Dihydroxyacetone esters as precursors of triglycerides during intestinal absorption.

In work previously reported from this laboratory it was found that CWlabeled glycerol, completely hydrolyzed from glycerides during digestion, was not utilized for the resynthesis of lymph glycerides (1). This suggests that glycerol per se may not be the precursor of glyceride glycerol. Since absorbed fatty acids appear in the lymph as triglycerides, it is necessary to account for the origin of the glycerol required to form lymph and body fat from the large amounts of dietary fat an animal may consume and digest in a few hours. It is known that dihydroxyacetone and glyceraldehyde are products of glucose metabolism. It is possible these substances act as precursors of glyceride glycerol by forming the monoand diesters with fatty acids, then being reduced to glycerol, and finally forming the triglyceride. It was decided to test this hypothesis by feeding the monopalmitic acid ester of dihydroxyacetone labeled in both the acetone and fatty acid moieties, and examining the lymph for labeled glycerol. The relative amounts of labeled glycerol and labeled dihydroxyacetone in lymph glycerides should be a measure of the extent to which the absorbed dihydroxyacetone was converted to glycerol. The difference in percentages of recovery in the lymph of labeled alcohol (dihydroxyacetone and glycerol) and labeled fatty acid is a measure of the degree of hydrolysis of the absorbed palmitoxyhydroxyacetone since it represents the relative amount of alcohol lost.