Influence of gender on DHA synthesis: the response of rat liver to low dietary α-linolenic acid evidences higher ω3 a†4-desaturation index in females

The conversion rate of alpha-linolenic acid (ALA) into docosahexaenoic acid (DHA) is determined by dietary and non-dietary factors. Higher capacity of DHA synthesis has been evidenced in females, indicating that sex factors influence the conversion pathway. To evaluate the extent to which sexual dimorphism of DHA synthesis is subordinated to nutritional handling, we measured the omega 3 a dagger 4-desaturation index in male and female rats receiving adequate or inadequate amounts of ALA. The omega 3 a dagger 4-desaturation index was drawn from the DHA to docosapentaenoic acid (omega 3DPA) ratio in liver phospholipids. Male and female rats born to omega 3-deficient dams were fed a supplemented diet supplying low, inadequate, intermediate, or adequate ALA (5, 20, 100, or 300 mg ALA/100 g diet, respectively). Control rats from both gender received the adequate diet from fetal life. Compared with control, low ALA feeding induced the omega 3 a dagger 4-desaturation index to increase by 38 and 70% in the phosphatidylethanolamine fraction of males and females, respectively, and by 67% in phosphatidylcholine in females only. Supplementations with increased doses of ALA progressively smoothed this gender effect. Moreover, the analysis of our data from a previous study shows that ovariectomy decreased, whereas estradiol treatment increased the omega 3 index to values comparable with those of diet-matched males and intact females, respectively. Females are more prone than males to increase their index of omega 3 a dagger 4-desaturation, especially in response to low supplies in ALA. Estradiol supports the omega 3 index, suggesting that this hormone plays a role in the effect of gender on DHA synthesis.