Epigallocatechin gallate decreases the micellar solubility of cholesterol via specific interaction with phosphatidylcholine

Differential effects of theasinensins and epigallocatechin-3-O-gallate on phospholipid bilayer structure and liposomal aggregation

(-)-Epigallocatechin-3-O-gallate (EGCg), the major catechin responsible for the health-enhancing and disease-preventive effects of green tea, is susceptible to auto-oxidation at physiological pH levels. However, whether the oxidized EGCg resulting from its oral consumption possesses any bioactive functions remains unclear. This study presents a differential analysis of intact and oxidized EGCg regarding their interactions with phosphatidylcholine liposomes, serving as a simple biomembrane model. In the presence of ascorbic acid, pre-oxidized EGCg induced liposomal aggregation in a dose-dependent manner, whereas intact EGCg did not. Toxicity evaluation using calcein-loaded liposomes revealed that liposomal aggregation is associated with minimal membrane damage. Through fractionation of the oxidized EGCg sample, the fraction containing theasinensins showed high liposomal aggregation activity. Overall, these results suggest that oxidatively condensed EGCg dimers may stimulate various cells by altering the plasma membrane in a manner different from that of EGCg monomers.

Effects of green tea and roasted green tea on human responses

Our objective was to elucidate the effects of tea consumption on refreshment and stress reduction/recovery through examining the multiple associations among factors such as various physiological responses and task performance. Participants included 20 healthy young men who performed a mental arithmetic task while 11 physiological responses were measured. The experiments were conducted twice under different beverage consumption conditions on separate days. The mental arithmetic task was executed six times in 1 day; participants ingested hot water, green tea, or roasted green tea (hojicha) before each task. Several subjective assessments: subjective fatigue, stress, mental workload, and flow were evaluated after each task. The R-R intervals, heart rate variability spectral components, the Poincaré plot indices (SD1 and SD2) and plethysmogram amplitude tended to decrease during task periods compared to resting periods. Tissue blood volume/flow (TBV, TBF) and near-infrared spectroscopy responses (NIRS) were lower in the tea condition than in the hot water condition. By scrutinizing various indicators, we found that aromatic stimulation of Japanese tea beverages has the potential to induce positive effects, enhance mental task performance, promote refreshment, and alleviate feelings of fatigue. These positive effects were observed even in small quantities and within a short duration, mirroring responses observed in daily consumption.

Green Tea Catechins Decrease Solubility of Raloxifene In Vitro and Its Systemic Exposure in Mice

PURPOSE

Green tea is a widely consumed beverage. A recent clinical study reported green tea decreased systemic exposure of raloxifene and its glucuronide metabolites by 34-43%. However, the underlying mechanism(s) remains unknown. This study investigated a change in raloxifene's solubility as the responsible mechanism.

METHODS

The effects of green tea extract, (-)-epigallocatechin gallate (EGCG), and (-)-epigallocatechin (EGC) on raloxifene's solubility were assessed in fasted state simulated intestinal fluids (FaSSIF) and fed state simulated intestinal fluids (FeSSIF). EGCG and EGC represent green tea's main bioactive constituents, flavan-3-gallate and flavan-3-ol catechins respectively, and the tested concentrations (mM) match the µg/mg of each compound in the extract. Our mouse study (n = 5/time point) evaluated the effect of green tea extract and EGCG on the systemic exposure of raloxifene.

RESULTS

EGCG (1 mM) and EGC (1.27 mM) decreased raloxifene's solubility in FaSSIF by 78% and 13%, respectively. Micelle size in FaSSIF increased with increasing EGCG concentrations (> 1000% at 1 mM), whereas EGC (1.27 mM) did not change micelle size. We observed 3.4-fold higher raloxifene solubility in FeSSIF compared to FaSSIF, and neither green tea extract nor EGCG significantly affected raloxifene solubility or micelle size in FeSSIF. The mice study showed that green tea extract significantly decreased raloxifene Cmax by 44%, whereas EGCG had no effect. Green tea extract and EGCG did not affect the AUC0-24 h of raloxifene or the metabolite-to-parent AUC ratio.

CONCLUSIONS

This study demonstrated flavan-3-gallate catechins may decrease solubility of poorly water-soluble drugs such as raloxifene, particularly in the fasted state.

Cholesterol-lowering activity of adzuki bean (Vigna angularis) polyphenols

BACKGROUND

Adzuki beans (ABs; Vigna angularis) were reported to show potential for prevention of cholesterol absorption and lowering of the blood cholesterol level. However, the main active compounds and some cellular effects remain unknown. In this study, we evaluated the potential cholesterol-lowering effects of (+)-catechin 7-O-β-D-glucopyranoside (C7G) and (+)-epicatechin 7-O-β-D-glucopyranoside (E7G), identified as abundant polyphenols in ABs.

