Leptin, a product of fat cells, provides a signal of nutritional status to the central nervous system. Leptin concentrations have ultradian and diurnal fluctuations. We conducted this study to assess ...sex differences in the levels of organization of frequently sampled leptin concentrations in healthy, normal weight women and men. Leptin levels were sampled every 7 min for 24 h in 14 healthy, normal weight individuals (6 women and 8 men). The 14 leptin time series containing a total of 2898 leptin measurements were assessed by 1) algorithms that characterize statistically significant pulsatility, 2) Spectral (Fourier) analysis, 3) analysis of time intervals and variability, and 4) approximate entropy. We found that frequently sampled plasma leptin concentrations have a 24-h profile that is numerically more than twice as high in women as in men, and leptin pulse amplitude is likewise more than twice as high in women. However, healthy men and women have nearly identical concentration-independent and frequency-related 24-h and ultradian patterns. Leptin concentrations have nonrandom fluctuations over 24 h, independent of their absolute value and underlying 24-h periodicity, that are similar in men and women. Ultradian periodicities detected by Fourier time series have similar values in men and women. The strongest distinction between the sexes in the level of organization of leptin concentration is not at the level of pulse organization or oscillation frequency, but, rather, in the mass or amount of leptin released (or removed) per unit time, indicating that women might be more resistant to the effects of leptin than men. Because leptin is clinically relevant to the regulation of body weight, future studies should examine whether the relative leptin resistance exhibited by women might contribute to their increased susceptibility to disorders whose pathophysiology involves dysregulation of food intake and body weight.
Leptin communicates nutritional status to regulatory centers in the brain. Because peripheral leptin influences the activity of the highly pulsatile adrenal and gonadal axes, we sought to determine ...whether leptin levels in the blood are pulsatile. We measured circulating leptin levels every 7 minutes for 24 hours, in six healthy men, and found that total circulating leptin levels exhibited a pattern indicative of pulsatile release, with 32.0 +/- 1.5 pulses every 24 hours and a pulse duration of 32.8 +/- 1.6 minutes. We also show an inverse relation between rapid fluctuations in plasma levels of leptin and those of adrenocorticotropic hormone (ACTH) and cortisol that could not be accounted for on the basis of glucocorticoid suppression of leptin. As leptin levels are pulsatile, we propose that a key function of the CNS is regulated by a peripheral pulsatile signal. In a separate pilot study we compared leptin pulsatility in 414 plasma samples collected every 7 minutes for 24 hours from one obese woman and one normal-weight woman. We found that high leptin levels in the obese subject were due solely to increased leptin pulse height; all concentration-independent pulsatility parameters were almost identical in the two women. Leptin pulsatility therefore can be preserved in the obese.
Healthy men exhibit a differential hypothalamic-pituitary-adrenal axis (HPA) response to exercise stress and fall into two groups: high responders (HR) and low responders (LR). The present study ...examined whether HR to physical stress also exhibit higher HPA reactivity to psychological stress than LR. We examined 14 HR and 13 LR classified based on their ACTH responses to high intensity exercise after pretreatment with dexamethasone. Both groups were of similar age, height, weight, and fitness level. Trait anxiety scores on the Spielberger Trait Anxiety Scale were not different. Subjects underwent a psychological stress test consisting of an interview and mental arithmetic. This test raised heart rate, blood pressure, and plasma ACTH and cortisol levels in both HR and LR. HR tended to have higher heart rates and blood pressures in anticipation of the psychological stress test than LR. ACTH responses of HR were higher, although not significantly, throughout the psychological stress test than LR. HR had a significantly (P < 0.05) greater net integrated cortisol response to the psychological stress than LR. This suggests that the adrenal cortexes of the HR are hypertropic and/or hypersensitive to ACTH. We conclude that men who are highly responsive to exercise stress are also highly responsive to psychological stress.
Medical records and follow-up data were reviewed in 297 genetically proven myotonic dystrophy type 2 (DM2) patients. Patients were selected by the criteria of cardiac sudden death before age 45. ...Sudden death occurred in four patients, three of whom were cardiological asymptomatic, and one with a history of heart failure. Cardiac histopathology showed dilated cardiomyopathy in all, and conduction system fibrosis in two patients. Pathogenetic CCUG ribonuclear inclusions were demonstrable in cardiomyocytes.
The central administration of corticotropin-releasing hormone (CRH) to experimental animals sets into motion a coordinated series of physiological and behavioral events that promote survival during ...threatening situation. A large body of evidence suggest that CRH in the central nucleus of the amygdala (CEA) induces fear-related behaviors and is essential to fear conditioning; however, evidence of CRH-mediated activation of the amygdala under physiological situation is still limited. We report here a study of the impact of a psychological stressor on hypothalamic and amygdala CRH systems in the rat. Non-footshocked rats placed in a floored compartment surrounded by footshocked rats were defined as the psychological stress group. Rats were exposed to psychological stress for 15 min, and then sacrificed 1.5 and 3 h after cessation of stress. We found that our psychological stressor induced an increase in both CRH mRNA levels, as assessed by in situ hybridization histochemistry, and CRH content, as assessed by micropunch RIA, in the CEA. Exposure to the psychological stressor also caused a significant increase in CRH mRNA levels with a trend for an increase in CRH content in the dorsolateral subdivision of the bed nucleus of the stria terminalis (BNST) which is anatomically associated with the CEA. In contrast, psychological stress induced a small, but significant increase in type-1 CRH receptor (CRHR-1) mRNA in the hypothalamic paraventricular nucleus (PVN), while it failed to elevate either PVN CRH mRNA levels or content, CRH content in the median eminence (ME), or levels of plasma ACTH or corticosterone (CORT). Thus, in the context of a psychological stressor, the activation of the amygdala CRH system can occur without robust activation of the hypothalamic CRH system. In the light of previous data that the psychological stress-induced loss of sleep was reversed by the central administration of a CRH antagonist, these data suggest that CRH in the CEA may contribute to the psychological stress-evoked fear-related behavior such as hyperarousal. These data also indicate that in response to a psychological stressor, the amygdala CRH system is much more sensitive than is the CRH system emanating from the PVN.
