Effect of Blueberry Consumption on Cardiometabolic Health Parameters in Men with Type 2 Diabetes: An 8-Week, Double-Blind, Randomized, Placebo-Controlled Trial.

BACKGROUND: Blueberries are dietary sources of polyphenols, specifically anthocyanins. Anthocyanins have been identified as having a strong association with type 2 diabetes risk reduction; however, to date few human clinical trials have evaluated the potential beneficial health effects of blueberries in populations with type 2 diabetes. OBJECTIVES: We investigated the effects of blueberry consumption for 8 wk on cardiometabolic parameters in men with type 2 diabetes. METHODS: In a double-blind, parallel-arm, randomized controlled trial, 52 men who are US veterans [mean baseline characteristics: age, 67 y (range: 51-75 y); weight, 102 kg (range: 80-130 kg); BMI (in kg/m2), 34 (range: 26-45)] were randomly assigned to 1 of 2 intervention groups. The interventions were either 22 g freeze-dried blueberries or 22 g placebo. The study participants were asked to consume 11 g freeze-dried blueberries or placebo with each of their morning and evening meals along with their typical diet. RESULTS: Mean ± SE hemoglobin A1c (7.1% ± 0.1% compared with 7.5% ± 0.2%; P = 0.03), fructosamine (275.5 ± 4.1 compared with 292.4 ± 7.9 µmol/L; P = 0.04), triglycerides (179.6 ± 10.1 compared with 199.6 ± 19.9 mg/dL; P = 0.03), aspartate transaminase (23.2 ± 1.4 compared with 30.5 ± 2.7 units/L; P = 0.02), and alanine transaminase (35.6 ± 1.5 compared with 48.3 ± 2.9 units/L; P = 0.0003) were significantly lower for those consuming blueberries for 8 wk than for those consuming the placebo. Fasting plasma glucose concentrations; serum insulin, total cholesterol, LDL-cholesterol, HDL-cholesterol, and C-reactive protein concentrations; blood pressure; and body weight were not significantly different after 8 wk consumption of blueberries compared with the placebo. CONCLUSIONS: Consumption of 22 g freeze-dried blueberries for 8 wk may beneficially affect cardiometabolic health parameters in men with type 2 diabetes.This trial was registered at clinicaltrials.gov as NCT02972996.

Probiotics Blunt the Anti-Hypertensive Effect of Blueberry Feeding in Hypertensive Rats without Altering Hippuric Acid Production.

Previously we showed that feeding polyphenol-rich wild blueberries to hypertensive rats lowered systolic blood pressure. Since probiotic bacteria produce bioactive metabolites from berry polyphenols that enhance the health benefits of berry consumption, we hypothesized that adding probiotics to a blueberry-enriched diet would augment the anti-hypertensive effects of blueberry consumption. Groups (n = 8) of male spontaneously hypertensive rats were fed one of four AIN '93G-based diets for 8 weeks: Control (CON); 3% freeze-dried wild blueberry (BB); 1% probiotic bacteria (PRO); or 3% BB + 1% PRO (BB+PRO). Blood pressure was measured at weeks 0, 2, 4, 6, and 8 by the tail-cuff method, and urine was collected at weeks 4 and 8 to determine markers of oxidative stress (F2-isoprostanes), nitric oxide synthesis (nitrites), and polyphenol metabolism (hippuric acid). Data were analyzed using mixed models ANOVA with repeated measures. Diet had a significant main effect on diastolic blood pressure (p = 0.046), with significantly lower measurements in the BB- vs. CON-fed rats (p = 0.035). Systolic blood pressure showed a similar but less pronounced response to diet (p = 0.220), again with the largest difference between the BB and CON groups. Absolute increase in blood pressure between weeks 0 and 8 tended to be smaller in the BB and PRO vs. CON and BB+PRO groups (systolic increase, p = 0.074; diastolic increase, p = 0.185). Diet had a significant main effect on hippuric acid excretion (p<0.0001), with 2- and ~1.5-fold higher levels at weeks 4 and 8, respectively, in the BB and BB+PRO vs. PRO and CON groups. Diet did not have a significant main effect on F2-isoprostane (p = 0.159) or nitrite excretion (p = 0.670). Our findings show that adding probiotics to a blueberry-enriched diet does not enhance and actually may impair the anti-hypertensive effect of blueberry consumption. However, probiotic bacteria are not interfering with blueberry polyphenol metabolism into hippuric acid.

Cranberries and wild blueberries treated with gastrointestinal enzymes positively modify glutathione mechanisms in Caco-2 cells in vitro.

