Blueberry Diet Research Articles

Blueberry polyphenols attenuate kainic acid-induced decrements in cognition and alter inflammatory gene expression in rat hippocampus

Cognitive impairment in age-related neurodegenerative diseases such as Alzheimer's disease may be partly due to long-term exposure and increased susceptibility to inflammatory insults. In the current study, we investigated whether polyphenols in blueberries can reduce the deleterious effects of inflammation induced by central administration of kainic acid by altering the expression of genes associated with inflammation. To this end, 4-month-old male Fischer-344 (F344) rats were fed a control, 0.015% piroxicam (an NSAID) or 2% blueberry diet for 8 weeks before either Ringer's buffer or kainic acid was bilaterally micro-infused into the hippocampus. Two weeks later, following behavioral evaluation, the rats were killed and total RNA from the hippocampus was extracted and used in real-time quantitative RT-PCR (qRT-PCR) to analyze the expression of inflammation-related genes. Kainic acid had deleterious effects on cognitive behavior as kainic acid-injected rats on the control diet exhibited increased latencies to find a hidden platform in the Morris water maze compared to Ringer's buffer-injected rats and utilized non-spatial strategies during probe trials. The blueberry diet, and to a lesser degree the piroxicam diet, was able to improve cognitive performance. Immunohistochemical analyses of OX-6 expression revealed that kainic acid produced an inflammatory response by increasing the OX-6 positive areas in the hippocampus of kainic acid-injected rats. Kainic acid up-regulated the expression of the inflammatory cytokines IL-1β and TNF-α, the neurotrophic factor IGF-1, and the transcription factor NF-κB. Blueberry and piroxicam supplementations were found to attenuate the kainic acid-induced increase in the expression of IL-1β, TNF-α, and NF-κB, while only blueberry was able to augment the increased IGF-1 expression. These results indicate that blueberry polyphenols attenuate learning impairments following neurotoxic insult and exert anti-inflammatory actions, perhaps via alteration of gene expression.

Blueberry-induced changes in spatial working memory correlate with changes in hippocampal CREB phosphorylation and brain-derived neurotrophic factor (BDNF) levels

Phytochemical-rich foods have been shown to be effective at reversing age-related deficits in memory in both animals and humans. We show that a supplementation with a blueberry diet (2% w/w) for 12 weeks improves the performance of aged animals in spatial working memory tasks. This improvement emerged within 3 weeks and persisted for the remainder of the testing period. Memory performance correlated well with the activation of cAMP-response element-binding protein (CREB) and increases in both pro- and mature levels of brain-derived neurotrophic factor (BDNF) in the hippocampus. Changes in CREB and BDNF in aged and blueberry-supplemented animals were accompanied by increases in the phosphorylation state of extracellular signal-related kinase (ERK1/2), rather than that of calcium calmodulin kinase (CaMKII and CaMKIV) or protein kinase A. Furthermore, age and blueberry supplementation were linked to changes in the activation state of Akt, mTOR, and the levels of Arc/Arg3.1 in the hippocampus, suggesting that pathways involved in de novo protein synthesis may be involved. Although causal relationships cannot be made among supplementation, behavior, and biochemical parameters, the measurement of anthocyanins and flavanols in the brain following blueberry supplementation may indicate that changes in spatial working memory in aged animals are linked to the effects of flavonoids on the ERK-CREB-BDNF pathway.

Blueberry diets improve glucose tolerance and decrease oxidative stress in spontaneously hypertensive stroke‐prone rats

Metabolic syndrome, characterized by insulin resistance, hyperglycemia and dyslipidemia, is a risk factor for cardiovascular disease. Eating fruits and vegetables benefits the symptoms of metabolic syndrome, and so we tested the effects of blueberries on insulin resistance in spontaneously hypertensive stroke‐prone rats (SHRSP). Control rats (WISTAR) and SHRSP were fed either a control AIN93G diet (CON) or a diet containing 1% or 3% freeze‐dried blueberry extract (BB) for 6 wks. All rats drank 2% NaCl. Plasma glucose and insulin were measured prior to and 15, 30, and 60 min following oral gavage of 40% glucose. The overall insulin response (AUC) to oral glucose was lower in SHRSP compared to WISTAR on CON diet (p<0.05), resulting in glucose being elevated in SHRSP at 15 minutes (p<0.001). In contrast, SHRSP fed 1% and 3% BB had insulin responses similar to WISTAR and there were no significant differences in plasma glucose levels between the groups. SHRSP showed signs of oxidative stress, with elevated levels of F2‐isoprostanes/creatinine in the urine (p<0.05). Feeding 3% BB lowered F2‐isoprostanes to normal values. There was no evidence of dyslipidemia in SHRSP. Our data suggest that SHRSP fed BB have less oxidative stress, and improved overall health. As well, feeding blueberries made animals better able to withstand a glucose challenge by increasing the insulin response, thereby decreasing blood glucose levels. Including blueberries in the diet may benefit metabolic syndrome. Funded by NSERC & Atlantic Innovation Fund.

