Chronic aerobic exercise attenuates leukocyte microparticle shedding via calcium modulation in high-fat diet rats

Leukocyte-derived microparticles (LMPs) contribute to endothelial dysfunction and atherogenesis through calcium-dependent membrane vesiculation. Whether chronic aerobic exercise modulates leukocyte vesicle shedding under dyslipidemic conditions, and whether this effect is mediated by intracellular calcium homeostasis, remains unclear. We hypothesized that 12 weeks of moderate-intensity aerobic exercise would reduce circulating LMP concentrations in high-fat diet (HFD)-fed rats through normalization of intracellular calcium dynamics, and would be accompanied by reduced endoglin-mediated endothelial shedding. Twenty-eight male Wistar rats were randomized into four groups ( n = 7/group at baseline): K1 (HFD + exercise), K2 (normal diet + exercise), K3 (HFD sedentary), and K4 (normal diet sedentary). Following five deaths unrelated to the interventions, 23 rats completed the study (K1, n = 5; K2, n = 6; K3, n = 6; K4, n = 6). Exercise consisted of a 12-week progressive treadmill protocol (14–16 m/min, approximately 65–70% VO₂max, 30 min/session, 4 days/week). Flow cytometry quantified circulating T-lymphocyte (CD3⁺), B-lymphocyte (CD45RA⁺), and monocyte (CD11a/b⁺) LMPs in platelet-free plasma. Basal and ATP-stimulated intracellular Ca²⁺ dynamics were measured in peripheral blood mononuclear cells; aortic endoglin (CD105) and serum soluble endoglin (sEng) were assessed by immunohistochemistry and ELISA, respectively. Contrary to our hypothesis for the diseased state, K1 (HFD + exercise) showed the lowest LMP concentrations across all three lineages (T-lymphocyte 1.94 ± 0.84%; B-lymphocyte 6.68 ± 1.90%; monocyte 2.02 ± 0.78%), significantly lower than K2, K3, and K4 ( p < 0.05). Unexpectedly, K2 (normal diet + exercise) — rather than the untreated HFD group — showed the highest LMP levels across all three lineages (T-lymphocyte 33.49 ± 7.90%), significantly exceeding K1 for all subtypes. Baseline intracellular Ca²⁺ differed significantly among groups in lymphocytes ( p = 0.001) and monocytes ( p = 0.004): K3 (HFD sedentary) unexpectedly showed the lowest values, while K2 showed the highest. Aortic endoglin and serum sEng did not differ significantly between groups ( p > 0.05 for all comparisons). These findings indicate that chronic moderate-intensity aerobic exercise is associated with lower leukocyte microparticle shedding specifically under high-fat diet conditions, paralleled by altered intracellular calcium handling; however, the unexpectedly high LMP and calcium levels observed in exercised, metabolically healthy animals (K2) indicate that this relationship depends on underlying metabolic status rather than being uniformly protective. Because aortic and soluble endoglin were unaffected, inferences regarding endothelial-level protection remain preliminary, and these findings should be regarded as hypothesis-generating rather than as direct support for a specific clinical application.