Absorption, tissue distribution and excretion of pelargonidin and its metabolites following oral administration to rats

Pelargonidin improves memory deficit in amyloid β25-35 rat model of Alzheimer's disease by inhibition of glial activation, cholinesterase, and oxidative stress

Alzheimer's disease (AD) is a multifactorial disorder with devastating outcomes and few mostly palliative available therapeutic strategies. Pelargonidin (Pel), an anthocyanin compound, is an estrogen receptor agonist with lower side effects versus estrogen. This study examined neuroprotective effect of Pel on intrahippocampal amyloid β25-35 (Aβ) rat model of AD. Rats were divided into groups of sham, Aβ, and Pel-pretreated Aβ (10mg/kg; p.o.). Animals underwent Morris water maze (MWM) test in addition to measurement of hippocampal oxidative stress, acetylcholinesterase (AChE) activity, glial fibrillary acidic protein (GFAP) and inducible nitric oxide synthase (iNOS). Pel pretreatment of Aβ group significantly improved escape latency and distance swum in MWM versus Aβ group and attenuated hippocampal malondialdehyde (MDA) and increased catalase activity with no significant change of nitrite. Meanwhile, Pel improved hippocampal AChE activity and lowered GFAP level with no significant change of iNOS. Our results suggest that Pel could improve Aβ25-35-induced memory deficit through mitigation of oxidative stress, cholinergic dysfunction, and astrocyte reaction.

Bioavailability of anthocyanins and colonic polyphenol metabolites following consumption of aronia berry extract

A single-dose pharmacokinetic trial was conducted in 6 adults to evaluate the bioavailability of anthocyanins and colonic polyphenol metabolites after consumption of 500mg aronia berry extract. UHPLC-MS methods were developed to quantitate aronia berry polyphenols and their metabolites in plasma and urine. While anthocyanins were bioavailable, microbial phenolic catabolites increased ∼10-fold more than anthocyanins in plasma and urine. Among the anthocyanins, cyanidin-3-O-galactoside was rapidly metabolized to peonidin-3-O-galactoside. Aronia polyphenols were absorbed and extensively metabolized with tmax of anthocyanins and other polyphenol catabolites from 1.0h to 6.33h in plasma and urine. Despite significant inter-individual variation in pharmacokinetic parameters, concentrations of polyphenol metabolites in plasma and urine at 24h were positively correlated with total AUC in plasma and urine (r=0.93, and r=0.98, respectively). This suggests that fasting blood and urine collections could be used to estimate polyphenol bioavailability and metabolism after aronia polyphenol consumption.

Determination of cyanidin 3-glucoside in rat brain, liver and kidneys by UPLC/MS-MS and its application to a short-term pharmacokinetic study

Anthocyanins exert neuroprotection in various in vitro and in vivo experimental models. However, no details regarding their brain-related pharmacokinetics are so far available to support claims about their direct neuronal bioactivity as well as to design proper formulations of anthocyanin-based products. To gather this missing piece of knowledge, we intravenously administered a bolus of 668 nmol cyanidin 3-glucoside (C3G) in anaesthetized Wistar rats and shortly after (15 s to 20 min) we collected blood, brain, liver, kidneys and urine samples. Extracts thereof were analysed for C3G and its expected metabolites using UPLC/MS-MS. The data enabled to calculate a set of pharmacokinetics parameters. The main finding was the distinctive, rapid distribution of C3G in the brain, with an apparently constant plasma/brain ratio in the physiologically relevant plasma concentration range (19-355 nM). This is the first report that accurately determines the distribution pattern of C3G in the brain, paving the way to the rational design of future tests of neuroprotection by C3G in animal models and humans.

Metabolic fingerprint after acute and under sustained consumption of a functional beverage based on grape skin extract in healthy human subjects

Grape-derived polyphenols are considered to be one of the most promising ingredients for functional foods due to their health-promoting activities. We applied a HPLC-MS-based untargeted metabolomic approach in order to evaluate the impact of a functional food based on grape skin polyphenols on the urinary metabolome of healthy subjects. Thirty-one volunteers participated in two dietary crossover randomized intervention studies: with a single-dose intake (187 mL) and with a 15-day sustained consumption (twice per day, 187 mL per day in total) of a functional beverage (FB). Postprandial (4-hour) and 24-hour urine samples collected after acute consumption and on the last day of sustained FB consumption, respectively, were analysed using an untargeted HPLC-qTOF-MS approach. Multivariate modelling with subsequent application of an S-plot revealed differential mass features related to acute and prolonged consumption of FB. More than half of the mass features were shared between the two types of samples, among which several phase II metabolites of grape-derived polyphenols were identified at confidence level II. Prolonged consumption of FB was specifically reflected in urine metabolome by the presence of first-stage microbial metabolites of flavanols: hydroxyvaleric acid and hydroxyvalerolactone derivatives. Overall, several epicatechin and phenolic acid metabolites both of tissular and microbiota origin were the most representative markers of FB consumption. To our knowledge, this is one of the first studies where an untargeted LC-MS metabolomic approach has been applied in nutrition research on a grape-derived FB.

The Reciprocal Interactions between Polyphenols and Gut Microbiota and Effects on Bioaccessibility

As of late, polyphenols have increasingly interested the scientific community due to their proposed health benefits. Much of this attention has focused on their bioavailability. Polyphenol-gut microbiota interactions should be considered to understand their biological functions. The dichotomy between the biotransformation of polyphenols into their metabolites by gut microbiota and the modulation of gut microbiota composition by polyphenols contributes to positive health outcomes. Although there are many studies on the in vivo bioavailability of polyphenols, the mutual relationship between polyphenols and gut microbiota is not fully understood. This review focuses on the biotransformation of polyphenols by gut microbiota, modulation of gut microbiota by polyphenols, and the effects of these two-way mutual interactions on polyphenol bioavailability, and ultimately, human health.

Experimental and Theoretical Data on the Mechanism by Which Red Wine Anthocyanins Are Transported through a Human MKN-28 Gastric Cell Model

The gastric absorption of red wine anthocyanins was evaluated using a gastric MKN-28 cell barrier model. Anthocyanin transport was not affected by the presence of 4% ethanol and decreased with the increase of pH. Gastric cells pretreated with anthocyanins were found to increase anthocyanin transport. The presence of d-(+)-glucose was found to decrease anthocyanin uptake, suggesting the involvement of glucose transporters. RT-PCR assays revealed that GLUT1, GLUT3, and MCT1 transporters were expressed in MKN-28 cells. Computational studies were performed to provide a structural characterization of the binding site of hGLUT1 to glucose or different anthocyanins under different forms. Docking results demonstrated that anthocyanins can bind to glucose transporters from both intracellular and extracellular sides. Anthocyanins seem to enter into the transporter by two main conformations: B ring or glucose. From MD simulations, hGLUT1 was found to form complexes with all anthocyanins tested in the different protonation states.

