Effects of insulin and insulin-like growth factor (IGF-I) on oligodendrocyte-enriched glial cultures

The brains from 1-week-old rat pups were used to prepare cultures of glial cells. After 24 hr in culture the cells were changed to a chemically defined serum-free medium (CDM). We have used antibodies against gangliosides (monoclonals A2B5 and LB1) and against galactocerebrosides to monitor the influence of insulin on the development of oligodendrocytes from precursor cells. In these oligodendrocyte-enriched cultures we investigated the influence of insulin and IGF-I on the activity of the marker enzymes 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase) and glycerol-3-phosphate dehydrogenase (G3PDH), and on lipid metabolism. 1) Incorporation of [35S] sulfate into sulfolipids was stimulated by insulin (optimal concentration 100 nM). A sharp peak in sulfolipid synthesis was seen at day 5-6 in culture. 2) Insulin stimulated the expression of CNPase and G3PDH in culture. 3) The stimulating effect of insulin on sulfolipid synthesis, CNPase, and G3PDH activity was mimicked by IGF-I (13 nM). 4) The incorporation of [35S] into sulfolipids and [2-3H]acetate into fatty acids and cholesterol was reversibly reduced by temporary omission of insulin from the medium. These results indicate that insulin and IGF-I stimulate the development of oligodendrocytes in our culture system and that insulin has a general anabolic effect on the lipid metabolism of the cells.