Soy protein peptic hydrolysate with bound phospholipids decreases micellar solubility and cholesterol absorption in rats and caco-2 cells

Rose polyphenols exert antiobesity effect in high-fat-induced obese mice by regulating lipogenic gene expression

Obesity presents a major risk factor in the development of cardiovascular diseases. Recent reports indicate that many kinds of polyphenols have the potential to prevent metabolic diseases. We hypothesized that rose polyphenols (ROSE) have the effect of improvement in lipid metabolism. In this study, we investigated whether rose polyphenols affected lipid metabolism and exerted antiobesity. To clarify the mechanism, C57BL/6J mice were fed a high-fat diet containing 0.25% ROSE for 35 days. Compared with the control group, body weight gain and adipose tissue weight in the 0.25% ROSE group were significantly decreased. Serum cholesterol and hepatic triglyceride concentrations significantly decreased, whereas fecal triglyceride was significantly increased in the 0.25% ROSE group. Liver stearoyl-CoA desaturase 1 (Scd1), 3-hydroxy-3-methylglutaryl-CoA reductase (Hmgcr), and acyl-CoA:cholesterol acyltransferase 1 (Acat1) mRNA as well as protein stearoyl-CoA desaturase 1 concentrations were significantly lower in the 0.25% ROSE group than that in the control group. The mRNA and the protein concentrations of adipose triglyceride lipase, hormone-sensitive lipase, and peroxisomal acylcoenzyme A oxidase 1 in white adipose tissue were significantly higher in the 0.25% ROSE group than that in the control group. The components in rose polyphenols were quantified by liquid chromatography-tandem mass spectrometry, and we consider that ellagic acid plays an important role in an antiobesity effect because the ellagic acid content is the highest among polyphenols in rose polyphenols. In summary, rose polyphenols exhibit antiobesity effects by influencing lipid metabolism-related genes and proteins to promote lipolysis and suppress lipid synthesis.

Pentapeptide IIAEK ameliorates cholesterol metabolism via the suppression of intestinal cholesterol absorption in mice

Dietary protein-derived peptides are effective in improving dyslipidemia and hypercholesterolemia. We previously identified a novel cholesterol-lowering pentapeptide IIAEK from milk beta-lactoglobulin. However, it remains unclear whether IIAEK affects the micellar solubility of cholesterol and the bile acid-binding ability to lower cholesterol. Moreover, there is no direct evidence that IIAEK inhibits intestinal cholesterol absorption and affects hepatic cholesterol and fecal steroid excretion in vivo. Herein, we showed that IIAEK did not affect the micellar solubility of cholesterol and the bile acid-binding ability. However, we found that IIAEK decreased serum and liver cholesterol levels and increased fecal steroid excretion in mice. Interestingly, IIAEK markedly suppressed the intestinal absorption of [3H]-cholesterol in mice. In conclusion, we found that IIAEK ameliorated cholesterol metabolism by suppressing intestinal cholesterol absorption without affecting in vitro micellar solubility of cholesterol and the bile acid-binding ability in mice.

Effects of bioactive peptides derived from feather keratin on plasma cholesterol level, lipid oxidation of meat, and performance of broiler chicks

In this research, the effect of mixed feather bioactive peptides (MFBPs) added in water, on intestinal health, meat quality, and plasma cholesterol level of broiler chickens, was evaluated. A total of 80 day-old male broiler chicks (Ross 308) were randomly divided into two treatments with four replication pens. The dietary treatments were the drinking water with no additives (control) and drinking water containing 50 mg/L of MFBPs. Live weight and feed intake were measured at the end of starter (1-10 days), grower (11-24 days), and finisher (25-36 days) periods by calculating the average daily gain and feed conversion ratio. The results indicate that body weight gain was greater (P < 0.05) in birds that received MFBPs in the final period. At 24 days of age, the villus height and muscle layer thickness in different parts of the intestine were higher in birds that received bioactive peptides but epithelial thickness was lower than that in control birds (P < 0.05). In addition, the administration of MFBPs decreased (P < 0.01) serum total cholesterol, triglyceride, and low-density lipoprotein in broilers. Supplementation with MFBPs significantly reduced (P < 0.01) the malondialdehyde (MDA) amount in the thigh muscle. In conclusion, using the MFBPs in the diet of broilers could improve meat quality, cholesterol concentration in serum, and gut health.

In Silico Screening of a Bile Acid Micelle Disruption Peptide for Oral Consumptions from Edible Peptide Database

Recently, many bioactive peptides have been identified using bioinformatics tools. Previously, our group developed a method to screen dual-functional peptides that have direct intestinal delivery with porous silica gel and bile acid micelle disruption. However, newly designed peptides were not found in any storage protein. Therefore, in this study, in silico screening was performed using a 350,000 edible peptide library consisting of 4- to 7-mer independent peptides. As an initial screening, all edible peptides were applied to the random forest model to select predicted positive peptides. For a second screening, the peptides were assessed for the possibility of intestinal delivery using a 3D color map. From this approach, three novel dual-functional peptides, VYVFDE, WEFIDF, and VEEFYC were identified, and all of them were derived from storage proteins (legumin, myosin, and 11S globulin). In particular, VEEFYCS, in which a serine residue (S) is added to VEEFYC, was assumed to be released by thermolysin from the 11S-globulin derived from Ginkgo biloba by LC-MS/MS analysis. VEEFYCS was found to have suitable direct intestinal delivery and bile acid micelle disruption activity.

