Limb Ischemic Preconditioning Research Articles

Ischemic preconditioning increases spinal excitability and voluntary activation during maximal plantar flexion contractions in men.

The enigmatic benefits of acute limb ischemic preconditioning (IP) in enhancing muscle force and exercise performance have intrigued researchers. This study sought to unravel the underlying mechanisms, focusing on increased neural drive and the role of spinal excitability while excluding peripheral factors. Soleus Hoffmann (H)-reflex /M-wave recruitment curves and unpotentiated supramaximal responses were recorded before and after IP or a low-pressure control intervention. Subsequently, the twitch interpolation technique was applied during maximal voluntary contractions to assess conventional parameters of neural output. Following IP, there was an increase in both maximum normalized force and voluntary activation (VA) for the plantar flexor group, with negligible peripheral alterations. Greater benefits were observed in participants with lower VA levels. Despite greater H-reflex gains, soleus volitional (V)-wave and sEMG amplitudes remained unchanged. In conclusion, IP improves muscle force via enhanced neural drive to the muscles. This effect appears associated, at least in part, to reduced presynaptic inhibition and/or increased motoneuron excitability. Furthermore, the magnitude of the benefit is inversely proportional to the skeletal muscle's functional reserve, making it particularly noticeable in under-recruited muscles. These findings have implications for the strategic application of the IP procedure across diverse populations.

Improvement of restless leg syndrome in maintenance hemodialysis patients with limb ischemic preconditioning: a single-center randomized controlled clinical trial

Objective This study evaluated the efficacy and safety of limb ischemic preconditioning (LIPC) in treating restless leg syndrome (RLS) in maintenance hemodialysis (MHD) patients. Methods A total number of 45 patients participated in the study. They were randomly divided into LIPC group and control group. The LIPC was performed by inflating the limb ischemic preconditioning training device in the patient’s thigh to 200 mmHg to create transient ischemia, whereas control group inflated the device to 20 mmHg. International Restless Legs Syndrome (IRLS), Clinical Global Impression Scale (CGI-S), and Medical Outputs Study Sleep Scale were employed to evaluate LIPC effectiveness. The primary endpoint was the ‘rate of clinical improvement in RLS severity’, defined as the percentage of patients who had an IRLS score decrease of ≥5 points in each group. Results After intervention, the rate of clinical improvement in RLS severity was 56.5% in the LIPC group and 13.6% in the control group (13 (56.5) vs 3 (13.6), p = 0.003). In addition, the LIPC group’s IRLS, CGI-S scores, the sleep disturbance and somnolence scores showed a significant downward trend compared to the control group (−5.5 ± 5.3 vs − 1.0 ± 3.8, p = 0.002; −1.7 ± 1.2 vs − 0.5 ± 1.4, p = 0.003; −15.5 ± 17.8 vs 3.7 ± 12.0, p < 0.001; −9.9 ± 18.8 vs − 2.4 ± 8.6, p = 0.003). During the study, there were no serious adverse event in any of the patients. Conclusions LIPC could be employed to effectively and safely alleviate the RLS symptoms in MHD patients.

Pretreatment with remote ischemic conditioning attenuates testicular damage after testicular ischemia and reperfusion injury in rats.

Testicular torsion is a urological emergency. However, surgical detorsion of the torsed spermatic cord can cause testicular reperfusion injury. Although remote ischemic preconditioning (RIPC) has been convincingly shown to protect organs against ischemia/reperfusion (I/R) injury, little is known regarding the effect of RIPC on testicular torsion/detorsion-induced reperfusion injury. Therefore, we aimed to evaluate the effect of RIPC on testes after testicular I/R injury in a rat model in vivo. Male Sprague-Dawley rats were randomly classified into 4 groups: sham-operated (sham), testicular I/R (TI/R), or remote liver (RIPC liver) and limb (RIPC limb) ischemic preconditioning groups. Testis I/R was induced by 3 h of right spermatic cord torsion (720° clockwise), and reperfusion was allowed for 3 hours. In the RIPC group, four cycles of 5 min of ischemia and 5 min of reperfusion were completed 30 min prior to testicular torsion. The ERK1/2 inhibitor U0126 was administered intravenously at the beginning of reperfusion (1 mg/kg). The testes were taken for the oxidative stress evaluations, histology, apoptosis, immunohistochemical and western blotting analysis. Remote liver and limb ischemic preconditioning attenuated ipsilateral and contralateral testicular damage after testicular I/R injury. For example. RIPC reduced testicular swelling and oxidative stress, lessened structural damage, and inhibited the testicular inflammatory response and apoptosis. Furthermore, RIPC treatment enhanced testicular ERK1/2 phosphorylation postI/R. Inhibition of ERK1/2 activity using U0126 eliminated the protection offered by RIPC. Our data demonstrate for the first time that RIPC protects testes against testicular I/R injury via activation of the ERK1/2 signaling pathway.

