Brain diffusion-weighted imaging in Friedreich's ataxia.

BACKGROUND: Friedreich ataxia (FRDA) is the commonest form of autosomal recessive ataxia. This study aimed to define the extent of the brain damage in FRDA patients and to identify in vivo markers of neurodegeneration, using diffusion-weighted imaging (DWI). METHODS: We studied 27 FRDA patients and 21 healthy volunteers using a 1.5 T scanner. Axial DW images were obtained and mean diffusivity (MD) maps were generated. Region of interests (ROIs) included medulla, pons, inferior, middle and superior cerebellar peduncles (ICP, SCP, MCP), dentate nucleus, cerebellar white matter, thalamus, caudate, putamen, pallidus, pyramidal tracts at level of posterior limb of internal capsule (PLIC), optic radiations (OR), and corpus callosum. Histograms of MD were generated for all pixels in the whole cerebral hemispheres and infratentorial compartment. Disease severity was assessed by the International Cooperative Ataxia Rating Scale (ICARS). RESULTS: FRDA patients had significantly higher MD values than controls in medulla (P < 0.001), ICP (P < 0.001), MCP (P < 0.01), SCP (P < 0.001), OR (P < 0.001), and at the level of the infratentorial structures such as brainstem (P < 0.01), cerebellar hemispheres (P < 0.01), and especially in the cerebellar vermis (P < 0.001). MD values were strongly correlated with disease duration and ICARS score. DISCUSSION: Our results showed that DWI is a suitable non-invasive technique to quantify the extent of neurodegeneration in FRDA, that appears more extended than previously reported, showing a microstructural involvement of structures such as OR and MCP.

Defective mitochondrial adenosine triphosphate production in skeletal muscle from patients with dominant optic atrophy due to OPA1 mutations.

OBJECTIVE: To assess whether impaired energy metabolism in skeletal muscle is a hallmark feature of patients with dominant optic atrophy due to several different mutations in the OPA1 gene. DESIGN: We used phosphorus 31 magnetic resonance spectroscopy to assess calf muscle oxidative metabolism in subjects with molecularly defined dominant optic atrophy carrying different mutations in the OPA1 gene. In a subset of patients, we also evaluated serum lactate levels after exercise and muscle biopsy results for histology and mitochondrial DNA analysis. SETTING: University neuromuscular and neurogenetics and magnetic resonance imaging units. PATIENTS: Eighteen patients with dominant optic atrophy were enrolled from 8 unrelated families, 7 of which carried an OPA1 mutation predicted to induce haploinsufficiency and 1 with a missense mutation in exon 27. Fifteen patients had documented optic atrophy. MAIN OUTCOME MEASURES: Presence of skeletal muscle mitochondrial oxidative phosphorylation dysfunction as assessed by phosphorus 31 magnetic resonance spectroscopy, serum lactate levels, and histological and mitochondrial DNA analysis. RESULTS: Phosphorus 31 magnetic resonance spectroscopy showed reduced phosphorylation potential in the calf muscle at rest in patients with an OPA1 mutation (-24% from normal mean; P = .003) as well as a reduced maximum rate of mitochondrial adenosine triphosphate synthesis (-36%; P < .001; ranging from -28% to -49% in association with different mutations). In 4 of 10 patients (40%), the serum lactate level after exercise was elevated. Only 2 of 5 muscle biopsies, from the 2 patients with a missense mutation, showed slight myopathic changes. Low levels of mitochondrial DNA multiple deletions were found in all muscle biopsies. CONCLUSIONS: Defective oxidative phosphorylation in skeletal muscle is a subclinical feature of patients with OPA1-related dominant optic atrophy, indicating a systemic expression of the OPA1 defect, similar to that previously reported for Leber hereditary optic neuropathy due to complex I dysfunction. This defect of oxidative phosphorylation does not appear to depend on the low amounts of mitochondrial DNA multiple deletions detected in muscle biopsies.

