Difference of the liver and kidney in glycine conjugation of ortho-substituted benzoic acids

Metabolomics Reveals that Dietary Ferulic Acid and Quercetin Modulate Metabolic Homeostasis in Rats

Phenolic compounds ingestion has been shown to have potential preventive and therapeutic effects against various metabolic diseases such as obesity and cancer. To provide a better understanding of these potential benefit effects, we investigated the metabolic alterations in urine and feces of rat ingested ferulic acid (FA) and quercetin (Qu) using NMR-based metabolomics approach. Our results suggested that dietary FA and/or Qu significantly decreased short chain fatty acids and elevated oligosaccharides in the feces, implying that dietary FA and Qu may modulate gut microbial community with inhibition of bacterial fermentation of dietary fibers. We also found that dietary FA and/or Qu regulated several host metabolic pathways including TCA cycle and energy metabolism, bile acid, amino acid, and nucleic acid metabolism. These biological effects suggest that FA and Qu display outstanding bioavailability and bioactivity and could be used for treatment of some metabolic syndromes, such as inflammatory bowel diseases and obesity.

Metabolic Profiling Analysis of the Alleviation Effect of the Fractions of Niuhuang Jiedu Tablet on Realgar Induced Toxicity in Rats

Niuhuang Jiedu Tablet (NJT) is a classical formula in treating acute tonsillitis, pharyngitis, and so on. In the formula, significant level of Realgar as a potentially toxic element is contained. Our previous experiments revealed that it was less toxic for combined Realgar in NJT. However, the active fraction of this prescription with toxicity alleviation effect on Realgar was still obscure. NJT was divided into five different polar fractions (NJT-PET, NJT-25, NJT-50, NJT-75, and NJT-95), and we explored the toxicity alleviation effect on Realgar. Based on 1H NMR spectra of urine and serum from rats, PCA and PLS-DA were performed to identify different metabolic profiles. Liver and kidney histopathology examinations and serum clinical chemistry analysis were also performed. With pattern recognition analysis of metabolites in urine and serum, Realgar group showed a clear separation from control group, while the metabolic profiles of NJT-PET, NJT-25, NJT-50, and NJT-95 groups were similar to Realgar group, and the metabolic profiles of NJT and NJT-75 groups were very close to control group. Statistics results were confirmed by the histopathological examination and biochemical assay. The present work indicated that 75% EtOH fraction of NJT was the most valid fraction with the toxicity alleviation effect on Realgar.

Toxicity assessment of Arisaematis Rhizoma in rats by a 1H NMR-based metabolomics approach

A ¹H NMR based metabolomics approach combined with serum biochemistry and histopathological examination was used to study the toxicity of Arisaematis Rhizoma by intragastrical administration for the first time.

System responses to chronic cold stress probed via1H NMR spectroscopy in plasma and urine matrices

The metabolic pathways in plasma and urine revealed the biochemical changes under chronic cold stress from a systematic and holistic view.

Metabonomic profiling of bladder cancer

Early diagnosis and life-long surveillance are clinically important to improve the long-term survival of bladder cancer patients. Currently, a noninvasive biomarker that is as sensitive and specific as cystoscopy in detecting bladder tumors is lacking. Metabonomics is a complementary approach for identifying perturbed metabolic pathways in bladder cancer. Significant progress has been made using modern metabonomic techniques to characterize and distinguish bladder cancer patients from control subjects, identify marker metabolites, and shed insights on the disease biology and potential therapeutic targets. With its rapid development, metabonomics has the potential to impact the clinical management of bladder cancer patients in the future by revolutionizing the diagnosis and life-long surveillance strategies and stratifying patients for diagnostic, surgical, and therapeutic clinical trials. An introduction to metabonomics, typical metabonomic workflow, and critical evaluation of metabonomic investigations in identifying biomarkers for the diagnosis of bladder cancer are presented.

Anti-fibrosis and anti-cirrhosis effects of Rhizoma paridis saponins on diethylnitrosamine induced rats

ETHNOPHARMACOLOGICAL RELEVANCE

Paris polyphylla var. yunnanensis as a traditional Chinese medicine has been used in the treatment of liver disease for thousands of years. Rhizoma paridis saponins (RPS), as the main active components of Paris polyphylla, have been used to treat liver injury. Anti-cirrhosis effect of Rhizoma paridis saponins (RPS) has not been known.

