Update on energy homeostasis and insufficient sleep

Sleep duration and depressive symptoms: a gene-environment interaction

OBJECTIVE

We used quantitative genetic models to assess whether sleep duration modifies genetic and environmental influences on depressive symptoms.

METHOD

Participants were 1,788 adult twins from 894 same-sex twin pairs (192 male and 412 female monozygotic [MZ] pairs, and 81 male and 209 female dizygotic [DZ] pairs] from the University of Washington Twin Registry. Participants self-reported habitual sleep duration and depressive symptoms. Data were analyzed using quantitative genetic interaction models, which allowed the magnitude of additive genetic, shared environmental, and non-shared environmental influences on depressive symptoms to vary with sleep duration.

RESULTS

Within MZ twin pairs, the twin who reported longer sleep duration reported fewer depressive symptoms (ec = -0.17, SE = 0.06, P < 0.05). There was a significant gene × sleep duration interaction effect on depressive symptoms (a'c = 0.23, SE = 0.08, P < 0.05), with the interaction occurring on genetic influences that are common to both sleep duration and depressive symptoms. Among individuals with sleep duration within the normal range (7-8.9 h/night), the total heritability (h2) of depressive symptoms was approximately 27%. However, among individuals with sleep duration within the low (< 7 h/night) or high (≥ 9 h/night) range, increased genetic influence on depressive symptoms was observed, particularly at sleep duration extremes (5 h/night: h2 = 53%; 10 h/night: h2 = 49%).

CONCLUSION

Genetic contributions to depressive symptoms increase at both short and long sleep durations.

Postprandial thermogenesis and substrate oxidation are unaffected by sleep restriction

Background/Objectives

The extent to which alterations in energy expenditure (EE) in response to sleep restriction contribute to the short sleep-obesity relationship is not clearly defined. Short sleep may induce changes in resting metabolic rate (RMR), thermic effect of food (TEF), and postprandial substrate oxidation.

Subjects/Methods

Ten females (age and BMI: 22-43 y and 23.4-28 kg/m²) completed a randomized, crossover study assessing the effects of short (4 h/night) and habitual (8 h/night) sleep duration on fasting and postprandial RMR and respiratory quotient (RQ). Measurements were taken after 3 nights using whole-room indirect calorimetry. The TEF was assessed over a 6-h period following consumption of a high-fat liquid meal.

Results

Short vs. habitual sleep did not affect RMR (1.01 ± 0.05 and 0.97 ± 0.04 kcal/min; p=0.23). Fasting RQ was significantly lower after short vs. habitual sleep (0.84 ± 0.01 and 0.88 ± 0.01; p=0.028). Postprandial EE (short: 1.13 ± 0.04 and habitual: 1.10 ± 0.04, p=0.09) and RQ (short: 0.88 ± 0.01 and habitual: 0.88 ± 0.01, p=0.50) after the high-fat meal were not different between conditions. TEF was similar between conditions (0.24 ± 0.02 kcal/min in both; p=0.98), as was the ~6-h incremental area under the curve (1.16 ± 0.10 and 1.17 ± 0.09 kcal/min x 356 min after short and habitual sleep, respectively; p=0.92).

Conclusions

Current findings observed in non-obese healthy premenopausal women do not support the hypothesis that alterations in TEF and postprandial substrate oxidation are major contributors to the higher rate of obesity observed in short sleepers. In exploring a role of sleep duration on EE, research should focus on potential alterations in physical activity to explain the increased obesity risk in short sleepers.

Experimental sleep curtailment causes wake-dependent increases in 24-h energy expenditure as measured by whole-room indirect calorimetry

BACKGROUND

Epidemiologic evidence has shown a link between short sleep and obesity. Clinical studies suggest a role of increased energy intake in this relation, whereas the contributions of energy expenditure (EE) and substrate utilization are less clearly defined.

OBJECTIVE

Our aim was to investigate the effects of sleep curtailment on 24-h EE and respiratory quotient (RQ) by using whole-room indirect calorimetry under fixed-meal conditions.

DESIGN

Ten females aged 22-43 y with a BMI (in kg/m²) of 23.4-27.5 completed a randomized, crossover study. Participants were studied under short- (4 h/night) and habitual- (8 h/night) sleep conditions for 3 d, with a 4-wk washout period between visits. Standardized weight-maintenance meals were served at 0800, 1200, and 1900 with a snack at 1600. Measures included EE and RQ during the sleep episode on day 2 and continuously over 23 h on day 3.

