Remote ischaemic conditioning in the context of type 2 diabetes and neuropathy: the case for repeat application as a novel therapy for lower extremity ulceration

The influence of cuff location on the oxygenation and reperfusion of the foot during ischemic preconditioning: A reliability study

Ischemic preconditioning (IPC) involves the application of occlusion cycles, typically prior to exercise. IPC is commonly applied at the arm or thigh for improving exercise performance, which can be combined with near-infrared spectroscopy (NIRS) to assess the microcirculation and tissue oxygenation. Despite the use of NIRS during IPC, few studies have investigated the reliability of NIRS during lower limb IPC with no relevant publications investigating IPC at the ankle. Therefore, the purpose of this study was to investigate the intra-session reliability in the NIRS measurements during repeated IPC at the thigh, ankle and arm. Eighteen participants volunteered. IPC was applied at the thigh (220 mmHg), ankle (individualized arterial occlusion pressure: 212 ± 24 mmHg) and arm (220 mmHg) in a randomized order involving 3 repeated cycles of 5-min occlusion and reperfusion, within a session. NIRS recorded tissue oxygen saturation (SO2), oxygenated (O2Hb) and deoxygenated hemoglobin (HHb) at the abductor hallucis muscle. Reliability was assessed using intraclass correlation coefficients. For all NIRS measurements assessed, there was excellent reliability (All ICC > 0.94) for the average, minimum and maximum values. The results indicate that IPC can successfully be applied at the ankle, offering reliable measures between three repeated occlusions within a session.

The effect of ellagic acid on the metabolic syndrome: A review article

Objective

(s): Metabolic syndrome is a collection of metabolic abnormalities that includes hyperglycemia, dyslipidemia, hypertension, and obesity. Ellagic acid is found in various fruits and vegetables. It has been reported to have several pharmacological properties, such as antibacterial, antifungal, antiviral, anti-inflammatory, hepatoprotective, cardioprotective, chemopreventive, neuroprotective, gastroprotective, and antidiabetic. Our current study aims to shed light on the probable efficiency of ellagic acid in managing metabolic syndrome and its complications.

Materials and methods

To prepare the present review, the databases or search engines utilized included Scopus, PubMed, Science Direct, and Google Scholar, and relevant articles have been gathered with no time limit until March 2023.

Results

Several investigations indicated that ellagic acid could be a potent compound for the treatment of many disorders such as diabetes, hypertension, and hyperlipidemia by various mechanisms, including increasing insulin secretion, insulin receptor substrate protein 1 expression, regulating glucose transporter 4, triglyceride, total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), attenuating tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), reactive oxygen species (ROS), malondialdehyde (MDA), and oxidative stress in related tissues. Furthermore, ellagic acid ameliorates mitochondrial function, upregulates uncoupling protein 1 (found in brown and white adipose tissues), and regulates blood levels of nitrate/nitrite and vascular relaxations in response to acetylcholine and sodium nitroprusside.

Conclusion

Ellagic acid can treat or manage metabolic syndrome and associated complications, according to earlier studies. To validate the beneficial effects of ellagic acid on metabolic syndrome, additional preclinical and clinical research is necessary.

Impact of red cell distribution width and red cell distribution width/albumin ratio on all-cause mortality in patients with type 2 diabetes and foot ulcers: a retrospective cohort study

Background

Red blood cell distribution width (RDW) has emerged as a prognostic factor for mortality in various diseases. Up to now, few studies have focused on the prognostic value of RDW in patients with diabetic foot ulcers (DFUs). This retrospective cohort study aimed to investigate the impact of RDW and RDW/albumin (ALB) ratio on all-cause mortality in patients with DFUs.

Methods

This study included 860 patients with DFUs in a tertiary academic hospital. The associations of RDW and RDW/ALB with all-cause mortality were assessed by multivariable cox regression analyses. The pairwise comparisons of receiver operating characteristic (ROC) curves were performed to compare the predictive performance of RDW and RDW/ALB ratio. Harrell’s concordance index, integrated discrimination improvement, and net reclassification improvement were used to estimate the improvements in risk discrimination.

