Hypocholesterolemic effect of rice protein is due to regulating hepatic cholesterol metabolism in adult rats

Methionine strengthens anti-inflammation of rice protein via depressing NF-κB activation and stimulating Msr expression in rats fed cholesterol-enriched diets

Oxidized low-density lipoprotein (ox-LDL) is an inducer of inflammation. To elucidate the link of depression of ox-LDL accumulation and anti-inflammatory function of rice protein (RP) whether dependent on methionine availability, growing and adult rats were fed RP and methionine-supplemented RP (RM) under cholesterol-enriched dietary condition. After two weeks feeding, RP and RMs exerted the anti-inflammatory effects through up-regulating IL-10, while RP and RMs significantly reduced ox-LDL levels and effectively suppressed the expressions of inflammatory mediators (COX-2, IL-1β, IL-6, TNF-α, iNOS). The anti-inflammatory molecular mechanism was to inhibit NF-κB activation and to simulate methionine sulfoxide reductase expression. Results showed, under cholesterol-enriched dietary condition, the anti-inflammatory action can be induced by RP and enhanced by methionine in growing and adult rats. The present study reveals a link of the decreased ox-LDL accumulation with the anti-inflammatory function of RP, which is dependent on methionine availability and independent of dietary cholesterol.

Rice protein stimulates endogenous antioxidant response attributed to methionine availability in growing rats

Methionine sulfoxide reductase (Msr) and glutathione (GSH) are two endogenous antioxidant systems for depressing oxidative stress. The aim of this study is to investigate the role of methionine in involving the stimulation of endogenous antioxidant capacity of rice protein (RP). Seven-week-old male Wistar rats (body weight 180-200 g) were fed with commercial pellets (as control), methionine, and RP for 2 weeks. Compared with control, GSH synthesis and expressions of MsrA, MsrB2, and MsrB3 were stimulated by methionine and RP. After 2 weeks of feeding, Nrf2 was activated by RP and methionine, whereas the expressions of Keap1 and Cul3 were depressed. The ARE-driven antioxidant expressions (GCLC, GCLM, GS, HO-1, NQO1, CAT, SOD, GR, GST, GPx) were upregulated by methionine and RP. Results suggest that the endogenous antioxidant response induced by RP is primarily attributed to the methionine availability, in which the stimulation of Msr and GSH antioxidant system via Nrf2-ARE pathway. PRACTICAL APPLICATIONS: Rice protein is a major plant protein, which is rich in sulfur-containing amino acids and widely consumed in the world. This paper emphasizes that the amino acid plays a key role in inducing the antioxidant activity of rice protein. The present study provides an insight that the methionine availability of rice protein will be a useful target for health promoting by activating endogenous antioxidant response against ROS-induced oxidative damage.

Unripe Rubus coreanus Miquel Extract Containing Ellagic Acid Regulates AMPK, SREBP-2, HMGCR, and INSIG-1 Signaling and Cholesterol Metabolism In Vitro and In Vivo

Our previous study demonstrated that a 5% ethanol extract of unripe Rubus coreanus (5-uRCK) has hypo-cholesterolemic and anti-obesity activity. However, the molecular mechanisms of its effects are poorly characterized. We hypothesized that 5-uRCK and one of its major bioactive compounds, ellagic acid, decrease cellular and plasma cholesterol levels. Thus, we investigated the hypocholesterolemic activity and mechanism of 5-uRCK in both hepatocytes and a high-cholesterol diet (HCD)-induced rat model. Cholesterol in the liver and serum was significantly reduced by 5-uRCK and ellagic acid. The hepatic activities of HMG-CoA and CETP were reduced, and the hepatic activity of LCAT was increased by both 5-uRCK extract and ellagic acid, which also caused histological improvements. The MDA content in the aorta and serum was significantly decreased after oral administration of 5-uRCK or ellagic acid. Further immunoblotting analysis showed that AMPK phosphorylation in the liver was induced by 5-uRCK and ellagic acid, which activated AMPK, inhibiting the activity of HMGCR by inhibitory phosphorylation. In contrast, 5-uRCK and ellagic acid suppressed the nuclear translocation and activation of SREBP-2, which is a key transcription factor in cholesterol biosynthesis. In conclusion, our results suggest that 5-uRCK and its bioactive compound, ellagic acid, are useful alternative therapeutic agents to regulate blood cholesterol.

