| In this experiment,16 strains of lactic acid bacteria isolated from traditional fermented products in Inner Mongolia were screened for their ability to reduce nitrosamines,acid resistance and bile salt resistance,and the effects of culture time and different cell components on the degradation rate were studied.The experimental mice were fed following long-term intake of containing excessive N-nitrosamines in sausage,and target strains was given gastric irrigation at the same time.The experimental animals were divided into control group(CO),common sausage control group(YC),model group(M),high dose group of lactic acid bacteria(RH),low dose group of lactic acid bacteria(RL)and inactivation group of lactic acid bacteria(RS).After 12 weeks of continuous feeding,the mice were sacrificed at 4th,8th and 12th weeks,respectively.Then blood and liver were collected,and liver tissue morphology,serum biochemical indexes,liver antioxidant indexes,NDMA content in plasma,expression of metabolic enzymes were detected.It was of great significance for preventing harm of N-nitrosamine to human body and protecting human health to study the protective effect and mechanism of the target strain on liver injury in mice induced by intake of sausage feed containing excessive N-nitrosamines.The results were as follows:(1)Four strains of lactic acid bacteria with high N-nitrosamine degradation ability were screened out,which were Lactobacillus plantarum AL6-1,Lactobacillus helveticus SL-1,Pediococcus pentosaceus 37X-11 and 37X-13,and the sum of degradation rates of N-dimethylnitrosamine(NDMA)and N-diethylnitrosamine(NDEA)were 49.28%,42.33%,41.43%and 39.82%,respectively.Then the growth characteristics,acid resistance and bile salt resistance of L.plantarum AL6-1 were studied.L.plantarum AL6-1 could grow at p H3.0 and 0.3%bile salt.The cell concentrations were 6.40×10~7and 4.33×10~6CFU/m L,respectively.And the number of viable cells was higher than 10~6CFU/m L,indicating that the strain could smoothly enter the intestine through the gastrointestinal environment.After36 h of culture,L.plantarum AL6-1 had the highest degradation rates of NDMA and NDEA,which were 63.90%and 61.65%,respectively.And its N-nitrosamine-clearing pathway was mainly through the degradation of intracellular extract.(2)L.plantarum AL6-1 was applied to mice to study the protective effect and mechanism of liver injury in mice induced by intake of sausage feed containing excessive N-nitrosamines.Compared with the Group CO,the body weight and liver index of mice in the Group M were significantly increased(P<0.05).In addition,there were cellular typical changes such as cell swelling,vacuolar degeneration,inflammatory cell infiltration and partial cell necrosis in hepatocytes;the levels of AST and ALT in serum were significantly increased(P<0.05),suggesting that the model of liver injury in mice can be successfully established by sausage containing excessive N-nitrosamines;the content of MDA in liver tissue of mice in Group M increased,and the levels of SOD and GSH-Px decreased significantly(P<0.05),indicating that intake of sausage containing excessive N-nitrosamines could cause oxidative stress injury in mice.And the level of NDMA in plasma significantly increased(P<0.05);the gene expression levels of liver metabolic enzymes CYP2E1,CYP2C37 and PXR increased,and the gene expression level of CYP1A2 significantly decreased(P<0.05).The intervention of high and low dose L.plantarum AL6-1 had improvement effect on the indicators of Group M.Compared with the Group M,the intervention of L.plantarum AL6-1 slowed down the weight gain of mice,reduced the liver index,improved the structure of hepatic lobule and the degree of vacuolar degeneration and inflammatory cell infiltration,and ALT and AST levels in serum was significantly decreased(P<0.05);MDA level in liver of mice decreased significantly(P<0.05),while SOD and GSH-Px levels increased significantly(P<0.05).The plasma levels of NDMA in mice at different stages were significantly lower than those in Group M(P<0.05),indicating that L.plantarum AL6-1 could promote the excretion of N-nitrosamines and reduce the accumulation of N-nitrosamines.And the gene expression levels of liver metabolic enzymes CYP2E1,CYP2C37 and PXR were significantly decreased,and the gene expression level of CYP1A2 was significantly increased(P<0.05),which indicated that regulating the expression of liver metabolic enzymes could alleviate liver injury in mice and inhibit the activation of N-nitrosamines. |
