Obesity Is a Major Determinant of Impaired Cardiac Energy Metabolism in Heart Failure with Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is a major health problem with limited treatment options. Although optimizing cardiac energy metabolism is a potential approach to treating heart failure, it is poorly understood what alterations in cardiac energy metabolism actually occur in HFpEF. To determine this, we used mice in which HFpEF was induced using an obesity and hypertension HFpEF protocol for 10 weeks. Next, carvedilol, a third-generation ß-blocker and a biased agonist that exhibits agonist-like effects through ß arrestins by activating extracellular signal-regulated kinase, was used to decrease one of these parameters, namely hypertension. Heart function was evaluated by invasive pressure-volume loops and echocardiography as well as by ex vivo working heart perfusions. Glycolysis and oxidation rates of glucose, fatty acids, and ketones were measured in the isolated working hearts. The development of HFpEF was associated with a dramatic decrease in cardiac glucose oxidation rates, with a parallel increase in palmitate oxidation rates. Carvedilol treatment decreased the development of HFpEF but had no major effect on cardiac energy substrate metabolism. Carvedilol treatment did increase the expression of cardiac ß arrestin 2 and proteins involved in mitochondrial biogenesis. Decreasing bodyweight in obese HFpEF mice increased glucose oxidation and improved heart function. This suggests that the dramatic energy metabolic changes in HFpEF mice hearts are primarily due to the obesity component of the HFpEF model. SIGNIFICANCE STATEMENT: Metabolic inflexibility occurs in heart failure with preserved ejection fraction (HFpEF) mice hearts. Lowering blood pressure improves heart function in HFpEF mice with no major effect on energy metabolism. Between hypertension and obesity, the latter appears to have the major role in HFpEF cardiac energetic changes. Carvedilol increases mitochondrial biogenesis and overall energy expenditure in HFpEF hearts.

Pattern of systemic antibiotic use and potential drug interactions: Evaluations through a point prevalence study in Ankara University Hospitals.

Background/aim: Most of the hospitalized patients are on a number of drugs for comorbidities and/or to prevent nosocomial infections. This necessitates a careful consideration of drug interactions not only to avoid possible toxicities but also to reach the highest efficiency with drug treatment. We aimed to investigate drug interactions related to systemic antibiotic use and compare three different databases to check for drug interactions while characterizing the main differences between medical and surgical departments. Materials and methods: This point prevalence study covered data on 927 orders for patients hospitalized between June 3 and 10, 2018 in Ankara University Hospitals. Systemic antibiotic use and related drug interactions were documented using UptoDate, Drugs, and Medscape and comparisons between the departments of medical and surgical sciences were made. Results: The number of orders, or the number of drugs or antibiotics per order were not different between the medical and surgical sciences departments. A total of 1335 antibiotic-related drug interactions of all levels were reported by one, two, or all three databases. UptoDate reported all common and major interactions. Pantoprazole was the most commonly prescribed drug and appeared in 63% of all orders. Among 75 different molecules, ceftriaxone and meropenem were the two most prescribed antibiotics by the surgical and medical departments, respectively. Conclusion: A dramatic variance existed amongst antibiotics prescribed by different departments. This indicated the requirement for a centralized role of an infectious diseases specialist. Especially for the hospitalized patient, prophylactic coverage with at least one antibiotic brought about a number of drug interactions. A precise evaluation of orders in terms of drug interactions by a clinical pharmacist (currently none on duty) will reduce possible drug-related hazards.

Activating PPARα prevents post-ischemic contractile dysfunction in hypertrophied neonatal hearts.