Dietary Blueberry Supplementation Affects Growth but Not Vascularization of Neural Transplants

Transplantation of neural tissue has been attempted as a treatment method for neurodegenerative disorders. Grafted neurons survive to a lesser extent into middle-aged or aged hosts, and survival rates of <10% of grafted neurons is common. Antioxidant diets, such as blueberry, can exert powerful effects on developing neurons and blood vessels in vitro, but studies are lacking that examine the effects of these diets on transplanted tissues. In this study, we examined the effects of a blueberry diet on survival, growth, and vascularization of fetal hippocampal tissue to the anterior chamber of the eye of young or middle-aged female rats. Previous work from our group showed significant increase in neuronal survival and development with blueberry diet in grafts. However, the effects of antioxidant diet on vascular development in grafts have not been explored previously. The age of the host affected individual vessel morphology in that aged hosts contained grafts with thick, undeveloped walls, and wider lumen. The blood-brain barrier also appeared to be affected by the age of the host. The blueberry diet did not affect vessel morphology or density of vessel-associated protein markers but gave rise to significantly increased growth capacity, cytoarchitecture, and the final size of hippocampal grafts.

A blueberry-enriched diet provides cellular protection against oxidative stress and reduces a kainate-induced learning impairment in rats

Young male Fischer-344 rats were fed a diet containing 2% blueberry (BB) extract or control diet for at least 8 weeks and then received bilateral hippocampal injections of kainic acid (KA 200 ng/0.5 μl) or phosphate buffered saline (PBS). One week later rats were trained in one-way active footshock avoidance in a straight runway followed the next day by training in a footshock motivated 14-unit T-maze with documented sensitivity to hippocampal glutamatergic manipulations. Based on analyses of several performance variables, KA-treated rats exhibited clearly impaired learning performance; however, the BB diet significantly reduced this impairment. Supporting the behavioral findings, stereological assessment of CA1 pyramidal neurons documented greater neuronal loss in KA-treated controls compared to KA-treated rats on the BB diet. In an in vitro experiment, FaO cells grown in medium supplemented with serum from BB-fed rats had enhanced viability after exposure to hydrogen peroxide. These findings suggest that BB supplementation may protect against neurodegeneration and cognitive impairment mediated by excitotoxicity and oxidative stress.

Effects of blueberry extracts on DNA damage levels and phase II enzyme activities in rats.

Blueberry extracts been shown to reduce oxidative stress and increase phase II enzyme activities in vitro. We examined these effects in vivo. Male Sprague-Dawley rats (n=8 per group) were fed AIN-93 or modified AIN-93 diets for 3 weeks. Modified diets were 10% freeze dried blueberries substituted for sucrose (BLU), blueberry polyphenol extract and sugars to match the 10% blueberry diet (POLY), sugars equivalent to the 10% blueberry diet, 1% blueberry flavonoids (1% FL) and 0.2% blueberry flavonoids. The polyphenol extract was obtained using a 40:40:20:0.1 (v:v:v:v) ratio of acetone/methanol/water/formic acid solution. By further purifying the polyphenol extract with an Oasis HLB cartridge then eluting with acidified methanol, total flavonoids were obtained. Liver and colon mucosa glutathione-S-transferase (GST) and quinone reductase (QR) and liver UDP-glucuronosyltransferase (UGT) activities were measured as were urinary F2-isoprostanes and liver and lymphocyte DNA damage. GST, QR and UGT activities were not significantly increased at p<0.05 by blueberries or blueberry fractions, but some slight increases in activity were seen. For example, compared to controls, the BLU, POLY, and 1% FL groups had 28%, 27% and 24% higher GST activity in liver tissue. DNA damage assessed with the Comet assay was lowest for both liver and colon mucosa in the 1%FL group, but results were not significant. This study shows that in vivo results do not always agree with in vitro findings and that extremely high doses may be required to elicit significant effects. Support: GA FOODPAC, GA Ag Exp Sta., GA Blueberry Growers Assoc.

