Control by the brain of vitamin A homeostasis
- Vitamin A is kept at a constant concentration in the blood but it is unknown how
- Hypothalamic tanycytes have the potential to sense vitamin A
- Vitamin A application to the hypothalamus alters systemic vitamin A distribution
- This reveals a possible role for the brain in the control of vitamin A homeostasis
Vitamin A is a micronutrient essential for vertebrate animals maintained in homeostatic balance in the body; however, little is known about the control of this balance.
This study investigated whether the hypothalamus, a key integrative brain region, regulates vitamin A levels in the liver and circulation. Vitamin A in the form of retinol or retinoic acid was stereotactically injected into the 3rd ventricle of the rat brain. Alternatively, retinoids in the mouse hypothalamus were altered through retinol-binding protein 4 (Rbp4) gene knockdown.
This led to rapid change in the liver proteins controlling vitamin A homeostasis as well as vitamin A itself in liver and the circulation. Prolonged disruption of Rbp4 in the region of the arcuate nucleus of the mouse hypothalamus altered retinol levels in the liver.
This supports the concept that the brain may sense retinoids and influence whole-body vitamin A homeostasis with a possible “vitaminostatic” role.