METHODS AND RESULTS

To investigate the cholesterol-lowering activity in vitro, cholesterol micelles, bile acids, and Caco-2 cells as an intestinal model were used in the study. C7G and E7G each inhibited micellar solubility in a dose-dependent manner, and their inhibitory activity was as strong as that of (+)-catechin (IC₅₀ values: C7G, 0.23 ± 0.03 mg/ml; E7G, 0.22 ± 0.02 mg/ml; (+)-catechin, 0.26 ± 0.11 mg/ml). The AB polyphenols showed binding activity toward bile acids and changed them into an insoluble form. When Caco-2 cells were treated with C7G or E7G, the amount of incorporated cholesterol was significantly decreased compared with vehicle-treated control cells, and no cytotoxicity was observed under the experimental conditions used. Meanwhile, quantitative real-time PCR revealed that the mRNA level of the cholesterol transporter NPC1L1 remained unchanged in the treated cells.

CONCLUSIONS

Taken together, the present findings suggest that C7G and E7G are the main active compounds in ABs, and have the ability to inhibit micellar solubility, bind to bile acids, and suppress cholesterol absorption. The present study supports the health benefits of ABs as a medicinal food and the application of AB polyphenols as medicinal supplements to suppress cholesterol elevation.

The Influence of Polyphenols on Atherosclerosis Development

Polyphenols have attracted tremendous attention due to their pro-health properties, including their antioxidant, anti-inflammatory, antibacterial and neuroprotective activities. Atherosclerosis is a vascular disorder underlying several CVDs. One of the main risk factors causing atherosclerosis is the type and quality of food consumed. Therefore, polyphenols represent promising agents in the prevention and treatment of atherosclerosis, as demonstrated by in vitro, animal, preclinical and clinical studies. However, most polyphenols cannot be absorbed directly by the small intestine. Gut microbiota play a crucial role in converting dietary polyphenols into absorbable bioactive substances. An increasing understanding of the field has confirmed that specific GM taxa strains mediate the gut microbiota-atherosclerosis axis. The present study explores the anti-atherosclerotic properties and associated underlying mechanisms of polyphenols. Moreover, it provides a basis for better understanding the relationship between dietary polyphenols, gut microbiota, and cardiovascular benefits.

Impact of molecular interactions between hydrophilic phytosterol glycosyl derivatives and bile salts on the micellar solubility of cholesterol

Hydrophilic phytosterol glycosyl derivatives are synthetic phytosterol analogues by coupling with the glycosyl moiety to improve the water solubility and bioaccessibility of free phytosterols. The aim of this study is to clarify the molecular interaction of phytosterol glycosyl derivatives with bile salts and the consequent impact on cholesterol solubilization. Sharp nonlinear decrease in the micellar solubility of cholesterol and accompanying changes in particle size, zeta potential and microtopography of mixed micelles were observed when phytosterol glycosyl derivatives were introduced in cholesterol-loaded bile salt micelles. These results suggested that β-sitosterol glycosyl derivatives molecules indeed participated in the formation of mixed micelles. Further, nuclear magnetic resonance showed that the structural change of mixed micelles was caused by the insertion of β-sitosterol glycosyl derivatives via hydrogen bonds with sodium taurocholate, which resulted in the low cholesterol solubilization. Moreover, the hydrogen-bond interactions were apparently influenced by the glycosyl moiety of β-sitosterol glycosyl derivatives. These molecular mechanisms may contribute to the development of cholesterol-absorption inhibitors.

Interactions of (-)-epigallocatechin-3-gallate with model lipid membranes

(-)-Epigallocatechin-3-gallate (EGCG) is a flavonoid known for its good antioxidant potential and health benefits. It is one of the most intriguing flavonoids, especially because of its specific interactions with model lipid membranes. It was noticed that EGCG might form EGCG rich domains/rafts at certain compositions of lipid membranes. In this article, we investigate whether EGCG forms EGCG rich domains when incorporated in 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) liposomes. Our results show that EGCG decreases lipid ordering parameter in ordered membranes and increases it in the case of disordered ones. Also, incorporation of EGCG does not affect the zeta-potential and shape of the liposomes, but it can induce aggregation of liposomes. Our study also demonstrates that liposomes with incorporated EGCG are highly protected against UV-light induced oxidation.

