The relationship between sex hormones, sex hormone binding globulin and peripheral artery disease in older persons.

OBJECTIVE: The prevalence of peripheral artery disease (PAD) increases with aging and is higher in persons with metabolic syndrome and diabetes. PAD is associated with adverse outcomes, including frailty and disability. The protective effect of testosterone and sex hormone binding globulin (SHBG) for diabetes in men suggests that the biological activity of sex hormones may affect PAD, especially in older populations. METHODS: Nine hundred and twenty-one elderly subjects with data on SHBG, testosterone (T), estradiol (E2) were selected from InCHIANTI study. PAD was defined as an Ankle-Brachial Index (ABI) < 0.90. Logistic regression models adjusted for age (Model 1), age, BMI, insulin, interleukin-6, physical activity, smoking, chronic diseases including metabolic syndrome (Model 2), and a final model including also sex hormones (Model 3) were performed to test the relationship between SHBG, sex hormones and PAD. RESULTS: The mean age (±SD) of the 419 men and 502 women was 75.0 ± 6.8 years. Sixty two participants (41 men, 21 women) had ABI < 0.90. Men with PAD had SHBG levels lower than men without PAD (p = 0.03). SHBG was negatively and independently associated with PAD in men (p = 0.028) but not in women. The relationship was however attenuated after adjusting for sex hormones (p = 0.07). The E2 was not significantly associated with PAD in both men and women. In women, but not in men, T was positively associated with PAD, even after adjusting for multiple confounders, including E2 (p = 0.01). CONCLUSIONS: Low SHBG and high T levels are significantly and independently associated with the presence of PAD in older men and women, respectively.

The hormonal pathway to cognitive impairment in older men.

In older men there is a multiple hormonal dysregulation with a relative prevalence of catabolic hormones such as thyroid hormones and cortisol and a decline in anabolic hormones such as dehydroepiandrosterone sulphate, testosterone and insulin like growth factor 1 levels. Many studies suggest that this catabolic milieu is an important predictor of frailty and mortality in older persons. There is a close relationship between frailty and cognitive impairment with studies suggesting that development of frailty is consequence of cognitive impairment and others pointing out that physical frailty is a determinant of cognitive decline. Decline in cognitive function, typically memory, is a major symptom of dementia. The "preclinical phase" of cognitive impairment occurs many years before the onset of dementia. The identification of relevant modifiable factors, including the hormonal dysregulation, may lead to therapeutic strategies for preventing the cognitive dysfunction. There are several mechanisms by which anabolic hormones play a role in neuroprotection and neuromodulation. These hormones facilitate recovery after brain injury and attenuate the neuronal loss. In contrast, elevated thyroid hormones may increase oxidative stress and apoptosis, leading to neuronal damage or death. In this mini review we will address the relationship between low levels of anabolic hormones, changes in thyroid hormones and cognitive function in older men. Then, giving the contradictory data of the literature and the multi-factorial origin of dementia, we will introduce the hypothesis of multiple hormonal derangement as a better determinant of cognitive decline in older men.

Morning increase of whole blood viscosity in obstructive sleep apnea syndrome.

OBJECTIVE: Patients affected by obstructive sleep apnea syndrome (OSAS) have an increased risk of cardiovascular diseases such as stroke and myocardial infarction. The pathophysiological mechanisms leading to increased vascular risk are still matter of debate. A relative morning hyperviscosity could be one of the leading mechanisms of cardiovascular morbidity which is actually known to be especially high in the morning hours. METHODS: Whole blood viscosity (WBV) at seven shear rates, ranging from 0.47 to 118 sec(-1), haematocrit (Hct), and plasma fibrinogen (F) concentration, were measured on venous blood samples in 12 patients with OSAS and in 8 healthy controls at 8-9 p.m. and at 7-8 a.m. the morning after. WBV values were normalized on Hct by the computation of the standardised normal deviate z on the normal database of the laboratory. RESULTS: No changes were observed in controls. Hct, F and normalized WBV (independently from Hct changes) significantly increased in the morning hours in OSAS patients. CONCLUSIONS: Viscosity of whole blood increases in the morning in OSAS patients but not in healthy controls. This condition may be related to the increased susceptibility to cerebral ischemia in patients affected by OSAS, particularly evident in the early morning.

