QPRT and acute kidney injury: Thus, the amount of rescued Sirt1 in the kidney may not have been sufficient to increase pgc-1α, which regulates the expression of the de novo NAD+ biosynthesis gene, Qprt. As such, our results indicate that the de novo pathway in the AKI model used in the present investigation was disrupted and that the rescued NAD+ after 24 hours, therefore, did not affect pgc-1α or its downstream target genes.