Investigation of the hypocholesterolemic mechanism of action of lupin peptides

Lupin is a legume and this generic term indicates four species: Lupinus albus (white lupin), Lupinus angustifolius (narrow-leaf lupin), Lupinus luteus (yellow lupin), and Lupinus mutabilis (Andean lupin). The seeds of these plants have some favorable features, in particular the protein percentage is comparable to that of soybean1 and the content of indispensable amino acids is only slightly inferior. Previous experiments in suitable animal models and in mild hypercholesterolemic individuals have shown that the consumption of lupin proteins may be useful for controlling total and low-density-lipoprotein (LDL) cholesterol levels. The objective of the present study was to characterize in detail the molecular mechanism at the basis of the cholesterol lowering properties of L. albus protein observed in experimental and clinical investigations. Starting from the hypothesis that the activity may depend on specific peptides encrypted in the protein sequences, a total protein extract from lupin seed was hydrolyzed either with pepsin (P peptides) or with trypsin (T peptides). The HepG2 cell line was treated with both kinds of peptides and molecular and functional investigations were performed on the LDLR-SREBP2 and PI3K/Akt pathways, using a combination of techniques