Dietary fish oil does not protect rats exposed to restraint or sleep deprivation stress

The Pituitary-Adrenal Response to Paradoxical Sleep Deprivation Is Similar to a Psychological Stressor, Whereas the Hypothalamic Response Is Unique

Stressors of different natures induce activation of the hypothalamic-pituitary-adrenal (HPA) axis at different magnitudes. Moreover, the HPA axis response to repeated exposure is usually distinct from that elicited by a single session. Paradoxical sleep deprivation (PSD) augments ACTH and corticosterone (CORT) levels, but the nature of this stimulus is not yet defined. The purpose of the present study was to qualitatively compare the stress response of animals submitted to PSD to that of rats exposed once or four times to cold, as a physiological stress, movement restraint (RST) as a mixed stressor and predator odour (PRED) as the psychological stressor, whilst animals were submitted for 1 or 4 days to PSD and respective control groups. None of the stressors altered corticotropin releasing factor immunoreactivity in the paraventricular nucleus of the hypothalamus (PVN), median eminence (ME) or central amygdala, compared to control groups, whereas vasopressin immunoreactivity in PSD animals was decreased in the PVN and increased in the ME, indicating augmented activity of this system. ACTH levels were higher after repeated stress or prolonged PSD than after single- or 1 day-exposure and control groups, whereas the CORT response was habituated by repeated stress, but not by 4-days PSD. This dissociation resulted in changes in the CORT : ACTH ratio, with repeated cold and RST decreasing the ratio compared to single exposure, but no change was seen in PRED and PSD groups. Comparing the magnitude and pattern of pituitary-adrenal response to the different stressors, PSD-induced responses were closer to that shown by PRED-exposed rats. In contrast, the hypothalamic response of PSD-exposed rats was unique, inasmuch as this was the only stressor which increased the activity of the vasopressin system. In conclusion, we propose that the pituitary-adrenal response to PSD is similar to that induced by a psychological stressor.

Effects of different periods of paradoxical sleep deprivation and sleep recovery on lipid and glucose metabolism and appetite hormones in rats

Sleep has a fundamental role in the regulation of energy balance, and it is an essential and natural process whose precise impacts on health and disease have not yet been fully elucidated. The aim of this study was to assess the consequences of different periods of paradoxical sleep deprivation (PSD) and recovery from PSD on lipid profile, oral glucose tolerance test (OGTT) results, and changes in insulin, corticosterone, ghrelin, and leptin concentrations. Three-month-old male Wistar rats weighing 250–350 g were submitted to 24, 96, or 192 h of PSD or 192 h of PSD with 480 h of recovery. The PSD was induced by the multiple platforms method. Subsequently, the animals were submitted to an OGTT. One day later, the animals were killed and the levels of triglycerides, total cholesterol, lipoproteins (low-density lipoprotein, very-low-density lipoprotein, and high-density lipoprotein), insulin, ghrelin, leptin, and corticosterone in plasma were quantified. There was a progressive decrease in body weight with increasing duration of PSD. The PSD induced basal hypoglycemia over all time periods evaluated. Evaluation of areas under the curve revealed progressive hypoglycemia only after 96 and 192 h of PSD. There was an increase in corticosterone levels after 192 h of PSD. We conclude that PSD induces alterations in metabolism that are reversed after a recovery period of 20 days.

Short sleep duration and its association with energy metabolism

A growing body of observational evidence suggests that short sleep duration is a risk factor for the development of obesity. Although increased energy intake is the most prevailing causal explanation for this association, we should also consider possible effects on energy metabolism to understand fully the potential impact of short sleep duration on the regulation of energy balance. We performed a search of the literature from 1970 to 2011, including original papers, investigating the relation between short sleep and energy metabolism in animals and humans. Although the limited number of experimental studies in humans precludes any definitive conclusions about causality, short sleep duration does not seem to substantially affect total daily energy expenditure, nor is there sufficient evidence in support of any meaningful effect of restricted sleep on the specific components of energy metabolism (i.e. resting metabolic rate, intentional as well as unintentional physical activity, diet-induced thermogenesis, and substrate utilization). As studies on rats suggest that other factors that can potentially influence energy metabolism could be affected (i.e. hormonal systems and thermoregulation), we included these factors in our literature search and found some indications in support of an up-regulation of thyroid hormones and glucocorticoids as well as increased heat dissipation following total or severe sleep deficit. Although we found some evidence also in humans that suggests a possible effect on energy metabolism, the limitations of the studies make it difficult to draw conclusions on the effect of short sleep on energy metabolism under relevant free living conditions. To explore this area further, more studies using suitable methodology under relevant conditions to mimic real-life situations are needed.