Application Value of Limb Ischemic Preconditioning in Preventing Intradialytic Hypotension during Maintenance Hemodialysis

Introduction: The aim of this study was to investigate the efficacy and safety of limb ischemia preconditioning (LIPC) in the treatment of intradialytic hypotension (IDH) in patients with maintenance hemodialysis (MHD). Methods: This was a single-center, prospective, and randomized controlled case study. A total of 38 patients with MHD who met the inclusion criteria from September 2021 to August 2022 were selected from the Blood Purification Center of our hospital. They were randomly divided into the LIPC group (n = 19) and the control group (n = 19). For patients in the LIPC group, the femoral artery blood flow was blocked with an LIPC instrument for 5 min (pressurized to 200 mm Hg) before each dialysis, and they were reperfused for 5 min. The cycle was repeated five times, with a total of 50 min for 12 weeks. The control group was pressurized to 20 mm Hg with an LIPC instrument, and the rest was the same as the LIPC group. The blood pressure of 0 h, 1 h, 2 h, 3 h, 4 h, and body weight before and after hemodialysis were measured in the two groups during hemodialysis, the incidence of IDH and the changes of serum troponin I (TNI) and creatine kinase isoenzyme MB (CK-MB) levels before and after the intervention were observed, and the ultrafiltration volume and ultrafiltration rate were recorded. Results: At the 8th and 12th week after intervention, the MAP in the LIPC group was higher than that in the control group (103.28 ± 12.19 mm Hg vs. 93.18 ± 11.11 mm Hg, p = 0.04; 101.81 ± 11.36 mm Hg vs. 91.81 ± 11.92 mm Hg, p = 0.047). The incidence of IDH in the LIPC group was lower than that in the control group (36.5% vs. 43.1%, p = 0.01). The incidence of clinical treatment in IDH patients in the LIPC group was lower than that in the control group (6.3% vs. 12.4%, p = 0.00). The incidence of early termination of hemodialysis in the LIPC group was lower than that in the control group (1.6% vs. 3.8%, p = 0.01). The levels of TNI and CK-MB in the LIPC group after the intervention were lower than those in the control group (322.30 ± 13.72 ng/dL vs. 438.50 ± 24.72 ng/dL, p = 0.00; 159.78 ± 8.48 U/dL vs. 207.00 ± 8.70 U/dL, p = 0.00). The changes of MAP before and after the intervention were negatively correlated with the changes of TNI and CK-MB before and after the intervention (r = −0.473, p = 0.04; r = −0.469, p = 0.04). There were no differences in dry body mass and ultrafiltration rate between the two groups before and after the LIPC intervention (p > 0.05). Multiple linear regression analysis shows that TNI is the main influencing factor of ΔMAP. No LIPC-related adverse events were found during the study period. Conclusion: LIPC can effectively reduce the incidence of IDH in patients with MHD and may be associated with the alleviation of myocardial damage.

Ischemic limb preconditioning-induced anti-arrhythmic effect in reperfusion-induced myocardial injury: is it mediated by the RISK or SAFE pathway?

