Protection against overfeeding-induced weight gain in mice is preserved in obesity but does not require FGF21 or MC4R

Experimental overfeeding triggers homeostatic compensatory mechanisms that counteract weight gain. Here, we utilized intragastric overfeeding in mice to investigate the physiological and molecular responses to forced weight gain. Both lean and diet-induced obese (DIO) mice exhibited a potent and prolonged lowering of voluntary food intake following overfeeding-induced weight gain. Although overfeeding resulted in a marked increase in circulating fibroblast growth factor 21 (FGF21), experiments with FGF21 knockout (KO) mice demonstrated that FGF21 is dispensable for the homeostatic defense against experimental weight gain. Targeted proteomics unveiled novel circulating factors linked to overfeeding, including the protease legumain (LGMN). Notably, administration of recombinant LGMN lowered body weight and food intake in DIO mice. The protection against weight gain was also associated with reduced vascularization in the hypothalamus and sustained reductions in transcript levels of the orexigenic neuropeptides, Npy and AgRP, suggesting a role of hypothalamic signaling in the homeostatic recovery from overfeeding. Overfeeding of melanocortin 4 receptor (MC4R) KO mice showed that these mice can suppress voluntary food intake and counteract the enforced weight gain, although their rate of weight recovery is impaired. Collectively, these findings demonstrate that the defense against overfeeding-induced weight gain remains intact in obesity and involves mechanisms independent of both FGF21 and MC4R. Overall design: 18-week-old chow-fed male C57BL6/J mice were fed by liquid infusion. On day 14, overfeeding was terminated and switched to sterile water infusion. On day 14 control and overfed mice were sacrificed to collect brain. On day 17 (d14+3), control and overfed mice were sacrificed, and the same tissue were collected.