Lyubachevskaya G, Boyle-Roden E
Department of Nutrition and Food Science, University of Maryland, College Park 20742, USA.
Lipids. 2000 Dec;35(12):1353-8. doi: 10.1007/s11745-000-0652-5.
In the metabolism of triacylglycerol (TG)-rich lipoproteins, 2-monoacylglycerols (2-MG) are produced by lipoprotein lipase (LPL) hydrolysis of TG. The metabolic fate of 2-MG is not known with certainty. 2-MG that accumulate on the chylomicra surface have been proposed to isomerize spontaneously to 1(3)-MG, which are then hydrolyzed by LPL to free fatty acids and glycerol. In this study the rate and the effect of acyl chain saturation on the spontaneous acyl migration of 2-MG in in vitro model chylomicra emulsions were determined. After 1 h of incubation at 37 degrees C, less than 20% of 2-monoolein (2-MO) or 2-monopalmitin (2-MP) spontaneously isomerized to 1(3)-MO or 1(3)-MP, respectively. Accordingly, it was concluded that spontaneous isomerization of 2-MG is not the major mechanism for 2-MG metabolism post-TG hydrolysis in chylomicra. Isomerization rates, expressed as decrease in percentage of 2-MG remaining per hour, were -5.12 and -5.86 in water, and -0.43 and -0.41 in hexane for 2-MO and 2-MP, respectively. There was no significant difference between the isomerization rates of 2-MO and 2-MP. Thus, in the present study, saturation of the MG acyl chain did not influence spontaneous acyl migration in either water or hexane, but isomerization of 2-MG was faster in water than in hexane.
在富含三酰甘油（TG）的脂蛋白代谢过程中，脂蛋白脂肪酶（LPL）水解TG可产生2-单酰甘油（2-MG）。2-MG的代谢命运尚不确定。有观点认为，积聚在乳糜微粒表面的2-MG会自发异构化为1(3)-MG，然后LPL将其水解为游离脂肪酸和甘油。在本研究中，测定了体外模型乳糜微粒乳液中2-MG自发酰基迁移的速率以及酰基链饱和度对其的影响。在37℃孵育1小时后，分别少于20%的2-单油精（2-MO）或2-单棕榈酸甘油酯（2-MP）自发异构化为1(3)-MO或1(3)-MP。因此，得出结论：2-MG的自发异构化不是乳糜微粒中TG水解后2-MG代谢的主要机制。2-MO和2-MP在水中的异构化速率（以每小时剩余2-MG百分比的下降表示）分别为-5.12和-5.86，在己烷中分别为-0.43和-0.41。2-MO和2-MP的异构化速率之间没有显著差异。因此，在本研究中，MG酰基链的饱和度在水或己烷中均不影响自发酰基迁移，但2-MG在水中的异构化比在己烷中更快。
