Interplay between obesity and aging on myocardial geometry and function: Role of leptin-STAT3-stress signaling

BACKGROUND

Uncorrected obesity facilitates premature aging and cardiovascular anomalies. This study examined the interaction between obesity and aging on cardiac remodeling and contractile function.

METHODS

Cardiac echocardiographic geometry, function, morphology, intracellular Ca²⁺ handling, oxidative stress (DHE fluorescence), STAT3 and stress signaling were evaluated in young (3-mo) and old (12- and 18-mo) lean and leptin deficient ob/ob obese mice. Cardiomyocytes from young and old lean and ob/ob mice were treated with leptin (1 nM) for 4 h in vitro prior to assessment of mechanical and biochemical properties. High fat diet (45% calorie from fat) and the leptin receptor mutant db/db obese mice at young and old age were evaluated for comparison.

RESULTS

Our results displayed reduced survival in ob/ob mice. Obesity but less likely older age dampened echocardiographic, geometric, cardiomyocyte function and intracellular Ca²⁺ properties, elevated O₂^- and p^47phox NADPH oxidase levels with a more pronounced geometric change at older age. Immunoblot analysis revealed elevated p^47phox NADPH oxidase and dampened phosphorylation of STAT3, with a more pronounced response in old ob/ob mice, the effects were restored by leptin. Obesity and aging inhibited phosphorylation of Akt, eNOS, AMPK, and p38 while promoting phosphorylation of JNK and IκB. Leptin reconciled cardiomyocyte dysfunction, O₂^- yield, p^47phox upregulation, STAT3 dephosphorylation and stress signaling in ob/ob mice although its action on stress signaling cascades were lost at old age. High fat diet-induced and db/db obesity displayed aging-associated cardiomyocyte anomalies reminiscent of ob/ob model albeit lost leptin response.

CONCLUSIONS

Our data suggest disparate age-associated obesity response in cardiac remodeling and contractile dysfunction due to phosphorylation of Akt, eNOS and stress signaling-related oxidative stress.

Association of the IL-4R Q576R polymorphism and asthma in the Chinese Han population: a meta-analysis

The IL-4R Q576R polymorphism has been reported to increase susceptibility to asthma, but the results are controversial. Thus, we performed a meta-analysis to evaluate the association of the IL-4R Q576R polymorphism and asthma risk in the Chinese Han population. A total of sixteen eligible case-control studies that evaluated the relationship between the IL-4R Q576R polymorphism and asthma in the Chinese Han population were obtained by comprehensive literature search incorporating electronic databases, and included 2077 asthma cases and 1589 controls. Our analysis detected a significant association between the IL-4R Q576R polymorphism and the risk of asthma in the Chinese Han population (Allelic model: OR = 1.481, 95%CI = 1.134-1.935, P = 0.004; Dominant model: OR = 1.542, 95%CI = 1.194-1.990, P = 0.001; Recessive model: OR = 1.695, 95%CI = 1.170-2.456, P = 0.005, Additive model: OR = 1.897, 95%CI = 1.299-2.771, P = 0.005). The year of publication and size of total sample might be sources of between-study heterogeneity. Upon subgroup analysis by size of total sample of each study, the significant association only remained in a subgroup with a small sample size. In summary, our meta-analysis suggested that the IL-4R Q576R polymorphism is associated with asthma in the Chinese Han population.

