AJP - Endocrinology and Metabolism, Vol 238, Issue 3 267-E275, Copyright © 1980 by American Physiological Society
Effects of wheat germ agglutinin on insulin binding and insulin sensitivity of fat cells
J. N. Livingston and B. J. Purvis
The plant lectin (wheat germ agglutinin, WGA) produces several alterations
in the ability of fat cells to bind and respond to insulin. Although WGA
markedly stimulated glucose oxidation, it caused only a modest stimulation
of glucose transport. WGA (0.25-20 micrograms/ml) increased the binding of
insulin by adipocytes, apparently by increasing the binding affinity of the
insulin receptor. With low WGA concentrations (0.25-2.5 micrograms/ml), the
elevation in binding was accompanied by an increase in the sensitivity of
the adipocytes to insulin stimulation of glucose transport. However, the
sensitivity of these cells to vitamin K5 and H2O2 was not altered. With
higher WGA concentrations (5-20 micrograms/ml), stimulation of the glucose
transport system by insulin, vitamin K5, or H2O2 was markedly inhibited, an
effect that is reversed by the addition of ovomucoid. These findings
suggest that low WGA concentrations increase the affinity of the insulin
receptor and the insulin sensitivity of the cells. At higher
concentrations, the lectin appears to act at another site(s) to inhibit the
activation of the transport system by insulin or other agents.
