0366: A role for focal adhesion kinase in the stimulation of glucose transport in cardiomyocytes

Abstract

Stimulation of glucose transport in response to insulin or metabolic stress is an important determinant of cardiomyocytes function and survival, particularly during ischemia-reperfusion episodes. Stimulation of glucose transport is markedly impaired in cardiomyocytes exposed to free fatty acids (FA), despite relative preservation of insulin- or metabolic stress signaling. To determine whether Focal Adhesion Kinase (FAK) activity is required for stimulation of glucose transport in cardiomyocytes, and whether FAK downregulation participates in FA-induced impairment of glucose transport stimulation. Glucose transport, measured in isolated cardiomyocytes, was acutely stimulated either by insulin treatment, or by metabolic inhibition with oligomycin resulting in AMP-activated kinase (AMPK) activation. FAK activity was inhibited pharmacologically by preincubation with PF-573,228 (PF). FAK activity was assessed from its autophosphorylation on residue Y397, and from the phosphorylation of paxillin on Y118. Y397 FAK phosphorylation was reduced in cardiomyocytes chronically exposed to FA. Preincubation with PF prior to determination of glucose transport resulted in a significant reduction of oligomycin-stimulated glucose transport, with a modest reduction in insulin-stimulated glucose transport. Insulin and AMPK signaling was unaffected by PF preincubation. Intriguingly metabolic stress provoked Y397 FAK dephosphorylation and deactivation, as evidenced by a concomitant reduction in Y118 paxillin phosphorylation. stimulation of glucose transport by insulin or metabolic stress in cardiomyocytes requires FAK activity prior to stimulation; FAK activity is however acutely reduced during metabolic stress. The chronic reduction of FAK activity in cardiomyocytes exposed to FFA partially explains the loss of glucose transport responsiveness to insulin or metabolic inhibition.