Reduced Production of Hydrogen Sulfide and Sulfane Sulfur Due to Low Cystathionine ß-Synthase Levels in Brain Astrocytes of Stroke-Prone Spontaneously Hypertensive Rats.

Stroke-prone spontaneously hypertensive rats (SHRSP/Izm; SHRSP) develop severe hypertension and die of cerebral stroke. However, the genetic mechanisms underlying their stroke susceptibility have not been clarified yet. In this study, we used astrocytes from the newborn brain cortex of spontaneously hypertensive rats (SHR/Izm; SHR) and SHRSP to find the difference of genetic characteristics. Astrocytes are known to have functions of vasodilation and nutrient uptake for neurons in the brain. The continuous generation of hydrogen peroxide (H2O2) dose-dependently causes cell death in astrocytes, and SHRSP was more vulnerable than SHR. We found that the total thiols decreased in SHRSP astrocytes but the total glutathione (GSH) did not change. Hydrogen sulfide (H2S), which is known to protect cells through anti-oxidant and vasodilatory effects, is produced by cystathionine ß-synthase (CBS) in astrocytes. We found that H2S production was significantly decreased in SHRSP as compared to SHR. This was caused by the decreasing expression of mRNA, protein and enzyme activity of CBS in astrocytes. We also found that astrocyte cell death from oxidative stress could be prevented by GYY4137 H2S donor. H2S is also known to cause protein S-sulfhydration to modify enzyme activity. Sulfane sulfur in astrocytes was significantly lower in SHRSP and decreased by CBS inhibitor. We showed that astrocytes in SHRSP vulnerable to oxidative stress may be caused by reduction of H2S through lower expression and activity of CBS.

An inverse association between magnesium in 24-h urine and cardiovascular risk factors in middle-aged subjects in 50 CARDIAC Study populations.

Serum, plasma and dietary magnesium (Mg) have been reported to be inversely associated with cardiovascular disease risk factors. We examined the associations between the 24-h urinary Mg/creatinine (Cre) ratio and cardiovascular disease risk factors, such as body mass index (BMI), blood pressure (BP), serum total cholesterol (TC) and prevalence of obesity, hypertension and hypercholesterolemia. A cross-sectional analysis was conducted among 4211 participants (49.7% women) aged 48-56 years in 50 population samples from 22 countries in the World Health Organization-coordinated Cardiovascular Diseases and Alimentary Comparison (CARDIAC) Study (1985-1994). In linear regression analyses, Mg/Cre ratio was inversely associated with BMI, systolic BP (SBP), diastolic BP (DBP) and TC (P for linear trend <0.001 for each). These associations were not markedly altered by adjustment for traditional risk factors, urinary markers or cohort effects. Multivariate-adjusted mean values for the subjects in the highest Mg/Cre ratio quintile were 6.3, 3.4, 5.3 and 4.6% lower than those for the subjects in the lowest quintile for BMI, SBP, DBP and TC (P < 0.001, respectively). The prevalence of obesity, hypertension and hypercholesterolemia was 2.10 (95% confidence interval: 1.50, 2.95), 1.55 (1.25, 1.92) and 2.06 (1.63, 2.62) times higher (P < 0.001, respectively) among the subjects in the lowest Mg/Cre ratio quintile than in the subjects in the highest quintile. These associations were not appreciably altered by adjustment for potential confounding variables. In conclusion, higher 24-h urinary Mg/Cre ratio was associated with lower cardiovascular disease risk factors, including BMI, BP, TC, obesity, hypertension and hypercholesterolemia.

New chromone derivative terminalianone from African plant Terminalia brownii Fresen (Combretaceae) in Tanzania.

A new chromone derivative named terminalianone (1) was isolated from the African plant, Terminalia brownii Fresen (Combretaceae) in Tanzania. Its structure was determined to be 7-hydroxy-3-[6'-hydroxyphenyl-2'-oxo-ethyl]chromone by FAB-MS and NMR spectral data.

