Aleksandra S Kristo

University of Maine, Orono, Minnesota, United States

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Publications (10)27.85 Total impact

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    ABSTRACT: This study evaluates the effect of wild blueberry (WB) consumption on the biomechanical properties of the aorta in the obese Zucker rat (OZR), a model of the metabolic syndrome. Thirty-six OZRs and 36 lean controls (lean Zucker rats) were placed either on a WB-enriched or a control (C) diet for 8 weeks. Phenylephrine (Phe)-mediated vasoconstriction and acetylcholine (Ach)-mediated vasorelaxation in the aortic vessel were investigated, as well as the contribution of the nitric oxide synthase and cyclooxygenase (COX) pathways in each of the above responses by using specific inhibitors. Obese Zucker rats exhibited a reduced vasocontstrictor response to Phe and an exaggerated vasorelaxant response to Ach. The WB diet partially restored Phe-induced constrictor responses and attenuated Ach-induced relaxant responses in OZR. Plasma nitric oxide was significantly attenuated (22.1 ± 1.1 μmol·L(-1), WB vs 25.6 ± 1.4 μmol·L(-1), C, p ≤ 0.05) with the WB diet. Thromboxane A2 levels in the aortic effluent were not significantly affected in the WB diet group, while PGI2 concentration significantly increased (766.5 ± 92.2 pg·mg(-1) aorta in the WB vs 571.7 ± 37.8 pg·g(-1) aorta in the C group, p ≤ 0.05). Downregulation of inducible nitric oxide synthase and COX2 expression in the OZR aorta was observed in the WB diet group. In conclusion, WB consumption altered the biomechanical properties of the OZR aorta by partially restoring the impaired Phe-induced constrictor responses and attenuating the exaggerated response to Ach-induced vasorelaxation.
    No preview · Article · Feb 2014 · Applied Physiology Nutrition and Metabolism
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    ABSTRACT: Abstract The role of wild blueberries (WB) on key signaling steps of nitric oxide (NO) and cyclooxygenase (COX) pathways was examined in spontaneously hypertensive rats (SHRs) after eight weeks on a control (C) or an 8% w/w WB diet. Aortic rings from SHRs were stimulated with phenylephrine (Phe) in the absence or presence of inhibitors of: soluble guanylyl cyclase (sGC), phosphodiesterase-5 (PDE5), prostaglandin I2 (PGI2) synthase and thromboxane A2 (TXA2) synthase. Additionally, enzymatic activities in these pathways were determined by the concentration of NO, cyclic guanosine monophosphate (cGMP), PGI2 and TXA2. In the WB-fed SHR, attenuation of Phe-induced vasoconstriction was mediated by an increased synthesis or preservation of cGMP. Despite an increased release of PGI2 in the WB group, neither inhibition of PGI2 or TXA2 synthase resulted in a different response to Phe between the control and the WB rings. Hence, in the SHR, WB decrease Phe-mediated vasoconstriction under basal conditions by enhancing NO-cGMP signaling without a significant involvement of the COX pathway.
    No preview · Article · Aug 2013 · International Journal of Food Sciences and Nutrition
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    ABSTRACT: The present study investigated the potential of a wild blueberry (WB)-enriched diet to improve blood lipid profile and modulate the expression of genes related to lipid homeostasis in obese Zucker rats (OZR), a model of the metabolic syndrome with severe dyslipidaemia. For this purpose, twenty OZR and twenty lean Zucker rats (LZR; controls) were placed either on a control (C) or an 8 % WB diet for 8 weeks. Plasma total cholesterol (TC), HDL-cholesterol and TAG concentrations were determined. The relative expression of six genes involved in lipid metabolism was also determined in both the liver and the abdominal adipose tissue (AAT). Plasma TAG and TC concentrations were significantly lower in the OZR following WB consumption (4228 (sem 471) and 2287 (sem 125) mg/l, respectively) than in those on the C diet (5475 (sem 315) and 2631 (sem 129) mg/l, P< 0·05), while there was no change in HDL-cholesterol concentration. No significant effects were observed for plasma lipids in the LZR. Following WB consumption, the expression of the transcription factors PPARα and PPARγ in the OZR was increased in the AAT, while that of sterol regulatory element-binding protein 1 (SREBP-1) was decreased in the liver and AAT. The expression of fatty acid synthase was significantly decreased in both the liver and AAT and that of ATP-binding cassette transporter 1 was increased in the AAT following WB consumption. In conclusion, WB consumption appears to improve lipid profiles and modulate the expression of key enzymes and transcription factors of lipid metabolism in severely dyslipidaemic rats.
