RESUMO
This study aimed to investigate the behavioral responses and circadian rhythms of mice to both rapid and gradual increases in photoperiod, mimicking the transition from winter to summer, which is associated with a heightened prevalence of hospitalizations for mania and suicidal behavior. Behavioral tests were performed in C57BL/6 male mice exposed to a transitional photoperiod, from short to long durations. To determine if circadian rhythms are affected, we measured spontaneous locomotor activity and body temperature. Mice exhibited heightened exploratory and risk-taking behaviors compared with equatorial and static long (16:8 h of light-dark cycle for several days) groups. These behaviors were prevented by lithium. Spontaneous locomotor activity and body temperature rhythms persisted and were effectively synchronized; however, the relative amplitude of activity and interdaily stability were diminished. Additionally, the animals displayed increased activity during the light phase. Photoperiodic transition modulates behavior and circadian rhythms, mirroring certain features observed in bipolar disorder patients. This study introduces an animal model for investigating mania-like behavior induced by photoperiodic changes, offering potential insights for suicide prevention strategies and the management of mood disorders.
RESUMO
The association between chronotypes and season of birth (SOB) remains an inconclusive issue due, in some extension, to the lack of investigations of mediation mechanisms. We evaluated the association of photoperiod at birth (PAB) with chronotypes and sleep duration in Brazil (n = 810), and the mediating effect of meteorological factors, sex, age and rs4753426 polymorphism in the melatonin receptor MTNR1B. Longer PAB was associated with a delayed mid-sleep phase with a suppressive effect of maximum environmental temperature. No significant interactions were identified for the other variables. These findings suggest that photoperiod and environmental temperature modulate chronotype development at early stages.
Assuntos
Ritmo Circadiano , Fotoperíodo , Sono , Brasil , Feminino , Humanos , Recém-Nascido , Masculino , Gravidez , TemperaturaRESUMO
Recent studies have shown that transcriptomes from different tissues present circadian oscillations. Therefore, the endogenous variation of total RNA should be considered as a potential bias in circadian studies of gene expression. However, normalization strategies generally include the equalization of total RNA concentration between samples prior to cDNA synthesis. Moreover, endogenous housekeeping genes (HKGs) frequently used for data normalization may exhibit circadian variation and distort experimental results if not detected or considered. In this study, we controlled experimental conditions from the amount of initial brain tissue samples through extraction steps, cDNA synthesis, and quantitative real time PCR (qPCR) to demonstrate a circadian oscillation of total RNA concentration. We also identified that the normalization of the RNA's yield affected the rhythmic profiles of different genes, including Per1-2 and Bmal1. Five widely used HKGs (Actb, Eif2a, Gapdh, Hprt1, and B2m) also presented rhythmic variations not detected by geNorm algorithm. In addition, the analysis of exogenous microRNAs (Cel-miR-54 and Cel-miR-39) spiked during RNA extraction suggests that the yield was affected by total RNA concentration, which may impact circadian studies of small RNAs. The results indicate that the approach of tissue normalization without total RNA equalization prior to cDNA synthesis can avoid bias from endogenous broad variations in transcript levels. Also, the circadian analysis of 2-Cycle threshold (Ct) data, without HKGs, may be an alternative for chronobiological studies under controlled experimental conditions.
Assuntos
Ritmo Circadiano , Perfilação da Expressão Gênica/métodos , Genes Essenciais , Algoritmos , Animais , Encéfalo/metabolismo , Primers do DNA , Regulação da Expressão Gênica , Camundongos , Camundongos Endogâmicos C57BL , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Fatores de Tempo , TranscriptomaRESUMO
An association between Parkinson's disease (PD) and brain-derived neurotrophic factor (BDNF) was suggested by several studies, with contradictory results. BDNF is necessary for the survival of dopaminergic neurons in substantia nigra. Val66Met is a common polymorphism of the BDNF gene that affects cognitive and motor processes. The authors studied 104 Brazilian patients with PD and 96 control participants. The G/G genotype was significantly associated with depression and anxiety symptoms and development of PD. This is the first study that associates this genotype with PD.
Assuntos
Ansiedade/genética , Fator Neurotrófico Derivado do Encéfalo/genética , Depressão/genética , Predisposição Genética para Doença/genética , Doença de Parkinson/genética , Polimorfismo Genético/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Progressão da Doença , Feminino , Estudos de Associação Genética , Genótipo , Humanos , Masculino , Metionina/genética , Pessoa de Meia-Idade , Valina/genéticaRESUMO
BACKGROUND: Seasonal variations in suicides have been reported worldwide, however, there may be a different seasonal pattern in suicide attempts. The aim of this study was to perform a systematic review on seasonality of suicide attempts considering potential interfering variables, and a statistical analysis for seasonality with the collected data. METHOD: Observational epidemiological studies about seasonality in suicide attempts were searched in PubMed, Web of Science, LILACS and Cochrane Library databases with terms attempted suicide, attempt and season. Monthly or seasonal data available were evaluated by rhythmic analysis softwares. RESULTS: Twenty-nine articles from 16 different countries were included in the final review. It was observed different patterns of seasonality, however, suicide attempts in spring and summer were the most frequent seasons reported. Eight studies indicated differences in sex and three in the method used for suicide attempts. Three articles did not find a seasonal pattern in suicide attempts. Cosinor analysis identified an overall pattern of seasonal variation with a suggested peak in spring, considering articles individually or grouped and independent of sex and method used. A restricted analysis with self-poisoning in hospital samples demonstrated the same profile. LIMITATIONS: Grouping diverse populations and potential analytical bias due to lack of information are the main limitations. CONCLUSIONS: The identification of a seasonal profile suggests the influence of an important environmental modulator that can reverberate to suicide prevention strategies. Further studies controlling interfering variables and investigating the biological substrate for this phenomenon would be helpful to confirm our conclusion.
Assuntos
Periodicidade , Estações do Ano , Tentativa de Suicídio/estatística & dados numéricos , Adulto , Estudos Epidemiológicos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Observacionais como Assunto , Fatores SexuaisRESUMO
There is little evidence for the involvement of microRNAs (miRs) in the regulation of circadian rhythms, despite the potential relevance of these elements in the posttranscriptional regulation of the clock machinery. The present work aimed to identify miRs targeting circadian genes through a predictive analysis of conserved miRs in mammals. Besides 23 miRs previously associated with circadian rhythms, we found a number of interesting candidate genes, equally predicted by the 3 software programs used, including miR-9, miR-24, miR25, miR-26, miR-27, miR-29, miR-93, miR-211, miR-302, and miR-346. Moreover, several miRs are predicted to be regulated by circadian transcription factors, such as CLOCK/BMAL, DEC2, and REV-ERBalpha. Using real-time PCR we demonstrated that the selected candidate miR-27b showed a daily variation in human leukocytes. This study presents predicted feedback loops for mammalian molecular clock and the first description of an miR with in vivo daily variation in humans.