Dietary choline content and HDL levels contribute to a pro-atherogenic plasma metabolomic profile in mice

Gut microbiota can influence atherosclerosis development by metabolizing dietary choline: experimental and observational studies have highlighted a positive correlation between increased plasma choline-derived TMAO concentrations and adverse cardiovascular events. This study was aimed at investigating how the plasma metabolome of mice prone to atherosclerosis development was modulated by HDL levels and the dietary intake of choline.Low-fat, no cholesterol diets with different choline content (0.09% or 1.2%) were administered for 16 weeks to two groups of atherosclerosis-prone female mice: 1) extremely low-HDL mice, deficient for both murine apoA-I and apoE (DKO); 2) high-HDL mice, deficient for both apoA-I/apoE, but overexpressing human apoA-I (DKO/hA-I). At sacrifice, atherosclerosis was evaluated, and a targeted metabolomics of plasma was performed. As expected, atherosclerosis, evaluated at the aortic sinus, was strongly increased in DKO vs DKO/hA-I mice. Surprisingly, although the high-choline diet resulted into elevated plasma TMAO levels in both genotypes, choline supplementation significantly worsened plaque development only in DKO/hA-I mice. Noteworthy, high-choline diet led to an increased concentration of plasma lipids only in DKO/hA-I mice: mainly triglycerides and hexosylceramides, but also ceramides and sphingomyelins. Several markers of increased cardiovascular disease risk and compromised renal function such as asymmetric dimethylarginine, symmetric dimethylarginine, indoxyl sulfate, creatinine and the microbiota-derived metabolite phenylacetylglutamine were increased only in high-choline-fed DKO/hA-I mice. Interestingly, the antioxidant histidine-containing dipeptide carnosine and its methylated form anserine were also increased by high-choline diet in DKO/hA-I. In conclusion, our results indicate that dietary choline supplementation worsens atherosclerosis development only in the presence of HDL. Plasma metabolomics clearly indicated that choline supplementation increases the concentration of different lipid classes as well as of different metabolites indicative of augmented cardiovascular risk and impaired kidney function. Further studies are under way to assess the impact of the gut microbiota composition in regulating the biosynthesis of these molecules.