The metabolic representation of ischemia in rat brain slices: A hyperpolarized 13 C magnetic resonance study

The ischemic penumbra in stroke is not clearly defined by today's available imaging tools. This study aimed to develop a model system and noninvasive biomarkers of ischemic brain tissue for an examination that might potentially be performed in humans, very quickly, in the course of stroke triage. Perfused rat brain slices were used as a model system and 31 P spectroscopy verified that the slices were able to recover from an ischemic insult of about 3.5 min of perfusion arrest. This was indicated as a return to physiological pH and adenosine triphosphate levels. Instantaneous changes in lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH) activities were monitored and quantified by the metabolic conversions of hyperpolarized [1-13 C]pyruvate to [1-13 C]lactate and [13 C]bicarbonate, respectively, using 13 C spectroscopy. In a control group (n = 8), hyperpolarized [1-13 C]pyruvate was administered during continuous perfusion of the slices. In the ischemia group (n = 5), the perfusion was arrested 30 s prior to administration of hyperpolarized [1-13 C]pyruvate and perfusion was not resumed throughout the measurement time (approximately 3.5 min). Following about 110 s of the ischemic insult, LDH activity increased by 80.4 ± 13.5% and PDH activity decreased by 47.8 ± 25.3%. In the control group, the mean LDH/PDH ratio was 16.6 ± 3.3, and in the ischemia group, the LDH/PDH ratio reached an average value of 38.7 ± 16.9. The results suggest that monitoring the activity of LDH and PDH, and their relative activities, using hyperpolarized [1-13 C]pyruvate, could serve as an imaging biomarker to characterize the changes in the ischemic penumbra.

3D 31 P MR spectroscopic imaging of the human brain at 3 T with a 31 P receive array: An assessment of 1 H decoupling, T1 relaxation times, 1 H-31 P nuclear Overhauser effects and NAD. NMR Biomed 2021;34:e4169. [PMID: 31518036 PMCID: PMC8244063 DOI: 10.1002/nbm.4169]

³¹ P MR spectroscopic imaging (MRSI) is a versatile technique to study phospholipid precursors and energy metabolism in the healthy and diseased human brain. However, mainly due to its low sensitivity, ³¹ P MRSI is currently limited to research purposes. To obtain 3D ³¹ P MRSI spectra with improved signal-to-noise ratio on clinical 3 T MR systems, we used a coil combination consisting of a dual-tuned birdcage transmit coil and a ³¹ P eight-channel phased-array receive insert. To further increase resolution and sensitivity we applied WALTZ4 ¹ H decoupling and continuous wave nuclear Overhauser effect (NOE) enhancement and acquired high-quality MRSI spectra with nominal voxel volumes of ~ 17.6 cm³ (effective voxel volume ~ 51 cm³ ) in a clinically relevant measurement time of ~ 13 minutes, without exceeding SAR limits. Steady-state NOE enhancements ranged from 15 ± 9% (γ-ATP) and 33 ± 3% (phosphocreatine) to 48 ± 11% (phosphoethanolamine). Because of these improvements, we resolved and detected all ³¹ P signals of metabolites that have also been reported for ultrahigh field strengths, including resonances for NAD⁺ , NADH and extracellular inorganic phosphate. T₁ times of extracellular inorganic phosphate were longer than for intracellular inorganic phosphate (3.8 ± 1.4s vs 1.8 ± 0.65 seconds). A comparison of measured T₁ relaxation times and NOE enhancements at 3 T with published values between 1.5 and 9.4 T indicates that T₁ relaxation of ³¹ P metabolite spins in the human brain is dominated by dipolar relaxation for this field strength range. Even although intrinsic sensitivity is higher at ultrahigh fields, we demonstrate that at a clinical field strength of 3 T, similar ³¹ P MRSI information content can be obtained using a sophisticated coil design combined with ¹ H decoupling and NOE enhancement.

Phosphocyclocreatine is the dominant form of cyclocreatine in control and creatine transporter deficiency patient fibroblasts

Creatine transporter deficiency (CTD) is a metabolic disorder resulting in cognitive, motor, and behavioral deficits. Cyclocreatine (cCr), a creatine analog, has been explored as a therapeutic strategy for the treatment of CTD. We developed a rapid, selective, and accurate HILIC ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to simultaneously quantify the intracellular concentrations of cCr, creatine (Cr), creatine-d3 (Cr-d3), phosphocyclocreatine (pcCr), and phosphocreatine (pCr). Using HILIC-UPLC-MS/MS, we measured cCr and Cr-d3 uptake and their conversion to the phosphorylated forms in primary human control and CTD fibroblasts. Altogether, the data demonstrate that cCr enters cells and its dominant intracellular form is pcCr in both control and CTD patient cells. Therefore, cCr may replace creatine as a therapeutic strategy for the treatment of CTD.

Lactate infusion increases brain energy content during euglycemia but not hypoglycemia in healthy men

A special characteristic of the brain is the usage of lactate as alternative fuel instead of glucose to preserve its energy homeostasis. This physiological function is valid for sufficient cerebral glucose supply, as well as presumably during hypoglycemia, given that exogenous lactate infusion suppresses hormonal counterregulation. However, it is not yet clarified whether this effect is mediated by the use of lactate as an alternative cerebral energy substrate or any other mechanism. We hypothesized that under conditions of limited access to glucose (ie, during experimental hypoglycemia) lactate infusion would prevent hypoglycemia-induced neuroenergetic deficits in a neuroprotective way. In a randomized, double-blind, crossover study, lactate vs placebo infusion was compared during hyperinsulinemic-hypoglycemic clamps in 16 healthy young men. We measured the cerebral high-energy phosphate content - ie, adenosine triphosphate (ATP), phosphocreatine (PCr) and inorganic phosphate (Pi) levels - by ³¹ P-magnetic resonance spectroscopy as well as the neuroendocrine stress response. During euglycemia, lactate infusion increased ATP/Pi as well as PCr/Pi ratios compared with baseline values and placebo infusion. During hypoglycemia, there were no differences between the lactate and the placebo condition in both ratios. Hormonal counterregulation was significantly diminished upon lactate infusion. Our data demonstrate an elevated cerebral high-energy phosphate content upon lactate infusion during euglycemia, whereas there was no such effect during experimental hypoglycemia. Nevertheless, lactate infusion suppressed hypoglycemic hormonal counterregulation. Lactate thus adds to cerebral energy provision during euglycemia and may contribute to an increase in ATP reserves, which in turn protects the brain against neuroglucopenia under recurrent hypopglycemic conditions, eg, in diabetic patients.

Facile High-Performance Liquid Chromatography Mass Spectrometry Method for Analysis of Cyclocreatine and Phosphocyclocreatine in Complex Mixtures of Amino Acids

Creatine transporter deficiency (CTD) is caused by a defect in the X-linked creatine transporter SLC6A8 gene leading to severe neurologic and physiologic conditions. Cyclocreatine and phosphocyclocreatine supplementation is seen as a potential treatment, but the presence of these compounds within commercially available dietary supplements presents the risk of self-medication. High-performance liquid chromatography-mass spectrometry (HPLC-MS) is an excellent technique to assess composition of complex amino acid mixtures. Herein, we have developed a facile HPLC-MS method using a cyano column in hydrophilic interaction liquid chromatography (HILIC) mode with isocratic elution over 4 min to identify the main components of two commercially available dietary supplements. The relative standard deviation (RSD) for retention time and extracted ion integrated area are <0.3% and 4%, respectively, showing excellent reproducibility. Cyclocreatine and phosphocyclocreatine were not detectable within the dietary supplements, even at ppm levels, demonstrating the power and importance of the developed HPLC-MS method in analyzing complex mixtures.

Creatine and phosphocreatine mapping of mouse skeletal muscle by a polynomial and Lorentzian line-shape fitting CEST method

PURPOSE

To obtain high-resolution Cr and PCr maps of mouse skeletal muscle using a polynomial and Lorentzian line-shape fitting (PLOF) CEST method.

METHODS

Wild-type mice and guanidinoacetate N-methyltransferase-deficient (GAMT-/-) mice that have low Cr and PCr concentrations in muscle were used to assign the Cr and PCr peaks in the Z-spectrum at 11.7 T. A PLOF method was proposed to simultaneously extract and quantify the Cr and PCr by assuming a polynomial function for the background and 2 Lorentzian functions for the CEST peaks at 1.95 ppm and 2.5 ppm.

RESULTS

The Z-spectra of phantoms revealed that PCr has 2 CEST peaks (2 ppm and 2.5 ppm), whereas Cr only showed 1 peak at 2 ppm. Comparison of the Z-spectra of wild-type and GAMT-/- mice indicated that, contrary to brain, there was no visible protein guanidinium peak in the skeletal-muscle Z-spectrum, which allowed us to extract clean PCr and Cr CEST signals. High-resolution PCr and Cr concentration maps of mouse skeletal muscle were obtained by the PLOF CEST method after calibration with in vivo MRS.

CONCLUSIONS

The PLOF method provides an efficient way to map Cr and PCr concentrations simultaneously in the skeletal muscle at high MRI field.

Two repetition time saturation transfer (TwiST) with spill-over correction to measure creatine kinase reaction rates in human hearts

BACKGROUND

Phosphorus saturation transfer (ST) magnetic resonance spectroscopy can measure the rate of ATP generated from phosphocreatine (PCr) via creatine kinase (CK) in the human heart. Recently, the triple-repetition time ST (TRiST) method was introduced to measure the CK pseudo-first-order rate constant kf in three acquisitions. In TRiST, the longitudinal relaxation time of PCr while γ-ATP is saturated, T1`, is measured for each subject, but suffers from low SNR because the PCr signal is reduced due to exchange with saturated γ-ATP, and the short repetition time of one of the acquisitions. Here, a two-repetition time ST (TwiST) method is presented. In TwiST, the acquisition with γ-ATP saturation and short repetition time is dropped. Instead of measuring T1`, an intrinsic relaxation time T1 for PCr, T1 (intrinsic), is assumed. The objective was to validate TwiST measurements of CK kinetics in healthy subjects and patients with heart failure (HF).

