Repeated Oral Administration of Flavan-3-ols Induces Browning in Mice Adipose Tissues Through Sympathetic Nerve Activation

We previously found increases in uncoupling protein (Ucp)-1 transcription in brown adipose tissue (BAT) of mice following a single oral dose of flavan 3-ols (FL), a fraction of catechins and procyanidins. It was confirmed that these changes were totally reduced by co-treatment of adrenaline blockers. According to these previous results, FL possibly activates sympathetic nervous system (SNS). In this study, we confirmed the marked increase in urinary catecholamine (CA) s projecting SNS activity following a single dose of 50 mg/kg FL. In addition, we examined the impact of the repeated administration of 50 mg/kg FL for 14 days on adipose tissues in mice. In BAT, FL tended to increase the level of Ucp-1 along with thermogenic transcriptome factors, such as peroxisome proliferator-activated receptor γ coactivator (PGC)-1α and PR domain-containing (PRDM)1. Transcription of browning markers, such as CD137 and transmembrane protein (TMEM) 26 in addition to PGC-1α were increased in epididymal adipose (eWAT) by FL. A multilocular morphology with cell size reduction was shown in the inguinal adipose (iWAT), together with increasing the level of Ucp-1 following administration of FL. These results suggest that FL produces browning in adipose through activation of the SNS.