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-1 alpha 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.Sao Paulo Research Foundation (FAPESP)Sao Paulo Research Foundation (FAPESP)National Institute of Science and Technology (INCT)National Institute of Science and Technology (INCT)National Council for Scientific and Technological Development (CNPq)National Council for Scientific and Technological Development (CNPq

Quantitative phenotypic and functional analyses of islet immune cells before and after diabetes onset in the BB rat.

Inflammatory cells invading islets are thought to be mediators of islet destruction in spontaneous autoimmune diabetes mellitus. Thus methods were developed to isolate and characterize in situ islet inflammatory cells from 75-95-day-old prediabetic and diabetic BB rats. Islet inflammatory cells were structurally examined using single- and double-colour flow cytometry. Functional studies consisted of cytolytic assays using normal rat islet target cells and in situ islet or spleen effector cells. Structural data reveal natural killer cells to be the major cell population (70%) of total immune cells present in inflamed islets during prediabetes. At diabetes onset, the natural killer cell population remained at a high level (47%), but an increasing population of T cells (40%) was noted also. Analyses of T-cell subsets before and after diabetes onset revealed CD4+ T cells as predominant (50-55% of total T cells) with double-negative (CD4-CD8-) T cells (25-30%) and CD8+ T cells (15-20%) also present in significant quantities. Activated T cells accounted only for a minority of T cells (< 3%). Functional studies indicate that in situ islet-derived cytolytic effector cells are more potent killers (ten-fold) of normal islet target cells than are splenic effector cells. These data suggest that in situ islet inflammatory cells (a) can be quantitatively studied both structurally and functionally; (b) express structural phenotypes differing substantially from splenic mononuclear cell populations; (c) are considerably more cytolytic than splenic effectors; and (d) should prove informative in determining the most significant autoimmune functional events prior to and during islet beta-cell destruction