Metabolomic Analysis On Toxic Mechanisms Of Ochratoxin A

As a secondary metabolite,Ochratoxin A(OTA)is a mycotoxin produced by some fungi and widely distributed in the grain,wine,meat etc.Previous studies have shown that the OTA is nephrotoxic,hepatotoxic,teratogenic,mutagenic and potentiallycarcinogenic to both rodents and human.To explore from the metabolic level and reveal the toxicology of OTA,We used metabonomics as main means,combined with the traditional technology such as pathological section to analyze the OTA-induced changes in fluids and metabolic pathways of the target organs and explore the possible mechanism of OTA on fatty acid metabolism.In this paper,the main results are as follows:(1)To understand the systems responses to OTA exposure,GC/MS-and 1H NMR-based metabolomic profiling together with clinical biochemistry and histopathologic assessments were applied to analyze the urine and plasma samples of OTA-exposed rats.We found that OTA exposure caused significant elevation of amino acids(alanine,glycine,leucine etc.),pentose(ribose,glucitol and xylitol etc.)and nucleic acid metabolites(pseudouridine,adenosine and uridine).Moreover,myo-inositol,trimethylamine oxidase(TMAO),pseudouridine and leucine were identified as potential biomarkers.The primary pathways,in which the differential metabolites were involved,were pentose phosphate pathway(PPP),Kreb's cycle(TCA),creatine pathway and gluconeogenesis.The elevated PPP attributed to the high requirements for NADPH,which involved in OTA metabolism through cytochrome P450(CYP450).The elevated gluconeogenesis from glucogenic amino acid and TCA suggest that the energy metabolism was activated.The up-regulated synthesis of creatinine reveals the elevated catabolism of protein,which meet the requirement of activated energy metabolism.(2)Using GC-MS and LC/ESI-MS metabonomics as main means,we analyzed the body fluids and target organs samples of rats with acute toxic effect of OTA.Similar to low doses OTA-induced chronic kidney damage,OTA acute toxicity specific damage area was also the renal tubular epithelial cells.Like the chronic toxicity of OTA,inositol,which might be a potential biomarker of OTA toxicity,was significantly improved in both body fluids and target organs.OTA raised the Krebs cycle,the pentose phosphate pathway,sugar dysplasia and fatty acid oxidation in rats,all these pathways were energy metabolism-associated.In another word,OTA raised the level of energy metabolism.However,OTA inhibit the oxidation of fatty acids,but promoted the Krebs cycle and sugar dysplasia in rat kidney.Structural damage to the kidney caused by OTA may be associated with different regulation of metabolism in liver and kidney to OTA.(3)On the basis of LC-TOF-MS metabonomics,we analyzed the humor and target organs samples from wild type and MPC1 knockout heterozygous mice.1 mg/kg b.w.dose of OTA was used for gavage of mice through the mouth for a week induced renal tubular epithelial degeneration expansion and exfoliation of epidermal cell.Due to the high antioxidant levels in the body of MPC1 knockout heterozygous mice,protective effect to the OTA-caused kidneys damage was shown.Influence of OTA on fatty acid metabolism is one of the main ways for OTA to interfere with normal metabolism.OTA induced mice liver fat oxidation and improved the ability of using fat.These phenomena in MPC1 knockout heterozygous type were more significant.OTA induced MPC1 type knockout heterozygous mice serum arginine decomposition product 2-carbonyl arginine and ornithine increased.The urea cycle was suppressed because of the obstruction in ornithine turning into arginine.