Our goal is to understand the molecular basis of two control mechanisms that contribute to the onset of obesity and its complications, notably NIDDM. These mechanisms include: l. control of expression of the obese (leptin) gene in the adipocyte, and 2. transcriptional control of the stearoylCoA desaturase genes (SCD1 and SCD2) in the adipocyte and hepatocyte. Leptin, a secretory protein expressed only by adipose tissue, regulates appetite (via receptors in the hypothalamus) and energy metabolism. The 3T3-L1 adipocyte system, pioneered in this laboratory, will be used as a cell culture model that mimics adipocytes in vivo. Our studies show that leptin is expressed/secreted by 3T3-L1 adipocytes and its expression is dramatically regulated in vivo by changes in physiological state. We have cloned/sequenced the regulatory 5' flanking region of the gene for use in the studies proposed. We plan to: * characterize the factors that regulate expression of the leptin gene and its mRNA, and * identify critical cis-regulatory elements within the leptin gene promoter that control its expression. We will identify and characterize the cognate trans-acting nuclear factors that interact with the cis- elements and determine how these interactions regulate transcription. The SCD genes catalyze delta9 cis-desaturation of fatty acids, and thereby determine the degree of unsaturation and functional properties of membrane phospholipids and storage/secretory triacylglycerols). Expression of the SCD1 and SCD2 genes is induced during adipocyte differentiation and is feed-back inhibited by polyunsaturated fatty acids (notably arachidonate) in certain cell types. We have cloned, sequenced and characterized the mouse SCD1 and SCD2 genes. A preadipocyte -repressive element (or PRE) and its binding protein (PRE-BP1) was discovered that maintains the SCD2 gene in the repressed state prior to differentiation. A similar, but distinct, element and binding protein have been identified for the SCD1 gene. We plan to: * sequence, express and characterize PRE-BP1 (SCD2) and the PRE-BP for the SCD1 gene. * investigate their site-specific binding interactions and repression/derepression mechanisms and role in negative-feedback control by arachidonate, and * determine the physiological basis (preadipocyte differentiation, negative feedback, etc.) for derepression and repression of the SCD1 and SCD2 genes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK014575-29
Application #
2684069
Study Section
Metabolism Study Section (MET)
Program Officer
Haft, Carol Renfrew
Project Start
1975-09-01
Project End
2001-03-31
Budget Start
1998-04-01
Budget End
1999-03-31
Support Year
29
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Cooke, D W; Lane, M D (1999) The transcription factor nuclear factor I mediates repression of the GLUT4 promoter by insulin. J Biol Chem 274:12917-24
Cornelius, P; MacDougald, O A; Lane, M D (1994) Regulation of adipocyte development. Annu Rev Nutr 14:99-129
Swick, A G; Lane, M D (1992) Identification of a transcriptional repressor down-regulated during preadipocyte differentiation. Proc Natl Acad Sci U S A 89:7895-9
Bamberger, M J; Lane, M D (1990) Possible role of the Golgi apparatus in the assembly of very low density lipoprotein. Proc Natl Acad Sci U S A 87:2390-4
Bamberger, M J; Lane, M D (1988) Assembly of very low density lipoprotein in the hepatocyte. Differential transport of apoproteins through the secretory pathway. J Biol Chem 263:11868-78