Effect of dietary fat, ALA and estrogen on conversion of ALA into EPA and DHA in ovaiectomized rats

Abstract

ABSTRACT

Effect of dietary fat, ALA and estrogen on conversion of ALA into EPA and DHA in ovariectomized rats

Conversion of α-linolenic acid (ALA) into the longer chain n-3 polyunsaturated fatty acids (n-3 PUFAs) has been suggested to be affected by intake of dietary fat, but the mechanism is not well-known. Therefore, the purpose of this study was to evaluate the effect of low fat diet with and without estrogen on the fatty acid conversion enzymes and transcription factors in ovariectomized rats. Rats were fed a modified AIN-93G diet with 0% n-3 PUFAs diet or ALA in low fat diet or high fat diet during 12 weeks. At 8 weeks, rats were injected corn oil with or without 17β-estradiol-3-benzoate (E) for the last 3 weeks. Both low fat and E significantly increased the hepatic expressions of peroxisomal proliferator activated receptor-α (PPAR-α), fatty acid desaturase 2 (FADS2), elongase of very long chain fatty acids 2 (ELOVL2) and ELOVL5, but decreased sterol regulatory element binding protein 1 (SREBP1). Low fat diet but not E increased the hepatic expression of FADS1, and E alone increased the hepatic expression of estrogen receptor-α and -β. Low fat diet and E had synergic effects on serum and liver levels of DHA and hepatic expression of PPAR-α. In conclusion, low fat diet and estrogen increased conversion of ALA into DHA by up-regulation of elongase and desaturase of fatty acid through regulating expression of transcription factors such as PPAR-α and SREBP1. In addition, low fat and E had synergic effect on serum and liver levels of DHA through increasing expression of PPAR-α.