Overexpression of Fructose Bisphosphatase 2 in muscle increases insulin-mediated glucose uptake.   — ASN Events
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Overexpression of Fructose Bisphosphatase 2 in muscle increases insulin-mediated glucose uptake.   (#129)

Ishita Bakshi 1 , Eurwin Suryana 2 , Amanda Brandon 1 , Nigel Turner 3 , Greg J Cooney 4
  1. Diabetes and Metabolism, Garvan Institute for Medical Research, Darlinghurst, NSW, Australia
  2. Sydney University, Sydney, NSW, Australia
  3. Department of Pharmacology, University of New South Wales, Sydney, NSW, Australia
  4. Charles Perkin Centre, Sydney, NSW, Australia

Skeletal muscle is a major tissue for storing glucose as glycogen, converting glucose to lactate and fully oxidising glucose to CO2. Muscle also has a limited capacity for gluconeogenesis converting lactate and alanine to glycogen. This gluconeogenesis requires FBP2, a muscle specific form of fructose bisphosphatase that converts fructose-1,6-bisphosphate (F-1,6-bisP) to fructose-6-phosphate (F-6-P) opposing the activity of the ATP-consuming enzyme phosphofructokinase (PFK). In mammalian muscle, the activity of FBP2 is normally 100 times lower than PFK and therefore energy wasting between F-1,6-bisP/F-6-P cycling is low, although, cycling can increase with an increase in muscle metabolism during exercise, cold exposure or thyroid treatment. In an attempt to increase substrate cycling between F-6-P and F-1,6-bisP and alter glucose metabolism, we overexpressed FBP2 using a muscle-specific adeno-associated virus (AAV-tMCK-FBP2). AAV was injected into the right tibialis muscle of 60g male Wistar rats, while the left tibialis received a saline injection. The animals were then fed a chow or 45% fat diet (HFD) for 5 weeks after which euglycaemic hyperinsulinaemic clamps was performed. The glucose infusion rate was significantly lower in HFD compared to chow (21.2±2.3 vs 37.1±2.8 mg/kg/min, p<0.001) indicating whole body insulin resistance. Transfection of the right tibialis with AAV-tMCK-FBP2 increased FBP2 activity 10 fold on average in chow and HFD rats (p<0.0001). Insulin-stimulated glucose uptake was significantly lower in tibialis of HFD compared to chow rats (2-way ANOVA, diet p=0.01). Overexpression of FBP2 significantly increased insulin-stimulated glucose uptake in tibialis of chow animals (control 14.3±1.7; FBP2 17.6±1.6µmol/min/100g) and HFD animals (control 9.6±1.1; FBP2 11.2±1.1 µmol/min/100g) (2-way ANOVA, FBP2 p<0.001). These results suggest that overexpressing FBP2 can increase the capacity for cycling between F-6-P and F-1,6-P, which can increase the metabolism of glucose by introducing a futile cycle in muscle.

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