Zinc and taurine in Friedreich's ataxia

Characterization of biometal profiles in neurological disorders

This review summarizes the findings on dysregulation of metal ions in neurological diseases and tries to develop and predict specific biometal profiles.

Synchrotron X-ray fluorescence reveals abnormal metal distributions in brain and spinal cord in spinocerebellar ataxia: a case report

For the first time, synchrotron rapid-scanning X-ray fluorescence (RS-XRF) was used to simultaneously localize and quantify iron, copper, and zinc in spinal cord and brain in a case of spinocerebellar ataxia (SCA). In the normal medulla, a previously undescribed copper enrichment was seen associated with spinocerebellar fibers and amiculum olivae. This region was virtually devoid of all metals in the SCA case. Regions with neuronal loss and gliosis in the cerebellar cortex, inferior olivary, and dentate nuclei and areas showing loss of myelinated fibers were also low in all metals in SCA compared to control. In contrast, the ventral columns of the spinal cord that exhibited only moderate myelin pallor had increased metal levels. Iron and zinc were also elevated in the globus pallidus pars externa in SCA relative to control. We hypothesize that metals increase as part of the initial neurodegenerative process, but once degeneration is advanced, the metal levels drop. This implies a role for multiple metals in SCA neurodegeneration, but further study is required to establish a causative role. We suggest that if these findings are generally true of at least some cases of SCA, not only iron but also copper and zinc should be considered as possible therapeutic targets.

Oscillatory potentials and light microscopic changes demonstrate an interaction between zinc and taurine in the developing rat retina

Our objective was to investigate whether zinc interacts with taurine to influence the development of retinal structure and function. Virgin female Sprague-Dawley rats were bred overnight and assigned to one of four treatments in a 2 x 2 factorial design with two levels of zinc (50 micrograms/g through gestation and 50 micrograms/g after parturition; 15 micrograms/g through gestation and 7.5 micrograms/g after parturition) and two levels of taurine (2 or 0 mumol/g). The control diet contained 50 micrograms/g zinc and 2 mumol/g taurine. Guanidinoethyl sulfonate (10 g/L), a taurine transport inhibitor, was added to the drinking water of the rats receiving 0 mumol/g taurine. At postnatal d 23, male pups (n = 10) were weaned onto their respective diets. Pup eyes were examined by biomicroscope and indirect ophthalmoscope at 4 and 7 wk; retinal folds and choroidal atrophy were detected in the pups deficient in zinc and taurine. Analysis of plasma zinc and tibial zinc concentrations revealed a significant interaction in these tissues (P < 0.05). Dark-adapted oscillatory potentials (OP) were recorded at 7.5-8.5 wk. Two-way ANOVA showed a significant interaction between zinc and taurine for OP2 and OP3 amplitudes; marginal zinc deficiency decreased the amplitude of the OP only when rats were also deficient in taurine. A significant depressing effect of marginal zinc deficiency was noted for OP1 amplitude. Taurine deficiency significantly depressed the amplitude of OP1 and OP4. Histological examination of the retinas from rats deficient in both zinc and taurine revealed photoreceptor degeneration and confirmed retinal dysplasia. These data provide evidence for an interaction between zinc and taurine in retinal morphology and function.

Hair trace elements in cerebellar degeneration: low copper levels in late cortical cerebellar atrophy

The levels of ten elements in the hair of 7 patients with olivopontocerebellar atrophy (OPCA), 10 patients with late cortical cerebellar atrophy (LCCA) and 1489 healthy persons were determined by inductively coupled plasma emission spectrometry. The phosphorus, zinc, selenium, calcium, magnesium, iron, manganese, aluminium and mercury concentrations did not show any statistically significant difference among the three groups. The copper concentration was significantly lower in the patients with LCCA than in the patients with OPCA, and in the healthy controls. The possibility that LCCA is associated with a mild degree of copper deficiency is considered.

Zinc-binding proteins in the brain

As an essential substance, zinc is involved in maintaining the functions and/or the structures of at least 200 metalloenzymes that participate in numerous biochemical reactions, including the metabolism of proteins and nucleic acids. The steady-state concentration of zinc in the brain must be regulated firmly since both an excess and a deficiency of zinc have been implicated in neurological disorders including epilepsy. Zinc-binding proteins have been detected in the bovine hippocampus, cerebellum, and pineal gland. A metallothionein-like protein has been identified recently in the rat brain which resembles in some but not all aspects a hepatic metallothionein. The synthesis of this protein is stimulated following the administration of zinc and copper but not of cadmium. The zinc-stimulated protein incorporates 35S cysteine 24-fold higher than the native, unstimulated protein; is blocked by actinomycin D; produces two isoforms by ion exchange chromatography on DEAE Sephadex A 25 columns; and by high performance liquid chromatography, depicts a similar but not identical profile to zinc-stimulated hepatic metallothionein. Since the synthesis of this protein is stimulated following the administration of zinc and is depressed in the brains of zinc-deficient rats, it is postulated that the unbound pool of zinc may serve as one of the factors involved in regulating the synthesis of this protein. Since zinc in physiological concentrations stimulates a number of pyridoxal phosphate-dependent reactions and in pharmacological doses inhibits an extensive number of SH-containing enzymes and receptor sites for neurotransmitters, we postulate that the metallothionein-like protein in the brain may have function(s) associated with zinc homeostasis and perhaps events related to synaptic functions.