Blueberry polyphenols alter gut microbiota & phenolic metabolism in rats

Dietary Polyphenols and Gut Microbiota Cross-Talk: Molecular and Therapeutic Perspectives for Cardiometabolic Disease: A Narrative Review

The intricate interplay between the gut microbiota and polyphenols has emerged as a captivating frontier in understanding and potentially harnessing the therapeutic potential of these bioactive compounds. Phenolic compounds, renowned for their antioxidant, anti-inflammatory, antidiabetic, and anticancer properties, are subject to intricate transformations within the gut milieu, where the diverse microbial ecosystem exerts profound effects on their metabolism and bioavailability. Conversely, polyphenols exhibit a remarkable capacity to modulate the composition and activity of the gut microbiota, fostering a bidirectional relationship that extends beyond mere nutrient processing. This symbiotic interaction holds significant implications for human health, particularly in cardiometabolic diseases such as diabetes mellitus, metabolic-dysfunction-associated steatotic liver disease, and cardiovascular disease. Through a comprehensive exploration of molecular interactions, this narrative review elucidates the reciprocal dynamics between the gut microbiota and polyphenols, unveiling novel avenues for therapeutic intervention in cardiometabolic disorders. By unravelling the intricate cross-talk between these two entities, this review underscores the multifaceted roles of polyphenols in overall health and the pivotal role of gut microbiota modulation as a promising therapeutic strategy in mitigating the burden of cardiometabolic diseases.

The state of the science on the health benefits of blueberries: a perspective

Mounting evidence indicates that blueberry consumption is associated with a variety of health benefits. It has been suggested that regular consumption of blueberries can support and/or protect against cardiovascular disease and function, pre-diabetes and type 2 diabetes, and brain and cognitive function in individuals with health conditions and age-related decline. Further, mechanistic investigations highlight the role of blueberry anthocyanins in mediating these health benefits, in part through interactions with gut microbiota. Also, nutritional interventions with blueberries have demonstrated the ability to improve recovery following exercise-induced muscle damage, attributable to anti-inflammatory effects. Despite these advancements in blueberry health research, research gaps persist which affects the generalizability of findings from clinical trials. To evaluate the current state of knowledge and research gaps, a blueberry health roundtable with scientific experts convened in Washington, DC (December 6-7, 2022). Discussions centered around five research domains: cardiovascular health, pre-diabetes and diabetes, brain health and cognitive function, gut health, and exercise recovery. This article synthesizes the outcomes of a blueberry research roundtable discussion among researchers in these domains, offering insights into the health benefits of blueberries and delineating research gaps and future research directions.

Determination of Flavonoids and Phenolic Acids in the Liver of Wistar Rats after a Dietary Enrichment with Corinthian Currant (Vitis vinifera L., var. Apyrena): A Liquid Chromatography-Tandem Mass Spectrometry Study

Corinthian currants are dried fruits produced from Vitis vinifera L. var. Apyrena grape. This study investigated the distribution of phenolic compounds in male Wistar rat livers following two distinct Corinthian currant long-term dietary intake protocols (3 and 10% w/w). Method optimization, comparing fresh and lyophilized tissues, achieved satisfactory recoveries (>70%) for most analytes. Enzymatic hydrolysis conditions (37 °C, pH 5.0) minimally affected phenolics, but enzyme addition showed diverse effects. Hydrolyzed lyophilized liver tissue from rats consuming Corinthian currants (3 and 10% w/w) exhibited elevated levels of isorhamnetin (20.62 ± 2.27 ng/g tissue and 33.80 ± 1.38 ng/g tissue, respectively), along with similar effects for kaempferol, quercetin, and chrysin after prolonged Corinthian currant intake. This suggests their presence as phase II metabolites in the fasting-state liver. This study is the first to explore phenolic accumulation in rat liver, simulating real conditions of dried fruit consumption, as seen herein with Corinthian currant.

