Luiz Menna-Barreto

Diabetes and sleep: A complex cause-and-effect relationship

Strong associations of diabetes with sleep impairment have been frequently reported. In the present review, we discuss current evidence and hypotheses for how type 1 and type 2 diabetes mellitus are associated with sleep impairment. This association may be described as a vicious circle, where sleep disorders favor the development of type 2 diabetes or exacerbate the metabolic control of both types of diabetes, whereas diabetes itself, especially when associated with poor metabolic control, is often followed by sleep disorders. In this review, novel findings concerning the neuro-endocrine-metabolic mediation of the mentioned circle are highlighted. Understanding how this association occurs, the impact of sleep impairment on diabetes, and the impact of diabetes on the development or exacerbation of sleep disorders should lead to potential new therapeutic strategies for treating both conditions.

Effect of Circadian Phase on Performance of Rats in the Morris Water Maze Task

The authors examined spatial working memory in the Morris water maze during the activity and rest periods ofWistar rats. Wheel-running activity was measured continuously as a marker of circadian phase. To minimize possible masking effects on performance, animals were placed in constant dim light the day before testing and tested in similar light conditions. Three experiments were run, each of them using animals varying in their previous experience in the water maze. Half of the animals of each experiment were tested 2 to 3 h after activity onset (active group), and the other half were tested 14 to 15 h after activity onset (inactive group). In the three experiments, a significant phase effect was observed in the animals’ performance in the water maze; animals tested in the active phase showed steeper acquisition curves. These phase effects on performance are due to the animals’ search pattern and not to a better acquisition and maintenance of spatial information; rats tested in the inactive phase found the platform faster on the first trial of the test, when the information on the location of the platform had not been presented to the animals. This effect vanished as the amount of training in the pool increased. Finally, swimming speed also showed a temporal effect, suggesting the existence of a phase effect for motivation to escape from the water; rats tested during their inactive phase tended to swim faster. All together, the data suggest a modulating effect of the biological clock on performance in the water maze, particularly when the animals are less experienced.

Sleep-Wake Cycle Expression in Adolescence: Influences of Social Context

Sleep/wake cycle (SWC) characteristics change with development. During adolescence there is a reduction in night sleep duration. A difference between sleep duration on weekdays and at weekends is also observed. Adolescents usually sleep much longer at weekends. A SWC phase delay related to puberal stage is described. In this study, we have investigated SWC patterns among populations living in different environments, either urban (one population) or non-urban (two populations). 423 adolescents studying in the morning period participated in the study. Some characteristics of adolescents’ SWC have been investigated based on a questionnaire previously validated by an actigraphic study. Bedtimes and wake up times were compared by means of ANOVA. Adolescents living in the urban environment showed later bedtimes (p < 0.001) and wake up times (p < 0.001) when compared with adolescents living in rural environments. No differences were found when the rural populations were compared.

Sleep–Wake Cycle in Rural Populations

The light/dark cycle is the main zeitgeber acting on the mammalian circadian system; nevertheless, distinct environments, such as those with and without electricity may provoke important resetting effects on the clock. The aim of this study was to describe sleep/wake patterns of adolescents living in two Brazilian rural regions. In the first population, 120 adolescents participated in the study, 35 of whom did not have electricity at home. They filled out a questionnaire which included questions concerning their sleep habits. It was found that electricity at home influenced sleep patterns. Adolescents with electricity at home had later wake-up times on school days (p < 0.05) and on weekends (p < 0.05), and tendencies towards later bedtimes on school days (0.05 < p < 0.10) and weekends (0.05 < p < 0.10). In the second population, 461 adolescents filled out the same questionnaire, 66 of whom did not have television at home. ANOVA showed that having TV at home was related to later bedtimes during school days (p < 0.05) and weekends (p < 0.05). These results support the idea that sleep patterns are influenced by technological advances.

Melatonin synthesis impairment as a new deleterious outcome of diabetes‐derived hyperglycemia

Melatonin is a neurohormone that works as a nighttime signal for circadian integrity and health maintenance. It is crucial for energy metabolism regulation, and the diabetes effects on its synthesis are unresolved. Using diverse techniques that included pineal microdialysis and ultrahigh‐performance liquid chromatography, the present data show a clear acute and sustained melatonin synthesis reduction in diabetic rats as a result of pineal metabolism impairment that is unrelated to cell death. Hyperglycemia is the main cause of several diabetic complications, and its consequences in terms of melatonin production were assessed. Here, we show that local high glucose (HG) concentration is acutely detrimental to pineal melatonin synthesis in rats both in vivo and in vitro. The clinically depressive action of high blood glucose concentration in melatonin levels was also observed in type 1 diabetes patients who presented a negative correlation between hyperglycemia and 6‐sulfatoxymelatonin excretion. Additionally, high‐mean‐glycemia type 1 diabetes patients presented lower 6‐sulfatoxymelatonin levels when compared to control subjects. Although further studies are needed to fully clarify the mechanisms, the present results provide evidence that high circulating glucose levels interfere with pineal melatonin production. Given the essential role played by melatonin as a powerful antioxidant and in the control of energy homeostasis, sleep and biological rhythms and knowing that optimal glycemic control is usually an issue for patients with diabetes, melatonin supplementation may be considered as an additional tool to the current treatment.

