Osteocalcin and Calcium Homeostasis in Type I Diabetes

This work was designed to clarify the influence of a vitamin D3 bolus on bone metabolic turnover as manifested by serum osteocalcin, calcium, and other parameters. Bone, like other tissues, in diabetics displays microangiopathy, particularly in the case of type I diabetes. Insulin-dependent diabetics (IDD) without retinopathy (Group I, n=18), with retinopathy (Group II, n=16), and healthy persons (Group III, n=16) were studied. Fasting and 2-h postprandial serum glucose, Ca2+ (total and ionized), albumin, alkaline phosphatase (ALP), osteocalcin (OC), parathormone (PTH), 25(OH)D3, 1, 25(OH)2D3, and 24-h urinary calcium were evaluated. Diabetics were injected I.M. with 600, 000 IU of vitamin D3, and were maintained on their dietary and antidiabetic regimen. There was a significant decrease in serum Ca2+ (total and ionized), urinary calcium, OC, 1, 25(OH)2D3 and serum albumin and significant increases in glucose and ALP in both diabetic groups compared with the control. Vitamin D3 injection in diabetics led to increase in plasma 25(OH)D3 and 1, 25(OH)2D3 and decrease in PTH levels together with normalization of serum Ca2+ (total and ionized) and 24-h urinary calcium, ALP, and OC. This could be due to the specific action of vitamin D3. The insignificant difference in calcium levels and its controlling hormones between complicated and uncomplicated diabetics suggests that development of angiopathy neither exaggerates osteopathy nor impairs the osteogenic effect of vitamin D3. Hepatic and renal metabolism of the latter were intact. Vitamin D3 injection could ameliorate diabetic hyperglycaemia and improve hypoalbuminaemia.