Insulin-like growth factor-1 (IGF-1)-induced inhibition of growth hormone secretion is associated with sleep suppression

Growth hormone and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a prevalent cause of liver disease and metabolic comorbidities. Obesity is strongly associated with NAFLD and is also a state of relative deficiency of growth hormone (GH). Evidence supports a role of reduced GH and insulin-like growth factor-1 (IGF-1) in NAFLD pathogenesis. Physiological actions of GH in the liver include suppression of de novo lipogenesis (DNL) and promotion of lipid beta-oxidation, and GH also appears to have anti-inflammatory actions. Physiologic actions of IGF-1 include suppression of inflammatory and fibrogenic pathways important in the evolution from steatosis to steatohepatitis and fibrosis. Rodent models of impaired hepatic GH signaling show the development of steatosis, sometimes accompanied by inflammation, hepatocellular damage, and fibrosis, and these changes are ameliorated by treatment with GH and/or IGF-1. In humans, individuals with GH deficiency and GH resistance demonstrate an increased prevalence of NAFLD compared to controls, with improvement in hepatic lipid, steatohepatitis, and fibrosis following GH replacement. As a corollary, individuals with GH excess demonstrate lower hepatic lipid compared to controls along with increased hepatic lipid following treatment to normalize GH levels. Clinical trials demonstrate that augmentation of GH reduces hepatic lipid content in individuals with NAFLD and may also ameliorate steatohepatitis and fibrosis. Taken together, evidence supports an important role for perturbations in the GH/IGF-1 axis as one of the pathogenic mechanisms of NAFLD and suggests that further study is needed to assess whether augmentation of GH and/or IGF-1 may be a safe and effective therapeutic strategy for NAFLD.

Lower serum insulin-like growth factor 1 concentrations in patients with chronic insomnia disorder

Objectives

Insulin-like growth factor 1 (IGF-1) is a crucial neurotrophin that is produced in the brain and periphery and may play an important role in insomnia and mood disorders. We aimed to analyze its serum concentrations in patients with chronic insomnia disorder (CID).

Methods

Patients with CID were enrolled in this study and divided into the CID group [Generalized Anxiety Disorder-7 (GAD-7) score < 10] and the CID with anxiety group (GAD-7 score ≥ 10). Age-and sex-matched healthy volunteers were recruited as controls. The Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep quality and the GAD-7 and the Patient Health Questionnaire-9 to assess emotional status. All subjects were monitored via polysomnography, and the serum IGF-1 concentrations in their peripheral blood were detected via enzyme-linked immunosorbent assays.

Results

We enrolled 65 patients with CID (of whom 35 had anxiety) and 36 controls. The PSQI score and IGF-1 concentration in the CID and CID with anxiety groups were higher than those in the control group. The apparent difference in IGF-1 concentration between the CID and CID with anxiety groups was not statistically significant. The IGF-1 concentration in patients with CID was linearly correlated with the GAD-7 score, PSQI score, and stage 3 non-rapid eye movement (stage N3) time.

Conclusion

The serum IGF-1 concentration in patients with CID was lower than that of participants without CID, negatively correlated with anxiety score and sleep quality, and positively correlated with stage N3 time.

The human circadian metabolome

The circadian clock orchestrates many aspects of human physiology, and disruption of this clock has been implicated in various pathologies, ranging from cancer to metabolic syndrome and diabetes. Although there is evidence that metabolism and the circadian clockwork are intimately linked on a transcriptional level, whether these effects are directly under clock control or are mediated by the rest-activity cycle and the timing of food intake is unclear. To answer this question, we conducted an unbiased screen in human subjects of the metabolome of blood plasma and saliva at different times of day. To minimize indirect effects, subjects were kept in a 40-h constant routine of enforced posture, constant dim light, hourly isocaloric meals, and sleep deprivation. Under these conditions, we found that ~15% of all identified metabolites in plasma and saliva were under circadian control, most notably fatty acids in plasma and amino acids in saliva. Our data suggest that there is a strong direct effect of the endogenous circadian clock on multiple human metabolic pathways that is independent of sleep or feeding. In addition, they identify multiple potential small-molecule biomarkers of human circadian phase and sleep pressure.

