The peroxisome proliferator-activated receptors (PPAR) have been extremely successful as drug targets, with numerous marketed drugs targeting the alpha and gamma PPARs. Now, work by researchers at GlaxoSmithKline plc (GSK, London, U.K.) suggests that the function of a third member of the family, PPAR delta, is adaptation to changes in the lipid content of the diet.

PPARs are members of the nuclear hormone receptor superfamily that are important for storing and breaking down fatty acids. Three PPAR subtypes (alpha, gamma and