Engineered plant extracellular vesicles for natural delivery across physiological barriers

Extracellular vesicles (EVs) are nanoscale luminal vesicles that participate in the information transfer of proteins, nucleic acids, and lipids between cells, thereby playing a role in the treatment of diseases and the delivery of nutrients. In recent years, plant-derived EVs (PDEVs) containing bioactive compounds have attracted increasing interest due to their better biocompatibility and lower cytotoxicity in healthy tissues. In the biomedical field, PDEVs have been used as cargo carriers to achieve various functions through engineering modification techniques. This review focuses on the biogenesis, isolation, and identification of PDEVs. We discuss the surface functionalization of PDEVs to enhance therapeutic efficacy, thereby improving their efficiency as a next-generation drug delivery vehicle and their feasibility to treat diseases across the physiological barriers, while critically analyzing the current challenges and opportunities.

Effect of free and bound polyphenols from Rosa roxburghii Tratt distiller's grains on moderating fecal microbiota

Rosa roxburghii Tratt distiller's grains (R. roxburghii DGs), the main by-product of wine processing, showed functional value and potential for high-value usage which benefited from their rich polyphenols. In this study, the free and bound polyphenols from R. roxburghii DGs were extracted and their potential effect on modulating fecal microbiota was investigated using in vitro fecal fermentation. The free polyphenols (26.32-26.45 mg GAE/g) showed higher antioxidant activity compared to the bound polyphenols (8.76-9.01 mg GAE/g). The free and bound polyphenols significantly improved the fecal microbiota community structure and enhanced short chain fatty acids concentrations after the stimulated colonic fermentation for 24 h. Furthermore, the effect of R. roxburghii DGs polyphenols on modulating fecal microbiota was primarily attributed to quercetin, catechin, kaempferol, cyanidin and baicalin. This research suggests that R. roxburghii DGs are a promising source of natural antioxidants and prebiotic foods.

Bioactive Components in Fruit Interact with Gut Microbes

Fruits contain many bioactive compounds, including polysaccharides, oligosaccharides, polyphenols, anthocyanins, and flavonoids. All of these bioactives in fruit have potentially beneficial effects on gut microbiota and host health. On the one hand, fruit rich in active ingredients can act as substrates to interact with microorganisms and produce metabolites to regulate the gut microbiota. On the other hand, gut microbes could promote health effects in the host by balancing dysbiosis of gut microbiota. We have extensively analyzed significant information on bioactive components in fruits based on Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Although the deep mechanism of action of bioactive components in fruits on gut microbiota needs further study, these results also provide supportive information on fruits as a source of dietary active ingredients to provide support for the adjunctive role of fruits in disease prevention and treatment.

A mixture of Nordic berries improves cognitive function, metabolic function and alters the gut microbiota in C57Bl/6J male mice

Our diets greatly influence our health. Multiple lines of research highlight the beneficial properties of eating berries and fruits. In this study, a berry mixture of Nordic berries previously identified as having the potential to improve memory was supplemented to young C57Bl/6J male mice to investigate effects on cognition function, metabolic health, markers of neuroinflammation, and gut microbiota composition. C57Bl/6J male mice at the age of 8 weeks were given standard chow, a high-fat diet (HF, 60%E fat), or a high-fat diet supplemented with freeze-dried powder (20% dwb) of a mixture of Nordic berries and red grape juice (HF + Berry) for 18 weeks (n = 12 animals/diet group). The results show that supplementation with the berry mixture may have beneficial effects on spatial memory, as seen by enhanced performance in the T-maze and Barnes maze compared to the mice receiving the high-fat diet without berries. Additionally, berry intake may aid in counteracting high-fat diet induced weight gain and could influence neuroinflammatory status as suggested by the increased levels of the inflammation modifying IL-10 cytokine in hippocampal extracts from berry supplemented mice. Furthermore, the 4.5-month feeding with diet containing berries resulted in significant changes in cecal microbiota composition. Analysis of cecal bacterial 16S rRNA revealed that the chow group had significantly higher microbial diversity, as measured by the Shannon diversity index and total operational taxonomic unit richness, than the HF group. The HF diet supplemented with berries resulted in a strong trend of higher total OTU richness and significantly increased the relative abundance of Akkermansia muciniphila, which has been linked to protective effects on cognitive decline. In conclusion, the results of this study suggest that intake of a Nordic berry mixture is a valuable strategy for maintaining and improving cognitive function, to be further evaluated in clinical trials.

