Acute AKT signaling increases glucose phosphorylation and contribution to glycogen in hepatocytes. Stefkovich et al.

Description

Insulin’s regulation of hepatic glucose production and glycogen are critical for postprandial glucose disposal. AKT, a serine-threonine kinase and insulin signaling target, regulates liver glucose metabolism through transcriptional and posttranslational mechanisms. However, current knowledge largely stems from genetic loss of function models, precluding observation of AKT’s non-transcriptional effects. To measure rapid changes to glucose and glycogen metabolism, isotope tracing using [U-13C]-glucose and [U14C]-glucose was coupled with the AKT inhibitor MK-2206 in primary rat hepatocytes. MK-2206 treatment decreased AKT phosphorylation and glucose contribution to glucose 6-phosphate and uridine diphosphate glucose within minutes without affecting metabolite pool sizes or protein levels of glucokinase, glucose 6-phosphatase or phosphoenolpyruvate carboxykinase. MK-2206 also decreased glucose contribution to glycogen, independent of glycogen breakdown or glycogen synthase phosphorylation. These results demonstrate that AKT acutely regulates glucose contribution to glycogen and upstream precursors, suggesting a transcription-independent mechanism proximal to glucose 6-phosphate generation for glycogen synthesis.

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Protein ladder used for western blots is the BioRad Precision Plus Protein Dual Color Standards #1610374. From top to bottom, ladder bands are 250 kDa, 150 kDa, 100 kDa, 75 kDa, 50 kDa, 37 kDa, 25 kDa, 20 kDa, 15 kDa, and 10 kDa. For microscopy images, samples are named such that "Control_1.1" refers to control sample Replicate 1, Field of View #1. In some cases, multiple fields of view were imaged within the same sample and their quantification averaged to ensure a quantification that was as representative of the sample as possible.

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• University of Pennsylvania

  Pennsylvania, Philadelphia

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