Single Cell RNA Profiling Reveals Adipocyte to Macrophage Signaling Sufficient to Enhance Thermogenesis

Adipocytes deficient in fatty acid synthase (iAdFASNKO) emit signals that mimic cold exposure to enhance the appearance of thermogenic beige adipocytes in mouse inguinal white adipose tissues (iWAT). Both cold- and iAdFASNKO-induced iWAT “browning” pathways upregulate the sympathetic nerve fiber (SNF) modulator Nrg4 and activate SNFs adjacent to beige adipocytes. Adipocyte cAMP/protein kinase A signaling is necessary for beige adipocyte appearance, as we show here it is blocked in Gsa deficient cold exposed or iAdFASNKO mice. Surprisingly however, denervation of iWAT failed to block adipocyte browning in iAdFASNKO mice, as it does in cold-exposed mice. Similarly, Nrg4 deficiency markedly reduced iWAT UCP1 in the cold, but not in double FASN/Nrg4 KO mice. Single-cell transcriptomic analysis of iWAT stromal cells revealed increased macrophages displaying gene expression signatures of the alternately activated type in iAdFASNKO mice, and their depletion abrogated iWAT beiging. Altogether, these findings reveal divergent cellular pathways are sufficient to cause adipocyte browning. Importantly, adipocyte signaling to enhance alternatively activated macrophages in iAdFASNKO mice is associated with enhanced adipose thermogenesis independent of the sympathetic neuron involvement this process requires in the cold. Overall design: We pooled SVF cells from iWAT from 7 control (C57BL/6) and 8 iAdFASNKO mice. The cells were separate into immune and non-immune cells via magnetic cell sorting. Single cell library preparation was performed using the 10X Genomics Single Cell 3' v3 according to the manufacturer's instructions.