Simultaneous attenuation of hyperglycemic memory-induced retinal, pulmonary, and glomerular dysfunctions by proinsulin C-peptide in diabetes.

Background: Hyperglycemic memory (HGM) is a pivotal phenomenon in the development of diabetic complications. Although coincident diabetic complications are reported, research on their development and treatment is limited. Thus, we investigated whether C-peptide can simultaneously inhibit HGM-induced retinal, pulmonary, and glomerular dysfunctions in diabetic mice supplemented with insulin.

Methods: Insulin-treated diabetic mice were supplemented with human C-peptide by subcutaneous implantation of K9-C-peptide depots for 4 weeks, and reactive oxygen species (ROS) generation, transglutaminase (TGase) activity, and vascular leakage were examined in the retina, lung, and kidney.

Results: We found hyperglycemia-induced persistent ROS generation and TGase activation after blood glucose normalization in the retina, lung, and kidney of insulin-supplemented diabetic mice. These pathological events were inhibited by systemic supplementation of human C-peptide via subcutaneous implantation of a thermosensitive biopolymer-conjugated C-peptide depot. ROS generation and TGase activation were in a vicious cycle after glucose normalization, and C-peptide suppressed the vicious cycle and subsequent endothelial permeability in human retinal endothelial cells. Moreover, C-peptide supplementation ameliorated HGM-induced retinal vascular leakage and neurodegeneration, pulmonary vascular leakage and fibrosis, and glomerular adherens junction disruption and vascular leakage.

Conclusions: Overall, our findings demonstrate that C-peptide supplementation simultaneously attenuates vascular and neuronal dysfunctions in the retina, lung, and glomerulus of insulin-supplemented diabetic mice.