ARS | Publication request: A blueberry enriched diet attenuates nephropathy in a rat model of hypertension via reduction in oxidative stress

Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 2, 2011
Publication Date: September 15, 2011
Citation: Elks, C.M., Mariappan, N., Shukitt Hale, B., Joseph, J.A., Ingram, D.K., Francis, J. 2011. A blueberry enriched diet attenuates nephropathy in a rat model of hypertension via reduction in oxidative stress. PLoS One. 6(9)e24028.

Interpretive Summary: Oxidative stress appears to be involved in the development of hypertension (high blood pressure) and related kidney damage. Previous research has indicated that pharmaceutical antioxidants can reduce hypertension and associated kidney dysfunction. Therefore, dietary supplementation of similar antioxidants has become an area of interest, particularly blueberries, which are among plant foods with the highest levels of antioxidants. In this study, rats prone to hypertension were fed a diet enriched with blueberry for six or twelve weeks. These rats, as compared to control-fed rats, showed improved blood pressure as well as decreases in various markers of oxidative stress in kidney, brain, and liver tissue. All of these changes are consistent with reduced pathology and improved function. The results found in these studies led to the conclusion that long-term feeding of blueberry-enriched diet had healthful effects in regard to blood pressure, blood circulation in the kidneys, and defense against oxidative damage in the kidneys of hypertensive rats. This indicates potential in the use of antioxidant-rich fruits and vegetables to delay, or potentially reverse, kidney damage associated with hypertensive injury.

Technical Abstract: Objective: To assess renoprotective effects of a blueberry-enriched diet in a rat model of hypertension. Background: 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 Results: Male 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. This was evidence of “hormesis” during brief exposure, which dissipated with time as indicated by enhanced levels of catalase in heart and liver of BB group. Conclusion: Long-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.