Berry Phenolic Compounds Increase Expression of Hepatocyte Nuclear Factor-1α (HNF-1α) in Caco-2 and Normal Colon Cells Due to High Affinities with Transcription and Dimerization Domains of HNF-1α

Hepatocyte nuclear factor-1α (HNF-1α) is found in the kidneys, spleen, thymus, testis, skin, and throughout the digestive organs. It has been found to promote the transcription of various proteins involved in the management of type II diabetes, including dipeptidyl peptidase-IV (DPP-IV). Phenolic compounds from berries and citrus fruits are known to inhibit DPP-IV, but have not been tested for their interactions with wild-type HNF-1α. By studying the interactions of compounds from berries and citrus fruits have with HNF-1α, pre-transcriptional mechanisms that inhibit the expression of proteins such as DPP-IV may be elucidated. In this study, the interactions of berry phenolic compounds and citrus flavonoids with the dimerization and transcriptional domains of HNF-1α were characterized using the molecular docking program AutoDock Vina. The anthocyanin delphinidin-3-O-arabinoside had the highest binding affinity for the dimerization domain as a homodimer (-7.2 kcal/mol) and transcription domain (-8.3 kcal/mol) of HNF-1α. Anthocyanins and anthocyanidins had relatively higher affinities than resveratrol and citrus flavonoids for both, the transcription domain and the dimerization domain as a homodimer. The flavonoid flavone had the highest affinity for a single unit of the dimerization domain (-6.5 kcal/mol). Nuclear expression of HNF-1α was measured in Caco-2 and human normal colon cells treated with blueberry and blackberry anthocyanin extracts. All extracts tested increased significantly (P O-glucoside increased by 3-fold nuclear HNF-1α expression in Caco-2 cells (P肝细胞核因子1α（Hepatocyte nuclear factor-1α, HNF-1α）广泛表达于肾脏、脾脏、胸腺、睾丸、皮肤及整个消化器官。研究证实，其可促进参与Ⅱ型糖尿病调控的多种蛋白的转录，其中包括二肽基肽酶-IV（Dipeptidyl peptidase-IV, DPP-IV）。已知浆果与柑橘类水果中的酚类化合物可抑制DPP-IV活性，但尚未有研究检测其与野生型HNF-1α的相互作用。通过探究浆果与柑橘类水果中的化合物与HNF-1α的相互作用，有望阐明抑制DPP-IV等蛋白表达的转录前调控机制。 本研究采用分子对接程序AutoDock Vina，对浆果酚类化合物与柑橘类黄酮和HNF-1α的二聚化结构域及转录结构域的相互作用进行了表征。结果显示，花青素飞燕草素-3-O-阿拉伯糖苷（delphinidin-3-O-arabinoside）与HNF-1α同源二聚体的二聚化结构域（结合能-7.2 kcal/mol）及转录结构域（结合能-8.3 kcal/mol）结合时，展现出最高的结合亲和力。相较于白藜芦醇（resveratrol）与柑橘类黄酮，花青素及花色素（anthocyanidins）在结合上述两个结构域时，均表现出相对更高的亲和力。黄酮类化合物黄酮（flavone）对二聚化结构域的单体重单元展现出最高结合亲和力（-6.5 kcal/mol）。 研究人员检测了经蓝莓与黑莓花青素提取物处理后的Caco-2细胞及正常人结肠细胞中HNF-1α的核表达水平。所有受试提取物均能显著上调HNF-1α的核表达（P；其中飞燕草素-3-O-葡萄糖苷可使Caco-2细胞内的HNF-1α核表达提升3倍（P