MATERIALS AND METHODS

We analyzed diethylnitrosamine (DEN)-induced metabonomic changes in multiple biological matrices (plasma and urine) of rats by using (1)H-NMR spectroscopy together with clinical biochemistry assessments, oxidative stress test and DNA fragmentation assay.

RESULTS

Mechanisms of RPS that participated in the inhibition of the fibrotic process included anti-oxidant, anti-apoptosis, and metabolic disturbance such as decreasing lipid oxidation, regulation of TCA cycle, carbohydrate, and amino acid metabolisms in DEN-induced liver tissues.

CONCLUSIONS

Integrated NMR analysis of serum and urine samples, together with traditional clinical biochemical assays provided a holistic method for elucidating mechanisms of potential anti-fibrotic agent, RPS.

Glycine conjugation: importance in metabolism, the role of glycine N-acyltransferase, and factors that influence interindividual variation

INTRODUCTION

Glycine conjugation of mitochondrial acyl-CoAs, catalyzed by glycine N-acyltransferase (GLYAT, E.C. 2.3.1.13), is an important metabolic pathway responsible for maintaining adequate levels of free coenzyme A (CoASH). However, because of the small number of pharmaceutical drugs that are conjugated to glycine, the pathway has not yet been characterized in detail. Here, we review the causes and possible consequences of interindividual variation in the glycine conjugation pathway.

AREAS COVERED

The authors review the importance of CoASH in metabolism, formation and toxicity of xenobiotic acyl-CoAs, and mechanisms for restoring levels of CoASH. They focus on GLYAT, glycine conjugation, how genetic variation in the GLYAT gene could influence glycine conjugation, and the emerging roles of glycine metabolism in cancer and musculoskeletal development.

EXPERT OPINION

The substrate selectivity of GLYAT and its variants needs to be further characterized, as organic acids can be toxic if the corresponding acyl-CoA is not a substrate for glycine conjugation. GLYAT activity affects mitochondrial ATP production, glycine availability, CoASH availability, and the toxicity of various organic acids. Therefore, variation in the glycine conjugation pathway could influence liver cancer, musculoskeletal development, and mitochondrial energy metabolism.

The glycine deportation system and its pharmacological consequences

The glycine deportation system is an essential component of glycine catabolism in man whereby 400 to 800mg glycine per day are deported into urine as hippuric acid. The molecular escort for this deportation is benzoic acid, which derives from the diet and from gut microbiota metabolism of dietary precursors. Three components of this system, involving hepatic and renal metabolism, and renal active tubular secretion help regulate systemic and central nervous system levels of glycine. When glycine levels are pathologically high, as in congenital nonketotic hyperglycinemia, the glycine deportation system can be upregulated with pharmacological doses of benzoic acid to assist in normalization of glycine homeostasis. In congenital urea cycle enzymopathies, similar activation of the glycine deportation system with benzoic acid is useful for the excretion of excess nitrogen in the form of glycine. Drugs which can substitute for benzoic acid as substrates for the glycine deportation system have adverse reactions that may involve perturbations of glycine homeostasis. The cancer chemotherapeutic agent ifosfamide has an unacceptably high incidence of encephalopathy. This would appear to arise as a result of the production of toxic aldehyde metabolites which deplete ATP production and sequester NADH in the mitochondrial matrix, thereby inhibiting the glycine deportation system and causing de novo glycine synthesis by the glycine cleavage system. We hypothesize that this would result in hyperglycinemia and encephalopathy. This understanding may lead to novel prophylactic strategies for ifosfamide encephalopathy. Thus, the glycine deportation system plays multiple key roles in physiological and neurotoxicological processes involving glycine.