The mechanisms of action of flavonoids in the brain: Direct versus indirect effects

The projected increase in the incidence of dementia in the population highlights the urgent need for a more comprehensive understanding of how different aspects of lifestyle, in particular exercise and diet, may affect neural function and consequent cognitive performance throughout the life course. In this regard, flavonoids, found in a variety of fruits, vegetables and derived beverages, have been identified as a group of promising bioactive compounds capable of influencing different aspects of brain function, including cerebrovascular blood flow and synaptic plasticity, both resulting in improvements in learning and memory in mammalian species. However, the precise mechanisms by which flavonoids exert these actions are yet to be fully established, although accumulating data indicate an ability to interact with neuronal receptors and kinase signaling pathways which are key to neuronal activation and communication and synaptic strengthening. Alternatively or concurrently, there is also compelling evidence derived from human clinical studies suggesting that flavonoids can positively affect peripheral and cerebrovascular blood flow, which may be an indirect effective mechanism by which dietary flavonoids can impact on brain health and cognition. The current review examines the beneficial effects of flavonoids on both human and animal brain function and attempts to address and link direct and indirect actions of flavonoids and their derivatives within the central nervous system (CNS).

Bioavailability of dietary polyphenols: Factors contributing to their clinical application in CNS diseases

The anatomical location of the central nervous system (CNS) renders it immunologically and pharmacologically privileged due to the blood brain barrier (BBB). Although this limits the transport of unfavorable molecules to the CNS, the ensuing privilege could be disadvantageous for therapeutic compounds. Hence, the greatest challenge in the pharmacotherapy of CNS diseases is to ensure efficient brain targeting and drug delivery. Research evidences indicate that dietary polyphenols have neuroprotective potential against CNS diseases. However, their selective permeability across BBB, poor absorption, rapid metabolism and systemic elimination limit their bioavailability and therapeutic efficacy. Consequently, the beneficial effects of these orally administered agents in the CNS still remain a subject of debate. This has also limited its clinical application either as independent or adjunctive therapy. Improving the in vivo bioavailability by novel methods could improve the therapeutic feasibility of polyphenols and assist in evolving novel drugs and their derivatives with improved efficacy in vivo. Here we review the mechanistic and pharmacological issues related to the bioavailability of polyphenols with therapeutic implications for CNS diseases. We surmise that improving the bioavailability of polyphenols entails efficient in vivo transport across BBB, biochemical stability, improved half-life and persistent neuroprotection in the CNS.

Assessing Antioxidant Capacity in Brain Tissue: Methodologies and Limitations in Neuroprotective Strategies

The number of putative neuroprotective compounds with antioxidant activity described in the literature continues to grow. Although these compounds are validated using a variety of in vivo and in vitro techniques, they are often evaluated initially using in vitro cell culture techniques in order to establish toxicity and effective concentrations. Both in vivo and in vitro methodologies have their respective advantages and disadvantages, including, but not limited to, cost, time, use of resources and technical limitations. This review expands on the inherent benefits and drawbacks of in vitro and in vivo methods for assessing neuroprotection, especially in light of proper evaluation of compound efficacy and neural bioavailability. For example, in vivo studies can better evaluate the effects of protective compounds and/or its metabolites on various tissues, including the brain, in the whole animal, whereas in vitro studies can better discern the cellular and/or mechanistic effects of compounds. In particular, we aim to address the question of appropriate and accurate extrapolation of findings from in vitro experiment-where compounds are often directly applied to cellular extracts, potentially at higher concentrations than would ever cross the blood-brain barrier-to the more complex scenario of neuroprotection due to pharmacodynamics in vivo.

Pomegranate extract protects against cerebral ischemia/reperfusion injury and preserves brain DNA integrity in rats

AIM

Interruption to blood flow causes ischemia and infarction of brain tissues with consequent neuronal damage and brain dysfunction. Pomegranate extract is well tolerated, and safely consumed all over the world. Interestingly, pomegranate extract has shown remarkable antioxidant and anti-inflammatory effects in experimental models. Many investigators consider natural extracts as novel therapies for neurodegenerative disorders. Therefore, this study was carried out to investigate the protective effects of standardized pomegranate extract against cerebral ischemia/reperfusion-induced brain injury in rats.

MAIN METHODS

Adult male albino rats were randomly divided into sham-operated control group, ischemia/reperfusion (I/R) group, and two other groups that received standardized pomegranate extract at two dose levels (250, 500 mg/kg) for 15 days prior to ischemia/reperfusion (PMG250+I/R, and PMG500+I/R groups). After I/R or sham operation, all rats were sacrificed and brains were harvested for subsequent biochemical analysis.

KEY FINDINGS

Results showed reduction in brain contents of MDA (malondialdehyde), and NO (nitric oxide), in addition to enhancement of SOD (superoxide dismutase), GPX (glutathione peroxidase), and GRD (glutathione reductase) activities in rats treated with pomegranate extract prior to cerebral I/R. Moreover, pomegranate extract decreased brain levels of NF-κB p65 (nuclear factor kappa B p65), TNF-α (tumor necrosis factor-alpha), caspase-3 and increased brain levels of IL-10 (interleukin-10), and cerebral ATP (adenosine triphosphate) production. Comet assay showed less brain DNA (deoxyribonucleic acid) damage in rats protected with pomegranate extract.

SIGNIFICANCE

The present study showed, for the first time, that pre-administration of pomegranate extract to rats, can offer a significant dose-dependent neuroprotective activity against cerebral I/R brain injury and DNA damage via antioxidant, anti-inflammatory, anti-apoptotic and ATP-replenishing effects.

Anthocyanin metabolites are abundant and persistent in human urine

LC-MS/MS revealed that metabolites of anthocyanins (Acn) were abundant in human urine (n = 17) even after 5 days with no dietary Acn. After intake of 250 mL of blueberry juice, parent Acn were 4% and Acn metabolites were 96% of the total urinary Acn for the following 24 h. Multiple reaction monitoring revealed 226 combinations of mass transition × retention times for known Acn and predicted Acn metabolites. These were dominated by aglycones, especially aglycone glucuronides. The diversity of Acn metabolites could include positional isomers of Acn conjugates and chalcones. The persistence of Acn metabolites suggested enterohepatic recycling leading to prolonged residence time. The prevalence of Acn metabolites based on pelargonidin, which is not present in blueberry juice, may reflect ongoing dehydroxylation and demethylation of other Acn via xenobiotic and colonic bacterial action. The results suggest that exposure to Acn-based flavonoid moieties is substantially greater than suggested by earlier research.

