Milk fat structure of a patient with type 1 hyperlipidemia

Structural analyses were performed on milk fat samples obtained 3-10 days postpartum from a lactating patient with primary Type 1 hyperlipidemia. The milk triacylglycerols contained 3-7% C10, 14-21% C12, 20-30% C14, 22-26% C16 and 20-30% C18 (largely oleic) acids. Gas liquid chromatographic (GLC) analyses of the X-1,3- and X-1,2-diacylglycerols on polar siloxane columns showed a markedly non-random association of acyl chains. Stereospecific analyses indicated that the short chain length fatty acids were confined essentially to the sn-3-position of the triacylglycerol molecule. Furthermore, these acids were largely absent from the phosphatidylcholines and the endogenous sn-1,2-diacylglycerols of the milk fat. It is concluded that the short chain fatty acids are incorporated into the milk triacylglycerols during the final stage of biosynthesis via the phosphatidic acid pathway, and that the overall fatty acid distribution is consistent with the 1-random 2-random 3-random hypothesis.