Results

Patients with high RDW and RDW/ALB had lower overall survival rates (all P < 0.001). The multivariable Cox regression revealed that high RDW [adjusted hazard ratio (HR) 2.426, 95% confidence interval (CI): 1.557–3.778, P < 0.001] and high RDW/ALB (adjusted HR 2.360, 95% CI: 1.414–3.942, P = 0.001) were independent associated with high all-cause mortality. In subgroup analyses, the comparative analysis of ROC curves revealed that the discriminating ability of the RDW/ALB ratio was significantly superior to RDW in patients with no severe DFUs or no severe peripheral artery disease, or in young and middle-aged patients (all P < 0.05). Adding RDW and RDW/ALB ratio to base models improved discrimination and risk reclassification for all-cause mortality.

Conclusions

RDW and RDW/ALB ratio are robust and independent prognostic markers in patients with DFUs. The RDW/ALB ratio appears to be of more predictive value for mortality in younger and less severely ill patients with DFUs. Both RDW and RDW/ALB ratio can provide incremental predictive value for all-cause mortality over traditional risk factors. RDW and RDW/ALB ratio can be used to identify high-risk patients with DFUs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01534-4.

Impact of repeated remote ischemic conditioning on diabetic foot ulcers: A proof-of-concept study

Patients with a diabetic foot ulcer (DFU) suffer disabilities and are at increased risk for lower extremity amputation. Current standard of care includes debridement, topical antibiotics, and weight off-loading-still resulting in low rates of healing. Previous small-scale research has indicated that repeated remote ischemic conditioning (rRIC) is a novel modality that delivers significantly higher DFU healing rates. This proof-of-concept study was performed to expand the research on the utility of rRIC as an adjunctive treatment in the healing of chronic DFUs. Forty subjects (41 wounds) received rRIC treatment three times weekly in addition to standard of care for 12 weeks. Subjects that did not heal in this time frame but had a significant reduction in wound size were eligible to continue for an 8-week extension period. By the end of the extension period, 31 of the 41 DFU wounds (75.6%) in this study were determined to be healed. This compares favourably to the 25-30% standard of care average healing rate. For additional comparison, another group of patients receiving standard of care alone, by the same investigator, was selected and matched by wound size at baseline and wound location. For this matching cohort, after 20 weeks of treatment, only 15 of the 41 DFU comparison wounds (36.6%) were determined to be healed, in line with other standard of care results. In the rRIC treatment group, the 10 wounds that did not heal, experienced an average reduction in wound area of 54.3%. The results of this proof-of-concept study reinforce earlier evidence that the addition of rRIC to local wound care significantly improves the healing of chronic diabetic foot ulcers.

Impaired dermal microvascular reactivity and implications for diabetic wound formation and healing: an evidence review

Diabetic foot ulcers (DFUs) are among the most consequential and costly complications faced by patients with diabetes and the global healthcare system. Acknowledged risk factors for DFUs include diabetic peripheral neuropathy (DPN), peripheral arterial disease (PAD), microtrauma and foot deformities. Research on additional risk factors for DFUs has recently focused on dysregulated, autonomic vasomotor control in the skin of patients with DPN. In particular, impaired dermal microvascular reactivity (IDMR) with its attendant reduction in nutritive capillary blood flow has been identified as an emerging risk factor. This especially relates to refractory wounds noted in patients without overt PAD signs. In this paper, evidence will be reviewed supporting the evolving understanding of IDMR and its impact on DFU formation and healing. Advances in diagnostic instrumentation driving this research along with the most promising potential therapies aimed at improving microvascular function in the diabetic foot will be discussed in brief.

