Extent of Total Hydrolysis of Dietary Glycerides during Digestion and Absorption in the Human

Abstract

The opportunity to obtain thoracic duct lymph from human beings (1,2) has prompted us to undertake a study of the extent of hydrolysis of dietary glycerides during digestion and absorption in man. From animal experiments it is known that glycerol once liberated from the triglycerides by hydrolysis in the intestinal lumen is not utilized for resynthesis of glycerides. The ratio of label in the acid to that in glycerol of the lymph glycerides after feeding double labeled glyceride, when compared with the same ratio in the fed glycerides, gives percentage of glyceride molecules which have been completely hydrolyzed during digestion and absorption process.

Methods. Subjects: Our subjects were 2 patients with diagnosed adenocarcinoma of the left lung. Patient A was a 60-year-old man. weight 56 kg. Patient B was a 56-year-old man, weight 72 kg. In both patients a supraclavicular biopsy of the lymph nodes was performed and a plastic cannula was inserted into the thoracic duct as described earlier(1). In Patient A the cannula was inserted into one of the 2 stems of equal diameter present on operation. In patient B the catheter was inserted into the thoracic duct in such a way that the major portion of lymph flow bypassed the catheter. Only a portion of total lymph flow was therefore obtained during collection periods from these patients. This fact does not. however, influence the results as these are based on the ratio of label in acid and glycerol of the glycerides. Labelled material. Linoleic acid-1-C¹⁴ and glycerol-1-C¹⁴ (obtained from Radiochemical Centre, Amersham, England) were synthesized into glyceride via the acid chlorides. Free fatty acids were removed by passing the reaction mixtures through Amberlite TRA-400 columns and the triglyceride isolated by chromatography on silicic acid(2).