Diabetes, Vol 34, Issue 11 1075-1081, Copyright © 1985 by American Diabetes Association
Pyruvate dehydrogenase activity in cardiac mitochondria from genetically diabetic mice
TH Kuo, F Giacomelli, J Wiener and K Lapanowski-Netzel
Pyruvate dehydrogenase (PDH) was studied in isolated heart mitochondria
from genetically diabetic mice (C57BL/KsJ db/db) with progressive
cardiomyopathy. Both the basal activity (active enzyme) and the total
activity (the sum of active and inactive enzyme) were determined. In
mitochondrial extracts from 8-18-wk-old db/db mice, there was a 73%
decrease of basal activity accompanied by a 38% decrease of total activity
as compared with controls. The lower basal activity at 8 wk of age suggests
an increased conversion of the enzyme into the phosphorylated (inactive)
form. Evidence is also given that the conversion of inactive
(phosphorylated) enzyme into active (dephosphorylated) enzyme is inhibited
in cardiac mitochondria prepared from 8-wk and older db/db mice. These
changes coincide with the onset of defective oxidative metabolism and can
explain the depressed pyruvate oxidation reported previously.