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Alterations in myocardial energy metabolism have been implicated in the pathophysiology of cardiac diseases such as heart failure and diabetic cardiomyopathy. 31P magnetic resonance spectroscopy (MRS) is a powerful tool to investigate cardiac energetics non-invasively in vivo, by detecting phosphorus ( 31P)-containing metabolites involved in energy supply and buffering. In this article, we review the historical development of cardiac 31P MRS, the readouts used to assess cardiac energetics from 31P MRS, and how 31P MRS studies have contributed to the understanding of cardiac energy metabolism in heart failure and diabetes. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

Background: A high-fat diet has been recommended for correction of biochemical abnormalities and muscle energy state in patients with complex I (NADH dehydrogenase) deficiency (CID). Objective: This study evaluated the effects of intravenous infusion of isoenergetic amounts of triacylglycerol or glucose on substrate oxidation, glycolytic carbohydrate metabolism, and energy state in patients with CID. Design: Four CID patients and 15 matched control subjects were infused with triacylglycerol (1.85 mg(.)kg(-1.)min(-1)) or glucose (5 mg(.)kg(-1.)min(-1)) while at rest. Respiratory calorimetry was used to evaluate mitochondrial substrate oxidation. Metabolism of glycolytic carbohydrate was determined on the basis of the rates of appearance and concentrations of plasma lactate from dilution of [1-C-13]lactate measurements. In addition, high-energy phosphate metabolism was measured in forearm muscle by P-31 magnetic resonance spectroscopy. Results: Whole-body oxygen consumption rates were higher in the patients than in the control subjects (P

Background: A high-fat diet has been recommended for correction of biochemical abnormalities and muscle energy state in patients with complex I (NADH dehydrogenase) deficiency (CID). Objective: This study evaluated the effects of intravenous infusion of isoenergetic amounts of triacylglycerol or glucose on substrate oxidation, glycolytic carbohydrate metabolism, and energy state in patients with CID. Design: Four CID patients and 15 matched control subjects were infused with triacylglycerol (1.85 mg(.)kg(-1.)min(-1)) or glucose (5 mg(.)kg(-1.)min(-1)) while at rest. Respiratory calorimetry was used to evaluate mitochondrial substrate oxidation. Metabolism of glycolytic carbohydrate was determined on the basis of the rates of appearance and concentrations of plasma lactate from dilution of [1-C-13]lactate measurements. In addition, high-energy phosphate metabolism was measured in forearm muscle by P-31 magnetic resonance spectroscopy. Results: Whole-body oxygen consumption rates were higher in the patients than in the control subjects (P

Background: A high-fat diet has been recommended for the treatment of patients with mitochondrial myopathy due to complex I (NADH dehydrogenase) deficiency (CID).Objective: This study evaluated the effects of intravenous infusion of isoenergetic amounts of triacylglycerol or glucose on substrate oxidation, glycolytic carbohydrate metabolism, and exercise endurance time and energy state of muscle in CID patients.Design: Four CID patients and 15 control subjects were infused with triacylglycerol (3.7 mg(.)kg(-1.)min(-1)) or glucose (10 mg(.)kg(-1.)min(-1)) during low-intensity leg exercise. Respiratory calorimetry was used to evaluate mitochondrial substrate oxidation. The concentration and rate of appearance of plasma lactate (from dilution of [1-C-13]lactate) were used to evaluate glycolytic carbohydrate metabolism. P-31 magnetic resonance spectroscopy was used to determine ratios of phosphocreatine to inorganic o-phosphate in forearm muscle during exercise.Results: In 3 patients, leg exercise endurance time was better during the triacylglycerol infusion than during the glucose infusion. In all 4 patients, whole-body oxygen consumption rates during exercise were higher during triacylglycerol infusion than during the glucose infusion. In 3 patients, the concentration and rate of appearance of plasma lactate were lower during triacylglycerol infusion than during the glucose infusion. Ratios of phosphocreatine to inorganic o-phosphate during exercise were not significantly different between the 2 infusion studies or between the patients and control subjects.Conclusions: Triacylglycerol infusion is associated with a greater oxidation of substrates, lower rates of appearance and concentrations of plasma lactate, and greater leg exercise endurance time in myopathic CID patients than is glucose infusion. The energy state of muscle during exercise, however, was not significantly different after infusion of triacylglycerol or glucose.

Nunes PM, van de Weijer T, Veltien A, Arnts H, Hesselink MK, Glatz JF, Schrauwen P, Tack CJ, Heerschap A. Increased intramyocellular lipids but unaltered in vivo mitochondrial oxidative phosphorylation in skeletal muscle of adipose triglyceride lipase-deficient mice. Am J Physiol Endocrinol Metab 303: E71-E81, 2012. First published April 10, 2012; doi: 10.1152/ajpendo.00597.2011.-Adipose triglyceride lipase (ATGL) is a lipolytic enzyme that is highly specific for triglyceride hydrolysis. The ATGL-knockout mouse (ATGL(-/-)) accumulates lipid droplets in various tissues, including skeletal muscle, and has poor maximal running velocity and endurance capacity. In this study, we tested whether abnormal lipid accumulation in skeletal muscle impairs mitochondrial oxidative phosphorylation, and hence, explains the poor muscle performance of ATGL(-/-) mice. In vivo H-1 magnetic resonance spectroscopy of the tibialis anterior of ATGL(-/-) mice revealed that its intramyocellular lipid pool is approximately sixfold higher than in WT controls (P = 0.0007). In skeletal muscle of ATGL(-/-) mice, glycogen content was decreased by 30% (P

Background: A high-fat diet has been recommended for the treatment of patients with mitochondrial myopathy due to complex I (NADH dehydrogenase) deficiency (CID). Objective: This study evaluated the effects of intravenous infusion of isoenergetic amounts of triacylglycerol or glucose on substrate oxidation, glycolytic carbohydrate metabolism, and exercise endurance time and energy state of muscle in CID patients. Design: Four CID patients and 15 control subjects were infused with triacylglycerol (3.7 mg(.)kg(-1.)min(-1)) or glucose (10 mg(.)kg(-1.)min(-1)) during low-intensity leg exercise. Respiratory calorimetry was used to evaluate mitochondrial substrate oxidation. The concentration and rate of appearance of plasma lactate (from dilution of [1-C-13]lactate) were used to evaluate glycolytic carbohydrate metabolism. P-31 magnetic resonance spectroscopy was used to determine ratios of phosphocreatine to inorganic o-phosphate in forearm muscle during exercise. Results: In 3 patients, leg exercise endurance time was better during the triacylglycerol infusion than during the glucose infusion. In all 4 patients, whole-body oxygen consumption rates during exercise were higher during triacylglycerol infusion than during the glucose infusion. In 3 patients, the concentration and rate of appearance of plasma lactate were lower during triacylglycerol infusion than during the glucose infusion. Ratios of phosphocreatine to inorganic o-phosphate during exercise were not significantly different between the 2 infusion studies or between the patients and control subjects. Conclusions: Triacylglycerol infusion is associated with a greater oxidation of substrates, lower rates of appearance and concentrations of plasma lactate, and greater leg exercise endurance time in myopathic CID patients than is glucose infusion. The energy state of muscle during exercise, however, was not significantly different after infusion of triacylglycerol or glucose.