31P magnetic resonance spectroscopy detects a functional abnormality in liver metabolism after acetaminophen poisoning

In-vivo31P-MRS of skeletal muscle and liver: A way for non-invasive assessment of their metabolism

In addition to direct assessment of high energy phosphorus containing metabolite content within tissues, phosphorus magnetic resonance spectroscopy (³¹P-MRS) provides options to measure phospholipid metabolites and cellular pH, as well as the kinetics of chemical reactions of energy metabolism in vivo. Even though the great potential of ³¹P-MR was recognized over 30 years ago, modern MR systems, as well as new, dedicated hardware and measurement techniques provide further opportunities for research of human biochemistry. This paper presents a methodological overview of the ³¹P-MR techniques that can be used for basic, physiological, or clinical research of human skeletal muscle and liver in vivo. Practical issues of ³¹P-MRS experiments and examples of potential applications are also provided. As signal localization is essential for liver ³¹P-MRS and is important for dynamic muscle examinations as well, typical localization strategies for ³¹P-MR are also described.

Magnetic resonance spectroscopy to study hepatic metabolism in diffuse liver diseases, diabetes and cancer

This review provides an overview of the current state of the art of magnetic resonance spectroscopy (MRS) in in vivo investigations of diffuse liver disease. So far, MRS of the human liver in vivo has mainly been used as a research tool rather than a clinical tool. The liver is particularly suitable for static and dynamic metabolic studies due to its high metabolic activity. Furthermore, its relatively superficial position allows excellent MRS localization, while its large volume allows detection of signals with relatively low intensity. This review describes the application of MRS to study the metabolic consequences of different conditions including diffuse and chronic liver diseases, congenital diseases, diabetes, and the presence of a distant malignancy on hepatic metabolism. In addition, future prospects of MRS are discussed. It is anticipated that future technical developments such as clinical MRS magnets with higher field strength (3 T) and improved delineation of multi-component signals such as phosphomonoester and phosphodiester using proton decoupling, especially if combined with price reductions for stable isotope tracers, will lead to intensified research into metabolic syndrome, cardiovascular disease, hepato-biliary diseases, as well as non-metastatic liver metabolism in patients with a distant malignant tumor.

Phase II study of the oxygen saturation curve left shifting agent BW12C in combination with the hypoxia activated drug mitomycin C in advanced colorectal cancer

BW12C (5-[2-formyl-3-hydroxypenoxyl] pentanoic acid) stabilizes oxyhaemoglobin, causing a reversible left-shift of the oxygen saturation curve (OSC) and tissue hypoxia. The activity of mitomycin C (MMC) is enhanced by hypoxia. In this phase II study, 17 patients with metastatic colorectal cancer resistant to 5-fluorouracil (5-FU) received BW12C and MMC. BW12C was given as a bolus loading dose of 45 mg kg(-1) over 1 h, followed by a maintenance infusion of 4 mg kg(-1) h(-1) for 5 h. MMC 6 mg m(-2) was administered over 15 min immediately after the BW12C bolus. The 15 evaluable patients had progressive disease after a median of 2 (range 1-4) cycles of chemotherapy. Haemoglobin electrophoresis 3 and 5 h after the BW12C bolus dose showed a fast moving band consistent with the BW12C-oxyhaemoglobin complex, accounting for approximately 50% of total haemoglobin. The predominant toxicities--nausea/vomiting and vein pain--were mild and did not exceed CTC grade 2. Liver 31P magnetic resonance spectroscopy of patients with hepatic metastases showed no changes consistent with tissue hypoxia. The principle of combining a hypoxically activated drug with an agent that increases tissue hypoxia is clinically feasible, producing an effect equivalent to reducing tumour oxygen delivery by at least 50%. However, BW12C in combination with MMC for 5-FU-resistant colorectal cancer is not an effective regimen. This could be related to drug resistance rather than a failure to enhance cytotoxicity.

31P magnetic resonance spectroscopy of the liver in HELLP syndrome

OBJECTIVES

Using magnetic resonance spectroscopy (MRS) to measure phosphorus-containing metabolites in the liver, this study aimed to investigate non-invasively whether or not women with haemolysis, elevated liver enzymes and low platelets (HELLP) have detectable abnormalities of hepatic energetics.

SETTING

John Radcliffe Hospital, Oxford.

DESIGN

Prospective study.

METHODS

After giving informed consent, patients with HELLP syndrome (n = 7) and controls with severe pre-eclampsia (n = 3), were studied by 31P MRS of the liver as soon as possible after delivery (range 2-4 days) and compared with normal nonpregnant controls (n = 6). Haematological and biochemical tests were performed serially and on the day of the MRS in all pregnant patients.

