Impact of serum vitamin D level on selected bone-related markers in obese- type 2 diabetes patients

Abstract

Background: Type 2 diabetes mellitus (T2DM) is accompanied by an increased risk for skeletal fractures. The causes are probably a mix of factors, including poor glycemic control, a higher risk of falling due to hypoglycemia, osteopenia, bone quality deterioration, and drug side effects related to bone fragility. Undercarboxylated osteocalcin (ucOC) is a protein generated by osteoblasts that affects insulin secretion and sensitivity. Methods: A total number of 47 obese (BMI ˃ 30) patients with confirmed type 2 diabetes were selected depending on the American Diabetes Association ADA criteria. The control participants were similar to the patients in age and gender, with a total number of 43 obese (BMI ˃ 30) and healthy subjects chosen from the general population. The selected subjects were grouped according to their serum vitamin D levels. Their blood specimen was used for assaying ucOC, parathyroid hormone (PTH), and vitamin D3 levels by specific ELISA kits, and to estimate calcium (Ca2+) levels and inorganic phosphate (PO43−) via enzymatic colorimetric methods. Results: Serum parathyroid hormone and inorganic phosphate median (IQR) values were markedly increased in patients with T2DM when compared to healthy controls, whereas serum calcium and ucOC levels were lowered significantly in diabetic patients when compared to healthy controls. This was irrespective of serum vitamin D levels.    Conclusions: Elevated serum levels of PTH and PO43− values in obese type 2 diabetic patients compared to obese non-diabetic controls were accompanied by a significant decrease in ucOC and Ca2+ levels, irrespective of serum vitamin D levels. Hence, serum vitamin D3 levels had no significant impact on levels of ucOC, PTH, Ca2+, and PO43− in obese patients with type 2 diabetes.