Influence of high glucose and advanced glycation end-products (ages) levels in human osteoblast-like cells gene expression

Abstract

Background: Type 2 diabetes mellitus (T2DM) is associated with an increased risk of osteoporotic fracture. Several factors have been identified as being potentially responsible for this risk, such as alterations in bone remodelling that may have been induced by changes in circulating glucose or/and by the presence of non-oxidative end products of glycosylation (AGEs). The aim of this study is to assess whether such variations generate a change in the gene expression related to the differentiation and osteoblast activity (OPG, RANKL, RUNX2, OSTERIX, and AGE receptor) in primary cultures of human osteoblast-like cells (hOB). Methods: We recruited 32 patients; 10 patients had osteoporotic hip fractures (OP group), 12 patients had osteoporotic hip fractures with T2DM (T2DM group), and 10 patients had hip osteoarthritis (OA group) with no osteoporotic fractures and no T2DM. The gene expression was analyzed in hOB cultures treated with physiological glucose concentration (4.5 mM) as control, high glucose (25 mM), and high glucose plus AGEs (2 μg/ml) for 24 h. Results: The hOB cultures from patients with hip fractures presented slower proliferation. Additionally, the hOB cultures from the T2DM group were the most negatively affected with respect to RUNX2 and OSX gene expression when treated solely with high glucose or with high glucose plus AGEs. Moreover, high levels of glucose induced a major decrease in the RANKL/OPG ratio when comparing the OP and the T2DM groups to the OA group. Conclusions: Our data indicates an altered bone remodelling rate in the T2DM group, which may, at least partially, explain the reduced bone strength and increased incidence of non-traumatic fractures in diabetic patients. Abbreviations: AGER, Advanced glycation end products receptor; AGEs, Advanced glycation end products; AP, Alkaline phosphatase; BMD, Bone mass density; BMI, Body mass index; cDNA, Complementary deoxyribonucleic acid; DM, Diabetes mellitus; DMEM, Dulbecco’s modified eagle medium; HbA1c, Glycated haemoglobin; hOB, Human osteoblasts-like cells; IGF-I, Insulin-like growth factor I; OA, Osteoarthritis; OP, Osteoporosis; OPG, Osteoprotegerin; OSX, Osterix; P1NP, Procollagen I N-terminal peptide; PBS, Phosphate-buffered saline; PSF, Penicillin/streptomycin/fungizone mix; PTH, Parathyroid hormone; RANK, Receptor activator of nuclear factor kβ; RANKL, Receptor activator of nuclear factor kβ ligand; RNA, Ribonucleic acid; T2DM, Type 2 diabetes mellitus; β-CTX, Carboxy-terminal telopeptide of type I collagen