High cerebral guanidinoacetate and variable creatine concentrations in argininosuccinate synthetase and lyase deficiency: implications for treatment?

Cerebral creatine and guanidinoacetate and blood and urine metabolites were studied in four patients with argininosuccinate synthetase (ASS) or argininosuccinate lyase (ASL) deficiency receiving large doses of arginine. Urine and blood metabolites varied largely. Cerebral guanidinoacetate was increased in all patients, while cerebral creatine was low in ASS and high in ASL deficiency. Because high cerebral guanidinoacetate might be toxic, lowering the arginine supplementation with additional creatine supplementation might be important.

Decreased energy and phosphorylation status in the liver of lung cancer patients with weight loss.

BACKGROUND/AIMS: Altered energy status has been reported in the liver of tumour-bearing animals, but data on energy status in humans are scarce. Therefore, bioenergetics in tumour-free liver of lung cancer patients were monitored using 31P magnetic resonance spectroscopy (MRS) with infusion of L-alanine as a gluconeogenic challenge. METHODS: Twenty-one overnight-fasted lung cancer patients without liver metastases, with (CaWL) or without weight loss (CaWS), and 12 healthy control subjects (C) were studied. Hepatic energy status was monitored before and during an i.v. L-alanine infusion of 1.4-2.8 mmol/kg + 2.8 mmol x kg(-1) x h(-1) for 90 min by 31p MR spectroscopy. RESULTS: Baseline levels of ATP in WL lung cancer patients, expressed relative to total MR-detectable phosphate, were reduced (CaWL, 9.5+/-0.9% vs. CaWS, 12.6+/-0.8% and C, 12.4+/-0.8%; p<0.05) and inversely correlated with the degree of weight loss in lung cancer patients (r=-0.46, p=0.03). Pi/ATP ratios were increased (p<0.05), indicating reduced liver phosphorylation status. During L-alanine infusion, ATP levels decreased in all groups (p<0.05); in CaWL, ATP levels were lower at all time-points between 0-90 min as compared to both CaWS and C (p<0.05). Pi/ATP ratios were significantly higher after 70-90 min of L-alanine infusion in CaWL compared to CaWS and C (p<0.05). CONCLUSIONS: Hepatic ATP and phosphorylation status are reduced in WL lung cancer patients, in contrast to WS patients and healthy subjects, and continue to decrease during infusion of a gluconeogenic substrate, suggesting impaired energy regenerating capacity in these patients.

Hepatic sugar phosphate levels reflect gluconeogenesis in lung cancer: simultaneous turnover measurements and 31P magnetic resonance spectroscopy in vivo.

Stable-isotope tracers were used to assess whether levels of phosphomonoesters (PME) and phosphodiesters (PDE) in the livers of lung cancer patients, as observed by (31)P magnetic resonance (MR) spectroscopy, reflect elevated whole-body glucose turnover and gluconeogenesis from alanine. Patients with advanced non-small-cell lung cancer without liver metastases (n=24; weight loss 0-24%) and healthy control subjects (n=13) were studied after an overnight fast. (31)P MR spectra of the liver in vivo were obtained, and glucose turnover and gluconeogenesis from alanine were determined simultaneously using primed-constant infusions of [6, 6-(2)H(2)]glucose and [3-(13)C]alanine. Liver PME concentrations were 6% higher in lung cancer patients compared with controls (not significant); PME levels in patients with >/=5% weight loss were significantly higher than in patients with <5% weight loss (P<0.01). PDE levels did not differ between the groups. In lung cancer patients, whole-body glucose production was 19% higher (not significant) and gluconeogenesis from alanine was 42% higher (P<0. 05) compared with healthy subjects; turnover rates in lung cancer patients with >/=5% weight loss were significantly elevated compared with both patients with <5% weight loss and healthy subjects (P<0. 05). PME levels were significantly correlated with glucose turnover and gluconeogenesis from alanine in lung cancer patients (r=0.48 and r=0.48 respectively; P<0.05). In conclusion, elevated PME levels in lung cancer patients appear to reflect increased glucose flux and gluconeogenesis from alanine. These results are consistent with the hypothesis that elevated PME levels are due to contributions from gluconeogenic intermediates.

Understanding the discrepancies between 31P MR spectroscopy assessed liver metabolite concentrations from different institutions.

The high divergence between the liver metabolite concentrations and pH values reported in previous quantitative 31P magnetic resonance studies, for instance phosphomonoester (0.7-3.8 mM) and phosphodiester (3.5-9.7 mM), has not been addressed in the literature. To assess what level of discrepancy can be caused by processing and metabolite integration, in this study chemical shift imaging localized 31P magnetic resonance spectra of human liver were quantitated by three methods currently applied in clinical practice: peak areas defined manually by placement of two cursors vs. frequency domain curve fitting with the assumption of either Gaussian or Lorentzian line shapes. Large reproducible differences were found in liver metabolite peak areas but not in pH, indicating that processing and peak integration methods can only explain part of the discrepancies between the results from different institutions.

