Chrono-Specific Calcium Intervention Disrupts Hepatic Lipid Metabolism via the PER1-PPARα Axis.

Background and objective: Controversies exist regarding the effects of calcium supplementation on lipid metabolism, and the time-specific effects and underlying mechanisms remain unclear. This study aims to elucidate the differential impacts of calcium intervention at different times (morning/evening) on hepatic lipid metabolism and the molecular mechanisms involved.

Methods: Forty female CD-1 (ICR) mice were randomly divided into four groups: Morning Control Group (MCN), Morning Calcium Intervention Group (MCI, intragastric administration of calcium carbonate at 08:00), Evening Control Group (ECN), and Evening Calcium Intervention Group (ECI, intragastric administration of calcium carbonate at 20:00). Mice were fed a normal calcium or low-calcium diet for 10 wk. In vitro experiments used HepG2 cells, which were divided into groups simulating whole-day (CON), daytime (DC, high calcium from 08:00 to 20:00), and nighttime (NC, high calcium from 20:00 to 08:00) calcium exposure. PER1 was knocked down using siRNA. Serum/hepatic/cellular lipid levels, hepatic pathology, transcriptome, and gene/protein expressions (PER1, PPARα, CPT1A, APOA5, etc.) were detected.

Results: Morning calcium intervention (MCI) in mice significantly increased serum and hepatic total cholesterol (TC), triglyceride (TG), and low-density lipoprotein (LDL) levels, and induced lipid droplet deposition and swelling in hepatocytes. Transcriptome and validation experiments showed upregulated hepatic PER1 expression in the MCI group, while PPARα and its downstream lipid metabolism genes (CPT1A, APOA5) were downregulated. In HepG2 cells, nighttime calcium incubation (NC) significantly increased intracellular TG and LDL contents, upregulated PER1 expression, and inhibited PPARα, CPT1A, and APOA5 expressions. Knocking down PER1 reversed the abnormal gene expression and lipid-elevating effects in the NC group. Collectively, our findings demonstrate that the circadian timing of calcium intake critically regulates hepatic lipid homeostasis via the PER1-PPARα axis, highlighting the importance of chrono-nutrition in metabolic health.