Decrease in Mitochondrial Oxidative Respiratory Function in Liver of Cricetulus barabensis Under Long and Short Photoperiods: The Role of Mitochondrial Fission and Apoptosis

Abstract

The photoperiod is a crucial factor affecting the seasonal rhythms of mammals. Under the seasonal rhythms, the growth and development of the body are closely related to the oxidative respiratory function of mitochondria, but the influence of the single seasonal factor photoperiod on it remains unclear. In this study, mitochondrial dynamics and associated regulatory mechanisms were investigated in the livers of striped dwarf hamsters (Cricetulus barabensis) exposed to three distinct photoperiod regimes: short photoperiod (SP), moderate photoperiod (MP) and long photoperiod (LP). Results indicated that: (1) Liver mass responses to photoperiod varied with changes in body weight. (2) ATP synthase activity was significantly decreased under LP, whereas citrate synthase activity (CS) was selectively diminished under SP. (3) The Bcl2 associated X protein (bax) to b cell lymphoma 2 (bcl2) ratio increased under both SP and LP. (4) Dynamin-related protein 1 (DRP1) protein abundance increased under both LP and SP conditions, while mitochondrial fission factor (MFF) decreased under LP, signifying divergent remodelling of mitochondrial fission signalling. (5) Caspase3 activity unchanged under SP. In conclusion, under LP and SP treatment, the oxidative respiratory function of liver mitochondria in striped dwarf hamsters may be weakened, potentially due to increased mitochondrial membrane permeability, as indicated by an elevated bax/bcl2 ratio. Compared to long photoperiod treatment, the upregulation of the liver mitochondrial fission signalling and the lower level of apoptosis under short photoperiod conditions may help facilitate thermogenic adaptation to increased energetic demands in winter.