Integrative Metabolomics and Systems Pharmacology Reveal PPARγ-Centered Antidiabetic Mechanisms of Caulerpa racemosa and Its Bioactive Compounds

Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder requiring safe, multitarget therapeutic strategies. Marine macroalgae represent an underexplored source of bioactives with pleiotropic metabolic effects. This study investigated the antidiabetic potential of an ultrasound-assisted ethanolic extract of Caulerpa racemosa (UAECr) and its key phytosterol, campesterol, through an integrative framework combining metabolomics, network pharmacology, molecular docking, molecular dynamics simulation, and in vitro validation. Untargeted ultra-high-performance liquid chromatography–high-resolution mass spectrometry (UHPLC–HRMS) metabolomics characterized UAECr constituents, followed by in silico bioactivity prediction, target-network analysis, molecular docking, and 100 ns molecular dynamics simulation of the peroxisome proliferator-activated receptor gamma (PPARγ)–campesterol complex. Functional validation was performed in differentiated 3T3-L1 adipocytes assessing glucose uptake, PPARγ expression, dipeptidyl peptidase 4 (DPP-4) inhibition, and cytotoxicity. Metabolomics identified campesterol as a prominent bioactive. Network pharmacology highlighted PPARγ as a central hub, supported by strong docking affinity of campesterol toward PPARγ (−11.4 kcal/mol) and DPP-4 (−8.3 kcal/mol). Molecular dynamics simulations demonstrated stable PPARγ–campesterol interactions, with preserved protein compactness and low residue fluctuation. In vitro, UAECr and campesterol significantly enhanced glucose uptake (up to 134% vs. control, p < 0.001), upregulated PPARγ expression (4-fold, p < 0.0001), and moderately inhibited DPP-4 activity (p < 0.01) without cytotoxicity. C. racemosa-derived extracts and campesterol exert antidiabetic effects primarily via stable PPARγ-mediated insulin sensitization with complementary DPP-4 modulation, supporting its potential as a marine-derived functional food candidate.