Orotic Acid, More Than Just an Intermediate of Pyrimidine de novo Synthesis

Metabolomic changes in children with autism

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by deficits in social communication and repetitive behaviors. Metabolomic profiling has emerged as a valuable tool for understanding the underlying metabolic dysregulations associated with ASD.

AIM

To comprehensively explore metabolomic changes in children with ASD, integrating findings from various research articles, reviews, systematic reviews, meta-analyses, case reports, editorials, and a book chapter.

METHODS

A systematic search was conducted in electronic databases, including PubMed, PubMed Central, Cochrane Library, Embase, Web of Science, CINAHL, Scopus, LISA, and NLM catalog up until January 2024. Inclusion criteria encompassed research articles (83), review articles (145), meta-analyses (6), systematic reviews (6), case reports (2), editorials (2), and a book chapter (1) related to metabolomic changes in children with ASD. Exclusion criteria were applied to ensure the relevance and quality of included studies.

RESULTS

The systematic review identified specific metabolites and metabolic pathways showing consistent differences in children with ASD compared to typically developing individuals. These metabolic biomarkers may serve as objective measures to support clinical assessments, improve diagnostic accuracy, and inform personalized treatment approaches. Metabolomic profiling also offers insights into the metabolic alterations associated with comorbid conditions commonly observed in individuals with ASD.

CONCLUSION

Integration of metabolomic changes in children with ASD holds promise for enhancing diagnostic accuracy, guiding personalized treatment approaches, monitoring treatment response, and improving outcomes. Further research is needed to validate findings, establish standardized protocols, and overcome technical challenges in metabolomic analysis. By advancing our understanding of metabolic dysregulations in ASD, clinicians can improve the lives of affected individuals and their families.

Providing insight into the mechanism of action of cationic lipidated oligomers using metabolomics

The increasing resistance of clinically relevant microbes against current commercially available antimicrobials underpins the urgent need for alternative and novel treatment strategies. Cationic lipidated oligomers (CLOs) are innovative alternatives to antimicrobial peptides and have reported antimicrobial potential. An understanding of their antimicrobial mechanism of action is required to rationally design future treatment strategies for CLOs, either in monotherapy or synergistic combinations. In the present study, metabolomics was used to investigate the potential metabolic pathways involved in the mechanisms of antibacterial activity of one CLO, C12-o-(BG-D)-10, which we have previously shown to be effective against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300. The metabolomes of MRSA ATCC 43300 at 1, 3, and 6 h following treatment with C12-o-(BG-D)-10 (48 µg/mL, i.e., 3× MIC) were compared to those of the untreated controls. Our findings reveal that the studied CLO, C12-o-(BG-D)-10, disorganized the bacterial membrane as the first step toward its antimicrobial effect, as evidenced by marked perturbations in the bacterial membrane lipids and peptidoglycan biosynthesis observed at early time points, i.e., 1 and 3 h. Central carbon metabolism and the biosynthesis of DNA, RNA, and arginine were also vigorously perturbed, mainly at early time points. Moreover, bacterial cells were under osmotic and oxidative stress across all time points, as evident by perturbations of trehalose biosynthesis and pentose phosphate shunt. Overall, this metabolomics study has, for the first time, revealed that the antimicrobial action of C12-o-(BG-D)-10 may potentially stem from the dysregulation of multiple metabolic pathways.IMPORTANCEAntimicrobial resistance poses a significant challenge to healthcare systems worldwide. Novel anti-infective therapeutics are urgently needed to combat drug-resistant microorganisms. Cationic lipidated oligomers (CLOs) show promise as new antibacterial agents against Gram-positive pathogens like methicillin-resistant Staphylococcus aureus (MRSA). Understanding their molecular mechanism(s) of antimicrobial action may help design synergistic CLO treatments along with monotherapy. Here, we describe the first metabolomics study to investigate the killing mechanism(s) of CLOs against MRSA. The results of our study indicate that the CLO, C12-o-(BG-D)-10, had a notable impact on the biosynthesis and organization of the bacterial cell envelope. C12-o-(BG-D)-10 also inhibits arginine, histidine, central carbon metabolism, and trehalose production, adding to its antibacterial characteristics. This work illuminates the unique mechanism of action of C12-o-(BG-D)-10 and opens an avenue to design innovative antibacterial oligomers/polymers for future clinical applications.

Genetically predicted blood metabolites mediate the association between circulating immune cells and pancreatic cancer: A Mendelian randomization study

BACKGROUND

Pancreatic cancer is characterized by metabolic dysregulation and unique immunological profiles. Nevertheless, the comprehensive understanding of immune and metabolic dysregulation of pancreatic cancer remains unclear. In the present study, we aimed to investigate the causal relationship of circulating immune cells and pancreatic cancer and identify the blood metabolites as potential mediators.

METHODS

The exposure and outcome genome-wide association studies (GWAS) data used in the present study were obtained from the GWAS open-access database (https://gwas.mrcieu.ac.uk). The study used 731 circulating immune cell features, 1400 types of blood metabolites and pancreatic cancer from GWAS. We then performed bidirectional Mendelian randomization (MR) analyses to explore the causal relationships between the circulating immune cells and pancreatic cancer, and two-step MR to discover potential mediating blood metabolites in this process. All statistical analyses were performed in R software. The STROBE-MR (i.e. Strengthening the Reporting of Observational Studies in Epidemiology using Mendelian Randomization) checklist for the reporting of MR studies was also used.

RESULTS

MR analysis identified seven types of circulating immune cells causally associated with pancreatic cancer. Furthermore, there was no strong evidence that genetically predicted pancreatic cancer had an effect on these seven types of circulating immune cells. Further two-step MR analysis found 10 types of blood metabolites were causally associated with pancreatic cancer and the associations between circulating CD39+CD8+ T cells and pancreatic cancer were mediated by blood orotates with proportions of 5.18% (p = 0.016).

CONCLUSIONS

The present study provides evidence supporting the causal relationships between various circulating immune cells, especially CD39+CD8+ T cells, and pancreatic cancer, with a potential effect mediated by blood orotates. Further research is needed on additional risk factors as potential mediators and establish a comprehensive immunity-metabolism network in pancreatic cancer.

Recent Development of Transition Metal Complexes as Chemotherapeutic Hypoxia Activated Prodrug (HAP)

Hypoxia is a state characterized by low concentration of Oxygen. Hypoxic state is often found in the central region of solid tumors. Hypoxia is associated with abnormal neovascularization resulted in poor blood flow in tissues and increased proliferation of tumor cells, imbalance between O2 supply and O2 consumption in tumor cells, high concentration of proton and strong reducibility. And, these abnormalities enhance the survival potency of the hypoxic tumours and increase the resistance towards chemotherapy and radiotherapy. One of the approach for treating hypoxic region of tumour is to use reducing environment of hypoxic tumours for reducing a molecule (hypoxia activated prodrug, HAP) and as a result the active drug will be released in hypoxic region in a controlled manner from the prodrug and kill the hypoxic tumour. Co(III) and Pt(IV) complexes with monodentate active drug molecule in the axial position can be reduced to Co(II) and Pt(II) moieties and as a result, the axial ligands (active drug) could come out from the metal center and could show its anticancer activity. In this review we have highlighted the research articles where transition metal-based complexes are used as chemotherapeutic hypoxia activated prodrug molecules which are reported in last 5 years.

Highly sensitive rapid determination of orotic acid in urine samples using a field-amplified sample stacking approach in capillary electrophoresis coupled with contactless conductivity detection

Orotic aciduria is a severe, hereditary, life-threatening condition, particularly in newborns. An increased orotic acid (OA) content in urine may be a strong indicator of this condition. In this study, we developed a rapid, simple, highly sensitive diagnostic method for use in monitoring the OA levels in urine samples, which were successfully determined using capillary electrophoresis combined with capacitively coupled contactless conductivity detection (CE-C4D). A straightforward analysis with an increased sensitivity towards OA and an analysis time of approximately 5 min were realized, and the limit of detection of the developed method was 0.014 mg/L in aqueous solution. The optimized composition of the separation electrolyte was 20 mM 2-(N-morpholino)ethanesulfonic acid/histidine with 0.1 mM cetyltrimethylammonium bromide at a pH of 6.5. The sensitivity of the developed method was significantly increased using a sample stacking approach with a 10% acetonitrile (v/v) plug solution. The method was validated, and satisfactory recoveries of 80.0-92.3% were obtained. The amounts of OA in five urine samples were successfully determined.