Flavonoids in modulation of cell survival signalling pathways

Flavonoids, a family of polyphenols, generally found in various fruits and vegetables, as well as in many plant beverages such as tea, pomegranate juice, raspberry, blueberries, and red wine. Recently, studies on flavonoids have attracted scientific attention as a potential nutritional strategy to prevent a broad range of chronic disorders. Many studies suggest that consumption of these flavonoids in sufficient amount plays neuroprotective, cardioprotective, anti-inflammatory, and chemopreventive roles. While there has been a major focus on the antioxidant properties, there is an emerging view that flavonoids and their in vivo metabolites do not act only as conventional antioxidants but may also exert modulatory actions on cellular system through direct action on various signalling pathways. These pathways include phosphoinositide 3-kinase, Akt/protein kinase B, mitogen-activated protein kinase, tyrosine kinases, and protein kinase C. Various inhibitory or stimulatory actions of flavonoids on these pathways greatly affect cellular functions by altering the phosphorylation state of targeted molecules. In addition, flavonoids also modulate various gene expressions through activation of various transcription factors. Thus, the present review will bestow a breathing overview regarding the prime role of flavonoids in modulation of survival signalling pathways at cellular system.

Chemical analysis and effect of blueberry and lingonberry fruits and leaves against glutamate-mediated excitotoxicity

Phenolic compounds are a large class of phytochemicals that are widespread in the plant kingdom and known to have antioxidant capacities. This study aimed to determine the antioxidant capacities as well as the content of total soluble phenolics, anthocyanins, tannins, and flavonoids in the fruits and leaves of blueberries and lingonberries growing in Newfoundland. This study also determined the potential neuroprotective effect of extracts from fruits and leaves against glutamate-mediated excitotoxicity, which is believed to contribute to disorders such as stroke and neurodegenerative diseases. Lingonberry and blueberry plants were found to be rich sources of phenolic compounds. Total antioxidant capacities in terms of radical scavenging activity and reducing power were much higher in leaves of both plants as compared to their fruits. These results were in correlation with phenolic contents including total flavonoids, anthocyanins, and tannins. Brain-derived cell cultures from rats were prepared and grown for about 2 weeks. Cell cultures were treated with glutamate (100 μM) for 24 h, and the effect of extracts was determined on cells subjected to this excitotoxicity. Glutamate treatment caused approximately 23% cell loss when measured after 24 h of exposure. Whereas lingonberry fruit extract did not provide protection from glutamate toxicity, blueberry fruit extracts were extremely protective. Leaf extracts of both lingonberry and blueberry showed a significant neuroprotective effect. The greater protective effect of leaf extracts was in correlation with the levels of phenolics and antioxidant capacity. These findings suggest that berries or their components may contribute to protecting the brain from various pathologies.

Interaction of anthocyanins with human serum albumin: influence of pH and chemical structure on binding

The affinity of anthocyanins for human serum albumin (HSA) was determined by a fluorescence quenching method. The effects of pH and structure of anthocyanins on the binding constants were studied. The constants for binding of anthocyanins to HSA ranged from 1.08×10(5) to 13.2×10(5) M(-1). A hydrophobic effect at acidic pH was shown by the relatively high positive entropy values under the conditions studied. Electrostatic interactions, including hydrogen bonding, contributed to the binding at pH 7.4. The effect of structure of anthocyanins on the affinity was pH-dependent, particularly the effect of additional hydroxyl substituents. Hydroxyl substituents and glycosylation of anthocyanins decreased the affinity for binding to HSA at lower pH (especially pH 4), but increased the strength of binding at pH 7.4. In contrast, methylation of a hydroxyl group enhanced the binding at acidic pH, whilst this substitution reduced the strength of binding at pH 7.4. This paper shows that changes in anthocyanin structure or reductions in pH, which may occur in the region of inflammatory sites, have an effect on the binding of anthocyanins to HSA.

Dietary (poly)phenolics in human health: structures, bioavailability, and evidence of protective effects against chronic diseases

Human intervention trials have provided evidence for protective effects of various (poly)phenol-rich foods against chronic disease, including cardiovascular disease, neurodegeneration, and cancer. While there are considerable data suggesting benefits of (poly)phenol intake, conclusions regarding their preventive potential remain unresolved due to several limitations in existing studies. Bioactivity investigations using cell lines have made an extensive use of both (poly)phenolic aglycones and sugar conjugates, these being the typical forms that exist in planta, at concentrations in the low-μM-to-mM range. However, after ingestion, dietary (poly)phenolics appear in the circulatory system not as the parent compounds, but as phase II metabolites, and their presence in plasma after dietary intake rarely exceeds nM concentrations. Substantial quantities of both the parent compounds and their metabolites pass to the colon where they are degraded by the action of the local microbiota, giving rise principally to small phenolic acid and aromatic catabolites that are absorbed into the circulatory system. This comprehensive review describes the different groups of compounds that have been reported to be involved in human nutrition, their fate in the body as they pass through the gastrointestinal tract and are absorbed into the circulatory system, the evidence of their impact on human chronic diseases, and the possible mechanisms of action through which (poly)phenol metabolites and catabolites may exert these protective actions. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes.

Anthocyanins suppress the cleavable complex formation by irinotecan and diminish its DNA-strand-breaking activity in the colon of Wistar rats

In the present study, the question was addressed whether anthocyanins interfere with the topoisomerase I poison irinotecan in vivo. In vivo complexes of enzyme to DNA bioassay was used to detect irinotecan-induced stabilization of topoisomerase I/DNA complexes and single cell gel electrophoresis to determine DNA-strand-break induction in the colon of male Wistar rats. Furthermore, analysis of anthocyanin concentrations in rat plasma and rat colon was included in the testing, demonstrating that anthocyanins reach the colon and the concentrations do not differ between rats that only received anthocyanins and the anthocyanin/irinotecan group. Blackberry extract was found to significantly reduce irinotecan-mediated topoisomerase I/DNA cleavable complex formation. Overall, anthocyanins did not notably increase cleavable complex formation. However, a significant increase of DNA damage was shown after a single dose of irinotecan as well as the single compounds cyanidin (cy) and cyanidin-3-glucoside (cy-3-g). Furthermore, a significant reduction of irinotecan-induced DNA-strand breaks after a pretreatment with cy, cy-3-g and blackberry extract was observed. Thus, the question arises whether anthocyanin-rich preparations might interfere with chemotherapy or whether, due to low systemic bioavailability, the preparations might provide protective potential in the gastrointestinal tract.

