Mitochondrial dysfunction and oxidative stress participate in the development of
diabetic complications, however, the mechanisms of their origin are not entirely clear.
Coenzyme Q has an important function in mitochondrial bioenergetics and is also a powerful
antioxidant.
Coenzyme Q (CoQ) regenerates
alpha-tocopherol to its active form and prevents
atherogenesis by protecting
low-density lipoproteins against oxidation. The aim of this study was to ascertain whether the experimentally induced
diabetes mellitus is associated with changes in the content of
endogenous antioxidants (
alpha-tocopherol,
coenzymes Q9 and Q10) and in the intensity of lipoperoxidation. These biochemical parameters were investigated in the blood and in the isolated heart and liver mitochondria. Diabetes was induced in male Wistar rats by a single
intravenous injection of
streptozotocin (45 mg x kg(-1)),
insulin was administered once a day for 8 weeks (6 U x kg(-1)). The concentrations of
glucose,
cholesterol,
alpha-tocopherol and CoQ homologues in the blood of the diabetic rats were increased. The
CoQ9/
cholesterol ratio was reduced. In heart and liver mitochondria of the diabetic rats we found an increased concentration of
alpha-tocopherol, however, the concentrations of
CoQ9 and
CoQ10 were decreased. The formation of
malondialdehyde was enhanced in the plasma and heart mitochondria. The results have demonstrated that experimental diabetes is associated with increased lipoperoxidation, in spite of the increased blood concentrations of
antioxidants alpha-tocopherol and CoQ. These changes may be associated with disturbances of lipid metabolism in diabetic rats. An important finding is that heart and liver mitochondria from the diabetic rats contain less
CoQ9 and
CoQ10 in comparison with the controls. We suppose that the deficit of
coenzyme Q can participate in disturbances of mitochondrial energy metabolism of diabetic animals.