RATIONALE: Post-ischemic contractile dysfunction is a contributor to morbidity and mortality after the surgical correction of congenital heart defects in neonatal patients. Pre-existing hypertrophy in the newborn heart can exacerbate these ischemic injuries, which may partly be due to a decreased energy supply to the heart resulting from low fatty acid ß-oxidation rates. OBJECTIVE: We determined whether stimulating fatty acid ß-oxidation with GW7647, a peroxisome proliferator-activated receptor-α (PPARα) activator, would improve cardiac energy production and post-ischemic functional recovery in neonatal rabbit hearts subjected to volume overload-induced cardiac hypertrophy. METHODS AND RESULTS: Volume-overload cardiac hypertrophy was produced in 7-day-old rabbits via an aorto-caval shunt, after which, the rabbits were treated with or without GW7647 (3 mg/kg per day) for 14 days. Biventricular working hearts were subjected to 35 minutes of aerobic perfusion, 25 minutes of global no-flow ischemia, and 30 minutes of aerobic reperfusion. GW7647 treatment did not prevent the development of cardiac hypertrophy, but did prevent the decline in left ventricular ejection fraction in vivo. GW7647 treatment increased cardiac fatty acid ß-oxidation rates before and after ischemia, which resulted in a significant increase in overall ATP production and an improved in vitro post-ischemic functional recovery. A decrease in post-ischemic proton production and endoplasmic reticulum stress, as well as an activation of sarcoplasmic reticulum calcium ATPase isoform 2 and citrate synthase, was evident in GW7647-treated hearts. CONCLUSIONS: Stimulating fatty acid ß-oxidation in neonatal hearts may present a novel cardioprotective intervention to limit post-ischemic contractile dysfunction.

Synthesis, biological evaluation and docking studies of new pyrrolo[2,3-d] pyrimidine derivatives as Src family-selective tyrosine kinase inhibitors.

In this study, the synthesis and potential enzyme interactions of new Pyrrolo[2,3-d]pyrimidine derivatives along with their inhibitory activity against SFK enzymes such as Fyn, Lyn, Hck, and c-Src were reported. The results indicated that compounds were slightly active of tested SFK enzymes in comparison with PP2 for Fyn, A-419259 for Lyn and CGP77675 for c-Src. Compound N-((2-amino-4-oxo-4,7-dihydro-3H-pyrrolo[2,3-d]pyrimidin-5-yl)methyl)-4-(3,4-dimethoxyphenyl)butanamide (5) was identified as a non-selective slight inhibitor against Fyn, Lyn and c-Src. However, compounds did not show any inhibitory effects on Hck. Docking studies were performed to analyze the binding mode of compounds against SFKs. The best interaction was obtained between compound 5 and the active site of Fyn and c-Src enzymes in comparison with reference compounds PP2 and CGP77675, respectively.

Niosomes encapsulating paclitaxel for oral bioavailability enhancement: preparation, characterization, pharmacokinetics and biodistribution.

In this study, niosome formulations were prepared and evaluated for their effects on improving the oral bioavailability of paclitaxel (PCT). Niosomes were prepared from Span 40 and coated with bioadhesive carbopol polymers. The niosomes encapsulated 98.7% ± 0.8 of the initially added PCT and their size ranged from 133 ± 6 nm to 320 ± 6 nm. The stability of Carbopol 974P coated niosomes in bile salts was better than uncoated niosomes. Extended release of PCT was observed. After oral administration of formulations to Wistar rats, higher drug plasma concentrations were observed for niosomes comparing to PCT suspension. The high PCT accumulation in intestine and liver obtained after Carbopol 974P coated niosomes administration indicated their potential regarding effective treatment of localized carcinomas in intestine and liver. The relative bioavailability of PCT was increased 3.8- and 1.4-fold by uncoated and Carbopol 974P coated niosomes emphasizing the ability of niosomes on improving the oral bioavailability of PCT.

Past and present of beta arrestins: A new perspective on insulin secretion and effect.

BACKGROUND: Beta arrestins had been known as intracellular adaptors that uncouple and inactivate the G protein-coupled receptors that they interact with. Their roles as signal initiators for some receptors have recently been recognized. SCOPE OF REVIEW: In this review, we focused on their role in mediating metabolic modulation primarily in relation to insulin signaling. Commenced by the upstream receptor, they seem to act like intracellular hubs that divert the metabolic profile of the cell. The amount of metabolic substrates in circulation and their usage/deposition by tissues are controlled by the contribution of all systems in the organism. This control is enabled by the release of hormones such as insulin, glucagon and glucagon-like peptide-1. Intriguingly, some ligands -either agonists or antagonists-of different classes of receptors have preferential properties mediated by ß arrestins. This is not surprizing considering that substrate supply and usage should parallel physiological function such as hormone release or muscle contraction. MAJOR CONCLUSIONS: Available data indicate that ß arrestins conduct the regulatory role in insulin secretion and action. They may be good candidates to target when the upstream signal demands the function that may compromise the cell. An example is carvedilol that is protective by preventing the stimulatory effects of excessive catecholamines, stimulates mitochondrial function and has preferential clinical outcomes in metabolic disorders.