Neuroprotective effect of Pycnogenol® following traumatic brain injury

Traumatic brain injury (TBI) involves primary and secondary injury cascades that underlie delayed neuronal dysfunction and death. Oxidative stress is one of the most celebrated secondary injury mechanisms. A close relationship exists between levels of oxidative stress and the pathogenesis of TBI. However, other cascades, such as an increase in proinflammatory cytokines, also play important roles in the overall response to the trauma. Pharmacologic intervention, in order to be successful, requires a multifaceted approach. Naturally occurring flavonoids are unique in possessing not only tremendous free radical scavenging properties but also the ability to modulate cellular homeostasis leading to a reduction in inflammation and cell toxicity. This study evaluated the therapeutic role of Pycnogenol (PYC), a patented combinational bioflavonoid. Young adult Sprague-Dawley rats were subjected to a unilateral moderate cortical contusion and treated post injury with PYC or vehicle. At either 48 or 96 h post trauma, the animals were killed and the cortex and hippocampus analyzed for changes in enzymatic and non-enzymatic oxidative stress markers. In addition, possible changes in both pre- and post-synaptic proteins (synapsin-1, PSD-95, drebrin, synapse associated protein-97) were analyzed. Finally, a separate cohort of animals was used to evaluate two proinflammatory cytokines (IL-6, TNF-α). Following the trauma there was a significant increase in oxidative stress in both the injured cortex and the ipsilateral hippocampus. Animals treated with PYC significantly ameliorated levels of protein carbonyls, lipid peroxidation, and protein nitration. The PYC treatment also significantly reduced the loss of key pre- and post-synaptic proteins with some levels in the hippocampus of PYC treated animals not significantly different from sham operated controls. Although levels of the proinflammatory cytokines were significantly elevated in both injury groups, the cohort treated with PYC showed a significant reduction compared to vehicle treated controls. These results are the first to show a neuroprotective effect of PYC following TBI. They also suggest that the diverse effects of bioflavonoids may provide a unique avenue for possible therapeutic intervention following head trauma.

Effects of acute consumption of a fruit and vegetable purée-based drink on vasodilation and oxidative status

Epidemiological studies indicate that diets rich in fruits and vegetables (F&V) are protective against CVD. Puréed F&V products retain many beneficial components, including flavonoids, carotenoids, vitamin C and dietary fibres. The present study aimed to establish the physiological effects of acute ingestion of a F&V purée-based drink (FVPD) on vasodilation, antioxidant status, phytochemical bioavailability and other CVD risk factors. A total of twenty-four subjects, aged 30–70 years, completed the randomised, single-blind, controlled, crossover test meal study. Subjects consumed 400 ml of the FVPD, or a fruit-flavoured sugar-matched control, after following a low-flavonoid diet for 5 d. Blood and urine samples were collected throughout the study day, and vascular reactivity was assessed at 90 min intervals using laser Doppler iontophoresis. The FVPD significantly increased plasma vitamin C (P= 0·002) and total nitrate/nitrite (P= 0·001) concentrations. There was a near significant time by treatment effect onex vivoLDL oxidation (P= 0·068), with a longer lag phase after consuming the FVPD. During the 6 h after juice consumption, the antioxidant capacity of plasma increased significantly (P= 0·003) and there was a simultaneous increase in plasma and urinary phenolic metabolites (P< 0·05). There were significantly lower glucose and insulin peaks after ingestion of the FVPD compared with control (P= 0·019 and 0·003) and a trend towards increased endothelium-dependent vasodilation following FVPD consumption (P= 0·061). Overall, FVPD consumption significantly increased plasma vitamin C and total nitrate/nitrite concentrations, with a trend towards increased endothelium-dependent vasodilation. Puréed F&V products are useful vehicles for increasing micronutrient status, plasma antioxidant capacity andin vivoNO generation, which may contribute to CVD risk reduction.

The Glu298Asp single nucleotide polymorphism in the endothelial nitric oxide synthase gene differentially affects the vascular response to acute consumption of fruit and vegetable puree based drinks

SCOPE

Diets low in fruits and vegetables (FV) are responsible for 2.7 million deaths from cardiovascular diseases (CVD) and certain cancers annually. Many FV and their juices contain flavonoids, some of which increase endothelial nitric oxide synthase (eNOS) activity. A single nucleotide polymorphism in the eNOS gene, where thymine (T) replaces guanine (G) at position 894 predicting substitution of glutamate for aspartate at codon 298 (Glu298Asp), has been associated with increased CVD risk due to effects on nitric oxide synthesis and subsequently vascular reactivity. Individuals can be homozygous for guanine (GG), thymine (TT) or heterozygous (GT).

METHODS AND RESULTS

We investigated the effects of acute ingestion of a FV-puree-based-drink (FVPD) on vasodilation and antioxidant status in subjects retrospectively genotyped for this polymorphism. Healthy volunteers (n = 24; 11 GG, 11 GT, 2 TT) aged 30-70 were recruited to a randomized, controlled, crossover, acute study. We showed that acute consumption of 400 mL FVPD differentially affected individuals depending on their genotype. There was a significant genotype interaction for endothelium-dependent vasodilation measured by laser Doppler imaging with iontophoresis (P < 0.05) and ex vivo low-density lipoproteins (LDL) oxidation (P = 0.002). GG subjects had increased endothelium-dependent vasodilation 180 min (P = 0.028) and reduced ex vivo LDL oxidation (P = 0.013) after 60 min after FVPD compared with control, no differences were observed in GT subjects.

CONCLUSION

eNOS Glu298Asp genotype differentially affects vasodilation and ex vivo LDL oxidation after consumption of FV in the form of a puree-based drink.

