Cocoa extract exerts sex-specific anti-diabetic effects in an aggressive type-2 diabetes model: A pilot study.

Type 2 diabetes (T2D) is characterized by hyperglycemia and insulin resistance. Cocoa may slow T2D development and progression. This study employed male and female BTBR.Cg-Lepob/ob/WiscJ (ob/ob) and wild type (WT) controls to assess the potential for cocoa to ameliorate progressive T2D and compare responses between sexes. Mice received diet without (WT, ob/ob) or with cocoa extract (ob/ob + c) for 10 weeks. Acute cocoa reduced fasting hyperglycemia in females, but not males, after 2 weeks. Chronic cocoa supplementation (6-10 weeks) ameliorated hyperinsulinemia in males and worsened hyperlipidemia and hyperinsulinemia in females, yet also preserved and enhanced beta cell survival in females. The underlying mechanisms of these differences warrant further study. If sex differences are apparent in subsequent preclinical studies, clinical studies will be warranted to establish whether these differences are relevant in humans. Sex differences may need to be considered when designing human dietary interventions for T2D.

Blueberry intervention mitigates detrimental microbial metabolite trimethylamine N-oxide by modulating gut microbes.

Gut microbes play a pivotal role in host physiology by producing beneficial or detrimental metabolites. Gut bacteria metabolize dietary choline and L-carnitine to trimethylamine (TMA) which is then converted to trimethylamine-N-oxide (TMAO). An elevated circulating TMAO is associated with diabetes, obesity, cardiovascular disease, and cancer in humans. In the present study, we investigated the effect of dietary blueberries and strawberries at a nutritional dosage on TMA/TMAO production and the possible role of gut microbes. Blueberry cohort mice received a control (C) or freeze-dried blueberry supplemented (CB) diet for 12 weeks and subgroups received an antibiotics cocktail (CA and CBA). Strawberry cohort mice received a control (N) or strawberry-supplemented (NS) diet and subgroups received antibiotics (NA and NSA). Metabolic parameters, choline, TMA, and TMAO were assessed in addition to microbial profiling and characterization of berry powders. Blueberry supplementation (equivalent to 1.5 human servings) reduced circulating TMAO in CB versus C mice (~48%) without changing choline or TMA. This effect was not mediated through alterations in metabolic parameters. Dietary strawberries did not reduce choline, TMA, or TMAO. Depleting gut microbes with antibiotics in these cohorts drastically reduced TMA and TMAO to not-quantified levels. Further, dietary blueberries increased the abundance of bacterial taxa that are negatively associated with circulating TMA/TMAO suggesting the role of gut microbes. Our phenolic profiling indicates that this effect could be due to chlorogenic acid and increased phenolic contents in blueberries. Our study provides evidence for considering dietary blueberries to reduce TMAO and prevent TMAO-induced complications.

Gut Microbiota Depletion Using Antibiotics to Investigate Diet-Derived Microbial Metabolites: An Efficient Strategy.

SCOPE: Gut microbiota depletion using antibiotics in drinking water is a valuable tool to investigate the role of gut microbes and microbial metabolites in health and disease. However, there are challenges associated with this model. Animals avoid drinking water because of the antibiotic bitterness, which affects their metabolic health. The present study develops an efficient strategy to deplete gut microbes without affecting metabolic parameters. METHODS AND RESULTS: Male C57BL/6J mice (7 weeks old) are fed a control (C) or high-fat (HF) diet. Subgroups of C and HF mice receive an antibiotic cocktail in drinking water (CA and HA). The antibiotic dosage is gradually increased so that the animals adapt to the taste of antibiotics. Metabolic parameters, gut microbiome, and microbial metabolites are assessed after 12 weeks treatment. Culture methods and 16s rRNA amplification confirm the depletion of gut microbes in antibiotic groups (CA and HA). Further, antibiotic treatment does not alter metabolic parameters (body weight, body fat, lean body mass, blood glucose, and glucose/insulin tolerance), whereas it suppresses the production of diet-derived microbial metabolites (trimethylamine and trimethylamine-N-oxide). CONCLUSION: This strategy effectively depletes gut microbes and suppresses the production of microbial metabolites in mice without affecting their metabolic health.

Dietary phenolics and their microbial metabolites are poor inhibitors of trimethylamine oxidation to trimethylamine N-oxide by hepatic flavin monooxygenase 3.