Carvedilol suppresses fatty acid oxidation and stimulates glycolysis in C2C12 cells.

Beta adrenergic receptor blocking drugs (ß-blockers) are used chronically in many cardiovascular diseases such as hypertension, ischemic heart disease, arrhythmia, and heart failure. Beneficial effects are associated with the inhibition of symphathetic nervous system hyperactivity, reduction of heart rate, and remodeling by blocking the mitogenic activity of catecholamines. A possible effect of ß-blockers on substrate metabolism has also been suggested. The direct effects of ß-blockers on mouse C2C12 cells were investigated in this study. C2C12 cells were grown in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum (FBS) and differentiated into myotubes in the same medium that contained 1% FBS. Palmitic acid oxidation and glycolysis were measured by using [9,10-(3)H]palmitate and [5-(3)H]glucose, respectively. The amount of (3)H(2)O was measured as an indicator of substrate usage. Carvedilol (100 µmol/L) inhibited palmitate oxidation and increased glycolysis by nearly 50%. Prazosin altered substrate metabolism in a similar fashion as carvedilol, whereas propranolol or bisoprolol were devoid of metabolic effects. When added to mimic sympathetic activation, epinephrine stimulated glycolysis but did not alter fatty acid oxidation. Based on these results, carvedilol appears to have direct effects on substrate metabolism that are related to the blockade of α1 adrenergic receptors.

SARS-CoV-2 Infection may be Prevented with Cytochrome Inhibitors: Cobicistat and Ritonavir.

Objective: Highly contagious character of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the lack of specific drugs have led many scientists worldwide to re-evaluate the molecules currently in use for other diseases/viruses. Thus, high-throughput screening with docking studies has the rationale to identify potential therapeutics from existing drug molecules. Conflicting results of the studies, including SARS-CoV-2 and human immunodeficiency virus (HIV) coinfected population, suggested a possible preventive effect of antiretroviral regimens they have been receiving. Materials and Methods: Interactions between the widely used antiretroviral molecules, in particular; abacavir, cobicistat, dolutegravir, elvitegravir, emtricitabine, lamivudine, raltegravir, and tenofovir, and the main proteins on SARS-CoV-2 that may be targeted for SARS-CoV-2 infection were analyzed using molecular docking studies. Results: Analysis of the compounds strikingly revealed that not the antiretroviral drugs but cobicistat and ritonavir, the inhibitors of cytochrome P450, had strong interactions with the main protease active site and RNA polymerase on SARS-CoV-2, as well as the active site of angiotensin-converting-enzyme 2, the protein that enables the entry of the virus into human cells. Conclusion: Our results suggest cobicistat and ritonavir may be used to prevent SARS-CoV-2 infection.

Pleiotropic vascular effects of ivabradine in streptozotocin-induced diabetes.

AIMS: Ivabradine (IVA) reduces heart rate (HR) by inhibiting hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in sinoatrial node. Studies suggest that IVA has other beneficial effects on cardiovascular system that are not related to its effect on HR such as prevention of endothelial injury and the antioxidant effects. In addition to sinoatrial node, HCN channels exist in other tissues and their expression pattern differs in certain pathologies such as hypertension and hypertrophy. We investigated the mechanism of IVA effect in the setting of streptozotocin (STZ)-induced cardiovascular damage. Direct effects of IVA and their mechanism on thoracic aorta as well as possible prevention of vascular dysfunction in diabetes were investigated in this study. METHODS AND RESULTS: The effects of IVA on vascular function were investigated in control and STZ-diabetic rats. Some control and diabetic rats were treated with IVA. IVA treatment prevented diabetes-induced increase in plasma p-selectin and vascular cell adhesion molecule-1 levels and the decrease in nitric oxide content in the aortas of diabetic animals. When added to isolated organ bath, IVA induced concentration-dependent relaxations in thoracic aorta. Pre-incubation with Nω-Nitro- L -arginine methyl ester reduced IVA-induced relaxations. Expression patterns of all isoforms of HCN proteins were affected by both diabetes and IVA treatment. CONCLUSION: IVA improves vascular function in diabetes and HCN channels support vascular activity against damaging effects of diabetes. IVA may be added to prevent diabetic cardiovascular dysfunction with these beneficial effects that are unrelated to its primary mechanism of action.

