A rare case of Brugada syndrome induced by hyperglycemia

Brugada syndrome is a rare genetic disorder of the cardiac sodium channels associated with an increased risk of sudden cardiac death. It is characterized by an electrocardiogram (EKG) showing a right bundle branch block with an elevation in the ST segment. This condition is associated with mutations in several pathologic genes including the most notable mutation in the SCN5A gene, which encodes for a voltage-gated cardiac sodium channel. The Brugada pattern on EKG can be spontaneous but can also be induced by a variety of etiologies including fever, electrolyte abnormalities, increased vagal tone and drugs such as sodium channel blockers, calcium channel blockers, tricyclic antidepressants and alcohol. One uncommon cause of Brugada syndrome is hyperglycemia. Of particular importance in diabetic patients, hyperglycemia can induce chronic cardiovascular complications as well as acute cardiac events via the induction of the Brugada pattern on EKG. We present a case of a 21-year-old non-insulin compliant diabetic man presenting to the Emergency Department with diabetic ketoacidosis (DKA) who exhibits the Brugada pattern EKG prior to developing ventricular tachycardia followed by cardiac arrest. The patient’s condition was induced by prolonged hyperglycemia in the setting of DKA with relatively mild electrolyte and pH abnormalities. Herein, this case is presented to highlight the Brugada pattern leading to cardiac arrest as a potential consequence of hyperglycemia and inform physicians on its incidence.

Selective Deletion of Heparan Sulfotransferase Enzyme, Ndst1, in Donor Endothelial and Myeloid Precursor Cells Significantly Decreases Acute Allograft Rejection

Early damage to transplanted organs initiates excess inflammation that can cause ongoing injury, a leading cause for late graft loss. The endothelial glycocalyx modulates immune reactions and chemokine-mediated haptotaxis, potentially driving graft loss. In prior work, conditional deficiency of the glycocalyx-modifying enzyme N-deacetylase-N-sulfotransferase-1 (Ndst1^f/f TekCre⁺) reduced aortic allograft inflammation. Here we investigated modification of heparan sulfate (HS) and chemokine interactions in whole-organ renal allografts. Conditional donor allograft Ndst1 deficiency (Ndst1^−/−; C57Bl/6 background) was compared to systemic treatment with M-T7, a broad-spectrum chemokine-glycosaminoglycan (GAG) inhibitor. Early rejection was significantly reduced in Ndst1^−/− kidneys engrafted into wildtype BALB/c mice (Ndst1^+/+) and comparable to M-T7 treatment in C57Bl/6 allografts (P < 0.0081). M-T7 lost activity in Ndst1^−/− allografts^, while M-T7 point mutants with modified GAG-chemokine binding displayed a range of anti-rejection activity. CD3+ T cells (P < 0.0001), HS (P < 0.005) and CXC chemokine staining (P < 0.012), gene expression in NFκB and JAK/STAT pathways, and HS and CS disaccharide content were significantly altered with reduced rejection. Transplant of donor allografts with conditional Ndst1 deficiency exhibit significantly reduced acute rejection, comparable to systemic chemokine-GAG inhibition. Modified disaccharides in engrafted organs correlate with reduced rejection. Altered disaccharides in engrafted organs provide markers for rejection with potential to guide new therapeutic approaches in allograft rejection.

C/EBPbeta, when expressed from the C/ebpalpha gene locus, can functionally replace C/EBPalpha in liver but not in adipose tissue

Knockout of C/EBPalpha causes a severe loss of liver function and, subsequently, neonatal lethality in mice. By using a gene replacement approach, we generated a new C/EBPalpha-null mouse strain in which C/EBPbeta, in addition to its own expression, substituted for C/EBPalpha expression in tissues. The homozygous mutant mice C/ebpalpha(beta/beta) are viable and fertile and show none of the overt liver abnormalities found in the previous C/EBPalpha-null mouse line. Levels of hepatic PEPCK mRNA are not different between C/ebpalpha(beta/beta) and wild-type mice. However, despite their normal growth rate, C/ebpalpha(beta/beta) mice have markedly reduced fat storage in their white adipose tissue (WAT). Expression of two adipocyte-specific factors, adipsin and leptin, is significantly reduced in the WAT of C/ebpalpha(beta/beta) mice. In addition, expression of the non-adipocyte-specific genes for transferrin and cysteine dioxygenase is reduced in WAT but not in liver. Our study demonstrates that when expressed from the C/ebpalpha gene locus, C/EBPbeta can act for C/EBPalpha to maintain liver functions during development. Moreover, our studies with the C/ebpalpha(beta/beta) mice provide new insights into the nonredundant functions of C/EBPalpha and C/EBPbeta on gene regulation in WAT.

The role of HNF-1alpha in controlling hepatic catalase activity

Mice deficient in hepatocyte nuclear factor 1alpha (HNF-1alpha) develop Laron dwarfism and non-insulin-dependent diabetes mellitus (Lee et al., 1998). Oxidative stress was present in the diabetic HNF-1alpha-null mice. To understand the mechanism underlying the oxidative stress in HNF-1alpha-null mice, we examined whether HNF-1alpha deficiency affects the integrity of the cellular defense system against oxidative stress. The glutathione level and activities of superoxide dismutase and glutathione reductase in liver and other tissues examined were not affected by HNF-1alpha deficiency. However, activities of cytosolic glutathione peroxidase and catalase, two enzymes responsible for detoxification of hydrogen peroxide within cells, were reduced specifically in liver of HNF-1alpha-null mice. The mRNA and protein levels of hepatic catalase in HNF-1alpha-null mice did not differ from those in normal mice. The loss of hepatic catalase activity in HNF-1alpha-null mice is probably caused by an insufficient heme pool in liver cells, because the mRNA level of ferrochelatase, the enzyme that catalyzes the last step of heme biosynthesis, was significantly reduced in liver, and the daily hemin treatment restored partial catalase activity in liver of HNF-1alpha-null mice. Furthermore, our results of cell transfection and luciferase reporter assay indicated that the mouse ferrochelatase promoter could be trans-activated directly by HNF-1alpha.