Magnetic Resonance Imaging of Iron Metabolism with T2* Mapping Predicts an Enhanced Clinical Response to Pharmacologic Ascorbate in Patients with GBM.

PURPOSE: Pharmacologic ascorbate (P-AscH-) is hypothesized to be an iron (Fe)-dependent tumor-specific adjuvant to chemoradiation in treating glioblastoma (GBM). This study determined the efficacy of combining P-AscH- with radiation and temozolomide in a phase II clinical trial while simultaneously investigating a mechanism-based, noninvasive biomarker in T2* mapping to predict GBM response to P-AscH- in humans. PATIENTS AND METHODS: The single-arm phase II clinical trial (NCT02344355) enrolled 55 subjects, with analysis performed 12 months following the completion of treatment. Overall survival (OS) and progression-free survival (PFS) were estimated with the Kaplan-Meier method and compared across patient subgroups with log-rank tests. Forty-nine of 55 subjects were evaluated using T2*-based MRI to assess its utility as an Fe-dependent biomarker. RESULTS: Median OS was estimated to be 19.6 months [90% confidence interval (CI), 15.7-26.5 months], a statistically significant increase compared with historic control patients (14.6 months). Subjects with initial T2* relaxation < 50 ms were associated with a significant increase in PFS compared with T2*-high subjects (11.2 months vs. 5.7 months, P < 0.05) and a trend toward increased OS (26.5 months vs. 17.5 months). These results were validated in preclinical in vitro and in vivo model systems. CONCLUSIONS: P-AscH- combined with temozolomide and radiotherapy has the potential to significantly enhance GBM survival. T2*-based MRI assessment of tumor iron content is a prognostic biomarker for GBM clinical outcomes. See related commentary by Nabavizadeh and Bagley, p. 255.

Vitamin D status and its association with insulin resistance among type 2 diabetics: A case -control study in Ghana.

BACKGROUND: Vitamin D plays a major role in physiological processes that modulate mineral metabolism and immune function with probable link to several chronic and infectious conditions. Emerging data suggests a possible influence of vitamin D on glucose homeostasis. This study sought to provide preliminary information on vitamin D status among Ghanaian type 2 diabetics and assessed its association with glucose homeostasis. METHODS: In a case control study, 118 clinically diagnosed Type 2 Diabetes Mellitus (T2DM) patients attending Diabetic Clinic at the Nkawie Government Hospital were enrolled between October and December 2015. Hundred healthy non-diabetics living in Nkawie district were selected as controls. Structured questionnaires were administered to obtain socio-demographic data. Venous blood samples were taken from both cases and controls to estimate their FBG, Lipid profile spectrophotometrically and IPTH, 25OHD by ELISA. Statistical analyses were performed using SPSS v20.0 Statistics. RESULTS: The average age of the study participants was 58.81years for cases and 57.79year for controls. There was vitamin D deficiency of 92.4% among T2DM cases and 60.2% among the non diabetic controls. Vitamin D deficiency did not significantly associate with HOMA-ß [T2DM: r2 = 0.0209, p = 0.1338 and Control: r2 = 0.0213, p = 0.2703] and HOMA-IR [T2DM: r2 = 0.0233, p = 0.1132 and Control: r2 = 0.0214, p = 0.2690] in both the controls and the cases. CONCLUSION: Vitamin D deficiency is prevalent in both T2DM and non-diabetics. There is no association between vitamin D deficiency and insulin resistance or beta cell function in our study population. Vitamin D supplementation among type 2 diabetics is recommended.

Role of NADPH oxidase and xanthine oxidase in mediating inducible VT/VF and triggered activity in a canine model of myocardial ischemia.

BACKGROUND: Ventricular tachycardia or fibrillation (VT/VF) of focal origin due to triggered activity (TA) from delayed afterdepolarizations (DADs) is reproducibly inducible after anterior coronary artery occlusion. Both VT/VF and TA can be blocked by reducing reactive oxygen species (ROS). We tested the hypothesis that inhibition of NADPH oxidase and xanthine oxidase would block VT/VF. METHODS: 69 dogs received apocynin (APO), 4 mg/kg intraveneously (IV), oxypurinol (OXY), 4 mg/kg IV, or both APO and OXY (BOTH) agents, or saline 3 h after coronary occlusion. Endocardium from ischemic sites (3-D mapping) was sampled for Rac1 (GTP-binding protein in membrane NADPH oxidase) activation or standard microelectrode techniques. Results (mean±SE, * p<0.05): VT/VF originating from ischemic zones was blocked by APO in 6/10 *, OXY in 4/9 *, BOTH in 5/8 * or saline in 1/27; 11/16 VT/VFs blocked were focal. In isolated myocardium, TA was blocked by APO (10(-6) M) or OXY (10(-8) M). Rac1 levels in ischemic endocardium were decreased by APO or OXY. CONCLUSION: APO and OXY suppressed focal VT/VF due to DADs, but the combination of the drugs was not more effective than either alone. Both drugs inhibited ischemic Rac1 with inhibition by OXY suggesting ROS-induced ROS. The inability to totally prevent VT/VF suggests that other mechanisms also contribute to ischemic VT.

