A Blueberry-Enriched Diet Attenuates Nephropathy in a Rat Model of Hypertension via Reduction in Oxidative Stress

Abstract

Objective and BackgroundTo assess renoprotective effects of a blueberry-enriched diet in a rat model of hypertension. Oxidative stress (OS) appears to be involved in the development of hypertension and related renal injury. Pharmacological antioxidants can attenuate hypertension and hypertension-induced renal injury; however, attention has shifted recently to the therapeutic potential of natural products as antioxidants. Blueberries (BB) have among the highest antioxidant capacities of fruits and vegetables.Methods and ResultsMale spontaneously hypertensive rats received a BB-enriched diet (2% w/w) or an isocaloric control diet for 6 or 12 weeks or 2 days. Compared to controls, rats fed BB-enriched diet for 6 or 12 weeks exhibited lower blood pressure, improved glomerular filtration rate, and decreased renovascular resistance. As measured by electron paramagnetic resonance spectroscopy, significant decreases in total reactive oxygen species (ROS), peroxynitrite, and superoxide production rates were observed in kidney tissues in rats on long-term dietary treatment, consistent with reduced pathology and improved function. Additionally, measures of antioxidant status improved; specifically, renal glutathione and catalase activities increased markedly. Contrasted to these observations indicating reduced OS in the BB group after long-term feeding, similar measurements made in rats fed the same diet for only 2 days yielded evidence of increased OS; specifically, significant increases in total ROS, peroxynitrite, and superoxide production rates in all tissues (kidney, brain, and liver) assayed in BB-fed rats. These results were evidence of “hormesis” during brief exposure, which dissipated with time as indicated by enhanced levels of catalase in heart and liver of BB group.ConclusionLong-term feeding of BB-enriched diet lowered blood pressure, preserved renal hemodynamics, and improved redox status in kidneys of hypertensive rats and concomitantly demonstrated the potential to delay or attenuate development of hypertension-induced renal injury, and these effects appear to be mediated by a short-term hormetic response.

Tart cherry supplementation improves working memory, hippocampal inflammation, and autophagy in aged rats

“…Previous studies from our laboratory and others found no differences in food intake when rats were fed diets supplemented with various berry fruits (e.g., blueberry, cranberry, and strawberry) Ahmet et al 2009;Shaughnessy et al 2009;Elks et al 2011;Malin et al 2011). Therefore, it was unexpected that tart cherry-fed rats would consume significantly more food than control-fed rats.…”

Natriuretic Peptide Receptor-C Attenuates Hypertension in Spontaneously Hypertensive Rats

“…47 In the present study, we demonstrate that the VSMC and aorta from SHRs exhibit decreased levels of NO which may be because of the decreased expression of eNOS as well as to the enhanced levels of O 2 − . In this regard, the decreased expression of eNOS and NO has been reported in cardiac myocyte and vascular smooth muscle of hypertensive animals 35,48,49 and suggests that the increased BP in SHRs may also be attributed to the decreased levels of NO. Furthermore, eNOS knockout mice were shown to exhibit increased BP.…”

“…Furthermore, our results showing that the levels of ONOO − and nitrotyrosine were increased in VSMC, aorta, and kidney from SHRs that may be formed by the reaction of NO with O 2 − are in accordance with the studies of other investigators who have also reported an increased levels of ONOO − and nitrotyrosine content in aorta and mesenteric arteries as well as in kidney from SHRs without and with typical symptoms of metabolic syndrome. 35,36,49 However, we report for the first time that in vivo C-ANP [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] treatment decreased the enhanced levels of ONOO − and nitrotyrosine in VSMC, aorta, and kidney from SHRs. Thus, it may be suggested that C-ANP 4-23 -induced decreased levels of NO because of decreased expression of eNOS, O 2 − , and ONOO− and resultant decreased nitroxidative stress may be responsible for C-ANP 4-23 -induced attenuation of high BP.…”

Blueberries and Neuronal Aging

“…Another interesting possibility for the long-term beneficial effects of blueberries is an effect called hormesis [21]. It may be that short-term exposure to plant substances, such as blueberries, could increase reactive oxygen/reactive nitrogen species which, in turn, would lead to upregulation of antioxidant defense mechanisms to enhance long-term protection.…”

“…It may be that short-term exposure to plant substances, such as blueberries, could increase reactive oxygen/reactive nitrogen species which, in turn, would lead to upregulation of antioxidant defense mechanisms to enhance long-term protection. A recent study [21 ]has shown that 2-day feeding with a blueberry diet resulted in significant increases in total reactive oxygen species, superoxide, and peroxynitrite production in kidney, brain, and liver tissues compared to control-fed rats. However, after long-term feeding (6–12 weeks), there was evidence of reduced reactive oxygen/reactive nitrogen species.…”