The assembled investigative team has recently developed new synthetic approaches that have led to the identification of a novel PSGL-1 glycopeptide mimetic, GSnP-6, as a low nanomolar antagonist of PSGL- 1/P-selectin interactions. Specifically, GSnP-6 was identified as the result of a screening program directed at the rational design of PSGL-1 mimetics in which critical, high affinity, carbohydrate and peptide recognition epitopes were preserved. As a synthetic molecule, GSnP-6 is amenable to further modification, which provides for great flexibility in drug design and delivery. In concert with thee efforts, recent computational simulations have confirmed that GSnP-6 provides a unique structural scaffold for the design of a range of highly potent selectin-specific antagonists for prevention and treatment of obesity induced metabolic syndrome and insulin resistance. Using GSnP-6 as a pharmacological `tool compound', we intend to: (1) Define the potency of GSnP-6 in murine models of obesity associated insulin resistance. In the first phase of our investigations, we will define the pharmacokinetic profile of GSnP-6, as well as poly(ethylene glycol) (PEG) conjugates of GSnP-6. The dosing regimen that affords the best drug delivery profile will be selected for subsequent in vivo studies. In the second phase of these investigations, the efficacy of GSnP-6 and/or PEG-GSnP-6 will be defined using murine models of diet-induced obesity. These studies will define the capacity of GSnP-6 to improve insulin sensitivity and glucose homeostasis, as well as reduce obesity-induced inflammatory changes in adipose tissue, thus, validating this therapeutic approach. (2) Design new structurally simpler PSGL-1 glycomimetics that display high selectin binding affinity. Molecular dynamics (MD) simulations have indicated that not all of the monosaccharides in the native PSGL-1 ligand or GSnP-6 contribute directly to binding affinity. Thus, computational studies will be pursued to guide the structure-activity relationship (SAR) studies and to identify novel structurally simpler, high affinity selectin inhibitors. A chemo-enzymatic scheme is currently used for the synthesis of GSnP-6 and related glycomimetics. However, the design of a total chemical synthesis for the generation of PSGL-1 glycomimetics offers the potential advantage of improved overall yield and will serve as a parallel focus for this Aim. (3) Determine the effectiveness of GSnP-6 and related analogues to improve lipid metabolism, prevent or reverse hepatic steatosis, and limit adipose tissue induced atherosclerosis. Obesity leads to impaired lipid metabolism, hepatic steatosis, and atherosclerosis. In the first phase of these investigations, the ability of GSnP-6 and the most promising structurally simplified P-selectin antagonist identified in Aim 2 to improve lipid metabolism and prevent hepatic steatosis will be assessed in ApoE?/? mice fed a Western diet. In the second phase of these studies, we will examine the capacity of these agents to limit atherosclerosis in ApoE?/? mice by attenuating systemic pro-inflammatory effects, as well as adipose tissue induced perivascular inflammation.
A screening program directed at the design of P-selectin glycoprotein ligand-1 (PSGL-1) mimetics has identified a stable, high affinity glycomimetic, GSnP-6, that effectively blocks PSGL-1/selectin interactions. Recent computational simulations have further enhanced our understanding of the structural biology of this glycopeptide mimetic and have confirmed its capacity to serve as a structural scaffold for the design of a broad range of highly potent selectin-specific antagonists. We believe that GSnP-6, as well as related analogues represent a promising new class of selectin-specific agent that provide a rational strategy for the prevention and treatment of the adverse metabolic effects of obesity.
