MULTIPHASIC METABOLIC CHANGES IN THE HEART OF RATS FED A SUCROSE-RICHDIET

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.