Effects of polyphenols on brain ageing and Alzheimer's disease: focus on mitochondria

The global trend of the phenomenon of population ageing has dramatic consequences on public health and the incidence of neurodegenerative diseases. Physiological changes that occur during normal ageing of the brain may exacerbate and initiate pathological processes that may lead to neurodegenerative disorders, especially Alzheimer's disease (AD). Hence, the risk of AD rises exponentially with age. While there is no cure currently available, sufficient intake of certain micronutrients and secondary plant metabolites may prevent disease onset. Polyphenols are highly abundant in the human diet, and several experimental and epidemiological evidences indicate that these secondary plant products have beneficial effects on AD risks. This study reviews current knowledge on the potential of polyphenols and selected polyphenol-rich diets on memory and cognition in human subjects, focusing on recent data showing in vivo efficacy of polyphenols in preventing neurodegenerative events during brain ageing and in dementia. Concentrations of polyphenols in animal brains following oral administration have been consistently reported to be very low, thus eliciting controversial discussion on their neuroprotective effects and potential mechanisms. Whether polyphenols exert any direct antioxidant effects in the brain or rather act by evoking alterations in regulatory systems of the brain or even the body periphery is still unclear. To understand the mechanisms behind the protective abilities of polyphenol-rich foods, an overall understanding of the biotransformation of polyphenols and identification of the various metabolites arising in the human body is also urgently needed.

Dietary polyphenols as modulators of brain functions: biological actions and molecular mechanisms underpinning their beneficial effects

Accumulating evidence suggests that diet and lifestyle can play an important role in delaying the onset or halting the progression of age-related health disorders and to improve cognitive function. In particular, polyphenols have been reported to exert their neuroprotective actions through the potential to protect neurons against injury induced by neurotoxins, an ability to suppress neuroinflammation, and the potential to promote memory, learning, and cognitive function. Despite significant advances in our understanding of the biology of polyphenols, they are still mistakenly regarded as simply acting as antioxidants. However, recent evidence suggests that their beneficial effects involve decreases in oxidative/inflammatory stress signaling, increases in protective signaling and neurohormetic effects leading to the expression of genes that encode antioxidant enzymes, phase-2 enzymes, neurotrophic factors, and cytoprotective proteins. Specific examples of such pathways include the sirtuin-FoxO pathway, the NF-κB pathway, and the Nrf-2/ARE pathway. Together, these processes act to maintain brain homeostasis and play important roles in neuronal stress adaptation and thus polyphenols have the potential to prevent the progression of neurodegenerative pathologies.

The strawberry: composition, nutritional quality, and impact on human health

Strawberries are a common and important fruit in the Mediterranean diet because of their high content of essential nutrients and beneficial phytochemicals, which seem to have relevant biological activity in human health. Among these phytochemicals, anthocyanin and ellagitannins are the major antioxidant compounds. Although individual phytochemical constituents of strawberries have been studied for their biological activities, human intervention studies using whole fruits are still lacking. Here, the nutritional contribution and phytochemical composition of the strawberry are reviewed, as is the role played by the maturity, genotype, and storage effects on this fruit. Specific attention is focused on fruit absorption, metabolism, and the possible beneficial biological activity on human health.

Impact of the quantity and flavonoid content of fruits and vegetables on markers of intake in adults with an increased risk of cardiovascular disease: the FLAVURS trial

PURPOSE

Limited robust randomised controlled trials investigating fruit and vegetable (F&V) intake in people at risk of cardiovascular disease (CVD) exist. We aimed to design and validate a dietary strategy of increasing flavonoid-rich versus flavonoid-poor F&V consumption on nutrient biomarker profile.

METHODS

A parallel, randomised, controlled, dose-response dietary intervention study. Participants with a CVD relative risk of 1.5 assessed by risk scores were randomly assigned to one of the 3 groups: habitual (control, CT), high-flavonoid (HF) or low-flavonoid (LF) diets. While the CT group (n = 57) consumed their habitual diet throughout, the HF (n = 58) and LF (n = 59) groups sequentially increased their daily F&V intake by an additional 2, 4 and 6 portions for 6-week periods during the 18-week study.

RESULTS

Compliance to target numbers and types of F&V was broadly met and verified by dietary records, and plasma and urinary biomarkers. Mean (± SEM) number of F&V portions/day consumed by the HF and LF groups at baseline (3.8 ± 0.3 and 3.4 ± 0.3), 6 weeks (6.3 ± 0.4 and 5.8 ± 0.3), 12 weeks (7.0 ± 0.3 and 6.8 ± 0.3) and 18 weeks (7.6 ± 0.4 and 8.1 ± 0.4), respectively, was similar at baseline yet higher than the CT group (3.9 ± 0.3, 4.3 ± 0.3, 4.6 ± 0.4, 4.5 ± 0.3) (P = 0.015). There was a dose-dependent increase in dietary and urinary flavonoids in the HF group, with no change in other groups (P = 0.0001). Significantly higher dietary intakes of folate (P = 0.035), non-starch polysaccharides (P = 0.001), vitamin C (P = 0.0001) and carotenoids (P = 0.0001) were observed in both intervention groups compared with CT, which were broadly supported by nutrient biomarker analysis.

CONCLUSIONS

The success of improving nutrient profile by active encouragement of F&V intake in an intervention study implies the need for a more hands-on public health approach.

Flavonoids as modulators of memory and learning: molecular interactions resulting in behavioural effects

There is considerable interest in the potential of a group of dietary-derived phytochemicals known as flavonoids in modulating neuronal function and thereby influencing memory, learning and cognitive function. The present review begins by detailing the molecular events that underlie the acquisition and consolidation of new memories in the brain in order to provide a critical background to understanding the impact of flavonoid-rich diets or pure flavonoids on memory. Data suggests that despite limited brain bioavailability, dietary supplementation with flavonoid-rich foods, such as blueberry, green tea and Ginkgo biloba lead to significant reversals of age-related deficits on spatial memory and learning. Furthermore, animal and cellular studies suggest that the mechanisms underpinning their ability to induce improvements in memory are linked to the potential of absorbed flavonoids and their metabolites to interact with and modulate critical signalling pathways, transcription factors and gene and/or protein expression which control memory and learning processes in the hippocampus; the brain structure where spatial learning occurs. Overall, current evidence suggests that human translation of these animal investigations are warranted, as are further studies, to better understand the precise cause-and-effect relationship between flavonoid intake and cognitive outputs.

Chronic cyanidin-3-glucoside administration improves short-term spatial recognition memory but not passive avoidance learning and memory in streptozotocin-diabetic rats

This research study was conducted to evaluate the efficacy of chronic cyanidin-3-glucoside (C3G) on alleviation of learning and memory deficits in diabetic rats as a result of the observed antidiabetic and antioxidant activity of C3G. Male Wistar rats were divided into control, diabetic, C3G-treated-control and -diabetic groups. The C3G was administered i.p. at a dose of 10 mg/kg on alternate days for eight weeks. For evaluation of learning and memory, initial latency (IL) and step-through latency (STL) were determined at the end of study using passive avoidance test. Meanwhile, spatial recognition memory was assessed as alternation in the Y-maze task. Oxidative stress markers in brain tissue were also measured. It was found that the alternation score of the diabetic rats was lower than that of control (p < 0.01) and C3G-treated diabetic rats showed a higher alternation score as compared to diabetic group (p < 0.05). Diabetic rats also developed a significant impairment in retention and recall in passive avoidance test (p < 0.01) and C3G treatment of diabetic rats did not produce any significant improvement. Meanwhile, increased level of malondialdehyde (MDA) in diabetic rats was significantly reduced following C3G treatment (p < 0.05). Taken together, chronic C3G could improve short-term spatial recognition memory disturbance in the Y-maze test but not retention and recall capability in passive avoidance test in STZ-diabetic rats.