Type of diet modulates the metabolic response to sleep deprivation in rats

BACKGROUND

Evidence suggests that sleep loss is associated with an increased risk of obesity and diabetes; however, animal models have failed to produce weight gain under sleep deprivation (SD). Previous studies have suggested that this discrepancy could be due to more extreme SD conditions in experimental animals, their higher resting metabolic rate than that of humans, and the decreased opportunity for animals to ingest high-calorie foods. Thus, our objective was to determine whether diets with different textures/compositions could modify feeding behavior and affect the metabolic repercussions in SD in rats.

METHODS

Three groups of male rats were used: one was designated as control, one was sleep deprived for 96 h by the platform technique (SD-96h) and one was SD-96h followed by a 24-h recovery (rebound). In the first experiment, the animals were fed chow pellets (CPs); in the second, they received high-fat diet and in the third, they were fed a liquid diet (LD).

RESULTS

We observed that SD induces energy deficits that were related to changes in feeding behavior and affected by the type of diet consumed. Regardless of the diet consumed, SD consistently increased animals' glucagon levels and decreased their leptin and triacylglycerol levels and liver glycogen stores. However, such changes were mostly avoided in the rats on the liquid diet. SD induces a wide range of metabolic and hormonal changes that are strongly linked to the severity of weight loss.

CONCLUSIONS

The LD, but not the CP or high-fat diets, favored energy intake, consequently lessening the energy deficit induced by SD.

Fish oil consumption prevents glucose intolerance and hypercorticosteronemy in footshock-stressed rats

BACKGROUND

Environmental stress plays an important role in the development of glucose intolerance influencing lipid and glucose metabolism through sympathetic nervous system, cytokines and hormones such as glucocorticoids, catecholamines and glucagon. Otherwise, fish oil prevents glucose intolerance and insulin resistance. Although the mechanisms involved are not fully understood, it is known that sympathetic and HPA responses are blunted and catecholamines and glucocorticoids concentrations can be modulated by fish consumption. The aim of the present study was to evaluate whether fish oil, on a normal lipidic diet: 1) could prevent the effect of footshock-stress on the development of glucose intolerance; 2) modified adiponectin receptor and serum concentration; and 3) also modified TNF-α, IL-6 and interleukin-10 (IL-10) levels in adipose tissue and liver. The study was performed in thirty day-old male Wistar randomly assigned into four groups: no stressed (C) and stressed (CS) rats fed with control diet, and no stressed (F) and stressed (FS) rats fed with a fish oil rich diet. The stress was performed as a three daily footshock stress sessions.

RESULTS

Body weight, carcass fat and protein content were not different among groups. FS presented a reduction on the relative weight of RET. Basal serum glucose levels were higher in CS and FS but 15 min after glucose load just CS remained with higher levels than other groups. Serum corticosterone concentration was increased in CS, this effect was inhibited in FS. However, 15 min after footshock-stress, corticosterone levels were similar among groups. IL-6 was increased in EPI of CS but fish oil consumption prevented IL-6 increase in FS. Similar levels of TNF-α and IL-10 in RET, EPI, and liver were observed among groups. Adipo R1 protein concentration was not different among groups. Footshock-stress did not modify AdipoR2 concentration, but fish oil diet increases AdipoR2 protein concentration.

CONCLUSIONS

Footshock-stress promotes glucose intolerance associated to corticosterone serum level and epididymal white adipose tissue IL-6 concentration increase. The fish oil consumption by stressed rats normalized the stress responses. These results suggested that fish oil intake could be useful to minimize or prevent the development of diseases associated to the stress.

Omega-3 fatty acids supplementation does not affect serum lipids in chronic hemodialysis patients

OBJECTIVE

The aim of this study was to test the hypothesis that omega-3 fatty acids have an effect on serum lipids and inflammation markers in chronic hemodialysis (HD) patients.

DESIGN

The study followed a single-blind, randomized, crossover design.

SETTING

The study was conducted at the Hemodialysis Unit of the Laikon General Hospital in Athens, Greece.