Relationship of sleep interictal epileptiform discharges to sigma activity (12-16 Hz) in benign epilepsy of childhood with rolandic spikes.

OBJECTIVE: The activation of interictal epileptic discharges (IEDs) by NREM sleep is a well-known phenomenon in benign epilepsy of childhood with rolandic spikes (BECRS). The activating properties of NREM sleep on IEDs have been attributed to increased synchronization within thalamocortical neurons. During NREM sleep two synchronizing mechanisms lead to the appearance of spindles and delta waves on the EEG. Spectral analysis technique is a suitable method that can be used to quantitatively describe the dynamics of delta (slow wave activity (SWA) 0.5-4.0 Hz) and sigma activity (12.0-16.0 Hz) during sleep. METHODS: In order to define more accurately the relationship between synchronizing mechanisms (spindles and delta activities) and IEDs during sleep in BECRS, we have performed overnight continuous EEG polysomnography studies in 9 patients (mean age 7.4 +/- 2.5 years). The temporal series of SWA and sigma values, derived from spectral analysis, have been obtained from a spike-free derivation lead. The IEDs count has been performed on the most active lead. Relationships between sigma and SWA and time series of IEDs were tested by means of correlation techniques after data normalization. RESULTS: Our results revealed a significant higher correlation between IEDs and sigma activity with respect to SWA in all the subjects, in total sleep time. The same analysis limited to NREM sleep highlights the better correlation between sigma and IEDs. CONCLUSIONS: Data suggest that during sleep of BECRS patients, IEDs are more sensitive to the promoting action of the spindle-generating mechanism than to the SWA-producing one.

A quantified analysis of sleep electroencephalography in anorectic adolescents.

BACKGROUND: Previous studies on sleep characteristics in anorexia nervosa have led to controversial results. This may be due to either the heterogeneity of the samples studied or to an intrinsic inadequacy of the scoring criteria. To obtain a more detailed analysis we have investigated sleep characteristics in a group of adolescents affected by anorexia nervosa using spectral analysis techniques. METHODS: After a baseline night, the sleep-electroencephalograms of 10 adolescent anorectic girls (age +/- SD = 14 +/- 2 years) and 10 age-matched control subjects were recorded and processed by a fast Fourier transformation routine. RESULTS: Anorectics showed an increased number of awakenings and wakefulness after sleep onset and a reduction of sleep efficiency and slow-wave sleep. Spectral analysis results revealed a significant reduction in the power spectral values of slow-wave activity (SWA; 0.5-4.5 Hz) band in all NREM-REM cycles of sleep and in the undisturbed and stable stage 4. Moreover the anorectic group was characterized by a concentration of SWA in the first NREM-REM cycle with an abrupt decay in the second part of the night. A positive correlation (r2 = .58, p < .01) between body mass index and the amount of SWA was found. CONCLUSIONS: Sleep of anorectic patients seems to be characterized by a weakness of SWA producing mechanisms. The positive correlation between body mass index and the amount of SWA appears to be consistent with the neurobiological consequences of the malnutrition state.

Comparison between visual scoring of cyclic alternating pattern (CAP) and computerized assessment of slow EEG oscillations in the transition from light to deep non-REM sleep.

Ten healthy volunteers (six men and four women) aged between 20 and 30 years underwent a nocturnal polygraphic recording on paper and on tape. Spectral analysis was accomplished and EEG sleep scored according to standard criteria and to the guidelines for the identification of cyclic alternating pattern (CAP). The initial 25 min of sleep, starting from the first clear-cut k-complex and ending within stage 4, was subdivided into five consecutive blocks of 5 min each. Using a zero-crossing technique, we evaluated the number of total power oscillations in each block and we tested the hypothesis of significant modifications of the number of total power oscillations and of their periodicity in the successive sessions. In addition, we measured the gap between the maximum and minimum values, respectively, of two successive half-waves making up each oscillation. The hypothesis of time-related trends of the values of the gaps was tested by means of linear regression techniques. Within the 25-min time span, the number of periodic oscillations and the number of CAP cycles showed significant increases. The amplitude gaps underwent a decreasing trend. The present data suggest that slow rhythmic oscillations expressed by CAP can be detected by means of spectral analysis. Their dynamics suggests a close relationship with the EEG synchronization processes.

