Apple procyanidins decrease cholesterol esterification and lipoprotein secretion in Caco-2/TC7 enterocytes

Chronic consumption of probiotics, oats, and apples has differential effects on postprandial bile acid profile and cardiometabolic disease risk markers compared with an isocaloric control (cornflakes): a randomized trial

BACKGROUND

Dietary components that impact the gut microbiota may beneficially affect cardiometabolic health, possibly by altered bile acid metabolism. However, impacts of these foods on postprandial bile acids, gut microbiota, and cardiometabolic risk markers are unclear.

OBJECTIVES

The aim of this study was to determine the chronic effects of probiotics, oats, and apples on postprandial bile acids, gut microbiota, and cardiometabolic health biomarkers.

METHODS

Using an acute within chronic parallel design, 61 volunteers (mean ± SD: age 52 ± 12 y; BMI 24.8 ± 3.4 kg/m²) were randomly assigned to consume 40 g cornflakes (control), 40 g oats or 2 Renetta Canada apples each with 2 placebo capsules per day or 40 g cornflakes with 2 Lactobacillus reuteri capsules (>5 × 10⁹ CFU) per day, for 8 wk. Fasting and postprandial serum/plasma bile acids and cardiometabolic health biomarkers, fecal bile acids, and gut microbiota composition were determined.

RESULTS

At week 0, oats and apples significantly decreased postprandial serum insulin [area under the curve (AUC): 25.6 (17.4, 33.8) and 23.4 (15.4, 31.4) vs. 42.0 (33.7, 50.2) pmol/L × min and incremental AUC (iAUC): 17.8 (11.6, 24.0) and 13.7 (7.7, 19.8) vs. 29.6 (23.3, 35.8) pmol/L × min] and C-peptide responses [AUC: 599 (514, 684) and 550 (467, 632) vs. 750 (665, 835) ng/mL × min], whereas non-esterified fatty acids were increased [AUC 135 (117, 153) vs. 86.3 (67.9, 105) and iAUC 96.2 (78.8, 114) vs. 60 (42.1, 77.9) mmol/L × min] after the apples vs. control (P ≤ 0.05). Postprandial unconjugated [AUC: predicted means (95% CI) 1469 (1101, 1837) vs. 363 (-28, 754) μmol/L × min and iAUC: 923 (682, 1165) vs. 22.0 (-235, 279) μmol/L × min)] and hydrophobic [iAUC: 1210 (911, 1510) vs. 487 (168, 806) μmol/L × min] bile acid responses were increased after 8 wk probiotic intervention vs. control (P ≤ 0.049). None of the interventions modulated the gut microbiota.

CONCLUSIONS

These results support beneficial effects of apples and oats on postprandial glycemia and the ability of the probiotic Lactobacillus reuteri to modulate postprandial plasma bile acid profiles compared with control (cornflakes), with no relationship evident between circulating bile acids and cardiometabolic health biomarkers.

Dietary Intake of Hydrolyzable Tannins and Condensed Tannins to Regulate Lipid Metabolism

Lipid metabolism disorder is a multifactor issue, which contributes to several serious health consequences, such as obesity, hyperlipidemia, atherosclerosis diabetes, non-alcoholic fatty liver etc. Tannins, applied as natural derived plant, are commonly used in the study of lipid metabolism disease with excellent safety and effectiveness, while producing less toxic and side effects. Meanwhile, recognition of the significance of dietary tannins in lipid metabolism disease prevention has increased. As suggested by existing evidence, dietary tannins can reduce lipid accumulation, block adipocyte differentiation, enhance antioxidant capacity, increase the content of short-chain fatty acids, and lower blood lipid levels, thus alleviating lipid metabolism disorder. This study is purposed to sum up and analyze plenty of documents on tannins, so as to provide the information required to assess the lipid metabolism of tannins.

Proanthocyanidins and Where to Find Them: A Meta-Analytic Approach to Investigate Their Chemistry, Biosynthesis, Distribution, and Effect on Human Health

Proanthocyanidins (PACs) are a class of polyphenolic compounds that are attracting considerable interest in the nutraceutical field due to their potential health benefits. However, knowledge about the chemistry, biosynthesis, and distribution of PACs is limited. This review summarizes the main chemical characteristics and biosynthetic pathways and the main analytical methods aimed at their identification and quantification in raw plant matrices. Furthermore, meta-analytic approaches were used to identify the main plant sources in which PACs were contained and to investigate their potential effect on human health. In particular, a cluster analysis identified PACs in 35 different plant families and 60 different plant parts normally consumed in the human diet. On the other hand, a literature search, coupled with forest plot analyses, highlighted how PACs can be actively involved in both local and systemic effects. Finally, the potential mechanisms of action through which PACs may impact human health were investigated, focusing on their systemic hypoglycemic and lipid-lowering effects and their local anti-inflammatory actions on the intestinal epithelium. Overall, this review may be considered a complete report in which chemical, biosynthetic, ecological, and pharmacological aspects of PACs are discussed.

The Structure of Relationships between the Human Exposome and Cardiometabolic Health: The Million Veteran Program

The exposome represents the array of dietary, lifestyle, and demographic factors to which an individual is exposed. Individual components of the exposome, or groups of components, are recognized as influencing many aspects of human physiology, including cardiometabolic health. However, the influence of the whole exposome on health outcomes is poorly understood and may differ substantially from the sum of its individual components. As such, studies of the complete exposome are more biologically representative than fragmented models based on subsets of factors. This study aimed to model the system of relationships underlying the way in which the diet, lifestyle, and demographic components of the overall exposome shapes the cardiometabolic risk profile. The current study included 36,496 US Veterans enrolled in the VA Million Veteran Program (MVP) who had complete assessments of their diet, lifestyle, demography, and markers of cardiometabolic health, including serum lipids, blood pressure, and glycemic control. The cohort was randomly divided into training and validation datasets. In the training dataset, we conducted two separate exploratory factor analyses (EFA) to identify common factors among exposures (diet, demographics, and physical activity) and laboratory measures (lipids, blood pressure, and glycemic control), respectively. In the validation dataset, we used multiple normal regression to examine the combined effects of exposure factors on the clinical factors representing cardiometabolic health. The mean ± SD age of participants was 62.4 ± 13.4 years for both the training and validation datasets. The EFA revealed 19 Exposure Common Factors and 5 Physiology Common Factors that explained the observed (measured) data. Multivariate regression in the validation dataset revealed the structure of associations between the Exposure Common Factors and the Physiology Common Factors. For example, we found that the factor for fruit consumption was inversely associated with the factor summarizing total cholesterol and low-density lipoprotein cholesterol (LDLC, p = 0.008), and the latent construct describing light levels of physical activity was inversely associated with the blood pressure latent construct (p < 0.0001). We also found that a factor summarizing that participants who frequently consume whole milk are less likely to frequently consume skim milk, was positively associated with the latent constructs representing total cholesterol and LDLC as well as systolic and diastolic blood pressure (p = 0.0006 and <0.0001, respectively). Multiple multivariable-adjusted regression analyses of exposome factors allowed us to model the influence of the exposome as a whole. In this metadata-rich, prospective cohort of US Veterans, there was evidence of structural relationships between diet, lifestyle, and demographic exposures and subsequent markers of cardiometabolic health. This methodology could be applied to answer a variety of research questions about human health exposures that utilize electronic health record data and can accommodate continuous, ordinal, and binary data derived from questionnaires. Further work to explore the potential utility of including genetic risk scores and time-varying covariates is warranted.

