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Downregulation of Carnitine acyl-carnitine translocase by miRNAs
132 and 212 amplifies glucose-stimulated insulin secretion
Mufaddal S. Soni1, Mary E. Rabaglia1, Sushant Bhatnagar1, Jin Shang2, Olga Ilkayeva3,
Randall Mynatt4, Yun Ping Zhou2, Eric E. Schadt6, Nancy A.Thornberry2, Deborah M. Muoio5,
Mark P. Keller1 and Alan D. Attie1
From the 1Department of Biochemistry, University of Wisconsin, Madison, Wisconsin;
2Department of Metabolic Disorders Diabetes, Merck Research Laboratories, Rahway, New
Jersey; 3Sarah W. Stedman Nutrition and Metabolism Center, Duke Institute of Molecular
Physiology, 5Departments of Medicine and Pharmacology and Cancer Biology, Durham, North
Carolina. 4Pennington Biomedical Research Center, Louisiana State University system, Baton
Rouge, Louisiana; 6Institute for Genomics and Multiscale Biology, Mount Sinai School of
Medicine, New York, New York.
Corresponding author Alan D. Attie, 543A Biochemistry Addition, 433 Babcock Drive, Department of Biochemistry, University of Wisconsin Madison, Madison, Wisconsin, (608) 262 1372 (Ph), (608) 263 9608 (fax), [email protected].
Running Title: Fatty acyl carnitines enhance insulin secretion
Abstract word count: 163
Main text Word count: 3960
Number of tables: 0
Number of figures: 5
Diabetes Publish Ahead of Print, published online June 26, 2014 Diabetes Page 2 of 288
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ABSTRACT
We previously demonstrated that micro RNAs 132 and 212 are differentially upregulated in response to obesity in two mouse strains that differ in their susceptibility to obesity induced diabetes. Here we show the overexpression of micro RNAs 132 and 212 enhances insulin secretion (IS) in response to glucose and other secretagogues including non fuel stimuli. We determined that carnitine acyl carnitine translocase (CACT, Slc25a20) is a direct target of these miRNAs. CACT is responsible for transporting long chain acyl carnitines into the mitochondria for β oxidation. SiRNA mediated knockdown of CACT in β cells led to the accumulation of fatty acyl carnitines, and enhanced IS. The addition of long chain fatty acyl carnitines promoted
IS from INS 1 β cells as well as primary mouse islets. The effect in INS 1 cells was augmented in response to suppression of CACT. A non hydrolyzable ether analog of palmitoyl carnitine stimulated IS, showing that β oxidation of palmitoyl carnitine is not required for its stimulation of IS. These studies establish a link between miRNA dependent regulation of CACT and fatty acyl carnitine mediated regulation of IS.
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INTRODUCTION
Cells have evolved mechanisms to regulate fuel utilization in response to changes in
substrate availability. Glucose oxidation leads to inhibition of β oxidation through the production
of malonyl CoA, a potent inhibitor of carnitine palmitoyl transferase