Lipofuscin

…Even if nerve cells decrease with age, their function is maintained because the brain has compensatory functions such as an increase in the terminals of dendrites that compensate for the function of lost nerve cells, and because synapses are plastic. However, aged nerve cells do not have much room for these functions, and even slight changes in the body or environment can cause them to stop functioning. In aged nerve cells, deposition of brown lipofuscin (aging pigment) is seen in the cytoplasm, and in pathological conditions, Alzheimer's fibrillary changes, in which abnormal fibrous proteins appear, are seen. Lipofuscin is thought to be an inactive substance that has processed harmful free radicals and lipid peroxides that are generated in metabolic processes that are important for cell survival. It is found in large amounts in cells with active redox reactions, but if the amount of deposition increases, it physically impairs the function of the cell. …

*Some of the terminology that mentions "lipofuscin" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…高齢になって神経細胞が減っても機能が保たれるのは，失われた神経細胞の機能を補う樹状突起の末端の増加などの代償機能が脳にあり，シナプスに可塑（かそ）性があるためであるが，老化した神経細胞ではこれらの余裕もあまりなく，わずかな身体や環境の状態の変化で機能しなくなる。老化した神経細胞では細胞質に褐色のリポフスチンlipofuscin(老化色素)の沈着がみられ，また病的状態では異常な繊維タンパク質が出現するアルツハイマー原繊維変化がみられる。リポフスチンは，細胞の生存に重要な代謝過程で生じた有害なフリーラジカル，過酸化脂質などを処理した不活性物質と考えられ，酸化還元反応の活発な細胞に多いが，沈着量が多くなると物理的に細胞の機能が障害される。…

※「lipofuscin」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報