van der Krieken Sophie E, Popeijus Herman E, Bendik Igor, Böhlendorf Bettina, Konings Maurice C J M, Tayyeb Jehad, Mensink Ronald P, Plat Jogchum
NUTRIM School of Nutrition and Translational Research in Metabolism, Department of Nutrition and Movement Sciences, Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands.
DSM Nutritional Products Ltd, Research and Development, Human Nutrition and Health, PO Box 2676, Basel, Switzerland.
Lipids. 2018 Nov;53(11-12):1021-1030. doi: 10.1002/lipd.12116. Epub 2019 Feb 1.
Increasing apolipoprotein A-I (apoA-I), the predominant protein of high-density lipoprotein (HDL) particles, has favorable effects on atherogenic risk factors. Here, we investigated the effects of peroxisome proliferator-activated receptor α (PPARα) transactivating compounds on apoA-I transcription in HepG2 cells. A transient PPARα agonist transactivation assay was used to screen 2500 natural compounds. To analyze the effects on apoA-I transcription, human hepatocellular liver carcinoma (HepG2) were exposed to 0.1, 1, and 10 μg/mL of the natural PPARα transactivators. ApoA-I mRNA expression was determined by quantitative polymerase chain reaction. Extensive dose-response experiments were performed using compounds that increased apoA-I transcription by minimally 20%. Kelch-like ECH-associated protein 1 (KEAP) and carnitine palmitoyltransferase 1 alpha (CPT1α) expression were used respectively to confirm Bromodomain-containing protein 4 inhibition or PPARα activation. Twenty-eight natural compounds increased PPARα transactivation by at least twofold. Despite the increased CPT1α expression seen after the addition of most PPARα activating compounds, CPT1α expression and PPARα transactivation did not correlate. Addition of 0.05 μg/mL 9S-hydroxy-10E,12Z,15Z-octadecatrienoic acid (9(S)-HOTrE) increased apoA-I mRNA expression by 35%, whereas 10-25 μg/mL of cymarin increased apoA-I transcription by 37%. However, combining cymarin and 9(S)-HOTrE did not result in a synergistic effect, in contrast this combination even decreased apoA-I transcription. ApoA-I transcription involves multiple regulatory players, and PPARα transactivation alone is not sufficient. A search for natural compounds resembling the molecular structure of 9(S)-HOTrE or cymarin could aid to find additional components that increase apoA-I transcription.
载脂蛋白A-I（apoA-I）是高密度脂蛋白（HDL）颗粒的主要蛋白质，增加其水平对动脉粥样硬化危险因素具有有益作用。在此，我们研究了过氧化物酶体增殖物激活受体α（PPARα）反式激活化合物对HepG2细胞中apoA-I转录的影响。采用瞬时PPARα激动剂反式激活试验筛选2500种天然化合物。为了分析对apoA-I转录的影响，将人肝细胞肝癌（HepG2）细胞暴露于0.1、1和10μg/mL的天然PPARα反式激活剂中。通过定量聚合酶链反应测定apoA-I mRNA表达。使用使apoA-I转录至少增加20%的化合物进行了广泛的剂量反应实验。分别使用kelch样ECH相关蛋白1（KEAP）和肉碱棕榈酰转移酶1α（CPT1α）表达来确认含溴结构域蛋白4抑制或PPARα激活。28种天然化合物使PPARα反式激活至少增加两倍。尽管添加大多数PPARα激活化合物后可见CPT1α表达增加，但CPT1α表达与PPARα反式激活并不相关。添加0.05μg/mL的9S-羟基-10E，12Z，15Z-十八碳三烯酸（9(S)-HOTrE）使apoA-I mRNA表达增加35%，而10-25μg/mL的 cymarin使apoA-I转录增加37%。然而，与9(S)-HOTrE联合使用cymarin并未产生协同效应，相反，这种组合甚至降低了apoA-I转录。apoA-I转录涉及多个调节因子，仅PPARα反式激活是不够的。寻找与9(S)-HOTrE或cymarin分子结构相似的天然化合物可能有助于找到增加apoA-I转录的其他成分。