METHODS

Bloch equation simulations that included the effect of spillover irradiation on PCr were used to derive formulae for T1 (intrinsic) and kf measured by both TRiST and TwiST methods. Spillover was quantified from an unsaturated PCr measurement used in the current protocol for determining PCr and ATP concentrations. Cardiac TRiST and TwiST data were acquired at 3 T from 12 healthy and 17 HF patients.

RESULTS

Simulations showed that both kf measured by TwiST and T1 (intrinsic) require spill-over corrections. In human heart at 3 T, the spill-over corrected T1 (intrinsic) = 8.4 ± 1.4 s (mean ± SD) independent of study group. TwiST and TRiST kf measurements were the same, but TwiST was 9 min faster. Spill-over corrected TwiST kf was 0.33 ± 0.08 s(-1) vs. 0.20 ± 0.06 s(-1) in healthy vs HF hearts, respectively (p < 0.0001).

CONCLUSION

TwiST was validated against TRiST in the human heart at 3 T, generating the same results 9 min faster. TwiST detected significant reductions in CK kf in HF compared to healthy subjects, consistent with prior 1.5 T studies using different methodology.

L-Arginine Affects Aerobic Capacity and Muscle Metabolism in MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-Like Episodes) Syndrome

Objective

To study the effects of L-arginine (L-Arg) on total body aerobic capacity and muscle metabolism as assessed by ³¹Phosphorus Magnetic Resonance Spectroscopy (³¹P-MRS) in patients with MELAS (Mitochondrial Encephalomyopathy with Lactic Acidosis and Stroke-like episodes) syndrome.

Methods

We performed a case control study in 3 MELAS siblings (m.3243A>G tRNA^leu(UUR) in MTTL1 gene) with different % blood mutant mtDNA to evaluate total body maximal aerobic capacity (VO_2peak) using graded cycle ergometry and muscle metabolism using ³¹P-MRS. We then ran a clinical trial pilot study in MELAS sibs to assess response of these parameters to single dose and a 6-week steady-state trial of oral L-Arginine.

Results

At baseline (no L-Arg), MELAS had lower serum Arg (p = 0.001). On ³¹P-MRS muscle at rest, MELAS subjects had increased phosphocreatine (PCr) (p = 0.05), decreased ATP (p = 0.018), and decreased intracellular Mg²⁺ (p = 0.0002) when compared to matched controls. With L-arginine therapy, the following trends were noted in MELAS siblings on cycle ergometry: (1) increase in mean % maximum work at anaerobic threshold (AT) (2) increase in % maximum heart rate at AT (3) small increase in VO_2peak. On ³¹P-MRS the following mean trends were noted: (1) A blunted decrease in pH after exercise (less acidosis) (2) increase in Pi/PCr ratio (ADP) suggesting increased work capacity (3) a faster half time of PCr recovery (marker of mitochondrial activity) following 5 minutes of moderate intensity exercise (4) increase in torque.

Significance

These results suggest an improvement in aerobic capacity and muscle metabolism in MELAS subjects in response to supplementation with L-Arg. Intramyocellular hypomagnesemia is a novel finding that warrants further study.

Classification of Evidence

Class III evidence that L-arginine improves aerobic capacity and muscle metabolism in MELAS subjects.

Trial Registration

ClinicalTrials.gov NCT01603446.

Exercising calf muscle T₂∗ changes correlate with pH, PCr recovery and maximum oxidative phosphorylation

Skeletal muscle metabolism is impaired in disorders like diabetes mellitus or peripheral vascular disease. The skeletal muscle echo planar imaging (EPI) signal (S(EPI) ) and its relation to energy metabolism are still debated. Localised ³¹P MRS and S(EPI) data from gastrocnemius medialis of 19 healthy subjects were combined in one scanning session to study direct relationships between phosphocreatine (PCr), pH kinetics and parameters of T₂∗ time courses. Dynamic spectroscopy (semi-LASER) and EPI were performed immediately before, during and after 5 min of plantar flexions. Data were acquired in a 7 T MR scanner equipped with a custom-built ergometer and a dedicated ³¹P/¹H radio frequency (RF) coil array. Using a form-fitted multi-channel ³¹P/¹H coil array resulted in high signal-to-noise ratio (SNR). PCr and pH in the gastrocnemius medialis muscle were quantified from each ³¹P spectrum, acquired every 6 s. During exercise, SEPI (t) was found to be a linear function of tissue pH(t) (cross-correlation r = -0.85 ± 0.07). Strong Pearson's correlations were observed between post exercise time-to-peak (TTP) of SEPI and (a) the time constant of PCr recovery τPCr recovery (r = 0.89, p < 10⁻⁶), (b) maximum oxidative phosphorylation using the linear model, Q(max, lin) (r = 0.65, p = 0.002), the adenosine-diphosphate-driven model, Q(max,ADP) (r = 0.73, p = 0.0002) and (c) end exercise pH (r = 0.60, p = 0.005). Based on combined accurately localised ³¹P MRS and T₂∗ weighted MRI, both with high temporal resolution, strong correlations of the skeletal muscle SEPI during exercise and tissue pH time courses and of post exercise SEPI and parameters of energy metabolism were observed. In conclusion, a tight coupling between skeletal muscle metabolic activity and tissue T₂∗ signal weighting, probably induced by osmotically driven water shift, exists and can be measured non-invasively, using NMR at 7 T.

Defective mitochondrial function in vivo in skeletal muscle in adults with Down's syndrome: a 31P-MRS study

Down's syndrome (DS) is a developmental disorder associated with intellectual disability (ID). We have previously shown that people with DS engage in very low levels of exercise compared to people with ID not due to DS. Many aspects of the DS phenotype, such as dementia, low activity levels and poor muscle tone, are shared with disorders of mitochondrial origin, and mitochondrial dysfunction has been demonstrated in cultured DS tissue. We undertook a phosphorus magnetic resonance spectroscopy ((31)P-MRS) study in the quadriceps muscle of 14 people with DS and 11 non-DS ID controls to investigate the post-exercise resynthesis kinetics of phosphocreatine (PCr), which relies on mitochondrial respiratory function and yields a measure of muscle mitochondrial function in vivo. We found that the PCr recovery rate constant was significantly decreased in adults with DS compared to non-DS ID controls (1.7 ± 0.1 min(-1) vs 2.1 ± 0.1 min(-1) respectively) who were matched for physical activity levels, indicating that muscle mitochondrial function in vivo is impaired in DS. This is the first study to investigate mitochondrial function in vivo in DS using (31)P-MRS. Our study is consistent with previous in vitro studies, supporting a theory of a global mitochondrial defect in DS.

[Cytoprotective effect of creamide drug in the experimental model of the brain ischemia/reperfusion in rats]

The influence of creatine or its derivates on the cell energy potential may be one of the possibl approaches to induce neuroprotection. Effect of creamide (creatinylglycine ethylic ether fumarate) on the brain injury was studied in the experimental model of the brain ischemia/reperfusion in rats. The experiments were carried out in 14-20 weeks old male Wistar rats weighing 240-300 g, anesthetized by chloral hydrate (430 mg/kg). Creamide was administered intravenously at the doses of 50, 70, 140, and 280 mg/kg. For comparison phosphocreatine was used at the dose of 255 mg/kg. Creamide and phosphocreatine were administered intravenously (in volume of 1 ml within 5 min) 30 min before cerebral middle artery occlusion. Focal cerebral ischemia for 30 min was produced by endovascular suture occlusion with the subsequent 48 h reperfusion period. Creamide administration resulted in dose-dependent decrease of brain ischemic injury. Creamide administered at the doses of 140 and 280 mg/kg was more effective as compared with phosphocreatine (255 mg/kg). The data obtained open new perspectives for further research and development of new creatine-derived drugs with neuroprotective action.

Cyclocreatine treatment improves cognition in mice with creatine transporter deficiency

The second-largest cause of X-linked mental retardation is a deficiency in creatine transporter (CRT; encoded by SLC6A8), which leads to speech and language disorders with severe cognitive impairment. This syndrome, caused by the absence of creatine in the brain, is currently untreatable because CRT is required for creatine entry into brain cells. Here, we developed a brain-specific Slc6a8 knockout mouse (Slc6a8-/y) as an animal model of human CRT deficiency in order to explore potential therapies for this syndrome. The phenotype of the Slc6a8-/y mouse was comparable to that of human patients. We successfully treated the Slc6a8-/y mice with the creatine analog cyclocreatine. Brain cyclocreatine and cyclocreatine phosphate were detected after 9 weeks of cyclocreatine treatment in Slc6a8-/y mice, in contrast to the same mice treated with creatine or placebo. Cyclocreatine-treated Slc6a8-/y mice also exhibited a profound improvement in cognitive abilities, as seen with novel object recognition as well as spatial learning and memory tests. Thus, cyclocreatine appears promising as a potential therapy for CRT deficiency.

[Posthypoxic myocardial ischemia in newborn: diagnosis and treatment of severe type]

Were analyzed publications devoted to the problem of diagnostics and treatment of posthypoxia myocardial ischemia. A description and estimation of the pathophysiological processes occurring in children who had perinatal hypoxia. The analysis of changes in the myocardium, and violations of intracardiac hemodynamics in newborns with posthypoxia myocardial ischemia. Describes modern methods of treatment of myocardial ischemia, including use of phosphokreatinine as a cardiotrophic therapy.

Creatine and creatine analogues in hypertension and cardiovascular disease

BACKGROUND

The creatine kinase system, the central regulatory system of cellular energy metabolism, provides ATP in situ at ATP-ases involved in ion transport and muscle contraction. Furthermore, the enzyme system provides relative protection from tissue ischaemia and acidosis. The system could therefore be a target for pharmacologic intervention.

OBJECTIVES

To systematically evaluate evidence regarding the effectiveness of interventions directly targeting the creatine kinase system as compared to placebo control in adult patients with essential hypertension or cardiovascular disease.

SEARCH METHODS

Electronic databases searched: Medline (1950 - Feb 2011), Embase (up to Feb 2011), the Cochrane Controlled Trials Register (issue 3, Aug 2009), Latin-American/Caribbean databank Lilacs; references from textbooks and reviews; contact with experts and pharmaceutical companies; and searching the Internet. There was no language restriction.