Mitochondrial HMG-CoA synthase partially contributes to antioxidant protection in the kidney of stroke-prone spontaneously hypertensive rats.

OBJECTIVE: Increased oxidative stress plays an important role in cardiovascular diseases including hypertension and stroke. Evidence has indicated that ketone bodies could exert antioxidative effects. We explored the role of renal mitochondrial 3-hydroxy-3-methylglutaryl-coenzyme A synthase (HMGCS2) expression, a key control site of ketogenesis, in stroke-prone spontaneously hypertensive rats (SHRSPs) and their ancestral hypertensive but stroke-resistant spontaneously hypertensive rats (SHRs). METHODS: Two groups of SHRSPs were fed a standard chow or standard chow supplemented with clofibrate (an agonist of HMGCS2 promoter), respectively, and SHRs fed with a standard chow were used as controls. The renal levels of HMGCS2, Akt, and phosphorylated protein kinase B (Akt) were measured by western blotting. Malondialdehyde, catalase, superoxide dismutase, and glutathione peroxidase were detected by assay kits. RESULTS: Compared with SHRs, lower HMGCS2 protein expression, enhanced phosphorylated Akt signal, higher malondialdehyde levels, and higher catalase activity were observed in kidney tissues in SHRSPs (P < 0.05). No differences in superoxide dismutase and glutathione peroxidase activities were observed between SHRSPs and SHRs. Clofibrate treatment significantly upregulated renal HMGCS2 expressions, inhibited phosphorylation of Akt, and decreased malondialdehyde levels and catalase activities in SHRSP kidney tissues (P < 0.05). CONCLUSION: These results demonstrated the difference in HMGCS2 expression and oxidative stress in kidney tissues between SHRSPs and their SHR controls. The enhanced oxidative stress was partly due to the lower HMGCS2 expression regulated possibly by the Akt signaling pathway.

Resting heart rate in relation to blood pressure: results from the World Health Organization-Cardiovascular Disease and Alimentary Comparison study.

BACKGROUND: Epidemiological studies have reported that increased heart rate (HR) is associated with cardiovascular mortality. We aimed in assessing the hypothesis that HR may influence the outcomes of cardiovascular disease via a pathway related to increases in blood pressure (BP). METHODS: Data from the World Health Organization-Cardiovascular Disease and Alimentary Comparison (CARDIAC) Study were analyzed to examine the association between resting HR and BP in a sample of 8541 adults aged 48-56 participating in the CARDIAC baseline surveys. RESULTS: Increased heart rates were significantly correlated with both systolic and diastolic BP (SBP and DBP) in men and women. The overall results (e.g. the pooled regression coefficients) suggest that an increase in each unit of heart rate (beat per minute) was associated with 0.27 mmHg increase in SBP, and 0.09 mmHg in DBP in the total study population sample, and 0.203 mmHg increase in SBP, and 0.252 mmHg increase in DBP in the sub-sample in which subjects with anti-hypertensive medication use were excluded in the analysis. CONCLUSION: The study, by using a large population-based sample, indicates that increased resting heart rates are associated with increased blood pressure. The result supports the hypothesis that the influence of heart rates on cardiovascular mortality may be mediated by elevated blood pressure.

Taurine as the nutritional factor for the longevity of the Japanese revealed by a world-wide epidemiological survey.

The initial observation that taurine (T) prevented stroke in stroke-prone spontaneously hypertensive rats (SHRSP) led us to study the effects of T on cardiovascular diseases (CVD), as well as the epidemiological association of T and mortality rates, by using the data from WHO-coordinated Cardiovascular Disease and Alimentary Comparison Study, which covered 61 populations in 25 countries. In this study, 24 hour urine (24-U) samples were examined along with biomarkers of CVD risk. The mortality rate from ischemic heart disease (IHD), which was lowest among the Japanese compared to the populations of other developed countries, was positively related to total serum cholesterol (TC) and inversely related to 24-U taurine excretion (24-UT), as well as the n-3 fatty acid to total phospholipids ratio of the plasma membrane, both biomarkers of seafood intake. Analysis of 5 diet-related factors revealed that TC and BMI were positively associated with IHD mortality in both genders while Mg and T were negatively associated with IHD mortality. TC and sodium (Na) were negatively and positively associated with stroke mortality, respectively. 24-UT was negatively associated with stroke mortality. These five diet-related factors explained 61 and 49% of IHD and stroke variances in male, 63 and 36% of IHD and stroke variances in female, respectively.

