Effects Of Liver And Serum Metabolomic Analysis Of Long-term Exposure To Sausage On Rats

Objective:The purpose of the current study was to observe the effect of long-term exposure to sausage and N-nitrosodimethylamine(NDMA)on rats,as well as its possible liver damage.Moreover,the study also explored to find characteristic metabolites to identify different stages of liver damage(hepatitis-hepatic-cirrhosis-liver cancer),and their potential value to apply in clinical diagnosis.Methods:SD male adult rats(200.8g± 23.9g)were randomly assigned to five groups:the control group,the control group with 18%sausage(18%commom sausage added into the feed),18%sausage group(18%sausage with NDMA exceed standard added into the feed),36%sausage(36%sausage with NDMA exceed standard added into the feed),and the positive group(with 30 ug/kg NDMA in the drinking water).The feeding continued for 33 weeks,and the positive group was given ordinary drinking water after 12th week.The liver tissues and serum were collected at different time points to analysis the histopathology of livers and the clinical biochemical indicators,the serum samples of rats were collected at different time points to measure metabonomic by gas chromatography-mass spectrometry(GC/MS).Results:The pathological changes of liver in the positive group were hepatitis,hepatic,cirrhosis,cancer at 7th,17th,25th,33th week respectively.Compared the pathological results of five groups at the same time,the degree of liver damage was the lowest in the control group,and the liver still normal at 7th,17th,25th weeks.The degree of liver damage in the control group with 18%sausage,18%sausage group and 36%sausage group was deeper stepwise but lighter than that in positive group.At the end of the experiment,the damage of liver in 36%sausage group was only liver cirrhosis.The result of clinical biochemical indicators and the oxidation antioxidant index in serum showed that T-CHO,AKP,GOT,GPT,MDA,SOD,GSH-PX were different,significantly.The result of metabolomics analysis showed that some metabolites associated with energy metabolism,amino acid metabolism,lipid metabolism,and nucleic acid metabolism were significantly different between the control group and the other four group,such as citric acid,’N-methyl-DL-alanine,proline,3-hydroxy-L-proline,L-cysteine,3-cyano alanine,threonine,Tyrosine,5’-methylthioadenosine(MAT),palmitic acid,5-methoxytryptamine(tryptophan metabolite),putrescine,glycine,taurine,β-alanine,3-aminoisobutyric acid,ethanolamine.Conclusions:The model of liver cancer in rats was successfully established by using sausage and NDMA.The results showed that long-term intake of sausage could lead to liver damage.And the traditional biochemical indicators could not exactly reflect the state of liver damage.Some metabolites associated with energy metabolism,amino acid metabolism,and lipid metabolism in the serum were significantly different between the control group and the other four group.And these metabolites could provide clues for further exploration of the mechanism of liver damage.