Oxidation of high doses of serotonin favors lipid accumulation in mouse and human fat cells.
Ključne riječi
Sažetak
METHODS
The ingestion of serotonin-rich food (bananas, chocolate) increases 5-hydroxytryptamine (5-HT) in blood and its corresponding oxidation products in urines but without direct central consequences since the neurotransmitter does not easily cross the blood-brain barrier. However, there are numerous peripheral effects of serotonin, and recently, 5-HT aldehydic oxidation products have been demonstrated to behave as ligands of peroxisome proliferator-activated receptor γ (PPAR-γ). Since this nuclear factor manages lipid handling by adipose tissue, the response of fat cells to 5-HT exposure needed further investigation.
RESULTS
Serotonin oxidation was studied on human adipose tissue homogenates and mouse 3T3F442A preadipocytes by fluorometric and radiometric methods. Gene expression was assessed by real-time RT-PCR in human adipocytes and in 3T3F442A after mid- and long-term exposure to 5-HT while triacylglycerols and proteins were assessed by spectrophotometry. Six-hour exposure of human adipocytes to 250 μM 5-HT increased gene expression of lipid-binding proteins, glucose carriers, and enzymes of triacylglycerol synthesis (FABP4, CD36, GLUT1, and phosphoenolpyruvate carboxykinase), as did rosiglitazone treatment. Long-term serotoninergic stimulation of cultured 3T3F442A preadipocytes by 100-250 μM 5-HT enhanced fat storage and upregulation of PPAR-γ-responsive genes, in a manner sensitive to MAO- or PPAR-γ inhibition. Our observations suggest an unpredicted peripheral effect of serotonin on adipose tissue that depends on its amine oxidation.
CONCLUSIONS
Besides being centrally active on eating behavior, 5-HT may promote PPAR-γ activation and subsequent lipogenic effects in fat cells, raising the interest to consider its level in future diet formulations.
