MMP12 and Insulin resistance: Moreover, expression of nitric oxide synthase 2 (Nos2), a marker of M1, classically activated, proinflammatory macrophages and insulin resistance, was markedly decreased in adipose tissue of MMP12−/− mice (but also in stimulated dendritic cells and macrophages), while significantly increased in WAT of MMP12+/+ mice under a HFD, suggesting that MMP12 deficiency alters macrophage recruitment and polarization under nutrient stress in mice.