Rice Protein Exerts Anti-Inflammatory Effect in Growing and Adult Rats via Suppressing NF-κB Pathway

To elucidate the effect of rice protein (RP) on the depression of inflammation, growing and adult rats were fed with caseins and RP for 2 weeks. Compared with casein, RP reduced hepatic accumulations of reactive oxygen species (ROS) and nitro oxide (NO), and plasma activities of alanine transaminase (ALT) and aspartate transaminase (AST) in growing and adult rats. Intake of RP led to increased mRNA levels, and protein expressions of phosphoinositide 3 kinase (PI3K), protein kinase B (Akt), nuclear factor-κB 1 (NF-αB1), reticuloendotheliosis viral oncogene homolog A (RelA), tumor necrotic factor α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and monocyte chemoattractant protein-1 (MCP-1) were decreased, whereas hepatic expressions of interleukin-10 (IL-10) and heme oxygenase 1 (HO-1) were increased by RP. The activation of NF-κB was suppressed by RP through upregulation of inhibitory κB α (IκBα), resulting in decreased translocation of nuclear factor-κB 1 (p50) and RelA (p65) to the nucleus in RP groups. The present study demonstrates that RP exerts an anti-inflammatory effect to inhibit ROS-derived inflammation through suppression of the NF-κB pathway in growing and adult rats. Results suggest that the anti-inflammatory capacity of RP is independent of age.

Rice protein reduces DNA damage by activating the p53 pathway and stimulating endogenous antioxidant response in growing and adult rats

BACKGROUND

Reactive oxygen species (ROS) can cause DNA damage. Rice protein (RP) inhibits ROS accumulation. However, a link between the reduction of ROS-derived DNA damage and the intake of RP is far from clear. The main objective of this study is to elucidate the effects of RPs on the reduction of DNA damage in growing and adult rats.

RESULTS

An intake of RP for 2 weeks significantly reduced the hepatic accumulation of ROS and 8-hydroxydeoxyguanosine (8-OHdG) in growing and adult rats, whereas the hepatic p53 content was markedly increased by RPs. After 2 weeks' feeding, the mRNA levels and protein expressions of p53, ataxia-telangiectasia mutated (ATM), and Checkpoint kinase 2 (Chk2) were up-regulated by RPs, whereas Murine Double Minute 2 (MDM2) expressions were markedly inhibited by RPs, resulting in more p53 being translocated into the nucleus. Nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) was activated by RP by reducing Kelch-like ECH-associated protein 1 (Keap1), resulting in the up-regulation of antioxidant expressions of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in RP groups.

CONCLUSION

Rice protein can exert an endogenous antioxidant activity to reduce ROS-derived DNA damage by activating the Nrf2-Keap1 pathway. This study suggests that the activation of the ATM-Chk2-p53 pathway might be one of the mechanisms exerted by RP for reducing DNA damage in growing and adult rats. © 2019 Society of Chemical Industry.

The Association between Serum Testosterone and Risk Factors for Atherosclerosis

Objective

To study the associations between serum testosterone and risk factors for atherosclerosis in 119 men from general population.

Methods

Systolic pressure, body mass index (BMI), testosterone, fasting glucose, glucose tolerance test, apolipoprotein A-1 (ApoA-1), apolipoprotein B (ApoB), and ApoB/ApoA-1 ratio were assessed. Subjects classified into hypogonadal (testosterone ≤ 12 nmol/l), and eugonadal men (testosterone > 12 nmol/l).

