Renal resistance to vasopressin in poorly controlled type 1 diabetes mellitus

To investigate the hypothesis that diabetes induces nephrogenic diabetes in sipidus, we studied the urine-concentrating ability in response to vasopres sin (AVP) in 12 patients with insulin-dependent diabetes mellitus (IDDM) an d 12 nondiabetic controls. Subjects were euglycemic-clamped, and after oral water loading, AVP was infused intravenously for 150 min. AVP induced a gr eater (P< 0.001) rise in urine osmolality in controls (67.6 +/- 10.7 to 720 +/- 31.1 mosmol/ kg, P< 0.001) than in IDDM patients (64.3 +/- 21.6 to 516 .7 +/- 89.3 mosmol/ kg, P< 0.001). Urinary aquaporin-2 concentrations after AVP infusion were higher in controls (611.8 +/- 105.6 fmol/mg creatinine) than in IDDM (462.0 +/- 94.9 fmol/mg creatinine, P = 0.003). Maximum urine osmolality in IDDM was inversely related to chronic blood glucose control, as indicated by Hb A(Ic) (r = 0.87, P = 0.002). To test the hypothesis that improved glycemic control could reverse resistance to AVP, 10 IDDM subject s with poor glycemic control (Hb A(Ic) >9%) were studied before (B) and aft er (A) intensified glycemic control. Maximum urine osmolality in response t o AVP increased with improved glycemic control (B, 443.8 +/- 49.0; A, 640.0 +/- 137.2 mosmol/ kg, P, 0.001), and urinary aquaporin-2 concentrations af ter AVP increased from 112.7 +/- 69 to 375 +/- 280 fmol/mg creatinine (P = 0.006), with improved glycemic control. Poorly controlled IDDM is associate d with reversible renal resistance to AVP.