The role of cytochrome p-450 in salt-sensitive stroke in stroke-prone spontaneously hypertensive rats.

Stroke-prone spontaneously hypertensive rats (SHRSP/Izm) are salt sensitive: they develop severe hypertension and die of stroke within a short time after salt loading. We studied the role of cytochrome P-450 (CYP) isoforms in the brain and the effect of clofibrate to investigate the mechanism of salt sensitive stroke-proneness in SHRSP/Izm. Male SHRSP/Izm at 9 weeks of age were fed a regular diet with or without 0.25% clofibrate and given a 1% NaCl solution for drinking water for 10 d. The expression levels of CYP4A1, 2C11, and 2C23 were measured by Western blotting. Cerebral blood flow was measured with a laser Doppler method and blood vessel diameters were measured under microscopic observation. SHRSP/Izm died within 60 d after salt loading; however, clofibrate prolonged the survival (mean life span, 33+/-7 vs. 215+/-23 d, p<0.0001) without significant attenuation of the severe hypertension. CYP4A1 and CYP2C11 expression levels were lower in SHRSP/Izm than those in age-matched male spontaneously hypertensive rats (SHR/Izm) in the cerebral cortex (p<0.05). Salt loading down-regulated CYP2C11 expression in the cerebral cortex of SHRSP/Izm (p<0.05). No obvious change in cerebral CYP4A1 was observed in either salt-loaded SHRSP/Izm or SHR/Izm. Clofibrate significantly up-regulated the expression of cerebral CYP2C11 and significantly attenuated its salt-induced suppression (p<0.05). Additionally, clofibrate significantly increased blood vessel diameters (p<0.01) and cerebral blood flow (p<0.0001). CYP2C11 plays an important role in regulating cerebral blood flow and, as a result, in preventing stroke in the salt-sensitive stroke-prone SHRSP/Izm.

High-fat diet up-regulates caveolin-1 expression in aorta of diet-induced obese but not in diet-resistant rats.

OBJECTIVE: Caveolin-1 (Cav-1) is considered as a negative regulator of endothelial nitric oxide synthase (eNOS) and influences various cardiovascular functions. The objective of the study is to investigate the effects of high-fat diet on vascular Cav-1 expression and eNOS activities. METHODS: Male outbred Sprague-Dawley rats were fed with a high-fat diet for 15 weeks to induce obesity. The diet-induced obese (DIO) rats were then divided into two groups. One group (DIO-LF) was fed a normal diet and another group (DIO-HF) along with diet-resistance (DR) rats were fed a high-fat diet for 8 more weeks. Cav-1 expression was determined using reverse transcription (RT)-PCR, Western blotting, and immunohistochemistry techniques. NOS activities were assessed using Griess reagents. Protein kinase B (PKB/Akt) and eNOS expression and phosphorylation were determined by Western blotting. RESULTS: A high-fat diet up-regulated Cav-1 and down-regulated eNOS expression in aorta of DIO rats, but not in that of DR rats. These effects were reversed in DIO rats after switching to a low-fat diet for 8 weeks. Decreased NOS activities in aortas were observed in DIO rats, but not in DR rats. Phosphorylation of PKB/Akt and eNOS (Ser1177) were enhanced in aortas of DIO rats of both DIO-HF and DIO-LF groups. CONCLUSION: These findings suggest that the decrease of vascular NOS activities in rats fed a high-fat diet were due, at least in part, to the up-regulation of Cav-1 expression.

