Serum levels of numerous obesity-linked chemokines promoting adipocyte proliferation (TIMP-1 [38]) and adipose macrophage infiltration (CXCL1 [39, 40], CXCL2 [41], CXCL12 [42], CCL3 [43], and CCL5 [44]) were found to be significant predictors of in vivo hippocampal TSPO signals. Here, TSPO is linked to obesity due to melanocortin 4 receptor deficiency.