Novel Approaches to Treatment and Prevention of Diabetic Nephropathy

Abstract: Several studies have reported beneficial effects of C-peptide supplementation in diabetic patients and animal models of insulinopenic diabetes. However, it is also established that good glycemic control is essential to minimize the risk of diabetes-induced complications. This thesis investigates potential mechanisms for the beneficial effect of C-peptide on glomerular hyperfiltration, and a novel, painless route of insulin administration.The results demonstrate that both C-peptide and its C-terminal penta-peptide sequence reduce the diabetes-induced glomerular hyperfiltration within an hour. The results also indicate that C-peptide possibly reduces diabetes-induced hyperfiltration via three different mechanisms: 1. Constriction of the afferent arteriole was demonstrated on isolated vessels from diabetic mice. 2. A net dilation of the efferent arteriole was evident in vivo. 3. Inhibition of the Na+/K+-ATPase was demonstrated in vivo in diabetic rats as well as in vitro on isolated proximal tubular cells from diabetic rats. All these mechanisms are known regulators of the net glomerular filtration pressure.The last part of this thesis demonstrates that intradermal administration with a newly developed patch-like microneedle device results in similar insulin concentration compared to standard subcutaneous delivery.These findings provide an insight for the beneficial effects of C-peptide on diabetic kidney function, and shows that this effect can be achieved by infusion of the C-terminal penta-peptide sequence alone. This thesis also presents a novel, painless alternative to insulin injections that is controllable, requires minimal training, and therefore presents several advantages compared to current standard therapy.