SELECTION CRITERIA

Randomized controlled trials comparing creatine, creatine phosphate, or cyclocreatine (any route, dose or duration of treatment) with placebo; in adult patients with essential hypertension, heart failure, or myocardial infarction. We did not include papers on the short-term use of creatine during cardiac surgery.

DATA COLLECTION AND ANALYSIS

The outcomes assessed were death, total myocardial infarction (fatal or non-fatal), hospitalizations for congestive heart failure, change in ejection fraction, and changes in diastolic and systolic blood pressure in mm Hg or as percent change.

MAIN RESULTS

Full reports or abstracts from 1164 papers were reviewed, yielding 11 trials considering treatment with creatine or creatine analogues in 1474 patients with heart failure, ischemic heart disease or myocardial infarction. No trial in patients with hypertension was identified. Eleven trials (1474 patients, 35 years or older) comparing add-on therapy of the creatine-based drug on standard treatment to placebo control in patients with heart failure (6 trials in 1226 / 1474 patients ), or acute myocardial infarction (4 trials in 220 / 1474 patients) or 1 in ischemic heart disease (28 / 1474 patients) were identified. The drugs used were either creatine, creatine phosphate (orally, intravenously, or intramuscular) or phosphocreatinine. In the trials considering heart failure all three different compounds were studied; creatine orally (Gordon 1995, Kuethe 2006), creatine phosphate via intravenous infusion (Ferraro 1996, Grazioli 1992), and phosphocreatinine orally (Carmenini 1994, Maggi 1990). In contrast, the acute myocardial infarction trials studied intravenous creatine phosphate only. In the ischemic heart disease trial (Pedone 1984) creatine phosphate was given twice daily through an intramuscular injection to outpatients and through an intravenous infusion to inpatients. The duration of the study intervention was shorter for the acute patients, from a two hour intravenous infusion of creatine phosphate in acute myocardial infarction (Ruda 1988, Samarenko 1987), to six months in patients with heart failure on oral phosphocreatinine therapy (Carmenini 1994). In the acute myocardial infarction patients the follow-up period varied from the acute treatment period (Ruda 1988) to 28 days after start of the symptoms (Samarenko 1987) or end of the hospitalization period (Zochowski 1994). In the other trials there was no follow-up after discontinuation of treatment, except for Gordon 1995 which followed the patients until four days after stopping the intervention.Only two out of four trials in patients with acute myocardial infarction reported mortality outcomes, with no significant effect of creatine or creatine analogues (RR 0.73, CI: 0.22 - 2.45). In addition, there was no significance on the progression of myocardial infarction or improvement on ejection fraction. The main effect of the interventions seems to be on improvement of dysrhythmia.

AUTHORS' CONCLUSIONS

This review found inconclusive evidence to decide on the use of creatine analogues in clinical practice. In particular, it is not clear whether there is an effect on mortality, progression of myocardial infarction and ejection fraction, while there is some evidence that dysrhythmia and dyspnoea might improve. However, it is not clear which analogue, dose, route of administration, and duration of therapy is most effective. Moreover, given the small sample size of the discussed trials and the heterogeneity of the population included in these reports, larger clinical studies are needed to confirm these observations.

Resting cardiac energy metabolism is inversely associated with heart rate in healthy young adult men

BACKGROUND

31-Phosphorus-magnetic resonance spectroscopy may provide pathophysiological insights into the high-energy phosphate metabolism of the myocardium as measured by phosphocreatine to adenosine triphosphate (PCr/ATP) ratio. Aim of the present study was to determine in vivo the relation between cardiac PCr/ATP ratio and heart rate in normal male subjects.

METHODS

One hundred twelve apparently healthy, young male individuals (age 34 ± 10 years) were prospectively evaluated. They underwent cardiac cine magnetic resonance imaging to assess left ventricular (LV) function and morphology and 3D-ISIS (31)P-magnetic resonance spectroscopy of the LV to assess the PCr/ATP ratio (a recognized in vivo marker of myocardial energy metabolism). Data were analyzed after segregation by tertiles of the resting PCr/ATP ratio.

RESULTS

A significant inverse association between PCr/ATP ratios and resting heart rate was observed (Spearman ρ: r=-0.37; P < .0001). PCr/ATP ratios were also inversely associated with body mass index, diastolic blood pressure, wall mass and with insulin resistance, but in multiple regression analysis heart rate was found to be independently related to PCr/ATP.

CONCLUSIONS

The present study shows that resting heart rate is proportionally lower across tertiles of increasing PCr/ATP ratio of the LV in apparently healthy young male individuals, supporting the hypothesis that heart rate is a major determinant of cardiac energy stores. These findings may explain the prognostic role of heart rate in the general population as evidenced by previous large epidemiological studies.

Phosphorylation potential in the dominant leg is lower, and [ADPfree] is higher in calf muscles at rest in endurance athletes than in sprinters and in untrained subjects

It has been reported that various types of mammalian muscle fibers differ regarding the content of several metabolites at rest. However, to our knowledge no data have been reported in the literature, concerning the muscle energetic status at rest in high class athletes when considering the dominant and non-dominant leg separately. We have hypothesised that due to higher mechanical loads on the dominant leg in athletes, the metabolic profile in the dominant leg at rest in the calf muscles, characterized by [PCr], [ADP(free)], [AMP(free)] and DeltaG(ATP), will significantly differ among endurance athletes, sprinters and untrained individuals. In this study we determined the DeltaG(ATP) and adenine phosphates concentrations in the dominant and non-dominant legs in untrained subjects (n = 6), sprinters (n = 10) and endurance athletes (n = 7) at rest. The (mean +/- SD) age of the subjects was 23.4 +/- 4.3 years. Muscle metabolites were measured in the calf muscles at rest, by means of (31)P-MRS, using a 4.7 T superconducting magnet (Bruker). When taking into account mean values in the left and right leg, phosphocreatine concentration ([PCr]) and DeltaG(ATP) were significantly lower (p<0.05, Wilcoxon-Mann-Whitney test), and [ADP(free)] was significantly higher (p = 0.04) in endurance athletes than in untrained subjects. When considering the differences between the left and right leg, [PCr] in the dominant leg was significantly lower in endurance athletes than in sprinters (p = 0.01) and untrained subjects (p = 0.02) (25.91 +/- 2.87 mM; 30.02 +/- 3.12 mM and 30.71 +/- 2.88 mM, respectively). The [ADP(free)] was significantly higher (p = 0.02) in endurance athletes than in sprinters and untrained subjects (p = 0.02) (42.19 +/- 13.44 microM; 27.86 +/- 10.19 microM; 25.35 +/- 10.97 microM, respectively). The DeltaG(ATP) in the dominant leg was significantly lower (p = 0.02) in endurance athletes than in sprinters and untrained subjects (p = 0.01) (-60.53 +/- 2.03 kJ.M(-1); -61.82 +/- 1.05 kJ.M(-1), -62.29 +/- 0.73 kJ.M(-1), respectively). No significant differences were found when comparing [PCr], [ADP(free)], [AMP(free)], [Mg(2+)(free)], DeltaG(ATP) in the dominant leg and the mean values for both legs in sprinters and untrained subjects. Moreover, no significant differences were found when comparing the metabolites in non-dominant legs in all groups of subjects. We postulate that higher [ADP(free)] and lower DeltaG(ATP) at rest is a feature of endurance-trained muscle. Moreover,when studying the metabolic profile of the locomotor muscles in athletes one has to consider the metabolic differences between the dominant and non-dominant leg.

Conditions of wound healing and cutaneous growth affect metabolic performance of skin following plastic surgery

The mechanical and structural properties of skin subjected to expansion have been widely investigated in the context of plastic surgery. To determine the actual metabolic state of skin following skin expander placement, we determined the basic biochemical parameters for various conditions of postsurgical wound healing and cutaneous growth. Studying, for the first time, comprehensive metabolic profiles ("metabolomics") of the skin in a minipig model, we found that the lactate/alanine ratios were significantly increased (p<0.05) in skin attached to noninflated expanders vs. control skin, indicating increased anaerobic glycolysis. Furthermore, creatine/phosphocreatine ratios were decreased in skin from inflated vs. noninflated expanders, implying an improved energetic state for stretched skin. In contrast, no significant differences were detected for these parameters on comparing skin from four inflated expanders with different surface structures, even where the histologically determined capsule thickness was significantly different. Overall, the metabolic performance of skin recovering and growing under stretch was found to be superior to that of skin from noninflated expanders, and comparable to that of control skin. Our results are consistent with the assumptions of (i) major hypoxia/ischemia due to reduced perfusion in skin recovering from surgery without an appropriate supportive structure and (ii) minimal metabolic effects of expander surface structures.

Evidence of brain mitochondrial activities after oxygen inhalation by 31P magnetic resonance spectroscopy at 3T

The purpose of this study was to explore mitochondrial activities after oxygen inhalation by 31P magnetic resonance spectroscopy. Six healthy volunteers were studied using a GE 3T scanner. A spin-echo MRS sequence was utilized with a GE service coil. TR was 2000 msec and TE 35 msec with 128 scan averages. Before 31P scan, a 1H MRS pre-scan was performed to obtain shimming values. Exact two 31P scans were performed before and after oxygen inhalation through nasal cannula at a flow rate of 10 L/min. Data were processed offline using the SAGE/IDL software. Peak integral values of inorganic phosphor, phosphocreatine, and ATPs were measured. Peak integral values of inorganic phosphor were decreased from 1.44% to 16.62% (mean+/-SD, 8.2+/-4.60). Peak integral values of phosphocreatine were increased from 1.06% to 8.64% (4.54+/-2.74). Peak integral values of gammaATP were increased from 0.75% to 15.97% (5.94+/-6.10); alphaATP from 1.21% to 16.05% (7.04+/-6.14); betaATP from 1.01% to 7.12% (3.08+/-2.30). Brain mitochondrial activities were increased and more ATPs were produced after oxygen inhalation in healthy volunteers.