Potential therapeutic effects of green tea on obese lipid profile - a systematic review

Background: Green tea, obtained from the plant Camellis sinensis, is one of the oldest drinks in the world and contains numerous bioactive compounds. Studies have demonstrated the efficacy of green tea in preventing obesity and cardiovascular diseases that may be related to the reduction of lipid levels. Aim: This study aimed to evidence, through a systematic review, the therapeutic potential of green tea on the lipid profile in preclinical studies in obese animals and clinical studies in obese individuals. Methods: This systematic review follows the recommendations of the preferred report items for systematic reviews and meta-analyses. The electronic databases, PubMed (Medline), Science Direct, Scopus, and Web of Science were consulted. Articles from January 2009 to December 2019 were selected. Results: This search resulted in twenty-nine articles were included cirtically reviewed. In experimental studies, green tea administration has been shown to reduce total cholesterol, triglycerides and low-density lipoprotein cholesterol in animals exposed to obesity-inducing diet. In humans' studies green tea was not shown to be effective for obese lipid control. Because supplementation with green tea extract reduced total cholesterol, triglycerides, low-density lipoprotein for three months at a specific dose. Conclusion: Therefore, green tea appears to act as a protective agent for dyslipidemia in obesity-induced animals. In human studies, green tea has not been shown to be effective in controlling obese lipids.

Green Tea from the Far East to the Drug Store: Focus on the Beneficial Cardiovascular Effects

Cardiovascular diseases (CVD) are the leading cause of death worldwide. Evidence from observational and randomized controlled studies showing the potential benefits of green tea on lowering CVD risk has been emerging rapidly during the past few decades. These benefits include reduced risk for major cardiovascular events, lowering of blood pressure, decreased LDL cholesterol levels and weight loss. At the same time, the understanding of the physiological mechanisms behind these alterations is advancing. Consumption of green tea originated from China thousands of years ago, but since then, it expanded all over the world. Recent advances in understanding the role of tea polyphenols, mainly catechins, as mediators of tea's health benefits, have caused the emergence of various types of green tea extracts (GTE) on the market. While taking green tea is generally considered safe, there are concerns about the safety of using tea extracts. The present article reviews the current evidence of green tea consumption leading to reduced CVD risk, its potential biological mechanisms and the safety of using GTE.

Structural changes of ethanolamine plasmalogen during intestinal absorption

Considerable attention has been paid to the absorption mechanisms of plasmalogen (Pls) because its intake has been expected to have preventive effects on brain-related diseases. Possible structural changes of Pls during absorption (i.e., preferential arachidonic acid re-esterification at the sn-2 position and base conversion of ethanolamine Pls (PE-Pls) into choline Pls (PC-Pls)) have previously been proposed. Since the physiological functions of Pls differ according to its structure, further elucidation of such structural changes during absorption is important to understand how Pls exerts its physiological effects in vivo. Hence, the absorption mechanism of Pls was investigated using the lymph-cannulation method and the everted jejunal sac model, with a focus on Pls molecular species. In the lymph-cannulation method, relatively high amounts of PE-Pls 18:0/20:4 and PC-Pls 18:0/20:4 were detected from the lymph even though these species were minor in the administered emulsion. Moreover, a significant increase of PE-Pls 18:0/20:4 and PC-Pls 18:0/20:4 in the intestinal mucosa was also confirmed by the everted jejunal sac model. Therefore, structural changes of PE-Pls in the intestinal mucosa were strongly suggested. The results of this study may provide an understanding of the relationship between intestinal absorption of Pls and exertion of its physiological functions in vivo.

In vitro lipid-lowering properties of the fruits of two bignay [Antidesma bunius (L.) Spreng] cultivars as affected by maturity stage and thermal processing

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Crude polyphenols from bignay fruit differing in maturity had varied bioactivities.

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Kalabaw cultivar had higher in vitro lipid-lowering activities than Common cultivar.

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Cholesterol-binding ability of bignay crude polyphenols was similar to the control.

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Thermal processing decreased lipase inhibitory activity of bignay crude polyphenols.

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Bignay fruits have huge potential as functional food in relation to dyslipidemia.

Bignay [Antidesma bunius (L). Spreng] fruit contains an array of polyphenols and information on how these bioactive compounds vary with cultivar type, maturity stage, and process treatment are unclear. Also, the effects of these variations on the lipid-lowering potential of this Philippine indigenous berry have not been reported. This study aimed to evaluate the lipid-lowering properties of the fruits of two bignay cultivars as affected by maturity stage and thermal processing. In vitro lipid-lowering assays revealed that both bignay cultivars had appreciable pancreatic lipase inhibitory activity, bile acid binding capacity, and cholesterol micellar solubility inhibition, which were comparable to those of the known lipid-lowering agents used as positive controls in this study. Freeze-dried samples of the freshly harvested fruits of both bignay cultivars [i.e., Common Cultivar (CC) and Kalabaw cultivar (KC)] had the highest bile acid binding activity (41.9–45.5% for CC and 43.4–54.0% for KC) for all the three maturity stages implying the beneficial effects of fresh bignay fruits related to lipid metabolism. Steam-blanched fruits had the highest pancreatic lipase inhibition activity (17.8–37.4% for CC and 29.2–39.0% for KC), regardless of maturity stage, while water-blanched samples exhibited the highest cholesterol micellar solubility inhibition (39.6–42.2% for CC and 40.2–47.6% for KC). Thermal processing tended to lower the lipid-lowering properties of the bignay fruits relative to their freeze-dried fresh fruits. Results of this study showed the potential of Philippine bignay fruit as a functional food that may be helpful in the management of dyslipidemia.

