Humoral regulation of sleep

Sex-dependent impact of a short rest after lunch on hemodynamics as assessed by Doppler sonography

PURPOSE

Taking a short rest after lunch suppresses increases in blood flow to the digestive organs and maintains blood flow to the brain in the afternoon, possibly providing beneficial effects in preventing post-prandial drowsiness. The present study investigated sex-dependent influences on changes in hemodynamics produced by taking a short rest after lunch.

METHODS

Subjects comprised 20 healthy young adults (10 men, 10 women; mean age 21 ± 1 years). Doppler sonography was performed to measure blood flow in the superior mesenteric artery (SMA) and common carotid artery (CCA) before and after lunch every hour on each day, with and without a 15-min rest with eyes closed after lunch. Blood pressure and heart rate (HR) were also measured.

RESULTS

For both men and women, peak systolic velocity (PSV) in the SMA was suppressed by taking a rest. PSV in the CCA in men was increased at 0.5 h after lunch in the resting condition but was decreased in the non-resting condition (median 109%, interquartile range [IQR] 102-120% vs. median 98%, IQR 90-107%; P = 0.037). No such differences were observed in women. Although post-prandial increases in HR were observed in women, a similar increase was only found for men in the resting condition.

CONCLUSION

An increase in CCA blood flow was observed only in men. The present study suggests that a short rest after lunch could better promote the maintenance of blood flow to the brain in men than in women.

Possible effects of short rest after lunch on hemodynamics in the afternoon

PURPOSE

Drowsiness is often experienced in the afternoon after lunch. Decreases in blood flow to the brain secondary to increases in blood flow to the digestive organs after food intake could represent an underlying cause. As various beneficial effects of short rests on mental activities have been reported, the present study investigated hemodynamics using Doppler sonography of the common carotid artery (CCA) and superior mesenteric artery (SMA) after lunch, comparing resting and non-resting cases.

METHODS

Subjects comprised 24 healthy young adults (10 men, 14 women; mean age 22 ± 1 years). Sonography was performed to measure blood flow before and after lunch on each day, with and without a 15-min lying rest with eyes closed after lunch in each subject.

RESULTS

The timing of the peak velocity-time integral in the SMA in resting cases was delayed to 1.5 h after lunch compared to 0.5 h in non-resting cases. Although end-diastolic velocity in the CCA decreased after lunch, this decrease was suppressed in resting cases compared to non-resting cases even 4.5 h after lunch (median 96%, interquartile range [IQR] 83-102% vs. median 87%, IQR 77-92%; P = 0.037). Mean velocity (MV) in the CCA maintained unchanged after lunch in resting cases (P = 0.318), whereas non-resting cases showed decreased MV after lunch (P < 0.001).

CONCLUSION

These findings suggest that a short lying rest with eyes closed suppresses increases in blood flow to the digestive organ and maintains blood flow to the brain after lunch. These hemodynamic changes might help explain the benefits of afternoon rests.

Dietary fat and carbohydrate have different effects on body weight, energy expenditure, glucose homeostasis and behaviour in adult cats fed to energy requirement

The effects of dietary carbohydrate and fat on feline health are not well understood. The effects of feeding diets moderately high in fat (HF; n 10; 30 % fat, 26 % carbohydrate as fed) or carbohydrate (HC; n 10; 11 % fat, 47 % carbohydrate), for 84 d, were investigated in healthy, adult cats (3·5 (sd 0·5) years). Data on indirect calorimetry, blood biomarkers, activity, play and cognition were collected at baseline, and at intervals throughout the study. Body composition was measured by dual-energy X-ray absorptiometry at baseline and on day 85. There were no significant main effects of diet on body weight and composition. When data were analysed over study day within diet, cats fed HF diets experienced a significant increase in body fat (P = 0·001) and body weight (P = 0·043) in contrast to cats consuming the HC diet that experienced no change in body fat or body weight (P = 0·762) throughout the study. Overall, energy expenditure was similar between diets (P = 0·356 (fasted), P = 0·086 (postprandial)) and respiratory quotient declined with exposure to the HF diet and increased with exposure to the HC diet (P < 0·001; fasted and postprandial). There was no difference in insulin sensitivity as an overall effect of diet (P = 0·266). Activity declined from baseline with exposure to both diets (HC: P = 0·002; HF: P = 0·01) but was not different between diets (P = 0·247). There was no effect of diet on play (P = 0·387) and cats consuming either the HF or HC diet did not successfully learn the cognitive test. Overall, cats adapt to dietary macronutrient content, and the implications of feeding HC and HF diets on risk for adiposity as driven by metabolic and behavioural mechanisms are discussed.

