Christina Maier

Plasma NT-proBNP increases in response to LPS administration in healthy men

Circulating levels of B-type natriuretic peptide (BNP) and NH(2)-terminal-proBNP (NT-proBNP) increase in response to volume overload and help in the differential diagnosis of acute heart failure. Elevated plasma BNP levels are observed also in sepsis and do not always correspond to left ventricular dysfunction. Here, we investigated plasma NT-proBNP fluctuations in response to human bacterial endotoxinemia, an experimental model of systemic infection and inflammation. Escherichia coli endotoxin (LPS) (2 ng/kg) was administered to 10 healthy volunteers in a randomized, placebo-controlled, cross-over design. Plasma NT-proBNP, C-reactive protein (CRP), COOH terminal pro-endothelin-1 (CT-proET-1), and midregional-pro-adrenomedullin (MR-proADM) were measured at hourly intervals for 6 h. LPS administration induced a continuous increase in plasma NT-proBNP that reached peak values after 6 h (40.7 +/- 7.9 vs. 16.1 +/- 3.2 pg/ml in placebo days, mean +/- SE; P = 0.023). The profile of changes in NT-proBNP correlated to changes in body temperature (P < 0.001), heart rate (P = 0.005), CRP (P < 0.001), and CT-proET-1 (P = 0.008), but not to blood pressure values. Our results demonstrate that plasma NT-proBNP increases in a model of systemic infection/inflammation in healthy men with normal heart function. This finding emphasizes the necessity to consider concomitant infections when interpreting elevated circulating NT-proBNP concentrations.

Endothelial Markers May Link Kidney Function to Cardiovascular Events in Type 2 Diabetes

OBJECTIVE The increased cardiovascular risk in diabetes has been linked to endothelial and renal dysfunction. The aim of this study was to investigate the role of stable fragments of the precursors of adrenomedullin, endothelin-1, vasopressin, and atrial natriuretic peptide in progression of cardiovascular disease in patients with diabetes. RESEARCH DESIGN AND METHODS This was a prospective, observational study design with a composite end point (death or unexpected admission to hospital due to a cardiovascular event) on 781 patients with type 2 diabetes (54 events, median duration of observation 15 months). The four stable precursor peptides midregional adrenomedullin (MR-proADM), midregional proatrial natriuretic peptide (MR-proANP), COOH-terminal proendothelin-1 (CT-proET-1), and COOH-terminal provasopressin or copeptin (CT-proAVP) were determined at baseline, and their association to renal function and cardiovascular events was studied using stepwise linear and Cox logistic regression analysis and receiver operating characteristic analysis, respectively. RESULTS MR-proADM, CT-proET-1, CT-proAVP, and MR-proANP were all elevated in patients with future cardiovascular events and independently correlated to serum creatinine. MR-proADM and MR-proANP were significant predictors of a future cardiovascular event, with MR-proANP being the stronger (area under the curve 0.802 ± 0.034, sensitivity 0.833, specificity 0.576, positive predictive value 0.132, and negative predictive value 0.978 with a cutoff value of 75 pmol/l). CONCLUSIONS The four serum markers of vasoactive and natriuretic peptides are related to both kidney function and cardiovascular events, thus linking two major complications of diabetes, diabetic nephropathy and cardiovascular disease.

Different mechanisms of saturated versus polyunsaturated FFA-induced apoptosis in human endothelial cells

Apoptosis and underlying mechanisms were evaluated in human umbilical vein endothelial cells (HUVECs), in target tissues of late diabetic vascular complications [human aortic endothelial cells (HAECs) and human retinal endothelial cells (HRECs)], and in endothelial progenitor cells (EPCs) exposed to FFAs, which are elevated in obesity and diabetes. Saturated stearic acid concentration dependently induced apoptosis that could be mediated via reduced membrane fluidity, because both apoptosis and membrane rigidity are counteracted by eicosapentaenoic acid. PUFAs triggered apoptosis at a concentration of 300 μmol/l in HUVECs, HAECs, and EPCs, but not HRECs, and, in contrast to stearic acid, involved caspase-8 activation. PUFA-induced apoptosis, but not stearic acid-induced apoptosis, strictly correlated (P < 0.01) with protein expression of E2F-1 (r = 0.878) and c-myc (r = 0.966). Lack of c-myc expression and activity owing to quiescence or transfection with dominant negative In373-Myc, respectively, renders HUVECs resistant to PUFA-induced apoptosis. Because c-myc is abundant in growing cells only, apoptosis triggered by PUFAs, but not by saturated stearic acid, obviously depends on the growth/proliferation status of the cells. Finally, this study shows that FFA-induced apoptosis depends on the vascular origin and growth/proliferation status of endothelial cells, and that saturated stearic acid-induced apoptosis and PUFA-induced apoptosis are mediated via different mechanisms.

