MM cells induce lipolysis in adipocytes. (A) LipidTOX-stained images of mature OP9 adipocytes alone or cocultured with 5TGM1 murine or OPM2 human MM cells. (B) Lipid droplet area was calculated by using ImageJ software (National Institutes of Health) and depicted for OP9 adipocytes alone or cultured along with 5TGM1 and OPM2 cells. (C) 5TGM1 cells were cultured alone or cocultured with OP9 adipocytes for 24 hours and were used for the detection of glycerol. Isoproterenol was used as a positive control. (D) Detection of glycerol in OP9 adipocytes cocultured with MM cell lines of human origin, including MM.1S, INA6, KMS-12, and OPM2. (E) Messenger RNA (mRNA) was isolated from the fat fractions of BM aspirates from HD and patients with MGUS/SMM, NDMM, and RRMM. Gene expression analysis was conducted by using a real-time PCR array of human peroxisome proliferator-activated receptor (PPAR) targets. Heatmap representing partial list of differentially expressed genes related to FA metabolism. mRNA expressions were quantified for genes involved in lipolysis (LPL, NR1H3, PPARα, LIPE, MGLL, PLIN1, and ABHD5) (F) and/or genes involved in FA synthesis and FA desaturation (ACSL1, ACSL4, FASN, SCD1, FASD1, and FASD2) (G) by quantitative PCR. Biospecimens from patients with MGUS and SMM were analyzed independently but were pooled together for analysis purposes. Data are presented as mean ± standard error of the mean. *P < .05.