Journal of Obesity & Metabolic Syndrome

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Korean J Obes 2005; 14(1): 9-15

Published online January 1, 2005

Copyright © Korean Society for the Study of Obesity.

Mechanism of Elevated Oxygen Consumption by Intralipid and Heparin Injection: Increased Skeletal Muscle Fat Oxidation and UCP3 Expression

Min Seon Kim,Jong Yeon Kim1,So Young Park1,Yong Woon Kim1

Department of Internal Medicine, Daegu Fatima Hospital, Department of Physiology1, College of Medicine, Yeungnam University

Abstract

Background: Energy homeostasis is maintained by the balance between energy uptake and expenditure. When energy uptake exceeds expenditure, surplus energy is accumulated to fat. Exercise and thermogenesis utilize energy substrate and the brown adipose tissue (BAT) and skeletal muscle are known to be responsible for the thermogenesis. However, it is still uncertain which is the main tissue responsible for energy consumption when fat is overloaded.
Methods: To evaluate which tissue utilizes overloaded fatty acid, fatty acid oxidation capacity was measured following intralipid plus heparin or saline injection in male Sprague-Dawley rats. UCP1, UCP3, leptin, and adiponectin mRNA expression were also analyzed in BAT, soleus muscle, and white adipose tissue (WAT).
Results: The oxygen consumption was increased by intralipid injection and maintained for 3 hours compared to saline injected rats. The palmitate oxidation was increased by intralipid injection in soleus muscle, however, there was no significant change in BAT. UCP3 mRNA expression in soleus was increased by intralipid injection but UCP1 and 3 mRNA expression were not increased in BAT by intralipid injection. There were no significant changes in leptin and adiponectin expression in WAT between saline and intralipid injected rats.
Conclusion: These results suggest that the main mechanism responsible for increased oxygen consumption following intralipid injection is the elevated fat oxidation capacity and UCP3 mRNA expression in skeletal muscle.

Keywords: Oxygen consumption, Skeletal muscle, Brown adipose tissue, Fat oxidation