Mechanisms of Interactions between Bile Acids and Plant Compounds-A Review

Plant compounds are described to interact with bile acids during small intestinal digestion. This review will summarise mechanisms of interaction between bile acids and plant compounds, challenges in in vivo and in vitro analyses, and possible consequences on health. The main mechanisms of interaction assume that increased viscosity during digestion results in reduced micellar mobility of bile acids, or that bile acids and plant compounds are associated or complexed at the molecular level. Increasing viscosity during digestion due to specific dietary fibres is considered a central reason for bile acid retention. Furthermore, hydrophobic interactions are proposed to contribute to bile acid retention in the small intestine. Although frequently hypothesised, no mechanism of permanent binding of bile acids by dietary fibres or indigestible protein fractions has yet been demonstrated. Otherwise, various polyphenolic structures were recently associated with reduced micellar solubility and modification of steroid and bile acid excretion but underlying molecular mechanisms of interaction are not yet fully understood. Therefore, future research activities need to consider the complex composition and cell-wall structures as influenced by processing when investigating bile acid interactions. Furthermore, influences of bile acid interactions on gut microbiota need to be addressed to clarify their role in bile acid metabolism.

Cinnamomum burmannii (Nees & T. Nees) Blume and Eleutherine palmifolia (L.) Merr. extract combination ameliorate lipid profile and heart oxidative stress in hyperlipidemic mice

Background and Aim:

Hyperlipidemia is an important risk factor for cardiovascular disease. The use of statins has adverse side effects that result in oxidative stress disorders. The objective of this study was to investigate the antihyperlipidemic effect of a combination of Cinnamomum burmannii and Eleutherine palmifolia extract in high-fat diet (HFD)-induced hyperlipidemia mice.

Materials and Methods:

Mice were divided into eight groups (n=4): Control group or healthy mice (normal), HFD-induced hyperlipidemic mice without any treatment (CE0), HFD-induced hyperlipidemic mice treated with 3.6 mg/kg body weight (BW) atorvastatin (atorvastatin), and HFD-induced hyperlipidemic mice treated with a combination of C. burmannii and E. palmifolia in the following ratios: 300:0 (C300), 225:75 (C225), 150:150 (CE150), 75:225 (E225), and 0:300 (E300). Mice were fed a HFD for 4 months to induce hyperlipidemia. Total cholesterol, cholesterol oxidase-peroxidase aminophenazone (CHOD-PAP), triglyceride-glycerine, and fat serum were analyzed with colorimetric method. The measurement of superoxide dismutase was done with the xanthine oxidase method and malondialdehyde measurement was done with the thiobarbituric acid method.

Results:

Results showed an increase in antihyperlipidemic characteristics as the concentration of E. palmifolia extract (p<0.05) increased. Duncan’s multiple range test also showed an increase in anti-stress oxidation as the concentration of C. burmannii extract (p<0.05) increased.

Conclusion:

The E225 group showed the most potential as a safe, antihyperlipidemic agent characterized by improvement in lipid profile and antioxidant balance.

Pleiotropic effects of polyphenols on glucose and lipid metabolism: Focus on clinical trials

Epidemiological evidence from observational studies suggests that dietary polyphenols (PPs) - phytochemicals found in a variety of plant-based foods - can reduce the risk of developing type 2 diabetes mellitus (T2DM). Clinical trials have also indicated that PPs may help manage the two key features of T2DM, hyperglycemia and dyslipidemia. Since the incidence of T2DM is dramatically increasing worldwide, identifying food-based approaches that can reduce the risk of developing it and help manage its main risk factors in early-stage disease has clinical and socioeconomic relevance. After a brief overview of current epidemiological data on the incidence of T2DM in individuals consuming PP-rich diets, we review the evidence from clinical trials investigating PP-enriched foods and/or PP-based nutraceutical compounds, report their main results, and highlight the knowledge gaps that should be bridged to enhance our understanding of the role of PPs in T2DM development and management.