Noninvasive detection of carboxypeptidase G2 activity in vivo

The pseudomonad protein, carboxypeptidase G2 (CPG2), is a prodrug-activating enzyme utilized in the targeted chemotherapy strategies of antibody- and gene-directed enzyme prodrug therapy (ADEPT and GDEPT). We have developed a noninvasive imaging approach to monitor CPG2 activity in vivo that will facilitate the preclinical and clinical development of CPG2-based ADEPT and GDEPT strategies. Cleavage of the novel reporter probe, 3,5-difluorobenzoyl-L-glutamic acid (3,5-DFBGlu), by CPG2, in human colon adenocarcinoma WiDr xenografts engineered to stably express CPG2, was monitored using (19)F MRSI. The high signal-to-noise ratio afforded by the two MR-equivalent (19)F nuclei of 3,5-DFBGlu, and the 1.4 ppm (19)F chemical shift difference on CPG2-mediated cleavage, enabled the dynamics and quantification of the apparent pharmacokinetics of 3,5-DFBGlu and its CPG2-mediated cleavage in the tumor to be evaluated. In addition, the apparent rate of increase of 3,5-difluorobenzoic acid concentration could also provide a biomarker of CPG2 activity levels in tumors of patients undergoing CPG2-based therapies, as well as a biomarker of treatment response. The addition of in vivo reporter probes, such as 3,5-DFBGlu, to the armamentarium of prodrugs cleaved by CPG2 affords new applications for CPG2 as a gene reporter of transgene expression.

Systems responses of rats to aflatoxin B1 exposure revealed with metabonomic changes in multiple biological matrices

Exposure to aflatoxins causes liver fibrosis and hepatocellular carcinoma posing a significant health risk for human populations and livestock. To understand the mammalian systems responses to aflatoxin-B1 (AFB1) exposure, we analyzed the AFB1-induced metabonomic changes in multiple biological matrices (plasma, urine, and liver) of rats using (1)H NMR spectroscopy together with clinical biochemistry and histopathologic assessments. We found that AFB1 exposure caused significant elevation of glucose, amino acids, and choline metabolites (choline, phosphocholine, and glycerophosphocholine) in plasma but reduction of plasma lipids. AFB1 also induced elevation of liver lipids, amino acids (tyrosine, histidine, phenylalanine, leucine, isoleucine, and valine), choline, and nucleic acid metabolites (inosine, adenosine, and uridine) together with reduction of hepatic glycogen and glucose. AFB1 further caused decreases in urinary TCA cycle intermediates (2-oxoglutarate and citrate) and elevation of gut microbiota cometabolites (phenylacetylglycine and hippurate). These indicated that AFB1 exposure caused hepatic steatosis accompanied with widespread metabolic changes including lipid and cell membrane metabolisms, protein biosynthesis, glycolysis, TCA cycle, and gut microbiota functions. This implied that AFB1 exposure probably caused oxidative-stress-mediated impairments of mitochondria functions. These findings provide an overview of biochemical consequences of AFB1 exposure and comprehensive insights into the metabolic aspects of AFB1-induced hepatotoxicity in rats.

Evaluation of a screening method by liquid chromatography-tandem mass spectrometry for estimating effect of drugs on the activation and β-oxidation of fatty acids in mitochondria

Objectives

Fatty acid metabolism is controlled not only by the acyl-coenzyme A (CoA) synthetases but by some enzymes in the β-oxidation cycle. Medium-chain and long-chain acyl-CoA esters are key metabolites in fatty acid metabolism. We have developed an enzymatic assay method for determining chain shortening of the acyl-CoAs via β-oxidation from palmitic and octanoic acids in liver mitochondria. We have evaluated the assay method for detecting whether drugs influence the activation or the β-oxidation of fatty acids.

Methods

Liver mitochondria were used for investigating the effect of drugs on fatty acid metabolism. The drugs selected were salicylic acid, diclofenac, valproic acid and paracetamol. Each acyl-CoA formed was analysed by liquid chromatography–tandem mass spectrometry.

Key findings

After less than 5 min of incubation, the levels of acyl-CoAs reflected the acyl-CoA synthetase activity, whereas after 60-min incubation they reflected the activity of some enzymes in the β-oxidation cycle. Salicylic acid, diclofenac and valproic acid inhibited the medium-chain acyl-CoA synthetases, whereas valproic acid only exhibited a weak inhibitory activity toward the β-oxidation of the medium-chain fatty acids. In the case of long-chain fatty acid metabolism, salicylic acid and diclofenac inhibited both the activation and β-oxidation, whereas valproic acid was a weak inhibitor for only the β-oxidation activity. Paracetamol showed hardly any influence on the metabolism of medium-chain and long-chain fatty acids.

