title: Obesity does not aggravate osteoporosis or osteoblastic insulin resistance in orchiectomized rats.
abstract: The present study aimed to test the hypothesis that testosterone deprivation impairs osteoblastic insulin signaling, decreases osteoblast survival, reduces bone density, and that obesity aggravates those deleterious effects in testosterone-deprived rats. Twenty four male Wistar rats underwent either a bilateral orchiectomy (O, n=12) or a sham operation (S, n=12). Then the rats in each group were further divided into two subgroups fed with either a normal diet (ND) or a high-fat diet (HF) for 12 weeks. At the end of the protocol, blood samples were collected to determine metabolic parameters and osteocalcin ratios. The tibiae were collected to determine bone mass using microcomputed tomography and for osteoblast isolation. The results showed that rats fed with HF (sham-operated HF-fed rats (HFS) and ORX HF-fed rats (HFO)) developed peripheral insulin resistance and had decreased trabecular bone density. In ND-fed rats, only the ORX ND-fed rats (NDO) group had decreased trabecular bone density. In addition, osteoblastic insulin resistance, as indicated by a decrease in tyrosine phosphorylation of the insulin receptor and Akt, were observed in all groups except the sham-operated ND-fed rats (NDS) rats. Those groups, again with the exception of the NDS rats, also had decreased osteoblastic survival. No differences in the levels of osteoblastic insulin resistance and osteoblastic survival were found among the NDO, HFS, and HFO groups. These findings suggest that either testosterone deprivation or obesity alone can impair osteoblastic insulin signaling and decrease osteoblastic survival leading to the development of osteoporosis. However, obesity does not aggravate those deleterious effects in the bone of testosterone-deprived rats.
authors.affiliation: Department of PharmacologyFaculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Saranyapin
authors.initials: S
authors.lastname: Potikanond
authors.affiliation: Neurophysiology Unit, Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Pinyada
authors.initials: P
authors.lastname: Rattanachote
authors.affiliation: Center of Calcium and Bone Research (COCAB)Faculty of Science, Mahidol University, Bangkok, Thailand.
authors.forename: Hiranya
authors.initials: H
authors.lastname: Pintana
authors.affiliation: Department of Physiology Faculty of Science, Mahidol University, Bangkok, Thailand.
authors.forename: Panan
authors.initials: P
authors.lastname: Suntornsaratoon
authors.affiliation: Cardiac Electrophysiology Unit Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Narattaphol
authors.initials: N
authors.lastname: Charoenphandhu
authors.affiliation: Center of Excellence in Cardiac Electrophysiology ResearchChiang Mai University, Chiang Mai, Thailand.
authors.forename: Nipon
authors.initials: N
authors.lastname: Chattipakorn
authors.affiliation: Department of Oral Biology and Diagnostic SciencesFaculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Siriporn
authors.initials: S
authors.lastname: Chattipakorn
mesh_terms: D000818:Animals; D017209:Apoptosis; D015519:Bone Density; D049109:Cell Proliferation / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D059305:Diet, High-Fat; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D009765:Obesity / Q000150:complications* / Q000503:physiopathology; D009919:Orchiectomy; D010006:Osteoblasts / Q000502:physiology*; D015675:Osteocalcin / Q000097:blood; D010024:Osteoporosis / Q000209:etiology / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D013739:Testosterone / Q000172:deficiency / Q000502:physiology*
chemical_list: D015675:Osteocalcin; D013739:Testosterone
keywords: high-fat diet induced obesity; osteoblastic insulin signaling; testosterone deprivation