Polyphenol-Rich Black Elderberry Extract Stimulates Transintestinal Cholesterol Excretion

Hypercholesterolemia is the primary risk factor for cardiovascular disease (CVD). Recent studies reported that the stimulation of transintestinal cholesterol excretion (TICE), a nonbiliary cholesterol excretion, can be a strategy for preventing CVD. Black elderberry (Sambucus nigra) has been reported to reduce the risk of CVD via its antioxidant, anti-inflammatory, and hypocholesterolemic effects. However, little is known about the role of black elderberry in intestinal cholesterol metabolism despite its well-known effects on cholesterol homeostasis regulation. To investigate the effects of polyphenol-rich black elderberry extract (BEE) on intestinal cholesterol metabolism, we measured the expression of genes involved in cholesterol biosynthesis and flux in Caco-2 cells. BEE significantly decreased the messenger RNA (mRNA) and protein levels of genes for cholesterol absorption, such as Niemann–Pick C1 Like 1 and ATP-binding cassette transporter A1 (ABCA1). In contrast, there was marked induction of low-density lipoprotein receptor, ABCG5/G8, and ABCB1 in BEE-treated Caco-2 cells. Furthermore, BEE decreased the expression of genes for lipogenesis and altered the mRNA levels of sirtuins. All of the genes altered by BEE were in the direction of flux cholesterol from the basolateral to apical side of enterocytes, indicating stimulation of TICE. These results support the hypocholesterolemic effects of BEE for the prevention of CVD.

Efficacy of Polyphenols in the Management of Dyslipidemia: A Focus on Clinical Studies

Polyphenols (PLPs), phytochemicals found in a wide range of plant-based foods, have gained extensive attention in view of their antioxidant, anti-inflammatory, immunomodulatory and several additional beneficial activities. The health-promoting effects noted in animal models of various non-communicable diseases explain the growing interest in these molecules. In particular, in vitro and animal studies reported an attenuation of lipid disorders in response to PLPs. However, despite promising preclinical investigations, the effectiveness of PLPs in human dyslipidemia (DLP) is less clear and necessitates revision of available literature. Therefore, the present review analyzes the role of PLPs in managing clinical DLP, notably by dissecting their potential in ameliorating lipid/lipoprotein metabolism and alleviating hyperlipidemia, both postprandially and in long-term interventions. To this end, PubMed was used for article search. The search terms included polyphenols, lipids, triglycerides, cholesterol, LDL-cholesterol and /or HDL-cholesterol. The critical examination of the trials published to date illustrates certain benefits on blood lipids along with co-morbidities in participant’s health status. However, inconsistent results document significant research gaps, potentially owing to study heterogeneity and lack of rigor in establishing PLP bioavailability during supplementation. This underlines the need for further efforts in order to elucidate and support a potential role of PLPs in fighting DLP.

Malus domestica: A Review on Nutritional Features, Chemical Composition, Traditional and Medicinal Value

Fruit-derived bioactive substances have been spotlighted as a regulator against various diseases due to their fewer side effects compared to chemical drugs. Among the most frequently consumed fruits, apple is a rich source of nutritional molecules and contains high levels of bioactive compounds. The main structural classes of apple constituents include polyphenols, polysaccharides (pectin), phytosterols, and pentacyclic triterpenes. Also, vitamins and trace elements complete the nutritional features of apple fruit. There is now considerable scientific evidence that these bioactive substances present in apple and peel have the potential to improve human health, for example contributing to preventing cardiovascular disease, diabetes, inflammation, and cancer. This review will focus on the current knowledge of bioactive substances in apple and their medicinal value for human health.

Ezetimibe impairs transcellular lipid trafficking and induces large lipid droplet formation in intestinal absorptive epithelial cells

Ezetimibe inhibits Niemann-Pick C1-like 1 (NPC1L1) protein, which mediates intracellular cholesterol trafficking from the brush border membrane to the endoplasmic reticulum, where chylomicron assembly takes place in enterocytes or in the intestinal absorptive epithelial cells. Cholesterol is a minor lipid constituent of chylomicrons; however, whether or not a shortage of cholesterol attenuates chylomicron assembly is unknown. The aim of this study was to examine the effect of ezetimibe, a potent NPC1L1 inhibitor, on trans-epithelial lipid transport, and chylomicron assembly and secretion in enterocytes. Caco-2 cells, an absorptive epithelial model, grown onto culture inserts were given lipid micelles from the apical side, and chylomicron-like triacylglycerol-rich lipoprotein secreted basolaterally were analyzed after a 24-h incubation period in the presence of ezetimibe up to 50 μM. The secretion of lipoprotein and apolipoprotein B48 were reduced by adding ezetimibe (30% and 34%, respectively). Although ezetimibe allowed the cells to take up cholesterol normally, the esterification was abolished. Meanwhile, oleic acid esterification was unaffected. Moreover, ezetimibe activated sterol regulatory element-binding protein 2 by approximately 1.5-fold. These results suggest that ezetimibe limited cellular cholesterol mobilization required for lipoprotein assembly. In such conditions, large lipid droplet formation in Caco-2 cells and the enterocytes of mice were induced, implying that unprocessed triacylglycerol was sheltered in these compartments. Although ezetimibe did not reduce the post-prandial lipid surge appreciably in triolein-infused mice, the results of the present study indicated that pharmacological actions of ezetimibe may participate in a novel regulatory mechanism for the efficient chylomicron assembly and secretion.

The Impact of Dietary Supplementation of Whole Foods and Polyphenols on Atherosclerosis

The purpose of this review is to highlight current research on the benefits of supplementation with foods with a diverse polyphenol composition, including fruits, vegetables, nuts, grains, oils, spices, and teas in blunting atherosclerosis. We searched PubMed for publications utilizing whole food or polyphenols prepared from whole foods in Apolipoprotein E (ApoE) or Low-Density Lipoprotein Receptor (LDLR) knockout mice, and identified 73 studies in which plaque was measured. The majority of the studies reported a reduction in plaque. Nine interventions showed no effect, while three using Agaricus blazei mushroom, HYJA-ri-4 rice variety, and safrole-2', 3'-oxide (SFO) increased plaque. The mechanisms by which atherosclerosis was reduced include improved lipid profile, antioxidant status, and cholesterol clearance, and reduced inflammation. Importantly, not all dietary interventions that reduce plaque showed an improvement in lipid profile. Additionally, we found that, out of 73 studies, only 9 used female mice and only 6 compared both sexes. Only one study compared the two models (LDLR vs. ApoE), showing that the treatment worked in one but not the other. Not all supplementations work in both male and female animals, suggesting that increasing the variety of foods with different polyphenol compositions may be more effective in mitigating atherosclerosis.

Trehalose itself plays a critical role on lipid metabolism: Trehalose increases jejunum cytoplasmic lipid droplets which negatively correlated with mesenteric adipocyte size in both HFD-fed trehalase KO and WT mice

Background

Trehalose is a functional disaccharide that has anti-metabolic activities such as suppression of adipocyte hypertrophy in mice and alleviation of impaired glucose tolerance in humans. Trehalase hydrolyzes trehalose in the small intestine into two glucose molecules. In this study, we investigated whether trehalose can suppress adipocyte hypertrophy in mice in the presence or absence of trehalase.

