Alpha-ketoglutarate for myocardial protection in heart surgery

Alpha-ketoglutarate supplementation reduces inflammation and thrombosis in type 2 diabetes by suppressing leukocyte and platelet activation

The interplay between platelets and leukocytes contributes to the pathogenesis of inflammation, thrombosis, and cardiovascular diseases (CVDs) in type 2 diabetes (T2D). Our recent studies described alpha-ketoglutarate (αKG), a Krebs cycle intermediate metabolite as an inhibitor to platelets and leukocytes activation by suppressing phosphorylated-Akt (pAkt) through augmentation of prolyl hydroxylase-2 (PHD2). Dietary supplementation with a pharmacological concentration of αKG significantly inhibited lung inflammation in mice with either SARS-CoV-2 infection or exposed to hypoxia treatment. We therefore investigated if αKG supplementation could suppress hyperactivation of these blood cells and reduce thromboinflammatory complications in T2D. Our study describes that dietary supplementation with αKG (8 mg/100 g body wt. daily) for 7 days significantly reduced the activation of platelets and leukocytes (neutrophils and monocytes), and accumulation of IL1β, TNFα, and IL6 in peripheral blood of T2D mice. αKG also reduced the infiltration of platelets and leukocytes, and accumulation of inflammatory cytokines in lungs by suppressing pAkt and pP65 signaling. In a cross-sectional investigation, our study also described the elevated platelet-leukocyte aggregates and pro-inflammatory cytokines in circulation of T2D patients. T2D platelets and leukocytes showed an increased aggregation and thrombus formation in vitro. Interestingly, a pre-incubation of T2D blood samples with octyl αKG significantly suppressed the activation of these blood cells and ameliorated aggregate/thrombus formation in vitro. Thus, suggesting a potential therapeutic role of αKG against inflammation, thrombosis, and CVDs in T2D.

Regenerating the heart by metabolically reprogramming the cardiomyocyte epigenome

In mammal adolescence, cardiomyocytes rapidly exit the cell cycle, and heart regeneration in adults is limited after cardiac injury. Recent work by Li et al. in Nature revealed that inhibition of fatty acid oxidation can rewire cell metabolism and lead to epigenetic reprogramming of cardiomyocytes to an immature state that facilitates cardiomyocyte cell-cycle reentry and heart regeneration in adult animals.

Alpha-ketoglutarate supplementation and BiologicaL agE in middle-aged adults (ABLE)-intervention study protocol

Targeting molecular processes of aging will enable people to live healthier and longer lives by preventing age-related diseases. Geroprotectors are compounds with the potential to increase healthspan and lifespan. Even though many of them have been tested in animal models, the translation to humans is limited. Alpha-Ketoglutarate (AKG) has been studied widely in model animals, but there are few studies testing its geroprotective properties in humans. ABLE is a double blinded placebo-controlled randomized trial (RCT) of 1 g sustained release Ca-AKG versus placebo for 6 months of intervention and 3 months follow up including 120 40-60-year-old healthy individuals with a higher DNA methylation age compared to their chronological age. The primary outcome is the decrease in DNA methylation age from baseline to the end of the intervention. A total of 120 participants will be randomized to receive either sustained release Ca-AKG or placebo. Secondary outcomes include changes in the inflammatory and metabolic parameters in blood, handgrip strength and leg extension strength, arterial stiffness, skin autofluorescence, and aerobic capacity from baseline to 3 months, 6 months, and 9 months. This study will recruit middle-aged participants with an older DNA methylation age compared to their chronological age, and test whether supplementation with Ca-AKG can reduce DNA methylation age. This study is unique in its inclusion of biologically older participants.

Cardiac macrophages and emerging roles for their metabolism after myocardial infarction

Interest in cardioimmunology has reached new heights as the experimental cardiology field works to tap the unrealized potential of immunotherapy for clinical care. Within this space is the cardiac macrophage, a key modulator of cardiac function in health and disease. After a myocardial infarction, myeloid macrophages both protect and harm the heart. To varying degrees, such outcomes are a function of myeloid ontogeny and heterogeneity, as well as functional cellular plasticity. Diversity is further shaped by the extracellular milieu, which fluctuates considerably after coronary occlusion. Ischemic limitation of nutrients constrains the metabolic potential of immune cells, and accumulating evidence supports a paradigm whereby macrophage metabolism is coupled to divergent inflammatory consequences, although experimental evidence for this in the heart is just emerging. Herein we examine the heterogeneous cardiac macrophage response following ischemic injury, with a focus on integrating putative contributions of immunometabolism and implications for therapeutically relevant cardiac injury versus cardiac repair.