The mechanism for limb ischemic precondition (RLIPC)-induced suppression of reperfusion arrhythmia remains unknown. The purpose of this study was to examine the roles of the pro-survival reperfusion injury salvage kinase (RISK) and survivor activating factor enhancement (SAFE) pathways in this RLIPC-mediated antiarrhythmic activity. Male Sprague Dawley rats were assigned to sham-operated, control, or RLIPC groups. All rats except for the sham rats had 5min of left main coronary artery occlusion with another 20min of reperfusion. RLIPC was initiated by four cycles of limb ischemia (5min) and reperfusion (5min) on the bilateral femoral arteries. Hearts in every group were taken for protein phosphorylation analysis. RLIPC ameliorated reperfusion-induced arrhythmogenesis and reduced the incidence of sudden cardiac death during the entire 20-min reperfusion period (66.7% of control rats had SCD vs. only 16.7% of RLIPC-treated rats). RLIPC enhances ventricular ERK1/2 phosphorylation after reperfusion. RLIPC-induced antiarrhythmic action and ERK1/2 phosphorylation are abolished in the presence of the ERK1/2 inhibitor U0126. Limb ischemic preconditioning protects the heart against myocardial reperfusion injury-induced lethal arrhythmia. These beneficial effects may involve the activation of ERK1/2 in the RISK signaling pathway.

IPC recovery length of 45 minutes improves muscle oxygen saturation during active sprint recovery

ABSTRACT Ischemic preconditioning (IPC) involves brief, repeated bouts of limb occlusion and reperfusion capable of improving exercise performance at least partially by enhancing local skeletal muscle oxygenation. This study sought to investigate the effect of a lower limb IPC protocol, with either a 5-min or 45-min post-application delay, on vastus lateralis tissue saturation index (TSI) and systemic cardiac hemodynamics at rest and during short-duration intense cycling. Twelve young adults randomly completed four interventions: IPC (at 220 mmHg) with 5-min delay (IPC5), IPC with 45-min delay (IPC45), SHAM (at 20 mmHg) with 5-min delay (SHAM5), and SHAM with 45-min delay (SHAM45). Following IPC intervention and recovery delay, participants completed 5, 60-s high-intensity (100% W peak) cycle sprints separated by 120-sec of active recovery (30% W peak). Compared to baseline, TSI immediately following IPC5, but pre-exercise, remained lower than the equivalent for IPC45 (−5.9 ± 1.5%, p = .002). IPC, imposed at least 45-min before the completion of five 60-s sprint cycling efforts, significantly enhanced TSI during active recovery between sprint intervals compared to a 5-min delay (6.6 ± 2.4%, p = .021), and identical SHAM conditions (SHAM5: 5.8 ± 2.2%, p = .024; SHAM45: 6.2 ± 2.5%, p = .029). A 45-min delay following IPC appears to provide heightened skeletal muscle metabolic rebound prior to intense sprint cycling as compared to a 5-min delay. Furthermore, IPC followed by a 45-min delay enhanced recovery of skeletal muscle oxygenation during low intensity active sprint recovery, despite an unchanged decline in skeletal muscle oxygenation during near-maximal sprinting efforts.

ZNF667 attenuates leukocyte-endothelial adhesion via downregulation of P-selectin in skin flap following remote limb ischemic preconditioning.

We assessed the effects and potential mechanism of romote ischemic preconditioning (RIPC) on leukocytes-endothelium cell adhesion in the flap microvessel after ischemia-reperfusion (I/R) injury. Eight hours after reperfusion, edema and intravascular leukocyte aggregation were reduced and microvessels were more obvious in the group with superficial inferior epigastric artery (SIEA) perforator flap (SIEA-flap) subjected to RIPC than in the I/R group. Zinc finger protein 667 (ZNF667) was significantly increased but P-selectin was decreased in the flaps subjected to RIPC, compared to those in the I/R group. The low expression of P-selectin was associated with ZNF667 expression and activation in human dermal microvascular endothelial cells in response to hypoxic preconditioning. ZNF667 bound to the P-selectin promoter region, suppressing its transcription through a special core sequence. The ablation of P-selectin by small interfering RNA effectively prevented the leukocytes-endothelium cell adhesion effect of ZNF667-knockdown. ZNF667 upregulation attenuates leukocyte-endothelial cell adhesion by negatively regulating the expression of P-selectin in SIEA-flap subjected to RIPC.

Limb Ischemic Preconditioning or Dezocine Pre-Treatment will Reduce Acute Gastric Mucosal Injury in Rats

Limb Ischemic Preconditioning or Dezocine Pre-Treatment will Reduce Acute Gastric Mucosal Injury in Rats

Limb Ischemic Preconditioning or Dezocine Pre-Treatment will Reduce Acute Gastric Mucosal Injury in Rats

Acute gastric mucosal lesions refer to acute inflammation of the gastric mucosa [1,2], Symptoms including gastric mucosal congestion, edema, and erosion...