Lack of association between a common polymorphism of the endothelial lipase gene and early-onset coronary artery disease in a Chinese Han population

A growing body of evidence suggests that the 584C/T polymorphism in the endothelial lipase (EL) gene contributes to the process of coronary artery disease (CAD). The present study aimed to reveal the potential relationship between the EL 584C/T gene polymorphism and early-onset CAD, CAD severity, and lipid levels in a Chinese Han population. Participants comprised 135 early-onset CAD patients and 166 controls. EL 584C/T genotypic and allelic frequencies were detected by PCR. The frequencies of the CC, CT, and TT genotypes were 58.4, 38.6, and 3.0%, respectively, within the control group, and 62.2, 33.3, and 4.5%, respectively, in the early-onset CAD group. There was no significant difference in the frequency of CC genotype and T allele carriers between early-onset CAD patients and controls. The frequency of the T allele was 22.3% in the control group and 21.1% in the early-onset CAD group. The T allele frequency of the variant was not significantly different between the two groups (P = 0.766), even after adjustments for age, gender, smoking status, hypertension, DM, and lipids were made. There was also no significant association between the genotype and the severity of CAD (P = 0.596). Furthermore, there was no correlation between the genotype and lipid levels or their ratios in both groups. The EL 584C/T gene polymorphism, therefore, was not associated with early-onset CAD or the severity of CAD in this Chinese Han population, suggesting that this variant is not always involved in the pathogenesis of early-onset CAD.

The protective action of ketanserin against lipopolysaccharide-induced shock in mice is mediated by inhibiting inducible NO synthase expression via the MEK/ERK pathway

Nitric oxide (NO) plays an important role in the pathogenesis of endotoxic shock. This work tested the hypothesis that ketanserin could attenuate endotoxic shock by inhibiting the expression of inducible NO synthase (iNOS). The results demonstrated that ketanserin could inhibit iNOS expression in the heart, lungs, liver, and kidneys and nitrate production in the serum upon endotoxic shock in mice. In RAW264.7 cells, ketanserin significantly inhibited the expression of iNOS and decreased the production of NO, TNFα, IL-6, and reactive oxygen species upon lipopolysaccharide (LPS) challenge. Ketanserin also increased the level of ATP and mitochondrial membrane potential in RAW264.7 cells upon LPS exposure. LPS-induced iNOS expression was inhibited by the 5-HT2A receptor antagonist ritanserin and not the α1 receptor antagonist prazosin. Knockdown of 5-HT2A receptor by siRNA abolished the inhibitory effect of ketanserin on the expression of iNOS. These results indicated that the inhibitory effect of ketanserin on the expression of iNOS is mediated by blocking the 5-HT2A receptor. Furthermore, ketanserin significantly inhibited the activation of ERK1/2 and NF-κB signal. Pretreatment with PD184352, a specific inhibitor of ERK1/2, blocked the inhibitory effect of ketanserin on the expression of iNOS and NO production, indicating a critical role for the MEK/ERK1/2 signaling pathway. Collectively, our findings indicate that inhibition of the expression of iNOS via the MEK/ERK pathway mediates the protective effects of ketanserin against LPS-induced shock in mice.

From hypertension to stroke: mechanisms and potential prevention strategies

Stroke is a major cause of disability and death worldwide. Prevention aimed at risk factors of stroke is the most effective strategy to curb the stroke pandemic. Hypertension is one of the most important risk factors for stroke. Despite the substantial evidence of the benefits of lowering blood pressure, conventional treatment does not normalize the burden of major cardiovascular events in patients with hypertension. Fully understanding the factors involved in the hypertension-induced stroke helps to develop new strategies for stroke prevention. Antihypertensive therapies selected should have positive blood pressure-independent effects on stroke risk. This review summarizes the factors involved in the hypertension-induced stroke, such as oxidative stress, inflammation, and arterial baroreflex dysfunction, and potential strategies for its prevention, therefore, provides clues for clinicians.

Effects of ketanserin on endotoxic shock and baroreflex function in rodents

BACKGROUND

Ketanserin, a 5-hydroxytryptamine receptor antagonist, is clinically used as an antihypertensive agent and could enhance baroreflex function. The present work tested the hypothesis that restoration of baroreflex function is an effective treatment for lipopolysaccharide (LPS)-induced shock.

