Ischemia-stimulated glucose uptake does not require catecholamines in rat heart

Area of Science:

• Cardiovascular Physiology
• Metabolic Regulation

Background:

• Insulin is a primary regulator of cardiac glucose uptake.
• The role of ischemia in modulating cardiac glucose metabolism independent of known pathways is not fully understood.

Purpose of the Study:

• To investigate whether ischemia stimulates glucose uptake in the rat heart independently of the insulin signaling pathway and endogenous catecholamines.
• To elucidate the mechanisms underlying ischemia-induced cardiac glucose uptake.

Main Methods:

• Isolated working rat hearts were perfused with glucose and oleate.
• Hearts were treated with insulin or subjected to low-flow ischemia and reperfusion.
• The phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin and adrenergic blockers (propranolol and phentolamine) were used to assess pathway involvement.

Main Results:

• Both insulin and ischemia significantly increased cardiac glucose uptake.
• Wortmannin abolished insulin-stimulated glucose uptake but did not affect ischemia-stimulated uptake.
• Adrenergic blockade did not inhibit ischemia-stimulated glucose uptake.
• Glycogen resynthesis during reperfusion was independent of PI3-K.

Conclusions:

• Insulin and ischemia stimulate cardiac glucose uptake through distinct mechanisms.
• Ischemia-induced glucose uptake is not mediated by catecholamines.
• Glycogen resynthesis post-ischemia is independent of the PI3-K pathway.