Causal relationship between human blood metabolites and risk of ischemic stroke: a Mendelian randomization study

Background: Ischemic stroke (IS) is a major cause of death and disability worldwide. Previous studies have reported associations between metabolic disorders and IS. However, evidence regarding the causal relationship between blood metabolites and IS lacking. Methods: A two-sample Mendelian randomization analysis (MR) was used to assess the causal relationship between 1,400 serum metabolites and IS. The inverse variance-weighted (IVW) method was employed to estimate the causal effect between exposure and outcome. Additionally, MR-Egger regression, weighted median, simple mode, and weighted mode approaches were employed as supplementary comprehensive evaluations of the causal effects between blood metabolites and IS. Tests for pleiotropy and heterogeneity were conducted. Results: After rigorous selection, 23 known and 5 unknown metabolites were identified to be associated with IS. Among the 23 known metabolites, 13 showed significant causal effects with IS based on 2 MR methods, including 5-acetylamino-6-formylamino-3-methyluracil, 1-ribosyl-imidazoleacetate, Behenoylcarnitine (C22), N-acetyltyrosine, and N-acetylputrescine to (N (1) + N (8))-acetate,these five metabolites were positively associated with increased IS risk. Xanthurenate, Glycosyl-N-tricosanoyl-sphingadienine, Orotate, Bilirubin (E,E), Bilirubin degradation product, C17H18N2O, Bilirubin (Z,Z) to androsterone glucuronide, Bilirubin (Z,Z) to etiocholanolone glucuronide, Biliverdin, and Uridine to pseudouridine ratio were associated with decreased IS risk. Conclusion: Among 1,400 blood metabolites, this study identified 23 known metabolites that are significantly associated with IS risk, with 13 being more prominent. The integration of genomics and metabolomics provides important insights for the screening and prevention of IS.

Cloning and Characterization of Yak DHODH Gene and Its Functional Studies in a Bisphenol S-Induced Ferroptosis Model of Fetal Fibroblasts

Dihydroorotate dehydrogenase (DHODH) is a rate-limiting enzyme of de novo biosynthesis of pyrimidine. Although the involvement of DHODH in resisting ferroptosis has been successively reported in recent years, which greatly advanced the understanding of the mechanism of programmed cell death (PCD), the genetic sequence of the yak DHODH gene and its roles in ferroptosis are still unknown. For this purpose, we firstly cloned the coding region sequence of DHODH (1188 bp) from yak liver and conducted a characterization analysis of its predictive protein that consists of 395 amino acids. We found that the coding region of the yak DHODH gene presented high conservation among species. Second, the expression profile of the DHODH gene in various yak tissues was investigated using RT-qPCR. The results demonstrated that DHODH was widely expressed in different yak tissues, with particularly high levels in the spleen, heart, and liver. Third, to investigate the involvement of DHODH in regulating ferroptosis in cells, yak skin fibroblasts (YSFs) were isolated from fetuses. And then, bisphenol S (BPS) was used to induce the in vitro ferroptosis model of YSFs. We observed that BPS decreased the cell viability (CCK8) and membrane potential (JC-1) of YSFs in a dose-dependent manner and induced oxidative stress by elevating reactive oxygen species (ROS). Simultaneously, it was evident that BPS effectively augmented the indicators associated with ferroptosis (MDA and BODIPY staining) and reduced GSH levels. Importantly, the co-administration of Ferrostatin-1 (Fer), a potent inhibitor of ferroptosis, significantly alleviated the aforementioned markers, thereby confirming the successful induction of ferroptosis in YSFs by BPS. Finally, overexpression plasmids and siRNAs of the yak DHODH gene were designed and transfected respectively into BPS-cultured YSFs to modulate DHODH expression. The findings revealed that DHODH overexpression alleviated the occurrence of BPS-induced ferroptosis, while interference of DHODH intensified the ferroptosis process in YSFs. In summary, we successfully cloned the coding region of the yak DHODH gene, demonstrating its remarkable conservation across species. Moreover, using BPS-induced ferroptosis in YSFs as the model, the study confirmed the role of the DHODH gene in resisting ferroptosis in yaks. These results offer valuable theoretical foundations for future investigations into the functionality of the yak DHODH gene and the underlying mechanisms of ferroptosis in this species.

Advances in regulation and function of stearoyl-CoA desaturase 1 in cancer, from bench to bed

Stearoyl-CoA desaturase 1 (SCD1) converts saturated fatty acids to monounsaturated fatty acids. The expression of SCD1 is increased in many cancers, and the altered expression contributes to the proliferation, invasion, sternness and chemoresistance of cancer cells. Recently, more evidence has been reported to further support the important role of SCD1 in cancer, and the regulation mechanism of SCD1 has also been focused. Multiple factors are involved in the regulation of SCD1, including metabolism, diet, tumor microenvironment, transcription factors, non-coding RNAs, and epigenetics modification. Moreover, SCD1 is found to be involved in regulating ferroptosis resistance. Based on these findings, SCD1 has been considered as a potential target for cancer treatment. However, the resistance of SCD1 inhibition may occur in certain tumors due to tumor heterogeneity and metabolic plasticity. This review summarizes recent advances in the regulation and function of SCD1 in tumors and discusses the potential clinical application of targeting SCD1 for cancer treatment.

Orotic acid induces apoptotic death in ovarian adult granulosa tumour cells and increases mitochondrial activity in normal ovarian granulosa cells

Orotic acid (OA) is a natural product that acts as a precursor in the pyrimidine nucleotide biosynthesis pathway. Most studies concerning administration of OA focus on its therapeutic effects; however, its effect on tumours is unclear. We aimed to determine whether treatment with OA influences the viability and apoptosis of normal (HGrC1) and tumour-derived (KGN) human ovarian granulosa cells. The effects of OA (10-250 μM) on viability and apoptosis of both cell lines were determined by using alamarBlue and assessing caspase-3/7 activity, respectively. Annexin V binding and loss of membrane integrity were evaluated in KGN cells. The cell cycle and proliferation of HGrC1 cells were assessed by performing flow cytometric and DNA content analyses, respectively. The influence of OA (10 and 100 μM) on cell cycle- and apoptosis-related gene expression was assessed by RT-qPCR in both cell lines. Mitochondrial activity was analysed by JC-1 staining in HGrC1 cells. In KGN cells, OA reduced viability and increased caspase-3/7 activity, but did not affect mRNA expression of Caspase 3, BAX, and BCL2. OA enhanced proliferation and mitochondrial activity in HGrC1 cells without activating apoptosis. This study demonstrates that the anti-cancer properties of OA in ovarian granulosa tumour cells are not related to changes in apoptosis-associated gene expression, but to increased caspase-3/7 activity. Thus, OA is a promising therapeutic agent for ovarian granulosa tumours. Further, our results suggest that differences in basal expression of cell cycle- and apoptosis-related genes between the two cell lines are responsible for their different responses to OA.

Genetic perturbation of mitochondrial function reveals functional role for specific mitonuclear genes, metabolites, and pathways that regulate lifespan

Altered mitochondrial function is tightly linked to lifespan regulation, but underlying mechanisms remain unclear. Here, we report the chronological and replicative lifespan variation across 167 yeast knock-out strains, each lacking a single nuclear-coded mitochondrial gene, including 144 genes with human homologs, many associated with diseases. We dissected the signatures of observed lifespan differences by analyzing profiles of each strain's proteome, lipidome, and metabolome under fermentative and respiratory culture conditions, which correspond to the metabolic states of replicative and chronologically aging cells, respectively. Examination of the relationships among extended longevity phenotypes, protein, and metabolite levels revealed that although many of these nuclear-encoded mitochondrial genes carry out different functions, their inhibition attenuates a common mechanism that controls cytosolic ribosomal protein abundance, actin dynamics, and proteasome function to regulate lifespan. The principles of lifespan control learned through this work may be applicable to the regulation of lifespan in more complex organisms, since many aspects of mitochondrial function are highly conserved among eukaryotes.

