Project description:Diabetic cardiomyopathy is a primary myocardial injury induced by diabetes with complex pathogenesis. In this study, we identify disordered cardiac retinol metabolism in type 2 diabetic male mice and patients characterized by retinol overload, all-trans retinoic acid deficiency. By supplementing type 2 diabetic male mice with retinol or all-trans retinoic acid, we demonstrate that both cardiac retinol overload and all-trans retinoic acid deficiency promote diabetic cardiomyopathy. Mechanistically, by constructing cardiomyocyte-specific conditional retinol dehydrogenase 10-knockout male mice and overexpressing retinol dehydrogenase 10 in male type 2 diabetic mice via adeno-associated virus, we verify that the reduction in cardiac retinol dehydrogenase 10 is the initiating factor for cardiac retinol metabolism disorder and results in diabetic cardiomyopathy through lipotoxicity and ferroptosis. Therefore, we suggest that the reduction of cardiac retinol dehydrogenase 10 and its mediated disorder of cardiac retinol metabolism is a new mechanism underlying diabetic cardiomyopathy.
Project description:Diabetic cardiomyopathy (DCM) is a primary myocardial injury induced by diabetes mellitus (DM) with a complex pathogenesis. In this study, we identified disordered cardiac retinol metabolism in T2DM mice and patients characterized by retinol (vitamin A, Rol) overload, all-trans retinoic acid (atRA) deficiency and retinoic acid receptors (RARs) reduction, and demonstrated that both cardiac Rol overload and atRA deficiency promote DCM by supplementing T2DM mice with Rol or atRA. Mechanically, by constructing cardiomyocyte-specific conditional RDH10-knockout mice and overexpressing RDH10 in T2DM mice via adeno-associated virus, we verified that the reduction in cardiac retinol dehydrogenase 10 (RDH10) is the initiating factor for cardiac retinol metabolism disorder and its resulting DCM. Additionally, lipotoxicity and ferroptosis contribute to the effect of retinol metabolism disorder on DCM. Based on these results, we suggest that the reduction of cardiac RDH10 and its mediated disorder of cardiac retinol metabolism is a new mechanism underlying DCM.
Project description:Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active cis-epoxyeicosatrienoic acids, which have potent vasodilatory, antiinflammatory, antiapoptotic, and antidiabetes properties. Here, we showed the effects of cardiac-specific overexpression of CYP epoxygenase 2J2 (CYP2J2) on diabetic cardiomyopathy and insulin resistance in high-fat (HF) diet fed, low-dose streptozotocin-treated mice. Diabetic cardiomyopathy was induced by HF and streptozotocin in cardiac-specific CYP2J2 transgenic mice. Physiological parameters and systemic metabolic parameters were monitored using ELISA kits. Intraperitoneal injection glucose tolerance test and hyperinsulinemic-euglycemic clamp study were implied to indicate insulin resistance. Cardiac function was assessed by echocardiography and Millar catheter system. Real-time PCR and Western blotting were used in signal pathway detection. αMHC-CYP2J2 transgenic mice showed significantly lower plasma glucose and insulin levels, improved glucose tolerance, and increased cardiac glucose uptake. Furthermore, αMHC-CYP2J2 transgenic mice were significantly protected from HF-streptozotocin-induced diabetic cardiomyopathy. Strikingly, CYP2J2 overexpression attenuated myocardial hypertrophy induced by diabetes. We conclude that cardiac-specific overexpression of CYP2J2 significantly protects against diabetic cardiomyopathy, which may be due to improved cardiac insulin resistance, glucose uptake, and reversal of cardiac hypertrophy. Relevant mechanisms may include up-regulation of peroxisome proliferator-activated receptor γ, activation of insulin receptor and AMP-activated protein kinase signaling pathways, and inhibition of nuclear factor of activated T cells c3 signal by enhanced atrial natriuretic peptide production. These results suggest that CYP2J2 epoxygenase metabolites likely play an important role in plasma glucose homeostasis, and enhancement of epoxyeicosatrienoic acids activation may serve as an effective therapeutic strategy to prevent diabetic cardiomyopathy.