N-Oleoyl-Phosphatidyl-Ethanolamine and Epigallo Catechin-3-Gallate Mitigate Oxidative Stress in Overweight and Class I Obese People on a Low-Calorie Diet

Oxidative stress and lipid peroxidation are considered key factors linking obesity with its associated complications. Epigallo catechin-3-gallate (EGCG) and oleoylethanolamide, together with its phospholipid precursor N-oleoyl-phosphatidylethanolamine (NOPE), are nutritional compounds that might improve the oxidative stress status of obese people. Unfortunately, the bioavailability of these compounds is low; however, the coadministration of NOPE with EGCG has been shown to ameliorate both the plasma availability of EGCG and the intestinal levels of NOPE in rats. This double-blind placebo-controlled study investigated the effects of 2 months' supplementation with EGCG complexed with NOPE, combined with moderate energy restriction, on plasma oxidative status of overweight and class I obese subjects. A total of 138 subjects (body mass index: 25-35 kg/m²) were recruited and randomized into two groups: the first (n = 67) received caps of placebo and the second (n = 71) caps of an oily dispersion of EGCG complexed with NOPE for 2 months. Subjects' supplementation was combined with moderate energy restriction (-800 kcal/day). Plasma oxidative status was determined by measuring the levels of oxidized low-density lipoprotein (Ox-LDL), malondialdehyde and reactive oxygen metabolites, and by calculating the lag time and the slope of Cu-induced lipid peroxidation kinetics. In total 116 subjects (27 M/89 F) completed the supplementation period, 49 in the placebo group and 67 in the treated group. Treatment induced a similar significant weight reduction in the two groups. Moreover, we found the mean changes of Ox-LDL significantly lower and the mean changes of antioxidant capacity (lag time) significantly higher in NOPE-EGCG group than in placebo group (treatment effect mean difference: -3.15 UL, P < .044 and +5.37 min, P < .0347, respectively). EGCG plasma levels were detectable only after 2 months of NOPE-EGCG diet. The NOPE-EGCG integration to a low-energy diet seems, therefore, useful for ameliorating oxidative stress-related markers, which are concomitant causes of obesity-induced disorders.

Cinnamomum burmannii (Nees & T. Nees) Blume and Eleutherine palmifolia (L.) Merr. extract combination ameliorate lipid profile and heart oxidative stress in hyperlipidemic mice

Background and Aim: Hyperlipidemia is an important risk factor for cardiovascular disease. The use of statins has adverse side effects that result in oxidative stress disorders. The objective of this study was to investigate the antihyperlipidemic effect of a combination of Cinnamomum burmannii and Eleutherine palmifolia extract in high-fat diet (HFD)-induced hyperlipidemia mice. Materials and Methods: Mice were divided into eight groups (n=4): Control group or healthy mice (normal), HFD-induced hyperlipidemic mice without any treatment (CE0), HFD-induced hyperlipidemic mice treated with 3.6 mg/kg body weight (BW) atorvastatin (atorvastatin), and HFD-induced hyperlipidemic mice treated with a combination of C. burmannii and E. palmifolia in the following ratios: 300:0 (C300), 225:75 (C225), 150:150 (CE150), 75:225 (E225), and 0:300 (E300). Mice were fed a HFD for 4 months to induce hyperlipidemia. Total cholesterol, cholesterol oxidase-peroxidase aminophenazone (CHOD-PAP), triglyceride-glycerine, and fat serum were analyzed with colorimetric method. The measurement of superoxide dismutase was done with the xanthine oxidase method and malondialdehyde measurement was done with the thiobarbituric acid method. Results: Results showed an increase in antihyperlipidemic characteristics as the concentration of E. palmifolia extract (p<0.05) increased. Duncan's multiple range test also showed an increase in anti-stress oxidation as the concentration of C. burmannii extract (p<0.05) increased. Conclusion: The E225 group showed the most potential as a safe, antihyperlipidemic agent characterized by improvement in lipid profile and antioxidant balance.

Dietary Approaches to Stop Hypertension (DASH): potential mechanisms of action against risk factors of the metabolic syndrome

The metabolic syndrome is a cluster of disorders dominated by abdominal obesity, hypertriacylglycerolaemia, low HDL-cholesterol, high blood pressure and high fasting glucose. Diet modification is a safe and effective way to treat the metabolic syndrome. Dietary Approaches to Stop Hypertension (DASH) is a dietary pattern rich in fruits, vegetables and low-fat dairy products, and low in meats and sweets. DASH provides good amounts of fibre, K, Ca and Mg, and limited quantities of total fat, saturated fat, cholesterol and Na. Although DASH was initially designed for the prevention or control of hypertension, using a DASH diet has other metabolic benefits. In the present review, the effect of each dietary component of DASH on the risk factors of the metabolic syndrome is discussed. Due to limited fat and high fibre and Ca content, individuals on the DASH diet are less prone to overweight and obesity and possess lower concentrations of total and LDL-cholesterol although changes in TAG and HDL-cholesterol have been less significant and available evidence in this regard is still inconclusive. Moreover, high amounts of fruit and vegetables in DASH provide great quantities of K, Mg and fibre, all of which have been shown to reduce blood pressure. K, Mg, fibre and antioxidants have also been effective in correcting glucose and insulin abnormalities. Evidence is provided from cross-sectional investigations, cohort studies and randomised controlled trials, and, where available, from published meta-analyses. Mechanisms are described according to human studies and, in the case of a lack of evidence, from animal and cell culture investigations.