Metabolic effects of carvedilol through ß-arrestin proteins: investigations in a streptozotocin-induced diabetes rat model and in C2C12 myoblasts.

BACKGROUND AND PURPOSE: Carvedilol is a third-generation ß-adrenoceptor antagonist, which also stimulates ß-arrestins. ß-arrestins initiate intracellular signalling and are involved in insulin release and sensitivity. Carvedilol is superior in effectiveness to other drugs that are used for similar indications and does not cause insulin resistance or diabetes, which can occur with other ß-antagonists. We have shown that carvedilol increased glucose usage in C2C12 cells. We investigate the biased agonist efficacy of carvedilol on ß-arrestins. EXPERIMENTAL APPROACH: Streptozotocin (STZ)-induced diabetes rat model was used to induce metabolic and cardiac disorders. After 8 weeks of diabetes, animals were treated with carvedilol or vehicle for another 4 weeks. In vitro heart function was evaluated at baseline as well as with increasing concentrations of isoprenaline. Effects of diabetes and carvedilol treatment on ß-arrestins, ERK, PPARα, CD36 proteins and pyruvate kinase activity were evaluated. ß-arrestins were silenced in C2C12 cells by using siRNA. Acute effects of carvedilol on ERK, CD36, mitochondrial transcription factor A, cardiolipin proteins and citrate synthase activity were investigated. KEY RESULTS: Carvedilol reversed the deterioration of cardiac function in diabetes and diabetes-induced decrease in ß-arrestins in rats. Carvedilol decreased the expression of CD36 in diabetes and increased mitochondrial transcription factor A and cardiolipin proteins. Silencing of ß-arrestins in cells prevented the effects of carvedilol on these proteins. CONCLUSION AND IMPLICATIONS: The metabolic effects of carvedilol seem to be related to biased activation of ß-arrestins. Patients with cardiovascular and metabolic disorders may benefit from new compounds that selectively act on ß-arrestins.

QbD guided early pharmaceutical development study: Production of lipid nanoparticles by high pressure homogenization for skin cancer treatment.

This research attempts to bring together the positive aspects of lipid nanoparticles and Quality by Design (QbD) approach for developing a novel drug delivery system for skin cancers and aktinic keratosis. Lipid nanoparticles which is one of the most efficacious options for topical treatment of skin diseases were prepared due to their ability to overcome the complex structure of skin barrier and to enhance the skin penetration. Since the formulation development contains complex variables of active ingredients, raw materials or production method; all the variables of the product should be elaborated. QbD approach which refers to design and develop formulations and manufacturing processes to maintain the prescribed product quality was also successfully adopted to achieve a time- and cost-saving process ensuring a high-quality product. 5-Fluorouracil (5-FU) loaded lipid nanoparticles, both solid lipid nanoparticles and nanostructured lipid carriers, were developed and characterized by following QbD steps. Optimal lipid nanoparticle formulation with guaranteed quality which was within the design space has been reached through the artificial neural networks. The optimal lipid nanoparticle formulation which is a NLC formulation with a mean particle size of 205,8 ±â€¯9,34 nm, narrow size distribution (0.279 ±â€¯0.01) and negative zeta potantial -30,20 ±â€¯0,92 was produced by high pressure homogenization method. Cytotoxicity profiles of the optimal NLC was determined by cell culture studies on epidermoid carcinoma cells and human keratinocyte cells. Optimal NLC showed significantly higher anticancer effect on epidermoid carcinoma cells than free 5-FU and also less cytotoxicity towards human keratinocyte cells. Optimal NLC was formulated in hydrogel formulation for ease of application which has suitable occlusive and mechanical properties, viscocity and pH for patient complience. The cumulative amount of 5-FU in dermal tissues of rat skin was found 20.11 ±â€¯2.14 µg/cm2 and 9.73 ±â€¯0.87 µg/cm2 after application of NLC enriched hydrogel and 5-FU hydrogel respectively. In conclusion, this study showed that a time and cost saving process ensuring a high-quality product can be obtained by QbD guided formulation development study with the help of artificial neural networks. A novel semisolid dosage form enriched by NLC which is promising for topical treatment of skin cancers was developed.