Association among intracardiac T-wave alternans, ischemia, and spontaneous ventricular arrhythmias after coronary artery occlusion in a canine model.

T-wave alternans (TWA) has been investigated as a marker for susceptibility to lethal ventricular arrhythmia. In this article, we studied intracardiac TWA and ischemia as predictors of spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF) in a canine model of coronary artery occlusion (CAO). Anesthetized, open-chest dogs were studied. Electrograms from intracardiac bipolar electrodes (IBEs) were assessed for TWA and spontaneous VT or VF. TWA was defined on IBE as T wave voltage change on every other complex. In each heart, we examined 62 electrograms measured in the risk zone and surrounding normal sites, filtered from 3 to 1300 Hz. Ischemia was measured as percent of all IBE recorded that had QRS voltage drop >45%. Mapping localized the three-dimensional origin of spontaneous VT or VF. The data from dogs with VF (n = 5), VT (n = 8), or controls (no VT or VF, n = 8) were analyzed before left CAO, at the 20th min after CAO and times immediately preceding VT and VF. We found a correlation between intracardiac TWA and ischemia. More importantly, increases in intracardiac TWA peaked immediately preceding spontaneous VF and VT and were significantly higher compared to controls at comparable times. At VT/VF origins and adjacent sites, the mean TWA magnitude and discordance of TWA distinguished between VT/VF and controls at comparable times but not between VT and VF or between reentry and focal mechanisms. TWA was more common than ischemia at VT/VF origins. In summary, changes in intracardiac TWA and ischemia correlate with impending spontaneous VT/VF in a clinically applicable canine model of CAO.

Specific recognition of Rac2 and Cdc42 by DOCK2 and DOCK9 guanine nucleotide exchange factors.

Recognition of cognate Rho GTPases by guanine-nucleotide exchange factors (GEF) is fundamental to Rho GTPase signaling specificity. Two main GEF families use either the Dbl homology (DH) or the DOCK homology region 2 (DHR-2) catalytic domain. How DHR-2-containing GEFs distinguish between the GTPases Rac and Cdc42 is not known. To determine how these GEFs specifically recognize the two Rho GTPases, we studied the amino acid sequences in Rac2 and Cdc42 that are crucial for activation by DOCK2, a Rac-specific GEF, and DOCK9, a distantly related Cdc42-specific GEF. Two elements in the N-terminal regions of Rac2 and Cdc42 were found to be essential for specific interactions with DOCK2 and DOCK9. One element consists of divergent amino acid residues in the switch 1 regions of the GTPases. Significantly, these residues were also found to be important for GTPase recognition by Rac-specific DOCK180, DOCK3, and DOCK4 GEFs. These findings were unexpected because the same residues were shown previously to interact with GTPase effectors rather than GEFs. The other element comprises divergent residues in the beta3 strand that are known to mediate specific recognition by DH domain containing GEFs. Remarkably, Rac2-to-Cdc42 substitutions of four of these residues were sufficient for Rac2 to be specifically activated by DOCK9. Thus, DOCK2 and DOCK9 specifically recognize Rac2 and Cdc42 through their switch 1 as well as beta2-beta3 regions and the mode of recognition via switch 1 appears to be conserved among diverse Rac-specific DHR-2 GEFs.

Ngly1, a mouse gene encoding a deglycosylating enzyme implicated in proteasomal degradation: expression, genomic organization, and chromosomal mapping.

In species as diverse as yeast and mammals, peptide:N-glycanase (PNG1 in yeast; Ngly1 in mouse) is believed to play a key role in the degradation of misfolded glycoproteins by the proteasome. In this study, we report the genomic organization and mRNA distribution of the mouse Ngly1. Mouse Ngly1 spans 61kb and is composed of 12 exons, the organization of which is conserved throughout vertebrates. Comparison of the mouse and human genomic sequence identifies a conserved gene structure with significant sequence similarity extending into introns. A 2.6kb Ngly1 message was detected in all mouse tissues examined, with the highest abundance in the testis. In addition, a lower molecular weight transcript of 2.4kb was detected in the testis. From analysis of dbESTs the alternative transcript of Ngly1 is predicted to be present in the human placenta. Given the key role Ngly1 plays in glycoprotein degradation, we predict that Ngly1 may be a contributing factor in "disease" susceptibility. To begin to address this question, we used radiation hybrid mapping to localize mouse Ngly1 to chromosome 14 and the human orthologue to chromosome 3 with a strong link with known genes.