C3 and obesity due to melanocortin 4 receptor deficiency: In conclusion, the results of this study indicate that cats with obesity present alterations in the concentrations of serum proteins with increase in Ig-like domain-containing protein, Alpha-2-HS-glycoprotein, Complement C8 gamma chain, Antithrombin-III, Serpin family A member 1, Complement factor H, C3-beta-c, Albumin, and C4b-binding protein alpha chain, and decrease in Alpha-1-B glycoprotein, Solute carrier family 12 member 4, and Fibronectin.