Amelioration of glucose tolerance by hepatic inhibition of nuclear factor kappaB in db/db mice

Recent studies have identified the involvement of inhibitor IkappaB kinase (IKK) in the pathogenesis of insulin resistance. To investigate the mechanism involved, we examined the role of nuclear factor kappaB (NF-kappaB), the distal target of IKK, in hepatic glucose metabolism.

To inhibit NF-kappaB activity, db/db mice were infected with adenovirus expressing the IkappaBalpha super-repressor.

The IkappaBalpha super-repressor adenovirus infection caused a moderate reduction of NF-kappaB activity in liver. The treatment was associated with improved glucose tolerance, reduction in the serum insulin level, and increased hepatic triacylglycerol and glycogen contents, but had no effect on insulin-stimulated phosphorylation of Akt. On the other hand, quantification of mRNA in the liver revealed marked reduction of expression of gluconeogenic genes, such as those encoding phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase, concurrent with reduced expression of gene encoding peroxisome proliferator-activated receptor gamma coactivator-1alpha (PPARGC1A, also known as PGC-1alpha). Furthermore, the production of super-repressor IkappaBalpha suppressed the increase in blood glucose level after pyruvate injection.

Our results indicate that moderate inhibition of NF-kappaB improved glucose tolerance through decreased gluconeogenesis associated with reduced PGC-1alpha gene expression in db/db mice, and suggest that inhibition of NF-kappaB activity in liver is a potentially suitable strategy for the normalisation of blood glucose concentration in type 2 diabetes.