Liver fructokinase: a new target for GLP-1 receptor agonists

FRANCINI F; MASSA ML; CASTRO MC; POLO MP; GAGLIARDINO JJ

Barcelona

Congreso; 49th EASD Annual Meeting; 2013

Europen Association for the Study of Diabetes

Background and aims: Normal rats fed with a fructose rich diet (FRD) portrait an increase in liver triglyceride (TG) and glycogen content, together with an increase in glucokinase (GK) activity. Since fructose metabolism in the liver starts with its phosphorylation by fructokinase (FK), the aim of this study was to evaluate the effect of co-administration of exendin-4 (GLP-1R agonist) or the DPP-IV inhibitor sitagliptin upon this enzyme as well as on liver TG content and GK activity in vivo and in vitro. Materials and methods: Adult male Wistar rats received (3 weeks) a standard commercial diet, without (C) or with 10% fructose (w/v) in the drinking water (F), with or without sitagliptin (115 mg/day per rat) (CS and FS) or exendin-4 (0.35 nmol/kg of bw, ip) (CE and FE). Human HepG2 cells were incubated for 72 with fructose 1.5 mM alone, plus exendin-4 (5 nM), exendin-9 (100 nM) or both. After the treatments, we measured in rats: 1) Serum glucose (G) (enzymatic method), insulin (I) (RIA) and TG (enzymatic method) levels; 2) GK activity in cytosolic (CF) and nuclear (DNF) fractions (enzyme-coupled photometric assay), 3) GK and PFK-2 protein expression (Western blot [Wb]), 4) liver TG content and 5) FK activity. In HepG2 cells we measured TG content, GK and FK activity. Results: Blood parameters: similar G values were recorded in all groups but F animals evinced a higher level of plasma TG (F: 1.2±0.12 vs. C: 0.5±0.01 mM, P