The mechanism of Intralipid®-mediated cardioprotection complex IV inhibition by the active metabolite, palmitoylcarnitine, generates reactive oxygen species and activates reperfusion injury salvage kinases

BACKGROUND

Intralipid® administration at reperfusion elicits protection against myocardial ischemia-reperfusion injury. However, the underlying mechanisms are not fully understood.

METHODS

Sprague-Dawley rat hearts were exposed to 15 min of ischemia and 30 min of reperfusion in the absence or presence of Intralipid® 1% administered at the onset of reperfusion. In separate experiments, the reactive oxygen species (ROS) scavenger N-(2-mercaptopropionyl)-glycine was added either alone or with Intralipid®. Left ventricular work and activation of Akt, STAT3, and ERK1/2 were used to evaluate cardioprotection. ROS production was assessed by measuring the loss of aconitase activity and the release of hydrogen peroxide using Amplex Red. Electron transport chain complex activities and proton leak were measured by high-resolution respirometry in permeabilized cardiac fibers. Titration experiments using the fatty acid intermediates of Intralipid® palmitoyl-, oleoyl- and linoleoylcarnitine served to determine concentration-dependent inhibition of complex IV activity and mitochondrial ROS release.

RESULTS

Intralipid® enhanced postischemic recovery and activated Akt and Erk1/2, effects that were abolished by the ROS scavenger N-(2-mercaptopropionyl)glycine. Palmitoylcarnitine and linoleoylcarnitine, but not oleoylcarnitine concentration-dependently inhibited complex IV. Only palmitoylcarnitine reached high tissue concentrations during early reperfusion and generated significant ROS by complex IV inhibition. Palmitoylcarnitine (1 µM), administered at reperfusion, also fully mimicked Intralipid®-mediated protection in an N-(2-mercaptopropionyl)-glycine -dependent manner.

CONCLUSIONS

Our data describe a new mechanism of postconditioning cardioprotection by the clinically available fat emulsion, Intralipid®. Protection is elicited by the fatty acid intermediate palmitoylcarnitine, and involves inhibition of complex IV, an increase in ROS production and activation of the RISK pathway.

Early mitochondrial dysfunction in glycolytic muscle, but not oxidative muscle, of the fructose-fed insulin-resistant rat

Although evidence that type 2 diabetes mellitus (T2DM) is accompanied by mitochondrial dysfunction in skeletal muscle has been accumulating, a causal link between mitochondrial dysfunction and the pathogenesis of the disease remains unclear. Our study focuses on an early stage of the disease to determine whether mitochondrial dysfunction contributes to the development of T2DM. The fructose-fed (FF) rat was used as an animal model of early T2DM. Mitochondrial respiration and acylcarnitine species were measured in oxidative (soleus) and glycolytic [extensor digitorum longus (EDL)] muscle. Although FF rats displayed characteristic signs of T2DM, including hyperglycemia, hyperinsulinemia, and hypertriglyceridemia, mitochondrial content was preserved in both muscles from FF rats. The EDL muscle had reduced complex I and complex I and II respiration in the presence of pyruvate but not glutamate. The decrease in pyruvate-supported respiration was due to a decrease in pyruvate dehydrogenase activity. Accumulation of C14:1 and C14:2 acylcarnitine species and a decrease in respiration supported by long-chain acylcarnitines but not acetylcarnitine indicated dysfunctional β-oxidation in the EDL muscle. In contrast, the soleus muscle showed preserved mitochondrial respiration, pyruvate dehydrogenase activity, and increased fatty acid oxidation, as evidenced by overall reduced acylcarnitine levels. Aconitase activity, a sensitive index of reactive oxygen species production in mitochondria, was reduced exclusively in EDL muscle, which showed lower levels of the antioxidant enzymes thioredoxin reductase and glutathione peroxidase. Here, we show that the glycolytic EDL muscle is more prone to an imbalance between energy supply and oxidation caused by insulin resistance than the oxidative soleus muscle.

