Ovine corticotropin-releasing factor administration in normal men. Pituitary and adrenal responses in the morning and evening

We administered ovine corticotropin-releasing factor (CRF) as a bolus intravenous injection (1 microgram/kg) at 09.00 and at 20.00 to assess the influence of circadian changes in the hypothalamic-pituitary-adrenal axis on the response to CRF. The increase in plasma ACTH levels after CRF was only slightly lower in the morning than in the evening. The plasma cortisol response to ACTH, however, was significantly greater in the evening than in the morning (p less than 0.005). At both times of day CRF administration had no effect on plasma concentrations of GH, PRL, LH, AVP, insulin, PRA or glucose. No effects were observed on the hematopoietic system, kidneys or liver. In addition, CRF had no effect on heart rate, blood pressure or respiratory rate at the dose employed. Approximately 10% of the subjects complained of a transient upper body and facial hot flush. These observations indicate that the magnitude of the plasma cortisol rise after CRF depends on the time of administration.     

Adrenal 11-hydroxylase activity in a hypercortisolemic New World primate: adaptive intra-adrenal changes

The squirrel monkey, a representative New World primate, has high plasma cortisol and aldosterone concentrations when compared to Old World primates. We measured adrenal mitochondrial 11-hydroxylase (11-OHase) activity in squirrel monkeys and in two representative Old World species (cynomolgus and rhesus macaques) in an effort to explain these elevated plasma glucocorticoid and mineralocorticoid levels. The activity of 11-OHase was 5-fold higher in the squirrel monkey than in the Old World species tested. Calculated 11-OHase Vmax was different in the squirrel monkey and the cynomolgus. However, the Km values were similar in the New World primate when compared to cynomolgus. The ability of metyrapone to block 11-OHase was less in the former than in the latter. The data are consistent with the hypothesis that the squirrel monkey adrenal cortex possesses an increased number of 11-hydroxylase enzyme units compared to that of Old World primate species, and is therefore more efficient in producing cortisol. This difference in 11-OHase activity in the squirrel monkey, in addition to other previously reported adrenal steroidogenic enzyme alterations, may be adaptive in nature, favoring increased cortisol and aldosterone production in this and possibly other New World primate species.     

In vitro-perifused rat testes secrete beta-endorphin and dynorphin: their effect on testosterone secretion

Leydig cells of many species synthesize and secrete opioid peptides, but the Sertoli and possibly the peritubular cells are the only intratesticular cells having opiate receptors. It is known that Sertoli and peritubular cells can modify the secretion of testosterone from Leydig cells. To test the hypothesis that testicular opioid peptides participate in a Leydig-Sertoli-peritubular-Leydig cell feedback loop that can regulate the intratesticular concentration of testosterone, we have developed a method for the in vitro perifusion of rat testicular fragments in which the intratesticular structure and thus the paracrine feedback loop remains intact. Our data show that both immunoreactive (IR)-beta-endorphin and IR-dynorphin were present in the testicular perifusion effluent; gel chromatography of pooled perifusion effluent show that the bulk of the secreted IR-beta-endorphin had the apparent mol. wt. of synthetic rat beta-endorphin whereas most of the secreted IR-dynorphin was composed of smaller than 4000 mol. wt. forms. On the other hand, the bulk of IR-dynorphin present in rat testicular tissue homogenates eluted in two higher mol. wt. peaks. The effect of mu and kappa opioid agonists and naloxone (a universal opioid antagonist) on both basal and gonadotropin-stimulated testosterone secretion from perifused testicular fragments was then examined; no stimulatory or inhibitory effect of the opioid receptor agonists or naloxone was found on basal and gonadotropin-stimulated testosterone secretion. Parallel experiments with Leydig cells in culture gave similar results.(ABSTRACT TRUNCATED AT 250 WORDS)     

