Couloubaly S, Deloménie C, Rousseau D, Paul J L, Grynberg A, Pourci M L
UMR 1154-INRA, and IFR 141, Université Paris-Sud11, Châtenay-Malabry, France.
Eur J Clin Invest. 2007 Sep;37(9):692-9. doi: 10.1111/j.1365-2362.2007.01843.x.
The nature of fatty acids provided by the diet as well as plasma lipid metabolism can modify the composition and properties of plasma membrane and thus the activity of membrane proteins. In humans, as well as in experimental models, diabetes is associated with both an alteration in serum lipid profile and a documented endothelial dysfunction. This in vitro study investigated on an immortalized human endothelial cell line (EA.hy 926) the specific effects of several free fatty acids (FFAs) on the composition of cellular membranes and the regulation of endothelial nitric oxide synthase (eNOS).
0.1% of lipid deprived serum was added to the incubation medium with 25 mM glucose in order to study the effects of individual fatty acids: myristic acid, palmitic acid, stearic acid, oleic acid or linoleic acid at 100 microM bound with albumin. The effects of the FFAs on the endothelial nitric oxide synthase were investigated on mRNA level by quantitative PCR, on protein level and Ser1177 phosphorylation by Western blot and on enzymatic activity on living cells using radiolabelled arginine.
Free linoleic acid increased the membrane content in n-6 fatty acids (mainly C18: n-6 and its metabolites) with a decrease in saturated and monounsaturated fatty acids. These conditions decreased the basal eNOS activity and reduced the phosphorylation of eNOS-Ser1177 due to activation by histamine. Free palmitic acid enriched the membranes with 16 : 0 with a slight decrease in monounsaturated fatty acids. These conditions increased eNOS activation without increasing Ser1177 phosphorylation upon histamine activation. The addition of the other FFAs also resulted in modifications of membrane composition, which did not to affect eNOS-Ser1177 phosphorylation.
Among the fatty acids used, only modification of the membrane composition due to linoleic acid supply disturbed the basal enzymatic activity and Ser1177 phosphorylation of eNOS in a way that limited the role of histamine activation. Linoleic acid might involve the dysfunction of both eNOS basal activity and its phosphorylation status and may then contribute to an impaired vasodilatation in vivo.
饮食提供的脂肪酸性质以及血浆脂质代谢可改变质膜的组成和特性，进而影响膜蛋白的活性。在人类以及实验模型中，糖尿病与血清脂质谱改变和已证实的内皮功能障碍均有关联。本体外研究在永生化人内皮细胞系（EA.hy 926）上探究了几种游离脂肪酸（FFA）对细胞膜组成和内皮型一氧化氮合酶（eNOS）调节的具体影响。
向含有25 mM葡萄糖的孵育培养基中添加0.1%的无脂血清，以研究与白蛋白结合的100 microM肉豆蔻酸、棕榈酸、硬脂酸、油酸或亚油酸等单一脂肪酸的作用。通过定量PCR在mRNA水平、通过蛋白质印迹在蛋白质水平和Ser1177磷酸化水平以及使用放射性标记的精氨酸在活细胞上的酶活性方面研究FFA对内皮型一氧化氮合酶的影响。
游离亚油酸增加了n-6脂肪酸（主要是C18: n-6及其代谢产物）的膜含量，同时饱和脂肪酸和单不饱和脂肪酸减少。这些情况降低了基础eNOS活性，并由于组胺激活而降低了eNOS-Ser1177的磷酸化。游离棕榈酸使膜中16 : 0富集，单不饱和脂肪酸略有减少。这些情况增加了组胺激活时的eNOS激活，但未增加Ser1177磷酸化。添加其他FFA也导致膜组成的改变，但未影响eNOS-Ser1177磷酸化。
在所使用的脂肪酸中，仅亚油酸供应导致的膜组成改变以限制组胺激活作用的方式扰乱了eNOS的基础酶活性和Ser1177磷酸化。亚油酸可能涉及eNOS基础活性及其磷酸化状态的功能障碍，进而可能导致体内血管舒张受损。
