| Abstract |
Inflammatory bowel diseases (IBD) are considered to be a chronic
inflammatory process of the gastrointestinal tract. The incidence of IBD worldwide
varies from 0.5-24.5 /100.000 for UC and 0.1-16/100.000 habitants for Crohn
disease. The incidence of IBD in western populations seems to be double
compared with population from Middle East. (Annual incidence rates in western
populations are for CD patients 6.5/100.000, and for UC patients 10.8/100.000,
while in populations in Asia the annual incidence rates for Crohn disease is
3.1/100.000 and for UC 4.1/100.000 habitants respectively). It is well known that
IBD patients present low bone mineral density (BMD) and they show an
increased risk of osteoporotic fractures, 40% higher than the general population
which is increased with age. The pathogenetic mechanism of osteoporosis is
multifactorial in IBD patients and only partially understood. Some of the factors
that affect the homeostasis of calcium and bone remodeling are the chronic
inflammation, vitamin D deficiency, smoking, use of steroids, and low BMI. There
are indications that low BMD is not in direct proportion with the fracture risk, fact
that underlines the necessity of finding more risk factors for the evaluation of
osteoporotic facture risk. WHO has recently developed FRAX score, which is an
algorithm for the evaluation of fracture risk based on clinical factors considering or
not the measurement of BMD. This algorithm was calculated based on population
cohort studies and provides two basic results. Firstly, the 10-year probability of a
major osteo- porotic fracture (clinical spine, hip, forearm or shoulder), and
secondly, the 10-year probability of a hip fracture alone. The algorithm is
available through the web at: http://www.shef.ac.uk/FRAX/index.
Body mass index (BMI) is negatively correlated with high fracture rates and
bone mineral density (BMD) is positively correlated with increased fat mass. It
has been hypothesized that these associations could probably be caused by the
action of hormone-like substances called adipocytes derived directly from the fat
tissue. Experimental data in rats showed that chemerin, visfatin και vaspin have
an impact on BMD with different mechanisms. More specifically, inhibition of
chemerin or CMKLR1 receptor influences negatively osteoblastogenesis and
bone mineralization and also has an inhibitory action in osteoclastogenesis.
Visfatin has been shown to stimulate the proliferation of osteoblasts in a dose
dependent fashion and also to block osteoclast differentiation by suppressing
RANK, NFATc1 and cathepsin K expression [19]. Recent data showed that
vaspin has also a double sword action as it inhibits the RANKL-induced
osteoclastogenesis and promotes osteoblastogenesis due to the suspension of
the apoptosis of osteoblasts. Aim of the present study was:
- To find the incidence of osteoporosis in IBD Greek patients.
- To evaluate the accuracy of pre-BMD FRAX score in Greek IBD population in
order to identify the patients who need medical therapy, scanning with DXA, or
just close follow-up/reassurance. We also evaluated and compared the fracture
risk in patients with Crohn’s disease (CD) and ulcerative colitis (UC).
- To investigate the role of fat mass and adipocytes chemerin, visfatin, and vaspin
in the development of osteoporosis in IBD patients.
Reduced BMD was found in 73 (61%) IBD patients, of whom 48 (40%) had
osteopenia and 25 (21%) osteoporosis. Osteoporotic patients had a significantly
lower total fat mass than the osteopenic patients and the patients with normal
BMD (OR: 0.89, 95%CI 0.83-0.95 p=0.01). The median 10-year probability of a
major osteoporotic fracture for IBD patients based on clinical data was 7.1 %, and
including the BMD was 6.2 %. A significant overestimation with the first method
was found (P = 0.01). Both scores with and without BMD were significantly higher
in CD patients compared with UC patients (P = 0.02 and P = 0.005, respectively).
Serum chemerin was higher in IBD patients than HC (CD: 13.67.1±5.8,
UC: 13.9±4.3 vs. HC: 7.8±2.6 ng/mL, OR 0.95, 95%CI 0.93-0.98, P<0.0001).
Serum visfatin levels in CD patients were significantly higher than UC
patients (9.3±14.01 vs. 6.5±7.2 ng/mL, OR 0.86, 95%CI 0.80 -0.92, P=0.039). In
multivariate logistic regression analysis, a significant independent association of
osteoporosis (T-score ≥2.5 SD) with age (OR 1.04, 95%CI 1.01-1.08, P=0.02),
visfatin (OR 0.78, 95%CI 0.63-0.97, P=0.02), and chemerin levels (OR 0.83,
95%CI 0.70-0.98, P=0.03) but not with body mass index or body composition was
found.
The results of the present study illustrate the impact of adipocytes action
on the BMD of Greek IBD patients, as well as the great importance of predicting
the risk of a major osteoporotic fracture, using FRAX algorithm. So though these
results, the important role of white adipose tissue regarding the osteoporotic
status of IBD patients is revealed, offering an opened field for further
investigations.
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