Ex vivo measurement of lipoprotein lipase-dependent very low density lipoprotein (VLDL)-triglyceride hydrolysis in human VLDL:: An alternative to the postheparin assay of lipoprotein lipase activity?
Ex vivo measurement of lipoprotein lipase-dependent very low density lipoprotein (VLDL)-triglyceride hydrolysis in human VLDL:: An alternative to the postheparin assay of lipoprotein lipase activity?
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DOI：
10.1210/jc.86.2.797
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发表时间：
2001-02-01
影响因子：
5.8
通讯作者：
Moulin, P
中科院分区：
文献类型：
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作者：
Pruneta, V;Autran, D;Moulin, P
脂蛋白脂酶（LPL）的活性是血浆中富含甘油三酯（TG）的脂蛋白的主要脂解作用。尽管对我们分析某些病理生理情况很重要，但确定LPL依赖性脂解的程度并不容易。这主要是由于LPL与血管内皮的管腔表面结合所致。在注射肝素（一种从内皮释放LPL的程序）后，已经实现了整个推定LPL活性的测量。然而，这种肝素后脂解试验（PHLA）的生理病理学相关性仍然值得怀疑，因为它从来没有被证明，大部分的内皮结合LPL是activated.It最近已被证明，一小部分的LPL与循环脂蛋白在nonheparinized血浆，提高这种循环LPL介导的脂解可能反映了整体LPL依赖性TG水解血浆中的可能性。为了解决这个问题，我们开发了一种新的脂解试验，其中极低密度脂蛋白（VLDL）结合的LPL依赖性VLDL-TG水解（LVTH）直接确定通过测量非酯化脂肪酸（NEFA）释放在体外孵育过程中。在对照组、2型糖尿病患者、杂合子或纯合子LPL缺陷患者中进行LVTH测量。在后者中，LVTH值极低。杂合子患者和糖尿病患者的那些类似地相对于对照组降低约40%。血浆TG浓度与LVTH水平呈负相关。在一个亚组的受试者中，LVTH和PHLA呈正相关，LVTH与血浆或VLDL-TG浓度的负相关性强于PHLA。为了进一步研究这种新的检测方法的有效性，我们测量了9名受试者的LVTH，他们被研究了稳定同位素标记的VLDL。没有观察到直接肝清除VLDL和LVTH之间的关系，而后者是惊人的VLDL到中间密度lipoprotein.Collective考虑这些研究结果的转化率相关强烈表明，LVTH是一个生理相关的指标，可以有利地取代测量PHLA在许多生理病理情况。
The plasma lipolysis of triglyceride (TG)-rich lipoproteins is mainly due to the activity of lipoprotein lipase (LPL). Albeit important for our analysis of certain physiopathological situations, the determination of the magnitude of LPL-dependent lipolysis is not easy to perform. This essentially results from the binding of LPL to the luminal surface of vascular endothelium. The measurements of the whole putative LPL activity have been achieved after injection of heparin, a procedure that releases LPL from endothelium. However, the physiopathological relevance of this postheparin lipolysis assay (PHLA) remains questionable because it has never been demonstrated that the bulk of endothelium-bound LPL was active.It has been recently shown that a small part of LPL is associated to circulating lipoproteins in nonheparinized plasma, raising the possibility that the lipolysis mediated by this circulating LPL might reflect the overall LPL-dependent TG hydrolysis in plasma. To address this question, we developed a new lipolysis assay in which the very low density lipoprotein (VLDL)-bound LPL-dependent VLDL-TG hydrolysis (LVTH) was directly determined through the measurement of nonesterified fatty acid (NEFA) release during in vitro incubations. LVTH measurements were performed in control subjects, in type 2 diabetics, and in either heterozygous or homozygous LPL-deficient patients. In the latter group, LVTH Values were extremely low. Those of heterozygous patients and of diabetics were similarly decreased by about 40% with respect to control group. Plasma TG concentrations exhibited an inverse relationship with LVTH level. In a subgroup of subjects, LVTH and PHLA were positively correlated and the inverse correlation of LVTH with plasma or VLDL-TG concentration was stronger than that obtained with PHLA. To further study the validity of this new assay, we measured LVTH in nine subjects who were studied for their catabolism of VLDL labeled with stable isotope. No relation was observed between the direct hepatic removal of VLDL and LVTH, whereas the latter was strikingly correlated with the rate of conversion of VLDL to intermediary density lipoprotein.Collective consideration of these findings strongly suggests that LVTH is a physiologically relevant index which could advantageously replace the measurements of PHLA in numerous physiopathological situations.