Accuracy of MRI/MRSI-based transrectal ultrasound biopsy in peripheral and transition zones of the prostate gland in patients with prior negative biopsy.

The purpose of the study was to evaluate the accuracy of transrectal ultrasound biopsy (TRUS-biopsy) performed on regions with abnormal MRI and/or MRSI for both the transition (TZ) and the peripheral (PZ) zones in patients with suspected prostate cancer with prior negative biopsy, and to analyze the relationship between MRSI and histopathological findings. MRI and MRSI were performed in 54 patients (mean age: 63.9 years, mean PSA value: 11.4 ng/mL) and the ability of MRI/MRSI-directed TRUS biopsy was evaluated. A three-point score system was used for both techniques to distinguish healthy from malignant regions. Descriptive statistics and ROC analyses were performed to evaluate the accuracy and the best cut-off in the three-point score system. Twenty-two out of 54 patients presented cancer at MRI/MRSI-directed TRUS biopsy, nine presented cancer only in PZ, eight both in PZ and TZ, and five exclusively in TZ. On a patient basis the highest accuracy was obtained by assigning malignancy on a positive finding with MRSI and MRI even though it was not significantly greater than that obtained using MRI alone (area under the ROC curve, AUC: 0.723 vs 0.676). On a regional (n = 648) basis the best accuracy was also obtained by considering positive both MRSI and MRI for PZ (0.768) and TZ (0.822). MRSI was false positive in 11.9% of the regions. Twenty-eight percent of cores with prostatitis were false positive findings on MRSI, whereas only 2.7% of benign prostatic hyperplasia was false positive. In conclusion, the accuracy of MRI/MRSI-directed biopsies in localization of prostate cancer is good in patient (0.723) and region analyses (0.768). The combination of both MRI and MRSI results makes TRUS-biopsy more accurate, particularly in the TZ (0.822) for patients with prior negative biopsies. Histopathological analysis showed that the main limitation of MRSI is the percentage of false positive findings due to prostatitis.

Magnetic resonance diagnostic markers in clinically sporadic prion disease: a combined brain magnetic resonance imaging and spectroscopy study.

The intra vitam diagnosis of prion disease is challenging and a definite diagnosis still requires neuropathological examination in non-familial cases. Magnetic resonance imaging has gained increasing importance in the diagnosis of prion disease. The aim of this study was to compare the usefulness of different magnetic resonance imaging sequences and proton magnetic resonance spectroscopy in the differential diagnosis of patients with rapidly progressive neurological signs compatible with the clinical diagnosis of sporadic prion disease. Twenty-nine consecutive patients with an initial diagnosis of possible or probable sporadic prion disease, on the basis of clinical and electroencephalography features, were recruited. The magnetic resonance protocol included axial fluid-attenuated inversion recovery-T2- and diffusion-weighted images, and proton magnetic resonance spectroscopy of the thalamus, striatum, cerebellum and occipital cortex. Based on the clinical follow-up, genetic studies and neuropathology, the final diagnosis was of prion disease in 14 patients out of 29. The percentage of correctly diagnosed cases was 86% for diffusion-weighted imaging (hyperintensity in the striatum/cerebral cortex), 86% for thalamic N-acetyl-aspartate to creatine ratio (cutoff 1.05 (100% specificity and 100% positive predictive value). Univariate logistic regression analysis showed that the combination of thalamic N-acetyl-aspartate to creatine ratio and diffusion-weighted imaging correctly classified 93% of the patients. The combination of thalamic proton magnetic resonance spectroscopy (10 min acquisition duration) and brain diffusion-weighted imaging (2 min acquisition duration) may increase the diagnostic accuracy of the magnetic resonance scan. Both sequences should be routinely included in the clinical work-up of patients with suspected prion disease.

Distribution of neurochemical abnormalities in patients with narcolepsy with cataplexy: An in vivo brain proton MR spectroscopy study.

