Supplementation with the Gut Microbiome‐Derived Metabolite Trimethylamine N‐Oxide Induces Aortic Stiffening in Young Mice

Abstract

Elevated plasma levels of the gut‐derived metabolite trimethylamine N‐oxide (TMAO) cause atherosclerosis in mice and predict cardiovascular (CV) risk in humans. Stiffening of the large elastic arteries is a major risk factor and antecedent to atherosclerosis and other CV diseases (CVD), but it is unknown if TMAO contributes to arterial stiffening.PurposeTo determine if increased circulating TMAO induces arterial stiffness in young mice.MethodsYoung C57BL/6 mice (6 mo.) were fed a defined‐choline (0.07%) diet supplemented either without (Control; n=11) or with 0.12% TMAO (n=11) for 6 months. Arterial stiffness was measured in vivo by aortic pulse wave velocity (aPWV). After sacrifice, intrinsic mechanical stiffness of the aorta was measured using wire myography. A stress‐strain curve was constructed, and the elastic moduli (EM) were calculated as the slopes of the high‐force collagen‐dominant (collagen EM) and low‐force elastin‐dominant (elastin EM) regions of the curve. Abundance of arterial structural proteins was measured in aortic lysates via Western blotting.ResultsTMAO supplementation increased plasma TMAO levels vs. Control (TMAO: 31.5±4.1 μM, Control: 2.9±0.6 μM, p= 0.01), with no effect on body weight (TMAO: 41.5±1.6 g, Control: 39.7±1.6 g, p = 0.43). aPWV was higher in the TMAO group vs. Control (483±32 vs. 392±20 cm.s−1, p= 0.04). This greater aPWV in the TMAO‐supplemented group was associated with a higher collagen EM in the TMAO‐supplemented group (TMAO: 8642±437 kPa, Control: 7056±625 kPa, p= 0.05), which was accompanied by strong trends toward higher protein abundance of type 1 collagen (TMAO: 1.62±0.33 A.U., Control: 0.99±0.08 A.U., p= 0.08) and advanced glycation end products (TMAO: 1.69±0.36 A.U., Control: 1.00±0.07 A.U., p= 0.08). There were no group differences in the elastin EM (TMAO: 642±40 kPa, Control: 620±54 kPa, p= 0.75) or elastin protein expression (TMAO: 1.09±0.04 A.U., Control: 1.00±0.04 A.U., p= 0.83).ConclusionTMAO supplementation induced a marked increase in circulating TMAO concentration and aortic stiffness in young mice. The increase in aortic stiffness appeared to be mediated by increased deposition of collagen (fibrosis) and abundance of advanced glycation end products, which form crosslinks between arterial structural proteins. These preliminary results introduce a novel mechanistic link between elevated plasma TMAO levels and CV risk, suggesting that TMAO may be a promising target to prevent arterial dysfunction and reduce consequent risk of CVD.Support or Funding InformationR01 HL134887, F32 HL140875This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.