Sleep characteristics in children with growth hormone deficiency

BACKGROUND/AIMS

Growth hormone (GH) is preferentially secreted during slow wave sleep and the interactions between human sleep and the somatotropic system are well documented, although only few studies have investigated the sleep EEG in children with GH deficiency (GHD). The aim of this study was to evaluate the sleep structure of children with dysregulation of the GH/insulin-like growth factor axis.

METHODS

Laboratory polysomnographic sleep recordings were obtained from 10 GHD children and 20 normal healthy age-matched children. The classical sleep parameters were evaluated together with sleep microstructure, by means of the cyclic alternating pattern (CAP), in GHD patients and compared to the control group.

RESULTS

GHD children showed a significant decrease in total sleep time, sleep efficiency, movement time and in non-rapid eye movement sleep stage 2. Although some indicators of sleep fragmentation were increased in GHD children, we found a general decrease in EEG arousability represented by a significant global decrease in the CAP rate, involving all CAP A phase subtypes.

CONCLUSIONS

The analysis of sleep microstructure by means of CAP, in children with GHD, showed a reduction of transient EEG amplitude oscillations. Further studies are needed in order to better clarify whether GH therapy is able to modify sleep microstructure in GHD children, and the relationships between sleep microstructure, hormonal secretion and neurocognitive function in these patients.

Study of weight and height development in children after adenotonsillectomy

The daily clinical observation of weight-height growth delays in children with obstructive hypertrophy of the pharyngeal and palatine tonsils is a workaday practice in pediatric otorhinolaryngology, and the surgical correction of this condition, when properly done in time, through adenotonsillectomy, can lead to a “catch up growth”.

Aim

To investigate the real weight-height gain present in this population when they are surgically treated.

Materials and Methods

Through a clinical prospective study, two groups of children carrying pharyngopalatine hypertrophy were followed up: group 1 was submitted to surgical intervention, and group 2 was not. All patients underwent standardization of anthropometrical measurements (weight and height), including their age-related percentiles, in the beginning and at the end of 06 (six) months.

Results

While group 1 increased its height average in relation to the initial average in 6.66cm, the control group increased its average in 1.9cm (p=0.0004). In relation to weight, group 1 increased 2150g in average, while group 2 presented an average increase of 690g (p=0.0010).

Conclusions

The children that underwent adenotonsillectomy acquired a higher weight-height growth potential in relation to those children who were not operated.

Neurochemical regulation of sleep

This review summarizes recent developments in the field of sleep regulation, particularly in the role of hormones, and of synthetic GABA(A) receptor agonists. Certain hormones play a specific role in sleep regulation. A reciprocal interaction of the neuropeptides growth hormone (GH)-releasing hormone (GHRH) and corticotropin-releasing hormone (CRH) plays a key role in sleep regulation. At least in males GHRH is a common stimulus of non-rapid-eye-movement sleep (NREMS) and GH and inhibits the hypothalamo-pituitary adrenocortical (HPA) hormones, whereas CRH exerts opposite effects. Furthermore CRH may enhance rapid-eye-movement sleep (REMS). Changes in the GHRH:CRH ratio in favor of CRH appear to contribute to sleep EEG and endocrine changes during depression and normal ageing. In women, however, CRH-like effects of GHRH were found. Besides CRH somatostatin impairs sleep, whereas ghrelin, galanin and neuropeptide Y promote sleep. Vasoactive intestinal polypeptide appears to be involved in the temporal organization of human sleep. Beside of peptides, steroids participate in sleep regulation. Cortisol appears to promote REMS. Various neuroactive steroids exert specific effects on sleep. The beneficial effect of estrogen replacement therapy in menopausal women suggests a role of estrogen in sleep regulation. The GABA(A) receptor or GABAergic neurons are involved in the action of many of these hormones. Recently synthetic GABA(A) agonists, particularly gaboxadol and the GABA reuptake inhibitor tiagabine were shown to differ distinctly in their action from allosteric modulators of the GABA(A) receptor like benzodiazepines as they promote slow-wave sleep, decrease wakefulness and do not affect REMS.