Project description:Mitochondrial aldehyde dehydrogenase (ALDH2) offers proven cardiovascular benefit, although its impact on diabetes remains elusive. This study examined the effects of ALDH2 overexpression and knockout on diabetic cardiomyopathy and the mechanism involved with a focus on mitochondrial integrity. Mice challenged with streptozotocin (STZ, 200 mg/kg, via intraperitoneal injection) exhibited pathological alterations, including reduced respiratory exchange ratio, dampened fractional shortening and ejection fraction, increased left ventricular end-systolic and diastolic diameters, cardiac remodeling, cardiomyocyte contractile anomalies, intracellular Ca2+ defects, myocardial ultrastructural injury, oxidative stress, apoptosis, and mitochondrial damage, which were overtly attenuated or accentuated by ALDH2 overexpression or knockout, respectively. Diabetic patients also exhibited reduced plasma ALDH2 activity, cardiac remodeling, and diastolic dysfunction. In addition, STZ challenge altered expression levels of mitochondrial proteins (PGC-1α and UCP2) and Ca2+ regulatory proteins (SERCA, Na+-Ca2+ exchanger, and phospholamban), dampened autophagy and mitophagy (LC3B ratio, TOM20, Parkin, FUNDC1, and BNIP3), disrupted phosphorylation of Akt, GSK3β, and Foxo3a, and elevated PTEN phosphorylation, most of which were reversed or worsened by ALDH2 overexpression or knockout, respectively. Furthermore, the novel ALDH2 activator torezolid, as well as the classical ALDH2 activator Alda-1, protected against STZ- or high glucose-induced in vivo or in vitro cardiac anomalies, which was nullified by inhibition of Akt, GSK3β, Parkin, or mitochondrial coupling. Our data discerned a vital role for ALDH2 in diabetic cardiomyopathy possibly through regulation of Akt and GSK3β activation, Parkin mitophagy, and mitochondrial function.
Project description:Background and purposeGlucagon-like peptide-1 (GLP-1) receptor activation decreases stroke risk in people with Type 2 diabetes (T2D), while animal studies have shown the efficacy of this strategy to counteract stroke-induced acute brain damage. However, whether GLP-1 receptor activation also improves recovery in the chronic phase after stroke is unknown. We investigated whether post-acute, chronic administration of the GLP-1 receptor agonist, exendin-4, improves post-stroke recovery and examined possible underlying mechanisms in T2D and non-T2D mice.Experimental approachWe induced stroke via transient middle cerebral artery occlusion (tMCAO) in T2D/obese mice (8 months of high-fat diet) and age-matched controls. Exendin-4 was administered for 8 weeks from Day 3 post-tMCAO. We assessed functional recovery by weekly upper-limb grip strength tests. Insulin sensitivity and glycaemia were evaluated at 4 and 8 weeks post-tMCAO. Neuronal survival, stroke-induced neurogenesis, neuroinflammation, atrophy of GABAergic parvalbumin+ interneurons, post-stroke vascular remodelling and fibrotic scar formation were investigated by immunohistochemistry.Key resultsExendin-4 normalised T2D-induced impairment of forepaw grip strength recovery in correlation with normalised glycaemia and insulin sensitivity. Moreover, exendin-4 counteracted T2D-induced atrophy of parvalbumin+ interneurons and decreased microglia activation. Finally, exendin-4 normalised density and pericyte coverage of micro-vessels and restored fibrotic scar formation in T2D mice. In non-T2D mice, the exendin-4-mediated recovery was minor.Conclusion and implicationsChronic GLP-1 receptor activation mediates post-stroke functional recovery in T2D mice by normalising glucose metabolism and improving neuroplasticity and vascular remodelling in the recovery phase. The results warrant clinical trial of GLP-1 receptor agonists for rehabilitation after stroke in T2D.Linked articlesThis article is part of a themed issue on GLP1 receptor ligands (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.4/issuetoc.
Project description:Purpose of reviewInsulin is at the heart of diabetes mellitus (DM). DM alters cardiac metabolism causing cardiomyopathy, ultimately leading to heart failure. Polyamines, organic compounds synthesized by cardiomyocytes, have an insulin-like activity and effect on glucose metabolism, making them metabolites of interest in the DM heart. This review sheds light on the disrupted microRNA network in the DM heart in relation to developing novel therapeutics targeting polyamine biosynthesis to prevent/mitigate diabetic cardiomyopathy.Recent findingsPolyamines prevent DM-induced upregulation of glucose and ketone body levels similar to insulin. Polyamines also enhance mitochondrial respiration and thereby regulate all major metabolic pathways. Non-coding microRNAs regulate a majority of the biological pathways in our body by modulating gene expression via mRNA degradation or translational repression. However, the role of miRNA in polyamine biosynthesis in the DM heart remains unclear. This review discusses the regulation of polyamine synthesis and metabolism, and its impact on cardiac metabolism and circulating levels of glucose, insulin, and ketone bodies. We provide insights on potential roles of polyamines in diabetic cardiomyopathy and putative miRNAs that could regulate polyamine biosynthesis in the DM heart. Future studies will unravel the regulatory roles these miRNAs play in polyamine biosynthesis and will open new doors in the prevention/treatment of adverse cardiac remodeling in diabetic cardiomyopathy.
