Helsley Robert N, Zelows Mikala M, Noffsinger Victoria P, Anspach Garrett B, Dharanipragada Nikitha, Mead Anna E, Cobo Isidoro, Carter Abigail, Wu Qinglin, Shalaurova Irina, Saito Kai, Morganti Josh M, Gordon Scott M, Graf Gregory A
Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine (R.N.H., M.M.Z., G.B.A., N.D.), University of Kentucky, Lexington.
Department of Pharmacology and Nutritional Sciences (R.N.H., G.B.A., N.D.), University of Kentucky, Lexington.
Arterioscler Thromb Vasc Biol. 2025 Aug;45(8):1368-1388. doi: 10.1161/ATVBAHA.125.322473. Epub 2025 Jun 12.
Genome- and epigenome-wide association studies have associated variants and methylation status of CPT1a (carnitine palmitoyltransferase 1a) to reductions in VLDL (very low-density lipoprotein) cholesterol and triglyceride levels. The objective of this study was to determine the mechanisms by which CPT1a-dependent mitochondrial fatty acid oxidation influences hepatic and lipoprotein metabolism.
Eight-week-old male and female -floxed mice () and -floxed mice expressing the human apo B transgene (/B100) were administered control adeno-associated virus or adeno-associated virus encoding Cre-recombinase under control of a liver-specific promoter (TBG-Cre [thyroxin-binding globulin]). Control and liver-specific knockout mice were placed on a low-fat control or western-type diet (42% kcal fat, 0.2% cholesterol) for 16 weeks. Livers were collected and used for histological and lipid analysis, while gene and protein expression were measured by bulk RNA-sequencing and immunoblotting, respectively. Lipoprotein composition in plasma was determined by size exclusion chromatography and nuclear magnetic resonance. Rates of VLDL-triglyceride secretion were quantified after lipase inhibition with poloxamer 407. Liquid and gas chromatography-mass spectrometry were used to measure bile acid species and fecal neutral sterols, respectively.
We report significant associations between the presence of SNPs (single nucleotide polymorphisms) and reductions in plasma cholesterol, as well as positive associations between hepatic Cpt1a expression and plasma cholesterol levels across inbred mouse strains. Mechanistic studies show that both wild-type and human apo B (apoB)-transgenic mice with liver-specific deletion of (liver-specific knockout) display lower circulating apoB levels consistent with reduced LDL (low-density lipoprotein)-cholesterol and LDL particle number. Despite a reduction in steady-state plasma lipids, VLDL-triglyceride and VLDL cholesterol secretion rates are increased, suggesting accelerated clearance of apoB-LPs (apoB-containing lipoproteins) in liver-specific knockout mice. Mechanistic approaches show greater PPARα (peroxisome proliferator-activated receptor α) signaling which favors enhanced lipoprotein lipase-mediated metabolism of apoB-LPs, including increases in apo AIV and apo CII and reductions in apo CIII and Angptl3 (angiopoietin-like 3).
These studies provide mechanistic insight linking genetic variants and methylation status of to reductions in circulating apoB-LPs in humans.
全基因组和全表观基因组关联研究已将CPT1a（肉碱棕榈酰转移酶1a）的变体和甲基化状态与极低密度脂蛋白（VLDL）胆固醇和甘油三酯水平的降低联系起来。本研究的目的是确定CPT1a依赖性线粒体脂肪酸氧化影响肝脏和脂蛋白代谢的机制。
给8周龄的雄性和雌性floxed小鼠（）和表达人载脂蛋白B转基因的floxed小鼠（/B100）注射对照腺相关病毒或在肝脏特异性启动子（TBG-Cre [甲状腺素结合球蛋白]）控制下编码Cre重组酶的腺相关病毒。将对照小鼠和肝脏特异性敲除小鼠置于低脂对照饮食或西式饮食（42%千卡脂肪，0.2%胆固醇）中16周。收集肝脏用于组织学和脂质分析，同时分别通过大量RNA测序和免疫印迹测量基因和蛋白质表达。通过尺寸排阻色谱法和核磁共振法测定血浆中的脂蛋白组成。在用泊洛沙姆407抑制脂肪酶后，对VLDL-甘油三酯分泌率进行定量。分别使用液相色谱-质谱联用和气相色谱-质谱联用测量胆汁酸种类和粪便中性固醇。
我们报告了单核苷酸多态性（SNP）的存在与血浆胆固醇降低之间的显著关联，以及在近交小鼠品系中肝脏Cpt1a表达与血浆胆固醇水平之间的正相关。机制研究表明，野生型和人载脂蛋白B（apoB）转基因小鼠肝脏特异性缺失（肝脏特异性敲除）均表现出较低的循环apoB水平，这与低密度脂蛋白（LDL）胆固醇和LDL颗粒数量减少一致。尽管稳态血浆脂质减少，但VLDL-甘油三酯和VLDL胆固醇分泌率增加，表明肝脏特异性敲除小鼠中apoB脂蛋白（含apoB的脂蛋白）的清除加速。机制研究表明，过氧化物酶体增殖物激活受体α（PPARα）信号增强，这有利于增强脂蛋白脂肪酶介导的apoB脂蛋白代谢，包括apo AIV和apo CII增加以及apo CIII和血管生成素样3（Angptl3）减少。
这些研究提供了将CPT1a的基因变体和甲基化状态与人类循环中apoB脂蛋白减少联系起来的机制性见解。
