Fucoxanthin and Its Metabolite Fucoxanthinol Do Not Induce Browning in Human Adipocytes

Rodent studies suggest that the antiobesity effects of fucoxanthin relate to activation of brown fat and conversion of white adipocytes to the brown phenotype. To evaluate the browning effect in human adipocytes, we investigated the genes involved in browning and measured the oxygen consumption rate (OCR). Data were analyzed by one way ANOVA. Relative to control, fucoxanthinol (1 mu M, 0.1 mu M, 0.01 mu M, 1 nM, 0.1 nM), the metabolite present in human plasma, stimulated lipolysis acutely (mean +/- SEM: 4.2 +/- 0.8, 3.1 +/- 0.6, 4.1 +/- 0.9, 3.8 +/- 0.7, 3.8 +/- 0.7, respectively, p < 0.01). There was no effect on OCR or the mRNA expression of UCP1, CPT-1 beta, and GLUT4, the genes associated with browning of adipose tissue, when human adipocytes were treated with fucoxanthin or fucoxanthinol. -mRNA expression of PGC-1 alpha, PPAR alpha, PPAR gamma, PDK4, FAS, and the lipolytic enzymes was not significantly altered by fucoxanthinol treatment (p > 0.05). Thus, in human adipocytes, fucoxanthin and its metabolite do not stimulate conversion of white adipocytes to the brown phenotype.