da-Silva Wagner S, Harney John W, Kim Brian W, Li Jing, Bianco Suzy D C, Crescenzi Alessandra, Christoffolete Marcelo A, Huang Stephen A, Bianco Antonio C
Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine, Brigham and Women's Hospital, 77 Avenue Louis Pasteur, HIM Bldg. #643, Boston, MA 02115, USA.
Diabetes. 2007 Mar;56(3):767-76. doi: 10.2337/db06-1488.
Disturbances in energy homeostasis can result in obesity and other metabolic diseases. Here we report a metabolic pathway present in normal human skeletal muscle myoblasts that is activated by the small polyphenolic molecule kaempferol (KPF). Treatment with KPF leads to an approximately 30% increase in skeletal myocyte oxygen consumption. The mechanism involves a several-fold increase in cyclic AMP (cAMP) generation and protein kinase A activation, and the effect of KPF can be mimicked via treatment with dibutyryl cAMP. Microarray and real-time PCR studies identified a set of metabolically relevant genes influenced by KPF including peroxisome proliferator-activated receptor gamma coactivator-1alpha, carnitine palmitoyl transferase-1, mitochondrial transcription factor 1, citrate synthase, and uncoupling protein-3, although KPF itself is not a direct mitochondrial uncoupler. The cAMP-responsive gene for type 2 iodothyronine deiodinase (D2), an intracellular enzyme that activates thyroid hormone (T3) for the nucleus, is approximately threefold upregulated by KPF; furthermore, the activity half-life for D2 is dramatically and selectively increased as well. The net effect is an approximately 10-fold stimulation of D2 activity as measured in cell sonicates, with a concurrent increase of approximately 2.6-fold in the rate of T3 production, which persists even 24 h after KPF has been removed from the system. The effects of KPF on D2 are independent of sirtuin activation and only weakly reproduced by other small polyphenolic molecules such as quercetin and fisetin. These data document a novel mechanism by which a xenobiotic-activated pathway can regulate metabolically important genes as well as thyroid hormone activation and thus may influence metabolic control in humans.
能量稳态的紊乱会导致肥胖和其他代谢性疾病。在此，我们报告了一条存在于正常人类骨骼肌成肌细胞中的代谢途径，该途径可被小多酚分子山奈酚（KPF）激活。用KPF处理可使骨骼肌细胞耗氧量增加约30%。其机制涉及环磷酸腺苷（cAMP）生成增加数倍以及蛋白激酶A激活，并且KPF的作用可通过用二丁酰cAMP处理来模拟。微阵列和实时PCR研究确定了一组受KPF影响的与代谢相关的基因，包括过氧化物酶体增殖物激活受体γ共激活因子-1α、肉碱棕榈酰转移酶-1、线粒体转录因子1、柠檬酸合酶和解偶联蛋白-3，尽管KPF本身并非直接的线粒体解偶联剂。2型碘甲状腺原氨酸脱碘酶（D2）的cAMP反应基因是一种细胞内酶，可将甲状腺激素（T3）激活以供细胞核利用，该基因被KPF上调约三倍；此外，D2的活性半衰期也显著且选择性地增加。净效应是在细胞超声裂解物中测得的D2活性受到约10倍的刺激，同时T3生成速率增加约2.6倍，即使在从系统中去除KPF后24小时，这种增加仍持续存在。KPF对D2的作用独立于沉默调节蛋白激活，并且其他小多酚分子如槲皮素和漆黄素只能微弱地重现这种作用。这些数据证明了一种新机制，即一种外源性物质激活的途径可以调节代谢重要基因以及甲状腺激素激活，从而可能影响人类的代谢控制。
