L-glutamine supplementation prevents the development of experimental diabetic cardiomyopathy in streptozotocin-nicotinamide induced diabetic rats

Anaplerotic filling in heart failure: a review of mechanism and potential therapeutics

Heart failure (HF) is a complex syndrome and a leading cause of mortality worldwide. While current medical treatment is based on known pathophysiology and is effective for many patients, the underlying cellular mechanisms are poorly understood. Energy deficiency is a characteristic of HF, marked by complex alterations in metabolism. Within the tricarboxylic acid cycle, anaplerosis emerges as an essential metabolic process responsible for replenishing lost intermediates, thereby playing a crucial role in sustaining energy metabolism and consequently cardiac function. Alterations in cardiac anaplerosis are commonly observed in HF, demonstrating potential for therapeutic intervention. This review discusses recent advances in understanding the anaplerotic adaptations that occur in HF. We also explore therapeutics that can directly modulate anaplerosis or are likely to confer cardioprotective effects through anaplerosis, which could potentially be implemented to rescue the failing heart.

Insulin oxidation and oxidative modifications alter glucose uptake, cell metabolism, and inflammatory secretion profiles

Insulin participates in glucose homeostasis in the body and regulates glucose, protein, and lipid metabolism. Chronic hyperglycemia triggers oxidative stress and the generation of reactive oxygen species (ROS), leading to oxidized insulin variants. Oxidative protein modifications can cause functional changes or altered immunogenicity as known from the context of autoimmune disorders. However, studies on the biological function of native and oxidized insulin on glucose homeostasis and cellular function are lacking. Native insulin showed heterogenous effects on metabolic activity, proliferation, glucose carrier transporter (GLUT) 4, and insulin receptor (INSR) expression, as well as glucose uptake in cell lines of five different human tissues. Diverse ROS compositions produced by different gas plasma approaches enabled the investigations of variously modified insulin (oxIns) with individual oxidative post-translational modification (oxPTM) patterns as identified using high-resolution mass spectrometric analysis. Specific oxIns variants promoted cellular metabolism and proliferation in several cell lines investigated, and nitrogen plasma emission lines could be linked to insulin nitration and elevated glucose uptake. In addition, insulin oxidation modified blood glucose levels in the chicken embryos (in ovo), underlining the importance of assessing protein oxidation and function in health and disease.

Antinociceptive Behavior, Glutamine/Glutamate, and Neopterin in Early-Stage Streptozotocin-Induced Diabetic Neuropathy in Liraglutide-Treated Mice under a Standard or Enriched Environment

Diabetic neuropathy (DN) is a common complication of long-lasting type 1 and type 2 diabetes, with no curative treatment available. Here, we tested the effect of the incretin mimetic liraglutide in DN in mice with early-stage type 1 diabetes bred in a standard laboratory or enriched environment. With a single i.p. injection of streptozotocin 150 mg/kg, we induced murine diabetes. Liraglutide (0.4 mg/kg once daily, i.p. for ten days since the eighth post-streptozotocin day) failed to decrease the glycemia in the diabetic mice; however, it alleviated their antinociceptive behavior, as tested with formalin. The second phase of the formalin test had significantly lower results in liraglutide-treated mice reared in the enriched environment vs. liraglutide-treated mice under standard conditions [2.00 (0.00-11.00) vs. 29.00 (2.25-41.50) s, p = 0.016]. Liraglutide treatment, however, decreased the threshold of reactivity in the von Fray test. A significantly higher neopterin level was demonstrated in the diabetic control group compared to treatment-naïve controls and the liraglutide-treated diabetic mice (p < 0.001). The glutamine/glutamate ratio in both liraglutide-treated groups, either reared under standard conditions (p = 0.003) or an enriched environment (p = 0.002), was significantly higher than in the diabetic controls. This study demonstrates an early liraglutide effect on pain sensation in two streptozotocin-induced diabetes mouse models by reducing some inflammatory and oxidative stress parameters.