Safety and Tolerability of Both Arm Ischemic Conditioning in Patients With Major Depression: A Proof of Concept Study.

PurposeA substantial proportion of patients with major depressive disorder (MDD) does not respond or cannot tolerate to currently available treatments. This study was to assess the safety and tolerability of Remote Limb Ischemic Preconditioning (RLIPC) as an adjunctive therapy in patients with MDD.Patients and MethodsEnrolled patients underwent RLIPC, five cycles of simultaneous bilateral arm ischemia, 5 min and followed by reperfusion of each cycle, and once daily for eight consecutive weeks. Depression and anxiety severity, and quality of life were assessed every 2 weeks. Descriptive analysis was used for safety and tolerability data.ResultsThirty-seven participants completed at least one RLIPC. Twenty-four of them (64.9%) completed the study. Twelve patients prematurely discontinued the study due to poor adherence, and one due to a mild side effect. The changes in HRSD-17, GAD-7 and QOL-6 total scores from baseline to the endpoint were significant from the end of second week treatment onwards. The responder and remission rates were 59.46% (22/37) and 54.05% (20/37) at the endpoint, respectively.ConclusionRLIPC was safe and well tolerated, and may be effective in reducing depressive symptoms in patients with MDD. Large studies are warranted to test its efficacy and safety as monotherapy or adjunctive therapy in the treatment of MDD.

Modulation of spinal cord excitability following remote limb ischemic preconditioning in healthy young men.

Remote limb ischemic preconditioning (RIPC) has shown to improve dynamic postural control in humans. However, studies on the underlying adaptations of spinal cord networks have never been performed. The present work addresses this issue by investigating parameters from the soleus H-reflex recruitment curve (RC), presynaptic mechanisms of reflex modulation (presynaptic inhibition-PSI, and post activation depression-PAD), and the excursion of the center of pressure (CP) recorded during 1min in upright stance over a compliant surface. A sham ischemic protocol (partial obstruction of blood flow) was applied to the contralateral thigh along four consecutive days. The same procedure was repeated with full obstruction (RIPC) three days after ending the sham protocol. Data were collected before and after both sham and RIPC protocols. The follow-up data were collected five days after the last ischemic intervention. Significant reduction was detected for both the fast oscillations of the CP (higher frequency components) and the parameter estimated from the RC corresponding to the high amplitude H-reflexes (p < 0.05). Even though the magnitude of effects was similar, it was washed out within three days after sham, but persisted for at least five days after RIPC. No significant differences were found for PSI and PAD levels across conditions. These findings indicate that RIPC leads to enduring changes in spinal cord excitability for the latest reflexively recruited motoneurons, along with improvement in balance control. However, these adaptations were not mediated by the presynaptic mechanisms currently assessed.

Remote liver ischaemic preconditioning protects rat brain against cerebral ischaemia-reperfusion injury by activation of an AKT-dependent pathway.

What is the central question of this study? Can remote liver ischaemic preconditioning (RLIPC) protect rat brain against cerebral ischaemia-reperfusion injury? What is the main finding and its importance? Pretreatment with RLIPC reduced cerebral infarct volume, improved neurological outcomes and inhibited neuron apoptosis. RLIPC led to increased phosphorylation of AKT, while inhibition of AKT abolished the effects of RLIPC. Our data suggest that liver ischaemic preconditioning exerts a strong neuroprotective effect against cerebral ischaemia-reperfusion injury by activating an AKT-dependent pathway. Remote limb ischaemic preconditioning has been shown to have beneficial effects in protecting brains against ischaemia-reperfusion (I/R) injury. However, little is known regarding the effect of remote liver ischaemic conditioning (RLIPC). We therefore investigated the effect of RLIPC on brain tissues suffering from I/R injury. Rats were randomly assigned to a sham group, a control group or a RLIPC group. Rats in all groups except for the sham group received middle cerebral artery occlusion (MCAO) for 1h, followed by 48h of reperfusion. For the RLIPC rats, four cycles of 5min of liver ischaemia (portal vein, hepatic arterial and venous trunk occlusion) with 5min intermittent reperfusion were carried out before cerebral ischaemia. Infarct volume was assessed after 48h of reperfusion. Blood samples were taken for serum lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) tests. Morphological changes of cortical tissue and cellular apoptosis were determined. Right cortex tissues were taken for western blotting measurements. Our data demonstrate that RLIPC reduced cerebral I/R injury, decreased the volume of the MCAO-evoked infarct region, decreased serum levels of LDH and CK-MB, and reduced neurological deficits and apoptosis after I/R injury. Moreover, rats receiving RLIPC showed increased cortical AKT phosphorylation, but protein phosphorylation level was unchanged in the survivor activating factor enhancement (SAFE) signalling pathway. Accordingly, inhibition of AKT with wortmannin abolished the neuroprotective action of liver preconditioning. Our study showed for the first time that liver ischaemic preconditioning effectively protects brain against cerebral I/R injury by activating an AKT-dependent pathway.