Narcolepsy with cataplexy is characterised by excessive daytime sleepiness, sudden drops of muscle tone triggered by emotions, termed cataplexy, disrupted nocturnal sleep and other dissociated rapid eye movement (REM) sleep phenomena. Narcolepsy has been linked to a loss of hypothalamic neurons producing hypocretins, neuropeptides implicated in the regulation of the arousal system. Neuroimaging and neurometabolic studies have shown the pathophysiological involvement of other brain structures such as cerebral cortex and thalamus, but, overall with inconsistent results. We investigated, by using an advanced quantitative MR technique, proton MR spectroscopy ((1)H-MRS), the distribution of brain neurochemical abnormalities in narcolepsy with cataplexy patients. Single voxel (1)H-MRS study was performed in the thalamus, hypothalamus, and parietal-occipital cortex of hypocretin deficient, narcolepsy with cataplexy patients, HLA-DQB1*0602-positive, drug free. No significant changes were detected in the thalamus and parietal-occipital cortex of the patients. On the other hand, the neuronal marker N-acetyl-aspartate was reduced in the hypothalamus of narcolepsy with cataplexy patients compared to controls. These (1)H-MRS findings further support that in narcolepsy with cataplexy patients, the hypothalamus is the primary site of neural lesions. The absence of (1)H-MRS neurodegenerative changes in the thalamus and cerebral cortex suggests that the abnormalities detected in these brain regions by other neuroimaging techniques are likely of functional nature.

The complex relationship between magnesium and serum parathyroid hormone: a study in patients with chronic intestinal failure.

In this study we compared the content of muscle free [Mg2+] assessed by 31P MRS to that of serum total Mg assessed by routine colorimetric assays in 15 patients affected by Chronic Intestinal Failure (CIF) on long-term Home Parenteral Nutrition (HPN) or who had undergone isolated intestinal transplantation. We also investigated in the same cohort of patients the relationship of muscle free [Mg2+] and serum total Mg with parathyroid hormone (PTH) serum content. All patients showed a normal cytosolic free [Mg2+] in the calf muscle despite about half of them having a content of total serum [Mg] below or at the lower edge of the boundary limits. Muscle free Mg2+ and serum total Mg displayed an opposite correlation versus serum PTH, showing that the intracellular free form possesses a different functional metabolic meaning in the regulation of PTH secretion.

Cytosolic pH buffering during exercise and recovery in skeletal muscle of patients with McArdle's disease.

Cellular pH control is important in muscle physiology, and for interpretation of (31)P magnetic resonance spectroscopy (MRS) data. Cellular acidification in exercise results from coupled glycolytic ATP production mitigated by cytosolic buffering, 'consumption' of H(+) by phosphocreatine (PCr) breakdown, and membrane transport processes. Ex vivo methods for cytosolic buffer capacity are vulnerable to artefact, and MRS methods often require assumptions. (31)P MRS of early exercise, when pH increases unopposed by glycolysis, is conceptually simple, but limited in normal muscle by time resolution and signal-to-noise. A therapeutic trial (Martinuzzi A et al. Musc Nerve 37: 350-357, 2007) in McArdle's disease (glycogen phosphorylase deficiency), where pH does not decrease with exercise, offered the opportunity to test (31)P MRS data obtained throughout incremental plantar flexion exercise and recovery in ten McArdle's patients against the simple model of cellular pH control. Changes in pH, [Pi] and [PCr] throughout exercise and recovery were quantitatively consistent with mean +/- SEM buffer capacity of 10 +/- 1 mM/(pH unit), which was not significantly different from the control subjects under the initial-exercise conditions where the comparison could be made. The simple model of cellular acid-base balance therefore gives an adequate account of cellular pH changes during both exercise and recovery in McArdle's disease.

Diffusion-weighted brain imaging study of patients with clinical diagnosis of corticobasal degeneration, progressive supranuclear palsy and Parkinson's disease.

Corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) are two neurodegenerative disorders within the category of tauopathies, which must be considered in differential diagnosis of Parkinson's disease. Although specific clinical and neuroradiological features help to guide the clinician to a likely diagnosis of Parkinson's disease, CBD or PSP, differential diagnosis remains difficult. The aim of our study was to analyse apparent diffusion coefficient (ADC(ave)) maps from patients with clinical diagnosis of CBD (corticobasal syndrome, CBS), classical phenotype of PSP (Richardson's syndrome, RS) and Parkinson's disease (PD) in order to identify objective markers to discriminate between these groups. Thirteen Parkinson's disease patients, 10 RS patients, 7 CBS patients and 9 healthy volunteers were recruited and studied in a 1.5 T MR scanner. Axial diffusion-weighted images were obtained and the ADC(ave) map was generated. Regions of interest (ROIs) included mesencephalon, corpus callosum and left and right superior cerebellar peduncle (SCP), thalamus, caudate, putamen, pallidus, posterior limb of internal capsule, frontal and parietal white matter. Histograms of ADC(ave) were generated for all voxels in left and right cerebral hemispheres and in left and right deep grey matter regions separately, and the 50th percentile values (medians) were determined. The ratio of the smaller to the larger median value (symmetry ratio) was calculated for left and right hemispheres and for left and right deep grey matter regions (1 = perfect symmetry). Putaminal ADC(ave) values in CBS and RS were significantly greater than those in Parkinson's disease and healthy volunteers, but could not distinguish CBS from RS patients. In CBS patients, the values of the medians of cerebral hemispheres histograms were significantly higher than those in RS, Parkinson's disease and healthy volunteers, while the hemispheric symmetry ratio in CBS (0.968, range 0.952-0.976) was markedly reduced compared with RS (0.993, range 0.992-0.994), Parkinson's disease (0.991, range 0.988-0.993) and healthy controls (0.990, range 0.988-0.993). The hemispheric symmetry ratio differentiated CBS patients from RS and Parkinson's disease patients with a sensitivity and specificity of 100%. In RS patients, the ADC(ave) values of the SCPs were significantly greater than those in Parkinson's disease and healthy volunteers. Our findings confirm that putaminal ADC(ave) values evaluation provides a good discrimination between Parkinson's disease and atypical parkinsonisms, including RS and CBS. Furthermore, diffusion-weighted imaging, by detecting the brain microstructural correlates of the typical asymmetric signs and symptoms in CBS and the SCP involvement in RS, was shown to aid characterization and differentiation of atypical parkinsonism.

Apparent diffusion coefficient of the superior cerebellar peduncle differentiates progressive supranuclear palsy from Parkinson's disease.

The early diagnosis of progressive supranuclear palsy (PSP) may be challenging, because of clinical overlapping features with Parkinson's disease (PD) and other parkinsonian syndromes such as the Parkinsonian variant of multiple system atrophy (MSA-P). Conventional MRI can help in differentiating parkinsonian disorders but its diagnostic accuracy is still unsatisfactory. On the basis of the pathological demonstration of superior cerebellar peduncle (SCP) atrophy in patients with PSP, we assessed the SCP apparent diffusion coefficient (ADC) values in patients with PSP, PD, and MSA-P in order to evaluate its differential diagnostic value in vivo. Twenty-eight patients with PSP (14 with possible-PSP and 14 with probable-PSP), 15 PD, 15 MSA-P, and 16 healthy subjects were studied by using diffusion weighted imaging (DWI). ADC was calculated in regions of interest defined in the left and right SCP by two clinically blinded operators. Intrarater (r = 0.98, P < 0.001) and interrater reliability (r = 0.97; P < 0.001) for SCP measurements were high. Patients with PSP had higher SCP rADC values (median 0.98 x 10(-3)mm(2)/s) than patients with PD (median 0.79 x 10(-3) mm(2)/s, P < 0.001), MSA-P (median 0.79 x 10(-3) mm(2)/s, P < 0.001), and healthy controls (median 0.80 x 10(-3) mm(2)/s, P < 0.001). DWI discriminated patients with PSP from PD and healthy subjects on the basis of SCP rADC individual values (100% sensitivity and specificity) and from patients with MSA-P (96.4% sensitivity and 93.3% specificity). The higher values of rADC in SCP of patients with PSP correspond with the in vivo microstructural feature of atrophy detected postmortem and provide an additional support for early discrimination between PSP and other neurodegenerative parkinsonisms.