Plant-derived peptides improving lipid and glucose metabolism

Plant protein-derived peptides, focusing especially on soybean protein-derived peptides have considerable effects on metabolic regulation and modulation such as cholesterol lowering, triglyceride lowering, anti-obesity, inhibition of fatty acid synthase, and antidiabetic effects. The molecules targeted to study the metabolic regulatory functions of the peptides included the following: intestinal cholesterol micelle, cholesterol metabolism-related genes for cholesterol lowering, triglyceride metabolism-related genes for triglyceride lowering and anti-obesity, dipeptidyl peptidase-IV (DPP-IV), α-amylase, α-glucosidase, or glucose metabolism-related genes for lowering blood glucose levels. This review article outlines the physiological functions of plant protein-derived peptides for the improvement of lipid and glucose metabolism in vitro or in vivo.

Anti-Obesity and Hypocholesterolemic Actions of Protamine-Derived Peptide RPR (Arg-Pro-Arg) and Protamine in High-Fat Diet-Induced C57BL/6J Mice

Dietary protamine can ameliorate hyperlipidemia; however, the protamine-derived active peptide and its hypolipidemic mechanism of action are unclear. Here, we report the discovery of a novel anti-obesity and hypocholesterolemic peptide, RPR (Arg-Pro-Arg), derived from protamine in mice fed a high-fat diet for 50 days. Serum cholesterol levels were significantly lower in the protamine and RPR groups than in the control group. White adipose tissue weight was significantly decreased in the protamine and RPR groups. The fecal excretion of cholesterol and bile acid was significantly higher in the protamine and RPR groups than in the control group. We also observed a significant decrease in the expression of hepatic SCD1, SREBP1, and adipocyte FAS mRNA, and significantly increased expression of hepatic PPARα and adipocyte PPARγ1 mRNA in the protamine group. These findings demonstrate that the anti-obesity effects of protamine are linked to the upregulation of adipocyte PPARγ1 and hepatic PPARα and the downregulation of hepatic SCD1 via SREBP1 and adipocyte FAS. RPR derived from protamine has a crucial role in the anti-obesity action of protamine by evaluating the effective dose of adipose tissue weight loss.

Indigestible cowpea proteins reduced plasma cholesterol after long-term oral administration to Sprague-Dawley rats

Abstract

Cowpea protein isolate (CPI) was subjected to various dry and wet heat pretreatments followed by sequential digestion with pepsin and pancreatin; the undigested residues were isolated as the indigestible cowpea proteins (ICPs). All the ICPs exhibited in vitro bile acid-binding capacity but ICP from the slow cooling-induced gelation had the highest yield (68%) and was used for rat feeding experiments to determine effect on plasma total cholesterol (TC). Groups consisting of 3 male and 3 female Sprague-Dawley rats each were fed hypercholesterolemic diets that contained casein only or casein that was partially substituted with ICP of CPI for 6 weeks. Results showed diet that contained 5% (w/w) ICP was more effective in preventing TC increase (1.8 mmol/L) when compared to increases of 9.34 and 4.15 mmol/L for CPI and casein only diets, respectively.

Graphical abstract

Identification of peptides in blood following oral administration of β-conglycinin to Wistar rats

In this study, β-conglycinin (100 mg/kg) was orally administered to Wistar rats in order to identify peptides that may be derived from the protein in the blood. Plasma samples taken from the tail vein up to 8 h after administration were analyzed by matrix-assisted laser desorption/ionization (MALDI) and liquid chromatography-time-of-flight (LC-TOF) mass spectrometry (MS). In total, 126 signals were detected by MALDI-MS. Among the signals, nine oligopeptides (SEL, KGPL, SILGA, DSEL, GDANI, SYFV, CLQSC, GEQPRPF, and LVINEGDA) were successfully identified as β-conglycinin-derived peptides by LC-TOF/MS at a plasma concentration of 0.75-756 pmol/mL. The results demonstrated that β-conglycinin could be the dietary source protein for the oligopeptides produced prior to entering the circulating bloodstream of rats.

