The effect of brain-derived neurotrophic factor Val66Met polymorphism on adolescent activity and rest rhythms, circadian preferences and attentional performance.

BACKGROUND: Variations in circadian regulating mechanisms generate different individual preferences in respect of sleep and activity timing, which are known as chronotypes. In this sense, specifically during adolescence, there is a greater tendency for an eveningness chronotype. One factor that has been shown to have an impact on circadian rhythm patterns, as well as on some aspects of cognitive function, is the relatively common Val66Met (rs6265) polymorphism in the human brain-derived neurotrophic factor gene. OBJECTIVE: This study aimed to evaluate the effect of the BDNF Val66Met polymorphism on the performance of adolescents in attentional tests, circadian preferences and activity-rest rhythm. METHODS: 85 healthy high school students completed the Morningness-Eveningness Questionnaire to assess their circadian preferences; were evaluated using the Psychological Battery for Attention Assessment; and were categorized as carriers and non-carriers of the rs6265 polymorphism using the TaqMan rt-PCR technique. A subsample of 42 students had their activity/rest rhythm recorded by actigraphy for nine days from which sleep parameters were estimated. RESULTS: Circadian preference did not affect attentional performance (p > 0.1), but the time that the students attended school had an impact on all types of attention with morning shift students scoring higher, regardless of chronotype (p < 0.05). The presence of the BDNF Val66Met polymorphism was associated only with alternate attention performance (p < 0.05). Regarding actigraphy evaluation, the carriers of the polymorphism demonstrated significantly higher total time in bed, total sleep time, social jetlag, and earlier sleep onset. CONCLUSIONS: The results indicate some degree of adaptation in the students' attentional performance, according to their school schedules. The presence of BDNF polymorphism demonstrated a counterintuitive impact on attentional performance, comparing to previous findings. The findings reinforce the effect of genetic traits on sleep-wake rhythm parameters, when objectively evaluated.

Maternal methionine supplementation in mice affects long-term body weight and locomotor activity of adult female offspring.

Methionine is a precursor of s-adenosylmethionine, the main donor of methyl radicals for methylation of DNA and other compounds. Previous studies have shown that reduced availability of methyl radicals during pregnancy/lactation decreased offspring perigonadal white adipose tissue (PWAT) and body weight. Therefore, we aimed to evaluate the effects of methionine supplementation during early development, a time of great ontogenic plasticity, by assessing the biometric, biochemical and behavioural parameters of the offspring of adult Swiss female mice supplemented with 1 % methionine in water 1 month before pregnancy, during pregnancy or pregnancy/lactation. After birth, the offspring were distributed into three groups: control (CT), methionine supplementation during pregnancy (SP) and methionine supplementation during pregnancy and lactation (SPL), and were followed until postnatal day (PND) 300. No changes were observed in offspring birth weight in both sexes. At PND 5, 28 and 90, no differences in body weight were found in females; however, at PND 300, SP and SPL females showed an increase in body weight when compared with the control group. This increase in body weight was accompanied by a total and relative increase in PWAT, and a decrease in locomotor activity in these groups. No differences in the body and organ weights were found in male offspring. In conclusion, the increased availability of methyl radicals during pregnancy and lactation impacted long-term body composition and locomotor activity in female offspring.