Dietary fat effects on hepatic lipid peroxidation and enzymes of H2O2 metabolism and NADPH Generation |
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| Authors: | Li-Chuan Chen Gilbert Boissonneault Michael G Hayek Ching K Chow |
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| Affiliation: | (1) Graduate Center for Toxicology, University of Kentucky, 40506 Lexington, Kentucky;(2) Department of Clinical Sciences, University of Kentucky, 40506 Lexington, Kentucky;(3) Multidisciplinary Ph.D. Program in Nutritional Sciences, University of Kentucky, 40506 Lexington, Kentucky;(4) Department of Nutrition & Food Science, University of Kentucky, 212 Funkhouser Building, 40506-0054 Lexington, KY;(5) Present address: Differentiation Control Section, Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Building 37 Room 3A-13, 20892 Bethesda, MD;(6) Present address: USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, 02111 Boston, MA |
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| Abstract: | The purpose of this study was to determine the effects of dietary fat quantity and fatty acid composition on hepatic H2O2-metabolizing systems, activities of NADPH-generating enzymes and lipid peroxidation. Onemonth-old male C57BL/6J mice were
fed one of six diets: (i) 5% fat, rich in 18∶2n−6 fatty acid (5% N−6); (ii) 20% fat, rich in 18∶3n−3 (N−3); (iii) 20% fat,
rich in 18∶2n−6 (N−6); (iv) 20% fat, rich in 18∶1n−9 (N−9); (v) 20% fat, rich in saturated fatty acids (SAT); and (vi) 20%
fat, deficient in essential fatty acids (EFAD); for 11 wk. Comparisons between animal groups receiving different fat quantities
showed that activities of glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) and malic enzyme (ME, EC 1.1.1.40) and the
levels of conjugated dienes were significantly lower in the N−6 than in 5% N−6 group. Conversely, activities of catalase (CAT,
EC 1.11.1.6) and seleniumglutathione peroxidase (SeGSHPx, EC 1.11.1.9) were higher in the N−6 than in 5% N−6 group. Among
the five dietary groups receiving 20% fat but differing in fatty acid composition, CAT activity was lower in the N−9 group,
SeGSHPx activity was lower in the EFAD group, and glutathione reductase (GSSGR, EC 1.6.4.2) activity was higher in the N−6
than in the N−3, N−9, SAT and EFAD groups. The EFAD group had much higher levels of total lipids and conjugated dienes, as
well as activities of NADPH-generating enzymes, including G6PDH, ME and isocitrate dehydrogenase (EC 1.1.1.42), than the other
four high-fat groups. The hepatic levels of malondialdehyde were not different among the five groups fed 20% fat. In the EFAD
group, higher hepatic lipid content can be attributed to higher activities of NADPH-generating enzymes, and the elevation
of conjugated diene levels may be related to increased oxygenation of 20∶−6 (Mead acid)via the lipoxygenase/cyclooxygenase pathway. In short, both dietary fat quantity and fatty acid composition selectively affected
hepatic H2O2-metabolizing systems, activities of NADPH-generating enzymes and lipid peroxidation status. |
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