An integrated model of sleep regulation.

We present a new model of sleep regulation which integrates the two process model and the limit cycle reciprocal interaction model. In the two process model the interaction of a homeostatic process (S signal) and of a circadian process determines the timing of sleep and waking. In the limit cycle model, the NREM-REM sleep cycle is generated by the reciprocal interaction of two coupled cell population. The present model integrates the two considered models introducing the trigger REM-NREM generated by the REM-ON signal and activated when REM-ON overcomes the S signal.

Ultradian aspects of sleep in narcolepsy.

Following a baseline night recording, 9 narcoleptic subjects and 9 sex and age-matched control subjects were maintained on 16 hours of diurnal sleep deprivation. Thereafter subjects were submitted to a 32 hour bed rest protocol in a sound-light attenuated room. The EEG was recorded and processed using a Fast Fourier Transform. Narcoleptic patients did not differ from control subjects in total sleep time over the whole time-span. An ultradian tendency to sleep seems to be predominant in narcoleptic patients and evidence of a strong basic rest activity cycle is shown. The coupling between the homeostatic process of sleep regulation and an ultradian drive to sleep would explain the peculiar 4 hour distribution pattern of SWA in narcoleptic patients.

Dynamics of slow wave activity in narcoleptic patients under bed rest conditions.

Following a baseline night recording, 9 narcoleptic subjects and 9 sex- and age-matched control subjects were maintained on 16 h of diurnal sleep deprivation. Thereafter subjects were submitted to a 32 h bed rest protocol in a sound- and light-attenuated room. The EEG was recorded and processed by a Fast Fourier Transform. Narcoleptics did not differ from controls in total sleep time over the whole 32 h, but spent more time sleeping during the daytime (DT). In both groups slow wave activity (SWA) showed an exponential decaying trend during the first night (N1); a similar exponential trend during the second night (N2) was evident only in controls. In controls SWA showed a circadian-circasemidian distribution that was hardly detectable in nacroleptics. Narcoleptics showed an ultradian distribution of SWA with periodic emergence every 4 h during DT and N2. Our data confirm that a homeostatic mechanism is evident in narcolpetics when stimulated by diurnal sleep deprivation, while circadian and circasemidian mechanisms are less evident during DT and N2. These findings suggest a different coupling between homeostatic sleep regulating and circadian drives to sleep in narcoleptics. Ultradian drives to sleep seem to be predominant in these patients, thus probably acting as a means for the avoidance of stressful attempts to counteract a weaker waking state maintenance mechanism.

Synthesis, absolute configuration, conformational analysis and binding affinity properties of enantiomeric forms of DAU 5750, a novel M1-M3 muscarinic receptor antagonist.

Both the enantiomeric forms of DAU 5750, a novel muscarinic receptor antagonist, have been synthesized in order to assess the relevance of configurational/conformational features for high affinity binding to muscarinic receptor subtypes. The attribution of absolute stereochemistry and conformational analysis by means of molecular modelling and NMR techniques are also reported.

Antagonistic properties of McNeil-A-343 at 5-HT4 and 5-HT3 receptors.