Revegetated Saline Pastures as a Forage Reserve for Sheep: 1. Effects of Season and Grazing on Morphology and Nutritive Value of Saltbush

This study determined the impact of grazing on the kind of material selected by sheep from a saltbush (Atriplex amnicola) plantation and the changes in the chemical composition of saltbush plants associated with season. Saltbush plants in four plots of about 0.9 hectares each were scored from 1 to 5 on the basis of leafiness. Ten Merino wethers were grazed on each plot, giving a stocking rate of about 11 per hectare. The results demonstrated that sheep selected only stem material of less than 1.5 mm diameter, while the grazing pressure on saltbush plants, as described by the number of stems eaten per 0.1 m2, increased from less than one to an average of 18 to 20 stems in 5 to 7 weeks. Grazing had a significant effect on dry matter digestibility (DMD) and nitrogen concentration of whole plant samples. During six weeks of grazing the DMD of whole plant samples cut 10 cm from the tips of the branches dropped from 0.53 to 0.25 (P<0.05), whereas the nitrogen content declined from 11 g/kg to 8 g/kg (P<0.05). At the end of grazing the nutritional value of whole plant samples was very poor and sheep refused to eat stem that was thicker than 1.5 mm. These findings question the grazable fraction reported in the literature for saltbush plantation. when the stem diameters used in calculations are not reported or thicker stems were assumed grazable. Season also had a significant effect on the ratio of leaf to stem and the mineral content. The concentration of sodium in saltbush leaf was negatively correlated (r = -0.93) with both nitrogen and potassium.

Loss of Intralipid®- but not sevoflurane-mediated cardioprotection in early type-2 diabetic hearts of fructose-fed rats: importance of ROS signaling

BACKGROUND

Insulin resistance and early type-2 diabetes are highly prevalent. However, it is unknown whether Intralipid® and sevoflurane protect the early diabetic heart against ischemia-reperfusion injury.

METHODS

Early type-2 diabetic hearts from Sprague-Dawley rats fed for 6 weeks with fructose were exposed to 15 min of ischemia and 30 min of reperfusion. Intralipid® (1%) was administered at the onset of reperfusion. Peri-ischemic sevoflurane (2 vol.-%) served as alternative protection strategy. Recovery of left ventricular function was recorded and the activation of Akt and ERK 1/2 was monitored. Mitochondrial function was assessed by high-resolution respirometry and mitochondrial ROS production was measured by Amplex Red and aconitase activity assays. Acylcarnitine tissue content was measured and concentration-response curves of complex IV inhibition by palmitoylcarnitine were obtained.

RESULTS

Intralipid® did not exert protection in early diabetic hearts, while sevoflurane improved functional recovery. Sevoflurane protection was abolished by concomitant administration of the ROS scavenger N-2-mercaptopropionyl glycine. Sevoflurane, but not Intralipid® produced protective ROS during reperfusion, which activated Akt. Intralipid® failed to inhibit respiratory complex IV, while sevoflurane inhibited complex I. Early diabetic hearts exhibited reduced carnitine-palmitoyl-transferase-1 activity, but palmitoylcarnitine could not rescue protection and enhance postischemic functional recovery. Cardiac mitochondria from early diabetic rats exhibited an increased content of subunit IV-2 of respiratory complex IV and of uncoupling protein-3.

CONCLUSIONS

Early type-2 diabetic hearts lose complex IV-mediated protection by Intralipid® potentially due to a switch in complex IV subunit expression and increased mitochondrial uncoupling, but are amenable to complex I-mediated sevoflurane protection.