Flavonoids, cognition, and dementia: actions, mechanisms, and potential therapeutic utility for Alzheimer disease

There is increasing evidence that the consumption of flavonoid-rich foods can beneficially influence normal cognitive function. In addition, a growing number of flavonoids have been shown to inhibit the development of Alzheimer disease (AD)-like pathology and to reverse deficits in cognition in rodent models, suggestive of potential therapeutic utility in dementia. The actions of flavonoid-rich foods (e.g., green tea, blueberry, and cocoa) seem to be mediated by the direct interactions of absorbed flavonoids and their metabolites with a number of cellular and molecular targets. For example, their specific interactions within the ERK and PI3-kinase/Akt signaling pathways, at the level of receptors or kinases, have been shown to increase the expression of neuroprotective and neuromodulatory proteins and increase the number of, and strength of, connections between neurons. Concurrently, their effects on the vascular system may also lead to enhancements in cognitive performance through increased brain blood flow and an ability to initiate neurogenesis in the hippocampus. Additional mechanisms have been suggested for the ability of flavonoids to delay the initiation of and/or slow the progression of AD-like pathology and related neurodegenerative disorders, including a potential to inhibit neuronal apoptosis triggered by neurotoxic species (e.g., oxidative stress and neuroinflammation) or disrupt amyloid β aggregation and effects on amyloid precursor protein processing through the inhibition of β-secretase (BACE-1) and/or activation of α-secretase (ADAM10). Together, these processes act to maintain the number and quality of synaptic connections in key brain regions and thus flavonoids have the potential to prevent the progression of neurodegenerative pathologies and to promote cognitive performance.

Do polyphenols enter the brain and does it matter? Some theoretical and practical considerations

Although several epidemiological and intervention studies suggest that polyphenols (PPs) and PP-rich foods may improve memory and cognition in animals and humans, PPs' mode of action is only poorly understood. To help distinguish between the different modes of action that have been proposed for PPs, it is obviously important to know how much PPs can accumulate in the brain, if any at all. However, reliable data on PP uptake into the brain of animals are limited as many studies failed to report important control procedures during data acquisition. In this paper, we summarize published data on the penetration of PPs into animal brain and review some hypotheses to explain the biological basis of potentially health-beneficial effects of PPs to the brain. Finally, we highlight promising new approaches, especially those of a hormetic dose-response and gut microbiota-brain interaction, which may allow a better understanding of PPs' mode of action in animals and humans.

Bioavailability of dietary flavonoids and phenolic compounds

This paper reviews recent human studies on the bioavailability of dietary flavonoids and related compounds, including chlorogenic acids and ellagitannins, in which the identification of metabolites, catabolites and parent compounds in plasma, urine and ileal fluid was based on mass spectrometric methodology. Compounds absorbed in the small intestine appear in the circulatory system predominantly as glucuronide, sulfate and methylated metabolites which seemingly are treated by the body as xenobiotics as they are rapidly removed from the bloodstream. As a consequence, while analysis of plasma provides valuable information on the identity and pharmacokinetic profiles of circulating metabolites after acute supplementation, it does not provide accurate quantitative assessments of uptake from the gastrointestinal tract. Urinary excretion, of which there are great variations with different classes of flavonoids, provides a more realistic figure but, as this does not include the possibility of metabolites being sequestered in body tissues, this too is an under estimate of absorption, but to what degree remains to be determined. Even when absorption occurs in the small intestine, feeding studies with ileostomists reveal that substantial amounts of the parent compounds and some of their metabolites appear in ileal fluid indicating that in volunteers with a functioning colon these compounds will pass to the large intestine where they are subjected to the action of the colonic microflora. A diversity of colonic-derived catabolites is absorbed into the bloodstream and passes through the body prior to excretion in urine. There is growing evidence that these compounds, which were little investigated until recently, are produced in quantity in the colon and form a key part of the bioavailability equation of dietary flavonoids and related phenolic compounds.

Oral pelargonidin exerts dose-dependent neuroprotection in 6-hydroxydopamine rat model of hemi-parkinsonism

Parkinson's disease (PD) is a neuropathological and debilitating disorder involving the degeneration of mesencephalic dopaminergic neurons. Neuroprotective effect of pelargonidin (Pel) has already been reported, therefore, this study examined whether Pel administration would attenuate behavioural and structural abnormalities and markers of oxidative stress in an experimental model of PD in rat. For this purpose, unilateral intrastriatal 6-hydroxydopamine (6-OHDA, 12.5mug/5mul of saline-ascorbate)-lesioned rats were pre-treated p.o. with Pel (10 and/or 20mg/kg). Pel administration dose-dependently attenuated the rotational behavior in lesioned rats and protected the neurons of SNC against 6-OHDA toxicity. In addition, pre-treatment with Pel (20mg/kg) significantly decreased the 6-OHDA-induced thiobarbituric acid reactive substances (TBARS) formation, indicative of a neuroprotection against lipid peroxidation. Furthermore, the increase of nitrite levels induced by 6-OHDA, indicate the nitric oxide formation and free radicals production and the decrease of antioxidant defense enzyme superoxide dismutase (SOD) was non-significantly prevented by Pel (20mg/kg). In summary, Pel administration has a dose-dependent neuroprotective effect against 6-OHDA toxicity, partly through attenuating oxidative stress. Our findings suggest that pelargonidin could provide benefits, along with other therapies, in neurodegenerative disorders including PD.

