Maria A. Bednarek

Potency optimization of Huwentoxin-IV on hNav1.7: A neurotoxin TTX-S sodium-channel antagonist from the venom of the Chinese bird-eating spider Selenocosmia huwena

The spider venom peptide Huwentoxin-IV (HwTx-IV) 1 is a potent antagonist of hNav1.7 (IC50 determined herein as 17 ± 2 nM). Nav1.7 is a voltage-gated sodium channel involved in the generation and conduction of neuropathic and nociceptive pain signals. We prepared a number of HwTx-IV analogs as part of a structure-function study into Nav1.7 antagonism. The inhibitory potency of these analogs was determined by automated electrophysiology and is reported herein. In particular, the native residues Glu(1), Glu(4), Phe(6) and Tyr(33) were revealed as important activity modulators and several peptides bearing mutations in these positions showed significantly increased potency on hNav1.7 while maintaining the original selectivity profile of the wild-type peptide 1 on hNav1.5. Peptide 47 (Gly(1), Gly(4), Trp(33)-HwTx) demonstrated the largest potency increase on hNav1.7 (IC50 0.4 ± 0.1 nM).

A novel glucagon‐like peptide 1/glucagon receptor dual agonist improves steatohepatitis and liver regeneration in mice

Because nonalcoholic steatohepatitis (NASH) is associated with impaired liver regeneration, we investigated the effects of G49, a dual glucagon‐like peptide‐1/glucagon receptor agonist, on NASH and hepatic regeneration. C57Bl/6 mice fed chow or a methionine and choline–deficient (MCD) diet for 1 week were divided into 4 groups: control (chow diet), MCD diet, chow diet plus G49, and M+G49 (MCD diet plus G49). Mice fed a high‐fat diet (HFD) for 10 weeks were divided into groups: HFD and H+G49 (HFD plus G49). Following 2 (MCD groups) or 3 (HFD groups) weeks of treatment with G49, partial hepatectomy (PH) was performed, and all mice were maintained on the same treatment schedule for 2 additional weeks. Analysis of liver function, hepatic regeneration, and comprehensive genomic and metabolic profiling were conducted. NASH was ameliorated in the M+G49 group, manifested by reduced inflammation, steatosis, oxidative stress, and apoptosis and increased mitochondrial biogenesis. G49 treatment was also associated with replenishment of intrahepatic glucose due to enhanced gluconeogenesis and reduced glucose use through the pentose phosphate cycle and oxidative metabolism. Following PH, G49 treatment increased survival, restored the cytokine‐mediated priming phase, and enhanced the proliferative capacity and hepatic regeneration ratio in mice on the MCD diet. NASH markers remained decreased in M+G49 mice after PH, and glucose use was shifted to the pentose phosphate cycle and oxidative metabolism. G49 administered immediately after PH was also effective at alleviating the pathological changes induced by the MCD diet. Benefits in terms of liver regeneration were also found in mice fed HFD and treated with G49. Conclusion: Dual‐acting glucagon‐like peptide‐1/glucagon receptor agonists such as G49 represent a novel therapeutic approach for patients with NASH and particularly those requiring PH. (Hepatology 2017;65:950‐968).

Apelin-36 Modulates Blood Glucose and Body Weight Independently of Canonical APJ Receptor Signaling.

Apelin-36 was discovered as the endogenous ligand for the previously orphan receptor APJ. Apelin-36 has been linked to two major types of biological activities: cardiovascular (stimulation of cardiac contractility and suppression of blood pressure) and metabolic (improving glucose homeostasis and lowering body weight). It has been assumed that both of these activities are modulated through APJ. Here, we demonstrate that the metabolic activity of apelin-36 can be separated from canonical APJ activation. We developed a series of apelin-36 variants in which evolutionarily conserved residues were mutated, and evaluated their ability to modulate glucose homeostasis and body weight in chronic mouse models. We found that apelin-36(L28A) retains full metabolic activity, but is 100-fold impaired in its ability to activate APJ. In contrast to its full metabolic activity, apelin-36(L28A) lost the ability to suppress blood pressure in spontaneously hypertensive rats (SHR). We took advantage of these findings to develop a longer-acting variant of apelin-36 that could modulate glucose homeostasis without impacting blood pressure (or activating APJ). Apelin-36-[L28C(30kDa-PEG)] is 10,000-fold less potent than apelin-36 at activating the APJ receptor but retains its ability to significantly lower blood glucose and improve glucose tolerance in diet-induced obese mice. Apelin-36-[L28C(30kDa-PEG)] provides a starting point for the development of diabetes therapeutics that are devoid of the blood pressure effects associated with canonical APJ activation.

Contribution of regional brain melanocortin receptor subtypes to elevated activity energy expenditure in lean, active rats.

Physical activity and non-exercise activity thermogenesis (NEAT) are crucial factors accounting for individual differences in body weight, interacting with genetic predisposition. In the brain, a number of neuroendocrine intermediates regulate food intake and energy expenditure (EE); this includes the brain melanocortin (MC) system, consisting of MC peptides as well as their receptors (MCR). MC3R and MC4R have emerged as critical modulators of EE and food intake. To determine how variance in MC signaling may underlie individual differences in physical activity levels, we examined behavioral response to MC receptor agonists and antagonists in rats that show high and low levels of physical activity and NEAT, that is, high- and low-capacity runners (HCR, LCR), developed by artificial selection for differential intrinsic aerobic running capacity. Focusing on the hypothalamus, we identified brain region-specific elevations in expression of MCR 3, 4, and also MC5R, in the highly active, lean HCR relative to the less active and obesity-prone LCR. Further, the differences in activity and associated EE as a result of MCR activation or suppression using specific agonists and antagonists were similarly region-specific and directly corresponded to the differential MCR expression patterns. The agonists and antagonists investigated here did not significantly impact food intake at the doses used, suggesting that the differential pattern of receptor expression may by more meaningful to physical activity than to other aspects of energy balance regulation. Thus, MCR-mediated physical activity may be a key neural mechanism in distinguishing the lean phenotype and a target for enhancing physical activity and NEAT.