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Right-to-left ventricular differences in the expression of mitochondrial hexokinase and phosphorylation of Akt
Petra Waskova-Arnostova1, Barbara Elsnicova, Dita Kasparova
1Department of Physiology, Faculty of Science, Charles University in Prague, Prague.
Insights
The right ventricle (RV) shows higher expression of hexokinase (HK) enzymes compared to the left ventricle (LV). This suggests the RV has greater aerobic glycolytic metabolism for responding to stress.
Area of Science:
- Cardiovascular Physiology
- Metabolic Regulation
- Enzymology
Background:
- Hexokinase (HK) is crucial for glucose homeostasis in cardiomyocytes.
- HK1 supports oxidative phosphorylation, while HK2 can prevent apoptosis.
- Differential expression and localization of HK isoforms in heart ventricles are not fully understood.
Purpose of the Study:
- To investigate the expression and subcellular localization of HK1 and HK2 isoforms.
- To compare these aspects between the left ventricle (LV) and right ventricle (RV) in adult male Wistar rats.
Main Methods:
- Real-Time RT-PCR for gene expression analysis.
- Western blotting for protein level quantification.
- Quantitative immunofluorescence microscopy for subcellular localization.
Main Results:
- Significantly higher mRNA and protein expression of both HK1 and HK2 in the RV compared to the LV.
- Immunofluorescence confirmed higher HK levels in the RV.
- Elevated ratios of phosphorylated Akt (p-Akt) were observed in the RV.
Conclusions:
- The RV exhibits higher aerobic glycolytic metabolism than the LV.
- This metabolic profile may enhance the RV's capacity to respond to stressful stimuli.
- Findings highlight potential functional differences between cardiac ventricles.
Background/Aims:
Hexokinase (HK) is a key glycolytic enzyme which promotes the maintenance of glucose homeostasis in cardiomyocytes. HK1 isoform is predominantly bound to the outer mitochondrial membrane and highly supports oxidative phosphorylation by increasing the availability of ADP for complex V of the respiratory chain. HK2 isoform is under physiological conditions predominantly localized in the cytosol and upon stimulation of PI3K/ Akt pathway associates with mitochondria and thus can prevent apoptosis. The purpose of this study was to investigate expression and subcellular localization of both HK isoforms in left (LV) and right (RV) heart ventricles of adult male Wistar rats.
Methods:
Real-Time RT-PCR, Western blotting, and quantitative immunofluorescence microscopy were used.
Results:
Our results showed a significantly higher expression of both HK1 and HK2 at mRNA and protein levels in the RV compared to the LV. These findings were corroborated by immunofluorescence staining which revealed substantially higher fluorescence signals of both HKs in the RV than in the LV. The ratios of phospho-Ser473-Akt/non-phospho-Akt and phospho-Thr308-Akt/non-phospho-Akt were also markedly higher in the RV than in the LV.
Conclusion:
These results suggest that the RV has a higher activity of aerobic glycolytic metabolism and may be able to respond faster and more powerfully to stressful stimuli than the LV.
