165. Liver-Directed Gene Therapy for Murine Glycogen Storage Disease Type IB

Glycogen storage disease type Ib (GSD-Ib) deficient in the glucose-6-phosphate transporter (G6PT or SLC37A4) is characterized impaired glucose homeostasis, myeloid dysfunction, and long-term complication of hepatocellular adenoma (HCA). We have shown that gene therapy mediated by a recombinant (r) AAV8 vector expressing G6PT directed by the chicken β-actin promoter/CMV enhancer enabled the G6pt-/- mice lived to over 51 weeks but all 5 transduced G6pt-/- mice expressed only low levels of hepatic G6PT activity and two developed multiple HCAs with one undergoing malignant transformation. We now examined the safety and efficacy of rAAV8-GPE-G6PT, a rAAV8 vector expressing G6PT directed by the gluconeogenic tissue-specific human G6PC promoter/enhancer (GPE). Of the fifteen rAAV8-GPE-G6PT-treated G6pt-/- mice that lived over age 60 weeks expressed 2-62% of wild-type hepatic G6PT activity with only one developed HCA. The treated mice, including the HCA-bearing mouse exhibit a leaner phenotype along with normal blood metabolite, display normal glucose tolerance profiles, maintain normoglycemia over a 24-hour fast, and retain insulin sensitivity. We further show that activation of hepatic ChREBP signaling that improves glucose tolerance and insulin sensitivity is one mechanism that protects the rAAV-GPE-G6PT-treated G6pt-/- mice against age-related obesity and insulin resistance.