Supplementation with α-ketoglutarate improved the efficacy of anti-PD1 melanoma treatment through epigenetic modulation of PD-L1

Patients with advanced melanoma have shown an improved outlook after anti-PD1 therapy, but the low response rate restricts clinical benefit; therefore, enhancing anti-PD1 therapeutic efficacy remains a major challenge. Here, our findings showed a significantly increased abundance of α-KG in healthy controls, anti-PD1-sensitive melanoma-bearing mice, and anti-PD1-sensitive melanoma patients; moreover, supplementation with α-KG enhanced the efficacy of anti-PD1 immunotherapy and increased PD-L1 expression in melanoma tumors via STAT1/3. We also found that supplementation with α-KG significantly increased the activity of the methylcytosine dioxygenases TET2/3, which led to an increased 5-hydroxymethylcytosine (5-hmC) level in the PD-L1 promoter. As a consequence, STAT1/3 binding to the PD-L1 promoter was stabilized to upregulate PD-L1 expression. Importantly, single-cell sequencing of preclinical samples and analysis of clinical data revealed that TET2/3-STAT1/3-CD274 signaling was associated with sensitivity to anti-PD1 treatment in melanoma. Taken together, our results provide novel insight into α-KG's function in anti-PD1 treatment of melanoma and suggest supplementation with α-KG as a novel promising strategy to improve the efficacy of anti-PD1 therapy.

Alpha-Ketoglutarate dietary supplementation to improve health in humans

Alpha-ketoglutarate (AKG) is an intermediate in the Krebs cycle involved in various metabolic and cellular pathways. As an antioxidant, AKG interferes in nitrogen and ammonia balance, and affects epigenetic and immune regulation. These pleiotropic functions of AKG suggest it may also extend human healthspan. Recent studies in worms and mice support this concept. A few studies published in the 1980s and 1990s in humans suggested the potential benefits of AKG in muscle growth, wound healing, and in promoting faster recovery after surgery. So far there are no recently published studies demonstrating the role of AKG in treating aging and age-related diseases; hence, further clinical studies are required to better understand the role of AKG in humans. This review will discuss the regulatory role of AKG in aging, as well as its potential therapeutic use in humans to treat age-related diseases.

Labile Photo-Induced Free Radical in α-Ketoglutaric Acid: a Universal Endogenous Polarizing Agent for In Vivo Hyperpolarized 13 C Magnetic Resonance

Hyperpolarized (HP) 13 C magnetic resonance enables non-invasive probing of metabolism in vivo. To date, only 13 C-molecules hyperpolarized with persistent trityl radicals have been injected in humans. We show here that the free radical photo-induced in alpha-ketoglutaric acid (α-KG) can be used to hyperpolarize photo-inactive 13 C-molecules such as [1-13 C]lactate. α-KG is an endogenous molecule with an exceptionally high radical yield under photo-irradiation, up to 50 %, and its breakdown product, succinic acid, is also endogenous. This radical precursor therefore exhibits an excellent safety profile for translation to human studies. The labile nature of the radical means that no filtration is required prior to injection while also offering the opportunity to extend the 13 C relaxation time in frozen HP 13 C-molecules for storage and transport. The potential for in vivo metabolic studies is demonstrated in the rat liver following the injection of a physiological dose of HP [1-13 C]lactate.

Labile Photo-Induced Free Radical in α-Ketoglutaric Acid: a Universal Endogenous Polarizing Agent for In Vivo Hyperpolarized 13C Magnetic Resonance

Hyperpolarized (HP) 13C magnetic resonance enables non-invasive probing of metabolism in vivo. To date, only 13C-molecules hyperpolarized with persistent trityl radicals have been injected in humans. We show here that the free radical photo-induced in alpha-ketoglutaric acid (α-KG) can be used to hyperpolarize photo-inactive 13C-molecules such as [1-13C]lactate. α-KG is an endogenous molecule with an exceptionally high radical yield under photo-irradiation, up to 50 %, and its breakdown product, succinic acid, is also endogenous. This radical precursor therefore exhibits an excellent safety profile for translation to human studies. The labile nature of the radical means that no filtration is required prior to injection while also offering the opportunity to extend the 13C relaxation time in frozen HP 13C-molecules for storage and transport. The potential for in vivo metabolic studies is demonstrated in the rat liver following the injection of a physiological dose of HP [1-13C]lactate.