Beneficial effects of regular exercise on sleep in old F344 rats

With aging there is a significant decline in the normal architecture of sleep and a reduction in the diurnal amplitude of core body temperature. Regular moderate exercise has been shown to have a positive impact in the elderly and here we investigate whether sleep-wake patterning can also be improved. Young (3 months) and old (22 months) F344 rats were exercised once a day for 50min at night onset over an 8-week period. Thereafter, polysomnographic recordings were obtained immediately after exercise. To determine the lasting consequences of exercise, sleep was also recorded 2 days and 2 weeks after exercise had ended. Old rats that were exercised had a significant weight loss, were awake more during the last third of their active period, had less sleep fragmentation and the amplitude of the diurnal rhythm of core body temperature was significantly increased. Old exercised rats also had an overall increase in the amplitude of EEG power (0.5-16Hz) during wake and theta EEG power during REM sleep. In young rats regular exercise increased EEG delta power (0.5-4Hz) during NREM sleep. Our data indicate regular exercise in old rats improves sleep architecture, EEG power and diurnal rhythm of temperature.

Sleep in spontaneous dwarf rats

Spontaneous dwarf rats (SDRs) display growth hormone (GH) deficiency due to a mutation in the GH gene. This study investigated sleep in SDRs and their somatotropic axis and compared to Sprague-Dawley rats. SDRs had almost undetectable levels of plasma GH. Hypothalamic GH-releasing hormone (GHRH) mRNA was increased, whereas GHRH-receptor (GHRH-R) and somatostatin mRNAs were decreased in SDRs. Hypothalamic GHRH and somatostatin peptide content decreased in SDRs. Quantitative immunohistochemistry for GHRH and GHRH-R corroborated and extended these findings. In the arcuate nucleus, the number of GHRH-positive cells was significantly higher, whereas GHRH-R-positive perikarya were diminished in SDRs. Cortical GHRH and GHRH-R measurements showed similar expression characteristics as those found in the hypothalamus. SDRs had less rapid eye movement sleep (REMS) and more non-REMS (NREMS) than the control rats during the light period. The electroencephalogram (EEG) delta and theta power decreased during NREMS in the SDRs. After 4-h of sleep deprivation, SDRs had a significantly reduced REMS rebound compared to the controls, whereas NREMS rebound was normal in SDRs. The enhancement in delta power was significantly less than in the control group during recovery sleep. Intracerebroventricular (icv) administration of GHRH promoted NREMS in both strains of rats; however, increased REMS and EEG delta activity was observed only in control rats. Icv injection of insulin-like growth factor 1 increased NREMS in control rats, but not in the SDRs. These results support the ideas that GHRH is involved in NREMS regulation and that GH is involved in the regulation of REMS and in EEG slow wave activity regulation during NREMS.

GHRH and sleep

A significant portion of the total daily growth hormone (GH) secretion is associated with deep non-REM sleep (NREMS). GH secretion is stimulated by the hypothalamic neurohormone, GH-releasing hormone (GHRH). Exogenous GHRH promotes NREMS in various species. Suppression of endogenous GHRH (competitive antagonist, antibodies, somatostatinergic stimulation, high doses of GH or insulin-like growth factor) results in simultaneous inhibition of NREMS. Mutant and transgenic animals with a defect in GHRHergic activity display permanently reduced NREMS which cannot be reversed by means of GH supplementation. GHRH contents and mRNA levels in the hypothalamus correlate with sleep-wake activity during the diurnal cycle and sleep deprivation and recovery sleep. Stimulation of NREMS by GHRH is a hypothalamic action. GABAergic neurons in the anterior hypothalamus/preoptic region are candidates for mediating promotion of NREMS by GHRH. In contrast to NREMS, stimulation of REMS by GHRH is mediated by GH. Simultaneous stimulation of NREMS and GH secretion by GHRH may promote adjustment of tissue anabolism to sleep.