Methods

Trehalase knockout (KO) mice and wild-type (WT) mice were fed a high fat diet (HFD) and administered water with 0.3% (w/v) or without trehalose for 8 weeks. At the end of the experimental period, mesenteric adipose tissues and the small intestine were collected and the adipocyte size and proportion of cytoplasmic lipid droplets (CLDs, %) in jejunum epithelium were measured by image analysis.

Results

Trehalose treatment was associated with suppressed adipocyte hypertrophy in both trehalase KO and WT mice. The rate of CLDs in the jejunal epithelium was increased in both trehalase KO and WT mice given water containing trehalose relative to untreated control mice. There was a negative correlation between jejunal epithelial lipid droplet volume and mesenteric adipocyte size. Chylomicron-TG tended to be decreased in both trehalose-treated trehalase KO and WT mice. Addition of trehalose to differentiated Caco-2 cells in vitro increased intracytoplasmic lipid droplets and decreased secretion of the chylomicron marker ApoB-48. Moreover, the jejunal epithelium containing lipid droplets falled into the intestinal lumen, and triglyceride (TG) levels in feces tended to be higher in the KO/HFD/Tre group than in the KO/HFD/Water group. Since then, the accumulation of CLDs has been reported to suppress CM secretion, and along with our results, the effect of trehalose to increase jejunum CLDs may induce adipocyte hypertrophy.

Conclusions

The suppression of adipocyte hypertrophy in the presence and absence of trehalase indicates that trehalose mediates effects prior to being hydrolyzed into glucose. In both trehalase KO and WT mice, trehalose treatment increased the rate of CLDs in jejunal epithelium, reduced chylomicron migration from the intestinal epithelium to the periphery, and suppressed adipocyte hypertrophy. Thus, trehalose ingestion could prevent metabolic syndrome by trapping fat droplets in the intestinal epithelium and suppressing rapid increases in chylomicrons.

Acute whole apple consumption did not influence postprandial lipaemia: a randomised crossover trial

Whole apples are a source of pectin and polyphenols, both of which show potential to modulate postprandial lipaemia (PPL). The present study aimed to explore the effects of whole apple consumption on PPL, as a risk factor for CVD, in generally healthy but overweight and obese adults. A randomised, crossover acute meal trial was conducted with seventeen women and nine men (mean BMI of 34·1 (sem0·2) kg/m2). Blood samples were collected for 6 h after participants consumed an oral fat tolerance test meal that provided 1 g fat/kg body weight and 1500 mg acetaminophen per meal for estimating gastric emptying, with and without three whole raw Gala apples (approximately 200 g). Plasma TAG (with peak postprandial concentration as the primary outcome), apoB48, chylomicron-rich fraction particle size and fatty acid composition, glucose, insulin and acetaminophen were analysed. Differences between with and without apples were identified by ANCOVA. Apple consumption did not alter postprandial TAG response, chylomicron properties, glucose or acetaminophen (P> 0·05), but did lead to a higher apoB48 peak concentration and exaggerated insulin between 20 and 180 min (P< 0·05). Overall, as a complex food matrix, apples did not modulate postprandial TAG when consumed with a high-fat meal in overweight and obese adults, but did stimulate insulin secretion, potentially contributing to an increased TAG-rich lipoprotein production.

Characterization of the direct interaction between apple condensed tannins and cholesterol in vitro

To provide the scientific evidences for a possible new hypocholesterolemic mechanism of apple condensed tannins (ACT), the direct interaction of ACT with cholesterol (CH) was investigated in the present study. Our results suggested that the quenching of ACT fluorescence by CH was carried out according to a static mechanism, while the interaction between ACT and CH in vitro was a spontaneous process. ACT were capable of binding with CH directly, and the CH-binding capacity (35.9-43.9%) of ACT remarkably enhanced with the increase of ACT concentration (0.5-2.0 mg proanthocyanidin B₂ equivalent/mL). Besides, spectroscopic methods and morphological analysis were used to characterize the ACT-CH coprecipitates, the findings indicated that ACT were able to precipitate CH via ionic interactions, hydrophobic interactions and intermolecular hydrogen bonds rather than covalent bonds. In conclusion, the direct interaction of ACT with CH might play a role in their CH-lowering effects in humans and animals.

SAR1B GTPase is necessary to protect intestinal cells from disorders of lipid homeostasis, oxidative stress, and inflammation

Genetic defects in SAR1B GTPase inhibit chylomicron (CM) trafficking to the Golgi and result in a huge intraenterocyte lipid accumulation with a failure to release CMs and liposoluble vitamins into the blood circulation. The central aim of this study is to test the hypothesis that SAR1B deletion (SAR1B^−/−) disturbs enterocyte lipid homeostasis (e.g., FA β-oxidation and lipogenesis) while promoting oxidative stress and inflammation. Another issue is to compare the impact of SAR1B^−/− to that of its paralogue SAR1A^−/− and combined SAR1A^−/−/B^−/−. To address these critical issues, we have generated Caco-2/15 cells with a knockout of SAR1A, SAR1B, or SAR1A/B genes. SAR1B^−/− results in lipid homeostasis disruption, reflected by enhanced mitochondrial FA β-oxidation and diminished lipogenesis in intestinal absorptive cells via the implication of PPARα and PGC1α transcription factors. Additionally, SAR1B^−/−cells, which mimicked enterocytes of CM retention disease, spontaneously disclosed inflammatory and oxidative characteristics via the implication of NF-κB and NRF2. In most conditions, SAR1A^−/− cells showed a similar trend, albeit less dramatic, but synergetic effects were observed with the combined defects of the two SAR1 paralogues. In conclusion, SAR1B and its paralogue are needed not only for CM trafficking but also for lipid homeostasis, prooxidant/antioxidant balance, and protection against inflammatory processes.

Effect of Nutrient and Micronutrient Intake on Chylomicron Production and Postprandial Lipemia

Postprandial lipemia, which is one of the main characteristics of the atherogenic dyslipidemia with fasting plasma hypertriglyceridemia, low high-density lipoprotein cholesterol and an increase of small and dense low-density lipoproteins is now considered a causal risk factor for atherosclerotic cardiovascular disease and all-cause mortality. Postprandial lipemia, which is mainly related to the increase in chylomicron production, is frequently elevated in individuals at high cardiovascular risk such as obese or overweight patients, type 2 diabetic patients and subjects with a metabolic syndrome who share an insulin resistant state. It is now well known that chylomicron production and thus postprandial lipemia is highly regulated by many factors such as endogenous factors: circulating factors such as hormones or free fatty acids, genetic variants, circadian rhythms, or exogenous factors: food components, dietary supplements and prescription drugs. In this review, we focused on the effect of nutrients, micronutrients and phytochemicals but also on food structure on chylomicron production and postprandial lipemia.

Proanthocyanidins of Natural Origin: Molecular Mechanisms and Implications for Lipid Disorder and Aging-Associated Diseases

Proanthocyanidins are phytonutrients formed by oligomerization or polymerization of subunits catechin, epicatechin, and their gallic acid esters. Proanthocyanidins are a component of many plants and thus form an integral part of the human diet. Oligomeric proanthocyanidins are currently marketed as medicinal products that target vascular disorders and chronic pathological conditions, many of which are age-associated. Proanthocyanidins are also characterized by their effects on energy homeostasis. Not dissimilar to their chemically synthesized counterparts, naturally extracted proanthocyanidins act via inhibition of lipases, stimulation of energy expenditure, or suppression of appetite. Here we review the current knowledge-base and highlight challenges and future impacts regarding involvement of proanthocyanidins in global lipid metabolism, with a focus on the molecular mechanisms and pathological conditions that progress with aging.