Targeting the Metabolic Paradigms in Cancer and Diabetes

Dysregulated metabolic dynamics are evident in both cancer and diabetes, with metabolic alterations representing a facet of the myriad changes observed in these conditions. This review delves into the commonalities in metabolism between cancer and type 2 diabetes (T2D), focusing specifically on the contrasting roles of oxidative phosphorylation (OXPHOS) and glycolysis as primary energy-generating pathways within cells. Building on earlier research, we explore how a shift towards one pathway over the other serves as a foundational aspect in the development of cancer and T2D. Unlike previous reviews, we posit that this shift may occur in seemingly opposing yet complementary directions, akin to the Yin and Yang concept. These metabolic fluctuations reveal an intricate network of underlying defective signaling pathways, orchestrating the pathogenesis and progression of each disease. The Warburg phenomenon, characterized by the prevalence of aerobic glycolysis over minimal to no OXPHOS, emerges as the predominant metabolic phenotype in cancer. Conversely, in T2D, the prevailing metabolic paradigm has traditionally been perceived in terms of discrete irregularities rather than an OXPHOS-to-glycolysis shift. Throughout T2D pathogenesis, OXPHOS remains consistently heightened due to chronic hyperglycemia or hyperinsulinemia. In advanced insulin resistance and T2D, the metabolic landscape becomes more complex, featuring differential tissue-specific alterations that affect OXPHOS. Recent findings suggest that addressing the metabolic imbalance in both cancer and diabetes could offer an effective treatment strategy. Numerous pharmaceutical and nutritional modalities exhibiting therapeutic effects in both conditions ultimately modulate the OXPHOS-glycolysis axis. Noteworthy nutritional adjuncts, such as alpha-lipoic acid, flavonoids, and glutamine, demonstrate the ability to reprogram metabolism, exerting anti-tumor and anti-diabetic effects. Similarly, pharmacological agents like metformin exhibit therapeutic efficacy in both T2D and cancer. This review discusses the molecular mechanisms underlying these metabolic shifts and explores promising therapeutic strategies aimed at reversing the metabolic imbalance in both disease scenarios.

The essential role of glutamine metabolism in diabetic cardiomyopathy: A review

Diabetic cardiomyopathy (DCM) is a pathophysiological condition caused by diabetes mellitus and is the leading cause of diabetes mellitus-related mortality. The pathophysiology of DCM involves various processes, such as oxidative stress, inflammation, ferroptosis, and abnormal protein modification. New evidence indicates that dysfunction of glutamine (Gln) metabolism contributes to the pathogenesis of DCM by regulating these pathophysiological mechanisms. Gln is a conditionally essential amino acid in the human body, playing a vital role in maintaining cell function. Although the precise molecular mechanisms of Gln in DCM have yet to be fully elucidated, recent studies have shown that supplementing with Gln improves cardiac function in diabetic hearts. However, excessive Gln may worsen myocardial injury in DCM by generating a large amount of glutamates or increasing O-GlcNacylation. To highlight the potential therapeutic method targeting Gln metabolism and its downstream pathophysiological mechanisms, this article aims to review the regulatory function of Gln in the pathophysiological mechanisms of DCM.

LRH-1 activation alleviates diabetes-induced podocyte injury by promoting GLS2-mediated glutaminolysis

Alteration of metabolic phenotype in podocytes directly contributes to the development of albuminuria and renal injury in conditions of diabetic kidney disease (DKD). This study aimed to identify and evaluate liver receptor homologue-1 (LRH-1) as a possible therapeutic target that alleviates glutamine (Gln) metabolism disorders and mitigates podocyte injury in DKD. Metabolomic and transcriptomic analyses were performed to characterize amino acid metabolism changes in the glomeruli of diabetic mice. Next, Western blotting, immunohistochemistry assays, and immunofluorescence staining were used to detect the expression of different genes in vitro and in vivo. Furthermore, Gln and glutamate (Glu) content as well as ATP generation were examined. A decrease in LRH-1 and glutaminase 2 (GLS2) expression was detected in diabetic podocytes. Conversely, the administration of LRH-1 agonist (DLPC) upregulated the expression of GLS2 and promoted glutaminolysis, with an improvement in mitochondrial dysfunction and less apoptosis in podocytes compared to those in vehicle-treated db/db mice. Our study indicates the essential role of LRH-1 in governing the Gln metabolism of podocytes, targeting LRH-1 could restore podocytes from diabetes-induced disturbed glutaminolysis in mitochondria.

Repurposing Pitavastatin and L-Glutamine: Replenishing β-Cells in Hyperlipidemic Type 2 Diabetes Mouse Model

