There was a inhaled orally insulin in US until recently. It was made by Pfizer, and was called Exubera. However, it was not easy to titrate doses, caused irritation and patient acceptance was low. So they stopped making it.

The insulin for nasal application is different as it goes thru the nerves in the olfactory bulb in the nose directly to the brain.
Insulin does not cross the blood brain barrier, and so what gets into the brain will not come out. How to get the nasal to do both jobs then for the body and brain is problematic dose wise because insulin is very carefully measured for each person's needs.
I believe what was used in the studies is something that is not FDA approved yet for mass consumption.

Here is more to read about it:
http://www.diabetesnet.com/about-dia...nhaled-insulin

Type 3 diabetes, is relatively new, and low insulin in the brain is also tied to other neurological conditions in the brain, like Parkinson's as well. With some time, we may hear more about this.

But understand that nasal application of drugs goes to the brain rapidly and because of that one needs to be very careful with neti pots or other drugs. Cocaine of course is the most well known...and chronic use of IT erodes the septum and destroys the membranes as well as the nose being the royal road to euphoria.