Serum brain-derived neurotrophic factor: Determinants and relationship with depressive symptoms in a community population of middle-aged and elderly people

OBJECTIVES: Brain-derived neurotrophic factor (BDNF) is involved in major depressive disorder and neurodegenerative diseases. Clinical studies, showing decreased serum BDNF levels, are difficult to interpret due to limited knowledge of potential confounders and mixed results for age and sex effects. We explored potential determinants of serum BDNF levels in a community sample of 1230 subjects. METHODS: Multiple linear regression analyses with serum BDNF level as the dependent variable were conducted to explore the effect of four categories of potential BDNF determinants (sampling characteristics, sociodemographic variables, lifestyle factors and somatic diseases) and of self-reported depressive symptoms (Beck's Depression Inventory (BDI). RESULTS: Our results show that BDNF levels decline with age in women, whereas in men levels remain stable. Moreover, after controlling for age and gender, the assays still showed lower serum BDNF levels with higher BDI sum scores. Effects remained significant after correction for two main confounders (time of sampling and smoking), suggesting that they serve as molecular trait factors independent of lifestyle factors. CONCLUSIONS: Given the age-sex interaction on serum BDNF levels and the known association between BDNF and gonadal hormones, research is warranted to delineate the effects of the latter interaction on the risk of psychiatric and neurodegenerative diseases

Time-domain representation of ventricular-arterial coupling as a windkessel and wave system

The differences in shape between central aortic pressure (P-Ao) and flow waveforms have never been explained satisfactorily in that the assumed explanation (substantial reflected waves during diastole) remains controversial. As an alternative to the widely accepted frequency-domain model of arterial hemodynamics, we propose a functional, time-domain, arterial model that combines a blood conducting system and a reservoir (i.e., Frank's hydraulic integrator, the windkessel). In 15 anesthetized dogs, we measured P-Ao, flows, and dimensions and calculated windkessel pressure (P-Wk) and volume (V-Wk). We found that P-Wk is proportional to thoracic aortic volume and that the volume of the thoracic aorta comprises 45.1 +/- 2.0% (mean +/- SE) of the total V-Wk. When we subtracted P-Wk from P-Ao, we found that the difference (excess pressure) was proportional to aortic flow, thus resolving the differences between P-Ao and flow waveforms and implying that reflected waves were minimal. We suggest that P-Ao is the instantaneous summation of a time-varying reservoir pressure (i.e., P-Wk) and the effects of (primarily) forward-traveling waves in this animal model

Time-domain representation of ventricular-arterial coupling as a windkessel and wave system

The differences in shape between central aortic pressure (P-Ao) and flow waveforms have never been explained satisfactorily in that the assumed explanation (substantial reflected waves during diastole) remains controversial. As an alternative to the widely accepted frequency-domain model of arterial hemodynamics, we propose a functional, time-domain, arterial model that combines a blood conducting system and a reservoir (i.e., Frank\u27s hydraulic integrator, the windkessel). In 15 anesthetized dogs, we measured P-Ao, flows, and dimensions and calculated windkessel pressure (P-Wk) and volume (V-Wk). We found that P-Wk is proportional to thoracic aortic volume and that the volume of the thoracic aorta comprises 45.1 +/- 2.0% (mean +/- SE) of the total V-Wk. When we subtracted P-Wk from P-Ao, we found that the difference (excess pressure) was proportional to aortic flow, thus resolving the differences between P-Ao and flow waveforms and implying that reflected waves were minimal. We suggest that P-Ao is the instantaneous summation of a time-varying reservoir pressure (i.e., P-Wk) and the effects of (primarily) forward-traveling waves in this animal model