Cycles of ischemia-reperfusion (IR) that occur during peripheral arterial disease (PAD) are associated with significant morbi-mortality, and aging is an irreversible risk factor of PAD. However, the effects of advanced age on IR-induced skeletal muscle mitochondrial dysfunction are not well known. Young and aged mice were therefore submitted to hindlimb IR (2 h ischemia followed by 2 h reperfusion). Skeletal muscle mitochondrial respiration, calcium retention capacity (CRC) and reactive oxygen species (ROS) production were determined using high resolution respirometry, spectrofluorometry and electronic paramagnetic resonance. IR-induced impairment in mitochondrial respiration was enhanced in old animals (V_ADP; from 33.0 ± 2.4 to 18.4 ± 3.8 and 32.8 ± 1.3 to 5.9 ± 2.7 pmol/s/mg wet weight; −44.2 ± 11.4% vs. −82.0 ± 8.1%, in young and aged mice, respectively). Baseline CRC was lower in old animals and IR similarly decreased the CRC in both groups (from 11.8 ± 0.9 to 4.6 ± 0.9 and 5.5 ± 0.9 to 2.1 ± 0.3 µmol/mg dry weight; −60.9 ± 7.3 and −60.9 ± 4.6%, in young and aged mice, respectively). Further, IR-induced ROS production tended to be higher in aged mice. In conclusion, aging exacerbated the deleterious effects of IR on skeletal muscle mitochondrial respiration, potentially in relation to an increased oxidative stress.

Intermittent hypoxia (IH) is a landmark of obstructive sleep apnea (OSA) at the core of the cardiovascular consequences of OSA. IH triggers oxidative stress, a major underlying mechanism for elevated blood pressure (BP) and increased infarct size. L-citrulline is an amino acid that has been demonstrated to be protective of the cardiovascular system and exert pleiotropic effects. Therefore, we tested the impact of citrulline supplementation on IH-induced increase in BP and infarct size. Four groups of rats exposed to normoxia (N) or IH [14 days (d), 8 h/day, 30 s-O₂ 21%/30 s-O₂ 5%] and were supplemented or not with citrulline (1 g·kg⁻¹·d⁻¹). After 14 d, BP was measured, and hearts were submitted to global ischemia-reperfusion to measure infarct size. Histological and biochemical analyses were conducted on hearts and aorta to assess oxidative stress. Citrulline significantly reduced BP (–9.92%) and infarct size (–18.22%) under IH only. In the aorta, citrulline supplementation significantly decreased superoxide anion and nitrotyrosine levels under IH and abolished the IH-induced decrease in nitrite. Citrulline supplementation significantly decreased myocardial superoxide anion levels and xanthine oxidase enzyme activity under IH. Citrulline shows a cardioprotective capacity by limiting IH-induced pro-oxidant activity. Our results suggest that citrulline might represent a new pharmacological strategy in OSA patients with high cardiovascular risk.

Peripheral arterial disease (PAD) strikes more than 200 million people worldwide and has a severe prognosis by potentially leading to limb amputation and/or death, particularly in older patients. Skeletal muscle mitochondrial dysfunctions and oxidative stress play major roles in this disease in relation with ischemia-reperfusion (IR) cycles. Mitochondrial dynamics through impairment of fission–fusion balance may contribute to skeletal muscle pathophysiology, but no data were reported in the setting of lower-limb IR despite the need for new therapeutic options. We, therefore, investigated the potential protective effect of mitochondrial division inhibitor-1 (mDivi-1; 50 mg/kg) in young (23 weeks) and old (83 weeks) mice submitted to two-hour ischemia followed by two-hour reperfusion on systemic lactate, muscle mitochondrial respiration and calcium retention capacity, and on transcripts specific for oxidative stress and mitochondrial dynamics. At the systemic levels, an IR-related increase in circulating lactate was still major despite mDivi-1 use (+305.9% p < 0.0001, and +269.4% p < 0.0001 in young and old mice, respectively). Further, IR-induced skeletal muscle mitochondrial dysfunctions (more severely impaired mitochondrial respiration in old mice (OXPHOS CI state, –68.2% p < 0.0001 and −84.9% p < 0.0001 in 23- and 83-week mice) and reduced calcium retention capacity (–46.1% p < 0.001 and −48.2% p = 0.09, respectively) were not corrected by mDivi-1 preconditioning, whatever the age. Further, mDivi-1 treatment did not oppose superoxide anion production (+71.4% p < 0.0001 and +37.5% p < 0.05, respectively). At the transcript level, markers of antioxidant enzymes (SOD 1, SOD 2, catalase, and GPx) and fission markers (Drp1, Fis) remained unchanged or tended to be decreased in the ischemic leg. Fusion markers such as mitofusin 1 or 2 decreased significantly after IR in both groups. In conclusion, aging enhanced the deleterious effects or IR on muscle mitochondrial respiration, and in this setting of lower-limb IR, mDivi-1 failed to protect the skeletal muscle both in young and old mice.

