My physician believes (along with two of my former medical professors) that in Type II Diabetes, when diet and exercise bring blood sugar levels into the healthy range and insulin is no longer needed (by those who used it) then the patient is cured. I'm not sure I accept this. There is some evidence that cinnamon can help to reduce insulin resistance (lay people can read about it at WebMD), but scientific proof is lacking. Otherwise, I think natural cures for diabetes are bunk.
However, NIH shows that 60% of patients with Type I Diabetes can, after receiving a transplant of islets of Langerhans into the pancreas, discontinue use of insulin for some period of time. Clinical trials are ongoing and this is the method I think will be perfected.
Another method is patented and involves introducing a virus to carry insulin-producing genes; but this is in the animal trial stages, nearing the use of human trials. It sounds good, but we'll have to wait for results.
Unless a patient has a miracle, I think there may be no cures... Except for one patient of ours who had Type II Diabetes, suffered a minor head trauma, and never needed insulin again afterward. Freaky.