Fecal selenium excretion is regulated by dietary selenium intake

Area of Science:

• Biochemistry
• Toxicology
• Nutritional Science

Background:

• Whole-body selenium homeostasis is crucial for health.
• Previous studies using isotopic tracers suggested limited regulation of fecal selenium excretion.
• Understanding selenium excretion mechanisms is vital for preventing toxicity and deficiency.

Purpose of the Study:

• To investigate the regulation of whole-body selenium by measuring urinary and fecal excretion in mice across a wide range of selenium intakes.
• To compare the regulatory roles of urinary and fecal selenium excretion.
• To elucidate the mechanisms underlying selenium excretion.

Main Methods:

• Mice were fed varying intakes of sodium selenite, from deficient to near-toxic levels.
• Urinary and fecal selenium excretion were measured.
• Tissue and whole-body selenium concentrations were analyzed.
• Selenium accumulation in selenoproteins was assessed.

Main Results:

• Tissue and whole-body selenium concentrations increased significantly with intake up to adequate levels, then plateaued.
• A 31-fold increase in selenium intake resulted in less than a doubling of tissue selenium, indicating effective excretion.
• Urinary selenium excretion increased proportionally with selenium intake.
• Fecal selenium excretion, comprising 20-30% of total excretion at physiological intakes, responded to moderately high intake but not to very high intake.

Conclusions:

• Mice effectively regulate whole-body selenium through excretion.
• Fecal selenium excretion contributes significantly to selenium regulation at physiological intakes.
• The distinct responses of urinary and fecal excretion to varying selenium intakes suggest different underlying mechanisms for each route.