Availability of abundant thiamine determines efficiency of thermogenic activation in human neck area derived adipocytes

Brown/beige adipocytes express uncoupling protein-1 (UCP1) that enables them to dissipate energy as heat. Systematic activation of this process can alleviate obesity. Human brown adipose tissues are interspersed in distinct anatomical regions including deep neck. We found that UCP1 enriched adipocytes differentiated from precursors of this depot highly expressed ThTr2 transporter of thiamine and consumed thiamine during thermogenic activation of these adipocytes by cAMP which mimics adrenergic stimulation. Inhibition of ThTr2 led to lower thiamine consumption with decreased proton leak respiration reflecting reduced uncoupling. In the absence of thiamine, cAMP-induced uncoupling was diminished but restored by thiamine addition reaching the highest levels at thiamine concentrations larger than present in human blood plasma. Thiamine is converted to thiamine pyrophosphate (TPP) in cells; the addition of TPP to permeabilized adipocytes increased uncoupling fueled by TPP-dependent pyruvate dehydrogenase. ThTr2 inhibition also hampered cAMP-dependent induction of UCP1, PGC1a, and other browning marker genes, and thermogenic induction of these genes was potentiated by thiamine in a concentration dependent manner. Our study reveals the importance of amply supplied thiamine during thermogenic activation in human adipocytes which provides TPP for TPP-dependent enzymes not fully saturated with this cofactor and by potentiating the induction of thermogenic genes. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=179 SRC="FIGDIR/small/490662v3_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@f8b9a9org.highwire.dtl.DTLVardef@1653d1corg.highwire.dtl.DTLVardef@18f3266org.highwire.dtl.DTLVardef@35f78d_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIAbundant thiamine is required for efficient activation of UCP1 dependent thermogenesis in human deep neck derived adipocytes C_LIO_LIInhibition of thiamine transporters leads to decreased thermogenic response C_LIO_LIIn stimulated adipocytes, thiamine supply provides extra thiamine pyrophosphate for increasing pyruvate dehydrogenase activity to generate sufficient fuel of UCP1 dependent respiration C_LIO_LIAdrenergic stimulation of thermogenic gene expression is potentiated by thiamine in a concentration dependent manner C_LI