Proteomic analysis of mitochondrial proteins in a mouse model of type 2 diabetes

MALDI-IMS as a Tool to Determine the Myocardial Response to Syndecan-2-Selected Mesenchymal Stromal Cell Application in an Experimental Model of Diabetic Cardiomyopathy

PURPOSE

Mesenchymal stromal cells (MSC) are an attractive tool for treatment of diabetic cardiomyopathy. Syndecan-2/CD362 has been identified as a functional marker for MSC isolation. Imaging mass spectrometry (IMS) allows for the characterization of therapeutic responses in the left ventricle. This study aims to investigate whether IMS can assess the therapeutic effect of CD362⁺ -selected MSC on early onset experimental diabetic cardiomyopathy.

EXPERIMENTAL DESIGN

1 × 10⁶ wild type (WT), CD362^- , or CD362⁺ MSC are intravenously injected into db/db mice. Four weeks later, mice are hemodynamically characterized and subsequently sacrificed for IMS combined with bottom-up mass spectrometry, and isoform and phosphorylation analyses of cardiac titin.

RESULTS

Overall alterations of the cardiac proteome signatures, especially titin, are observed in db/db compared to control mice. Interestingly, only CD362⁺ MSC can overcome the reduced titin intensity distribution and shifts the isoform ratio toward the more compliant N2BA form. In contrast, WT and CD362^- MSCs improve all-titin phosphorylation and protein kinase G activity, which is reflected in an improvement in diastolic performance.

CONCLUSIONS AND CLINICAL RELEVANCE

IMS enables the characterization of differences in titin intensity distribution following MSC application. However, further analysis of titin phosphorylation is needed to allow for the assessment of the therapeutic efficacy of MSC.

UQCRC1 downregulation is correlated with lymph node metastasis and poor prognosis in CRC

BACKGROUND

Mitochondrial dysfunction is common in cancer. UQCRC1 is a nuclear-encoded protein localized to the inner mitochondrial membrane; however, little is known about it in colorectal cancer (CRC). The purpose of this study was to investigate the expression pattern and the possible clinical significance of UQCRC1 in CRC.

METHODS

A total of 197 patients with CRC were enrolled in this study. Immunohistochemistry was used to evaluate the expression pattern of UQCRC1. The relationship between UQCRC1 and clinical characteristics, especially lymph node metastasis, was also assessed. In addition, we evaluated the significance of UQCRC1 in the prognosis for CRC patients.

RESULTS

UQCRC1 was downregulated in 28.9% (57/197) of human CRCs. Downregulation of UQCRC1 was correlated with increased lymph node metastasis (p < 0.001) and decreased disease-free survival (DFS) and overall survival (OS). Multivariate analysis revealed that downregulation of UQCRC1 was an independent prognostic factor both for DFS (HR 3.009; 95% CI: 1.613-8.548, P = 0.009) and OS (HR 4.062; 95% CI: 2.835-8.910, P = 0.001). In addition, downregulation of UQCRC1 was correlated with increased VEGF-C expression (P = 0.002).

CONCLUSION

UQCRC1 was downregulated in human CRC. Downregulation of UQCRC1 was correlated with increased lymph node metastasis and finally associated with decreased survival in CRC.

Insight from mitochondrial functions and proteomics to understand cardiometabolic disorders in survivors of acute lymphoblastic leukemia

BACKGROUND

Childhood acute lymphoblastic leukemia (cALL) is the most prevalent form of cancer in children. Due to advances in treatment and therapy, young cALL subjects now achieve a 90% survival rate. However, this tremendous advance does not come without consequence since ~2/3 of cALL survivors are affected by long-term and late, severe complications. Although the metabolic syndrome is a very serious sequel of cALL, the mechanisms remain undefined. It is also surprising to note that the mitochondrion, a central organelle in metabolic functions and the main cellular energy generator, have not yet been explored.

