suggesting toleration of small substituents at this position.

If the N1 IC adenovirus acted in an Rbp J dependent manner to promote HGP, one would predict that it would be unable to do so in L Rbpj mice. Indeed, hepatic N1 IC transduction in L Rbpj mice failed to increase plasma insulin or expression of Notch targets and gluconeogenic genes. secretase inhibitors reduce HGP and improve glucose Dub inhibitor tolerance After ligand binding, Notch receptor heterodimers dissociate and undergo sequential cleavage by membrane bound ADAM/TACE and secretase complex9. Notch receptor dimerization is calcium dependent and chelation with EDTA causes ligand independent Notch activation 21. We activated endogenous Notch1 by treating primary hepatocytes with EDTA to generate NICD, this was prevented by co treatment with Compound E, a cellpermeable secretase inhibitor 22. EDTA treatment increased Notch target and G6pc expression in a GSI inhibitable manner. In the absence of EDTA, relying on physiologic Notch1 activation in serum free conditions, GSI treatment Meristem inhibited Notch target and G6pc expression, decreased glucose production, and altered the dose response curve of insulin to suppress glucose release. GSI blunted glucose output from hepatocytes derived from control and L Foxo1, but not L Rbpj mice, as well as from hepatocytes expressing FoxO1 shRNA, indicating that its effects are Notch dependent, but FoxO1 independent We next evaluated the in vivo effects of dibenzazepine, a well characterized and bioavailable GSI23. Following a single dose of DBZ, WT mice demonstrated decreased fasting and refed plasma glucose levels, a 5 day course of DBZ yielded similar reductions in fasting glucose, without altered insulin levels or body weight. Consistent with Foretinib decreased HGP, DBZ treated animals demonstrated markedly improved glucose tolerance, accompanied by marked reduction in G6pc, Pck1 and other Notch and FoxO1 specific targets. DBZ treatment resulted in transient hepatic glycogen accumulation, as well as mild intestinal metaplasia 24. To test whether GSIs would be able to reverse the effects of chronic insulin resistance, we treated diet induced obese and leptin deficient ob/ob mice with DBZ. Both cohorts showed markedly improved glucose levels and glucose tolerance with GSI, ob/ ob mice additionally demonstrated decreased insulin levels, suggestive of increased insulin sensitivity. Chronic, intermittent therapy with DBZ did not alter food intake, body weight or body composition but was similarly effective in improving glucose tolerance, suggesting that GSI effects do not wane over time. Glucose and insulin measurements in the ad libitum fed state demonstrated that the hypoglycemic effect of GSI lasts ~24 h and is associated with lower insulin levels. Hepatic phosphorylation of Akt1 and IRS1 were increased, suggestive of increased hepatic insulin sensitivity with GSI treatment.