Integrative transcriptomic analysis of tissue-specific metabolic crosstalk after myocardial infarction

Myocardial infarction (MI) promotes a range of systemic effects, many of which are unknown. Here, we investigated the alterations associated with MI progression in heart and other metabolically active tissues (liver, skeletal muscle, and adipose) in a mouse model of MI (induced by ligating the left ascending coronary artery) and sham-operated mice. We performed a genome-wide transcriptomic analysis on tissue samples obtained 6- and 24 hr post MI or sham operation. By generating tissue-specific biological networks, we observed: (1) dysregulation in multiple biological processes (including immune system, mitochondrial dysfunction, fatty-acid beta-oxidation, and RNA and protein processing) across multiple tissues post MI and (2) tissue-specific dysregulation in biological processes in liver and heart post MI. Finally, we validated our findings in two independent MI cohorts. Overall, our integrative analysis highlighted both common and specific biological responses to MI across a range of metabolically active tissues.

The human body is like a state-of-the-art car, where each part must work together with all the others. When a car breaks down, most of the time the problem is not isolated to only one part, as it is an interconnected system. Diseases in the human body can also have systemic effects, so it is important to study their implications throughout the body. Most studies of heart attacks focus on the direct impact on the heart and the cardiovascular system. Learning more about how heart attacks affect rest of the body may help scientists identify heart attacks early or create improved treatments.

Arif and Klevstig et al. show that heart attacks affect the metabolism throughout the body. In the experiments, mice underwent a procedure that mimics either a heart attack or a fake procedure. Then, Arif and Klevstig et al. compared the activity of genes in the heart, muscle, liver and fat tissue of the two groups of mice 6- and 24-hours after the operations. This revealed disruptions in the immune system, metabolism and the production of proteins. The experiments also showed that changes in the activity of four important genes are key to these changes. This suggests that this pattern of changes could be used as a way to identify heart attacks.

The experiments show that heart attacks have important effects throughout the body, especially on metabolism. These discoveries may help scientists learn more about the underlying biological processes and develop new treatments that prevent the harmful systemic effects of heart attacks and boost recovery.

Myocardial protection during minimally invasive cardiac surgery through right mini-thoracotomy

BACKGROUND

Myocardial damage is an independent predictor of adverse outcome following cardiac surgery and myocardial protection is one of the key factors to achieve successful outcomes. Cardioplegia with Custodiol is currently the most used cardioplegia during minimally invasive cardiac surgery (MICS). Different randomized controlled trials compared blood and Custodiol cardioplegia in the context of traditional cardiac surgery. No data are available for MICS.

AIM

The aim of this study was to compare the efficacy of cold blood versus Custodiol cardioplegia during MICS.

METHOD

We retrospectively evaluated 90 patients undergoing MICS through a right mini-thoracotomy in a three-year period. Myocardial protection was performed using cold blood (44 patients, CBC group) or Custodiol (46 patients, Custodiol group) cardioplegia, based on surgeon preference and complexity of surgery.

RESULTS

The primary outcomes were post-operative cardiac troponin I (cTnI) and creatine kinase MB (CKMB) serum release and the incidence of Low Cardiac Output Syndrome (LCOS). Aortic cross-clamp and cardiopulmonary bypass times were higher in the Custodiol group. No difference was observed in myocardial injury enzyme release (peak cTnI value was 18±46 ng/ml in CBC and 21±37 ng/ml in Custodiol; p=0.245). No differences were observed for mortality, LCOS, atrial or ventricular arrhythmias onset, transfusions, mechanical ventilation time duration, intensive care unit and total hospital stay.

CONCLUSIONS

Custodiol and cold blood cardioplegic solutions seem to assure similar myocardial protection in patients undergoing cardiac surgery through a right mini-thoracotomy approach.

