What are the functions of lipofuscin?

Lipofuscin is often referred to as "age pigment" and primarily functions as a marker of cellular aging and oxidative stress. It accumulates in various tissues, particularly in post-mitotic cells like neurons and cardiac muscle cells, as a byproduct of lysosomal degradation of damaged proteins and lipids. While it does not have a known metabolic function, its accumulation is associated with age-related decline in cellular function and may contribute to cellular senescence. Additionally, lipofuscin is thought to play a role in the cellular response to oxidative stress, although its precise functions remain an area of research.