Persistence of rhythmic human growth hormone release during sheep in fasted and nonisocalorically fed normal subjects

Acute Sleep Disruption Does Not Diminish Pulsatile Growth Hormone Secretion in Pubertal Children

Context

In children, growth hormone (GH) pulses occur after sleep onset in association with slow-wave sleep (SWS). There have been no studies in children to quantify the effect of disrupted sleep on GH secretion.

Objective

This study aimed to investigate the effect of acute sleep disruption on GH secretion in pubertal children.

Methods

Fourteen healthy individuals (aged 11.3-14.1 years) were randomly assigned to 2 overnight polysomnographic studies, 1 with and 1 without SWS disruption via auditory stimuli, with frequent blood sampling to measure GH.

Results

Auditory stimuli delivered during the disrupted sleep night caused a 40.0 ± 7.8% decrease in SWS. On SWS-disrupted sleep nights, the rate of GH pulses during N2 sleep was significantly lower than during SWS (IRR = 0.56; 95% CI, 0.32-0.97). There were no differences in GH pulse rates during the various sleep stages or wakefulness in disrupted compared with undisrupted sleep nights. SWS disruption had no effect on GH pulse amplitude and frequency or basal GH secretion.

Conclusion

In pubertal children, GH pulses were temporally associated with episodes of SWS. Acute disruption of sleep via auditory tones during SWS did not alter GH secretion. These results indicate that SWS may not be a direct stimulus of GH secretion.

Sleep changes in fasting rats after chronic glycerol feeding

Species which do not enter torpor during fasting and which were efficiently able to spare their body proteins during the first two phases of fasting (which are commonly comprised of 3 successive phases) also increase their daily amount of slow-wave sleep (SWS) during the first two phases. Since in fasting animals the ability to spare proteins was reported to be improved when they were previously fed with a diet enriched with glycerol, it was supposed that, after such a diet, food-deprived rats would increase their daily quota of SWS. In addition, the tolerance to food deprivation, defined as the time elapsed to reach the end of phase II, should also be improved since this tolerance is known to be critically modulated by protein utilization. The daily proportions of wakefulness (W), SWS and paradoxical sleep (PS) were thus studied in Wistar rats after 16 weeks of feeding (i.e., when they were 27 weeks old) with an enriched glycerol diet. These daily W and sleep state proportions were then evaluated until the middle of fasting phase II (MII), i.e., when protein catabolism in the rat appears to be at its lowest level. The rats were able to tolerate more than 5 weeks of food deprivation, which represented an increase of 123% of the fasting tolerance previously reported in rats of the same age but which were fed normally before fasting onset. At MII the daily proportion of SWS was significantly (vs. fed state, p less than 0.01) increased (due to an increase in the daily mean episode duration), at the expense of W (due to a lowering in the daily occurrence of W episodes).(ABSTRACT TRUNCATED AT 250 WORDS)

Sleep changes in fasting rats

The proportion and the distribution of wakefulness (W) slow-wave sleep (SWS) and paradoxical sleep (PS) were studied in 27-week-old rats over 24 hr periods, both in the fed state and after having been deprived of food for 2 to 3 weeks. In these rodents, prolonged fasting has been characterized by 3 successive metabolic phases which have been found to correspond to changes in protein metabolism. Sleep-waking changes were not studied during the first phase which was often of short duration (24 hr). During the second phase, i.e., when proteins were spared, the 24 hr proportions of W and sleep states remained unchanged. There were, however, profound changes in the daily mean episodic characteristics of each vigilance state (duration and frequency) except in the case of PS. During the phase II, the differences in the day/night proportions observed in each vigilance state were less than in the fed state. This reflected a lowering in the amplitude of their daily rhythms. In contrast, when protein use rose (phase III), W was increased sharply at the expense of SWS and PS, the latter being almost completely suppressed. During this last phase, which was also of short duration (by mean 3 days) alertness was greatly enhanced and the rats, which were typically nocturnal when fed, became diurnal. The changes in sleep and wakefulness were examined in relation to their effects on the homeostatic and cyclic components of sleep mechanisms and adaptive strategy to food deprivation in rat.

Hypothalamic control of GH secretion: pathophysiology and clinical implications

GH is secreted episodically. Its pattern is regulated by the interplay of a releasing and a release-inhibiting hormone of hypothalamic origin. Modulation occurs by metabolic factors (glucose, free fatty acids, ketone bodies, amino acids). Altered GH secretion has been observed in states of metabolic derangement such as diabetes mellitus, malnutrition and obesity. Further modulation occurs by extrahypothalamic CNS structures. In man--but not in animals, including subhuman primates--sleep has an important effect on GH secretion. A defective GH secretory pattern has been found to occur in several states of sleep disturbance, such as sleep deprivation, narcolepsy, severe psychosocial derangement, the apallic syndrome. Other CNS influences on GH secretion are related to stress, emotional changes and psychiatric disturbances. The exact mechanisms by which most of these influences are relayed to the GH secretory apparatus of the hypothalamus remain yet to be investigated.

