INS and metabolic disease: While existing reviews broadly cover topics such as oral delivery strategies (bioavailability enhancement) [32,34,35,48,50,53,55,57] and their use in specific biomacromolecules such as insulin [32,34,38,43,44,45,46,54,56], this article reviews a distinct perspective by focusing on the clinical application of biomacromolecules in the treatment of metabolic diseases.