Role of SNRK in cardiac metabolism and development of heart failure

 描述（由申请人提供）：心力衰竭（HF）是发达国家发病率和死亡率的主要原因，但导致HF发生的分子机制尚未完全了解。哺乳动物Snf 1相关激酶（SNRK）是一种丝氨酸/苏氨酸激酶，与AMP激活激酶（AMPK）具有序列相似性;然而，其主要功能尚不清楚。为了更好地确定SNRK在心脏代谢中的功能，我们已经产生了在心脏中过表达SNRK的转基因（TG）小鼠。SNRK TG小鼠显示葡萄糖和脂肪酸（FA）氧化减少30- 50%，尽管保持正常的心脏功能，但耗氧量减少，表明它们在底物利用方面更有效。代谢效率的机制似乎是通过改善线粒体偶联，因为SNRK TG小鼠中解偶联蛋白（UCP）-3水平降低，状态3/状态4呼吸增加。为了确定SNRK调节线粒体偶联的机制，我们进行了酵母双杂交筛选以鉴定SNRK的新结合伴侣。Tribbles同源物3（Trib 3）是Akt活化和葡萄糖代谢的负调节剂，被发现与SNRK结合并被SNRK上调。我们还发现SNRK通过涉及Trib 3和PPARα的途径调节UCP 3和线粒体偶联。该提议的中心假设是SNRK通过减少底物利用和增加线粒体偶联来影响心脏代谢，并且SNRK过表达防止HF和缺血性损伤的发展。在目的1中，我们将评估SNRK的缺失是否会导致其过表达的相反表型，即，增加葡萄糖和FA代谢，具有相似的心力。我们已经产生了全局SNRK+/-小鼠和心脏特异性SNRK敲除（KO）小鼠，并将测量这些动物的心脏代谢参数。我们还将评估Trib 3、UCP 3和PPARα在这一过程中的作用。在目标2中，我们将测试SNRK TG小鼠心脏中发生的葡萄糖和FA代谢降低是否是通过Trib 3介导的。我们已经产生了SNRK TG/Trib 3 KO小鼠，并将测量它们心脏中的葡萄糖和FA代谢。我们还将研究SNRK对Trib 3的调节机制，以及Trib 3对PPARα的调节机制。最后，在目标3中，我们将确定SNRK是否对HF和缺血性损伤的发展具有保护作用，并将研究这种保护作用的机制。我们将使SNRK TG小鼠经受缺血再灌注和压力超负荷，随后测量心脏功能和活性氧产生（使用新型荧光探针）。为了确定其机制，我们将评估Trib 3/PPARα/UCP 3通路在这一过程中的作用。我们的研究表明，SNRK降低FA和葡萄糖代谢，改善线粒体偶联有望提高我们对心脏代谢在HF中的作用的认识，并可能导致这种疾病的新疗法的开发。

 DESCRIPTION (provided by applicant): Heart failure (HF) is a major cause of morbidity and mortality in the developed world, but the molecular mechanisms that lead to the development of HF are not totally understood. Mammalian Snf1-related kinase (SNRK) is a serine/threonine kinase with sequence similarity to AMP-activated kinases (AMPK); however, its primary function is unknown. To better define the function of SNRK in cardiac metabolism, we have generated a transgenic (TG) mice that overexpress SNRK in the heart. SNRK TG mice display 30- 50% less glucose and fatty acid (FA) oxidation and have reduced oxygen consumption despite maintaining normal cardiac function, suggesting that they are more efficient in substrate utilization. The mechanism for metabolic efficiency appears to be through improved mitochondrial coupling, as the levels of uncoupling protein (UCP)-3 are reduced in SNRK TG mice, and state 3/state 4 respiration is increased. To determine the mechanism by which SNRK regulates mitochondrial coupling, we performed a yeast two hybrid screen to identify novel binding partners of SNRK. Tribbles homolog 3 (Trib3), a negative regulator of Akt activation and glucose metabolism, was found to bind to and be upregulated by SNRK. We also showed that SNRK regulates UCP3 and mitochondrial coupling through a pathway that involves Trib3 and PPARα. The central hypothesis of this proposal is that SNRK affects cardiac metabolism by reducing substrate utilization and increasing mitochondrial coupling, and that SNRK overexpression protects against the development of HF and ischemic injury. In Aim 1, we will assess whether deletion of SNRK will result in the opposite phenotype of its overexpression, i.e., increased glucose and FA metabolism with similar cardiac force. We have generated global SNRK+/- mice and cardiac-specific SNRK knockout (KO) mice, and will measure cardiac metabolic parameters in these animals. We will also assess the role of Trib3, UCP3 and PPARα in this process. In Aim 2, we will test whether the reduced glucose and FA metabolism that occurs in the hearts of SNRK TG mice is mediated through Trib3. We have generated SNRK TG/Trib3 KO mice, and will measure glucose and FA metabolism in their hearts. We will also investigate the mechanism of Trib3 regulation by SNRK, and PPARα regulation by Trib3. Finally, in Aim 3, we will determine whether SNRK is protective against the development of HF and ischemic damage, and will study the mechanism for this protective effect. We will subject SNRK TG mice to ischemia-reperfusion and pressure overload, followed by the measurement of cardiac function and reactive oxygen species production (using novel fluorescence probes). To determine the mechanism, we will assess the role of Trib3/PPARα/UCP3 pathway in this process. Our studies showing that SNRK reduces FA and glucose metabolism and improves mitochondrial coupling promise to advance our knowledge of the role of cardiac metabolism in HF, and may lead to the development of novel therapies for this disorder.