Limb ischemic preconditioning ameliorates renal microcirculation through activation of PI3K/Akt/eNOS signaling pathway after acute kidney injury

PurposeContrast-induced acute kidney injury (CI-AKI) resulting from administration of iodinated contrast media (CM) is the third leading cause of hospital-acquired acute kidney injury and is associated with substantial morbidity and mortality. Deteriorated renal microcirculation plays an important role in CI-AKI. Limb ischemic preconditioning (LIPC), where brief and non-injurious ischemia/reperfusion is applied to a limb prior to the administration of the contrast agent, is emerging as a promising strategy for CI-AKI prevention. However, it is not known whether the renal protection of LIPC against CI-AKI is mediated by regulation of renal microcirculation and the molecular mechanisms remain largely unknown.MethodsIn this study, we examined the renal cortical and medullary blood flow in a stable CI-AKI model using 5/6-nephrectomized (NE) rat. The LIPC and sham procedures were performed prior to the injection of CM. Furthermore, we analyzed renal medulla hypoxia using in vivo labeling of hypoxyprobe. Pharmacological inhibitions and western blotting were used to determine the underlying molecular mechanisms.ResultsIn this study, we found LIPC significantly ameliorated CM-induced reduction of medullary blood flow and attenuated CM-induced hypoxia. PI3K inhibitor (wortmannin) treatment blocked the regulation of medullary blood flow and the attenuation of hypoxia of LIPC. Phosphorylation of Akt/eNOS was significantly decreased via wortmannin treatment compared with LIPC. Nitric oxide synthase-inhibitor [Nω-nitro-l-arginine methyl ester (L-NAME)] treatment abolished the above effects and decreased phosphorylation of eNOS, but not Akt.ConclusionsCollectively, the results demonstrate that LIPC ameliorates CM-induced renal vasocontraction and is mediated by activation of PI3K/Akt/eNOS signaling pathway.

Ferritin Genes Overexpression in PBMC and a Rise in Exercise Performance as an Adaptive Response to Ischaemic Preconditioning in Young Men.

Objectives The proposal of this study was to evaluate the effect of acute and ten-day ischaemic preconditioning (IPC) training procedure on the Wingate Anaerobic Test (WAnT), the ferritin H (FTH), ferritin L (FTL), and transferrin receptor 1 (TFRC) mRNA expression in peripheral blood mononuclear cells (PBMC), and anaerobic performance. Method 34 healthy men volunteers (aged 20.7 ± 1.22 years) participated in the study. The effects of bilateral upper limb IPC and sham controlled condition were assessed in two experimental protocols: (a) the influence of acute (one time) IPC based on an experimental crossover study design and (b) the influence of ten-day IPC training treatment based on a random group assignment. At the beginning and at the end of each experiment upper body WAnT was performed and blood samples were collected to assess gene expression via quantitative PCR (qPCR). Results No significant effect of one-time ischaemic preconditioning procedure was observed on upper body WAnT performance. Ten-day IPC training significantly increased upper limbs relative mean power (from 5.29 ± 0.50 to 5.79 ± 0.70 (W/kg), p < 0.05). One-time IPC caused significant decrease in FTH, FTL, and TFRC mRNA levels while 10 days of IPC resulted in significant increase of FTH and FTL mRNA (from 2 ∧254.2 to 2 ∧1678.6 (p = 0.01) for FTH and 2 ∧81.5 to 2 ∧923 (p = 0.01) for FTL) and decrease in TFRC mRNA. Conclusions Our findings suggest that ten-day IPC training intervention significantly affects upper limb relative peak power. The observed overexpression of FTH and FTL genes could be associated with adaptation response induced by prolonged IPC.

