Giovana Dantas

Obesity and shift work: chronobiological aspects.

The present review has the objective of summarising chronobiological aspects of shift work and obesity. There was a systematic search in PubMed databases, using the following descriptors: shift work; obesity; biological clock. Shift work is extremely frequent in several services and industries, in order to systematise the needs for flexibility of the workforce, necessary to optimise productivity and business competitiveness. In developing countries, this population represents a considerable contingent workforce. Recently, studies showed that overweight and obesity are more prevalent in shift workers than day workers. In addition, the literature shows that shift workers seem to gain weight more often than those workers submitted to a usual work day. In conclusion, there is considerable epidemiological evidence that shift work is associated with increased risk for obesity, diabetes and CVD, perhaps as a result of physiological maladaptation to chronically sleeping and eating at abnormal circadian times. The impact of shift work on metabolism supports a possible pathway to the development of obesity and its co-morbities. The present review demonstrated the adverse cardiometabolic implications of circadian misalignment, as occurs chronically with shift workers.

Depression Scores Associate With Chronotype and Social Jetlag in a Rural Population

In public health, mood disorders are among the most important mental impairments. Patients with depressive episodes exhibit daily mood variations, abnormal patterns in sleep-wake behavior, and in the daily rhythms of several endocrine-metabolic parameters. Although the relationship between the sleep/circadian processes and mood disorders is poorly understood, clock-related therapies, such as light therapy, sleep deprivation, and rigid sleep schedules, have been shown to be effective treatments. Several studies investigated the relationship between circadian phenotype (chronotype) and depression. These focused mainly on urban populations and assessed diurnal preferences (Morningness-Eveningness score) rather than the actual timing of sleep and activity. Here, we used the Beck Depression Inventory (BDI) in an essentially rural population (N = 4051), and investigated its relation to circadian phenotype (chronotype and social jetlag), assessed with the Munich Chronotype Questionnaire (MCTQ). In our study design, we (i) normalized both chronotype and BDI scores for age and sex (MSFsas and BDIas, respectively); (ii) calculated individual social jetlag (misalignment of the biological and social time); and (iii) investigated the relationship between circadian phenotypes and BDI scores in a population homogeneous in respect to culture, socioeconomic factors, and daily light exposure. A 15.65% (N = 634) of the participants showed mild to severe depressive BDI scores. Late chronotypes had a higher BDIas than intermediate and early types, which was independent of whether or not the participants were smokers. Both chronotype and BDIas correlated positively with social jetlag. BDIas was significantly higher in subjects with >2 h of social jetlag than in the rest of the population—again independent of smoking status. We also compared chronotype and social jetlag distributions between BDI categories (no symptoms, minimal symptoms, and mild to severe symptoms of depression) separately for men and women and for four age groups; specifically in the age group 31–40 yrs, subjects with mild to severe BDI scores were significantly later chronotypes and suffered from higher social jetlag. Our results indicate that misalignment of circadian and social time may be a risk factor for developing depression, especially in 31- to 40-yr-olds. These relationships should be further investigated in longitudinal studies to reveal if reduction of social jetlag should be part of prevention strategies. (Author correspondence: karla.allebrandt@med.uni-muenchen.de)

Long-lasting delayed hyperalgesia after chronic restraint stress in rats—effect of morphine administration

Different effects upon the nociceptive response have been observed with exposure to acute and chronic stress in rats. In the present study we repeatedly submitted rats to restraint for 40 days, inducing hyperalgesia using the tail-flick test. A new session of acute stress was applied at the end of 40 days period, and the chronically-stressed animals demonstrated analgesia after forced swimming, but not after restraint. The effect of stress interruption for 14 or 28 days on the nociceptive threshold was then investigated. The basal tail-flick latency remained decreased for at least 28 days (hyperalgesic effect). Following the periods of suspension, the animals were submitted to new session of acute restraint, and stress-induced analgesia was observed only after 28 days of stress interruption. Thus, the mechanisms involved in the long-lasting hyperalgesia presented in this study are not exactly the same as those responsible for the analgesia induced by acute stressors. After 40 days of chronic stress treatment, morphine was injected i.p. (1.0, 5.0 mg/kg or saline). The repeatedly stressed rats displayed decreased morphine effects on nociception compared to unstressed controls. The tolerance of the response to morphine agrees with previous studies suggesting that chronic restraint stress could modify the activity of opioid systems.

Neonatal handling alters feeding behavior of adult rats.

Stress during the neonatal period leads to a large number of behavioral and biochemical alterations in adult life. The aim of this study is to verify the effects of handling and tactile stimulation during the first 10 days of life on feeding behavior in adult rats. Litters were divided into (1). intact; (2). handled (10 min/day); and (3). handled and tactile stimulated (10 min/day). Procedures were performed on Days 1-10 after birth. When adults, rats were tested for ingestion of sweet and savory snacks. We also measured body weight, ingestion of standard lab chow, and consumption of water and 1% glucose and 1.5% NaCl solutions. Stressed rats (handling and handling+tactile stimulation groups) consumed more sweet (two-way ANOVA, P=.008) or savory snacks (P=.001) than intact ones. This effect was observed in males and females. There were no differences in body weight, ingestion of standard lab chow, water, or in the ingestion of sweetened or salty solutions between groups. The same animals were tested later in life (15 months of age), and the effect was still evident. We suggest that handling during the neonatal period leads to alterations in the CNS of rats, causing an increased ingestion of palatable food in adult life, and this alteration probably persists throughout the whole life.

