Sleep deprivation activated AMPK/FOXO3a signaling mediates pineal autophagy impairment to reduce melatonin secretion in CUMS + SD rats leading to depression combined with insomnia

This study established an animal model of comorbid depression and insomnia by combining chronic unpredictable mild stress (CUMS) with sleep deprivation (SD). The pathogenesis of comorbid depression and insomnia may be associated with impaired AMPK/FOXO3a signaling, which mediates autophagy inhibition, leading to decreased pineal melatonin secretion. The findings revealed that CUMS + SD rats exhibited more pronounced depression-like behaviors, sleep disorders, increased central oxidative stress, and exacerbated neuroinflammation, accompanied by reduced levels of 5-hydroxytryptophan (5-HT) and melatonin in the pineal gland. Notably, further investigations revealed that impaired mitochondrial autophagy in the pineal gland is closely linked to the significant suppression of AMPK/FOXO3a signaling. The combined intervention of venlafaxine and melatonin effectively ameliorated the impaired mitochondrial autophagy in the pineal gland of CUMS + SD rats and stimulated melatonin secretion. Consequently, the study proposes that dysfunctional mitochondrial autophagy regulated by the AMPK/FOXO3a pathway can influence melatonin secretion, thereby playing a pivotal role in the pathogenesis of depression combined with insomnia.