Although the mechanism of decreased insulin gene expression can be largely attributed to decreased PDX-1 gene expression, what might account for the latter? Recently, Kaneto et al. (14) observed that adenoviral overexpression of dominant-negative c-Jun NH2-terminal kinase (DN-JNK) protected both PDX-1 binding to DNA and insulin gene mRNA from hydrogen peroxide-induced oxidative stress as well as from the adverse effects of hyperglycemia in a transplantation model. However, the degree to which the hydrogen peroxide and DN-JNK effects on insulin mRNA and PDX-1 binding activity were clearly separated from apoptosis is not clear. Fluorescein diacetate fluorescence was used to demonstrate β-cell viability, but no quantitative analysis of cell death or β-cell mass was provided to document that these variables were quantitatively comparable under control and experimental conditions. Nonetheless, this work provides the potentially important clue that JNK may be involved in the adverse effects of glucose toxicity. Definitive demonstration of the actual mechanism by which JNK might interfere with PDX-1 gene expression and insulin mRNA level awaits further experimentation.