High circulating levels of trimethylamine N-oxide (TMAO) have been associated with cardiovascular disease risk. TMAO is formed through a microbiome-host pathway utilizing primarily dietary choline as a substrate. Specific gut microbiota transform choline into trimethylamine (TMA), and, when absorbed, host hepatic flavin-containing monooxygenase 3 (FMO3) oxidizes TMA into TMAO. Chlorogenic acid and its metabolites reduce microbial TMA production in vitro. However, little is known regarding the potential for chlorogenic acid and its bioavailable metabolites to inhibit the last step: hepatic conversion of TMA to TMAO. We developed a screening methodology to study FMO3-catalyzed production of TMAO from TMA. HepG2 cells were unable to oxidize TMA into TMAO due to their lack of FMO3 expression. Although Hepa-1 cells did express FMO3 when pretreated with TMA and NADPH, they lacked enzymatic activity to produce TMAO. Rat hepatic microsomes contained active FMO3. Optimal reaction conditions were: 50 µM TMA, 0.2 mM NADPH, and 33 µL microsomes/mL reaction. Methimazole (a known FMO3 competitive substrate) at 200 µM effectively reduced FMO3-catalyzed conversion of TMA to TMAO. However, bioavailable chlorogenic acid metabolites did not generally inhibit FMO3 at physiological (1 µM) nor supra-physiological (50 µM) doses. Thus, the effects of chlorogenic acid in regulating TMAO levels in vivo are unlikely to occur through direct FMO3 enzyme inhibition. Potential effects on FMO3 expression remain unknown. Intestinal inhibition of TMA production and/or absorption are thus likely their primary mechanisms of action.

Vitis vinifera L. Bioactive Components Modulate Adipose Tissue Metabolic Markers of Healthy Rats in a Photoperiod-Dependent Manner.

SCOPE: The beneficial health effects of (poly)phenol-rich foods such as red grapes mainly depend on both the type and concentration of (poly)phenols. Since fruit (poly)phenol content is influenced by growing conditions, the study examines the seasonal effects of red grapes (Vitis vinifera L.), grown under various cultivation conditions, on metabolic markers of adipose tissue in healthy rats. METHODS AND RESULTS: For this purpose, Fischer 344 rats are exposed into three different light-dark cycles and daily supplemented with 100 mg kg-1 of either conventionally or organically grown red grapes for 10 weeks (n = 6). Seasonal consumption of organic grapes (OGs), which are richer in anthocyanins, increases energy expenditure (EE) of animals exposed to long photoperiod and enhances uncoupling protein 1 (UCP1) protein expression in brown adipose tissue of animals under standard photoperiod. Additionally, red grape consumption affects the gene expression profile of white adipose tissue (WAT), upregulating browning markers of subcutaneous WAT in 12 h light (L12) and 18 h light (L18) photoperiods, and downregulating adipogenic and lipolytic markers of visceral WAT in 6 h light (L6) and L12 photoperiods. CONCLUSIONS: These results clearly show that bioactive compounds of grapes can modulate the metabolic markers of white and brown adipose tissues in a photoperiod and depot-dependent manner, partly affecting EE when consumed out of season.

Phenolic-rich beverages reduce bacterial TMA formation in an ex vivo-in vitro colonic fermentation model.

The production of pro-atherogenic trimethylamine N-oxide (TMAO) is dependent on the gut microbiota metabolism of quaternary amines (i.e., choline) into trimethylamine (TMA). Nutritional strategies that target microbial conversion of choline into TMA could reduce cardiovascular disease and atherosclerosis burden by reducing subsequent formation of TMAO. This study aimed to evaluate (1) whether beverages rich in known inhibitors of TMA production (chlorogenic acid, catechin and epicatechin) can reduce TMA formation and (2) the effect of upper gastrointestinal digestion on efficacy. To do this, either raw or digested coffee, tea and cocoa beverages were evaluated for their TMA-d9 production inhibition in our ex vivo-in vitro fermentation model with human fecal slurries and choline-d9 substrate. Results showed that digestion was required to unlock the TMA-d9 production inhibition potential of coffee and cocoa beverages, and that teas did not possess a strong inhibition potential either digested or undigested. By fractionating digested bioactive beverages, we determined that those fractions rich in chlorogenic acid were the most bioactive. Overall, this study suggests that regular cocoa and coffee consumption could be a nutritional strategy able to reduce TMAO levels. In vivo studies should be carried out to confirm the potential of these beverages as strategies to inhibit TMA production.

Potential of Phenolic Compounds and Their Gut Microbiota-Derived Metabolites to Reduce TMA Formation: Application of an In Vitro Fermentation High-Throughput Screening Model.

