Effects of source of protein and supplementary extracted isoflavones and anthocyanins on longevity of Stroke-prone Spontaneously Hypertensive (SHRSP) rats

Abstract

Amount of dietary protein is known to influence blood pressure in humans and animal models. However, contradictory reports are available on the influence of source of dietary protein and soy isoflavones on blood pressure. Information on potential effect of anthocyanins, potent flavonoid antioxidants widely distributed in fruits and vegetables, on hypertension is also limited. Therefore, this study was conducted to examine whether source of dietary protein (casein vs. soybean protein, washed by alcohol to remove most isoflavones), dietary extracted isoflavones and anthocyanins modulate the lifespan of Stroke-prone Spontaneously Hypertensive (SHRSP) rats, one of the most suitable models for hemorrhagic stroke. Body weight and systolic blood-pressure matched groups of 47 day-old SHRSP rats (n = 16) received semi-purified diets containing 200 g/kg protein (casein or soybean) supplemented with 0 or 500 mg/kg isoflavones (NOVASOY^TM, a commercial soy isoflavones supplement extracted from soybean), and 0 or 500 mg/kg anthocyanins (extracted from elderberry). The drinking water contained 10 g/l sodium chloride to induce early hypertension. Survival times and survival rates of rats were determined. The survival rates were determined for each group and expressed as a percentage of the original number of rats still alive on a given day. The survival times and survival rates of animals fed casein and soybean protein diets were not different (P > 0.05). However, there was a significant effect of supplementation with isoflavones or anthocyanins on survival times and survival rates. Death occurred significantly earlier (P < 0.05) in the isoflavones- or anthocyanins-supplemented groups.