The role of fat-bone interactions in the pathogenesis of osteoporosis in chronic obstructive
pulmonary disease (COPD) is poorly understood. Our aim was to investigate expressions
of leptin and osteoprotegerin (OPG) in the adipose tissue, and their relationships
to osteoporosis in patients with COPD.
In 39 patients with stable COPD, bone mineral density (BMD) and body composition was
assessed by Dual Energy X-Ray Absorptiometry. Serum leptin was determined by the enzyme-linked
immunosorbent assay, and bone turnover markers osteocalcin and β-crosslaps by the
electrochemiluminiscence immunoassays. Subcutaneous adipose tissue samples were analyzed
using real-time PCR.
Twenty-one patients without, and 18 with osteoporosis were enrolled (35 men; age 62.2
± 7.3years). Compared to patients without osteoporosis, those with the disease had
significantly lower serum levels and adipose tissue expressions of leptin, in association
with increased serum β-crosslaps (p=0.028, p=0.034, p=0.022, respectively). Log adipose
tissue leptin was inversely related to serum β-crosslaps (p=0.015), and directly to
serum leptin (p<0.001) and to the total, femoral, and lumbar BMD and T-score (p<0.02
for all relationships). Adipose tissue OPG expression was related to all variables
of bone density except for lumbar BMD and T-score (p<0.05 for all relationships).
Log adipose tissue leptin and OPG expressions predicted femoral T-score independently
of age, gender and pulmonary function (p<0.001, adjusted R(2)=0.383; p=0.008, adjusted
R(2)=0.301, respectively). Introducing body mass (or fat mass) index into these models
eliminated independent predictive value of leptin and OPG expressions.
Our results suggest that adipose tissue leptin and OPG expressions are related to
osteoporosis in patients with COPD, and appear to act as mediators between fat mass
and BMD.
Copyright © 2011 Elsevier Inc. All rights reserved.