ó. Gómez Torres: None. S. Artigas Jerónimo: None. E. Burgos Ramos: None. I. Ramos: None. J. Poveda Colado: None. C. Arribas Mocoroa: None. A. Andres: None. N. Gallardo: None. Leptin regulates glucagon secretion, but the contribution of central leptin resistance to circulating glucagon levels and hepatic glucagon signaling is poorly studied. To analyze the effects of deficient hypothalamic leptin signaling on glucagon levels and hepatic glucagon signaling, we infused intracerebroventricularly a rat-specific leptin receptor antagonist SLA (0,2 µg/day) for 21 days to male 3-month-old Wistar rats (n=12) or PBS (n=12). At day 21 of treatment and 30 min before sacrifice, a glucagon challenge (100 µg/kg) was performed in 16h fasted rats. After sacrifice, blood and liver samples were collected for analysis. Serum hormones, urea, and total and branched-chain amino acids (BCAA) levels were determined using commercial kits and by RP-HPLC. Hepatic neutral lipid was extracted and quantified using an enzymatic kit and the hepatic content of mRNA and proteins involved in lipid and amino acid metabolism were measured by RT-PCR and Western-Blot. Additionally, the HOMA-IR and glucagon-alanine index were determined in all rats. Blocking central leptin signaling led to impaired fat oxidation and triglyceride export capacity in the liver, resulting in a 50% increase in hepatic triglyceride content in SLA-treated rats. Glucagonemia increased in SLA-treated rats, indicating impaired hepatic glucagon sensitivity. In fact, in response to exogenous glucagon, the hepatic phosphorylation of CREB was reduced by 55% in SLA-infused compared to control rats. Importantly, SLA treatment significantly decreases the expression and the activity of BCKDH (branched-chain alpha-keto acid dehydrogenase) in the liver, leading to a reduction in the BCAA degradation in SLA-treated rats, hyperaminoacidemia, and decreased serum urea levels. In conclusion, deficient hypothalamic leptin signaling alters glucose, lipid, and amino acid homeostasis, highlighting the relevance of central leptin action in the control of peripheral metabolism and glucagon sensitivity. Funding: Work supported by Ministerio de Ciencia, Innovación y Universidades under project grants RTI2018-098643-B-I00, PID2021-128243OB-I00, and from the University of Castilla-La Mancha and the European Regional Development Fund (FEDER) under project grant 2023- GRIN-34280. Presentation: 6/1/2024

Revealing the Mechanism of Ketonization of Acetic Acid on HBEA Zeolite via Metadynamics Simulations

Ketonization of biomass‐derived carboxylic acids offers a promising approach to remove oxygen and upgrade into valuable chemicals. However, the mechanism on Brønsted acid site (BAS) confined in micropores of zeolite remains elusive, due to the difficulty to observe the reaction intermediates experimentally and to locate the transition state via static density functional theory (DFT) calculations. Herein, ketonization of acetic acid on HBEA at 673 K was studied by metadynamics simulations based on DFT. The first reaction step was the concerted protonation and dehydroxylation of acetic acid, resulting in an electrophilic acylium cation and H2O (ΔG‡ = 1.53 eV). The subsequent likely steps, including C‐C coupling through the nucleophilic attack of acetic acid (path I), ketene (path II), and 1,1‐dihydroxyethene and (path III) toward acylium cation were tracked and compared. The high barriers for formation of more nucleophilic intermediates of ketene and 1,1‐dihydroxyethene made the overall path II and III less favorable than the direct coupling between acetic acid and acylium cation (path I, ΔG‡ = 2.15 eV). These results indicate that acylium cation is a key intermediate, and the C‐C coupling between acetic acid and acylium cation via nucleophilic attach is the most favorable path on BAS confined in zeolite.

Metabolic and Molecular Insights Into Nicotiana benthamiana Trichome Exudates: An Ammunition Depot for Plant Resistance Against Insect Pests.

Nicotiana benthamiana, a widely acknowledged laboratory model plant for molecular studies, exhibits lethality to certain insect pests and can serve as a dead-end trap plant for pest control in the field. However, the underlying mechanism of N. benthamiana'sresistance against insects remains unknown. Here, we elucidate that the lethal effect of N. benthamiana on the whitefly Bemisia tabaci arises from the toxic glandular trichome exudates. By comparing the metabolite profiles of trichome exudates, we found that 51 metabolites, including five O-acyl sugars (O-AS) with medium-chain acyl moieties, were highly accumulated in N. benthamiana. Silencing of two O-AS biosynthesis genes, branched-chain keto acid dehydrogenase (BCKD) and Isopropyl malate synthase-C (IPMS-C), significantly reduced the O-AS levels in N. benthamiana and its resistance against whiteflies. Additionally, we demonstrated that the higher expression levels of BCKD and IPMS-C in the trichomes of N. benthamiana contribute to O-AS synthesis and consequently enhance whitefly resistance. Furthermore, overexpression of NbBCKD and NbIPMS-C genes in the cultivated tobacco Nicotiana tabacum enhanced its resistance to whiteflies. Our study revealed the metabolic and molecular mechanisms underlying the lethal effect of N. benthamiana on whiteflies and presents a promising avenue for improving whitefly resistance.