Brain-immune interactions in sleep

This chapter discusses various levels of interactions between the brain and the immune system in sleep. Sleep-wake behavior and the architecture of sleep are influenced by microbial products and cytokines. On the other hand, sleep processes, and perhaps also specific sleep states, appear to promote the production and/or release of certain cytokines. The effects of immune factors such as endotoxin and cytokines on sleep reveal species specificity and usually strong dependence on parameters such as substance concentration, time relative to administration or infection with microbial products, and phase relation to sleep and/or the light-dark cycle. For instance, endotoxin increased SWS and EEG SWA in humans only at very low concentrations, whereas higher concentrations increased sleep stage 2 only, but not SWS. In animals, increases in NREM sleep and SWA were more consistent over a wide range of endotoxin doses. Also, administration of pro-inflammatory cytokines such as IL-6 and IFN-alpha in humans acutely disturbed sleep while in rats such cytokines enhanced SWS and sleep. Overall, the findings in humans indicate that strong nonspecific immune responses are acutely linked to an arousing effect. Although subjects feel subjectively tired, their sleep flattens. However, some observations indicate a delayed enhancing effect on sleep which could be related to the induction of secondary, perhaps T-cell-related factors. This would also fit with results in animals in which the T-cell-derived cytokine IL-2 enhanced sleep while cytokines with immunosuppressive functions like IL-4 and L-10 suppressed sleep. The most straightforward similarity in the cascade of events inducing sleep in both animals and humans is the enhancing effect of GHRH on SWS, and possibly the involvement of the pro-inflammatory cytokine systems of IL-1 beta and TNF-alpha. The precise mechanisms through which administered cytokines influence the central nervous system sleep processes are still unclear, although extensive research has identified the involvement of various molecular intermediates, neuropeptides, and neurotransmitters (cp. Fig. 5, Section III.B). Cytokines are not only released and found in peripheral blood mononuclear cells, but also in peripheral nerves and the brain (e.g., Hansen and Krueger, 1997; März et al., 1998). Cytokines are thereby able to influence the central nervous system sleep processes through different routes. In addition, neuronal and glial sources have been reported for various cytokines as well as for their soluble receptors (e.g., Kubota et al., 2001a). Links between the immune and endocrine systems represent a further important route through which cytokines influence sleep and, vice versa, sleep-associated processes, including variations in neurotransmitter and neuronal activity may influence cytokine levels. The ability of sleep to enhance the release and/or production of certain cytokines was also discussed. Most consistent results were found for IL-2, which may indicate a sleep-associated increase in activity of the specific immune system. Furthermore, in humans the primary response to antigens following viral challenge is enhanced by sleep. In animals results are less consistent and have focused on the secondary response. The sleep-associated modulation in cytokine levels may be mediated by endocrine parameters. Patterns of endocrine activity during sleep are probably essential for the enhancement of IL-2 and T-cell diurnal functions seen in humans: Whereas prolactin and GH release stimulate Th1-derived cytokines such as IL-2, cortisol which is decreased during the beginning of nocturnal sleep inhibits Th1-derived cytokines. The immunological function of neurotrophins, in particular NGF and BDNF, has received great interest. Effects of sleep and sleep deprivation on this cytokine family are particularly relevant in view of the effects these endogenous neurotrophins can have not only on specific immune functions and the development of immunological memories, but also on synaptic reorganization and neuronal memory formation.

Effect of supplemental oxygen on sleep architecture and cardiorespiratory events in preterm infants

OBJECTIVE

To investigate the effect of low-flow supplemental oxygen (SupOx) on sleep architecture and cardiorespiratory events in asymptomatic preterm infants.