Design, synthesis and docking studies of benzimidazole derivatives as potential EGFR inhibitors.

In this study, a series of benzimidazoles bearing thiosemicarbazide chain or triazole and thiadiazole rings were designed and synthesized. Crystal and molecular structure of the compound 5c has been characterized by single crystal X-ray crystallographic analysis. EGFR kinase inhibitory potencies of synthesized compounds were compared with erlotinib in vitro and most of the compounds exhibited significant activities. Cell culture studies were also carried out for selected compounds and 12b was found to be the most active compound. To understand the binding mode of synthesized benzimidazoles, three compounds (12b, 16, 16c) were selected and placed on the binding site of EGFR tyrosine kinase based on their kinase inhibitor potencies and cell culture studies. Docking study indicated that compound 12b showed two-hydrogen bonding interactions with residues of LYS721 and THR830 at the binding pocket.

Synthesis and Pharmacologic Evaluation of Some Benzimidazole Acetohydrazide Derivatives as EGFR Inhibitors.

OBJECTIVES: In this study, some novel 2-(2-phenyl)-1H-benzo[d]imidazol-1-yl)-N'-(arylmethylene) acetohydrazide derivatives (1-12) were designed and synthesized. MATERIALS AND METHODS: Compounds 1-12 were obtained by condensing 2-(2-phenyl)-1H-benzo[d]imidazol-1-yl)acetohydrazide (III) with the corresponding aromatic aldehyde derivatives in the presence of catalytic amounts of hydrochloric acid in ethanol. RESULTS: Following the structure elucidation, epidermal growth factor receptor kinase inhibitor activity was measured. The ADP-GloTM kinase assay determines kinase activity based on the quantification of the amount of ADP produced during a kinase reaction. CONCLUSION: Almost all of the compounds' kinase inhibitor activities were rather limited.

Skin Localization of Lipid Nanoparticles (SLN/NLC): Focusing the Influence of Formulation Parameters.

BACKGROUND: In this study, fluorescein labeled SLN and NLC formulations were prepared for improving the dermal distribution of the hydrophilic active ingredients and for enhancing the skin penetration. METHODS: To determine skin distribution of the lipid nanoparticles ex-vivo penetration/ permeation experiments were performed using full thickness rat skin by means of Franz diffusion cells. Studies on the localization of fluorescence labeled nanoparticles were performed by confocal laser scanning microscopy (CLSM). Cellular uptake studies were performed on human keratinocyte cell line (HaCaT) and visualized by fluorescence microscope. Both tissue and cell uptake were also quantitatively determined by means of fluorimetric method in the skin extract or cell extract. RESULTS: Both imaging and quantification studies suggest that the dermal localization of the lipid nanoparticles depends on their dimensions and particle size distribution. The CLSM images clearly show that the Tripalmitin based lipid nanoparticles have higher accumulation in the skin. It is possible to overcome the stratum corneum barrier function with T-NLC05 coded lipid nanoparticle formulation. Additionally cellular uptake of this NLC formulation is time dependent. Conclusion: It can be concluded that this formulation is promising for treating local skin disorders without systemic side effects. On the other hand obtained results suggest that optimum formulation (T-NLC05) might be an interesting option even for novel cosmetic products.

Development of etofenamate-loaded semisolid sln dispersions and evaluation of anti-inflammatory activity for topical application.

