Estrogen and Insulin Replacement Therapy Modulates the Expression of Insulin‐Like Growth Factor‐I Receptors in the Salivary Glands of Diabetic Mice

Abstract

Diabetes mellitus results in various complications, also compromising the salivary glands. Hormone levels and interactions with cellular receptors are altered, intensifying the damage caused by this disease. Hormone replacement therapy alone or combined with other treatments may reverse this damage, but doubts still exist regarding the efficacy of this procedure. The objective of this study was to evaluate the effect of estrogen replacement therapy combined with insulin treatment on salivary secretory cells and on the expression of insulin-like growth factor (IGF)-I receptors in salivary glands of spontaneously diabetic (NOD) mice. Twenty-five mice were divided into five groups of five animals each: group I (NOD diabetic), group II (NOD diabetic treated with insulin), group III (NOD diabetic treated with estrogen), group IV (NOD diabetic treated with insulin and estrogen), and group V (control Balb/c mice). Group II received insulin, group III received estrogen, and group IV received insulin plus estrogen administered daily for 20 days. Groups I and V received saline for the same period of time to simulate treatment. Glucose and estrogen levels were monitored during treatment, and salivary gland samples were collected at the end of treatment for stereological analysis and immunofluorescence detection of IGF-I receptors. Tissue restructuring and regulation of IGF-I receptors expression were observed in animals submitted to estrogen replacement therapy plus insulin. Estrogen effectively promoted the recovery of salivary secretory cells, demonstrating that this hormone alone, and especially when combined with insulin, might be important for the reversal of hyperglycemia-induced tissue injury.