Glucagon-like peptide 1 (GLP-1), an incretin hormone well known for its glucose-lowering effect, was recently reported to exert an anabolic effect on bone. Although the exact mechanism is not known, it likely involves the GLP-1 receptor (GLP-1R), which is expressed in some osteoblastic cell lines. Adipose-derived stem cells (ADSCs) have mesenchymal stem cell-specific characteristics, including osteoblastic differentiation potential. We evaluated the expression of GLP-1R during osteogenic differentiation of ADSCs.
ADSCs were isolated from subcutaneous adipose tissue obtained from three male donors during plastic surgery and were subjected to osteogenic induction. Mineralization was assessed by Alizarin Red staining on day 21. Expression of alkaline phosphatase (ALP), osteocalcin (OC), and GLP-1R was measured by real-time polymerase chain reaction in triplicate for each patient on days 0, 7, 14, and 21. Target mRNA expression levels were normalized to that of β-actin.
ADSCs were fibroblast-like in morphology, adhered to plastic, and had multipotent differentiation potential, as assessed using specific antigen markers. The osteogenic markers ALP and OC were notably upregulated at 21 days. Osteogenic differentiation resulted in a time-dependent increase in the expression of GLP-1R (
We demonstrated upregulation of GLP-1R gene expression during osteogenic differentiation of ADSCs. This finding suggests that GLP-1 may induce osteogenic differentiation in bone tissue.
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Incretin-based therapies are rapidly becoming one of the main glycemic control strategies in diabetes. Considering the large numbers of papillary thyroid carcinomas (PTCs) and possible effects of glucagon-like peptide-1 (GLP-1) on cell proliferation, the expression of GLP-1 receptor (GLP-1R) in PTC is likely to have clinical significance. We performed this study to evaluate the expression of GLP-1R in PTC and the clinical meaning of GLP-1R expression in PTC.
Fifty-six cases of PTC, four cases of medullary thyroid cancer (MTC), seven cases of nodular hyperplasia and 56 normal thyroid tissue samples were selected for immunostaining for GLP-1R. Clinical parameters were obtained by retrospective review of medical records.
Immunohistochemical staining for GLP-1R showed immunoreactivity in 18 of 56 cases of PTC (32.1%). All four cases of MTC exhibited cytoplasmic GLP-1R expression. Nodular hyperplasia exhibited immunoreactivity in two of seven cases (28.6%). All normal thyroid follicular cells showed negative immunoreactivity. In univariable and multivariable analyses, tumor multifocality was negatively correlated with GLP-1R expression. Extrathyroidal extension showed positive association with GLP-1R expression that was almost significant. Sex, age, tumor size, and lymph node metastasis were not significantly associated with GLP-1R expression.
Some parts of PTC tissues express GLP-1R, and GLP-1R expression in PTC was negatively correlated with tumor multifocality. The long-term influence of pharmacologically increased GLP-1 on thyroid follicular cells and development and progression of tumors originating from thyroid follicular cells should be investigated.
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