METHODS

Kunming mice were injected with LPS (30 mg/kg; intraperitoneal) to induce endotoxic shock. Ketanserin (0.3, 1, 3, or 10 mg/kg; intraperitoneal) was administered immediately after LPS injection. Survival time was monitored, and serum cytokines were analyzed after the onset of LPS. Effects of ketanserin were also examined in IL-10-deficient mice and mice with sinoaortic denervation. Finally, effects of ketanserin on blood pressure, heart rate, and baroreflex sensitivity were examined in Wistar-Kyoto (WKY) rats with endotoxic shock.

RESULTS

Ketanserin significantly increased survival time and decreased serum levels of tumor necrosis factor α and interleukin (IL) 1β in mice with endotoxic shock. At a dose of 10 mg/kg, ketanserin also significantly increased serum IL-10 concentration. The antishock effect of ketanserin was also apparent in IL-10-knockout mice. In mice with sinoaortic denervation, however, ketanserin had little antishock effects. In WKY rats, ketanserin significantly prevented the baroreflex impairment induced by LPS and prolonged the survival time.

CONCLUSIONS

Ketanserin could ameliorate endotoxic shock by restoring baroreflex function.

Effects of low-dose ketanserin on atherosclerosis in rats and rabbits

The present study was designed to test the hypothesis that a small dose of ketanserin, which enhances baroreflex activity, prevents the early lesions of atherosclerosis. In experiment 1, baroreflex sensitivity (BRS) was measured in 31 spontaneously hypertensive rats (SHRs) in a conscious state using a computerized blood pressure monitoring system. Four weeks later, the rats were administered vitamin D3 and fed a high-cholesterol diet for 8 weeks to induce atherosclerosis. Then their hearts and aortae were removed for pathological examination. A negative correlation was found between BRS and the scores of coronary (r = -0.460, P < 0.01) and aortic atherosclerosis (r = -0.448, P < 0.05) in SHR. In experiment 2, SHRs were divided into 3 groups (n = 10 in each group) and received a dose of ketanserin of 0.3, 1.0, and 3.0 mg/kg (i.g.), respectively. At the smallest dose (0.3 mg/kg), ketanserin did not lower blood pressure but enhanced BRS. In experiment 3, SHRs were administered vitamin D3, fed a high-cholesterol diet, and simultaneously treated with low-dose ketanserin. The atherosclerosis scores of the treatment group were significantly lower than those of the control group (coronary score: 0.90 ± 0.14 vs. 1.76 ± 0.27, P < 0.05; aortic scores: 1.00 ± 0.39 vs. 2.18 ± 0.41, P < 0.05). In experiment 4, male New Zealand White rabbits were fed a high-cholesterol diet and treated with low-dose ketanserin at the same time. The atherosclerosis scores of the treatment group were significantly lower than those of the control group (aortic scores: 0.26 ± 0.20 vs. 0.60 ± 0.31, P < 0.05). In conclusion, the present study demonstrated, for the first time, that low-dose ketanserin prevented the development of atherosclerosis independent of its blood pressure lowering action in SHRs and New Zealand White rabbits at least in part via enhancement of arterial baroreflex function.

A novel animal model for motion sickness and its first application in rodents

The present work was designed to establish a novel animal model for motion sickness (MS) in rodents and to evaluate the effects of a combination of scopolamine and modafinil on MS with this novel method. It was found that the rats and mice presented several symptoms induced by rotation such as, piloerection, tremble, urinal and fecal incontinence. As the rats and mice are lack of emesis response to rotation, we used a score based on abovementioned symptoms as an index for the severity of MS in rodents. MS index was determined in 260 mice with this novel method. It was found that the distribution of MS index was normal (W=0.99; P=0.23. P>0.05 considered values' normal distribution). The effects of scopolamine on MS were studied in mice and rats. It was found that scopolamine significantly decreased MS index at the dose of 0.3 mg/kg in mice and 1.0 mg/kg in rats. Finally, the effects of a combination of scopolamine and modafinil were observed with this novel method in rats. It was found that the efficacy of the combination (5.0+5.0 mg/kg) was greater than the single drugs (10 mg/kg). Even the smallest dose of the combination (0.5+0.5 mg/kg) had a similar effect to large dose of scopolamine or modafinile when they were used alone. In conclusion, this animal model is suitable for MS study in rats and mice and the combination of scopolamine and modafinil might be a new method to treat or prevent MS.