Remote ischemic conditioning: A potential therapeutic strategy of type 2 diabetes

Type 2 diabetes (T2D) is one of the major public diseases which is characterized by peripheral insulin resistance (IR) and progressive pancreatic β-cell failure. While in the past few years, some new factors, such as inflammation, oxidative stress, immune responses and other potential pathways, have been identified to play critical roles in T2D, and thereby provide novel promising targets for the treatment of T2D. Remote ischemic conditioning (RIC) is a non-invasive and convenient operation performed by transient, repeated ischemia in distant place. Nowadays, RIC has been established as a potentially powerful therapeutic tool for many diseases, especially in I/R injuries. Through activating a series of neural, humoral and immune pathways, it can release multiple protective signals, which then regulating inflammation, oxidative stress, immune response and so on. Interestingly, several recent studies have discovered that the beneficial effects of RIC on I/R injuries might be abolished by T2D, wherein the higher basal levels of inflammation and oxidative stress, dysregulation of immune system and some potential pathways secondary to hyperglycemia may play critical roles. In contrast, a higher intensity of conditioning could restore the protective effects. Based on the overlapped mechanisms RIC and T2D performs, we provide a hypothesis that RIC may also play a protective role in T2D via targeting these signaling pathways.

Effects of Remote Ischaemic Preconditioning on Arterial Stiffness in Patients Undergoing Lower Limb Angiographic Procedures: A Randomised Clinical Trial

OBJECTIVES

Remote ischaemic preconditioning (RIPC) is a phenomenon that promotes protection of tissues and organs against ischaemia reperfusion injury. RIPC has been shown to reduce myocardial and renal injury but its effect on arterial stiffness in patients undergoing lower limb digital subtraction angiography (DSA) is unknown. The aim of this study was to evaluate the effect of RIPC on arterial stiffness in patients with peripheral arterial disease (PAD) undergoing lower limb DSA.

METHODS

In the RIPC intervention, the blood pressure cuff on the arm was inflated to 200 mmHg or to 20 mmHg above systolic pressure, and in the sham intervention to 20 mmHg. For both, the procedure was repeated for four five minute cycles at five minute intervals between the cycles. Changes in heart rate corrected augmentation index (AIx@75), augmentation index (AIx), carotid femoral pulse wave velocity (PWV), and haemodynamic parameters were measured before and 24 h after DSA.

RESULTS

111 (RIPC 54, sham 57) patients with symptomatic lower limb PAD scheduled for DSA were randomised. 102 patients (RIPC 47, sham 55) were included in final analysis. RIPC significantly improved AIx (-5.46% in RIPC and -1.45% in sham group; p = .05), but not AIx@75 (-4.88% in RIPC and -1.38% in sham group; p = .07) or PWV (-0.41 m/s in RIPC and -0.27 m/s in sham group; p = .74). In the RIPC group a significant reduction in AIx (p = .002) and AIx@75 (p = .003) was noted after stenting when compared with the sham intervention. AIx (p = .001), AIx@75 (p = .002), mean arterial (p = .01), peripheral (p = .02), and central systolic blood pressure (p = .006) were significantly reduced only in the RIPC group 24 h after DSA.

CONCLUSION

This study evaluates for the first time the effects of RIPC on arterial stiffness parameters in patients with symptomatic PAD following DSA. RIPC may modulate arterial stiffness following a DSA procedure and is more pronounced in patients after stent placement.

Perioperative Cardioprotection by Remote Ischemic Conditioning

Remote ischemic conditioning has been investigated for cardioprotection to attenuate myocardial ischemia/reperfusion injury. In this review, we provide a comprehensive overview of the current knowledge of the signal transduction pathways of remote ischemic conditioning according to three stages: Remote stimulus from source organ; protective signal transfer through neuronal and humoral factors; and target organ response, including myocardial response and coronary vascular response. The neuronal and humoral factors interact on three levels, including stimulus, systemic, and target levels. Subsequently, we reviewed the clinical studies evaluating the cardioprotective effect of remote ischemic conditioning. While clinical studies of percutaneous coronary intervention showed relatively consistent protective effects, the majority of multicenter studies of cardiac surgery reported neutral results although there have been several promising initial trials. Failure to translate the protective effects of remote ischemic conditioning into cardiac surgery may be due to the multifactorial etiology of myocardial injury, potential confounding factors of patient age, comorbidities including diabetes, concomitant medications, and the coadministered cardioprotective general anesthetic agents. Given the complexity of signal transfer pathways and confounding factors, further studies should evaluate the multitarget strategies with optimal measures of composite outcomes.

