Molecular mechanisms of enhanced [18F] fluorodeoxy glucose (FDG) uptake in isochemically injured myocardium: the role of glucose transporter and hexokinase expression. Final technical report for period August 1, 1993--November 30, 1997

We determined that there were no regional differences in GLUT1 or GLUT4 expression in normal dog heart. We demonstrated that glucose uptake was relatively enhanced in regions of severe ischemia in this model. We showed that GLUT1 mRNA and polypeptide expression but not GLUT4 expression were substantially and significantly increased in both ischemic and nonischemic myocardial regions after 6 hours. We also found that GLUT4 translocation and glucose uptake induced by ischemia in perfused rat hearts were not inhibited by Wortmannin, a PI3 kinase inhibitor, whereas insulin-stimulatd increases in GLUT4 translocation and glucose uptake were inhibited. To determine whether some of the same phenomena occurred in humans with chronic myocardial ischemia, we investigated myocardial GLUT mRNA expression in 11 patients who underwent coronary artery bypass surgery. We have cultured neonatal rat cardiomyocytes and tested the effects of several factors including hypoxia and insulin

Characterization of sodium channel alpha- and beta-subunits in rat and mouse cardiac myocytes.

BACKGROUND: Sodium channels isolated from mammalian brain are composed of alpha-, beta(1)-, and beta(2)-subunits. The composition of sodium channels in cardiac muscle, however, has not been defined, and disagreement exists over which beta-subunits are expressed in the myocytes. Some investigators have demonstrated beta(1) expression in heart. Others have not detected any auxiliary subunits. On the basis of Northern blot analysis of total RNA, beta(2) expression has been thought to be exclusive to neurons and absent from cardiac muscle. METHODS AND RESULTS: The goal of this study was to define the subunit composition of cardiac sodium channels in myocytes. We show that cardiac sodium channels are composed of alpha-, beta(1)-, and beta(2)-subunits. Nav1.5 and Nav1.1 are expressed in myocytes and are associated with beta(1)- and beta(2)-subunits. Immunocytochemical localization of Nav1.1, beta(1), and beta(2) in adult heart sections showed that these subunits are expressed at the Z lines, as shown previously for Nav1.5. Coexpression of Nav1.5 with beta(2) in transfected cells resulted in no detectable changes in sodium current. CONCLUSIONS: Cardiac sodium channels are composed of alpha- (Nav1.1 or Nav1.5), beta(1)-, and beta(2)-subunits. Although beta(1)-subunits modulate cardiac sodium channel current, beta(2)-subunit function in heart may be limited to cell adhesion

Transcriptomic analysis of diabetic kidney disease and neuropathy in mouse models of type 1 and type 2 diabetes

Diabetic kidney disease (DKD) and diabetic peripheral neuropathy (DPN) are common complications of type 1 (T1D) and type 2 (T2D) diabetes. However, the mechanisms underlying pathogenesis of these complications are unclear. In this study, we optimized a streptozotocin-induced db/+ murine model of T1D and compared it to our established db/db T2D mouse model of the same C57BLKS/J background. Glomeruli and sciatic nerve transcriptomic data from T1D and T2D mice were analyzed by self-organizing map and differential gene expression analysis. Consistent with prior literature, pathways related to immune function and inflammation were dysregulated in both complications in T1D and T2D mice. Gene-level analysis identified a high degree of concordance in shared differentially expressed genes (DEGs) in both complications and across diabetes type when using mice from the same cohort and genetic background. As we have previously shown a low concordance of shared DEGs in DPN when using mice from different cohorts and genetic backgrounds, this suggests that genetic background may influence diabetic complications. Collectively, these findings support the role of inflammation and indicate that genetic background is important in complications of both T1D and T2D. © 2023 Company of Biologists Ltd. All rights reserved.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The deacylase sirtuin 5 reduces malonylation in nonmitochondrial metabolic pathways in diabetic kidney disease

Early diabetic kidney disease (DKD) is marked by dramatic metabolic reprogramming due to nutrient excess, mitochondrial dysfunction, and increased renal energy requirements from hyperfiltration. We hypothesized that changes in metabolism in DKD may be regulated by Sirtuin 5 (SIRT5), a deacylase that removes posttranslational modifications derived from acyl-coenzyme A and has been demonstrated to regulate numerous metabolic pathways. We found decreased malonylation in the kidney cortex (∼80% proximal tubules) of type 2 diabetic BKS db/db mice, associated with increased SIRT5 expression. We performed a proteomics analysis of malonylated peptides and found that proteins with significantly decreased malonylated lysines in the db/db cortex were enriched in nonmitochondrial metabolic pathways: glycolysis and peroxisomal fatty acid oxidation. To confirm relevance of these findings in human disease, we analyzed diabetic kidney transcriptomic data from a cohort of Southwestern American Indians, which revealed a tubulointerstitial-specific increase in Sirt5 expression. These data were further corroborated by immunofluorescence data of SIRT5 from nondiabetic and DKD cohorts. Furthermore, overexpression of SIRT5 in cultured human proximal tubules demonstrated increased aerobic glycolysis. Conversely, we observed reduced glycolysis with decreased SIRT5 expression. These findings suggest that SIRT5 may lead to differential nutrient partitioning and utilization in DKD. Taken together, our findings highlight a previously unrecognized role for SIRT5 in metabolic reprogramming in DKD. © 2023 The AuthorsOpen access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]