Satoru Tsuchikura

Establishment of a new animal model of metabolic syndrome: SHRSP fatty (fa/fa) rats.

1. We established a new animal model of metabolic syndrome, SHRSP fatty (fa/fa) rats, by crossing stroke‐prone spontaneously hypertensive rats of the Izumo strain (SHRSP/Izm) to Zucker fatty (ZF) (fa/fa) rats.

Serial changes in adipocytokines and cardiac function in a rat model of the metabolic syndrome.

Obesity is associated with high chronic cardiac workload due to the need to supply more blood to peripheral tissue, and frequently leads to left ventricular (LV) dysfunction. The present study examined serial changes in cardiac function in the SHR/NDmcr‐cp (SHR/cp) strain, an experimental model of obesity plus hypertension and metabolic syndrome. Transthoracic echocardiography was used to define cardiac dimensions and function in male spontaneously hypertensive rats (SHR/lean), SHR/cp and Wistar‐Kyoto rats. We also assessed age‐related changes in plasma and LV adipocytokine levels in this model. Although there were no significant differences in LV end‐diastolic diameter and end‐systolic diameter among the three rat strains until 24 weeks of age, these parameters were significantly higher and LV fractional shortening (%FS) was significantly lower in SHR/cp compared with SHR/lean at 32 weeks of age. At the same age, pronounced interstitial fibrosis and infiltration of macrophages and T lymphocytes into the LV was noted in SHR/cp relative to the other strains. In the myocardium, adiponectin levels were significantly lower and resistin levels and the expression of proinflammatory cytokines (tumour necrosis factor‐α and interleukin‐6) were significantly higher in SHR/cp than SHR/lean at 32 weeks of age. Using echocardiography, we demonstrated reduced systolic function in 32‐week‐old SHR/cp. Changes in myocardial cytokine concentrations could be involved in worsening of cardiac function in our animal model of metabolic syndrome.

High Susceptibility of Obese Hypertensive SHRSP.Z-Leprfa/IzmDmcr Rats to Lipid Deposition in the Mesenteric Artery

1. Atherosclerosis is commonly observed in obesity. Obese atherosclerosis‐prone animals may be a promising tool for understanding the pathophysiology of obesity‐associated atherosclerosis. However, most rat strains are resistant to atherosclerosis. The aim of the present study was to assess the susceptibility of two obese hypertensive rat models, namely SHRSP.Z‐Leprfa/IzmDmcr rats (SHRSP‐fatty) and SHR.Cg‐Leprcp/NDmcr rats (SHR‐cp), to arterial lipid deposition, an initial stage of atherosclerosis, by comparing these strains with non‐obese stroke‐prone spontaneously hypertensive rats (SHRSP).

EFFECT OF DIETARY WHEAT ALEURONE ON BLOOD PRESSURE AND BLOOD GLUCOSE AND ITS MECHANISMS IN OBESE SPONTANEOUSLY HYPERTENSIVE RATS: PRELIMINARY REPORT ON COMPARISON WITH A SOY DIET

1 There are less epidemiological surveys or intervention studies on whole grains compared with those on soybeans, both of which contain phytoestrogens, lignans and isoflavones. Soybeans have so far been proven to exhibit profound effects on cardiovascular disease risk reduction in animal models and humans. 2 The effect of a dietary intake of wheat aleurone on the risks of metabolic syndrome was compared to that of a soy diet in obese spontaneously hypertensive rats, SHR/NDmcr‐cp (cp/cp). 3 Protein and fat intakes were significantly lower and fibre intake was significantly higher in the aleurone diet group (ALR) than in the soy diet group (SOY). Wheat aleurone maintained blood pressure, 24‐hour urinary sodium (Na), potassium (K) excretion and the Na/K ratio lower than soy. Blood glucose and HOMA‐R were significantly lower in ALR than in SOY at 20 weeks of age. 4 Wheat aleurone, rich in dietary fibre and lignans, is more effective for reducing the risks of hypertension and hyperglycemia than soy.

Interaction between Dietary Calcium and Sodium in Stroke-prone SHR (SHRSP)

Na loading accelerates urinary Ca excretion and this calciuretic effect of Na is possibly related to the aggravation of hypertension by Na loading in SHRSP. Our observation on Na-loaded SHRSP, so far indicated bones were more fragile, so that excess Na intake might be pathogenically involved in the development of osteoporosis. Therefore, Na-loaded SHRSP could be a good model for osteoporosis. On the other hand, Ca supplementation attenuated the development of severe hypertension and stroke in SHRSP. Since urinary Na excretion was increased in the group given the Casupplemented diet, the beneficial effect of Ca appeared to be ascribed to the acceleration of urinary Na excretion. Thus, it can be concluded under excess Na intake, enough Ca intake is important for the prevention not only of hypertensive diseases but also of osteoporosis.