31P magnetic resonance spectroscopy detection of response-predictive adenosine triphosphate decrease in irradiated radiation-induced fibrosarcoma-1 tumors.

RATIONALE AND OBJECTIVES: In previous phosphorus-31 (31P) magnetic resonance (MR) spectroscopy studies of radiation-induced fibrosarcoma (RIF-1), tumor model single-dose x-ray irradiation was applied at subcurative doses. A more effective x-ray does was used in this study, allowing correlation of treatment efficacy with the early changes observed in the 31P MR spectra of RIF-1 tumors. METHODS: Subcutaneous RIF-1 tumors of 60 mice were examined by 31P MR spectroscopy shortly before a single localized x-ray dose of 40 Gy and at eight times (2, 12, 24, 48, 72, 120, 168, and 216 hours) thereafter. RESULTS: Early increases in the relative concentration of inorganic phosphate and decreases in adenosine triphosphate (ATP), most notably at 2 and 12 hours (each P < 0.00001), were observed that lasted up to 48 hours after irradiation. Phosphomonoester and tumor pH showed decreases that reversed even earlier. Reduction of ATP measured at 48 hours after irradiation was, however, correlated with percent tumor shrinkage observed during the subsequent weeks (r = -0.59; P < 0.00001). CONCLUSIONS: Sustained loss of RIF-1 tumor ATP is predictive of treatment efficacy. Temporary depression of high-energy phosphate in favor of inorganic phosphate does not necessarily lead to cell death.

Gd-enhanced MR imaging of brain metastases: contrast as a function of dose and lesion size.

MR imaging contrast of brain metastases after cumulative doses of gadolinium chelate is quantitated and compared in order to assess the clinical utility of high dosage. T1-weighted spin-echo MR images of 39 patients with metastatic brain tumors were made before and after each of three equal doses cumulating to 0.1, 0.2 and 0.3 mmol Gd-complex per kg body weight. Quantitation of MRI contrast was limited to homogeneous brain metastases larger than 3 mm (n = 246). Post-Gd MRI contrast doubled with dose escalation from 0.1 to 0.3 mmol/kg and also increased with lesion size, by a factor of 2.5 between metastases of 3 and 16 mm diameter, that is after correcting for partial volume effect. At 0.2 and 0.3 mmol/kg the respective numbers of visible metastases increased by 15% and 43% compared with 0.1 mmol/kg (p < 0.0001, both). Image contrast figures differed significantly between doses (p = 0.018). Both the number of metastases and the image contrast is significantly higher when dose escalation is performed. It is indicated that the number of detected metastases will increase further at Gd doses beyond 0.3 mmol/kg. Post-Gd MRI contrast increases with lesion size, to an extent that can not be attributed to partial volume attenuation.

31P magnetic resonance spectroscopy as predictor of clinical response in human extremity sarcomas treated by single dose TNF-alpha + melphalan isolated limb perfusion.

Irresectable extremity sarcomas are large (grade II/III) tumors requiring amputation of the limb for local control. Limb salvage can be achieved by isolated limb perfusion (ILP) with tumor necrosis factor alpha (TNF-alpha), interferon-gamma and melphalan. To obtain insight into the effects of single dose ILP on extremity tumors, phosphate metabolism was monitored by 31P magnetic resonance spectroscopy (MRS) using the chemical shift imaging (CSI) technique. 2D CSI was used in combination with a slice select gradient in the third dimension to obtain true 3D localization. Spectral maps obtained prior to ILP revealed reductions in phosphocreatine (PCr) level and increases in phosphomonoester (PME) and phosphodiester (PDE) in tumor compared with muscle tissue. ILP treated tumors showed highly divergent changes in Pi while PME decreased in all cases (n = 11). Tumor volume, unchanged on day 8 after ILP, was decreased by 58 +/- 29% (mean +/- SD) at 2 months. Linear regression analysis revealed correlation between the changes in tumor metabolites measured on day 8, with percent volume decrease (Pi: r = -0.88, p < 0.001) and percent necrosis at resection (PME: r = -0.79, p -0.01). Correlation between pretreatment spectra and effectiveness of ILP treatment was not found. It is concluded that a single ILP with TNF-alpha + melphalan induced changes in tumor metabolite levels (measured on day 8) that reflect treatment efficacy. 31P MRS can thus provide information facilitating the decision as to when to remove tumor (residue) and, in the case where tumor remains inoperable, whether or not to apply additional therapy.

Multinuclear MR investigation of the metabolic response of the murine RIF-1 tumor to 5-fluorouracil chemotherapy.

The metabolic response of the RIF-1 tumor to 5-fluorouracil (a single dose of 260 mg 5FU/kg, ip) was monitored in 10 mice using 19F and 31P MR spectroscopy. 19F MRS revealed a continuous drop in tumor 5FU level and an increase in the fluoronucleotide (Fnuc) signal to a plateau value of 50% of the initial 5FU level, during the first 2 h after chemotherapy. Although the 31P MR spectra of the tumors showed no significant initial changes, the total level of MR visible tumor phosphate decreased and tumor pH increased during the subsequent days. The changes in phosphate metabolism and tumor pH did not correlate with the detected fluorine levels or tumor response. However, the pretreatment Pi level, the plateau Fnuc level, and the 5FU induced decrease in tumor volume showed significant correlation. This indicates that both 19F and 31P MR spectroscopy have potential for predicting response to 5FU chemotherapy.

