Dual-agonist incretin peptides from fish with potential for obesity-related Type 2 diabetes therapy – A review

•Proglucagon-derived peptide from phylogenetically ancient fish are dual-agonists at GLP1R and GCGR.•Paddlefish glucagon and lamprey GLP-1 are the most potent and effective in stimulating insulin release from BRIN-BD11 cells.•Long-acting analogs improve glucose tolerance and insulin sensitivity in high fat-fed mice.•The analogs stimulate β-cell proliferation and protect against apoptosis, improve the lipid profile and reduce food intake.•Fish dual-agonist peptides provide templates for development into therapeutic agents for obesity-related T2DM.