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

Inoue N, Nagao K, Sakata K, Yamano N, Gunawardena PE, Han SY, Matsui T, Nakamori T, Furuta H, Takamatsu K, Yanagita T - Lipids Health Dis (2011)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Applied Biochemistry and Food Science, Saga University, Saga 840-8502, Japan.

ABSTRACT

Background: Soy 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.

Results: In 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.

Conclusion: Novel active peptides with TG-lowering effects from soy protein have been isolated.

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Related in: MedlinePlus

Effects of soy peptides on triglyceride (TG) synthesis in HepG2 cells (1 or 10 mg/mL) and hepatic TG level in Otsuka Long-Evans Tokushima fatty (OLETF) rats. Values are expressed as mean ± standard error of 5 samples in vitro and 6 rats in vivo. Different letters indicate a significant difference at P < 0.05.
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Figure 4: Effects of soy peptides on triglyceride (TG) synthesis in HepG2 cells (1 or 10 mg/mL) and hepatic TG level in Otsuka Long-Evans Tokushima fatty (OLETF) rats. Values are expressed as mean ± standard error of 5 samples in vitro and 6 rats in vivo. Different letters indicate a significant difference at P < 0.05.

Mentions: Several reports have suggested that the amino acid composition of dietary proteins and peptides influences their bioactivities [11]. It has been reported that high amounts of histidine and hydrophobic amino acids contribute to antioxidant potency and that hydrophobic peptides can bind bile acids, thereby enhancing fecal steroid excretion [20,48-50]. In the second part of the current study, we evaluated the effects of hydrophobic and hydrophilic fractions, separated from SCP-LD3 with hydrophobic synthetic absorbent, on TG synthesis in HepG2 cells. As shown in Table 1, the hydrophobic fraction was found to contain a higher amount of phenylalanine, whereas the hydrophilic fraction contained a higher amount of glutamine compared to SCP-LD3. In HepG2 cells, incorporation of [1-14C] acetate into the cellular TG fraction was significantly and dose-dependently lowered by hydrophilic fraction treatment (Figure 4A). In the next in vivo experiment, we evaluated the effects of the hydrophilic fraction on lipid metabolism in OLETF rats. Though there was no significant alteration in growth parameters (Table 2), feeding of the hydrophilic fraction alleviated hepatomegaly and hepatic TG accumulation in OLETF rats (Table 2, Figure 4B). Moreover, despite the fact that the degree of supplementation with the hydrophilic fraction in the diet (substituted for 10% casein) was half that of SCP-LD3 (substituted for 20% casein), the TG-lowering effects of these 2 diets were almost the same. In agreement with the in vitro study, the TG-lowering effects were attributable to the suppression of fatty acid synthesis (represented by lowered activities of FAS, G6PDH, and malic enzyme) and TG synthesis (represented by lowered PAP activity) in the liver of OLETF rats.


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

Inoue N, Nagao K, Sakata K, Yamano N, Gunawardena PE, Han SY, Matsui T, Nakamori T, Furuta H, Takamatsu K, Yanagita T - Lipids Health Dis (2011)

Effects of soy peptides on triglyceride (TG) synthesis in HepG2 cells (1 or 10 mg/mL) and hepatic TG level in Otsuka Long-Evans Tokushima fatty (OLETF) rats. Values are expressed as mean ± standard error of 5 samples in vitro and 6 rats in vivo. Different letters indicate a significant difference at P < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3116501&req=5

Figure 4: Effects of soy peptides on triglyceride (TG) synthesis in HepG2 cells (1 or 10 mg/mL) and hepatic TG level in Otsuka Long-Evans Tokushima fatty (OLETF) rats. Values are expressed as mean ± standard error of 5 samples in vitro and 6 rats in vivo. Different letters indicate a significant difference at P < 0.05.
Mentions: Several reports have suggested that the amino acid composition of dietary proteins and peptides influences their bioactivities [11]. It has been reported that high amounts of histidine and hydrophobic amino acids contribute to antioxidant potency and that hydrophobic peptides can bind bile acids, thereby enhancing fecal steroid excretion [20,48-50]. In the second part of the current study, we evaluated the effects of hydrophobic and hydrophilic fractions, separated from SCP-LD3 with hydrophobic synthetic absorbent, on TG synthesis in HepG2 cells. As shown in Table 1, the hydrophobic fraction was found to contain a higher amount of phenylalanine, whereas the hydrophilic fraction contained a higher amount of glutamine compared to SCP-LD3. In HepG2 cells, incorporation of [1-14C] acetate into the cellular TG fraction was significantly and dose-dependently lowered by hydrophilic fraction treatment (Figure 4A). In the next in vivo experiment, we evaluated the effects of the hydrophilic fraction on lipid metabolism in OLETF rats. Though there was no significant alteration in growth parameters (Table 2), feeding of the hydrophilic fraction alleviated hepatomegaly and hepatic TG accumulation in OLETF rats (Table 2, Figure 4B). Moreover, despite the fact that the degree of supplementation with the hydrophilic fraction in the diet (substituted for 10% casein) was half that of SCP-LD3 (substituted for 20% casein), the TG-lowering effects of these 2 diets were almost the same. In agreement with the in vitro study, the TG-lowering effects were attributable to the suppression of fatty acid synthesis (represented by lowered activities of FAS, G6PDH, and malic enzyme) and TG synthesis (represented by lowered PAP activity) in the liver of OLETF rats.

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Applied Biochemistry and Food Science, Saga University, Saga 840-8502, Japan.

ABSTRACT

Background: Soy 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.

Results: In 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.

Conclusion: Novel active peptides with TG-lowering effects from soy protein have been isolated.

Show MeSH
Related in: MedlinePlus