RESULTS

Short compared with habitual sleep resulted in significantly higher (± SEM) 24-h EE (1914.0 ± 62.4 compared with 1822.1 ± 43.8 kcal; P = 0.012). EE during the scheduled sleep episode (0100-0500 and 2300-0700 in short- and habitual-sleep conditions, respectively) and across the waking episode (0800-2300) were unaffected by sleep restriction. RQ was unaffected by sleep restriction.

CONCLUSIONS

Short compared with habitual sleep is associated with an increased 24-h EE of ~92 kcal (~5%)--lower than the increased energy intake observed in prior sleep-curtailment studies. This finding supports the hypothesis that short sleep may predispose to weight gain as a result of an increase in energy intake that is beyond the modest energy costs associated with prolonged nocturnal wakefulness.

Effects of sleep restriction on the human plasma metabolome

This study examined the effects of recurrent sleep restriction on the plasma metabolome of adults with familial risk of type 2 diabetes. Eleven healthy adults (6M/5F; mean [SD] age: 26 [3]years; BMI 23.5 [2.3]kg/m(2)) with parental history of type 2 diabetes participated in a two-condition, two-period randomized crossover study at the Clinical Resource Center at an academic hospital. Each participant completed two 8-night inpatient sessions with restricted (5.5-h time-in-bed) vs. adequate (8.5-h time-in-bed) sleep opportunity while daily food intake and physical activity were carefully controlled. A combination of two UHPLC/MS/MS platforms and one GC/MS platform was used to measure 362 biochemicals in fasting plasma samples collected from study participants the morning after each 8-night sleep treatment. Relative concentrations of 12 amino acids and related metabolites were increased when sleep was curtailed. Sleep restriction also induced elevations in several fatty acid, bile acid, steroid hormone, and tricarboxylic acid cycle intermediates. In contrast, circulating levels of glucose, some monosaccharides, gluconate, and five-carbon sugar alcohols tended to decline when sleep was reduced. Recurrent sleep curtailment affected multiple pathways of intermediary metabolism in adults at risk for type 2 diabetes. An elevation in plasma amino acids and related biochemicals was the most pronounced metabolic signature seen in response to 8 nights of sleep restriction.

Short sleep duration and large variability in sleep duration are independently associated with dietary risk factors for obesity in Danish school children

BACKGROUND

Lack of sleep and increased consumption of energy-dense foods and sugar-sweetened beverages (SSBs) have all been suggested as factors contributing to the increased prevalence of overweight and obesity.

OBJECTIVE

To evaluate whether objectively measured sleep duration (average and day-to-day variability) as well as parent-reported sleep problems are independently associated with proposed dietary risk factors for overweight and obesity in 8-11-year-old children.

DESIGN

In this cross-sectional study, data on sleep duration and day-to-day variability in sleep duration were measured in 676 Danish, apparently healthy children by an objective measure (actigraphy) for 8 nights, and the Children's Sleep Habits Questionnaire (CSHQ) was filled out by the parents. Diet was recorded using a web-based food record for 7 consecutive days. Fasting blood samples were obtained for measurements of plasma leptin and ghrelin levels.

RESULTS

Sleep duration (h per night) was negatively associated with energy density (ED) of the diet (β = -0.32 kJ g(-1)), added sugar (β = -1.50 E%) and SSBs (β = -1.07 E%) (all P ≤ 0.003). Furthermore, variability in sleep duration (10-min per night) was positively associated with SSBs (β = 0.20 E%, P = 0.03), independent of sleep duration, and CSHQ score was positively associated with ED (β = 0.16 kJ g(-1), P = 0.04). All of these associations were independent of potential confounders (age, sex, pubertal status, height, weight, screen time, moderate-to-vigorous physical activity and parental education and ethnicity).

CONCLUSION

Our study suggests that short sleep duration, high sleep duration variability and experiencing sleep problems are all associated with a poor, obesity-promoting diet in children.

Partial sleep restriction modulates secretory activity of thyrotropic axis in healthy men

Sleep and endocrine function are known to be closely related, but studies on the effect of moderate sleep loss on endocrine axes are still sparse. We examined the influence of partial sleep restriction for 2 days on the secretory activity of the thyrotropic axis. Fifteen healthy, normal-weight men were tested in a balanced, cross-over study. Serum concentrations of thyrotrophin (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) were monitored at 1-h intervals during a 15-h daytime period (08:00-23:00 h) following two nights of restricted sleep (bedtime 02:45-07:00 h) and two nights of regular sleep (bedtime 22:45-07:00 h), respectively. Serum concentrations of fT3 (P < 0.026) and fT4 (P = 0.089) were higher after sleep restriction than regular sleep, with a subsequent blunting of TSH concentrations in the evening hours of the sleep restriction condition (P = 0.008). These results indicate profound alterations in the secretory activity of the thyrotropic axis after 2 days of sleep restriction to ~4 h, suggesting that acute partial sleep loss impacts endocrine homeostasis, with potential consequences for health and wellbeing.