Conclusions

These findings suggest that salicylic acid, diclofenac, valproic acid and paracetamol exert a different influence on fatty acid metabolism depending on the length of the acyl chain. This assay allows sensitive and selective analysis for predicting the pathways by which drugs exert a greater influence over fatty acid metabolism.

An insight into the metabolic responses of ultra-small superparamagnetic particles of iron oxide using metabonomic analysis of biofluids

Ultra-small superparamagnetic particles of iron oxides (USPIO) have been developed as intravenous organ/tissue-targeted contrast agents to improve magnetic resonance imaging (MRI) in vivo. However, their potential toxicity and effects on metabolism have attracted particular attention. In the present study, uncoated and dextran-coated USPIO were investigated by analyzing both rat urine and plasma metabonomes using high-resolution NMR-based metabonomic analysis in combination with multivariate statistical analysis. The wealth of information gathered on the metabolic profiles from rat urine and plasma has revealed subtle metabolic changes in response to USPIO administration. The metabolic changes include the elevation of urinary alpha-hydroxy-n-valerate, o- and p-HPA, PAG, nicotinate and hippurate accompanied by decreases in the levels of urinary alpha-ketoglutarate, succinate, citrate, N-methylnicotinamide, NAG, DMA, allantoin and acetate following USPIO administration. The changes associated with USPIO administration included a gradual increase in plasma glucose, N-acetyl glycoprotein, saturated fatty acid, citrate, succinate, acetate, GPC, ketone bodies (beta-hydroxybutyrate, acetone and acetoacetate) and individual amino acids, such as phenylalanine, lysine, isoleucine, glycine, glutamine and glutamate and a gradual decrease of myo-inositol, unsaturated fatty acid and triacylglycerol. Hence USPIO administration effects are reflected in changes in a number of metabolic pathways including energy, lipid, glucose and amino acid metabolism. The size- and surface chemistry-dependent metabolic responses and possible toxicity were observed using NMR analysis of biofluids. These changes may be attributed to the disturbances of hepatic, renal and cardiac functions following USPIO administrations. The potential biotoxicity can be derived from metabonomic analysis and serum biochemistry analysis. Metabonomic strategy offers a promising approach for the detection of subtle physiological responses on mammalian metabolism, and can be employed to investigate the potential adverse effects of other nanoparticles and nanomaterials on the environment and human health.

NMR-based metabonomic study of the sub-acute toxicity of titanium dioxide nanoparticles in rats after oral administration

As titanium dioxide nanoparticles (TiO(2) NPs) are widely used commercially, their potential toxicity on human health has attracted particular attention. In the present study, the oral toxicological effects of TiO(2) NPs (dosed at 0.16, 0.4 and 1 g kg( - 1), respectively) were investigated using conventional approaches and metabonomic analysis in Wistar rats. Serum chemistry, hematology and histopathology examinations were performed. The urine and serum were investigated by (1)H nuclear magnetic resonance (NMR) using principal components and partial least squares discriminant analysis. The metabolic signature of urinalysis in TiO(2) NP-treated rats showed increases in the levels of taurine, citrate, hippurate, histidine, trimethylamine-N-oxide (TMAO), citrulline, alpha-ketoglutarate, phenylacetylglycine (PAG) and acetate; moreover, decreases in the levels of lactate, betaine, methionine, threonine, pyruvate, 3-D-hydroxybutyrate (3-D-HB), choline and leucine were observed. The metabonomics analysis of serum showed increases in TMAO, choline, creatine, phosphocholine and 3-D-HB as well as decreases in glutamine, pyruvate, glutamate, acetoacetate, glutathione and methionine after TiO(2) NP treatment. Aspartate aminotransferase (AST), creatine kinase (CK) and lactate dehydrogenase (LDH) were elevated and mitochondrial swelling in heart tissue was observed in TiO(2) NP-treated rats. These findings indicate that disturbances in energy and amino acid metabolism and the gut microflora environment may be attributable to the slight injury to the liver and heart caused by TiO(2) NPs. Moreover, the NMR-based metabolomic approach is a reliable and sensitive method to study the biochemical effects of nanomaterials.

