Alteración del metabolismo de la galactosa / Galactose metabolism defect

Las alteraciones del metabolismo de la galactosa se producen por el defecto de las enzimas: galactoquinasa (GALK), galactosa-1-fosfato-uridil transferasa (GAL1-PUT) y uridin difosfato galactosa 4' epimerasa (UDPGAL); de ellas la más frecuente es la galactosemia clásica producida por la deficiencia de GAL1PUT. Producto de este defecto se acumula galactosa-1-fosfato, galactosa libre y galactitol en sangre y tejidos, los que producen alteraciones hepáticas, renales y cerebrales. Su herencia es autosómica recesiva y la incidencia estimada a nivel mundial fluctúa entre 1:60.000 a 1:33.000 recién nacidos. Los síntomas y signos más característicos son vómito, diarrea, ictericia, hepatomegalia, cataratas. Si la enfermedad no es tratada oportunamente ocasiona la muerte del niño. El tratamiento consiste en eliminar la lactosa y galactosa de la alimentación, lo que incluye alimentos tales como la leche de todo tipo y sus derivados, la galactosa y alimentos o medicamentos que contenga alguno de estos productos. Se entrega leche de soya y los requerimientos de macro y micro nutrientes se indican según las recomendaciones para edad y sexo. La dieta dura toda la vida ya que la galactosa se transforma en galactitol, existiendo riesgo de producir catarata y daño renal en cualquier momento de la vida. Un buen control se obtiene al mantener el nivel sanguíneo de galactosa-1-fosfato igual o menor a 3.0 mg/dL y urinario de galactitol bajo 0.8 mmol/mol de creatinina.

Protective effect of L-cysteine and glutathione on the modulated suckling rat brain Na+, K+, -ATPase and Mg2+ -ATPase activities induced by the in vitro galactosaemia.

UNLABELLED: Galactosaemia is an inborn error of galactose (Gal) metabolism characterized by irreversible brain damage. The aim of this study was to evaluate whether the antioxidants L-cysteine (Cys) and the reduced glutathione (GSH) could reverse the alterations of brain total antioxidant status (TAS) and the modulated activities of the enzymes Na+,K+ -ATPase and Mg2+ -ATPase in in vitro galactosaemia. Mixture A (mix. A: galactose-1-phosphate (Gal-1-P, 2mM) plus galactitol (Galtol, 2mM) plus Gal (4mM) = classical galactosaemia) or Mixture B (mix. B: Galtol (2mM) plus Gal (1mM) = galactokinase deficiency galactosaemia) were preincubated in the presence or absence of Cys (0.83mM) or GSH (0.83 mM) with whole brain homogenates of suckling rats at 37 degrees C for 1h. TAS and the enzyme activities were determined spectrophotometrically. The preincubation of brain homogenates with mix. A or mix. B resulted in a decrease of TAS to 30% (P < 0.01), while the presence of Cys or GSH increased TAS to 20% (P < 0.01) and 60% ( P < 0.001), respectively. The antioxidants reversed the inhibited Na+,K+ -ATPase by mix. A or mix. B and the stimulated Mg2+ -ATPase by mix. B to control values, whereas no effect was observed on the enormously activated Mg2+ -ATPase by mix. A. CONCLUSIONS: (a) Gal and its derivatives may produce free radicals in the suckling rat brain, reported for first time, (b) Na+,K+ -ATPase inhibition and Mg2+ -ATPase activation are probably due to the oxidative stress from the above compounds, (c) Cys or GSH could play a protective role reversing the inhibited Na+,K+ -ATPase toward normal in in vitro galactosaemia and (d) the addition of the above antioxidants may reduce the consequences of brain Mg2+ -ATPase activation by Gal and Galtol in galactokinase deficiency galactosaemia.

Galactitol is not a cause of senile cataract.

It has been postulated that the accumulation of sugar alcohol, galactitol, from milk induces cataract in the eye lens through an osmotic mechanism. In this study the concentrations of galactitol and other sugar alcohols (sorbitol, mannitol and inositol) were measured by sensitive gas chromatography in the lenses of 15 patients operated on for senile idiopathic cataracts and in 14 clear lenses removed at autopsy. Large amounts of inositol (mean +/- SD, 4.1 +/- 3.1 vs 4.7 +/- 3.0 mumol/g lens wet weight) and small amounts of mannitol and sorbitol were detected in both study groups. Galactitol levels remained clearly below the detection limit (2 nmol/g) in all lenses. It seems unlikely that senile cataract is a result of the accumulation of galactitol in the eye lens.

Phase II studies of dianhydrogalactitol and VP-16-213 in colorectal cancer.

Phase II chemotherapy trials of dianhydrogalactitol and VP-16-213 were conducted in patients with metastatic colorectal cancer who had measurable malignant disease which served as indicators of response to therapy. Dianhydrogalactitol was given in a 5-day course at a dosage of 30 mg/m2/day. Toxic reactions included nausea, vomiting, leukopenia, thrombocytopenia, and anemia. There was a definite tendency to a compounding of hematologic toxicity with repeated courses. No evidence of objective therapeutic response was observed among 30 patients treated. VP-16-213 was given at a dosage of 130 mg/m2 on Days 1, 3, and 5. Toxic reactions included nausea, vomiting, alopecia, leukopenia, thrombocytopenia, and anemia. Hematologic toxicity was more severe in patients with elevated serum bilirubin levels. No evidence of objective therapeutic response was observed among 28 patients treated.

Phase I trial of dianhydrogalactitol administered Iv in a weekly schedule.

Dianhydrogalactitol was given to 28 patients with a variety of advanced solid tumors on a weekly schedule in iv doses ranging from 2 to 80 mg/m2. No significant toxicity was encountered at doses up to 40 mg/m2/week for 4 weeks. At higher doses mild-to-moderate nausea and vomiting and hematologic toxicity were noted. Thrombocytopenia was more common than granulocytopenia and frequently resolved more slowly. No adverse drug-realted effects on liver, renal, coagulation, or cardiac function were seen. Although no patient had significant antitumor response (as strictly defined), objective improvement was noted in two patients, one with hypernephroma and the other with malignant melanoma. for phase II studies, a weekly dose of 70 mg/m2 is recommended for patients with normal hematopoiesis, with reduction by 25% (55 mg/m2) in patients with extensive prior radiation therapy, prior chemotherapy, and/or widespread metastasis to the bone.