Bone tissue engineering offers a promising alternative to autografts and allografts for treating critical bone defects. Hydrogels, three-dimensional hydrophilic polymer networks, have emerged as leading scaffold materials due to their ability to mimic native extracellular matrix properties while providing tunable biocompatibility, biodegradability, mechanical characteristics, and high water content, enabling nutrient transport and cell viability. These scaffolds can be loaded with bioactive cues, including growth factors, peptides, and nanoparticles, and can deliver stem cells, supporting localised and sustained bone regeneration. Recent advances in hydrogel design have improved osteoinductivity and osteoconductivity through controlled physical, chemical, and mechanical properties, and sophisticated fabrication strategies such as 3D bioprinting and nanostructuring. This review provides a comprehensive overview of hydrogel-based scaffolds for bone tissue engineering, discussing material types, bioactive factor delivery, host tissue interactions, including immune modulation and osteogenic differentiation, and the latest preclinical and clinical applications. Finally, we highlight the remaining challenges and critical design requirements for developing next-generation hydrogels that integrate structural integrity with biological functionality.

Energy homeostasis arises from a complex interplay between gut-derived hormones, the central nervous system, and pancreatic function. Beyond the classical incretin axis, a broad spectrum of gut peptides acts in concert to coordinate appetite regulation, nutrient sensing, gastric motility, and systemic bioenergetic balance. Perturbation of this network contributes to metabolic disorders such as obesity, type 2 diabetes, and cachexia, underscoring its pivotal role in physiological and pathological energy regulation. This review provides an integrated analysis of the mechanisms through which gut–brain–pancreas communication maintains metabolic homeostasis, with particular attention to the dynamic cross-talk between peripheral endocrine signals and central regulatory circuits. Alterations in these pathways are examined in relation to their impact on energy expenditure and substrate utilisation, alongside recent translational efforts exploiting multi-receptor peptide agonism and combinatorial hormonal modulation to restore metabolic equilibrium. Emerging therapeutic approaches increasingly aim to engage multiple bioenergetic pathways simultaneously, supported by advances in peptide engineering and molecular design. By conceptualising metabolic regulation as a coordinated network rather than a linear hormonal cascade, this article delineates a physiological and translational framework for next-generation interventions targeting bioenergetic dysfunction in human disease.