Blood pressure variability, cardiac baroreflex sensitivity and organ damage in experimentally hypertensive rats

1. The present study was designed to investigate the haemodynamic features and morphological changes in experimentally hypertensive rat models. 2. Sprague-Dawley rats were used to prepare the experimentally hypertensive models, including two-kidney, one-clip renovascular hypertensive (2K1C) rats, deoxycorticosterone acetate salt hypertensive (DOCA) rats and N(G)-nitro-l-arginine methyl ester-induced hypertensive (l-NAME) rats. Six weeks after the induction of hypertension, 24 h blood pressure was recorded and blood pressure variability (BPV) expressed by 24 h (or 12 h in the daytime and night-time study) standard deviation of the variables was calculated. Then, cardiac baroreflex sensitivity (BRS) was determined and four endogenous factors (tumour necrosis factor-alpha, interleukin-1beta, angiotensin II and endothelin-1) were measured. Finally, morphological changes were examined. 3. It was found that an increase in BPV and a decrease in BRS were accompanied by an elevation of blood pressure in all three hypertensive models. The DOCA rats had the highest BPV, whereas the l-NAME rats had the lowest BRS. 4. Morphological changes were similar in DOCA and l-NAME rats and the cardiac changes were relatively slight in 2K1C rats. Tumour necrosis factor-alpha was increased in all the three models, especially in DOCA rats. Endothelin-1 was higher in DOCA rats and angiotensin II was increased in 2K1C rats and decreased in DOCA rats. 5. In conclusion, increased BPV and decreased BRS accompanied the elevation of blood pressure in all three hypertensive models. The DOCA rats had the highest BPV and the l-NAME rats had the lowest BRS. Obvious organ damage was seen in all three hypertensive models 6 weeks after the induction of hypertension.

Gradual upregulation of OCI-5 expression during occurrence and progression of rat hepatocellular carcinoma

BACKGROUND

OCI-5, the rat homologene of human glypican 3 (GPC3), is confirmed upregulated in hepatocellular carcinoma (HCC). The present study was undertaken to detect gene expression change of OCI-5 during occurrence and progression of rat HCC.

METHODS

Male Sprague-Dawley rats were given diethylnitrosamine (DENA) to induce HCC. Three DENA-induced rats and one control rat were sacrificed every week for 18 weeks during the development of HCC. Tissues specimens were snap-frozen in liquid nitrogen and total RNA was isolated. Sk-Hep1 cells were treated with DENA at different concentrations. The gene expression levels of OCI-5 and GPC3 were detected with the RT-PCR method.

RESULTS

OCI-5 was not expressed in normal rat liver tissues. When HCC occurred and aggravated, OCI-5 expression was gradually elevated to a very high level. GPC3 was not expressed in the DENA-treated Sk-Hep1 cells.

CONCLUSIONS

OCI-5 was not expressed in normal rat liver tissues but in rat HCC tissues. High-expression of OCI-5 in DENA-induced rat HCC model was the gene expression change of HCC not the DENA-induced gene expression. The expression level of OCI-5 was not only elevated in rat HCC but also gradually along the occurrence and progression of HCC, indicating that GPC3 might serve as a sensitive marker of early stage HCC.