Identification of a novel cholesterol-lowering dipeptide, phenylalanine-proline (FP), and its down-regulation of intestinal ABCA1 in hypercholesterolemic rats and Caco-2 cells

There has been no report about in vivo active cholesterol-lowering dipeptide in any protein origin, despite their potential health benefits. Cattle heart protein hydrolysate ultra-filtrate (HPHU, molecular weight < ca. 1,000 Da peptide mixture) exhibits cholesterol-lowering activity in hypercholesterolemic rats, but the active peptide in HPHU that lowers serum cholesterol levels and its molecular mechanism are unknown. In this study, we separated and purified HPHU to identify a novel cholesterol-lowering dipeptide (phenylalanine-proline, FP) and characterized the mechanism underlying its effects in vivo and in vitro. We identified FP as an active peptide from HPHU by MALDI-TOF mass spectrometry. FP significantly decreased serum total and non-HDL cholesterol and hepatic cholesterol levels in rats. FP significantly increased serum HDL cholesterol, accompanied by a significant decrease in the atherogenic index. FP also significantly increased fecal cholesterol and acidic steroid excretion. Moreover, FP significantly decreased ATP-binding cassette transporter A1 (ABCA1) expression in the rat jejunum and reduced cholesterol absorption in Caco-2 cells. We found a novel cholesterol-lowering dipeptide FP that could improve cholesterol metabolism via the down-regulation of intestinal ABCA1. The cholesterol-lowering action induced by FP was disappeared in PepT1KO mice. FP-induced cholesterol-lowering action is mediated via PepT1 in mice.

Transepithelial Transport Characteristics of the Cholesterol- Lowing Soybean Peptide, WGAPSL, in Caco-2 Cell Monolayers

Recent studies have shown that soybean protein and its peptides have cholesterol-lowering activities. However, it is not clear whether these peptides could overcome physiological barriers, such as phase II metabolism in gastrointestinal tract and poor permeability, to reach the blood stream in its intact form. Therefore, the transepithelial transport characteristics of soybean peptide Trp-Gly-Ala-Pro-Ser-Leu (WGAPSL) with cholesterol- lowering activity were investigated in Caco-2 cells. In this study; the transepithelial absorption of WGAPSL was studied using human intestinal Caco-2 cell monolayers. The results showed that WGAPSL had good stability (83.9% ±1.98%) after simulated gastric and intestinal digestion. During the apical (AP) side to basolateral (BL) side transport, WGAPSL was absorbed intact through Caco-2 cell monolayers with apparent permeability coefficient (Papp) values of 4.4 × 10-8 to 1.2 × 10-8 cm/s. Cytochalasin D loosened the tight junctions of Caco-2 cell monolayers and significantly (p < 0.05) improved the transport process. Sodium azide, wortmannin, and Gly-Pro had minimal effects on transport, demonstrating that the major transport route of WGAPVL was paracellular via tight junctions. Finally, LC-MS analysis showed that Gly-Ala-Pro (GAP) was the important part for the intact absorption of WGAPVL and Trp (W) was the most unstable amino acid residue.

Antihyperlipidemic and antioxidant effects of feather protein hydrolysate in high-fat diet-fed mice

The hyperlipidemia is a serious health problem that increases the risk of many complications including cardiovascular disease. This study aims to evaluate the possible antihyperlipidemic effects of the feather protein hydrolysate (FPH) in a mice fed with a high-fat diet (HFD)-fed mice during 5 weeks. The FPH administration improved dose-dependent lipid profile, as well as the liver and renal dysfunction indices in hyperlipidemic mice. The FPH also restored the antioxidant status in liver, kidney, and heart by lowering the lipid peroxidation and enhancing the antioxidant enzymes (catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase [SOD]). Moreover, the histological studies proved that FPH administration prevents hepatic steatosis, glomerular hyperfiltration risk, and cardiac muscle hypertrophy. Accordingly, the FPH is a promising novel medicinal ingredient for possible use in the hyperlipidemic treatment and related complications.

Inhibitory effects of Tiliacora triandra (Colebr.) Diels on cholesterol absorption

Background Natural supplements and herbal medicines have been attracted to use for managing elevated cholesterol levels. Tiliacora triandra (Colebr.) Diels (TT) or Yanang (in Thai) is commonly used as an ingredient in various types of Thai foods. In this study, we investigated the effect of methanolic TT leaf extract on cholesterol absorption by measuring the uptake and the efflux of cholesterol and cholesterol micellar solubility. In addition, we tested the effect of TT leaf extract on pancreatic lipase activity. Methods The uptake and efflux of cholesterol was determined by quantification of radioactivity in differentiated Caco-2 cells after treatment with radioactive cholesterol. Cholesterol mixed micelles were prepared for cholesterol uptake, efflux and solubility studies. The pancreatic lipase activity was determined using 4-methylumbelliferyl oleate as a substrate. Results Our finding showed that TT extract decreased the uptake of cholesterol by approximately 48% but did not affect the efflux of cholesterol. TT inhibited pancreatic lipase activity with the IC50 at 273.5 μg/mL and also decreased cholesterol micellar solubility. Conclusions These findings suggest that TT leaf extract seems to be a potential candidate as cholesterol-lowering agents.

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 β-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).

