| Objective: Diabetes (DM) and osteoporosis (OP) are two main metabolic diseases. With the longevity and aging of the population, the incidence of diabetes with oeteoporosis has been increasing. Therefore, the study between their relationships becomes a hotspot. OP may happen in population with any age and gender, and especially, postmenopausal women are more susceptible to OP due to decreased estrogen levels in circulation, which is also termed as primary OP. In addition, secondary OP can be induced by many diseases, and DM is considered to be one of the main causes. It is already indentified that DM closely correlated with the pathogenesis of OP, however, previous studies about their relationships were more confined to the impact of high glucose and some non-mechanical factors under various pathological conditions on bone mineral density, such as Endocrine, cell growth factor, vitamin D, calcium and bone cells. Recently, more and more evidences have showed that, biomechanical factors may play an important role in maintaining bone structure and strength and even in the pathogenesis of OP, indicating there might be an inner relationship between bone mass and body composition. However, so far results from studies about the impact of lean and fat which are important in body composition on BMD are quite inconsistent. Therefore, in the present study, we aim to explore the relationship between BMD and body composition in menopausal patients with type 2 diabetes, to clarify impact of lean and fat mass on the bone mass in these patients.Methods: 68 postmenopausal women with type 2 diabetes (DM) were chosen as study group and 73 healthy non-diabetic postmenopausal women were chosen as controls (NC). BMD of L2~L4 lumbar vertebrae, femur (neck, trochanter, InterTro and total), whole body fat, lean composition were measured by DEXA (dual energy X-ray absorptiometry) in all subjects. Clinical parameter and related analysis were all preformed. According to BMD, patients with DM had been further divided into diabetes with OP (DM-OP) and without OP (DM-NP). According to body index(BMI≥25kg/m2), DM patients were also divided in to diabetes with obesity (DM-B) and without obesity (DM-A) separately.Clinical parameters were obtained:①BMD were measured by OSTEOCORE 3 (MEDI LINK, France),②hemoglobin A1c was determined by DCA2000+(Bayer Co. Germany).③fasting plasma insulin (FINS) level was measured by radioimmunoassay.④Fasting and postprandial 2 hours blood glucose levels were measured in venous blood ,⑤homeostasis model assessment (HOMA ) was used to calculate insulin resistance index (HOMA-IR)by formula : Fasting insulin (FINS)×fasting blood glucose (FBG) / 22.5.⑥Height and body weight of patient were all recorded and body mass index was calculated.⑥Age, years of Menopause (MPY), and course of diabetes in DM patients were all recorded.Results:1 Results of regression analysis1.1 Results of univariate linear analysis.In DM patients, BMD in L2-4,total hip were negatively correlated with age, diabetic course, FBG, HbA1c and MPY, and positively correlated with BMI, FINS and lean, adipose tissue content. In DM-B patients, FINS, HOMA-IR were positively correlated with body adipose tissue content (TKFM).1.2 Results from linear regression analysisIn DM patients, BMD in L2-4 and femur were positively related with age, MPY, diabetes course, BMI, TLM and TKLM.2 The Characteristics in different groups2.1 Comparison between NC and DM group: there were no significant differences found in age, BMI, MPY between two groups (P>0.05). Compared with NC group, patients with DM have higher FBG,PBG,HbA1c levels (all P<0.05), but lower BMD in L2-4, femoral neck(NK) and greater trochanter(GT) (P<0.05). Lean masses in trunk, legs and the total were significantly lower (P<0.05) whereas total and trunk fat mass were higher in DM patients compared with NC group (P<0.05);2.2 Comparison between diabetic patients with osteoporosis (DM-OP)and without osteoporosis (DM-NP): there were no differences existed in age, BMI and MPY between two groups (P> 0.05); DM course, FBG, PBG and HbA1c were higher in DM-OP group when compared with DM-NP group(P<0.05); Lean mass in trunk, legs, and total were significantly lower whereas total fat mass were higher in DM-OP group than those in DM-NP group. There were no differences found in fat mass in trunk and legs between these two groups.2.3 Comparison between DM-A and DM-B group: there were no differences found between two groups in age and MPY (P> 0.05); of patients in DM-B group seemed to have higher FBG than DM-A group but didn't reach statistical difference (P> 0.05). However, fasting insulin levels, insulin resistance index and BMD of L2-4 and femoral neck were all significantly higher in DM-B patients than those in DM-A group (P<0.05). There was no difference in lean mass between two groups (P> 0.05). Trunk and the total fat mass were significantly higher in DM-B than DM-A group (P <0.05).Conclusion:1 Postmenopausal patients with type 2 diabetes were prone to osteoporosis than normal women.2 lean and fat mass in Postmenopausal patients with type 2 diabetes were closely correlated with BMD. However, lean mass seems to have more impact on BMD than fat mass, supporting the idea that lean mass determine the bone density.3 The local fat distribution, particularly in abdominal, in postmenopausal obese patients with type 2 diabetes, might be the key reason for insulin resistance.
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