31P NMR study of cisplatin- and doxorubicin-induced changes in tumour metabolism in rats with a cisplatin-sensitive or -resistant immunocytoma.

The response of tumours to treatment with the cytostatic drugs cisplatin (CDDP) or doxorubicin (DXR) was followed in vivo by 31P NMR spectroscopy. A CDDP-sensitive parent line (IgM-I) and a CDDP-resistant subline (IgM/CDDP) of the IgM-immunocytoma grown s.c. on LOU/M WsL rats were used. Animals from both tumour groups (n = 33) were divided into 3 subgroups: CDDP-treated (1 mg/kg), DXR-treated (10 mg/kg) and control. In 3 out of the 4 treated subgroups where the tumours regressed to less than one half of the initial size, 31P NMR spectroscopy revealed alkaline shifts of 0.31-0.41 pH units at day 4, while the ratio of nucleoside triphosphate to Pi in the tumours, increased continuously to 250-435%. Following CDDP treatment, the 31P NMR spectra of the non-responding IgM/CDDP tumours showed a similar pH increase (0.37 units). The ratio of NTP/Pi showed a temporary decrease to 63 +/- 14% SEM at day 1, which was followed by a recovery to 130 +/- 12% at day 2 and 119 +/- 15% at day 4. The control tumours showed no change in pH and a gradual decrease in the ratio of NTP/Pi. In DXR-treated rats the concentrations of DXR in the immunocytoma tumour and its subline were similar, but in the CDDP-treated rats the IgM-I tumours contained significantly higher levels of platinum than the IgM/CDDP tumours, both measured at 3 and 4 days after administration. The continuous increase in NTP/Pi ratio observed in the responding tumours, is a phenomenon characteristic of tumour regression, while the early temporary decrease in tumour NTP/Pi ratio could be associated with resistance to CDDP. Whether the reported response-specific spectral change applies to other tumour types and other treatment regimens remains to be established.

Human breast cancer in vivo: H-1 and P-31 MR spectroscopy at 1.5 T.

To assess the potential of in vivo magnetic resonance (MR) spectroscopy for breast cancer, hydrogen-1 and phosphorus-31 MR spectra of five malignant human breast tumors were compared with those of unaffected breast tissue. The water-to-fat ratio was high in the tumors (average, 2.2) but low in the unaffected tissue (average, 0.3). The P-31 spectrum of normal breast tissue showed low levels of phosphomonoesters (PMEs), inorganic phosphate, phosphodiesters (PDEs), and ATP. In addition, an intense phosphocreatine (PCr) signal was observed in breast tissue of young women: The relative intensities of the PCr and ATP signals had a mean value of 1.9. The tumor spectrum showed elevated levels of PMEs, Pi, and PDEs, while no PCr was seen (PCr/ATP less than 0.2). In two breast cancers treated with radiation therapy, resulting in a decrease of tumor volume of more than 50%, a similar change in the tumor P-31 spectrum was observed: An intense PCr signal developed (PCr/ATP = 1.1). Control experiments indicated that the appearance of PCr after radiation therapy was the result of a radiation-induced metabolic change in the tumor itself.

Murine mammary tumor response to hyperthermia and radiotherapy evaluated by in vivo 31P-nuclear magnetic resonance spectroscopy.

The response of the s.c.-implanted murine mammary carcinoma NU-82 to hyperthermia was followed as a function of time by 31P-nuclear magnetic resonance spectroscopy. Treatment consisted of elevation of the temperature of the tumors to 41-45 degrees C during 15 min. At 18 h after temperatures of up to 42, 43, 44, and 45 degrees C the ratio of ATP/Pi was unchanged, decreased, largely decreased, and approaching zero, respectively. After the higher doses the relative concentrations (in percentage of total phosphate as visible in the nuclear magnetic resonance spectrum) of phosphomonoesters (mainly phosphoethanolamine) and phosphocreatine also decreased in favor of Pi. The changes in phosphodiesters (mainly glycerophosphocholine) correlated linearly with the changes in ATP (r = 0.84, P less than 0.025). Whereas the limited spectral changes after a dose of 43 degrees C were nullified within 24 h, the more drastic changes after a dose of 45 degrees C lasted at least 8 days. The heavier dose not only induced temporary decreases in tumor perfusion like the lower dose (phase 1) but subsequently, unlike the lower dose, resulted in formation of necrosis (phase 2). In the same tumor we found increases in Pi and decreases in ATP and phosphodiesters after radiotherapy with a dose of 20 Gy. Radiotherapy (20 Gy) combined with hyperthermia (44 degrees C) appeared to strengthen these effects and resulted in an improved tumor response (regression).