Egg-Yolk Sphingomyelin and Phosphatidylcholine Attenuate Cholesterol Absorption in Caco-2 Cells

Phospholipids have been shown to modulate intestinal cholesterol absorption in cells and animals, a process that is regulated by several transporter proteins. Of these proteins, Niemann-Pick C1-Like 1 (NPC1L1) is a major contributor to this process. The mechanism by which phospholipids modulate cholesterol absorption remains unknown. Here, we evaluate the effects of egg-yolk phospholipids on cholesterol absorption and transport in human colon carcinoma cell line (Caco-2 cells) and on the expression of NPC1L1 and others proteins associated with cholesterol absorption (ABCG5, ABCG8, ABCA1, ACAT2, MTP, CAV-1, ANX-2). The roles of SREBP-1 and SREBP-2 in this process were also investigated. The results show that egg-yolk sphingomyelin (CerPCho) and phosphatidylcholine (PtdCho) inhibit cholesterol transport in the Caco-2 monolayer in a dose-dependent manner. These might be due to the decrease of the cholesterol solubility in micelles as well as to the increases in the micellar sizes and the bile acid-binding capacity. Furthermore, the treatments with egg-yolk CerPCho or PtdCho at 1.2 mmol/L reduced the expression levels of NPC1L1 protein to 21 or 22%, respectively, and its mRNA to 9 or 31% of that in the control group (p < 0.05). Moreover, there was a general inhibitory effect of egg-yolk PtdCho and CerPCho on the mRNA levels of SREBP-1, and SREBP-2. These results suggest that the inhibitory effect of egg-yolk CerPCho and PtdCho on cholesterol transport might be due to their interference with the physicochemical properties of micelles and their regulations on the expression of the NPC1L1 gene.

Structural Basis of Bioactivity of Food Peptides in Promoting Metabolic Health

Bioactive peptides have many structural features that enable them to become functional in controlling several biological processes in the body, especially those related to metabolic health. This chapter provides an overview of the multiple targets of food-derived peptides against metabolic health problems (e.g., hypertension, dyslipidemia, hyperglycemia, oxidative stress) and discusses the importance of structural chemistry in determining the bioactivities of peptides and protein hydrolysates.

Safety and nutritional value of a dried killed bacterial biomass from Escherichia coli (FERM BP-10942) (PT73 (TM)) as a feed material for pigs, ruminants and salmonids

PT73 (TM) is a dried, heat-inactivated bacterial biomass used as a feed material produced from an Escherichia coli K-12 strain, which was genetically modified to overproduce threonine. The recipient organism E. coli MG 1655 is considered to be safe. The traits introduced in the final modified strain E. coli FERM BP-10942 are mainly limited to the overproduction of threonine. No full-length antibiotic resistance genes or other sequences of concern remain in the modified strain. In conclusion, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP): does not identify risks for human and animal health or the environment from this biomass regarding the genetic modification of the strain. The proposed recommended use level for dairy cows (8% PT73 (TM) of feed dry matter (~ 7% in complete feed)) and salmonids (13%) is considered safe for these target animals. The conclusion form dairy cows could be extended to other ruminants (from the beginning of rumination). Complete feed for pigs for fattening may contain up to 10% PT73 (TM). The toxicological data indicate effects of PT73 (TM) on blood coagulation and liver, which are considered to be adverse. As a consequence, the FEEDAP Panel is unable to conclude on the safety for the consumer of products derived from animals receiving feed containing PT73 (TM). PT73 (TM) is not considered a skin/eye irritant but should be considered as a potential skin and respiratory sensitiser. Moreover, any exposure of users to dust from the product via the inhalation route should be considered a serious risk. The FEEDAP Panel considers that substitution of PT73 (TM) for other protein-rich feed materials will not adversely affect the environment.

Safety and nutritional value of a dried killed bacterial biomass from Escherichia coli (FERM BP-10941) (PL73 (LM)) as a feed material for pigs, ruminants and salmonids

PL73 (LM) is a dried, heat‐inactivated bacterial biomass used as a feed material produced from an Escherichia coli K‐12 strain, which was genetically modified to overproduce lysine. The recipient organism E. coli K‐12S B‐7 is considered to be safe. The traits introduced in the final modified strain E. coli FERM BP‐10941 are mainly limited to the overproduction of lysine. No full‐length antibiotic resistance genes or other sequences of concern remain in the modified strain. In conclusion, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) does not identify risks for human and animal health or the environment from the biomass regarding the genetic modification of the strain. Although considering the zootechnical end‐points only, the maximum safe level for dairy cows would be 6% PL73 (LM) of feed dry matter (~ 5% in complete feed) and for pigs for fattening up to 6% PL73 (LM), the unexplained effects on blood coagulation, on plasma lipoproteins in dairy cows and on total plasma bilirubin and liver weight in pigs prevent a clear conclusion of safe dietary levels for ruminants and pigs for fattening. PL73 (LM) is safe for salmonids up to a dietary concentration of 13%. The toxicological data indicate adverse effects of PL73 (LM) on blood coagulation and liver, which also occur in target species. As a consequence, the FEEDAP Panel is unable to conclude on the safety for the consumer of products derived from animals receiving feed containing PL73 (LM). PL73 (LM) is not considered a skin/eye irritant but should be considered as a potential skin and respiratory sensitiser. Moreover, any exposure of users to dust from the product via the inhalation route should be considered a serious risk. The FEEDAP Panel considers that substitution of PL73 (LM) for other protein‐rich feed materials will not adversely affect the environment.