Dermal application of various active substances is widely preferred for topical or systemic delivery. SLNs consist of biocompatible and non-toxic lipids and have a great potential for topical application in drugs. In this study, semisolid SLN formulations were successfully prepared by a novel one-step production method as a topical delivery system of etofenamate, an anti-inflammatory drug. Compritol 888 ATO and Precirol ATO 5 were chosen as lipid materials for the fabrication of the formulations. In-vitro evaluation of the formulations was performed in terms of encapsulation efficiency, particle size, surface charge, thermal behavior, rheological characteristics, in vitro drug release profile, kinetics, mechanisms, stability, and anti-inflammatory activity. The colloidal size and spherical shape of the particles were proved. According to the results of the rheological analysis, it was demonstrated that the semisolid SLN formulations have a gel-like structure. Stability studies showed that semisolid SLNs were stable at 4°C for a six month period. Zero order release was obtained with Precirol ATO 5, while Compritol 888 ATO followed the square root of time (Higuchi's pattern) dependent release. Semisolid SLNs showed higher inhibitory activity of COX in comparison with pure etofenamate. In conclusion, etofenamate-loaded semisolid SLN formulations can be successfully prepared in a novel one-step production method and useful for topical application.

Effect of fatty acids on human bone marrow mesenchymal stem cell energy metabolism and survival.

Successful stem cell therapy requires the optimal proliferation, engraftment, and differentiation of stem cells into the desired cell lineage of tissues. However, stem cell therapy clinical trials to date have had limited success, suggesting that a better understanding of stem cell biology is needed. This includes a better understanding of stem cell energy metabolism because of the importance of energy metabolism in stem cell proliferation and differentiation. We report here the first direct evidence that human bone marrow mesenchymal stem cell (BMMSC) energy metabolism is highly glycolytic with low rates of mitochondrial oxidative metabolism. The contribution of glycolysis to ATP production is greater than 97% in undifferentiated BMMSCs, while glucose and fatty acid oxidation combined only contribute 3% of ATP production. We also assessed the effect of physiological levels of fatty acids on human BMMSC survival and energy metabolism. We found that the saturated fatty acid palmitate induces BMMSC apoptosis and decreases proliferation, an effect prevented by the unsaturated fatty acid oleate. Interestingly, chronic exposure of human BMMSCs to physiological levels of palmitate (for 24 hr) reduces palmitate oxidation rates. This decrease in palmitate oxidation is prevented by chronic exposure of the BMMSCs to oleate. These results suggest that reducing saturated fatty acid oxidation can decrease human BMMSC proliferation and cause cell death. These results also suggest that saturated fatty acids may be involved in the long-term impairment of BMMSC survival in vivo.

Acute regulation of cardiac metabolism by the hexosamine biosynthesis pathway and protein O-GlcNAcylation.

OBJECTIVE: The hexosamine biosynthesis pathway (HBP) flux and protein O-linked N-acetyl-glucosamine (O-GlcNAc) levels have been implicated in mediating the adverse effects of diabetes in the cardiovascular system. Activation of these pathways with glucosamine has been shown to mimic some of the diabetes-induced functional and structural changes in the heart; however, the effect on cardiac metabolism is not known. Therefore, the primary goal of this study was to determine the effects of glucosamine on cardiac substrate utilization. METHODS: Isolated rat hearts were perfused with glucosamine (0-10 mM) to increase HBP flux under normoxic conditions. Metabolic fluxes were determined by (13)C-NMR isotopomer analysis; UDP-GlcNAc a precursor of O-GlcNAc synthesis was assessed by HPLC and immunoblot analysis was used to determine O-GlcNAc levels, phospho- and total levels of AMPK and ACC, and membrane levels of FAT/CD36. RESULTS: Glucosamine caused a dose dependent increase in both UDP-GlcNAc and O-GlcNAc levels, which was associated with a significant increase in palmitate oxidation with a concomitant decrease in lactate and pyruvate oxidation. There was no effect of glucosamine on AMPK or ACC phosphorylation; however, membrane levels of the fatty acid transport protein FAT/CD36 were increased and preliminary studies suggest that FAT/CD36 is a potential target for O-GlcNAcylation. CONCLUSION/INTERPRETATION: These data demonstrate that acute modulation of HBP and protein O-GlcNAcylation in the heart stimulates fatty acid oxidation, possibly by increasing plasma membrane levels of FAT/CD36, raising the intriguing possibility that the HBP and O-GlcNAc turnover represent a novel, glucose dependent mechanism for regulating cardiac metabolism.

Impact of lactate in the perfusate on function and metabolic parameters of isolated working rat heart.

