Several companies provide arginine/citruline supplements that induce the production of endogenous intracellular Nitric Oxide.  Nitric Oxide is a mediator molecule that causes the vascular musculature to dilate.  This in turn can restore blood flow to the heart, brain, and periphery caused by atherosclerosis and arteriosclerosis, as well as tissues compromised by damage to the vasculature due to diabetes.  There have been reports of calcific arteriosclerosis reversing because of this formula.  I have seen hypertension and angina resolved due to the dilation of the central and peripheral vasculature.

The treatment period to significant resolution of symptoms is usually about 3 months to see a significant restoration of function and reduction of symptoms, although the time may be much longer or shorter.  A wide range of symptoms have been ameliorated with this therapy, simply because the blood flow to tissues was augmented by vascular dilation.  

The mechanism of action of Argiinine/Citrulline is proposed to be the stimulation of an enzyme (Nitric Oxide Synthetase) which is responsible for the formation of Nitric Oxide.  The nitric oxide in turn participates in a cascade of actions which ultimately results in the dilation of the vascular musculature.