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Parker L, Lin X, Garnham A, McConell G, Stepto NK, Hare DL, Byrnes E, Ebeling PR, Seeman E, Brennan-Speranza TC, Levinger I. Glucocorticoid-Induced Insulin Resistance in Men Is Associated With Suppressed Undercarboxylated Osteocalcin. J Bone Miner Res 2019; 34:49-58. [PMID: 30138543 DOI: 10.1002/jbmr.3574] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 08/05/2018] [Accepted: 08/08/2018] [Indexed: 12/15/2022]
Abstract
In mice, glucocorticoid-induced insulin resistance occurs largely through impaired osteoblast function and decreased circulating undercarboxylated osteocalcin (ucOC). Whether these mechanisms contribute to glucocorticoid-induced insulin resistance in humans has yet to be established. In addition, the effects of glucocorticoids on the exercise-induced increase in circulating ucOC and insulin sensitivity are also unknown. We hypothesized that acute glucocorticoid treatment would lead to basal and postexercise insulin resistance in part through decreased circulating ucOC and ucOC-mediated skeletal muscle protein signaling. Nine healthy men completed two separate cycling sessions 12 hours after ingesting either glucocorticoid (20 mg prednisolone) or placebo (20 mg Avicel). The homeostatic model assessment was used to assess basal insulin sensitivity and a 2-hour euglycemic-hyperinsulinemic clamp was commenced 3 hours after exercise to assess postexercise insulin sensitivity. Serum ucOC and skeletal muscle protein signaling were measured. Single-dose glucocorticoid ingestion increased fasting glucose (27%, p < 0.01) and insulin (83%, p < 0.01), and decreased basal insulin sensitivity (-47%, p < 0.01). Glucocorticoids reduced insulin sensitivity after cycling exercise (-34%, p < 0.01), reduced muscle GPRC6A protein content (16%, p < 0.05), and attenuated protein phosphorylation of mTORSer2481 , AktSer374 , and AS160Thr642 (59%, 61%, and 50%, respectively; all ps < 0.05). Serum ucOC decreased (-24%, p < 0.01) which correlated with lower basal insulin sensitivity (r = 0.54, p = 0.02), lower insulin sensitivity after exercise (r = 0.72, p < 0.05), and attenuated muscle protein signaling (r = 0.48-0.71, p < 0.05). Glucocorticoid-induced basal and postexercise insulin resistance in humans is associated with the suppression of circulating ucOC and ucOC-linked protein signaling in skeletal muscle. Whether ucOC treatment can offset glucocorticoid-induced insulin resistance in human subjects requires further investigation. © 2018 American Society for Bone and Mineral Research.
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Affiliation(s)
- Lewan Parker
- Institute for Physical Activity and Nutrition (IPAN), Deakin University, Geelong, VIC, Australia.,Institute of Health and Sport (IHES), Victoria University, Melbourne, VIC, Australia
| | - Xuzhu Lin
- Institute of Health and Sport (IHES), Victoria University, Melbourne, VIC, Australia
| | - Andrew Garnham
- Institute for Physical Activity and Nutrition (IPAN), Deakin University, Geelong, VIC, Australia.,Institute of Health and Sport (IHES), Victoria University, Melbourne, VIC, Australia
| | - Glenn McConell
- Institute of Health and Sport (IHES), Victoria University, Melbourne, VIC, Australia
| | - Nigel K Stepto
- Institute of Health and Sport (IHES), Victoria University, Melbourne, VIC, Australia.,Australian Institute for Musculoskeletal Science (AIMSS), Department of Medicine-Western Health, Melbourne Medical School, The University of Melbourne, Melbourne, VIC, Australia.,Monash Centre of Health Research and Implementation (MCHRI), School of Public Health and Preventative Medicine, Monash University, Melbourne, VIC, Australia
| | - David L Hare
- University of Melbourne and the Department of Cardiology, Austin Health, Melbourne, VIC, Australia
| | | | - Peter R Ebeling
- Department of Medicine, School of Clinical Sciences, Monash University, Melbourne, VIC, Australia
| | - Ego Seeman
- Department of Endocrinology, Austin Health, University of Melbourne, Melbourne, VIC, Australia.,Mary Mackillop Institute of Health Research, Australian Catholic University, Melbourne, VIC, Australia
| | | | - Itamar Levinger
- Institute of Health and Sport (IHES), Victoria University, Melbourne, VIC, Australia.,Australian Institute for Musculoskeletal Science (AIMSS), Department of Medicine-Western Health, Melbourne Medical School, The University of Melbourne, Melbourne, VIC, Australia.,University of Melbourne and the Department of Cardiology, Austin Health, Melbourne, VIC, Australia
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