Baroreflex control of sympathetic activity is impaired in severe congestive heart failure (CHF), probably causing the marked sympathetic activation typical of this condition. Little information ...exists, however, as to whether baroreflex impairment and related sympathetic activation also occur in mild CHF.
We studied 19 patients (age, 57.5 +/- 2.2 years, mean +/- SEM) with CHF in New York Heart Association (NYHA) class III or IV and with a marked reduction in left ventricular ejection fraction (LVEF, 30.1 +/- 1.5% from echocardiography) and 17 age-matched patients with CHF in NYHA class I or II and with an only slightly reduced LVEF (44.9 +/- 3.3%) that never was < 40%. Seventeen age-matched healthy subjects served as control subjects. Primary measurements included beat-to-beat arterial blood pressure (with the Finapres technique), heart rate (from ECG), and postganglionic muscle sympathetic nerve activity (MSNA, from microneurography at the peroneal nerve). Measurements were performed at baseline and during baroreceptor stimulation (intravenous phenylephrine infusion), baroreceptor deactivation (intravenous nitroprusside infusion), and cold-pressor test. Baseline blood pressure was similar in the three groups, whereas heart rate was progressively greater from control subjects to patients with mild and severe CHF, MSNA (bursts per 100 heart beats) increased significantly and markedly from control subjects to patients with mild and severe CHF (47.1 +/- 2.9 versus 64.4 +/- 6.2 and 82.1 +/- 3.4, P < .05 and P < .01, respectively). Heart rate and MSNA were progressively reduced by phenylephrine infusion and progressively increased by nitroprusside infusion. Compared with control subjects, the responses were strikingly impaired in severe CHF patients, but a marked impairment also was seen in mild CHF patients. On average, baroreflex sensitivity in mild CHF patients was reduced by 59.1 +/- 5.5% (MSNA) and 64.8 +/- 4.8% (heart rate). In contrast, reflex responses to the cold-pressor test were similar in the three groups.
These results demonstrate that in mild CHF patients the baroreceptor inhibitor influence on heart rate and MSNA is already markedly impaired. This impairment may be responsible for the early sympathetic activation that occurs in the course of CHF.
Human obesity is characterized by profound alterations in the hemodynamic and metabolic states. Whether these alterations involve sympathetic drive is controversial. In 10 young obese subjects (body ...mass index, 40.5 plus/minus 1.2 kg/m, mean plus/minus SEM) with normal blood pressure and 8 age-matched lean normotensive control subjects, we measured beat-to-beat arterial blood pressure (Finapres technique), heart rate (electrocardiogram), postganglionic muscle sympathetic nerve activity (microneurography at the peroneal nerve), and venous plasma norepinephrine (high-performance liquid chromatography). The measurements were performed in baseline conditions and, with the exception of plasma norepinephrine, during baroreceptor stimulation and deactivation caused by increases and reductions of blood pressure via intravenous infusions of phenylephrine and nitroprusside. Baseline blood pressure and heart rate were similar in obese and control subjects. Plasma norepinephrine was also similar in the two groups. Muscle sympathetic nerve activity, however, was 38.6 plus/minus 5.1 bursts per minute in obese subjects and less than half that level in control subjects (18.7 plus/minus 1.3 bursts per minute), the difference being highly statistically significant (P < .02). Muscle sympathetic nerve activity and heart rate were reduced during phenylephrine infusion and increased during nitroprusside infusion, but the changes were about half as great in obese subjects as in control subjects. Thus, even in the absence of any blood pressure alteration, human obesity is characterized by a marked sympathetic activation, possibly because of an impairment of reflex sympathetic restraint. This may be involved in the high rate of hypertension and cardiovascular complications seen in obesity. (Hypertension. 1995;25part 1:560-563.)