Bioavailability of strawberry antioxidants in human subjects

Strawberries contain many antioxidant phytochemicals such as vitamin C, carotenoids and phenolic compounds including anthocyanins (ACN). In the present study, antioxidant composition of fresh strawberries (FS) and stored strawberries (SS) and the bioavailability of the main strawberry bioactive compounds were determined in human subjects. Thirteen healthy volunteers consumed 300 g of FS and SS on two separate occasions. Blood, before and at different time points from meal consumption, as well as 24 h urine, was collected, and parent compounds and metabolites of the different compounds were determined by HPLC or LC/MS/MS. A reduction in α-carotene plasma concentrationsv.baseline values was recorded after the consumption of FS, although the amount of this carotenoid was higher in the SS. On the contrary, a significant increase of plasma vitamin C after 2, 3 and 5 h (P < 0·05) of FS and SS consumption was recorded. No quercetin and ACN were found in plasma, while coumaric acid, 4-hydroxybenzoic acid (4HBA, 56 and 54 % of pelargonidin-3-glucoside (Pel-glc) ingested with FS and SS, respectively) and protocatechuic acid (59 and 34 % of cyanidin-3-glucoside ingested with FS and SS, respectively) over 8 h from strawberry consumption were retrieved in the plasma. Pelargonidin glucuronide, pelargonidin glucoside and pelargonidin aglycone peaked in urine within 2 h of strawberry consumption, and the 24 h amount excreted was always approximately 0·9 % of the Pel-glc dose ingested. The data indicated that the content of phytochemicals in strawberries may influence the bioavailability of individual compounds. Furthermore, in the present study, the metabolism of Pel-glc was elucidated, and, for the first time, 4HBA was suggested to be a major human metabolite of Pel-glc.

Beyond antioxidants: the cellular and molecular interactions of flavonoids and how these underpin their actions on the brain

The consumption of flavonoid-rich foods and beverages has been suggested to limit the neurodegeneration associated with a variety of neurological disorders and to prevent or reverse normal or abnormal deteriorations in cognitive performance. Flavonoids mediate these effects via a number of routes, including a potential to protect neurons against injury induced by neurotoxins, an ability to suppress neuroinflammation and a potential to promote memory, learning and cognitive function. Originally, it was thought that such actions were mediated by the antioxidant capacity of flavonoids. However, their limited absorption and their low bioavailability in the brain suggest that this explanation is unlikely. Instead, this multiplicity of effects appears to be underpinned by three separate processes: first, through their interactions with important neuronal and glial signalling cascades in the brain, most notably the phosphatidylinositol 3-kinase/Akt and mitogen-activated protein kinase pathways that regulate pro-survival transcription factors and gene expression; second, through an ability to improve peripheral and cerebral blood flow and to trigger angiogenesis and neurogenesis in the hippocampus; third, by their capacity to directly react with and scavenge neurotoxic species and pro-inflammatory agents produced in the brain as a result of both normal and abnormal brain ageing. The present review explores the potential inhibitory or stimulatory actions of flavonoids within these three systems and describes how such interactions are likely to underlie neurological effects.

Xenobiotic metabolism and berry flavonoid transport across the blood-brain barrier

A compelling body of literature suggests berry phytochemicals play beneficial roles in reversing age-related cognitive impairment and protect against neurodegenerative disorders. Anthocyanins are bioactive phytochemicals in berries suspected to be responsible for some of these neuroprotective effects. The plausible mechanisms of anthocyanin bioactivity in brain tissue are dependent on their bioavailability to the brain. Pigs were fed 2% whole freeze-dried, powdered blueberry in the diet for 8 weeks. Anthocyanin and anthocyanin glucuronides were measured in the cortex, cerebellum, and midbrain and diencephalon by LC-MS/MS. Anthocyanins and their glucuronides were found in the range of femtomoles per gram of fresh weight of tissue at 18 h postprandial, after anthocyanins had been removed from the blood by xenobiotic metabolism. Xenobiotic metabolism, anthocyanin interaction, and transporter barriers to brain bioavailability are briefly discussed. The plausible mechanism of neuroprotective action of anthocyanins may be via modulation of signal transduction processes and/or gene expression in brain tissue rather than by direct antioxidant radical quenching.

Berry anthocyanins and anthocyanidins exhibit distinct affinities for the efflux transporters BCRP and MDR1

BACKGROUND AND PURPOSE

Dietary anthocyanins hold great promise in the prevention of chronic disease but factors affecting their bioavailability remain poorly defined. Specifically, the role played by transport mechanisms at the intestinal and blood-brain barriers (BBB) is currently unknown.

EXPERIMENTAL APPROACH

In the present study, 16 anthocyanins and anthocyanidins were exposed to the human efflux transporters multidrug resistance protein 1 (MDR1) and breast cancer resistance protein (BCRP), using dye efflux, ATPase and, for BCRP, vesicular transport assays.

KEY RESULTS

All test compounds interacted with the BCRP transporter in vitro. Of these, seven emerged as potential BCRP substrates (malvidin, petunidin, malvidin-3-galactoside, malvidin-3,5-diglucoside, cyanidin-3-galactoside, peonidin-3-glucoside, cyanidin-3-glucoside) and 12 as potential inhibitors of BCRP (cyanidin, peonidin, cyanidin-3,5-diglucoside, malvidin, pelargonidin, delphinidin, petunidin, delphinidin-3-glucoside, cyanidin-3-rutinoside, malvidin-3-glucoside, pelargonidin-3,5-diglucoside, malvidin-3-galactoside). Malvidin, malvidin-3-galactoside and petunidin exhibited bimodal activities serving as BCRP substrates at low concentrations and, at higher concentrations, as BCRP inhibitors. Effects on MDR1, in contrast, were weak. Only aglycones exerted mild inhibitory activity.

CONCLUSIONS AND IMPLICATIONS

Although the anthocyanidins under study may alter pharmacokinetics of drugs that are BCRP substrates, they are less likely to interfere with activities of MDR1 substrates. The present data suggest that several anthocyanins and anthocyanidins may be actively transported out of intestinal tissues and endothelia, limiting their bioavailability in plasma and brain.

Radiolabelled cyanidin 3-O-glucoside is poorly absorbed in the mouse

Anthocyanins are natural pigments abundant in various fruits and berries that are involved in the prevention of various chronic diseases. Their low concentrations in plasma and urine are explained in part by their complex chemistry and the formation of still uncharacterised metabolites. The aim of the present study was to follow the distribution of anthocyanins in the body using 14C-labelled cyanidin 3-O-glucoside (Cy3G) fed by gavage to mice. After the administration of 22.2 kBq 14C-Cy3G (0.93 mg), radioactivity was detected in most organs tested over the following 24 h with a peak observed in inner tissues at 3 h. The major fraction of the radioactivity (44.5 %) was found in the faeces collected 24 h after ingestion. At 3 h after oral administration of 141 kBq 14C-Cy3G (4.76 mg), most of the radioactivity (87.9 % of intake) was recovered in the gastrointestinal (GI) tract, especially in the small intestine (50.7 %) and the caecum (23 %). At this time, 3.3 % of the radioactivity was detected in urine. There was minimal accumulation (0.76 %) of radioactivity in tissues outside the GI tract. Distribution of radioactivity varied among organs, with liver, gallbladder and kidneys showing the highest radioactivity. Taken as a whole, these results show that Cy3G is poorly absorbed in the mouse.