1. This study describes the in vitro interaction of the muscarinic ligand McNeil-A-343 with two 5-hydroxytryptamine (5-HT) receptor subtypes, the 5-HT4 and 5-HT3 receptors, using functional as well as radioligand binding studies. 2. In the rat oesophageal muscularis mucosae, precontracted with carbachol, McNeil-A-343 was a competitive antagonist (pA2 6.2) of the 5-HT4 receptor which mediates the relaxation induced by 5-HT. The compound per se relaxed the oesophagus at high concentration only (> or = 10 microM), an effect unchanged by desensitization of the 5-HT4 receptor with 10 microM 5-methoxytryptamine. In the same preparation in the absence of tone, McNeil-A-343 displaced the carbachol concentration-response curve to the right, yielding an apparent affinity (pA2) of 4.9 for muscarinic receptors. 3. In the rat isolated superior cervical ganglion preparation, after blockade of muscarinic and nicotinic receptors, McNeil-A-343 caused a concentration-dependent depolarization that was unaffected by 100 nM ondansetron. The concentration-fast depolarization curve to 5-HT, mediated by the 5-HT3 receptor, was displaced to the right by McNeil-A-343, which showed an apparent affinity (pA2) of 4.8 for the 5-HT3 subtype. 4. In binding studies, McNeil-A-343 recognized a single population of 5-HT4 receptors in pig caudate nucleus, with a pKI of 5.9. The binding affinity of McNeil-A-343 for 5-HT3 receptors in NG 108-15 cells was approximately four times lower (pKI 5.3). Binding affinities (pKI) for muscarinic receptor subtypes in rat tissues were 5.3 (M1, cortex), 5.2 (M2, heart) and 4.9 (M3, submandibular glands), respectively. 5. McNeil-A-343 is an antagonist at 5-HT4 and 5-HT3 receptors; the interaction of the compound with these receptor subtypes (notably the 5-HT4) occurs in a range of concentrations which generally overlaps that relevant to the interaction with muscarinic receptors.

Medicinal chemistry of muscarinic agonists for the treatment of dementia disorders.

Alzheimer disease (AD) is a neurodegenerative disorder lacking an effective therapy. The etiology is controversial and among different drug strategies, the cholinergic approach has gained great interest owing to biochemical and pharmacological evidence of the crucial role of acetylcholine in cognitive functions. Several attempts exploiting the boosting of the cholinergic system are currently under way. Inhibitors of the acetylcholinesterase enzyme sustain the availability of the natural transmitter by limiting its removal from the synapse. In a different approach, exogenous agonists may substitute acetylcholine itself. In this way the issue of the extensive cholinergic cell loss occurring in AD and leading to a reduction of cholinergic functions, could be advantageously bypassed. Moreover the discovery of different muscarinic receptor subtypes, most notably the M1 subtype as that involved in the postsynaptic transmission, has offered new opportunities to face the problem in a very specific way. In this line of research, we have now identified BIMC 182 as a new functionally selective M1 agonist. Whereas its affinity for the different receptor subtypes is almost similar (radioreceptor binding), its functional selectivity is pointed out by specific "in vitro" models. BIMC 182 behaves as a full agonist at M1 (rat superior cervical ganglion, pD2 4.8) and as a partial agonist at M2 and M3 sites (g.p. heart pD2 = 5.4 and g.p. ileum pD2 = 4.5). The agonist profile is further confirmed in hm1 transfected CHO cells where the compound stimulates PI turnover. BIMC 182 penetrates well the brain as shown by the increase in the energy of the low frequency band (theta waves) in the cortical EEG of rabbits (3 mg/kg i.v.).(ABSTRACT TRUNCATED AT 250 WORDS)

Gastroprokinetic properties of the benzimidazolone derivative BIMU 1, an agonist at 5-hydroxytryptamine4 and antagonist at 5-hydroxytryptamine3 receptors.

We have investigated the in vivo motor stimulating and gastroprokinetic properties of the azabicycloalkyl benzimidazolone derivative BIMU 1 (3-ethyl-2,3-dihydro-N-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2-oxo-1H- benzimidazole-1-carboxamide hydrochloride) and its binding profile at 5-hydroxytryptamine3 and 5-hydroxytryptamine4 receptors, in an attempt to assess the serotonergic mechanism underlying its prokinetic action. BIMU 1 dose-dependently (0.01-0.3 mg/kg i.v.) increased the motility of a denervated pouch of canine stomach. This excitatory action was sensitive to muscarinic blockade. A similar stimulatory effect was exerted by the benzamidic prokinetic agent cisapride (0.03-0.3 mg/kg i.v.) but not by the 5-HT3 receptor antagonist ondansetron (up to 1 mg/kg i.v.). The significance for propulsive efficacy of the motor stimulating activity of BIMU 1 was evaluated in a model of gastric emptying of liquids in the conscious dog. The emptying rate of a non-caloric liquid meal instilled through a gastric fistula was accelerated by both BIMU 1 (0.01-1 mg/kg i.v. and 0.1-3 mg/kg p.o.) and cisapride (0.03-1 mg/kg i.v. and 0.3-10 mg/kg p.o.). Ondansetron (1 mg/kg i.v.) did not show any effect. The activity of the 5-HT4 receptor antagonist DAU 6285 was evaluated in the gastric emptying model per se and in interaction experiments on the accelerating action of BIMU 1 (0.3 mg/kg i.v.).(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of serotonin 5-HT4 recognition sites in the porcine caudate nucleus by radioligand binding.

