[Bone turnover and bone density in type 1 diabetics in the initial stages of diabetic nephropathy]

To compare the bone turnover and bone mineral density in type 1 diabetic patients with normoalbuminuria and type 1 diabetic patients with diabetic nephropathy with microalbuminuria or mild proteinuria.

We studied 18 type 1 diabetic patients (Group A) with normoalbuminuria (UAE < 10 micrograms/min) and 8 type 1 diabetic patients (Group B) with UAE 100-1000 micrograms/min and serum creatinine below 150 mumol/l. Markers of bone formation (bone alkaline phosphatase--ALP-B, serum osteocalcin) and bone resorption (serum tartrate-resistant acid phosphatase--ACP-TR, urinary hydroxyproline) were determined. Bone mineral density (BMD) was measured at lumbar spine and right femoral neck.

Serum ALP-B was higher in group B [median (95% CI), 518 (405-1070) nkat/l] compared with group A [380 (355-510) nkat/l] (p < 0.05). Urinary hydroxyproline excretion was higher in group B [U-Hxp/U-creat 46.7 (22.9-80) mumol/mmol] compared with group A [18.3 (8.9-22.7) mumol/mmol] (p < 0.001). No difference was found in serum osteocalcin and ACP-TR and in BMD at L2-L4 and femoral neck.

We conclude that bone turnover was increased in type 1 diabetic patients with incipient stage of diabetic nephropathy but there was no difference in BMD as compared with type 1 diabetic patients without nephropathy. This finding might indicate that biochemical markers unlike densitometry reflect initial changes in bone metabolism in preclinical diabetic nephropathy earlier. (Tab. 2, Ref. 17.)