Trimethylamine-N-Oxide (TMAO) Promotes Vascular Remodeling And Potential Mechanism In Mice

Objective: To explore the development and possible mechanism of vascular remodeling promoted by Trimethylamine-N-oxide(TMAO)in mice.Methods: 24-week-old healthy male SAMP8 and SAMR1 mice were randomly divided into TMAO group and control group respectively: SAMP8-TMAO group(P8-T),SAMP8-Control group(P8-C),SAMR1-TMAO group(R1-T)and SAMR1-Control group(R1-C).Mice fed with or without TMAO as TMAO group and Control group.The intervention period was 16 weeks.The following experiments were performed at the end of intervention.(1)The body weight(BW)of the mice was measured;(2)Vascular functions of aortic ring: including systolic function,endothelium-dependent vasodilation and endothelium-independent vasodilation were tested;(3)The parameters of morphology of aorta including the media thickness(MT),lumen diameter(LD),medial area(MA)and the ratio of media thickness and lumen diameter(MT/LD)(HE staining),collagen area of aorta(EVG staining)were measured or calculated;(4)The expressions of collagen I,collagen III,transforming growth factor(TGF-?1),Smad protein 3(Smad3),endothelial nitric oxide synthase(e NOS),matrix metalloproteinase-2(MMP-2),and matrix metalloproteinase inhibitor 2(TIMP-2)on aorta were evaluated with Immunohistochemistry.The expressions of proteins above exclusive of MMP-2,TIMP-2 were also tested with western blot.Results:(1)At the beginning of the experiment,it showed no significant differences in BW between P8-C and R1-C,R1-T and R1-C,P8-T and P8-C,R1-T and P8-T groups,respectively(p=0.4946,0.7880,0.7250,0.9466),while the BWs of R1-T group and P8-T group were significantly lower than R1-C group and P8-C group,respectively(p<0.0001).(2)The endothelium-dependent diastolic function and the expression of e NOS of aorta were distinctly decreased at the early stage of P8-C group when compared to the R1-C group.And the similar results were also observed in P8-T versusP8-C group and R1-T versus R1-C group.However,there was no remarkable difference in non-endothelium-dependent diastolic function of aorta among the 4 groups.(3)P8-C group showed that more morphological changes occurred in aorta of mice,with increase in MT,MT/LD,MA(p=0.0375,0.0349,0.0278),and higher collagen content in the aorta(p=0.0279)when compared to R1-C group.MT,MT/LD,MA and the percentage of collagen in R1-T group(p=0.0007,0.0017,0.0123,0.0131)and P8-T group(p=0.0088,0.0435,0.0474,0.0365)were higher than those in R1-C group and P8-C group,respectively.The expressions of MMP-2,collagen I,collagen III,TGF-?1 and Smad3 on aorta were upregulated but TIMP-2 downregulated in both P8-T and R1-T groups when compared to P8-C and R1-C groups,respectively.Conclusions:(1)The degree of vascular remodeling in aorta of SAMP8 shows more obvious than that in SAMR1 at the same age of 40 weeks.(2)TMAO not only accelerates SAMP8 but also promotes vascular remodeling of aorta in SAMR1.(3)The possible underlying mechanisms of TAMO promotes vascular remodeling may be that it can induces imbalance of MMPs/TIMPs and deposition of collagen in aorta.