DGAT 1 (acyl CoA:diacylglycerol Acyltransferase 1) Catalyzes the Formation of Many Types of Retinyl Ester in Mice

Acyl CoA:diacylglycerol acyltransferase 1 (DGAT1) catalyzes the final step of triacylglycerol formation. Our experiments with knockout mice showed that DGAT1 could catalyze retinyl ester (RE) synthesis. Subsequent research confirmed that DGAT1 is an important acyl CoA:retinol acyltransferase (ARAT), but suggested that there may be several ARATs with different specificities for fatty acids. We reexamined our data on the effect of a high fat diet on RE concentrations in DGAT1 knockout and wild type mice. We analyzing individual RE peaks generated from reversed-phase C-18 chromatography with diode array detection. Retinyl palmitate accounted for approximately 82% of the RE formed. Other major RE, in order of concentration, appeared to be retinyl stearate, retinyl oleate and retinyl myristate. DGAT1 knockout mice fed a high fat diet appeared to have higher concentrations of each of these RE in their livers compared to wild type mice. However, concentration differences were significant only for retinyl palmitate and retinyl stearate, while retinyl myristate concentrations were only slightly elevated. Our results show that DGAT1 catalyzes the formation of many types of RE, but has some selectivity in RE formation. Our results are compatible with, but do not prove, the hypothesis that there are several ARATs with differing compatibilities for fatty acids. Further studies are essential to elucidate the role of DGAT1 in retinoid metabolism.