Trimethylamine N-oxide (TMAO) is a pro-atherosclerotic product of dietary choline metabolism generated by a microbiome-host axis. The first step in this pathway is the enzymatic metabolism of choline to trimethylamine (TMA) by the gut microbiota. This reaction could be targeted to reduce atherosclerosis risk. We aimed to evaluate potential inhibitory effects of select dietary phenolics and their relevant gut microbial metabolites on TMA production via a human ex vivo-in vitro fermentation model. Various phenolics inhibited choline use and TMA production. The most bioactive compounds tested (caffeic acid, catechin, and epicatechin) reduced TMA-d9 formation (compared to control) by 57.5 ± 1.3 to 72.5 ± 0.4% at 8 h and preserved remaining choline-d9 concentrations by 194.1 ± 6.4 to 256.1 ± 6.3% at 8 h. These inhibitory effects were achieved without altering cell respiration or cell growth. However, inhibitory effects decreased at late fermentation times, which suggested that these compounds delay choline metabolism rather than completely inhibiting TMA formation. Overall, caffeic acid, catechin, and epicatechin were the most effective noncytotoxic inhibitors of choline use and TMA production. Thus, these compounds are proposed as lead bioactives to test in vivo.

Utilizing preclinical models of genetic diversity to improve translation of phytochemical activities from rodents to humans and inform personalized nutrition.

Mouse models are an essential tool in different areas of research, including nutrition and phytochemical research. Traditional inbred mouse models have allowed the discovery of therapeutical targets and mechanisms of action and expanded our knowledge of health and disease. However, these models lack the genetic variability typically found in human populations, which hinders the translatability of the results found in mice to humans. The development of genetically diverse mouse models, such as the collaborative cross (CC) or the diversity outbred (DO) models, has been a useful tool to overcome this obstacle in many fields, such as cancer, immunology and toxicology. However, these tools have not yet been widely adopted in the field of phytochemical research. As demonstrated in other disciplines, use of CC and DO models has the potential to provide invaluable insights for translation of phytochemicals from rodents to humans, which are desperately needed given the challenges and numerous failed clinical trials in this field. These models may prove informative for personalized use of phytochemicals in humans, including: predicting interindividual variability in phytochemical bioavailability and efficacy, identifying genetic loci or genes governing response to phytochemicals, identifying phytochemical mechanisms of action and therapeutic targets, and understanding the impact of genetic variability on individual response to phytochemicals. Such insights would prove invaluable for personalized implementation of phytochemicals in humans. This review will focus on the current work performed with genetically diverse mouse populations, and the research opportunities and advantages that these models can offer to phytochemical research.

Development of a High-Throughput Method to Study the Inhibitory Effect of Phytochemicals on Trimethylamine Formation.

Choline is metabolized by the gut microbiota into trimethylamine (TMA), the precursor of pro-atherosclerotic molecule trimethylamine N-oxide (TMAO). A reduction in TMA formation has shown cardioprotective effects, and some phytochemicals may reduce TMA formation. This study aimed to develop an optimized, high-throughput anaerobic fermentation methodology to study the inhibition of choline microbial metabolism into TMA by phenolic compounds with healthy human fecal starter. Optimal fermentation conditions were: 20% fecal slurry (1:10 in PBS), 100 µM choline, and 12 h fermentation. Additionally, 10 mM of 3,3-dimethyl-1-butanol (DMB) was defined as a positive TMA production inhibitor, achieving a ~50% reduction in TMA production. Gallic acid and chlorogenic acid reported higher TMA inhibitory potential (maximum of 80-90% TMA production inhibition), with IC50 around 5 mM. Neither DMB nor gallic acid or chlorogenic acid reduced TMA production through cytotoxic effects, indicating mechanisms such as altered TMA-lyase activity or expression.

Use of dietary phytochemicals for inhibition of trimethylamine N-oxide formation.

Trimethylamine-N-oxide (TMAO) has been reported as a risk factor for atherosclerosis development, as well as for other cardiovascular disease (CVD) pathologies. The objective of this review is to provide a useful summary on the use of phytochemicals as TMAO-reducing agents. This review discusses the main mechanisms by which TMAO promotes CVD, including the modulation of lipid and bile acid metabolism, and the promotion of endothelial dysfunction and oxidative stress. Current knowledge on the available strategies to reduce TMAO formation are discussed, highlighting the effect and potential of phytochemicals. Overall, phytochemicals (i.e., phenolic compounds or glucosinolates) reduce TMAO formation by modulating gut microbiota composition and/or function, inhibiting host's capacity to metabolize TMA to TMAO, or a combination of both. Perspectives for design of future studies involving phytochemicals as TMAO-reducing agents are discussed. Overall, the information provided by this review outlines the current state of the art of the role of phytochemicals as TMAO reducing agents, providing valuable insight to further advance in this field of study.