Small Angle Intensities from Double Bragg Reflections in Cold?Worked Metals

The small angle intensity from a cold-worked polygrained metal is treated in terms of double Bragg reflections. It is assumed that cold work breaks up the original grains into subgrains with varying orientations, such that a first reflection in one subgrain can be followed by a second reflection in another subgrain of the original grain. For an initial sample which is polygrained with random orientation, the small angle intensity resulting from cold work is given in absolute units in terms of two parameters; an average initial grain size G, and a subgrain correlation function p( ep) giving the distribution in orientation of subgrains with respect to any average subgrain of the original grain. Under favourable conditions, both of these quantities can be obtained from the small angle intensity curve. For polygrained metals, small angle scattering is a useful tool -for obtaining the subgrain correlation function peep), a quantity not obtainable from the usual high angle measurements.

X-Ray Measurement of Twin Faulting in Face-centred Cubic Metals

It was shown by Paterson that in a cold�worked face-centred cubic metal, deformation faults produce a peak shift, and twin faults produce a peak asymmetry. If the peak shape is represented by a Fourier series, the asymmetry is expressed by the sine terms. However, the evaluation of the sine coefficients is difficult, due to overlapping of the tails of neighbouring refleotions and uncertainty in the peak origin. In this paper, a method is developed which combines the tails of the (Ill) and (200) reflections. This allows a determination of the twin fault probability in face-centred cubic metals which is more nearly independent of overlapping of the tails and choice of the peak origin.

Eccentric Exercise Causes Specific Adjustment in Pyruvate Oxidation by Mitochondria

INTRODUCTION

The impact of eccentric exercise on mitochondrial function has only been poorly investigated and remains unclear. This study aimed to identify the changes in skeletal muscle mitochondrial respiration, specifically triggered by a single bout of eccentric treadmill exercise.

METHODS

Male adult mice were randomly divided into eccentric (ECC; downhill running), concentric (CON; uphill running), and unexercised control groups ( n = 5/group). Running groups performed 18 bouts of 5 min at 20 cm·s -1 on an inclined treadmill (±15° to 20°). Mice were sacrificed 48 h after exercise for blood and quadriceps muscles collection. Deep proximal (red) and superficial distal (white) muscle portions were used for high-resolution respirometric measurements.

RESULTS

Plasma creatine kinase activity was significantly higher in the ECC compared with CON group, reflecting exercise-induced muscle damage ( P < 0.01). The ECC exercise induced a significant decrease in oxidative phosphorylation capacity in both quadriceps femoris parts ( P = 0.032 in proximal portion, P = 0.010 in distal portion) in comparison with the CON group. This observation was only made for the nicotinamide adenine dinucleotide (NADH) pathway using pyruvate + malate as substrates. When expressed as a flux control ratio, indicating a change related to mitochondrial quality rather than quantity, this change seemed more prominent in distal compared with proximal portion of quadriceps muscle. No significant difference between groups was found for the NADH pathway with glutamate or glutamate + malate as substrates, for the succinate pathway or for fatty acid oxidation.

CONCLUSIONS

Our data suggest that ECC exercise specifically affects pyruvate mitochondrial transport and/or oxidation 48 h after exercise, and this alteration mainly concerns the distal white muscle portion. This study provides new perspectives to improve our understanding of the mitochondrial adaptation associated with ECC exercise.

Machine Learning to Predict Outcomes of Endovascular Intervention for Patients With PAD

Importance

Endovascular intervention for peripheral artery disease (PAD) carries nonnegligible perioperative risks; however, outcome prediction tools are limited.

Objective

To develop machine learning (ML) algorithms that can predict outcomes following endovascular intervention for PAD.

Design, Setting, and Participants

This prognostic study included patients who underwent endovascular intervention for PAD between January 1, 2004, and July 5, 2023, with 1 year of follow-up. Data were obtained from the Vascular Quality Initiative (VQI), a multicenter registry containing data from vascular surgeons and interventionalists at more than 1000 academic and community hospitals. From an initial cohort of 262 242 patients, 26 565 were excluded due to treatment for acute limb ischemia (n = 14 642) or aneurysmal disease (n = 3456), unreported symptom status (n = 4401) or procedure type (n = 2319), or concurrent bypass (n = 1747). Data were split into training (70%) and test (30%) sets.