Results

BMI (28 vs. 26 kg/ m², p = 0.01), systolic pressure (129 vs. 123 mmHg, p = 0.03), fasting glucose (5.9 vs. 5.5 mmol/l, p = 0.03), ApoB (1.1 vs. 1.0 g/l, p = 0.03), and ApoB/ApoA-1 ratio (0.8 vs. 0.7, p = 0.03) were higher in hypogonadal compared to eugonadal men, respectively. In adjusted multivariate regression analysis model, testosterone showed negative associations with BMI (β = -1.832, p = 0.030, 95% CI = -3.485--0.180), fasting glucose (β = -0.394, p = 0.011, 95% CI = -0.696--0.091), glucose tolerance test (β = -0.957, p = 0.045, 95% CI = -1.892--0.022), ApoB (β = -0.157, p = 0.017, 95% CI = -0.286--0.029), and ApoB/ApoA-1 ratio (β = -0.118, p = 0.046, 95% CI = -0.234--0.002).

Conclusions

These results suggest an inverse association between testosterone levels and risk factors for atherosclerosis.

Methionine Augments Antioxidant Activity of Rice Protein during Gastrointestinal Digestion

To elucidate the influence of methionine, which is an essential sulfur-containing amino acid, on the antioxidant activity of rice protein (RP), methionine was added to RP (RM). The addition of methionine to RM0.5, RM1.0, RM1.5, RM2.0, and RM2.5 was 0.5-, 1.0-, 1.5-, 2.0-, and 2.5-fold of methionine of RP, respectively. Using the in vitro digestive system, the antioxidant capacities of scavenging free radicals (superoxide; nitric oxide; 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, ABTS), chelating metal (iron), and reducing power were investigated in the hydrolysates of RP and RMs. Upon pepsin-pancreatin digestion, the weakest antioxidant capacity was produced by RP. With the addition of methionine, RMs exhibited more excellent responses to free radical scavenging activities and reducing power than RP, whereas RMs did not produce the marked enhancements in iron chelating activity as compared to RP. The present study demonstrated that RMs differently exerted the free radical scavenging activities that emerged in the protein hydrolysates, in which the strongest scavenging capacities for ABTS, superoxide, and nitric oxide were RM1.5, RM2.0, and RM2.5, respectively. Results suggested that the availability of methionine is a critical factor to augment antioxidant ability of RP in the in vitro gastrointestinal tract.

Fractionation and antioxidant properties of rice bran protein hydrolysates stimulated by in vitro gastrointestinal digestion

Rice bran was used as a starting material to prepare protein concentrate through enzyme-assisted extraction. The hydrolysis of protein concentrate under in vitro gastrointestinal digestion (pepsin-trypsin system) greatly improved the antioxidant properties. Rice bran protein hydrolysate was further fractionated by membrane ultrafiltration (UF, F1: molecular weight (MW) <3kDa, F2: MW 3-5kDa, and F3: MW 5-10kDa). Peptides with smaller MW possessed higher antioxidant activities (P<0.05). UF showed a great efficacy to selectively separate the metal-chelating peptides. Tyrosine and phenylalanine had positive correlations with their DPPH & ABTS radicals scavenging activities and ferric reducing antioxidant power (r>0.831). A major peptide fragment was detected at m/z 1088 by a MALDI-TOF mass spectrometry. There is high potential that antioxidative peptides from rice bran might also be produced in the gastrointestinal tract of the human body.

In vitro antioxidant activity of rice protein affected by alkaline degree and gastrointestinal protease digestion

BACKGROUND

To elucidate whether and how alkali treatment, which is a common process for rice protein (RP) extraction, affects antioxidant activity of RP, the different degree of alkali (from 0.1% to 0.4% of NaOH) was used to extract RP (RP-1, RP-2, RP-3, RP-4).

