Elevated plasma fatty acid concentrations stimulate the cardiac autonomic nervous system in healthy subjects

Background: Fatty acids have been shown to stimulate the sympathetic nervou s system in rats. Power spectral analysis of heart rate variability (HRV) i s a safe and useful tool with which to evaluate cardiac autonomic nervous s ystem (ANS) activity. Whether changes in plasma fatty acid concentrations a ffect the sympathetic nervous system or HRV in humans is unknown. Objective: We investigated the possible changes in HRV after a significant increase in plasma fatty acid concentration. Design: Subjects were randomly assigned to receive an infusion of lipid emu lsion (10% triacylglycerol emulsion for 180 min) + heparin (a bolus of 200 U followed by 0.2 U.min(-1).kg body wt(-1); n = 20) or 0.9% NaCl (for 180 m in; n = 10). Results: Lipid emulsion + heparin infusion was associated with a rise in pl asma epinephrine and norepinephrine concentrations. The rise in plasma fatt y acid concentration was associated with a significant decline in the RR in terval (P < 0.03) and in total power (P < 0.03). Analysis of the different components of HRV showed that lipid emulsion + heparin infusion stimulated low-frequency (LF) components (P < 0.03 at the second hour and P < 0.01 at the third hour) and inhibited high-frequency (HF) components (P < 0.03 at t he second and third hours). Consequently, the LF-HF ratio was significantly stimulated (P < 0.03 at. the second hour and P < 0.01 at the third hour). Such results persisted, although attenuated, when the study was repeated in association with a propranolol infusion (n = 8). Conclusion: Elevated plasma fatty acid concentrations may stimulate cardiac autonomic nervous system activity.