Type 2 diabetes (T2D) is associated with obesity and declining β-cells. L-glutamine has been implicated in the amelioration of T2D by virtue of its incretin secretagogue property while, there are mixed reports on pitavastatin's adiponectin potentiating ability. We aimed to investigate the effect of pitavastatin (P), L-glutamine (LG), and combination (P + LG) on glycemic control and β-cell regeneration in a high-fat diet (HFD) + streptozotocin (STZ)-induced T2D mouse model. C57BL6/J mice treated with HFD + STZ were divided into four groups: diabetes control (HFD + STZ), P, LG, and P + LG, while the control group (NCD) was fed with the normal-chow diet. Significant amelioration was observed in the combination therapy as compared to monotherapies in respect of (i) insulin resistance, glucose intolerance, lipid profile, adiponectin levels, and mitochondrial complexes I, II, and III activities, (ii) reduced phosphoenolpyruvate carboxykinase, glucose 6-phophatase, glycogen phosphorylase, and GLUT2 transcript levels with increased glycogen content in the liver, (iii) restoration of insulin receptor 1β, pAkt/Akt, and AdipoR1 protein levels in skeletal muscle, and (iv) significant increase in islet number due to β-cell regeneration and reduced β-cell death. L-glutamine and pitavastatin in combination can ameliorate T2D by inducing β-cell regeneration and regulating glucose homeostasis.

The association of dietary glutamine supplementation with the development of high salt-induced hypertension in rats

Glutamine supplementation has been reported to affect blood pressure (BP). However, its role in the progression of hypertension induced by high salt diet (HSD) has not been elucidated. Male normotensive Wistar rats were exposed to high salt diet and treated with different doses of glutamine supplementation. Rats aged 6 weeks were assigned to five groups: (1) Normal-salt diet (0.3% NaCl, NSD); (2) High-salt diet (8% NaCl, HSD); (3) High-salt + low-dose diet (8% NaCl, 0.5 g of L-glutamine/kg body weight, HSLGD); (4) High-salt + middle-dose diet (8% NaCl, 1.5 g of L-glutamine/kg body weight, HSMGD); and (5) High-salt + high-dose diet (8% NaCl, 2.5 g of L-glutamine/kg body weight, HSHGD). After supplementing different doses of glutamine to male Wistar 6-week-old rats fed with HSD for 7 weeks, we found no difference in body weight among groups. Importantly, we showed that dietary L-glutamine supplementation could prevent the development of hypertension in a dose-dependent manner [dramatically lowering systolic blood pressure (SBP) and slightly reducing diastolic blood pressure (DBP) of hypertensive rats, while the differences of DBP between groups did not reach statistical significance]. Our data further elucidated that dietary glutamine supplementation mildly alleviated the degree of left ventricular hypertrophy, including interventricular septal thickness (IVST) and left ventricular posterior wall thickness (LVPWT) in hypertensive rats. Together, our results offer evidence that the dietary uptake of glutamine may be associated with attenuating the development of high salt-induced hypertension and slightly alleviating the degree of left ventricular hypertrophy in hypertensive rats. Therefore, glutamine supplementation may act as a prospective dietary intervention for the treatment of hypertension.

Combined use of systemic quercetin, glutamine and alpha-tocopherol attenuates myocardial fibrosis in diabetic rats

This study aimed to analyze the effects of the quercetin (100 mg/kg), 1% glutamine and 1% α-tocopherol antioxidants in the myocardium of rats with streptozotocin-induced diabetes mellitus. Twenty male rats were subdivided into four groups (n = 5): N (normoglycemic); D (diabetic); NT (normoglycemic treated with antioxidants); and DT (diabetic treated with antioxidants) treated for 60 days. Clinical parameters, oxidative stress markers, inflammatory cytokines, myocardial collagen fibers and immunoexpression of superoxide dismutase 1 (SOD-1), glutathione peroxidase-1 (GPx-1), interleukin-1β (IL-1-β), transforming growth factor-beta (TGF-β), and fibroblast growth factor-2 (FGF-2) were evaluated. Results showed reduced body weight, hyperphagia, polydipsia and hyperglycemic state in groups D and DT. The levels of glutathione (GSH) were higher in NT and DT compared to N (p < 0.01) and D (p < 0.001) groups, respectively. Greater GSH levels were found in DT when compared to N animals (p < 0.001). In DT, there was an increase in IL-10 in relation to N, D and NT (p < 0.05), while GPx-1 expression was similar to N and lower compared to D (p < 0.001). TGF-β expression in DT was greater than N (p < 0.001) group, whereas FGF-2 in DT was higher than in the other groups (p < 0.001). A significant reduction in collagen fibers (type I) was found in DT compared to D (p < 0.05). The associated administration of quercetin, glutamine and α-tocopherol increased the levels of circulating interleukin-10 (IL-10) and GSH, and reduced the number of type I collagen fibers. Combined use of systemic quercetin, glutamine and alpha-tocopherol attenuates myocardial fibrosis in diabetic rats.

