Influence of mental stress and circadian cycle on pastprandial lipemia

Background: Mental stress produces alterations in serum lipids and lipoprot eins. Objective: The objective was to assess the effect of mental stress during t he day and night on postprandial lipoproteins. Design: Fourteen healthy subjects aged 26.6 +/- 5.0 y were given randomly t he same meal either at night (0100) or during the day (1300), with or witho ut (control session) a mental stress challenge. The meal contained 40% of e stimated daily energy needs. The mental task was performed on a computer an d consisted of a task of choice reaction. Blood samples were drawn at basel ine and hourly for 7 h after the meal. Results: Urinary epinephrine concentrations were higher (P < 0.012) during the mental task than during the control sessions. Repeated-measures analysi s of variance showed that mean postprandial triacylglycerol concentrations were significantly higher (P < 0.02) and total cholesterol (P < 0.0001) and HDL-cholesterol concentrations were significantly lower (P < 0.0001) at ni ght than during the day. The mean postprandial VLDL-triacylglycerol concent ration was significantly higher (P < 0.04) during the mental task than duri ng the control sessions. Similarly, the VLDL-cholesterol response, calculat ed as the area under the postprandial curve, was significantly greater (P < 0.02) during the mental task than during the control sessions. There was n o interaction between mental stress and nyctohemeral cycle on postprandial lipoprotein responses, suggesting that both indexes act independently on po stprandial lipid metabolism. Conclusions: Mental stress is associated with increased concentrations of p ostprandial triacylglycerol-rich lipoprotein fractions. Therefore, postpran dial hyperlipidemia is one possible mechanism contributing to the higher ri sk of ischemic heart disease in stressed people.