A novel relationship between creatine transport at the blood-brain and blood-retinal barriers, creatine biosynthesis, and its use for brain and retinal energy homeostasis

Evidence is increasing that the creatine/phosphocreatine shuttle system plays an essential role in energy homeostasis in the brain and retina to ensure proper development and function. Thus, our understanding of the mechanism of creatine supply and creatine usage in the brain and retina and of creatine supplementation in patients with creatine deficiency syndromes is an important step towards improved therapeutic strategies for brain and retinal disorders. Our recent research provides novel molecular-anatomical evidence that (i) at the blood-brain barrier and the inner blood-retinal barrier, the creatine transporter (CRT/SLC6AS) functions as a major pathway for supplying creatine to the brain and retina, and that (ii) local creatine is preferentially synthesized in the glial cells, e.g., oligodendrocytes, astrocytes, and Müller cells, in the brain and retina. Thus, the blood-brain barrier and inner blood-retinal barrier play important roles not only in supplying energy sources (glucose and lactate), but also in supplying an energy 'buffer' (creatine). These findings lead to the novel insight that the creatine/phosphocreatine shuttle system is based on an intricate relationship between the blood-brain barrier, inner blood-retinal barrier, glia, and neurons (photoreceptor cells) to maintain and ensure energy homeostasis in the brain and retina.

The relationship between the VO2 slow component, muscle metabolites and performance during very-heavy exhaustive exercise

This study examined the relationship between the V O(2) response, particularly the slow component (SC), muscle metabolite changes and performance during very-heavy exhaustive exercise. Sixteen active females performed a graded exercise test to determine V O(2peak) and the lactate threshold followed 48h later by a constant-load cycle test to exhaustion (ET) at 85% V O(2peak) intensity. Muscle biopsies and capillary blood samples were obtained before and after the ET to determine changes in muscle ATP, pH, lactate and phosphocreatine and also plasma pH and lactate. Breath-by-breath data from the ET were smoothed using 5-s averages and fit to a three-component exponential model. The mean time to exhaustion (t(exh)) during the ET was 16.8 (+/-6.4) min. Results showed no correlation between the SC and t(exh) or any muscle metabolite changes (p>0.05). Significant correlations (p<0.05) were evident between t(exh) and tau; tau(0) (r=-0.54), tau(1) (r=-0.65), change in (Delta) pH(b) (r=-0.60), Delta[La(-)](b) (r=-0.58) and [La(-)](b post) (r=-0.64). Significant correlations (p<0.05) were also evident between tau(1) and [La(-)](b post) (r=0.54). Furthermore, a negative value resulted when the accumulated oxygen deficit was calculated for the entire duration of the ET. Results showed no association between the amplitude of the SC and t(ext) or to changes in muscle/blood metabolites, suggesting that the SC is not a determinant of high-intensity exercise tolerance. Furthermore, it is possible that a reduced perturbation of anaerobic energy sources, as a result of a faster tau(1), may have contributed to a longer t(exh).

A selective inhibitor of Na+/Ca2+ exchanger, SEA0400, preserves cardiac function and high-energy phosphates against ischemia/reperfusion injury

The Ca2+ overload by Ca2+ influx via Na+/Ca2+ exchanger (NCX) is a critical mechanism in myocardial ischemia/reperfusion injury. We investigated protective effects of a novel selective inhibitor of NCX, SEA0400, on cardiac function and energy metabolism during ischemia and reperfusion. Langendorff-perfused rat hearts were exposed to 35 minutes global ischemia and 40 minutes reperfusion. Using 31P nuclear magnetic resonance spectroscopy, cardiac phosphocreatine (PCr), ATP, and pHi were monitored. SEA0400 did not change the basic cardiac function, but improved the recovery of left ventricular developed pressure (LVDP) after reperfusion (27.6 +/- 4.9 mm Hg in control, 101.2 +/- 19.3 mm Hg in 0.1 microM, and 115.5 +/- 13.3 mm Hg in 1 microM SEA0400, means +/- SE, n = 6, P < 0.05). SEA0400 reduced left ventricular end-diastolic pressure and increased coronary flow after reperfusion. SEA0400 improved the recoveries of cardiac phosphocreatine and ATP after reperfusion, but did not affect pHi. There were significant linear correlations between left ventricular developed pressure and cardiac phosphocreatine (r = 0.79, P < 0.05), and left ventricular developed pressure and ATP (r = 0.80, P < 0.05). However, SEA0400 increased the incidence and duration of reperfusion ventricular arrhythmias. SEA0400 added only after reperfusion also improved both the contractile function and energy metabolism. It is concluded that the selective inhibition of NCX may be effective to preserve high-energy phosphates and to improve cardiac function after reperfusion, but may not be able to prevent fatal arrhythmias.

Hypoxia-induced Bax and Bcl-2 protein expression, caspase-9 activation, DNA fragmentation, and lipid peroxidation in mitochondria of the cerebral cortex of newborn piglets: the role of nitric oxide

The present study tests the hypothesis that cerebral hypoxia results in increased ratio of Bax/Bcl-2, activation of caspase-9, lipid peroxidation, and DNA fragmentation in mitochondria of the cerebral cortex of newborn piglets and that the inhibition of nitric oxide synthase by N-nitro-L-arginine during hypoxia will prevent the events leading to mitochondrial DNA fragmentation. To test this hypothesis, six piglets, 3-5 days old, were divided into three groups: normoxic (n=5), hypoxic (n=5), and hypoxic-nitric oxide synthase (n=4). Hypoxic animals were exposed to a FiO2 of 0.6 for 60 min. Nitric oxide synthase (40 mg/kg) was infused over 60 min prior to hypoxia. Tissue hypoxia was confirmed by measuring levels of ATP and phosphocreatine. Cerebral cortical tissue mitochondria were isolated and purified using a discontinuous ficoll gradient. Mitochondrial Bax and Bcl-2 proteins were determined by Western blot. Caspase-9 activity in mitochondria was determined spectro-fluorometrically using fluorogenic substrate for caspase-9. Fluorescent compounds, an index of mitochondrial membrane lipid peroxidation, were determined spectrofluorometrically. Mitochondrial DNA was isolated and separated by electrophoresis on 1% agarose gel and stained with ethidium bromide. ATP levels (micromol/g brain) were 4.52+/-0.34 in normoxic, 1.18+/-0.29 in hypoxic (P<0.05) and 1.00+/-0.26 in hypoxic-nitric oxide synthase animals (P<0.05 vs. normoxic). Phosphocreatine levels (micromol/g brain) were 3.61+/-0.33 in normoxic, 0.70+/-0.20 in hypoxic (P<0.05 vs. normoxic) and 0.57+/-0.14 in hypoxic-nitric oxide synthase animals (P<0.05 vs. normoxic, P=NS vs. hypoxic). Bax density in mitochondrial membranes was 160+/-28 in normoxic and 324+/-65 in hypoxic (P<0.001 vs. normoxic). Bcl-2 density mitochondria was 96+/-18 in normoxic and 98+/-20 in hypoxic (P=NS vs. normoxic). Mitochondrial caspase-9 activity (nmol/mg protein/h) was 1.32+/-0.23 in normoxic and 2.25+/-0.24 in hypoxic (P<0.01 vs. normoxic). Levels of fluorescent compounds (microg of quinine sulfate/g protein) were 12.48+/-4.13 in normoxic and 37.92+/-7.62 in hypoxic (P=0.003 vs. normoxic). Densities (ODxmm2) of low molecular weight DNA fragments were 143+/-38 in normoxic, 365+/-152 in hypoxic, (P<0.05 vs. normoxic) and 163+/-25 in hypoxic-nitric oxide synthase animals (P<0.05 vs. hypoxic, P=NS vs. normoxic). The data demonstrate that hypoxia results in increased mitochondrial proapoptotic protein Bax, increased mitochondrial caspase-9 activity, increased mitochondrial lipid peroxidation, and increased fragmentation of DNA in mitochondria of the cerebral cortex of newborn piglets. The administration of a nitric oxide synthase inhibitor, nitric oxide synthase, prior to hypoxia prevented fragmentation of mitochondrial DNA, indicating that the hypoxia-induced mitochondrial DNA fragmentation is NO-mediated. We propose that NO free radicals generated during hypoxia lead to NO-mediated altered expression of Bax leading to increased ratio of pro-apoptotic/anti-apoptotic protein resulting in modification of mitochondrial membrane, and subsequently Ca2+-influx and fragmentation of mitochondrial DNA.

Loss of lipoprotein lipase-derived fatty acids leads to increased cardiac glucose metabolism and heart dysfunction

Long-chain fatty acids (FAs) are the predominant energy substrate utilized by the adult heart. The heart can utilize unesterified FA bound to albumin or FA obtained from lipolysis of lipoprotein-bound triglyceride (TG). We used heart-specific lipoprotein lipase knock-out mice (hLpL0) to test whether these two sources of FA are interchangeable and necessary for optimal heart function. Hearts unable to obtain FA from lipoprotein TG were able to compensate by increasing glucose uptake, glycolysis, and glucose oxidation. HLpL0 hearts had decreased expression of pyruvate dehydrogenase kinase 4 and increased cardiomyocyte expression of glucose transporter 4. Conversely, FA oxidation rates were reduced in isolated perfused hLpL0 hearts. Following abdominal aortic constriction expression levels of genes regulating FA and glucose metabolism were acutely up-regulated in control and hLpL0 mice, yet all hLpL0 mice died within 48 h of abdominal aortic constriction. Older hLpL0 mice developed cardiac dysfunction characterized by decreased fractional shortening and interstitial and perivascular fibrosis. HLpL0 hearts had increased expression of several genes associated with transforming growth factor-beta signaling. Thus, long term reduction of lipoprotein FA uptake is associated with impaired cardiac function despite a compensatory increase in glucose utilization.

High-energy phosphate metabolism in the calf muscle during moderate isotonic exercise under different degrees of cuff compression: A phosphorus 31 magnetic resonance spectroscopy study

BACKGROUND

The purpose of this study was to investigate phosphocreatine (PCr) and inorganic phosphate levels as well as pH changes in exercising muscle at a workload of 4.5 W under progressive cuff stenoses, whereby the flow reduction due to cuff compression was quantified by flow-sensitive magnetic resonance imaging.

