Summary of cholesterol synthesis in brain cell subtypes
| Cell type | Subtypes | Function of cell | Function of cholesterol | Cholesterol synthesis | K-R or Bloch pathway? |
|---|---|---|---|---|---|
| Neurons | Subtypes many | Processing and transmission of cellular signals | Regulates membrane fluidity, required for cell membranes and myelin sheaths [29]. Present in lipid rafts and facilitates ion channel function, neuron receptor localization, neurotransmitter transport, and cellular growth and development [2, 26, 29]. | High during embryonic development [28, 30]. Low during adulthood, when cholesterol is mainly sourced from astrocytes [26, 31]. | Both [24, 28] |
| Glial cells | Astrocytes | Maintenance of CNS homeostasis, provision of biochemical and nutritional support to neurons and blood-brain barrier, synaptic transmission, immune function | Required for cell membrane fluidity regulation, lipid raft formation, and carbohydrate metabolism [32]. Cholesterol is exported to other brain cells [32, 33]. | Low during embryonic development [28]. High after birth [26, 34]. | Bloch [24] |
| Oligodendrocytes | Synthesis and maintenance of myelin sheaths to insulate neuronal axons for faster signal transmission | Required for synthesis of myelin sheaths [35–37]. | High after birth and in early childhood [9, 35]. Dynamic during adulthood. Cholesterol is sourced locally and from astrocytes [38, 39]. | Possibly K-R [24] but requires further study | |
| Microglia | Brain macrophage; immune function and injury repair | Lipid composition modulates microglial function in phagocytosis, immune surveying, synapse pruning [33, 40, 41]. Desmosterol (cholesterol precursor) activates LXR signaling to resolve inflammation and promote oligodendrocyte maturation [42]. | Synthesis rate low, sourced from astrocytes [43]. | Possibly K-R [24] but requires further study |
Note that many neuronal subtypes are present in the brain, but for the purpose of this review the main role of neurons and their cholesterol synthesis is discussed