Secretion of HDL from the liver into the circulatory system regulates the release of HL into the body's bloodstream. This is because factors that increase the release of HDL (such as fasting, leading to low levels of HDL) increases the amount of HL bound to HDL and released into the bloodstream. Another lipoprotein, ApoA-I, which increases release of HDL was shown to have a similar effect by mutating the gene that coded it. Mutated ApoA-I protein caused a decrease in HL release and thus decreased the amount of HL bound to HDL and released into the bloodstream.