Effects of androgens on the insulin-like growth factor system in an androgen-responsive human osteoblastic cell line
Authors: C A Conover
L C Hofbauer
F Gori
S Khosla
Journal: Endocrinology (1999)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: Androgens; Bone metabolism; Insulin-like growth factors (IGFs); IGF-binding proteins (IGFBPs); Osteoblast proliferation
Affiliations: Endocrine Research Unit, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905

Abstract:  Although androgens have significant effects on bone metabolism, the mediators of their effects are still unclear. As the insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) have important effects on osteoblast proliferation and differentiation, we examined androgen effects on the IGF system in a conditionally immortalized human fetal osteoblastic cell line, hFOB/AR-6, which displays a mature osteoblastic phenotype and physiological levels of functional androgen receptors. The nonaromatizable androgen, 5alpha-dihydrotestosterone (5alphaDHT), and testosterone, but not dehydroepiandrosterone, increased IGF-I messenger RNA (mRNA) levels up to 4-fold in a dose (10(-12)-10(-6) M)- and time (2-72 h)-dependent fashion. These changes were prevented by the specific androgen receptor antagonist, hydroxyflutamide. In addition, 5alpha-DHT decreased IGFBP-4 mRNA and protein levels by 2- and 4-fold, respectively, and increased IGFBP-2 and -3 mRNA and protein levels by 6- and 7-fold (for mRNA) and 3- and 5-fold (for protein), respectively. hFOB/AR-6 cells expressed the type-I IGF receptor, but this was not regulated by 5alphaDHT. 5alphaDHT and IGFBP-3 specifically increased hFOB/AR-6 cell proliferation, and a monoclonal antibody specific for IGF-I blocked this effect. Thus, androgens increase the expression of IGF-I, IGFBP-2, and IGFBP-3, but decrease levels of the inhibitory IGFBP-4 in an androgen-responsive human osteoblastic cell line. Our data are consistent with the hypothesis that the effects of androgen on bone cells may be mediated at least in part by increases in IGF-I production and by differential regulation of IGFBPs. 

Retracted: No

PubPeer comments:
 Could authors please check. ![file] , 
 #1 This was many years ago, but in reviewing the blot, it is clear that what Francesca did was reprobe the same blot for IGF-I in Fig 3 and IGFBP-2, 3, and 4 in Fig 4. This is commonly done, and the b-actin control was the same for all the analyses (as a control for loading). , 
 #2 Even if b-actin blot is reprobed, It appears that the blots C and A in the above image are not same. , 
 Thank You Sundeep. Indeed, it was many years ago, exactly 21. I do not have in my lab the films from these studies. As Dr. Khosla mentioned above the same blot was sequentially probed for IGF-I in Fig 3 and IGFBP-2, 3, and 4 in Fig 4 and than with b-actin for loading control to validate increased levels of IGF signaling pathway. , 
 #4 Thanks authors for clarification that same loading control blot was re-probed and re-used for all of the experimental blots in Fig 3 and Fig 4. Was the b-actin blot same for all three independent experiments as stated in the figures. It also appears that C and aDHT lanes were switched in IGF1 and IGFB2 lanes for the blots shown above. ,