Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences, Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China; College of Animal Sciences, Zhejiang University, Hangzhou 310058, P. R. China.
Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences, Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China.
J Dairy Sci. 2018 May;101(5):4586-4594. doi: 10.3168/jds.2017-14061. Epub 2018 Feb 15.
Increased production of long-chain unsaturated fatty acids (LCUFA) can have a positive effect on the nutritional value of ruminant milk for human consumption. In nonruminant species, fatty acid elongase 5 (ELOVL5) is a key enzyme for endogenous synthesis of long-chain unsaturated fatty acids. However, whether ELOVL5 protein plays a role (if any) in ruminant mammary tissue remains unclear. In the present study, we assessed the mRNA abundance of ELOVL5 at 3 stages of lactation in goat mammary tissue. Results revealed that ELOVL5 had the lowest expression at peak lactation compared with the nonlactating and late-lactating periods. The ELOVL5 was overexpressed or knocked down to assess its role in goat mammary epithelial cells. Results revealed that ELOVL5 overexpression increased the expression of perilipin2 (PLIN2) and decreased diacylglycerolacyltransferase 2 (DGAT2) and fatty acid desaturase 2 (FADS2) mRNA, but had no effect on the expression of DGAT1, FADS1, and stearoyl-CoA desaturase 1 (SCD1). Overexpression of ELOVL5 decreased the concentration of C16:1n-7, whereas no significant change in C18:1n-7 and C18:1n-9 was observed. Knockdown of ELOVL5 decreased the expression of PLIN2 but had no effect on DGAT1, DGAT2, FADS1, FADS2, and SCD1 mRNA expression. Knockdown of ELOVL5 increased the concentration of C16:1n-7 and decreased that of C18:1n-7. The alterations of expression of genes related to lipid metabolism after overexpression or knockdown of ELOVL5 suggested a negative feedback regulation by the products of ELOVL5 activation. However, the content of triacylglycerol was not altered by knockdown or overexpression of ELOVL5 in goat mammary epithelial cells, which might have been due to the insufficient availability of substrate in vitro. Collectively, these are the first in vitro results highlighting an important role of ELOVL5 in the elongation of 16-carbon to 18-carbon unsaturated fatty acids in ruminant mammary cells.
增加长链不饱和脂肪酸（LCUFA）的产量可以对反刍动物奶的人类消费营养价值产生积极影响。在非反刍动物中，脂肪酸延长酶 5（ELOVL5）是内源性合成长链不饱和脂肪酸的关键酶。然而，ELOVL5 蛋白在反刍动物乳腺组织中是否发挥作用（如果有）尚不清楚。在本研究中，我们评估了 ELOVL5 在山羊乳腺组织泌乳 3 个阶段的 mRNA 丰度。结果表明，与非泌乳期和泌乳后期相比，ELOVL5 在泌乳高峰期的表达最低。过表达或敲低 ELOVL5 以评估其在山羊乳腺上皮细胞中的作用。结果表明，ELOVL5 过表达增加了 perilipin2（PLIN2）的表达，降低了二酰基甘油酰基转移酶 2（DGAT2）和脂肪酸去饱和酶 2（FADS2）的 mRNA，但对 DGAT1、FADS1 和硬脂酰辅酶 A 去饱和酶 1（SCD1）的表达没有影响。ELOVL5 的过表达降低了 C16:1n-7 的浓度，而 C18:1n-7 和 C18:1n-9 没有明显变化。ELOVL5 的敲低降低了 PLIN2 的表达，但对 DGAT1、DGAT2、FADS1、FADS2 和 SCD1 mRNA 的表达没有影响。ELOVL5 的敲低增加了 C16:1n-7 的浓度，降低了 C18:1n-7 的浓度。ELOVL5 过表达或敲低后与脂质代谢相关基因的表达变化表明，ELOVL5 激活产物存在负反馈调节。然而，ELOVL5 在山羊乳腺上皮细胞中的敲低或过表达并未改变三酰甘油的含量，这可能是由于体外底物供应不足所致。总的来说，这些是首次在体外研究中突出 ELOVL5 在反刍动物乳腺细胞中 16-碳到 18-碳不饱和脂肪酸伸长中的重要作用的结果。