Previous studies have shown that essential hypertension and obesity are both characterized by sympathetic activation coupled with a baroreflex impairment. The present study was aimed at determining ...the effects of the concomitant presence of the 2 above-mentioned conditions on sympathetic activity as well as on baroreflex cardiovascular control. In 14 normotensive lean subjects (aged 33.5±2.2 years, body mass index 22.8±0.7 kg/m mean±SEM), 16 normotensive obese subjects (body mass index 37.2±1.3 kg/m), 13 lean hypertensive subjects (body mass index 24.0±0.8 kg/m), and 16 obese hypertensive subjects (body mass index 37.5±1.3 kg/m), all age-matched, we measured beat-to-beat arterial blood pressure (by Finapres device), heart rate (HR, by ECG), and postganglionic muscle sympathetic nerve activity (MSNA, by microneurography) at rest and during baroreceptor stimulation and deactivation induced by stepwise intravenous infusions of phenylephrine and nitroprusside, respectively. Blood pressure values were higher in lean hypertensive and obese hypertensive subjects than in normotensive lean and obese subjects. MSNA was significantly (P <0.01) greater in obese normotensive subjects (49.1±3.0 bursts per 100 heart beats) and in lean hypertensive subjects (44.5±3.3 bursts per 100 heart beats) than in lean normotensive control subjects (32.2±2.5 bursts per 100 heart beats); a further increase was detectable in individuals with the concomitant presence of obesity and hypertension (62.1±3.4 bursts per 100 heart beats). Furthermore, whereas in lean hypertensive subjects, only baroreflex control of HR was impaired, in obese normotensive subjects, both HR and MSNA baroreflex changes were attenuated, with a further attenuation being observed in obese hypertensive patients. Thus, the association between obesity and hypertension triggers a sympathetic activation and an impairment in baroreflex cardiovascular control that are greater in magnitude than those found in either of the above-mentioned abnormal conditions alone.
The pressor and tachycardic effects of cigarette smoking are associated with an increase in plasma catecholamines, suggesting the dependence of these effects on adrenergic stimulation. Whether the ...stimulation occurs at a central or a peripheral level and whether reflex mechanisms are involved is unknown.
In nine normotensive healthy subjects (age, 33.0 +/- 3.5 years, mean +/- SEM), we measured blood pressure (Finapres device), heart rate (ECG), calf blood flow and vascular resistance (venous occlusion plethysmography), plasma norepinephrine and epinephrine (high-performance liquid chromatography assay), and postganglionic muscle sympathetic nerve activity (microneurography from the peroneal nerve) while subjects were smoking a filter cigarette (nicotine content, 1.1 mg) or were in control condition. Cigarette smoking (which raised plasma nicotine measured by high-performance liquid chromatography from 1.0 +/- 0.9 to 44.2 +/- 7.1 ng/mL) markedly and significantly increased mean arterial pressure (+13.2 +/- 2.3%), heart rate (+30.3 +/- 4.7%), calf vascular resistance (+12.1 +/- 4.9%), plasma norepinephrine (+34.8 +/- 7.0%), and plasma epinephrine (+90.5 +/- 39.0%). In contrast, muscle sympathetic nerve activity showed a marked reduction (integrated activity -31.8 +/- 5.1%, P < .01). The reduction was inversely related to the increase in mean arterial pressure (r = -.67, P < .05), but the slope of the relation was markedly less (-54.1 +/- 7.5%, P < .05) than that obtained by intravenous infusion of phenylephrine in absence of smoking. The hemodynamic and neurohumoral changes were still visible 30 minutes after smoking and occurred again on smoking a second cigarette. Sham smoking was devoid of any hemodynamic and neurohumoral effect.
These data support the hypothesis that in humans the sympathetic activation induced by smoking depends on an increased release and/or a reduced clearance of catecholamines at the neuroeffector junctions. Central sympathetic activity is inhibited by smoking, presumably via a baroreceptor stimulation triggered by the smoking-related pressor response. The baroreflex is impaired by smoking, however, indicating that partial inability to reflexly counteract the effect of sympathetic activation is also responsible for the pressor response.
BACKGROUNDPrevious studies have shown that obesity is characterized by a sympathetic overactivity coupled with an insulin resistance state and a baroreflex impairment. The present study was set out ...to compare the effects of peripheral versus central obesity on sympathetic, metabolic and reflex function.
METHODSIn 36 lean subjects (age 35.8 ± 1.4 years, mean ± SEM), 20 subjects with peripheral obesity (PO) and 26 subjects with central obesity (CO), all age-matched and with normal blood pressure values, we measured beat-to-beat arterial blood pressure (Finapres), heart rate (HR, ECG), homeostasis model assessment (HOMA) index, plasma norepinephrine (NE, high-performance liquid chromatography) and postganglionic muscle sympathetic nerve traffic (MSNA, microneurography) at rest and during baroreceptor stimulation and deactivation induced by stepwise intravenous infusions of phenylephrine and nitroprusside, respectively.
RESULTSBoth HOMA index, NE and MSNA values were significantly increased (P < 0.01) in obese as compared with lean individuals. Subjects with CO displayed MSNA and HOMA values significantly greater than those found in individuals with PO (65.4 ± 2.0 versus 47.9 ± 1.9 bs/100hb and 2.85 ± 0.10 versus 2.43 ± 0.11 a.u., respectively, P < 0.05 for both). Both in male and female subjects with CO or PO, MSNA, HOMA index and waist-to-hip ratio were significantly related to each other. Baroreceptor-HR and -MSNA control was significantly (P < 0.01) impaired in obese as compared with lean subjects, the degree of impairment being similar in CO and PO.