Histidine and other amino acids in blood and urine after administration of Bretschneider solution (HTK) for cardioplegic arrest in patients: effects on N-metabolism

Bretschneider (histidine-tryptophan-ketoglutarate, HTK) solution employed for induction of cardioplegic arrest possesses a high histidine concentration (198 mM). Due to the large volume administered, massive amounts of histidine are incorporated. The aim of the study was to evaluate alterations in amino acid and nitrogen metabolism originating from histidine degradation. Between 07/2014 and 10/2014, a total of 29 consecutive patients scheduled for elective isolated coronary artery bypass grafting with cardiopulmonary bypass (CPB) were enrolled in this prospective observational study. The patients received 1.6 L cardioplegic Bretschneider solution on average. Blood gas and urine samples obtained were analyzed for amino acid as well as urea and ammonium concentrations. After CPB initiation, plasma histidine concentration greatly increased to 21,000 µM to reach 8000 µM at the end. Within the operative period, plasma concentrations of aspartate, glutamate, asparagine, alanine, and glutamine increased variable in magnitude. During the same time, urinary analysis revealed histidine excretion of 19,500 µmol in total and marked elevations in glutamate and glutamine excretion. The absolute amounts of urea and ammonium excreted additionally were 3 mmol and 8 mmol, respectively. Already during CPB, distinct amounts of the histidine administered are metabolized, mainly to other amino acids, but only small amounts to urea and ammonia. Thus, the impact of the histidine incorporated on acid–base status in the intraoperative phase is minor. On the other hand, intraoperative provision of several amino acids arising from histidine metabolism might mitigate postaggression syndrome.

Low T3 State Is Correlated with Cardiac Mitochondrial Impairments after Ischemia Reperfusion Injury: Evidence from a Proteomic Approach

Mitochondria are major determinants of cell fate in ischemia/reperfusion injury (IR) and common effectors of cardio-protective strategies in cardiac ischemic disease. Thyroid hormone homeostasis critically affects mitochondrial function and energy production. Since a low T3 state (LT3S) is frequently observed in the post infarction setting, the study was aimed to investigate the relationship between 72 h post IR T3 levels and both the cardiac function and the mitochondrial proteome in a rat model of IR. The low T3 group exhibits the most compromised cardiac performance along with the worst mitochondrial activity. Accordingly, our results show a different remodeling of the mitochondrial proteome in the presence or absence of a LT3S, with alterations in groups of proteins that play a key role in energy metabolism, quality control and regulation of cell death pathways. Overall, our findings highlight a relationship between LT3S in the early post IR and poor cardiac and mitochondrial outcomes, and suggest a potential implication of thyroid hormone in the cardio-protection and tissue remodeling in ischemic disease.

Brain metabolism and Alzheimer's disease: the prospect of a metabolite-based therapy

The brain is one of the most energy-demanding organs in the body. It has evolved intricate metabolic networks to fulfill this need and utilizes a variety of substrates to generate ATP, the universal energy currency. Any disruption in the supply of energy results in various abnormalities including Alzheimer's disease (AD), a condition with markedly diminished cognitive ability. Astrocytes are an important participant in maintaining the cerebral ATP budget. However, under oxidative stress induced by numerous factors including aluminum toxicity, the ability of astroctyes to generate ATP is impaired due to dysfunctional mitochondria. This leads to globular, glycolytic, lipogenic and ATP-deficient astrocytes, cerebral characteristics common in AD patients. The reversal of these perturbations by such natural metabolites as pyruvate, α-ketoglutarate, acetoacetate and L-carnitine provides valuable therapeutic cues against AD.

Which way does the citric acid cycle turn during hypoxia? The critical role of α-ketoglutarate dehydrogenase complex

The citric acid cycle forms a major metabolic hub and as such it is involved in many disease states involving energetic imbalance. In spite of the fact that it is being branded as a "cycle", during hypoxia, when the electron transport chain does not oxidize reducing equivalents, segments of this metabolic pathway remain operational but exhibit opposing directionalities. This serves the purpose of harnessing high-energy phosphates through matrix substrate-level phosphorylation in the absence of oxidative phosphorylation. In this Mini-Review, these segments are appraised, pointing to the critical importance of the α-ketoglutarate dehydrogenase complex dictating their directionalities.

