r-Galactonolactone in experimental galactosemic animals

Area of Science:

• Biochemistry
• Metabolic Disorders
• Toxicology

Background:

• Galactosemia is a metabolic disorder characterized by the inability to metabolize galactose.
• Galactose can be metabolized via oxidative or reductive pathways, producing different metabolites.

Purpose of the Study:

• To investigate the tissue distribution and excretion of galactose metabolites, specifically galactose-1,4-lactone and galactitol, in galactosemic guinea pigs.
• To explore the relationship between oxidative and reductive galactose metabolism under toxic conditions.

Main Methods:

• Galactosemic guinea pigs were fed a high galactose diet (40%) for varying durations (2 days to 6 weeks).
• Tissue and serum levels of galactose-1,4-lactone and galactitol were quantified.
• The effect of aldose reductase inhibition on metabolite accumulation and excretion was examined.

Main Results:

• Galactose-1,4-lactone accumulated in various tissues, with the highest concentrations in the liver.
• Galactitol content was highest in the lens.
• Urinary excretion of galactose-1,4-lactone occurred slowly after diet withdrawal, while rapid decrease was observed after short-term high galactose intake.
• Aldose reductase inhibition led to increased lactone accumulation in tissues and circulation, with exclusive urinary excretion.

Conclusions:

• High galactose levels promote galactose-1,4-lactone production in tissues.
• Galactose-1,4-lactone is slowly released into circulation and primarily excreted via urine.
• A significant interplay exists between the oxidative and reductive pathways of galactose metabolism at toxic levels.