PUGNAc is a 1,5-hydroximolactone, acting as an inhibitor of a variety of N-acetylhexosaminidases. It was long thought that increased levels of O-GlcNAc in human cells lead to Type II diabetes. O-GlcNAc levels were artificially raised with PUGNAc, which inhibits O-GlcNAcase, a beta-exo-N-acetylhexosaminidase which cleaves beta-O-linked-N-acetylglucosamine residues from glycoproteins. As a result of this inhibition, a type II diabetic phenotype was observed. Recent pharmacological studies using a more selective O-GlcNAcase inhibitor did not see this effect. However, genetic manipulation of O-GlcNAc levels is consistent with the effects observed by PUGNAc, namely insulin resistance upon elevation of O-GlcNAc levels.