Obesity and sleep disturbances: meaningful sub-typing of obesity

Obesity, excessive daytime sleepiness (EDS), and self-reported short sleep duration appear to be on the rise, while there is evidence that obesity and these sleep disorders are strongly connected. In this paper, we review data that challenge the common belief that the sleep apnoea and sleep loss, frequently associated with obesity, are the primary determinants of obesity-related objective daytime sleepiness and subjective fatigue (tiredness without increased sleep propensity). Specifically, obesity is associated with objective and subjective EDS regardless of the presence of sleep apnoea. The association between obesity and EDS was confirmed in recent studies of large random samples of the general population or clinical samples, which showed that the primary determinants of subjective EDS were depression, metabolic disturbances, i.e. obesity/diabetes and insulin resistance, and lack of physical activity, and, secondarily, sleep apnoea or sleep loss. Paradoxically, within the obese, with or without sleep apnoea, those who slept objectively better at night are sleepier (objectively) during the day than those who slept worse. The distinguishing factor between those that slept better vs. those that slept worse appears to be level of emotional stress. Furthermore, many studies reported that obesity is associated with self-reported short sleep duration; however, it appears that short sleep duration is a marker of emotional stress rather than a reflection of true sleep loss. Based on these data, we propose that obesity-related deeper sleep and objective EDS are primarily related to metabolic disturbances, whereas obesity-related poorer sleep and subjective fatigue appear to be the result of psychological distress. Furthermore, based on data from studies in normal controls and patients with sleep disorders, it appears that the interaction of the hypothalamic-pituitary-adrenal (HPA) axis and pro-inflammatory cytokines determines the level of sleep/arousal within the 24-hour cycle, i.e. "eucortisolemia" or "hypocortisolemia" plus hypercytokinemia is associated with high sleep efficiency and objective sleepiness, whereas "hypercortisolemia" plus hypercytokinemia is associated with low sleep efficiency and fatigue. In conclusion, we propose that the above-reviewed data provide the basis for a meaningful phenotypic and pathophysiologic sub-typing of obesity. One subtype is associated with emotional distress, poor sleep, fatigue, HPA axis "hyperactivity," and hypercytokinemia while the other is associated with non-distress, better sleep but more sleepiness, HPA axis "normo or hypoactivity," and hypercytokinemia. This proposed sub-typing may lead to novel, preventive and therapeutic strategies for obesity and its associated sleep disturbances.     

Low- versus high-baseline epinephrine output shapes opposite innate cytokine profiles: presence of Lewis- and Fischer-like neurohormonal immune phenotypes in humans?

Immunogenetic mechanisms operating within the immune system are known to influence cytokine profiles and disease susceptibility. Yet the role of the individual's neurohormonal background in these processes remains undefined. Hormonal imbalances are documented in immune-related diseases, but it is unclear whether this represents a secondary phenomenon or a primary "defect" related to specific neurohormonal immune phenotype(s). We report that in a large subpopulation of healthy humans the baseline epinephrine output (but not cortisol and sex steroid hormones) correlated inversely with proinflammatory and positively with anti-inflammatory cytokine production. Thus, low vs high epinephrine excretors had a 2- to 5-fold higher TNF-alpha and IL-12 production but 2-fold lower IL-10 production induced by LPS ex vivo. In alternative settings, we found low baseline levels and profoundly blunted stress-induced epinephrine responses but high TNF-alpha levels in Lewis vs Fischer inbred rats. Additionally, isoproterenol, a beta adrenoreceptor agonist suppressed LPS-induced TNF-alpha production, with more pronounced effect in Lewis than in Fischer rats. In human monocytes, epinephrine and the beta(2) adrenoreceptor agonist fenoterol potently inhibited LPS-induced TNF-alpha and IL-12, but stimulated IL-10 production. The order of potency for hormones able to inhibit IL-12 production ex vivo was: epinephrine > norepinephrine > or = 1,25-(OH)(2) vitamin D(3) > hydrocortisone. This indicates that baseline epinephrine conditions cytokine responsiveness and through this mechanism intrinsic hypo- or hyperactive adrenal medullas in some individuals may shape opposite cytokine profiles. Since Lewis and Fischer rats have opposite susceptibility to experimental immunological diseases, this suggests that the parallel human phenotypes could be linked to differing responsiveness and susceptibility to infections and immune/inflammatory-related conditions.     

CRHR1 Receptor binding and lipophilicity of pyrrolopyrimidines, potential nonpeptide corticotropin-releasing hormone type 1 receptor antagonists.

A series of compounds related to N-butyl-N-ethyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amine (1, antalarmin) have been prepared and evaluated for their CRHR1 binding affinity as the initial step in the development of selective high affinity hydrophilic nonpeptide corticotropin-releasing hormone type 1 receptor (CRHR1) antagonists. Calculated log P (Clog P) values were used to evaluate the rank order of hydrophilicity for these analogues. Introducing oxygenated functionalities (delta-hydroxy or bis-beta-ethereal) into 1 gave more hydrophilic compounds, which had good affinity for the receptor. Introducing an amino group or shortening the alkyl side chain was detrimental to CRHR1 affinity. The alcohol 4-[ethyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amino]butan-1-ol (3), bearing a terminal hydroxyl group on an N-alkyl side-chain, showed the highest CRHR1 binding affinity among these compounds (K(i)=0.68 nM), and is one of the highest affinity CRHR1 ligands known. Compounds 3-5, and 8, which are likely to be less lipophilic than 1, have high CRHR1 affinity and may be valuable probes to further study the CRH system.