To determine the relationship between glycerol and nonesterified fatty acid (NEFA) release from adipose tissue, and to test whether forearm muscle and abdominal adipose tissue are capable of extracting these two lipolytic products from the circulation, 13 male subjects were studied after an overnight fast during combined infusion of radiolabeled palmitate and glycerol. Blood samples were taken from a radial artery, a deep forearm vein, and a superficial abdominal vein before and during a 2-h infusion of glucose at ~7 mg · kg¹ · min¹. The ratio of the appearance rates of total NEFA to glycerol was ~3/1 during the baseline period but decreased to 1.3/1 during glucose infusion. There was significant extraction of both glycerol and NEFA by forearm muscle. In contrast, there was no apparent uptake of glycerol by adipose tissue. Adipose tissue NEFA uptake was undetectable during the baseline period but became significant during glucose infusion. These data indicate that there is very little to no in situ reesterification of NEFA in adipose tissue after an overnight fast. During glucose infusion, there was apparently a relative increase in the fraction of glycerol derived from the action of lipoprotein lipase and an increase in reesterification in situ.

lipolysis; insulin; glucose; tracer

This article has been cited by other articles:

				C. Moro, S. Bajpeyi, and S. R. Smith Determinants of intramyocellular triglyceride turnover: implications for insulin sensitivity Am J Physiol Endocrinol Metab, February 1, 2008; 294(2): E203 - E213. [Abstract] [Full Text] [PDF]

				G. C. Henderson, J. A. Fattor, M. A. Horning, N. Faghihnia, M. L. Johnson, T. L. Mau, M. Luke-Zeitoun, and G. A. Brooks Lipolysis and fatty acid metabolism in men and women during the postexercise recovery period J. Physiol., November 1, 2007; 584(3): 963 - 981. [Abstract] [Full Text] [PDF]

				G. A. Wallis, A. L. Friedlander, K. A. Jacobs, M. A. Horning, J. A. Fattor, E. E. Wolfel, G. D. Lopaschuk, and G. A. Brooks Substantial working muscle glycerol turnover during two-legged cycle ergometry Am J Physiol Endocrinol Metab, October 1, 2007; 293(4): E950 - E957. [Abstract] [Full Text] [PDF]

				A. L. Friedlander, K. A. Jacobs, J. A. Fattor, M. A. Horning, T. A. Hagobian, T. A. Bauer, E. E. Wolfel, and G. A. Brooks Contributions of working muscle to whole body lipid metabolism are altered by exercise intensity and training Am J Physiol Endocrinol Metab, January 1, 2007; 292(1): E107 - E116. [Abstract] [Full Text] [PDF]

				C. B. Djurhuus, C. H. Gravholt, S. Nielsen, S. B. Pedersen, N. Moller, and O. Schmitz Additive effects of cortisol and growth hormone on regional and systemic lipolysis in humans Am J Physiol Endocrinol Metab, March 1, 2004; 286(3): E488 - E494. [Abstract] [Full Text]

				E. Hagstrom-Toft, V. Qvisth, I. Nennesmo, M. Ryden, H. Bolinder, S. Enoksson, J. Bolinder, and P. Arner Marked Heterogeneity of Human Skeletal Muscle Lipolysis at Rest Diabetes, December 1, 2002; 51(12): 3376 - 3383. [Abstract] [Full Text] [PDF]

				K. Evans, G. C. Burdge, S. A. Wootton, M. L. Clark, and K. N. Frayn Regulation of Dietary Fatty Acid Entrapment in Subcutaneous Adipose Tissue and Skeletal Muscle Diabetes, September 1, 2002; 51(9): 2684 - 2690. [Abstract] [Full Text] [PDF]

				E. Moberg, S. Sjoberg, E. Hagstrom-Toft, and J. Bolinder No apparent suppression by insulin of in vivo skeletal muscle lipolysis in nonobese women Am J Physiol Endocrinol Metab, August 1, 2002; 283(2): E295 - E301. [Abstract] [Full Text] [PDF]

				K. H. W. Lange, J. Lorentsen, F. Isaksson, L. Simonsen, J. Bulow, and M. Kjar Lipolysis in human adipose tissue during exercise: comparison of microdialysis and a-v measurements J Appl Physiol, March 1, 2002; 92(3): 1310 - 1316. [Abstract] [Full Text] [PDF]

				G. B. McClelland, P. W. Hochachka, S. P. Reidy, and J.-M. Weber High-altitude acclimation increases the triacylglycerol/fatty acid cycle at rest and during exercise Am J Physiol Endocrinol Metab, September 1, 2001; 281(3): E537 - E544. [Abstract] [Full Text] [PDF]

				E. Hagstrom-Toft, A. Thorne, S. Reynisdottir, E. Moberg, S. Rossner, J. Bolinder, and P. Arner Evidence for a Major Role of Skeletal Muscle Lipolysis in the Regulation of Lipid Oxidation During Caloric Restriction In Vivo Diabetes, July 1, 2001; 50(7): 1604 - 1611. [Abstract] [Full Text] [PDF]

				T. J. Horton and J. O. Hill Prolonged fasting significantly changes nutrient oxidation and glucose tolerance after a normal mixed meal J Appl Physiol, January 1, 2001; 90(1): 155 - 163. [Abstract] [Full Text] [PDF]

				S. R. Commerford, M. J. Pagliassotti, C. L. Melby, Y. Wei, E. C. Gayles, and J. O. Hill Fat oxidation, lipolysis, and free fatty acid cycling in obesity-prone and obesity-resistant rats Am J Physiol Endocrinol Metab, October 1, 2000; 279(4): E875 - E885. [Abstract] [Full Text] [PDF]

				B. Kalderon, N. Mayorek, E. Berry, N. Zevit, and J. Bar-Tana Fatty acid cycling in the fasting rat Am J Physiol Endocrinol Metab, July 1, 2000; 279(1): E221 - E227. [Abstract] [Full Text] [PDF]

				R. Mora-Rodriguez and E. F. Coyle Effects of plasma epinephrine on fat metabolism during exercise: interactions with exercise intensity Am J Physiol Endocrinol Metab, April 1, 2000; 278(4): E669 - E676. [Abstract] [Full Text] [PDF]

				E. Montell, C. Lerin, C. B. Newgard, and A. M. Gomez-Foix Effects of Modulation of Glycerol Kinase Expression on Lipid and Carbohydrate Metabolism in Human Muscle Cells J. Biol. Chem., January 18, 2002; 277(4): 2682 - 2686. [Abstract] [Full Text] [PDF]