Retinol-Binding Protein (RBP) is a protein involved in the transport of retinol (vitamin A) in the bloodstream. Vitamin A is essential for various physiological processes, including vision, immune function, and cellular growth.
Retinol-Binding Protein is responsible for binding to retinol and ensuring its transport from the liver, where it is stored, to target tissues and organs throughout the body. It plays a crucial role in maintaining adequate levels of vitamin A and supporting its functions.
Retinol-Binding Protein is often used as a biomarker to assess vitamin A status in the body. Measuring the levels of Retinol-Binding Protein in serum can provide insights into an individual's vitamin A status, which is important for assessing nutritional deficiencies or imbalances. Low levels of RBP can indicate a potential deficiency in vitamin A, which can have significant health implications, particularly in terms of vision health and immune system function. Monitoring RBP levels and ensuring adequate vitamin A intake is important for overall health and well-being.
Retinol-binding protein is most often found bound to transthyretin, but a small, unbound fraction (< 10%) passes freely through glomerular membranes and is reabsorbed by renal proximal tubule cells where it is catabolized. Due to extensive tubular reabsorption, under normal conditions, very little of the filtered retinol-binding protein appears in the final excreted urine.
Serum concentrations of Retinol-Binding Protein reflect the synthesis capacity of the liver and may indicate early malnutrition, acute and chronic hepatic disease, advanced chronic renal insufficiency, nephritic syndrome, protein-losing enteropathy, and cystic fibrosis. Due to the short half-life of approximately 12 hours, RBP may be suitable for monitoring the nutritional status and efficacy of parenteral nutrition.