METHODS

By using a whole-body 1.5-T magnetic resonance scanner and an exercise bench, serial phosphorus 31 (31P) magnetic resonance spectroscopy with a time resolution of 30 seconds was performed in 10 healthy men. Percentage changes in PCr, inorganic phosphate (Pi), and pH were statistically evaluated in comparison with baseline. The exercise protocol was characterized by a constant workload level of 4.5 W. Ischemic conditions were achieved by a cuff that was placed at the upper leg. Consecutively, increments of 0, 60, 90, 120, and 150 mm Hg were applied. Each increment lasted for 3 minutes. The following rest period was 10 minutes.

RESULTS

Blood flow increased significantly immediately after the onset of muscle exercise. No significant changes in blood flow were detected as long as the air pressure of the pneumatic cuff was 60 to 90 mm Hg. Significant reductions in blood flow were observed immediately after inflation of the cuff to 120 and 150 mm Hg. PCr passed into a steady state during the first increment with 0 mm Hg and showed no substantial changes during the increment with 60, 90, and 120 mm Hg. PCr hydrolysis seemed progressive during the 150-mm Hg increment. Pi passed into a plateau level at the onset of exercise and increased significantly at the increment of 150 mm Hg. The pH turned into a steady state with no significant changes during the increments up to 120 mm Hg. At 150 mm Hg, pH decreased progressively. PCr levels at the end of the 150-mm Hg increment correlated significantly and moderately with the reduction in blood flow.

CONCLUSIONS

Our study shows that the ischemic condition during constant muscle exercise is clearly characterized by PCr and Pi kinetics, as well as by pH changes. The correlation between the degree of blood flow reduction and PCr levels in the exercising muscle groups, which are supplied by the stenosed arteries, is the first essential of using 31P magnetic resonance spectroscopy in the assessment of the effect of arterial stenoses on muscle function in claudicants.

Phosphorous-31 Magnetic Resonance Spectroscopy of Cervical Cancer Using Transvaginal Surface Coil

We developed a new transvaginal coil tuned for phosphorous-31 and measured its magnetic resonance spectroscopy ((31)P MRS) of uterine cervical cancer. In a 50-year-old woman with uterine cervical cancer (International Federation of Gynecology and Obstetrics [FIGO] stage IIIb), (31)P MRS with the new coil clearly differentiated the low intensity of phosphocreatinine (PCr) and high intensity of phosphomonoester (PME) in tumor from those in muscle. Results suggests that this method will be useful for assessing uterine cervical cancer.

Effects of alpha-phenyl-N-tert-butyl nitrone (PBN)on brain cell membrane function and energy metabolism during transient global cerebral hypoxia-ischemia and reoxygenation-reperfusion in newborn piglets

We sought to know whether a free radical spin trap agent, alpha-phenyl-N-tert-butyl nitrone (PBN) influences brain cell membrane function and energy metabolism during and after transient global hypoxia-ischemia (HI) in the newborn piglets. Cerebral HI was induced by temporary complete occlusion of bilateral common carotid arteries and simultaneous breathing with 8% oxygen for 30 min, followed by release of carotid occlusion and normoxic ventilation for 1 hr (reoxygenation-reperfusion,RR). PBN (100 mg/kg) or vehicle was administered intravenously just before the induction of HI or RR. Brain cortex was harvested for the biochemical analyses at the end of HI or RR. The level of conjugated dienes significantly increased and the activity of Na+, K+ -ATPase significantly decreased during HI,and they did not recover during RR. The levels of ATP and phosphocreatine (PCr)significantly decreased during HI, and recovered during RR. PBN significantly decreased the level of conjugated dienes both during HI and RR, but did not influence the activity of Na+, K+ -ATPase and the levels of ATP and PCr. We demonstrated that PBN effectively reduced brain cell membrane lipid peroxidation, but did not reverse ongoing brain cell membrane dysfunction nor did restore brain cellular energy depletion, in our piglet model of global hypoxic-ischemic brain injury.

Abnormal mitochondrial function and muscle wasting, but normal contractile efficiency, in haemodialysed patients studied non-invasively in vivo

BACKGROUND

Muscle dysfunction, which contributes to morbidity in patients on haemodialysis, has several manifestations and a number of possible causes. We applied the non-invasive techniques of (31)P-magnetic resonance spectroscopy ((31)P-MRS), magnetic resonance imaging (MRI) and near-infrared spectroscopy (NIRS) to calf muscle of dialysed patients to define the abnormalities in muscle cross-sectional area (CSA), contractile efficiency, mitochondrial function and vascular O(2) supply.

METHODS

We performed (31)P-MRS/NIRS/MRI studies on the lateral gastrocnemius during isometric plantarflexion and recovery in 23 male patients on haemodialysis (age 24-71 years; haemoglobin 9.9-14.2 g/dl; bicarbonate 17-30 mmol/l; urea reduction ratio 53-77%; parathyroid hormone 1-95 U/l) and 15 male controls (age 29-71 years). To understand the relationships between calf CSA and body mass we also performed MRI only in a further six male patients and 18 male controls.

RESULTS

In patients, exercise duration was 30+/-11% lower than in controls. Muscle CSA was lower by 26+/-5%, but contractile efficiency (force/CSA/ATP turnover) was normal. Slowing of post-exercise phosphocreatine (PCr) recovery implied a 22+/-5% defect in effective 'mitochondrial capacity'. That PCr recovery was slow relative to NIRS recovery suggests that this is largely an intrinsic mitochondrial problem (not the result of impaired O(2) supply), one which, furthermore, correlated with CSA. Urea reduction ratio showed a negative correlation with body mass and CSA, but none with PCr rate constant.

CONCLUSIONS

The relationships to urea reduction ratio reflect the effect of muscle mass on dialysis efficiency, rather than direct effects on muscle CSA or metabolism. The relationship between PCr recovery and calf CSA suggests a role for the mitochondrial defect, whatever its cause, in the development of muscle wasting, although a common cause (e.g. physical inactivity) for both abnormalities cannot be ruled out.

[Effects of metabolic substrates and mannitol on efficiency of cardioplegic protection in isolated rat heart]

The aim of this work was to study rationality of addition of aspartic acid, phosphocreatine, mannitol and tris(bydroxymethyl) aminomethane (trisamine) to a sanguineous cardioplegic solution. Isolated perfused rat hearts were subjected to 40-min normothermic total ischemia and 30-min reperfusion. Cardioplegic solutions were infused for 5 min prior to ischemia. A modified Ringer solution with 25 mM KCI was used as control. Osmolarity and pH of cardioplegic solutions were 340+/-5 mOms and 7.6+/-0.1 at 22 degreesC, respectively. Efficiency of myocardial protection was evaluated by recovery of contractile and pump function during reperfusion. The optimal solution contained aspartic acid (21.5 mM), mannitol (20.0 mM) and trisamine (5 mM). By the end of reperfusion the heart protected by this solution showed almost complete recovery of coronary flow (98+/-3% of the initial value vs. 77+/-3% in the control), and 2.6-fold higher recovery of stroke volume compared to the control. As a result, recovery of external cardiac work index, calculated as cardiac output-mean perfusion pressure, was 64+/-1% of the initial value vs. 24+/-5% in the control. Increase in buffer capacity of this cardioplegic solution by trisamine (up to 20.0 mM) as well as addition of phosphocreatine (10.0 mM) did not result in further augmentation of cardiac function recovery. The results suggest promising perspectives for development of medicinal form of this solution.

Potential of phosphorus nuclear magnetic resonance spectroscopy in studies of the energy metabolism of skeletal muscles

The aim of the present study was to investigate the possibility of phosphorus magnetic resonance spectroscopy (MR spectroscopy) in the diagnosis of metabolic lesions of skeletal musculature in patients with intermittent claudication syndrome, chronic cardiac failure, and varicose diseases of the lower limbs. Studies included 50 males: 20 patients with intermittent claudication, 10 patients with chronic cardiac failure, and 10 patients with varicose veins. The control group consisted of 10 healthy volunteers. The following measures were determined: the phosphocreatinine index, the intracellular pH in the gastrocnemius muscle, and the half-recovery time for the phosphocreatinine index. The phosphocreatinine index and the pH at rest did not differ between study groups. Isotonic exercise produced no change in the phosphocreatinine index in the control group; patients with intermittent claudication showed a 26.1% decrease, patients with chronic cardiac failure showed an 8% decrease, and patients with varicose veins showed a 25.6% decrease. The only group showing a significant decrease in pH during exercise was the group of patients with intermittent claudication. This group also showed an inverse correlation between the pressure index and the extent of the decrease in the phosphocreatinine index. Thus, MR spectroscopy provides a non-invasive diagnostic method for lesions of energy metabolism in skeletal musculature in patients with deranged peripheral hemodynamics.

Proton magnetic resonance spectroscopy of bipolar disorder versus intermittent explosive disorder in children and adolescents

OBJECTIVE

The diagnosis of bipolar disorder in juveniles is controversial. This study was designed to compare proton magnetic resonance spectroscopy ((1)H MRS) in patients with bipolar disorder or intermittent explosive disorder, two groups with symptomatic overlap but categorical distinction. Children with intermittent explosive disorder designate patients whose illness clinically resembles pediatric bipolar disorder but does not satisfy DSM-IV criteria for mania. Based on the authors' previous report of higher levels of (1)H MRS cingulate myo-inositol/creatine in youngsters with bipolar disorder than in normal comparison subjects, they hypothesized that patients with bipolar disorder would have higher cingulate myo-inositol/creatine-phosphocreatine measurements than patients with intermittent explosive disorder and normal comparison subjects.

METHOD

Myo-inositol levels were measured with a 2x2x2 cm(3) voxel placed in the anterior cingulate for acquisition of (1)H MRS in 10 patients with bipolar disorder, 10 patients with intermittent explosive disorder, and 13 normal comparison subjects. N-Acetylaspartate, choline moieties, creatine-phosphocreatine, and glutamate-glutamine metabolite levels were also measured.

