Accumulation And Damage Of Dietary CML On Gastrotestinal Tract In Rats

Advanced glycation end products(AGEs)are a heterogeneous group of compounds that generated by the spontaneous reaction between reducing sugars and free amino groups in protein.Carboxymethyllysine(CML)is one of the best characterized AGEs,and is usually used as a marker of both dietary AGEs and in vivo levels.Dietary CML has two forms: free and bound to lysine residues within peptides and protein.CML belonging to bound form may be distinguished from the free form by been protein-bound whereas free CML are mainly derived free amino acids.The difference of bounding form leads to a variable absorption rate of CML in the GI tract,various absorption degrees of free and bound CML could cause different physiological activities.In the present study,we used free and protein-bound predominant CML diet from the glucose-lysine model system and bread crust,used healthy SD rats as animal modelsto evaluate the its effect on blood glucose and glucose metabolism of rats.In addition,we investigate the accumulation and effect of dietary CML on the different segment of GI tract on rats.The conclusion were as follows:(1)After 6,12,and 18 weeks of feeding the CML-riched diet,there was not significantchanges in fasting plasma glucose,fasting insulin and glucose tolerance(p> 0.05),but after 18 weeks,dietary free and bound CML significantly increased the level of HOMA-IR(p<0.05).In addition,there was no significant difference in fasting blood glucose,fasting insulin and glucose tolerance between the BC and GL groups(p> 0.05).(2)After 6,12,and 18 weeks of feeding the free and bound CML diet,the content of motilin(MTL)and gastrin(GAS)in serum were decreased,but the difference was not significant(p>0.05).The levels of MTL and GAS in the serum of rats fed with bound CML were lower than those in the rats fed with free CML,but there was no significant difference(p> 0.05).After 12 weeks of feeding time,the accumulation of CML in the ileum in the BC group and GL group was significantly increased(p<0.05).After 18 weeks of feeding time,the accumulation of CML in the duodenum,jejunum,ileum and colon was significantly increased(p<0.05),and the content of CML in GI tract of GL group was higher than BC group,but there was no significant difference between GL group and GL group(p<0.05).(3)After 18 weeks of feeding the free and bound CML diet,the histology of the intestinal tract was changed.The state of oxidative stress in the gastrointestinal tract were increased in the duodenum,jejunum,ileum and colon of BC and GL rats.In addition,the levels of inflammatory factors were significantly increased in colonic tissue of rats(p<0.05).Compared with rats fed the bound CML,the increased contents of inflammatory cytokines in GL group were more obvious,but there was no significant difference between GL group and GL group(p<0.05).