Jonathan Knott

Introduction: Hypertension remains one of the most important preventable causes of mortality world-wide. (1) It is estimated that more than 40% of persons greater than 25 years old have hypertension. The damage caused by long standing, uncontrolled hypertension can lead to a variety of serious complications including myocardial infarction, stroke, renal failure, left ventricular hypertrophy, and death. (2) It has been proposed that increases in certain inflammatory mediators such as TNF-a, IL-6, and NF-kB can lead to decreased endothelial nitric oxide production, causing endothelial dysfunction. This endothelial dysfunction leads to vascular remodeling that increases systemic vascular resistance and causes hypertension. (3,4,5,6) The Dietary Approach to Stop Hypertension (DASH) diet has been shown to decrease levels of these circulating inflammatory mediators and reduce blood pressure. (4,7) A large component of the diet consists of fruits and vegetables, so one study examined the effects of polyphenols extracted from apple peels on the expression of pro-inflammatory compounds such as TNF-a, IL-6, NF-kB, prostaglandin E2, and COX-2. (8) Methods: Using 80% McIntosh apples and a 20% blend of a variety of apples, the team extracted both a crude apple peel powder and purified polyphenic fraction. For their experiment, they used an epithelial colorectal adenocarcinoma Caco-2/15 cell line. They simulated the induction of both oxidative stress and inflammation to the cell line by pre-exposing them to Iron/Ascorbate (Fe/Asc) and LPS, respectively. Crude apple peel extract and purified polyphenols extract were added to the cell line 24 hours before incubation with Fe/Asc or LPS. Next, they quantified the amount of oxidative stress in the cell by measuring the amount malondialdehyde (MDA) released from the cells via lipid peroxidation. They quantified the amount of inflammation in the cells by using Western Blot analysis to measure the amount of TNF-a, IL-6, NF-kB prostaglandin E2, and COX-2. (8) Results: The team found that the cell lines incubated with the apple peel extract or the purified polyphenol extract had decreased production of TNF-a (P<0.001), IL-6 (P<0.001), and prostaglandin E2 (P<0.001). There was also decreased expression of both COX-2 (P<0.001), and NF-kB (P<0.001). (8) Conclusions: The study found that the polyphenol compounds in apple peels reduce a variety of inflammatory mediators that have been shown to inhibit nitric oxide produce and lead to hypertension. The high intake of fruits and vegetable associated with the DASH diet can decrease systemic inflammation and be an effective treatment or preventative measure in the development of hypertension.

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