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United States Department of Agriculture

Agricultural Research Service

Title: Porcine Somatotropin Differentially Down-Regulates Expression of the Glut4 and Fatty Acid Synthase Genes in Pig Adipose Tissue

Authors
item Donkin, S - PURDUE UNIVERSITY
item Chiu, P - LONG ISLAND JEWISH MED CT
item Yin, D - PENNSYLVANIA STATE UNIVER
item Louveau, I - PENNSYLVANIA STATE UNIVER
item Swenki, B - PENNSYLVANIA STATE UNIVER
item Vockroth, J - PENNSYLVANIA STATE UNIVER
item Clover, Christina
item Peters, J - PENNSYLVANIA STATE UNIVER
item Etherton, T - PENNSYLVANIA STATE UNIVER

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 1996
Publication Date: N/A

Interpretive Summary: 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 periods of time (7 or 14 days and from 60 to 90 kg of liveweight). The most important finding of the present study is that the effects of pST on GLUT4 gene expression are different than observed for expression of the FAS gene. The effects of pST on glucose metabolism in the adipocyte appear to be selective in that the reduction in FAS gene expression was consistently observed and was of much greater magnitude than what we observed for expression of the GLUT4 gene. The antagonistic effect of pST on insulin action is more potent when glucose transport is maximized than when glucose concentration limits glucose entry into the cell.

Technical Abstract: 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 periods of time (7 or 14 days and from 60 to 90 kg of liveweight). In these experiments, pST 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%). 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.

Last Modified: 10/21/2014
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