Possible role of nutritional factors in the incidence of cerebral lesions in stroke-prone spontaneously hypertensive rats.

Abstract

SUMMARYThe incidence of cerebral lesions in stroke-prone spontaneously hypertensive rats appears to depend on the severity of the hypertension and nutritional factors. Comparison of American and Japanese commercial rat diets revealed a much higher incidence of stroke in rats receiving the Japanese diet (88% vs 30% by 9 months of age). Analyses of the diets indicate that perhaps the most important difference in the two diets is the protein content. Based on complete amino acid analyses of the protein in these diets, it appears that the American diet contains about 22% protein as compared to about 15% for the Japanese diet. Minor differences in vitamin and mineral contents are not remarkable. Comparison of the findings in this experimental rat model with epidemiologic studies suggest that nutritional factors may also play a role in the incidence of stroke in humans. INCREASED blood pressure appears to be one of the primary risk factors related to the incidence of hemorrhagic stroke in humans.' It was of interest therefore when Yamori et al, 2 reported the development of a rat strain that had very high blood pressure and a high incidence of stroke. This strain was derived from the spontaneously hypertensive rats (SHR) developed by Okamoto and Aoki 3 and exhibited an 80% to 90% incidence of cerebral lesions during the first year of life. This stroke-prone substrain is designated SHRSP and uniformly develops arterial blood pressure of over 200 mm Hg by 6 months of age. In 1975, this substrain was established in the breeding colonies of the National Institutes of Health (NIH) and used for studies on the pathogenesis of hypertension in this genetic model. It has subsequently become apparent to us that the incidence of cerebral lesions in the SHRSP in our laboratory was dramatically lower than that reported in Japan. The mean blood pressures observed in From the Section on Biochemical Pharmacology, HypertensionEndocrine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland (Dr. Lovenberg); the Department of Pathology, Shimane Medical University, Izumo, Japan (Drs. Yamori, Horie, Fujiwara, Nara, and Tanase).Present address for Dr. the NIH-SHRSP were significantly higher than in the SHR and were similar to the values reported for SHRSP in Japan. These observations suggested that perhaps environmental factors interacted with the genetic traits for hypertension to account for the high incidence of stroke in this strain of rats in Japan. We therefore undertook experiments to determine if the different incidence of stroke could be related to the diet. Materials and MethodsMale SHRSP rats were obtained from the Animal Production section of the NIH at 5 weeks of age and were assigned randomly to Groups 1 and 2 that were to receive either the Japanese rat diet (Funahashi-SP diet, Funahashi Farm, Funahashi City, Chiba Prefecture, Japan) or the NIH open formula diet (Ralston-Purina, Inc., St. Louis, Missouri). These groups were fed ad libitum and received tap water. Starting at 6 ...

Hypotensive effect of taurine. Possible involvement of the sympathetic nervous system and endogenous opiates.

“…It is well known that dietary nutrients such as sodium, potassium, calcium, and magnesium influence blood pressure (3)(4)(5)(6). Moreover, several investigators have suggested that dietary protein and amino acids could also influence blood pressure and thus affect the development of hypertension (7,8). Recently, emphasis has been focused on the relationship between taurine, a sulfur amino acid, and cardiovascular disease (9).…”

The relationship between dietary protein intake and blood pressure: results from the PREMIER study

“…First, an increase in protein intake may increase plasma amino acids that may directly influence proximal sodium reabsorption or alter cell permeability and subsequently increase renal plasma flow, renal size and glomerular filtration rate. [24][25][26][27] Second, the amino acid arginine may act as a vasodilator through nitric oxide and contribute to BP lowering. 28 Plant foods including soy products, nuts, seeds and certain whole grains like oats are all good sources of arginine but so are animal foods such as animal meats, seafood, dairy products and eggs.…”

Dietary Protein, but Not Carbohydrate, Is a Primary Determinant of the Onset of Stroke in Stroke-Prone Spontaneously Hypertensive Rats

“…13 As the most important difference in the 2 diets was the protein content, it has been proposed that the increased protein proportion present in the American rat diet could prevent stroke in SHRSP, although fat and carbohydrate proportions that also differ were not considered. 13 In humans, in the Nurses' Health Study, animal protein intake or saturated fatty acid intake was inversely associated with intraparenchymal hemorrhage, and the excess risk associated with low saturated fat intake was observed primarily among women with a history of hypertension. 1 In the same cohort, high carbohydrate intake was associated with an elevated risk of hemorrhagic stroke.…”