Contrast Between Rat Heart and Diaphragm Muscle in Expression of Genes Involved in Carbohydrate and Lipid Metabolism

Abstract

Heart (H) and diaphragm (D) contract rhythmically without cessation, and thus need proper metabolic machinery to meet long-term energetic demands. To determine whether metabolic strategies are shared, gene expression was assessed using microarrays (n=6 each). There were 594 genes with >2-fold differential expression between H and D; 307 were expressed H>D and 287 D>H. Assignment of all 594 genes to gene ontology groups revealed over-representation for “carbohydrate metabolism” (n=32 genes, P=0.0011) and “lipid metabolism” (n=48 genes, P=0.000015). For carbohydrate there were 14 genes with H>D and 18 genes with D>H, and for lipid there were 30 genes with H>D and 18 genes with D>H. The magnitude of differential expression between H and D ranged from 2- to 30-fold (mean 7.2) for carbohydrate and from 2- to 59-fold (mean 5.1) for lipid. For carbohydrate most genes are involved in cellular energetics (eg. Pfkm, Pgm1, Pgam1, Pfkfb1, Pfkfb2), whereas the lipid group included genes related to both energy metabolism and other processes. These data suggest H and D have differential strategies for meeting the energetic demands of long-term rhythmic contractions. SUPPORT: VA Research Service, NHLBI