17b Estradiol Increases Liver and Serum Docosahexaenoic Acid in Mice Fed Varying Levels of a Linolenic Acid

Key Findings:

With decreasing fish stocks a concern for omega 3 intakes, it is imperative to better understand the conversion of ALA to DHA. Women show better conversion to DHA than men which appears to be due to the activity of the hormone 17b estradiol (E2).  In mice fed two different levels of dietary ALA with elevated E2 level, DHA levels were shown here to be higher in liver and serum, but not in brain. The authors review research indicating that increases in DHA through enhanced conversion from ALA may have significant cardiovascular health benefits and support the observation of why dietary ALA reduces sudden cardiac death more so in women than men.  The results suggest that ALA dietary recommendations would have greater effect on DHA status in people with higher E2 status (women vs.  men; pre-menopausal vs. postmenopausal women). Data indicated that high ALA intake results in significantly elevated ALA and long chain n3 metabolites in the serum, liver and brain. Higher DHA in mice receiving E2 with 0.6 or 11.2 per cent ALA indicates that the positive effect of E2 is present at both of these intakes of ALA.

Abstract:

Docosahexaenoic acid (DHA) is considered to be important for cardiac and brain function, and 17bestradiol (E2) appears to increase the conversion of a linolenic acid (ALA) into DHA. However, the effect of varying ALA intake on the positive effect of E2 on DHA synthesis is not known. Therefore, the objective of this study was to investigate the effects of E2 supplementation on tissue and serum fatty acids in mice fed a low ALA corn oil-based diet (CO, providing 0.6 per cent fatty acids as ALA) or a high ALA flaxseed meal-based diet (FS, providing 11.2 per cent ALA). Ovariectomized mice were implanted with a slow release E2 pellet at 3 weeks of age and half the mice had the pellet removed at 7 weeks of age. Mice were then randomized onto either the CO or FS diet. After 4 weeks, the DHA concentration was measured in serum, liver and brain. A significant main effect of E2 was found for liver and serum DHA, corresponding to 25 and 15  per cent higher DHA in livers of CO and FS rats, respectively, and 19 and 13 per cent in serum of CO and FS rats, respectively, compared to unsupplemented mice. There was no effect of E2 on brain DHA. E2 results in higher DHA in serum and liver, at both levels of dietary ALA investigated presently, suggesting that higher ALA intake may result in higher DHA in individuals with higher E2 status.