Action site of ketanserin enhancing baroreflex function is within the rostral ventrolateral medulla in anesthetized rats

In our previous studies, it was found that ketanserin enhanced baroreflex sensitivity (BRS) in rats and this effect was not blood pressure dependent. The present work was designed to investigate the effects of ketanserin on BRS within the nucleus tractus solitarus (NTS) and the rostral ventrolateral medulla (RVLM). In anesthetized rats, BRS were evaluated by the changes in depressor action of aortic nerve stimulation and bradycardiac response to rapid pressor action of intravenous phenylephrine. It was found that bilateral injection of ketanserin (250 pmol for each side) into the NTS not only significantly increased blood pressure, but also attenuated baroreflex function. Interestingly, when ketanserin was bilaterally injected into RVLM, a significant enhancement of BRS was found and there were no modifications in basal blood pressure and heart period. The present study demonstrates that ketanserin-induced enhancement of BRS mainly occurred within the RVLM, which might contribute to the systemic effects of ketanserin on BRS.

Diminished responses to nifedipine imply severe end-organ damage in spontaneously hypertensive rats

This study was designed to investigate the effect of end-organ damage (EOD), the initial blood pressure levels, and baroreflex sensitivity (BRS) on the blood pressure-lowering effect of nifedipine in spontaneously hypertensive rats (SHRs). Nifedipine was intravenously administered at a dose of 1 mg/kg. BP was continuously recorded in the conscious state before and after nifedipine administration. BRS was determined before drug administration. Two days after the blood pressure (BP) recording, rats were killed for organ-damage evaluation. Univariate correlation analysis showed that BP changes induced by nifedipine injection were negatively correlated with EOD score and aortic weight/length but positively correlated with left kidney weight/body weight and basal BP levels. Stepwise multiple linear regression analysis demonstrated that increase in overall end-organ damage was most significantly related to the decrease in hypotensive effect of nifedipine; increase in aortic hypertrophy was also related to a decreased fall in systolic and diastolic BP induced by nifedipine, whereas increase in initial BP levels was associated with increased hypotensive effect of nifedipine. In conclusion, the severity of overall EOD contributed more than basal BP levels to the diminished responses to nifedipine, and aortic hypertrophy was also involved in diminished drug responses.

Arterial baroreflex dysfunction promotes atherosclerosis in rats

The present study was designed to test the hypothesis that arterial baroreflex dysfunction promotes the development of atherosclerosis. Experiment 1: the baroreflex sensitivity (BRS) was measured in 30 Sprague-Dawley (SD) rats in conscious state with a computerized blood pressure monitoring system. Four weeks later, the rats were administered with Vitamin D3, and fed with the high-cholesterol diet for 8 weeks to induce atherosclerosis. The hearts and aortae were removed for pathological examination. A negative correlation was found between BRS and the scores of coronary (r=-0.464, P<0.01) or aortic atherosclerosis (r=-0.524, P<0.01) in SD rats. Experiment 2: sinoaortic denervation (SAD) was performed in SD rats. Then atherosclerosis was also induced. The atherosclerosis scores in SAD rats were significantly higher than those in sham-operated rats (aortic score: 1.50+/-0.41 versus 1.10+/-0.39, P<0.05; coronary score: 1.70+/-0.35 versus 1.25+/-0.54, P<0.05). Using immunohistochemistry and Western blotting methods, it was found that the expressions of C-reactive protein, intercellular adhesion molecule-1 and vascular-cell adhesion molecule-1 in coronary artery and aorta were increased in SAD rats compared with sham-operated rats. These results indicate that arterial baroreflex dysfunction promotes the development of atherosclerosis in rats, and that inflammation may be involved in this process.

GREATER HYPERTROPHY IN RIGHT THAN LEFT VENTRICLES IS ASSOCIATED WITH PULMONARY VASCULOPATHY IN SINOAORTIC-DENERVATED WISTAR-KYOTO RATS

