Retinoid metabolism in human leucocytes

Area of Science:

• Biochemistry
• Immunology
• Nutrition Science

Background:

• Retinoids, vitamin A derivatives, are crucial for various physiological processes, including immune function.
• Leukocytes play a role in immune response and retinoid metabolism.
• Age-related changes in immune function and nutrient status are well-documented.

Purpose of the Study:

• To investigate age-related changes in retinoid and retinoid-binding protein concentrations within human leukocyte fractions.
• To identify specific retinoids and associated binding proteins in different leukocyte types across the lifespan.

Main Methods:

• Human subjects aged 0-80 years were recruited.
• Leukocytes were isolated and separated into mononuclear and granulocyte fractions.
• Retinoids (retinol, retinoic acid, and other retinoids) and retinoid-binding proteins were quantified in each fraction.

Main Results:

• Both mononuclear and granulocyte fractions contained retinol, retinoic acid, and an additional retinoid.
• Retinoic acid constituted up to 40% of total retinoids in some samples.
• Retinoid-binding proteins identified included a 200 kDa protein and several 14-18 kDa proteins.
• Plasma retinol levels remained stable with age.
• Leukocyte retinoid and retinoid-binding protein concentrations showed a quadratic increase with age.
• Granulocytes from young children had undetectable levels of retinoids.

Conclusions:

• Leukocyte retinoid metabolism and storage exhibit significant age-dependent modulation.
• The observed increase in leukocyte retinoids with age suggests altered distribution or accumulation.
• The near absence of retinoids in young children's granulocytes warrants further investigation into early-life retinoid requirements for immune development.