OBJECTIVES

To determine whether cALL survivors exhibit impairments in their mitochondrial functions and proteomic profiling in relationship with metabolic disorders in cALL survivors compared to healthy controls.

METHODS AND RESULTS

Anthropometric measures, metabolic characteristics and lipid profiles were assessed, mitochondria isolated from peripheral blood mononuclear cells, and proteomic analyzed. Our data demonstrated that metabolically. Unhealthy survivors exhibited several metabolic syndrome components (e.g. overweight, insulin resistance, dyslipidemia, inflammation) whereas Healthy cALL survivors resemble the Controls. In line with these abnormalities, functional experiments in these subjects revealed a significant decrease in the protein expression of mitochondrial antioxidant superoxide dismutase, PGC1-α transcription factor (a key modulator of mitochondrion biogenesis), and an increase in pro-apoptotic cytochrome c. Proteomic analysis of mitochondria by mass spectrometry revealed changes in the regulation of proteins related to inflammation, apoptosis, energy production, redox and antioxidant activity, fatty acid β-oxidation, protein transport and metabolism, and signalling pathways between groups.

CONCLUSIONS

Through the use of proteomic analysis, our work demonstrated a number of significant alterations in protein expression in mitochondria of cALL survivors, especially the metabolically Unhealthy survivor group. Further investigation of these proteins may help delineate the mechanisms by which mitochondrial dysfunctions exert cardiometabolic derangements in cALL survivors.

Proteomics of the Rat Myocardium during Development of Type 2 Diabetes Mellitus Reveals Progressive Alterations in Major Metabolic Pathways

Congestive heart failure and poor clinical outcome after myocardial infarction are known complications in patients with type-2 diabetes mellitus (T2DM). Protein alterations may be involved in the mechanisms underlying these disarrays in the diabetic heart. Here we map proteins involved in intracellular metabolic pathways in the Zucker diabetic fatty rat heart as T2DM develops using MS based proteomics. The prediabetic state only induced minor pathway changes, whereas onset and late T2DM caused pronounced perturbations. Two actin-associated proteins, ARPC2 and TPM3, were up-regulated at the prediabetic state indicating increased actin dynamics. All differentially regulated proteins involved in fatty acid metabolism, both peroxisomal and mitochondrial, were up-regulated at late T2DM, whereas enzymes of branched chain amino acid degradation were all down-regulated. At both onset and late T2DM, two members of the serine protease inhibitor superfamily, SERPINA3K and SERPINA3L, were down-regulated. Furthermore, we found alterations in proteins involved in clearance of advanced glycation end-products and lipotoxicity, DCXR and CBR1, at both onset and late T2DM. These proteins deserve elucidation with regard to their role in T2DM pathogenesis and their respective role in the deterioration of the diabetic heart. Data are available via ProteomeXchange with identifiers PXD009538, PXD009554, and PXD009555.

Ubiquinol-cytochrome c reductase core protein 1 may be involved in delayed cardioprotection from preconditioning induced by diazoxide

This study aimed to use long-term diazoxide treatment to establish a loss-of-cardioprotection model and then perform proteomics analysis to explore which proteins of mitochondrial inner membrane (MIM) are potentially involved in delayed cardioprotection. Rats received 1 to 8 weeks of diazoxide treatments (20 mg•kg-1•d-1) to establish a loss-of-cardioprotection model in different groups. Detection of serum cTnI levels and cell apoptosis assays in heart tissue were performed. Then, rats MIM after 0, 4 and 6 weeks of diazoxide treatment was isolated and proteomics analysis was performed. An invitro model of H9C2 cells was performed to explore the effects of targeted protein on delayed cardioprotection. The effect of delayed cardioprotection by diazoxide preconditioning disappeared when diazoxide treatments were given for six weeks or longer. Ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) was identified in the proteomics analysis. UQCRC1 expression was upregulated by diazoxide treatment in H9C2 cells, and UQCRC1 down-regulation could increase the lactate dehydrogenase release and apoptosis rate after injury induced by oxygen glucose deprivation. These results showed that UQCRC1 might contribute to the loss-of-cardioprotection model induced by long-term diazoxide treatment and play a role in delayed cardioprotection.

