Volume 90, Issue 5, November (2003), pp. 953-960 © The Author 2003
doi:10.1079/BJN2003000968

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Effect of high-fat feeding on metabolic efficiency and mitochondrial oxidative capacity in adult rats

Susanna Iossa¹, Lillà Lionetti¹, Maria P. Mollica¹, Raffaella Crescenzo¹, Monica Botta¹, Antonio Barletta¹, Giovanna Liverini^1
1Department of General and Environmental Physiology, University of Naples ‘FEDERICO II’, Via Mezzocannone 8, I-80134 Napoli, Italy

 (Received 20 December 2002–Revised 23 May 2003–Accepted 18 June 2003)

The changes in metabolic efficiency, body composition, and nutrient partitioning induced by high-fat feeding were evaluated in adult rats (90 d of age). The alterations in serum free triiodothyronine, insulin, and leptin levels, as well as in hepatic and skeletal muscle metabolism, were also assessed. Rats were fed either a low- or a high-fat diet for 2 weeks. Relative to the low-fat feeding, energy intake and expenditure, as well as body-energy gain, lipid gain, and energetic efficiency, were increased by the high-fat feeding. Increased serum leptin levels accompanied these variations. A positive correlation between serum leptin levels and percentage of body fat was found in the rats fed the low- or high-fat diet, with a significant divergence between the slope of the regression lines. Furthermore, a negative correlation between serum leptin level and energy intake was found in the rats fed the low-fat diet, while a positive correlation was found in the rats fed the high-fat diet. Finally, the high-fat feeding decreased the hepatic and skeletal muscle mitochondrial oxidative capacity. It is concluded that, in adult rats, a nutritional factor such as a high level of fat in the diet induces obesity, leptin resistance, and impairment of mitochondrial capacity, all phenomena typical of unrestrained aged rats.

Keywords:
Energy balance, Mitochondrial capacity, Triiodothyronine, Leptin

Abbreviations:
α-GPDH, α-glycerophosphate dehydrogenase, BSA, bovine serum albumin, HEPES, N′-(2-hydroxyethyl)piperazine-N-2-ethanesulfonic acid, ME, metabolisable energy, NEFA, non-esterified fatty acids, T₃, triiodothyronine