Unsaturated fatty acids regulate gene expression of cellular retinol-binding protein, type II in rat jejunum

We have shown that cellular retinol-binding protein, type II (CRBP II) mRNA and its protein levels are elevated in the jejunum of rats fed a diet rich in long-chain triacylglycerols. In the present study, we explored which types of fatty acids modulate CRBP II gene expression. Rats previously fed a low fat, high starch diet were force-fed a basal fat-free diet or the diet supplemented with 0.21 mol/L of various fatty acids (i.e., caprylic, palmitic, stearic, oleic, linoleic and alpha-linolenic acids). Force-feeding a diet containing linoleic acid produced an elevation of CRBP II mRNA levels in rats in both a dose-dependent (0.053-0.21 mol/L) and time-dependent (up to 6 h) manner. Among fatty acids tested, all unsaturated fatty acids (oleic, linoleic and alpha-linolenic acids) were able to enhance CRBP II mRNA levels by 54-63% within 6 h, whereas a medium-chain fatty acid (caprylic acid) and a saturated fatty acid (stearic acid) elicited little effect on the CRBP II mRNA levels; palmitic acid produced only a small elevation (16%) of the CRBP II mRNA level. Transcripts of both retinoid X receptor alpha and peroxisome proliferator-activated receptor (PPAR), which are thought to interact as a heterodimer with the cis-element located in the CRBP II promoter and to be activated by 9-cis retinoic acid and long-chain fatty acids, respectively, were constitutively expressed in the rat jejunum.(ABSTRACT TRUNCATED AT 250 WORDS)