Identification of the active protein in rice bran protein having an inhibitory activity of cholesterol micellar solubility

In our previous study, rice bran protein (RBP) inhibited cholesterol micellar solubility in vitro and decreased serum cholesterol level in rats. In the present study, RBP was separated and purified by size-exclusion chromatography and reversed-phase chromatography. The active protein of RBP related to cholesterol micellar solubility was identified as lectin and non-specific lipid-transfer protein 1 using MALDI-TOF mass spectrometry analysis.

Lactoferrin interacts with bile acids and increases fecal cholesterol excretion in rats

Lactoferrin (LF) is a multifunctional cationic protein (pI 8.2–8.9) in mammalian milk. We previously reported that enteric-LF prevented hypercholesterolemia and atherosclerosis in a diet-induced atherosclerosis model using Microminipig, although the underlying mechanisms remain unclear. Because LF is assumed to electrostatically interact with bile acids to inhibit intestinal cholesterol absorption, LF could promote cholesterol excretion. In this study, we assessed the interaction between LF and taurocholate in vitro, and the effect of LF on cholesterol excretion in rats. The binding rate of taurocholate to LF was significantly higher than that to transferrin (pI 5.2–6.3). When rats were administered a high-cholesterol diet (HCD) containing 5% LF, LF was detected using ELISA in the upper small intestine from 7.5 to 60 min after the administration. Rats were fed one of the following diets: control, HCD, or HCD + 5% LF for 21 days. Fecal neutral steroids and hepatic cholesterol levels in the HCD group were significantly higher than those in the control group. The addition of LF to a HCD significantly increased fecal neutral steroids levels (22% increase, p < 0.05) and reduced hepatic cholesterol levels (17% decrease, p < 0.05). These parameters were inversely correlated (R = −0.63, p < 0.05). These results suggest that LF promotes cholesterol excretion via interactions with bile acids.

Hypocholesterolemic effect of sericin-derived oligopeptides in high-cholesterol fed rats

The beneficial effect of cholesterol-lowering proteins and/or peptides derived from various dietary sources is continuously reported. A non-dietary protein from silk cocoon, sericin, has also demonstrated cholesterol-lowering activity. A sericin hydrolysate prepared by enzymatic hydrolysis was also expected to posses this effect. The present study was aimed at investigating the cholesterol-lowering effect of sericin peptides, so called "sericin-derived oligopeptides" (SDO) both in vivo and in vitro. The results showed that SDO at all three doses tested (10 mg kg^-1 day^-1, 50 mg kg^-1 day^-1, and 200 mg kg^-1 day^-1) suppressed serum total and non-HDL cholesterol levels in rats fed a high-cholesterol diet. Triglyceride and HDL-cholesterol levels were not significantly changed among all groups. The fecal contents of bile acids and cholesterol did not differ among high-cholesterol fed rats. SDO dose-dependently reduced cholesterol solubility in lipid micelles, and inhibited cholesterol uptake in monolayer Caco-2 cells. SDO also effectively bound to all three types of bile salts including taurocholate, deoxytaurocholate, and glycodeoxycholate. Direct interaction with bile acids of SDO may disrupt micellar cholesterol solubility, and subsequently reduce the absorption of dietary cholesterol in intestines. Taking all data together, SDO or sericin peptides exhibit a beneficial effect on blood cholesterol levels and could be potentially used as a health-promoting dietary supplement or nutraceutical product.

Protective Effects of Soy Oligopeptides in Ultraviolet B-Induced Acute Photodamage of Human Skin

Aim. We explored the effects of soy oligopeptides (SOP) in ultraviolet B- (UVB-) induced acute photodamage of human skin in vivo and foreskin ex vivo. Methods. We irradiated the forearm with 1.5 minimal erythemal dose (MED) of UVB for 3 consecutive days, establishing acute photodamage of skin, and topically applied SOP. Erythema index (EI), melanin index, stratum corneum hydration, and transepidermal water loss were measured by using Multiprobe Adapter 9 device. We irradiated foreskin ex vivo with the same dose of UVB (180 mJ/cm(2)) for 3 consecutive days and topically applied SOP. Sunburn cells were detected by using hematoxylin and eosin staining. Apoptotic cells were detected by using terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Cyclobutane pyrimidine dimers (CPDs), p53 protein, Bax protein, and Bcl-2 protein were detected by using immunohistochemical staining. Results. Compared with UVB group, UVB-irradiated skin with topically applied SOP showed significantly decreased EI. Compared with UVB group, topical SOP significantly increased Bcl-2 protein expression and decreased CPDs-positive cells, sunburn cells, apoptotic cells, p53 protein expression, and Bax protein expressions in the epidermis of UVB-irradiated foreskin. Conclusion. Our study demonstrated that topical SOP can protect human skin against UVB-induced photodamage.