Diet-induced obesity in genetically diverse collaborative cross mouse founder strains reveals diverse phenotype response and amelioration by quercetin treatment in 129S1/SvImJ, PWK/EiJ, CAST/PhJ, and WSB/EiJ mice.

Significant evidence suggests protective effects of flavonoids against obesity in animal models, but these often do not translate to humans. One explanation for this disconnect is use of a few mouse strains (notably C57BL/6 J) in obesity studies. Obesity is a multifactorial disease. The underlying causes are not fully replicated by the high-fat C57BL/6 J model, despite phenotypic similarities. Furthermore, the impact of genetic factors on the activities of flavonoids is unknown. This study was designed to explore how diverse mouse strains respond to diet-induced obesity when fed a representative flavonoid. A subset of Collaborative Cross founder strains (males and females) were placed on dietary treatments (low-fat, high-fat, high-fat with quercetin, high-fat with quercetin and antibiotics) longitudinally. Diverse responses were observed across strains and sexes. Quercetin appeared to moderately blunt weight gain in male C57 and both sexes of 129S1/SvImJ mice, and slightly increased weight gain in female C57 mice. Surprisingly, quercetin dramatically blunted weight gain in male, but not female, PWK/PhJ mice. For female mice, quercetin blunted weight gain (relative to the high-fat phase) in CAST/PhJ, PWK/EiJ and WSB/EiJ mice compared to C57. Antibiotics did not generally result in loss of protective effects of quercetin. This highlights complex interactions between genetic factors, sex, obesity stimuli, and flavonoid intake, and the need to move away from single inbred mouse models to enhance translatability to diverse humans. These data justify use of genetically diverse Collaborative Cross and Diversity Outbred models which are emerging as invaluable tools in the field of personalized nutrition.

Changes in arterial blood pressure caused by long-term administration of grape seed proanthocyanidins in rats with established hypertension.

The development of hypertension (HTN) in cafeteria (CAF) diet-fed rats was demonstrated to be attenuated after grape seed proanthocyanidin extract (GSPE) administration. However, the long-term antihypertensive effect of GSPE in animals with established HTN has not been investigated. Thus, the aim of this study was to evaluate if GSPE shows a blood pressure-lowering effect in hypertensive rats after its administration for 3 weeks. Wistar rats were fed a standard or CAF diet for 12 weeks, and during the last 3 weeks, animals were administered vehicle, captopril or a low dose of GSPE (25 mg per kg body weight, bw). Both systolic and diastolic blood pressure (SBP and DBP) were monitored weekly. The liver reduced glutathione (GSH) levels, plasma angiotensin converting enzyme activity and endothelial gene expression of eNOS, KLF-2, Sirt-1, NOX4 and ET-1 were studied at the end-point. The results demonstrated that 3 weeks of CAF diet administration with 25 mg per kg bw GSPE significantly reduced SBP and DBP in hypertensive rats. GSPE induced the upregulation of Sirt-1 gene expression and downregulated the vasoconstrictor ET-1, suggesting the vasoprotective effect of GSPE and increased the antioxidant GSH activity. The administration of 25 mg per kg bw GSPE for 3 weeks significantly reduced BP in CAF diet fed animals with established HTN.

Implication of Opioid Receptors in the Antihypertensive Effect of a Novel Chicken Foot-Derived Peptide.

The peptide AVFQHNCQE demonstrated to produce nitric oxide-mediated antihypertensive effect. This study investigates the bioavailability and the opioid-like activity of this peptide after its oral administration. For this purpose, in silico and in vitro approaches were used to study the peptide susceptibility to GI digestion. In addition, AVFQHNCQE absorption was studied both in vitro by using Caco-2 cell monolayers and in vivo evaluating peptide presence in plasma from Wistar rats by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and by ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). Both in vivo and in vitro experiments demonstrated that peptide AVFQHNCQE was not absorbed. Thus, the potential involvement of opioid receptors in the BP-lowering effect of AVFQHNCQE was studied in the presence of opioid receptors-antagonist Naloxone. No changes in blood pressure were recorded in rats administered Naloxone, demonstrating that AVFQHNCQE antihypertensive effect is mediated through its interaction with opioid receptors. AVFQHNCQE opioid-like activity would clarify the antihypertensive properties of AVFQHNCQE despite its lack of absorption.

