Kolesterolhomeostasen

Kolesterolhomeostasen refers to the physiological processes by which the body maintains stable cholesterol levels within cells and in the bloodstream. It involves a dynamic balance between synthesis, uptake, transport, storage, and disposal of cholesterol.

Endogenous synthesis occurs mainly in the liver, with HMG-CoA reductase as a key rate-limiting enzyme. Dietary cholesterol and intestinal absorption, mediated in part by the transporter NPC1L1, contribute to the systemic pool. Cholesterol is transported in the plasma by lipoproteins; low-density lipoprotein (LDL) delivers cholesterol to tissues, while high-density lipoprotein (HDL) participates in reverse cholesterol transport by collecting excess cholesterol from cells and tissues for disposal in the liver. Cellular uptake is driven by receptors such as the LDL receptor, and cholesterol can be stored in lipid droplets or effluxed via transporters like ABCA1 to apolipoprotein A-I to form HDL.

Regulation involves transcription factors and nuclear receptors that respond to cellular cholesterol levels, including SREBP and LXR, as well as hormonal and nutritional signals. Bile acid synthesis from cholesterol provides a major excretory route, linking hepatic cholesterol balance to gut excretion.

Imbalances in cholesterol homeostasis contribute to health issues such as atherosclerosis and familial hypercholesterolemia. Interventions aim to adjust synthesis, absorption, or clearance of cholesterol, with approaches including lifestyle changes and pharmacologic therapies that modulate these pathways.