Identification of Picrasidine C as a Subtype-Selective PPARα Agonist Shuai Zhao, † Yuichiro Kanno,* ,‡ Wei Li,* ,§ Tatsunori Sasaki, § Xiangyu Zhang, ⊥ Jian Wang, ⊥ Maosheng Cheng, ⊥ Kazuo Koike, § Kiyomitsu Nemoto, ‡ and Huicheng Li* ,† † College of Life Science, Northeast Forestry University, Harbin 150040, People’s Republic of China ‡ Department of Molecular Toxicology, Faculty of Pharmaceutical Sciences, Toho University, Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan § Faculty of Pharmaceutical Sciences, Toho University, Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan ⊥ Key Laboratory of Structure-Based Drug Design and Discovery of Ministry of Education, Shenyang Pharmaceutical University, Shenyang 110016, People’s Republic of China ABSTRACT: Picrasidine C (1), a dimeric β-carboline-type alkaloid isolated from the root of Picrasma quassioides, was identified to have PPARα agonistic activity by a mammalian one-hybrid assay from a compound library. Among the PPAR subtypes, 1 selectively activated PPARα in a concentration- dependent manner. Remarkably, 1 also promoted PPARα transcriptional activity by a peroxisome proliferator response element-driven luciferase reporter assay. Furthermore, 1 induced the expression of PPARα-regulated genes involved in lipid, glucose, and cholesterol metabolism, such as CPT-1, PPARα, PDK4, and ABCA1, which was abrogated by the PPARα antagonist MK-886, indicating that the effect of 1 was dependent on PPARα activation. This is the first report to demonstrate 1 to be a subtype-selective PPARα agonist with potential application in treating metabolic diseases, such as hyperlipidemia, atherosclerosis, and hypercholesterolemia. P eroxisome proliferator activated receptors (PPARs) are ligand-activated transcription factors that belong to the nuclear receptor superfamily. 1,2 PPARs contain three known subtypes, PPARα,-γ, and -β/δ, which share high sequence and structural homology, but have unique tissue expression and physiological functions. 3,4 When activated by their ligand, PPARs heterodimerize with the retinoid X receptor (RXR), bind to PPREs (peroxisome proliferator hormone response elements), and regulate the transcription of various genes (such as CPT-1, PPARα, PDK4, and ABCA1), thereby influencing various cellular functions, including the regulation of glucose, lipid, and cholesterol metabolism. They have consequently been identified as ideal targets for treating metabolic diseases, including diabetes, obesity, hypertension, and dyslipidemia. The identification of novel PPAR agonists for drug develop- ment has attracted an increasing amount of attention. In rodents and humans, PPARα is expressed in tissues with high rates of fatty acid oxidation, including the liver, kidney, heart, skeletal muscle, and brown adipose tissue; 5,6 it is also expressed in a range of vascular cells, such as endothelial cells, vascular smooth muscle cells (VSMCs), and monocytes/ macrophages. 7 Previous investigations have demonstrated the critical role that PPARα plays in regulating lipid homeostasis, and it has also been an attractive molecular target for drug development. For example, fibrates, which predominantly target PPARα, have become a well-established class of drugs for treating hypertriglyceridemia and mixed dyslipidemia over the last several decades. 8 However, these synthetic hypolipidemic fibrate drugs, such as fenofibrate, ciprofibrate, and bezafibrate, showed only modest selectivity for PPARα over the other PPAR subtypes, 9 resulting in side effects and safety issues that were identified during clinical trials to be associated with the induction of other PPAR subtypes. 10 Efforts to improve the fibrate class or nonfibrate compounds’ pharmacological profiles led to the synthesis of selective PPARα agonists. However, only a few of such compounds were identified, such as GW7647 11 and WY14643, 12 to have varying degrees of PPARα selectivity. Therefore, identifying more potent subtype-selective PPARα agonists is an important goal. Plants used in traditional medicine have been attracting attention for their ability to ameliorate metabolic diseases, including diabetes mellitus and hyperlipidemia- and hyper- cholesterolemia-associated abnormal lipid metabolism. Both extracts and natural compounds have been reported to exert the hypolipidemic effects through activating PPARα. 13-19 With the aim of identifying selective PPAR subtype agonists, we screened a compound library extracted from natural products using a mammalian one-hybrid assay. We identified picrasidine C (1), a dimeric β-carboline-type alkaloid, which was isolated from the root of Picrasma quassioides, as a subtype- selective PPARα agonist that could induce mRNA expression of PPARα-regulated genes, such as CPT-1, PPARα, PDK4, and ABCA1. Received: September 28, 2016 Article pubs.acs.org/jnp © XXXX American Chemical Society and American Society of Pharmacognosy A DOI: 10.1021/acs.jnatprod.6b00883 J. Nat. Prod. XXXX, XXX, XXX-XXX