Molecular Mechanism by Which Tea Catechins Decrease the Micellar Solubility of Cholesterol

Tea polyphenols lower the levels of cholesterol in the blood by decreasing the cholesterol micellar solubility. To clarify this mechanism, the interactions between taurocholic acid and (-)-epigallocatechin gallate (EGCg) and its derivatives were investigated. ¹³C NMR studies revealed remarkable chemical-shift changes for the carbonyl carbon atom and the 1″- and 4″-positions in the galloyl moiety. Furthermore, ¹H NMR studies using (-)-EGCg derivatives showed that the number of hydroxyl groups on the B ring did not affect these interactions, whereas the carbonyl carbon atom and the aromatic ring of the galloyl moiety had remarkable effects. The configuration at the 2- and 3-positions of the catechin also influenced these interactions, with the trans-configuration resulting in stronger inhibition activity than the cis-configuration. Additionally, a 1:1 component ratio for the catechin-taurocholic acid complex was determined by electrospray ionization-mass spectrometry. These molecular mechanisms contribute to the development of cholesterol-absorption inhibitors.

Polyphenol Health Effects on Cardiovascular and Neurodegenerative Disorders: A Review and Meta-Analysis

Several studies have demonstrated that polyphenol-enriched diets may have beneficial effects against the development of degenerative diseases, including atherosclerosis and disorders affecting the central nervous system. This activity has been associated not only with antioxidant and anti-inflammatory properties, but also with additional mechanisms, such as the modulation of lipid metabolism and gut microbiota function. However, long-term studies on humans provided controversial results, making the prediction of polyphenol impact on health uncertain. The aim of this review is to provide an overview and critical analysis of the literature related to the effects of the principal dietary polyphenols on cardiovascular and neurodegenerative disorders. We critically considered and meta-analyzed randomized controlled clinical trials involving subjects taking polyphenol-based supplements. Although some polyphenols might improve specific markers of cardiovascular risk and cognitive status, many inconsistent data are present in literature. Therefore, definitive recommendations for the use of these compounds in the prevention of cardiovascular disease and cognitive decline are currently not applicable. Once pivotal aspects for the definition of polyphenol bioactivity, such as the characterization of pharmacokinetics and safety, are addressed, it will be possible to have a clear picture of the realistic potential of polyphenols for disease prevention.

Surface Plasmon Resonance for Measuring Interactions of Proteins with Lipids and Lipid Membranes

Surface plasmon resonance (SPR) is an established method for studying molecular interactions in real time. It allows obtaining qualitative and quantitative data on interactions of proteins with lipids or lipid membranes. In most of the approaches a lipid membrane or a membrane-mimetic surface is prepared on the surface of Biacore (GE Healthcare) sensor chips HPA or L1, and the studied protein is then injected across the surface. Here we provide an overview of SPR in protein-lipid and protein-membrane interactions, different approaches described in the literature and a general protocol for conducting an SPR experiment including lipid membranes, together with some experimental considerations.

Egg White Hydrolysate Can Be a Low-Allergenic Food Material to Suppress Ectopic Fat Accumulation in Rats Fed an Equicaloric Diet

Egg white (EW) is known as a nutritional protein but can induce allergic reactions in humans. We investigated the dietary effects of EW and its hydrolysate (EWH), which contains less allergen, on body fat accumulation in Wistar rats fed an equicaloric high-fat and high-sucrose diet for 8 wk (Exp A). The pair-feeding of EW and equicaloric-feeding of EWH increased fecal fat excretion and suppressed lipid accumulation in the liver and muscles but not in the abdominal adipose tissues, carcass, or total body. Dietary EWH also suppressed the serum glucose level and alkaline phosphatase activity. Further, we showed a higher dispersibility of EW and EWH in physicochemical assay (Exp B). Next, we investigated the suppressive effects of a single administration of EW and EWH on lipid-induced hypertriglyceridemia and small intestinal meal transit in ddY mice (Exp C). However, a single administration of EW or EWH did not suppress the lipid-induced hypertriglyceridemia nor did it delay the rate of small intestinal transit. These findings indicated that dietary EW and EWH reduce hepatic and muscular (ectopic) fat accumulation mainly by suppressing fat absorption and supplying fat to the liver and muscles. Therefore, the low-allergenic EWH can be effective for the prevention of high-fat-diet-induced obesity.