Specific binding for the serotonin 5-HT4 receptor (5-HT4R) radioligand [3H]GR 113808 was identified in pig caudate nucleus and characterized by serotonin subtype selective drugs. Binding was inhibited by serotonin and by synthetic indoles, benzamides and benzimidazolones known to characterize the 5-HT4R in functional tests. Rank order of potency of 5-HT4R antagonists was: GR 125487 (Ki, 0.19 nM) > GR 113808 >> SC 53606 > SDZ 205,557 > RS 235971/190 > DAU 6285 > tropisetron > DAU 6215. GR 125487 and GR 113808 were highly selective with respect to the 5-HT3 receptor (5-HT3R). Rank order of potency of 5-HT4R agonists was: SC 53116 (Ki, 21 nM) > BIMU 1 > cisapride > BIMU 8 > serotonin > renzapride > S-zacopride > metoclopramide > R-zacopride > 5-methoxytryptamine >> 5-carboxamidotryptamine. BIMU 8, renzapride, metoclopramide and the zacopride enantiomers gave shallow competition curves. The agonists were substantially less selective than the antagonists with respect to the 5-HT3R. With only two exceptions, SCH 23390 and metergoline, which bound with sub-microM affinity to the 5-HT4R, binding was not inhibited by compounds selective for other G-protein-coupled or channel-gated receptors. Highly significant correlations in affinities of compounds for 5-HT4R in caudata of pigs, guinea pigs and humans were found suggesting no difference among mammalian species.

Synthesis and muscarinic activity of the chiral forms of methylenemuscarones.

The synthesis of the two pairs of enantiomers of methylenemuscarones 3 and 4 has been accomplished by using (R)- and (S)-lactic esters as starting materials. Due to the existence of different muscarinic receptor subtypes, the compounds were examined for their ability to bind membranes from cerebral cortex (M1), heart (M2), and salivary glands (M3) and were assayed in "in vitro" functional tests as well. The results of such an investigation put in evidence that, in both binding and functional tests, (-)-3 (2S,5S) and (-)-4 (2R,5S) were the eutomers and shared the stereochemistry of the eutomer of muscarone and allomuscarone respectively. It is worth noting that the distomer of 3 and 4 behaves as a partial agonist in the cardiac tissue and as a full agonist in the other preparations. This peculiarity of the chiral forms of 3 and 4 could account for the remarkable selectivity for the ileum observed in the corresponding racemates.

Characterization of BIBN 99: a lipophilic and selective muscarinic M2 receptor antagonist.

The present study was designed to characterize the receptor selectivity profile of the novel muscarinic M2 receptor antagonist BIBN 99 (5,11-dihydro-8-chloro-11-[[4-[3-[(2,2-dimethyl-1- oxopentyl)ethylamino]propyl]-1-piperidinyl]acetyl]-6H- pyrido[2,3-b][1,4]benzodiazepin-6-one). In radioligand binding studies BIBN 99 showed high affinity for m2/M2 sites (pKi = 7.52/7.57), intermediate affinity for m4 sites (pKi = 6.76) and low affinity for m1/M1 (pKi = 5.97/6.17), m3/M3 (pKi = 6.11/6.04) and m5 sites (pKi = 5.84). Functional studies in vitro showed BIBN 99 to be a competitive antagonist and to have an 11- to 25-fold higher affinity for M2 receptors than for putative M1 receptors in the rabbit vas deferens or M3 receptors in guinea-pig trachea. In vivo studies revealed that BIBN 99 is able to cross the blood-brain barrier, and although showing an approximately 3-fold higher affinity for M2 binding sites BIBN 99 appeared to be 7- to 18-fold less potent than AF-DX 116 in inhibiting muscarinic agonist or vagally induced bradycardia in rats and guinea-pigs. The results show that BIBN 99 is the first lipophilic muscarinic M2 receptor antagonist to have remarkable M2 versus M1 selectivity (30-fold). In addition, BIBN 99 possesses central nervous system activity and only minor peripheral cardiac effects.

