The association between bone turnover markers and microvascular complications of type 2 diabetes

BACKGROUND Global epidemic of diabetes is a serious health care concern because of its complications and consequently reduced life expectancy and increased morbidity. However, the bone turnover and thus bone health may be affected or even compromised by diabetes and its complications. The aim of this study was to assess whether bone turnover markers are associated with diabetes micro-vascular complications. METHODS A total of 204 type 2 diabetes patients (104 patients with diabetic micro-vascular complications (retinopathy and/or nephropathy) as a case group and 100 patients without retinopathy and/or nephropathy) as a control group were recruited in this case-control study. The biochemical and metabolic parameters and bone turnover markers were assessed in all patients. RESULTS Our findings showed serum levels of osteocalcin (OC) (p = 0.0001) and, carboxy-terminal collagen crosslinks (CTX) (p = 0.006) were higher in diabetic patients with both diabetic retinopathy and nephropathy compared with control group. However, there was no significant difference in serum levels of procollagen I aminoterminal propeptide (P1NP) between diabetic patients with diabetic retinopathy (DR) and/or diabetic nephropathy (DN) compared with control. In diabetes patients with complications, there were significant negative correlation between OC and CTX with estimated-glomerular filtration rate (e-GFR) and also positive correlation between each bone marker (OC and CTX) and PTH levels (p = 0.0001) and BUN (p = 0.0001). In a general linear model, after adjusting for age, sex and BMI, and microvascular complications, there was not any significant association between three bone turnover markers and metabolic markers including fasting glucose, insulin, and lipid profile. Among kidney markers, there were significant positive associations between serum levels of CTX and OC with BUN (p < 0.05) as well as PTH (p < 0.0001). CONCLUSIONS Our data suggest the possible role of PTH and BUN levels in modulating bone turnover markers in diabetic patients.