Assessment of a novel variation in DHODH gene causing Miller syndrome: The first report in Chinese population

BACKGROUND

Miller syndrome is a rare type of postaxial acrofacial dysostosis caused by biallelic mutations in the DHODH gene, which is characterized mainly by craniofacial malformations of micrognathia, orofacial clefts, cup-shaped ears, and malar hypoplasia, combined with postaxial limb deformities like the absence of fifth digits.

METHODS

In this study, a prenatal case with multiple orofacial-limb abnormities was enrolled, and a thorough clinical and imaging examination was performed. Subsequently, genetic detection with karyotyping, chromosomal microarray analysis (CMA) and whole-exome sequencing (WES) was carried out. In vitro splicing analysis was also conducted to clarify the impact of one novel variant.

RESULTS

The affected fetus displayed typical manifestations of Miller syndrome, and WES identified a diagnostic compound heterozygous variation in DHODH, consisting of two variants: exon(1-3)del and c.819 + 5G > A. We conducted a further in vitro validation with minigene system, and the result indicated that the c.819 + 5G > A variant would lead to an exon skipping in mRNA splicing.

CONCLUSIONS

These findings provided with the first exonic deletion and first splice site variant in DHODH, which expanded the mutation spectrum of Miller syndrome and offered reliable evidence for genetic counseling to the affected family.

In vitro to in vivo extrapolation and high-content imaging for simultaneous characterization of chemically induced liver steatosis and markers of hepatotoxicity

Chemically induced steatosis is characterized by lipid accumulation associated with mitochondrial dysfunction, oxidative stress and nucleus distortion. New approach methods integrating in vitro and in silico models are needed to identify chemicals that may induce these cellular events as potential risk factors for steatosis and associated hepatotoxicity. In this study we used high-content imaging for the simultaneous quantification of four cellular markers as sentinels for hepatotoxicity and steatosis in chemically exposed human liver cells in vitro. Furthermore, we evaluated the results with a computational model for the extrapolation of human oral equivalent doses (OED). First, we tested 16 reference chemicals with known capacities to induce cellular alterations in nuclear morphology, lipid accumulation, mitochondrial membrane potential and oxidative stress. Then, using physiologically based pharmacokinetic modeling and reverse dosimetry, OEDs were extrapolated from data of any stimulated individual sentinel response. The extrapolated OEDs were confirmed to be within biologically relevant exposure ranges for the reference chemicals. Next, we tested 14 chemicals found in food, selected from thousands of putative chemicals on the basis of structure-based prediction for nuclear receptor activation. Amongst these, orotic acid had an extrapolated OED overlapping with realistic exposure ranges. Thus, we were able to characterize known steatosis-inducing chemicals as well as data-scarce food-related chemicals, amongst which we confirmed orotic acid to induce hepatotoxicity. This strategy addresses needs of next generation risk assessment and can be used as a first chemical prioritization hazard screening step in a tiered approach to identify chemical risk factors for steatosis and hepatotoxicity-associated events.

Acute physiological effects following Bacillus subtilis DE111 oral ingestion - a randomised, double blinded, placebo-controlled study

Previous studies using ileostomy samples from study participants demonstrated that the spore-forming probiotic Bacillus subtilis DE111® can germinate in the small intestine as early as 4 hours after ingestion. Metabolomics, proteomics and sequencing technologies, enabled further analysis of these samples for the presence of hypoglycaemic, hypolipidemic, antioxidant, anti-inflammatory and antihypertensive molecules. In the DE111 treatment group, the polyphenols trigonelline and 2,5-dihydroxybenzoic acid, orotic acid, the non-essential amino acid cystine and the lipokine 12,13-diHome were increased. DE111 also reduced acetylcholine levels in the ileostomy samples, and increased the expression of leucocyte recruiting proteins, antimicrobial peptides and intestinal alkaline phosphatases of the brush border in the small intestine. The combination of B. subtilis DE111 and the diet administered during the study increased the expression of the proteins phosphodiesterase ENPP7, ceramidase ASAH2 and the adipokine Zn-alpha-2-glycoprotein that are involved in fatty acid and lipid metabolism. Acute B. subtilis DE111 ingestion had limited detectable effect on the microbiome, with the main change being its increased presence. These findings support previous data suggesting a beneficial role of DE111 in digestion, metabolism, and immune health that appears to begin within hours of consumption.

Microbiome Dysbiosis Shows Strong Association of Gut-Derived Altered Metabolomic Profile in Gulf War Chronic Multisymptom Illness Symptom Persistence Following Western Diet Feeding and Development of Obesity

The pathophysiology of Gulf War Illness (GWI) remains elusive even after three decades. The persistence of multiple complex symptoms along with metabolic disorders such as obesity worsens the health of present Gulf War (GW) Veterans often by the interactions of the host gut microbiome and inflammatory mediators. In this study, we hypothesized that the administration of a Western diet might alter the host metabolomic profile, which is likely associated with the altered bacterial species. Using a five-month symptom persistence GWI model in mice and whole-genome sequencing, we characterized the species-level dysbiosis and global metabolomics, along with heterogenous co-occurrence network analysis, to study the bacteriome-metabolomic association. Microbial analysis at the species level showed a significant alteration of beneficial bacterial species. The beta diversity of the global metabolomic profile showed distinct clustering due to the Western diet, along with the alteration of metabolites associated with lipid, amino acid, nucleotide, vitamin, and xenobiotic metabolism pathways. Network analysis showed novel associations of gut bacterial species with metabolites and biochemical pathways that could be used as biomarkers or therapeutic targets to ameliorate symptom persistence in GW Veterans.

Metabolomic and transcriptomic response to imatinib treatment of gastrointestinal stromal tumour in xenograft-bearing mice

BACKGROUND

Although imatinib is a well-established first-line drug for treating a vast majority of gastrointestinal stromal tumours (GIST), GISTs acquire secondary resistance during therapy. Multi-omics approaches provide an integrated perspective to empower the development of personalised therapies through a better understanding of functional biology underlying the disease and molecular-driven selection of the best-targeted individualised therapy. In this study, we applied integrative metabolomic and transcriptomic analyses to elucidate tumour biochemical processes affected by imatinib treatment.

MATERIALS AND METHODS

A GIST xenograft mouse model was used in the study, including 10 mice treated with imatinib and 10 non-treated controls. Metabolites in tumour extracts were analysed using gas chromatography coupled with mass spectrometry (GC-MS). RNA sequencing was also performed on the samples subset (n=6).

RESULTS

Metabolomic analysis revealed 21 differentiating metabolites, whereas next-generation RNA sequencing data analysis resulted in 531 differentially expressed genes. Imatinib significantly changed the profile of metabolites associated mainly with purine and pyrimidine metabolism, butanoate metabolism, as well as alanine, aspartate, and glutamate metabolism. The related changes in transcriptomic profiles included genes involved in kinase activity and immune responses, as well as supported its impact on the purine biosynthesis pathway.

CONCLUSIONS

Our multi-omics study confirmed previously known pathways involved in imatinib anticancer activity as well as correlated imatinib-relevant downregulation of expression of purine biosynthesis pathway genes with the reduction of respectful metabolites. Furthermore, considering the importance of the purine biosynthesis pathway for cancer proliferation, we identified a potentially novel mechanism for the anti-tumour activity of imatinib. Based on the results, we hypothesise metabolic modulations aiming at the reduction in purine and pyrimidine pool may ensure higher imatinib efficacy or re-sensitise imatinib-resistant tumours.

