Deficit of Coenzyme Q in Heart and Liver Mitochondria of Rats with
Streptozotocin-Induced Diabetes
J. Kucharská1, Z. Braunová1,
O. Ulièná 1, L. Zlatoš2,
A. Gvozdjáková1
1Pharmacobiochemical Laboratory and 2Institute of
Pathophysiology, Faculty of Medicine, Comenius University, Bratislava, Slovak
Republic
Received October 6, 1999
Accepted January 18, 2000
Summary
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.kg-1),
insulin was administered once a day for 8 weeks (6 U.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.
Key words
Diabetes mellitus · Mitochondria ·
Alpha-tocopherol · Coenzyme Q ·
Oxidative stress
Reprint requests
J. Kucharská, Pharm.D., Ph.D., Pharmacobiochemical
Laboratory, Faculty of Medicine, Comenius University, Hlboká 7, 811 05
Bratislava, Slovak Republic. Fax: 00421 7 5249 1422.
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