Adverse effects of α-ketoglutarate/malate in a rat model of acute kidney injury

Acute kidney injury (AKI) is the most common kidney disease in hospitalized patients with high mortality. Ischemia and reperfusion (I/R) is one of the major causes of AKI. The combination of α-ketoglutarate+malate (αKG/MAL) showed the ability to reduce hypoxia-induced damage to isolated proximal tubules. The present study utilizes a rat model of I/R-induced AKI accompanied by intensive biomonitoring to examine whether αKG/MAL provides protection in vivo. AKI was induced in male Sprague-Dawley rats by bilateral renal clamping (40 min) followed by reperfusion (240 min). αKG/MAL was infused continuously for 60 min before and 45 min after ischemia. Normoxic and I/R control groups received 0.9% NaCl solution. The effect of αKG/MAL was evaluated by biomonitoring, blood and plasma parameters, histopathology, and immunohistochemical staining for kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL), as well as by determination of tissue ATP and nonesterified fatty acid concentrations. Intravenous infusion of αKG/MAL at a cumulative dose of 1 mmol/kg each (146 mg/kg αKG and 134 mg/kg MAL) did not prevent I/R-induced increases in plasma creatinine, histopathological alterations, or cortical ATP depletion. On the contrary, the most notable adverse affect in animals receiving αKG/MAL was the decrease in mean arterial blood pressure, which was also accompanied by a reduction in heart rate. Supplementation with αKG/MAL, which is very protective against hypoxia-induced injury in isolated proximal tubules, does not protect against I/R-induced renal injury in vivo, possibly due to cardiovascular depressive effects.

Potential cardiovascular applications of glutamate, aspartate, and other amino acids

Cardioplegic solutions rich in the hydrophilic, basic amino acids, glutamate and aspartate, have enhanced myocardial preservation and left ventricular function. This has been demonstrated in assorted animal preparations involving ischemia with and without reperfusion. Published clinical data, though limited, strongly support the contention that these amino acids have myocardial protective properties. Several biochemical mechanisms exist by which certain amino acids may attenuate ischemic or reperfusion injury. Glutamate and aspartate may become preferred myocardial fuels in the setting of ischemia. They may also reduce myocardial ammonia production and reduce cytoplasmic lactate levels, thereby deinhibiting glycolysis. Some amino acids may become substrate for the citric acid cycle. Glutamate and aspartate also move reducing equivalents from cytoplasm to mitochondria where they are necessary for oxidative phosphorylation and energy generation. A rationale exists for the use of an amino acid-rich cardioplegia-like solution in myocardial infarction. These solutions are safe and inexpensive.

Zinc toxicity alters mitochondrial metabolism and leads to decreased ATP production in hepatocytes

Although zinc (Zn) is a known environmental toxicant, its impact on the cellular energy-producing machinery is not well established. This study investigated the influence of this divalent metal on the oxidative ATP producing network in human hepatocellular carcinoma (HepG2) cells. Zn-challenged cells contained more oxidized proteins and lipids compared with control cells. Zn severely impeded mitochondrial functions by inhibiting aconitase, alpha-ketoglutarate dehydrogenase, isocitrate dehydrogenase-NAD+ dependent, succinate dehydrogenase and cytochrome C oxidase Zn-exposed cells had a disparate mitochondrial metabolism compared with the control cells and produced significantly less ATP. However, the expression of isocitrate dehydrogenase-NADP+ dependent was more prominent in cells treated with Zn. Hence, Zn-induced pathologies may be due to the inability of the mitochondria to generate energy effectively.

Protective role of pinacidil against adrenaline-induced myocardium injury in guinea pig liver mitochondria

We investigated the role of the ATP-sensitive potassium channel opener pinacidil and blocker glibenclamide on guinea pig liver mitochondrial function, and a possible significance of pinacidil in the pharmacological treatment during myocardium dystrophy. First, a series of experiments was performed to determine the effect of pinacidil and glibenclamide on mitochondrial oxygen consumption. We found that pinacidil increased the rate of mitochondrial respiration for FAD-generated substrate (succinate oxidation), but was most effective for α-ketoglutarate oxidation with enhancement of respiratory control ratio. Oxidation of FAD-generated substrate inhibited efficiency of phosphorylation for α-ketoglutarate oxidation in pinacidil-treated animals. Glibenclamide decreased the rate of respiration with the lowest value of efficiency of phosphorylation, especially for α-ketoglutarate oxidation. A second series of experiments was performed to determine the effects of pinacidil and glibenclamide on oxidative phosphorylation during adrenaline-induced myocardium dystrophy. The increase in respiratory control ratio and efficiency of phosphorylation for α-ketoglutarate oxidation was greater than for succinate oxidation in mitochondria of pinacidil-pretreated animals during myocardium dystrophy. Inhibitory analysis with malonate suggested that endogenous succinate increased oxidation of NADH-generated substrates in mitochondria. Pinacidil is mainly involved in the adrenaline-induced alterations of mitochondrial function due to elevation of phosphorylation efficiency for α-ketoglutarate oxidation and a decreased level of lipid peroxidation.