The impact of growth hormone on proteomic profiles: a review of mouse and adult human studies

Growth hormone (GH) is a protein that is known to stimulate postnatal growth, counter regulate insulin's action and induce expression of insulin-like growth factor-1. GH exerts anabolic or catabolic effects depending upon on the targeted tissue. For instance, GH increases skeletal muscle and decreases adipose tissue mass. Our laboratory has spent the past two decades studying these effects, including the effects of GH excess and depletion, on the proteome of several mouse and human tissues. This review first discusses proteomic techniques that are commonly used for these types of studies. We then examine the proteomic differences found in mice with excess circulating GH (bGH mice) or mice with disruption of the GH receptor gene (GHR^-/-). We also describe the effects of increased and decreased GH action on the proteome of adult patients with either acromegaly, GH deficiency or patients after short-term GH treatment. Finally, we explain how these proteomic studies resulted in the discovery of potential biomarkers for GH action, particularly those related with the effects of GH on aging, glucose metabolism and body composition.

Important mitochondrial proteins in human omental adipose tissue show reduced expression in obesity

Impaired mitochondrial function is important in obesity and the development of insulin resistance and diabetes. The aim of this study was to identify human adipocyte-derived mitochondrial proteins associated with obesity. Mitochondrial proteins from 20 abdominal omental adipose tissue biopsies (13 obese and 7 control subjects) were separated by anion-exchange chromatography coupled to SDS-PAGE. Protein contents were compared and identified by MALDI-TOF-TOF mass spectrometry. Proteins of interest were validated, verified and quantified using immuno dot blot assays in a total of 76 mitochondrial preparations from both obese and non-obese patients. Mass spectrometric comparison of 20 mitochondrial proteomes yielded 62 proteins that were differentially expressed in adipose tissue of obese subjects. The immunological quantification of 12 mitochondrial proteins from 76 omental adipose tissue biopsies revealed four proteins, citrate synthase, HADHA, LETM1 and mitofilin inversely being associated with BMI, and mitofilin being inversely correlated with gender.

BIOLOGICAL SIGNIFICANCE

The finding that obese human subjects have reduced levels of important mitochondrial proteins in adipocytes of omental adipose tissue as compared to non-obese controls gives new insights in the impairment of mitochondrial function in this specialized compartment of human adipose tissue in obesity and may eventually lead to the definition of valuable obesity markers.

A systematic review of fetal genes as biomarkers of cardiac hypertrophy in rodent models of diabetes

Pathological cardiac hypertrophy activates a suite of genes called the fetal gene program (FGP). Pathological hypertrophy occurs in diabetic cardiomyopathy (DCM); therefore, the FGP is widely used as a biomarker of DCM in animal studies. However, it is unknown whether the FGP is a consistent marker of hypertrophy in rodent models of diabetes. Therefore, we analyzed this relationship in 94 systematically selected studies. Results showed that diabetes induced with cytotoxic glucose analogs such as streptozotocin was associated with decreased cardiac weight, but genetic or diet-induced models of diabetes were significantly more likely to show cardiac hypertrophy (P<0.05). Animal strain, sex, age, and duration of diabetes did not moderate this effect. There were no correlations between the heart weight:body weight index and mRNA or protein levels of the fetal genes α-myosin heavy chain (α-MHC) or β-MHC, sarco/endoplasmic reticulum Ca²⁺-ATPase, atrial natriuretic peptide (ANP), or brain natriuretic peptide. The only correlates of non-indexed heart weight were the protein levels of α-MHC (Spearman's ρ = 1, P<0.05) and ANP (ρ = −0.73, P<0.05). These results indicate that most commonly measured genes in the FGP are confounded by diabetogenic methods, and are not associated with cardiac hypertrophy in rodent models of diabetes.

