Vitamin A: too good to be bad?

Area of Science:

• Nutrition Science
• Biochemistry
• Hepatology

Background:

• Vitamin A is an essential lipophilic micronutrient vital for vision, cell growth, reproduction, and immunity.
• Both vitamin A deficiency (hypovitaminosis A) and excess intake lead to significant health issues, particularly affecting the liver.
• The liver plays a central role in vitamin A storage, metabolism, and homeostasis, with hepatic stellate cells being the primary storage site and involved in inflammation.

Purpose of the Study:

• To review and discuss controversial and unresolved issues in understanding vitamin A biology.
• To highlight the liver's critical response to vitamin A status, including damage from excess and functional alterations from deficiency.
• To examine the multifaceted roles of hepatic stellate cells in vitamin A homeostasis and liver inflammation.

Main Methods:

• Literature review and synthesis of existing research on vitamin A metabolism and function.
• Analysis of the impact of vitamin A status on liver morphology and function.
• Exploration of differential responses in animal disease models to varying vitamin A levels.

Main Results:

• Both vitamin A deficiency and excess consumption result in severe health consequences, notably liver damage, fibrosis, and altered liver function.
• Hepatic stellate cells are key players in vitamin A storage and modulate inflammatory responses within the liver.
• Observed inconsistencies in how different animal disease models respond to vitamin A status indicate complex interactions.

Conclusions:

• Understanding vitamin A biology remains complex, with significant unresolved questions, particularly concerning its impact on liver health.
• Further research into the interactions between vitamin A, animal genomes, and epigenetic settings is necessary to clarify these complexities.
• Precise regulation of vitamin A levels is critical for maintaining liver health and overall physiological function.