There is an interesting theory that blood levels of nitric oxide are generally low in autism/aspergers. Nitric oxide is very important signaling molecule in the brain.
But also, nitric oxide is a major control system for the opening and closing of arteries. (Incidentally, it is also nitric oxide that is responsible for erection: viagra works by increasing nitric oxide in the penis, and this causes the arteries to dilate and open, thus bringing in more blood).
So if you have poor circulation you you hands and feet, it might be because your arteries are a little on the contracted side, due to low nitric oxide.
One way of raising nitric oxide is to drink beetroot juice, which is high in nitrates, and these nitrates help produce nitric oxide.
Beetroot juice is also a good treatment for high blood pressure (when your arteries are contracted, blood pressure goes up; when your arteries are relaxed (dilated), blood pressure goes down: Drinking beetroot juice lowers blood pressure.
Meditation also naturally increases nitric oxide in the brain.