Myocardial glycolysis and gene expression in the adult mouse heart

The heart uses primarily fatty acids and glucose for deriving energy. The majority of energy in the healthy heart derives from fat utilization, with the remainder coming primarily from the catabolism of glucose. Classical studies by Randle and colleagues describe the ability of the heart to switch its mode of utilization facilely and reversibly between glucose and fatty acids (myocardial glucose-fatty acid cycle or Randle cycle). However, under conditions of pathological stress, reliance of the heart on fatty acids decreases with a concomitant increase in reliance on glucose. It is unclear how such changes in metabolism regulate gene expression in the heart. Therefore, we examined how regulation of glycolysis at the level of phosphofructokinase modulates gene expression in the heart. We performed transcriptomic analysis of hearts from mice expressing either kinase-deficient phosphofructokinase 2 (GlycoLo) or phosphatase-deficient phosphofructokinase 2 (GlycoHi) under the control of the -MHC promoter, which restricted expression of the transgenes to the heart. Phosphofructokinase 2 only controls the ability of the myocyte to regulate abundance of a single metabolite, F-2,6-P2, which is an allosteric regulator of the rate-limiting and committed step in glycolysis. Parallel radiometric and metabolomic studies showed the expected increases or decreases in glycolytic flux along with diametrically opposite changes in fat metabolism, which is consistent with the myocardial glucose-fatty acid cycle. Transcriptomic analyses showed remarkable changes in gene transcription in these hearts, which indicates that glucose and/or fatty acid metabolism is a driver of transcriptional programs in the heart. Furthermore, glycolytic activity coordinately regulated numerous genes in the heart, including genes important for cardiac remodeling as well as genes regulating gluconeogenic and ancillary biosynthetic pathway activity. These findings reveal that glycolytic rate is a critical regulator of gene expression in the heart and can coordinate programs that modulate cardiac metabolism, growth, and hypertrophy.

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