Topical Topiramate Improves Wound Healing in an Animal Model of Hyperglycemia.

Wound healing is severely affected in hyperglycemia and other metabolic conditions. Finding new therapeutic approaches that accelerate wound healing and improve the quality of the scar may reduce the morbidity commonly associated with skin lesions in diabetes. This study evaluated the effect of topical topiramate (TPM) on wound healing in C57 mice. Streptozotocin-induced hyperglycemic mice were subjected to a wound on the back and randomly allocated for treatment with either vehicle or topical TPM cream (2%) once a day for 14 days. Polymerase chain reaction, Western blotting, and microscopy were performed for the analysis. TPM improved wound healing (complete resolution at Day 10, 98% ± 5 for TPM vs. 81% ± 28 for vehicle), increased organization and deposition of collagen Type I, and enhanced the quality of the scars as determined by microscopy. In addition, TPM modulated the expression of cytokines and proteins of the insulin-signaling pathway: In early wound-healing stages, expression of interleukin-10, an anti-inflammatory marker, increased, whereas at the late phase, the pro-inflammatory markers tumor necrosis factor-α and monocyte chemoattractant protein-1 increased and there was increased expression of a vascular endothelial growth factor. Proteins of the insulin-signaling pathway were stimulated in the late wound-healing phase. Topical TPM improves the quality of wound healing in an animal model of hyperglycemia. The effect of TPM is accompanied by modulation of inflammatory and growth factors and proteins of the insulin-signaling pathway. Therefore, topical TPM presents as a potential therapeutic agent in skin wounds in patients with hyperglycemia.

Topical insulin accelerates wound healing in diabetes by enhancing the AKT and ERK pathways: a double-blind placebo-controlled clinical trial.

BACKGROUND: Wound healing is impaired in diabetes mellitus, but the mechanisms involved in this process are virtually unknown. Proteins belonging to the insulin signaling pathway respond to insulin in the skin of rats. OBJECTIVE: The purpose of this study was to investigate the regulation of the insulin signaling pathway in wound healing and skin repair of normal and diabetic rats, and, in parallel, the effect of a topical insulin cream on wound healing and on the activation of this pathway. RESEARCH DESIGN AND METHODS: We investigated insulin signaling by immunoblotting during wound healing of control and diabetic animals with or without topical insulin. Diabetic patients with ulcers were randomized to receive topical insulin or placebo in a prospective, double-blind and placebo-controlled, randomized clinical trial (NCT 01295177) of wound healing. RESULTS AND CONCLUSIONS: Expression of IR, IRS-1, IRS-2, SHC, ERK, and AKT are increased in the tissue of healing wounds compared to intact skin, suggesting that the insulin signaling pathway may have an important role in this process. These pathways were attenuated in the wounded skin of diabetic rats, in parallel with an increase in the time of complete wound healing. Upon topical application of insulin cream, the wound healing time of diabetic animals was normalized, followed by a reversal of defective insulin signal transduction. In addition, the treatment also increased expression of other proteins, such as eNOS (also in bone marrow), VEGF, and SDF-1α in wounded skin. In diabetic patients, topical insulin cream markedly improved wound healing, representing an attractive and cost-free method for treating this devastating complication of diabetes. TRIAL REGISTRATION: ClinicalTrials.gov NCT01295177.

Up-regulation of the phosphatidylinositol 3-kinase/protein kinase B pathway in the ovary of rats by chronic treatment with hCG and insulin.

Polycystic ovary syndrome (PCOS) manifests as chronic anovulation, ovarian hyperandrogenism, and follicular cysts, which are amplified by insulin as well as the inability of the hormone to stimulate glucose uptake in classic target tissues such as muscle and fat. In the present study, we evaluated the regulation of the insulin-signaling pathways by using immunoprecipitation and immunoblotting in whole extracts of ovaries from non-pregnant human chorionic gonadotropin (hCG)-treated rats, hyperinsulinemic-induced rats and hyperinsulinemic-induced rats, treated with hCG for 22 consecutive days. There were increased associations of insulin receptor substrate (IRS)-1 and IRS-2 with phosphatidylinositol (PI) 3-kinase, followed by enhanced protein kinase B (Akt) serine and threonine phosphorylation, in the ovaries of rats that were treated with hCG, either alone or with insulin. In contrast, the skeletal muscle demonstrated a reduced IRS-1/PI 3-kinase/Akt pathway in hyperinsulinemic-induced rats. These intracellular modifications were accompanied by follicular cysts, detected by optical microscopy, and increased androstenedione serum levels. In summary, our data show that chronic treatment with hCG or hCG plus insulin can induce changes in ovaries that simulate PCOS. In these situations, an increase in the insulin-induced IRS/PI 3-kinase/Akt pathway occurs in the ovary, suggesting that the activation of this pathway may have a role in the development of PCOS.

Novel signal transduction pathway for luteinizing hormone and its interaction with insulin: activation of Janus kinase/signal transducer and activator of transcription and phosphoinositol 3-kinase/Akt pathways.

The actions of LH are mediated through a single class of cell surface LH/human chorionic gonadotropin receptor, which is a member of the G protein-coupled receptor family. In the present study we showed that LH induced rapid tyrosine phosphorylation and activation of the Janus kinase 2 (JAK2) in rat ovary. Upon JAK2 activation, tyrosine phosphorylation of signal transducer and activator of transcription-1 (STAT-1), STAT-5b, insulin receptor substrate-1 (IRS-1), and Src homology and collagen homology (Shc) were detected. In addition, LH induced IRS-1/phosphoinositol 3-kinase and Shc /growth factor receptor-binding protein 2 (Grb2) associations and downstream AKT (protein kinase B, homologous to v-AKT) serine phosphorylation and ERK tyrosine phosphorylation, respectively. The simultaneous infusion of insulin and LH induced higher phosphorylation levels of JAK2, STAT5b, IRS-1, and AKT compared with each hormone alone in the whole ovary of normal rats. By immunohistochemistry we demonstrated that these late events take place in follicular cells and both external and internal theca. These results indicate a new signal transduction pathway for LH and show that there is positive cross-talk between the insulin and LH signaling pathways at the level of phosphoinositol 3-kinase/AKT pathway in this tissue.