Theaflavin-3-gallate specifically interacts with phosphatidylcholine, forming a precipitate resistant against the detergent action of bile salt

Black tea is a highly popular beverage, and its pigments, polymerized catechins such as theaflavins (TFs), are attracting attention due to their beneficial health effects. In this study, to test the inhibitory activities of TFs on the intestinal absorption of cholesterol, we investigated their effects on phosphatidylcholine (PC) vesicles in the absence or presence of a bile salt. (−)-Epicatechin gallate, (−)-epigallocatechin gallate, and TFs formed insoluble complexes with PC vesicles. Galloylated TFs such as TF2A, TF2B, and TF3 precipitated far more than other polyphenols. The subsequent addition of taurocholate redispersed the polyphenol-PC complexes, except that a large amount of TF2A remained insoluble. After incubation with taurocholate-PC micelles, TF2A elevated the turbidity of the micelle solution, providing red sediments. The TF2A-specific effect was dependent on the PC concentration. These results suggest that TF2A interacts with PC and aggregates in a specific manner different from catechins and other TFs.

Randomized controlled trial of the effects of consumption of 'Yabukita' or 'Benifuuki' encapsulated tea-powder on low-density lipoprotein cholesterol level and body weight

Background: Previous studies have reported controversial results for the association between green tea consumption and low-density lipoprotein (LDL)-cholesterol and body weight. Objective: The objective of this trial was to determine the effects of two kinds of green tea on LDL-cholesterol and body weight. Methods: We randomly assigned 151 participants (98 men, 53 women) aged 30-70 years into three groups: Yabukita green tea group, Benifuuki green tea group, or placebo group. Participants consumed 1.8 g/day of green tea extract powder or placebo for 12 weeks. The primary outcomes were LDL-cholesterol level and body weight, and the secondary outcomes were risk factors for cardiovascular disease. Results: Both Yabukita and Benifuuki green tea significantly lowered LDL-cholesterol. The magnitudes of the lipid-lowering effect of both types of tea were significantly larger than that of placebo. No differences with respect to changes in LDL-cholesterol were observed between the Yabukita and Benifuuki green tea groups. Neither Yabukita nor Benifuuki green tea had any effect on body weight and no difference was observed among groups regarding changes in body weight. Conclusion: Both Yabukita and Benifuuki green tea lowered LDL-cholesterol, and the lipid-lowering effects of these two green teas were not different. Neither tea lowered body weight.

Wheat alkylresorcinols reduce micellar solubility of cholesterol in vitro and increase cholesterol excretion in mice

Epidemiological studies have shown that the consumption of whole grains can reduce risk for metabolic disorders. We recently showed that chronic supplementation with wheat alkylresorcinols (ARs) prevents glucose intolerance and insulin resistance with hepatic lipid accumulation induced in mice by a high-fat high-sucrose diet (HFHSD). This study examines the effects of ARs on the micellar solubility of cholesterol in vitro, as well as the effects of transient AR supplementation on faecal lipid excretion and plasma lipid levels in mice. We found that ARs formed bile micelles with taurocholate independently of phospholipids, and dose-dependently decreased the micellar solubility of cholesterol in a biliary micelle model. Transient AR supplementation with HFHSD increased faecal cholesterol and triglyceride contents and decreased plasma cholesterol concentrations. These suggest that one underlying mechanism through which ARs suppress diet-induced obesity is by interfering with the micellar cholesterol solubilisation in the digestive tract, which subsequently decreases cholesterol absorption.

The Powdering Process with a Set of Ceramic Mills for Green Tea Promoted Catechin Extraction and the ROS Inhibition Effect

For serving green tea, there are two prominent methods: steeping the leaf or the powdered leaf (matcha style) in hot water. The purpose of the present study was to reveal chemical and functional differences before and after the powdering process of green tea leaf, since powdered green tea may contribute to expanding the functionality because of the different ingesting style. In this study, we revealed that the powdering process with a ceramic mill and stirring in hot water increased the average extracted concentration of epigallocatechin gallate (EGCG) by more than three times compared with that in leaf tea using high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass Spectrometry (LC-MS/MS) analyses. Moreover, powdered green tea has a higher inhibition effect of reactive oxygen species (ROS) production in vitro compared with the same amount of leaf tea. Our data suggest that powdered green tea might have a different function from leaf tea due to the higher catechin contents and particles.

