Key result
Metabolic syndrome is linked to impaired mitochondrial calcium uptake and ~70% greater AF susceptibility.
Why the study?
Patients with metabolic syndrome have an increased risk of AF, but whether impaired mitochondrial Ca2+ handling underlies this association remains poorly explored.
Demonstrates that improved mitochondrial calcium uptake reduces atrial fibrillation in metabolic syndrome, suggesting a potential therapeutic approach.
BACKGROUND Patients with metabolic syndrome (MetS) have an increased risk of atrial fibrillation (AF). Impaired Ca2+ homeostasis and mitochondrial dysfunction have emerged as an arrhythmogenic substrate in both patients and animal models of MetS. Whether impaired mitochondrial Ca2+ handling underlies AF associated with MetS remains poorly explored. OBJECTIVES The aim of this study was to determine the initial mechanisms related to AF susceptibility and mitochondrial dysfunction encountered in metabolic cardiomyopathy. METHODS A total of 161 mice and 34 patients were studied. Mitochondrial Ca2+ and mitochondrial Ca2+ uniporter complex (MCUC) were investigated in right atrial tissue of patients with (n = 18) or without (n = 16) MetS and of C57Bl/6J mice fed with a high-fat sucrose diet (HFS) for 2 (n = 42) or 12 (n = 39) weeks. Susceptibility to AF was evaluated in isolated sinoatrial tissue and in vivo in mice. RESULTS Increased expression of the MICUs subunits of the MCUC (1.00 ± 0.33 AU vs 1.29 ± 0.23 AU; P = 0.034) was associated with impaired mitochondrial Ca2+ uptake in patients (168.7 ± 31.3 nmol/min/mg vs 127.3 ± 18.4 nmol/min/mg; P = 0.026) and HFS mice (0.10 ± 0.04 ΔF/F0 × ms-1 vs 0.06 ± 0.03 ΔF/F0 × ms-1; P = 0.0086, and 0.15 ± 0.07 ΔF/F0 × ms-1 vs 0.046 ± 0.03 ΔF/F0 × ms-1; P = 0.0076 in 2- and 12-week HFS mice, respectively). HFS mice elicited a 70% increased susceptibility to AF. The MCUC agonist kaempferol restored MCUC activity in vitro and abolished the occurrence of AF in HFS mice. CONCLUSIONS Impaired MCUC activity and mitochondrial Ca2+ homeostasis from the early stage of metabolic cardiomyopathy in mice lead to AF. Given that similar defects in cardiac mitochondrial Ca2+ handling are present in MetS patients, the modulation of the MCUC activity represents an attractive antiarrhythmic strategy.
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Fossier et al. (2022) studied Metabolic syndrome and atrial fibrillation (n=195). Metabolic syndrome vs. Without metabolic syndrome was evaluated on Mitochondrial Ca2+ uptake in patients (p=0.026). Metabolic syndrome was associated with impaired mitochondrial calcium uptake in patients (127.3 vs 168.7 nmol/min/mg; P=0.026) and a 70% increased susceptibility to atrial fibrillation in mice.
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