Hydroxyproline Excretion is Increased in Diabetes Mellitus and Related to the Presence of Microalbuminuria

Abstract

Increased fracture frequency and low bone mass have each been reported in patients with diabetes. To see if these were related to increased bone resorption we have measured the urinary excretion of hydroxyproline in 73 patients with Type 1 (insulin-dependent) diabetes, 67 patients with Type 2 (non-insulin-dependent) diabetes, and 75 control subjects. Hydroxyproline excretion was increased in both types of diabetes: Type 1: 21 (10-36) (median (IQR) mumol mmol creatinine-1; Type 2: 25 (13-43) mumol mmol creatinine-1; control: 10 (6-22) mumol mmol creatinine-1 (p < 0.0001 and < 0.0002, respectively). Hydroxyproline excretion was not related to age, duration of diabetes or blood glucose control. Neither was it different in patients with or without retinopathy, neuropathy and macrovascular disease. However it was higher in patients with microalbuminuria at 35 (20-53) mumol mmol creatinine-1 than in those with normal protein excretion (25(13-37) mumol mmol creatinine-1 p = 0.03) or those with established proteinuria (18(8-26) mumol mmol creatinine-1 p = 0.001). We conclude that there is evidence of increased bone resorption in diabetes and that this is related to alterations in renal function.