Abstract 16043: The Role of eNOS Signaling in Wound Healing in a Murine Model of Diet-Induced Obesity

Abstract

Background and Rationale: Type 2-diabetes is associated with the depletion of circulating endothelial progenitor cells (EPCs) and deficits in wound healing; conditions that have been linked to decreased activity of endothelial nitric oxide synthase (eNOS). However, it is not clear how, in the context of insulin resistance, increasing eNOS would affect EPC levels and wound healing. Therefore, we measured EPC levels and recovery from hind-limb ischemia (HLI) in wild-type and eNOS-transgenic (Tg) mice in a model of diet-induced obesity. Methods and Results: Wild-type (WT) C57BL/6 and eNOS-Tg mice were placed on a low (LFD) or high fat diet (HFD). After 12 weeks, the mice were subjected to HLI, and tissue perfusion was assessed by Laser Doppler Imaging. Levels of EPCs (Flk-1+/Sca-1+-cells) were measured by flow cytometry. HFD feeding, for 4-12 weeks, decreased circulating EPC levels while the levels of EPCs in the bone marrow were increased. Insulin (100 nM; 15 min) stimulated Akt and eNOS phosphorylation in aorta of LFD, but not HFD-fed mice, indicating insulin resistance. HFD decreased plasma NOx levels and activated the pro-inflammatory NF-κBα pathway in aorta, heart, liver, skeletal muscle and adipose tissue as analyzed by Western blot analysis. Recovery of blood perfusion, 2 weeks after HLI, was significantly higher in LFD than HFD-fed mice (76±3% vs. 21±4%; p<0.05, n=5). Overexpression of eNOS prevented HFD-induced vascular insulin resistance, and enhanced recovery from HLI in both LFD (+64±4%) and HFD (+17±7%) fed mice. HLI decreased circulating EPC levels by about 30% in WT mice, while no changes in EPC levels were found in eNOS-Tg mice. Bone marrow EPCs were reduced after HLI in eNOS-Tg (28±8% of sham), but not in WT (94±27% of sham), mice. Conclusions: HFD impairs recovery from HLI, which may be related in part to vascular insulin resistance and decreased EPC mobilization. Deficits in the wound healing response due to diet-induced obesity could be overcome by increasing NO production via eNOS. Treatment strategies to increase NO bioavailability could promote wound healing in diabetic patients and prevent diabetic complications such as critical limb ischemia.