Lipid is the primary fuel for the beating heart. In fact, glucose utilization is inhibited by oxidation of fatty acids in heart. In exercise studies, it has been suggested that endogenous triacylglycerols (TG) are quantitatively unimportant as a metabolic fuel because of the small absolute decrease in TG content seen after work. In these studies, TG synthesis was not measured. This is an important factor because turnover rate of the intracellular TG pool in muscle is rapid. Therefore, TG synthesis and hydrolysis will be measured in hearts of exercise-trained rats. In the second study, the cAMP system appears to regulate TG lipolysis in muscle. In this context, we have observed a decrease in TG stores in hearts treated with epinephrine, dibutyryl cAMP, and 3-isobutyl-1-methylxanthine. We attributed this effect to an increase in TG hydrolysis. Since TG turnover is rapid in muscle, it is necessary to measure TG synthesis and hydrolysis in the same heart. A unique aspect of the TG turnover work is that a TG lipase sensitive to cAMP will be measured (intracellular lipoprotein lipase). In the third study, an attempt will be made to determine if cAMP regulates intra-cellular TG metabolism in hearts of exercised rats. In the next study, we plan to determine if intracellular lipoprotein lipase (LPL) in skeletal muscle possesses the classical characteristics of LPL similar to that seen in heart. Further, we plan to determine if intracellular LPL in fast red, fast white, and soleus muscle is under hormonal control. Further, we plan to obtain information regarding enzyme-substrate interaction in skeletal muscle. The question here is whether intracellular LPL makes physical contact with the endogenous TG droplet. This work is important because little is known about LPL in skeletal muscle.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases (NIADDK)
Type
Research Project (R01)
Project #
2R01AM017357-11
Application #
3151058
Study Section
Respiratory and Applied Physiology Study Section (RAP)
Project Start
1977-05-01
Project End
1988-06-30
Budget Start
1985-07-01
Budget End
1986-06-30
Support Year
11
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of Illinois at Chicago
Department
Type
Other Specialized Schools
DUNS #
121911077
City
Chicago
State
IL
Country
United States
Zip Code
60612
Oscai, L B; Tsika, R W; Essig, D A (1992) Exercise training has a heparin-like effect on lipoprotein lipase activity in muscle. Can J Physiol Pharmacol 70:905-9
Scotellaro, P A; Ji, L L; Gorski, J et al. (1991) Body fat accretion: a rat model. Med Sci Sports Exerc 23:275-9
Palmer, W K; Oscai, L B; Bechtel, P J et al. (1990) Dibutyryl cAMP-induced increases in triacylglycerol lipase activity in developing L8 myotube cultures. Can J Physiol Pharmacol 68:689-93
Oscai, L B; Gorski, J; Miller, W C et al. (1988) Role of the alkaline TG lipase in regulating intramuscular TG content. Med Sci Sports Exerc 20:539-44
Gorski, J; Miller, W C; Palmer, W K et al. (1988) Effect of colchicine on alkaline triglyceride lipase activity and triglyceride content in rat skeletal muscle. Can J Physiol Pharmacol 66:1555-9
Oscai, L B; Palmer, W K (1988) Muscle lipolysis during exercise. An update. Sports Med 6:23-8
Arnall, D A; Palmer, W K; Miller, W C et al. (1988) Effect of fasting on myocardial substrates in male and female rats. Am J Physiol 254:C560-3
Miller, W C; Palmer, W K; Arnall, D A et al. (1987) Effect of cholera toxin on triacylglycerol lipase activity and triacylglycerol content of rat heart. Can J Physiol Pharmacol 65:60-3
Oscai, L B; Miller, W C; Arnall, D A (1987) Effects of dietary sugar and of dietary fat on food intake and body fat content in rats. Growth 51:64-73
Miller, W C; Palmer, W K; Arnall, D A et al. (1987) Characterization of the triacylglycerol lipase activity in three types of rat skeletal muscle. Can J Physiol Pharmacol 65:317-22

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