Screening of ordinary commercial varieties of apple fruits under different storage conditions for their potential vascular and metabolic protective properties

Epidemiological studies reported that apple consumption is associated with a decrease of cardiovascular and metabolic dysfunction, probably due to the polyphenols and fibers present in this fruit. The storage conditions and genetic origin of apples have been reported to influence their content and, as a consequence, their pharmacological properties. The present study evaluated the influence of varieties and storage conditions of traditional and highly appreciated apples including Gala, Golden Delicious, Granny Smith and Pink Lady varieties after harvest and storage under classic cold conditions, under a controlled atmosphere, or under extreme ultra-low oxygen conditions. Thus, a multi-parametric screening on cell models associated with vascular and metabolic dysfunctions - such as endothelial and smooth muscle cells, hepatocytes, adipocytes and macrophages - in relation to the apple polyphenol content has been developed. This strategy demonstrated that, overall, peeled apple samples exhibited a vascular tropism and acted mainly on proliferation and oxidative stress in endothelial and smooth muscle cells. Apple extracts appeared to be less effective on adipocytes and macrophages, but they exhibited antioxidant properties in hepatocytes. Among the varieties, Gala and Golden Delicious were the most efficient against the processes involved in the development of atherosclerosis. Concerning storage conditions, most of the apple varieties were more efficient under harvest conditions, while they could not be discriminated under all other cold conditions and the concentration used, except for the Gala samples. Interestingly, pharmacological properties were associated with the polyphenol profiles of freeze dried apple flesh powder. The present report revealed the potential use of some apple extracts as effective food supplements or nutraceuticals for the prevention and/or management of cardiovascular and metabolic diseases.

Apple Cider Vinegar Attenuates Oxidative Stress and Reduces the Risk of Obesity in High-Fat-Fed Male Wistar Rats

Metabolic syndrome is a serious consequence of obesity characterized by increased cardiovascular risk factors such as hypertension, dyslipidemia, and glucose intolerance. While diets enriched with natural antioxidants showed beneficial effects on oxidative stress, blood pressure, and serum lipid composition, diet supplementation with synthetic antioxidants showed contradictive results. Thus, we tested, in this study, whether a daily dosage of Apple Cider Vinegar (ACV) would affect cardiovascular risk factor associated with obesity in high-fat diet (HFD)-induced hyperlipidemic Wistar rats. Obese rats showed increased serum total cholesterol, triglyceride, low-density lipoprotein-cholesterol (LDL-C), very low density lipoprotein (VLDL) and atherogenic index after 6 and 9 weeks of being fed an HFD. Importantly, ACV ameliorated all of these parameters significantly. Oxidative stress already developed after 6 weeks of HFD and was significantly reduced by daily doses of ACV. Oral administration of ACV normalized various biochemical and metabolic changes since it exhibited a very significant (P < .001) reduction in malondialdehyde levels, whereas an increase in thiol group concentrations and antioxidant status (superoxide dismutase [SOD], glutathione peroxidase [GPx], and catalase [CAT] activities and vitamin E concentrations). In addition, a modulation in trace element levels was observed when compared with HFD groups. These findings suggested that HFD alters the oxidant-antioxidant balance, as evidenced by a reduction in the antioxidant enzyme activities and vitamin E level, and enhanced lipid peroxidation. ACV can be beneficial for the suppression of obesity-induced oxidative stress in HFD rats through the modulating antioxidant defense system and reduces the risk of obesity-associated diseases by preventing the atherogenic risk.

Food Stabilizing Antioxidants Increase Nutrient Bioavailability in the in Vitro Model

OBJECTIVE

We investigated whether antioxidants may enhance bioavailability of lipids and carbohydrates and therefore increase the risk of obesity development.

METHODS

We tested how supplementation with antioxidants (0.01% butylated hydroxytoluene [BHT], α-tocopherol, and green tea catechins) of a diet containing butter and wheat bread affects bioavailability of fats and carbohydrates. The absorption of the in vitro digested diet was estimated in the intestinal epithelia model of the Caco-2 cells cultured in Transwell chambers.

RESULTS

In the case of the antioxidant-supplemented diets, we observed increased bioavailability of glucose, cholesterol, and lipids, as well as elevated secretion of the main chylomicron protein apoB-48 to the basal compartment. Importantly, we did not detect any rise in the concentrations of lipid peroxidation products (malondialdehyde, MDA) in the control samples prepared without antioxidants.

CONCLUSIONS

Addition of antioxidants (in particular BHT) to the diet increases bioavailability of lipids and carbohydrates, which consequently may increase the risk of obesity development. The dose of antioxidants is a factor of fundamental importance, particularly for catechins: low doses increase absorption of lipids, whereas high doses exert the opposite effect.

Optimized ultra-high-pressure-assisted extraction of procyanidins from lychee pericarp improves the antioxidant activity of extracts

To establish optimal ultra-high-pressure (UHP)-assisted extraction conditions for procyanidins from lychee pericarp, a response surface analysis method with four factors and three levels was adopted. The optimum conditions were as follows: 295 MPa pressure, 13 min pressure holding time, 16.0 mL/g liquid-to-solid ratio, and 70% ethanol concentration. Compared with conventional ethanol extraction and ultrasonic-assisted extraction methods, the yields of the total procyanidins, flavonoids, and phenolics extracted using the UHP process were significantly increased; consequently, the oxygen radical absorbance capacity and cellular antioxidant activity of UHP-assisted lychee pericarp extracts were substantially enhanced. LC-MS/MS and high-performance liquid chromatography quantification results for individual phenolic compounds revealed that the yield of procyanidin compounds, including epicatechin, procyanidin A2, and procyanidin B2, from lychee pericarp could be significantly improved by the UHP-assisted extraction process. This UHP-assisted extraction process is thus a practical method for the extraction of procyanidins from lychee pericarp.

Apples and cardiovascular health--is the gut microbiota a core consideration?

There is now considerable scientific evidence that a diet rich in fruits and vegetables can improve human health and protect against chronic diseases. However, it is not clear whether different fruits and vegetables have distinct beneficial effects. Apples are among the most frequently consumed fruits and a rich source of polyphenols and fiber. A major proportion of the bioactive components in apples, including the high molecular weight polyphenols, escape absorption in the upper gastrointestinal tract and reach the large intestine relatively intact. There, they can be converted by the colonic microbiota to bioavailable and biologically active compounds with systemic effects, in addition to modulating microbial composition. Epidemiological studies have identified associations between frequent apple consumption and reduced risk of chronic diseases such as cardiovascular disease. Human and animal intervention studies demonstrate beneficial effects on lipid metabolism, vascular function and inflammation but only a few studies have attempted to link these mechanistically with the gut microbiota. This review will focus on the reciprocal interaction between apple components and the gut microbiota, the potential link to cardiovascular health and the possible mechanisms of action.

