Increased GLUT1 expression and localization to Golgi apparatus of acinar cells in the parotid gland of Goto-Kakizaki diabetic rats

Patients with diabetes are known to have high salivary glucose levels. But the mechanisms are still unclear. We hypothesized that the topological changes of glucose transporters affect the salivary glucose level. We used adult Goto-Kakizaki (GK) rats, an animal model of advanced diabetes, and Wistar rats as a control, with or without glucose load. The sections of salivary glands from the animals were processed for standard histological, immunohistochemical, and immunofluorescent staining. Parotid acinar cells of GK rats appeared like mucous filled with low-eosin-stained granules and possessing a flat nucleus located basally, whereas those of Wistar rats appeared as a typical serous gland with eosin-rich cytoplasm and a spherical nucleus. Cytoplasmic granules of GK rat parotid acinar cells showed no reaction of polysaccharide staining. In acinar cell cytoplasm of GK rats, intense GLUT1 immunoreactivity was observed compared to Wistar rats. By double immunostaining for GLUT1 and Golgi apparatus-specific markers, it was determined that GLUT1 was localized to the Golgi apparatus. By glucose loading in starved GK rats, the distribution of GLUT1-immunoreactive signals was spread out clearly from the apical side of the nucleus to the basolateral side. In rat model of diabetes, highly localized GLUT1 at Golgi apparatus in acinar cells seems to increase taking up cytoplasmic glucose to form exocytotic vesicles. This phenomenon may transform parotid glands from serous to mucous-like and result in saccharide-rich saliva. •Goto-Kakizaki diabetic rats had mucus-like, other than serous, parotid acinar cells.•Glucose transporter 1 (GLUT1) was localized mainly to trans-Golgi network.•GLUT1 seems to take up glucose to be released as mammary glands do.•By glucose loading, the distribution of GLUT1 was changed.•Chronic high blood glucose levels may change parotid glands to mucous-like by GLUT1.