Peripheral Mechanisms of Remote Ischemic Conditioning

Ischemic conditioning induces an endogenous protective mechanism that allows organisms to develop resistance to subsequent insults. The conditioning effect occurs across organs and species. Recently, much attention has been given to remote ischemic limb conditioning due to its non-invasive nature and potential therapeutic applications. While tolerance is induced at the primary injury site (e.g. the heart in cardiac ischemia and the brain in stroke), the site of conditioning application is away from the target organ, suggesting the protective factors are extrinsic in nature rather than intrinsic. This review will focus on the peripheral factors that account for the induction of tolerance. Topics of particular interest are blood flow changes, peripheral neural pathways, humoral factors in circulation, and the peripheral immune system. This review will also discuss how conditioning may negatively affect metabolically compromised conditions, its optimal dose, and window for therapy development.

Short-Term Glucocorticoid Treatment Normalizes the Microcirculatory Response to Remote Ischemic Conditioning in Early Complex Regional Pain Syndrome

BACKGROUND

The early phase of complex regional pain syndrome (CRPS) is characterized by an inflammatory state and therefore often treated with anti-inflammatory acting glucocorticoids. Recently, we demonstrated that remote ischemic conditioning (RIC), a cyclic application of nondamaging ischemia on a remote extremity, reduces blood flow and increases oxygen extraction in the CRPS-affected extremity.

AIM

The aim of the presented study was to analyze the effect of short-term pain treatment including glucocorticoid pulse treatment on the RIC-induced perfusion parameters.

METHOD

Independently from the study, pain treatment was started with an oral glucocorticoid pulse (180 to 360 mg prednisolone) in 12 patients with CRPS (disease duration < 1 year). RIC was conducted before and after pulse treatment. Three cycles of 5 minutes ischemia and 10 minutes reperfusion were applied to the contralateral limb. Blood flow, tissue oxygenation, and oxygen extraction fraction were assessed ipsilateral before and during RIC. Current pain was assessed on the numeric rating scale (0 to 10), and finger-palm distance was measured.

RESULTS

Pain level (5.8 ± 1.5 vs. 3.1 ± 1.1) and finger-palm distance (5 ± 1.9 cm vs. 3.7 ± 1.9 cm) were decreased significantly by the treatment. RIC decreased blood flow by 32.8% ± 42.8% (P < 0.05) and increased oxygen extraction fraction by 8.5% ± 10.3% (P < 0.05) solely before the treatment. After treatment, all parameters remained unchanged after RIC (P < 0.05 vs. before), comparable to healthy subjects.

CONCLUSION

Confirming previous results, RIC presumably unmasks luxury perfusion in untreated CRPS patients. In accordance with the clinical improvement, the short-term pain treatment with glucocorticoids as major component normalizes impaired perfusion. These results might underline the rationale for anti-inflammatory treatment in early-phase CRPS.

Lower extremity arterial disease in patients with diabetes: a contemporary narrative review

Lower-extremity arterial disease (LEAD) is a major endemic disease with an alarming increased prevalence worldwide. It is a common and severe condition with excess risk of major cardiovascular events and death. It also leads to a high rate of lower-limb adverse events and non-traumatic amputation. The American Diabetes Association recommends a widespread medical history and clinical examination to screen for LEAD. The ankle brachial index (ABI) is the first non-invasive tool recommended to diagnose LEAD although its variable performance in patients with diabetes. The performance of ABI is particularly affected by the presence of peripheral neuropathy, medial arterial calcification, and incompressible arteries. There is no strong evidence today to support an alternative test for LEAD diagnosis in these conditions. The management of LEAD requires a strict control of cardiovascular risk factors including diabetes, hypertension, and dyslipidaemia. The benefit of intensive versus standard glucose control on the risk of LEAD has not been clearly established. Antihypertensive, lipid-lowering, and antiplatelet agents are obviously worthfull to reduce major cardiovascular adverse events, but few randomised controlled trials (RCTs) have evaluated the benefits of these treatments in terms of LEAD and its related adverse events. Smoking cessation, physical activity, supervised walking rehabilitation and healthy diet are also crucial in LEAD management. Several advances have been achieved in endovascular and surgical revascularization procedures, with obvious improvement in LEAD management. The revascularization strategy should take into account several factors including anatomical localizations of lesions, medical history of each patients and operator experience. Further studies, especially RCTs, are needed to evaluate the interest of different therapeutic strategies on the occurrence and progression of LEAD and its related adverse events in patients with diabetes.

