TY - JOUR
T1 - Brain glycogen and its role in supporting glutamate and GABA homeostasis in a type 2 diabetes rat model
AU - Sickmann, Helle Mark
AU - Waagepetersen, Helle S.
AU - Schousboe, Arne
AU - Benie, Andrew James
AU - Bouman, Stephan Daniel
N1 - Copyright © 2012 Elsevier Ltd. All rights reserved.
PY - 2012/2
Y1 - 2012/2
N2 - The number of people suffering from diabetes is hastily increasing and the condition is associated with altered brain glucose homeostasis. Brain glycogen is located in astrocytes and being a carbohydrate reservoir it contributes to glucose homeostasis. Furthermore, glycogen has been indicated to be important for proper neurotransmission under normal conditions. Previous findings from our laboratory suggested that glucose metabolism was reduced in type 2 diabetes, and thus we wanted to investigate more specifically how brain glycogen metabolism contributes to maintain energy status in the type 2 diabetic state. Also, our objective was to elucidate the contribution of glycogen to support neurotransmitter glutamate and GABA homeostasis. A glycogen phosphorylase (GP) inhibitor was administered to Sprague-Dawley (SprD) and Zucker Diabetic Fatty (ZDF) rats in vivo and after one day of treatment [1-(13)C]glucose was used to monitor metabolism. Brain levels of (13)C labeling in glucose, lactate, alanine, glutamate, GABA, glutamine and aspartate were determined. Our results show that inhibition of brain glycogen metabolism reduced the amounts of glutamate in both the control and type 2 diabetes models. The reduction in glutamate was associated with a decrease in the pyruvate carboxylase/pyruvate dehydrogenase ratio in the control but not the type 2 diabetes model. In the type 2 diabetes model GABA levels were increased suggesting that brain glycogen serves a role in maintaining a proper ratio between excitatory and inhibitory neurotransmitters in type 2 diabetes. Both the control and the type 2 diabetic states had a compensatory increase in glucose-derived (13)C processed through the TCA cycle following inhibition of glycogen degradation. Finally, it was indicated that the type 2 diabetes model might have an augmented necessity for compensatory upregulation at the glycolytic level.
AB - The number of people suffering from diabetes is hastily increasing and the condition is associated with altered brain glucose homeostasis. Brain glycogen is located in astrocytes and being a carbohydrate reservoir it contributes to glucose homeostasis. Furthermore, glycogen has been indicated to be important for proper neurotransmission under normal conditions. Previous findings from our laboratory suggested that glucose metabolism was reduced in type 2 diabetes, and thus we wanted to investigate more specifically how brain glycogen metabolism contributes to maintain energy status in the type 2 diabetic state. Also, our objective was to elucidate the contribution of glycogen to support neurotransmitter glutamate and GABA homeostasis. A glycogen phosphorylase (GP) inhibitor was administered to Sprague-Dawley (SprD) and Zucker Diabetic Fatty (ZDF) rats in vivo and after one day of treatment [1-(13)C]glucose was used to monitor metabolism. Brain levels of (13)C labeling in glucose, lactate, alanine, glutamate, GABA, glutamine and aspartate were determined. Our results show that inhibition of brain glycogen metabolism reduced the amounts of glutamate in both the control and type 2 diabetes models. The reduction in glutamate was associated with a decrease in the pyruvate carboxylase/pyruvate dehydrogenase ratio in the control but not the type 2 diabetes model. In the type 2 diabetes model GABA levels were increased suggesting that brain glycogen serves a role in maintaining a proper ratio between excitatory and inhibitory neurotransmitters in type 2 diabetes. Both the control and the type 2 diabetic states had a compensatory increase in glucose-derived (13)C processed through the TCA cycle following inhibition of glycogen degradation. Finally, it was indicated that the type 2 diabetes model might have an augmented necessity for compensatory upregulation at the glycolytic level.
U2 - 10.1016/j.neuint.2011.12.019
DO - 10.1016/j.neuint.2011.12.019
M3 - Journal article
C2 - 22244844
SN - 0197-0186
VL - 60
SP - 267
EP - 275
JO - Neurochemistry International
JF - Neurochemistry International
IS - 3
ER -
