Long term feeding a sucrose-rich diet (SRD) to normal Wistar rats led
to multiphasic changes in the activity of the pyruvate dehydrogenase c
omplex (PDH), characterized by a significant decrease in PDHa (active
form) in the short term on SRD (3 weeks) when compared to control rats
fed the standard chow (STD). Although PDHa returned spontaneously to
control values in the medium term (6-8 weeks) on SRD, an even more: pr
onounced decrease was recorded when rats were kept long term on the SR
D(15 weeks). Low PDHa levels recorded in the short and long term were
accompanied by a two fold increase in heart acetyl-CoA concentration a
nd the acetyl-CoA/CoASH ratio. Tissue long-chain acyl-CoA and triacylg
lycerol levels were also significantly higher in SRD fed rats. Spontan
eous normalization of all the above metabolic parameters was observed
during the medium term on SRD. Glucose-6-phosphate levels remained wit
hin control values during the short and medium term, in contrast to a
two fold increase recorded in the long term on SRD. Glycogen concentra
tions were found moderately elevated only in the long term. Citrate co
ncentrations were slightly increased in the short and greatly in the l
ong term, and the fructose-2,6-bisphosphate/citrate ratio was found si
gnificantly decreased only during the long term on SRD. After 3 weeks
on SRD, the protal vein Insulin/Glucagon (I/G) molar ratio was three t
imes higher in SRD than STD rats, as opposed to an unchanged I/G ratio
found in the long term. Our findings suggest that the heart muscle of
rats fed chronically a SRD had an impaired glycolytic flux and glucos
e oxidation as a result of increased fatty acids availability probably
secondary to profound and changing shifts in the hormonal and metabol
ic milieu at different time periods of high sucrose intake.