QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Donkin, S. S. Articles by Etherton, T. D. Search for Related Content PubMed PubMed Citation Articles by Donkin, S. S. Articles by Etherton, T. D.

Porcine Somatotropin Differentially Down-Regulates Expression of the GLUT4 and Fatty Acid Synthase Genes in Pig Adipose Tissue^1,2,

S. S. Donkin^*,,3, P. Y. Chiu^*,,4, D. Yin^*, I. Louveau^*,5, B. Swencki^*, J. Vockroth^*, C. M. Evock-Clover^**,6, J. L. Peters^* and T. D. Etherton^*,,7

^* Department of Dairy and Animal Science The Graduate Program in Nutrition, The Pennsylvania State University, University Park, PA 16802 ^** USDA-ARS, Growth Biology Laboratory, Beltsville, MD 20705

The present study was conducted to determine whether porcine somatotropin (pST) differentially regulates expression of the GLUT4 and fatty acid synthase (FAS) genes in pig adipose tissue. Three different experiments were conducted in which pigs were treated daily with different doses of pST for different time periods (7 or 14 d and from 60 to 90 kg of body wt). In these experiments, pST significantly and consistently decreased FAS mRNA levels (80%, 66% and 85%, respectively); however, GLUT4 mRNA was not affected by pST in two of the three experiments, and in the one showing an effect (Experiment 2), the decrease was less than observed for FAS (44%). Because of these results, we conducted subsequent experiments to see if the effects of pST on glucose metabolism in cultured pig adipose tissue (48 h) differed when glucose concentrations were changed from 1 to 5 mmol/L. These studies revealed that the antagonistic effect of pST on insulin action was more potent when glucose transport was saturated (5 mmol/L) than when glucose concentration limited glucose entry into the cell (1 mmol/L). In summary, these results suggest that the effects of pST on glucose transport in pig adipocytes are secondary to changes elicited by the hormone on intracellular glucose use for lipogenesis. When considered in the context of the decrease previously observed in glucose transport in pig adipocytes, the findings reported herein suggest that pST acts to decrease GLUT4 protein activity and/or distribution between the plasma membrane and the intracellular pool with little alteration in GLUT4 gene expression or total cell GLUT4 protein.

KEY WORDS: • adipose tissue • fatty acid synthase • GLUT4 • insulin • porcine somatotropin • pigs

¹ Supported in part by USDA grant 91-37206-6740 (to TDE).

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ Current address: Department of Animal Sciences, Purdue University, West Lafayette, IN 47907.

⁴ Current address: Department of Urology, Long Island Jewish Medical Center, New Hyde Park, NY 11040.

⁵ Current address: Institut de la Recherche Agronomique, Station de Recherches Porcines, Saint Gilles, 35590 L'Hermitage, France.

⁶ Current address: Room 209, Building 200, BARC-East, USDA-ARS, Beltsville, MD 20705.

⁷ To whom correspondence should be addressed: 323 A.S.I. Bldg.

Manuscript received 19 January 1996. Revision accepted 7 July 1996.