Building the uracil skeleton in primitive ponds at the origins of life: carbamoylation of aspartic acid

A large set of nucleobases and amino acids is found in meteorites, implying that several chemical reservoirs are present in the solar system. The "geochemical continuity" hypothesis explores how protometabolic paths developed from so-called "bricks" in an enzyme-free prebiotic world and how they affected the origins of life. In the living cell, the second step of synthesizing uridine and cytidine RNA monomers is a carbamoyl transfer from a carbamoyl donor to aspartic acid. Here we compare two enzyme-free scenarios: aqueous and mineral surface scenarios in a thermal range up to 250 °C. Both processes could have happened in ponds under open atmosphere on the primeval Earth. Carbamoylation of aspartic acid with cyanate in aqueous solutions at 25 °C gives high N-carbamoyl aspartic acid yields within 16 h. It is important to stress that, while various molecules could be efficient carbamoylating agents according to thermodynamics, kinetics plays a determining role in selecting prebiotically possible pathways.

Milk metabolome reveals pyrimidine and its degradation products as the discriminant markers of different corn silage-based nutritional strategies

The purpose of this study was to evaluate the effect of 6 different feeding systems (based on corn silage as the main ingredient) on the chemical composition of milk and to highlight the potential of untargeted metabolomics to find discriminant marker compounds of different nutritional strategies. Interestingly, the multivariate statistical analysis discriminated milk samples mainly according to the high-moisture ear corn (HMC) included in the diet formulation. Overall, the most discriminant compounds, identified as a function of the HMC, belonged to AA (10 compounds), peptides (71 compounds), pyrimidines (38 compounds), purines (15 compounds), and pyridines (14 compounds). The discriminant milk metabolites were found to significantly explain the metabolic pathways of pyrimidines and vitamin B₆. Interestingly, pathway analyses revealed that the inclusion of HMC in the diet formulation strongly affected the pyrimidine metabolism in milk, determining a significant up-accumulation of pyrimidine degradation products, such as 3-ureidopropionic acid, 3-ureidoisobutyric acid, and 3-aminoisobutyric acid. Also, some pyrimidine intermediates (such as l-aspartic acid, N-carbamoyl-l-aspartic acid, and orotic acid) were found to possess a high discrimination degree. Additionally, our findings suggested that the inclusion of alfalfa silage in the diet formulation was potentially correlated with the vitamin B₆ metabolism in milk, being 4-pyridoxic acid (a pyridoxal phosphate degradation product) the most significant and up-accumulated compound. Taken together, the accumulation trends of different marker compounds revealed that both pyrimidine intermediates and degradation products are potential marker compounds of HMC-based diets, likely involving a complex metabolism of microbial nitrogen based on total splanchnic fluxes from the rumen to mammary gland in dairy cows. Also, our findings highlight the potential of untargeted metabolomics in both foodomics and foodomics-based studies involving dairy products.

Inborn Errors of Nucleoside Transporter (NT)-Encoding Genes (SLC28 and SLC29)

The proper regulation of nucleotide pools is essential for all types of cellular functions and depends on de novo nucleotide biosynthesis, salvage, and degradation pathways. Despite the apparent essentiality of these processes, a significant number of rare diseases associated with mutations in genes encoding various enzymes of these pathways have been already identified, and others are likely yet to come. However, knowledge on genetic alterations impacting on nucleoside and nucleobase transporters is still limited. At this moment three gene-encoding nucleoside and nucleobase transporter proteins have been reported to be mutated in humans, SLC29A1, SLC29A3, and SLC28A1, impacting on the expression and function of ENT1, ENT3, and CNT1, respectively. ENT1 alterations determine Augustine-null blood type and cause ectopic calcification during aging. ENT3 deficiency translates into various clinical manifestations and syndromes, altogether listed in the OMIM catalog as histiocytosis-lymphoadenopathy plus syndrome (OMIM#602782). CNT1 deficiency causes uridine-cytidineuria (URCTU) (OMIM#618477), a unique type of pyrimidineuria with an as yet not well-known clinical impact. Increasing knowledge on the physiological, molecular and structural features of these transporter proteins is helping us to better understand the biological basis behind the biochemical and clinical manifestations caused by these deficiencies. Moreover, they also support the view that some metabolic compensation might occur in these disturbances, because they do not seem to significantly impact nucleotide homeostasis, but rather other biological events associated with particular subtypes of transporter proteins.

Protein production, kinetic and biophysical characterization of three human dihydroorotate dehydrogenase mutants associated with Miller syndrome

Miller syndrome is a rare Mendelian disorder caused by mutations in the gene encoding human dihydroorotate dehydrogenase (DHODH). Human DHODH, a Class II DHODH, is an integral protein of the inner mitochondrial membrane (IMM) catalyzing the fourth step of the de novo pyrimidine biosynthesis pathway. Here we present a summary of the state of knowledge regarding Miller syndrome in the absence of any current review on the topic. We then describe the production and characterization of three distinct DHODH missense mutations (G19E, E52G, R135C) associated with Miller syndrome by means of enzyme kinetics and biophysical techniques. These human DHODH mutants were produced both in E. coli and in insect cells using the baculovirus expression vector system. We can show that the effects of these mutations differ from each other and the wild-type enzyme with respect to decreased enzymatic activity, decreased protein stability and probably disturbance of the correct import into the IMM. In addition, our results show that the N-terminus of human DHODH is not only a structural element necessary for correct mitochondrial import and location of DHODH on the outer side of the IMM, but also influences thermal stability, enzymatic activity and affects the kinetic parameters.Supplemental data for this article is available online at https://doi.org/10.1080/15257770.2021.2023749 .

Effects of Magnesium Orotate, Benfotiamine and a Combination of Vitamins on Mitochondrial and Cholinergic Function in the TgF344-AD Rat Model of Alzheimer's Disease

Glucose hypometabolism, mitochondrial dysfunction, and cholinergic deficits have been reported in early stages of Alzheimer’s disease (AD). Here, we examine these parameters in TgF344-AD rats, an Alzheimer model that carries amyloid precursor protein and presenilin-1 mutations, and of wild type F344 rats. In mitochondria isolated from rat hippocampi, we found reductions of complex I and oxidative phosphorylation in transgenic rats. Further impairments, also of complex II, were observed in aged (wild-type and transgenic) rats. Treatment with a “cocktail” containing magnesium orotate, benfotiamine, folic acid, cyanocobalamin, and cholecalciferol did not affect mitochondrial activities in wild-type rats but restored diminished activities in transgenic rats to wild-type levels. Glucose, lactate, and pyruvate levels were unchanged by age, genetic background, or treatment. Using microdialysis, we also investigated extracellular concentrations of acetylcholine that were strongly reduced in transgenic animals. Again, ACh levels in wild-type rats did not change upon treatment with nutrients, whereas the cocktail increased hippocampal acetylcholine levels under physiological stimulation. We conclude that TgF344-AD rats display a distinct mitochondrial and cholinergic dysfunction not unlike the findings in patients suffering from AD. This dysfunction can be partially corrected by the application of the “cocktail” which is particularly active in aged rats. We suggest that the TgF344-AD rat is a promising model to further investigate mitochondrial and cholinergic dysfunction and potential treatment approaches for AD.

