Ketone body 3-hydroxybutyrate as a biomarker of aggression.

Human aggression is a complex behaviour, the biological underpinnings of which remain poorly known. To gain insights into aggression biology, we studied relationships with aggression of 11 low-molecular-weight metabolites (amino acids, ketone bodies), processed using 1H nuclear magnetic resonance spectroscopy. We used a discovery sample of young adults and an independent adult replication sample. We studied 725 young adults from a population-based Finnish twin cohort born 1983-1987, with aggression levels rated in adolescence (ages 12, 14, 17) by multiple raters and blood plasma samples at age 22. Linear regression models specified metabolites as the response variable and aggression ratings as predictor variables, and included several potential confounders. All metabolites showed low correlations with aggression, with only one-3-hydroxybutyrate, a ketone body produced during fasting-showing significant (negative) associations with aggression. Effect sizes for different raters were generally similar in magnitude, while teacher-rated (age 12) and self-rated (age 14) aggression were both significant predictors of 3-hydroxybutyrate in multi-rater models. In an independent replication sample of 960 adults from the Netherlands Twin Register, higher aggression (self-rated) was also related to lower levels of 3-hydroxybutyrate. These exploratory epidemiologic results warrant further studies on the role of ketone metabolism in aggression.

Genetic architecture of motives for leisure-time physical activity: a twin study.

The aim of this study was to estimate the contribution of genetic and environmental influences on motives for engaging in leisure-time physical activity. The participants were obtained from the FinnTwin16 study. A modified version of the Recreational Exercise Motivation Measure was used to assess the motives for leisure-time physical activity in 2542 twin individuals (mean age of 34.1 years). Linear structural equation modeling was used to investigate the genetic and environmental influences on motive dimensions. The highest heritability estimates were found for the motive dimensions of "enjoyment" [men 33% (95% CI 23-43%), women 53% (95% CI 45-60%)] and "affiliation" [men 39% (95% CI 0.28-0.49%), women 35% (95% CI 0.25-0.43%)]. The lowest heritability estimates were found for others' expectations [men 13% (95% CI 0.04-0.25%), women 15% (95% CI 0.07-0.24%)]. Unique environmental influences explained the remaining variances, which ranged from 47% to 87%. The heritability estimates for summary variables of intrinsic and extrinsic motives were 36% and 32% for men and 40% and 24% for women, respectively. In conclusion, genetic factors contribute to motives for leisure-time physical activity. However, the genetic effects are, at most, moderate, implying the greater relative role of environmental factors.

Handedness in the helsinki ultrasound trial.

OBJECTIVES: To determine whether exposure to prenatal ultrasound increases non-right-handedness in boys. METHODS: The association between exposure to prenatal ultrasound and handedness was tested, using logistic regression analysis, in the Helsinki Ultrasound Trial data. We applied an intention-to-treat approach in this analysis of a subset of 4150 subjects whose parents answered a follow-up questionnaire on handedness when the children were aged 13-15 years. RESULTS: The odds ratio for non-right-handedness of children who had been exposed to prenatal ultrasound was 1.16 (0.98-1.37) for all subjects, 1.12 (0.89-1.41) for boys and 1.24 (0.97-1.58) for girls. CONCLUSIONS: We could not confirm the hypothesis that prenatal ultrasound exposure and handedness are associated. Our findings were independent of the particular definition of handedness used, whether it was considered according to the writing hand alone or defined using a laterality quotient.

Genetic origins of the association between verbal ability and alcohol dependence symptoms in young adulthood.

BACKGROUND: Cognitive deficits in alcohol dependence (AD) have been observed, poorer verbal ability being among the most consistent findings. Genetic factors influence both cognitive ability and AD, but whether these influences overlap is not known. METHOD: A subset of 602 monozygotic (MZ) and dizygotic (DZ) twins from FinnTwin16, a population-based study of Finnish twins, was used to study the associations of verbal ability with DSM-III-R diagnosis and symptoms of AD, the maximum number of drinks consumed in a 24-h period, and the Rutgers Alcohol Problem Index (RAPI) scores. These twins, most of them selected for within-pair discordance or concordance for their RAPI scores at age 18.5 years, were studied with neuropsychological tests and interviewed with the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) in young adulthood (mean age 26.2 years, range 23-30 years). RESULTS: All alcohol problem measures were associated with lower scores on the Vocabulary subtest of the Wechsler Adult Intelligence Scale - Revised (WAIS-R), a measure of verbal ability. In bivariate genetic models, Vocabulary and the alcohol problem measures had moderate heritabilities (0.54-0.72), and their covariation could be explained by correlated genetic influences (genetic correlations -0.20 to -0.31). CONCLUSIONS: Poorer verbal ability and AD have partly overlapping biological etiology. The genetic and environmental influences on the development of cognitive abilities, alcohol problems and risk factors for AD should be studied further with prospective longitudinal designs.