Beneficial health effects of cranberries (CBs) and wild blueberries (BBs), such as reduced levels of oxidative stress, have been demonstrated in feeding studies. These Vaccinium berries contain high levels of flavonoids; however, the bioavailability of flavonoids is generally low. We investigated the in vitro effects of these berries on intestinal cells, focusing on mitigating oxidative stress and associated reactive oxygen species (ROS). First, we simulated the passage of CB and BB through the gastrointestinal (GI) tract by treating berry homogenates to a battery of digestive enzymes. Then, Caco-2 cells, a model of small intestine epithelial uptake, were exposed to these homogenates for 60 min. Using a cell-free assay, we found that the antioxidant activity in CB homogenates was not affected by these enzymes, but that BB homogenates treated with gut enzymes had 43% lower free-radical quenching activity (P < 0.05). However, both of the enzyme-treated homogenates were still able to counteract the ROS-generating ability of H2O2 added exogenously to Caco-2 cells. Berry homogenates also increased mitochondrial metabolic rates at 60 min posttreatment, as measured by MTT assays. Enzyme-treated CB (but not BB) homogenates increased the levels of reduced glutathione (GSH) relative to oxidized glutathione (GSSG), a critical indicator of the cellular redox state (P < 0.05). Our data suggest that CBs do not lose their antioxidant ability when passing through the GI tract, and specifically, digested CB may serve to enhance cytoprotective effects in intestinal cells by reducing potential damage caused by free radicals and ROS derived from other food sources.

Choice of diet impacts the incidence of stroke-related symptoms in the spontaneously hypertensive stroke-prone rat model.

The spontaneously hypertensive stroke-prone (SHRSP) rat is a commonly used model of cerebrovascular disease and hypertension. SHRSP rats have been shown to develop stroke-related symptoms (SRS) by age 14 weeks when fed a purified diet, such as AIN-93G, supplemented with 1% NaCl. We conducted a pathology pilot study to compare the incidence of SRS in SHRSP rats fed either AIN-93G (with 1% NaCl in drinking water) or commercially available rat chow (with 4% NaCl in the diet), starting at 8 weeks of age. These results prompted us to analyze data from 5 earlier feeding trials using SHRSP rats. Overall, we found that SHRSP rats fed AIN-93G purified diet for 8 or 17 weeks did not demonstrate SRS (n = 18), whereas all SHRSP rats fed lab chow exhibited SRS at age 15.1 ± 0.6 weeks (n = 23). In addition, SHRSP rats fed lab chow had decreased mass gain starting at age 13 weeks, as well as decreased feed efficiencies after the first 5 weeks of feeding (p < 0.05). In conclusion, our data suggest that diet composition is a major contributor to the onset of stroke in SHRSP rats and that diet choice should be critically evaluated based on endpoint measures in the SHRSP model.

North American cranberry (Vaccinium macrocarpon) stimulates apoptotic pathways in DU145 human prostate cancer cells in vitro.

Diets rich in fruits and vegetables have been shown to improve patient prognosis in a variety of cancers, a benefit partly derived from phytochemicals, many of which target cell death pathways in tumor cells. Cranberries (Vaccinium macrocarpon) are a phytochemical-rich fruit containing a variety of polyphenolic compounds. As flavonoids have been shown to induce apoptosis in human tumor cells, this study investigated the hypothesis that cranberry-mediated cytotoxicity in DU145 human prostate adenocarcinoma cells involves apoptosis. The results showed that induction of apoptosis in these cells occurred in response to treatment with whole cranberry extract and occurred through caspase-8 mediated cleavage of Bid protein to truncated Bid resulting in cytochrome-C release from the mitochondria. Subsequent activation of caspase-9 ultimately resulted in cell death as characterized by DNA fragmentation. Increased Par-4 protein expression was observed, and this is suggested to be at least partly responsible for caspase-8 activation. Proanthocyanidin-enriched and flavonol-enriched fractions of cranberry also increased caspase-8 and caspase-9 activity, suggesting that these compounds play a possible role in apoptosis induction. These findings indicate that cranberry phytochemicals can induce apoptosis in prostate cancer cells in vitro, and these findings further establish the potential value of cranberry phytochemicals as possible agents against prostate cancer.

Feeding blueberry diets inhibits angiotensin II-converting enzyme (ACE) activity in spontaneously hypertensive stroke-prone rats.