Sleep and the single neuron: the role of global slow oscillations in individual cell rest

Sleep is universal in animals, but its specific functions remain elusive. We propose that sleep's primary function is to allow individual neurons to perform prophylactic cellular maintenance. Just as muscle cells must rest after strenuous exercise to prevent long-term damage, brain cells must rest after intense synaptic activity. We suggest that periods of reduced synaptic input ('off periods' or 'down states') are necessary for such maintenance. This in turn requires a state of globally synchronized neuronal activity, reduced sensory input and behavioural immobility - the well-known manifestations of sleep.

Tackling sleeplessness: psychological treatment options for insomnia in older adults

This paper provides a broad review of the extant literature involving the treatment of sleeplessness in older adults with insomnia. First, background information (including information regarding key issues in late-life insomnia and epidemiology of late-life insomnia) pertinent to achieving a general understanding of insomnia in the elderly is presented. Next, theories of insomnia in older adults are examined and discussed in relation to treatment of insomnia in late-life. With a general knowledge base provided, empirical evidence for both pharmacological (briefly) and psychological treatment options for insomnia in late-life are summarized. Recent advances in the psychological treatment of insomnia are provided and future directions are suggested. This review is not meant to be all-inclusive; however, it is meant to provide professionals across multiple disciplines (physicians; psychologists; applied and basic researchers) with a mix of breadth and depth of knowledge related to insomnia in late-life. It is our hope that readers will see the evidence in support of psychological treatments for late-life insomnia, and the utility in continuing to investigate this treatment modality.

Metabolic complications of obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome is a widely prevalent disorder, hallmarked by partial or total upper airway obstruction during sleep. These events fracture sleep integrity resulting in chronic partial sleep deprivation with destructive metabolic sequelae, the focus of this review.

Sleep quality, daytime sleepiness and fasting insulin levels in women with chronic obstructive pulmonary disease

STUDY OBJECTIVES

To test the clinical observations that patients with chronic obstructive pulmonary disease (COPD) have impaired sleep quality without excessive daytime sleepiness (EDS), and to analyse the aetiological factors.

PARTICIPANTS

Fifteen non-diabetic postmenopausal women with moderate to severe COPD and 20 community dwelling age-matched control women.

MEASUREMENTS AND RESULTS

Patients completed questionnaires, had a polysomnography and blood tests. Controls filled in the questionnaires. In the Basic Nordic Sleep Questionnaire, the average (+/-sd) scores for sleepiness (9.9+/-3.0 in patients vs. 7.6+/-3.2 in controls, P = 0.025, test range 4-20) and insomnia (18.3+/-3.4 vs. 16.6+/-4.4, P = 123, test range 7-35) were low. Although 53% had a good night's sleep seldom or never and 70% slept restlessly, only 33% felt tired in the mornings. Controls reported better sleep quality, less tiredness and sleepiness. With polysomnography, the total sleep time was 4h 41 min +/-1h 20 min in patients. Sleep was fragmented, the proportion of stage 1 sleep high and rapid eye movement (REM) latency delayed. Sleepiness correlated with fasting serum insulin levels (r = 0.59, P = 0.027) and body movements (r = 0.52, P = 0.047). In stepwise linear regression analyses, sleepiness was positively associated with insulin levels (P = 0.025) but not with body movements. Insulin explained 38.0% of the variance in the sleepiness score, when adjusted for body mass index (BMI).

CONCLUSIONS

Despite short and fragmented sleep, non-diabetic patients with COPD did not have marked EDS. An association between fasting insulin and sleepiness suggests that insulin resistance is involved in EDS.

Sleep in host defense

Sleep remains an important enigma in neurobiology; it has a robust adaptive value yet its function remains elusive. Changes in sleep are hallmarks of the acute phase response to infectious challenge. The molecular regulation of these responses involves a cytokine cascade within brain, including interleukin-1 and tumor necrosis factor, and several other substances such as growth hormone releasing hormone, prolactin, nitric oxide and nuclear factor kappaB. These substances are also involved in the regulation of normal spontaneous sleep. Fatigue and sleep disturbances are common in cancer patients and in those receiving cytokine therapy. Regardless, the role of sleep in cancer is relatively uninvestigated.