Down‐Regulation of Thioredoxin‐Interacting Protein by Repeated Non‐Invasive Limb Ischemic Preconditioning Protects Diabetic Heart from Myocardial Ischemia/Reperfusion Injury

BackgroundMyocardial ischemia/reperfusion injury (MIRI) is a major threat to human health, causing great cardiac morbidity and mortality worldwide. Yet, it's even more severe among diabetic subjects. Repeated non‐invasive limb ischemic preconditioning (rNLIP) can be effective in protecting the diabetic heart against MIRI, though the exact mechanism is still unclear. Thioredoxin‐interacting protein (TXNIP), a critical regulator with its inhibitory effect against antioxidation, is a novel target during MIRI. Also, TXNIP is found to be highly expressed concomitantly with hyperglycemia. This study aimed to investigate the role of TXNIP in the cardioprotective effect of rNLIP against MIRI in diabetes mellitus.MethodsDiabetes mellitus was induced by streptozotocin injection (65mg/kg) in Sprague‐Dawley rats. In vivo model of MIRI was established as 30 minutes occlusion of the left anterior descending coronary artery and subsequent 2 hours reperfusion. rNLIP was accomplished as three cycles of 5min ischemia (cuff inflation) and 5min reperfusion (cuff deflation) of the left hindlimb for three consecutive days before MIRI. In vitro hypoxia/re‐oxygenation (H/R) model was established as 6 hours of hypoxia and 12 hours of re‐oxygenation of H9C2 cells. Simulated remote hypoxic preconditioning (HPC), defined as three cycles of 5 min hypoxia and 5 min re‐oxygenation, was performed just 24 hours before H/R treatment to mimic the cardioprotective effect of rNLIP.ResultsThe expression of TXNIP was significantly elevated in the diabetic group, together with much greater infarct size and higher release of CK‐MB as well as lactate dehydrogenase (LDH) after MIRI, compared to non‐diabetic group. The application of rNLIP significantly reduced the infarct size, CK‐MB, and LDH release in both diabetic and non‐diabetic group. Furthermore, the expression of TXNIP, NLRP3 and IL‐1β were significantly reduced by rNLIP in both diabetic and nondiabetic group, with simultaneous suppression of apoptosis (lower cleaved caspases‐3 expression and bax/bcl‐2 ratio). In vitro study showed that TXNIP expression was significantly higher in high glucose (HG) group with concurrently greater cell injury and much higher LDH release after H/R treatment, compared to normal glucose (NG) group. HPC exhibited protective effect in both HG and NG group with reduced expression of TXNIP, NLRP3, and IL‐1β.ConclusionDown‐regulation of TXNIP and subsequent reduction of NLRP3 may represent a mechanism whereby rNLIP protects the diabetic heart from MIRI.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Repeated non‐invasive limb ischemic preconditioning attenuates myocardial ischemia‐reperfusion injury in diabetic rats by up‐regulating hexokinase II