Project description:Diabetes disrupts mitochondrial function and often results in diabetic cardiomyopathy (DCM). Paeonol is a bioactive compound that has been reported to have pharmacological potential for cardiac and mitochondrial protection. This study aims to explore the effects of paeonol on mitochondrial disorderes in DCM and the underlying mechanisms. We showed that paeonol promoted Opa1-mediated mitochondrial fusion, inhibited mitochondrial oxidative stress, and preserved mitochondrial respiratory capacity and cardiac performance in DCM in vivo and in vitro. Knockdown of Opa1 blunted the above protective effects of paeonol in both diabetic hearts and high glucose-treated cardiomyocytes. Mechanistically, inhibitor screening, siRNA knockdown and chromatin immunoprecipitation experiments showed that paeonol-promoted Opa1-mediated mitochondrial fusion required the activation of Stat3, which directly bound to the promoter of Opa1 to upregulate its transcriptional expression. Moreover, pharmmapper screening and molecular docking studies revealed that CK2α served as a direct target of paeonol that interacted with Jak2 and induced the phosphorylation and activation of Jak2-Stat3. Knockdown of CK2α blunted the promoting effect of paeonol on Jak2-Stat3 phosphorylation and Opa1-mediated mitochondrial fusion. Collectively, we have demonstrated for the first time that paeonol is a novel mitochondrial fusion promoter in protecting against hyperglycemia-induced mitochondrial oxidative injury and DCM at least partially via an Opa1-mediated mechanism, a process in which paeonol interacts with CK2α and restores its kinase activity that subsequently increasing Jak2-Stat3 phosphorylation and enhancing the transcriptional level of Opa1. These findings suggest that paeonol or the promotion of mitochondrial fusion might be a promising strategy for the treatment of DCM.
Project description:Skeletal fragility is associated with type 2 diabetes mellitus (T2D), but the underlying mechanism is not well understood. Here, in a mouse model for youth-onset T2D, we show that both trabecular and cortical bone mass is reduced due to diminished osteoblast activity. Stable isotope tracing in vivo with 13C-glucose demonstrates that both glycolysis and glucose fueling of the TCA cycle are impaired in diabetic bones. Similarly, Seahorse assays show suppression of both glycolysis and oxidative phosphorylation by diabetes in bone marrow mesenchymal cells as a whole, whereas single-cell RNA sequencing reveals distinct modes of metabolic dysregulation among the subpopulations. Metformin not only promotes glycolysis and osteoblast differentiation in vitro, but also improves bone mass in diabetic mice. Finally, osteoblast-specific overexpression of either Hif1a, a general inducer of glycolysis, or Pfkfb3 which stimulates a specific step in glycolysis, averts bone loss in T2D mice. The study identifies osteoblast-intrinsic defects in glucose metabolism as an underlying cause of diabetic osteopenia, which may be targeted therapeutically.
Project description:ALDH1L1 (10-formyltetrahydrofolate dehydrogenase), an enzyme of folate metabolism highly expressed in liver, metabolizes 10-formyltetrahydrofolate to produce tetrahydrofolate (THF). This reaction might have a regulatory function towards reduced folate pools, de novo purine biosynthesis, and the flux of folate-bound methyl groups. To understand the role of the enzyme in cellular metabolism, Aldh1l1-/- mice were generated using an ES cell clone (C57BL/6N background) from KOMP repository. Though Aldh1l1-/- mice were viable and did not have an apparent phenotype, metabolomic analysis indicated that they had metabolic signs of folate deficiency. Specifically, the intermediate of the histidine degradation pathway and a marker of folate deficiency, formiminoglutamate, was increased more than 15-fold in livers of Aldh1l1-/- mice. At the same time, blood folate levels were not changed and the total folate pool in the liver was decreased by only 20%. A two-fold decrease in glycine and a strong drop in glycine conjugates, a likely result of glycine shortage, were also observed in Aldh1l1-/- mice. Our study indicates that in the absence of ALDH1L1 enzyme, 10-formyl-THF cannot be efficiently metabolized in the liver. This leads to the decrease in THF causing reduced generation of glycine from serine and impaired histidine degradation, two pathways strictly dependent on THF.