Table 1.

Comparison of metabolic flux and physiological parameters assessed in 12-week-old C57BL/10 and mdx mouse hearts perfused with ¹³C-labeled substrates.

Measured parameters	mdx vs. C57BL/10 (ratio)
(1) Metabolic flux parameters assessed at 30 min
(A) Cytosolic	↑(1.62)*
Glycolysis (production of lactate and pyruvate)
(B) Mitochondria
(i) Relative contribution of substrates to citrate synthesis
–Carbohydrate oxidation: pyruvate decarboxylation (PDC/CS)	↑ (2.20)**
–Fatty acid oxidation: oleate β-oxydation (OLE/CS)	↓ (0.73)*
–Oxidation of other substrates (OS/CS)	NS
–Anaplerosis: pyruvate carboxylation (PC/CS)	↓ (0.81)*
(ii) Citric acid cycle-related parameters
–Citric acid cycle intermediate levels	↓ (0.66)**
–Aconitase activity	↓ (0.72)*
–Citrate synthase activity	NS
–Calculated ATP production rates	↑ (1.17)*
(2) Physiological parameters assessed at 25–30 min
–Aortic flow	↑ (0.83)*
–Coronary flow	NS
–Left ventricular systolic pressure	↓ (0.90)*
–Left ventricular end diastolic pressure	NS
–Heart rate	NS
–dP/dtmax	↓ (0.84)**
–dP/dtmin	↓ (0.87)*
–Oxygen consumption	↑ (1.18)**
–Lactate dehydrogenase release	↑ (2.60)**

Metabolic and functional data are from [8]. The following metabolic parameters were assessed in working hearts perfused for 30 min with physiological concentrations of carbohydrates (11 mM glucose, 1.5 mM lactate and 0.2 mM pyruvate) and a fatty acid (0.4 mM oleate bound to albumin) using ¹³C-labeled substrates and mass isotopomer analysis by gas chromatography-mass spectrometry: (A) Glycolysis reflecting the production of lactate and pyruvate from ¹³C-glucose (μmol×min⁻¹). (B.i) Substrate flux ratios reflecting the contribution of exogenous fatty acids (oleate) and carbohydrates (CHOs: lactate, pyruvate and glucose) to citrate formation via (i) acetyl-CoA (energy) from oleate β-oxidation (OLE) and pyruvate decarboxylation (PDC), or (ii) oxaloacetate (anaplerosis) from pyruvate carboxylation (PC), all expressed relative to citrate synthesis (CS); (B.ii) Tissue concentration of citric acid cycle (CAC) intermediates (in μmol×g wet weight⁻¹), tissue aconitase and citrate synthase activity (μmol×min⁻¹×mg protein⁻¹) and calculated ATP production rates.

^*p<0.05,

^#p< 0.001 for mdx versus control mouse hearts; NS: not significant.