Expression of intestinal-type alkaline phosphatase mRNA in liver of Akp3 knockout mice

Previously, we discovered that the rat liver showed enhanced expression of intestinal-type alkaline phosphatase (ALP) on high fat-feeding. Here we tested the hypothesis that intestinal-type ALP (Akp3 or Akp6) might also be regulated in the liver of Akp3-/- mice upon high fat-feeding. C57Bl/6J male Akp3-/-, Akp3+/-, or wild-type mice were fed a normal control or high-fat diet and the effects on intestinal-type ALP mRNA in liver were investigated. We found that Akp3 mRNA is only expressed in the intestine and not in the liver, while Akp6 mRNA is expressed in both the upper intestine and liver of wild-type mice. The intensity of Akp6 mRNA expression in the liver was not enhanced in the Akp3-/- mice compared with the wild-type mice fed on a high-fat diet. The nucleotide sequence of the PCR product of Akp6 from the liver was identified as being the same as that of Akp6 in the intestine. This is the first report concerning IAP mRNA expression in the mouse liver, but further studies will be needed to determine if this ectopic expression of intestinal-type ALP is associated with any unique function.