Morningness–eveningness, use of stimulants, and minor psychiatric disorders among undergraduate students

Morningness-eveningness dimension in humans have been indicated to influence social behavior and individual health. The aim of the present study was to investigate the association of the morningness-eveningness dimension with behavioral and health aspects in a sample of undergraduate students. We assessed demographic data; the Pittsburgh Sleep Quality Index was used to evaluate sleep quality; the Morningness/Eveningness Questionnaire to determine morningness-eveningness, and the Self-Reporting Questionnaire to assess minor psychiatric disorders. A total of 372 students (66.7% females), on average 21.6 years old, participated in this study. Among them, 92.2% did not smoke, 58.9% engaged in physical activities, and 19.7% were night-shift workers. In regard to morningness-eveningness, 55.9% of the participants were intermediate between evening (39.5%) and morning (4.6%) types. Poor sleep quality (OR = 1.89), minor psychiatric disorders (OR = 1.92), and tobacco consumption (OR = 3.65) predominated among evening types. Evening types were predominantly males (OR = 1.72). This study suggests that evening types are more vulnerable to sleep and psychiatric disturbances, and tend to smoke more than morning types.

Long-term effect of morphine administration in young rats on the analgesic opioid response in adult life

Neonates, infants and children are often exposed to pain from invasive procedures during intensive care and during the post‐operative period. Opioid anesthesia and post‐operative opioid analgesia have been used in infants and result in clinical benefits. The objectives of this study were to verify the effect of repeated 5 μg morphine administration (subcutaneous), once a day for 7 days in 8‐day‐old rats, at P8 until P14. To verify the long‐term effect of morphine, the animals were submitted to a second exposure of 5 mg/kg (intraperitoneal) of morphine at P80 until P86. Animals that received morphine for 7 days, at P14 did not develop tolerance, however at P80, rats demonstrated greater morphine analgesia. At P86, after 7 days of morphine administration, animals showed classical tolerance. These findings may have important implications for the human neonate, suggesting a possible explanation for the differences in the requirements of morphine observed in the youngest patients.

Repeated Restraint Stress Reduces Opioid Receptor Binding in Different Rat CNS Structures

Different effects of exposure to acute or to repeated stress have been observed upon the nociceptive response in rats. In the present study, we repeatedly submitted Wistar rats to restraint for 40 days, a treatment known to induce an increase in the nociceptive response in the tail-flick test. Afterwards, the effect of repeated restraint stress on the density of opioid receptors in rat spinal cord, frontal cortex, and hippocampus was investigated. Results showed that repeatedly stressed rats displayed a significant decrease in opioid receptors density in all structures studied; cortex (141.3 ± 5.7 for control and 103.3 ± 15.9 for stressed rats), hippocampus (92.4 ± 7.2 for control and 64.8 ± 7.7 for stressed rats), and spinal cord (122.2 ± 12.8 for control and 79.7 ± 9.7 for stressed rats). These findings suggest opioid mediation of the altered responses observed in these repeatedly-stressed animals, although the participation of non-opioid mechanisms in this phenomenon cannot be ruled out.

6-Sulfatoxymelatonin as a predictor of clinical outcome in depressive patients

This study established the value of the 6‐sulfatoxymelatonin (aMT6s) urine concentration as a predictor of the therapeutic response to noradrenaline reuptake inhibitors in depressive patients.

Impact of the time in an animal model of mood disorder

UNLABELLED The objective of the study is to evaluate whether intervening and testing in different rest-activity periods of the day would produce different measurements in animal behavior studies. METHODOLOGY Thirty-five, 60-day-old male Wistar rats were submitted to an inescapable foot shock (IFS) stress model and behavioral tests (Light-Dark Box test). The animals received intervention and were tested in both light and dark phases, resulting in the following groups: control L (tested in the light), control D (tested in the dark), LL (IFS and tested in the light), LD (IFS in the light and tested in the dark), DL (IFS in the dark and tested in the light), and DD (IFS and tested in the dark). RESULTS The Light-Dark Box test showed that control L was not significantly different from other groups in any of the parameters. However, when comparing control D with the intervention groups, we observed a difference in the mean length of time spent in the light compartment (t=2.56; p=0.045). A significant difference in the number of crossings into the light compartment was only observed between the control D and the LL and LD groups (t=-2.608; p=0.028; t=-2.571; p=0.030, respectively). The latency time for the control D group was significantly lower than that of the DD group (t=-2.556; p=0.043). CONCLUSIONS These results show that behavior testing during the animals period of highest activity (dark period) revealed differences caused by the intervention, whereas no differences were apparent when the control group was observed during the day.