Anti-F4/80 monoclonal antibody, clone CN9.2 [Biotin]

Background: Visceral white adipose tissue (WAT) hypertrophy, adipokine production, inflammation and fibrosis are strongly associated with obesity, but the time-course of these changes in-vivo are not fully understood. Therefore, the aim of this study was to establish the time-course of changes in adipocyte morphology, adipokines and the global transcriptional landscape in visceral WAT during the development of diet-induced obesity. Results: C57BL/6 J mice were fed a high-fat diet (HFD) or normal diet (ND) and sacrificed at 8 time-points over 24 weeks. Excessive fat accumulation was evident in visceral WAT depots (Epidydimal, Perirenal, Retroperitoneum, Mesentery) after 2-4 weeks. Fibrillar collagen accumulation was evident in epidydimal adipocytes at 24 weeks. Plasma adipokines, leptin, resistin and adipsin, increased early and time-dependently, while adiponectin decreased late after 20 weeks. Only plasma leptin and adiponectin levels were associated with their respective mRNA levels in visceral WAT. Time-course microarrays revealed early and sustained activation of the immune transcriptome in epididymal and mesenteric depots. Up-regulated inflammatory genes included pro-inflammatory cytokines, chemokines (Tnf, Il1rn, Saa3, Emr1, Adam8, Itgam, Ccl2, 3, 4, 6, 7 and 9) and their upstream signalling pathway genes (multiple Toll-like receptors, Irf5 and Cd14). Early changes also occurred in fibrosis, extracellular matrix, collagen and cathepsin related-genes, but histological fibrosis was only visible in the later stages. Conclusions: In diet-induced obesity, early activation of TLR-mediated inflammatory signalling cascades by CD antigen genes, leads to increased expression of pro-inflammatory cytokines and chemokines, resulting in chronic low-grade inflammation. Early changes in collagen genes may trigger the accumulation of ECM components, promoting fibrosis in the later stages of diet-induced obesity. New therapeutic approaches targeting visceral adipose tissue genes altered early by HFD feeding may help ameliorate the deleterious effects of diet-induced obesity.

Autophagy is induced during differentiation of human monocytes into macrophages that is mediated by CSF1/CSF-1/M-CSF (colony stimulating factor 1 [macrophage]). However, little is known about the molecular mechanisms that link CSF1 receptor engagement to the induction of autophagy. Here we show that the CAMKK2-PRKAA1-ULK1 pathway is required for CSF1-induced autophagy and human monocyte differentiation. We reveal that this pathway links P2RY6 to the induction of autophagy, and we decipher the signaling network that links the CSF1 receptor to P2RY6-mediated autophagy and monocyte differentiation. In addition, we show that the physiological P2RY6 ligand UDP and the specific P2RY6 agonist MRS2693 can restore normal monocyte differentiation through reinduction of autophagy in primary myeloid cells from some but not all chronic myelomonocytic leukemia (CMML) patients. Collectively, our findings highlight an essential role for PRKAA1-mediated autophagy during differentiation of human monocytes and pave the way for future therapeutic interventions for CMML.