Metabolism of protocatechuic acid influences fatty acid oxidation in rat heart: new anti-angina mechanism implication.
Protocatechuic acid (PA), a structurally typical phenolic acid in danshen, shows anti-angina efficacy. But until now, besides scavenging of oxygen free radicals, the understanding of its anti-angina mechanism has been limited. In our study, based on a novel metabolic route of PA identified in rat heart and its influence on fatty acid oxidation (FAO), we proposed a new mechanism for its anti-angina. In detail, three metabolites, catechol methylated metabolite, acyl-coenzyme (CoA) thioester and glycine conjugation, were identified in rat heart. A novel metabolic pathway was confirmed based on several metabolic systems incubated with heart mitochondria, cytosol, microsomes and homogenate. Results indicated that PA was firstly methylated in microsomes and cytosol, which was regarded as the prerequisite step for further metabolism and could be inhibited by tolcapone, and then the resulting methylated metabolite (vanillic acid) diffused into mitochondria where it was converted into acyl-CoA thioester, in similar with FAO. In addition, part of the acyl-CoA thioester was transformed into glycine conjugation, a step also localized within mitochondria. Furthermore, based on isolated rat heart perfusion, it was found that PA markedly decreased FAO, which was shown by higher residual fatty acid level in perfusate (p<0.05) and lower acy-CoA/CoA ratio in heart (p<0.05). The FAO inhibiting effect of PA could be largely reversed by its methylation inhibitor tolcapone, indicating the effect was closely related with the identified metabolic pathway of PA in heart. The decrease of FAO may switch heart energy substrate preference from fatty acid to glucose, which is beneficial for ischemia heart.
Cao
Yan-Guang
YG
Center of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing City 210009, PR China.
Zhang
Lin
L
Ma
Chen
C
Chang
Bo-Bo
BB
Chen
Yuan-Cheng
YC
Tang
Yi-Qun
YQ
Liu
Xiao-Dong
XD
Liu
Xiao-Quan
XQ
D000789:Angina, Unstable / Q000378:metabolism* / Q000517:prevention & control*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism*; D006321:Heart / Q000502:physiology*; D062385:Hydroxybenzoates / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley
D005227:Fatty Acids; D062385:Hydroxybenzoates; C009091:protocatechuic acid