The impact of preoperative micronutrient supplementation in lung surgery. A prospective randomized trial of oral supplementation of combined alpha-ketoglutaric acid and 5-hydroxymethylfurfural

OBJECTIVE

Preoperative micronutrient supplementation in fast-track surgery programs have shown to reduce complications, shorten recovery, and thereby lower costs. In a prospective randomized study, the metabolic effects of a combination of alpha-ketoglutaric acid (alpha-KG) and 5-hydroxymethylfurfural (5-HMF) were evaluated concerning their impact on improvement of exercise capacity and reduction of oxidative stress in lung surgery.

METHODS

Thirty-two consecutive patients admitted for lung resection due to NSCLC were randomized to the study protocol. All patients received preoperative nutritional guidelines according to general recommendations. In 16 (study group), a supplementation of 7.2g alpha-KG and 720 mg 5-HMF/day (SANOPAL) was administered from days 1 to 10. Spiroergometric evaluation was carried out at baseline and day 10 after micronutrient supplementation. Blood samples for the determination of oxidative stress, i.e. carbonyl proteins (CPs) and isoprostanes (IPs) were taken on at baseline, in the operating room just before resection treatment, and 25 min after single lung ventilation (SLV).

RESULTS

Spiroergometric re-evaluation showed a significant increase of VO2max (p=0.0108) and Watt's (p=0.011) in favor of the study group. Determination of oxidative stress showed a significant reduction of CPs before (p=0.048) and after SLV (p=0.0001) for the study group compared to the control group. The same is true for IPs before (p=0.003) and after SLV (p=0.02). Hospitalization and intensive care unit (ICU) of the study group showed a significant reduction compared to the control group (p=0.03 and p=0.02, respectively).

CONCLUSIONS

Simple oral supplementation using a combination of alpha-KG and 5-HMF of preoperative micronutrition may therefore be one further step in a multimodality approach of fast-track surgery programs also in lung surgery.

Myocardial Metabolism is Better Preserved After Blood Cardioplegia in Infants

BACKGROUND

We have previously reported improved hemodynamic function after blood cardioplegia in comparison with crystalloid cardioplegia. Furthermore, lactate was released from the heart after crystalloid cardioplegia but not after blood cardioplegia. The purpose of this study was to determine whether the difference in substrate metabolism between the two cardioplegia methods was restricted to lactate, or whether the difference in metabolic derangement was more extensive.

METHODS

Thirty consecutive infants with complete atrioventricular septal defects were included in this prospective, randomized, controlled study. Arterial and coronary sinus blood concentrations of substrates and amino acids were measured after weaning from bypass.

RESULTS

After crystalloid cardioplegia, there was a myocardial uptake of glutamate (p = 0.003), leucine (p = 0.03), lysine (p = 0.003), and beta-hydroxybutyrate (p = 0.004), whereas lactate was released (p = 0.03). After blood cardioplegia, there was a myocardial uptake of free fatty acids (p = 0.01) but no uptake of amino acids and no release of lactate.

CONCLUSIONS

There are differences in myocardial substrate metabolism between blood cardioplegia and crystalloid cardioplegia, which involve carbohydrates and amino acids. The differences may include lipids but our data in this respect are not conclusive.

Blood Cardioplegia Provides Superior Protection in Infant Cardiac Surgery

BACKGROUND

We hypothesized that blood cardioplegia preserves myocardial metabolism and function more effectively than St Thomas' crystalloid cardioplegia in infant cardiac surgery.

METHODS

Thirty infants with atrioventricular septal defects were randomly allocated to either blood or crystalloid intermittent cold (4 degrees C) cardioplegia. Arterial and coronary sinus blood was analyzed for lactate and oxygen. Cardiac output (thermodilution) and left ventricular function (echocardiography) were evaluated.