Interaction between Tea Polyphenols and Bile Acid Inhibits Micellar Cholesterol Solubility

The molecular mechanism by which tea polyphenols decrease the micellar solubility of cholesterol is not completely clear. To clarify this mechanism, this study investigated the interaction between tea polyphenols (catechins and oolongtheanins) and cholesterol micelles. A nuclear magnetic resonance (NMR) study was performed on a micellar solution containing taurocholic acid and epigallocatechin gallate (EGCg), and high-performance liquid chromatography (HPLC) analysis was carried out on the precipitate and the supernatant that formed when EGCg was added to a cholesterol-micelle solution. The data indicated a regiospecific interaction of EGCg with taurocholic acid. Therefore, the ability of EGCg to lower the solubility of phosphatidylcholine (PC) and cholesterol in micellar solutions can be attributed to their elimination from the micelles due to interaction between taurocholic acids and EGCg.

Green tea beverages enriched with catechins with a galloyl moiety reduce body fat in moderately obese adults: a randomized double-blind placebo-controlled trial

We investigated the effects of ingesting a green tea beverage enriched with catechins with a galloyl moiety during a meal on body fat reduction in moderately obese adults.

A study on the inhibitory mechanism for cholesterol absorption by α-cyclodextrin administration

Background: Micelle formation of cholesterol with lecithin and bile salts is a key process for intestinal absorption of lipids. Some dietary fibers commonly used to reduce the lipid content in the body are thought to inhibit lipid absorption by binding to bile salts and decreasing the lipid solubility. Amongst these, α-cyclodextrin (α-CD) is reportedly one of the most powerful dietary fibers for decreasing blood cholesterol. However, it is difficult to believe that α-CD directly removes cholesterol because it has a very low affinity for cholesterol and its mechanism of action is less well understood than those of other dietary fibers. To identify this mechanism, we investigated the interaction of α-CD with lecithin and bile salts, which are essential components for the dissolution of cholesterol in the small intestine, and the effect of α-CD on micellar solubility of cholesterol.

Results: α-CD was added to Fed-State Simulated Intestinal Fluid (FeSSIF), and precipitation of a white solid was observed. Analytical data showed that the precipitate was a lecithin and α-CD complex with a molar ratio of 1:4 or 1:5. The micellar solubility of cholesterol in the mixture of FeSSIF and α-CD was investigated, and found to decrease through lecithin precipitation caused by the addition of α-CD, in a dose-dependent manner. Furthermore, each of several other water-soluble dietary fibers was added to the FeSSIF, and no precipitate was generated.

Conclusion: This study suggests that α-CD decreases the micellar solubility of cholesterol in the lumen of the small intestine via the precipitation of lecithin from bile salt micelles by complex formation with α-CD. It further indicates that the lecithin precipitation effect on the bile salt micelles by α-CD addition clearly differs from addition of other water-soluble dietary fibers. The decrease in micellar cholesterol solubility in the FeSSIF was the strongest with α-CD addition.

Inhibiting epigenetic enzymes to improve atherogenic macrophage functions

Macrophages determine the outcome of atherosclerosis by propagating inflammatory responses, foam cell formation and eventually necrotic core development. Yet, the pathways that regulate their atherogenic functions remain ill-defined. It is now apparent that chromatin remodeling chromatin modifying enzymes (CME) governs immune responses but it remains unclear to what extent they control atherogenic macrophage functions. We hypothesized that epigenetic mechanisms regulate atherogenic macrophage functions, thereby determining the outcome of atherosclerosis. Therefore, we designed a quantitative semi-high-throughput screening platform and studied whether the inhibition of CME can be applied to improve atherogenic macrophage activities. We found that broad spectrum inhibition of histone deacetylases (HDACs) and histone methyltransferases (HMT) has both pro- and anti-inflammatory effects. The inhibition of HDACs increased histone acetylation and gene expression of the cholesterol efflux regulators ATP-binding cassette transporters ABCA1 and ABCG1, but left foam cell formation unaffected. HDAC inhibition altered macrophage metabolism towards enhanced glycolysis and oxidative phosphorylation and resulted in protection against apoptosis. Finally, we applied inhibitors against specific HDACs and found that HDAC3 inhibition phenocopies the atheroprotective effects of pan-HDAC inhibitors. Based on our data, we propose the inhibition of HDACs, and in particular HDAC3, in macrophages as a novel potential target to treat atherosclerosis.

Atheroprotective effects of (poly)phenols: a focus on cell cholesterol metabolism

Collated observations from several epidemiological studies have demonstrated that dietary intake of (poly)phenols from nuts, coffee, cocoa, grapes, and berries may protect against the development of atherosclerosis. Whereas this beneficial activity has previously been linked mainly to antioxidant or anti-inflammatory properties, recently emerging data suggest mechanisms by which (poly)phenolic substances can modulate cellular lipid metabolism, thereby mitigating atherosclerotic plaque formation. In this review, both experimental studies and clinical trials investigating the atheroprotective effects of the most relevant dietary (poly)phenols are critically discussed.