Randomized, placebo-controlled, double-blind pilot trial of ramipril in McArdle's disease.

McArdle's disease causes limitation in exercise capacity as well as disability, the severity of which has been associated with the angiotensin-converting enzyme (ACE) insertion (I)/deletion (D) haplotype-patients with the genotype associated with higher ACE activity show the most severe phenotype. Modulation of ACE activity through the use of inhibitors may thus positively affect disease expression. In a double-blind, randomized, placebo-controlled trial, we assessed the efficacy of an ACE inhibitor (2.5 mg ramipril) in 8 patients with McArdle's disease. End-points were changes in parameters of exercise physiology (cycloergometer and muscle 31P-magnetic resonance spectroscopy), quality of life (QoL) according to the Short Form 36 (SF-36), and disability according to the World Health Organization-Disability Assessment Scale II (WHO-DAS II). Patients had lower QoL and higher disability than controls. Measures of exercise physiology were not changed by ramipril in the whole group, but treatment induced higher peak VO2 (P = 0.017) in ACE D/D patients, yet not in I/D patients. Treatment significantly improved disability (P < 0.05). McArdle's disease is a disabling condition affecting patients' QoL. Treatment with ramipril improves disability and modifies exercise physiology only in D/D patients, raising the possibility of a differential haplotype-linked sensitivity to the treatment.

Prostate cancer: sextant localization with MR imaging, MR spectroscopy, and 11C-choline PET/CT.

PURPOSE: To retrospectively compare sensitivity and specificity of magnetic resonance (MR) imaging, three-dimensional (3D) MR spectroscopy, combined MR imaging and 3D MR spectroscopy, and carbon 11 (11C)-choline positron emission tomography (PET)/computed tomography (CT) for intraprostatic tumor sextant localization, with histologic findings as reference standard. MATERIALS AND METHODS: The local ethics committee on human research provided approval and a waiver of informed consent for the retrospective study. MR imaging, 3D MR spectroscopy, and 11C-choline PET/CT results were retrospectively reviewed in 26 men with biopsy-proved prostate cancer (mean age, 64 years; range, 51-75 years) who underwent radical prostatectomy. Cancer was identified as areas of nodular low signal intensity on T2-weighted MR images. At 3D MR spectroscopy, choline-plus-creatine-to-citrate and choline-to-creatine ratios were used to distinguish healthy from malignant voxels. At PET/CT, focal uptake was visually assessed, and maximum standardized uptake values (SUVs) were recorded. Agreement between 3D MR spectroscopic and PET/CT results was calculated, and ability of maximum SUV to help localize cancer was assessed with receiver operating characteristic analysis. Significant differences between positive and negative sextants with respect to mean maximum SUV were calculated with a paired t test. RESULTS: Sensitivity, specificity, and accuracy were, respectively, 55%, 86%, and 67% at PET/CT; 54%, 75%, and 61% at MR imaging; and 81%, 67%, and 76% at 3D MR spectroscopy. The highest sensitivity was obtained when either 3D MR spectroscopic or MR imaging results were positive (88%) at the expense of specificity (53%), while the highest specificity was obtained when results with both techniques were positive (90%) at the expense of sensitivity (48%). Concordance between 3D MR spectroscopic and PET/CT findings was slight (kappa=0.139). CONCLUSION: In localizing cancer within the prostate, comparable specificity was obtained with either 3D MR spectroscopy and MR imaging or PET/CT; however, PET/CT had lower sensitivity relative to 3D MR spectroscopy alone or combined with MR imaging.