Cholesterol regulatory effects and antioxidant activities of protein hydrolysates from zebra blenny (Salaria basilisca) in cholesterol-fed rats

This study aims to explore the hypocholesterolemic effects and antioxidative activities of zebra blenny protein hydrolysates (ZBPHs) in rats fed with a hypercholesterolemic diet. The rats were fed during eight weeks a standard laboratory diet (normal rats), a high-cholesterol diet (HCD) (1%) or a HCD and orally treated with ZBPHs or undigested zebra blenny proteins (UZBPs) (400 mg per kg per day). Results showed that a hypercholesterolemic diet induced the increase of total cholesterol (TC), triglycerides (TG), and low-density lipoprotein cholesterol (LDL-C). Treatment with ZBPHs increased the level of high-density lipoprotein cholesterol (HDL-C) and decreased significantly the levels of TC, TG, and LDL-C. In addition, ZBPH treatment showed significant normalization of thiobarbituric acid-reactive substance (TBARS) levels as well as catalase, superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities in renal and hepatic tissues. Furthermore, ZBPHs may also exert significant protective effects on liver and kidney functions, evidenced by a marked decrease in the level of serum urea, uric acid, creatinine, alkaline phosphatase (ALP), and alanine aminotransferase (ALAT). Histological studies confirmed that ZBPHs effectively protected the livers and kidneys against hypercholesterolemia-mediated oxidative damage. Therefore, the study strengthens the hypothesis that ZBPHs can be used as novel antioxidants and hypocholesterolemic compounds against hyperlipidemia induced atherosclerosis.

Effect of arginine : lysine ratio in free amino acid and protein form onl-NAME induced hypertension in hypercholesterolemic Wistar rats

Arginine : lysine in the ratio of 5 : 1 plays an important role in cardiovascular diseases, especially as a nitric oxide precursor leading to vasodilation and inhibiting angiotensin-I converting enzyme in renin angiotensin system.

Dietary ɛ-Polylysine Decreased Serum and Liver Lipid Contents by Enhancing Fecal Lipid Excretion Irrespective of Increased Hepatic Fatty Acid Biosynthesis-Related Enzymes Activities in Rats

ɛ-Polylysine (EPL) is used as a natural preservative in food. However, few studies have been conducted to assess the beneficial functions of dietary EPL. The purpose of this study was to elucidate the mechanism underlying the inhibition of neutral and acidic sterol absorption and hepatic enzyme activity-related fatty acid biosynthesis following EPL intake. EPL digest prepared using an in vitro digestion model had lower lipase activity and micellar lipid solubility and higher bile acid binding capacity than casein digest. Male Wistar rats were fed an AIN-93G diet containing 1% (wt/wt) EPL or l-lysine. After 4 weeks of feeding these diets, the marked decrease in serum and liver triacylglycerol contents by the EPL diet was partly attributed to increased fecal fatty acid excretion. The activities of hepatic acetyl-coenzyme A carboxylase and glucose-6-phosphate dehydrogenase, which are key enzymes of fatty acid biosynthesis, were enhanced in rats fed EPL diet. The increased fatty acid biosynthesis activity due to dietary EPL may be prevented by the enhancement of fecal fatty acid excretion. The hypocholesterolemic effect of EPL was mediated by increased fecal neutral and acidic sterol excretions due to the EPL digest suppressing micellar lipid solubility and high bile acid binding capacity. These results show that dietary EPL has beneficial effects that could help prevent lifestyle-related diseases such as hyperlipidemia and atherosclerosis.

Cholesterol-lowering effect of rice bran protein containing bile acid-binding proteins

Dietary plant protein is well known to reduce serum cholesterol levels. Rice bran is a by-product of rice milling and is a good source of protein. The present study examined whether feeding rats a high-cholesterol diet containing 10% rice bran protein (RBP) for 10 d affected cholesterol metabolism. Rats fed dietary RBP had lower serum total cholesterol levels and increased excretion of fecal steroids, such as cholesterol and bile acids, than those fed dietary casein. In vitro assays showed that RBP strongly bound to taurocholate, and inhibited the micellar solubility of cholesterol, compared with casein. Moreover, the bile acid-binding proteins of the RBP were eluted by a chromatographic column conjugated with cholic acid, and one of them was identified as hypothetical protein OsJ_13801 (NCBI accession No. EAZ29742) using MALDI-TOF mass spectrometry analysis. These results suggest that the hypocholesterolemic action of the RBP may be caused by the bile acid-binding proteins.

Hypocholesterolaemic effect of rat-administered oral doses of the isolated 7S globulins from cowpeas and adzuki beans

The role of seed proteins, especially soyabean 7S globulins, in controlling dyslipidaemia is widely acknowledged. Amino acid sequence homology among the proteins of this family could reflect similar biological functions in other species. The aim of the present study was to unveil a hypolipidaemic effect of the 7S globulins from cowpeas (7S-C) and adzuki beans (7S-A), administered orally to rats fed a hypercholesterolaemic (HC; high cholesterol and TAG) diet for 28 d. A total of forty-five rats were divided into five groups (nine rats per group): (1) standard (STD) diet; (2) HC diet; (3) HC diet + 7S-C (300 mg/kg per d); (4) HC diet + 7S-A (300 mg/kg per d); and (5) HC diet + simvastatin (SVT; 50 mg/kg per d), as a control. Significant decreases in food intake and final body weight of rats receiving HC + 7S-C and HC + 7S-A diets compared with groups fed the HC and STD diets were observed. Significant decreases in serum total and non-HDL-cholesterol of 7S-C, 7S-A and SVT groups were also observed. HDL-cholesterol levels increased in the 7S-C, 7S-A and SVT groups, while hepatic cholesterol and TAG concentrations were significantly lower than in the HC diet group for the 7S-C-supplemented group only. Faecal excretions of fat and cholesterol in HC diet groups were considerably higher in animals consuming the 7S globulins. The results show that cowpea and adzuki bean 7S globulins promote cholesterol-decreasing effects in hypercholesterolaemic rats even at low dosages, as already observed for other legume seed storage proteins of this family. This main effect is discussed in relation to the possible mechanisms of action.