Mammalian target of rapamycin (mTOR) inhibition with rapamycin improves cardiac function in type 2 diabetic mice: potential role of attenuated oxidative stress and altered contractile protein expression

Elevated mammalian target of rapamycin (mTOR) signaling contributes to the pathogenesis of diabetes, with increased morbidity and mortality, mainly because of cardiovascular complications. Because mTOR inhibition with rapamycin protects against ischemia/reperfusion injury, we hypothesized that rapamycin would prevent cardiac dysfunction associated with type 2 diabetes (T2D). We also investigated the possible mechanisms and novel protein targets involved in rapamycin-induced preservation of cardiac function in T2D mice. Adult male leptin receptor null, homozygous db/db, or wild type mice were treated daily for 28 days with vehicle (5% DMSO) or rapamycin (0.25 mg/kg, intraperitoneally). Cardiac function was monitored by echocardiography, and protein targets were identified by proteomics analysis. Rapamycin treatment significantly reduced body weight, heart weight, plasma glucose, triglyceride, and insulin levels in db/db mice. Fractional shortening was improved by rapamycin treatment in db/db mice. Oxidative stress as measured by glutathione levels and lipid peroxidation was significantly reduced in rapamycin-treated db/db hearts. Rapamycin blocked the enhanced phosphorylation of mTOR and S6, but not AKT in db/db hearts. Proteomic (by two-dimensional gel and mass spectrometry) and Western blot analyses identified significant changes in several cytoskeletal/contractile proteins (myosin light chain MLY2, myosin heavy chain 6, myosin-binding protein C), glucose metabolism proteins (pyruvate dehydrogenase E1, PYGB, Pgm2), and antioxidant proteins (peroxiredoxin 5, ferritin heavy chain 1) following rapamycin treatment in db/db heart. These results show that chronic rapamycin treatment prevents cardiac dysfunction in T2D mice, possibly through attenuation of oxidative stress and alteration of antioxidants and contractile as well as glucose metabolic protein expression.

Conundrum of pathogenesis of diabetic cardiomyopathy: role of vascular endothelial dysfunction, reactive oxygen species, and mitochondria

Diabetic cardiomyopathy and heart failure have been recognized as the leading causes of mortality among diabetics. Diabetic cardiomyopathy has been characterized primarily by the manifestation of left ventricular dysfunction that is independent of coronary artery disease and hypertension among the patients affected by diabetes mellitus. A complex array of contributing factors including the hypertrophy of left ventricle, alterations of metabolism, microvascular pathology, insulin resistance, fibrosis, apoptotic cell death, and oxidative stress have been implicated in the pathogenesis of diabetic cardiomyopathy. Nevertheless, the exact mechanisms underlying the pathogenesis of diabetic cardiomyopathy are yet to be established. The critical involvement of multifarious factors including the vascular endothelial dysfunction, microangiopathy, reactive oxygen species (ROS), oxidative stress, mitochondrial dysfunction has been identified in the mechanism of pathogenesis of diabetic cardiomyopathy. Although it is difficult to establish how each factor contributes to disease, the involvement of ROS and mitochondrial dysfunction are emerging as front-runners in the mechanism of pathogenesis of diabetic cardiomyopathy. This review highlights the role of vascular endothelial dysfunction, ROS, oxidative stress, and mitochondriopathy in the pathogenesis of diabetic cardiomyopathy. Furthermore, the review emphasizes that the puzzle has to be solved to firmly establish the mitochondrial and/or ROS mechanism(s) by identifying their most critical molecular players involved at both spatial and temporal levels in diabetic cardiomyopathy as targets for specific and effective pharmacological/therapeutic interventions.