RESULTS

The lactate concentration in coronary sinus blood early after bypass was significantly higher after crystalloid cardioplegia than after blood cardioplegia (2.1 +/- 0.3 vs 1.3 +/- 0.1 mmol/L, p = 0.006), with a significant myocardial release of lactate after crystalloid but not after blood cardioplegia. Oxygen extraction (arterial-coronary sinus O2 content) was higher early after crystalloid cardioplegia (3.02 +/- 0.13 vs 2.35 +/- 0.22 mmol/L, p = 0.01), possibly reflecting a difference in oxygen debt. The cardiac index was higher after blood cardioplegia (4.9 +/- 0.3 vs 4.0 +/- 0.3 L/min(-1)/m(-2), p = 0.04) and echocardiographic grading of left ventricular function was better (4.1 +/- 0.17 vs 3.5 +/- 0.22 arbitrary units, p = 0.046).

CONCLUSIONS

This study indicates that blood cardioplegia preserves myocardial metabolism and function more effectively than crystalloid cardioplegia in infant cardiac surgery. The clinical significance of this finding is uncertain, but the more than 20% increase in cardiac index in the critical phase during weaning from bypass may be advantageous.

Cold blood cardioplegia versus cold crystalloid cardioplegia: A prospective randomized study of 1440 patients undergoing coronary artery bypass grafting

OBJECTIVES

A large number of experimental studies have indicated that blood cardioplegia might be superior to crystalloid cardioplegia for myocardial protection during ischemic arrest. However, no prospectively randomized studies of large patient series have been undertaken to prove potential differences in clinical course.

METHODS

Over a 52-month period, all patients undergoing on-pump coronary artery bypass operated on by 2 surgeons were prospectively randomized to receive either cold crystalloid cardioplegia (group C) or cold blood cardioplegia (group B) during aortic crossclamping.

RESULTS

Altogether, 1440 patients aged 37 to 89 years (median, 66 years) entered the study (group C, n = 719; group B, n = 721). The groups were comparable in all major demographic, preoperative, and operative variables. The clinical course turned out to be nearly identical for both groups. No statistically significant differences were seen concerning spontaneous sinus rhythm after aortic declamping, use of inotropic drugs or intra-aortic balloon pumping, postoperative ventilatory support, bleeding and rate of allogeneic blood transfusions, perioperative myocardial infarction, episodes of atrial fibrillation, stroke or minor neurologic dysfunction, renal function, infections, physical rehabilitation, or mortality. Also, in subgroups of patients at higher operative risk (female sex, age >70 years, unstable angina, diabetes, emergency operation, ejection fraction <0.50, crossclamping time >50 minutes, and EuroSCORE >4), no statistically significant differences could be demonstrated between the groups.

CONCLUSIONS

There were no significant differences whether myocardial protection was performed with cold blood cardioplegia or cold crystalloid cardioplegia during aortic crossclamping in patients undergoing coronary artery bypass grafting. The extra costs related to blood cardioplegia might be saved.

Effects of alpha-ketoglutarate on antioxidants and lipid peroxidation products in rats treated with ammonium acetate

The effects of alpha-ketoglutarate (alpha-KG) on hyperammonemia induced by ammonium acetate were studied biochemically in experimental rats. The levels of circulatory urea and non-protein nitrogen increased significantly in rats treated with ammonium acetate and decreased significantly in rats treated with alpha-KG and ammonium acetate. In liver and kidney tissues, similar patterns of alterations across groups were observed in the levels of thiobarbituric acid-reactive substances and lipid profile variables (free fatty acids, triacylglycerols, phospholipids, and cholesterol). Further, enzymatic (superoxide dismutase, catalase, and glutathione peroxidase) and non-enzymatic (reduced glutathione) antioxidants in both tissues decreased significantly in rats treated with ammonium acetate and increased significantly in rats treated with alpha-KG and ammonium acetate. The biochemical alterations during alpha-KG treatment might have been due to 1) the detoxification of excess ammonia, 2) participation in the non-enzymatic oxidative decarboxylation during hydrogen peroxide decomposition, and 3) enhancement of the proper metabolism of fats that could suppress oxygen radical generation and thus prevent lipid peroxidative damages in rats.

Renal effects of alpha-ketoglutarate early after coronary operations

BACKGROUND

Alpha-ketoglutarate (alpha-KG) is a Krebs cycle intermediate and the carbon skeleton of glutamate. Alpha-ketoglutarate has provoked interest in heart surgery because of its proposed critical role in myocardial metabolism. This study investigates the role of alpha-KG in renal function after cardiac surgical procedures.