The goal of this study was to investigate the effect of 1 mM exogenous lactate on cardiac function, and some metabolic parameters, such as glycolysis, glucose oxidation, lactate oxidation, and fatty acid oxidation, in isolated working rat hearts. Hearts from male Sprague-Dawley rats were isolated and perfused with 5 mM glucose, 1.2 mM palmitate, and 100 microU/ml insulin with or without 1 mM lactate. The rates of glycolysis, glucose, lactate, and fatty acid oxidation were determined by supplementing the buffer with radiolabeled substrates. Cardiac function was similar between lactate+ and lactate- hearts. Glycolysis was not affected by 1 mM lactate. The addition of lactate did not alter glucose oxidation rates. Interestingly, palmitate oxidation rates almost doubled when 1 mM lactate was present in the perfusate. This study suggests that subst rate supply to the heart is crucially important when evaluating the data from metabolic studies.

Alpha-lipoic acid increases cardiac glucose oxidation independent of AMP-activated protein kinase in isolated working rat hearts.

Alpha-lipoic acid (ALA) is a naturally occurring enantiomer of lipoic acid and is a cofactor of key metabolic enzyme complexes catalyzing the decarboxylation of alpha-keto acids. It was recently shown that ALA increases insulin sensitivity by activating AMP-activated protein kinase (AMPK) in skeletal muscle. Also, administration of ALA to obese rats increases insulin-stimulated glucose uptake in the whole body. We investigated the metabolic effects of ALA on isolated working rat hearts. ALA (500 microM) stimulated glucose oxidation (157+/-31 nmol.dry wt(-1).min(-1) in control vs 315+/-63 nmol.dry wt(-1).min(-1) in ALA-treated, p<0.05) without affecting glycolysis, lactate oxidation, or palmitate oxidation. Cardiac work was not affected by ALA treatment. The effect of ALA on glucose oxidation was not associated with an activation of AMPK. AMPK activity was 190+/-14 pmol.mg protein(-1).min(-1) in control vs 190+/-16 pmol.mg protein(-1).min(-1) in ALA-treated hearts. This study shows that ALA stimulates glucose oxidation in isolated working rat hearts independent of AMPK activation. The beneficial effects of ALA treatment in diabetic patients may be at least in part related to its effect on glucose metabolism.

The effects of chronic trimetazidine treatment on mechanical function and fatty acid oxidation in diabetic rat hearts.

Clinical and experimental evidence suggest that increased rates of fatty acid oxidation in the myocardium result in impaired contractile function in both normal and diabetic hearts. Glucose utilization is decreased in type 1 diabetes, and fatty acid oxidation dominates for energy production at the expense of an increase in oxygen requirement. The objective of this study was to examine the effect of chronic treatment with trimetazidine (TMZ) on cardiac mechanical function and fatty acid oxidation in streptozocin (STZ)-diabetic rats. Spontaneously beating hearts from male Sprague-Dawley rats were subjected to a 60-minute aerobic perfusion period with a recirculating Krebs-Henseleit solution containing 11 mmol/L glucose, 100 muU/mL insulin, and 0.8 mmol/L palmitate prebound to 3% bovine serum albumin (BSA). Mechanical function of the hearts, as cardiac output x heart rate (in (mL/min).(beats/min).10-2), was deteriorated in diabetic (73 +/- 4) and TMZ-treated diabetic (61 +/- 7) groups compared with control (119 +/- 3) and TMZ-treated controls (131 +/- 6). TMZ treatment increased coronary flow in TMZ-treated control (23 +/- 1 mL/min) hearts compared with untreated controls (18 +/- 1 mL/min). The mRNA expression of 3-ketoacyl-CoA thiolase (3-KAT) was increased in diabetic hearts. The inhibitory effect of TMZ on fatty acid oxidation was not detected at 0.8 mmol/L palmitate in the perfusate. Addition of 1 mumol/L TMZ 30 min into the perfusion did not affect fatty acid oxidation rates, cardiac work, or coronary flow. Our results suggest that higher expression of 3-KAT in diabetic rats might require increased concentrations of TMZ for the inhibitory effect on fatty acid oxidation. A detailed kinetic analysis of 3-KAT using different concentrations of fatty acid will determine the fatty acid inhibitory concentration of TMZ in diabetic state where plasma fatty acid levels are increased.