Ontogeny of intestinal adaptation in rats in response to isocaloric changes in dietary lipids

Alterations in dietary lipids of the nursing mother result in variations in the lipid content of her milk. Maternal rats, weanlings, and 10-wk-old animals were fed chow or a semisynthetic isocaloric diet enriched with either saturated fatty acids (S) or polyunsaturated fatty acids (P). The jejunal and ileal in vitro uptake of varying concentrations (4-64 mM) of D-glucose and D-fructose or single concentrations of medium- and long-chain fatty acids and cholesterol were assessed in 18- to 21-day-old suckling rats, in 5-wk-old weanling animals, and in 12-wk-old young adults. The rate of uptake of D-glucose and D-fructose was unaffected in suckling rats by changing the lipid content of the diet of the nursing dams, whereas sugar uptake was greater in weanlings or adults fed S compared with P. The jejunal uptake of long-chain fatty acids was not influenced in suckling by changing the mother's diet, whereas in weanlings the uptake of 18:0 and 18:3 was higher with feeding S vs. P. In summary, jejunal uptake of cholesterol was greater in sucklings than in weanlings fed S vs. P. In suckling animals there are different adaptive patterns between the jejunum and the ileum and varying patterns of adaptation in response to alterations in the lipids in the diet when comparing suckling vs. weanling rats. These differences in nutrient uptake could not be explained by age- or diet-associated alterations in villus height. It is concluded that the age of the rat influences the intestinal adaptation of nutrient transport, which occurs in response to changes in dietary lipids, and dietary lipids fed to nursing dams and their offspring are important in the development of the intestine.