PATIENTS

A total of 25 chronic HD patients were included in the study (16 men, 9 women, age: 51 ± 15 years).

INTERVENTION

Patients were randomly assigned to one of the following 2 intervention groups: omega-3 fatty acids plus α-tocopherol (920 mg eicosapentaenoic Acid (EPA), 760 mg docosahexaenoic acid (DHA), 8 mg α-tocopherol in total per day) or α-tocopherol supplement (100 mg/week resulting in 14.2 mg/day) alone for 4 weeks. After a washout period of 4 weeks, the 2 groups were crossed.

MAIN OUTCOME MEASURES

Medical history data were collected and anthropometric and nutritional intake evaluation was performed at the beginning and at the end of both interventions. Hematological and biochemical parameters as well as C-reactive protein levels were measured.

RESULTS

No statistically significant results were recorded in the lipidemic profiles of the participants between baseline and the 2 interventions. C-reactive protein levels also did not change significantly between the 2 interventions (5.54 ± 3.33 to 6.70 ± 5.01 mg/L [P = .19] with vitamin E vs. 7.13 ± 5.04 to 6.87 ± 5.24 [P = .78] with omega-3, P overall = .53).

CONCLUSION

The results of this study do not provide support for the positive effects of omega-3 fatty acid supplementation in HD patients.

Orexin activation precedes increased NPY expression, hyperphagia, and metabolic changes in response to sleep deprivation

Several pieces of evidence support that sleep duration plays a role in body weight control. Nevertheless, it has been assumed that, after the identification of orexins (hypocretins), the molecular basis of the interaction between sleep and energy homeostasis has been provided. However, no study has verified the relationship between neuropeptide Y (NPY) and orexin changes during hyperphagia induced by sleep deprivation. In the current study we aimed to establish the time course of changes in metabolite, endocrine, and hypothalamic neuropeptide expression of Wistar rats sleep deprived by the platform method for a distinct period (from 24 to 96 h) or sleep restricted for 21 days (SR-21d). Despite changes in the stress hormones, we found no changes in food intake and body weight in the SR-21d group. However, sleep-deprived rats had a 25-35% increase in their food intake from 72 h accompanied by slight weight loss. Such changes were associated with increased hypothalamus mRNA levels of prepro-orexin (PPO) at 24 h followed by NPY at 48 h of sleep deprivation. Conversely, sleep recovery reduced the expression of both PPO and NPY, which rapidly brought the animals to a hypophagic condition. Our data also support that sleep deprivation rapidly increases energy expenditure and therefore leads to a negative energy balance and a reduction in liver glycogen and serum triacylglycerol levels despite the hyperphagia. Interestingly, such changes were associated with increased serum levels of glucagon, corticosterone, and norepinephrine, but no effects on leptin, insulin, or ghrelin were observed. In conclusion, orexin activation accounts for the myriad changes induced by sleep deprivation, especially the hyperphagia induced under stress and a negative energy balance.

Dietary fish oil did not prevent sleep deprived rats from a reduction in adipose tissue adiponectin gene expression

Sleep deprivation in humans has been related to weight gain and consequently, increased risk for insulin resistance. In contrast, there is a significant loss of weight in sleep deprived rats suggesting a state of insulin resistance without obesity interference. Thus, we aimed to assess the effects of a rich fish oil dietetic intervention on glucose tolerance, serum insulin and adiponectin, and adipose tissue gene expression of adiponectin and TNF-α of paradoxically sleep deprived (PSD) rats. The study was performed in thirty day-old male Wistar randomly assigned into two groups: rats fed with control diet (soybean oil as source of fat) and rats fed with a fish oil rich diet. After 45 days of treatment, the animals were submitted to PSD or maintained as home cage control group for 96 h. Body weight and food intake were carefully monitored in all groups. At the end of PSD period, a glucose tolerance test was performed and the total blood and adipose tissues were collected. Serum insulin and adiponectin were analyzed. Adipose tissues were used for RT-PCR to estimate the gene expression of adiponectin and TNF-α. Results showed that although fish oil diet did not exert any effect upon these measurements, PSD induced a reduction in adiponectin gene expression of retroperitoneal adipose tissues, with no change in serum adiponectin concentration or in adiponectin and TNF-α gene expression of epididymal adipose tissue. Thus, the stress induced by sleep deprivation lead to a desbalance of adiponectin gene expression.