Exosomes transport trace amounts of (poly)phenols.

(Poly)phenols have varied biological activities that may account for the beneficial effects of fruits and vegetables as part of a healthy diet. Although their cellular absorption and their many mechanisms of action have been partly elucidated, their transport through the systemic circulation, other than their binding to albumin, is poorly described. We aimed at determining whether (poly)phenols can be transported by extracellular vesicles. We supplemented rats with a dietary grape seed polyphenol extract (GSPE) and we quantified (poly)phenols and their metabolites at 3 and 7 h post-gavage. After quantitative LC-MS/MS analysis of circulating aglycones, and microbial-derived, or phase II-derived metabolites we recorded a quantitatively very modest transport of (poly)phenols in plasma exosomes when isolated by commercial ultracentrifugation or precipitation kits. Our data suggest that GSPE-derived (poly)phenols are minimally, if at all, transported by exosomes.

Optimization of extraction methods for characterization of phenolic compounds in apricot fruit (Prunus armeniaca).

Fruits are rich in phenolic compounds with health-promoting activities. However, phenolic profiles vary between fruits. Hence, specific extraction methods are required for accurate profiling of the functional compounds. This study aims to develop an optimised method by response surface methodology to extract phenolics from apricots (Prunus armeniaca) and correctly characterise apricots' phenolic profile. For this, the effects of the solid-to-liquid ratio, temperature, extraction solvent, extraction time and sequential extraction steps on the extraction of major phenolic families were investigated. Methanol- and ethanol-based extractions were suitable, although methanol was the optimal solvent. The optimised extraction conditions were 20 g mL-1, 38 °C and 72% methanol (1% formic acid). When this method was used in apricots, the characterisation of their phenolic profile by HPLC-ESI-MS/MS showed a higher extraction of phenolic compounds than other studies in the literature that use non-specific extraction methods. The developed method is fast and economically feasible for accurate characterisation of the phenolic profile of apricot fruits and thus can be routinely used to extract apricot phenolic compounds for their characterisation.

Optimization and characterization of Royal Dawn cherry (Prunus avium) phenolics extraction.

To correlate the beneficial effects of cherry consumption with their phenolic composition, a full and precise characterization is required. However, there is not a specific method to fully extract all phenolic compounds from sweet cherries. Thus, this study aimed to optimize the extraction of sweet cherry phenolics by response surface methodology and fully characterize the phenolic profile of Royal Dawn sweet cherries by HPLC-ESI-MS/MS. Extraction conditions were evaluated and optimized to 55 °C, MeOH 72%, 12 mL/g in two extraction steps. Royal Dawn sweet cherries presented rutin as the predominant phenolic compound, unlike most sweet cherry varieties. Additionally, ethanol was evaluated as a replacement solvent, obtaining lower extraction rates, especially for anthocyanins. However, in terms of total amounts, non-anthocyanin compounds were similarly extracted. The developed methodology was fast and can be routinely used in the evaluation of the phenolic profile of sweet cherries and to produce phenolic-rich extracts for the food industry.

A comparative study on the bioavailability of phenolic compounds from organic and nonorganic red grapes.

The health-promoting functions of fruit phenolic compounds are mainly attributed to their metabolites. The organic cultivation of fruits is becoming increasingly popular. Thus, this study evaluates whether the differences in red Grenache grapes derived from organic culture conditions influence the bioavailability and metabolism of phenolic compounds in rats. Organic and nonorganic (conventional) red Grenache grapes (OG and CG, respectively) were characterized and administered to Wistar rats (65 mg gallic acid equivalents/kg bw). Serum was recollected at different time points, and the phenolic metabolites were quantified by HPLC-ESI-MS/MS. The results showed that organic cultivation increased the oligomeric proanthocyanidin and anthocyanidin contents and decreased the content of free flavanols and dietary fiber. The serum profile of OG-administered rats showed higher metabolite concentrations at 2 h and reduced metabolite concentration at 24 h compared with the CG-administered rats. Thus, this particular serum kinetic behavior might influence the bioactivity of their phenolic compounds.

Exposure of Fischer 344 rats to distinct photoperiods influences the bioavailability of red grape polyphenols.

