Impact of dietary choline supplementation on plasma metabolome and hepatic transcriptome in apolipoprotein E knock-out mice

Epidemiological studies proved a positive correlation between cardiovascular risk and TMAO plasma levels, a microbiota-derived metabolite of choline. With the aim of investigating if dietary choline could modulate cardiovascular risk affecting additional metabolic pathways, a multi-omics approach was performed. Ten-weeks-old EKO female mice were fed two chow diets, differing for a standard (0.09%, STD) or high (1.2%, HC)choline content. To test whether the choline-shaped microbiota might impact host metabolism, after 16 weeks of dietary treatment, the cecal content of STD and HC microbiota-donor mice was transplanted into antibiotic-treated, microbiota-recipient, EKO female mice (FMT-STD and FMT-HC), fed STD for16 weeks. In all mice, atherosclerosis development, targeted plasma metabolome and hepatic transcriptome were evaluated.In microbiota-donor mice, HC diet worsened atherosclerosis development. Moreover, HC increased TMAO plasma levels together with those of methionine, sarcosine, glycine, carnitine, propionyl carnitine and butyryl carnitine and lowered homocysteine. Consistently, liver transcriptome showed that the expression of 1247 genes was upregulated in HC mice. These genes enriched pathways mainly involved in the amino acid and one-carbon metabolism. In microbiota-recipient mice atherosclerosis development was comparable, but plasma metabolome of those that received the HC-shaped microbiota showed a lower concentration of several triglyceride species. Again, consistently with metabolomic findings, the analysis of liver transcriptome revealed that several among the 477 genes downregulated in FMT-HC mice were involved in pathways linked to metabolic processes, in particular lipid metabolism. In conclusion, dietary choline supplementation impacted on the hepatic transcriptional profile and influenced atherosclerosis development not only by increasing TMAO levels, but also by modifying several metabolites belonging to one-carbon metabolism. Finally, the gut microbiota shaped by the HC diet per se was able to influence liver metabolism by leading to reduced synthesis of several triglyceride species. These results suggest new choline-dependent mechanisms implicated in atherosclerosis development which deserve further investigation.