RESULTS

The patients with bipolar disorder showed significantly higher anterior cingulate myo-inositol/creatine-phosphocreatine and myo-inositol (mmol/liter) levels than the patients with intermittent explosive disorder and the normal comparison subjects. No significant differences were found across groups for myo-inositol or other metabolites in the occipital cortex.

CONCLUSIONS

These data provide evidence that differences in the concentration of myo-inositol (mmol/liter) in the anterior cingulate cortex in (1)H MRS may differentiate these two populations. Follow-up studies involving larger samples may conclusively estimate the biological specificity between pediatric bipolar disorder and other disorders, which overlap clinically.

Proton MRS profile of cerebral metabolic abnormalities in Krabbe disease

BACKGROUND

Krabbe disease (globoid cell leukodystrophy [GLD]) is an autosomal recessive lysosomal disorder affecting the central and peripheral nervous system. The authors performed MRS to characterize metabolic alterations and their regional variation in brain tissue in GLD in vivo.

METHODS

Abnormalities of cerebral metabolite concentrations were assessed in seven patients with biochemically proven GLD-four with infantile, two with juvenile, and one with adult subtype-using quantitative localized proton MRS of standardized brain regions.

RESULTS

In infantile GLD, pronounced elevation of both myo-inositol and choline-containing compounds in affected white matter reflected demyelination and glial proliferation. The accompanying decrease of N-acetylaspartate pointed to neuroaxonal loss. Gray matter showed similar, albeit much milder alterations. In juvenile GLD, MRS indicated astrocytosis with minor neuroaxonal damage in white matter. In a patient with adult GLD, results of MRS of affected white matter were close to normal. MRS data are in agreement with histopathologic features of GLD.

CONCLUSION

Proton MRS provides a powerful tool for assessing metabolic disturbances and the extent of brain damage noninvasively in GLD.

Effects of epinephrine and norepinephrine on hemodynamics, oxidative metabolism, and organ energetics in endotoxemic rats

OBJECTIVE

To determine whether epinephrine increases lactate concentration in sepsis through hypoxia or through a particular thermogenic or metabolic pathway.

DESIGN

Prospective, controlled experimental study in rats.

SETTING

Experimental laboratory in a university teaching hospital.

INTERVENTIONS

Three groups of anesthetized, mechanically ventilated male Wistar rats received an intravenous infusion of 15 mg/kg Escherichia coli O127:B8 endotoxin. Rats were treated after 90 min by epinephrine ( n=14), norepinephrine ( n=14), or hydroxyethyl starch ( n=14). Three groups of six rats served as time-matched control groups and received saline, epinephrine, or norepinephrine from 90 to 180 degrees min. Mean arterial pressure, aortic, renal, mesenteric and femoral blood flow, arterial blood gases, lactate, pyruvate, and nitrate were measured at baseline and 90 and 180 min after endotoxin challenge. At the end of experiments biopsy samples were taken from the liver, heart, muscle, kidney, and small intestine for tissue adenine nucleotide and lactate/pyruvate measurements.

MEASUREMENTS AND RESULTS

Endotoxin induced a decrease in mean arterial pressure and in aortic, mesenteric, and renal blood flow. Plasmatic and tissue lactate increased with a high lactate/pyruvate (L/P) ratio. ATP decreased in liver, kidney, and heart. The ATP/ADP ratio did not change, and phosphocreatinine decreased in all organs. Epinephrine and norepinephrine increased mean arterial pressure to baseline values. Epinephrine increased aortic blood flow while renal blood low decreased with both drugs. Plasmatic lactate increased with a stable L/P ratio with epinephrine and did not change with norepinephrine compared to endotoxin values. Nevertheless epinephrine and norepinephrine when compared to endotoxin values did not change tissue L/P ratios or ATP concentration in muscle, heart, gut, or liver. In kidney both drugs decreased ATP concentration.

CONCLUSIONS

Our data demonstrate in a rat model of endotoxemia that epinephrine-induced hyperlactatemia is not related to cellular hypoxia.

Metabolite alterations in basal ganglia associated with methamphetamine-related psychiatric symptoms. A proton MRS study

Following the chronic use of methamphetamine, some individuals experience psychosis and anxiety. One reason may be the persistence of metabolite abnormalities in the brain of currently abstinent former methamphetamine users. In this study, N-acetylaspartate (NAA), creatine plus phosphocreatine (Cr+PCr), and choline-containing compound (Cho) levels were measured in the left and right basal ganglia using proton magnetic resonance spectroscopy (MRS) in 13 abstinent methamphetamine users and 11 healthy comparison subjects with no history of illicit drug use. The methamphetamine users showed a significantly reduced Cr+PCr/Cho ratio in the bilateral basal ganglia compared with the healthy comparison subjects. Furthermore, the reduction in the Cr+PCr/Cho ratio was significantly correlated with the duration of methamphetamine use and with the severity of residual psychiatric symptoms. NAA/Cho ratios in the bilateral basal ganglia did not significantly differ between methamphetamine users and comparison subjects. These findings suggest that protracted use of methamphetamine may cause metabolite alterations in the basal ganglia. Furthermore, residual psychiatric symptoms may be attributable to the metabolite alterations in the basal ganglia.

Fast imaging of phosphocreatine in the normal human myocardium using a three-dimensional RARE pulse sequence at 4 Tesla

PURPOSE

To investigate the use of a three-dimensional rapid acquisition with relaxation enhancement (RARE) pulse sequence for direct acquisition of phosphocreatine (PCr) images of the human myocardium.

MATERIALS AND METHODS

A short elliptical birdcage radiofrequency (RF) body coil was constructed to produce a uniform flip angle throughout the chest cavity. In vivo images using a spectrally-selective RARE sequence with a spatial resolution of 1.2 cm x 1.2 cm x 2.5 cm (4 cm(3)) were acquired in nine minutes and 40 seconds.

RESULTS

Scans of phantoms demonstrated excellent spectral selectivity. The signal-to-noise ratio in the myocardium ranged from 12.6 in the anterior wall to 5.3 in the mid septum.

CONCLUSION

This study demonstrates that PCr data can be acquired using a three-dimensional RARE sequence with greater spatial and temporal resolution than spectroscopic techniques.

Role of creatine kinase isoenzymes on muscular and cardiorespiratory endurance: genetic and molecular evidence

The ability to perform well in activities that require muscular and cardiorespiratory endurance is a trait influenced, in a considerable part, by the genetic make-up of individuals. Early studies of performance and recent scans of the human genome have pointed at various candidate genes responsible for the heterogeneity of these phenotypes within the population. Among these are the genes for the various creatine kinase (CK) isoenzyme subunits. CK and phosphocreatine (PCr) form an important metabolic system for temporal and spatial energy buffering in cells with large variations in energy demand. The different CK isoenzyme subunits (CK-M and CK-B) are differentially expressed in the tissues of the body. Although CK-M is the predominant form in both skeletal and cardiac muscle, CK-B is expressed to a greater extent in heart than in skeletal muscle. Studies in humans and mice have shown that the expression of CK-B messenger RNA (mRNA) and the abundance and activity of the CK-MB dimer increase in response to cardiorespiratory endurance training. Increases in muscle tissue CK-B content can be energetically favourable because of its lower Michaelis constant (Km) for ADP. The activity of the mitochondrial isoform of CK (Scmit-CK) has also been significantly and positively correlated to oxidative capacity and to CK-MB activity in muscle. In mice where the CK-M gene has been knocked out, significant increases in fatigue resistance together with cellular adaptations increasing aerobic capacity have been observed. These observations have led to the notion that this enzyme may be responsible for fatigue under normal circumstances, most likely because of the local cell compartment increase in inorganic phosphate concentration. Studies where the Scmit-CK gene was knocked out have helped demonstrate that this isoenzyme is very important for the stimulation of aerobic respiration. Human studies of CK-M gene sequence variation have shown a significant association between a polymorphism, distinguished by the NcoI restriction enzyme, and an increase in cardiorespiratory endurance as indexed by maximal oxygen uptake following 20 weeks of training. In conclusion, there is now evidence at the tissue, cell and molecular level indicating that the CK-PCr system plays an important role in determining the phenotypes of muscular and cardiorespiratory endurance. It is envisioned that newer technologies will help determine how the genetic variability of these genes (and many others) impact on performance and health-related phenotypes.

[Phosphorus magnetic resonance in studying energy metabolism in skeletal muscles]

The present study objective involved evaluation of possibilities of magnetic resonance spectroscopy with phosphorus (31P-MRS) in diagnosis of metabolic disorders of skeletal muscles in patients with intermittent claudication, chronic heart failure and varicose disease of the lower extremities. In 20 patients with intermittent claudication, 10 patients with chronic heart failure, 10 patients with varicose disease and 10 volunteers, 31P-MRS was performed with 1.5 T MR system (Magnetom SP 63, Siemens). The following parameters were computed: phosphorus-creatinine index, intracellular pH in calf muscle, and time of half-recovery of the phosphorus-creatinine index. At rest, the phosphorus-creatinine indexes were similar in all groups; pH values at rest did not vary either. During isotonic exercise the phosphorus-creatinine index in the control group remained uncharged. In patients with intermittent claudication, the phosphorus-creatinine index at peak of exercise was decreased by 26.1% (p < 0.001), in patients with varicose disease--by 25.6% (p < 0.001), in patients with chronic heart failure by 8% (p < 0.001). PCr recovery half-time was increased in all patients. The patient group with intermittent claudication showed a reverse correlation between the pressure index and the degree of phosphorus-creatinine index decrease.

CONCLUSION

31P-MRS makes it possible to carry out non-invasive diagnosis of energy metabolic disorders of skeletal muscles in patients with impaired peripheral hemodynamics.

Pyruvate/dichloroacetate supply during reperfusion accelerates recovery of cardiac energetics and improves mechanical function following cardioplegic arrest

OBJECTIVES

Cardioplegic arrest during cardiac surgery induces severe abnormalities of the pyruvate metabolism, which may affect functional recovery of the heart. We aimed to evaluate the effect of pyruvate and dichloroacetate administration during reperfusion on recovery of mechanical function and energy metabolism in the heart subjected to prolonged cardioplegic arrest.

