TLR4 and type 2 diabetes mellitus: However, during the progression of T2D, fatty acids stimulate pancreatic β-cells to produce chemokines that promote intra-islet accumulation of M1 macrophages5,25, and together with other TLR2/6 and TLR4 ligands stimulate the secretion of proinflammatory factors such as IL-1β from macrophages35.