The rationale for someone with diabetics increasing glutathione is based on the evidence contained in the abstracts below, which describe the role of oxidative stress in diabetes. Other supporting abstracts can also be found.
Glutathione plays a crucial role in maintaining the oxidant/anti oxidant balance. When glutathione is depleted this tilts the balance in favor of the oxidants - this results in oxidative stress. This contributes to cardiovascular disease, cataracts and neuropathy in diabetes. Glutathione helps scavenge the free radicals and thus reduce the risk of developing complications.