Carnitine Palmitoyltransferase-1 in Neonatal Pig Heart

Duna Penn, MD, MS, Principal Investigator
Chittaranjan Debata, MD
Michael Lan, PhD

Abstract
Carnitine palmitoyltransferase-1 (CPT-1) is a key enzyme regulating the oxidation of fatty acids (FA), a major energy fuel for the heart. CPT-1 consists of 2 isoforms (L-CPT-1 and M-CPT-1) that differ in requirement for carnitine and sensitivity to inhibition by malonyl-CoA . Unique among organs, the heart contains both isoforms and their relative contribution to total CPT-1 activity changes during postnatal development. To test the working hypothesis that CPT-1 isoform gene expression in the neonatal heart may be affected by clinically relevant conditions with potentially profound effects on myocardial FA oxidation, the following specific aims are proposed: 1) To determine the normal developmental pattern of gene expression (RNA analysis by Northern blot and real-time PCR) and enzymatic activity (radiotracer method with/without DNP etomoxir) for CPT-1 isoforms using heart tissues obtained from sow-fed piglets at 1,3,7,14,21,and 30 days of age; 2) To test the hypothesis that carnitine deprivation will delay maturation of the gene expression pattern and enzymatic activity for CPT-1 isoforms using heart tissues obtained from a piglet model for nutritional carnitine deficiency developed in our laboratory; and 3) To test the hypothesis that hyperinsulinemia will accelerate maturation of the gene expression pattern and enzymatic activity for CPT-1 isoforms using heart tissues obtained from piglets subjected to hyperinsulinemic/euglycemic clamp conditions for 3 days. Although CPT-1 regulation has been studied in cardiac hypertrophy and failure, little is known about myocardial CPT-1 isoforms during development in the pig, a preferred animal model for the human neonate. Altered CPT-1 protein activity could potentially lead to serious postnatal consequences. Demonstration of delayed or accelerated maturation with nutritional and hormonal manipulation would support the concept of CPT-1 gene expression plasticity in the neonatal heart. It would also address 2 clinically interesting questions. Carnitine deprivation of the neonate is still commonly practiced in the form of carnitine-free parenteral nutrition. Does this practice adversely affect the newborn heart? Both diabetes mellitus and insulin administration have profound effects on CPT-1 activity in various organs. Infants of diabetic mothers are hyperinsulinemic and often have cardiomyopathy. Does CPT-1 play a role in this pathology?

Collaborations
Jeanie McMillin, PhD, University of Texas at Houston
Jessica Thomson, LSUHSC Department of Public Health and Preventive Medicine
Gebre Woldegiorgis, PhD, Oregon Graduate Institute of Science and Technology

Sponsor: DHHS
Duration: 04/04 - 03/06