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Keywords:

  • Arterial hypertension;
  • insulin resistance;
  • Na+/H+ antiporter;
  • obesity;
  • type 2 diabetes mellitus

Abstract. The aim of this work is to evaluate whether type 2 diabetes mellitus, obesity and arterial hypertension, three conditions characterized by the presence of insulin resistance, share some common genetic markers. A potential candidate is the Na+/H+ anti-porter, the increased activity of which is considered a marker of essential hypertension. This ion exchanger seems to be related to the Na+/Li+ countertransport, that is considered a marker of insulin resistance in essential hypertension and in type 1 diabetes mellitus. In this study we wished to clarify whether the activity of the Na+/H+ antiporter is increased not only in hypertensive subjects, but also in obese and type 2 diabetic patients, both in the presence and in the absence of arterial hypertension. The activity of the ion exchanger was measured in peripheral blood lymphocytes (PBL) by clamping intracellular pH (pHi) at 5·8–6·2 and then detecting the rate of the proton efflux after sodium addition. In the absence of arterial hypertension, no significant difference in this parameter was observed in obese and type 2 diabetic patients in comparison with normal subjects. In the presence of arterial hypertension, there was a significant increase in the Na+-induced H+ efflux at the internal pH (pHi) values of 5·8 and 6·2 both in hypertensive controls and in hypertensive obese and type 2 diabetic patients (P= 0·05–0·0001 vs. normotensive subjects and patients). In particular, H+ efflux at pH 5·8 (mmol l-1 min-1) was 35·36 ± 2·48 in normotensive and 42·77 ± 1·63 in hypertensive control subjects (P= 0·045), 33·06 ± 1·88 in normotensive and 50·40 ± 5·21 in hypertensive obese patients (P= 0·009), 31·16 ± 1·84 in normotensive and 55·54 ± 5·83 in hypertensive type 2 diabetic patients (P= 0·0001). H+ efflux showed a significant correlation with both systolic (at pHi 5·8, r = 0·473, P= 0·001; at pHi 6·2, r = 0·357, P= 0·016) and diastolic blood pressure (at pHi 5·8, r = 0·600, P= 0·0001; at pHi 6·2, r = 0·555, P= 0·0001). Therefore, our study demonstrates that the hyperactivity of the Na+/H+ exchanger in peripheral blood lymphocytes is also a marker of arterial hypertension in obesity and in type 2 diabetes mellitus, and that the exchanger activity is not increased in these two conditions in the absence of arterial hypertension.