Tissue/Biofluid Specific Molecular Cartography of Leishmania donovani Infected BALB/c Mice: Deciphering Systemic Reprogramming

Pathophysiology of visceral leishmaniasis (VL) is not fully understood and it has been widely accepted that the parasitic components and host immune response both contribute to the perpetuation of the disease. Host alterations during leishmaniasis is a feebly touched area that needs to be explored more to better understand the VL prognosis and diagnosis, which are vital to reduce mortality and post-infection sequelae. To address this, we performed untargeted metabolomics of Leishmania donovani (Ld) infected, uninfected and treated BALB/c mice’s tissues and biofluids to elucidate the host metabolome changes using gas chromatography–mass spectrometry. Univariate and multivariate data treatments provided numerous significant differential hits in several tissues like the brain, liver, spleen and bone marrow. Differential modulations were also observed in serum, urine and fecal samples of Ld-infected mice, which could be further targeted for biomarker and diagnostic validations. Several metabolic pathways were found to be upregulated/downregulated in infected (TCA, glycolysis, fatty acids, purine and pyrimidine, etcetera) and treated (arginine, fumaric acid, orotic acid, choline succinate, etcetera) samples. Results also illustrated several metabolites with different pattern of modulations in control, infected and treated samples as well as in different tissues/biofluids; for e.g. glutamic acid identified in the serum samples of infected mice. Identified metabolites include a range of amino acids, saccharides, energy-related molecules, etcetera. Furthermore, potential biomarkers have been identified in various tissues—arginine and fumaric acid in brain, choline in liver, 9-(10) EpOME in spleen and bone marrow, N-acetyl putrescine in bone marrow, etcetera. Among biofluids, glutamic acid in serum, hydrazine and deoxyribose in urine and 3-Methyl-2-oxo pentanoic acid in feces are some of the potential biomarkers identified. These metabolites could be further looked into for their role in disease complexity or as a prognostic marker. The presented profiling approach allowed us to attain a metabolic portrait of the individual tissue/biofluid modulations during VL in the host and represent a valuable system readout for further studies. Our outcomes provide an improved understanding of perturbations of the host metabolome interface during VL, including identification of many possible potential diagnostic and therapeutic targets.

A comprehensive drug repurposing study for COVID19 treatment: novel putative dihydroorotate dehydrogenase inhibitors show association to serotonin-dopamine receptors

Dihydroorotate dehydrogenase (DHODH) is a key enzyme required for de novo pyrimidine synthesis and it is suggested as a target for COVID19 treatment due to high pyrimidine demand by the virus replication in the infected host cells as well as its proven effect of blocking of cytokine release by the immune cells to prevent inflammation leading to acute respiratory distress. There are a number of clinical trials underway for COVID19 treatment using DHODH inhibitors; however, there are only a small number of known DHODH antagonists available for testing. Here, we have applied a methodology to identify DHODH antagonist candidates, and compared them using in silico target prediction tools. A large set of 7900 FDA-approved and clinical stage drugs obtained from DrugBank were docked against 20 different structures DHODH available in PDB. Drugs were eliminated according to their predicted affinities by Autodock Vina. About 28 FDA-approved and 79 clinical trial ongoing drugs remained. The mode of interaction of these molecules was analyzed by repeating docking using Autodock 4 and DS Visualiser. Finally, the target region predictions of 28 FDA-approved drugs were determined through PASS and SwissTargetPrediction tools. Interestingly, the analysis of in silico target predictions revealed that serotonin-dopamine receptor antagonists could also be potential DHODH inhibitors. Our candidates shared a common attribute, a possible interaction with serotonin-dopamine receptors as well as other oxidoreductases, like DHODH. Moreover, the Bruton Tyrosine Kinase-inhibitor acalabrutunib and serotonin-dopamine receptor inhibitor drugs on our list have been found in the literature that have shown to be effective against Sars-CoV-2, while the path of activity is yet to be identified. Identifying an effective drug that can suppress both inflammation and virus proliferation will play a crucial role in the treatment of COVID. Therefore, we suggest experimental investigation of the 28 FDA-approved drugs on DHODH activity and Sars-CoV-2 virus proliferation. Those who are found experimentally effective can play an important role in COVID19 treatment. Moreover, we suggest investigating COVID19 case conditions in patients using schizophrenia and depression drugs.

Hypoxia Active Platinum(IV) Prodrugs of Orotic Acid Selective to Liver Cancer Cells

Platinum(IV) complexes of orotic acid selectively target liver cancer cells displaying enhanced activity and higher uptake in Hep G2. The comparatively higher expression of Organic Anion Transporter 2 (OAT2) in Hep G2 and decrease in toxicity in the presence of OAT2 inhibitor suggest its involvement in the uptake of the complexes. They are resistant to sequestration by the copper transporter ATP7B, unlike cisplatin and oxaliplatin.

Selective Targeting of Cancerous Mitochondria and Suppression of Tumor Growth Using Redox-Active Treatment Adjuvant

Redox-active substances and their combinations, such as of quinone/ascorbate and in particular menadione/ascorbate (M/A; also named Apatone®), attract attention with their unusual ability to kill cancer cells without affecting the viability of normal cells as well as with the synergistic anticancer effect of both molecules. So far, the primary mechanism of M/A-mediated anticancer effects has not been linked to the mitochondria. The aim of our study was to clarify whether this “combination drug” affects mitochondrial functionality specifically in cancer cells. Studies were conducted on cancer cells (Jurkat, Colon26, and MCF7) and normal cells (normal lymphocytes, FHC, and MCF10A), treated with different concentrations of menadione, ascorbate, and/or their combination (2/200, 3/300, 5/500, 10/1000, and 20/2000 μM/μM of M/A). M/A exhibited highly specific and synergistic suppression on cancer cell growth but without adversely affecting the viability of normal cells at pharmacologically attainable concentrations. In M/A-treated cancer cells, the cytostatic/cytotoxic effect is accompanied by (i) extremely high production of mitochondrial superoxide (up to 15-fold over the control level), (ii) a significant decrease of mitochondrial membrane potential, (iii) a decrease of the steady-state levels of ATP, succinate, NADH, and NAD⁺, and (iv) a decreased expression of programed cell death ligand 1 (PD-L1)—one of the major immune checkpoints. These effects were dose dependent. The inhibition of NQO1 by dicoumarol increased mitochondrial superoxide and sensitized cancer cells to M/A. In normal cells, M/A induced relatively low and dose-independent increase of mitochondrial superoxide and mild oxidative stress, which seems to be well tolerated. These data suggest that all anticancer effects of M/A result from a specific mechanism, tightly connected to the mitochondria of cancer cells. At low/tolerable doses of M/A (1/100-3/300 μM/μM) attainable in cancer by oral and parenteral administration, M/A sensitized cancer cells to conventional anticancer drugs, exhibiting synergistic or additive cytotoxicity accompanied by impressive induction of apoptosis. Combinations of M/A with 13 anticancer drugs were investigated (ABT-737, barasertib, bleomycin, BEZ-235, bortezomib, cisplatin, everolimus, lomustine, lonafarnib, MG-132, MLN-2238, palbociclib, and PI-103). Low/tolerable doses of M/A did not induce irreversible cytotoxicity in cancer cells but did cause irreversible metabolic changes, including: (i) a decrease of succinate and NADH, (ii) depolarization of the mitochondrial membrane, and (iii) overproduction of superoxide in the mitochondria of cancer cells only. In addition, M/A suppressed tumor growth in vivo after oral administration in mice with melanoma and the drug downregulated PD-L1 in melanoma cells. Experimental data suggest a great potential for beneficial anticancer effects of M/A through increasing the sensitivity of cancer cells to conventional anticancer therapy, as well as to the immune system, while sparing normal cells. We hypothesize that M/A-mediated anticancer effects are triggered by redox cycling of both substances, specifically within dysfunctional mitochondria. M/A may also have a beneficial effect on the immune system, making cancer cells “visible” and more vulnerable to the native immune response.

Intermediate metabolites of the pyrimidine metabolism pathway extend the lifespan of C. elegans through regulating reproductive signals

The pyrimidine metabolism pathway has important biological functions; it not only maintains appropriate pyrimidine pools but also produces bioactive intermediate metabolites. In a previous study, we identified that the pyrimidine metabolism pathway is associated with aging regulation. However, the molecular mechanism by which the pyrimidine metabolism pathway regulates aging remains unclear. Here, we investigated the longevity effect of pyrimidine intermediates on Caenorhabditis elegans (C. elegans). Our results demonstrated that the supplementation of some pyrimidine intermediates could extend the lifespan of C. elegans. In addition, the RNAi knockdown of essential enzymes involved in pyrimidine metabolism could also significantly affect lifespan. We further investigated the molecular mechanism by which a representative intermediate metabolite, thymine, extends the lifespan of worms and found that thymine-induced longevity required the nuclear receptors DAF-12 and NHR-49, and the transcription factor DAF-16/FOXO. Further pathway analysis revealed that the longevity effect of thymine depended on the inhibition of reproductive signals. Additionally, we found that other pyrimidine intermediates functioned in a manner similar to thymine to prolong lifespan in C. elegans. Taken together, our results revealed that pyrimidine intermediates increased lifespan by inhibiting reproductive signals and subsequently inducing the function of DAF-12, NHR-49 and DAF-16 in C. elegans.

