Biochemical properties of porcine white adipose tissue mitochondria and relevance to fatty acid oxidation.
The capacity of white adipose tissue mitochondria to support a high beta-oxidative flux was investigated by comparison to liver mitochondria. Based on marker enzyme activities and electron microscopy, the relative purity of the isolated mitochondria was similar thus allowing a direct comparison on a protein basis. The results confirm the comparable capacity of adipose tissue and liver mitochondria for palmitoyl-carnitine oxidation. Relative to liver, both citrate synthase and alpha-ketoglutarate dehydrogenase were increased 7.87- and 10.38-fold, respectively. In contrast, adipose tissue NAD-isocitrate dehydrogenase was decreased (2.85-fold). Such modifications in the citric acid cycle are expected to severely restrict citrate oxidation in porcine adipose tissue. Except for cytochrome c oxidase, activities of the enzyme complexes comprising the electron transport chain were not significantly different. The decrease in adipose cytochrome c oxidase activity could partly be attributed to a decreased inner membrane as suggested by lipid and enzyme analysis. In addition, Western blotting indicated that adipose and liver mitochondria possess similar quantities of cytochrome c oxidase protein. Taken together these results indicate that not only is the white adipose tissue protoplasm relatively rich in mitochondria, but that these mitochondria contain comparable enzymatic machinery to support a relatively high beta-oxidative rate.
Koekemoer
T C
TC
Department of Biochemistry & Microbiology, University of Port Elizabeth, P.O. Box 1600, 6000, Port Elizabeth, South Africa.
Oelofsen
W
W
D000273:Adipose Tissue / Q000737:chemistry* / Q000648:ultrastructure; D000818:Animals; D015153:Blotting, Western; D002331:Carnitine / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry*; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D008055:Lipids / Q000737:chemistry; D008099:Liver / Q000648:ultrastructure; D008854:Microscopy, Electron; D008928:Mitochondria / Q000737:chemistry*; D008930:Mitochondria, Liver / Q000737:chemistry* / Q000648:ultrastructure; D010100:Oxygen / Q000378:metabolism*; D010169:Palmitic Acids; D013552:Swine
D005227:Fatty Acids; D008055:Lipids; D010169:Palmitic Acids; D007521:Isocitrate Dehydrogenase; D007655:Ketoglutarate Dehydrogenase Complex; D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase; D002331:Carnitine; D010100:Oxygen