Kinetics of 2-monoacylglycerol acyl migration in model chylomicra

In the metabolism of triacylglycerol (TC)-rich lipoproteins, 2-monoacylglyc erols (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 o n 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 spont aneous acyl migration of 2-MG in in vitro model chylomicra emulsions were d etermined. After 1 h of incubation at 37 degreesC, less than 20% of 2-monoo lein (2-MO) or 2-monopalmitin (2-MP) spontaneously isomerized to 1(3)-MO or 1(3)-MP, respectively. Accordingly, it was concluded that spontaneous isom erization of 2-MG is not the major mechanism for 2-MG metabolism post-TC hy drolysis in chylomicra. Isomerization rates, expressed as decrease in perce ntage 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 significa nt difference between the isomerization rates of 2-MO and 2-MP. Thus, in th e present study, saturation of the MG acyl chain did not influence spontane ous acyl migration in either water or hexane, but isomerization of 2-MG was faster in water than in hexane.