Blueberry diets delay the onset of hypertension and reduce insulin resistance in spontaneously hypertensive stroke prone rats

Hypertension is a major risk factor for cardiovascular disease, the number one cause of disability and death in North America. Thus, strategies (e.g. diet modification, drugs) to manage hypertension are essential. Lowbush blueberries (Vaccinium angustifolium) are rich in polyphenolic antioxidants which are beneficial to stroke, and may have vasorelaxation effects. We fed spontaneously hypertensive stroke-prone rats (SHrSP) and control rats (CON) either control diet or a diet containing 3% freeze-dried blueberry extract for 8 wks, to determine effects of blueberry diets on systolic blood pressure (BP). BP increased in both SHrSP groups over 8 wks. However BP in SHrSP on control diets was significantly higher than in CON by wk 4 (p=0.016), while BP in SHrSP consuming blueberries was not significantly elevated relative to CON until wk 7 (p=0.001). Maximum BP was 216 ± 11 mmHg (wk 7), and 178 ± 15 mmHg (wk 8) in SHrSP consuming control and blueberry diets respectively. At wk 6, BP of SHrSP on blueberry diet was 30% lower (p=0.002) than in SHrSP on control diet. In a separate group of SHrSP fed blueberries for 6 wks, a 48% lower glucose/insulin ratio was seen compared to rats on control diet (P=0.08, n=3). These results indicate that a 3% blueberry diet is capable of delaying the onset and reducing the magnitude of hypertension, and may reduce insulin resistance in SHrSP. Supported by NSERC and AIF in grants to MS and KGP.

Beneficial effects of fruit extracts on neuronal function and behavior in a rodent model of accelerated aging

Exposing young rats to particles of high-energy and charge (HZE particles) enhances indices of oxidative stress and inflammation and disrupts the functioning of the dopaminergic system and behaviors mediated by this system in a manner similar to that seen in aged animals. Previous research has shown that diets supplemented with 2% blueberry or strawberry extracts have the ability to retard and even reverse age-related deficits in behavior and signal transduction in rats, perhaps due to their antioxidant and anti-inflammatory properties. This study evaluated the efficacy of these diets on irradiation-induced deficits in these parameters by maintaining rats on these diets or a control diet for 8 weeks prior to being exposed to whole-body irradiation with 1.5Gy of 1GeV/n high-energy 56Fe particles. Irradiation impaired performance in the Morris water maze and measures of dopamine release 1 month following radiation; these deficits were protected by the antioxidant diets. The strawberry diet offered better protection against spatial deficits in the maze because strawberry-fed animals were better able to retain place information (a hippocampally mediated behavior) compared to controls. The blueberry diet, on the other hand, seemed to improve reversal learning, a behavior more dependent on intact striatal function. These data suggest that 56Fe particle irradiation causes deficits in behavior and signaling in rats which were ameliorated by an antioxidant diet and that the polyphenols in these fruits might be acting in different brain regions.

Wild blueberry ( Vaccinium angustifolium) consumption affects the composition and structure of glycosaminoglycans in Sprague-Dawley rat aorta

It has been documented that increased intake of polyphenols may provide protection against coronary heart disease and stroke. Blueberries ( Vaccinium angustifolium) are one of the richest sources of antioxidants among fruits and vegetables. Phenolic compounds from berry extracts inhibit human low density lipoprotein and liposome oxidation. Glycosaminoglycans (GAGs) and proteoglycans (PGs) are structural components of aortas with great structural diversity. Their interaction with compounds such as enzymes, cytokines, growth factors, proteins and lipoproteins and their subsequent role in degenerative diseases has been documented. We investigated the effects of a diet rich in blueberries on the content and structure of GAGs. Sprague-Dawley rats were fed either a control (C) or a blueberry (B) diet for 13 weeks. Aortic tissue GAGs were isolated with papain digestion, alkaline borohydride treatment and anion-exchange chromatography. Cellulose acetate electrophoresis and treatment of the fractions with specific lyases revealed the presence of three GAG populations, i.e. hyaluronan (HA), heparan sulfate (HS) and galactosaminoglycans (GalAGs). Disaccharide composition was determined by high-performance capillary electrophoresis following enzymatic degradation. A 13% higher amount of total GAGs in aortas of B-fed rats was attributed to a higher content of GalAGs (67%). Determination of the sulfated disaccharides showed an overall lower concentration of oversulfated disaccharides in both HS and GalAG populations in the aortas of the B group. Our results demonstrate for the first time that a diet rich in blueberries results in structural alterations in rat aortic tissue GAGs. These changes may affect cellular signal transduction pathways and could have major consequences for the biological function of GAG molecules within the vascular environment.