Metabolic Fate of Lignin in Birch Glucuronoxylan Extracts as Dietary Fiber Studied in a Rat Model

SCOPE

While previously considered inert, recent studies suggest lignin metabolism with unknown metabolic fates is occurring in the gastrointestinal tract of several animal models. This study focuses on analyzing the potential metabolites of lignin.

METHODS AND RESULTS

The diets of rats include relatively pure birch glucuronoxylan (pureGX) with residual lignin or lignin-rich GX (GXpoly) in their diet. Nuclear magnetic spectroscopy of the lignin isolated from the GXpoly-fed rats fecal sample shows high alteration in chemical structure, whereas lignin-carbohydrate complexes (LCCs) are enriched in fecal samples from the pureGX group. Moreover, the increased syringyl-to-guaiacyl (S/G) ratio suggests that lignin G-units are predominantly metabolized based on pyrolysis gas chromatography-mass spectrometry (pyr-GC/MS). The presence of small phenolic metabolites identified in urine samples of the GXpoly group, for example, ferulic and sinapic acids, their sulfate and glucuronide derivatives, and 4-sulfobenzylalcohol, suggests that the small fragmented lignin metabolites in the large intestine enter the plasma, and are further processed in the liver. Finally, the relative abundances of polyphenol-degrading Enterorhabdus and Akkermansia in the gut microbiota are associated with lignin metabolism.

CONCLUSION

These findings give further evidence to lignin metabolism in the gut of nonruminants and provide insight to the potential microbes and metabolic routes.

Moderate consumption of freeze-dried blueberry powder increased net bone calcium retention compared with no treatment in healthy postmenopausal women: a randomized crossover trial

BACKGROUND

Preclinical studies suggest that blueberry consumption is associated with improved bone health.

OBJECTIVES

We conducted a blueberry dose-response study in ovariectomized (OVX)-rats that informed a study in postmenopausal women using the urinary appearance of calcium (Ca) tracers from prelabeled bone to reflect changes in bone balance. We hypothesized that blueberry consumption would reduce bone loss in a dose-dependent manner compared with no treatment.

METHODS

OVX rats were fed 4 doses of blueberry powder (2.5%, 5%, 10%, and 15%) in randomized order to determine bone 45Ca retention. Fourteen healthy, nonosteoporotic women ≥4 y past menopause were dosed with 50 nCi of 41Ca, a long-lived radioisotope, and equilibrated for 5 mo to allow 41Ca deposition in bone. Following a 6-wk baseline period, participants were assigned to a random sequence of 3 6-wk interventions, a low (17.5 g/d), medium (35 g/d), or high (70 g/d) dose of freeze-dried blueberry powder equivalent to 0.75, 1.5, or 3 cups of fresh blueberries incorporated into food and beverage products. Urinary 41Ca:Ca ratio was measured by accelerator mass spectrometry. Serum bone resorption biomarkers and urinary polyphenols were measured at the end of each control and intervention period. Data were analyzed using a linear mixed model and repeated measures analysis of variance.

RESULTS

In both OVX rats and postmenopausal women, blueberry interventions benefited net bone calcium balance at lower but not at higher doses. In women, net bone calcium retention increased by 6% with the low (95% CI: 2.50, 8.60; P < 0.01) and 4% with the medium (95% CI: 0.96, 7.90; P < 0.05) dose compared with no treatment. Urinary excretion of hippuric acid increased dose-dependently with blueberry consumption. No significant relationships were found between bone resorption biomarkers, 25-hydroxyvitamin D, and interventions.

CONCLUSIONS

Moderate consumption (<1 cup/d) of blueberries may be an effective strategy to attenuate bone loss in healthy postmenopausal women. This trial was registered at clinicaltrials.gov as NCT02630797.

