Metabolism of Sorbitol in the Intact Organism

Abstract

Uniformly labeled sorbitol and D-fructose, respectively, are compared in the rat after intragastral administration in regard to their incorporation patterns into respiratory CO2, fatty acids and glycerol of adipose tissue triacylglycerols, liver cholesterol and glycogen. Fructose cannot be considered as the sole or main intermediate of the metabolic degradation of orally administered sorbitol in the intact organism. When sulfanilamide undergoes acetylation in the rat after intragastral application of U-14C-labeled precursors, acetylsulfanilamide isolated from the urine possesses a much higher specific radioactivity after sorbitol than after fructose administration. Human volunteers of both sexes exhale considerable quantities of H2 after oral sorbitol administration but only small amounts after fructose administration. Sorbitol is absorbed only partially in the small intestine, and undergoes fermentation in lower parts of the digestive tract (cecum in rats, colon in men) which leads, among other products, to acetate. Products of microbial metabolism are absorbed and utilized by the host organism. Different isotope incorporation patterns, varying specific radioactivities in acetylsulfanilamide, and H2 formation in men are thus explained. Therefore the degradation of orally administered sorbitol does not proceed in the intact organism, to a remarkable extent, as is the case with fructose or other monosaccharides; pecularities of the effects of dietary sorbitol become understandable.