Divergence in the metabolome between natural aging and Alzheimer's disease

Alzheimer's disease (AD) is a progressive and debilitating neurodegenerative disorder and one of the leading causes of death in the United States. Although amyloid plaques and fibrillary tangles are hallmarks of AD, research suggests that pathology associated with AD often begins 20 or more years before symptoms appear. Therefore, it is essential to identify early-stage biomarkers in those at risk for AD and age-related cognitive decline (ARCD) in order to develop preventative treatments. Here, we used an untargeted metabolomics analysis to define system-level alterations following cognitive decline in aged and APP/PS1 (AD) mice. At 6, 12, and 24 months of age, both control (Ctrl) and AD mice were tested in a 3-shock contextual fear conditioning (CFC) paradigm to assess memory decline. AD mice exhibited memory deficits across age and these memory deficits were also seen in naturally aged mice. Prefrontal cortex (PFC), hippocampus (HPC), and spleen were then collected and analyzed for metabolomic alterations. A number of significant pathways were altered between Ctrl and AD mice and naturally aged mice. By identifying systems-level alterations following ARCD and AD, these data could provide insights into disease mechanisms and advance the development of biomarker panels.

The Human Breast Milk Metabolome in Overweight and Obese Mothers

Pre-pregnancy body mass index (BMI) is a major relevance factor, since maternal overweight and obesity can impair the pregnancy outcome and represent risk factors for several neonatal, childhood, and adult conditions, including excessive weight gain, cardiovascular disease, diabetes mellitus, and even behavioral disorders. Currently, breast milk (BM) composition in such category of mothers was not completely defined. In this field, metabolomics represents the ideal technology, able to detect the whole profile of low molecular weight molecules in BM. Limited information is available on human BM metabolites differences in overweight or obese compared to lean mothers. Analyzing all the metabolomics studies published on Medline in English language, this review evaluated the effects that 8 specific types of metabolites found altered by maternal overweight and obesity (nucleotide derivatives, 5-methylthioadenosine, sugar-alcohols, acylcarnitine and amino acids, polyamines, mono-and oligosaccharides, lipids) can exert on the risk of offspring obesity development and other potentially associated health outcomes and complications. However, metabolites variations in samples collected from overweight and obese mothers and the potentially correlated effects highlighted below still need further investigations and should be confirmed in future metabolomics studies on larger samples. Finally, the positive or negative influence of maternal overweight and obesity on the offspring, potentially exerted by breastfeeding, should be analyzed in close correlation with maternal age, genetic and environmental factors, including diet, and taking into account the interactions occurring between BM metabolites and lactobiome. The evaluation of all the factors affecting BM metabolites in overweight and obese mothers can lead to the comprehensive description of such biofluid and the related effects on breastfed subjects, potentially highlighting personalized needs of BM supplementation or short- and long-term prevention strategies to optimize offspring health.

Multifaceted Roles of Mitochondrial Components and Metabolites in Metabolic Diseases and Cancer

Mitochondria are essential cellular components that ensure physiological metabolic functions. They provide energy in the form of adenosine triphosphate (ATP) through the electron transport chain (ETC). They also constitute a metabolic hub in which metabolites are used and processed, notably through the tricarboxylic acid (TCA) cycle. These newly generated metabolites have the capacity to feed other cellular metabolic pathways; modify cellular functions; and, ultimately, generate specific phenotypes. Mitochondria also provide intracellular signaling cues through reactive oxygen species (ROS) production. As expected with such a central cellular role, mitochondrial dysfunctions have been linked to many different diseases. The origins of some of these diseases could be pinpointed to specific mutations in both mitochondrial- and nuclear-encoded genes. In addition to their impressive intracellular tasks, mitochondria also provide intercellular signaling as they can be exchanged between cells, with resulting effects ranging from repair of damaged cells to strengthened progression and chemo-resistance of cancer cells. Several therapeutic options can now be envisioned to rescue mitochondria-defective cells. They include gene therapy for both mitochondrial and nuclear defective genes. Transferring exogenous mitochondria to target cells is also a whole new area of investigation. Finally, supplementing targeted metabolites, possibly through microbiota transplantation, appears as another therapeutic approach full of promises.

Untargeted Metabolomics Screen of Mid-pregnancy Maternal Serum and Autism in Offspring

Discovering pathophysiologic networks in a blood-based approach may help to generate valuable tools for early treatment or preventive measures in autism. To date targeted or untargeted metabolomics approaches to identify metabolic features and pathways affecting fetal neurodevelopment have rarely been applied to pregnancy samples, that is, an early period potentially relevant for the development of autism spectrum disorders (ASD). We conducted a population-based study relying on autism diagnoses retrieved from California Department of Developmental Services record. After linking cases to and sampling controls from birth certificates, we retrieved stored maternal mid-pregnancy serum samples collected as part of the California Prenatal Screening Program from the California Biobank for children born 2004 to 2010 in the central valley of California. We retrieved serum for 52 mothers whose children developed autism and 62 population controls originally selected from all eligible children matched by birth year and child's sex. Also, we required that these mothers were relatively low or unexposed to air pollution and select pesticides during early pregnancy. We identified differences in metabolite levels in several metabolic pathways, including glycosphingolipid biosynthesis and metabolism, N-glycan and pyrimidine metabolism, bile acid pathways and, importantly, C21-steroid hormone biosynthesis and metabolism. Disturbances in these pathways have been shown to be relevant for neurodevelopment in rare genetic syndromes or implicated in previous studies of autism. This study provides new insight into maternal mid-pregnancy metabolic features possibly related to the development of autism and an incentive to explore whether these pathways and metabolites are useful for early diagnosis, treatment, or prevention. LAY SUMMARY: This study found that in mid-pregnancy the blood of mothers who give birth to a child that develops autism has some characteristic features that are different from those of blood samples taken from control mothers. These features are related to biologic mechanisms that can affect fetal brain development. In the future, these insights may help identify biomarkers for early autism diagnosis and treatment or preventive measures. Autism Res 2020, 13: 1258-1269. © 2020 International Society for Autism Research, Wiley Periodicals, Inc.

Effects of Cyclic High Ambient Temperature and Dietary Supplementation of Orotic Acid, a Pyrimidine Precursor, on Plasma and Muscle Metabolites in Broiler Chickens

The aim of this study was to evaluate the effects of high ambient temperature (HT) and orotic acid supplementation on the plasma and muscle metabolomic profiles in broiler chickens. Thirty-two 14-day-old broiler chickens were divided into four treatment groups that were fed diets with or without 0.7% orotic acid under thermoneutral (25 ± 1 °C) or cyclic HT (35 ± 1 °C for 8 h/day) conditions for 2 weeks. The chickens exposed to HT had higher plasma malondialdehyde concentrations, suggesting an increase in lipid peroxidation, which is alleviated by orotic acid supplementation. The HT environment also affected the serine, glutamine, and tyrosine plasma concentrations, while orotic acid supplementation affected the aspartic acid, glutamic acid, and tyrosine plasma concentrations. Untargeted gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS)-based metabolomics analysis identified that the HT affected the plasma levels of metabolites involved in purine metabolism, ammonia recycling, pyrimidine metabolism, homocysteine degradation, glutamate metabolism, urea cycle, β-alanine metabolism, glycine and serine metabolism, and aspartate metabolism, while orotic acid supplementation affected metabolites involved in pyrimidine metabolism, β-alanine metabolism, the malate-aspartate shuttle, and aspartate metabolism. Our results suggest that cyclic HT affects various metabolic processes in broiler chickens, and that orotic acid supplementation ameliorates HT-induced increases in lipid peroxidation.

