Soy ß-Conglycinin Peptide Attenuates Obesity and Lipid Abnormalities in Obese Model OLETF Rats.

We previously reported that soy ß-conglycinin (ßCG) improves obesity-induced metabolic abnormalities, but not obesity, in obese model Otsuka Long-Evans Tokushima fatty (OLETF) rats. In the present study, we aimed to investigate the effects of ßCG-derived peptide consumption on obesity and lipid abnormality in OLETF rats. To this end, wild-type Long-Evans Tokushima Otsuka and OLETF rats were provided a normal diet containing 20% casein for four weeks as a control. In addition, we prepared ßCG peptide by enzymatic hydrolysis, and OLETF rats were fed a diet in which half of the casein was replaced by ßCG peptide (ßCG peptide group). Consequently, rats in the ßCG peptide group showed decreased abdominal white adipose tissue weight and lipid content (serum and liver triglycerides, and serum and liver cholesterol) compared to control OLETF rats. Further analysis demonstrated that ßCG peptide consumption decreased lipogenic enzyme activity and increased lipolytic enzyme activity in the liver of OLETF rats. In addition, suppressive effects on both synthesis and absorption of cholesterol were observed in ßCG peptide-fed OLETF rats. These findings suggest that peptidization of ßCG enhanced the anti-obese and hypolipidemic effects of ßCG.

Structure-function properties of hypolipidemic peptides.

This review addresses the structure-function properties of hypolipidemic peptides. The cholesterol-lowering peptide (lactostatin: IIAEK) operates via a new regulatory pathway in the calcium-channel-related mitogen-activated protein kinase (MAPK) signaling pathway of cholesterol degradation. The bile acid binding peptide (soystatin, VAWWMY) inhibits the micellar solubility of cholesterol in vitro and cholesterol absorption in vivo. VVYP is the most effective peptide having hypotriglyceridemic action in globin digests. The suppressive effect of globin digest on postprandial hyperlipidemia has been reported in humans. The ability of peptides (KRES, Apolipoprotein A-I mimetic peptides) to interact with lipids, remove LOOH and activate antioxidant enzymes associated with high-density lipoprotein determines their anti-inflammatory and anti-atherogenic properties. The ß-conglycinin derived peptides KNPQLR, EITPEKNPQLR, and RKQEEDEDEEQQRE inhibit fatty acid synthase in vitro. These promising findings indicate the need for more conclusive molecular, cellular, and animal and human studies to design innovative new peptides that ameliorate cholesterol and lipid metabolism. PRACTICAL APPLICATIONS: Prevention and amelioration of hypercholesterolemia by dietary regulation are important. Dietary protein and peptides are very useful as regulators of serum cholesterol concentration. Diets low in saturated fat and cholesterol that include soy protein may reduce the risk of heart disease. In Japan, the concept of "food for specified health use" has been introduced for the prevention and treatment of life-style related disease. Thus, peptides derived from food proteins and sources other than food proteins such as peptide-rich functional foods and nutraceutical products, have considerable potential to prevent lifestyle-related diseases, especially hyperlipidemia, as discussed in this review. Furthermore, various strategies have been used for the efficient screening, development, and application of new hypolipidemic peptides. These include the use of phage display (for anti-obesity peptide), peptide mimetics (for anti-atherogenic peptide), and molecular targets such as CYP7A1 (for hypocholesterolemic peptide) and prohibitin (for anti-obesity peptide).

Effective Food Ingredients for Fatty Liver: Soy Protein ß-Conglycinin and Fish Oil.

Obesity is prevalent in modern society because of a lifestyle consisting of high dietary fat and sucrose consumption combined with little exercise. Among the consequences of obesity are the emerging epidemics of hepatic steatosis and nonalcoholic fatty liver disease (NAFLD). Sterol regulatory element-binding protein-1c (SREBP-1c) is a transcription factor that stimulates gene expression related to de novo lipogenesis in the liver. In response to a high-fat diet, the expression of peroxisome proliferator-activated receptor (PPAR) γ2, another nuclear receptor, is increased, which leads to the development of NAFLD. ß-Conglycinin, a soy protein, prevents NAFLD induced by diets high in sucrose/fructose or fat by decreasing the expression and function of these nuclear receptors. ß-Conglycinin also improves NAFLD via the same mechanism as for prevention. Fish oil contains n-3 polyunsaturated fatty acids such as eicosapentaenoic acid and docosahexaenoic acid. Fish oil is more effective at preventing NAFLD induced by sucrose/fructose because SREBP-1c activity is inhibited. However, the effect of fish oil on NAFLD induced by fat is controversial because fish oil further increases PPARγ2 expression, depending upon the experimental conditions. Alcohol intake also causes an alcoholic fatty liver, which is induced by increased SREBP-1c and PPARγ2 expression and decreased PPARα expression. ß-Conglycinin and fish oil are effective at preventing alcoholic fatty liver because ß-conglycinin decreases the function of SREBP-1c and PPARγ2, and fish oil decreases the function of SREBP-1c and increases that of PPARα.