BackgroundIschemic heart disease is the leading cause of mortality in patients with diabetes mellitus. Although remote ischemic preconditioning achieved by non‐invasively occluding the brachial artery (non‐invasive limb ischemic preconditioning, NLIP) lost its cardioprotection in diabetes, our recent study demonstrated that repeated NLIP (rNLIP, applying 3 cycles of 5 minutes occlusion/5 minutes reperfusion in a unilateral hindlimb daily for 3 days) reduced myocardial infarction, but the mechanism is unclear. Hexokinase II (HKII) is a key glycolytic enzyme that regulates cell survival when bonds to out mitochondrial membrane. However, it is unknown whether HKII is involved in the cardioprotection of diabetic myocardial ischemia/reperfusion(I/R) injury conferred by rNLIP and warrants investigation.Methods and ResultsType 1 diabetic rat model was established by intravenous injection of streptozotocin (60 mg/kg). Myocardial I/R was induced by ligating the left anterior descending artery for 30 minutes followed by 2 hours reperfusion. The results showed that HKII was down‐regulated in the myocardium of diabetic rats(p&lt;0.05, vs. non‐diabetic rats), while myocardial I/R injury was aggravated, as evidenced by increases in post‐ischemic myocardial infarct size, lactate dehydrogenase and circulating levels of troponin I (cardiac injury markers, p&lt;0.05 vs. non‐diabetic rats with I/R), concomitantly with enhanced cardiac apoptosis level (reduced Bcl2/Bax ratio, increased cleaved caspase‐3 level and more TUNEL‐staining positive cells) and aggravated inflammatory responses (increased mRNA levels of pro‐inflammatory cytokines IL1β, IL6 and TNFα). rNLIP significantly up‐regulated the expression of HKII in the myocardium of non‐diabetic and diabetic rats (the up‐regulation level is more pronounced in diabetic rats). The rNLIP‐induced HKII expression in diabetic rats was paralleled by reductions in myocardial infarct size, cardiac apoptosis and inflammatory responses.ConclusionrNLIP attenuates diabetic heart I/R injury through inhibiting cell apoptosis and inflammatory response via up‐regulation of HKII in cardiomyocytes and that targeting HKII expression may be a potential clinical therapeutic intervention for the management of ischemic heart disease in diabetes.Support or Funding InformationThe study was supported by Guangdong Natural Science Foundation (2018A030313535, Guangdong, China) and HMRF (05161826) of Hong Kong.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Improved Long-term Survival with Remote Limb Ischemic Preconditioning in a Rat Fixed-Pressure Hemorrhagic Shock Model.

We investigated whether bilateral, lower limb remote ischemic preconditioning (RIPC) improved long-term survival using a rat model of hemorrhagic shock/resuscitation. Rats were anesthetized, intubated and ventilated, and randomly assigned to RIPC, induced by inflating bilateral pressure cuffs around the femoral arteries to 200mmHg for 5min, followed by 5-min release of the cuffs (repeated for 4cycles), or control group (cuffs were inflated to 30mmHg). Hemorrhagic shock was induced by withdrawing blood to a fixed mean blood pressure of 30mmHg for 30min, followed by 30min of resuscitation with shed blood. Rats remained anesthetized for 1h during which hemodynamics were monitored then they were allowed to survive for 6weeks. The percentage of estimated total blood volume withdrawn to maintain a level of 30mmHg was similar in both groups. RIPC significantly increased survival at 6weeks: 5 of 27 (19%) rats in the control group and 13 of 26 (50%; p = 0.02) rats in the RIPC group survived. Blood pressure was higher in the RIPC group. The diastolic internal dimension of the left ventricle, an indicator of circulating intravascular blood volume, was significantly larger in the RIPC group at 1h after initiation of resuscitation compared to the control group (p = 0.04). Left ventricular function assessed by fractional shortening was comparable in both groups at 1h after initiation of resuscitation. Blood urea nitrogen (BUN) was within normal range in the RIPC group (17.3 ± 1.2mg/dl) but elevated in the control group (22.0 ± 1.7mg/dl) at 48h after shock. RIPC significantly improved short-term survival in rats that were subjected to hemorrhagic shock, and this benefit was maintained long term. RIPC led to greater circulating intravascular blood volume in the early phase of resuscitation and improved BUN.

Lower limb ischemic preconditioning combined with dietary nitrate supplementation does not influence time-trial performance in well-trained cyclists

ObjectivesDietary nitrate (NO3−) supplementation and ischaemic preconditioning (IPC) can independently improve exercise performance. The purpose of this study was to explore whether NO3− supplementation, ingested prior to an IPC protocol, could synergistically enhance parameters of exercise. DesignDouble-blind randomized crossover trial. MethodsTen competitive male cyclists (age 34±6years, body mass 78.9±4.9kg, V⋅O2peak 55±4 mLkgmin−1) completed an incremental exercise test followed by three cycling trials comprising a square-wave submaximal component and a 16.1km time-trial. Oxygen uptake (V⋅O2) and muscle oxygenation kinetics were measured throughout. The baseline (BASE) trial was conducted without any dietary intervention or IPC. In the remaining two trials, participants received 3×5min bouts of lower limb bilateral IPC prior to exercise. Participants ingested NO3−-rich gel (NIT+IPC) 90min prior to testing in one trial and a low NO3− placebo in the other (PLA+IPC). Plasma NO3− and nitrite (NO2−) were measured immediately before and after application of IPC. ResultsPlasma [NO3−] and [NO2−] were higher before and after IPC in NIT+IPC compared to BASE (P<0.001) but did not differ between BASE and PLA+IPC. There were no differences in V⋅O2 kinetics or muscle oxygenation parameters between trials (all P>0.4). Performance in the time-trial was similar between trials (BASE 1343±72s, PLA+IPC 1350±75s, NIT+IPC 1346±83s, P=0.98). ConclusionsPre-exercise IPC did not improve sub-maximal exercise or performance measures, either alone or in combination with dietary NO3− supplementation.