Feeding flavonoid-rich blueberries to spontaneously hypertensive stroke-prone rats (SHRSP) lowers blood pressure. To determine whether this is due to inhibition of angiotensin-converting enzyme (ACE) activity, as seen with other flavanoid-rich foods, we fed blueberries to SHRSP and normotensive rats and analyzed ACE activity in blood and tissues. After 2 weeks on a control diet, the hypertensive rats showed 56% higher levels of ACE activity in blood as compared with the normotensive rats (p < 0.05). Feeding a 3% blueberry diet for 2 weeks lowered ACE activity in the SHRSP (p < 0.05) but not the normotensive rats. ACE activity in plasma of SHRSP was no longer elevated at weeks 4 and 6, but blueberry feeding inhibited ACE in SHRSP after 6 weeks. Blueberry diets had no effect on ACE activity in lung, testis, kidney, or aorta. Our results suggest that dietary blueberries may be effective in managing early stages of hypertension, partially due to an inhibition of soluble ACE activity.

Diets containing blueberry extract lower blood pressure in spontaneously hypertensive stroke-prone rats.

Oxidative stress in the vasculature and kidneys contributes to hypertension, a major risk factor for cardiovascular disease. Blueberries (BB) are rich in antioxidants, and so we hypothesized that feeding diets enriched with BB would slow the development of hypertension in spontaneously hypertensive stroke-prone rats (SHRSP). Eight-week-old normotensive rats and SHRSP were fed either a control diet (Con) or a diet enriched with 3% freeze-dried BB for 8 weeks. Systolic blood pressure (SBP) was measured at weeks 2, 4, 6, 7, and 8 by the tail cuff method, and urine was collected at weeks 4 and 8. The SBP was elevated in SHRSP relative to normotensive rats over the entire 8-week feeding period. In SHRSP consuming BB, SBP was 19% lower at week 4 and 30% lower at week 6, relative to SHRSP on Con. Maximum SBP was 216 +/- 11 mm Hg in SHRSP consuming Con vs 178 +/- 15 mm Hg in the BB-fed group (P = .036). Spontaneously hypertensive stroke-prone rats had elevated levels of urine F2-isoprostanes/creatinine relative to normotensive rats, indicating systemic oxidative stress in this strain. Blueberry feeding had no effect on urinary excretion of F2-isoprostanes; therefore, it is unlikely that a systemic antioxidant effect of BB is responsible for the antihypertensive effects at weeks 4 and 6. Blueberry-fed rats had reduced markers of renal oxidative stress, such as proteinuria and kidney nitrites. Thus, a 3% BB diet may be capable of protecting the kidneys from oxidative damage in SHRSP, thereby reducing the magnitude of hypertension.

Inhibition of matrix metalloproteinase activity in DU145 human prostate cancer cells by flavonoids from lowbush blueberry (Vaccinium angustifolium): possible roles for protein kinase C and mitogen-activated protein-kinase-mediated events.

Regulation of the matrix metalloproteinases (MMPs) is crucial to regulate extracellular matrix (ECM) proteolysis which is important in metastasis. This study investigated the mechanism(s) by which three flavonoid-enriched fractions from lowbush blueberry (Vaccinium angustifolium) down-regulate MMP activity in DU145 human prostate cancer cells. Metalloproteinase activity was evaluated from cells exposed to "crude," anthocyanin-enriched (AN) and proanthocyanidin-enriched (PAC) fractions. Differential down-regulation of MMPs was observed. The activity of the endogenous tissue inhibitors of metalloproteinases (TIMPs) from these cells was also evaluated. Increases in TIMP-1 and TIMP-2 activity were observed in response to these fractions. The possible involvement of protein kinase C (PKC) and mitogen-activated protein (MAP) kinase pathways in the flavonoid-mediated decreases in MMP activity was observed. These findings indicate that blueberry flavonoids may use multiple mechanisms in down-regulating MMP activity in these cells.

Blueberry flavonoids inhibit matrix metalloproteinase activity in DU145 human prostate cancer cells.

Regulation of the matrix metalloproteinases (MMPs), the major mediators of extracellular matrix (ECM) degradation, is crucial to regulate ECM proteolysis, which is important in metastasis. This study examined the effects of 3 flavonoid-enriched fractions (a crude fraction, an anthocyanin-enriched fraction, and a proanthocyanidin-enriched fraction), which were prepared from lowbush blueberries (Vaccinium angustifolium), on MMP activity in DU145 human prostate cancer cells in vitro. Using gelatin gel electrophoresis, MMP activity was evaluated from cells after 24-hr exposure to blueberry fractions. All fractions elicited an ability to decrease the activity of MMP-2 and MMP-9. Of the fractions tested, the proanthocyanidin-enriched fraction was found to be the most effective at inhibiting MMP activity in these cells. No induction of either necrotic or apoptotic cell death was noted in these cells in response to treatment with the blueberry fractions. These findings indicate that flavonoids from blueberry possess the ability to effectively decrease MMP activity, which may decrease overall ECM degradation. This ability may be important in controlling tumor metastasis formation.