Associations between Metabolic Syndrome and Bone Mineral Density and Trabecular Bone Score in Postmenopausal Women with Non-Vertebral Fractures

Medical, social, and economic relevance of osteoporosis is caused by reducing quality of life, increasing disability and mortality of the patients as a result of fractures due to the low-energy trauma. This study is aimed to examine the associations of metabolic syndrome components, bone mineral density (BMD) and trabecular bone score (TBS) in menopausal women with non-vertebral fractures. 1161 menopausal women aged 50-79 year-old were examined and divided into three groups: A included 419 women with increased body weight (BMI 25.0-29.9 kg/m2), B – 442 females with obesity (BMI >29.9 kg/m2)i and C – 300 women with metabolic syndrome (diagnosis according to IDF criteria, 2005). BMD of lumbar spine (L1-L4), femoral neck, total body and forearm was investigated with usage of dual-energy X-ray absorptiometry. The bone quality indexes were measured according to Med-Imaps installation. All analyses were performed using Statistical Package 6.0. BMD of lumbar spine (L1-L4), femoral neck, total body, and ultradistal radius was significant higher in women with obesity and metabolic syndrome compared to the pre-obese ones (p<0.001). TBS was significantly higher in women with increased body weight compared to obese and metabolic syndrome patients. Analysis showed significant positive correlation between waist circumference, triglycerides level and BMD of lumbar spine and femur. Significant negative association between serum HDL level and BMD of investigated sites was established. The TBS (L1-L4) indexes positively correlated with HDL (high-density lipoprotein) level. Despite the fact that BMD indexes were better in women with metabolic syndrome, the frequency of non-vertebral fractures was significantly higher in this group of patients. Keywords—Bone mineral density, trabecular bone score, metabolic syndrome, fracture.


I. INTRODUCTION
STEOPOROSIS and metabolic syndrome are important public health problems, due to the decreasing of quality and reducing life expectancy of patients as a result of lowtrauma fractures in a case of osteoporosis and the possibility of cardiovascular, endocrine and other complications in a case of metabolic syndrome development [1], [5].The frequency of V. Povoroznyuk is with the D.F. Chebotarev Institute of Gerontology of NAMS of Ukraine, Kyiv, 04074 Ukraine (phone: 38-097-3734189; fax: 38-044-4304174; e-mail: okfpodac@ukr.net).
Lar. Martynyuk and Lil.Martynyuk are with State Higher Educational Institution "I.Horbachevsky Ternopil State Medical University of Ministry of Health of Ukraine" (e-mail: l_martynyuk@yahoo.com,lili_marty@ukr.net)Syzonenko is with Kyiv City Center for radiation protection of citizens affected by the Chernobyl disaster, Kyiv, Ukraine (e-mail: irynasyzonenko@rambler.ru).
both diseases increases with age of patient and duration of menopausal period as a result of slowdown in metabolism and estrogen deficiency development [8], [11].
Traditionally, osteoporosis is diagnosed according to the history of low-energy fractures or the results of BMD (Tscore), which are determined by using X-ray densitometry [10]; however, BMD provides only 70-75% of bone strength [13].Other factors that affect it include state of cortical bone macro-geometry and trabecular bone micro-architecture, presence damages and cracks in it, which can be calculated by index TBS, patented by MED-I maps (m.Bordeaux, France) in 2006 [3].In our opinion, evaluation of TBS is important to perform this work.
Scientists paid much attention to the study of the relationships between metabolic syndrome and osteoporosis.Abdominal obesity, high glucose (as a result of insulin deficiency or insulin resistance), high triglycerides and low high density lipoproteins which are the main components of metabolic syndrome have significant impact on bone tissue and fractures development but published research results are contradictory [4], [7], [12], [14], [16].The discrepancy of opinions prompted this investigation.
The aim of our study was to evaluate the relationships between metabolic syndrome components and BMD, TBS in postmenopausal women with low-trauma non-vertebral fractures.
The Statistical Package 6.0 ©StatSoft, Inc. was used for analyses.Continuous variables were reported as mean ± SD.Pearson correlations examined the relationship between continuous variables, significance set at p<0.05.
BMD of lumbar spine (L1-L4) was significantly higher in patients of groups B and C without fractures (Table I).BMD of femoral neck was significantly lower in female with obesity and non-vertebral fractures (Table II).BMD of total body and ultradistal radius significantly better in all groups of women without fractures compared to patients with non-vertebral fractures (Tables III and IV).TBS (L1-L4) was significantly higher in patients without fractures in the groups of women with increased body weight and obesity (p<0.05)(Table V).
The analysis of the metabolic syndrome laboratory components (serum triglycerides and HDL indexes) was carried out.We established significantly higher triglycerides level (A -1.049±0.381g/cm 2 , B -1.030±0.322g/cm 2 ; C -1.605±0.703g/cm 2 ; F=162.669;p<0.001) and significantly lower HDL level (A -1.531±0.372g/cm 2 , B -1.509±0.314g/cm 2 ; C -1.170±0.256g/cm 2 ; F=126.832;p<0.001) in patients with metabolic syndrome.There was no difference of triglycerides level in female with non-vertebral fractures and without them in all investigated groups (Table VI).The level of HDL was significantly lower in patients with non-vertebral fractures and metabolic syndrome (Table VII).In analysis of metabolic syndrome components, the waist circumference component was positively associated with BMD of lumbar spine and femur (Fig. 1).The study reveals significant positive correlation between serum triglycerides level and both investigated BMD sites (Fig. 2).A number of investigators have suggested relationship in accordance with our own findings [2].It was found a significant positive correlation between HDL serum level and TBS and inversely association with BMD of lumbar spine and femur (Fig. 3).
We calculated the percentage of non-vertebral fractures in anamnesis (Fig. 4).
Low-trauma non-vertebral fractures occurred in 14.6% female with increased body weight, 17.4% of women with obesity and 21.3% of patients with metabolic syndrome.Fig. 4 Frequency of low-trauma vertebral fractures in women with increase bode weight (A), obesity (B) and with metabolic syndrome (C) Significant differences were not found in the frequency of non-vertebral fractures in the groups of women with obesity and increased body weight or metabolic syndrome (X2=1.312,p>0.05 and X2=1.780, p>0.05, respectively), but it was significant in the groups of pre-obese female and patients with metabolic syndrome (X2=5.590,p<0.05).The similar results were found by other investigators [9].

IV. CONCLUSION
Menopausal women with obesity and metabolic syndrome have a significantly higher BMD at all measured sites compared to females with pre-obesity.TBS is significantly lower in women with non-vertebral fractures and increased body weight or obesity.A significant positive correlation is established between waist circumference, triglycerides level and BMD of lumbar spine and femoral neck.Correlation between HDL level and BMD at all levels is significant and negative.At the same time, it is positively associated with TBS indexes.There is no significant difference in frequency of low-trauma non-vertebral fractures in the groups of preobese and obese women.At the same time, the incidence of osteoporotic non-vertebral fractures is significantly higher in female with metabolic syndrome in compared to other patients.Metabolic syndrome may not protect from any type of fractures, but future investigations are necessary.