Gamma-irradiated resveratrol negatively regulates LPS-induced MAPK and NF-κB signaling through TLR4 in macrophages

Resveratrol was irradiated at various doses of 15, 30, 50, and 70kGy for the development of physiological functionalities through modification of the structural properties. Gamma irradiation induced a decrease in the resveratrol peak, and the appearance of several new peaks by gamma irradiation was gradually increased up to 70kGy. Gamma-irradiated resveratrol did not exert cytotoxicity to macrophages in dose ranges from 15 to 70kGy; therefore, 70kGy gamma-irradiated resveratrol was used as the maximum dose throughout subsequent experiments. Treatment of LPS-stimulated macrophages with 70kGy gamma-irradiated resveratrol resulted in a dose-dependent decrease in iNOS-mediated NO, PGE2, and pro-inflammatory cytokine level, such as TNF-α, IL-6 and IL-1β. 70kGy gamma-irradiated resveratrol significantly inhibited cyclooxygenase-2 levels, as well as the expression of cell surface molecules, such as CD80 and CD86, in LPS-induced macrophages. Furthermore, the inhibitory action of these pro-inflammatory mediators occurred through an inhibition of MAPKs (ERK1/2, p38 and JNK) and NF-κB signaling pathways based on a toll-like receptor 4 in macrophages, which may be closely mediated with the radiolysis products of resveratrol transformed by gamma-irradiation. From these findings, it seems likely that gamma irradiation can be an effective tool for a reduction of the toxicity and play a potent role in the treatment of inflammatory disease.

Effect and mechanisms of action of vinegar on glucose metabolism, lipid profile, and body weight

The aim of this review is to summarize the effects of vinegar on glucose and lipid metabolism. Several studies have demonstrated that vinegar can help reduce hyperglycemia, hyperinsulinemia, hyperlipidemia, and obesity. Other studies, however, have shown no beneficial effect on metabolism. Several mechanisms have been proposed to explain these metabolic effects, including delayed gastric emptying and enteral absorption, suppression of hepatic glucose production, increased glucose utilization, upregulation of flow-mediated vasodilation, facilitation of insulin secretion, reduction in lipogenesis, increase in lipolysis, stimulation of fecal bile acid excretion, increased satiety, and enhanced energy expenditure. Although some evidence supports the use of vinegar as a complementary treatment in patients with glucose and lipid abnormalities, further large-scale long-term trials with impeccable methodology are warranted before definitive health claims can be made.

Dietary polyphenols as potential nutraceuticals in management of diabetes: a review

In recent years, there is growing evidence that plant-foods polyphenols, due to their biological properties, may be unique nutraceuticals and supplementary treatments for various aspects of type 2 diabetes mellitus. In this article we have reviewed the potential efficacies of polyphenols, including phenolic acids, flavonoids, stilbenes, lignans and polymeric lignans, on metabolic disorders and complications induced by diabetes. Based on several in vitro, animal models and some human studies, dietary plant polyphenols and polyphenol-rich products modulate carbohydrate and lipid metabolism, attenuate hyperglycemia, dyslipidemia and insulin resistance, improve adipose tissue metabolism, and alleviate oxidative stress and stress-sensitive signaling pathways and inflammatory processes. Polyphenolic compounds can also prevent the development of long-term diabetes complications including cardiovascular disease, neuropathy, nephropathy and retinopathy. Further investigations as human clinical studies are needed to obtain the optimum dose and duration of supplementation with polyphenolic compounds in diabetic patients.

Role of the apical and basolateral domains of the enterocyte in the regulation of cholesterol transport by a high glucose concentration

We have recently shown that a high glucose (HG) concentration raised intestinal cholesterol (CHOL) transport and metabolism in intestinal epithelial cells. The objective of the present work is to determine whether the stimulus for increased CHOL absorption by glucose originates from the apical site (corresponding to the intestinal lumen) or from the basolateral site (related to blood circulation). We tackled this issue by using differentiated Caco-2/15 cells. Only basolateral medium, supplemented with 25 mmol/L glucose, stimulated [(14)C]-CHOL uptake via the up-regulation of the critical CHOL transporter NPC1L1 protein, as confirmed by its specific ezetimibe inhibitor that abolished the rise in glucose-mediated CHOL capture. No significant changes were noted in SR-BI and CD36. Elevated CHOL uptake was associated with an increase in the transcription factors SREBP-2, LXR-β, and ChREBP, along with a fall in RXR-α. Interestingly, although the HG concentration in the apical medium caused modest changes in CHOL processing, its impact was synergetic with that of the basolateral medium. Our results suggest that HG concentration influences positively intestinal CHOL uptake when present in the basolateral medium. In addition, excessive consumption of diets containing high levels of carbohydrates may strengthen intestinal CHOL uptake in metabolic syndrome, thereby contributing to elevated levels of circulating CHOL and, consequently, the risk of developing type 2 diabetes and cardiovascular disease.

Procyanidin dimer B2-mediated IRAK-M induction negatively regulates TLR4 signaling in macrophages

Polyphenolic compounds have been found to possess a wide range of physiological activities that may contribute to their beneficial effects against inflammation-related diseases; however, the molecular mechanisms underlying this anti-inflammatory activity are not completely characterized, and many features remain to be elucidated. In this study, we investigated the molecular basis for the down-regulation of toll-like receptor 4 (TLR4) signal transduction by procyanidin dimer B2 (Pro B2) in macrophages. Pro B2 markedly elevated the expression of the interleukin (IL)-1 receptor-associated kinase (IRAK)-M protein, a negative regulator of TLR signaling. Lipopolysaccharide (LPS)-induced expression of cell surface molecules (CD80, CD86, and MHC class I/II) and production of pro-inflammatory cytokines (tumor necrosis factor-α, IL-1β, IL-6, and IL-12p70) were inhibited by Pro B2, and this action was prevented by IRAK-M silencing. In addition, Pro B2-treated macrophages inhibited LPS-induced activation of mitogen-activated protein kinases such as extracellular signal-regulated kinase 1/2, p38, and c-Jun N-terminal kinase and the translocation of nuclear factor κB and p65 through IRAK-M. We also found that Pro B2-treated macrophages inactivated naïve T cells by inhibiting LPS-induced interferon-γ and IL-2 secretion through IRAK-M. These novel findings provide new insights into the understanding of negative regulatory mechanisms of the TLR4 signaling pathway and the immune-pharmacological role of Pro B2 in the immune response against the development and progression of many chronic diseases.

Proteomic analysis of lipid droplets from Caco-2/TC7 enterocytes identifies novel modulators of lipid secretion

In enterocytes, the dynamic accumulation and depletion of triacylglycerol (TAG) in lipid droplets (LD) during fat absorption suggests that cytosolic LD-associated TAG contribute to TAG-rich lipoprotein (TRL) production. To get insight into the mechanisms controlling the storage/secretion balance of TAG, we used as a tool hepatitis C virus core protein, which localizes onto LDs, and thus may modify their protein coat and decrease TRL secretion. We compared the proteome of LD fractions isolated from Caco-2/TC7 enterocytes expressing or not hepatitis C virus core protein by a differential proteomic approach (isobaric tag for relative and absolute quantitation (iTRAQ) labeling coupled with liquid chromatography and tandem mass spectrometry). We identified 42 proteins, 21 being involved in lipid metabolism. Perilipin-2/ADRP, which is suggested to stabilize long term-stored TAG, was enriched in LD fractions isolated from Caco-2/TC7 expressing core protein while perilipin-3/TIP47, which is involved in LD synthesis from newly synthesized TAG, was decreased. Endoplasmic reticulum-associated proteins were strongly decreased, suggesting reduced interactions between LD and endoplasmic reticulum, where TRL assembly occurs. For the first time, we show that 17β-hydroxysteroid dehydrogenase 2 (DHB2), which catalyzes the conversion of 17-keto to 17 β-hydroxysteroids and which was the most highly enriched protein in core expressing cells, is localized to LD and interferes with TAG secretion, probably through its capacity to inactivate testosterone. Overall, we identified potential new players of lipid droplet dynamics, which may be involved in the balance between lipid storage and secretion, and may be altered in enterocytes in pathological conditions such as insulin resistance, type II diabetes and obesity.

