ATG4B and obesity due to melanocortin 4 receptor deficiency: Interestingly, the amelioration of obesity-linked parameters observed in spermidine-treated mice was associated with increased expression of ATG4B protein in spermidine-treated mice, which supports our results from Atg4b-null mice pointing to a protective anti-obesity role for ATG4B protease and autophagy pathway in diverse experimental settings.