Fig. 2

Metabolic characteristics of M2/M [IL-4/IL-10] macrophages. (I) Arginine is metabolized by arginase to urea and ornithine, which participates in the synthesis of polyamines; (II) glycolytic activity is decreased, as M2 may selectively express PFKFB1, which has a low net activity to maintain higher F2,6BP concentrations that can promote PFK1 activity; (III) PPP activity is decreased because of CARKL upregulation; (IV) the TCA cycle is intact; (V) FAO pathway activity is enhanced; and (VI) glutamine metabolism is increased. Glutamine can contribute to replenishment of the TCA cycle and the production of UDP-GlcNAc, which promotes the glycosylation of lectin/mannose receptors—among the most typical M2 polarization markers. In addition, GS is expressed in M2 macrophages and plays a positive role in M2 (IL-10) polarization. GLUT, glucose transporter; HK, hexokinase; G6P, glucose-6-phosphate; F6P, fructose 6-phosphate; F1,6BP, fructose-1,6-bisphosphate; F2,6BP, fructose-2,6-bisphosphate; RU5P, ribulose-5-phosphate; α-KG, α-ketoglutarate; CARKL, carbohydrate kinase-like protein; PKM2, pyruvate kinase; PFK1, phosphofructokinase1; PDH, pyruvate dehydrogenase; CPT, carnitine palmitoyltransferase; FA, fatty acid; LAL, lysosomal acid lipase; GLS, glutaminase; GS, glutamine synthetase; Arg1, arginase 1