Oligodendrocytes

Oligodendrocytes are a type of glial cell that function as the brain's primary site of steroidogenesis, producing pregnenolone locally rather than merely storing hormones from the adrenals and gonads. 2 Peat argued that these cells have receptors for stress and valium, and they synthesize pregnenolone when activated, challenging the textbook view that their main role is electrical insulation for saltatory conduction. 2 He considered the "insulating" myelin dogma a fetish that obstructed progress, proposing instead that the steroid hormones produced by oligodendrocytes are directly relevant to the nerve conduction processes of the cells they surround. 4

Structurally, oligodendrocytes are unusual among glial cells because they possess sheet-like processes rather than just thread-like ones. 2 Under the influence of thyroid hormone, these cells wrap themselves in thin layers around the conductive axons of nerve cells, leaving a multilayered myelin coating composed of proteins, complex lipids, and a high concentration of cholesterol. 2 The absorption of thyroid hormone by these glial cells is promoted by butyrate, an anti-stress substance found in butter and coconut oil, which Peat noted increases T3 uptake. 2 The synthesis of myelin itself depends on adequate energy, with sugar, thyroid, and progesterone acting as limiting factors for its rapid formation. 6

Peat drew a sharp distinction between the pathologies of oligodendrocytes in different degenerative conditions. In multiple sclerosis, the problem is specifically a failure of myelination, without defects in the nerve cells themselves or the formation of senile plaques. 1 In contrast, he cited early research by Hiroisi and Lee showing that degenerating oligodendrocytes were the source of the senile plaques or amyloid deposits characteristic of Alzheimer's disease, ending as translucent "mucoid" spots. 1 This led him to suggest that Alzheimer's might involve a specific premature loss of brain pregnenolone production by these cells, while thyroid function remains intact, whereas multiple sclerosis reflects a broader hypothyroid problem impairing the myelination process. 2

The decline of oligodendrocyte function is central to Peat's view of brain aging. He observed that brain steroid levels fall to about 5% of their youthful concentration in old age, correlating with the degeneration of these cells into amyloid-producing forms. 1 He speculated that the halo of oligodendrocytes sometimes seen surrounding degenerating nerve cells might represent a protective reaction to supply the neuron with any pregnenolone the glial cells are still able to synthesize. 1 The maintenance of mental clarity into advanced age through supplementation with pregnenolone, DHEA, progesterone, and thyroid underscores the functional importance of restoring the steroidogenic activity that normally originates with these glial cells. 1