Determining the Biological Effects of Mitochondrial Acyl Toxicity

项目总结 在急性代谢应激和慢性代谢性疾病期间，如肥胖和糖尿病， 脂肪酸氧化中间代谢物长期以来一直被怀疑具有毒性。在这些可能性中 脂毒性代谢物是长链酰基肉碱(LCACs)，据称它会干扰关键的生理功能 这些过程包括胰岛素信号、钙稳态和线粒体功能。然而， 将这些过程中的缺陷与LCAC积累机械地联系起来一直是困难的，因为缺乏 LCAC-积累临床前模型。我们克服了这一障碍，开发了一种独特的小鼠模型 通过缺失分解LCACs的酶--肉碱棕榈酰基转移酶-2来实现LCAC的蓄积 在骨骼肌中(Cpt2Sk-/-)。与LCACs对生物学的影响的可疑作用相一致，我们的初步研究 数据表明，Cpt2Sk-/-肌肉的力量产生减少，线粒体功能障碍。我们的 初步数据还显示，氧化性肌肉纤维中LCACs的大量积累，因此是最多的 易受潜在的LCAC毒性影响。虽然我们的Cpt2Sk-/-型号提供持续提升的LCAC，但 由于线粒体粮农组织缺乏而导致的能量匮乏，使生理结果变得混乱。为了减轻 围绕这个令人困惑的变量，我们将使用三个免费的小鼠肌肉模型- 粮农组织特有的缺陷：1)Cpt2Sk-/-在整个细胞内积累LCACs；2)肉碱酰卡尼汀转位酶 (CactSk-/-)小鼠，在线粒体外积累LCACs；3)酰基辅酶A合成酶1(Acsl1Sk-/-) 完全不积累LCAC的小鼠。在这里，我们将使用这三个模型系统来确定 LCACs对胰岛素信号、钙稳态和线粒体功能的影响。结果将是第一个提供 揭示LCACs对细胞生理的直接和间接影响所必需的实验对比。

PROJECT SUMMARY During acute metabolic stress and chronic metabolic disease, such as obesity and diabetes, the accumulation of fatty acid oxidation intermediary metabolites has long been suspected of toxicity. Among these possible lipotoxic metabolites are long-chain acylcarnitines (LCACs), which purportedly interfere with critical physiological processes including insulin signaling, calcium homeostasis, and mitochondrial function. However, mechanistically linking defects in these processes to LCAC accumulation has been difficult due to a lack of LCAC-accumulating pre-clinical models. We overcame this barrier by developing a unique mouse model of LCAC accumulation by deleting the enzyme that catabolizes LCACs, carnitine palmitoyltransferase-2 specifically in skeletal muscle (Cpt2Sk-/-). Consistent with the suspected roles of LCACs effects on biology, our preliminary data demonstrate that Cpt2Sk-/- muscles have reduced force production and mitochondrial dysfunction. Our preliminary data also demonstrate large accumulation of LCACs within oxidative muscle fibers, thus are the most vulnerable to potential LCAC toxicity. While our Cpt2Sk-/- model provides consistently elevated LCACs, the physiological outcomes are confounded by energy deprivation due to mitochondrial FAO deficiency. To mitigate concerns surrounding this confounding variable, we will employ three complimentary mouse models of muscle- specific FAO deficiency: 1) Cpt2Sk-/- that accumulate LCACs across the cell; 2) carnitine acylcarnitine translocase (CactSk-/-) mice that accumulate LCACs outside of the mitochondria; and 3) acyl-CoA synthetase 1 (Acsl1Sk-/-) mice that do not accumulate LCACs at all. Here, we will use this three-model system to determine the role of LCACs on insulin signaling, calcium homeostasis, and mitochondrial function. Results will be the first to provide requisite experimental contrast to unveil direct versus indirect effects of LCACs on cell physiology.