Human Tissue Kallikrein Gene Delivery Attenuates Cardiac Glycogen Accumulation in Streptozotocin-Induced Diabetic Rats
The tissue kallikrein-kinin system is locally present in the heart and is reduced under diabetic conditions. In the present study, we explored the effects of kallikrein gene delivery in the heart under diabetic conditions. Intravenous injection of streptozotocin (STZ) (60mg/kg) into 8-week-old male Sprague-Dawley rats produced hyperglycemia (460 ± 10 mg/dl, n=30). Three weeks after STZ treatment, adenovirus containing the human tissue kallikrein gene (Ad.CMV-cHK) or green fluorescence protein gene (Ad.CMV-GFP) under the control of CMV promoter/enhancer were injected via the tail vein into STZ-diabetic rats. Adenovirus-mediated kallikrein gene delivery caused a significant reduction of blood pressure as compared to control rats receiving control virus (170.8 ± 3.5 vs. 187.4 ± 4.2 mmHg, n=8, P<0.01). Rats were sacrificed and tissues were collected for analysis at 16 days after gene delivery. Histological examination of heart sections stained with periodic acid-Schiff (PAS) showed marked accumulation of glycogen in cardiomyocytes of diabetic rats. Kallikrein gene delivery significantly reduced cardiac glycogen accumulation as compared to rats receiving control adenovirus. Quantitative analysis confirmed the morphological observation that kallikrein gene delivery significantly reduced cardiac glycogen levels as compared to control diabetic rats injected withAd.CMV-GFP (0.5 ± 0.07 vs. 2.15 ± 0.83 mg glycogen/mg protein, n=6, P<0.05). Cardiac cAMP levels were significantly increased after kallikrein gene delivery. This is the first study to demonstrate that kallikrein gene delivery exerts a protective effect in the reduction of glycogen accumulation in cardiomyocytes of STZ-induced diabetic rats.