Male cardiovascular mortality and dietary markers in 25 population samples of 16 countries.

OBJECTIVE: To examine associations between various dietary markers and mortality from ischemic heart disease (IHD) and stroke. DESIGN AND SETTING: A multi-center cross-sectional study, involved 25 co-operative study centers in 16 countries. METHOD: In the report, data for males (n = 2462), aged 48-56 years, from 25 centers were included. Various dietary markers were measured from individual's blood and 24-h urine samples. Age-standardized male mortality rates for IHD and stroke were collected for the region encompassing each study center. Ecological cross-center associations between dietary markers and the mortality were analyzed using univariate and multivariate analysis techniques. RESULTS: Bivariate correlation analyses showed that IHD mortality was associated positively with body mass index (BMI), serum total cholesterol (TC), urinary potassium (K) and serum phospholipid palmitic acid, and negatively with urinary taurine, sodium (Na) and Na/K (potassium) ratio, n-3 polyunsaturated (n-3PU) fatty acids and polyunsaturated-to-saturated (P/S) fatty acid ratio. Stroke mortality was associated positively with Na and Na/K ratio and phospholipid arachidonic acid (AA), and negatively with TC and K. Stepwise linear regression analyses indicated that 59% of the variance in IHD mortality could be explained by the variance in taurine and P/S ratio and that 57% of stroke mortality could be explained by Na/K ratio and phospholipid AA. CONCLUSION: Although ecological associations do not necessarily imply causality, and the present findings are limited to male samples only, the study extends our understanding of dietary markers in relation to worldwide IHD and stroke mortality rates, and indicates useful avenues for further study on IHD and stroke prevention.

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. 2. The SHRSP fatty (fa/fa) rats have a missense mutation of the leptin receptor gene and plasma leptin concentrations are augmented. The SHRSP fatty (fa/fa) rats develop obesity and hypertension simultaneously. 3. Plasma metabolic parameters, including glucose, insulin and total cholesterol and triglyceride levels, were markedly elevated in SHRSP fatty (fa/fa) rats compared with SHRSP/Izm rats. Plasma triglyceride concentrations in SHRSP fatty (fa/fa) rats were significantly elevated compared with those in ZF (fa/fa) rats. The weight of adipose tissues in SHRSP fatty (fa/fa) rats was greater than that of SHRSP/Izm rats. The phenotype of SHRSP fatty (fa/fa) rats is similar to that of human metabolic syndrome.

Black and green tea polyphenols attenuate blood pressure increases in stroke-prone spontaneously hypertensive rats.

Oxidative stress was reported to be involved not only in cardiovascular diseases, but also in hypertension. Epidemiologic studies indicated that tea consumption slightly reduces blood pressure. We conducted two studies to determine whether black and green tea can lower blood pressure (BP) in stroke-prone spontaneously hypertensive rats (SHRSP). Male SHRSP (n=15) were allowed to recover for 2 wk after a transmitter for measuring BP was implanted in the peritoneal cavity. The rats were divided into three groups: the control group consumed tap water (30 mL/d); the black tea polyphenol group (BTP) consumed water containing 3.5 g/L thearubigins, 0.6 g/L theaflavins, 0.5 g/L flavonols and 0.4 g/L catechins; and the green tea polyphenol group (GTP) consumed water containing 3.5 g/L catechins, 0.5 g/L flavonols and 1 g/L polymetric flavonoids. The telemetry system was used to measure BP, which were recorded continuously every 5 min for 24 h. During the daytime, systolic and diastolic BP were significantly lower in the BTP and GTP groups than in the controls. Protein expressions of catalase and phosphorylated myosin light chain (MLC-p) were measured in the aorta by Western blotting. GTP significantly increased catalase expression, and BTP and GTP significantly decreased MLC-p expression in the aorta. These data demonstrate that both black and green tea polyphenols attenuate blood pressure increases through their antioxidant properties in SHRSP. Furthermore, because the amounts of polyphenols used in this experiment correspond to those in approximately 1 L of tea, the regular consumption of black and green tea may also provide some protection against hypertension in humans.