RESULTS

The severity of HELLP varied as follows: peak aspartate aminotransferase (range 129-2574), peak gamma glutamyl transferase (range 28-96), peak lactate dehydrogenase (range 305-2820), nadir platelets (range 25-114), peak international normalised ratio for prothrombin time (before fresh frozen plasma) (range 0.9-1.9). One pregnancy was terminated but all others resulted in live births and all mothers made uneventful, rapid recoveries. MRS-determined relative hepatic concentrations of phosphorus-containing metabolites and absolute concentrations of adenosine triphosphate did not differ significantly between groups. One patient with the most clinically severe HELLP syndrome (by laboratory criteria) exhibited magnetic resonance spectra which showed a relative increase in phosphomonoester and an absolute decrease in hepatic adenosine triphosphate (to 62% of control).

CONCLUSIONS

Enthusiasm for the conservative management of HELLP syndrome that develops remote from term has been tempered by the inability to identify patients at risk for progression to hepatic necrosis. We found that most patients with HELLP syndrome had normal liver metabolism as assessed by MRS. However, clinically severe HELLP syndrome can be associated with disturbed hepatic metabolism consistent with that seen in hepatic ischaemia and/or granulocytic infiltration of the liver.

Treatment options for osteoporosis in chronic liver disease patients requiring liver transplantation

As patient life expectancy rises after liver transplantation, osteoporosis becomes a significant contributor to morbidity and mortality. Patients who undergo liver transplant have an increased risk of bone fractures secondary to osteoporosis, relative to the general population. Risk factors (pre- and posttransplant) include treatment with steroids, alcohol abuse, smoking, poor nutritional status, immobility, reduced muscle mass, menopause, and hypogonadism. The role of cholestatic liver disease is well recognized, but as of yet, the underlying etiology is unknown. The role of immunosuppressants is also evident, but their exact contribution remains to be established. Currently, there are no established therapies for osteoporosis secondary to liver transplantation. Most of the therapeutic options have been extrapolated from usual treatment options for osteoporosis in the general population. It is reasonable to attempt to lower steroid dosages, especially with the availability of new and more potent immunosuppressants such as mycophenolate mofetil and tacrolimus. Potentially, high-risk patients could be identified early with BMD screening. Preventive measures could be instituted and patients could be monitored more closely for objective signs of osteoporosis, such as decline in BMD and early fractures. Calcium and vitamin D supplementation may be helpful in those with deficiencies or poor nutritional intake, as well as in women older than 25 years. The role of bisphosphonates and hormone replacement therapy remains equivocal as studies in transplant patients are currently lacking. Risk versus benefit must be weighed on an individual basis. Lifestyle measures should be instituted in all patients if possible.

Molar quantitation of hepatic metabolites in vivo in proton-decoupled, nuclear Overhauser effect enhanced 31P NMR spectra localized by three-dimensional chemical shift imaging

Proton decoupling and nuclear Overhauser effect (NOE) enhancement significantly improve the signal-to-noise ratio and enhance resolution of metabolites in in vivo 31P MRS. We obtained proton-decoupled, NOE-enhanced, phospholipid-saturated 31P spectra localized to defined regions within the normal liver using three-dimensional chemical shift imaging. Proton-decoupling resulted in the resolution of two major peaks in the phosphomonoester (PME) region, three peaks in the phosphodiester (PDE) region and a diphosphodiester peak. In order to obtain molar quantitation, we measured the NOE of all hepatic phosphorus resonances, and we corrected for saturation effects by measuring hepatic metabolite T1 using the variable nutation angle method with phase-cycled, B1-independent rotation, adiabatic pulses. After corrections for saturation effects, NOE enhancement, B1 variations and point spread effects, the following mean concentrations (mmol/l of liver) (+/-SD) were obtained: [PME1] = 1.2 +/- 0.4, [PME2 + 2,3-DPG] = 1.1 +/- 0.1, [Pi + 2,3-DPG] = 2.8 +/- 0.5, [GPEth] = 2.8 +/- 0.7, [GPChol] = 3.5 +/- 0.6 and [beta-NTP] = 3.8 +/- 0.3. T1 and NOE enhancement were strongly correlated (r = 90), and indicated that the fractional contribution of 1H-31P dipolar relaxation to total 31P relaxation is minimal for NTPs, moderate for PMEs and high for PDEs in liver. Proton-decoupling and NOE enhancement permit one to obtain more information about in vivo metabolism of liver than previously available and should enhance the utility of 31P MRS for the study of hepatic disorders.