Diffusion-weighted imaging study of patients with essential tremor.

The pathophysiology of essential tremor (ET) is unknown. PET and fMRI studies have revealed bilateral activation and (1)H-MRS studies metabolic abnormalities in the cerebellum and other functionally related brain structures in ET. Diffusion-weighted imaging (DWI) was used to search for evidence of tissue integrity abnormalities in these areas in ET patients and 10 matched controls by calculating water apparent diffusion coefficients (ADCs). Regions of interest included the left and right cerebellum, red nucleus, thalamus, caudate, putamen, pallidum, and frontal white matter. Histograms of ADCs were generated for all pixels in the infratentorial compartment and manually segmented areas corresponding to brainstem, vermis, and cerebellar hemispheres. ADC values were similar in all brain areas in patients and controls. Our study did not detect changes affecting the investigated brain regions in ET patients. These findings argue against major structural damage in the ET brain, although more subtle neurodegenerative changes cannot be ruled out.

Proton magnetic resonance spectroscopy study of brain metabolism in obstructive sleep apnoea syndrome before and after continuous positive airway pressure treatment.

STUDY OBJECTIVES: Obstructive sleep apnoea syndrome (OSAS) causes sleep related oxygen desaturation, excessive daytime sleepiness (EDS), and cognitive impairment. The role of hypoxic brain damage, sleep fragmentation, and the associated comorbidities (hypertension, vascular disorders) in the pathogenesis of cognitive deficits remains controversial. The aim of this study was to evaluate the cerebral metabolism of OSAS patients in vivo before and after CPAP treatment. DESIGN AND PATIENTS: Fourteen OSAS patients without cardiovascular or cerebrovascular impairment underwent the same protocol before and after 6 months of CPAP including: overnight videopolysomnography (VPSG), Multiple Sleep Latency Test (MSLT), and within the next 2 days neuropsychological and 1H-MRS evaluations. Single voxel 1H-MRS was performed in the parietal-occipital cortex, and absolute concentrations of N-acetyl-aspartate (NAA), creatine, and choline were measured, acquiring spectra at multiple echo-times and using water as internal standard. Ten matched controls were also studied. RESULTS: OSAS patients had a mean RDI of 58/hr, a mean arousal index of 57/hr, and a mean nadir SpO2 of 71%. Before CPAP, all patients showed a normal global cognitive functioning, with only a small number of pathological tasks in working memory and attention tests in a minority of patients. CPAP therapy was effective in resolving sleep apnoea and normalizing sleep structure, and improving EDS and neuropsychological alterations. Before CPAP treatment cortical [NAA] in OSAS (11.86 mM +/- 0.80, mean +/- SD) was significantly lower than in controls (12.85 +/- 0.93; P = 0.01) and positively correlated with minimum SpO2 during sleep (r = 0.69; P = 0.006) and MSLT scores (r = 0.62; P = 0.01). Cortical [NAA] reduction persisted after therapy (11.94 +/- 1.33; P = 0.87 versus pre-CPAP). CONCLUSIONS: OSAS patients have cortical metabolic changes consistent with neuronal loss even in the absence of vascular comorbidities. Metabolic changes persisted after CPAP in the absence of EDS, nocturnal arousals, and major cognitive deficits, likely related to hypoxic damage prior to CPAP treatment.

Apparent diffusion coefficient measurements of the middle cerebellar peduncle differentiate the Parkinson variant of MSA from Parkinson's disease and progressive supranuclear palsy.

