Beneficial Effects of Insulin on Cell Proliferation and Protein Metabolism in Skin Donor Site Wound

Core-shell insulin-loaded nanofibrous scaffolds for repairing diabetic wounds

Patients with diabetes mellitus have up to a 15% lifetime risk of non-healing and poorly healing wounds. This work develops core-shell nanofibrous bioactive insulin-loaded poly-D-L-lactide-glycolide (PLGA) scaffolds that release insulin in a sustained manner for repairing wounds in diabetic rats. To prepare the biodegradable core-shell nanofibers, PLGA and insulin solutions were fed into two capillary tubes of different sizes that were coaxially electrospun using two independent pumps. The scaffolds sustainably released insulin for four weeks. The hydrophilicity and water-containing capacity of core-shell nanofibrous insulin/PLGA scaffolds significantly exceeded those of blended nanofibrous scaffolds. The nanofibrous core-shell insulin-loaded scaffold reduced the amount of type I collagen in vitro, increased the transforming growth factor-beta content in vivo, and promoted diabetic would repair. The core-shell insulin-loaded nanofibrous scaffolds prolong the release of insulin and promote diabetic wound healing.

Clinical study on local application of low-dose insulin for promoting wound healing after operation for deep burns

Transplanted free skin flaps are often needed to treat deep burns; their survival, however, is less than optimal. This study examined whether local low-dose insulin injections can promote flap survival and wound healing after surgery. A total of 165 patients who underwent free skin flap transplantation for simple deep burns were enrolled in the study and divided into 5 groups of 33 patients each: Blank control group (no local subcutaneous drug injections), saline control group (saline injections), low-dose insulin group (0.5 units regular insulin injections), medium-dose group (1.0 units regular insulin injections) and high-dose group (2.0 units regular insulin injections). Wound healing and flap survival conditions were assessed and compared among groups. The best wound healing rate found was that of the low-dose insulin injection group where all the parameters measured improved significantly: The healing time was shorter; the blood flow volume, the flap survival, the number of fibroblasts and new vessels increased; the re-epithelialization occurred faster; the infiltration of inflammatory cells was reduced; the expression levels of heat shock protein-90, vascular endothelial growth factor, transforming growth factor-β and interleukin-1 were higher; and the plasma glucose levels only fluctuated slightly. The results clearly demonstrate that a local low-dose insulin regime after flap transplantation can accelerate the healing time and improve the surgical outcome without exerting detrimental secondary effects on the glucose plasma level of deep burn patients.

Effect of local insulin injection on wound vascularization in patients with diabetic foot ulcer

The aim of the present study was to investigate the effect of local insulin injection on granulation tissue formation in the wounds of patients with diabetic foot ulcer. Thirty-two patients with diabetic foot ulcer were randomly divided into an insulin (n=18) and a control (n=14) group. In the diabetic foot ulcer wound, the insulin group were administered insulin and the control group were administered an equal volume of saline. Prior to injection and at 0.5, 1.0, 2.0 and 4.0 h after injection, the fingertip blood glucose levels were determined. The growth of granulation tissue was assessed continuously for 12 days. Wound tissue was harvested at 0, 5, 7 and 12 days for the detection of CD34 expression by immunohistochemistry. The microvessel density (MVD) was calculated. No significant difference in the fasting blood glucose level was found between the two groups at any time-point (P>0.05). Growth of granulation tissue in the insulin group was more marked from 7 days after local insulin injection (24.87±0.24) and was significantly different from that in the control group (18.66±0.45) (P<0.01). New vessels were observed in the insulin group 3 days after insulin injection; however, there was no significant difference in MVD compared with the control group (P>0.05). The MVD in the insulin group increased markedly from 5 days after treatment, and the difference between the two groups was significant (P<0.01). In conclusion, local injection of insulin into the base of a diabetic foot ulcer has a significant effect on systemic blood glucose and may promote wound healing by improving the growth of granulation tissue.