Anthocyanin absorption, metabolism, and distribution from a wild blueberry-enriched diet (Vaccinium angustifolium) is affected by diet duration in the Sprague-Dawley rat

The effect of wild blueberry consumption on anthocyanin (ACNs) distribution and metabolism in Sprague-Dawley (SD) rats was investigated. Thirty-two rats were fed for 4 or 8 weeks with a control (C) or a wild blueberry-enriched diet (8%) (WB). Anthocyanin profile in plasma, urine, feces, brain, and liver was evaluated by LC-MS/MS, and significantly increased in urine and not in feces after 8 weeks on the WB diet compared to that in 4 weeks, but no anthocyanins were detected in plasma, liver, and brain samples either in the C or WB groups. Metabolites of ACNs were detected in the plasma, urine, feces, and tissues of both the C and WB groups, but the urinary excretion of hippuric acid increased significantly after 4 and 8 weeks of WB consumption. Thus, it seems that ACNs are metabolized by the intestinal microflora to respective phenyl-alkyl acids, which can be further metabolized to benzoic acid. In conclusion, ACNs are bioavailable in rats, and the extent of their metabolism and excretion is based on diet duration. Additionally, urinary hippuric acid content could represent a potential biomarker of ACNs absorption and metabolism in the SD rat under the present experimental conditions.

Tissue distribution of anthocyanins in rats fed a blackberry anthocyanin-enriched diet

Anthocyanins are natural dietary pigments that could be involved in various health effects. The aim of this study was to investigate the distribution of anthocyanins to various organs (bladder, prostate, testes, heart and adipose tissue) in rats fed with a blackberry anthocyanin-enriched diet for 12 days. Identification and quantification of anthocyanins were carried out by HPLC-DAD. The urinary excretion of total anthocyanins (native anthocyanins and their metabolites) was low (0.20 +/- 0.03%, n = 8). Proportions of anthocyanin derivatives (methylated anthocyanins and glucurono-conjugated derivatives) differed according to the organ considered. The bladder contained the highest levels of anthocyanins followed by the prostate. Prostate, testes and heart contained native cyanidin 3-glucoside and a small proportion of cyanidin monoglucuronide. Cyanidin 3-glucoside and methylated derivatives were present in adipose tissue. Thus, anthocyanin feeding in rats resulted in a wide distribution of anthocyanin derivatives to several organs. Identification of target tissues of anthocyanins may then help to understand the mechanisms of action of anthocyanins in vivo.

Evaluation of antihyperglycemia and antihypertension potential of native Peruvian fruits using in vitro models

Local food diversity and traditional crops are essential for cost-effective management of the global epidemic of type 2 diabetes and associated complications of hypertension. Water and 12% ethanol extracts of native Peruvian fruits such as Lucuma (Pouteria lucuma), Pacae (Inga feuille), Papayita arequipeña (Carica pubescens), Capuli (Prunus capuli), Aguaymanto (Physalis peruviana), and Algarrobo (Prosopis pallida) were evaluated for total phenolics, antioxidant activity based on 2, 2-diphenyl-1-picrylhydrazyl radical scavenging assay, and functionality such as in vitro inhibition of alpha-amylase, alpha-glucosidase, and angiotensin I-converting enzyme (ACE) relevant for potential management of hyperglycemia and hypertension linked to type 2 diabetes. The total phenolic content ranged from 3.2 (Aguaymanto) to 11.4 (Lucuma fruit) mg/g of sample dry weight. A significant positive correlation was found between total phenolic content and antioxidant activity for the ethanolic extracts. No phenolic compound was detected in Lucuma (fruit and powder) and Pacae. Aqueous extracts from Lucuma and Algarrobo had the highest alpha-glucosidase inhibitory activities. Papayita arequipeña and Algarrobo had significant ACE inhibitory activities reflecting antihypertensive potential. These in vitro results point to the excellent potential of Peruvian fruits for food-based strategies for complementing effective antidiabetes and antihypertension solutions based on further animal and clinical studies.

sPhospholipase A(2) is inhibited by anthocyanidins

Epidemiological studies suggest that nutritional antioxidants may reduce the incidence of neurodegenerative disorders and age-related cognitive decline. Specifically, protection against oxidative stress and inflammation has served as a rationale for promoting diets rich in vegetables and fruits. The present study addresses secretory phospholipase A(2) (sPLA(2)) as a novel candidate effector of neuroprotection conferred by anthocyanins and anthocyanidins. Using a photometric assay, 15 compounds were screened for their ability to inhibit PLA(2). Of these, cyanidin, malvidin, peonidin, petunidin, and delphinidin achieved K(i) values <or=18 microM, suggesting a modulatory role for berry polyphenols in phospholipid metabolism.

Sirtuin activators

BACKGROUND

Sirtuin 1-7 (SIRT1-7) are deacetylases that are dependent on NAD(+) for their activity. SIRT1 down-regulates p53 activity, increasing lifespan, cell survival, and neuroprotection; it also deacetylates peroxisome proliferator-activated receptor-gamma and its coactivator 1alpha, promoting fat mobilization, increasing mitochondrial size and number, and positively regulating insulin secretion. Sirtuins link nutrient availability and energy metabolism. Calorie restriction, which increases lifespan and is beneficial in age-related disorders, activates sirtuin. Major efforts are thus focused to developing sirtuin activators.

OBJECTIVE

After discussing the potential involvement of sirtuins in pathophysiological processes, this review looks at new, synthetic sirtuin activators.

CONCLUSIONS

To date, resveratrol is the most potent natural compound able to activate SIRT1, mimicking the positive effect of calorie restriction. Resveratrol might help in the treatment or prevention of obesity and in preventing the aging-related decline in heart function and neuronal loss. As resveratrol has low bioavailability and interacts with multiple molecular targets, the development of new molecules with better bioavailability and targeting sirtuin at lower concentrations is a promising field of the medicinal chemistry. New SIRT1 activators that are up to 1000 times more effective than resveratrol have recently been identified. These improve the response to insulin and increase the number and activity of mitochondria in obese mice. Human trials with a formulation of resveratrol with improved bioavailability and with a synthetic SIRT1 activator are in progress.