Green tea improves the metabolism of peripheral tissues in β3-adrenergic receptor-knockout mice

Our goal was to establish the requirement of beta 3 adrenoceptor (beta 3Adr) for green tea (GT) effects on the energy metabolism of obese mice. This study was carried out in wild-type (WT) and beta 3Adr knockout (KO) male mice fed with a standard diet or a high-fat diet (HFD/16 weeks) treated or not with GT (0.5 g/kg of body weight (BW)/12 weeks). GT-treatment attenuated final BW, BW gain, and adiposity index increased by HFD, improving insulin resistance (IR) and FGF21 level, without changing the food intake of WT mice. GT-treatment of beta 3AdrKO mice attenuated only IR, denoting GT-effects independent of beta 3Adr. We observed increased lipolysis accompanied by decreased adipocyte size in white adipose tissue (WAT) as well as browning of the subcutaneous WAT induced by GT in a way dependent on beta 3Adr. In brown adipose tissue (BAT) mRNA levels of lipolytic/oxidative genes, including beta 3Adr/Ucp1 and energy expenditure (EE) was increased by GT dependent on beta 3Adr. GT-treatment increased adiponectin independent of beta 3Adr. Also, independent of beta 3Adr pathway GT promoted an increase in beta 2Adr/Ucp1 mRNA levels and EE in BAT whereas; in the liver, GT has a dual role in increasing lipid synthesis and oxidation. These data lead us to suggest that GT uses beta 3Adr pathway activation to achieve some of its beneficial health effects.