Crop, Host, and Gut Microbiome Variation Influence Precision Nutrition: An Example of Blueberries

Epidemiological studies have shown associations between polyphenol-rich fruit intake and bone health, and preclinical studies have shown that blueberries improve bone health. To determine the genotype and dose of blueberries that are effective in ameliorating age-related bone loss, a multi-institutional team of investigators performed in vitro, preclinical, and clinical studies on blueberry varieties that differed in flavonoid profiles. Principal component analysis was used to select blueberry genotypes that varied in anthocyanin profiles. Total phenolic content did not predict the bioavailability of polyphenolic compounds in rats. A range in bioavailability was observed in individual polyphenolic compounds across genotypes. Both alpha and beta diversity analyses indicated that gut microbiome profiles varied with blueberry dose in rats. Additionally, the identification of specific taxa, such as Prevotellaceae_UCG-001 and Coriobacteriales, increasing after blueberry consumption adds to the mounting evidence of their role in polyphenol metabolism. All of the sources of variation can inform blueberry breeding practices to influence precision nutrition.

The Antioxidant Effect of Dietary Bioactives Arises from the Interplay between the Physiology of the Host and the Gut Microbiota: Involvement of Short-Chain Fatty Acids

The maintenance of redox homeostasis is associated with a healthy status while the disruption of this mechanism leads to the development of various pathological conditions. Bioactive molecules such as carbohydrates accessible to the microbiota (MACs), polyphenols, and polyunsaturated fatty acids (PUFAs) are food components best characterized for their beneficial effect on human health. In particular, increasing evidence suggests that their antioxidant ability is involved in the prevention of several human diseases. Some experimental data indicate that the activation of the nuclear factor 2-related erythroid 2 (Nrf2) pathway-the key mechanism in the maintenance of redox homeostasis-is involved in the beneficial effects exerted by the intake of PUFAs and polyphenols. However, it is known that the latter must be metabolized before becoming active and that the intestinal microbiota play a key role in the biotransformation of some ingested food components. In addition, recent studies, indicating the efficacy of the MACs, polyphenols, and PUFAs in increasing the microbial population with the ability to yield biologically active metabolites (e.g., polyphenol metabolites, short-chain fatty acids (SCFAs)), support the hypothesis that these factors are responsible for the antioxidant action on the physiology of the host. The underlying mechanisms through which MACs, polyphenols, and PUFAs might influence the redox status have not been fully elucidated, but based on the efficacy of SCFAs as Nrf2 activators, their contribution to the antioxidant efficacy of dietary bioactives cannot be excluded. In this review, we aimed to summarize the main mechanisms through which MACs, polyphenols, and PUFAs can modulate the host's redox homeostasis through their ability to directly or indirectly activate the Nrf2 pathway. We discuss their probiotic effects and the role played by the alteration of the metabolism/composition of the gut microbiota in the generation of potential Nrf2-ligands (e.g., SCFAs) in the host's redox homeostasis.

Dietary Polyphenol, Gut Microbiota, and Health Benefits

Polyphenols, which are probably the most important secondary metabolites produced by plants, have attracted tremendous attention due to their health-promoting effects, including their antioxidant, anti-inflammatory, antibacterial, anti-adipogenic, and neuro-protective activities, as well as health properties. However, due to their complicated structures and high molecular weights, a large proportion of dietary polyphenols remain unabsorbed along the gastrointestinal tract, while in the large intestine they are biotransformed into bioactive, low-molecular-weight phenolic metabolites through the residing gut microbiota. Dietary polyphenols can modulate the composition of intestinal microbes, and in turn, gut microbes catabolize polyphenols to release bioactive metabolites. To better investigate the health benefits of dietary polyphenols, this review provides a summary of their modulation through in vitro and in vivo evidence (animal models and humans), as well as their possible actions through intestinal barrier function and gut microbes. This review aims to provide a basis for better understanding the relationship between dietary polyphenols, gut microbiota, and host health.

Bioactives in the Food Supply: Effects on CVD Health

PURPOSE OF REVIEW

Interest in preventing atherosclerosis and cardiovascular disease extends beyond essential nutrients and dietary patterns. This article reviews the potential for bioactive compounds to play a role in prevention and the recent process in guidance for developing policy for bioactives.

RECENT FINDINGS

A framework for developing recommended intakes of bioactives dietary substances was recently developed and the first guideline expected is for a bioactive targeted for cardiometabolic health. Bioactives target endothelial health, the gut microbiome, serum lipids, blood pressure, inflammation, and oxidative stress. The evidence base is growing and will be enhanced further with the discovery of good biomarkers of exposure and health outcomes. A robust evidence base is essential to develop policy and influence clinical practice for bioactives, an exciting and growing area of research.