RESULTS

The antioxidant capacities of scavenging free radicals [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid] diammonium salt, ABTS; 1,1-diphenyl-2-picrylhydrazyl, DPPH), chelating metals (iron, copper) and reducing power investigated in the hydrolysates of RPs (RP-1, RP-2, RP-3, RP-4) during in vitro pepsin-pancreatin digestion were effectively affected by alkali treatment. The present study demonstrated that the weakest antioxidant responses to ABTS radical-scavenging activity, DPPH radical-scavenging activity, iron chelating activity, copper chelating activity and reducing power were produced by RP-4 extracted by the highest alkali proportion (0.4% NaOH).

CONCULSION

The present study indicates that antioxidant capacity of RP could be more readily depressed by strict alkali degree and affected by gastrointestinal proteases. Results suggest that alkali extraction is a vital process to regulate the antioxidant activity of RP through modifying the compositions of amino acids, which are dependent on alkali magnitude. © 2016 Society of Chemical Industry.

Preventive obesity agent montmorillonite adsorbs dietary lipids and enhances lipid excretion from the digestive tract

Western diets are typically high in fat and are associated with long-term complications such as obesity and hepatic steatosis. Because of the enjoyable taste of high-fat diets (HFDs), we are interested in determining how to decrease lipid absorption and enhance lipid excretion from the digestive tract after the consumption of eating fatty foods. Montmorillonite was initially characterized as a gastrointestinal mucosal barrier protective agent for the treatment of diarrhoea. Dietary lipid adsorbent- montmorillonite (DLA-M) was isolated and purified from Xinjiang montmorillonite clay via the water extraction method. Here, we show that DLA-M has an unexpected role in preventing obesity, hyperlipidaemia and hepatic steatosis in HFD-fed rats. Interestingly, combined application of polarized light microscopy and lipid staining analyses, showed that DLA-M crystals have dietary lipid-adsorbing ability in vitro and in vivo, which enhances lipid excretion via bowel movements. In summary, our results indicate that DLA-M prevent HFD-induced obesity. This novel dietary lipid-adsorbing agent can help prevent obesity and its comorbidities.

Influence of Sorghum Kafirin on Serum Lipid Profile and Antioxidant Activity in Hyperlipidemic Rats (In Vitro and In Vivo Studies)

The aim of this study was to compare in vitro the antioxidant potential of sorghum kafirin and sorghum flour and their influence on lipids and antioxidant capacity in rats. The antioxidant activity in sorghum kafirin extract measured by the DPPH and TEAC methods was increased 30 and 65 times, respectively, compared to that of its counterpart, sorghum flour. According to electrophoresis assay, the kafirins tert-butanol extract showed a high proportion of α-kafirin monomers, and its amino acid composition revealed higher hydrophobic amino acid content such as alanine, isoleucine, leucine, tyrosine and phenylalanine than sorghum flour extract. Diets supplemented with sorghum kafirin extract have improved lipid metabolism and increased the serum antioxidant potential (67%) especially in rats fed with added cholesterol. The bioactive peptides generated from kafirin in vivo hydrolysis appear to be associated with the positive effect on serum lipids and antioxidant activity. According to these results, sorghum kafirin extract at the levels used in this study apparently could be used for prevention of atherosclerosis and other chronic diseases.

Effect of testosterone deficiency on cholesterol metabolism in pigs fed a high-fat and high-cholesterol diet

Background

Testosterone deficiency is associated with increased serum cholesterol levels. However, how testosterone deficiency precisely affects cholesterol metabolism remains unclear. Therefore, in the current study, we examined the effect of testosterone deficiency on cholesterol metabolism and liver gene expression in pigs fed a high-fat and high-cholesterol (HFC) diet.

Methods

Sexually mature male miniature pigs (6–7 months old) were randomly divided into 3 groups as follows: intact male pigs fed an HFC diet (IM + HFC), castrated male pigs fed an HFC diet (CM + HFC), and castrated pigs with testosterone replacement fed an HFC diet (CM + HFC + T). Serum testosterone levels and lipid profiles were measured, and gene expression levels associated with hepatic cholesterol metabolism were determined. Furthermore, total hepatic cholesterol contents and the activities of enzymes mediating hepatic cholesterol metabolism were measured.