The α' subunit of ß-conglycinin and various glycinin subunits of soy are not required to modulate hepatic lipid metabolism in rats.

PURPOSE: This study examined the effect of soy proteins with depletion of different subunits of the two major storage proteins, ß-conglycinin and glycinin, on hepatic lipids and proteins involved in lipid metabolism in rats, since the bioactive component of soy responsible for lipid-lowering is unclear. METHODS: Weanling Sprague Dawley rats were fed diets containing either 20% casein protein in the absence (casein) or presence (casein + ISF) of isoflavones or 20% alcohol-washed soy protein isolate (SPI) or 20% soy protein concentrates derived from a conventional (Haro) or 2 soybean lines lacking the α' subunit of ß-conglycinin and the A1-3 (1TF) or A1-5 (1a) subunits of glycinin. After 8 weeks, the rats were necropsied and liver proteins and lipids were extracted and analysed. RESULTS: The results showed that soy protein diets reduced lipid droplet accumulation and content in the liver compared to casein diets. The soy protein diets also decreased the level of hepatic mature SREBP-1 and FAS in males, with significant decreases in diets 1TF and 1a compared to the casein diets. The effect of the soy protein diets on female hepatic mature SREBP-1, FAS, and HMGCR was confounded since casein + ISF decreased these levels compared to casein alone perhaps muting the decrease by soy protein. A reduction in both phosphorylated and total STAT3 in female livers by ISF may account for the gender difference in mechanism in the regulation and protein expression of the lipid modulators. CONCLUSIONS: Overall, soy protein deficient in the α' subunit of ß-conglycinin and A1-5 subunits of glycinin maintain similar hypolipidemic function compared to the conventional soy protein. The exact bioactive component(s) warrant identification.

Proteomics for exploiting diversity of lupin seed storage proteins and their use as nutraceuticals for health and welfare.

UNLABELLED: Lupins have a variety of both traditional and modern uses. In the last decade, reports assessing the benefits of lupin seed proteins have proliferated and, nowadays, the pharmaceutical industry is interested in lupin proteins for human health. Modern genomics and proteomics have hugely contributed to describing the diversity of lupin storage genes and, above all, proteins. Most of these studies have been centered on few edible lupin species. However, Lupinus genus comprises hundreds of species spread throughout the Old and New Worlds, and these resources have been scarcely explored and exploited. We present here a detailed review of the literature on the potential of lupin seed proteins as nutraceuticals, and the use of -omic tools to analyze seed storage polypeptides in main edible lupins and their diversity at the Lupinus inter- and intra-species level. In this sense, proteomics, more than any other, has been a key approach. Proteomics has shown that lupin seed protein diversity, where post-translational modifications yield a large number of peptide variants with a potential concern in bioactivity, goes far beyond gene diversity. The future extended use of second and third generation proteomics should definitely help to go deeper into coverage and characterization of lupin seed proteome. BIOLOGICAL SIGNIFICANCE: Some important topics concerning storage proteins from lupin seeds are presented and analyzed in an integrated way in this review. Proteomic approaches have been essential in characterizing lupin seed protein diversity, which goes far beyond gene diversity since the protein level adds to the latter differential proteolytic cleavage of conglutin pro-proteins and a diverse array of glycosylation forms and sites. Proteomics has also proved helpful for screening and studying Lupinus germplasm with the future aim of exploiting and improving food production, quality, and nutritional values.

Soy ß-conglycinin improves obesity-induced metabolic abnormalities in a rat model of nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) has a variety of causes including calorie over-intake, an unbalanced diet, and/or genetic dysfunction of lipid metabolism. We hypothesized that NAFLD symptoms could be mitigated by specific nutritional factors. Here, we show that the potential for soy ß-conglycinin (ßCG) to improve obesity-induced metabolic abnormalities in the Otsuka Long Evans Tokushima fatty (OLETF) rat model of NAFLD. Long Evans Tokushima Otsuka (i.e., wild-type) and OLETF rats were provided a normal diet containing 20% casein for 4 weeks as a control. In a third (ßCG) group, OLETF rats were fed a diet in which half of the casein was replaced by ßCG. There was no difference in food intake between groups. Rats in the ßCG group had decreased liver weight and lipid content (triglycerides, cholesterol, and phospholipids) compared to controls. In addition, ßCG consumption decreased fatty acid synthase gene expression and enzymatic activity. These findings indicate that dietary intake of ßCG can improve obesity-induced metabolic dysfunction, possibly via suppression of de novo fatty acid synthesis.

