It is well known that many HCAR2 ligands, including niacin, acipimox, and acifran, have been approved for clinical treatment of dyslipidemia, whereas their therapeutic value is limited by an uncomfortable cutaneous flushing effect, attributed to the activation of HCAR2 on Langerhans cells and keratinocytes [24,25]. This evidence concerns the gene HCAR2 and metabolic syndrome.