A recent Japanese study (1) reasserts the correlation between ABO blood group and secretor status and intestinal alkaline phosphatase (IAP), an enzyme that aids digestion of fat in the diet. The study also concludes that evaluation of metabolic syndrome would be better if ABO blood group and secretor status are taken into account.

The abstact of the study, to be published in the journal Biochemical and Biophysical Research Communications, starts:

"Serum levels of intestinal alkaline phosphatase (IAP), a protein implicated in transcellular transport of chylomicrons, vary among ABO blood groups."

Background: the body produces proteins which bind with lipids (fats) and are transported around the bloodstream together as lipoproteins, where the fats are needed or stored. One way of measuring the amount of lipids transported in the blood is by measuring the proteins associated with lipid transport. An apolipoprotein is the protein component that combines with a lipid to form a lipoprotein. Chylomicrons are lipoprotein particles that are created by cells in the small intestine. Chylomicrons transport lipids to adipose tissue.

Variation in IAP according to blood group has been known for decades from previous studies, and is one of the reasons why individuals of different blood groups vary in their tolerance and metabolism of dietary fats.

To determine whether IAP is associated with chylomicron secretion in humans as well as rats, the researchers used the following method:

"Serum samples from 40 healthy subjects were obtained after overnight fast and 3h after a high-fat meal, and assayed for IAP and apolipoprotein B-48 (apoB-48), both proteins exclusive to intestine, although only apoB-48 is found in chylomicrons.

"The two proteins were greater in subjects without blood antigen A (B and O) than in those with this antigen (A and A; 2.4- and 4.7-fold for IAP and 1.5- and 2.0-fold for apoB-48 before and after the meal, respectively."

This is a significant difference between IAP and apoB-48 levels even when fasting.

The study concludes:

"Moreover, IAP and apoB-48 levels were strongly correlated in the subjects with the secretor phenotype (r>0.81). These results indicate that IAP is strongly involved in chylomicron formation and fatty acid metabolism might change among ABO blood type."

"In addition, ABO blood type classification in apoB-48 measurement would improve the diagnostic value in the evaluation of metabolic syndrome."

In other words, this is a mechanism by which non-secretors are more likely to get syndrome X than are secretors, and can be monitored with blood tests for IAP and apoB-48.

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Reference:

Involvement of intestinal alkaline phosphatase in serum apolipoprotein B-48 level and its association with ABO and secretor blood group types.

Nakano T, Shimanuki T, Matsushita M, et. al.

Biochem Biophys Res Commun, January 5, 2006.

Pubmed [16412386 ]