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Before insulin can stimulate myocytes to take up glucose, it must first move from the circulation to the interstitial space. The continuous endothelium of skeletal muscle (SkM) capillaries restricts insulin's access to myocytes. The mechanism by which insulin crosses this continuous endothelium is critical to understand insulin action and insulin resistance; however, methodological obstacles have limited understanding of endothelial insulin transport in vivo. Here, we present an intravital microscopy technique to measure the rate of insulin efflux across the endothelium of SkM capillaries. This method involves development of a fully bioactive, fluorescent insulin probe, a gastrocnemius preparation for intravital microscopy, an automated vascular segmentation algorithm, and the use of mathematical models to estimate endothelial transport parameters. We combined direct visualization of insulin efflux from SkM capillaries with modeling of insulin efflux kinetics to identify fluid-phase transport as the major mode of transendothelial insulin efflux in mice. Model-independent experiments demonstrating that insulin movement is neither saturable nor affected by insulin receptor antagonism supported this result. Our finding that insulin enters the SkM interstitium by fluid-phase transport may have implications in the pathophysiology of SkM insulin resistance as well as in the treatment of diabetes with various insulin analogs., Introduction Interorgan communication is essential for maintaining physiological homeostasis. One way organs communicate with each other is by sending molecular signals through the circulation. Before these signals can stimulate biological [...]

Research describing the design of a small group of beta-beta-alpha peptides is presented. The paper suggests that the ologomeric scaffold will lead to the synthesis of alpha-beta superstructures.

Four 14-residue peptides have recently been linked to a cavitand containing methyl feet, to develop a de novo protein with a hydrophobic template. The synthetic use of phosphate-footed cavitands is demonstrated through the reaction of suitably activated peptides with phosphate-footed bromomethyl and phosphate-footed thiomethyl cavitands, which form the de novo protein with links to a hydrophilic template.

It has been possible to identify a new loop-truncated form of a beta-beta-alpha peptide that creates a well-defined homotrimer in water. The removal of two amino acids in the loop region of the monomer was vital to switching the motif to a discrete oligomeric state.

The therapeutic management of antibody-mediated autoimmune disease typically involves immunosuppressant and immunomodulatory strategies. However, perturbing the fundamental role of the neonatal Fc receptor (FcRn) in salvaging IgG from lysosomal degradation provides a novel approach - depleting the body of pathogenic immunoglobulin by preventing IgG binding to FcRn and thereby increasing the rate of IgG catabolism. Herein, we describe the discovery and preclinical evaluation of fully human monoclonal IgG antibody inhibitors of FcRn. Using phage display, we identified several potent inhibitors of human-FcRn in which binding to FcRn is pH-independent, with over 1000-fold higher affinity for human-FcRn than human IgG-Fc at pH 7.4. FcRn antagonism in vivo using a human-FcRn knock-in transgenic mouse model caused enhanced catabolism of exogenously administered human IgG. In non-human primates, we observed reductions in endogenous circulating IgG of >60% with no changes in albumin, IgM, or IgA. FcRn antagonism did not disrupt the ability of non-human primates to mount IgM/IgG primary and secondary immune responses. Interestingly, the therapeutic anti-FcRn antibodies had a short serum half-life but caused a prolonged reduction in IgG levels. This may be explained by the high affinity of the antibodies to FcRn at both acidic and neutral pH. These results provide important preclinical proof of concept data in support of FcRn antagonism as a novel approach to the treatment of antibody-mediated autoimmune diseases. [ABSTRACT FROM AUTHOR]

The chemical synthesis of insulin has been a longstanding challenge, mainly because of the notorious hydrophobicity of the A chain and the complicated topology of this 51-mer peptide hormone consisting of two chains and three disulfide bonds. Reported herein is a new synthetic route utilizing the isoacyl peptide approach to address the hydrophobicity problems. The incorporation of isoacyl dipeptide segments into both A and B chains greatly improved their preparation and purification, and the RP-HPLC recovery of the chain ligation intermediates. The new route affords human insulin with a yield of 68 % based on the starting purified A chain and an overall yield of 24 % based on the substitution of the resin used for the preparation of A chain. To the best of our knowledge, this represents the most efficient route of human insulin chemical synthesis reported to date. [ABSTRACT FROM AUTHOR]

The design, synthesis and characterization of eight cavitand-based de novo four-helix bundles are presented. The proteins, each containing the basis sequence EELLKKLEELLKKG, are determined to be highly helical and exhibit extreme stability against the denaturant guanidine hydrochloride (GuHCl). The presence of flexible cavitand-peptide linkers, however, caused the helical structures to become more susceptible to GuHCl denaturation.

Abstract: Peptides targeting the human neonatal Fc receptor (FcRn) were conjugated to poly(ethylene glycol) (PEG) polymers to study their effect on inhibition of the IgG:FcRn protein–protein interaction both in vitro and in mice. Both linear (5–40kDa) and branched (20, 40kDa) PEG aldehydes were conjugated to an amine-containing linker of a homodimeric anti-FcRn peptide using reductive alkylation chemistry. It was found that conjugation of PEG to the peptide compromised the in vitro activity, with larger and branched PEGs causing the most dramatic losses in activity. The conjugates were evaluated in transgenic mice for their ability to accelerate the catabolism of human IgG. Optimal pharmacodynamic properties were observed with PEG–peptide conjugates that contained 20–40kDa linear PEGs and a 20kDa branched PEG. The optimal PEG–peptide conjugates were more effective in vivo than the unconjugated peptide control on a mole:mole and mg/kg basis, and represent potential new longer-acting peptide therapeutics for the treatment of humorally-mediated autoimmune disease. [Copyright &y& Elsevier]