Sleep deprivation-induced gnawing—relationship to changes in feeding behavior in rats

We have recently reported that food spillage increases during sleep deprivation in rats, which may lead to an overestimation of food intake in this condition. The objective of this study was to verify whether sleep deprivation induces an increase in gnawing behavior that could account for increased food spillage and apparent increase in food intake. We introduced wood blocks as objects for gnawing and determined the effects of their availability on food consumption and food spillage during sleep deprivation. Wood block availability reduced the amount of food removed from hoppers and decreased the amount of food spilled. However, weight loss still occurred during the sleep deprivation period, especially in the first 24 h, and it was related to a reduction in food intake. Sleep deprivation causes an increase in stereotyped gnawing behavior which largely accounts for increased food spillage observed during deprivation. Specifically, the observed increase in food removed from feeders seems to be due to an increase in gnawing and not to increased hunger. However, even when appropriately corrected for spillage, food intake decreased in the first 24 h of sleep deprivation, which accounted for most of the body weight loss seen during the 96 h of sleep deprivation.

The influence of sleep and sleep loss upon food intake and metabolism

The present review investigates the role of sleep and its alteration in triggering metabolic disorders. The reduction of the amount of time sleeping has become an endemic condition in modern society and the current literature has found important associations between sleep loss and alterations in nutritional and metabolic aspects. Studies suggest that individuals who sleep less have a higher probability of becoming obese. It can be related to the increase of ghrelin and decrease of leptin levels, generating an increase of appetite and hunger. Sleep loss has been closely associated with problems in glucose metabolism and a higher risk for the development of insulin resistance and diabetes, and this disturbance may reflect decreased efficacy of the negative-feedback regulation of the hypothalamic–pituitary–adrenal axis. The period of sleep is also associated with an increase of blood lipid concentrations, which can be intensified under conditions of reduced sleep time, leading to disorders in fat metabolism. Based on a review of the literature, we conclude that sleep loss represents an important risk factor for weight gain, insulin resistance, type 2 diabetes and dyslipidaemia. Therefore, an adequate sleep pattern is fundamental for the nutritional balance of the body and should be encouraged by professionals in the area.

Paradoxical sleep deprivation and sleep recovery: effects on the hypothalamic-pituitary-adrenal axis activity, energy balance and body composition of rats

Numerous studies indicate that sleep deprivation alters energy expenditure. However, this conclusion is drawn from indirect measurements. In the present study, we investigated alterations of energy expenditure, body composition, blood glucose levels, plasma insulin, adrenocorticotropic hormone (ACTH) and corticosterone levels immediately after 4 days of sleep deprivation or after 4 days of sleep recovery. Rats were sleep deprived or maintained in a control environment (groups sleep-deprived/deprivation and control/deprivation). One half of these animals were sacrificed at the end of the deprivation period and the other half was transported to metabolic cages, where they were allowed to sleep freely (groups sleep-deprived/recovery and control/recovery). At the end of the sleep recovery period, these rats were sacrificed. After sleep deprivation, sleep-deprived rats exhibited loss of body weight, augmented energy expenditure and reduced metabolic efficiency compared to control rats. These alterations were normalised during the sleep recovery period. The body composition of sleep-deprived rats was altered insofar as there was a loss of fat content and gain of protein content in the carcass compared to control rats. However, these alterations were not reversed by sleep recovery. Finally, plasma levels of insulin were reduced during the sleep deprivation period in both control and sleep deprived groups compared to the recovery period. After the deprivation period, plasma ACTH and corticosterone levels were increased in sleep-deprived rats compared to control rats, and although ACTH levels were similar between the groups after the sleep recovery period, corticosterone levels remained elevated in sleep-deprived rats after this period. By means of direct measurements of metabolism, our results showed that sleep deprivation produces increased energy expenditure and loss of fat content. Most of the alterations were reversed by sleep recovery, except for corticosterone levels and body composition.