General anesthesia and electrocardiographic parameters in in vivo experiments involving rats

In in vivo cardiovascular or toxicological studies involving rat models, changes in selected electrocardiographic (ECG) parameters are monitored after various interventions to assess the origin and development of heart rhythm disorders. Each ECG parameter has diagnostic significance; as such, commonly evaluated ECG parameters, including heart rate, PR interval, P wave duration, P wave amplitude, QRS complex, QT and QTc interval duration, R wave and T wave amplitude, of rats under various types of general anesthesia were the focus of this study. Studies that performed in vivo cardiovascular or toxicological experiments in rats were retrieved from a search of the Web of Science database for articles published mainly between 2000 and 2021. In total, the search retrieved 123 articles. ECG parameters that were reported as baseline or control values were summarized and averages with ranges were calculated. It is important to be cautious when interpreting results and, in discussions addressing the mechanisms underlying a given type of arrhythmia, acknowledge that initial ECG parameters may already be affected to some extent by the general anesthesia as well as by sex and the time of day the experiments were performed.

A comprehensive insight into the effect of glutamine supplementation on metabolic variables in diabetes mellitus: a systematic review

Diabetes mellitus is one of the most important threats to human health in the twenty-first century. The use of complementary and alternative medicine to prevent, control, and reduce the complications of diabetes mellitus is increasing at present. Glutamine amino acid is known as a functional food. The purpose of this systematic review is to determine the potential role of glutamine supplementation on metabolic variables in diabetes mellitus. For this review, PubMed, SCOPUS, Embase, ProQuest, and Google Scholar databases were searched from inception through April 2020. All clinical trial and animal studies assessing the effects of glutamine on diabetes mellitus were eligible for inclusion. 19 studies of 1482 articles met the inclusion criteria. Of the 19 studies, nine studies reported a significant increase in serum GLP-1 levels. Also, eight studies showed reducing in serum levels of fasting blood sugar, four studies reducing in postprandial blood sugar, and triglyceride after glutamine supplementation. Although glutamine resulted in a significant increase in insulin production in seven studies, the findings on Hb-A1c levels were inconclusive. In addition to, despite of the results was promising for the effects of glutamine on weight changes, oxidative stress, and inflammation, more precise clinical trials are needed to obtain more accurate results. In conclusion, glutamine supplementation could improve glycemic control and levels of incretins (such as GLP-1 and GIP) in diabetes mellitus. However, more studies are needed for future studies.

Impaired Amino Acid and TCA Metabolism and Cardiovascular Autonomic Neuropathy Progression in Type 1 Diabetes

While diabetes is characterized by hyperglycemia, nutrient metabolic pathways like amino acid and tricarboxylic acid (TCA) cycle are also profoundly perturbed. As glycemic control alone does not prevent complications, we hypothesized that these metabolic disruptions are responsible for the development and progression of diabetic cardiovascular autonomic neuropathy (CAN). We performed standardized cardiovascular autonomic reflex tests and targeted fasting plasma metabolomic analysis of amino acids and TCA cycle intermediates in subjects with type 1 diabetes and healthy control subjects followed for 3 years. Forty-seven participants with type 1 diabetes (60% female and mean ± SD age 35 ± 13 years, diabetes duration 13 ± 7 years, and HbA_1c 7.9 ± 1.2%) had lower fumarate levels and higher threonine, serine, proline, asparagine, aspartic acid, phenylalanine, tyrosine, and histidine levels compared with 10 age-matched healthy control subjects. Higher baseline fumarate levels and lower baseline amino acid levels-asparagine and glutamine-correlate with CAN (lower baseline SD of normal R-R interval [SDNN]). Baseline glutamine and ornithine levels also associated with the progression of CAN (lower SDNN at 3 years) and change in SDNN, respectively, after adjustment for baseline HbA_1c, blood glucose, BMI, cholesterol, urine microalbumin-to- creatinine ratio, estimated glomerular filtration rate, and years of diabetes. Therefore, significant changes in the anaplerotic flux into the TCA cycle could be the critical defect underlying CAN progression.

The Emerging Role of l-Glutamine in Cardiovascular Health and Disease

Emerging evidence indicates that l-glutamine (Gln) plays a fundamental role in cardiovascular physiology and pathology. By serving as a substrate for the synthesis of DNA, ATP, proteins, and lipids, Gln drives critical processes in vascular cells, including proliferation, migration, apoptosis, senescence, and extracellular matrix deposition. Furthermore, Gln exerts potent antioxidant and anti-inflammatory effects in the circulation by inducing the expression of heme oxygenase-1, heat shock proteins, and glutathione. Gln also promotes cardiovascular health by serving as an l-arginine precursor to optimize nitric oxide synthesis. Importantly, Gln mitigates numerous risk factors for cardiovascular disease, such as hypertension, hyperlipidemia, glucose intolerance, obesity, and diabetes. Many studies demonstrate that Gln supplementation protects against cardiometabolic disease, ischemia-reperfusion injury, sickle cell disease, cardiac injury by inimical stimuli, and may be beneficial in patients with heart failure. However, excessive shunting of Gln to the Krebs cycle can precipitate aberrant angiogenic responses and the development of pulmonary arterial hypertension. In these instances, therapeutic targeting of the enzymes involved in glutaminolysis such as glutaminase-1, Gln synthetase, glutamate dehydrogenase, and amino acid transaminase has shown promise in preclinical models. Future translation studies employing Gln delivery approaches and/or glutaminolysis inhibitors will determine the success of targeting Gln in cardiovascular disease.