Prevention of osteoporosis by oral administration of phytate-removed and deamidated soybean ß-conglycinin.

Phytate-removed and deamidated soybean ß-conglycinin (PrDS) prepared by ion-exchange resins was supplemented to be 4% in the diet administered to ovariectomized rats to investigate its preventive effect on osteoporosis. The apparent calcium absorption rate decreased following ovariectomy and was not replenished by oral administration of phytate-removed soybean ß-conglycinin (PrS) or casein. On the other hand, administration of PrDS restored the calcium absorption rate to the same level as the sham group. Markers of bone resorption, such as serum parathyroid hormone (PTH) and urinary deoxypyridinoline (DPD), increased, and the bone mineral density and breaking stress decreased following ovariectomy. However, PrDS supplementation suppressed the changes caused by the decrease in calcium absorption from the small intestine. Therefore, PrDS supplementation shows promise for the prevention of postmenopausal osteoporosis.

Soy ß-conglycinin improves glucose uptake in skeletal muscle and ameliorates hepatic insulin resistance in Goto-Kakizaki rats.

Although the underlying mechanism is unclear, ß-conglycinin (ßCG), the major component of soy proteins, regulates blood glucose levels. Here, we hypothesized that consumption of ßCG would normalize blood glucose levels by ameliorating insulin resistance and stimulating glucose uptake in skeletal muscles. To test our hypothesis, we investigated the antidiabetic action of ßCG in spontaneously diabetic Goto-Kakizaki (GK) rats. Our results revealed that plasma adiponectin levels and adiponectin receptor 1 messenger RNA expression in skeletal muscle were higher in ßCG-fed rats than in casein-fed rats. Phosphorylation of adenosine monophosphate-activated protein kinase (AMP kinase) but not phosphatidylinositol-3 kinase was activated in ßCG-fed GK rats. Subsequently, ßCG increased translocation of glucose transporter 4 to the plasma membrane. Unlike the results in skeletal muscle, the increase in adiponectin receptor 1 did not lead to AMP kinase activation in the liver of ßCG-fed rats. The down-regulation of sterol regulatory element-binding factor 1, which is induced by low insulin levels, promoted the increase in hepatic insulin receptor substrate 2 expression. Based on these findings, we concluded that consumption of soy ßCG improves glucose uptake in skeletal muscle via AMP kinase activation and ameliorates hepatic insulin resistance and that these actions may help normalize blood glucose levels in GK rats.

Protective and reparative effects of peptides from soybean ß-conglycinin on mice intestinal mucosa injury.

Peptides derived from alcalase digestion of soybean ß-conglycinin, containing 8.52% carbohydrate, exhibits an inhibition effect on pathogen adhesion or translocation to intestinal cells in vitro. In this study, the protective and reparative effects of ß-conglycinin peptides on intestinal mucosa injury in vivo were studied using mice with dextran sulfate sodium (DSS)-induced intestinal mucosa injury. The results showed that ß-conglycinin peptides contained approximately 21.77% glutamic acid (Glu), and significantly reduced the histological injury in mice both in the protective and reparative experiments. The myeloperoxidase activity of mice treated with ß-conglycinin peptides decreased compared with those treated DSS in the positive control group. Immunohistochemical analysis also showed that ß-conglycinin peptides inhibited the expression of inflammatory factor NF-κB/p65. These results suggested that peptides derived from soybean ß-conglycinin exhibited protective and reparative effects on mice intestinal mucosa injury.

Beneficial effects of ß-conglycinin on renal function and nephrin expression in early streptozotocin-induced diabetic nephropathy rats.

The objective of the present study was to investigate the effects of ß-conglycinin and soya isoflavones on diabetic nephropathy (DN). DN was induced by an intravenous injection of streptozotocin (25 mg/kg) in spontaneously hypertensive rats. DN rats were divided into a non-diabetic group (C, control group) and three DN groups (D, DN with control diet; B, DN+control diet with one-eighth of casein replaced by ß-conglycinin as the protein source; and I, DN+control diet with 0·01 % soya isoflavones). After a 4-week experimental period, we found that fasting blood sugar and plasma and kidney advanced glycation end product levels and 24 h urinary protein excretion of the B group were significantly lower than those of the D group and insulin sensitivity and nephrin expression of the B group were significantly higher than those of the D group. In addition, systolic blood pressure, angiotensin-converting enzyme activity, angiotensin II level and plasma TAG level of the B group were significantly lower than those of the D group, whereas only the levels of plasma TAG and thiobarbituric acid-reactive substances of the I group were lower than those of the D group. In conclusion, ß-conglycinin may be beneficial for retarding DN progression and this effect cannot be completely explained by its isoflavone content.