Circadian growth hormone and prolactin blood concentration during a self-limited viral infection and artificial hyperthermia in man

Growth hormone and prolactin blood concentrations were measured in five human volunteers over 28-hour periods including 24 hourly samples (0800 to 0800 hours) followed by an oral glucose tolerance test (0800 to 1100 hours) both preexposure and during the peak febrile phase of a self-limited viral infection, Sandfly fever. Several months after recovery, three of the subjects were studied for 24-hour periods while they sat in a tub of water at 41 degrees C for 2 hours from 1300 to 1500 hours. During all studies, mealtimes (0800 hours, 1130 hours, 1630 hours) and dark phase (2300 to 700 hours) were fixed. Growth-hormone concentrations were strikingly elevated throughout the 24-hour study done during the febrile period of Sandfly fever infection (P less than .01) except for the period of normal nocturnal release when they were not significantly different from the baseline study. No additional nocturnal surge was noted the already elevated growth-hormone values during the viral-induced fever. Growth-hormone values tended to decline slowly during the night but increased considerably during the glucose-tolerance test the following morning. These changes were similar to responses previously reported in patients with cases of malnutrition. A clear-cut increase in growth-hormone concentrations (P less than .001) was also seen during a brief 2-hour period of artificial hyperthermia, suggesting that elevated body temperature alone may explain part of the increase in growth-hormone values seen during the fever of infection. A nocturnal surge of growth hormone was still seen in the artificial hyperthermia study, albeit somewhat delayed.(ABSTRACT TRUNCATED AT 250 WORDS)

Pituitary secretions and wake-sleep cycle

Neurohumoral correlations of sleep are considered from three aspects: 1. Metabolism and cerebral blood circulation (CBF, EEG, endocranial pressure, cerebral temperature); 2. Neuromediators and neuropeptides (5-HT, hypnogen neuropeptides); 3. The influence of the sleeping-waking cycle on adeno-hypophyseal secretion rhythms (GH, PRL, LH, TSH). Variations of these parameters can play an important role in the onset of night crises of migraine and cluster headache.

Sleep related growth hormone and prolactin secretion in children during constant rate enteral nutrition

The aim of this study was to investigate the nocturnal secretion of growth hormone and prolactin in a particular model where nutrients are delivered continuously. Six children with severe intestinal diseases undergoing total constant rate enteral nutrition for 1.5 to 8 months have been studied; all children had a normal nutritional status at the time of the recording. Sleep patterns were studied by the usual polygraphic methods from 10 p.m. to 8 a.m. Blood samples were taken every 20 min through an indwelling catheter for growth hormone and prolactin plasma level determination. Several growth hormone peaks were observed with a peak always secreted in connection with stage III-IV of the first cycle. This early peak was significantly higher than the following ones. Nocturnal patterns of prolactin secretion showed individual differences characterized by a series of episodic releases which consisted of a few long rises (4 patients) and several small fluctuations; no correlation was found with the sleep patterns; no increase in the level throughout the night was observed. Loss of the rhythmicity of alimentation does not alter the secretion of growth hormone during sleep.

A chronometric approach to the study of feeding behavior

In many mammalian genera, the stimulus to feed is intimately associated with circadian rhythms. This stimulus arises from within the brain from biological time-keeping systems. Such a chronometric approach to feeding behavior follows from a consideration of the terrestrial mammal's space-time pattern within the ecological niche. The ecological niche is a division of time as well as space. The restriction of certain behaviors to certain times of day and the concomitant evolution of nocturnality or diurnality represent strong advantages for survival in the wild. Experimental data, primarily from studies on the rat, in support of the chronometric approach, include: the reinstatement of cyclic feeding patterns after food deprivation; the continuation of circadian pattern of wheel running and nocturnal drinking during food deprivation; consideration of the ontogeny of the feeding pattern; the phenomenon of anticipatory appetite--the experimental demonstration that time of day can act as a conditioned stimulus for feeding; the evaluation of rhythms in digestion, absorption and assimilatory biochemical processes; the realization that many of these rhythms are not simply a consequence of the presence of food in the gut; the realization that the brain exerts considerable control over the peripheral rhythmic nutritional processes via ANS and endocrinological systems; and the fact that within the brain the SCN and structures well known to be involved in nutritional regulation, such as the VMH, LHA and monoamine systems, may all be involved in the circadian pattern of feeding. Further, the function of these neurological structures may be understood better by consideration of data from temporal changes in feeding patterns.

Simultaneous study of cortisol, growth hormone and prolactin nyctohemeral variations in normal and obese subjects. Influence of prolonged fasting in obesity

Hourly integrated concentrations (IC) of growth hormone (GH), prolactin (PRL) and cortisol were determined by a continuous sampling procedure in six obese women, before and at the end of a 12 day fast, and in eight normal controls under basal conditions. Hormonal 24 h IC and nyctohemeral variations were calculated from these data. Nyctohemeral rhythms were investigated by the periodogram method. A significant increase over basal values of 24 h IC of PRL, GH and cortisol was observed at the end of the fasting period. Nyctohemeral variations--but not nyctohemeral rhythm--of IC-GH were found in normal subjects. They were abolished in obese patients under basal conditions but restored during fasting. The circadian rhythm of cortisol was not altered in obesity. A shift of the normal nyctohemeral rhythm of PRL was observed in obese patients, but the normal pattern was restored during fasting.