REGULATION OF PALMITIC ACID SYNTHESIS IN CULTURED GLIAL CELLS: EFFECTS OF LIPID ON FATTY ACID SYNTHETASE, ACETYL‐CoA CARBOXYLASE, FATTY ACID AND STEROL SYNTHESIS1

Abstract— C6 glial cells in culture were utilized to study the regulation of the important lipogenic enzymes, fatty acid synthetase and acetyl‐CoA carboxylase, and the synthesis of fatty acids and sterols. Regulation of these phenomena by lipid was demonstrated by the following observations. First, removal of serum from the culture medium was accompanied over the next five days by 2–3‐fold increases in the lipogenic enzymatic activities and in 5–15‐fold increases in rates of incorporation of acetate into fatty acids and sterols. Second, cells grown in delipidated serum exhibited approx 2‐fold higher levels of activity of the lipogenic enzymes and 5–10‐fold higher rates of synthesis of fatty acids and sterols than cells grown in normal calf serum. Third, cells grown in serum‐free medium supplemented with concentrations of fatty acid comparable to those present in medium supplemented with serum exhibited activities of fatty acid synthetase comparable to those exhibited by cells grown in the serum‐supplemented medium. The mechanism of these effects on fatty acid synthetase was shown by immunochemical techniques to involve alterations in content rather than in catalytic efficiency of the enzyme. The changes in content of the synthetase were caused by alterations in enzyme synthesis. In view of morphological and biochemical data suggesting that C6 cells are related to differentiating cells with properties of both astrocytes and oligodendroglia, the present data may indicate that regulation of palmitic acid synthesis by fatty acid or a product thereof occurs in brain during development.