Effects of rotational delay shiftwork/jetlag on circadian rhythm, stress and inflammatory responses in the diurnal mammal Funambulus pennantii

Although delay-based shiftwork/jetlag schedules are often considered less disruptive than advances and are increasingly adopted in occupational settings, their long-term impact on physiological homeostasis remains underexplored. In this study, we investigated the consequences of repeated phase delays on circadian alignment, oxidative balance, endocrine function, and systemic inflammation in the diurnal rodent Funambulus pennantii. Animals were kept either under a stable 12:12 hour light-dark (LD) cycle or subjected to a successive delay rotational shift (SDRS) schedule for 28 days. In the SDRS schedule, the light phase was delayed by 8 hours every two days, and every seventh day, animals were returned to the normal LD cycle for rest. SDRS exposure led to marked circadian misalignment, evident from disrupted and desynchronized locomotor activity rhythms. Biochemical analyses revealed reduced serum melatonin and antioxidant enzyme activity (SOD, CAT), along with elevated corticosterone levels, indicating stress induction. Moreover, animals under SDRS showed significant increases in pro-inflammatory cytokines (TNF-α, IL-6, IL-1β), highlighting immune activation. Our results highlight that delay-based shift schedules, often considered less harmful, can significantly impair physiological resilience, warranting a re-evaluation of their perceived safety due to their stress and inflammatory effects in diurnal systems.