Exposures

A total of 112 predictive features (75 preoperative [demographic and clinical], 24 intraoperative [procedural], and 13 postoperative [in-hospital course and complications]) from the index hospitalization were identified.

Main Outcomes and Measures

Using 10-fold cross-validation, 6 ML models were trained using preoperative features to predict 1-year major adverse limb event (MALE; composite of thrombectomy or thrombolysis, surgical reintervention, or major amputation) or death. The primary model evaluation metric was area under the receiver operating characteristic curve (AUROC). After selecting the best performing algorithm, additional models were built using intraoperative and postoperative data.

Results

Overall, 235 677 patients who underwent endovascular intervention for PAD were included (mean [SD] age, 68.4 [11.1] years; 94 979 [40.3%] female) and 71 683 (30.4%) developed 1-year MALE or death. The best preoperative prediction model was extreme gradient boosting (XGBoost), achieving the following performance metrics: AUROC, 0.94 (95% CI, 0.93-0.95); accuracy, 0.86 (95% CI, 0.85-0.87); sensitivity, 0.87; specificity, 0.85; positive predictive value, 0.85; and negative predictive value, 0.87. In comparison, logistic regression had an AUROC of 0.67 (95% CI, 0.65-0.69). The XGBoost model maintained excellent performance at the intraoperative and postoperative stages, with AUROCs of 0.94 (95% CI, 0.93-0.95) and 0.98 (95% CI, 0.97-0.99), respectively.

Conclusions and Relevance

In this prognostic study, ML models were developed that accurately predicted outcomes following endovascular intervention for PAD, which performed better than logistic regression. These algorithms have potential for important utility in guiding perioperative risk-mitigation strategies to prevent adverse outcomes following endovascular intervention for PAD.

Procedure-Related Mortality in Aspiration Thrombectomy for Pulmonary Embolism: A MAUDE Database Analysis of the Inari FlowTriever and Penumbra Indigo Systems

BACKGROUND

Pulmonary embolism (PE) is an important cause of death and disability. Advances in catheter-directed therapies have led to the use of devices, such as the Inari FlowTriever and Penumbra Indigo system for aspiration thrombectomy (AT) for both massive and sub-massive PE. However, limited data exist on causes of procedural mortality.

METHODS

Analysis of the Food and Drug Administration's (FDA) Manufacture and User Facility Device Experience (MAUDE) database was performed. Data for the Inari FlowTriever and Penumbra Indigo aspiration thrombectomy systems were evaluated for mortality events and classified by cause of death from January 1, 2015, to December 31, 2023.

RESULTS

The review identified 26 mortality events related to the Inari FlowTriever and 28 related to the Penumbra Indigo device. Pulmonary vascular perforation (n=26) and right heart injury/tamponade (n=9) were the most common source of mortality. Clot migration (n=4) and acute right heart failure (n=5) were less frequently observed.

CONCLUSIONS

This study reveals more mortality events than have been captured in the literature to date. Vascular perforation and cardiac injury are the most common and also potentially preventable sources of mortality. Strategies to mitigate complications related to aspiration thrombectomy are described.

CLINICAL IMPACT

Analysis of mortality in aspiration thrombectomy (AT) for acute pulmonary embolism is necessary to better understand the safety profile of this procedure. This analysis of the MAUDE database reports the largest single cohort of 54 deaths. Potentially preventable procedure-related mortality in AT has been documented to be the result of vascular perforation and cardiac perforation with tamponade. Preparation for emergent pericardiocentesis should be considered in mechanical thrombectomy. Clot migration may result from thrombus maceration or migration of clot in transit, thus, careful pre-procedure examination for clot in transit with echocardiography is suggested.

