Bound lectins that mimic insulin produce persistent insulin-like activities

|December 1, 1983

Summary

Wheat germ agglutinin activates fat cell lipogenesis persistently by binding to cell surface receptors. This binding mimics insulin

Area of Science:

Background:

Insulin signaling regulates lipogenesis and lipolysis in adipocytes.
The mechanism of insulin-induced persistent bioactivation is not fully understood.
External cell surface interactions can influence cellular metabolic pathways.

Purpose of the Study:

To investigate the persistent effects of lectins on adipocyte metabolism.
To explore the role of cell surface determinants in insulin-like signaling.
To differentiate lectin-induced persistent bioactivation from insulin signaling.

Main Methods:

Incubation of rat adipocytes with wheat germ agglutinin (WGA) and other lectins.
Measurement of lipogenesis and lipolysis.
Assessment of lectin binding, internalization, and dissociation using N-acetyl-D-glucosamine.
Comparison with insulin's effects.

Main Results:

Wheat germ agglutinin induced persistent lipogenesis activation in adipocytes for at least 3 hours.
Bound WGA inhibited isoproterenol-stimulated lipolysis.
Other insulinomimetic lectins (Concanavalin A, wax bean agglutinin) showed similar persistent effects.
N-acetyl-D-glucosamine terminated WGA-induced lipogenesis, indicating lectin adsorption to external determinants.
Unlike insulin, WGA's persistent bioactivation was not terminated by hormone removal.

Conclusions:

Fat cell surface determinants exist that, when continuously occupied, produce persistent insulin-like activities.
Initial cell perturbation by lectins is sufficient to activate the insulin machinery.
Internalization and processing of hormone-receptor complexes are not the sole pathway for termination of bioactivation.

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