Excess frequent insufficient sleep in American Indians/Alaska natives

OBJECTIVE

Frequent insufficient sleep, defined as ≥14 days/past 30 days in which an adult did not get enough rest or sleep, is associated with adverse mental and physical health outcomes. Little is known about the prevalence of frequent insufficient sleep among American Indians/Alaska Natives (AI/AN).

METHODS

We assessed racial/ethnic differences in the prevalence of frequent insufficient sleep from the combined 2009-2010 Behavioral Risk Factor Surveillance Survey among 810,168 respondents who self-identified as non-Hispanic white (NHW, n = 671,448), non-Hispanic black (NHB, n = 67,685), Hispanic (n = 59,528), or AI/AN (n = 11,507).

RESULTS

We found significantly higher unadjusted prevalences (95% CI) of frequent insufficient sleep among AI/AN (34.2% [32.1-36.4]) compared to NHW (27.4% [27.1-27.6]). However, the age-adjusted excess prevalence of frequent insufficient sleep in AI/AN compared to NHW was decreased but remained significant with the addition of sex, education, and employment status; this latter relationship was further attenuated by the separate additions of obesity and lifestyle indicators, but was no longer significant with the addition of frequent mental distress to the model (PR  =  1.05; 95% CI : 0.99-1.13). This is the first report of a high prevalence of frequent insufficient sleep among AI/AN. These results further suggest that investigation of sleep health interventions addressing frequent mental distress may benefit AI/AN populations.

What is metabolic syndrome, and why are children getting it?

Metabolic syndrome comprises a cluster of cardiovascular risk factors (hypertension, altered glucose metabolism, dyslipidemia, and abdominal obesity) that occur in obese children. However, metabolic syndrome can also occur in lean individuals, suggesting that obesity is a marker for the syndrome, not a cause. Metabolic syndrome is difficult to define, due to its nonuniform classification and reliance on hard cutoffs in the evaluation of disorders with non-Gaussian distributions. Defining the syndrome is even more difficult in children, owing to racial and pubertal differences and lack of cardiovascular events. Lipid partitioning among specific fat depots is associated with insulin resistance, which can lead to mitochondrial overload and dysfunctional subcellular energy use and drive the various elements of metabolic syndrome. Multiple environmental factors, in particular a typical Western diet, drive mitochondrial overload, while other changes in Western society, such as stress and sleep deprivation, increase insulin resistance and the propensity for food intake. These culminate in an adverse biochemical phenotype, including development of altered glucose metabolism and early atherogenesis during childhood and early adulthood.

The role of sleep duration in the regulation of energy balance: effects on energy intakes and expenditure

Short sleep duration and obesity are common occurrence in today's society. An extensive literature from cross-sectional and longitudinal epidemiological studies shows a relationship between short sleep and prevalence of obesity and weight gain. However, causality cannot be inferred from such studies. Clinical intervention studies have examined whether reducing sleep in normal sleepers, typically sleeping 7-9 h/night, can affect energy intake, energy expenditure, and endocrine regulators of energy balance. The aim of this review is to evaluate studies that have assessed food intake, energy expenditure, and leptin and ghrelin levels after periods of restricted and normal sleep. Most studies support the notion that restricting sleep increases food intake, but the effects on energy expenditure are mixed. Differences in methodology and component of energy expenditure analyzed may account for the discrepancies. Studies examining the effects of sleep on leptin and ghrelin have provided conflicting results with increased, reduced, or unchanged leptin and ghrelin levels after restricted sleep compared to normal sleep. Energy balance of study participants and potential sex differences may account for the varied results. Studies should strive for constant energy balance and feeding schedules when assessing the role of sleep on hormonal profile. Although studies suggest that restricting sleep may lead to weight gain via increased food intake, research is needed to examine the impact on energy expenditure and endocrine controls. Also, studies have been of short duration, and there is little knowledge on the reverse question: does increasing sleep duration in short sleepers lead to negative energy balance?