Feasibility of Artificial Intelligence Powered Adverse Event Analysis: Using a Large Language Model to Analyze Microwave Ablation Malfunction Data

Objectives: Determine if a large language model (LLM, GPT-4) can label and consolidate and analyze interventional radiology (IR) microwave ablation device safety event data into meaningful summaries similar to humans. Methods: Microwave ablation safety data from January 1, 2011 to October 31, 2023 were collected and type of failure was categorized by human readers. Using GPT-4 and iterative prompt development, the data were classified. Iterative summarization of the reports was performed using GPT-4 to generate a final summary of the large text corpus. Results: Training (n = 25), validation (n = 639), and test (n = 79) data were split to reflect real-world deployment of an LLM for this task. GPT-4 demonstrated high accuracy in the multiclass classification problem of microwave ablation device data (accuracy [95% CI]: training data 96.0% [79.7, 99.9], validation 86.4% [83.5, 89.0], test 87.3% [78.0, 93.8]). The text content was distilled through GPT-4 and iterative summarization prompts. A final summary was created which reflected the clinically relevant insights from the microwave ablation data relative to human interpretation but had inaccurate event class counts. Conclusion: The LLM emulated the human analysis, suggesting feasibility of using LLMs to process large volumes of IR safety data as a tool for clinicians. It accurately labelled microwave ablation device event data by type of malfunction through few-shot learning. Content distillation was used to analyze a large text corpus (>650 reports) and generate an insightful summary which was like the human interpretation.

Moving away from metal: Step toward the future with bioresorbable vascular scaffolds and novel antiproliferative agents

Background

Peripheral arterial disease (PAD) is a common source of morbidity and mortality globally and is expected to raise increase in prevalence. Many endovascular techniques exist to manage PAD; however, there remains room for improvement, especially as it relates to below-the-knee vessels. Recent evidence and devices are leading to a resurgence of interest in bioresorbable vascular scaffolds and the -limus family of antiproliferative drugs in the PAD treatment space.

Methods

This nonsystematic review examines emerging technology for treatment of PAD with a specific focus on below-the-knee vessels and bioresorbable vascular scaffolds. Additional emerging and early technology such as novel delivery platforms are also briefly discussed with directions of future research highlighted.

Results

Bioresorbable vascular scaffold biomechanics and history are highlighted. Foundational knowledge of antiproliferative agents and evolving agents in peripheral vascular disease are also described.

Conclusions

Bioresorbable vascular scaffolds are an additional endovascular tool for the treatment of peripheral vascular disease. The integration with an antiproliferative agent may result in improved patency and performance; however, there is a paucity of data in the literature at present.

Pan-Canadian consensus recommendations for GIST management in high- and low-throughput centres across Canada

Gastrointestinal stromal tumours (GISTs) are mesenchymal tumours that originate from the interstitial cells of Cajal. GISTs are mainly driven by gain-of-function mutations in receptor tyrosine kinase or platelet-derived growth factor receptor alpha. Surgical resection is the only curative treatment for localized tumours and all currently approved medical GIST treatments are based on orally available tyrosine kinase inhibitors. Recent discoveries in the molecular and clinical features of GISTs have greatly impacted GIST management. Due to the provincially rather than nationally administered Canadian healthcare system, there have been inconsistencies in the treatment of GISTs across the country. Therefore, guidance on the latest knowledge, clinical management and treatment of GIST is needed to standardize the approach to GIST management nationwide. To establish pan-Canadian guidance, provide up-to-date data and harmonize the clinical practice of GIST management in high- and low-throughput centres across Canada; a panel of 20 physicians with extensive clinical experience in GIST management reviewed relevant literature. This included radiologists, pathologists, interventional radiologists, surgeons and medical oncologists across Canada. The structured literature focused on seven key domains: molecular profiling, radiological techniques/reporting, targeted localized therapy, intricacies of systemic treatments, emerging tests, multidisciplinary care and patient advocacy. This literature review, along with clinical expertise and opinion, was used to develop this concise and clinically relevant consensus paper to harmonize the knowledge and clinical practice on GIST management across Canada. The content presented here will help guide healthcare providers, especially in Canada, in terms of approaching and managing GIST.