160 | Short-term mild caloric restriction induces early adaptive metabolic and mitochondrial responses in the liver of healthy rats

Martina Coletta¹, Vincenzo Migliaccio¹, Giuliana Panico², Ilaria Di Gregorio¹, Assunta Lombardi², Lillà Lionetti¹ | ¹Dept Chemistry and Biology "A Zambelli", University of Salerno, Italy; ²Dept Biology, University of Naples Federico II, Naples, Italy.

Caloric restriction (CR) is widely recognized as a powerful non-pharmacological intervention capable of improving metabolic health and promoting longevity. However, most studies have focused on severe or long-term CR protocols in pathological models, while the effects of mild and short-term CR under physiological conditions remain poorly characterized. In this study, we investigated the hepatic effects of a moderate (15%) and short-term (14 days) CR in adult healthy rats, focusing on metabolic, inflammatory, and mitochondrial adaptations. Our results showed that CR significantly reduces body weight gain without affecting liver mass and reduces both hepatic lipid accumulation and glycogen content, as assessed by histological analyses. At the molecular level redox homeostasis of tissue detected by monitoring both reactive oxygen species (ROS) accumulation and the thiobarbituric reactive substances (TBARS) levels, was preserved. In addition, CR did not evidence changes in hepatic inflammatory markers, as indicated by unchanged Cluster of Differentiation 68 (CD68) and Monocyte Chemoattractant Protein-1 (MCP-1) protein expression, while circulating pro-inflammatory cytokines, analysed by using protein array, were reduced. Notably, CR induced a significant increase in circulating Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) levels, which was associated with reduced phosphorylation of AKT in ser-473 in the liver, suggesting a downregulation of anabolic signaling pathways involved in glycogen synthesis. Markers of endoplasmic reticulum stress like the phosphorilation in ser-51 of the eukaryotic translation initiation factor 2 subunit alpha (pEIF2α), the Glucose-Regulated Protein (GRP78) and the C/EBP homologous protein (CHOP) were significantly decreased in CR animals, indicating improved proteostatic balance. Despite this, no activation of autophagy was observed. Interestingly, focusing mitochondria, subfractionation analysis revealed a selective reduction of ROS levels and lipid peroxydes in the mitochondrial subpopulation principally characterized by small mitochondria, suggesting a compartment-specific redox adaptation induced by CR. Overall, these findings demonstrate that mild and short-term CR promotes early adaptive metabolic and mitochondrial responses in the liver without triggering stress, inflammation, or structural damage, supporting its potential role as a preventive strategy to enhance hepatic metabolic resilience.