L-Arginine
Andrew Hoey discussed another consequence of the missing dystrophin, the reduced amount of one particular component of the dystrophin-glycoprotein complex, the enzyme neuronal nitric oxide synthase, nNOS.
This enzyme produces nitric oxide, NO, from the amino acid Larginine. Although NO is a gas, it acts like a hormone and regulates, among other effects, the dilation of blood vessels which is important for the normal supply of blood and therefore of energy to the muscles. When nNOS is missing, cardiac fibrosis develops and this may be the cause of increased fibrosis in hearts of mdx mice and also of Duchenne patients.
Daily administration of L-arginine for 6 months commencing in 6-month old mdx mice reduced the fibrosis in their hearts, increased the coronary blood flow and improved their heart function. In ongoing experiments, the mechanism of this effect of L-arginine is being investigated before much further work can be done to see whether L-argine can become a drug for Duchenne boys.
From Günter Scheuerbrandt Report of the PPMD Conference 2006: