In an attempt to provide a mechanistic explanation for this association, Koeth and colleagues used a common model of
atherosclerosis, the ApoE /-mouse[8].
Mice were fed large amounts ofL-carnitine (2000 mg/kg/day) resulting in elevated plasma TMAO levels.
TMAO was correlated with increased atherosclerotic lesion size, possibly resulting from a 35% decrease
in reverse cholesterol transport (RCT) compared to control [8].
Although ApoE/mice have been used extensively as an atherosclerosis model, they lack cholesteryl-ester transfer protein
(CETP), a key enzyme in the RCT, which transfers cholesterol ester from high density lipoprotein (HDL) to low density lipoprotein cholesterol (LDL)[30].
In addition, the small numbers of animals that showed larger aortic lesions (only in four out of 11 animals)
and the lack of doseeresponse (a single TMAO dose has been assessed) made it difficult to understand the nature of the relationship between TMAO plasma levels and effects on lesion size [8].
More recently, the same authors reported that diet-induced gbutyrobetaine had similar effects on the aortic lesion size[31].
These effects are resolved with antibiotic treatment, which reduce the conversion ofL-carnitine to TMA[8,31].