Coenzyme Q10 and key enzyme activities in papillary muscle related to left ventricle function in mitral valve disease.

Coenzyme Q10 (CoQ10) was studied in papillary muscle from 18 patients (52-67 years, 2 females) subjected to open heart surgery due to mitral valve disease. In addition the enzyme activities of lactate dehydrogenase (LD) with its five isozymes, citrate synthase (CS) and mitochondrial CK (CK-MIT) were determined. Myocardial function was assessed by means of left ventricle (LV) angiography. CoQ10 averaged 0.39 (range 0.26-0.59) micrograms x mg-1 dw. On an individual basis CoQ10 was related to CS activity although not as closely as CK-MIT (r = 0.45, p less than 0.05 versus r = 0.86, p less than 0.001). The ratio (CoQ10) x (CS activity)-1 was calculated to represent mitochondrial quality. The level of LD3 fraction increase was used to mark for the degree of metabolic stress in the heart. LD3 fraction was negatively related to the quality index (r = -0.71, p less than 0.001). Thus, those with a low CoQ10 per unit of CS activity had also a high LD3 isozyme fraction. In a subset of 12 patients with isolated mitral regurgitation due to myxomatous valve degeneration, CoQ10 and the ratio CoQ10 over CS decreased with the degree of LV function impairment (r = -0.58, p less than 0.05 and r = -0.68, p less than 0.05, respectively). The quality index takes into account not only enzyme activity but also the potential for control of free oxygen radicals.