The Diurnal Blood Metabolome and Effects of Vitamin D Supplementation: A Randomised Crossover Trial in Postmenopausal Women

A way to maintain an adequate vitamin D status is through supplementation. Demonstration of blood-metabolome rhythmicity of vitamin D₃ post-dosing effects is lacking in the pharmaco-metabonomics area. Thus, the overall aim of this study was to investigate the diurnal changes in the blood metabolome and how these are affected by vitamin D₃ supplementation. The study was conducted as a crossover study, and the treatment included 200 µg (8000 IU) of vitamin D₃ as compared with placebo with a washout period of at least 10 days. The participants were postmenopausal women aged 60–80 years (N = 29) with vitamin D insufficiency (serum 25-hydroxyvitamin D < 50 nmol/L) but otherwise healthy. During the intervention day, blood samples were taken at 0 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, and 24 h, and plasma was analysed by proton nuclear magnetic resonance (NMR) spectroscopy as a metabolomics approach. In general, diurnal effects were identified for the majority of the 20 quantified metabolites, and hierarchical cluster analysis revealed a change in the overall plasma metabolome around 12 AM (6 h after intervention), suggesting that the diurnal rhythm is reflected in two diurnal plasma metabolomes; a morning metabolome (8–12 AM) and an afternoon/evening metabolome (2–8 PM). Overall, the effect of vitamin D supplementation on the blood metabolome was minor, with no effect on the diurnal rhythm. However, a significant effect of the vitamin D supplementation on plasma acetone levels was identified. Collectively, our findings reveal an influence of diurnal rhythm on the plasma metabolome, while vitamin D supplementation appears to have minor influence on fluctuations in the plasma metabolome.     

Relational benefits of relational aggression: Adaptive and maladaptive associations with adolescent friendship quality.

Two longitudinal studies examined associations between relational aggression and friendship quality during adolescence. In Study 1, 62 adolescents in Grades 6 (25.8%), 7 (32.3%), and 8 (41.9%) completed assessments of friendship affiliations, relational and overt aggression, and friendship quality at 2 time points, 1 year apart. Results using actor partner interdependence modeling indicated that high levels of relational aggression predicted increases in self-reported positive friendship quality 1 year later. In Study 2, 56 adolescents in Grades 9 (66.7%) and 10 (33.3%) attended a laboratory session with a friend in which their conversations were videotaped and coded for relationally aggressive talk. Target adolescents completed measures of positive and negative friendship quality during the laboratory session and during a follow-up phone call 6 months later. Analyses revealed that high levels of relationally aggressive talk at Time 1 predicted increases in negative friendship quality 6 months later. In addition, among adolescents involved in a reciprocal best friendship, high levels of observed relationally aggressive talk predicted increases in positive friendship quality over time. Taken together, these studies provide support for the idea that relational aggression may be associated with adaptive as well as maladaptive outcomes within the dyadic context of adolescent friendship. (PsycINFO Database Record (c) 2011 APA, all rights reserved)