PPARD and metabolic syndrome: For example, ligand-mediated PPARδ activation significantly increased HDL cholesterollevels, possibly in association with decreased lipoprotein lipaseactivity, in insulin-resistant middle-aged obese rhesus monkeys [38]. In a primate model of the metabolic syndrome,PPARδ activationloweredplasma insulin levels, without any adverse effect on glycemiccontrol [38].