ATRN and obesity due to melanocortin 4 receptor deficiency: As a demonstration of theparamount role of this protein for the kidney structure, attractin-deficientmice have a severe loss of extracellular proteoglycans between kidneytubules in addition to a loss of glycosylated material within theintratubular brush border. The reductionin the abundance of α-1-acid glycoproteins (α1-AGP) 1and 2, which are known to affect vascular permeability, unveils anotherpotential mechanism for the nephroprotective effects of weight lossin patients with obesity.