一个更新的 ANGPTL3-4-8 模型作为脂肪和氧化组织之间甘油三酯分配的机制。

An updated ANGPTL3-4-8 model as a mechanism of triglyceride partitioning between fat and oxidative tissues.

机构信息

Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University, 540 East Canfield Street, Detroit, MI 48201, USA.

Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University, 540 East Canfield Street, Detroit, MI 48201, USA.

出版信息

Prog Lipid Res. 2022 Jan;85:101140. doi: 10.1016/j.plipres.2021.101140. Epub 2021 Nov 16.

Abstract

In mammals, triglyceride (TG), the main form of lipids for storing and providing energy, is stored in white adipose tissue (WAT) after food intake, while during fasting it is routed to oxidative tissues (heart and skeletal muscle) for energy production, a process referred to as TG partitioning. Lipoprotein lipase (LPL), a rate-limiting enzyme in this fundamental physiological process, hydrolyzes circulating TG to generate free fatty acids that are taken up by peripheral tissues. The postprandial activity of LPL declines in oxidative tissues but rises in WAT, directing TG to WAT; the reverse is true during fasting. However, the molecular mechanism in regulating tissue-specific LPL activity during the fed-fast cycle has not been completely understood. Research on angiopoietin-like (ANGPTL) proteins (A3, A4, and A8) has resulted in an ANGPTL3-4-8 model to explain the TG partitioning between WAT and oxidative tissues. Food intake induces A8 expression in the liver and WAT. Liver A8 activates A3 by forming the A3-8 complex, which is then secreted into the circulation. The A3-8 complex acts in an endocrine manner to inhibit LPL in oxidative tissues. WAT A8 forms the A4-8 complex, which acts locally to block A4's LPL-inhibiting activity. Therefore, the postprandial activity of LPL is low in oxidative tissues but high in WAT, directing circulating TG to WAT. Conversely, during fasting, reduced A8 expression in the liver and WAT disables A3 from inhibiting oxidative-tissue LPL and restores WAT A4's LPL-inhibiting activity, respectively. Thus, the fasting LPL activity is high in oxidative tissues but low in WAT, directing TG to the former. According to the model, we hypothesize that A8 antagonism has the potential to simultaneously reduce TG and increase HDL-cholesterol plasma levels. Future research on A3, A4, and A8 can hopefully provide more insights into human health, disease, and therapeutics.

摘要

在哺乳动物中,甘油三酯(TG)是储存和提供能量的主要脂质形式,在进食后储存在白色脂肪组织(WAT)中,而在禁食期间,它被输送到氧化组织(心脏和骨骼肌)中以产生能量,这个过程被称为 TG 分配。脂蛋白脂肪酶(LPL)是这个基本生理过程中的限速酶,它将循环中的 TG 水解为游离脂肪酸,然后被外周组织吸收。LPL 在氧化组织中的餐后活性下降,但在 WAT 中上升,从而将 TG 导向 WAT;反之在禁食期间亦然。然而,在进食-禁食循环中调节组织特异性 LPL 活性的分子机制尚未完全理解。对血管生成素样(ANGPTL)蛋白(A3、A4 和 A8)的研究导致了一个 ANGPTL3-4-8 模型,用于解释 WAT 和氧化组织之间的 TG 分配。进食诱导肝脏和 WAT 中 A8 的表达。肝脏 A8 通过形成 A3-8 复合物来激活 A3,然后将其分泌到循环中。A3-8 复合物以内分泌方式作用于氧化组织中的 LPL 以抑制其活性。WAT A8 形成 A4-8 复合物,局部作用以阻止 A4 对 LPL 的抑制作用。因此,LPL 在氧化组织中的餐后活性较低,但在 WAT 中较高,从而将循环 TG 导向 WAT。相反,在禁食期间,肝脏和 WAT 中 A8 表达的减少使 A3 无法抑制氧化组织中的 LPL,并分别恢复 WAT A4 对 LPL 的抑制活性。因此,禁食期间氧化组织中的 LPL 活性较高,但 WAT 中的活性较低,从而将 TG 导向前者。根据该模型,我们假设 A8 拮抗作用有可能同时降低 TG 和增加 HDL-胆固醇的血浆水平。对 A3、A4 和 A8 的进一步研究有望为人类健康、疾病和治疗提供更多的见解。

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