AS160是胰岛素通路远端分子，可调控骨骼肌和脂肪中葡萄糖转运体GLUT4转位，进而调控葡萄糖稳态。它有两种剪接体L型和S型，骨骼肌和心脏主要表达L型剪接体，而S型主要存在于其它组织中。近期临床研究发现人群中存在一种AS160 p.R684X提前终止突变，该突变只存在于L型剪接体上，导致携带者罹患2型糖尿病。但该突变的致病机理尚不清楚。申请人前期对大鼠相应位点进行突变，制备了AS160R693X突变大鼠模型，发现它与病人类似，也会罹患2型糖尿病，表现出餐后高血糖、高胰岛素血症。并且申请人还发现AS160酶失活突变抑制小鼠心肌细胞吸收葡萄糖，但促进脂肪酸吸收。因此，申请人提出“AS160R684X突变可抑制骨骼肌葡萄糖吸收，但促进骨骼肌吸收利用脂肪酸，它与饮食互作最终导致2型糖尿病”的假说。本项目将利用AS160R693X突变大鼠模型结合多种生物学方法对这一假说进行深入研究。

AS160 is a distal signaling molecule in the insulin pathway, and plays an important role in glucose homeostasis by regulating translocation of glucose transporter 4 in the skeletal muscle and fat tissues in response to insulin stimulation. It has two splicing variants, long form and short form, which have distinct tissue expression patterns. The long form is dominant in the heart and skeletal muscle while the short form is mainly expressed in other tissues. A recent clinical study identified a pre-mature truncation mutation p.Arg684Ter on AS160 in the Inuit population. Patients bearing this mutation develop type 2 diabetes (T2D), and exhibit post-prandial hyperglycemia and hyperinsulinemia. However, the molecular mechanism underlying the pathogenesis of T2D in these patients is not clear. To address this question, we generated a rat model in which the orthologous site Arg693 on AS160 was mutated to a stop codon. Similar as the human patients, the resultant AS160Arg693Ter rat also developed T2D, displaying post-prandial hyperglycemia and hyperinsulinemia. These preliminary data demonstrate that the AS160Arg693Ter rat can model human patients bearing the AS160Arg684Ter mutation. Moreover, we found that insulin-stimulated glucose uptake was inhibited while lipid uptake was enhanced in primary cardiomyocytes isolated from the mice bearing an enzyme-inactive AS160Arg917Lys mutation. The traditional diets of Inuit used to consist of meat but not carbohydrates. We suspect that AS160Arg684Ter mutation might historically help to utilize fat at the expense of glucose absorption in Inuit. The change to carbohydrate-rich diets might cause T2D in these AS160Arg684Ter mutation-bearing patients. We will employ multiple methods to address this hypothesis using the AS160Arg693Ter rat in this proposal.