Eckel R H, Jensen D R, Schlaepfer I R, Yost T J
Department of Medicine, University of Colorado Health Sciences Center, Denver 80262, USA.
Am J Physiol. 1996 Nov;271(5 Pt 2):R1280-6. doi: 10.1152/ajpregu.1996.271.5.R1280.
Lipoprotein lipase (LPL) is a hydrolytic enzyme, involved in lipoprotein metabolism and nutrient partitioning, that is subject to tissue-specific regulation. Evidence for divergent regulation of the lipase by insulin has been demonstrated, but alterations in the tissue-specific response of LPL to catecholamines has not been studied in humans. The regulation of LPL in gluteal adipose tissue and vastus lateralis muscle by isoproterenol (epinephrine isopropyl homologue) in humans was examined over 2 h in subjects infused with 0 (saline) or 8 or 24 ng.kg-1.min-1 isoproterenol. The infusion of normal saline into control subjects failed to alter adipose tissue or skeletal muscle LPL activity. However, in the saline-infused subjects there was a positive correlation between the percent change in plasma norepinephrine concentrations and the percent change in muscle LPL activity (r = 0.826, P < 0.05). Isoproterenol infusion did not change LPL in either adipose tissue or muscle compared with saline-infused controls, but plasma insulin levels in addition to plasma glucose, free fatty acids, and glycerol were increased. To prevent the isoproterenol-induced hyperinsulinemia, a pancreatic clamp technique was utilized. An increase in muscle LPL was demonstrated (P = 0.037) with no change in adipose tissue LPL. The change in muscle LPL activity after the 2-h infusion correlated with the change in muscle mRNA (P = 0.021). Overall, these studies indicate that in humans the response of LPL to catecholamines is tissue specific with no effect in adipose tissue but a stimulation in skeletal muscle. Endogenous regulation of LPL in muscle by catecholamines could be important in muscle fuel metabolism and could relate to effects of adenosine 3',5'-cyclic monophosphate and/or fatty acids at the level of the LPL gene.
脂蛋白脂肪酶（LPL）是一种水解酶，参与脂蛋白代谢和营养分配，且受到组织特异性调控。胰岛素对该脂肪酶的调控存在差异已有证据证明，但LPL对儿茶酚胺的组织特异性反应变化在人类中尚未得到研究。在输注0（生理盐水）或8或24 ng·kg⁻¹·min⁻¹异丙肾上腺素（肾上腺素异丙基同系物）的受试者中，对人臀脂肪组织和股外侧肌中LPL受异丙肾上腺素的调控进行了2小时的研究。向对照受试者输注生理盐水未能改变脂肪组织或骨骼肌的LPL活性。然而，在输注生理盐水的受试者中，血浆去甲肾上腺素浓度的百分比变化与肌肉LPL活性的百分比变化之间存在正相关（r = 0.826，P < 0.05）。与输注生理盐水的对照组相比，输注异丙肾上腺素并未改变脂肪组织或肌肉中的LPL，但除了血浆葡萄糖、游离脂肪酸和甘油外，血浆胰岛素水平升高。为防止异丙肾上腺素诱导的高胰岛素血症，采用了胰腺钳夹技术。结果显示肌肉LPL增加（P = 0.037），而脂肪组织LPL无变化。2小时输注后肌肉LPL活性的变化与肌肉mRNA的变化相关（P = 0.021）。总体而言，这些研究表明，在人类中，LPL对儿茶酚胺的反应具有组织特异性，对脂肪组织无影响，但对骨骼肌有刺激作用。儿茶酚胺对肌肉中LPL的内源性调控在肌肉燃料代谢中可能很重要，并且可能与3',5'-环磷酸腺苷和/或脂肪酸在LPL基因水平的作用有关。
