Metabolic syndrome perturbs deglucosylation and reglucosylation in the glycoprotein folding cycle.

Deglucosylation and reglucosylation of glycoproteins by glucosidase II and uridine diphosphate-glucose: glycoprotein glucosyltransferase 1 (UGGT1), respectively, are important steps in glycoprotein quality control. Misfolded glycoprotein accumulation is associated with endoplasmic reticulum stress and can lead to protein misfolding diseases such as metabolic syndrome. Here, we analyzed the expression and activities of glucosidase II and UGGT1 in rat models of obesity and obese type 2 diabetes, and phenotypes associated with moderate and severe metabolic syndrome, respectively. In obesity, the mRNA and protein levels of glucosidase II and UGGT1 are decreased and their activities are reduced. In obese type 2 diabetes, the mRNA and protein levels of these enzymes are increased, and glucosidase II activity is slightly recovered, although UGGT1 activity is reduced. Our findings suggest that metabolic syndrome affects deglucosylation/reglucosylation enzymes according to disease severity.