Circadian rhythms in phonological and visuospatial storage components of working memory

Abstract Working memory is a basic cognitive process that temporarily maintains the information necessary for the performance of many complex tasks such as reading comprehension, learning and reasoning. Working memory includes two storage components: phonological and visuospatial, and a central executive control. The objective of this study was to identify possible circadian rhythms in phonological and visuospatial storage components of working memory using a constant routine protocol. Participants were eight female undergraduate students, aged 17.5±0.93, range = 16 – 19 years old. They were recorded in the laboratory in a constant routine protocol during 30 h. Rectal temperature was recorded every minute; subjective sleepiness and tiredness, as well as phonological and visuospatial working memory tasks, were assessed each hour. There were circadian variations in correct responses in phonological and visuospatial working memory tasks. Cross-correlation analysis showed a 1-h phase delay of the phonological storage component and a 3-h phase delay of the visuospatial storage component with respect to rectal temperature. This result may explain the changes in the performance of many complex tasks during the day.

Latitude and Social Habits as Determinants of the Distribution of Morning and Evening Types in Brazil

Previous application of a Portuguese version of the Horne and Ostberg (H&O) questionnaires in Brazil showed a displacement of the distribution of Morningness/Eveningness (M/E) types towards morningness, demanding a reclassification of the scores limits for each of the 5 possible M/E types. Among city, age and sex, city was the only factor determining significant group differences. In the present paper, the same version of the H&Os questionnaire was applied to a distinct population of 260 adults, balanced according to age, sex and city. Data were collected from October to December, to control the effect of the photoperiod. City remains the only factor determining significant group differences (p <0.001). Moreover, there does not appear a coherent latitude trend that could explain differences among cities as a function of photoperiod. Local social habits could probably explain our results, suggesting further investigations of peculiar temporal patterns.

Locomotor activity pattern of Brazilian cave catfishes under constant darkness (Siluriformes, Pimelodidae)

Abstract Troglobites ‐ cave restricted species ‐ are good models for chronobiological studies focusing on the functions of circadian rhythmicity since they provide a test for hypotheses on external versus internal selection. Cases of reduction in the circadian components of activity have been reported for cave fishes, beetles, and crustaceans, but the methods of data analysis are not fully comparable. We present the results of spectral analysis of locomotor activity in two species of troglobitic catfishes: the less specialized Pimelodella kronei (compared to its eyed close relative, P. transitoria) and a highly specialized Imparfinis, undescribed species. The activity of seven specimens off. transitoria, nine of P. kronei, and six of Imparfinis sp. was automatically recorded in an infra‐red photocell device, for four to ten consecutive days, under constant darkness. All the eyed catfishes showed significant free‐running circadian components, as did seven P. kronei and three Imparfinis specimens. Variable ...

Chronotype ontogeny related to gender

Chronotype is an established concept designed to identify distinct phase relationships between the expression of circadian rhythms and external synchronizers in humans. Although it has been widely accepted that chronotype is subjected to ontogenetic modulation, there is no consensus on the interaction between age and gender. This study aimed to determine the relationship between age- and gender-related changes in the morningness-eveningness character in a large sample of people. A total of 14,650 volunteers were asked to complete the Brazilian version of the Horne and Östberg chronotype questionnaire. The data demonstrated that, on average, women were more morning-oriented than men until the age of 30 and there were no significant differences between men and women from 30 to 45 years of age. In contrast to the situation observed until the age of 30, women older than 45 years were more evening-oriented than men. These results suggest that the ontogenetic development of the circadian timekeeping system is more plastic in men, as represented by the larger amplitude of chronotype changes throughout their aging process. The phase delay of adolescence and phase advance of the elderly seem to be phenomena that are more markedly present in men than in women. Thus, our data, for the first time, provide support that sharply opposes the view that there is a single path toward morningness as a function of age, regardless of gender.

Diagnóstico dos transtornos do sono relacionados ao ritmo circadiano

Insomnia and excessive sleepiness are common in the investigation of sleep-disordered breathing. Circadian rhythm sleep disorders are perhaps the most often overlooked conditions in the differential diagnosis of these symptoms. Circadian rhythm sleep disorders manifest as misalignment between the sleep period and the physical/social 24-h environmental cycle. The two most prevalent circadian rhythm sleep disorders are delayed sleep phase (common in adolescents) and advanced sleep phase (common in the elderly), situations in which the sleep period is displaced to a later or earlier time, respectively. It is important to keep these two disorders in mind, since they can be confused with insomnia and excessive sleepiness. However, there are nine possible diagnoses, and all nine are of clinical interest. Since light is the principal cue used in synchronizing the biological clock, blind individuals and night-shift/swing-shift workers are more prone to develop circadian rhythm sleep disorders. In this article, the new international classification of circadian rhythm sleep disorders is reviewed.