Clinical differentiation of parkinsonian syndromes such as the Parkinson variant of multiple system atrophy (MSA-P) and progressive supranuclear palsy (PSP) from Parkinson's disease is difficult in the early stage of the disease. In order to identify objective markers for differential diagnosis, we studied these three groups of patients with diffusion-weighted MRI (DWI). Sixteen MSA-P patients, 16 with PSP, 16 with Parkinson's disease and 15 healthy volunteers were studied. Regional apparent diffusion coefficients (rADC) were determined in different brain regions including basal ganglia, thalamus, white matter, pons and middle cerebellar peduncles (MCPs). rADC calculated in the MCP completely differentiated MSA-P patients (median: 0.93 x 10(-3) mm2/s) from PSP patients (median: 0.82 x 10(-3) mm2/s, P < 0.001), Parkinson's disease patients (median: 0.79 x 10(-3) mm2/s, P < 0.001) and healthy volunteers (median: 0.81 x 10(-3) mm2/s, P < 0.001). Other regions considered showed an overlapping among groups. DWI discriminates MSA-P from PSP and Parkinson's disease and healthy volunteers on the basis of MCP rADC values. These in vivo results confirm the pathological findings that the majority of MSA-P patients have moderate or severe degenerative changes not only in the nigrostriatal but also in the olivopontocerebellar systems. Our findings indicate that, in order to substantially contribute to the in vivo differential diagnosis of MSA-P, PSP and Parkinson's disease, rADC measurements should not be limited to the basal ganglia but should also include the MCP.

Assessment of glutamate and glutamine contribution to in vivo N-acetylaspartate quantification in human brain by (1)H-magnetic resonance spectroscopy.

N-Acetylaspartate (NAA) is one of the most important metabolites detectable by brain (1)H-MRS being considered an index of neuronal integrity. At the low magnetic field used in most clinical settings beta,gamma-glutamate/glutamine (Glx) resonances are very close and partially overlap the methyl-NAA resonance interfering with NAA quantification especially at low TE and in the presence of increased Glx signals. NAA overestimation due to Glx on a set of model solutions containing NAA, glutamate, and glutamine in variable amounts was evaluated and the result tested in vivo in six healthy controls and five age- and sex-matched patients with hepatic encephalopathy (HE), the latter having an increased Glx content. A method to assess in vivo the NAA overestimation caused by Glx is proposed. A perfect match was obtained between the assessment of Glx contamination on the NAA of healthy controls and that obtained on the model solutions. However, a substantial difference in NAA overestimation was found between controls and HE patients that cannot be explained by our model. An interpretative hypothesis is provided.

Quantitative mathematical expressions for accurate in vivo assessment of cytosolic [ADP] and DeltaG of ATP hydrolysis in the human brain and skeletal muscle.

Magnetic Resonance Spectroscopy affords the possibility of assessing in vivo the thermodynamic status of living tissues. The main thermodynamic variables relevant for the knowledge of the health of living tissues are: DeltaG of ATP hydrolysis and cytosolic [ADP], the latter as calculated from the apparent equilibrium constant of the creatine kinase reaction. In this study we assessed the stoichiometric equilibrium constant of the creatine kinase reaction by in vitro (31)P NMR measurements and computer calculations resulting to be: logK(CK)=8.00+/-0.07 at T=310 K and ionic strength I=0.25 M. This value refers to the equilibrium: PCr(2-)+ADP(3-)+ H(+)=Cr+ATP(4-). We also assessed by computer calculation the stoichiometric equilibrium constant of ATP hydrolysis obtaining the value: logK(ATP-hyd)=-12.45 at T=310 K and ionic strength I=0.25 M, which refers to the equilibrium: ATP(4-)+H(2)O=ADP(3-)+PO(4)(3-)+2H(+). Finally, we formulated novel quantitative mathematical expressions of DeltaG of ATP hydrolysis and of the apparent equilibrium constant of the creatine kinase reaction as a function of total [PCr], pH and pMg, all quantities measurable by in vivo (31)P MRS. Our novel mathematical expressions allow the in vivo assessment of cytosolic [ADP] and DeltaG of ATP hydrolysis in the human brain and skeletal muscle taking into account pH and pMg changes occurring in living tissues both in physiological and pathological conditions.

Free Mg2+ concentration in the calf muscle of glycogen phosphorylase and phosphofructokinase deficiency patients assessed in different metabolic conditions by 31P MRS.