    Preview · Article · Aug 2013 · The British journal of nutrition
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    ABSTRACT: The gastrointestinal tract is populated by an array of microbial species that play an important role in metabolic and immune functions. The composition of microorganisms is influenced by the components of the host's diet and can impact health. In the present study, dietary enrichment of lowbush wild blueberries (LWB) was examined to determine their effect on colon microbial composition and their potential in promoting gut health. The microbial composition and functional potential of the colon microbiota from Sprague Dawley rats fed control diets (AIN93) and LWB-enriched diets (AIN93+8% LWB powder substituting for dextrose) for 6 weeks were assessed using Illumina shotgun sequencing and bioinformatics tools. Our analysis revealed an alteration in the relative abundance of 3 phyla and 22 genera as representing approximately 14 and 8% of all phyla and genera identified, respectively. The LWB-enriched diet resulted in a significant reduction in the relative abundance of the genera Lactobacillus and Enterococcus. In addition, hierarchal analysis revealed a significant increase in the relative abundance of the phylum Actinobacteria, the order Actinomycetales, and several novel genera under the family Bifidobacteriaceae and Coriobacteriaceae, in the LWB group. Functional annotation of the shotgun sequences suggested that approximately 9% of the 4709 Kyoto Encyclopaedia of Gene and Genome (KEGG) hits identified were impacted by the LWB-diet. Open Reading Frames (ORFs) assigned to KEGG category xenobiotics biodegradation and metabolism were significantly greater in the LWB-enriched diet compared to the control and included the pathway for benzoate degradation [PATH:ko00362] and glycosaminoglycan degradation [PATH:ko00531]. Moreover, the number of ORFs assigned to the bacterial invasion of epithelial cells [PATH:ko05100] pathway was approximately 8 fold lower in the LWB group compared to controls. This study demonstrated that LWBs have the potential to promote gut health and can aid in the development of optimal diets.
    Preview · Article · Jun 2013 · PLoS ONE
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    ABSTRACT: The metabolic syndrome (MetS) is a major public health problem in the United States. Chronic inflammation is a critical component of the MetS, leading to dramatically increased risk of type II diabetes and cardiovascular disease. This study investigates the ability of a wild-blueberry-enriched diet to improve the proinflammatory status associated with MetS in the obese Zucker rat (OZR). Circulating levels of key inflammatory markers and their expression in the liver and abdominal adipose tissue were examined in OZR and its genetic control, the lean Zucker rat (LZR), after feeding a control or an 8% wild blueberry diet (WB) for 8 weeks from age 8 to 16 weeks. In the OZR, WB consumption resulted in decreased plasma concentrations of tumor necrosis factor (TNF)-α (-25.6%, P<.05), interleukin (IL)-6 (-14.9%, P<.05) and C-reactive protein (CRP) (-13.1%, P<.05) and increased adiponectin concentration (+21.8%, P<.05). Furthermore, expression of IL-6, TNF-α and nuclear factor (NF)-kB was down-regulated in both the liver (-65%, -59% and -25%, respectively) and the abdominal adipose tissue (-64%, -52% and -65%), while CRP expression was down-regulated only in the liver (-25%). In the abdominal adipose tissue, similar trends were also observed in LZR following WB treatment, with decreased liver expression of NF-kB, CRP, IL-6 and TNF-α (-24%, -16%, -21% and -50%) and increased adiponectin expression (+25%). Results of this study suggest that wild blueberry consumption exerts an overall anti-inflammatory effect in the OZR, a model of the metabolic syndrome.
