Abstract 3535: Overexpression of Coupling Factor 6 Links Hypertension to Diabetes by C-Src-Mediated Signaling Pathway in Mice
The lower intracellular pH values are commonly observed in various hypertensive states. It is also reported that intracellular acidosis is associated with the genesis of diabetes by insulin resistance in the skeletal muscle. We recently showed that the molecular rotary motor F1Fo complex, ATP synthase, is present at the plasma membrane, and that endogenous prostacyclin inhibitor coupling factor 6 (CF6), a component of ATP synthase, forces the backward rotation of Fo after binding to F1 at the plasma membrane, resulting in tissue acidosis. Using CF6-overexpressing transgenic (TG) mice, we tested the hypothesis that CF6 is a key molecule for the linkage of hypertension with diabetes. In TG mice, the introduced gene of human CF6 was expressed in overall tissues, and upregulated by 2 fold. Systolic arterial blood pressure at baseline measured by tail-cuff method under conscious state was elevated in TG mice compare with wild type (WT) mice at the age of 15 through 20 weeks (120±5 mmHg vs 110±3 mmHg, p<0.05). In the mesenteric arterioles obtained from TG mice, angiotensin II-induced vasoconstriction was enhanced compared with WT mice (p<0.05). Pretreatment with PP1, a c-Src inhibitor, blocked this angiotensin II-induced enhancement in TG mice. When the mice were fed with high-sucrose diet (20%) for 8 weeks, the TG mice exhibited insulin resistance: The levels of 12 hour-fasted plasma glucose and insulin were both increased in TG mice compared with WT mice (glucose,133±10 vs 108±1 mg/dl; insulin,698±87 vs 295±55 pg/ml, both p<0.05). In glucose-tolerance test, the plasma glucose level was higher until 1.5 hours (p<0.05, two-way ANOVA) and insulin level at 1 hour was higher by 2 fold in TG mice (1111±118 vs 400±54 pg/ml, p<0.05). The TG mice exhibited the decreases in the protein expression of insulin receptor substrate (IRS)-1 by 64±9% and the plasma membrane-bound GLUT-4 protein by 69±11% in skeletal muscle (n=5, both p<0.05). In the cultured skeletal myocyte cell line C2C12, CF6 at 10−7M phosphorylated phosphoinositide-dependent kinase-1 by acidosis-induced c-Src activation, and resulted in serine307 phosphorylation and degradation of IRS-1. These indicate that CF6 links hypertension to diet-induced type 2 diabetes by the common signaling pathway of c-Src.