Effect of salicylic acid and diclofenac on the medium-chain and long-chain acyl-CoA formation in the liver and brain of mouse

Medium-chain and long-chain acyl-CoA esters are key metabolites in fatty acid metabolism. Effects of salicylic acid on the in vivo formation of acyl-CoAs in mouse liver and brain were investigated. Further, inhibition of the medium-chain and long-chain acyl-CoA synthetases by salicylic acid and diclofenac was determined in mouse liver and brain mitochondria. Acyl-CoA esters were analyzed by liquid chromatography-tandem mass spectrometry. The amounts of medium-chain acyl-CoAs (C(6), C(8) and C(10)) were less than long-chain acyl-CoAs (C(16:0), C(18:0), C(18:1) and C(20:4)) in both liver and brain. The administration of salicylic acid decreased the levels of both the medium-chain (C(6), C(8) and C(10)) and long-chain acyl-CoAs (C(16:0), C(18:0), C(18:1) and C(20:4)) in liver. In brain, however, only long-chain acyl-CoAs were decreased. The level of salicylyl-CoA detected in brain was about 12% of that in liver. Salicylic acid had a strong inhibitory activity (IC(50) = 0.1 mm) for the liver mitochondrial formation of hexanoyl-CoA from hexanoic acid, whereas diclofenac was weak (IC(50) = 4.4 mm). In contrast, diclofenac (IC(50) = 1.4 mm) inhibited the liver mitochondrial long-chain acyl-CoA synthetases more potently than salicylic acid (IC(50) = 25.5 mm). Similar inhibitory activities for the acyl-CoA synthetases were obtained in the case of the brain and liver mitochondria, except for the weak inhibition of brain medium-chain acyl-CoA synthetases by salicylic acid (IC(50) = 1.8 mm). These findings suggest that salicylic acid and diclofenac exhibit different mechanisms of inhibition of fatty acid metabolism depending on the length of the acyl chain and tissues, and they may contribute to the further understanding of the toxic effects associated with these drugs.

Toxicological effects of cinnabar in rats by NMR-based metabolic profiling of urine and serum

Cinnabar, an important traditional Chinese mineral medicine, has been widely used as a Chinese patent medicine ingredient for sedative therapy. However, the pharmaceutical and toxicological effects of cinnabar, especially in the whole organism, were subjected to few investigations. In this study, an NMR-based metabolomics approach has been applied to investigate the toxicological effects of cinnabar after intragastrical administration (dosed at 0.5, 2 and 5 g/kg body weight) on male Wistar rats. Liver and kidney histopathology examinations and serum clinical chemistry analyses were also performed. The 1H NMR spectra were analyzed using multivariate pattern recognition techniques to show the time- and dose-dependent biochemical variations induced by cinnabar. The metabolic signature of urinalysis from cinnabar-treated animals exhibited an increase in the levels of creatinine, acetate, acetoacetate, taurine, hippurate and phenylacetylglycine, together with a decrease in the levels of trimethyl-N-oxide, dimethylglycine and Kreb's cycle intermediates (citrate, 2-oxoglutarate and succinate). The metabolomics analyses of serum showed elevated concentrations of ketone bodies (3-d-hydroxybutyrate and acetoacetate), branched-chain amino acids (valine, leucine and isoleucine), choline and creatine as well as decreased glucose, lipids and lipoproteins from cinnabar-treated animals. These findings indicated cinnabar induced disturbance in energy metabolism, amino acid metabolism and gut microflora environment as well as slight injury in liver and kidney, which might indirectly result from cinnabar induced oxidative stress. This work illustrated the high reliability of NMR-based metabolomic approach on the study of the biochemical effects induced by traditional Chinese medicine.

Liquid chromatography–tandem mass spectrometry analysis of protocatechuic aldehyde and its phase I and II metabolites in rat

A method using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) analysis was established for the identification of metabolites in rat after oral administration of protocatechuic aldehyde, a major bioactive phenolic acid in the roots of Salvia miltiorrhiza. Eleven metabolites in rat plasma and urine were firstly identified as protocatechuic aldehyde, protocatechuic acid and their methylated, glucuronized or glycine conjugates on the basis of their MS fragmentation behaviors, while nine of these metabolites (except protocatechuic aldehyde and protocatechuic acid) were detected in rat bile. In addition, the possible metabolic pathway was proposed for the first time. In the phase I metabolism, protocatechuic aldehyde could be oxidized to protocatechuic acid. The conjugates would be formed in rat intestine, liver and kidney and excreted from rat urine and bile. Enthrohepatic circulation played an important role in the metabolism of protocatechuic aldehyde. The results proved that the established method was simple, reliable and sensitive, revealing that it could be used to rapid screen and identify the structures of active components responsible for pharmacological effects of protocatechuic aldehyde and to better understand its in vivo metabolism.