Blueberry supplemented diet reverses age-related decline in hippocampal HSP70 neuroprotection

Dietary supplementation with antioxidant rich foods can decrease the level of oxidative stress in brain regions and can ameliorate age-related deficits in neuronal and behavioral functions. We examined whether short-term supplementation with blueberries might enhance the brain's ability to generate a heat shock protein 70 (HSP70) mediated neuroprotective response to stress. Hippocampal (HC) regions from young and old rats fed either a control or a supplemented diet for 10 weeks were subjected to an in vitro inflammatory challenge (LPS) and then examined for levels of HSP70 at various times post LPS (30, 90 and 240 min). While baseline levels of HSP70 did not differ among the various groups compared to young control diet rats, increases in HSP70 protein levels in response to an in vitro LPS challenge were significantly less in old as compared to young control diet rats at the 30, 90 and 240 min time points. However, it appeared that the blueberry diet completely restored the HSP70 response to LPS in the old rats at the 90 and 240 min times. This suggests that a short-term blueberry (BB) intervention may result in improved HSP70-mediated protection against a number of neurodegenerative processes in the brain. Results are discussed in terms of the multiplicity of the effects of the BB supplementation which appear to range from antioxidant/anti-inflammatory activity to signaling.

Anthocyanins in aged blueberry-fed rats are found centrally and may enhance memory

Research has shown that fruits and vegetables containing high levels of polyphenolics (flavonoids) display high total antioxidant activity. Our laboratory found that various fruit and vegetable extracts, particularly blueberry (BB), were effective in reversing age-related deficits in neuronal signaling and behavioral parameters following 8 weeks of feeding, possibly due to their polyphenolic content. However, it was unclear if these phytonutrients were able to directly access the brain from dietary BB supplementation (BBS). The present study examined whether different classes of polyphenols could be found in brain areas associated with cognitive performance following BBS. Thus, 19 month old F344 rats were fed a control or 2% BB diet for 8–10 weeks and tested in the Morris water maze (MWM), a measure of spatial learning and memory. LC–MS analyses of anthocyanins in the diet and subsequently in different brain regions of BBS and control rats were carried out. Several anthocyanins (cyanidin-3- O -ß-galactoside, cyanidin-3- O -ß-glucoside, cyanidin-3- O -ß-arabinose, malvidin-3- O -ß-galactoside, malvidin-3- O -ß-glucoside, malvidin-3- O -ß-arabinose, peonidin-3- O -ß-arabinose and delphinidin-3- O -ß-galactoside) were found in the cerebellum, cortex, hippocampus or striatum of the BBS rats, but not the controls. These findings are the first to suggest that polyphenolic compounds are able to cross the blood brain barrier and localize in various brain regions important for learning and memory. Correlational analyses revealed a relationship between MWM performance in BBS rats and the total number of anthocyanin compounds found in the cortex. These findings suggest that these compounds may deliver their antioxidant and signaling modifying capabilities centrally.

Wild Blueberry-Rich Diets Affect the Contractile Machinery of the Vascular Smooth Muscle in the Sprague–Dawley Rat