Hypolipidemic potential of squid homogenate irrespective of a relatively high content of cholesterol

Background

Our previous study has shown that regardless of a relatively high amount of cholesterol, squid homogenate lowers serum and hepatic cholesterol in animals. Since this work, we have developed a new method to inhibit autolysis of squid proteins with sodium citrate. This study aims to investigate how squid homogenate prepared with sodium citrate affects lipid metabolism in Sprague–Dawley rats at the molecular level.

Methods

We prepared squid homogenate with sodium citrate to inhibit autolysis of squid protein. In Experiment 1 (Exp. 1), rats were given a cholesterol-free control diet or a squid diet, with squid homogenate added at the level of 5% as dietary protein for 4 weeks. Blood, the liver and adipose tissue were taken after 6 hours fasting. Serum and hepatic lipids and activities of enzymes related to lipid metabolism were measured. In Experiment 2 (Exp. 2), the above-mentioned diets had cholesterol added at the level of 0.1% and given to rats. Lipid parameters, enzyme activities, and gene expression of proteins involved in lipid metabolism in the liver and the small intestine were determined. In addition, feces were collected for two days at the end of Exp. 2 to measure fecal excretion of steroids.

Results

In Exp.1, serum triglyceride and cholesterol were ~50% and ~20% lower, respectively, in the squid diet-fed rats than in the control diet-fed animals while hepatic cholesterol was ~290% higher in the squid diet-fed rats. When cholesterol was included into the diets (Exp. 2), serum lipids were significantly lower in the squid group while no difference of hepatic lipid was seen between two groups. Activities of hepatic lipogenic enzymes were significantly lower in rats on the squid diet while the enzyme responsible for fatty acid oxidation was not modified (Expt. 1 and 2). Hepatic level of mRNA of microsomal triglyceride transfer protein was significantly lower in the squid group. In the small intestine, the squid diet exhibited significantly lower gene expression of proteins involved in fatty acid transport and cholesterol absorption. Fecal secretion of acidic steroids, but not neutral steroids, was higher in rats fed the squid diet than in those fed the control diet.

Conclusion

These results imply that newly-developed squid homogenate has hypolipidemic potential primarily through decreased absorption of bile acids in the small intestine and suppressed lipogenesis in the liver.

Identification of a novel hypocholesterolemic protein, major royal jelly protein 1, derived from royal jelly

Royal jelly (RJ) intake lowers serum cholesterol levels in animals and humans, but the active component in RJ that lowers serum cholesterol level and its molecular mechanism are unclear. In this study, we set out to identify the bile acid-binding protein contained in RJ, because dietary bile acid-binding proteins including soybean protein and its peptide are effective in ameliorating hypercholesterolemia. Using a cholic acid-conjugated column, we separated some bile acid-binding proteins from RJ and identified the major RJ protein 1 (MRJP1), MRJP2, and MRJP3 as novel bile acid-binding proteins from RJ, based on matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Purified MRJP1, which is the most abundant protein of the bile acid-binding proteins in RJ, exhibited taurocholate-binding activity in vitro. The micellar solubility of cholesterol was significantly decreased in the presence of MRJP1 compared with casein in vitro. Liver bile acids levels were significantly increased, and cholesterol 7α-hydroxylase (CYP7A1) mRNA and protein tended to increase by MRJP1 feeding compared with the control. CYP7A1 mRNA and protein levels were significantly increased by MRJP1 tryptic hydrolysate treatment compared with that of casein tryptic hydrolysate in hepatocytes. MRJP1 hypocholesterolemic effect has been investigated in rats. The cholesterol-lowering action induced by MRJP1 occurs because MRJP1 interacts with bile acids induces a significant increase in fecal bile acids excretion and a tendency to increase in fecal cholesterol excretion and also enhances the hepatic cholesterol catabolism. We have identified, for the first time, a novel hypocholesterolemic protein, MRJP1, in RJ. Interestingly, MRJP1 exhibits greater hypocholesterolemic activity than the medicine β-sitosterol in rats.

