Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
Appl Physiol Nutr Metab. 2012 Dec;37(6):1200-11. doi: 10.1139/h2012-103. Epub 2012 Oct 10.
Docosahexaenoic acid (DHA, 22:6n-3) is higher in the blood and tissues of females relative to males, but the underlying mechanism is not clear. The present study examined the expression of enzymes involved in the biosynthesis of DHA from short-chain n-3 polyunsaturated fatty acids in male and female rats (n = 6 for each sex). Rats were maintained on an AIN-93G diet and sacrificed at 14 weeks of age after an overnight fast. Plasma, erythrocytes, liver, heart, and brain were collected for fatty acid composition analysis and the determination of enzyme and transcription factor expression by RT-PCR and immunoblotting. Females had higher DHA concentrations in the total lipids of liver, plasma, erythrocyte, and heart (53%, 75%, 36%, and 25% higher, respectively, compared with males) with no sex differences in brain DHA concentrations. The mRNA content of Δ5-desaturase, Δ6-desaturase, and elongase 2 was 1.0-, 1.4-, and 1.1-fold higher, respectively, in the livers of female rats compared with males, with no differences in the hearts or brains. The protein content of Δ6-desaturase was also higher in females. Higher hepatic mRNA of sterol-regulatory element-binding protein 1-c and estrogen receptor α in the females suggests that lipogenic and estrogen signaling mechanisms are involved. The sex difference in DHA concentration is tissue specific and is associated with higher Δ6-desaturase expression in females relative to males, which appears to be limited to the liver.
二十二碳六烯酸（DHA，22:6n-3）在女性的血液和组织中的含量高于男性，但潜在的机制尚不清楚。本研究检测了参与从短链 n-3 多不饱和脂肪酸生物合成 DHA 的酶在雄性和雌性大鼠中的表达（n = 6 只/性别）。大鼠维持在 AIN-93G 饮食中，在禁食过夜 14 周后处死。收集血浆、红细胞、肝脏、心脏和大脑进行脂肪酸组成分析，并通过 RT-PCR 和免疫印迹法测定酶和转录因子的表达。与男性相比，女性肝脏、血浆、红细胞和心脏中的总脂质 DHA 浓度分别高出 53%、75%、36%和 25%（53%、75%、36%和 25%），而大脑中的 DHA 浓度没有性别差异。Δ5-去饱和酶、Δ6-去饱和酶和延伸酶 2 的 mRNA 含量分别比雄性大鼠高 1.0 倍、1.4 倍和 1.1 倍，而心脏和大脑中没有差异。Δ6-去饱和酶的蛋白含量在雌性中也较高。雌性肝脏中固醇调节元件结合蛋白 1-c 和雌激素受体 α 的 mRNA 含量较高，表明脂生成和雌激素信号机制参与其中。DHA 浓度的性别差异是组织特异性的，与雌性相对于雄性的 Δ6-去饱和酶表达较高有关，这似乎仅限于肝脏。
