Tracking Systemic and Ocular Vitamin A

Area of Science:

• Ophthalmology
• Nutritional Science
• Biochemistry

Background:

• 11-cis-retinaldehyde, a form of vitamin A, is essential for vision.
• Vitamin A deficiency requires supplementation, while excess can lead to retinal diseases.
• Bisretinoids, like A2E, accumulate in the retina and are linked to photoreceptor damage.

Purpose of the Study:

• To measure systemic and ocular uptake of vitamin A and bisretinoids.
• To investigate the impact of dietary versus injected vitamin A on retinoid levels.
• To assess the influence of light exposure on retinoid metabolism and bisretinoid accumulation.

Main Methods:

• Mice were reared in light or darkness and received vitamin A via diet or intraperitoneal injection.
• Plasma and ocular retinoid levels (11-cis-retinaldehyde, atRAL, atRE) were quantified.
• Bisretinoid (A2E) levels were measured in ocular tissues.

Main Results:

• Intraperitoneal retinyl palmitate increased plasma ROL but not ocular 11-cis-retinaldehyde.
• Dietary retinyl palmitate was more effective for ocular 11-cis-retinaldehyde in dark-reared mice.
• Ocular atRAL increased with i.p. retinyl palmitate in dark-reared mice.
• Liver atRE and ocular 11-cis-retinaldehyde were elevated with dietary retinyl palmitate in dark-reared mice.
• Ocular atRE increased with i.p. retinyl palmitate in light-reared mice.
• Bisretinoid levels were not affected by retinyl palmitate but were lower in light-exposed mice due to photooxidation.
• Sustained darkness elevated ocular atRAL.

Conclusions:

• Dietary vitamin A intake influences ocular retinoid levels differently than injections.
• Plasma vitamin A levels do not reliably predict ocular retinoid or bisretinoid concentrations.
• Light exposure significantly reduces bisretinoid accumulation through photooxidation, impacting retinal health.