Cardiovascular regulation profile predicts developmental trajectory of BMI and pediatric obesity.

The present study examined the role of cardiovascular regulation in predicting pediatric obesity. Participants for this study included 268 children (141 girls) obtained from a larger ongoing longitudinal study. To assess cardiac vagal regulation, resting measures of respiratory sinus arrhythmia (RSA) and RSA change (vagal withdrawal) to three cognitively challenging tasks were derived when children were 5.5 years of age. Heart period (HP) and HP change (heart rate (HR) acceleration) were also examined. Height and weight measures were collected when children were 5.5, 7.5, and 10.5 years of age. Results indicated that physiological regulation at age 5.5 was predictive of both normal variations in BMI development and pediatric obesity at age 10.5. Specifically, children with a cardiovascular regulation profile characterized by lower levels of RSA suppression and HP change experienced significantly greater levels of BMI growth and were more likely to be classified as overweight/at-risk for overweight at age 10.5 compared to children with a cardiovascular regulation profile characterized by high levels of RSA suppression and HP change. However, a significant interaction with racial status was found suggesting that the association between cardiovascular regulation profile and BMI growth and pediatric obesity was only significant for African-American children. An autonomic cardiovascular regulation profile consisting of low parasympathetic activity represents a significant individual risk factor for the development of pediatric obesity, but only for African-American children. Mechanisms by which early physiological regulation difficulties may contribute to the development of pediatric obesity are discussed.

A novel mutation in the HCN4 gene causes symptomatic sinus bradycardia in Moroccan Jews.

OBJECTIVES: to conduct a clinical, genetic, and functional analysis of 3 unrelated families with familial sinus bradycardia (FSB). BACKGROUND: mutations in the hyperpolarization-activated nucleotide-gated channel (HCN4) are known to be associated with FSB. METHODS AND RESULTS: three males of Moroccan Jewish descent were hospitalized: 1 survived an out-of-hospital cardiac arrest and 2 presented with weakness and presyncopal events. All 3 had significant sinus bradycardia, also found in other first-degree relatives, with a segregation suggesting autosomal-dominant inheritance. All had normal response to exercise and normal heart structure. Sequencing of the HCN4 gene in all patients revealed a C to T transition at nucleotide position 1,454, which resulted in an alanine to valine change (A485V) in the ion channel pore found in most of their bradycardiac relatives, but not in 150 controls. Functional expression of the mutated ion channel in Xenopus oocytes and in human embryonic kidney 293 cells revealed profoundly reduced function and synthesis of the mutant channel compared to wild-type. CONCLUSIONS: we describe a new mutation in the HCN4 gene causing symptomatic FSB in 3 unrelated individuals of similar ethnic background that may indicate unexplained FSB in this ethnic group. This profound functional defect is consistent with the symptomatic phenotype.

Salivary alpha-amylase as a longitudinal predictor of children's externalizing symptoms: respiratory sinus arrhythmia as a moderator of effects.

Salivary alpha-amylase (sAA) was examined as a predictor of children's externalizing symptoms cross-sectionally when children were in the 3rd grade (T1; N=64) and again in the 5th grade (T2; N=54) and longitudinally over two years. Parasympathetic nervous system (PNS) activity, indexed by respiratory sinus arrhythmia (RSA), was examined as a moderator of the sAA and child externalizing link. Participants were healthy, typically developing children, 34% of whom were African American and the rest European American. At each time point, saliva samples were collected during afternoon laboratory visits and assayed for sAA. Children's RSA was measured during baseline conditions and in response to an inter-adult argument and a star-tracing task. Cross-sectional associations between sAA and externalizing symptoms at T1 and T2 were moderated by PNS functioning. Longitudinally, sAA was directly associated with changes in externalizing symptoms in a non-linear fashion. Specifically, lower externalizing symptoms were predicted for children with moderate levels of sAA, but higher externalizing was predicted for children with higher or lower levels of sAA. Findings highlight the importance of the contemporaneous assessment of SNS and PNS functioning in the prediction of child psychopathology, and the need to examine curvilinear relations between ANS functioning and behavior.

The effect of atropine on parasympathetic control of respiratory sinus arrhythmia in two ethnic groups.

The effects of low and high doses of atropine on respiratory sinus arrhythmia were assessed to ascertain whether any differences exist in the degree of parasympathetic control on cardiac rhythm between two ethnic groups. The standard deviation of the R-R interval (the R peak-to-peak interval of two QRS complexes of an electrocardiogram) has been used as a noninvasive parameter to measure the degree of parasympathetic cardiac control. Nine black and nine white healthy male volunteers took part in study after approval by the Research and Ethics Committee of the Medical University of South Africa. Thirty consecutive electrocardiographic complex were recorded during each of the following: 3 deep inspirations and expirations, incremental cumulative atropine injections of 0.001 mg/kg until 0.005 mg/kg, followed by two injections of 0.01 mg/kg and 0.015 mg/kg of atropine each. After each of the last two injections the deep inspiration and expiration procedure was repeated. No significant differences could be found at any stage for any parameter between the groups. In both groups the R-R interval variation increased threefold during voluntary induced respiratory sinus arrhythmia. This effect was blocked after 0.01 mg/kg of atropine. The degree of parasympathetic control was not affected by any respiratory maneuver, but was affected by atropine. A significant inverse quadratic relationship was found between parasympathetic control and heart rate change (R = .984 for whites, and R = .905 for blacks). A poor correlation was found between the R-R interval variation and heart rate changes. In conclusion, ethnicity does not affect parasympathetic activity.(ABSTRACT TRUNCATED AT 250 WORDS)