Journal of Animal Science, Vol 79, Issue 3 653-657, Copyright © 2001 by American Society of Animal Science

JOURNAL ARTICLE

Porcine leptin alters insulin inhibition of lipolysis in porcine adipocytes in vitro

T. G. Ramsay
Pennington Biomedical Research Center, Baton Rouge, LA, USA. tramsay@lpsi.barc.usda.gov

The present study determined whether porcine leptin can alter the lipolytic rate in porcine adipocytes produced in vitro. The stromal-vascular cell fraction of neonatal subcutaneous adipose tissue was isolated by collagenase digestion, filtration, and subsequent centrifugation. These stromal-vascular cells were seeded on 25-cm2 tissue culture flasks and proliferated to confluency in 10% fetal bovine serum in DMEM/F12 (50:50). Cultures were differentiated using 2% pig serum + 10 mM isobutyl methylxanthine + 1 microM dexamethasone for 48 h. This medium was replaced with 5% pig serum + 1 microM insulin to promote lipid filling of adipocytes for 7 d. Adipocyte-containing cultures were incubated overnight in serum-free medium and then used for experiments. Acute experiments assessed lipolysis in cultures exposed to porcine leptin (0 to 1,000 ng/mL medium) for 2 h. Chronic experiments used cultures incubated with 100 ng porcine leptin/mL of medium for 72 h prior to lipolysis measurements. Direct effects of leptin were examined by incubating cultures in DMEM/F12, 25 mM HEPES, 3% bovine serum albumin, 20 mU of adenosine deaminase/mL of medium in the presence of 0 to 1,000 ng of porcine leptin/mL of medium. Indirect effects of leptin were examined using the same incubation medium but also supplemented with 1 microM isoproterenol +/- 10 nM insulin in the presence of 0 to 1,000 ng of porcine leptin/mL of medium. Media glycerol concentration was measured at the end of 2-h incubations. Acute leptin exposure induced up to a 76% increase in lipolysis (P < 0.05) but had no effect on insulin's inhibition of lipolysis. Chronic exposure to leptin produced up to a 56% increase in lipolysis (P < 0.05) and reduced insulin's inhibition ofisoproterenol-stimulated lipolysis by up to 31% (P < 0.05). These data demonstrate leptin functions to promote the partitioning of energy away from lipid accretion within porcine adipose tissue by promoting lipolysis directly and indirectly by reducing insulin-mediated inhibition of lipolysis.

This article has been cited by other articles:

				G. J. Hausman, M. V. Dodson, K. Ajuwon, M. Azain, K. M. Barnes, L. L. Guan, Z. Jiang, S. P. Poulos, R. D. Sainz, S. Smith, et al. BOARD-INVITED REVIEW: The biology and regulation of preadipocytes and adipocytes in meat animals J Anim Sci, April 1, 2009; 87(4): 1218 - 1246. [Abstract] [Full Text] [PDF]

				T. Shan, Y. Wang, T. Wu, C. Liu, J. Guo, Y. Zhang, J. Liu, and Z. Xu Porcine sirtuin 1 gene clone, expression pattern, and regulation by resveratrol J Anim Sci, March 1, 2009; 87(3): 895 - 904. [Abstract] [Full Text] [PDF]

				T. Shan, Y. Wang, T. Wu, J. Guo, J. Liu, J. Feng, and Z. Xu Porcine adipose triglyceride lipase complementary deoxyribonucleic acid clone, expression pattern, and regulation by resveratrol J Anim Sci, August 1, 2008; 86(8): 1781 - 1788. [Abstract] [Full Text] [PDF]

				S. K. Jacobi, N. K. Gabler, K. M. Ajuwon, J. E. Davis, and M. E. Spurlock Adipocytes, myofibers, and cytokine biology: New horizons in the regulation of growth and body composition J Anim Sci, April 1, 2006; 84(13_suppl): E140 - E. [Abstract] [Full Text] [PDF]

				T. G. Ramsay Porcine preadipocyte proliferation and differentiation: A role for leptin? J Anim Sci, September 1, 2005; 83(9): 2066 - 2074. [Abstract] [Full Text] [PDF]

				E. Lord, S. Ledoux, B. D. Murphy, D. Beaudry, and M. F. Palin Expression of adiponectin and its receptors in swine J Anim Sci, March 1, 2005; 83(3): 565 - 578. [Abstract] [Full Text] [PDF]

				H. Bowen, T. D. Mitchell, and R. B. S. Harris Method of leptin dosing, strain, and group housing influence leptin sensitivity in high-fat-fed weanling mice Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2003; 284(1): R87 - R100. [Abstract] [Full Text] [PDF]