Cholinergic Regulation of Ghrelin and Peptide YY Release May Be Impaired in Obesity

OBJECTIVE—Ghrelin and peptide YY (PYY) are both hormones derived from the gastrointestinal tract involved in appetite regulation. The cholinergic part of the vagal nerve is involved in the regulation of glucose and insulin. The aim of this study was to examine the effects of the cholinergic antagonist atropine on ghrelin, PYY, glucose, and insulin under basal conditions and after meal ingestion in lean and obese subjects. REASEARCH DESIGN AND METHODS—Eight lean and eight obese subjects were included in a randomized, double-blind, placebo-controlled crossover study with 4 study days in randomized order (atropine/placebo ± breakfast). Plasma ghrelin, PYY, insulin, and glucose were measured. Hunger and satiety feelings were rated on a 10-cm visual analog scale. RESULTS—In lean individuals, atropine led to a decrease in ghrelin concentrations comparable and nonadditive with breakfast ingestion and a significant decrease in both basal and meal-induced PYY concentrations. In obese subjects, atropine did not significantly change ghrelin or PYY concentrations, whereas it induced a comparable increase in heart rate and meal-induced glucose concentrations in the two study groups. Only lean, not obese, subjects experienced sustained feelings of satiety after breakfast. CONCLUSIONS—The impaired cholinergic regulation of the postprandial drop in ghrelin concentrations and rise in PYY concentrations might be part of the deregulated food intake in obese subjects.

Acute effects of hydrocortisone on the metabolic response to a glucose load: increase in the first-phase insulin secretion

BACKGROUND AND AIM Several basic science studies support the existence of non-genomic glucocorticoid signaling in pancreas, liver, and adipocytes, but its clinical relevance has not yet been elucidated. This study aimed at investigating the rapid effects of hydrocortisone on the human metabolic response to glucose. SUBJECTS AND METHODS In a randomized placebo-controlled crossover study, ten healthy men received an i.v. bolus of 0.6 mg/kg hydrocortisone once and placebo once 4 min before the administration of 330 mg/kg glucose. Cortisol, glucose, insulin, C-peptide, ghrelin, and peptide YY (PYY) levels were measured during the following 3 h. Minimal model analysis was performed for evaluating the metabolic response. RESULTS Hydrocortisone attenuated the rise in plasma glucose during the initial 15 min following glucose administration (P=0.039), and it led to lower glucose levels during the first 2 h (P=0.017). This was accompanied by enhanced circulating insulin (P=0.02) and C-peptide (P=0.03) levels during the initial 15 min, and a 35% increase in the first-phase beta-cell function (P=0.003). Hydrocortisone decreased PYY concentrations during the initial 30 min (P=0.014), but it did not affect the ghrelin response to glucose. CONCLUSION One i.v. bolus of hydrocortisone induces rapid effects on carbohydrate metabolism increasing the first-phase beta-cell function. The modulation of PYY plasma levels suggests the possible non-genomic effects of glucocorticoids on appetite-regulatory hormones.

Dynamic contrast-enhanced MR imaging of the stimulated pituitary gland.

Apoplexy due to infarction and/or hemorrhage is a frequent complication of pituitary adenoma, occurring either spontaneously or precipitated by several factors, among them pituitary function test with hypothalamic releasing hormones. The mechanism by which releasing hormones cause pituitary apoplexy is unclear. It has been proposed that increase in pituitary size and/or alterations in blood flow could be responsible. The aim of this study was to explore the effects of intravenous administration of hypothalamic releasing hormones on pituitary size and hemodynamics in healthy subjects. Gadolinium-DTPA-enhanced dynamic magnetic resonance imaging (MRI) was performed in eight healthy volunteers under basal conditions and 20 min after injection of releasing hormones. Mean upslopes of Gadolinium-DTPA enhancement curves showed good correlation between basal and stimulated conditions (R = 0.89) and were significantly steeper after stimulation (P = 0.017). In contrast, pituitary height, width and length did not differ significantly between basal and stimulated conditions. In conclusion, the pituitary does not swell in healthy subjects in response to stimulation with hypothalamic releasing hormones, whereas transfer of contrast agent to tissue (blood flow and/or vessel permeability) is enhanced.

CRH-Receptors and their Ligands

It has long been postulated that the pituitary gland plays a central role in mediating the stress response (11). Later, it was hypothesized that higher brain centers are involved in the regulation of pituitary ACTH release and that the pituitary gland is under control of hypothalamic factors which would reach the adenohypophysis via hypothalamic-hypophyseal blood vessels (2). Further evidence for the existence of this hypothetical hypothalamic corticotropin releasing factor (CRF) was provided by demonstrating that hypothalamic organ extracts stimulated pituitary ACTH release (3 4).