Metabolism, Pharmacokinetics, and Excretion of the Substance P Receptor Antagonist CP-122,721 in Humans: Structural Characterization of the Novel Major Circulating Metabolite 5-Trifluoromethoxy Salicylic Acid by High-Performance Liquid Chromatography-Tandem Mass Spectrometry and NMR Spectroscopy

The metabolism, pharmacokinetics, and excretion of a potent and selective substance P receptor antagonist, CP-122,721 [(+)-(2S,3S)-3-(2-methoxy-5-trifluoromethoxybenzylamino)-2-phenylpiperidine], have been studied in six healthy male human subjects [four extensive metabolizers (EMs) and two poor metabolizers (PMs) of CYP2D6) following oral administration of a single 30-mg dose of [14C]CP-122,721. Approximately 84% of the administered radioactivity was recovered from the urine and feces of the subjects over a period of 312 h. Approximately 80% of the dose for EM subjects was recovered within 48 h. PM subjects, however, excreted only about 45% of the dose in 48 h and required the full 312 h to achieve nearly 80% recovery. Absorption of CP-122,721 was rapid in both extensive and poor metabolizers, as indicated by the rapid appearance of radioactivity in serum. The serum concentrations of total radioactivity were always much greater than those of unchanged drug indicating early formation of metabolites. The average CP-122,721 t1/2 was 6.7 h and 45.0 h for EM and PM subjects, respectively. The serum concentrations of CP-122,721 reached a peak of 7.4 and 69.8 ng/ml for extensive and poor metabolizers, respectively. The major metabolic pathways of CP-122,721 were due to O-demethylation, aromatic hydroxylation, and indirect glucuronidation. The minor metabolic pathways included aliphatic oxidation at the piperidine moiety, O-dealkylation of the trifluoromethoxy group, N-dealkylation, and oxidative deamination. In addition to the major human circulating metabolite 5-trifluoromethoxy salicylic acid (TFMSA), all other circulating metabolites of CP-122,721 were glucuronide conjugates of oxidized metabolites. TFMSA was identified using high pressure liquid chromatography/tandem mass spectrometry and NMR and mechanisms were proposed for its formation. There are no known circulating active metabolites of CP-122,721.

In vivo recognition of cyclopentadienyltricarbonylrhenium (CpTR) derivatives

In vivo metabolism of [(188)Re]tricarbonyl(carboxycyclopentadienyl)rhenium ([(188)Re]CpTR-COOH) and its glycine conjugate ([(188)Re]CpTR-Gly) was investigated to estimate the applicability of cyclopentadienyltricarbonylrhenium (CpTR) compounds to (186/188)Re-labeling reagents for polypeptides and peptides. Both [(188)Re]CpTR derivatives were stable after incubation in a buffered-solution and in murine plasma at 37 degrees C for 6 h. Plasma protein binding was hardly observed with the two derivatives. However, different biodistribution and metabolic fates were observed with the two CpTR derivatives. While more lipophilic [(188)Re]CpTR-COOH was excreted by both hepatobiliary and urinary excretion, the majority of less lipophilic [(188)Re]CpTR-Gly was excreted by urinary excretion. In addition, while [(188)Re]CpTR-Gly was rapidly excreted into urine as its intact structure, [(188)Re]CpTR-COOH was metabolized to more hydrophilic compounds including its glycine conjugate, [(188)Re]CpTR-Gly. Renal excretion of [(188)Re]CpTR-Gly was significantly reduced in probenecid retreated mice. The present studies reinforced that CpTR core remained stable under biological environment. CpTR-COOH was partially recognized as an aromatic acid and was metabolized as such. However, glycine conjugation rendered CpTR-COOH hydrophilic enough to be excreted into urine without further metabolism. These findings suggested that radiolabeling reagents that liberate [(186/188)Re]CpTR-Gly from covalently conjugated (186/188)Re-labeled polypeptides and peptides by the action of renal brush border enzymes would be useful to reduce renal radioactivity levels.