title: Stimulation of glucose transport in osteoblastic cells by parathyroid hormone and insulin-like growth factor I.
abstract: Insulin and parathyroid hormone (PTH) regulate glucose metabolism in bone cells. In order to differentiate between the effects of these hormones and to compare the potency of insulin with that of insulin-like growth factor (IGF) I, we treated rat bone-derived osteoblastic (PyMS) cells for different time periods and at different concentrations with insulin, IGF I, or PTH, and measured [1-(14)C]-2-deoxy-D-glucose (2DG) uptake and incorporation of D-[U-(14)C] glucose into glycogen. 2DG uptake was Na-independent with an apparent affinity constant (K (M)) of ~2 mmol/l. Expression of the high affinity glucose transporters (GLUT), GLUT1 and GLUT3 but not of GLUT4, was found by Northern and Western analysis. Similar to the findings with primary rat osteoblasts, but distinct from those in rat fibroblasts, 2DG uptake and glycogen synthesis were increased in this cell line after exposure to low concentrations (0.1 nmol/l and above) of PTH. IGF I at low doses (0.3 nmol/l and above) or insulin at higher doses (1 nmol/l and above) stimulated 2DG uptake and [(3)H] thymidine incorporation into DNA. 2DG transport was enhanced already after 30 min of IGF I treatment whereas the effect of PTH became significant after 6 h. It is concluded that IGF I rather than insulin may be a physiological regulator of 2DG transport and glycogen synthesis in osteoblasts.
authors.affiliation: Clinic for Endocrinology and Diabetes, University Hospital of Zurich, Zurich, Switzerland. ezoidis@aua.gr
authors.forename: E
authors.initials: E
authors.lastname: Zoidis
authors.forename: C
authors.initials: C
authors.lastname: Ghirlanda-Keller
authors.forename: C
authors.initials: C
authors.lastname: Schmid
mesh_terms: D000818:Animals; D001692:Biological Transport; D002417:Cattle; D002478:Cells, Cultured; D003847:Deoxyglucose / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics / Q000378:metabolism*; D051272:Glucose Transporter Type 1 / Q000378:metabolism; D051274:Glucose Transporter Type 3 / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007700:Kinetics; D010006:Osteoblasts / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D051246:Glucose Transport Proteins, Facilitative; D051272:Glucose Transporter Type 1; D051274:Glucose Transporter Type 3; D051275:Glucose Transporter Type 4; D007328:Insulin; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D012333:RNA, Messenger; D011994:Recombinant Proteins; C495679:Slc2a1 protein, rat; C495690:Slc2a3 protein, rat; C495694:Slc2a4 protein, rat; C025076:parathyroid hormone (1-34), bovine; D007334:Insulin-Like Growth Factor I; D006003:Glycogen; D003847:Deoxyglucose