CONCLUSIONSThese data suggest that CO is characterized by a sympathetic activation greater for magnitude than that detectable in PO. This appears not to be related to gender or to baroreflex mechanisms but rather to metabolic factors, i.e. to the greater insulin resistance characterizing CO.
Cirrhosis is associated with cardiovascular abnormalities. Scanty information is available as to whether these include left ventricle diastolic dysfunction and wall thickness increase. To this aim in ...27 cirrhotic patients with tense ascites, 17 cirrhotic patients with previous episodes of ascites (not actual), and 11 controls we investigated by echocardiography and echocolor Doppler left ventricle diastolic function (E wave, A wave, E/A ratio, deceleration time of E wave), systolic function (ejection fraction), and wall thickness (left ventricle posterior wall thickness + interventricular septum thickness) along with neurohumoral variables. All measurements (supine position) were repeated after total paracentesis (10.7 ± 0.6 L of ascites) in ascitic patients. Both in patients with and without ascites E/A ratio was reduced as compared with controls (0.93 ± 0.07 and 0.97 ± 0.06 vs. 1.18 ± 0.08, P < .05) while left ventricle wall thickness was increased (18.6 ± 0.6 and 20.1 ± 0.8 vs. 17.2 ± 0.7, P < .05 and P < .01, respectively), irrespective of the postviral or alcoholic cause of liver disease. In all cirrhotics both right and left atrial and right ventricle diameters were significantly greater. Ejection fraction was slightly but significantly (P < .01) reduced in ascitic patients. Paracentesis induced a reduction of the highly increased basal plasma renin activity, aldosterone, norepinephrine (P < .01), and epinephrine (P < .05) and improved diastolic function (E/A, P < .05). Systolic function was unaffected. Thus, irrespective of ascites and cause, advanced cirrhosis is associated with left ventricle diastolic dysfunction and wall thickness increase. We can speculate that neurohumoral overactivity, known to stimulate cardiac tissue growth, may challenge the heart, promoting fibrosis and exerting a further hindrance to ventricular relaxation in patients with cirrhosis experiencing episodes of ascites.
P.I157T is a CHEK2 missense mutation associated with a modest increase in breast cancer risk. Previously, another CHEK2 mutation, the protein truncating c.1100delC has been associated with poor ...prognosis of breast cancer patients. Here, we have investigated patient survival and characteristics of breast tumors of germ line p.I157T carriers.
We included in the analyses 26,801 European female breast cancer patients from 15 studies participating in the Breast Cancer Association Consortium. We analyzed the association between p.I157T and the clinico-pathological breast cancer characteristics by comparing the p.I157T carrier tumors to non-carrier and c.1100delC carrier tumors. Similarly, we investigated the p.I157T associated risk of early death, breast cancer-associated death, distant metastasis, locoregional relapse and second breast cancer using Cox proportional hazards models. Additionally, we explored the p.I157T-associated genomic gene expression profile using data from breast tumors of 183 Finnish female breast cancer patients (ten p.I157T carriers) (GEO: GSE24450). Differential gene expression analysis was performed using a moderated t test. Functional enrichment was investigated using the DAVID functional annotation tool and gene set enrichment analysis (GSEA). The tumors were classified into molecular subtypes according to the St Gallen 2013 criteria and the PAM50 gene expression signature.
P.I157T was not associated with increased risk of early death, breast cancer-associated death or distant metastasis relapse, and there was a significant difference in prognosis associated with the two CHEK2 mutations, p.I157T and c.1100delC. Furthermore, p.I157T was associated with lobular histological type and clinico-pathological markers of good prognosis, such as ER and PR expression, low TP53 expression and low grade. Gene expression analysis suggested luminal A to be the most common subtype for p.I157T carriers and CDH1 (cadherin 1) target genes to be significantly enriched among genes, whose expression differed between p.I157T and non-carrier tumors.
Our analyses suggest that there are fundamental differences in breast tumors of CHEK2:p.I157T and c.1100delC carriers. The poor prognosis associated with c.1100delC cannot be generalized to other CHEK2 mutations.
