Antiobesity therapeutics with complementary dual-agonist activities at glucagon and glucagon-like peptide 1 receptors.

AIM: To develop more effective and long-lasting antiobesity and antidiabetic therapeutics by employing novel chemical modifications of glucagon-like peptide-1 receptor (GLP-1R) agonists. METHODS: We constructed novel unimolecular dual agonists of GLP-1R and glucagon receptor prepared by linking sEx-4 and native glucagon (GCG) via lysine or triazole [sEx4-GCG(K) and sEx4-GCG(T), respectively] and evaluated their antiobesity and antidiabetic efficacy in the diabetic and obese mouse model. RESULTS: Both sEx4-GCG(K) and sEx4-GCG(T) showed the beneficial metabolic effects of GLP-1 and glucagon: they promoted weight loss and ameliorated insulin resistance and hepatic steatosis. They also increased thermogenesis in brown adipose tissue, and lipolysis and ß-oxidation in white adipose tissue, with concomitant suppression of lipogenesis. Furthermore, both dual agonists activated the 5'-AMP-activated protein kinase signalling pathway and prevented palmitate-induced oxidative stress in skeletal muscle cells. CONCLUSION: Through their complementary dual agonism, sEx4-GCG(T) and sEx4-GCG(K) induce more marked weight loss and metabolic improvements than conventional agonists, and could be developed as novel therapeutic agents for the treatment of obesity and associated metabolic disorders in humans.

Solution structure and functional analysis of HelaTx1: the first toxin member of the κ-KTx5 subfamily.

Scorpion venom comprises a cocktail of toxins that have proven to be useful molecular tools for studying the pharmacological properties of membrane ion channels. HelaTx1, a short peptide neurotoxin isolated recently from the venom of the scorpion Heterometrus laoticus, is a 25 amino acid peptide with two disulfide bonds that shares low sequence homology with other scorpion toxins. HelaTx1 effectively decreases the amplitude of the K+ currents of voltage-gated Kv1.1 and Kv1.6 channels expressed in Xenopus oocytes, and was identified as the first toxin member of the κ-KTx5 subfamily, based on a sequence comparison and phylogenetic analysis. In the present study, we report the NMR solution structure of HelaTx1, and the major interaction points for its binding to voltage-gated Kv1.1 channels. The NMR results indicate that HelaTx1 adopts a helix-loop-helix fold linked by two disulfide bonds without any ß-sheets, resembling the molecular folding of other cysteine-stabilized helix-loop-helix (Cs α/α) scorpion toxins such as κ-hefutoxin, HeTx, and OmTx, as well as conotoxin pl14a. A series of alanine-scanning analogs revealed a broad surface on the toxin molecule largely comprising positively-charged residues that is crucial for interaction with voltagegated Kv1.1 channels. Interestingly, the functional dyad, a key molecular determinant for activity against voltage-gated potassium channels in other toxins, is not present in HelaTx1. [BMB Reports 2020; 53(5): 260-265].