The outer mitochondrial membrane enzyme carnitine palmitoyltransferase I (CPT I) represents the initial and regulated step in the β-oxidation of fatty acids. It exists in at least two isoforms, denoted L (liver) and M (muscle) types, with very different kinetic properties and sensitivities to malonyl-CoA. Here we have examined the relative expression of the CPT I isoforms in two different models of adipocyte differentiation and in a number of rat tissues. Adipocytes from mice, hamsters and humans were also evaluated. Primary monolayer cultures of undifferentiated rat preadipocytes expressed solely L-CPT I, but significant levels of M-CPT I emerged after only 3 days of differentiation in vitro; in the mature cell M-CPT I predominated. In sharp contrast, the murine 3T3-L1 preadipocyte expressed essentially exclusively L-CPT I, both in the undifferentiated state and throughout the differentiation process in vitro. This was also true of the mature mouse white fat cell. Fully developed adipocytes from the hamster and human behaved similarly to those of the rat. Thus the mouse white fat cell differs fundamentally from those of the other species examined in terms of its choice of a key regulatory enzyme in fatty acid metabolism. In contrast, brown adipose tissue from all three rodents displayed the same isoform profiles, each expressing overwhelmingly M-CPT I. Northern blot analysis of other rat tissues established L-CPT I as the dominant isoform not only in liver but also in kidney, lung, ovary, spleen, brain, intestine and pancreatic islets. In addition to its primacy in skeletal muscle, heart and fat, M-CPT I was also found to dominate in the testis. The same inter-tissue isoform pattern (with the exception of white fat) was found in the mouse. Taken together, the data bring to light an intriguing divergence between white adipocytes of the mouse and other mammalian species. They also raise a cautionary note that should be considered in the choice of animal model used in further studies of fat cell physiology.
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October 1997
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Research Article|
October 01 1997
Mouse white adipocytes and 3T3-L1 cells display an anomalous pattern of carnitine palmitoyltransferase (CPT) I isoform expression during differentiation: Inter-tissue and inter-species expression of CPT I and CPT II enzymes
Nicholas F. BROWN;
Nicholas F. BROWN
*Department of Internal Medicine, Gifford Laboratories, Center for Diabetes Research, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235-9135, U.S.A.
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Jennifer K. HILL;
Jennifer K. HILL
*Department of Internal Medicine, Gifford Laboratories, Center for Diabetes Research, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235-9135, U.S.A.
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Victoria ESSER;
Victoria ESSER
*Department of Internal Medicine, Gifford Laboratories, Center for Diabetes Research, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235-9135, U.S.A.
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James L. KIRKLAND;
James L. KIRKLAND
‡Evans Department of Medicine and Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118-2393, U.S.A.
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Barbara E. CORKEY;
Barbara E. CORKEY
‡Evans Department of Medicine and Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118-2393, U.S.A.
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Daniel W. FOSTER;
Daniel W. FOSTER
*Department of Internal Medicine, Gifford Laboratories, Center for Diabetes Research, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235-9135, U.S.A.
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J. Denis MCGARRY
J. Denis MCGARRY
1
†Department of Biochemistry, Gifford Laboratories, Center for Diabetes Research, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235-9135, U.S.A.
1To whom correspondence should be addressed.
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Publisher: Portland Press Ltd
Received:
March 10 1997
Revision Received:
May 09 1997
Accepted:
May 29 1997
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1997
1997
Biochem J (1997) 327 (1): 225–231.
Article history
Received:
March 10 1997
Revision Received:
May 09 1997
Accepted:
May 29 1997
Citation
Nicholas F. BROWN, Jennifer K. HILL, Victoria ESSER, James L. KIRKLAND, Barbara E. CORKEY, Daniel W. FOSTER, J. Denis MCGARRY; Mouse white adipocytes and 3T3-L1 cells display an anomalous pattern of carnitine palmitoyltransferase (CPT) I isoform expression during differentiation: Inter-tissue and inter-species expression of CPT I and CPT II enzymes. Biochem J 1 October 1997; 327 (1): 225–231. doi: https://doi.org/10.1042/bj3270225
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