Identification of isosilybin a from milk thistle seeds as an agonist of peroxisome proliferator-activated receptor gamma.

Peroxisome proliferator-activated receptor gamma (PPARγ) is a key regulator of glucose and lipid metabolism. Agonists of this nuclear receptor are used in the treatment of type 2 diabetes and are also studied as a potential treatment of other metabolic diseases, including nonalcoholic fatty liver disease. Silymarin, a concentrated phenolic mixture from milk thistle (Silybum marianum) seeds, is used widely as a supportive agent in the treatment of a variety of liver diseases. In this study, the PPARγ activation potential of silymarin and its main constituents was investigated. Isosilybin A (3) caused transactivation of a PPARγ-dependent luciferase reporter in a concentration-dependent manner. This effect could be reversed upon co-treatment with the PPARγ antagonist T0070907. In silico docking studies suggested a binding mode for 3 distinct from that of the inactive silymarin constituents, with one additional hydrogen bond to Ser342 in the entrance region of the ligand-binding domain of the receptor. Hence, isosilybin A (3) has been identified as the first flavonolignan PPARγ agonist, suggesting its further investigation as a modulator of this nuclear receptor.

Citation

Eva-Maria Pferschy-Wenzig, Atanas G Atanasov, Clemens Malainer, Stefan M Noha, Olaf Kunert, Daniela Schuster, Elke H Heiss, Nicholas H Oberlies, Hildebert Wagner, Rudolf Bauer, Verena M Dirsch. Identification of isosilybin a from milk thistle seeds as an agonist of peroxisome proliferator-activated receptor gamma. Journal of natural products. 2014 Apr 25;77(4):842-7

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PMID: 24597776

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