Development and applications of in vivo clinical magnetic resonance spectroscopy

4.1 CURRENT STATUS. While an extensive clinical literature of MRS of muscle, brain, heart and liver has been achieved, the MRS technique is not considered essential for routine diagnosis because it is inherently insensitive and metabolic changes tend to be small. However, MRS techniques have proven to be of considerable value for prognosis in some circumstances, notably for predicting outcome following hypoxic-ischaemic injury in the newborn and also in predicting graft viability following organ transplantation. The chemical specificity of MRS has been illustrated, and exploiting the non-invasive nature of the technique, metabolic fingerprinting of pathophysiological processes throughout the natural history of a wide variety of diseases is now being accomplished. Particularly exciting are the applications of 13C MRS for measuring hepatic and muscle glycogen levels, for example in diabetics, and the use of hepatic 31P MRS for assessing liver function in cirrhosis. Other areas of excitement are the applications of 1H MRS in assessing neuronal function in epilepsy and stroke, and for measuring the evolution of lactate in stroke and hypoxic-ischaemic encephalopathy. Emphasis on technique development continues, and applications still tend to be technology-led. The availability of routine clinical MRI systems with spectroscopy capabilities has given MRS studies wider applicability. The recent improvements in spatial resolution have been impressive and the technique is slowly becoming more quantitative. 4.2. FUTURE PERSPECTIVES. Given the flexibility of clinical magnetic resonance techniques, particularly magnetic resonance imaging, it is likely that MRI will be the diagnostic tool of choice in a wider range of diseases, such as multiple sclerosis, stroke, neurodegenerative conditions, sports injuries and in staging malignancies. Since proton magnetic resonance spectroscopy packages have become a routine addition to many MRI systems, it is feasible to select the MRI sequences of most value in highlighting anatomical and pathological abnormalities and to incorporate specifically selected MRS sequences to emphasize biochemical differences. Improvements in technical methodologies are central to further developments. For example, use of internal coils, such as implantable or endoscopic coils, will enable small regions of tissue to be studied in considerable detail, which may otherwise be inaccessible to measurement. Chemical MRS studies have benefited from the use of higher magnetic fields, and the same may be expected for clinical MRS studies. Whole-body magnets up to 4 T have been used in a few centres, and certainly 3 T systems are becoming more widely available with the recent tremendous interest in functional imaging. Certainly, better control of artefacts can be expected; for example, improved definition of spectral changes due to voluntary or involuntary movements. Wider use of proton decoupling methods will improve the specificity of the spectra, by allowing definitive assignments of overlapping resonances, as well as the sensitivity. Comparing PET and MRS studies, it is becoming increasingly obvious that both will be required in parallel to explore parameters of brain metabolism and function. The ability to measure 13C MR signals in the brain has been demonstrated, which allows measurements of glutamate and glucose turnover. MRS measurements have the advantage of not requiring a radioactive isotope, as well as being insensitive to activity-related changes in regional cerebral blood flow. Also the study of cerebral glucose metabolism by MRS is very promising, allowing a resolution and sensitivity comparable to PET. A combination of MRS and PET studies will allow the pathogenesis of neuropsychiatric disorders to be better understood. (ABSTRACT TRUNCATED)

Chemotactic factors released from hepatocytes exposed to acetaminophen

To clarify the mechanism of neutrophil infiltration in the liver of acetaminophen-induced hepatic injury, chemotactic factor released from hepatocytes exposed to acetaminophen has been investigated. Hepatocytes exposed to acetaminophen release nondialyzable chemotactic factor, although acetaminophen in itself inhibits chemotaxis of neutrophils. Chemotactic activity of the nondialyzable chemotactic factor was reduced after treatment with heat (56 degrees C, 30 min) or trypsin. Chemotactic activity was demonstrated at the molecular weights of around 25 and 55 kDa. Chemotactic activity of the conditioned medium was not significantly reduced in the presence of antibody against rat KC/gro protein (interleukin-8-related cytokine in rodent). Chemotactic activity of a 25-kDa factor was reduced by the antibody against the antibody against KC/gro protein, but that of a 55-kDa factor was not reduced. Immunoblot analysis revealed that the peptide reacted with antibody against rat KC/gro protein was demonstrated at a molecular weight of around 20-25 kDa, but not around 55kDa, when the conditioned medium of acetaminophen-treated hepatocytes was electrophoresed. These results suggest that hepatocytes exposed to acetaminophen release two types of chemotactic factors for neutrophils and that a major part of the chemotactic factor could be different from a member of interleukin-8 family.