Human Fibroblasts Ubiquitously Express Glutamic Acid Decarboxylase 65 (GAD 65): Possible Effects of Connective Tissue Inflammation on GAD Antibody Titer

Background: Type 1 diabetes is caused by a destruction of pancreatic β cells due to autoimmunity. Autoantibody against glutamic acid decarboxylase (GAD) 65 expressed in pancreatic β cells is widely used as a predictive marker for pancreatic destruction. In this study, we hypothesized that if certain cells in periodontal tissues could express GAD, then it may influence GAD antibody titer. Methods: We used: 1) reverse transcription-polymerase chain reaction (PCR) analysis to detect GAD 65 mRNA in various cells; 2) nucleotide sequencing analysis to confirm that amplified PCR product is the gene encoding GAD; and 3) Western blotting to determine the expression of GAD 65 protein in human gingival fibroblasts. Immunohistochemical staining of GAD 65 protein in normal and inflamed gingiva was performed to examine the potential influence of periodontal inflammation on GAD 65 expression. GAD antibody titer in sera of periodontal patients as well as healthy subjects was measured to determine if periodontal patients ...