Exploring the response mechanism of Pseudomonas plecoglossicida to high-temperature stress by transcriptomic analyses for 2-keto gluconic acid production

High temperatures, particularly in summer, lead to decreased yields in the industrial application of Pseudomonas plecoglossicida for 2-keto gluconic acid (2KGA) fermentation. To address this, the alterations in the transcriptomics of P. plecoglossicida in response to high-temperature stress were examined at temperatures of 32 °C, 36 °C, and 40 °C. The analysis of differential expression revealed substantial discrepancies in the number of differentially expressed genes (DEGs) at 36 °C (357) and 40 °C (1,487), primarily affecting vital biological functions. Elevated temperatures resulted in a shift in the metabolic processing of glucose, transitioning from extracellular oxidation to intracellular phosphorylation. Notable changes were observed in metabolic pathways, including the pentose phosphate pathway and tricarboxylic acid cycle. A significant observation was the decline in the activity of genes associated with extracellular glucose oxidation, accompanied by an increase in the activity of genes involved in intracellular phosphorylation pathway. This indicates a prompt and dynamic response to high-temperature stress. The investigation revealed notable alterations in genes linked to glucose metabolism, emphasizing the strain's adaptive capabilities to endure high temperatures. The reveal of adaptations are crucial for optimizing 2KGA production in challenging industrial environments.

Metabolomic biomarkers and altered phenylalanine metabolic pathway in preschool children with atopic dermatitis - A pilot study.

Background Atopic dermatitis (AD) has high prevalence in children. Current AD diagnosis and management focuses only on clinical phenotypes, but do not explore the endophenotypes, which are more important because they are a series of biomarkers linking clinical phenotype and genotype Aims Metabolomics can qualitatively and quantitatively capture real-time dynamic changes in a wide range of small molecule metabolites. This pilot study evaluated metabolomics biomarkers and altered metabolic pathways in preschool children with AD, aiming to explore the underlying molecular mechanisms and signalling pathways of the disease. Methods Blood samples of 23 preschool children with AD and 23 healthy children without AD or any other skin disease were collected. The untargeted metabolomic measurements were performed on a SCIEX-AD ultraperformance liquid chromatography system coupled with an AB SCIEX X500B QTOF system. Characteristics of small molecules in AD children were assessed and their associations with AD clinical index were evaluated. Altered metabolic pathways in AD children were also analysed using a comprehensive metabolomics platform. Results A total of 1,969 metabolites were identified, of which AD children exhibited 377 significantly altered metabolites. Multivariate statistical analysis demonstrated that the AD group and the control group could be clearly separated. Volcano plot analysis illustrated that 144 metabolites were up-regulated and 233 metabolites were down-regulated in AD children. The Severity Scoring of Atopic Dermatitis (SCORAD index) showed a moderate-to-strong association with estrogens, carotenes, leukotrienes, flavonols and keto acids in AD children (|r|=0.440-0.557). Several pathways, including the phenylalanine metabolism, were identified as altered in AD children. Limitations A small group of children was included in the study; the results need to be validated in larger sample sizes. Conclusion Results of this study illustrate potential alterations in metabolites and the phenylalanine metabolic pathway in preschool children with AD. Although this is a pilot study with a limited sample size, it may provide a new perspective for exploring the pathogenesis of AD, and for personalised treatment modalities.

Mendelian randomization study of urolithiasis: exploration of risk factors using human blood metabolites