Glutamine deprivation induces metabolic adaptations associated with beta cell dysfunction and exacerbate lipotoxicity

Studies have reported that plasma glutamine is reduced in type 2 diabetes (T2D) patients. Glutamine supplementation improves glycaemic control, however the mechanisms are unclear. Here, we evaluated in vitro the pancreatic beta cell bioenergetic and insulin secretory responses to various levels of glutamine availability, or treatment in the presence of an inhibitor of intracellular glutamine metabolism. The impact of glutamine deprivation to the pathological events induced by the saturated fatty acid palmitate was also investigated. Glutamine deprivation induced a reduction in mitochondrial respiration and increase in glucose uptake and utilization. This phenotype was accompanied by impairment in beta cell function, as demonstrated by diminished insulin production and secretion, and activation of the unfolded protein response pathway. Palmitate led to insulin secretory dysfunction, loss of viability and apoptosis. Importantly, glutamine deprivation significantly exacerbated these phenotypes, suggesting that low glutamine levels could participate in the process of beta cell dysfunction in T2D.

Impact of Supplementary Amino Acids, Micronutrients, and Overall Diet on Glutathione Homeostasis

Glutathione (GSH) is a critical endogenous antioxidant found in all eukaryotic cells. Higher GSH concentrations protect against cellular damage, tissue degeneration, and disease progression in various models, so there is considerable interest in developing interventions that augment GSH biosynthesis. Oral GSH supplementation is not the most efficient option due to the enzymatic degradation of ingested GSH within the intestine by γ-glutamyltransferase, but supplementation of its component amino acids-cysteine, glycine, and glutamate-enhances tissue GSH synthesis. Furthermore, supplementation with some non-precursor amino acids and micronutrients appears to influence the redox status of GSH and related antioxidants, such as vitamins C and E, lowering systemic oxidative stress and slowing the rate of tissue deterioration. In this review, the effects of oral supplementation of amino acids and micronutrients on GSH metabolism are evaluated. And since specific dietary patterns and diets are being prescribed as first-line therapeutics for conditions such as hypertension and diabetes, the impact of overall diets on GSH homeostasis is also assessed.

Glutamine and type 1 diabetes mellitus: is there a role in glycemic control?

PURPOSE OF REVIEW

Recent literature suggests dietary glutamine supplementation may lower blood glucose in patients with type 1 diabetes (T1D), who have no residual insulin secretion. The mechanisms and potential relevance to the care of T1D remain unclear.

RECENT FINDINGS

Glutamine is involved in multiple pathways including gluconeogenesis, lipolysis, antioxidant defense, the production of nitric oxide, the secretion of peptides (e.g., glucagon-like peptide 1, GLP-1), or neuromediators (e.g., [Latin Small Letter Gamma]-aminobutyric acid), all processes that may impact insulin sensitivity and/or glucose homeostasis. The article reviews potential mechanisms and literature evidence suggesting a role in improving glucose tolerance in patients with illness associated with insulin resistance, as well as the preliminary evidence for the increased incidence of postexercise hypoglycemia in T1D after oral glutamine.

SUMMARY

Further studies are warranted to determine whether the lowering effect of glutamine on blood glucose is sustained over time. If so, long-term randomized trials would be warranted to determine whether there is a role for glutamine as an adjunct dietary supplement to improve glucose control in patients with T1D.

Chemogenetic generation of hydrogen peroxide in the heart induces severe cardiac dysfunction

Oxidative stress plays an important role in the pathogenesis of many disease states. In the heart, reactive oxygen species are linked with cardiac ischemia/reperfusion injury, hypertrophy, and heart failure. While this correlation between ROS and cardiac pathology has been observed in multiple models of heart failure, the independent role of hydrogen peroxide (H₂O₂) in vitro and in vivo is unclear, owing to a lack of tools for precise manipulation of intracellular redox state. Here we apply a chemogenetic system based on a yeast D-amino acid oxidase to show that chronic generation of H₂O₂ in the heart induces a dilated cardiomyopathy with significant systolic dysfunction. We anticipate that chemogenetic approaches will enable future studies of in vivo H₂O₂ signaling not only in the heart, but also in the many other organ systems where the relationship between redox events and physiology remains unclear.

