Endocrine Abstracts

Introduction and aim: Thyroid hormones (THs) regulates metabolism in adults, such as controlling energy balance by regulating energy expenditure and its storage. Hyperthyroidism increases thermogenesis, which results in the increase of the metabolic rate. THs, when combined with their receptor, can induce the expression of some genes, which can reflect on the content and activity of specific proteins. There are studies showing that THs affect the uptake of nutrients, such as glucose and peptides, but it is not well known how it works. Therefore, the current study has the aim to evaluate the impact of hypo and hyperthyroidism in the nutrients transporters content, such as carbohydrate, peptides and lipids transporters in the intestinal epithelium.

Materials and methods: In this study, mice C57BL/6, male and adults were distributed in three groups: control (vehicle/saline), hypothyroid (Propylthiouracil - PTU) and hyperthyroid (Triiodo-L-thyronine - T3). The animals were injected with saline, PTU (12.5 mg/Kg) or (T3 0.25 μg/g) for 30 days. At the end of the treatment, the mice were killed and the intestinal epithelium was removed to evaluate the transporters of carbohydrates (SGLT1, GLUT2 e GLUT5), protein hydrolysate (PEPT1) and lipids (NPC1L1, CD36/SR-B2 e FATP4) by Western blotting technique. Since NHE3 plays an important role in the sodium and peptides absorption, it was evaluated as well.

Results: Hyperthyroidism increased the GLUT2, CD36/SR-B2 and PEPT1content when compared to the control mice. SGLT1, GLUT5, FATP4 and NPC1L1 remained unchanged after T3 treatment. T3 induced a little increase of NHE3, but not statistically yet. The hypothyroidism did not affect the nutrients transporters nor NHE3 compared to the control group.

Conclusion: Since THs increase the glucose uptake by intestine through sodium independent mechanism, which is well-established, the increased GLUT2 in the intestine after T3 treatment could explain how THs stimulate glucose absorption. Furthermore, T3 also increased PEPT1 and CD36/SR-B2 content, which could be a physiological mechanism to provide nutrients (glucose, amino acids and fatty acids) and sustain the high metabolic demand and thermogenesis, which are common findings in the hyperthyroidism condition.