Fish and lifestyle-related disease prevention: experimental and epidemiological evidence for anti-atherogenic potential of taurine.

1. Taurine supplementation attenuated the development of hypertension and stroke in stroke-prone spontaneously hypertensive rats (SHRSP). 2. WHO-CARDIAC (Cardiovascular Diseases Alimentary Comparison) study revealed wide differences in 24-h urinary taurine excretion, which were inversely associated with age-adjusted mortality rates of coronary heart diseases (CHD). 3. Hypercholesterolemia as well as arterial fat deposition related to the cause of CHD was attenuated by dietary taurine supplementation in SHRSP on high-fat cholesterol diet. 4. Taurine affected the gene expression of 7alpha-hydroxylase and thus regulated serum cholesterol level through the control of the rate limiting step of cholesterol excretion into bile acids. 5. Taurine attenuated atherogenesis due to the control of oxidative stress through the inhibition of the production of oxidative LDL and to its scavenger effect on hypochlorous acid (HOCl) from leucocytes and macrophages. 6. Taurine may act as an immunomodulator of cytokine production, which is involved in atherogenesis.

Obesity, emerging risk in China: trend of increasing prevalence of obesity and its association with hypertension and hypercholesterolaemia among the Chinese.

1. The aim of the present study was to investigate the trend of the prevalence of obesity in China and its association with hypertension and hypercholesterolemia. 2. A multicentre cross-sectional study was conducted in Chinese men and women aged 48-56 years between 1985 and 2000. In the report, three study periods were classified as survey 1 (1985), survey 2 (1988-1989) and survey 3 (1997-2000) in order to describe the long-term trend. 3. The results show that: (i) mean body mass index (BMI), prevalence of obesity (BMI > or = 28 kg/m2) and overweight (BMI > or = 25 and < 28 kg/m2) increased significantly from 1985 to 2000 in both sexes (P < 0.001); (ii) similar to the trend for BMI, the prevalence of hypertension and hypercholesterolaemia (total cholesterol (TC) > or = 220 mg/dL) also increased significantly from 1985 to 2000 (P < 0.001); (iii) partial correlation and multiple linear regression analyses indicated that increased BMI was significantly positively correlated with blood pressure and TC and negatively correlated with serum high-density lipoprotein-cholesterol (P < 0.01 or P < 0.001); and (iv) multiple logistics regression analysis models indicated that obese subjects had a 3.9-fold higher risk of being hypertensive (relative risk (RR) 4.9; 95% confidence interval (CI) 3.4-7.3) compared with those subjects who had a BMI less than 25 kg/m2. The corresponding RR (95% CI) of obesity for hypercholesterolaemia was 2.63 (1.57-4.40). 4. In conclusion, the results highlight the epidemic of obesity, an emerging risk in China. Great efforts must be made to alter this unwelcome trend.

Tea polyphenols regulate nicotinamide adenine dinucleotide phosphate oxidase subunit expression and ameliorate angiotensin II-induced hyperpermeability in endothelial cells.

Out-of-control reactive oxygen species (ROS) signaling is one of the key events in the pathogenesis of endothelial dysfunction and essential hypertension. We observed that tea polyphenols decreased the production of ROS via regulation of the protein expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in bovine carotid artery endothelial cells (BCAECs). Both green tea polyphenols (GTP) and black tea polyphenols (BTP) down-regulated the expression of NADPH oxidase subunits p22phox and p67phox while up-regulating catalase expression (p < 0.05, respectively). Pre-treatment with GTP or BTP for 24 h significantly decreased the superoxide anion level (p < 0.05) and permeable fluorescence intensities in Ang II-stimulated BCAECs. A decrease in cell permeability was also observed by pre-treatment with diphenylene iodonium chloride (DPI) or vitamin E (p < 0.05, respectively). The result demonstrates that tea polyphenols alleviate angiotensin (Ang) II-induced hyperpermeability mainly by decreasing ROS production. Our results suggest that tea polyphenols regulate ROS-related protein expression and may be beneficial in preventing endothelial cell dysfunction and development of cardiovascular diseases, including hypertension.

