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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 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.

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]

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., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The neonatal Fc receptor, FcRn, regulates the half-life of IgG in vivo and may be a target in the treatment of autoimmune disease. Monomeric peptide antagonists of the human IgG-human FcRn interaction were dimerized using three different synthetic methodologies: thiol/alkyl halide coupling of unprotected peptides, reductive alkylation of unprotected peptides, and on-resin amide bond formation with protected peptides. It was found that dimerization of monomeric peptides increased the in vitro activity of the peptide monomers more than 200-fold. Human IgG catabolism experiments in human FcRn transgenic mice were used to assess the in vivo activity of peptide dimers that possessed different linkers, cyclizations, and affinities for FcRn. Overall, it was found that the linker joining two monomeric peptides had only a minor effect on the in vitro potency but that in vitro potency was predictive of in vivo activity.