Purification and Characterization of Insulin-Mimetic Inositol Phosphoglycan-Like Molecules From Grass Pea (Lathyrus sativus) Seeds

Covadonga Pañeda,Ana Victoria Villar,Félix M Goñi,Alicia Alonso,Isabel Varela-Nieto,Yolanda León,Federico Varela,Urs Brodbeck,David R Jones

doi:10.1007/bf03401850

Abstract

Signal transduction through the hydrolysis of glycosyl-phosphatidylinositol (GPI) leading to the release of the water-soluble inositol phosphoglycan (IPG) molecules has been demonstrated to be important for mediating some of the actions of insulin and insulin-like growth factor-I (IGF-I). In the present study, GPI from grass pea (Lathyrus sativus) seeds has been purified and partially characterized on the basis of its chromatographic properties and its compositional analysis. The results indicate that it shows similarities to GPI previously isolated from other sources such as rat liver. IPG was generated from L. sativus seed GPI by hydrolysis with a GPI-specific phospholipase D (GPI-PLD). This IPG inhibited protein kinase A (PKA) in an in vitro assay, caused cell proliferation in explanted cochleovestibular ganglia (CVG), and decreased 8-Br-cAMP-induced phosphoenolpyruvate carboxykinase (PEPCK) mRNA expression in cultured hepatoma cells. Our data indicate that L. sativus seed IPG possess insulin-mimetic activities. This may explain why L. sativus seeds have been used in some traditional medicines to ameliorate diabetic symptoms.

Highlights

Glycosyl-phosphatidylinositol (GPI) lipids have a structural role as protein anchors to the outer cell surface [1,2]
On the basis of our experience both in the area of inositol phosphoglycan (IPG) purification and assessment of its biological properties and the above considerations regarding the search for a suitable source of IPG, we started this study to determine the presence of IPG in L. sativus seeds with the objective of characterizing for the first time plant-derived IPG-like molecules
To determine if L. sativus seeds contained GPI-like molecules, we employed established protocols that have been used for the extraction of GPI from mammalian tissues and cultured cell lines [15]

Summary

Introduction

IPG is still to be found that would comply with the following criteria: (i) high yield of biologically active IPG, (ii) low cost of purification, and (iii) abundance of starting material These three criteria are considered essential for the large-scale preparation of IPG species. In spite of the modern advances in drug design to alleviate and delay the symptoms of diabetes, there still remains some interest in the use of nonregistered concoctions that originate from plant origin. Such plants including Medicago sativa [5], Ginkgo biloba [6,7], Bryonia alba [8,9], Burmelia sartorum [10], and others [11,12] have been considered to have “anti-diabetic properties.”. On the basis of our experience both in the area of IPG purification and assessment of its biological properties and the above considerations regarding the search for a suitable source of IPG, we started this study to determine the presence of IPG in L. sativus seeds with the objective of characterizing for the first time plant-derived IPG-like molecules

Materials and Methods

Methods

RESULTS AND DISCUSSION