Scavenging dicarbonyls with 5’-O-pentyl-pyridoxamine improves insulin sensitivity and reduces atherosclerosis through modulating inflammatory Ly6Chi monocytosis and macrophage polarization
BackgroundLipid peroxidation products impair HDL function and contribute to the development of atherosclerosis. Ours and other studies have shown that reactive dicarbonyls such as Isolevuglandins (IsoLG) and malondialdehyde (MDA), crosslink apoAI and impair the ability of HDL to promote cholesterol efflux. We examined whether scavenging of reactive dicarbonyls protects against the development of insulin resistance and atherosclerosis.Methods and ResultsHere, we found that 5’-O-pentyl-pyridoxamine (PPM), a potent scavenger of reactive dicarbonyls, abolished MDA-mediated crosslinking of apoAI in HDL by 80 % (P<0.05). In addition, PPM prevented the reduction in cholesterol efflux capacity of MDA treated HDL and preserved the cholesterol efflux capacity of MPO-modified HDL in Apoe−/− macrophages. Furthermore, PPM significantly improved the cholesterol efflux capacity and PON1 activity of HDL in Ldlr−/− mice (P<0.05), indicating that PPM protects HDL from modifications by reactive dicarbonyls and maintains HDL function in vivo. Importantly, PPM improved hyperglycemia and insulin sensitivity in male Ldlr−/− mice. Administration of 1 mg/mL of PPM, versus 1 mg/mL of the nonreactive analogue PPO, to Ldlr−/− mice consuming a western diet (WD) for 16 weeks reduced the extent of proximal aortic atherosclerosis by 48% and by 46% (P<0.05) in female and male Ldlr−/− mice. PPM also reduced the extent of en face aortic lesion by 52% in male Ldlr−/− mice. In addition, PPM reduced pro-inflammatory enzyme MPO expression by 57.5% and the number of TUNEL positive cells by 52% (P<0.01) in atherosclerotic lesions of Ldlr−/− mice. Immunohistochemistry studies revealed that PPM reduced the lesion macrophage content by 55% (P<0.05). Importantly, PPM increased M2 marker Arg1+ in macrophages of lesions and reduced the number of blood pro-inflammatory Ly6Chi monocytes and the ratio between Ly6Chi and Ly6Clow, but not the numbers of Ly6Clow, neutrophils in Ldlr−/− mice. Similarly, treatment of Apoe−/− mice on a WD for 16 weeks with PPM significantly reduced the extent of atherosclerotic lesions and also enhanced plaque stability as evidenced by a 47% increase in fibrous cap thickness and a 64.7% reduction in necrotic core area.ConclusionsReactive dicarbonyl scavenging with PPM in vivo preserves HDL function which improves insulin sensitivity and decreases atherosclerosis development. These results support the therapeutic potential of reactive dicarbonyl scavenging in the treatment of insulin resistance and atherosclerotic cardiovascular disease.