Abstract P238: Snf1-Related Kinase Is a Novel Regulator of Cardiomyocyte Metabolism
Background: Snf1-related Kinase (SNRK) is a serine/threonine kinase with sequence homology to AMP-activated kinase (AMPK). We have found that SNRK is upregulated in hearts from patients with ischemic cardiomyopathy, but the function of SNRK has not been studied in cardiomyocytes. Since previous gene array data show that SNRK alters expression of metabolic genes, we determined whether SNRK regulates cardiomyocyte metabolism.
Results: SNRK downregulation reduced ATP levels by 23.34% in neonatal rat cardiomyocytes compared to nonsilencing siRNA, and SNRK overexpression increased ATP by 20.67% compared to GFP control. SNRK knockdown reduced baseline oxygen consumption rate (OCR) by 23.69%, and by 54.53% with the mitochondrial uncoupler carbonyl cyanide 3-chlorophenylhydrazone (CCCP). SNRK overexpression increased OCR by 9.57% with CCCP. Mitochondrial content was unchanged as measured by mitochondrial DNA and cardiolipin staining. However, tetramethylrhodamine ethyl ester (TMRE) staining was increased by SNRK, suggesting that SNRK maintains mitochondrial membrane potential. Furthermore, the extracellular acidification rate was reduced 19.47% with SNRK knockdown and increased 12.57% with overexpression, signifying enhanced glycolytic flux. SNRK also increased lactate levels and mRNA of the glycolytic proteins hexokinase I and II. Glucose uptake increased 29.61% with SNRK overexpression, and expression of glucose transporters GLUT1 and GLUT4 was also increased, demonstrating an increase in cellular glucose import. Glycogen was also decreased 40.69% with SNRK knockdown and increased 46.03% with overexpression, demonstrating that SNRK reduces storage of glucose into glycogen. Additionally, OCR with palmitate over baseline was reduced 43.56% with SNRK downregulation and increased 285.6% with overexpression, suggesting enhanced fatty acid oxidation. Phosphorylation of acetyl-coA carboxylase was also increased by SNRK. Fatty acid uptake, however, was unchanged.
Conclusions: Our results demonstrate that SNRK increases ATP and oxygen consumption through augmented mitochondrial membrane potential, glucose utilization, and fatty acid oxidation. These findings reveal SNRK as a major modulator of cardiomyocyte metabolism.
- © 2011 by American Heart Association, Inc.