Weanling male Sprague-Dawley rats were randomly fed a control diet (AIN-93) (C) or a blueberry diet (B) for 13 weeks, or a reverse diet (R) (C diet for 13 weeks, switched to the B diet for 8 weeks). Aortas were excised, and two intact and two endothelium-denuded rings were immersed in tissue baths containing physiological salt solution at 37 degrees C and aerated with 95% O(2) and 5% CO(2) (pH 7.4). Following equilibration and preconditioning under 1.5-g preload, cumulative dose-response curves were generated with six doses of the alpha1-adrenergic receptor-selective agonist L-phenylephrine (L-Phe, 10(8)-3 x 10(-6) M) and relaxed with one dose of acetylcholine (3 x 10(-6) M) to assess intact endothelium. The maximum force of contraction (Fmax) and vessel sensitivity (pD(2)) were determined in intact and endothelium-denuded rings. A two-way analysis of variance test revealed that blueberry-fed animals (B and R diets) developed a significantly lower F (max) (0.873 +/- 0.0463 and 0.9266 +/- 0.0463 g, respectively) when contracted with L-Phe, compared with the animals on the C diet (1.109 +/- 0.0463 g) (P < .05). The pD(2) of the intact rings was not significantly different among diet groups. Additionally, diet did not significantly affect the mean F (max) or pD(2) of endothelium-denuded rings. Our results indicate for the first time that wild blueberries incorporated into the diet affect the vascular smooth muscle contractile machinery by suppressing the alpha1-adrenergic receptor agonist-mediated contraction while having no effect on membrane sensitivity of the endothelial or vascular smooth muscle cell layer. Furthermore, their mechanism of action seems to be accomplished through an endothelium-dependent pathway.

Effect of diet on the disruption of operant responding at different ages following exposure to 56Fe particles

Rats were exposed to 2.0 Gy of (56)Fe particles to study the relationship between age and diet in the heavy particle-induced disruption of performance on an ascending fixed-ratio task. Irradiation produced a disruption of operant responding in rats tested 5 and 8 months after exposure, which was prevented by maintaining the rats on a diet containing strawberry, but not blueberry, extract. When tested 13 and 18 months after irradiation there were no differences in performance between the radiated rats maintained on control, strawberry or blueberry diets. These observations suggest that the beneficial effects of antioxidant diets may be dependent upon the age of testing.

Blueberry Supplemented Diet: Effects on Object Recognition Memory and Nuclear Factor-kappa B Levels in Aged Rats

It has been reported that an antioxidant-rich, blueberry-supplemented rat diet may retard brain aging in the rat. The present study determined whether such supplementation could prevent impaired object recognition memory and elevated levels of the oxidative stress-responsive protein, nuclear factor-kappa B (NF-κB) in aged Fischer-344 rats. Twelve aged rats had been fed a 2% blueberry supplemented diet for 4 months prior to testing. Eleven aged rats and twelve young rats had been fed a control diet. The rats were tested for object recognition memory on the visual paired comparison task. With a 1-h delay between training and testing, aged control diet rats performed no better than chance. Young rats and aged blueberry diet rats performed similarly and significantly better than the aged control diet group. Levels of NF-κB in five brain regions of the above subjects were determined by western blotting assays. In four regions, aged control diet rats had significantly higher average NF-κB levels than young animals on the control diet. In four regions, aged blueberry diet rats had significantly lower levels of NF-κB than aged control diet rats. Normalized NF-κB levels (averaged across regions and in several individual regions) correlated negatively and significantly with the object memory scores.

Feeding Rats Diets Enriched in Lowbush Blueberries for Six Weeks Decreases Ischemia-induced Brain Damage

Oxidative stress is an important element in the etiology of ischemic stroke. Lowbush blueberries (Vaccinium angustifolium Aiton) have a high antioxidant capacity and thus we determined whether consumption of lowbush blueberries would protect neurons from stroke-induced damage. Rats were fed AIN-93G diets containing 0 or 14.3% blueberries (g fresh weight/100 g feed) for 6 weeks. Stroke was then simulated by ligation of the left common carotid artery (ischemia), followed by hypoxia. One week later, plasma and urine were collected, and neuronal damage in the hippocampus was determined histologically. In control rats, hypoxia-ischemia resulted in 40±2% loss of neurons in the hippocampus of the left cerebral hemisphere, as compared to the right hemisphere. Rats on blueberry-supplemented diets lost only 17±2% of neurons in the ischemic hippocampus. Neuroprotection was observed in the CA1 and CA2 regions, but not CA3 region, of the hippocampus. The blueberry diet had no detectable effects on the plasma or urine oxygen radical absorbance capacity (ORAC) or plasma lipids. We conclude that consumption of lowbush blueberries by rats confers protection to the brain against damage from ischemia, suggesting that inclusion of blueberries in the diet may improve ischemic stroke outcomes.