Changes in hypothalamic corticotropin-releasing hormone, neuropeptide Y, and proopiomelanocortin gene expression during chronic rapid eye movement sleep deprivation of rats

Chronic rapid eye movement (paradoxical) sleep deprivation (REM-SD) of rats leads to two conspicuous pathologies: hyperphagia coincident with body weight loss, prompted by elevated metabolism. Our goals were to test the hypotheses that 1) as a stressor, REM-SD would increase CRH gene expression in the hypothalamus and that 2) to account for hyperphagia, hypothalamic gene expression of the orexigen neuropeptide Y (NPY) would increase, but expression of the anorexigen proopiomelanocortin (POMC) would decrease. Enforcement of REM-SD of adult male rats for 20 d with the platform (flowerpot) method led to progressive hyperphagia, increasing to approximately 300% of baseline; body weight steadily declined by approximately 25%. Consistent with changes in food intake patterns, NPY expression rapidly increased in the hypothalamic arcuate nucleus by d 5 of REM-SD, peaking at d 20; by contrast, POMC expression decreased progressively during REM-SD. CRH expression was increased by d 5, both in mRNA and ability to detect neuronal perikaryal staining in paraventricular nucleus with immunocytochemistry, and it remained elevated thereafter with modest declines. Taken together, these data indicate that changes in hypothalamic neuropeptides regulating food intake are altered in a manner consistent with the hyperphagia seen with REM-SD. Changes in CRH, although indicative of REM-SD as a stressor, suggest that the anorexigenic actions of CRH are ineffective (or disabled). Furthermore, changes in NPY and POMC agree with current models of food intake behavior, but they are opposite to their acute effects on peripheral energy metabolism and thermogenesis.

Chronic REM-sleep deprivation of rats elevates metabolic rate and increases UCP1 gene expression in brown adipose tissue

A cluster of unique pathologies progressively develops during chronic total- or rapid eye movement-sleep deprivation (REM-SD) of rats. Two prominent and readily observed symptoms are hyperphagia and decline in body weight. For body weight to be lost despite a severalfold increase in food consumption suggests that SD elevates metabolism as the subject enters a state of negative energy balance. To test the hypothesis that mediation of this hypermetabolism involves increased gene expression of uncoupling protein-1 (UCP1), which dissipates the thermodynamic energy of the mitochondrial proton-motive force as heat instead of ATP formation in brown adipose tissue (BAT), we 1) established the time course and magnitude of change in metabolism by measuring oxygen consumption, 2) estimated change in UCP1 gene expression in BAT by RT-PCR and Western blot, and 3) assayed serum leptin because of its role in regulating energy balance and food intake. REM-SD of male Sprague-Dawley rats was enforced for 20 days with the platform (flowerpot) method, wherein muscle atonia during REM sleep causes contact with surrounding water and awakens it. By day 20, rats more than doubled food consumption while losing approximately 11% of body weight; metabolism rose to 166% of baseline with substantial increases in UCP1 mRNA and immunoreactive UCP1 over controls; serum leptin decreased and remained suppressed. The decline in leptin is consistent with the hyperphagic response, and we conclude that one of the mediators of elevated metabolism during prolonged REM-SD is increased gene expression of UCP1 in BAT.

Effects of sleep deprivation on gastric mucosal blood flow and gastric mucosal lesions in rats

AIM: To observe the changes of gastric mucosal blood flow and gastric mucosal lesions in rats after sleep deprivation.

METHODS: Sleep deprivation was induced in male Sprague-Dawley rats housed on small platform over water. Control mice were housed either in normal cages or on large platform over water. Laser Doppler blood flow meter was used to measure the gastric mucosal blood flow, and index of gastric mucosal lesions was quantified. The arterial plasma levels of endotoxin (ET) and calcitonin gene related peptide (CGRP) were measured by radioimmunoassay.

RESULTS: Compared with control mice in normal cage, on big platform, or the mice on the 1st day of sleep deprivation, the gastric mucosal blood flow of mice on the 3rd, 5th and 7th day of sleep deprivation (54.2±2.5, 53.7±3.0, 48.3±2.5 mv, respectively) were significantly lower. The gastric mucosal injury became more and more serious: the injury indices were 29.8±3.2, 3.7±3.6 and 34.8±3.5 on the 3rd, 5th and 7th day of sleep deprivation, respectively. The serum levels of ET were 123±28, 139±36 and 149±38 ng/L in mice on the 3rd, 5th and 7th day of sleep deprivation, and the levels of CGRP were 193±32 and 221±40 ng/L in the mice on the 5th and 7th day of sleep deprivation. All were significantly higher than those in control mice.

CONCLUSION: Sleep deprivation can cause the decrease of gastric mucosal blood flow and the gastric mucosal injury, which are accompanied by the elevation of serum ET and CGRP.