Targeted metabolomics highlights perturbed metabolism in the brain of autism spectrum disorder sufferers

INTRODUCTION

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by deficiencies in social interactions and communication, combined with restricted and repetitive behavioral issues.

OBJECTIVES

As little is known about the etiopathophysiology of ASD and early diagnosis is relatively subjective, we aim to employ a targeted, fully quantitative metabolomics approach to biochemically profile post-mortem human brain with the overall goal of identifying metabolic pathways that may have been perturbed as a result of the disease while uncovering potential central diagnostic biomarkers.

METHODS

Using a combination of ¹H NMR and DI/LC-MS/MS we quantitatively profiled the metabolome of the posterolateral cerebellum from post-mortem human brain harvested from people who suffered with ASD (n = 11) and compared them with age-matched controls (n = 10).

RESULTS

We accurately identified and quantified 203 metabolites in post-mortem brain extracts and performed a metabolite set enrichment analyses identifying 3 metabolic pathways as significantly perturbed (p < 0.05). These include Pyrimidine, Ubiquinone and Vitamin K metabolism. Further, using a variety of machine-based learning algorithms, we identified a panel of central biomarkers (9-hexadecenoylcarnitine (C16:1) and the phosphatidylcholine PC ae C36:1) capable of discriminating between ASD and controls with an AUC = 0.855 with a sensitivity and specificity equal to 0.80 and 0.818, respectively.

CONCLUSION

For the first time, we report the use of a multi-platform metabolomics approach to biochemically profile brain from people with ASD and report several metabolic pathways which are perturbed in the diseased brain of ASD sufferers. Further, we identified a panel of biomarkers capable of distinguishing ASD from control brains. We believe that these central biomarkers may be useful for diagnosing ASD in more accessible biomatrices.

Uridine Metabolism and Its Role in Glucose, Lipid, and Amino Acid Homeostasis

Pyrimidine nucleoside uridine plays a critical role in maintaining cellular function and energy metabolism. In addition to its role in nucleoside synthesis, uridine and its derivatives contribute to reduction of cytotoxicity and suppression of drug-induced hepatic steatosis. Uridine is mostly present in blood and cerebrospinal fluid, where it contributes to the maintenance of basic cellular functions affected by UPase enzyme activity, feeding habits, and ATP depletion. Uridine metabolism depends on three stages: de novo synthesis, salvage synthesis pathway and catabolism, and homeostasis, which is tightly relating to glucose homeostasis and lipid and amino acid metabolism. This review is devoted to uridine metabolism and its role in glucose, lipid, and amino acid homeostasis.

Orotic acid-treated hepatocellular carcinoma cells resist steatosis by modification of fatty acid metabolism

BACKGROUND

Orotic acid (OA) has been intensively utilized to induce fatty liver in rats. Although the capacity of OA to cause steatosis is species-specific, previous in vitro studies indicate that humans could also be susceptible to OA-induced fatty liver. The aim of the present study was to re-elucidate the potential of OA exposure to modulate the cellular mechanisms involved in both non-alcoholic fatty liver disease pathogenesis and cellular protection from lipid accumulation. In addition, alterations in detailed fatty acid (FA) profiles of cells and culture media were analyzed to assess the significance of lipid metabolism in these phenomena.

METHODS

In our experiments, human hepatocellular carcinoma HepG2 cells were exposed to OA. Bacterial endotoxin, lipopolysaccharide (LPS), was used to mimic hepatic inflammation. The lipogenic and inflammatory effects of OA and/or LPS on cells were assessed by labeling cellular lipids with Nile red stain and by performing image quantifications. The expression levels of key enzymes involved in de novo lipogenesis (DNL) and of inflammatory markers related to the disease development were studied by qRT-PCR. FA profiles of cells and culture media were determined from total lipids with gas chromatography-mass spectrometry.

RESULTS

Our data indicate that although OA possibly promotes the first stage of DNL, it does not cause a definite lipogenic transformation in HepG2 cells. Reduced proportions of 16:0, increased stearoyl-Coenzyme A desaturase 1 mRNA expression and relatively high proportions of 16:1n-7 suggest that active delta9-desaturation may limit lipogenesis and the accumulation of toxic 16:0. Inflammatory signaling could be reduced by the increased production of long-chain n-3 polyunsaturated FA (PUFA) and the active incorporation of certain FA, including 18:1n-9, into cells. In addition, increased proportions of 20:4n-6 and 22:6n-3, total PUFA and dimethyl acetal 18:0 suggest that OA exposure may cause increased secretion of lipoproteins and extracellular vesicles.

CONCLUSIONS

The present data suggest that, apart from the transcription-level events reported by previous studies, modifications of FA metabolism may also be involved in the prevention of OA-mediated steatosis. Increased delta9-desaturation and secretion of lipoproteins and extracellular vesicles could offer potential mechanisms for further studies to unravel how OA-treated cells alleviate lipidosis.

The pathway to pyrimidines: The essential focus on dihydroorotate dehydrogenase, the mitochondrial enzyme coupled to the respiratory chain

This paper is based on the Anne Simmonds Memorial Lecture, given by Monika Löffler at the International Symposium on Purine and Pyrimidine Metabolism in Man, Lyon 2019. It is dedicated to H. Anne Simmonds (died 2010) - a founding member of the ESSPPMM, since 2003 Purine and Pyrimidine Society - and her outstanding contributions to the identification and study of inborn errors of purine and pyrimidine metabolism. The distinctive intracellular arrangement of pyrimidine de novo synthesis in higher eukaryotes is important to cells with a high demand for nucleic acid synthesis. The proximity of the enzyme active sites and the resulting channeling in CAD and UMP synthase is of kinetic benefit. The intervening enzyme dihydroorotate dehydrogenase (DHODH) is located in the mitochondrion with access to the ubiquinone pool, thus ensuring efficient removal of redox equivalents through the constitutive activity of the respiratory chain, also a mechanism through which the input of 2 ATP for carbamylphosphate synthesis is balanced by Oxphos. The obligatory contribution of O₂ to de novo UMP synthesis means that DHODH has a pivotal role in adapting the proliferative capacity of cells to different conditions of oxygenation, such as hypoxia in growing tumors. DHODH also is a validated drug target in inflammatory diseases. This survey of selected topics of personal interest and reflection spans some 40 years of our studies from tumor cell cultures under hypoxia to in vitro assays including purification from mitochondria, localization, cloning, expression, biochemical characterization, crystallisation, kinetics and inhibition patterns of eukaryotic DHODH enzymes.

A Patient With CAD Deficiency Responsive to Uridine and Literature Review

CAD encodes a multifunctional enzyme involved in de novo pyrimidine biosynthesis, and pyrimidine can be alternatively recycled from uridine. Trio whole-exome sequencing identified CAD compound heterozygous mutations in a new male patient with global developmental delay (DD), refractory epilepsy, and anemia with anisopoikilocytosis. We further reviewed all published cases with CAD deficiency. Five patients were collected from two publications, including three males and two females, and all presented with DD, drug-resistant epilepsy, and anemia with anisopoikilocytosis. Four out of six patients (including the present case) were supplemented with uridine, which led to immediate cessation of seizures, resolved anemia with anisopoikilocytosis, and progress in global development. The other two patients, who were not treated with uridine, died at the ages of 4 and 5 years. In summary, CAD deficiency is probably a treatable neurometabolic disorder.

CAD, A Multienzymatic Protein at the Head of de Novo Pyrimidine Biosynthesis

CAD is a 1.5 MDa particle formed by hexameric association of a 250 kDa protein that carries the enzymatic activities for the first three steps in the de novo biosynthesis of pyrimidine nucleotides: glutamine-dependent Carbamoyl phosphate synthetase, Aspartate transcarbamoylase and Dihydroorotase. This metabolic pathway is essential for cell growth and proliferation and is conserved in all living organisms. However, the fusion of the first three enzymatic activities of the pathway into a single multienzymatic protein only occurs in animals. In prokaryotes, by contrast, these activities are encoded as distinct monofunctional enzymes that function independently or by forming more or less transient complexes. Whereas the structural information about these enzymes in bacteria is abundant, the large size and instability of CAD has only allowed a fragmented characterization of its structure. Here we retrace some of the most significant efforts to decipher the architecture of CAD and to understand its catalytic and regulatory mechanisms.