The neonatal Fc receptor FcRn provides lgG molecules with their characteristically long half-lives in vivo by protecting them from intracellular catabolism and then returning them to the extracellular space. Other investigators have demonstrated that mice lacking FcRn are protected from induction of various autoimmune diseases, presumably because of the accelerated catabolism of pathogenic lgGs in the animals. Therefore, targeting FcRn with a specific inhibitor may represent a unique approach for the treatment of autoimmune disease or other diseases where the reduction of pathogenic lgG will have a therapeutic benefit. Using phage display peptide libraries, we screened for ligands that bound to human FcRn (hFcRn) and discovered a consensus peptide sequence that binds to hFcRn and inhibits the binding of human lgG (hlgG) in vitro. Chemical optimization of the phage-identified sequences yielded the 26-amino acid peptide dimer SYN1436, which is capable of potent in vitro inhibition of the hlgG-hFcRn interaction. Administration of SYN1436 to mice transgenic for hFcRn induced an increase in the rate of catabolism of hlgG in a dose-dependent manner. Treatment of cynomolgus monkeys with SYN1436 led to a reduction of lgG by up to 80% without reducing serum albumin levels that also binds to FcRn. SYN1436 and related peptides thus represent a previously uncharacterized family of potential therapeutic agents for the treatment of humorally mediated autoimmune and other diseases. [ABSTRACT FROM AUTHOR]

LY3305677 (LY) is a synthetic peptide analog of mammalian oxyntomodulin with a fatty acyl side chain to extend time action. LY functions are mediated by binding and activation of both glucagon (GcgR) and glucagon-like peptide-1 (GLP-1R) receptors. LY is bound with potent binding affinity (Ki) to human and mouse GcgR (Ki: 17.7 nM and 15.9 nM, respectively) and GLP-1R (Ki: 28.6 nM and 25.1 nM, respectively). LY dose-dependently stimulated insulin secretion in mouse pancreatic islets (EC50: 5.2 nM) and in mice. In oral glucose tolerance tests of diet-induced obese (DIO) and streptozotocin-induced diabetic mice, a single subcutaneous (SC) dose of LY significantly reduced glucose area under the curve by up to 65%. SC injections of LY to DIO mice dose-dependently reduced serum triglycerides and PCSK9 (proprotein convertase subtilisin/kexin type 9) levels and dose-dependently increased FGF21 (fibroblast growth factor 21) levels. In DIO mice treated over 18 days, LY 30 nmol/kg reduced body weight to a greater extent (33%) than semaglutide 60 nmol/kg (12%), and decreased food intake by 50% compared to vehicle. At Day 18, LY 30 nmol/kg group lost 33% of initial bodyweight, which was primarily due to 70% reduced fat mass. LY reduced liver triglycerides by greater than 70% and increased serum ketones by more than 3-fold compared to vehicle, suggestive of increased fatty acid oxidation. LY decreased body weight in both GcgR knock-out (KO) and GLP-1R KO mice, indicating that activation of both receptors contributed to greater weight loss. To assess potential changes in energy expenditure, DIO mice were treated chronically with SC LY (15 nmol/kg), semaglutide (60 nmol/kg), or vehicle. LY, but not semaglutide, increased energy expenditure as compared with vehicle. These preclinical studies indicate that novel dual GcgR and GLP-1R agonist LY may have potential to enhance metabolic health by improving dyslipidemia, hyperglycemia, or obesity. Disclosure: Y. Chen: None. H. Qu: Employee; Self; Eli Lilly and Company, Stock/Shareholder; Self; Eli Lilly and Company. A. Mezo: None. T. Coskun: Employee; Self; Eli Lilly and Company, Stock/Shareholder; Self; Eli Lilly and Company. M. Song: None. W. C. Roell: Employee; Self; Eli Lilly and Company, Stock/Shareholder; Self; Eli Lilly and Company. K. B. Bokvist: Employee; Self; Eli Lilly and Company, Sanofi-Aventis Deutschland GmbH, Stock/Shareholder; Self; Johnson & Johnson, Sanofi-Aventis Deutschland GmbH, Stock/Shareholder; Spouse/Partner; Novo Nordisk A/S. J. S. Moyers: Employee; Self; Eli Lilly and Company, Stock/Shareholder; Self; Eli Lilly and Company. M. K. Thomas: Employee; Self; Eli Lilly and Company, Stock/Shareholder; Self; Eli Lilly and Company. F. Valenzuela: None. Funding: Eli Lilly and Company [ABSTRACT FROM AUTHOR]

The neonatal Fc receptor, FcRn, is responsible for controlling the half-life of IgG antibodies. As a result, inhibitors of FcRn have been investigated as a possible way to modulate IgG half-lives. Such inhibitors could have possible applications in reducing autoantibody levels in autoimmune disease states. To date, monoclonal antibodies, engineered Fc domains, and short peptides have been reported to inhibit FcRn function and modulate IgG half-lives in vivo. [ABSTRACT FROM AUTHOR]

Abstract: The neonatal Fc receptor, FcRn, prolongs the half-life of IgG in the serum and represents a potential therapeutic target for the treatment of autoimmune disease. Small molecules that block the protein–protein interactions of human IgG–human FcRn may lower pathogenic autoantibodies and provide effective treatment. A novel class of quinoxalines has been discovered as antagonists of the IgG:FcRn protein–protein interaction through optimization of a hit derived from a virtual ligand-based screen. [Copyright &y& Elsevier]