Excess membrane cholesterol is not responsible for metabolic and bioenergetic changes in AS-30D hepatoma mitochondria.
Using mitochondria isolated from normal rat liver and AS-30D hepatoma in addition to cholesterol-enriched mitochondria, we have evaluated the ability of membrane cholesterol to induce changes in mitochondrial function, specifically, the preferential export of citrate (i.e., truncation of the Krebs cycle). Two in vitro cholesterol-enrichment procedures failed to produce mitochondria with any physiologically significant increases in free membrane cholesterol. Alternatively, male Wistar rats were maintained on a 2% cholesterol diet to elevate mitochondrial cholesterol. This treatment resulted in liver mitochondria which contained 70% of the cholesterol levels found in AS-30D hepatoma mitochondria, yet only minor metabolic and bioenergetic alterations. Subfractionation of the various mitochondrial preparations revealed that cholesterol was located primarily in outer membranes of both the cholesterol-enriched and AS-30D preparations. We therefore conclude that an increase in membrane cholesterol is not sufficient to induce "truncation" of the citric acid cycle or any other mitochondrial abnormality in tumor cells.
Dietzen
D J
DJ
Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202.
Davis
E J
EJ
D000818:Animals; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D002784:Cholesterol / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism; D004734:Energy Metabolism; D005260:Female; D007425:Intracellular Membranes / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism* / Q000648:ultrastructure; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar
D002784:Cholesterol; D008291:Malate Dehydrogenase; D003576:Electron Transport Complex IV