Pioglitazone does not modify ANP levels of type 2 diabetic patients

Background: The atrial natriuretic peptide (ANP) regulates fluid volume redistribution between heart and the pulmonary vessels. In diabetic patients the physiological action of ANP appears to be seriously altered. Methods: 12 subjects (gender 6M/6F, age 47 ± 2 years, BMI 29.1 ± 0.1 kg/m), with type 2 diabetes and under stable conditions, were studied after one month of pioglitazione treatment (30 mg/die) by means of isotonic blood volume expansion. Results: After one month of pioglitazone treatment the metabolic profile of the subjects improved (decrease diastolic blood pressure: p = 0.05, total cholesterol: p = 0.01, triglycerides: p = 0.03 and blood glucose: p = 0.01) as the expansion of their plasma volume was found associated with the decrease of hematocrit (p < 0.05). The statistical comparison before versus after pioglitazone showed a significant decrease in the basal aldosterone levels post-treatment (p < 0.04). Nonetheless ANP plasma levels were similar before and after therapy. Conclusions: The inappropriately high concentrations of ANP induced by hyperglycemia and the abnormal responses to a physiological stimulus like an isotonic blood volume expansion are not reverted by one month of pioglitazone. This is in contrast with the brisk improvement of the metabolic profile seen for the same period of treatment. ANP secretion is modified by fluid load in diabetic patients. This anomaly is not reverted by pioglitazone.