FFriend, HRH has been fighting against anything more than the "prediabetes" diagnosis for years. He did a little bit of good for himself on the Nutri System "D" (for diabetes) plan for a few months. Lost some weight, brought A1C down some. But general better eating brought it down further, lots of veggies. He didn't stay with the NS any longer, but it probably taught him some things.
He has wished at times that he could do the usual higher protein diet that many try. But the first problem with that is a family tendency toward gout (arthritis), which is unbearable on a high-animal-products diet. Second problem is needing to take good care of his kidneys since he's had so many stones and one operation. Protein needs to be sufficient, but limited.
So except for eggs, he adopted more of the plant based diet for prediabetes. I saw a display of those books today at Whole Foods. I didn't recognize some new ones, but T. Colin Campbell's China Study was there along with both Rip and Caldwell Esselstyn's and Neal Barnard's books, plus the new line of foods from Rip Esselstyn. I bought their unsweetened vanilla almond milk for HRH to try.
He takes the smallest dose of Janumet in extended release form. Dr. didn't think his numbers showed he needed to go on Metformin, but did want him to try this one, which only has a part Metformin in it and only gives a little bit of the med at a time over hours. I didn't see much difference with it, but each good idea helps.
I hope your dh benefits a lot from this course of meds and study (sounds like he will). Also I hope he and others in the study find out they made a contribution in testing out a new med. That would be a good feeling.