Analysis of maternal profile of circulating microRNAs induced by gestational corticotherapy: translational approach

Abstract

In the last 30 years, therapies with synthetic corticosteroids in pregnant women have shown success in reducing the mortality of premature neonates and the incidence of respiratory distress syndrome. Despite the recognized immediate benefits arising out of corticotherapy, individuals who were born to mothers treated with betamethasone present an increased risk of insulin resistance development. Increased blood pressure in children born to mothers who received corticotherapy has also been reported. Other changes with potential metabolic impact, such as low birth weight, are also noted early after the use of corticosteroids during pregnancy. Although it is relatively well explored the long-term impacts for the children due to corticotherapy, it is not yet known if such therapeutic strategy carries some impact to maternal health. It is also unclear whether these effects would have a possible dose-response relationship. In a recent study it was shown that rats exposed to dexamethasone at the end of pregnancy display consistent late metabolic changes. These findings showed that exposure to glucocorticoids in the third gestational period did not alter the basal blood glucose and glucose tolerance during treatment and during lactation, but developed intolerance to glucose 3 months after delivery. This change persisted until the 12th month after delivery, and was concomitant with a reduction in the secretory capacity of insulin. In addition to functional characterization of the experimental model, we propose in this study a mechanism for the late establishment, based on the altered expression of microRNAs (miRNA). Thus, the aims of this project are (i) to compare the profiles of circulating microRNAs among women who did or did not use corticotherapy during pregnancy, and to correlate the findings with possible changes in the energy metabolism, and (ii) to establish an animal model that resembles the conditions of human gestational corticotherapy and to allow studies of the mechanisms involved in the possible changes observed. Wistar rats will be used in the 20th gestational day and treated with vehicle or 170 ¼g betamethasone per body weight in two doses with interval of 4 hours ("Clinically-equivalent dose" of 2 doses of 12 to 24 mg range). Both groups will be sacrificed (1) on the 21st day of pregnancy; (2) in the sixth month after delivery or after the establishment of glucose intolerance. For the study with humans, women that have delivered for at least 6 months and enrolled at the CAISM will be evaluated. Both in animals and humans GTT will be conducted along with fasting glucose, insulin, total cholesterol, triglycerides and HDL measurements and biochemical markers of liver function to design the metabolic profile. Molecular analysis will be based on large-scale expression of circulating miRNA to identify possible prognostic markers. In addition epigenetic markers will be assessed by western blot and DNA methylation in leukocytes. With the results of this project it is expected to identify altered miRNA involved in energetic metabolism, especially with regard to the establishment of metabolic disorders involved with DM2. Furthermore, it is expected to validate an animal model equivalent to corticotherapy used in women during pregnancy, allowing future studies of therapeutic strategies before the onset of the disease. (AU)