Clustering of risk factors in hypertensive insulin-dependent diabetics with high sodium-lithium countertransport

Clustering of risk factors in hypertensive insulin-dependent diabetics with high sodium-lithium countertransport. Diabetic nephropathy is more common in patients with a positive family history of hypertension and with elevated red blood cell sodium-lithium countertransport, a marker of risk for essential hypertension. To evaluate whether there is a relationship between this cation transport system and indicators of risk of renal and cardiovascular complications in diabetic patients before the development of clinical proteinuria, we studied 31 type 1 (insulin-dependent) diabetic patients with arterial hypertension, without clinical proteinuria and 12 normotensive normoalbuminuric diabetic patients. Sodium-lithium countertransport activity was significantly higher in hypertensive patients (0.43 ± 0.03 mmol/1 RBC x hr) than in normotensive patients (0.23 ± 0.03; P < 0.001). To better explore the nature of the association between this transport system and arterial hypertension, hypertensive patients were divided in two groups, with high (>0.41 mmol/1 RBC x hr) or normal (<0.41) sodium-lithium countertransport activity. The two groups of hypertensive diabetics were similar in age, sex, body mass index and blood pressure levels. Hypertensive patients with elevated rates of sodium-lithium counter-transport compared with those with normal sodium-lithium counter-transport activity showed elevated glomerular filtration rate (130 ± 4 ml/min/1.73 m2 vs. 122 ± 3; P < 0.05), albumin excretion rate (median 26 /Lcg/min vs. 11; P < 0.001), higher fractional proximal sodium reabsorption (74 ± 1.2% vs. 71.6 ± 0.9; P < 0.01), exchangeable sodium pool (2937 ± 62 mmol/1.73 m2 vs. 2767 ± 56; P < 0.01), larger kidney volume (317 ± 7 ml/1.73 m2 vs. 270 ± 8; P < 0.05) and left ventricular mass index (122 ± 4 g/m2 vs. 107 ± 5; P < 0.05). Hypertensive patients with normal sodium-lithium countertransport activity had renal parameters similar to normotensive diabetic patients, except higher left ventricular mass index and kidney volume. Hypertensive diabetic patients with elevated sodium-lithium countertransport activity also had higher levels of plasma triglycerides, lower plasma HDL-cholesterol and impaired insulin sensitivity (assessed by euglyce-mic insulin-glucose clamp) compared with the other two groups. In conclusion, renal, cardiac and metabolic abnormalities are prominent in hypertensive type 1 (insulin-dependent) diabetic patients with higher sodium-lithium countertransport