The hepatic clock synergizes with HIF-1α to regulate nucleotide availability during liver damage repair

Nucleotide availability is crucial for DNA replication and repair; however, the coordinating mechanisms in vivo remain unclear. Here, we show that the circadian clock in the liver controls the activity of the pentose phosphate pathway (PPP) to support de novo nucleotide biosynthesis for DNA synthesis demands. We demonstrate that disrupting the hepatic clock by genetic manipulation or mistimed feeding impairs PPP activity in male mice, leading to nucleotide imbalance. Such defects not only elicit DNA replication stress to limit liver regeneration after resection but also allow genotoxin-induced hepatocyte senescence and STING signalling-dependent inflammation. Mechanistically, the molecular clock activator BMAL1 synergizes with hypoxia-inducible factor-1α (HIF-1α) to regulate the transcription of the PPP rate-limiting enzyme glucose-6-phosphate dehydrogenase (G6PD), which is enhanced during liver regeneration. Overexpressing G6PD restores the compromised regenerative capacity of the BMAL1- or HIF-1α-deficient liver. Moreover, boosting G6PD expression genetically or through preoperative intermittent fasting potently facilitates liver repair in normal mice. Hence, our findings highlight the physiological importance of the hepatic clock and suggest a promising pro-regenerative strategy. During liver damage repair, the circadian clock in the liver is shown to act together with HIF-1α signalling to regulate pentose phosphate pathway activity and nucleotide availability.