Nutritional variation and cardiovascular risk factors in Tanzania--rural-urban difference.

OBJECTIVE: To assess the relationship between dietary factors and cardiovascular (CVD) risk factors in middle-aged men and women, in urban, rural and pastoral settings in Tanzania. DESIGN: Cross-sectional epidemiological study designed according to the protocol of the World Health Organisation (WHO) Cardiovascular Diseases and Alimentary Comparison (CARDIAC) study. SETTING: Three centres in Tanzania, namely Dar es Salaam (urban), Handeni (rural) and Monduli (pastoral population). SUBJECTS: The subjects, aged 47-57 years, were recruited randomly from administrative lists available from each centre. OUTCOME MEASURES: Blood pressure (BP) was measured using a centrally calibrated automatic BP machine (Khi machine). Dietary history of the participants was obtained using a standard questionnaire designed on the basis of a seven-day recall system. Height, weight, serum total cholesterol (TC) and high-density lipoprotein cholesterol (HDLC), haemoglobin A1c, sodium, potassium and magnesium were measured. RESULTS: The prevalence of hypertension (BP > or = 140/90 mmHg or antihypertensive drug use), obesity (body mass index (BMI) > or = 30 kg/m2) and hypercholesterolaemia (TC > 5.2 mmol/l) were lowest in the rural area. Consumption of green vegetables, milk, coconut milk, meat, and fish varied significantly between the three areas. Important determinants for BP among men were BMI (p < 0.001), and salt intake (p < 0.05). Among women, TC (p < 0.05), age (p < 0.05), BMI (p < 0.001) and coconut milk consumption (p < 0.001) were important BP determinants. Salt intake was positively associated with systolic BP (SBP) and diastolic BP (DBP) in men but not among women (both SBP and DBP p < 0.05 respectively). Dietary determinants of serum TC were meat, fish and green vegetable consumption. CONCLUSION: Differences in dietary habits contributed significantly to the urban-rural-pastoral variations in CVD risk pattern in Tanzania.

Sphingosine 1-phosphate induces the production of glial cell line-derived neurotrophic factor and cellular proliferation in astrocytes.

Sphingosine 1-phosphate (S1P) is a platelet-derived bioactive sphingolipid that evokes a variety of biological responses. To understand the role of S1P in the central nervous system, we have examined the effect of S1P on the production of glial cell line-derived neurotrophic factor (GDNF) and growth regulation of cortical astrocytes from rat embryo. Moreover, we examined the possibility that the expression of GDNF is regulated differently in cultured astrocytes from the stroke-prone spontaneously hypertensive rat (SHRSP) than in those from Wistar kyoto rats (WKY). The mRNA expression was quantitated by RT-PCR based on the fluorescent TaqMan methodology. A new instrument capable of measuring fluorescence in real time was used to quantify gene amplification in astrocytes. GDNF protein was investigated by enzyme-linked immunosorbent assay. S1P induced the expression of GDNF mRNA and the production of GDNF protein in a dose-dependent manner in WKY astrocytes. Moreover, S1P increased cell numbers and induced the proliferation of astrocytes. In addition, the level of mRNA expression and protein production of GDNF was significantly lower in SHRSP than WKY astrocytes following exposure to S1P. These findings revealed that S1P augments GDNF protein production and cellular growth in astrocytes. Also, our results indicate that production in SHRSP astrocytes was attenuated in response to S1P compared with that observed in WKY. We conclude that S1P specifically triggers a cascade of events that regulate the production of GDNF and cell growth in astrocytes. Our results also suggest that the reduced expression of GDNF caused by S1P is a factor in the stroke proneness of SHRSP.