Remote ischemic conditioning in ST-segment elevation myocardial infarction - an update

Acute myocardial infarction (AMI) and the heart failure (HF) that often results are among the leading causes of death and disability in the world. As such, novel strategies are required to protect the heart against the detrimental effects of acute ischemia/reperfusion injury (IRI), in order to reduce myocardial infarct (MI) size and prevent the onset of HF. The endogenous cardioprotective strategy of remote ischemic conditioning (RIC), in which cycles of brief ischemia and reperfusion are applied to a tissue or organ away from the heart, has been reported in experimental studies to reduce MI size in animal models of acute IRI. In the clinical setting, RIC can be induced by simply inflating and deflating a cuff placed on the upper arm or thigh to induce brief cycles of ischemia and reperfusion, a strategy which has been shown to reduce MI size in ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PPCI). The results of the ongoing CONDI2/ERIC-PPCI trial are eagerly awaited, and will provide definitive answers with regards to the cardioprotective effect and clinical outcome benefits of RIC in STEMI.

The application of remote ischemic conditioning in cardiac surgery

Perioperative myocardial ischemia and infarction are the leading causes of morbidity and mortality following anesthesia and surgery. The discovery of endogenous cardioprotective mechanisms has led to testing of new methods to protect the human heart. These approaches have included ischemic pre-conditioning, per-conditioning, post-conditioning, and remote conditioning of the myocardium. Pre-conditioning and per-conditioning include brief and repetitive periods of sub-lethal ischemia before and during prolonged ischemia, respectively; and post-conditioning is applied at the onset of reperfusion. Remote ischemic conditioning involves transient, repetitive, non-lethal ischemia and reperfusion in one organ or tissue (remote from the heart) that renders myocardium more resistant to lethal ischemia/reperfusion injury. In healthy, young hearts, many conditioning maneuvers can significantly increase the resistance of the heart against ischemia/reperfusion injury. The large multicenter clinical trials with ischemic remote conditioning have not been proven successful in cardiac surgery thus far. The lack of clinical success is due to underlying risk factors that interfere with remote ischemic conditioning and the use of cardioprotective agents that have activated the endogenous cardioprotective mechanisms prior to remote ischemic conditioning. Future preclinical research using remote ischemic conditioning will need to be conducted using comorbid models.

Effects of Remote Ischemic Preconditioning on Heme Oxygenase-1 Expression and Cutaneous Wound Repair

Skin wounds may lead to scar formation and impaired functionality. Remote ischemic preconditioning (RIPC) can induce the anti-inflammatory enzyme heme oxygenase-1 (HO-1) and protect against tissue injury. We aim to improve cutaneous wound repair by RIPC treatment via induction of HO-1. RIPC was applied to HO-1-luc transgenic mice and HO-1 promoter activity and mRNA expression in skin and several other organs were determined in real-time. In parallel, RIPC was applied directly or 24h prior to excisional wounding in mice to investigate the early and late protective effects of RIPC on cutaneous wound repair, respectively. HO-1 promoter activity was significantly induced on the dorsal side and locally in the kidneys following RIPC treatment. Next, we investigated the origin of this RIPC-induced HO-1 promoter activity and demonstrated increased mRNA in the ligated muscle, heart and kidneys, but not in the skin. RIPC did not change HO-1 mRNA and protein levels in the wound 7 days after cutaneous injury. Both early and late RIPC did not accelerate wound closure nor affect collagen deposition. RIPC induces HO-1 expression in several organs, but not the skin, and did not improve excisional wound repair, suggesting that the skin is insensitive to RIPC-mediated protection.