Excessive production of reactive oxygen species (ROS) is associated with cardiac dysfunction, but the causal role of ROS remains poorly understood. Here the authors use an in vivo chemogenetic approach to develop a heart failure model in which generation of hydrogen peroxide in the heart leads to systolic heart failure without fibrotic remodeling.

Glutamine Enhances the Hypoglycemic Effect of Insulin in L6 Cells via Phosphatidylinositol-3-Kinase (PI3K)/Protein Kinase B (AKT)/Glucose Transporter 4 (GLUT4) Signaling Pathway

Background

Diabetes mellitus (DM) is characterized by a decreased blood level of glutamine (Gln), which may contribute to the disturbance in the effect of insulin on skeletal muscle. Therefore, it is crucial to study how to improve the effect of insulin on skeletal muscle by increasing Gln. In the present study, we investigated the effect of Gln on the hypoglycemic action of insulin in skeletal muscle L6 cells at high glucose levels through the insulin signaling pathway and glycogen synthesis pathway.

Material/Methods

The L6 cells were cultured in and stimulated by Gln and insulin. The glutamine analogue, L-Gamma-Glutamyl-p-nitroanilide (GPNA), was used for verifying the effect of Gln. The expression of insulin signaling molecules, including phosphatidylinositol-3-kinase (PI3K), 3-phosphoinositide-dependent protein kinase-1 (PDK1), protein kinase B (AKT), protein kinase C zeta (PKCζ), and glucose transporter 4 (GLUT4), were detected by real-time PCR and Western blot analysis, GLUT4 translocation was observed by immunofluorescence staining, glycogen synthase kinase (GSK) was analyzed by Western blotting, and glucose uptake was measured by glucose oxidase method (GOD).

Results

The results demonstrated that Gln combined with insulin remarkably up-regulated PI3K and PDK1 and also increased AKT and PKCζ phosphorylation. The present study shows that Gln enhanced the impact of insulin on GLUT4 and its translocation. The results of glucose uptake and GSK phosphorylation further confirmed the hypoglycemic effect of Gln accompanied with insulin. The hypoglycemic effect of Gln was reversed by GPNA.

Conclusions

These findings suggest that Gln enhances the hypoglycemic role of insulin through the PI3K/AKT/GLUT4 signaling pathway and glycogen synthesis pathway.

Oleanolic acid protects against diabetic cardiomyopathy via modulation of the nuclear factor erythroid 2 and insulin signaling pathways

Oleanolic acid (OL) is a pentacyclic triterpene compound used for the treatment of hepatitis, liver fibrosis and liver cirrhosis. In China, there is no published research on the effect or biological utilization of OL on liver diseases. The aim of the present study was to investigate the protective effects of OL against diabetic cardiomyopathy and its possible mechanism. A rat model of diabetes was established using streptozotocin and the effect of OL on diabetic cardiomyopathy (DCM) was evaluated. The results demonstrated that OL significantly reversed the DCM-induced changes to body weight, heart rate, echocardiography and hemodynamics, phosphorylated-glycogen synthase (GS) and glycogen phosphorylase (GP) activity in diabetic rats (all P<0.01). Treatment of diabetic rats with OL significantly inhibited oxidative stress and activated heme oxygenase (HO)-1/nuclear factor erythroid 2 (Nrf2) signaling in a rat model of diabetes (both P<0.01). The results of the present study indicate that OL protects against DCM through the HO-1/Nrf2 and insulin modulating GS/GP signaling pathways.

Electrocardiography in rats: a comparison to human

Electrocardiography (ECG) in rats is a widely applied experimental method in basic cardiovascular research. The technique of ECG recordings is simple; however, the interpretation of electrocardiographic parameters is challenging. This is because the analysis may be biased by experimental settings, such as the type of anesthesia, the strain or age of animals. Here, we aimed to review electrocardiographic parameters in rats, their normal range, as well as the effect of experimental settings on the parameters variation. Furthermore, differences and similarities between rat and human ECG are discussed in the context of translational cardiovascular research.

Synthesis and preliminary therapeutic evaluation of copper nanoparticles against diabetes mellitus and -induced micro- (renal) and macro-vascular (vascular endothelial and cardiovascular) abnormalities in rats

Current study synthesized and investigated the effect of low-dose copper nanoparticles (CuNPs) against diabetes mellitus and -induced experimental micro- (nephropathy) and macro-vascular (cardio and endothelium) complications.