Results

Serum testosterone levels were significantly decreased in CM + HFC pigs, and testosterone replacement attenuated castration-induced testosterone deficiency. Castration significantly increased the serum levels of total cholesterol, low-density lipoprotein cholesterol and triglycerides, as well as hepatic lipid contents in pigs fed an HFC diet. Compared with IM + HFC and CM + HFC + T pigs, low-density lipoprotein receptor (LDLR) mRNA expression and protein levels were significantly decreased in the livers of CM + HFC pigs. In contrast, we found that compared with IM + HFC pigs, hepatic proprotein convertase subtilisin/kexin type 9 (PCSK9) mRNA and serum PCSK9 protein levels were significantly increased in CM + HFC pigs. Moreover, testosterone treatment reversed the increase in PCSK9 expression in CM + HFC pigs. However, neither castration nor testosterone replacement affected the expression of the other hepatic genes that were tested.

Conclusions

This study demonstrated that castration-induced testosterone deficiency caused severe hypercholesterolemia in pigs fed an HFC diet; furthermore, these effects could be reversed by testosterone replacement therapy. Altered hepatic PCSK9 and LDLR expression, resulting in reduced LDL-cholesterol clearance, may contribute to the increased serum cholesterol levels induced by testosterone deficiency and an HFC diet. These results deepen our understanding of the underlying molecular mechanisms that mediate the effects of testosterone deficiency on cholesterol metabolism.

Hypolipidemic and antioxidative effects of aqueous enzymatic extract from rice bran in rats fed a high-fat and -cholesterol diet

Purpose: The aqueous enzymatic extract from rice bran (AEERB) was rich in protein, γ-oryzanol and tocols. The aim of this study was to investigate the effects of AEERB on the regulation of lipid metabolism and the inhibition of oxidative damage. Methods: The antioxidant activity of AEERB in vitro was measured in terms of radical scavenging capacity, ferric reducing ability power (FRAP) and linoleic acid emulsion system-ferric thiocyanate method (FTC). Male Wistar rats were fed with a normal diet and a high-fat and high-cholesterol diet with or without AEERB. After treatment, biochemical assays of serum, liver and feces lipid levels, the antioxidant enzyme activity, malondialdehyde (MDA) and protein carbonyl were determined. Result: AEERB is completely soluble in water and rich in hydrophilic and lipophilic functional ingredients. AEERB scavenged DPPH• and ABTS^•+ and exhibited antioxidant activity slightly lower than that of ascorbic acid in the linoleic acid system. The administration of AEERB reduced serum lipid levels and the atherogenic index compared with those of the hyperlipidemic diet group (HD). The administration of AEERB significantly lowered liver lipid levels, inhibited hepatic 3-hydroxyl-3-methylglutaryl CoA reductase activity, and efficiently promoted the fecal excretion of total lipids and total cholesterol (TC) (p < 0.05). Dietary AEERB enhanced antioxidant status in the serum, liver and brain by increasing the antioxidant enzyme activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and decreasing the content of MDA and protein carbonyl. Conclusions: The results indicated that AEERB might act as a potent hypolipidemic and antioxidant functional food.

Hypocholesterolemic metabolism of dietary red pericarp glutinous rice rich in phenolic compounds in mice fed a high cholesterol diet

BACKGROUND/OBJECTIVES

The purpose of the current study was to investigate the effect of red pericarp glutinous rice rich in polyphenols (Jakwangchalbyeo, red rice) on serum and hepatic levels of cholesterol and hepatic protein expression linked to synthesis and degradation of cholesterol in a hypercholesterolemic mice diet as compared with brown rice.

MATERIALS/METHODS

C57BL/6 male mice were randomly divided into four groups (n = 5 each), which were fed different diets for a period of 12 weeks: American Institute of Nutrition (AIN)-93G diet, AIN-93G diet with 2% cholesterol, brown rice with 2% cholesterol, or red rice with 2% cholesterol.