Blueberry Polyphenols do not Improve Bone Mineral Density or Mechanical Properties in Ovariectomized Rats

Osteoporosis-related bone fragility fractures are a major public health concern. Given the potential for adverse side effects of pharmacological treatment, many have sought alternative treatments, including dietary changes. Based on recent evidence that polyphenol-rich foods, like blueberries, increase calcium absorption and bone mineral density (BMD), we hypothesized that blueberry polyphenols would improve bone biomechanical properties. To test this, 5-month-old ovariectomized Sprague-Dawley rats (n = 10/gp) were orally gavaged for 90 days with either a purified extract of blueberry polyphenols (0-1000 mg total polyphenols/kg bw/day) or lyophilized blueberries (50 mg total polyphenols/kg bw/day). Upon completion of the dosing regimen, right femur, right tibia, and L1-L4 vertebrae were harvested and assessed for bone mineral density (BMD), with femurs being further analyzed for biomechanical properties via three-point bending. There were no differences in BMD at any of the sites analyzed. For bone mechanical properties, the only statistically significant difference was the high dose group having greater ultimate stress than the medium dose, although in the absence of differences in other measures of bone mechanical properties, we concluded that this result, while statistically significant, had little biological significance. Our results indicate that blueberry polyphenols had little impact on BMD or bone mechanical properties in an animal model of estrogen deficiency-induced bone loss.

Designing, Conducting, and Documenting Human Nutrition Plant-Derived Intervention Trials

Best practices for designing, conducting, documenting, and reporting human nutrition randomized controlled trials were developed and published in Advances in Nutrition. Through an example of the randomized clinical trial on blueberries and bone health funded by the National Institutes of Health, this paper will illustrate the elements of those best practices that apply specifically to plant-based intervention clinical trials. Unique study design considerations for human feeding interventions with bioactive plant compounds include the difficulty of blinding the intervention, background nutritional status of participants, carry-over effects of the intervention, benefits of a run-in period, lack of safety/tolerability data, and nutrition-specific regulatory policies. Human nutrition randomized controlled trials are the gold standard for establishing causal relations between an intervention and health outcome measures. Rigorous studies and documentation define the quality of the evidence-base to inform public health guidelines and to establish personalized dietary recommendations for the health-promoting plant components.

Multiomics Approach to Precision Sports Nutrition: Limits, Challenges, and Possibilities

Most sports nutrition guidelines are based on group average responses and professional opinion. Precision nutrition for athletes aims to improve the individualization of nutrition practices to optimize long-term performance and health. This is a 2-step process that first involves the acquisition of individual-specific, science-based information using a variety of sources including lifestyle and medical histories, dietary assessment, physiological assessments from the performance lab and wearable sensors, and multiomics data from blood, urine, saliva, and stool samples. The second step consists of the delivery of science-based nutrition advice, behavior change support, and the monitoring of health and performance efficacy and benefits relative to cost. Individuals vary widely in the way they respond to exercise and nutritional interventions, and understanding why this metabolic heterogeneity exists is critical for further advances in precision nutrition. Another major challenge is the development of evidence-based individualized nutrition recommendations that are embraced and efficacious for athletes seeking the most effective enhancement of performance, metabolic recovery, and health. At this time precision sports nutrition is an emerging discipline that will require continued technological and scientific advances before this approach becomes accurate and practical for athletes and fitness enthusiasts at the small group or individual level. The costs and scientific challenges appear formidable, but what is already being achieved today in precision nutrition through multiomics and sensor technology seemed impossible just two decades ago.