METHODS

An overnight polysomnographic evaluation was conducted prospectively in 23 premature infants who were born at 30.0 +/- 3.2 (standard deviation) weeks' gestational age and studied at 38.1 +/- 4.4 weeks' postconceptional age. Infants were free of any adverse events, including cardiorespiratory monitor alarms in the nursery for at least 1 week before the study. Infants received room air (RA) or SupOx via nasal cannula at 0.25 L/min.

RESULTS

Quiet sleep density was increased during SupOx (33.3 +/- 10.8% vs 26.6 +/- 10.0% total sleep time [TST] in RA), and a reciprocal decrease in active sleep density was observed (61.5 +/- 11.1% vs 68.4 +/- 9.9% TST in RA). No differences in sleep efficiency emerged (69.7 +/- 10.6% SupOx vs 69.7 +/- 8.8% RA). SupOx elicited significant decreases in apnea index (3.8 +/- 2.4 events/h vs 11.1 +/- 6.4 events/h in RA) and in the percentage of time spent in periodic breathing (1.8 +/- 2.9% vs 6.7 +/- 8.9% in RA). In addition, SupOx decreased the frequency of bradycardic events (0.3 +/- 0.8 events vs 2.5 +/- 0.03 events in RA) and improved overall oxygen saturation (98.7 +/- 1.1% vs 96.4 +/- 2.2%). No changes in alveolar ventilation, as derived from end-tidal CO2 measurements, was detected (38.6 +/- 5.8 mm Hg in SupOx vs 38.4 +/- 5.4 mm Hg in RA).

CONCLUSIONS

Asymptomatic preterm infants exhibit frequent and potentially clinically adverse cardiorespiratory events when assessed in the sleep laboratory. Administration of SupOx to these infants is associated with an increase in the overall duration and percentage TST spent in quiet sleep with reciprocal changes in active sleep. In addition, improvement in respiratory stability is observed with the use of low-flow SupOx, as evidenced by a decrease in apnea, periodic breathing, and bradycardia, without adverse effects on alveolar ventilation.

Sleep of transgenic mice producing excess rat growth hormone

The effects of chronic excess of growth hormone (GH) on sleep-wake activity was determined in giant transgenic mice in which the metallothionein-1 promoter stimulates the expression of rat GH (MT-rGH mice) and in their normal littermates. In the MT-rGH mice, the time spent in spontaneous non-rapid eye movement sleep (NREMS) was enhanced moderately, and rapid eye movement sleep (REMS) time increased greatly during the light period. After a 12-h sleep deprivation, the MT-rGH mice continued to sleep more than the normal mice, but there were no differences in the increments in NREMS, REMS, and electroencephalogram (EEG) slow-wave activity (SWA) during NREMS between the two groups. Injection of the somatostatin analog octreotide elicited a prompt sleep suppression followed by increases in SWA during NREMS in normal mice. These changes were attenuated in the MT-rGH mice. The decreased responsiveness to octreotide is explained by a chronic suppression of hypothalamic GH-releasing hormone in the MT-rGH mice. Enhancements in spontaneous REMS are attributed to the REMS-promoting activity of GH. The increases in spontaneous NREMS are, however, not consistent with our current understanding of the role of somatotropic hormones in sleep regulation. Metabolic, neurotransmitter, or hormonal changes associated with chronic GH excess may indirectly influence sleep.

Deficiency of growth hormone-releasing hormone signaling is associated with sleep alterations in the dwarf rat

