What is Vitamin D Binding Protein (VDBP)?
Vitamin D Binding Protein is a multi-functional plasma protein with many important functions. The most well known one, and the reason for its name, is the transport of vitamin D metabolites . Because VDBP is the primary transporter of vitamin D, it has a role in maintaining the total levels of vitamin D in the body and in regulating the amounts of free (unbound) vitamin D available for specific tissues and cell types to utilise.
Other functions of VDBP are to control bone development, binding of fatty acids, sequestration of actin and a range of less-defined roles in modulating immune and inflammatory responses. The actin removal is considered to be a very important role for VDBP, actins being toxic and released into the body following cell death.
Two amino acids on this protein chain have been shown to be very strongly associated with the activation of macrophages. In some publications, the vitamin D binding protein is shown to respond to enzymes released by inflammation and this is often referred to as MAF (Macrophage Activating Factor). Studies show that this isoform not only activates macrophages, it turns them off when no longer needed, so it is an immune system regulator.
Studies in laboratory cultures have shown that Calcitriol (Vitamin D bound with VDBP) can significantly increase the number of dopamine neurons.
Vitamin D Binding Protein is otherwise know as:
- Transport protein
Sources of Vitamin D Binding Protein
VDBP is a protein that occurs naturally in all higher order animals and is often produced by the first milk of mothers (colostrum) that helps boost the immunity of their newborns.
- Human & animal plasma
- Pro-biotic yoghurts
- Bacular expression
- Laboratory synthesis
Factors that influence VDBP levels
Liver disease decreases levels of VDBP. Chronic liver disease will decrease levels less than acute liver failure. Trauma and surgery will decrease Vitamin DBP. Septic infections will consume Vitamin DBP faster than production can be increased.
Normal VDBP levels in serum are 350-500 mg/l. Levels of VDBP less than 80 mg/l yield positive and negative mortality predictive values of 85% and 43% respectively. Survivors had levels greater than 102 mg/l.