Downregulation of Pgc-1α expression by tea leaves and their by-products

Previous studies indicate that muscle Pgc-1α expression governs the proportion of muscle fibre types. As a first step in using diet to manipulate the proportion of muscle fibre types by using Pgc-1α expression, the present study investigates the modulation of Pgc-1α expression by feedstuffs. A luciferase-based Pgc-1α reporter construct (Pgc-1α(-2553)-luc) that contains the mouse Pgc-1α promoter (-2553 to +78 bp) was prepared. A screen of ethanol extracts from 33 feedstuffs indicated that oolong tea and roasted green tea extracts decreased Pgc-1α(-2553)-luc expression in C2C12 myoblasts. The transcriptional repression of Pgc-1α by tea leaf extracts was reproduced in hepatic HepG2 cells. We further examined the effects of the alcohol extracts of tea waste and its silage on Pgc-1α transcription; the tea waste silage extract inhibited Pgc-1α transcription. Treatment with the extracts of raw tea leaves, tea waste and tea waste silage effectively decreased Pgc-1α mRNA levels during myogenesis of myosatellite cells. The present results suggest that tea leaves and their by-products could be used to modulate proportions of muscle fibre types.