Increased glucose disposal induced by adenovirus-mediated transfer of glucokinase to skeletal muscle in vivo

In non-insulin-dependent diabetes mellitus, insulin-stimulated glucose upta ke is impaired in muscle, contributing in a major way to development of hyp erglycemia, We previously showed that expression of the glucose phosphoryla ting enzyme glucokinase (GK) in cultured human myocytes improved glucose st orage and disposal, suggesting that GK delivery to muscle in situ could pot entially enhance glucose clearance. Here we have tested this idea directly by intramuscular delivery of an adenovirus containing the liver GK cDNA (Ad CMV-GKL) into one hind limb, We injected an adenovirus containing the beta- galactosidase gene (AdCMV-lacZ) into the hind limb of newborn rats. beta-Ga lactosidase activity was localized in muscle for as long as 1 month after d elivery, with a large percentage of fibers staining positive in the gastroc nemius, Using the same approach with AdCMV-GKL, GK protein content was incr eased from zero to 50-400% of the GK in normal liver sample, and total gluc ose phosphorylating activity was increased in GK-expressing muscles relativ e to the counterpart uninfected muscle, Expression of GK in muscle improved glucose tolerance rather than changing basal glycemic control. Glucose lev els were reduced by similar to 35% 10 min after administration of a glucose bolus to fed animals treated with AdCMV-GKL relative to AdCMV-lacZ-treated controls. The enhanced rate of glucose clearance was reflected in increase s in muscle 2-deoxy glucose uptake and blood lactate levels. We conclude th at restricted expression of GK in muscle leads to an enhanced capacity for muscle glucose disposal and whole body glucose tolerance under conditions o f maximal glucose-insulin stimulation, suggesting that under these conditio ns glucose phosphorylation becomes rate-limiting. Our findings also show th at gene delivery to a fraction of the whole body is sufficient to improve g lucose disposal, providing a rationale for the development of new therapeut ic strategies for treatment of diabetes.