The protective role of the Bowman-Birk protease inhibitor in soybean lunasin digestion: the effect of released peptides on colon cancer growth

Abstract

Lunasin is a naturally-occurring peptide demonstrating chemopreventive, antioxidant and anti-inflammatory properties. To exhibit these activities, orally ingested lunasin needs to survive proteolytic attack of digestive enzymes to reach target tissues in active form/s. Preliminary studies suggested the protective role of protease inhibitors, such as the Bowman-Birk inhibitor and Kunitz-trypsin inhibitor, against lunasin's digestion by both pepsin and pancreatin. This work describes in depth the behaviour of lunasin under conditions simulating the transit through the gastrointestinal tract in the absence or presence of soybean Bowman-Birk isoinhibitor 1 (IBB1) in both active and inactive states. By liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS), the remaining lunasin at the end of gastric and gastro-duodenal phases was quantified. Protection against the action of pepsin was independent of the amount of IBB1 present in the analyzed samples, whereas an IBB1 dose-dependent protective effect against trypsin and chymotrypsin was observed. Peptides released from lunasin and inactive IBB1 were identified by MS/MS. The remaining lunasin and IBB1 as well as their derived peptides could be responsible for the anti-proliferative activity against colon cancer cells observed for the digests obtained at the end of simulated gastrointestinal digestion.

Kunitz trypsin inhibitor in addition to Bowman-Birk inhibitor influence stability of lunasin against pepsin-pancreatin hydrolysis

“…Lunasin belongs to the 2S soy albumin protein with 43 amino acid residues whose biological activity is attributed to the presence of a cell adhesion motif composed of arginine-glycine-aspartic acid residues and a carboxylic acid tail composed of 8 aspartic acid residues (Galvez & Lumen, 1999;Lule, Garg, Pophely, Hitesh & Tomar, 2015). Lunasin possessed different potential biological properties including anti-cancer (Shidal, Al-Rayyan, Yaddanapudi & Davis, 2016;Jiang, Pan, Cheng, Li, Liu & Li, 2016;Hsieh, Hernández-Ledesma, Jeong, Park, & de Lumen, 2010) anti-inflammatory (Dia, Wang, Oh, de Lumen & de Mejia, 2009;Cam & de Mejia, 2012;Cruz-Huerta et al, 2015;Hernández-Ledesma, Hsieh,& de Lumen, 2009) and immunomodulating properties (Yang et al, 2015;Tung et al, 2014). One potential issue on the use of lunasin as a chemopreventive and chemotherapeutic agents is its susceptibility to digestion as previous studies have shown that up to 97% of the lunasin is digested leading to low nanomolar concentrations found in human plasma after ingesting 50 g of soy protein (Dia, Torres, de Lumen, Erdman & de Mejia, 2009).…”

“…BBI protects protein digestion by inhibiting the activity of trypsin and chymotrypsin (Odani et al, 1973). Previous studies have shown the capability of BBI to protect lunasin from hydrolysis brought up by pepsin and pancreatin (Cruz-Huerta et al, 2015;Hsieh et al, 2010). In addition, BBI has possible health benefits such as being a chemopreventative (Clemente, Marín-manzano, Arques & Domoney, 2013) and anticarcinogenic agent (Kennedy, 1998).…”

Updating the research on the chemopreventive and therapeutic role of the peptide lunasin

“…observed the protection exerted by BBI when lunasin present in soybean‐derived foods was subjected to a sequential digestion with pepsin and pancreatin, suggesting the importance of the lunasin:BBI ratio on this protection . This hypothesis has been confirmed by Cruz‐Huerta and co‐workers that described the protective effect of the major isoinhibitor of the Bowman–Birk family (IBB1) on the in vitro digestion of synthetic lunasin simulating physiological conditions . In absence of IBB1, lunasin is completely hydrolysed by the action of digestive enzymes whereas partial hydrolysis of lunasin is observed when the isoinhibitor is present.…”

“…30 This hypothesis has been confirmed by Cruz-Huerta and co-workers that described the protective effect of the major isoinhibitor of the Bowman-Birk family (IBB1) on the in vitro digestion of synthetic lunasin simulating physiological conditions. 40 In absence of IBB1, lunasin is completely hydrolysed by the action of digestive enzymes whereas partial hydrolysis of lunasin is observed when the isoinhibitor is present. Peptides released from lunasin during simulated digestive process have been recently identified.…”

Recent advances in microbial fermentation for dairy and health

“…The known cancer-preventative peptide lunasin has been found to be proteolytically released during sourdough fermentation by LAB 34 . Further research has subsequently revealed increased protease resistance during in vitro gastrointestinal transit in the presence of naturally occurring protease inhibitors to allow lunasin to reach the large intestine 35 . Another recent study has found that the administration of milk fermented by a probiotic Lactobacillus casei strain modulated the immune response against a breast cancer tumour in a mouse model, with delayed or blocked tumour development in the fermented-milk-fed group as compared with unfermented milk as a control 36 .…”