Association of metabolic syndrome with reduced central serotonergic activity.

The aim of this study was to determine the differences between two groups of adolescents with metabolic syndrome (MetS) and normal controls in relation to brain serotonergic activity through intensity-dependent auditory-evoked potentials (IDAEPs) and plasma free fraction of L-tryptophan. Eighteen adolescents with MetS and thirteen controls were studied. Free fraction, bound and total plasma L-tryptophan, glucose, cholesterol, triglycerides, HDL-cholesterol, albumin and IDAEPs were determined. Glycemia, triglycerides were significantly elevated, and HDL-cholesterol in plasma was significantly reduced. Free fraction and free fraction/total L-tryptophan ratio were decreased. The slope of the amplitude/stimulus intensity function of the N1/P2 component significantly increased in adolescents with MetS. Decrease of free fraction of L-tryptophan in plasma and increase of the slope of the N1/P2 component suggest a low brain serotonin tone. Cortex responses are regulated by serotonergic innervations and may show a different behavior in young patients with MetS. Therefore, the slope of the N1/P2 component along with the free fraction of L-tryptophan in plasma, indicate that in adolescents with MetS the state of serotonergic brain activity is depressed and possibly related to psychiatric disorders.