Blueberry Counteracts Prediabetes in a Hypercaloric Diet-Induced Rat Model and Rescues Hepatic Mitochondrial Bioenergetics

The paramount importance of a healthy diet in the prevention of type 2 diabetes is now well recognized. Blueberries (BBs) have been described as attractive functional fruits for this purpose. This study aimed to elucidate the cellular and molecular mechanisms pertaining to the protective impact of blueberry juice (BJ) on prediabetes. Using a hypercaloric diet-induced prediabetic rat model, we evaluated the effects of BJ on glucose, insulin, and lipid profiles; gut microbiota composition; intestinal barrier integrity; and metabolic endotoxemia, as well as on hepatic metabolic surrogates, including several related to mitochondria bioenergetics. BJ supplementation for 14 weeks counteracted diet-evoked metabolic deregulation, improving glucose tolerance, insulin sensitivity, and hypertriglyceridemia, along with systemic and hepatic antioxidant properties, without a significant impact on the gut microbiota composition and related mechanisms. In addition, BJ treatment effectively alleviated hepatic steatosis and mitochondrial dysfunction observed in the prediabetic animals, as suggested by the amelioration of bioenergetics parameters and key targets of inflammation, insulin signaling, ketogenesis, and fatty acids oxidation. In conclusion, the beneficial metabolic impact of BJ in prediabetes may be mainly explained by the rescue of hepatic mitochondrial bioenergetics. These findings pave the way to support the use of BJ in prediabetes to prevent diabetes and its complications.

Effects of Concord grape juice flavor intensity and phenolic compound content on glycemia, appetite and cognitive function in adults with excess body weight: a randomized double-blind crossover trial

Background & aims: Concord grape (Vitis lambrusca) juice (CGJ) contains a unique combination of polyphenolic compounds with diverse effects on human health. It also has an intense sensory profile that may modify food choice. Daily consumption of CGJ over 8 weeks reduced fasting blood glucose. However, the impact on 24h-postprandial glucose response from CGJ is still not clear. The purpose of this study was to assess the effect of CGJ flavor intensity and phenolic content on 24 h postprandial glucose concentrations, appetitive sensations, and cognitive function in adults with excess body weight when consumed alone or with a meal. Methods: In a randomized, double-blind, crossover design study, participants consumed three types of beverages: 100% CGJ, a polyphenol-free grape flavored drink with the same flavor essence (LP) or a polyphenol-free grape flavored drink with reduced flavor essence (LPF) either without (trial I) or with (trial II) a meal. 24 h glucose was measured through continuous glucose monitoring. Phenolic metabolite excretion was assessed in 24 h urine samples. Appetite (hunger, thirst, fullness, desire to eat, and prospective consumption) and cognitive function (alertness, energetic, strength, calmness, and relaxation) were assessed hourly through visual analog scales. Results: Thirty-four adults completed trial I and 34 adults completed trial II. When consumed with a meal, beverages with customary flavor essence (CGJ and LP) reduced hunger, desire to eat, and prospective consumption and consumption of the polyphenol-free reduced flavor essence beverage was associated with higher 24 h glucose _tAUC. No consistent effects were observed for cognitive outcomes. When consumed alone, CGJ was related to lower glycemic responses by those excreting a higher concentration of the phenolic metabolite iso/ferulic-3'-O-glucuronide, but in beverages without CG phenolics and reduced flavor essence, glycemia was higher among those excreting higher concentrations of caffeic acid-O-sulfate. Conclusions: Both natural phenolics and flavor essence of CGJ may help to moderate appetite and glycemia. Clinical Trials registered at http://www.clinicaltrials.gov: NCT03409484 (trial I) and NCT03409497 (trial II).

(Poly)phenol toxicity in vivo following oral administration: A targeted narrative review of (poly)phenols from green tea, grape, and anthocyanin-rich extracts

Fruit- and vegetable-derived (poly)phenols are secondary plant metabolites that may have beneficial effects on human health when consumed regularly. Recent years have seen rapid growth in both consumer demand for and research interest in (poly)phenol-rich dietary supplements, natural colorants, and functional foods. As these products continue to enter the marketplace and (poly)phenol intake patterns change from traditional food products to these sources, attention must be paid to the potential for toxicity from consuming elevated doses of (poly)phenols. To date, much remains unknown regarding the safety of high doses of (poly)phenols, especially in vivo. In this targeted narrative review, we summarize evidence from in vivo investigations of (poly)phenol toxicity after oral administration of green tea extracts, grape-derived phenolics, and anthocyanin-rich extracts. There is limited evidence of overt toxicity from oral ingestion of these (poly)phenol-rich sources, though more research on the safety of high doses-as well as defining what constitutes a "high" dose of both individual and complex mixtures of (poly)phenols-is needed before these observations can be used to create dietary guidance for consumers.