Tissue Kallikrein Reverses Insulin Resistance and Attenuates Nephropathy in Diabetic Rats by Activation of Phosphatidylinositol 3-Kinase/Protein Kinase B and Adenosine 5′-Monophosphate-Activated Protein Kinase Signaling Pathways

We previously reported that iv delivery of the human tissue kallikrein (HK) gene reduced blood pressure and plasma insulin levels in fructose-induced hypertensive rats with insulin resistance. In the current study, we evaluated the potential of a recombinant adeno-associated viral vector expressing the HK cDNA (rAAV-HK) as a sole, long-term therapy to correct insulin resistance and prevent renal damage in streptozotocin-induced type-2 diabetic rats. Administration of streptozotocin in conjunction with a high-fat diet induced systemic hypertension, diabetes, and renal damage in rats. Delivery of rAAV-HK resulted in a long-term reduction in blood pressure, and fasting plasma insulin was significantly lower in the rAAV-HK group than in the control group. The expression of phosphatidylinositol 3-kinase p110 catalytic subunit and the levels of phosphorylation at residue Thr-308 of Akt, insulin receptor B, and AMP-activated protein kinases were significantly decreased in organs from diabetic animals. These changes were significantly attenuated after rAAV-mediated HK gene therapy. Moreover, rAAV-HK significantly decreased urinary microalbumin excretion, improved creatinine clearance, and increased urinary osmolarity. HK gene therapy also attenuated diabetic renal damage as assessed by histology. Together, these findings demonstrate that rAAV-HK delivery can efficiently attenuate hypertension, insulin resistance, and diabetic nephropathy in streptozotocin-induced diabetic rats.