Therapeutic potential of CNS-active M2 antagonists: novel structures and pharmacology.

Clinical trials with muscarinic agonists or acetylcholine esterase inhibitors for the treatment of Alzheimer's dementia have shown disappointing or equivocal results. An alternative treatment of this disease is the development of drugs which enhance the release of acetylcholine. It is believed, that of the five muscarinic receptor subtypes so far identified in the brain, M2 receptors are located presynaptically in the cortex and hippocampus and upon stimulation inhibit the release of acetylcholine. Based on this hypothesis, we initiated a drug discovery program with the aim of identifying selective and centrally active M2 antagonists which are capable of enhancing cholinergic transmission. These efforts resulted in the successful design and synthesis of novel muscarinic antagonists able to cross the blood brain barrier. Moreover, these compounds show few peripheral effects and possess a superior M2 versus M1 selectivity. The prototype of this novel class of M2 selective compounds, BIBN 99, could be a valuable tool to test the hypothesis that lipophilic M2 antagonists show beneficial effects in the treatment of cognitive disorders.

Synthesis and pharmacological investigation of the enantiomers of muscarone and allomuscarone.

A strategy based on the use of (R)- and (S)-lactic ester as starting materials allowed the synthesis of the two enantiomers of muscarone [(-)-1 and (+)-1] and allomuscarone [(-)-5 and (+)-5] in greater than 98% enantiomeric excess. The compounds were examined for their ability to bind to membranes from cerebral cortex (M1), heart (M2), and salivary glands (M3) and to recognize affinity agonist states of the muscarinic receptors. The two pairs of enantiomers were also tested in five functional assays, and their muscarinic potency was determined. In both binding and functional tests, (-)-1 (2S,5S) and (-)-5 (2R,5S) were the eutomers of muscarone and allomuscarone, respectively. The eudismic ratio of muscarone, evaluated in the functional tests, spanned a range of 280-440. These values are substantially different from ones (2.4-10.1) reported in the literature. From a stereochemical point of view, muscarone behaves as muscarine and all other major muscarinic agonists; as a consequence, the hypotheses advanced to account for the anomalies of muscarone no longer have reason to exist.

Synthesis and pharmacological investigation of stereoisomeric muscarines.

The synthesis of the eight stereoisomers of muscarine has been efficiently accomplished by utilizing the two enantiomers of lactic esters as starting material. The synthetic strategy is based on a SnCl4-catalyzed addition of allyltrimethylsilane to O-protected lactic aldehydes followed by an iodocyclization process. All the final derivatives possess an enantiomeric excess higher than 98%. The four pairs of enantiomers bound to M1, M2, and M3 muscarinic receptor subtypes in membranes from cerebral cortex, heart, and salivary glands, respectively, and recognized heterogeneous states of the receptors. Of the eight isomers, only natural muscarine (+)-1 recognized three affinity states of the M2 receptor. The compound was also the only one to show selectivity in the binding study, demonstrating 37- to 44-fold higher affinity for the M2 than for the M1 or M3 receptors. In addition, the compounds were tested in functional assays on isolated guinea pig atria (M2 receptors) and ileum (mixed population of M2 and M3 receptors) and their muscarinic potencies were determined. Among the eight isomers, again only (+)-1 enantiomer was found to be very active on both tissues. Its potency was more than two orders of magnitude higher than that of its enantiomer (-)-1 as well as the other six isomers. The eudismic ratios (E.R.) deduced from the two functional tests were 324 and 331.