Reduced leptin linked to osteoporosis in COPD patients
MedWire News: Altered fat metabolism may be a factor in the development of osteoporosis among patients with chronic obstructive pulmonary disease (COPD), say researchers.
Indeed, they report that expression of leptin - an adipose-derived hormone - significantly correlates with bone mineral density (BMD) in these patients.
Over the past decade, COPD has been increasingly recognised as a systemic disease characterized not only by pulmonary inflammation but also features such as systemic inflammation, cardiovascular comorbidities, and osteoporosis, explain Ruzena Tkacova (L Pasteur University Hospital, Kosice, Slovakia) and colleagues.
They add that adipokines such as leptin have recently emerged as mediators of the protective effects of fat on bone tissue, but the role of fat-bone interactions in the pathogenesis of osteoporosis in chronic obstructive pulmonary disease (COPD) is poorly understood.
Tkacova and team therefore investigated the expression of leptin and osteoprotegerin (OPG) - an osteoclastogenesis inhibitor - in the adipose tissue, and their relationships to osteoporosis in 39 patients (90% men; mean age 62 years) with stable COPD.
Of the patients, 18 (46.2%) had osteoporosis, diagnosed by dual energy X-ray absorptiometry, and 21 (53.8%) did not have the disease.
The patients with osteoporosis had lower levels of serum leptin than those without osteoporosis, at 2.35 versus 9.20 µg/ml.
In addition, leptin messenger RNA expression in the adipose tissue of patients with osteoporosis was approximately half the level of that in patients without the condition.
OPG expression was also lower in the osteoporosis patients relative to those without osteoporosis, but the difference did not reach statistical significance.
In spite of this, both leptin and OPG expression in adipose tissue significantly predicted femoral T-score independently of age, gender, and pulmonary function.
However, adjusting for body mass (or fat mass) index eliminated the independent predictive value of leptin and OPG expression.
"Taken together, these results suggest that leptin and OPG act as mediators between fat mass and BMD in patients with COPD," Tkacova and co-authors conclude in the journal Bone.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011
By Laura Dean