Development of a novel transgenic rice with hypocholesterolemic activity via high-level accumulation of the α' subunit of soybean β-conglycinin

Soybean 7S globulin, known as β-conglycinin, has been shown to regulate human plasma cholesterol and triglyceride levels. Furthermore, the α' subunit of β-conglycinin has specifically been shown to possess low-density lipoprotein (LDL)-cholesterol-lowering activity. Therefore, accumulation of the α' subunit of β-conglycinin in rice seeds could lead to the production of new functional rice that could promote human health. Herein, we used the low-glutelin rice mutant 'Koshihikari' (var. a123) and suppressed its glutelins and prolamins, the major seed storage proteins of rice, by RNA interference. The accumulation levels of the α' subunit in the lines with suppressed glutelin and prolamin levels were >20 mg in 1 g of rice seeds, which is considerably higher than those in previous studies. Oral administration of the transgenic rice containing the α' subunit exhibited a hypocholesterolemic activity in rats; the serum total cholesterol and LDL cholesterol levels were significantly reduced when compared to those of the control rice (var. a123). The cholesterol-lowering action by transgenic rice accumulating the α' subunit induces a significant increase in fecal bile acid excretion and a tendency to increase in fecal cholesterol excretion. This is the first report that transgenic rice exhibits a hypocholesterolemic activity in rats in vivo by using the β-conglycinin α' subunit.

Soy Protein Suppresses Gene Expression of Acetyl-CoA Carboxylase Alpha from Promoter PI in Rat Liver

Dietary soy protein isolate (SPI) reduces hepatic lipogenesis by suppressing gene expression of lipogenic enzymes, including acetyl-CoA carboxylase (ACC). In order to elucidate the mechanism of this regulation, the effect of dietary SPI on promoter (PI and PII) specific gene expression of ACC alpha was investigated. Rats were fed experimental diets containing SPI or casein as a nitrogen source. SPI feeding decreased the hepatic contents of total ACC mRNA as well as triglyceride (TG) content, but dietary SPI affected the amount of sterol-regulatory element binding protein (SREBP)-1 mRNA and protein very little. The amount of ACC mRNA transcribed from PII promoter containing SRE was not significantly affected by dietary protein, while a significant decrease in PI-generated ACC mRNA content was observed in rats fed the SPI diet. These data suggest that SPI feeding decreased the hepatic contents of ACC alpha mRNA mainly by regulating PI promoter via a nuclear factor(s) other than SREBP-1.

Lupin protein isolate versus casein modifies cholesterol excretion and mRNA expression of intestinal sterol transporters in a pig model

Background

Lupin proteins exert hypocholesterolemic effects in man and animals, although the underlying mechanism remains uncertain. Herein we investigated whether lupin proteins compared to casein modulate sterol excretion and mRNA expression of intestinal sterol transporters by use of pigs as an animal model with similar lipid metabolism as humans, and cellular cholesterol-uptake by Caco-2 cells.

Methods

Two groups of pigs were fed cholesterol-containing diets with either 230 g/kg of lupin protein isolate from L. angustifolius or 230 g/kg casein, for 4 weeks. Faeces were collected quantitatively over a 5 d period for analysis of neutral sterols and bile acids by gas chromatographically methods. The mRNA abundances of intestinal lipid transporters were analysed by real-time RT-PCR. Cholesterol-uptake studies were performed with Caco-2 cells that were incubated with lupin conglutin γ, phytate, ezetimibe or albumin in the presence of labelled [4-¹⁴C]-cholesterol.

Results

Pigs fed the lupin protein isolate revealed lower cholesterol concentrations in total plasma, LDL and HDL than pigs fed casein (P < 0.05). Analysis of faeces revealed a higher output of cholesterol in pigs that were fed lupin protein isolate compared to pigs that received casein (+57.1%; P < 0.05). Relative mRNA concentrations of intestinal sterol transporters involved in cholesterol absorption (Niemann-Pick C1-like 1, scavenger receptor class B, type 1) were lower in pigs fed lupin protein isolate than in those who received casein (P < 0.05). In vitro data showed that phytate was capable of reducing the uptake of labelled [4-¹⁴C]-cholesterol into the Caco-2 cells to the same extend as ezetimibe when compared to control (−20.5% vs. −21.1%; P < 0.05).

Conclusions

Data reveal that the cholesterol-lowering effect of lupin protein isolate is attributable to an increased faecal output of cholesterol and a reduced intestinal uptake of cholesterol. The findings indicate phytate as a possible biofunctional ingredient of lupin protein isolate.

Dietary soybean peptides containing a low-molecular fraction can lower serum and liver triglyceride levels in rats

We investigated the effects of dietary soybean peptides, particularly low-molecular-weight peptides, on serum and hepatic concentrations of lipids in rats. Soybean protein isolate (SPI) was digested with protease to produce low-molecular-weight peptides (LD) or a mixture of high- and low-molecular-weight peptides (HLD). Rats were fed diets containing 20% casein, SPI, LD or HLD as a nitrogen source, with or without 0.5% cholesterol, for 2 wk. Next, rats were fed cholesterol-free diets containing 0%, 5%, 10%, or 20% LD at the expense of casein for 2 wk. Serum triglyceride levels were the lowest in the LD group, and liver triglyceride levels were significantly lower in rats fed SPI and LD/HLD diets than in those fed casein diets, both in the presence and absence of dietary cholesterol. In addition, dietary LD significantly lowered serum and liver triglyceride levels in a dose-dependent manner. These results suggest that low-molecular-weight soybean peptides have a potent hypotriglyceridemic effect and may be beneficial for improving lipid metabolism.