The procyanidin trimer C1 inhibits LPS-induced MAPK and NF-κB signaling through TLR4 in macrophages

Natural products and dietary components rich in polyphenols have been shown to reduce inflammation; however, the molecular mechanisms underlying this anti-inflammatory activity are not completely characterized, and many features remain to be elucidated. This research was carried out to clarify the potential role of procyanidin trimer C1 in the anti-inflammatory effect of polyphenols. Procyanidin C1 inhibited inducible nitric oxide synthase-mediated nitric oxide production and the release of pro-inflammatory cytokines (interleukin-6 and tumor necrosis factor-α) in lipopolysaccharide (LPS)-induced macrophages. Treatment with procyanidin C1 resulted in a significant decrease in prostaglandin E2 and cyclooxygenase-2 levels, as well as the expression of cell surface molecules (CD80, CD86, and MHC class II), which was induced by LPS. Furthermore, our data demonstrated that the anti-inflammatory effect of procyanidin C1 occurs through inhibition of mitogen-activated protein kinase (p38 and c-Jun N-terminal kinase) and nuclear factor-κB signaling pathways. These 2 factors play a major role in controlling inflammation, through toll-like receptor 4, suggesting that procyanidin C1 plays a potent role in promoting anti-inflammatory activity in macrophages. These results represent a novel and effective therapeutic intervention for the treatment of inflammatory disease.

Microbial metabolites, but not other phenolics derived from grape seed phenolic extract, are transported through differentiated Caco-2 cell monolayers

Grape seed phenolic extract (GSE) is predicted to have health benefits, even though its bioavailability, including digestibility, permeability and ultimate metabolism, are still poorly understood. In vitro gastric and pancreatic digestion and in vitro ileal and faecal fermentation were combined with Caco-2 cell permeability studies for GSE samples. Qualitatively, there was no change in type/number of GSE compounds following gastric and pancreatic digestion and LC-MS analysis. However, the monomers were significantly (P<0.05) increased after gastric digestion, along with a significant (P<0.05) decrease in polymers. In addition, all forms of phenolic compounds decreased following pancreatic digestion. However, none of the original GSE phenolic compounds passed the Caco-2 cell monolayer, since all were recovered in the apical compartment. In contrast, the two intestinal microbiota metabolites with deprotonated molecular weights of [M-H]-165/121 and 193/175, that were found both in the ileal and faecal fermented samples, passed the Caco-2 cell monolayer.

The fiber and/or polyphenols present in lingonberries null the glycemic effect of the sugars present in the berries when consumed together with added glucose in healthy human volunteers

This study was undertaken on the broad hypothesis that lingonberry (Vaccinium vitis-idaea L.) has potential to reduce postprandial glycemic and lipemic response. More specifically, 2 postprandial crossover studies with healthy normal-weight male subjects were conducted to study the influence of commercial lingonberry powder on postprandial glycemia and lipemia. The test meals contained fat-free yoghurt with either glucose (50 g) or triacylglycerols (35 g) with or without (control) the lingonberry powder. The lingonberry powder provided the meals with a known amount of fiber and a known amount and composition of sugars, and it was a rich source of polyphenols. Postprandial glucose, insulin, and triacylglycerol responses were analyzed. There were no significant differences in the postprandial glucose concentration between the meals in the glycemia trial despite the fact that the lingonberry meal contained more glucose and fructose. When the meal did not contain added sugar but, instead, added triacylglycerol, no glycemia or lipemia-lowering effect was detected. On the contrary, there were indications of higher glycemic and insulinemic effect after the lingonberry meal. The results of this study indicate that the fibers and/or polyphenols present in lingonberries null the glycemic effect of the sugars present in the berries when consumed together with added glucose. By contrast, the lingonberry powder did not affect the postprandial lipemic response.

The proteome of cytosolic lipid droplets isolated from differentiated Caco-2/TC7 enterocytes reveals cell-specific characteristics

Background information. Intestinal absorption of alimentary lipids is a complex process ensured by enterocytes and leading to TRL [TAG (triacylglycerol)-rich lipoprotein] assembly and secretion. The accumulation of circulating intestine-derived TRL is associated with atherosclerosis, stressing the importance of the control of postprandial hypertriglyceridaemia. During the postprandial period, TAGs are also transiently stored as CLDs (cytosolic lipid droplets) in enterocytes. As a first step for determining whether CLDs could play a role in the control of enterocyte TRL secretion, we analysed the protein endowment of CLDs isolated by sucrose-gradient centrifugation from differentiated Caco-2/TC7 enterocytes, the only human model able to secrete TRL in culture and to store transiently TAGs as CLDs when supplied with lipids. Cells were analysed after a 24 h incubation with lipid micelles and thus in a state of CLD-associated TAG mobilization.

Results. Among the 105 proteins identified in the CLD fraction by LC-MS/MS (liquid chromatography coupled with tandem MS), 27 were directly involved in lipid metabolism pathways potentially relevant to enterocyte-specific functions. The transient feature of CLDs was consistent with the presence of proteins necessary for fatty acid activation (acyl-CoA synthetases) and for TAG hydrolysis. In differentiated Caco-2/TC7 enterocytes, we identified for the first time LPCAT2 (lysophosphatidylcholine acyltransferase 2), involved in PC (phosphatidylcholine) synthesis, and 3BHS1 (3-β-hydroxysteroid dehydrogenase 1), involved in steroid metabolism, and confirmed their partial CLD localization by immunofluorescence. In enterocytes, LPCAT2 may provide an economical source of PC, necessary for membrane synthesis and lipoprotein assembly, from the lysoPC present in the intestinal lumen. We also identified proteins involved in lipoprotein metabolism, such as ApoA-IV (apolipoprotein A-IV), which is specifically expressed by enterocytes and has been proposed to play many functions in vivo, including the formation of lipoproteins and the control of their size. The association of ApoA-IV with CLD was confirmed by confocal and immunoelectron microscopy and validated in vivo in the jejunum of mice fed with a high-fat diet.

Conclusions. We report for the first time the protein endowment of Caco-2/TC7 enterocyte CLDs. Our results suggest that their formation and mobilization may participate in the control of enterocyte TRL secretion in a cell-specific manner.