Myosins Are Differentially Expressed under Oxidative Stress in Chronic Streptozotocin-Induced Diabetic Rat Brains

Diabetes mellitus is a disease characterized by persistent hyperglycemia, which may lead to brain tissue damage due to oxidative stress and also contributes to neuronal death and changes in synaptic transmission. This study evaluated the effect of oxidative stress and the use of antioxidants supplementation on myosins expression levels in the brains of chronic diabetic rats induced by streptozotocin. Lipid peroxidation, antioxidant enzymes activities, and myosins-IIB and -Va expressions at transcriptional and translational levels were examined after 90 days induction. The chronic effect of the diabetes led to the upregulation of superoxide dismutase (SOD) and catalase (CAT) activities, and the downregulation of glutathione peroxidase (GPx), but there was no statistically significant increase in the malondialdehyde (MDA) levels. These alterations were accompanied by high myosin-IIB and low myosin-Va expressions. Although the antioxidant supplementation did not interfere on MDA levels, the oxidative stress caused by chronic hyperglycemia was reduced by increasing SOD and restoring CAT and GPx activities. Interestingly, after supplementation, diabetic rats recovered only myosin-Va protein levels, without interfering on myosins mRNA levels expressed in diabetic rat brains. Our results suggest that antioxidant supplementation reduces oxidative stress and also regulates the myosins protein expression, which should be beneficial to individuals with diabetes/chronic hyperglycemia.

Cardiac dysfunction and oxidative stress in the metabolic syndrome: an update on antioxidant therapies

The metabolic syndrome (MetS) is a cluster of risk factors including obesity, insulin resistance, dyslipidemia, elevated blood pressure and glucose intolerance. The MetS increases the risk for cardiovascular disease (CVD) and type 2 diabetes. Each component of the MetS causes cardiac dysfunction and their combination carries additional risk. The mechanisms underlying cardiac dysfunction in the MetS are complex and might include lipid accumulation, increased fibrosis and stiffness, altered calcium homeostasis, abnormal autophagy, altered substrate utilization, mitochondrial dysfunction and increased oxidative stress. Mitochondrial and extra-mitochondrial sources of reactive oxygen species (ROS) and reduced antioxidant defense mechanisms characterize the myocardium of humans and animals with the MetS. The mechanisms for increased cardiac oxidative stress in the MetS are not fully understood but include increased fatty acid oxidation, mitochondrial dysfunction and enhanced NADPH oxidase activity. Therapies aimed to reduce oxidative stress and enhance antioxidant defense have been employed to reduce cardiac dysfunction in the MetS in animals. In contrast, large scale clinical trials using antioxidants therapies for the treatment of CVD have been disappointing because of the lack of efficacy and undesired side effects. The focus of this review is to summarize the current knowledge about the mechanisms underlying cardiac dysfunction in the MetS with a special interest in the role of oxidative stress. Finally, we will update the reader on the results obtained with natural antioxidant and mitochondria-targeted antioxidant therapies for the treatment of CVD in the MetS.

Comparative mitochondrial proteomics: perspective in human diseases

Mitochondria are the most complex and the most important organelles of eukaryotic cells, which are involved in many cellular processes, including energy metabolism, apoptosis, and aging. And mitochondria have been identified as the "hot spot" by researchers for exploring relevant associated dysfunctions in many fields. The emergence of comparative proteomics enables us to have a close look at the mitochondrial proteome in a comprehensive and effective manner under various conditions and cellular circumstances. Two-dimensional electrophoresis combined with mass spectrometry is still the most popular techniques to study comparative mitochondrial proteomics. Furthermore, many new techniques, such as ICAT, MudPIT, and SILAC, equip researchers with more flexibilities inselecting proper methods. This article also reviews the recent development of comparative mitochondrial proteomics on diverse human diseases. And the results of mitochondrial proteomics enhance a better understanding of the pathogenesis associated with mitochondria and provide promising therapeutic targets.