BackgroundUrolithiasis is a highly prevalent global disease closely associated with metabolic factors; however, the causal relationship between blood metabolites and urolithiasis remains poorly understood.MethodIn our study, we employed a bi-directional two-sample Mendelian randomization (MR) analysis to investigate the causal associations between urolithiasis and metabolites. The random-effects inverse-variance weighted (IVW) estimation method was utilized as the primary approach, complemented by several other estimators including MR-Egger, weighted median, colocalization and MR-PRESSO. Furthermore, the study included replication and meta-analysis. Finally, we conducted metabolic pathway analysis to elucidate potential metabolic pathways.ResultsAfter conducting multiple tests for correction, glycerol might contribute to the urolithiasis and dehydroisoandrosterone sulfate (DHEA-S) might inhibit this process. Furthermore, several blood metabolites had shown potential associations with a causal relationship. Among the protective metabolites were lipids (dehydroisoandrosterone sulfate and 1-stearoylglycerol (1-monostearin)), amino acids (isobutyrylcarnitine and 2-aminobutyrate), a keto acid (acetoacetate) and a carbohydrate (mannose). The risk metabolites included lipids (1-palmitoylglycerophosphoethanolamine, glycerol and cortisone), a carbohydrate (erythronate), a peptide (pro-hydroxy-pro) and a fatty acid (eicosenoate). In reverse MR analysis, urolithiasis demonstrated a statistically significant causal relationship with butyrylcarnitine, 3-methyl-2-oxobutyrate, scyllo-inositol, leucylleucine and leucylalanine. However, it was worth noting that none of the blood metabolites exhibited statistical significance after multiple corrections. Additionally, we identified one metabolic pathway associated with urolithiasis.ConclusionThe results we obtained demonstrate the causal relevance between two metabolites and urolithiasis, as well as identify one metabolic pathway potentially associated with its development. Given the high prevalence of urolithiasis, further investigations are encouraged to elucidate the mechanisms of these metabolites and explore novel therapeutic strategies.

Redox signaling upon β-like oxidation of branched-chain keto acids essentially stimulates insulin secretion in pancreatic β-cells

Redox signaling upon β-like oxidation of branched-chain keto acids essentially stimulates insulin secretion in pancreatic β-cells

Review : Maple Syrup Urine Disease : A Rare Inherted Disorder of Amino Acid Metabolism

Maple syrup urine disease is a rare and serious condition in which the amino acid metabolism is impaired. Mostly it is inherited in an autosomal recessive pattern in neonates from birth itself. Normally our body breakdowns proteins into amino acid and further amino acids are broken down and removed from our body. but in this disease body loses it’s ability to breakdown amino acids causing harmful buildup of substances in blood and urine. It can cause life threatening cerebral oedema and dysmyelination in affected individuals. It is generally caused by the deficiency of enzyme complex (Branched chain alpha keto acid dehydrogenase(BCKDHA)) .this particular enzyme complex is necessary to breakdown the three branched chain amino acids(BCCA) leucine, isoleucine and valine. this results in the accumulation of all three amino acids in body producing toxic effects. The common symptoms of this disease in neonates includes: anorexia, sweet smell in the urine, irritability, weight loss. In classic MSUD neonates are even born asymptomatic but delay in treatment may lead to worsening of symptoms in their later stage of life. The toxic effects are due to accumulation of branched chain ketoacids(BCKAs)causing severe ketoacidosis and harmful effects of leucine on brain. however, this disease can be managed by a restricted diet containing low protein so that the three BCCAs are controlled to some extent and through continuous metabolic monitoring. Newborn screening for MSUD is also ver common now a days for diagnosis of MSUD in newborns.

Biosynthesis of the benzylpyrrolidine precursor in anisomycin by a unique ThDP-dependent enzyme

Anisomycin (compound 1), a multifunctional pyrrolidine antibiotic, primarily inhibits protein biosynthesis by binding to the ribosome. Upon binding to the ribosome, the para-phenol moiety of anisomycin inserts completely into the hydrophobic crevice of the A-site and blocks the access of the incoming aminoacyl-tRNAs, disrupting peptide bond formation. Hence, the para-methoxyphenyl group serves as a starting point for developing novel anisomycin analogs with potent antifungal and insecticidal properties. However, the activation and condensation mechanism of phenylpyruvic acid has not yet been elucidated. In this study, genetic manipulations of aniP and its homologue siAniP confirmed their indispensable role in 1 biosynthesis. Bioinformatics analysis suggested that AniP and siAniP function as transketolase. siAniP was found to catalyzed condensation between 4-hydroxyphenylpyruvic acid (3) and glyceraldehyde (GA), initiating pyrrolidine synthesis. siAniP was specific for aromatic keto acids and tolerant of aliphatic and aromatic aldehydes, and was able to catalyze the asymmetric intermolecular condensation of two keto acids, leading to the formation of 24 α-hydroxy ketone. To the best of our knowledge, siAniP is the first TK that catalyzes the transfer of a C2 ketol and symmetrical intermolecular coupling using aromatic keto acids as donor substrates. Structural analysis, docking model construction, and site-directed mutagenesis identified that I220, H275, R322 and W391 were crucial for substrate binding. Moreover, sequence similarity network (SSN)-based genome neighborhood network (GNN) analyses of AniP suggested the widespread occurrence of the AniP-like-mediated reaction in the biosynthesis of 1 and its analogs, particularly in the assembly of benzylpyrrolidine. These findings not only expand the repertoire of TKs but also provide a potent biocatalyst that could be used for the structural innovation of 1 and its derivatives.