This reminds me that we had a cat that developed diabetes. Besides the usual treatment, we changed the cat's diet "radically". Eventually the cat no longer required insulin shots, i.e. it was "cured". I remarked to my wife at the time that maybe the reason T2 diabetes is considered incurable is that it's all but impossible to get humans to radically change their diet.
After a time, however, the process that was killing them off in the first place often reappears and insulin is required again.
The biggest factor I've seen in previous cats with diabetes - dry vs wet food. Switch from free-feeding dry to measured, timed canned portions made a night/day difference.