From the Incretin System to the Entero–Pancreatico–Hepatico–Systemic Polyhormonal Metabolic Homeostasis Network

The remarkable evolution of incretin-based therapeutics from selective glucagon-like peptide-1 receptor agonists to dual, triple and emerging polyagonists has fundamentally expanded our understanding of metabolic regulation. Clinical trials have consistently demonstrated coordinated improvements in glycaemic control, hepatic steatosis, body composition, insulin sensitivity, cardiovascular and renal outcomes, inflammatory activity, mitochondrial metabolism and energy expenditure that extend well beyond the expected physiological effects of individual receptor activation. These observations suggest that the therapeutic efficacy of contemporary polyagonists cannot be adequately explained by isolated hormonal mechanisms but instead reflects modulation of an integrated physiological regulatory system. We propose the existence of an Entero–Pancreatico–Hepatico–Systemic Polyhormonal Metabolic Homeostasis Network (EPHS-PMHN), a dynamic endocrine, neural, immune and metabolic communication network in which gastrointestinal nutrient sensing initiates coordinated signaling through the enteroendocrine system, pancreatic islets, liver, central nervous system, adipose tissue, skeletal muscle, kidneys, cardiovascular system, immune system and peripheral mitochondria. Although incretin hormones constitute the principal initiating signals within this network, physiological regulation is ultimately achieved through integrated actions of both incretin and non-incretin mediators including insulin, glucagon, amylin, fibroblast growth factor-21, bile acid signaling pathways, adipokines, hepatokines, myokines, autonomic neural pathways, inflammatory mediators, circadian regulators and intracellular nutrient-sensing mechanisms. Within this framework, physiological variables traditionally regarded as independently regulated — including fasting and postprandial glycaemia, hepatic fat content, insulin-glucagon balance, hepatic gluconeogenesis, lipid oxidation, triglyceride synthesis, resting energy expenditure, metabolic flexibility, mitochondrial function and inflammatory tone — are interpreted as emergent properties of coordinated network behaviour rather than isolated homeostatic endpoints. Furthermore, neurobehavioral determinants including psychological stress, sleep architecture, cognitive function, emotional state, personality traits and environmental influences continuously modulate network activity, thereby contributing to the unique metabolic phenotype observed in each individual. Accordingly, obesity, type 2 diabetes mellitus, metabolic dysfunction-associated steatotic liver disease, dyslipidaemia, sarcopenic obesity and cardio-renal-metabolic syndrome are viewed not as isolated disorders but as diverse clinical expressions of differential dysregulation within the same integrated metabolic network. This framework provides a mechanistic explanation for the superior efficacy of polyagonist therapies as network-restorative interventions rather than hormone replacement strategies and establishes a conceptual foundation for precision metabolic medicine based on characterization of network function instead of isolated biochemical abnormalities.