The lipid-lowering effect of dietary proanthocyanidins in rats involves both chylomicron-rich and VLDL-rich fractions

Proanthocyanidins have been shown to improve postprandial hypertriacylglycerolaemia. The present study aims to determine the actual contribution of chylomicrons (CM) and VLDL in the hypotriacylglycerolaemic action of grape seed proanthocyanidin extract (GSPE) in the postprandial state and to characterise the mechanisms by which the GSPE treatment reduces TAG-rich lipoproteins in vivo. A plasma lipid tolerance test was performed on rats fasted for 14 h and orally loaded with lard containing either GSPE or not. GSPE (250 mg/kg body weight) markedly blocked the increase in plasma TAG induced by lard, with a statistically significant reduction of 22 % in the area under the curve. The VLDL-rich fraction was the major contributor (72 %) after 1 h, whereas the CM-rich fraction was the major contributor (85 %) after 3 h. At 5 and 7 h after treatment, CM-rich and VLDL-rich fractions showed a similar influence. Plasma post-heparin lipoprotein lipase (LPL) activity and LPL mRNA levels in white adipose tissue and muscle were not affected by GSPE. On the contrary, GSPE treatment significantly repressed (30 %) the secretion of VLDL-TAG. In the liver, GSPE treatment induced different effects on the expression of acyl-coenzyme A synthetase long-chain family member 1, Apoc3 and 3-hydroxy-3-methylglutaryl-coenzyme A reductase at 1 h and Cd36 at 5 h, compared to those induced by lard. Furthermore, GSPE treatment significantly increased the activity of carnitine palmitoyltransferase 1a at 1 h. In conclusion, both CM-rich and VLDL-rich fractions contributed to the hypotriacylglycerolaemic action of GSPE, but their influence depended on time. GSPE induces hypotriacylglycerolaemic actions by repressing lipoprotein secretion and not by increasing LPL activity.

A comprehensive review of apples and apple components and their relationship to human health

There has been an increasing appreciation and understanding of the link between dietary fruit and vegetable intake and improved health in humans. The widespread and growing intake of apples and apple juice/products and their rich phytochemical profile suggest their important potential to affect the health of the populations consuming them. This review summarizes current clinical, in vitro, and in vivo data and builds upon earlier published reports that apple may reduce the risk of chronic disease by various mechanisms, including antioxidant, antiproliferative, and cell signaling effects. Exposure to apples and apple products has been associated with beneficial effects on risk, markers, and etiology of cancer, cardiovascular disease, asthma, and Alzheimer's disease. Recent work suggests that these products may also be associated with improved outcomes related to cognitive decline of normal aging, diabetes, weight management, bone health, pulmonary function, and gastrointestinal protection.

Hypolipidemic effects of proanthocyanidins and their underlying biochemical and molecular mechanisms

Proanthocyanidins are the most abundant polyphenols in human diets. Epidemiological studies strongly suggest that proanthocyanidins protect against cardiovascular diseases. Despite the antioxidant and anti-inflammatory properties of these flavonoids, one of the mechanisms by which proanthocyanidins exert their cardiovascular protection is improving lipid homeostasis. Animal studies demonstrate that proanthocyanidins reduce the plasma levels of atherogenic apolipoprotein B-triglyceride-rich lipoproteins and LDL-cholesterol but increase antiatherogenic HDL-cholesterol. The results in humans, however, are less clear. This review summarizes the results that have been published on plasma triglyceride, apolipoprotein B, HDL-cholesterol and LDL-cholesterol levels in humans and animal models in response to proanthocyanidin extracts and proanthocyanidin-rich foods. The physiological processes and biochemical pathways that are related to lipid homeostasis and affected by proanthocyanidin consumption are also discussed. Intestinal lipid absorption, chylomicron secretion by the intestine and VLDL secretion by the liver are the processes that are most repressed by proanthocyanidins, which, therefore, induce hypolipidemic effects.

Dietary procyanidins enhance transcriptional activity of bile acid-activated FXR in vitro and reduce triglyceridemia in vivo in a FXR-dependent manner

Consumption of dietary flavonoids has been associated with reduced mortality and risk of cardiovascular disease, partially by reducing triglyceridemia. We have previously reported that a grape seed procyanidin extract (GSPE) reduces postprandial triglyceridemia in normolipidemic animals signaling through the orphan nuclear receptor small heterodimer partner (SHP) a target of the bile acid receptor farnesoid X receptor (FXR). Our aim was to elucidate whether FXR mediates the hypotriglyceridemic effect of procyanidins. In FXR-driven luciferase expression assays GSPE dose-dependently enhanced FXR activity in the presence of chenodeoxycholic acid. GSPE gavage reduced triglyceridemia in wild type mice but not in FXR-null mice, revealing FXR as an essential mediator of the hypotriglyceridemic actions of procyanidins in vivo. In the liver, GSPE downregulated, in an FXR-dependent manner, the expression of the transcription factor steroid response element binding protein 1 (SREBP1) and several SREBP1 target genes involved in lipogenesis, and upregulated ApoA5 expression. Altogether, our results indicate that procyanidins lower triglyceridemia following the same pathway as bile acids: activation of FXR, transient upregulation of SHP expression and subsequent downregulation of SREBP1 expression. This study adds dietary procyanidins to the arsenal of FXR ligands with potential therapeutic use to combat hypertriglyceridemia, type 2 diabetes and metabolic syndrome.

Apple cider vinegar attenuates lipid profile in normal and diabetic rats

In this study, the effect of apple cider vinegar on Fasting Blood Glucose (FBG), glycated haemoglobin (HbA1c) and lipid profile in normal and diabetic rats was investigated. Diabetes was induced in male Wistar rats (300+/-30 g) by the intraperitoneal injection of streptozotocin (60 mg kg(-1) of body weight). Both normal and diabetic animals were fed with standard animal food containing apple cider vinegar (6% w/w) for 4 weeks. Fasting blood glucose did not change, while HbA1c significantly decreased by apple cider vinegar in diabetic group (p<0.05). In normal rats fed with vinegar, significant reduction of low density lipoprotein-cholesterol (LDL-c) (p<0.005) and significant increase of high density lipoprotein-cholesterol (HDL-c) levels (p<0.005) were observed. Apple cider vinegar also reduced serum triglyceride (TG) levels (p<0.005) and increased HDL-c (p<0.005) in diabetic animals. These results indicate that apple cider vinegar improved the serum lipid profile in normal and diabetic rats by decreasing serum TG, LDL-c and increasing serum HDL-c and may be of great value in managing the diabetic complications.

Short-term adaptation of postprandial lipoprotein secretion and intestinal gene expression to a high-fat diet

Western diet is characterized by a hypercaloric and hyperlipidic intake, enriched in saturated fats, that is associated with the increased occurrence of metabolic diseases. To cope with this overload of dietary lipids, the intestine, which delivers dietary lipids to the body, has to adapt its capacity in lipid absorption and lipoprotein synthesis. We have studied the early effects of a high-fat diet (HFD) on intestinal lipid metabolism in mice. After 7 days of HFD, mice displayed normal fasting triglyceridemia but postprandial hypertriglyceridemia. HFD induced a decreased number of secreted chylomicrons with increased associated triglycerides. Secretion of larger chylomicrons was correlated with increased intestinal microsomal triglyceride transfer protein (MTP) content and activity. Seven days of HFD induced a repression of genes involved in fatty acid synthesis (FAS, ACC) and an increased expression of genes involved in lipoprotein assembly (apoB, MTP, and apoA-IV), suggesting a coordinated control of intestinal lipid metabolism to manage a high-fat loading. Of note, the mature form of the transcription factor SREBP-1c was increased and translocated to the nucleus, suggesting that it could be involved in the coordinated control of gene transcription. Activation of SREBP-1c was partly independent of LXR. Moreover, HFD induced hepatic insulin resistance whereas intestine remained insulin sensitive. Altogether, these results demonstrate that a short-term HFD is sufficient to impact intestinal lipid metabolism, which might participate in the development of dyslipidemia and metabolic diseases.

