Effects of apoptosis on liver aging.

As an irreversible and perennial process, aging is accompanied by functional and morphological declines in organs. Generally, aging liver exhibits a decline in volume and hepatic blood flow. Even with a preeminent regenerative capacity to restore its functions after liver cell loss, its biosynthesis and metabolism abilities decline, and these are difficult to restore to previous standards. Apoptosis is a programmed death process via intrinsic and extrinsic pathways, in which Bcl-2 family proteins and apoptosis-related genes, such as p21 and p53, are involved. Apoptosis inflicts both favorable and adverse influences on liver aging. Apoptosis eliminates transformed abnormal cells but promotes age-related liver diseases, such as nonalcoholic fatty liver disease, liver fibrosis, cirrhosis, and liver cancer. We summarize the roles of apoptosis in liver aging and age-related liver diseases.

Roles of aging in sleep.

With aging, various factors deteriorate the normal sleep process that is essential for the restoration of functional and physical performance. Due to aging-related diseases, life changes, or aging itself, disturbances in normal sleep cycles can profoundly affect healthy aging. To understand the interconnections between aging and the factors influencing sleep, with emerging evidence accumulated in recent years, this study elaborates on the roles of aging in sleep from four perspectives: cortical thinning, white matter degeneration, neurotransmitter dysregulation, and circadian disorganization. In brief, with aging, cortical thinning can be induced by the deposition of neurotoxic substances, and white matter degeneration can be induced by vascular abnormalities. These alterations emerging in the brain jointly disrupt sleep spindles and slow waves, leading to sleep disturbances. Age-related dysregulation in neurotransmitters (including galanin, orexin, serotonin, and adenosine) directly impairs the sleep modulation system. Disorganization in the circadian system consisting of suprachiasmatic nucleus dysfunction, reduced light transmission, and local circadian clock disruption collectively interrupts circadian rhythms, also causing sleep disturbances in the older. Of note is the bidirectional relationship between aging and sleep, which required us to examine this issue from different perspectives.