Shrivastav Shashi, Zhang Liyan, Okamoto Koji, Lee Hewang, Lagranha Claudia, Abe Yoshifusa, Balasubramanyam Ashok, Lopaschuk Gary D, Kino Tomoshige, Kopp Jeffrey B
Kidney Disease Section, National Institute of Diabetes and Digestive andKidney Diseases, National Institutes of Health,Bethesda, Maryland 20892-1268, USA.
Mol Endocrinol. 2013 Sep;27(9):1564-76. doi: 10.1210/me.2012-1370. Epub 2013 Jul 10.
HIV infection and its therapy are associated with disorders of lipid metabolism and bioenergetics. Previous work has suggested that viral protein R (Vpr) may contribute to the development of lipodystrophy and insulin resistance observed in HIV-1-infected patients. In adipocytes, Vpr suppresses mRNA expression of peroxisomal proliferator-activating receptor-γ (PPARγ)-responsive genes and inhibits differentiation. We investigated whether Vpr might interact with PPARβ/δ and influence its transcriptional activity. In the presence of PPARβ/δ, Vpr induced a 3.3-fold increase in PPAR response element-driven transcriptional activity, a 1.9-fold increase in pyruvate dehydrogenase kinase 4 (PDK4) protein expression, and a 1.6-fold increase in the phosphorylated pyruvate dehydrogenase subunit E1α leading to a 47% decrease in the activity of the pyruvate dehydrogenase complex in HepG2 cells. PPARβ/δ knockdown attenuated Vpr-induced enhancement of endogenous PPARβ/δ-responsive PDK4 mRNA expression. Vpr induced a 1.3-fold increase in mRNA expression of both carnitine palmitoyltransferase I (CPT1) and acetyl-coenzyme A acyltransferase 2 (ACAA2) and doubled the activity of β-hydroxylacyl coenzyme A dehydrogenase (HADH). Vpr physically interacted with the ligand-binding domain of PPARβ/δ in vitro and in vivo. Consistent with a role in energy expenditure, Vpr increased state-3 respiration in isolated mitochondria (1.16-fold) and basal oxygen consumption rate in intact HepG2 cells (1.2-fold) in an etomoxir-sensitive manner, indicating that the oxygen consumption rate increase is β-oxidation-dependent. The effects of Vpr on PPAR response element activation, pyruvate dehydrogenase complex activity, and β-oxidation were reversed by specific PPARβ/δ antagonists. These results support the hypothesis that Vpr contributes to impaired energy metabolism and increased energy expenditure in HIV patients.
HIV感染及其治疗与脂质代谢和生物能量学紊乱有关。先前的研究表明，病毒蛋白R（Vpr）可能与HIV-1感染患者中观察到的脂肪代谢障碍和胰岛素抵抗的发生有关。在脂肪细胞中，Vpr抑制过氧化物酶体增殖物激活受体γ（PPARγ）反应性基因的mRNA表达并抑制分化。我们研究了Vpr是否可能与PPARβ/δ相互作用并影响其转录活性。在存在PPARβ/δ的情况下，Vpr诱导PPAR反应元件驱动的转录活性增加3.3倍，丙酮酸脱氢酶激酶4（PDK4）蛋白表达增加1.9倍，磷酸化的丙酮酸脱氢酶亚基E1α增加1.6倍，导致HepG2细胞中丙酮酸脱氢酶复合物的活性降低47%。PPARβ/δ敲低减弱了Vpr诱导的内源性PPARβ/δ反应性PDK4 mRNA表达的增强。Vpr诱导肉碱棕榈酰转移酶I（CPT1）和乙酰辅酶A酰基转移酶2（ACAA2）的mRNA表达增加1.3倍，并使β-羟酰基辅酶A脱氢酶（HADH）的活性增加一倍。Vpr在体外和体内与PPARβ/δ的配体结合域发生物理相互作用。与在能量消耗中的作用一致，Vpr以依托莫昔芬敏感的方式增加分离线粒体中的状态3呼吸（1.16倍）和完整HepG2细胞中的基础氧消耗率（1.2倍），表明氧消耗率的增加是β-氧化依赖性的。Vpr对PPAR反应元件激活、丙酮酸脱氢酶复合物活性和β-氧化的影响被特异性PPARβ/δ拮抗剂逆转。这些结果支持了Vpr导致HIV患者能量代谢受损和能量消耗增加的假说。
