1335-P: Deciphering Liver Glycome Regulation by the PGC-1/FN3K Axis

Diabetes in general, and specifically in the context of obesity, is characterized by hyperglycemia resulting in non-enzymatic glycation of proteins, a key event in the pathophysiology of diabetes and its chronic complications. Yet, the full scope of molecular targets for glycation, particularly in liver, is incompletely understood. De-glycation, which removes the attached sugars, is controlled intracellularly by fructosamine-3-kinase (FN3K) , a kinase that phosphorylates the attached sugar and has been proposed to have a protective role against the deleterious effects of glycation related to diabetes. However, FN3K has been suggested to be ubiquitously expressed and to act as a constitutive housekeeping gene. Furthermore, whether intracellular de-glycation is regulated in physiological contexts and what factors are involved in its regulation remain unknown. Our data identify that regulation of protein glycation in liver is controlled by the key metabolic regulators PGC-1s (PGC-1alpha and PGC-1beta) in response to metabolic cues, particularly in the fed state. Liver-specific deletion of PGC-1s results in reduction of Fn3k expression and concomitant increase in specific protein glycation. In accordance, overexpression of PGC-1alpha in liver-derived cells induces Fn3k and a reduction in protein glycation. Purification of glycated proteins followed by mass spectrometric analysis reveals significant alterations in intracellular protein glycation in response to PGC1-alpha expression. Mechanistically, PGC-1alpha effect on Fn3k involves the activity of the transcription factor Foxo1. Thus, in liver, fasting and re-feeding govern intracellular protein glycation via PGC-1 dependent induction of FN3K. Our work reveals the scope and dynamic nature of the liver glycome, establishing the PGC1/FN3K axis as a key regulator of protein glycation.