The consumption of grapes, rich in polyphenols, have several health effects. These effects are mainly attributed to the polyphenol metabolites generated after their ingestion. Several factors that affects host's physiology can modulate the bioavailability of grape polyphenols and, in turn, their effects. Mammals undergo physiological and metabolic changes due to the different day length (photoperiod) within a year. Thus, the aim of this study is to investigate if the bioavailability of phenolic compounds from the same red grapes with a different polyphenol profile (i.e. red grape produced organically (OG) or non-organically (conventional, CG)) differs with the photoperiod exposure. For this, the serum phenolic metabolites of Fischer 344 rats keep at different photoperiods (18, 12 or 6 h of light per day) and administered with OG or CG for 10-week were profiled by HPLC-MS/MS. Our results indicated that rats administered with OG reported a higher total serum metabolite concentration independent of the photoperiod exposure and CG-administered rats showed a more varied serum metabolite profile depending of the photoperiod exposure. Those rats exposed to 6 h of light per day, which emulates winter light conditions, presented a higher bioavailability of grape phenolics. Therefore, grape cultivar and animal photoperiod exposure condition grape phenolics' bioavailability.

Optimization of a polyphenol extraction method for sweet orange pulp (Citrus sinensis L.) to identify phenolic compounds consumed from sweet oranges.

The consumption of sweet oranges has been linked to several health benefits, many of which are attributed to hesperidin, a flavanone that is present in high amounts in these fruits. However, other phenolic compounds can contribute to the bioactivity of sweet orange. To link those effects to their phenolic profile, the complete characterization of the phenolic profile is mandatory. Although many studies have profiled the phenolic composition of orange juices, their pulps, which retain phenolic compounds, are overlooked. This fact is particularly relevant because dietary guidelines recommend the consumption of whole fruits. Therefore, this study aimed to develop a specific method for the optimal extraction of phenolics from orange pulp and to use this method to characterize these fruits grown at different locations by HPLC-ESI-MS/MS. The extraction conditions that reported the highest total polyphenol content (TPC) and hesperidin contents were 20 mL/g, 55 °C, and 90% methanol. The extraction time and number of sequential steps were further evaluated and optimized as 20 min and two extraction steps, respectively. Although lower extraction rates were achieved when using ethanol as the extraction solvent, high TPC and hesperidin yields were obtained, suggesting the potential use of this methodology to produce phenolic-rich extracts for the food industry. By applying the optimized methodology and analyzing the extracts by HPLC-ESI-MS/MS, geographic cultivation regions were demonstrated to affect the phenolic profiles of oranges. In short, we developed a quick, easy-to-perform methodology that can be used to extract orange phenolics from pulp for their identification and quantification and to evaluate the factors that affect the phenolic profile in sweet orange pulps.

Evidence that Nitric Oxide is Involved in the Blood Pressure Lowering Effect of the Peptide AVFQHNCQE in Spontaneously Hypertensive Rats.

AVFQHNCQE is an antihypertensive nonapeptide obtained from a chicken foot protein hydrolysate. The present study aims to investigate the mechanisms involved in its blood pressure (BP)-lowering effect. Male (17⁻20 weeks old) spontaneously hypertensive rats (SHR) were used in this study. Rats were divided into two groups and orally administered water or 10 mg/kg body weight (bw) AVFQHNCQE. One hour post-administration, animals of both groups were intra-peritoneally treated with 1 mL of saline or with 1 mL of saline containing 30 mg/kg bw Nω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthesis, or with 1 mL of saline containing 5 mg/kg bw indomethacin, which is an inhibitor of prostacyclin synthesis (n = 6 per group). Systolic BP was recorded before oral administration and six hours after oral administration. In an additional experiment, SHR were administered water or 10 mg/kg bw AVFQHNCQE (n = 6 per group) and sacrificed six hours post-administration to study the mechanisms underlying the peptide anti-hypertensive effect. Moreover, the relaxation caused by AVFQHNCQE in isolated aortic rings from Sprague-Dawley rats was evaluated. The BP-lowering effect of the peptide was not changed after indomethacin administration but was completely abolished by L-NAME, which demonstrates that its anti-hypertensive effect is mediated by changes in endothelium-derived NO availability. In addition, AVFQHNCQE administration downregulated aortic gene expression of the vasoconstrictor factor endothelin-1 and the endothelial major free radical producer NADPH. Moreover, while no changes in plasma ACE activity were observed after its administration, liver GSH levels were higher in the peptide-treated group than in the water group, which demonstrates that AVFQHNCQE presents antioxidant properties.