Objectives: To assess whether group exercise and coping classes reduce physical and psychological impairments and functional disability in older women with prevalent vertebral fractures (VFs).
...Design: Randomized, controlled trial (modified cross‐over) with site as unit of assignment; testing at baseline and 3, 6, 9, and 12 months.
Setting: Nine North Carolina retirement communities.
Participants: One hundred eighty‐five postmenopausal Caucasian women (mean age 81), each with at least one VFs.
Intervention: The intervention group had 6 months of exercise (3 meetings weekly, 45 minutes each) and coping classes (2 meetings weekly, 45 minutes each) in Phase 1, followed by 6 months of self‐maintenance. The control group had 6 months of health education control intervention (1 meeting weekly, 45 minutes) in Phase 1, followed by the intervention described above.
Measurements: Change in trunk extension strength, change in pain with activities, and change in psychological symptoms.
Results: Between‐group differences in the change in trunk extension strength (10.68 foot pounds, P<.001) and psychological symptoms (−0.08, P=.011) were significant for Phase 1. Changes in pain with activities did not differ between groups (−0.03, P=.64); there was no change in the pain endpoint. In Phase 2, controls showed significant changes in trunk strength (15.02 foot pounds, P<.001) and psychological symptoms (−0.11, P=.006) from baseline. Change in pain with activities was not significant (−0.03, P=.70). During self‐maintenance, the intervention group did not worsen in psychological symptoms, but improved trunk extension strength was not maintained.
Conclusion: Weak trunk extension strength and psychological symptoms associated with VFs can be improved in older women using group treatment, and psychological improvements are retained for at least 6 months.
In experimental animals, stress and catecholamines stimulate endogenous interleukin-6 (IL-6) secretion, whereas glucocorticoids inhibit it. To examine whether physical stress alters the secretion of ...IL-6 in humans, and to what extent this is correlated with catecholamines and modified by glucocorticoids, we performed high-intensity treadmill exercise test runs on 15 male volunteers, in a double-blind crossover design, after pretreatment with placebo, hydrocortisone, or dexamethasone. Plasma epinephrine and norepinephrine concentrations peaked 15 min after the start of exercise, whereas plasma IL-6 concentrations peaked twice, 15 min and 45 min after the onset of the test run. There was no difference in either the epinephrine or norepinephrine peaks among the three treatments, but the net area under the curve for IL-6 was smaller after hydrocortisone or dexamethasone than after placebo and smaller after dexamethasone than after hydrocortisone. A positive correlation was observed between peak plasma epinephrine or norepinephrine and IL-6 levels at 15 min. These findings suggest that IL-6 secretion is stimulated during exercise, possibly by catecholamines, whereas exogenous glucocorticoids attenuate this effect without affecting the catecholamine levels.
In the rat, lactation suppresses a variety of physiological responses to stress. We investigated whether stress-responsive neurohormonal systems are also restrained during breast feeding in humans. ...We chose treadmill exercise as a stressor because this stimulus produces an exercise intensity-dependent activation of the hypothalamic-pituitary-adrenal axis and the sympathomedullary system that is independent of differences in physical conditioning among subjects. Ten lactating and ten nonlactating women who were between 7 and 18 weeks postpartum performed 20 min of graded treadmill exercise. The final 5 min of exercise was set to elicit 90% of the maximal oxygen uptake of each subject. Plasma ACTH, cortisol, and glucose responses to exercise were significantly attenuated in lactating women (P < 0.001, P < 0.05, and P < 0.001, respectively). Basal norepinephrine levels were also reduced in lactating women (P < 0.05). These results indicate that stress-responsive neurohormonal systems are restrained in lactating women.
We have recently found that susceptibility to streptococcal cell wall (SCW)-induced arthritis in Lewis (LEW/N) rats is due, in part, to defective inflammatory and stress mediator-induced activation ...of the hypothalamic-pituitary-adrenal (HPA) axis. Conversely, the relative arthritis resistance of histocompatible Fischer (F344/N) rats is related to their intact responses to the same stimuli. Specifically, LEW/N rats, in contrast to F344/N rats, have markedly impaired plasma corticotropin and corticosterone responses to SCW, recombinant human interleukin 1α , the serotonin agonist quipazine, or synthetic rat/human corticotropin-releasing hormone (CRH). To explore the mechanism of this defect, we examined the functional integrity of the hypothalamic CRH neuron in LEW/N rats compared to F344/N rats. LEW/N rats, in contrast to F344/N rats, showed profoundly deficient paraventricular nucleus CRH mRNA levels and hypothalamic CRH content in response to SCW. Compared to F344/N rats, there was no increase in LEW/N hypothalamic CRH content or CRH release from explanted LEW/N hypothalami in organ culture in response to recombinant interleukin 1α . These data provide strong evidence that the defective LEW/N corticotropin and corticosterone responses to inflammatory and other stress mediators, and the LEW/N susceptibility to experimental arthritis, are due in part to a hypothalamic defect in the synthesis and secretion of CRH. The additional finding of deficient expression in LEW/N rats of the hypothalamic enkephalin gene, which is coordinately regulated with the CRH gene in response to stress, suggests that the primary defect is not in the CRH gene but is instead related to its inappropriate regulation.
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