    No preview · Article · Mar 2013 · The Journal of nutritional biochemistry
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    ABSTRACT: We have previously reported that wild blueberry (Vaccinium angustifolium)-enriched diets (WB) attenuate aortic adrenergic response through endothelial-mediated pathways. The duration of dietary intervention necessary to induce the positive changes on vasomotor tone has not been studied to date. Thus, our objective was to investigate the temporal effect of WB consumption on vascular function and reactivity in Sprague-Dawley (SD) rat aorta after 4 and 7 weeks of dietary treatment. Forty male SD rats were randomly assigned to a control (AIN-93) (C) or a WB diet for 4 or 7 weeks. Vascular ring studies were conducted in 3-mm isolated rat aortic rings to investigate vasoconstriction induced by six doses of the α(1)-adrenergic agonist, L-phenylephrine (Phe, 10(-8)-3×10(-6) M) alone or in the presence of the NOS inhibitor, L-N(G)-monomethyl-arginine (L-NMMA, 10(-4)M). The maximum force of contraction (F(max)) and vessel sensitivity (pD(2)) were determined. Analysis of variance revealed no significant differences on F(max) after 4 weeks of the WB diet but only a significant increase in pD(2) in the absence of L-NMMA. Seven week WB consumption significantly attenuated contraction in response to L-Phe and resulted in lower pD(2). Inhibition of NOS induced a significant increase in the constrictor response in both diet groups at both time periods, with the WB group fed for 7 weeks having the greater response. Thus wild blueberries incorporated into the diet at 8% w/w positively affect vascular smooth muscle contractility and sensitivity but these effects are evident only after 7 weeks of WB consumption.
    Full-text · Article · Feb 2012 · Nutrition, metabolism, and cardiovascular diseases: NMCD
  • Dorothy Klimis-Zacas · Aleksandra S. Kristo
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    ABSTRACT: We were the first to document, that dietary wild blueberries, high in phenolics and anthocyanins, affect the arterial biomechanical properties in Sprague-Dawley (SD) rats with functional endothelium and adult Spontaneously Hypertensive Rats (SHRs) with endothelial dysfunction. Wild blueberry diets decrease phenylephrine (Phe)-induced vasoconstriction through endothelium-related pathways, such as nitric oxide (NO) and may affect acetylcholine (Ach)-induced relaxation by modulation of the cyclooxygenase (COX) pathway and possibly the production/activity of COX-derived prostanoids in the adult SHR. Furthermore wild blueberry-enriched diets result in structural alterations of aortic glycosaminoglycans (GAGs) such as concentration, redistribution and lower concentration of oversulfated disaccharides in galactosaminoglycan (GalAG) populations, affecting cellular signal transduction pathways and leading to a less atherogenic profile in the adult SHR. Thus, wild blueberry consumption may be important in regulation of vasomotor tone and atheroprotection with implications to preventing cardiovascular disease (CVD) and improving endothelial dysfunction.
