SRM and obesity due to melanocortin 4 receptor deficiency: Spermidine synthase (Srm) was decreased in the adipose tissue of ABA mice, and the product of this enzyme, spermidine, is known to play a role in lipolysis in visceral fat (Liao et al. 2021) and increased spermidine levels are associated with obesity (Gao et al. 2022).