rasvatilkade

Rasvatilkade, in Estonian scientific terminology, refer to lipid droplets, intracellular organelles that store neutral lipids such as triacylglycerols and cholesterol esters. They are found in most eukaryotic cells and serve as an energy reservoir as well as a source of lipid building blocks for membranes and signaling molecules.

Structure and composition: lipid droplets consist of a hydrophobic core of neutral lipids encased by a phospholipid monolayer and a surface coat of proteins. The protein layer includes members of the perilipin family (PLIN1-PLIN5) and various enzymes involved in lipid metabolism. The droplet surface regulates access of lipases and protects the core lipids from inappropriate lipolysis.

Formation and dynamics: lipid droplets originate mainly from the endoplasmic reticulum and grow by accumulating lipids synthesized within the cell. They can enlarge or shrink in response to metabolic state, and they may fuse or be partitioned as needed. Lipolysis, the breakdown of stored lipids, is driven by enzymes such as adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), and monoglyceride lipase (MGL), with proteins like CGI-58 (ABHD5) and perilipins modulating access.

Distribution and function: adipocytes contain large, abundant droplets, but lipid droplets are also present in liver, muscle, brain, and macrophages. Their primary function is to store energy, releasing fatty acids during fasting or energy demand, while also participating in lipid trafficking and cellular signaling.

Clinical relevance: abnormal lipid droplet biology is linked to metabolic disorders such as obesity, insulin resistance, hepatic steatosis, and certain lipodystrophies, as well as to cancer cell metabolism and aging.

Research and methods: lipid droplets are studied using microscopy, biochemical isolation, and molecular biology to understand their formation, regulation, and role in health and disease.