Leptin directly acts on peripheral tissues and alters energy metabolism in obese mice. It also has acute beneficial effects on these tissues via its hypothalamic action. However, it is not clear what effect chronic intracerebroventrical (ICV) leptin administration has on cardiac energy metabolism. We examined the effects of chronic ICV leptin on glucose and fatty acid metabolism in isolated working hearts from high-fat-fed and low-fat-fed mice. Mice were fed a high-fat (60% calories from fat) or low-fat (10% calories from fat) diet for 8 weeks before ICV leptin (5 μg/d) for 7 days. In low-fat-fed mice, leptin increased glucose oxidation rates in isolated working hearts when compared with control [203 ± 21 vs. 793 ± 93 nmol·(g dry weight)−1·min−1]. In high-fat-fed mice leptin inhibited fatty acid oxidation [476 ± 73 vs. 251 ± 38 nmol·(g·dry·wt)−1·min−1]. The increase in glucose oxidation in low-fat-fed mice was accompanied by increased pyruvate dehydrogenase activity. In high-fat-fed mice, leptin increased cardiac malonyl coenzyme A levels, secondary to a decrease in malonyl coenzyme A decarboxylase expression. These results suggest that ICV leptin alters cardiac energy metabolism opposite to its peripheral effects and that these effects differ depending on energy substrate supply to the mice.
From the Cardiovascular Research Centre, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada.
Received for publication September 4, 2010; accepted October 5, 2010.
Supported by a grant from the Canadian Diabetes Association to G. D. Lopaschuk.
G. D. Lopaschuk is an Alberta Heritage Foundation for Medical Research Medical Scientist. W. Keung is a Heart and Stroke Foundation of Canada and Alberta Heritage Foundation for Medical Research postdoctoral fellow.
The authors report no conflicts of interest.
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Reprints: Gary Lopaschuk, PhD, 423 Heritage Medical Research Centre, University of Alberta, Edmonton, Alberta, Canada T6G 2S2 (e-mail: firstname.lastname@example.org).