Effects of pediatric adiposity on heart rate variability

The relationship between obesity and heart rate variability (HRV) has been studied in adults and adolescents, but is not determined in young pediatrics. The purpose of this study was to assess autonomic activity using HRV in a pediatric population. We hypothesized that obese children would have reduced parasympathetic and increased sympathetic activity compared to age-matched subjects. 42 pediatric subjects (ages 3-5) were classified into 3 groups based on body mass index-for-age; normal, overweight and obese. HRV and respiratory rate were recorded during 3 minute baseline, 2 minute isometric handgrip and 3 minute recovery. HRV was analyzed in the time domain [heart rate (HR), RR interval (RRI) and RRI standard deviation (RRISD)] and frequency domain [low frequency (LF), high frequency (HF) and LF/HF ratio] using repeated measures ANOVA. Spearman’s correlations were used to examine the relations between BMI and HRV at rest. Significant condition effects were found between baseline, exercise and recovery, but these responses were not significantly different between the normal, overweight and obese children. BMI was negatively correlated with LF/HF, while BMI was positively correlated with RRISD, LF, HF and nHF. Our data demonstrate that higher BMI in the pediatric population is correlated with higher parasympathetic and lower sympathetic activity. These findings are contrary to HRV responses observed in adults and adolescents, suggesting complex relationships between age, obesity and autonomic control of the heart. The data supports the concept of an age reliance of HRV and a novel relationship between adiposity and body mass index in 3-5 year olds.

Plant-mediated effects on microbial diversity in mesocosms of an oligotrophic bog

Globally, peatlands occupy a small portion of terrestrial land area but contain up to one-third of all soil organic carbon. This carbon pool is vulnerable to increased decomposition under projected climate change scenarios but little is known about how plant functional groups will influence microbial communities responsible for regulating carbon cycling processes. Here we examined initial shifts in microbial community structure within two sampling depths under plant functional group manipulations in mesocosms of an oligotrophic bog. Microbial community composition for bacteria and archaea was characterized using targeted 16S rRNA Illumina gene sequencing. We found statistically distinct spatial patterns between the more shallow 10-20 cm sampling depth and the deeper 30-40 cm depth. Significant effects by plant functional groups were found only within the 10-20 cm depth, indicating plant-mediated microbial community shifts respond more quickly near the peat surface. Specifically, the relative abundance of Acidobacteria decreased under ericaceous shrub treatments in the 10-20 cm depth and was replaced by increased abundance of Gammaproteobacteria and Bacteroidetes. In contrast, the sedge rhizosphere continued to be dominated by Acidobacteria but also promoted an increase in the relative recovery of Alphaproteobacteria and Verrucomicrobia. These initial results suggest microbial communities under ericaceous shrubs may be limited by anaerobic soil conditions accompanying high water table conditions, while sedge aerenchyma may be promoting aerobic taxa in the upper peat rhizosphere regardless of ambient soil oxygen limitations.