Screening of soy protein-derived hypotriglyceridemic di-peptides in vitro and in vivo

Abstract

BackgroundSoy protein and soy peptides have attracted considerable attention because of their potentially beneficial biological properties, including antihypertensive, anticarcinogenic, and hypolipidemic effects. Although soy protein isolate contains several bioactive peptides that have distinct physiological activities in lipid metabolism, it is not clear which peptide sequences are responsible for the triglyceride (TG)-lowering effects. In the present study, we investigated the effects of soy protein-derived peptides on lipid metabolism, especially TG metabolism, in HepG2 cells and obese Otsuka Long-Evans Tokushima fatty (OLETF) rats.ResultsIn the first experiment, we found that soy crude peptide (SCP)-LD3, which was prepared by hydrolyze of soy protein isolate with endo-type protease, showed hypolipidemic effects in HepG2 cells and OLETF rats. In the second experiment, we found that hydrophilic fraction, separated from SCP-LD3 with hydrophobic synthetic absorbent, revealed lipid-lowering effects in HepG2 cells and OLETF rats. In the third experiment, we found that Fraction-C (Frc-C) peptides, fractionated from hydrophilic peptides by gel permeation chromatography-high performance liquid chromatography, significantly reduced TG synthesis and apolipoprotein B (apoB) secretion in HepG2 cells. In the fourth experiment, we found that the fraction with 0.1% trifluoroacetic acid, isolated from Frc-C peptides by octadecylsilyl column chromatography, showed hypolipidemic effects in HepG2 cells. In the final experiment, we found that 3 di-peptides, Lys-Ala, Val-Lys, and Ser-Tyr, reduced TG synthesis, and Ser-Tyr additionally reduced apoB secretion in HepG2 cells.ConclusionNovel active peptides with TG-lowering effects from soy protein have been isolated.

Dietary Soybean Peptides Containing a Low-Molecular Fraction Can Lower Serum and Liver Triglyceride Levels in Rats

“…The reduction in liver weights with LD feeding is concomitant with reductions in serum and liver triglyceride concentrations; moreover, the suppression of fatty liver was observed (Table 3). A similar finding was observed in Otsuka Long-Evans Tokushima fatty rats, showing the prevention of triglyceride accumulation in the liver with LD feeding (26). These results suggest that LD is one of the soybean peptide fractions responsible for the triglyceride-lowering activity.…”

“…In addition, the hypotriglyceridemic action of LD may be ascribed in part to the suppression of hepatic triglyceride secretion into the circulation and stimulation of fatty acid b-oxidation in the liver, as shown in our previous study (17). LD decreases triglyceride synthesis in HepG2 cells and the activities of enzymes involved in rat liver lipogenesis (26).…”

“…In this study, we used LD obtained by hydrolysis of intact SPI but not b-conglycinin. Dipeptides derived from LD have been found to exert hypotriglyceridemic effects through the suppression of hepatic triglyceride synthesis and apoB secretion in HepG2 cells (26). Therefore, the triglyceride-lowering activity of soybean protein appears to be triggered by LD per se, not by differences in amino acid composition, because the amino acid profiles of SPI, LD, and HLD are comparable ( Table 2).…”

Soy Protein Isolate Suppresses Lipodystrophy-induced Hepatic Lipid Accumulation in Model Mice

“…Multiple beneficial effects of SPI have been attributed to the bioactivities of β-conglycinin, one of major protein components in SPI 29,41 .…”

Identification of Peptides in Sediments Derived from an Acidic Enzymatic Soy Protein Hydrolysate Solution

“…In addition to their nutritional value, those peptides found in ESPH have been demonstrated to exert beneficial functions, including antihypertensive (Matsui et al, 2005), antihypertriglyceridemic (Inoue et al, 2011), and antiinflammatory (Kovacs-Nolan et al, 2012) effects. ESPH has also been investigated as a functional food ingredient to improve mental health (Maebuchi et al, 2013).…”