1. Biventricular hypertrophy has been described in a high blood pressure variability (BPV) model of sinoaortic-denervated (SAD) rats without systemic hypertension. To explore the possible involvement of the lung in SAD-induced right ventricular hypertrophy (RVH), we examined lung morphology, in addition to systemic haemodynamics and ventricle morphology, in Wistar-Kyoto rats 32 weeks after SAD. 2. In Wistar-Kyoto rats 32 weeks after SAD, there existed a substantial elevation in BPV, with no change in the average level of arterial pressure. Biventricular hypertrophy following SAD was characterized by a greater hypertrophy in right than left ventricles; both absolute and normalized right ventricular weights were significantly increased by 22 and 27%, respectively, and only normalized left ventricular weight was significantly increased by 12%. No infarcts were found in any ventricles examined. 3. In the lung, the most prominent change following SAD was pulmonary vasculopathy, including wall thickening, perivascular fibrosis and cell infiltration. In pulmonary arteries with an internal diameter of 70-130 microm, the external diameter, wall thickness and wall thickness to internal diameter ratio were increased in SAD compared with control rats. 4. There was no correlation between right and left ventricular weights. In contrast with BPV-correlated left ventricular weight, right ventricular weight was correlated with the wall thickness of the pulmonary artery, but not with BPV. 5. These findings suggest that greater RVH following SAD is associated with pulmonary vasculopathy, but is not secondary to the left ventricular problems or high BPV.

Morphological evidence of reinnervation of the baroreceptive regions in sinoaortic-denervated rats

1. The arterial baroreflex (ABR) plays an important role in the maintenance of the stability of blood pressure. Sinoaortic denervation (SAD) destroys the integrity of the reflex arc and produces severe organ damage in rats. However, partial recovery of ABR function has been observed following chronic denervation. The aim of the present study was to determine whether there was morphological evidence of reinnervation of the aortic arch and carotid sinus following SAD. 2. A substantial body of physiological and morphological evidence suggests that substance P (SP) may be a neurotransmitter contained in first-order sensory baroreceptor afferents; therefore, the patterns of vascular SP and neurofilament (NF) immunoreactive (IR) innervation of the aortic arch and carotid sinus were investigated in the present study. 3. Ten-week-old male Sprague-Dawley rats underwent SAD or sham operation. Whole mounts of carotid bifurcation and aortic arch were prepared for immunohistochemical study at various time points (1, 9 and 16 weeks after operation). 4. The results of computerized image analysis show that the mean density of NF- and SP-IR nerves of SAD rats 9 and 16 weeks after operation increased gradually and significantly compared with that of rats 1 week after operation. 5. In conclusion, the results indicate that there is reinnervation of the aortic arch and carotid sinus by NF- and SP-IR fibres in SAD rats, which may be the morphological basis for the partial restoration of ABR function over time after SAD.

The prevalence of dementia and Alzheimer's disease in Shanghai, China: impact of age, gender, and education

We report the prevalence rates for dementia and Alzheimer's disease (AD) obtained from a probability sample survey of 5,055 noninstitutionalized older persons in Shanghai, China. A two-stage procedure was used for case finding and case identification. A Chinese version of the Mini-Mental State Examination was used to determine cases of possible dementia. Three different cutoff points on this mental status test were used depending on the respondent's level of education. Clinical evaluations, based on functional assessments and psychiatric interview, medical and neurological examinations, three standardized mental status tests, and a selected group of psychometric tests, were made in the second stage of the study to ascertain the clinical diagnosis of dementia and AD utilizing the Diagnostic and Statistical Manual for Mental Disorders, edition 3 and National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria, respectively. The prevalence rate of dementia in persons 65 years and older was 4.6%. Clinically diagnosed AD accounted for 65% of the subjects with dementia. These findings indicate that the prevalence of dementia in Shanghai is very much higher than figures published earlier for China and Japan, and at the lower part of the range of values reported for community residents in the United States and other Western countries, but less than half of that reported in the recently published survey of the elderly in East Boston. Increasing age, gender (female), and low education are each highly significant and independent risk factors for dementia. One hypothesis to explain the increased prevalence in elderly women who had received no formal education invokes the possibility of an effect of early deprivation, perhaps lowering brain "reserve," allowing the symptoms of dementia to appear at an earlier date during disease progression.