Relationship between serum osteocalcin and glycaemic variability in Type 2 diabetes

1. Recent reports have described the role of osteocalcin in glucose metabolism and glycaemic variability has been proven to be associated with an increased risk of diabetes complications. However, the relationship between osteocalcin and glycaemic variability remains unclear. The aim of the present study was to examine the relationship between serum osteocalcin and glycaemic variability, as determined by a continuous glucose monitoring (CGM) system in patients with Type 2 diabetes mellitus (T2DM). 2. Fifty-nine T2DM patients with glycosylated haemoglobin (HbA1c) levels between 7.0% and 10.9% were recruited to the present study. Biochemical information and CGM parameters were collected at baseline and after 8 weeks of antihyperglycaemic therapy (either sulphonylurea, sulphonylurea + an α-glucosidase inhibitor or insulin + metformin combination therapy). 3. Compared with baseline, serum osteocalcin increased significantly (P = 0.014), whereas parameters related to glucose variability, including the mean amplitude of glycaemic excursions (MAGE) and the standard deviation of blood glucose values, decreased significantly (P < 0.001) after the 8 week treatment period. At baseline, there was a positive correlation between serum osteocalcin levels and fasting C-peptide levels (P = 0.004) and homeostatic model assessment of β-cell function (P = 0.048), but a negative correlation between serum osteocalcin levels and fasting plasma glucose (P = 0.023), HbA1c (P = 0.020), glycated albumin (P = 0.019) and 24 h mean blood glucose (P < 0.001). Multiple stepwise regression analysis indicated that baseline osteocalcin was the single parameter that best predicted the change in MAGE (β = -0.122; P = 0.039). 4. In conclusion, serum osteocalcin concentrations increased with improved glucose control. High initial osteocalcin levels were associated with subsequent improvements in glucose variability during glucose-lowering treatment.