Chronic treatment with long acting phosphodiesterase-5 inhibitor tadalafil alters proteomic changes associated with cytoskeletal rearrangement and redox regulation in Type 2 diabetic hearts

Diabetic patients are prone to metabolic perturbations that progressively contribute to structural, functional and proteomic alterations in the myocardium. Phosphodiesterase-5 (PDE-5) inhibitors exhibit cardioprotective effects against ischemic/reperfusion injury, however the effects of chronic administration of PDE-5 inhibitors, particularly under diabetic conditions, remain unknown. Hence, the present study was designed to identify novel protein targets related to long-acting PDE-5 inhibitor tadalafil-induced cardioprotection in diabetes. Using two-dimensional differential in-gel electrophoresis with 3 CyDye labeling and MALDI-TOF/TOF tandem mass spectrometry we identified alterations in the expressions of cardiac proteins in diabetic db/db mice treated with tadalafil. Tadalafil reversed the coordinated alterations of cytoskeletal/contractile proteins such as myosin light chain (MLY) 2 and 4, myosin heavy chain α and myosin-binding protein C which contributes to contractile dysfunction. The expression of intermediate filament protein vimentin and extra-cellular matrix proteins like cysteine and glycine rich protein-3 and collagen type VI α were upregulated in db/db mice indicating cardiac remodeling in diabetes. These detrimental proteomic alterations were reflected in cardiac function which were reversed in tadalafil treated mice. Tadalafil also enhanced antioxidant enzyme glutathione S-transferase Kappa-1 (GSKT-1) and downregulated redox regulatory chaperones like heat shock protein 8 (HSPA8), and 75 kD glucose regulatory protein (75GRP). Furthermore, tadalafil treatment significantly attenuated GSSG/GSH ratio and improved the metabolic status of db/db mice. Chronic treatment with tadalafil in db/db mice modulates proteins involved in cytoskeletal rearrangement and redox signaling of the heart, which may explain the beneficial effects of PDE-5 inhibition in diabetes.

The streptozotocin-induced rat model of diabetes mellitus evidences significant reduction of myosin-Va expression in the brain

Diabetes mellitus is a disease characterized by increased glucose levels in the blood. Hyperglycemia causes damage to the brain tissue, and induces significant changes in synaptic transmission. In this investigation, we have found a significant alteration in the expression of the molecular motor involved in the synaptic vesicles transport, myosin-Va, and its distribution in rat brains of streptozotocin-induced diabetes model. Brains were removed after 20 days, homogenized and analysed by Western blotting, qRT-PCR and immunohistochemistry. Myosin-Va presented significantly lower levels of both mRNA and protein in diabetic than those observed in non-diabetic animals. Moreover, neuronal and glial cells of the occipital and frontal cortex exhibited decreased myosin-Va immunostaining in diabetic rat brains. In conclusion, diabetic rat brains displayed altered expression and distribution of myosin-Va, and these finding may contribute to the basic understanding about this myosin role in brain function related to diabetes.

Proteomic changes in the heart of diet-induced pre-diabetic mice

The development of type 2 diabetes (T2D) is strongly associated with obesity. In humans, T2D increases the risk for end organ complications. Among these, heart disease has been ranked as the leading cause of death. We used a proteomic methodology to test the hypothesis that a pre-diabetic state generated by high-fat diet leads to changes in proteins related to heart function and structure. Over 300 protein spots were resolved by two-dimensional gel electrophoresis (2-DE). Fifteen protein spots were found to be altered (7 decreased and 8 increased) in pre-diabetic hearts. The protein spots were then identified by mass spectrometry and immunoblots. Among the decreased proteins, 3 are involved in heart structure (one isoform of desmin, troponin T2 and α-cardiac actin), 3 are involved in energy metabolism (mitochondrial ATP synthase β subunit, adenylate kinase and creatine kinase) and one is a component of the citric acid cycle (isocitrate dehydrogenase 3). In contrast, proteins involved in fatty acid oxidation (two isoforms of peroxisomal enoyl-CoA hydratase) and the citric acid cycle (three isoforms of malate dehydrogenase) were increased in pre-diabetic hearts. The results suggest that changes in the levels of several heart proteins may have implications in the development of the cardiac phenotype associated to T2D.