Palluth, L. | bioRxiv Science

bioRxiv2026

Nocturnin drives mitochondrial NADP(H)/NAD(H) rhythms to regulate steroid rhythm amplitude and time metabolism

Circadian rhythms are conserved biological timekeeping mechanisms crucial for the temporal compartmentalization of metabolic processes. However, the molecular pathways by which circadian rhythms are regulated within metabolism are not fully understood. Nocturnin (NOCT) is a highly rhythmic, clock-controlled NADP(H) phosphatase that has been implicated in numerous metabolic phenotypes. While it is known that NOCT significantly impacts the cellular NADP(H) and NAD(H) pools in vitro, NOCTs impact on their concentrations and rhythmicity in vivo has not yet been established. In fact, the rhythmicity of NADH, NADP+, and NADPH have yet to be quantified in mammalian nucleated cells. Here, we determined both the whole cell and mitochondrial NAD(H) and NADP(H) rhythms in wild-type and Noct-/-mouse livers. Unexpectedly, we found a robust rhythm in the mitochondrial NADP(H)/NAD(H) ratio that is antiphase to the respective whole cell rhythm. While loss of NOCT increases the amplitude of the whole cell NADP(H)/NAD(H) rhythm, the mitochondrial rhythm is completely damped in Noct-/-mice. The constitutively higher relative NADP(H) within Noct-/-mitochondria drives steroidogenesis, leading to an increased amplitude of plasma corticosterone. Both the acute increase in plasma corticosterone and the disruption of mitochondrial cofactor rhythms caused by loss of NOCT lead to widespread changes in hepatic metabolism. Collectively, we found that NOCTs control of mitochondrial NADP(H)/NAD(H) rhythms is a novel regulator of steroid amplitude and downstream metabolic rhythms.

physiology↗

bioRxiv2026

Two Stages of Dynamic Metabolic and Transcriptomic Remodeling During the Adaptation to Caloric Restriction in Male C57BL/6J

The molecular basis of caloric restriction (CR) has been defined primarily at a metabolic steady state, leaving the initiating events that drive the transition from ad libitum feeding to an adapted CR state largely unresolved. Here, we combine continuous indirect calorimetry with longitudinal bulk RNA-seq of liver and inguinal white adipose tissue (iWAT) sampled at six circadian timepoints across four stages of adaptation to 30% CR in male C57BL/6J mice. We show that whole-body metabolic adaptation proceeds through two discrete adaptive phases separated by a threshold at approximately 14 days; during this initial transition, consolidated feeding attenuates ketogenesis, establishing a distinct whole-body metabolic phenotype prior to long-term adaptation. To elucidate the molecular mechanisms underlying these physiological shifts, weighted gene co-expression network analysis (WGCNA) was performed, revealing that hepatic transcriptional remodeling is organized proportionally to fasting duration, whereas iWAT remodeling remains restricted to specific circadian timepoints. Because systemic adaptation requires coordinated inter-tissue communication, we conducted a cartographic analysis to evaluate network topology and inter-modular connectivity. This approach identifies restricted populations of early kinless and connector hub genes, nucleated by Casp3 in the liver and Lpl in iWAT, whose structural integration is established prior to the broader transcriptional remodeling observed at later timepoints. Functional annotation indicates the hepatic hub network is enriched for mitochondrial bioenergetics and FOXO/TP53-mediated transcription, while the iWAT hub network exhibits a bifurcated enrichment spanning ribosomal biosynthesis and immune-regulatory signaling. Although these tissues exhibit distinct transcriptional profiles, projecting both datasets onto a shared phenotypic eigenspace reveals a unified systemic response; as CR is maintained, dynamically regulated transcripts in both liver and iWAT converge on an adiponectin-coupled state. Ultimately, the identification of adiponectin as an integrative signal coordinating chronic adaptation across metabolically distinct tissues delineates the temporal sequence of early CR adaptation; furthermore, it establishes a mechanistic framework defining how early molecular and physiological shifts converge to achieve steady-state metabolic homeostasis.

systems biology↗