Serum lipid-improving effect of soyabean ß-conglycinin in hyperlipidaemic menopausal women.

To evaluate the effect of treatment with ß-conglycinin, a major soyabean protein, on blood lipids in menopausal women, we recruited 100 hyperlipidaemic women aged 40-60 years old. Participants were randomly allocated to three groups: placebo group (n 34, four casein tablets/d); low dose group (n 33, four tablets containing 2·3 g ß-conglycinin/d); high-dose group (n 33, eight tablets containing 4·6 g ß-conglycinin/d). The mean serum TAG concentration was significantly reduced after 6 and 12 weeks of ß-conglycinin intervention by 0·44 (sd 0·20) and 0·78 (sd 1·03) mmol/l in the low-dose group, and by 0·46 (sd 0·17) and 1·25 (sd 1·06) mmol/l in the high-dose group, respectively. One-way ANOVA revealed that serum TAG concentrations in the low-dose and high-dose groups were significantly lowered compared with the placebo group at weeks 6 and 12 (P< 0·05). The low dose and high dose consumptions of ß-conglycinin significantly decreased the LDL-cholesterol concentration by 0·46 (sd 0·72) and 0·52 (sd 0·97) mmol/l at week 12, respectively (P< 0·05). Compared with the changes from baseline in the placebo group, apoB and NEFA were significantly lowered in both the low-dose and high-dose ß-conglycinin groups (P< 0·05). In conclusion, the results suggest that ß-conglycinin intake significantly decreases serum TAG and LDL-cholesterol levels.

[Serum triacylglycerol-lowering effect of soybean beta-conglycinin in hyperlipidemic women].

OBJECTIVE: Improving effects on serum triacylglyceride in women with hypertriacylglycerolemia by soybean beta-conglycinin. METHODS: A placebo-controlled, randomized, double-blind study was conducted in 100 women aged 40-60 with TC > 6.22 mmol/L (or TG > 1.70 mmol/L). The subjects were administered beta-conglycinin 4.6g (high dose) in 8 test tablets and 2.3g(low dose) in 4 test tablets daily for the two test groups and 4 placebo tablets containing no beta-conglycinin for the control group for 12 weeks. RESULTS: Compared to the control group, serum triacylglycerol in the high dose group was significantly reduced at the 6th week (P < 0.001) and the 12th week (P = 0.001) of the trial. Serum triacylglycerol in the low dose group was reduced at the 6th week (P < 0.001) of the trial. CONCLUSION: Soybean beta-conglycinin seemed to have a positive effect of reducing serum triglycerides and improving serum lipids in people with hyperlipidemia.

ß-conglycinin combined with fenofibrate or rosuvastatin have exerted distinct hypocholesterolemic effects in rats.

BACKGROUND: There is increasing interest in non-pharmacological control of cholesterol and triglyceride levels in the plasma and diet-drug association represent an important area of studies. The objective of this study was to observe the hypocholesterolemic effect of soybean ß-conglycinin (7S protein) alone and combined with fenofibrate and rosuvastatin, two hypolipidemic drugs. METHODS: The protein and drugs were administered orally once a day to rats and the effects were evaluated after 28 days. Wistar rats were divided into six groups (n = 9): hypercholesterolemic diet (HC), HC+7S protein (300 mg.kg-1 day-1) (HC-7S), HC+fenofibrate (30 mg.kg-1 day-1)(HC-FF), HC+rosuvastatin (10 mg.kg-1 day-1)(HC-RO), HC+7S+fenofibrate (HC-7S-FF) and HC+7S+rosuvastatin (HC-7S-RO). RESULTS: Animals in HC-7S, HC-FF and HC-RO exhibited reductions of 22.9, 35.8 and 18.8% in total plasma cholesterol, respectively. In HC-7S-FF, animals did not show significant alteration of the level in HC+FF while the group HC-7S-RO showed a negative effect in comparison with groups taking only protein (HC-7S) or drug (HC-RO). The administration of the protein, fenofibrate and rosuvastatin alone caused increases in the plasma HDL-C of the animals, while the protein-drug combinations led to an increase compared to HC-FF and HC-RO. The plasma concentration of triacylgycerides was significantly reduced in the groups without association, while HC-7S-FF showed no alteration and HC-7S-RO a little reduction. CONCLUSION: The results of our study indicate that conglycinin has effects comparable to fenofibrate and rosuvastatin on the control of plasma cholesterol, HDL-C and triacylglycerides, when given to hypercholesterolemic rats, and suggests that the association of this protein with rosuvastatin alters the action of drug in the homeostasis of cholesterol.