There isn't much profit to Big Pharma in doing as he state. Here it is....They have metformin and things like that for the borderline diabetics already so why would they stop you from reaching that particular disease state? If we are speaking in terms of drive for profits only then it is much more profitable to fatten the pig for the slaughter (pun only partially intended). Lots more money to be made from a chronic disease state with some irreversible damage than from catching such a state in the early stages and preventing said damage.
From the other side (the legal and ethical end) artificially lowering insulin in non-diseased individuals would lead to various disease states including hyperglycemia and protein wasting. Basically there is no logical way to market such an item to a person.
Thats if we wanna be all logical about it and ONLY consider the drive for profit.