Rate and Extent of Absorption of the Fatty Acids of Fully Esterified Glycerol, Erythritol, Xylitol, and Sucrose as Measured in Thoracic Duct Cannulated Rats

Abstract

Rats were fed by stomach tube an emulsion diet in which the fat component consisted of 95 parts of unlabeled glycerol trioleate and 5 parts of one of the following: glycerol 1-¹⁴C-trioleate, erythritol 1-¹⁴C-tetraoleate, xylitol 1-¹⁴C-pentaoleate, or sucrose 1-¹⁴C-octaoleate. Thoracic duct lymph was collected in 2-hour increments for the subsequent 24 hours. The lipids from these fractions were assayed for ¹⁴C-oleate content. The percentage of the fed labeled acid that appeared in the lymph in 24 hours was 88% from the glycerol ester, 67% from the erythritol ester, 24% from the xylitol ester, and 2% from the sucrose ester. There were differences in the time of appearance in the lymph of the major portion of the fatty acids arising from the esters of these polyols. The dietary fatty acids that were esterified with glycerol appeared in the lymph most rapidly, 2 hours after feeding, the specific activity of the lymph lipids was 80% of that of the diet lipids, and from 8 to 14 hours after feeding the two had the same specific activity. By contrast, the transfer of the fatty acids of erythritol and xylitol into the lymph was slower; 2 hours after feeding the specific activity of the lymph lipids was only 10 to 20% of that in the diet and the maximum level was not attained until after 12 hours. Following the feeding of erythritol tetraoleate, none of this compound was detected in the thoracic duct lymph. It is proposed that the differences in the amounts and in the patterns of the appearance of the fatty acids of the various esters are related to the particular enzymes that hydrolyze these fats in the intestinal tract.