Nuclear factor-kappaB inhibitor peptide inhibits spontaneous and interleukin-1beta-induced sleep

Nuclear factor-kappaB (NF-kappaB) is a transcription factor that when activated promotes production of several sleep-promoting substances such as interleukin-1beta (IL-1beta), tumor necrosis factor-alpha, and nerve growth factor. Therefore, we hypothesized that inhibition of NF-kappaB activation would attenuate sleep. A NF-kappaB cell-permeable inhibitor peptide (IP) was injected intracerebroventricularly (5 and 50 microg for rats, 100 microg for rabbits). On a separate day, time-matched control injections of a cell-permeable inactive control peptide were done in the same animals. The 50-microg dose of IP in rats and the 100-microg dose in rabbits significantly inhibited non-rapid eye movement sleep and rapid eye movement sleep if administered during the light period. Moreover, pretreatment of rabbits with 100 microg of the IP 12 h before intracerebroventricular injection of IL-1beta (10 ng) significantly attenuated IL-1beta-induced sleep and febrile responses. The current data support the hypothesis that a brain cytokine network is involved in sleep regulation and that NF-kappaB is a crucial factor in physiological sleep regulation.

Influences of fat and carbohydrate on postprandial sleepiness, mood, and hormones

Paired studies were conducted in 18 healthy volunteers (9 men, 9 women) to investigate whether differences in mood and daytime sleepiness induced by high-fat-low-carbohydrate (CHO) and low-fat-high-CHO morning meals were associated with specific hormonal responses. Plasma insulin concentrations were significantly higher after low-fat-high-CHO meals, and cholecystokinin (CCK) concentrations were significantly higher after high-fat-low-CHO meals. Subjects tended to feel more sleepy and less awake 2-3 h after the high-fat-low-CHO meal, and ratings of fatigue were significantly greater 3 h after the high-fat-low-CHO meal than after the low-fat-high-CHO meal. The results of the present study are consistent with the hypothesis that there is an association between the lassitude experienced after a meal and the release of CCK.

Influences of fat, energy, and time of day on mood and performance

Paired studies testing the effects of lower energy high-fat, low-CHO meals (3181 kJ, fat:CHO energy ratio 54:41) and higher energy low-fat, high-CHO meals (3599 kJ, fat:CHO energy ratio 7:88) were conducted in 18 healthy males. The meals were eaten at 1030 h by group A (nine subjects) and 1230 h by group B (nine subjects). Subjective lassitude increased following ingestion of all four meals, but there was little change in performance. In addition, group A, but not group B, felt significantly less vigorous, imaginative, and antagonistic, and significantly more dreamy, feeble, and fatigued after the lower energy high-fat, low-CHO meal than after the higher energy low-fat, high-CHO meal. These results suggest that in the morning, fat exerts a greater depression on alertness and mood than carbohydrate irrespective of a reduction in energy content, but this effect varies according to the time at which food is eaten, and is less evident at lunch time.

Possible involvement of an endogenous benzodiazepine receptor ligand of the inverse agonist type in the regulation of rapid-eye movement (REM) sleep: an hypothesis

1. Rapid-eye movement (REM) sleep is a complex behavioral state characterized by desynchronized electroencephalographic (EEG) activity, postural atonia, rapid, saccadic movements of the eyes, and vivid dreaming. 2. A recently developed class of drugs, the inverse agonist beta-carboline-3-carboxylates, elicits a number of effects similar to the properties of REM sleep, such as desynchronized cortical EEG and penile erections. 3. The hypothesis is put forth that an endogenous beta-carboline-3-carboxylate exists which may initiate many aspects of REM sleep. 4. Clinical relevance of this hypothesis is discussed with regard to REM anxiety dreams, night terrors, narcolepsy, and depression.

Cytokines in sleep regulation

The central thesis of this essay is that the cytokine network in brain is a key element in the humoral regulation of sleep responses to infection and in the physiological regulation of sleep. We hypothesize that many cytokines, their cellular receptors, soluble receptors, and endogenous antagonists are involved in physiological sleep regulation. The expressions of some cytokines are greatly amplified by microbial challenge. This excess cytokine production during infection induces sleep responses. The excessive sleep and wakefulness that occur at different times during the course of the infectious process results from dynamic changes in various cytokines that occur during the host's response to infectious challenge. Removal of any one somnogenic cytokine inhibits normal sleep, alters the cytokine network by changing the cytokine mix, but does not completely disrupt sleep due to the redundant nature of the cytokine network. The cytokine network operates in a paracrine/autocrine fashion and is responsive to neuronal use. Finally, cytokines elicit their somnogenic actions via endocrine and neurotransmitter systems as well as having direct effects neurons and glia. Evidence in support of these postulates is reviewed in this essay.