METHODS

Four groups of rat hearts perfused in working mode were subjected to cardioplegic arrest (St. Thomas' No. 1), 4 h of ischaemia at 8 degrees C and reperfusion with either Krebs buffer alone (C) or with 2.8 mM pyruvate (P), with 1 mM dichloroacetate (D), or with a combination of both (PD). Mechanical function was recorded before cardioplegic arrest and at the end of experiments. In groups C and PD, additional experiments were performed using (31)P nuclear magnetic resonance spectroscopy in non-working Langendorff mode to evaluate cardiac high-energy phosphate concentration changes throughout the experiment.

RESULTS

Improved recovery of cardiac output (% of the preischaemic value+/-SEM, n=9-12) was observed in all three treated groups (65.7+/-4.3, 59.5+/-5.2 and 59.5+/-5.3% in PD, P and D, respectively) as compared with C (42.2+/-4.6%; P<0.05). Recovery of coronary flow was improved from 66.4+/-3.8 in C to 94.9+/-8.6% in PD (P<0.05). The phosphocreatine recovery rate in the first minutes of reperfusion was increased from 9.9+/-1.5 in C to 31.5+/-4.3 micromol/min per g dry wt in PD (P<0.001). No differences were observed in ATP or phosphocreatine concentrations at the end of experiment.

CONCLUSIONS

The administration of pyruvate and dichloroacetate improves the recovery of mechanical function following hypothermic ischaemia. Accelerated restoration of the energy equilibrium in the initial phase of reperfusion may underlie the metabolic mechanism of this effect.

Electrical stimulation of human muscle studied using 31P-nuclear magnetic resonance spectroscopy

This study used phosphorous nuclear magnetic resonance (31P-NMR) spectroscopy to examine the metabolic demand resulting from electrical muscle stimulation (EMS) applied to human skeletal muscle. For each of six subjects, the forearm flexor muscle group was monitored with 31P-NMR during both maximum voluntary and 6-s EMS-induced contractions. A simple protocol using a tourniquet was added in one subject to assess the role of blood flow in this model. Eight hertz (nontetanic) EMS showed less (p less than 0.025) depletion of phosphocreatine (36%) than did tetanic 70-Hz EMS (60%), voluntary isometric (66%), and voluntary isokinetic (68%). The results of the tourniquet studies suggested that the nontetanic EMS allowed relatively increased muscle blood flow and oxygen supply during contraction. Tetanic EMS provided a similar metabolic demand to that of conventional resistive exercise, as measured by 31P-NMR spectroscopy.

Abnormal in vivo skeletal muscle energy metabolism in Huntington's disease and dentatorubropallidoluysian atrophy

We studied in vivo muscle energy metabolism in patients with Huntington's disease (HD) and dentatorubropallidoluysian atrophy (DRPLA) using 31P magnetic resonance spectroscopy (MRS). Twelve gene-positive HP patients (4 presymptomatic patients) and 2 gene-positive DRPLA patients (1 presymptomatic patient) were studied. 31P-MRS at rest showed a reduced phosphocreatine-to-inorganic phosphate ratio in the symptomatic HD patients and DRPLA patient. Muscle adenosine triphosphate/(phosphocreatine + inorganic phosphate) at rest was significantly reduced in both groups of symptomatic and presymptomatic HD subjects and was below the normal range in the 2 DRPLA subjects. During recovery from exercise, the maximum rate of mitochondrial adenosine triphosphate production was reduced by 44% in symptomatic HD patients and by 35% in presymptomatic HD carriers. The maximum rate of mitochondrial adenosine triphosphate production in muscle was also reduced by around 46% in the 2 DRPLA subjects. Our findings show that HD and DRPLA share a deficit of in vivo mitochondrial oxidative metabolism, supporting a role for mitochondrial dysfunction as a factor involved in the pathogenesis of these polyglutamine repeat-mediated neurodegenerative disorders. The identification of 31P-MRS abnormalities may offer a surrogate biochemical marker by which to study disease progression and the effects of treatment in HD and DRPLA.

The effect of short-term coronary perfusion using oxygenated diluted blood following cold storage for long-term heart preservation

BACKGROUND

The aim of this study was to compare the results obtained from the use of both University of Wisconsin (UW) solution and diluted blood in short-term coronary perfusion following 12-hour cold storage.

METHODS

Following coronary vascular washout of adult mongrel dogs with the UW solution, the heart was excised and immersed in a cold (4 degrees C) UW solution for 12 hours followed by 1-hour of coronary perfusion. Two different solutions were used for the coronary perfusion; a 4 degrees C oxygenated UW solution (Group U, n=7) and 15 degrees C oxygenated diluted blood (Group B, n=7). Myocardial high energy phosphate (HEP) levels, tissue water content (TWC), interstitial tissue space (ITS) rates and histological findings were evaluated at 0- and 12-hour cold storage and also following coronary perfusion. The preserved graft was then evaluated through orthotopic transplantation. The control group in this experiment consisted of seven hearts transplanted after 12-hour cold storage without coronary perfusion.

RESULTS

Myocardial HEP levels significantly decreased after 12-hour cold storage. The recovery rate of myocardial HEP levels after coronary perfusion was significantly (p<0.05) higher in Group B than in Group U. The increase of myocardial TWC during coronary perfusion was significantly (p<0.01) higher in Group B than in Group U. After 1-hour coronary perfusion, the subendocardial ITS rate was significantly (p<0.01) higher compared with the value at 0-hour cold storage in Group U, whereas it demonstrated no significant change in Group B. PAS stain revealed the glycogen content of the subendocardial tissues was higher in Group B than in Group U. The recovery rate of hemodynamic parameters 2 hours after heart transplantation was higher in Group U and significantly (p<0.05) higher in Group B than in the control.

CONCLUSIONS

Myocardial HEP levels recovered significantly after additional coronary perfusion. Though the UW solution prevented myocardial cellular edema, subendocardial perfusion was incomplete and the recovery rate of myocardial HEP levels was lower, suggesting that diluted blood may become the solution of choice as a perfusate.

Nuclear magnetic resonance spectroscopy: its role in providing valuable insight into diverse clinical problems

Skeletal muscle plays an important role in respiratory and cardiovascular physiology. The ability to measure metabolic changes in skeletal muscle has been enhanced with the advent of magnetic resonance spectroscopy (MRS). MRS measurements have been used to understand the metabolic control of respiration and to evaluate metabolic changes in the muscle in patients with respiratory and cardiac diseases. The key to the respiratory control measurements is the ability to measure intracellular pH with MRS. Muscle oxidative metabolism has been measured in two ways: during steady-state exercise and using recovery kinetics. The similarities in the metabolic findings for pulmonary and coronary disease suggest the potential for some interesting common pathways.

Induced hypertension treatment to improve cerebral ischemic injury after transient forebrain ischemia

The effect of induced hypertension treatment on cerebral ischemia is still controversial. We investigated the preferred blood pressure manipulation level and pressor agent required to reduce cerebral ischemic injury following transient forebrain ischemia induced by bilateral occlusion of the common carotid arteries in anesthetized gerbils. Following 60-min cerebral ischemia, we evaluated the preferred blood pressure manipulation level and pressor agent required to treat cerebral ischemic injury after reperfusion by examining the effects of different levels of mean arterial blood pressure (MABP), increased with phenylephrine or angiotensin II or decreased by blood withdrawal, on cerebral blood flow (CBF), survival ratio, cerebral edema, and brain energy metabolism following transient forebrain ischemia in gerbils. Mild phenylephrine-induced hypertension treatment (21+/-4 mmHg) during post-cerebral ischemia-reperfusion improved the survival ratio and reduced cerebral edema, which was also associated with an increase in local CBF and a recovery of brain energy metabolism. However, intense phenylephrine-induced hypertension, angiotensin II-induced hypertension, or hypotension worsen the survival rate and produced extra cerebral edema, that were also associated with deterioration of brain energy metabolism. These results demonstrate that a mild induced hypertension with phenylephrine (21+/-4 mmHg above the baseline level) results in reduction of the cerebral edema and improves the survival ratio and brain energy metabolism. Furthermore, angiotensin II may have neurotoxic effect to use as the pressor agent for induced hypertension after cerebral ischemia.

Renal ischemia/reperfusion remotely improves myocardial energy metabolism during myocardial ischemia via adenosine receptors in rabbits: effects of "remote preconditioning"

OBJECTIVES

This study examined the changes in myocardial energy metabolism during myocardial ischemia after "remote preconditioning" and investigated the involvement of adenosine receptors in the mechanisms of this effect.

BACKGROUND

Recent studies have indicated that a brief period of ischemia and reperfusion (ischemic preconditioning, PC) in a remote organ reduces myocardial infarct size (IS) protecting against subsequent sustained myocardial ischemia. However, the mechanisms of "remote PC" remain unclear. We assessed myocardial energy metabolism during sustained myocardial ischemia and reperfusion after renal PC (RPC), in comparison with that after myocardial PC (MPC) in open-chest rabbits. It has been established that adenosine receptors are involved in the mechanisms of MPC.

METHODS

Rabbits that had been anesthetized with halothane were divided into six groups. The control (CNT) group underwent 40-min coronary occlusion followed by 120 min reperfusion. Before the procedure, the MPC group underwent an additional protocol of 5 min coronary artery occlusion and 20 min reperfusion, and the RPC group received a 10 min episode of renal artery occlusion and 20 min reperfusion. In additional experimental groups, 8 sulfophenyl-theophylline (SPT, 10 mg/kg), an adenosine receptor inhibitor, was intravenously injected before the 40 min myocardial ischemia (SPT, MPC + SPT and RPC + SPT groups, respectively). Myocardial levels of phosphocreatine (PCr), ATP and intracellular pH (pHi) were measured by 31P-NMR spectroscopy.

