The Impact of Mental Challenge on Indicators of Endothelial Function in Obese Individuals

摘要: A number of investigators have examined psychological stress-induced endothelial dysfunction, however, the underlying mechanisms for these responses have not been clearly elucidated. The purpose of this study was to compare the effects of mental challenge on forearm blood flow, total antioxidant capacity (a measure of oxidative stress), the release of norepinephrine (NE; stress induced neurotransmitter), and pro-inflammatory cytokine responses [both lipopolysaccharide (LPS)-stimulated TNF-[alpha] and IL-6 cytokine and mRNA] in lean and obese individuals. Twelve subjects who had a BMI above 30 kg/m2 and were above 30% body fat were categorized as obese and twelve subjects with a BMI below 25 kg/m2 and were below 25% body fat were categorized as lean subjects. Blood samples were drawn and forearm blood flow was assessed prior to and following subjects' participation in a mental challenge protocol consisting of a computer-based Stroop Color-Word task and mental arithmetic task, for a total of 20 minutes. The mental challenge elicited an elevation in HR and NE in both the lean and obese groups. Furthermore, both lean and obese groups demonstrated an increase in FBF following the mental challenge, whereas no changes in total antioxidant capacity were observed. In addition, the lean group exhibited an increase in LPS-stimulated TNF-[alpha] cytokine production from baseline to following the mental challenge, whereas the obese group demonstrated a decrease in LPS-stimulated TNF-[alpha] cytokines. This corresponded with a decrease in LPS-stimulated TNF-[alpha] mRNA expression in the obese group, although the obese subjects maintained higher levels of both measurements (LPS-stimulated TNF-[alpha] cytokine and mRNA expression) compared with the lean group. Furthermore, in the LPS-stimulated IL-6 cytokine response, the obese group demonstrated a greater increase than the lean group following the mental challenge, even though both groups showed an increase in LPS-stimulated IL-6 mRNA expression. These findings suggest that the magnitude and direction of LPS-stimulated TNF-[alpha] cytokine response and mRNA expression and LPS-stimulated IL-6 cytokine response to acute stress may be dependent upon the effects of the additional percentage of body fat seen in obese individuals.