Circadian dysregulation as a factor in impaired hepatic protein-synthetic function under chronic photoperiod disruption: the role of sex and chronobiotic correction.

backgroundLiver metabolism is under tight control of the circadian system. Disruption of key clock gene expression (desynchronosis) leads to the misalignment of metabolic pathways. However, the relationship between circadian dysregulation and hepatic protein-synthetic function, as well as its sexual dimorphism, remains poorly understood. To evaluate the effect of chronic photoperiod disruption on hepatic protein-synthetic function (total protein, albumin) and to establish its relationship with the expression of key circadian proteins (BMAL1, CLOCK, PER2) in male and female rats, as well as to assess the efficacy of exogenous melatonin in correcting the identified disturbances.

methodsThe study was performed on 240 adult Wistar rats (120 males, 120 females). Animals were divided into 3 groups: control (light: dark 10:14 h), dark deprivation (LL, constant light for 21 days), and LL + melatonin (12 mg/L drinking water). Plasma levels of total protein and albumin were measured. Immunohistochemistry was used to assess the percentage of positively stained hepatocytes for BMAL1, CLOCK, and PER2. Statistical analysis included two-way ANOVA, Pearson correlation analysis, ANCOVA, and ROC analysis.

resultsDark deprivation reduced albumin levels by 15.7% in males and by 15.9% in females compared to controls. Two-way ANOVA revealed significant effects of "lighting conditions" (F = 145.3, p < 0.0001), "sex" (F = 18.7, p < 0.01), and their interaction (F = 7.2, p < 0.05). BMAL1 and CLOCK expression decreased by more than 70% in both sexes, whereas PER2 expression paradoxically increased by 28.9-35.0%. Strong correlations were found between albumin levels and expression of BMAL1 (r = 0.79-0.81, p < 0.001), CLOCK (r = 0.69-0.74, p < 0.001), and PER2 (r= - 0.68 to - 0.71, p < 0.001). ANCOVA (R²=0.71, p < 0.0001) identified BMAL1 expression as the most significant independent predictor of albumin levels (β = 0.52, p < 0.0001), with sex retaining independent significance (p = 0.02). ROC analysis demonstrated high predictive performance of BMAL1 expression for hypoalbuminemia (AUC = 0.87-0.89, p < 0.0001). Melatonin treatment fully restored the expression of all examined circadian proteins and normalized protein synthetic parameters to control levels in both sexes.

conclusionChronic photoperiod disruption induces profound hepatic desynchronosis characterized by suppression of BMAL1/CLOCK and accumulation of PER2, which is associated with decreased protein synthetic function. A pronounced sexual dimorphism in susceptibility to desynchronosis was identified. BMAL1 expression is a highly informative predictor of hypoalbuminemia. Exogenous melatonin fully restores the impaired parameters, supporting its use as an effective chronobiotic.