Challenges and issues with streptozotocin-induced diabetes - A clinically relevant animal model to understand the diabetes pathogenesis and evaluate therapeutics

Streptozotocin (STZ) has been extensively used over the last three decades to induce diabetes in various animal species and to help screen for hypoglycemic drugs. STZ induces clinical features in animals that resemble those associated with diabetes in humans. For this reason STZ treated animals have been used to study diabetogenic mechanisms and for preclinical evaluation of novel antidiabetic therapies. However, the physiochemical characteristics and associated toxicities of STZ are still major obstacles for researchers using STZ treated animals to investigate diabetes. Another major challenges in STZ-induced diabetes are sustaining uniformity, suitability, reproducibility and induction of diabetes with minimal animal lethality. Lack of appropriate use of STZ was found to be associated with increased mortality and animal suffering. During STZ use in animals, attention should be paid to several factors such as method of preparation of STZ, stability, suitable dose, route of administration, diet regimen, animal species with respect to age, body weight, gender and the target blood glucose level used to represent hyperglycemia. Therefore, protocol for STZ-induced diabetes in experimental animals must be meticulously planned. This review highlights specific skills and strategies involved in the execution of STZ-induced diabetes model. The present review aims to provide insight into diabetogenic mechanisms of STZ, specific toxicity of STZ with its significance and factors responsible for variations in diabetogenic effects of STZ. Further this review also addresses ways to minimize STZ-induced mortality, suggests methods to improve STZ-based experimental models and best utilize them for experimental studies purported to understand diabetes pathogenesis and preclinical evaluation of drugs.

Monoamine oxidase-A is an important source of oxidative stress and promotes cardiac dysfunction, apoptosis, and fibrosis in diabetic cardiomyopathy

Oxidative stress is closely associated with the pathophysiology of diabetic cardiomyopathy (DCM). The mitochondrial flavoenzyme monoamine oxidase A (MAO-A) is an important source of oxidative stress in the myocardium. We sought to determine whether MAO-A plays a major role in modulating DCM. Diabetes was induced in Wistar rats by single intraperitoneal injection of streptozotocin (STZ). To investigate the role of MAO-A in the development of pathophysiological features of DCM, hyperglycemic and age-matched control rats were treated with or without the MAO-A-specific inhibitor clorgyline (CLG) at 1 mg/kg/day for 8 weeks. Diabetes upregulated MAO-A activity; elevated markers of oxidative stress such as cardiac lipid peroxidation, superoxide dismutase activity, and UCP3 protein expression; enhanced apoptotic cell death; and increased fibrosis. All these parameters were significantly attenuated by CLG treatment. In addition, treatment with CLG substantially prevented diabetes-induced cardiac contractile dysfunction as evidenced by decreased QRS, QT, and corrected QT intervals, measured by ECG, and LV systolic and LV end-diastolic pressure measured by microtip pressure transducer. These beneficial effects of CLG were seen despite the persistent hyperglycemic and hyperlipidemic environments in STZ-induced experimental diabetes. In summary, this study provides strong evidence that MAO-A is an important source of oxidative stress in the heart and that MAO-A-derived reactive oxygen species contribute to DCM.

Thymoquinone modulates nitric oxide production and improves organ dysfunction of sepsis

AIMS

The present investigation was designed to evaluate the effect of thymoquinone in a septic animal model and to explore the role of nitric oxide (NO) in the process.

MAIN METHODS

To achieve this, mice (n=12 per group) were treated in parallel with thymoquinone (0.75mg/kg/day) and/or NG-nitro-l-arginine methyl ester (L-NAME; 400μg/g/day) prior to sepsis induction with live Escherichia coli.

KEY FINDINGS

Thymoquinone significantly improved renal and hepatic functions alone and in combination with L-NAME. This was associated with less NO production and lower oxidative stress in treated animals. Tumor necrosis factor-α concentration with thymoquinone and L-NAME were 36.27±3.41pg/ml and 56.55±5.85pg/ml, respectively, as opposed to 141.11±6.46pg/ml in septic controls. Similarly, Interleukin-1α, 2, 6 and 10 levels decreased significantly upon treatment with thymoquinone and L-NAME as compared with untreated septic animals. NF-κB and NF-κB-DNA binding activity in nuclear proteins were also significantly down-regulated. Vascular responsiveness studies in isolated mouse aortae demonstrated a reduced relaxation to acetylcholine exposure in septic mice treated with thymoquinone.

SIGNIFICANCE

These findings suggest that thymoquinone prevents sequels of the multiple organ failure syndrome of sepsis by modulating the production of NO and its inflammatory sequela, and adjusting vascular responsiveness.

