However, protocatechuic acid (50 and 100 mg/kg) could significantly down-regulate the expressions of PKC β (p < 0.05), PKC δ (p < 0.01), PKC ε (p < 0.01) in the cardiac tissue of T2D rats when compared with T2D control rats. The gene discussed is PRKCB; the disease is type 2 diabetes mellitus.