The somatotropic axis, and particularly growth hormone-releasing hormone (GHRH), is implicated in the regulation of sleep-wake activity. To evaluate sleep in chronic somatotropic deficiency, sleep-wake activity was studied in dwarf (dw/dw) rats that are known to have a defective GHRH signaling mechanism in the pituitary and in normal Lewis rats, the parental strain of the dw/dw rats. In addition, expression of GHRH receptor (GHRH-R) mRNA in the hypothalamus/preoptic region and in the pituitary was also determined by means of reverse transcription-PCR, and GHRH content of the hypothalamus was measured. Hypothalamic/preoptic and pituitary GHRH-R mRNA levels were decreased in the dw/dw rats, indicating deficits in the central GHRHergic transmission. Hypothalamic GHRH content in dw/dw rats was also less than that found in Lewis rats. The dw/dw rats had less spontaneous nonrapid eye movement sleep (NREMS) (light and dark period) and rapid eye movement sleep (REMS) (light period) than did the control Lewis rats. After 4 hr of sleep deprivation, rebound increases in NREMS and REMS were normal in the dw/dw rat. As determined by fast Fourier analysis of the electroencephalogram (EEG), the sleep deprivation-induced enhancements in EEG slow-wave activity in the dw/dw rats were only one-half of the response in the Lewis rats. The results are compared with sleep findings previously obtained in GHRH-deficient transgenic mice. The alterations in NREMS are attributed to the defect in GHRH signaling, whereas the decreases in REMS might result from the growth hormone deficiency in the dw/dw rat.

The role of cytokines in physiological sleep regulation

Several growth factors (GFs) are implicated in sleep regulation. It is posited that these GFs are produced in response to neural activity and affect input-output relationships within the neural circuits where they are produced, thereby inducing a local state shift. These GFs also influence synaptic efficacy. All the GFs currently identified as sleep regulatory substances are also implicated in synaptic plasticity. Among these substances, the most extensively studied for their role in sleep regulation are interleukin-1beta (IL-1) and tumor necrosis factor alpha (TNF). Injection of IL-1 or TNF enhances non-rapid eye movement sleep (NREMS). Inhibition of either IL-1 or TNF inhibits spontaneous sleep and the sleep rebound that occurs after sleep deprivation. Stimulation of the endogenous production of IL-1 and TNF enhances NREMS. Brain levels of IL-1 and TNF correlate with sleep propensity; for example, after sleep deprivation, their levels increase. IL-1 and TNF are part of a complex biochemical cascade regulating sleep. Downstream events include nitric oxide, growth hormone releasing hormone, nerve growth factor, nuclear factor kappa B, and possibly adenosine and prostaglandins. Endogenous substances moderating the effects of IL-1 and TNF include anti-inflammatory cytokines such as IL-4, IL-10, and IL-13. Clinical conditions altering IL-1 or TNF activity are associated with changes in sleep, for example, infectious disease and sleep apnea. As our knowledge of the biochemical regulation of sleep progresses, our understanding of sleep function and of many clinical conditions will improve.

Central administration of the somatostatin analog octreotide induces captopril-insensitive sleep responses

The effects of intracerebroventricular injections of the long-lasting somatostatin analog octreotide (Oct) were studied on sleep and behavior in rats. Pyrogen-free physiological saline and Oct (0.001, 0.01, 0.1 microgram) or vehicle were administered at light onset, and the electroencephalogram (EEG), motor activity, and cortical brain temperature were recorded during the 12-h light period. Plasma growth hormone (GH) concentrations were measured in samples taken at 30-min intervals after Oct. Oct (0.01 and 0.1 microgram) suppressed non-rapid eye movement sleep (NREMS) for 1-2 h. NREMS intensity (delta EEG activity during NREMS) dose dependently increased in hour 3 postinjection and thereafter (0.1 microgram). Plasma GH concentrations were suppressed after Oct (0.01 and 0.1 microgram), but pulses of GH secretions occurred 90-120 min postinjection in each rat. Oct (0.1 microgram) enhanced behavioral activity, including prompt drinking followed by grooming, scratching, and feeding. Intracerebroventricular injection of the angiotensin-converting enzyme inhibitor captopril (30 microgram, 10 min before Oct), blocked these behavioral responses but not the Oct-induced sleep alterations. The changes in sleep after intracerebroventricular Oct suggest an intracerebral action site and might result from Oct-induced variations in the sleep-promoting activity of GH-releasing hormone.