BACKGROUND: The increase in cytosolic free Mg2+ occurring during exercise and initial recovery in human skeletal muscle is matched by a decrease in cytosolic pH as shown by in vivo phosphorus magnetic resonance spectroscopy (31P MRS). To investigate in vivo to what extent the homeostasis of intracellular free Mg2+ is linked to pH in human skeletal muscle, we studied patients with metabolic myopathies due to different disorders of glycogen metabolism that share a lack of intracellular acidification during muscle exercise. METHODS: We assessed by 31P MRS the cytosolic pH and free magnesium concentration ([Mg2+]) in calf muscle during exercise and post-exercise recovery in two patients with McArdle's disease with muscle glycogen phosphorylase deficiency (McArdle), and two brothers both affected by Tarui's disease with muscle phosphofructokinase deficiency (PFK). RESULTS: All patients displayed a lack of intracellular acidosis during muscle exercise. At rest only one PFK patient showed a [Mg2+] higher than the value found in control subjects. During exercise and recovery the McArdle patients did not show any significant change in free [Mg2+], while both PFK patients showed decreased free [Mg2+] and a remarkable accumulation of phosphomonoesters (PME). During initial recovery both McArdle patients showed a small increase in free [Mg2+] while in PFK patients the pattern of free [Mg2+] was related to the rate of PME recovery. CONCLUSION: i) homeostasis of free [Mg2+] in human skeletal muscle is strongly linked to pH as shown by patients' [Mg2+] pattern during exercise; ii) the pattern of [Mg2+] during exercise and post-exercise recovery in both PFK patients suggests that [Mg2+] is influenced by the accumulation of the phosphorylated monosaccharide intermediates of glycogenolysis, as shown by the increased PME peak signal. iii) 31P MRS is a suitable tool for the in vivo assessment of free cytosolic [Mg2+] in human skeletal muscle in different metabolic conditions.

The ND1 gene of complex I is a mutational hot spot for Leber's hereditary optic neuropathy.

A novel mitochondrial DNA (mtDNA) transition (3733G-->A) inducing the E143 K amino acid change at a very conserved site of the NADH dehydrogenase subunit 1 (ND1) was identified in a family with six maternally related individuals with Leber's hereditary optic neuropathy (LHON) and in an unrelated sporadic case, all negative for known mutations and presenting with the canonical phenotype. The transition was not detected in 1,082 control mtDNAs and was heteroplasmic in several individuals from both pedigrees. In addition, the mtDNAs of the two families were found to belong to different haplogroups (H and X), thus confirming that the 3733G-->A mutation occurred twice independently. Phosphorus magnetic resonance spectroscopy disclosed an in vivo brain and skeletal muscle energy metabolism deficit in the four examined patients. Muscle biopsy from two patients showed slight mitochondrial proliferation with abnormal mitochondria. Biochemical investigations in platelets showed partially insensitive complex I to rotenone inhibition. We conclude that the 3733G-->A transition is a novel cause of LHON and, after those at positions 3460 and 4171, is the third ND1 mutation to be identified in multiple unrelated families. This finding shows that, in addition to ND6, the ND1 subunit gene is also a mutational hot spot for LHON.

Deficit of in vivo mitochondrial ATP production in OPA1-related dominant optic atrophy.

Dominant optic atrophy has been associated with mutations in the OPA1 gene, which encodes for a dynamin-related GTPase, a mitochondrial protein implicated in the formation and maintenance of mitochondrial network and morphology. We used phosphorus magnetic resonance spectroscopy to assess calf muscle oxidative metabolism in six patients from two unrelated families carrying the c.2708-2711delTTAG deletion in exon 27 of the OPA1 gene. The rate of postexercise phosphocreatine resynthesis, a measure of mitochondrial adenosine triphosphate production rate, was significantly delayed in the patients. Our in vivo results show for the first time to our knowledge a deficit of oxidative phosphorylation in OPA1-related DOA.