    No preview · Chapter · Jan 2012
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    ABSTRACT: Glycosaminoglycans (GAGs) are essential polysaccharide components of extracellular matrix and cell surface with key roles on numerous vascular wall functions. Previous studies have documented a role of wild blueberries on the GAG profile of the Sprague-Dawley rat with a functional endothelium as well as in the vascular tone of the spontaneously hypertensive rat (SHR) with endothelial dysfunction. In the present study, the effect of wild blueberries on the composition and structure of aortic GAGs was examined in 20-week-old SHRs after 8 weeks on a control (C) or a wild blueberry-enriched diet (WB). Aortic tissue GAGs were isolated following pronase digestion and anion-exchange chromatography. Treatment of the isolated populations with specific GAG-degrading lyases and subsequent electrophoretic profiling revealed the presence of three GAG species, i.e., hyaluronic acid (HA), heparan sulfate (HS) and galactosaminoglycans (GalAGs). A notable reduction of the total sulfated GAGs and a redistribution of the aortic GAG pattern were recorded in the WB as compared to the C group: a 25% and 10% increase in HA and HS, respectively, and an 11% decrease in GalAGs. Fine biochemical analysis of GalAGs at the level of constituent disaccharides with high-performance capillary electrophoresis revealed a notable increase of nonsulfated (18.0% vs. 10.7%) and a decrease of disulfated disaccharides (2.2% vs. 5.3%) in the WB aorta. This is the first study to report the redistribution of GAGs at the level of composition and their fine structural characteristics with implications for the endothelial dysfunction of the SHR.
    No preview · Article · Sep 2011 · The Journal of nutritional biochemistry
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    ABSTRACT: The effect of a wild blueberry-enriched diet on vasoconstriction and vasorelaxation was examined in the adult, 20-week-old spontaneously hypertensive rat (SHR) after 8 weeks of a control (C) or an 8% wild blueberry (WB) diet. Nitric oxide (NO)- and cyclooxygenase (COX)-mediated aortic responses were examined ex vivo with the agonists L-phenylephrine (Phe) and acetylcholine (Ach), in the absence or presence of the NO synthase (NOS) inhibitor L-NG-monomethyl arginine (L-NMMA) or the COX inhibitor mefenamic acid (MFA). The vasoconstriction elicited by Phe was reduced in the WB group, attributed to the NO pathway, favoring a lower vascular tone under basal conditions. Acetylcholine-induced vasorelaxation in the WB group was possibly mediated through the COX, but not the NO pathway. These findings document the potential of wild blueberries to modify major pathways of vasomotor control and improve the vascular tone in the adult SHR with endothelial dysfunction.
    No preview · Article · Oct 2010 · Journal of Agricultural and Food Chemistry
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    ABSTRACT: We have previously reported on the positive effects of wild blueberries on arterial contractile response to alpha(1) adrenergic stimuli and on endothelium-mediated vasorelaxation. Our present study was designed to evaluate the effects of the dietary enrichment with wild blueberries on aortic function and reactivity in the developmental phase of essential hypertension in spontaneously hypertensive rats (SHR). We investigated the possible influence blueberries may have on the acetylcholine (Ach)-induced endothelium-dependent vasorelaxation and phenylephrine-induced vasoconstriction in young SHRs, as well as the contribution of the nitric oxide (NO) synthase and cyclooxygenase (COX) pathways in each of the above responses in an animal model with dysfunctional endothelium. Vascular ring studies were conducted in 3-mm isolated rat aortic ring preparations to investigate vasoconstriction induced by l-Phenylephrine (Phe, 10(-8) to 3x10(-6)M) and vasorelaxation induced by acetylcholine (Ach, 10(-9) to 3x10(-6)M). The major findings of our study were that in Phe-induced vasoconstriction, SHR-BB aortas relaxed to a greater degree in comparison to controls when mefenamic acid (MFA) was present and that the incubation with this COX inhibitor failed to restore - and in fact decreased - the maximum vasodilator response to Ach, in comparison to controls. Our vessel reactivity index (pD(2)) observations indicate that blueberries appear to modulate cell membrane-agonist (Ach) interactions primarily in response to Ach in the young SHR model, but not to the alpha(1) adrenoreceptor agonist. Incorporating wild blueberries in the diet seems to affect the endothelium-dependent vasorelaxation by modulating alternative metabolic pathway(s) (such as affecting the production/activity of COX-derived products) in the young SHR aorta.
    No preview · Article · Feb 2009 · The Journal of nutritional biochemistry

Publication Stats

98 Citations
27.85 Total Impact Points

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  • 2009-2014
    • University of Maine
      • Department of Food Science and Human Nutrition
      Orono, Minnesota, United States