Abstract Body: Background: Obesity and non-alcoholic fatty liver disease (NAFLD) is associated with platelet hyperactivity and thrombotic risk, yet its underlying mechanism remains poorly understood. Platelet function depends on spatiotemporal intracellular Ca²⁺ signaling, where oscillations support aggregation and sustained rise drive induce procoagulant activity. The regulatory role of mitochondrial calcium uniporter (MCU), the primary route for mitochondrial Ca²⁺ uptake, in regulating platelet hyperactivity in obesity and NAFLD remains unexplored.
Aim: Determine whether MCU acts as a key regulator of platelet hyperactivity in obesity and NAFLD.
Methods: Platelets from obese and NAFLD patients (BMI >30) and matched lean controls (BMI <25) were analyzed. WT and platelet-specific MCU knockout mice were fed chow or high-fat diet for 12–25 weeks. Aggregation and ATP secretion were assessed by aggregometry; αIIbβ3 activation and α-granule secretion by flow cytometry; Ca²⁺ mobilization by fluorometry; and signaling pathways by immunoblotting.
Results: In both early-onset obesity and obesity with NAFLD (in humans and mice), we observed increased PLC-γ activation, PKC substrate phosphorylation, and enhanced Ca²⁺ mobilization, indicating platelet hyperactivity. Platelets from early obesity exhibited GPVI- and GPCR agonist induced hyperaggregation, increased granule secretion, and enhanced αIIbβ3-activation (P<0.05 vs. lean controls). In contrast, platelets from obesity with NAFLD displayed a state of functional exhaustion with a greater propensity toward a procoagulant phenotype, characterized by increased phosphatidyl serine exposure. Next, we assessed platelet function in both conditions using platelet-specific MCU knockout and pharmacological inhibition of MCU. In early obesity, MCU inhibition attenuated GPVI- and GPCR-mediated aggregation and secretion. Similarly, MCU modulation prevented mitochondrial depolarization and procoagulant transformation associated with the exhausted platelet state. These antiplatelet effects were mechanistically linked to the prevention of MCU-mediated Ca²⁺ overload and preservation of mitochondrial membrane potential, supporting a central role for MCU in regulating cytosolic and mitochondrial Ca²⁺ homeostasis that drives a bioenergetic shift toward metabolic regulated thrombosis.
Conclusion: MCU functions a key regulator of platelet hyperactivity in obesity and NAFLD via coupling cytosolic Ca²⁺ signaling to mitochondrial bioenergetics.