Mitochondrial coenzyme q and oxidative phosphorylation in brain and myocardium of control and diabetic rats

Brain-heart relations in mitochondrial CoQ concentrations and in oxidative phosphorylation functions are examined in control rats and in rats made diabetic by streptozotocin injection. Rats were synchronized to a lighting regimen of 12 hours of light alternating with 12 hours of darkness, in two rooms with antiphasic regimens. Brain-heart relations were assessed by linear regression of original data for each variable, separately for control and diabetic rats. Maximal values of CoQ concentrations were found to be higher in the myocardium than in the brain of both groups. Maximal CoQ concentrations in the heart were lower in diabetic than in control rats. Whereas CoQ concentrations are non-significantly negatively correlated between heart and brain in control rats, they are statistically significantly positively correlated in diabetic rats. A statistically significant positive heart-brain correlation is also found for mitochondrial State 3 for Complex II and for OPR for Complex I in diabetic rats. A consistent positive heart-brain relation is found for ADP:O, reaching borderline statistical significance for Complex II in both control and diabetic rats. A strong positive heart-brain relation also characterizes S4 for Complex II in both control and diabetic rats. By contrast, no heart-brain relation could be detected in the case of RCI. CoQ production was reduced at Complex II of the respiratory chain only in diabetic rats. The stronger heart-brain relations observed in diabetic rats may be manifestations of a disrupted circadian system perhaps related to damaged mitochondrial function in diabetes. These observations may also account in part for the increased brain and cardiovascular risk associated with diabetes.