Levosimendan suppresses oxidative injury, apoptotic signaling and mitochondrial degeneration in streptozotocin-induced diabetic cardiomyopathy

Diabetic cardiomyopathy plays a major role in morbidity and mortality among cardiovascular disorder-related complications. This study was designed to explore long-term benefits of Levosimendan (LEVO) along with Ramipril and Insulin. Diabetic cardiomyopathy was induced using streptozotocin (STZ) at the dose of 25 mg/kg/body weight/day for three consecutive days in Wistar rats. Rats were randomly divided into 10 groups and treatments were started after 2 weeks of STZ administration. A gradual but severe hyperglycemia ((§§§)p < 0.001) was observed in all STZ-treated groups except those received insulin (2  U/day). LEVO alone and in combination with Ramipril and Insulin normalized (**p < 0.01) mean arterial pressure and heart rate, restored catalase, superoxide dismutase, malondialdehyde, glutathione level and also attenuated (***p < 0.001) the raised serum levels of creatine kinase-heart type, lactate dehydrogenase, tumor necrosis factor-alpha, C-reactive protein, and caspase-3 level in heart tissue altered after STZ treatment. Myofibril degeneration, mitochondrial fibrosis and vacuolization occurred after STZ treatment, were also reversed by LEVO in combination with Ramipril and Insulin. The combination of LEVO with Ramipril and Insulin improved hemodynamic functions, maintained cardiac enzymes and ameliorated myofibril damage in diabetic cardiomyopathy.

Effects of glutamine and valsartan on the brain natriuretic peptide and N-terminal pro-B-type natriuretic peptide of patients with chronic heart failure

OBJECTIVE

To analyze the effects of glutamine and valsartan on the brain natriuretic peptide (BNP) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) of patients with chronic heart failure (CHF).

METHODS

A total of 140 CHF patients were divided into a treatment group and a control group by random drawing, and were subjected to standard anti-heart failure treatment and administered with valsartan. Besides, the treatment group was also intravenously transfused glutamine. The treatment lasted eight weeks.

RESULTS

The overall efficacy of treatment group and control group were 98.6% and 90.0% respectively, with a statistically significant difference (P<0.05). The two groups had significantly increased left ventricular ejection fractions as well as significantly decreased left ventricular end-diastolic volumes and left ventricular end-diastolic dimensions after treatments (P<0.05) compared with those before. There were also inter-group differences between these values (P<0.05). After treatment, the levels of BNP, NT-proBNP and CD8(+) in both groups significantly decreased (P<0.05), whereas those of CD4(+) significantly increased (P<0.05). The two groups also had significantly different values (P<0.05).

CONCLUSION

Glutamine in combination with valsartan enhanced the therapeutic effects by improving cardiac function, which may be associated with decreased expressions of BNP and NT-proBNP and beneficial effects of glutamine on immune function.

Effect and mechanisms of zinc supplementation in protecting against diabetic cardiomyopathy in a rat model of type 2 diabetes

Diabetic cardiomyopathy is a prominent cause of heart failure in patients with diabetes mellitus. Currently, there is no specific treatment for diabetic cardiomyopathy. This study aimed to investigate the effect and underlying mechanisms of Zinc (Zn) supplementation in the protection against diabetic cardiomyopathy in a rat model of type 2 diabetes mellitus (T2DM). T2DM-like lesions in male Wistar rats were induced by introducing the high-fat diet and by administration of streptozocin (STZ). After STZ induction, animals with fasting plasma glucose level ≥16.7 mM were considered as diabetic, and randomly assigned to the group receiving physiological saline (control) or ZnSO4 for 56 days. On days 0, 7, 28 and 56 of treatment, animals were weighed, and their blood samples were analyzed. On day 56, hemodynamic assessment was performed right before the sacrifice of animals. Cardiac tissue specimens were collected and subjected to pathologic assessment, metallothionein (MT) concentration measurement and Western blot analysis of microtubule-associated protein light chain 3 (LC3), the marker of autophagy, and glucose-regulated protein-78 (GRP78), an oxidative stress marker. High-fat diet feeding followed by STZ administration resulted in weight loss, hyperglycemia, polydipsia, polyphagia, hemodynamic anomalies and a significant increase in the myocardial content of LC3 and GRP78 proteins, but not in MT protein. Zn supplementation effectively attenuated all these aberrations induced by high-fat diet and STZ. These findings suggest that Zn might be a protective factor in diabetic cardiomyopathy, acting in two ways: at least partially, through inhibiting autophagy and by endoplasmic reticulum stress.