Mitochondrial fatty acid oxidation is the major source of cardiac adenosine triphosphate production in heart failure with preserved ejection fraction.

AIMS: Heart failure with preserved ejection fraction (HFpEF) is a prevalent disease worldwide. While it is well established that alterations of cardiac energy metabolism contribute to cardiovascular pathology, the precise source of fuel used by the heart in HFpEF remains unclear. The objective of this study was to define the energy metabolic profile of the heart in HFpEF. METHODS AND RESULTS: Eight-week-old C57BL/6 male mice were subjected to a '2-Hit' HFpEF protocol [60% high-fat diet (HFD) + 0.5 g/L of Nω-nitro-L-arginine methyl ester]. Echocardiography and pressure-volume loop analysis were used for assessing cardiac function and cardiac haemodynamics, respectively. Isolated working hearts were perfused with radiolabelled energy substrates to directly measure rates of fatty acid oxidation, glucose oxidation, ketone oxidation, and glycolysis. HFpEF mice exhibited increased body weight, glucose intolerance, elevated blood pressure, diastolic dysfunction, and cardiac hypertrophy. In HFpEF hearts, insulin stimulation of glucose oxidation was significantly suppressed. This was paralleled by an increase in fatty acid oxidation rates, while cardiac ketone oxidation and glycolysis rates were comparable with healthy control hearts. The balance between glucose and fatty acid oxidation contributing to overall adenosine triphosphate (ATP) production was disrupted, where HFpEF hearts were more reliant on fatty acid as the major source of fuel for ATP production, compensating for the decrease of ATP originating from glucose oxidation. Additionally, phosphorylated pyruvate dehydrogenase levels decreased in both HFpEF mice and human patient's heart samples. CONCLUSION: In HFpEF, fatty acid oxidation dominates as the major source of cardiac ATP production at the expense of insulin-stimulated glucose oxidation.

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.

Stimulating cardiac glucose oxidation lessens the severity of heart failure in aged female mice.

Heart failure is a prevalent disease worldwide. While it is well accepted that heart failure involves changes in myocardial energetics, what alterations that occur in fatty acid oxidation and glucose oxidation in the failing heart remains controversial. The goal of the study are to define the energy metabolic profile in heart failure induced by obesity and hypertension in aged female mice, and to attempt to lessen the severity of heart failure by stimulating myocardial glucose oxidation. 13-Month-old C57BL/6 female mice were subjected to 10 weeks of a 60% high-fat diet (HFD) with 0.5 g/L of Nω-nitro-L-arginine methyl ester (L-NAME) administered via drinking water to induce obesity and hypertension. Isolated working hearts were perfused with radiolabeled energy substrates to directly measure rates of myocardial glucose oxidation and fatty acid oxidation. Additionally, a series of mice subjected to the obesity and hypertension protocol were treated with a pyruvate dehydrogenase kinase inhibitor (PDKi) to stimulate cardiac glucose oxidation. Aged female mice subjected to the obesity and hypertension protocol had increased body weight, glucose intolerance, elevated blood pressure, cardiac hypertrophy, systolic dysfunction, and decreased survival. While fatty acid oxidation rates were not altered in the failing hearts, insulin-stimulated glucose oxidation rates were markedly impaired. PDKi treatment increased cardiac glucose oxidation in heart failure mice, which was accompanied with improved systolic function and decreased cardiac hypertrophy. The primary energy metabolic change in heart failure induced by obesity and hypertension in aged female mice is a dramatic decrease in glucose oxidation. Stimulating glucose oxidation can lessen the severity of heart failure and exert overall functional benefits.

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.

Combined levothyroxine and testosterone treatment for restoring erectile dysfunction in propylthiouracil-induced hypothyroid rats.

BACKGROUND: Sexual dysfunction may indicate severe endocrine diseases. Recent research has suggested a link between hypothyroidism, low testosterone (T) levels, and erectile dysfunction (ED); however, the exact cause is unknown. AIM: We sought to investigate possible beneficial effects of levothyroxine and T alone or in combination on ED in propylthiouracil (PTU)-induced hypothyroid rats. METHODS: Adult Wistar rats (n = 35) were divided into 5 groups: control, PTU-induced hypothyroidism, PTU + levothyroxine, PTU + Sustanon (a mixture of 4 types of T: propionate, phenylpropionate, isocaproate, and decanoate) and PTU + levothyroxine + Sustanon. PTU was given in drinking water for 6 weeks. Four weeks after PTU administration, levothyroxine (20 µg microgram kg/day, oral) and Sustanon (10 mg/kg/week, intramuscular) were given for 2 weeks. Serum levels of total T, triiodothyronine (T3), and thyroxine (T4) were determined. In vivo erectile response and in vitro relaxant responses were measured. Localization of neuronal nitric oxide synthase (nNOS), endothelial NOS (eNOS), and phosphodiesterase type 5 (PDE5) were determined using immunohistochemical analysis. The relative area of smooth muscle to collagen was measured using Masson trichrome staining. OUTCOMES: Outcome variables included in vivo erectile function, in vitro relaxant and contractile responses of corpus cavernosum (CC) strips; protein localization of eNOS, nNOS, and PDE5; and smooth muscle content in penile tissue. RESULTS: The rat model of hypothyroidism showed a significant decline in serum levels of total T, T3, and T4. Levothyroxine increased T3 and T4 levels, whereas Sustanon normalized only total T levels. Combined treatment enhanced all hormone levels. Rats with hypothyroidism displayed the lowest erectile response (P < 0.001 vs controls). Combined treatment returned reduced responses, while partial amelioration was observed after levothyroxine and Sustanon treatment alone. Acetylcholine (P < 0.01 vs controls), electrical field stimulation (P < 0.001 vs controls), and sildenafil-induced relaxant responses (P < 0.05 vs controls) were decreased in the CC strips from hypothyroid rats. The combined treatment increased the reduction in relaxation responses. Levothyroxine and Sustanon restored decreases in eNOS and nNOS expression in the hypothyroid group. There was no significant difference in PDE5 expression among groups. Monotreatment partially enhanced reduced smooth muscle mass, while combined therapy completely recovered. CLINICAL IMPLICATIONS: The combination of thyroid hormones and T is likely to be a therapeutic approach for treatment of hypothyroidism-induced ED in men. STRENGTHS AND LIMITATIONS: Beneficial effects of levothyroxine and Sustanon treatment were shown in vitro and in vivo in PTU-induced hypothyroid rats. The main limitation of the study was the lack of measurement of androgen-sensitive organ weights and luteinizing hormone, follicle-stimulating hormone, and prolactin levels. CONCLUSION: These findings demonstrate that neurogenic and endothelium-dependent relaxation responses are reduced by hypothyroidism, which is detrimental to T levels and erectile responses. Levothyroxine and Sustanon combination medication was able to counteract this effect.

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.

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.