No agreement exists as to the mechanisms responsible for the sympathetic hyperactivity characterizing human obesity, which has been ascribed recently to a chemoreflex stimulation brought about by ...obstructive sleep apnea rather than to an increase in body weight, per se. In 86 middle-age normotensive subjects classified according to body mass index, waist-to-hip ratio, and apnea/hypopnea index (overnight polysomnographic evaluation) as lean and obese subjects without or with obstructive sleep apnea, we assessed via microneurography muscle sympathetic nerve traffic. The 4 groups were matched for age, gender, and blood pressure values, the 2 obese groups with and without obstructive sleep apnea showing a similar increase in body mass index (32.4 versus 32.0 kg/m, respectively) and waist-to-hip ratio (0.96 versus 0.95, respectively) compared with the 2 lean groups with or without obstructive sleep apnea (body mass index 24.3 versus 23.8 kg/m and waist-to-hip ratio 0.77 versus 0.76, respectively; P<0.01). Compared with the nonobstructive sleep apnea lean group, muscle sympathetic nerve activity showed a similar increase in the obstructive sleep apnea lean group and in the nonobstructive sleep apnea obese group (60.4±2.3 and 59.3±2.0 versus 40.9±1.8 bs/100 hb, respectively; P<0.01), a further increase being detected in obstructive sleep apnea subjects (73.1±2.5 bursts/100 heart beats; P<0.01). Our data demonstrate that the sympathetic activation of obesity occurs independently in obstructive sleep apnea. They also show that this condition exerts sympathostimulating effects independent of body weight, and that the obstructive sleep apnea–dependent and –independent sympathostimulation contribute to the overall adrenergic activation of the obese state.
Human studies have shown that the blood pressure lowering effects of angiotensin converting enzyme inhibitors are accompanied by a reduction in plasma norepinephrine levels. Whether this is due to ...central or peripheral mechanisms is unknown, however.
To evaluate the effects of chronic interference with the renin-angiotensin system on sympathetic nerve traffic and baroreflex control of vagal and adrenergic cardiovascular drive.
In 18 untreated mild to moderate essential hypertensive patients aged 48.5+/-1.9 years (mean+/-SEM), we measured mean arterial pressure (Finapres), heart rate (electrocardiogram), plasma renin activity (radioimmunoassay), plasma norepinephrine (high-performance liquid chromatography) and postganglionic muscle sympathetic nerve activity (microneurography at a peroneal nerve). In nine patients, measurements were performed before and after 2 months of oral administration of lisinopril (10 mg/day), while in the remaining nine patients they were performed before and after a 2 month observation period, without the drug administration. Measurements were performed at rest and during baroreflex stimulation and deactivation elicited by stepwise intravenous infusions of phenylephrine and nitroprusside, respectively.
Lisinopril induced a marked increase in plasma renin activity (from 1.1+/-0.2 to 6.4+/-1.3 ng/ml per h, P< 0.01) and a reduction in mean arterial pressure (from 109.6+/-3.1 to 98.7+/-2.9 mmHg, P < 0.01) without affecting the heart rate. Plasma norepinephrine and muscle sympathetic nerve activity values were not significantly different before and after lisinopril treatment (plasma norepinephrine values changed from 290.4+/-39.2 to 308.1+/-67.1 pg/ml; muscle sympathetic nerve activity changed from 56.4+/-5.3 to 50.6+/-6.6 bursts/100 heart beats). Neither the sympathoinhibitory nor the sympathoexcitatory responses to phenylephrine and nitroprusside were affected by lisinopril, nor the concomitant bradycardia and tachycardia. The curves relating mean arterial pressure to heart rate and muscle sympathetic nerve activity values during baroreceptor manipulation were shifted to the left, indicating a resetting of the baroreflex to the lower blood pressure values achieved during treatment. CONCLUSIONS In essential hypertension, sympathetic nerve traffic is not affected by chronic angiotensin converting enzyme inhibitor treatment that effectively interferes with the renin-angiotensin system and lowers the elevated blood pressure. The baroreflex ability to modulate heart rate and central sympathetic outflow is also unaffected. These data argue against the existence of a central sympathoexcitatory effect of angiotensin II in this condition. They also indicate that antihypertensive treatment with an angiotensin converting enzyme inhibitor preserves autonomic reflex control, with favorable consequences for cardiovascular homeostasis.
The present study assessed the antimicrobial activities of various natural products belonging to the terpenoids, alkaloids and phenolics against a collection of Gram-negative multidrug-resistant ...(MDR) bacteria. The results demonstrated that most of the compounds were extruded by bacterial efflux pumps. In the presence of the efflux pump inhibitor phenylalanine arginine β-naphthylamide (PAβN), the activities of laurentixanthone B (xanthone), plumbagin (naphthoquinone), 4-hydroxylonchocarpin (flavonoid) and MAB3 (coumarin) increased significantly against all studied MDR bacteria. Laurentixanthone B, 4-hydroxylonchocarpin and MAB3 contained the same pharmacophoric moiety as plumbagin. This study indicates that the AcrAB–TolC (Enterobacteriaceae) and MexAB–OprM (Pseudomonas aeruginosa) efflux pumps are involved in resistance of Gram-negative bacteria to most of the natural products.
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