Effect of Caffeine on Cardiac Tissue Metabolism in Rabbits

Abstract

Caffeine has been reported to influence skeletal muscle tissue metabolism at rest and during exercise (Goldstein et al 2010; Graham et al 1994). This study was designed to investigate the effect of caffeine on cardiac tissue metabolism in the rabbit.The study was carried out on adult male New Zealand rabbits (weighing 1.8–2.2Kg) divided into 3 groups (n=5). Group I rabbits were given 0.2ml/Kg of normal saline and served as control while groups II and III rabbits were administered with 2mg/Kg and 6mg/kg of caffeine respectively for 28 days. Blood samples (3.0ml/rabbit) were collected by retro orbital puncture to determine serum Myeloperoxidase (MPO) activity and nitrite concentration. The animals were sacrificed by cervical dislocation and cardiac tissue biopsies were collected on dry ice for biochemical and immunohistochemical analyses. Cardiac tissue glycogen concentration was determined with the aid of anthrone reagent. Cardiac tissue Carnitine Palmitol Transferase 1 (CPT1) activity and cAMP concentrations were determined by immunohistochemistry and colorimetry techniques respectively, with assay kits obtained from Biovision inc.The results showed that caffeine at 2mg/kg and 6mg/kg significantly inhibited MPO activity from 0.72±0.05 to 0.164±0.045 and 0.46±0.12 U/L respectively (p<0.05). Caffeine at 2mg/kg had no significant effect on serum nitrite concentration but at 6mg/Kg, caffeine significantly increased nitrite concentration from 28.01±6.53 to 45.25±3.88μM (p<0.05). Also caffeine at 2mg/kg and 6mg/kg increased cardiac tissue glycogen concentration from 15.62±0.73 to 40.69±6.35 and 38.82±6.91mg/100g, cAMP concentrations from 5.097±0.29 to 6.840±0.26 and 6.36±0.14 pmol/well and CPT1 activity from 18.3 to 20 and 25.2% respectively (p<0.05).In conclusion, this study demonstrates that caffeine exhibits strong effects on cardiac tissue metabolism thereby causing cardioprotection, cardiac hyperemia, glycogen sparing, increased cAMP concentration and cardiac utilization of fatty acids as source of energy.