Bone Turnover Is Suppressed in Insulin Resistance, Independent of Adiposity.
BACKGROUND
The contribution of insulin resistance vs adiposity to bone mineral density (BMD), bone turnover, and fractures in humans remains unclear.


OBJECTIVE
To evaluate BMD and bone turnover markers (BTMs) in lean (n = 18) and overweight/obese individuals with (n = 17) and without (n = 34, insulin-sensitive [Obsensitive, n=15] or insulin-resistant [Obresistant, n=19] by homeostasis model assessment insulin resistance) diabetes mellitus.


METHODS
Observational study.


METHODS
Insulin sensitivity was assessed using the hyperinsulinemic-euglycemic clamp; whole body BMD and fat mass (FM) using dual energy X-ray absorptiometry; and by measurement of BTMs [osteocalcin (OC), procollagen type 1 N-terminal propeptide (P1NP), and collagen type 1 cross-linked C-terminal telopeptide (CTx)], with the patient fasting and during clamp hyperinsulinemia.


RESULTS
Fasting BTMs correlated with glucose infusion rate/fat-free mass (GIR/FFM) and adiponectin and, inversely, with fasting insulin and visceral fat (P ≤ 0.04 for all). Obsensitive, Obresistant, and diabetic individuals were matched by their FM percentage. Clamp GIR/FFM was similar in the lean and Obsensitive subjects (P = 1) and approximately twofold greater (P < 0.001) than in the Obresistant and diabetic subjects. BMD was greater in Obresistant than in Obsensitive (P = 0.04) and lean (P = 0.001) subjects. At baseline, compared with Obsensitive and lean subjects, Obresistant and diabetic individuals had lower OC, P1NP, and CTx levels. This reached statistical significance for Obresistant vs lean and Obresistant vs Obsensitive for both OC and CTx and for diabetic vs lean for CTx (P ≤ 0.04 for all). During hyperinsulinemia, lean individuals suppressed CTx more than did diabetic individuals (P = 0.03). On multiple regression analysis, visceral adiposity explained 16.7% and 19.3% of the baseline OC and CTx variability, respectively.


CONCLUSIONS
Increased visceral adiposity and higher fasting insulin in insulin-resistant states are associated with lower fasting OC and CTx and failure to further suppress with more insulin.
Diabetes and Obesity Research Group, Garvan Institute of Medical Research, Darlinghurst, New South Wales 2010, Australia.|Department of Endocrinology and Diabetes, St Vincent's Hospital, Darlinghurst, New South Wales 2010, Australia.|University of New South Wales Faculty of Medicine, University of New South Wales Sydney, New South Wales 2052, Australia.
Katherine T
KT
Tonks
Department of Endocrinology and Metabolism, Prince of Wales Hospital, Randwick, New South Wales 2031, Australia.|University of New South Wales Faculty of Medicine, University of New South Wales Sydney, New South Wales 2052, Australia.
Christopher P
CP
White
Department of Endocrinology and Diabetes, St Vincent's Hospital, Darlinghurst, New South Wales 2010, Australia.|Osteoporosis and Bone Biology Division, Garvan Institute of Medical Research, Darlinghurst, New South Wales 2010, Australia.|University of New South Wales Faculty of Medicine, University of New South Wales Sydney, New South Wales 2052, Australia.
Jacqueline R
JR
Center
Diabetes and Obesity Research Group, Garvan Institute of Medical Research, Darlinghurst, New South Wales 2010, Australia.|University of New South Wales Faculty of Medicine, University of New South Wales Sydney, New South Wales 2052, Australia.
Dorit
D
Samocha-Bonet
Diabetes and Obesity Research Group, Garvan Institute of Medical Research, Darlinghurst, New South Wales 2010, Australia.|Department of Endocrinology and Diabetes, St Vincent's Hospital, Darlinghurst, New South Wales 2010, Australia.|University of New South Wales Faculty of Medicine, University of New South Wales Sydney, New South Wales 2052, Australia.
Jerry R
JR
Greenfield
D050154:Adiposity / Q000502:physiology*; D000328:Adult; D000368:Aged; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology; D016723:Bone Remodeling; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000378:metabolism / Q000503:physiopathology; D015536:Down-Regulation; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000378:metabolism / Q000503:physiopathology