Fractionation of polyphenol-enriched apple juice extracts to identify constituents with cancer chemopreventive potential

Apples and apple juices are widely consumed and rich sources of phytochemicals. The aim of the present study was to determine which apple constituents contribute to potential chemopreventive activities, using a bioactivity-directed approach. A polyphenol-enriched apple juice extract was fractionated by various techniques. Extract and fractions were tested in a series of test systems indicative of cancer preventive potential. These test systems measured antioxidant effects, modulation of carcinogen metabolism, anti-inflammatory and antihormonal activities, and antiproliferative potential. Regression analyses indicated that 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging potential correlated with the sum of low molecular weight (LMW) antioxidants (including chlorogenic acid, flavan-3-ols, and flavonols) and procyanidins, whereas peroxyl radicals were more effectively scavenged by LMW compounds than by procyanidins. Quercetin aglycone was identified as a potent Cyp1A inhibitor, whereas phloretin and (-)-epicatechin were the most potent cyclooxygenase 1 (Cox-1) inhibitors. Aromatase and Cyp1A inhibitory potential and cytotoxicity toward HCT116 colon cancer cells increased with increasing content in procyanidins. Overall, apple juice constituents belonging to different structural classes have distinct profiles of biological activity in these in vitro test systems. Since carcinogenesis is a complex process, combination of compounds with complementary activities may lead to enhanced preventive effects.

Absorption of dietary cholesterol oxidation products and their downstream metabolic effects are reduced by dietary apple polyphenols

Exogenous and endogenous cholesterol oxidation products (COPs) perturb various metabolic processes, and thereby they may induce various homeostasis-related disorders. Here, we observed that procyanidin-rich dietary apple polyphenol (APP) from unripe apples alleviates the perturbation of lipid metabolism by decreasing the exogenous COP levels in rats. Dietary COPs may be the greatest source of COPs found in the human body. Rats (4 weeks of age) were fed AIN-purified diets containing 0.3% COPs supplemented with 0.5 or 2.5% APP for 3 weeks. Dietary APP alleviated the growth inhibition action of the exogenous COPs. The modulations of the liver lipid profile by COPs remained unchanged. However, serum total cholesterol, high-density lipoprotein cholesterol, and triglyceride levels increased following the intake of dietary APP. Further, dietary APP inhibited the increase in lipid peroxide levels in the liver and serum by COPs. The activity of hepatic Delta6 desaturase was lowered by dietary APP in a dose-dependent manner, although exogenous COPs generally increased the activity of this enzyme. In keeping with this observation, Delta6 desaturation indices in the phospholipids and cholesteryl esters of the liver and serum lipids were lower in the APP-fed groups than those in the control group. Dietary APP also promoted the excretion of exogenous COPs, cholesterol, and acidic steroids in feces. Therefore, the inhibition of intestinal absorption of COPs may partly contribute to the alleviation of the perturbation of lipid metabolism and lipid peroxidation levels. Thus, APP may be an important removal agent of exogenous toxic material such as COPs contained in processed or fast foods.

Hypocholesterolemic effects of phenolic extracts and purified hydroxytyrosol recovered from olive mill wastewater in rats fed a cholesterol-rich diet

In our previous studies, a phenolic-rich extract of olive mill wastewaters (OMW) was prepared under optimal conditions, using a continuous countercurrent extraction unit, and hydroxytyrosol was purified from the obtained OMW extract. The antioxidant activity of OMW extract and hydroxytyrosol was determined by a series of models in vitro. In this study, the hypocholesterolemic effects of hydroxytyrosol and OMW extract in rats fed a cholesterol-rich diet were tested. Wistar rats, fed a standard laboratory diet or a cholesterol-rich diet for 16 weeks, were used. Serum lipid levels, as well as thiobarbituric acid reactive substances (TBARS) and superoxide dismutase and catalase activities in liver were examined. Cholesterol-rich diet-induced hypercholesterolemia was manifested in the elevation of serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C). Administration of a low-dose (2.5 mg/kg of body weight) of hydroxytyrosol and a high-dose (10 mg/kg of body weight) of OMW extract significantly lowered the serum levels of TC and LDL-C while increasing the serum levels of high-density lipoprotein cholesterol (HDL-C). Furthermore, the TBARS contents in liver, heart, kidney, and aorta decreased significantly after oral administration of hydroxytyrosol and OMW extract as compared with those of rats fed a cholesterol-rich diet. In addition, OMW phenolics increased CAT and SOD activities in liver. These results suggested that the hypocholesterolemic effect of hydroxytyrosol and OMW extract might be due to their abilities to lower serum TC and LDL-C levels as well as slowing the lipid peroxidation process and enhancing antioxidant enzyme activity.

One-month administration of hydroxytyrosol, a phenolic antioxidant present in olive oil, to hyperlipemic rabbits improves blood lipid profile, antioxidant status and reduces atherosclerosis development

The present study analysed the effects of hydroxytyrosol (HT) on blood lipids, antioxidant status and the progression of aortic lesions in hyperlipemic rabbits. Sixty-four rabbits were distributed into eight groups of animals (n = 8). Animal groups C, A and H were fed for 1-month with a control diet containing sunflower oil (C), an atherogenic diet (A) high in saturated fat and cholesterol or the A diet together with HT, respectively. The other five groups were fed for 2-months with diets C or A (groups CC or AA, respectively), or for 1-month with the A-diet followed by a further month with diet C, extra virgin olive oil diet (O) or diet C with HT (groups AC, AO and AH, respectively). Four milligram of HT/kg body weight were used in the study. Fifty and 42% decrease in total cholesterol and triacylglycerols, respectively, and a 2.3-fold increase in HDL-cholesterol were observed in the AH group but not in the H group. The HT-supplemented groups improved their antioxidant status and reduced the size of atherosclerotic lesions measured as intimal layer areas of the aortic arch when compared with control animals. We conclude that HT supplementation may have cardioprotective effects in vivo.

Adaptation of enterocytic Caco-2 cells to glucose modulates triacylglycerol-rich lipoprotein secretion through triacylglycerol targeting into the endoplasmic reticulum lumen

Enterocytes are responsible for the absorption of dietary lipids, which involves TRL [TG (triacylglycerol)-rich lipoprotein] assembly and secretion. In the present study, we analysed the effect on TRL secretion of Caco-2 enterocyte adaptation to a differential glucose supply. We showed that TG secretion in cells adapted to a low glucose supply for 2 weeks after confluence was double that of control cells maintained in high-glucose-containing medium, whereas the level of TG synthesis remained similar in both conditions. This increased secretion resulted mainly from an enlargement of the mean size of the secreted TRL. The increased TG availability for TRL assembly and secretion was not due to an increase in the MTP (microsomal TG transfer protein) activity that is required for lipid droplet biogenesis in the ER (endoplasmic reticulum) lumen, or to the channelling of absorbed fatty acids towards the monoacylglycerol pathway for TG synthesis. Interestingly, by electron microscopy and subcellular fractionation studies, we observed, in the low glucose condition, an increase in the TG content available for lipoprotein assembly in the ER lumen, with the cytosolic/microsomal TG levels being verapamil-sensitive. Overall, we demonstrate that Caco-2 enterocytes modulate TRL secretion through TG partitioning between the cytosol and the ER lumen according to the glucose supply. Our model will help in identifying the proteins involved in the control of the balance between TRL assembly and cytosolic lipid storage. This mechanism may be a way for enterocytes to regulate TRL secretion after a meal, and thus impact on our understanding of post-prandial hypertriglyceridaemia.