OPTN and diabetes mellitus: Interestingly, we found no differences in OPTN expression in retinas between control retinas from normal glucose (NM) rats and rats with STZ-induced diabetes mellitus (DM) at 2, 4, 8, and 12 weeks (Fig. 3A, B); however, a time-dependent increase in the level of global succinylation was detected starting from 2 weeks after STZ treatment compared to the control treatments (Fig. 3A).