Sirtuin 1 (SIRT1) is a deacetylase enzyme that plays crucial roles in controlling many cellular processes and its downregulation has been implicated in different metabolic disorders. Recently, several polyphenols have been considered as the effective therapeutic approaches that appear to influence SIRT1. The main goal of this study was to evaluate the effect of hesperetin, a citrus polyphenolic flavonoid, on SIRT1 and AMP-activated kinase (AMPK). HepG2 cells were treated with hesperetin in the presence or absence of EX-527, a SIRT1 specific inhibitor, for 24 h. Resveratrol was used as a positive control. SIRT1 gene expression, protein level, and activity were measured by RT-PCR, Western blotting, and fluorometric assay, respectively. AMPK phosphorylation was also determined by Western blotting. Our results indicated a significant increase in SIRT1 protein level and activity as well as an induction of AMPK phosphorylation by hesperetin. These effects of hesperetin were abolished by EX-527. Furthermore, hesperetin reversed the EX-527 inhibitory effects on SIRT1 protein expression and AMPK phosphorylation. These findings suggest that hesperetin can be a novel SIRT1 activator, even stronger than resveratrol. Therefore, the current study may introduce hesperetin as a new strategy aimed at upregulation SIRT1-AMPK pathway resulting in various cellular processes regulation.

中文翻译：

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橙皮素是一种有效的生物激活剂，可激活HepG2细胞中的SIRT1-AMPK信号通路。

Sirtuin 1（SIRT1）是一种脱乙酰基酶，在控制许多细胞过程中起着至关重要的作用，其下调与多种代谢异常有关。最近，几种多酚被认为是似乎影响SIRT1的有效治疗方法。这项研究的主要目的是评估橙皮苷（一种柑橘类多酚类黄酮）对SIRT1和AMP活化激酶（AMPK）的影响。在存在或不存在SIRT1特异性抑制剂EX-527的情况下，用橙皮素处理HepG2细胞24小时。白藜芦醇用作阳性对照。通过RT-PCR，Western印迹和荧光测定分别测量SIRT1基因表达，蛋白水平和活性。AMPK磷酸化也通过蛋白质印迹法确定。我们的结果表明，SIRT1蛋白水平和活性显着增加，以及橙皮素诱导的AMPK磷酸化。橙皮素的这些作用已被EX-527取消。此外，橙皮素逆转了EX-527对SIRT1蛋白表达和AMPK磷酸化的抑制作用。这些发现表明橙皮素可以是一种新型的SIRT1激活剂，甚至比白藜芦醇更强。因此，当前的研究可能引入橙皮素作为旨在上调SIRT1-AMPK途径导致各种细胞过程调控的新策略。这些发现表明橙皮素可以是一种新型的SIRT1激活剂，甚至比白藜芦醇更强。因此，当前的研究可能引入橙皮素作为旨在上调SIRT1-AMPK途径导致各种细胞过程调控的新策略。这些发现表明橙皮素可以是一种新型的SIRT1激活剂，甚至比白藜芦醇更强。因此，当前的研究可能引入橙皮素作为旨在上调SIRT1-AMPK途径导致各种细胞过程调控的新策略。