Fig 1.
Cardiac metabolism varies between Egyptian fruit bats and C57BL/6J mice.
(A) Schematic summary of the study protocol. n = 4 bats (n = 2 males, forearm length = 91.60 ± 2.50 mm, n = 2 females, forearm length = 87.90 ± 1.85 mm) and n = 4 C57/BL6J mice (Charles River, UK, male). (B-C) Partial Least Squares Discriminant Analysis (PLS-DA) (B) and heatmap of unsupervised hierarchical cluster analysis (C) of the cardiac metabolite concentrations determined by LC-MS and high-resolution 1H nuclear magnetic resonance spectroscopy showing distinct profile of bat and C57/BL6J mouse. (D-H) Fold change differences of myocardial intermediates within major metabolic pathways (glucose metabolism, lipid metabolism, Krebs cycle), redox equivalents and energy-providing substrates. Fold changes are expressed as comparisons between bats and C57/BL6J mouse. The normality of data distribution was examined using Shapiro–Wilk’s normality test. All metabolites followed a Gaussian distribution, with the exception of NADP, pyruvate, N-acetylaspartate, and glycine. Comparison between two groups was performed by Student’s t-test (Gaussian data distribution) or Mann-Whitney U test when data was not normally distributed (Panel E, F, and G, NADP, pyruvate, N-acetylaspartate, glycine), *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.
Fig 2.
CardioNet analysis reveals increased lipid oxidation flux in bats.
(A) Unsupervised hierarchical clustering of estimated z-scored flux rate changes reveals metabolic adaptation in bats vs mice. Z-scores were calculated to visualise how many standard deviations an estimated flux rate is away from the mean across all experimental groups. The z-score describes the distance from the mean for a given flux rate as a function of the standard deviation. The colour scale indicates the degree to which estimated flux rate changes are predicted to be respectively lower or higher bat vs mouse. (B) CardioNet in silico metabolic >5-fold flux changes bat versus C57/BL6J. The graph denotes the estimated flux distribution. The coloured nodes represent metabolites assigned to five compartments: extracellular space, cytosol, mitochondria, microsome, and lysosome. The black nodes indicate reactions; two reactions are linked by a directed edge, indicating the reaction flux. The line thickness of each edge is proportional to the predicted flux rate change. (C) Predicted myocardial oxygen consumption in simulations of bat flight, night activity and roost activity (n = 4/group). (D) Predicted substrate uptakes for glucose, β-hydroxybutrate (β-HB) and fatty acids (FA15, FA18:2) in simulations of bat flight, night activity and roost activity (n = 4/group). (E) Predicted flux rates for oxidative phosphorylation and electron transport chain in simulations of bat flight, night activity and roost activity (n = 4/group).