Genetic analysis of orotic acid predicted with Fourier transform infrared milk spectra

Fourier transform infrared spectral analysis is a cheap and fast method to predict milk composition. A not very well studied milk component is orotic acid. Orotic acid is an intermediate in the biosynthesis pathway of pyrimidine nucleotides and is an indicator for the metabolic cattle disorder deficiency of uridine monophosphate synthase. The function of orotic acid in milk and its effect on calf health, health of humans consuming milk or milk products, manufacturing properties of milk, and its potential as an indicator trait are largely unknown. The aims of this study were to determine if milk orotic acid can be predicted from infrared milk spectra and to perform a large-scale phenotypic and genetic analysis of infrared-predicted milk orotic acid. An infrared prediction model for orotic acid was built using a training population of 292 Danish Holstein and 299 Danish Jersey cows, and a validation population of 381 Danish Holstein cows. Milk orotic acid concentration was determined with nuclear magnetic resonance spectroscopy. For genetic analysis of infrared orotic acid, 3 study populations were used: 3,210 Danish Holstein cows, 3,360 Danish Jersey cows, and 1,349 Dutch Holstein Friesian cows. Using partial least square regression, a prediction model for orotic acid was built with 18 latent variables. The error of the prediction for the infrared model varied from 1.0 to 3.2 mg/L, and the accuracy varied from 0.68 to 0.86. Heritability of infrared orotic acid predicted with the standardized prediction model was 0.18 for Danish Holstein, 0.09 for Danish Jersey, and 0.37 for Dutch Holstein Friesian. We conclude that milk orotic acid can be predicted with moderate to good accuracy based on infrared milk spectra and that infrared-predicted orotic acid is heritable. The availability of a cheap and fast method to predict milk orotic acid opens up possibilities to study the largely unknown functions of milk orotic acid.

Tetra-n-butyl-ammonium orotate monohydrate: knowledge-based comparison of the results of accurate and lower-resolution analyses and a non-routine disorder refinement

The analysis of a hydro­phobic–hydro­philic ion-pair structure at two temperatures permits the comparative evaluation of the accurate geometric results obtained at low temperature and less accurate results at room temperature using a knowledge-based approach.

The title hydrated mol­ecular salt (systematic name: tetra-n-butyl­ammonium 2,6-dioxo-1,2,3,6-tetra­hydro­pyrimidine-4-carboxyl­ate monohydrate), C₁₆H₃₆N⁺·C₅H₃N₂O₄⁻·H₂O, crystallizes with N—H⋯O and O—H⋯O hydrogen-bonded double-stranded anti­parallel ribbons consisting of the hydro­philic orotate monoanions and water mol­ecules, separated by the bulky hydro­phobic cations. The hydro­phobic and hydro­philic regions of the structure are joined by weaker non-classical C—H⋯O hydrogen bonds. An accurate structure analysis conducted at T = 100 K is compared to a lower-resolution less accurate determination using data measured at T = 295 K. The results of both analyses are evaluated using a knowledge-based approach, and it is found that the less accurate room-temperature structure analysis provides geometric data that are similar to those derived from the accurate low-temperature analysis, with both sets of results consistent with previously analyzed structures. A minor disorder of one methyl group in the cation at low temperature was found to be slightly more complex at room temperature; while still involving a minor fraction of the structure, the disorder at room temperature was found to require a non-routine treatment, which is described in detail.

Regulation effects of rosemary (Rosmarinus officinalis Linn.) on hepatic lipid metabolism in OA induced NAFLD rats

Rosmarinus officinalis Linn. is a kind of medicinal and edible homologous plant, which is popular in the Mediterranean region with a significant effect on mind tranquilization, anti-oxidation, and metabolic improvement. However, the hypolipidemic effects and mechanism of rosemary ethanol extract (RO) and their metabolites are less known. In this study, the hypolipidemic effects of RO and its active compounds were clarified. The results showed that RO, rosmarinic acid (RA) and carnosic acid (CA) significantly reduced the contents of liver triglyceride (TG), total cholesterol (TC), free fatty acids (FFA) and improved cell hypertrophy, vacuolation, and cell necrosis in the liver of orotic acid induced non-alcoholic fatty liver disease (NAFLD) model rats. The mechanism and related pathways of RO and its main metabolites against lipid disorder were related to the up-regulation of the phosphorylation of adenosine 5'-monophosphate(AMP)-activated protein kinase (AMPK) and the inhibition of the sterol regulatory element binding protein-1c (SREBP-1c) cracking into the nucleus, following the down-regulation of fatty acid synthesis. In conclusion, our study demonstrates that RA and CA are active substances of RO, and provides scientific evidence to support functional food product development for improving NAFLD.

Metabolomic analysis of mouse prefrontal cortex reveals upregulated analytes during wakefulness compared to sleep

By identifying endogenous molecules in brain extracellular fluid metabolomics can provide insight into the regulatory mechanisms and functions of sleep. Here we studied how the cortical metabolome changes during sleep, sleep deprivation and spontaneous wakefulness. Mice were implanted with electrodes for chronic sleep/wake recording and with microdialysis probes targeting prefrontal and primary motor cortex. Metabolites were measured using ultra performance liquid chromatography-high resolution mass spectrometry. Sleep/wake changes in metabolites were evaluated using partial least squares discriminant analysis, linear mixed effects model analysis of variance, and machine-learning algorithms. More than 30 known metabolites were reliably detected in most samples. When used by a logistic regression classifier, the profile of these metabolites across sleep, spontaneous wake, and enforced wake was sufficient to assign mice to their correct experimental group (pair-wise) in 80-100% of cases. Eleven of these metabolites showed significantly higher levels in awake than in sleeping mice. Some changes extend previous findings (glutamate, homovanillic acid, lactate, pyruvate, tryptophan, uridine), while others are novel (D-gluconate, N-acetyl-beta-alanine, N-acetylglutamine, orotate, succinate/methylmalonate). The upregulation of the de novo pyrimidine pathway, gluconate shunt and aerobic glycolysis may reflect a wake-dependent need to promote the synthesis of many essential components, from nucleic acids to synaptic membranes.

New perspectives on the roles of pyrimidines in the central nervous system

Since 1956, when exogenous uridine and cytidine were found to be necessary for the maintenance of perfused rat brain function, the co-existence of de novo synthesis, salvage pathways and removal of pyrimidine bases in the CNS has been a controversial subject. Here, we review studies on metabolites and enzymes of pyrimidine metabolism through more than 60 years. In view of known and newly-described inherited pyrimidine and purine disorders - some with complex clinical profiles of neurological impairments - we underline the necessity to investigate how the different pathways work together in the developing brain and then sustain plasticity, regeneration and neuro-transmission in the adult CNS. Experimentally, early incorporation studies in animal brain slices and homogenates with radio-labelled nucleosides or precursors demonstrated salvage activity or de novo synthesis. Later, the nucleoside transporters and organic anionic transporters underlying uptake of metabolites and anti-pyrimidine drugs in the CNS were identified. Recently, the expression of de novo enzymes in glial cells and neurons was verified using (immuno) histochemical and in-situ-hybridization techniques. Adult brain was shown to take up or produce all pyrimidine (deoxy) ribonucleosides or, after uptake and phosphorolysis of nucleosides, to make use of ribose for different purposes, including energy. More recently, non-canonical pyrimidine bases (5mC, 5hmC) have been found most notably in brain, pointing to considerable postreplicative DNA metabolism, with the need for pyrimidine-specific enzymes. Even more perspectives are emerging, with advances in genome analysis and in the manipulation of expression from the gene.