The role of adenosine in up-regulation of p38 MAPK and ERK during limb ischemic preconditioning-induced brain ischemic tolerance

Our previous studies have demonstrated that limb ischemic preconditioning (LIP) induced brain ischemic tolerance and up-regulated the expression of p38 MAPK and ERK in the hippocampal CA1 region in rats. The present study was undertaken to investigate the role of adenosine in brain protection and up-regulation of p38 MAPK and ERK induced by LIP. It was found that adenosine A1 receptor antagonist DPCPX dose-dependently inhibited the protective effect of LIP. The up-regulation of p38 MAPK and ERK induced by LIP could be blocked by DPCPX. Furthermore, we observed the effect of adenosine on the brain ischemia. The results showed that pre-administration of adenosine could partly mimic the neuroprotective effect on the brain, up-regulate the expression of p38 MAPK and ERK. Based on the above results, it can be concluded that adenosine participated in brain protection and up-regulation of the expression of p38 MAPK and ERK during the induction of brain ischemic tolerance after LIP.

Abstract 186: Remote Limb Ischemic Preconditioning Improves Short and Long Term Survival and Maintains Intravascular Blood Volume During Resuscitation of Hemorrhagic Shock

Background: We further examined the protective effects of experimental bilateral lower limb remote ischemic preconditioning (RIPC) in rats undergoing experimental hemorrhagic shock. Methods: Sprague Dawley rats (both genders) were randomized into RIPC (n= 26) or control group (n= 27), and anesthetized with intraperitoneal ketamine/xylazine. RIPC was induced by 4 cycles of inflating small bilateral pressure cuffs to 200 mmHg around the femoral arteries for 5 minutes, followed by 5 minute deflation of the cuffs. Hemorrhagic shock was induced by withdrawing blood from the carotid artery. Target mean blood pressure of 30 mmHg was maintained for 30 minutes followed by reinfusion of shed blood within the next 30 min. Rats remained anesthetized for another 30 min before recovery; endpoints were survival at 72 hours and 6 weeks. Results: The % of estimated total blood volume withdrawn to maintain a level of 30 mmHg was similar in the RIPC group (41.7 ± 1.0 %) and control group (41.9 ± 1.0 %). Recovery of blood pressure during the early resuscitation phase was significantly improved in the RIPC group. The diastolic internal dimension of the left ventricle (echocardiogram), which indicates circulating intravascular blood volume, was significantly larger in the RIPC group at 1 hour after initiation of shed blood reinfusion (5.8 ± 0.1 mm) compared to 5.4 ± 0.1mm in the control group (p=0.04). Left ventricular fractional shortening was comparable between RIPC (50.9 ± 1.9 %) and control group (49.6 ± 1.8 %; p=0.64) at 1 hour after initiation of resuscitation. At 48 hours after shock, BUN was within normal range in the RIPC group (17.3 ± 1.2 mg/dl); but elevated in the control group (22.0 ± 1.7 mg/dl). At 72 hours after hemorrhagic shock injury, 6 of 27 (22.2 %) rats in the control group and 13 of 26 (50 %, p = 0.047) rats in the RIPC group survived. At 6 weeks, 5 of 27 (18.5 %) rats in the control group and 13 of 26 (50 %; p = 0.021) rats in the RIPC group survived. RIPC significantly increased survival rate at both 72 hours and 6 weeks. Conclusions: RIPC improved recovery of blood pressure and maintained more circulating intravascular blood volume in the early phase of resuscitation, improved BUN, and markedly and significantly improved short and long term survival in rats subjected to hemorrhagic shock.