High Glucose Reduces the Paracellular Permeability of the Submandibular Gland Epithelium via the MiR-22-3p/Sp1/Claudin Pathway

Abstract

Tight junctions (TJs) play an important role in water, ion, and solute transport through the paracellular pathway of epithelial cells; however, their role in diabetes-induced salivary gland dysfunction remains unknown. Here, we found that the TJ proteins claudin-1 and claudin-3 were significantly increased in the submandibular glands (SMGs) of db/db mice and high glucose (HG)-treated human SMGs. HG decreased paracellular permeability and increased claudin-1 and claudin-3 expression in SMG-C6 cells. Knockdown of claudin-1 or claudin-3 reversed the HG-induced decrease in paracellular permeability. MiR-22-3p was significantly downregulated in diabetic SMGs and HG-treated SMG-C6 cells. A miR-22-3p mimic suppressed claudin-1 and claudin-3 expression and abolished the HG-induced increases in claudin-1 and claudin-3 levels in SMG-C6 cells, whereas a miR-22-3p inhibitor produced the opposite effects. Specificity protein-1 (Sp1) was enhanced in diabetic SMGs and HG-treated SMG-C6 cells, which promoted claudin-1 and claudin-3 transcription through binding to the corresponding promoters. A luciferase reporter assay confirmed that miR-22-3p repressed Sp1 by directly targeting the Sp1 mRNA 3′-untranslated region (3′-UTR). Consistently, the miR-22-3p mimic suppressed, whereas the miR-22-3p inhibitor enhanced, the effects of HG on Sp1 expression. Taken together, our results demonstrate a new regulatory pathway through which HG decreases the paracellular permeability of SMG cells by inhibiting miR-22-3p/Sp1-mediated claudin-1 and claudin-3 expression.

Ginger Root Extract Improves GI Health in Diabetic Rats by Improving Intestinal Integrity and Mitochondrial Function

“…In the current study, compared to the Control rats, the DM rats show decreased intestinal barrier function, as demonstrated by decreased gene and protein (colon) expression of Claudin-3. Our findings are consistent with the previous studies using HFD-induced prediabetic mice [ 22 ] and db/db diabetic mice [ 23 , 24 ]. Nascimento et al reported that the tight junction-mediated barrier in intestinal tissues, such as the duodenum, jejunum, ileum and colon epithelia, was significantly weakened in prediabetic mice [ 22 ].…”

Western blot normalization: Time to choose a proper loading control seriously

“…There were 2 transcripts relative to actin and 4 transcripts relative to tubulin changing significantly in the aortas of Angiotensin II‐infused mice (Table S5). For diabetes mellitus, streptozotocin injected mice (GSE179718 [39], GSE179717 [39], and GSE155377), diabetes‐prone db/db mice (GSE169275 [40] and GSE141411 [41]), and diabetes‐resistant ob/ob mice (GSE169275 [39]) were analyzed. As a result, 1 transcript about actin and 1 transcript about tubulin changed significantly in visceral adipose tissue of streptozotocin‐injected mice.…”

Sp1 transcription factor represses transcription of phosphatase and tensin homolog to aggravate lung injury in mice with type 2 diabetes mellitus-pulmonary tuberculosis

“…The expression and mitochondrial fission of SP1 was found to be significantly increased in a diabetic or high-glucose environment [ 38 ]. Similarly, elevated SP1 level was detected in diabetic submandibular glands as well as the high-glucose-treated SMG-C6 cells, which was induced by the downregulation of its suppressor microRNA-22-3p [ 39 ]. As a transcription factor, SP1 bound to the promoter of phosphoglycerate mutase family member 5 to aggravate diabetic renal tubular injury [ 38 ].…”