RESULTS

RPC and MPC delayed the decreases in ATP levels, preserved pHi during 40-min myocardial ischemia and resulted in better recovery of ATP and PCr during 120 min reperfusion compared with the controls. SPT abolished the improvement in myocardial energy metabolism and the reduction in myocardial IS caused by MPC or RPC. Myocardial IS in the CNT (n = 8), MPC (n = 9), RPC (n = 9), SPT (n = 6), MPC + SPT (n = 8) and RPC + SPT (n = 8) groups averaged 42.8+/-3.5%, 18.2+/-1.8%*, 19.6+/-1.3%*, 44.9+/-5.0%, 35.6+/-2.7% and 34.8+/-3.6% of the area at risk (*p < 0.05 vs. CNT), respectively.

CONCLUSIONS

PC in a remote organ, similar to MPC, improved myocardial energy metabolism during ischemia and reperfusion and reduced IS in vivo by an adenosine-dependent mechanism in rabbits.

Rapid recovery of power output in females

The purpose of the present study was to examine whether the magnitude of the changes in the concentration of muscle metabolites influences the recovery of power output following short-term maximal intensity cycle exercise performed at different average pedalling rates. In part A of the study eight female subjects performed four trials on a cycle ergometer. Two trials involved maximal sprints of 30- and 6-s duration separated by a very short (2-3 s) recovery period. Average pedal rate during the first 30-s sprint was manipulated by employing resistances of either 7.5 or 10.1% of body weight; the second sprint always being performed against 7.5% BW. In two further trials subjects performed only a single 30-s sprint against the two resistances with pre- and post-exercise muscle biopsies and blood samples being taken. Peak power in the second sprint was significantly higher (442 +/- 31W vs. 402 +/- 33W; P < 0.05) following prior exercise against the greater resistance during which average pedal rate was lower (approximately 26%; P < 0.01) compared with the lesser resistance. However, despite this the muscle metabolite responses to the first sprint were similar (delta PCr (7.5 vs. 10.1% applied resistance) -55 vs. -59 mmol kg dry muscle-1: delta Lactate + 104 vs. +107 mmol kg dry muscle-1: both P > 0.05). In part B of the study six female subjects performed 19 trials in which the recovery interval between a maximal 30-s sprint (where average pedalling rate was manipulated in a manner similar to part A) and a 6-s sprint ranged from 0 to 300 s. The rate of restoration of power output was influenced by the average pedal rate in sprint 1 only for recovery durations of up to 3 s. These findings suggest that the recovery of power is not exclusively determined by muscle metabolites, in particular PCr, when the recovery duration is very short (< or = 3 s). As it has been previously shown that the pattern of muscle activation influences ionic balance it is speculated that ionic factors may be very important in the early and rapid recovery of power.

Administration of fructose 1,6-diphosphate during early reperfusion significantly improves recovery of contractile function in the postischemic heart

OBJECTIVES

Fructose-1,6-diphosphate is a glycolytic intermediate that has been shown experimentally to cross the cell membrane and lead to increased glycolytic flux. Because glycolysis is an important energy source for myocardium during early reperfusion, we sought to determine the effects of fructose-1,6-diphosphate on recovery of postischemic contractile function.

METHODS

Langendorff-perfused rabbit hearts were infused with fructose-1,6-diphosphate (5 and 10 mmol/L, n = 5 per group) in a nonischemic model. In a second group of hearts subjected to 35 minutes of ischemia at 37 degrees C followed by reperfusion (n = 6 per group), a 5 mmol/L concentration of fructose-1,6-diphosphate was infused during the first 30 minutes of reperfusion. We measured contractile function, glucose uptake, lactate production, and adenosine triphosphate and phosphocreatine levels by phosphorus 31-nuclear magnetic resonance spectroscopy.

RESULTS

In the nonischemic hearts, fructose-1,6-diphosphate resulted in a dose-dependent increase in glucose uptake, adenosine triphosphate, phosphocreatine, and inorganic phosphate levels. During the infusion of fructose-1,6-diphosphate, developed pressure and extracellular calcium levels decreased. Developed pressure was restored to near control values by normalizing extracellular calcium. In the ischemia/reperfusion model, after 60 minutes of reperfusion the hearts that received fructose-1,6-diphosphate during the first 30 minutes of reperfusion had higher developed pressures (83 +/- 2 vs 70 +/- 4 mm Hg, p < 0.05), lower diastolic pressures (7 +/- 1 vs 12 +/- 2 mm Hg, p < 0.05), and higher phosphocreatine levels than control untreated hearts. Glucose uptake was also greater after ischemia in the hearts treated with fructose-1,6-diphosphate.

CONCLUSIONS

We conclude that fructose-1,6-diphosphate, when given during early reperfusion, significantly improves recovery of both diastolic and systolic function in association with increased glucose uptake and higher phosphocreatine levels during reperfusion.

A comparison of the University of Wisconsin solution and the modified Kawakami solution for initial flush and coronary perfusion in long-term canine heart preservation

BACKGROUND

We compared two different solutions, the University of Wisconsin (UW) solution (intracellular-like) and the modified Kawakami (mK) solution (extracellular-like), for initial flush of coronary vascular beds before simple storage and following coronary perfusion.

METHODS

After a right thoracotomy in the 4th intercostal space, the donor heart was isolated by ligating the azygos vein and venae cavae, and cross-clamping the aorta. Cardiac arrest was then obtained with a cold GIK solution. Following initial flush of coronary vascular beds, the donor heart was resected, stored utilizing a combination of simple immersion and coronary perfusion, and then transplanted. A total of 48 mongrel dogs was divided into three groups each using different solutions for the initial flush of coronary vascular beds and for coronary perfusion. In group I (n=10) the UW solution was used for both initial flush and coronary perfusion. In group II (n=7) the mK solution was used for both initial flush and coronary perfusion, and in group III (n=7) the UW solution was used for initial flush and the mK solution for coronary perfusion. Intracellular high-energy phosphate was surveyed by 31P-nuclear magnetic resonance spectroscopy.

RESULTS

After 12-hour simple immersion and 1-hour coronary perfusion, phosphocreatine and adenosine triphosphate were significantly (p<0.05) higher in group III than in groups I and II. The high-energy phosphate levels of the graft tissue were better in groups I and III than in group II. Orthotopic transplantation was then performed using 10 preserved grafts in group I and seven preserved grafts of group III. After transplantation, left ventricular (LV) pressure of group I animals recovered to 82.3% and group III recovered to 95.8% of the control values. LV dp/dt of group I and III animals recovered to 76.5% and 96.7% of the control values, respectively.

CONCLUSIONS

The UW solution, which is acceptable for both initial flush and simple storage, is not suitable for continuous coronary perfusion even for a short period due to its high viscosity. A combination of the UW solution both for initial flush and the following cold simple immersion and the mK solution for continuous coronary perfusion is appropriate for long-term preservation of the canine heart.

Critical role of phosphagens in the energy cascade of cutaneous ischemia and protective action of phosphocreatine analogues in skin flap survival

A general understanding of the pivotal role of phosphocreatine (PCr) as the principal determinant of skin flap survival is now emerging. Definitive metabolic investigations using phosphorus (31P) and proton (1H) magnetic resonance spectroscopy (MRS) have established that the inability to replenish metabolically exhausted PCr reserves predictably correlates with skin flap necrosis. Furthermore, postoperative parenteral administration of PCr has been shown to augment effectively skin flap survival. We hypothesized that creatine kinase, the enzyme controlling the utilization of the high-energy phosphate component of PCr, is a critical determinant of the tolerance of a skin flap to ischemic insult. In other words, if the rate of utilization of PCr is too rapid, PCr stores will rapidly deplete, and the flap will not be able to withstand a period of ischemia. Alternatively, if the rate of dephosphorylation of PCr is reduced, survival of skin flaps during periods of ischemia could be extended. To test this hypothesis, we investigated the metabolic distribution and fate of cyclocreatine (cCr), a competent creatine analogue with a lower affinity for the creatine kinase enzyme. When administered as 1.5 percent (w/w) of the normal diet of laboratory rats, cCr accumulates in skin as the competent phosphagen, phosphocyclocreatine (PcCr). Cutaneous flaps elevated in these animals, and studied by 31P and 1H MRS, demonstrate that once depletion of PCr has occurred, PcCr continues to sustain ATP levels. This results in significant enhancement of skin flap survival (p < 0.005). These observations confirm the importance of the creatine kinase enzyme in cutaneous flap ischemia and suggest new approaches to augment skin flap survival.

Evaluation of altered myocardial high energy phosphate metabolism in patients on maintenance dialysis using phosphorus-31 magnetic resonance spectroscopy

RATIONALE AND OBJECTIVES

Assessment of left ventricular metabolism and function is important in patients on maintenance dialysis because congestive heart failure occurs quite frequently and has a poor prognosis. The purpose of this study was to evaluate the changes of myocardial high energy metabolism in dialysis patients by using phosphorus-31 (31P) magnetic resonance (MR) spectroscopy.

METHODS

Phosphorus-31 spectra were obtained from anteroseptal wall of the heart in six normal subjects (mean age, 24 +/- 1 years) and 14 dialysis patients (mean age, 52 +/- 11 years), using a 1.5-tesla clinical MR system. Four patients had previous history of heart failure. Echocardiography was performed in all patients to evaluate left ventricular (LV) hypertrophy and LV function.

RESULTS

The averaged ratio of phosphocreatine (PCr)/beta-adenosine triphosphate (beta-ATP) in dialysis patients (1.15 +/- 0.25 mean +/- standard deviation), was significantly lower than that in healthy subjects (1.63 +/- 0.21; P < 0.01). There was no significant difference in PCr/beta-ATP ratios between the non-LV hypertrophy group (1.21 +/- 0.24; n = 7) and the LV hypertrophy group (1.09 +/- 0.24; n = 7). The averaged PCr/beta-ATP ratio in four patients with history of heart failure (0.96 +/- 0.18) was significantly lower than that of the 10 patients without history of heart failure (1.22 +/- 0.23; P < 0.05).

CONCLUSIONS

These results indicate that patients on maintenance dialysis have decreased PCr/beta-ATP ratio and 31P MR spectroscopy can provide noninvasive assessment of altered high energy phosphate metabolism.