METHODS

Twenty-two patients with normal preoperative renal function were included in a prospective, randomized, and controlled study. Eleven patients received intravenous infusion of 30 g alpha-KG/hour after the operation. Measurements were performed before operation, immediately after operation, and after 30 minutes of alpha-KG infusion.

RESULTS

Renal blood flow was higher during alpha-KG infusion, 297% +/- 97% (of preoperative value), than in controls, 125% +/- 20% (p < 0.05). Filtration fraction was lower (12.3% +/- 0.05% versus 17.2% +/- 1.1%, p < 0.01), which prevented a significant difference in glomerular filtration rate. The renal arteriovenous differences of lactate, glutamate, glutamine, and glycine changed toward a net release during alpha-KG infusion.

CONCLUSIONS

Infusion of alpha-KG enhances renal blood flow early after coronary surgical procedures in patients with normal renal function. The mechanism is unclear, but could be associated with primarily metabolic effects, and may potentially convey a beneficial effect for renal function.

Beat-to-beat QRS amplitude variability after acute myocardial infarction and coronary artery bypass grafting

Ischemic myocardial injury has been demonstrated to be associated with increased beat-to-beat electrical variability of the depolarization phase. This can be quantified by electrocardiographic (ECG) signal variance analysis, a technique that has proven its diagnostic value in the detection of coronary artery disease (CAD). This study evaluates QRS amplitude variability during a 6-month follow-up period in 73 patients with acute myocardial infarction (AMI) and in 56 patients subjected to coronary artery bypass grafting (CABG). The beat-to-beat QRS amplitude variability was quantified with variance electrocardiography. The equipment allows computerized time domain analysis of high-fidelity ECG signals from 24 leads, and the detected electrical heterogeneity is then expressed as a nondimensional index ranging from 0 to 150, with values >90 being indicative of ischemic myocardial involvement. One week after AMI 55% of the patients presented with an abnormal QRS variability index >90. A significant (p <0.01) increase in the index values occurred during the follow-up period, but only in the patients with an initial index <70. In the CABG group 44% of the patients had a preoperative QRS variability index >90. The values increased (p <0.05) in all patients after surgery; the increase was transient in patients with an initial index <70 (p <0.01). The results demonstrate that the myocardial injury in patients with CAD is often associated with increased electrical variability of myocardial depolarization. The QRS amplitude variability index can be used as a marker of such an injury, and analysis of its changes in the course of ischemic cardiac events may provide new insights into the dynamics of ischemic heart disease and the myocardial healing process.

Antidotal efficacy of alpha-ketoglutaric acid and sodium thiosulfate in cyanide poisoning

Alpha-ketoglutaric acid and sodium thiosulfate antagonize the toxic effects of cyanide. The present study was performed to test whether a synergistic effect may occur. The alpha-ketoglutaric acid/sodium thiosulfate solutions were injected intraperitoneally into mice prior to exposure to hydrogen cyanide (HCN) in a dynamic inhalation chamber or preceding an intraperitoneal injection of sodium cyanide (NaCN). All lethal concentration (LCT) and lethal dose (LD) values were determined after a period of 24 h. Alpha-ketoglutaric acid alone provided no protection at 250 mg/kg when challenged with HCN. Sodium thiosulfate 500 mg/kg provided a 5% protection. However, when these doses of alpha-ketoglutaric acid and sodium thiosulfate were combined, protection was increased by 18%. Alpha-ketoglutaric acid (250 mg/kg) and sodium thiosulfate (1000 mg/kg) provided an additional 48% protection against a LCT88 of HCN. A single dose of alpha-ketoglutaric acid (500 mg/kg) and sodium thiosulfate (1000 mg/kg) solutions afforded a 70% increase in survivability of the exposed animals. When mice were injected ip with 100 mg/kg of alpha-ketoglutaric acid 15 min prior to the injection of 5.5 mg/kg (LD50) of NaCN, the lethality was reduced to an LD30. Two hundred mg/kg alpha-ketoglutaric acid, challenged with the same dose of NaCN, reduced the lethality to 23%. When mice were challenged with 6.0 mg/kg of NaCN (LD70) pretreated with 100 mg/kg of alpha-ketoglutaric acid or 200 mg/kg of sodium thiosulfate, the LD was not altered in the former but reduced to an LD15 in the latter. At higher doses of sodium thiosulfate (500 mg/kg), an LD60 occurred at 13.6 mg/kg NaCN (2.5 x LD50).(ABSTRACT TRUNCATED AT 250 WORDS)