Reduced brain creatine in gyrate atrophy of the choroid and retina with hyperornithinemia

OBJECTIVE

To analyze in vivo brain creatine (Cr) content in gyrate atrophy of the choroid and retina with hyperornithinemia (GA).

BACKGROUND

GA is caused by inherited deficiency of ornithine-delta-aminotransferase activity. Patients lose their vision by middle age and develop selective atrophy of type II skeletal muscle fibers. As demonstrated by MRS, the patients' skeletal muscles have diminished stores of high-energy Cr phosphate. Minor structural and electrophysiologic abnormalities in the brain of these patients also imply that the CNS may be affected.

METHODS

The authors acquired proton MR spectra of the basal ganglia of 22 healthy control subjects and 20 GA patients. Nine patients received supplementary Cr or its precursors, and one child was on an arginine-restricted diet to normalize plasma ornithine concentration. The ratios of N-acetylaspartate (NAA) to Cr, NAA to choline (Cho), and Cho to Cr, and the ratios of NAA, Cho, and Cr to tissue water were calculated.

RESULTS

NAA/Cr (Cho/Cr) in the untreated and treated patients and control subjects were (mean +/- SD) 3.3+/-0.4, 2.0+/-0.4, and 1.5+/-0.7 (1.9+/-0.3, 1.3+/-0.4, and 0.9+/-0.2), indicating that Cr content in untreated GA patients was proportionally and markedly diminished, and partially corrected by therapy (p < 0.0001). NAA/Cho was similar in all three groups. Cr/water in the untreated patients was only 46%, and increased to 75% of the control ratios in the treated patients (p < 0.0001).

CONCLUSIONS

Hyperornithinemia-associated Cr deficiency in GA also affects the CNS, further supporting the possibility that Cr deficiency also has a pathogenetic role in the retina. The deficiency was partially corrected by Cr supplementation and an arginine-restricted diet.

Insulin-like growth factor binding protein production in human follicular thyroid carcinoma cells

IGFs and IGF binding proteins (IGFBPs) appear to serve as regulators of non-malignant thyroid cells from several species, but little is known about their role in thyroid malignancy. We have examined IGFBP production and hormonal regulation in two human thyroid follicular carcinoma cell lines; FTC-133 line derived from a local tumor recurrence and FTC-236 cells from a tumor metastasis. Under basal conditions these cell lines produced IGFBP-3, IGFBP-4 and IGFBP-2. In both cell lines, EGF or TPA stimulated IGFBP-3 production while TSH or forskolin inhibited IGFBP-3 production and reduced the stimulation of IGFBP-3 seen with EGF or TPA. IGFBP-4 production was increased in the presence of TSH, forskolin, and EGF and was reduced by TPA. mRNA assessment revealed that IGFBP-3 mRNA, more abundant in FTC-236 than FTC-133 cells, increased in the presence of EGF or TPA, while IGFBP-4 mRNA content was increased in the presence of TSH, EGF, and forskolin. These results indicate that IGFBP production in human thyroid follicular carcinoma clones is under specific hormonal regulation. IGFBP-3 production is increased by dedifferentiation factors such as EGF and TPA and inhibited by TSH and forskolin, which enhance differentiated function. The highly specific regulation of IGFBP-3 and IGFBP-4 suggests a potential role for these peptides in modulating malignant thyroid growth.