Influence of dietary modifications on uptake of cholesterol, glucose, fatty acids, and alcohols into rabbit intestine.

The role of dietary modifications upon the rate of intestinal uptake of lipids and D-glucose was examined using a previously validated in vitro technique. Rabbits were fed for 6 wk on a control diet, or one containing 2% fat (F), 0.2% cholesterol (C), or 0.2% cholesterol plus 2% fat (CF). The rate of uptake Jd, of glucose into the jejunum and ileum was decreased from higher concentrations of glucose in CF, but was markedly increased in F and C. The Jd of a homologous series of saturated fatty acids into the jejunum was highest in C, intermediate in F and CF, and lowest in the control animals; the differences in Jd were most marked when the bulk phase was stirred to reduce the effective resistance of the intestinal unstirred layer, but the differences in lauric acid uptake persisted even when the bulk phase was unstirred and the effective resistance of the unstirred layer was high. The Jd of fatty alcohols was C greater than CF greater than F at each rate of stirring, and the relative rates of cholesterol Jd were control greater than CF greater than C greater than F. It is proposed that dietary lipid modifications are associated 1) with reciprocal changes in the effective resistance of the intestinal unstirred water layer and the passive permeability characteristics of the intestine; and 2) with alterations in the kinetic constants of the intestinal uptake of glucose; 3) there is a functional heterogenerity of the villus in response to variations in the lipid content of the diet, with quantitatively and qualitatively different changes in the passive uptake of fatty acids, fatty alcohols, and cholesterol. It is concluded that modification of the lipid content of the diet has a complex effect on intestinal membrane function and may affect both active and passive transport processes.