Background: Ischemic cardiomyopathy with comorbid obstructive sleep apnea syndrome is associated with worse long‐term outcomes. Intermittent hypoxia (IH), a key feature of obstructive sleep apnea, exacerbates sympathetic activity, hastening cardiac dysfunction and remodeling in ischemic cardiomyopathy rat models. This study explores whether targeted cardiac sympathetic denervation (CSD) can limit IH‐induced progression of ischemic cardiomyopathy. Methods: Male Wistar rats underwent CSD, through ablation of the left middle cervical and stellate ganglions, and simultaneously myocardial infarction, via permanent left coronary artery ligation. Three days post surgery, rats were exposed to IH (21%–5% fraction of inspired O ₂ , 60‐second cycle, 8 hours/day) or normoxia. At 6 weeks, calcium transient, sarcomere shortening, and adrenergic reserve in response to isoproterenol (100 nmol/L) were assessed in isolated cardiomyocytes. At 14 weeks, sympathovagal balance, cardiac function, and remodeling were evaluated. Results: Post myocardial infarction, CSD prevented IH‐induced blunting of cardiomyocyte response to isoproterenol challenge and reduced cardiac sympathetic activity. In hypoxic animals, CSD reduced post‐myocardial infarction alterations in long‐term ejection fraction and mitigated cardiomyocyte hypertrophy and apoptosis. Transcriptomic analysis unveiled that CSD triggered biological processes related to cardiac repair and regeneration. Immunohistochemistry further supported these findings, demonstrating increased cardiomyocyte proliferation in the hypoxic group, as indicated by elevated Ki67 expression colocalized with MF20 markers. Conclusions: Our data demonstrate that CSD prevents IH‐induced sympathetic hyperactivity, depletion of cardiac adrenergic reserve, and deterioration of cardiac function in a rat model of ischemic cardiomyopathy. This study highlights the intricate interplay between sympathetic activity and hypoxia in cardiac regeneration and underscores the importance of managing sympathetic hyperactivity in ischemic cardiomyopathy, particularly in the context of comorbid obstructive sleep apnea.

Aim: Chronic intermittent hypoxia (IH), a hallmark of obstructive sleep apnea (OSA), contributes to metabolic diseases and enhances associated cardiovascular (CV) complications through oxidative stress and metabolic alterations. We hypothesize that photobiomodulation (PBM), a non‐invasive low‐level laser therapy, prevents IH‐induced insulin resistance (IR), by preserving insulin signalization and reducing oxidative stress in insulin‐sensitive organs. Methods: Male C57BL/6J mice were randomized in 4 groups, submitted to either 2‐weeks IH (21%–5% FiO ₂ , 60 s cycle, 8 h/day) or normoxia (N), with or without PBM (630 nm, 5 J/cm ² , 32 mW, 120 s, 5 days/week). At day 11, insulin sensitivity was assessed by insulin tolerance test. Then, canonical insulin signaling pathway was explored by western‐blot, and oxidative stress was assessed by measurement of enzymatic activity, O ₂ · ⁻ content, and lipid and protein oxidation in liver, gastrocnemius (GC) muscle, and epididymal white adipose tissue (eWAT). Results: IH induces systemic IR, impairs insulin signaling in liver and eWAT, and increases hepatic O ₂ · ⁻ content, while pro/anti‐oxidant enzyme activities were unchanged. Interestingly, in IH group only, PBM significantly improves systemic insulin sensitivity, prevents eWAT insulin signaling alteration and decreases hepatic O ₂ · ⁻ content. Conclusion: PBM alleviates systemic insulin resistance, restores eWAT insulin signaling, and limits hepatic oxidative stress induced by IH. By enhancing insulin sensitivity, PBM could be proposed as a new therapeutic strategy against OSA‐associated metabolic comorbidities.