Insulin and wound healing

Skin is a dynamic and complex organ that relies on the interaction of different cell types, biomacromolecules and signaling molecules. Injury triggers a cascade of events designed to quickly restore skin integrity. Depending on the size and severity of the wound, extensive physiological and metabolic changes can occur, resulting in impaired wound healing and increased morbidity resulting in higher rates of death. While wound dressings provide a temporary barrier, they are inherently incapable of significantly restoring metabolic upsets, post-burn insulin resistance, and impaired wound healing in patients with extensive burns. Exogenous insulin application has therefore been investigated as a potential therapeutic intervention for nearly a century to improve wound recovery. This review will highlight the important achievements that demonstrate insulin's ability to stimulate cellular migration and burn wound recovery, as well as providing a perspective on future therapeutic applications and research directions.

Insulin and hypertonic glucose in the management of aseptic fat liquefaction of post-surgical incision: a meta-analysis and systematic review

A meta-analysis and systematic review assessing randomised controlled trials (RCTs) was sought to determine whether subcutaneous injection of insulin with hypertonic glucose promotes healing in postoperative incisions with aseptic fat liquefaction. We searched the Cochrane library, Pubmed, EMBASE, National Science Digital Library (NSDL) and China Biological Medicine Database (CBMdisc) for literature published from 1 January 1990 to 30 September 2011. RCTs that evaluated subcutaneous injection of insulin with hypertonic glucose as a treatment for postoperative wound with fat liquefaction were sought. Wound healing was the primary endpoint. Jadad score and Cochrane Collaboration's tool were used for assessing quality of studies and risk of bias. We abstracted data regarding time to wound healing, cost and adverse effects. The random-effects inverse variance model was used for all analyses using weighted mean difference and 95% confidence interval. Eight trials (414 participants) were identified that met the inclusion criteria. Subcutaneous injection of insulin with hypertonic glucose significantly reduces time to healing by 6·33 days compared with conventional drainage, with less cost. There was no report concerning adverse effects. Subcutaneous injection of insulin with hypertonic glucose may improve the healing process in postoperative wounds with aseptic fat liquefaction.

Hyperglycemia exacerbates burn-induced liver inflammation via noncanonical nuclear factor-κB pathway activation

Hyperglycemia and inflammation are hallmarks of burn injury. In this study, we used a rat model of hyperglycemia and burn injury to investigate the effects of hyperglycemia on inflammatory responses in the liver. Hyperglycemia was induced in male Sprague-Dawley rats with streptozotocin (STZ) (35-40 mg/kg), followed by a 60% third-degree scald burn injury. Cytokine levels (by multiplex, in cytosolic liver extracts), hormones (by enzyme-linked immunosorbent assay [ELISA], in serum), nuclear factor (NF)-κB protein deoxyribonucleic acid (DNA) binding (by ELISA, in nuclear liver extracts) and liver functional panel (using VetScan, in serum) were measured at different time points up to 7 d after burn injury. Blood glucose significantly increased after burn injury in both groups with different temporal patterns. Hyperglycemic rats were capable of endogenous insulin secretion, which was enhanced significantly versus controls 12 h after burn injury. DNA binding data of liver nuclear extracts showed a robust and significant activation of the noncanonical NF-κB pathway in the hyperglycemic versus control burn animals, including increased NF-κB-inducing kinase expression (p < 0.05). Liver acute-phase proteins and cytokine expression were increased, whereas secretion of constitutive proteins was decreased after burn injury in hyperglycemic versus control animals (p < 0.05). These results indicate that burn injury to the skin rapidly activated canonical and noncanonical NF-κB pathways in the liver. Robust activation of the NF-κB noncanonical pathway was associated with increased expression of inflammatory markers and acute-phase proteins, and impaired glucose metabolism. Hyperglycemia is detrimental to burn outcome by augmenting inflammation mediated by hepatic noncanonical NF-κB pathway activation.