Possible Role of Fatty Acids in Milk as the Regulator of the Expression of Cytosolic Binding Proteins for Fatty Acids and Vitamin A through PPARα in Developing Rats

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Fatty acids in milk are thought to play an important role in intestinal maturation and gene expression in the postnatal small intestine. In this study, we determined the jejunal mRNA levels, in rats, of peroxisome proliferator-activated receptor α(PPARα) and PPARδ which are nuclear receptors for fatty acids. We also measured expression of their target genes during the postnatal period, namely liver type fatty acid-binding protein (L-FABP) and cellular retinol-binding protein, type II (CRBPII). The mRNA levels of PPARα, L-FABP and CRBPII, but not PPARδ, gradually increased during the suckling period and then sharply declined to a low level at the end of the weaning period. Rat pups at 17d of age, weaned to a high-fat diet, showed significantly greater mRNA levels of PPARα, L-FABP and CRBPII than those weaned to a low-fat diet. Oral administration of PPARα ligand, WY14,643 during four consecutive days of the weanling period caused a parallel increase in the mRNA levels of PPARα, L-FABP and CRBPII genes. Furthermore, caprylic acid and oleic acid, which are major components of fatty acids in milk, induced jejunal PPARα, L-FABP and CRBPII gene expression. Our results suggest that fatty acids in milk may play a pivotal role in maintaining an enhanced level of expression of L-FABP and CRBPII genes in the small intestine, presumably by acting as inducers of PPARα gene expression.
日本ビタミン学会の論文