RESULT

Consumption of red rice resulted in a significant decrease in serum level of low-density lipoprotein cholesterol and hepatic levels of triglyceride and total-cholesterol. Expression of acyl-coenzyme A cholesterol acyltransferase-2 (ACAT-2), sterol regulatory element binding protein-2 (SREBP-2), and 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase was decreased, while expression of phosphorylated adenosine monophosphate activated protein kinase (p-AMPK)/AMPK ratio, cholesterol 7-α-hydroxylase (CYP7a1), and sterol 12-α-hydroxylase (CYP8b1) was increased in mice fed red rice. Brown rice had similar effects on cholesterol metabolism, but the effect of red rice was significantly greater than that of brown rice.

CONCLUSIONS

The current study suggested that red rice had a hypocholesterolemic effect by lowering hepatic cholesterol synthesis through ACAT-2, HMG-CoA reductase, and SREBP-2, and by enhancing hepatic cholesterol degradation through CYP7a1 and CYP8b1 in mice fed a hypercholesterolemic diet.

Antioxidant capacity responsible for a hypocholesterolemia is independent of dietary cholesterol in adult rats fed rice protein

Dietary cholesterol and aging are major risk factors to accelerate oxidation process for developing hypercholesterolemia. The major aim of this study is to elucidate the effects of rice protein on cholesterol level and oxidative stress in adult rats fed with and without cholesterol. After 2 weeks of feeding, hepatic and plasma contents of cholesterol, reduced glutathione (GSH), oxidized glutathione (GSSG), malondialdehyde (MDA) and protein carbonyl (PCO) were measured. In liver, total antioxidative capacity (T-AOC), activities of antioxidant enzymes (total superoxide dismutase, T-SOD; catalase, CAT), glutathione metabolizing enzyme activities and gene expression levels (γ-glutamylcysteine synthetase, γ-GCS; glutathione reductase, GR; glutathione peroxidase, GPx) were determined. Under cholesterol-free/enriched dietary condition, T-AOC, activities of T-SOD and CAT, glutathione metabolism related enzymes' activities and mRNA levels (γ-GCS, GR and GPx) were effectively stimulated by rice proteins as compared to caseins. Compared with caseins, rice proteins significantly increased hepatic and plasma GSH contents, whereas hepatic and plasma accumulations of MDA, PCO and GSSG were significantly reduced by rice protein-feedings. As a result, the marked reductions of cholesterol in the plasma and in the liver were observed in adult rats fed rice proteins with and without cholesterol. The present study demonstrates that the hypocholesterolemic effect of rice protein is attributable to inducing antioxidative response and depressing oxidative damage in adult rats fed cholesterol-free/enriched diets. Results suggest that the antioxidant capability involved in the hypocholesterolemic action exerted by rice protein is independent of dietary cholesterol during adult period.

Rice protein exerts a hypocholesterolemic effect through regulating cholesterol metabolism-related gene expression and enzyme activity in adult rats fed a cholesterol-enriched diet

The major aim of this study is to elucidate the hypocholesterolemic mechanism exerted by rice protein (RP) in adult rats under cholesterol-enriched dietary condition. Compared with casein, the cholesterol levels in plasma and the liver were significantly reduced by RP, accompanying significant inhibition of cholesterol absorption. RP increased the activity and mRNA level of cholesterol 7α-hydroxylase, whereas acyl-CoA:cholesterol acyltransferase activity and gene expression were significantly depressed with consumption of RP. Neither the activity nor gene expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase of RP differed from that of casein. The gene expression of the peroxisome proliferator-activated receptor α and liver X receptor α were significantly activated by consumption of RP. RP did not modify the mRNA level of sterol regulatory element-binding protein-2 with respect to casein. These results suggest RP can induce a cholesterol-lowering effect through modifying cholesterol metabolism-related gene expression and enzyme activity in adult rats.