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Objective: The mitochondrial nicotinamide adenine dinucleotide (NAD) kinase (MNADK) mediates de novo mitochondrial NADP biosynthesis by catalyzing the phosphorylation of NAD to yield NADP. In this study, we investigated the function and mechanistic basis by which MNADK regulates metabolic homeostasis. Methods: Generalized gene set analysis by aggregating human patient genomic databases, metabolic studies with genetically engineered animal models, mitochondrial bioenergetic analysis, as well as gain- and loss- of-function studies were performed to address the functions and mechanistic basis by which MNADK regulates energy metabolism and redox state associated with metabolic disease. Results: Human MNADK common gene variants or decreased expression of the gene are significantly associated with the occurrence of type-2 diabetes, non-alcoholic fatty liver disease (NAFLD), or hepatocellular carcinoma (HCC). Ablation of the MNADK gene in mice led to decreased fat oxidation, coincident with increased respiratory exchange ratio (RER) and decreased energy expenditure upon energy demand triggered by endurance exercise or fasting. On an atherogenic high-fat diet (HFD), MNADK-null mice exhibited hepatic insulin resistance and glucose intolerance, indicating a type-2 diabetes-like phenotype in the absence of MNADK. MNADK deficiency led to a decrease in mitochondrial NADP(H) but an increase in cellular reactive oxygen species (ROS) in mouse livers. Consistently, protein levels of the major metabolic regulators or enzymes were decreased, while their acetylation modifications were increased in the livers of MNADK-null mice. Feeding mice with a HFD caused S-nitrosylation (SNO) modification, a posttranslational modification that represses protein activities, on MNADK protein in the liver. Reconstitution of an SNO-resistant MNADK variant, MNADK-S193, into MNADK-null mice mitigated hepatic steatosis induced by HFD. Conclusion: MNADK, the only known mammalian mitochondrial NAD kinase, plays important roles in preserving energy homeostasis to mitigate the risk of metabolic disorders.

Fusarium graminearum is a major global pathogen of cereals and is considered the main causal agent of Fusarium head blight disease in wheat. Infection with Fusarium graminearum causes a significant reduction in crop yield and quality; therefore, it is very important to improve wheat pathogen resistance. In the present study, the plasmid pAHCht-2 harboring the rice chitinase (Cht-2) gene for pathogen resistance and the plasmid pAB6 containing the gus reporter and bar selectable marker genes were used for genetic transformation of immature embryo-derived calli of the Egyptian wheat cultivar Giza 164 using particle bombardment. Associated changes in defense mechanisms in the transgenic plants were investigated. The transgenic plants had significantly decreased total protein content, phenolic compounds and antioxidant enzyme activities (peroxidase and catalase), and significantly increased phenylalanine ammonia lyase and chitinase activities compared with non-transgenic plants under biotic stress conditions caused by F. graminearum infection. Our results show that activating a specific program of gene expression related to environmental stress conditions can reduce the cost of the stress on plant metabolism.

Retinal hyperpermeability and subsequent macular edema is a cardinal feature of early diabetic retinopathy (DR). Here, we investigated the role of bioactive lipid metabolites, in particular 12/15-lipoxygenase (LOX)-derived metabolites, in this process. LC/MS lipidomic screen of human retinal endothelial cells (HRECs) demonstrated that 15-HETE was the only significantly increased metabolite (2.4 ± 0.4-fold, P = 0.0004) by high glucose (30 mM) treatment. In the presence of arachidonic acid, additional eicosanoids generated by 12/15-LOX, including 12- and 11-HETEs, were significantly increased. Fluorescein angiography and retinal albumin leakage showed a significant decrease in retinal hyperpermeability in streptozotocin-induced diabetic mice lacking 12/15-LOX compared with diabetic WT mice. Our previous studies demonstrated the potential role of NADPH oxidase in mediating the permeability effect of 12- and 15-HETEs, therefore we tested the impact of intraocular injection of 12-HETE in mice lacking the catalytic subunit of NADPH oxidase (NOX2). The permeability effect of 12-HETE was significantly reduced in NOX2−/− mice compared with the WT mice. In vitro experiments also showed that 15-HETE induced HREC migration and tube formation in a NOX-dependent manner. Taken together our data suggest that 12/15-LOX is implicated in DR via a NOX-dependent mechanism.

Background/Aim: Hepatic injury is a hallmark adverse reaction to Valproate (VPA), a common used drug in the management of numerous CNS disorders, including epilepsy. DHA has a myriad of health benefits, including renal- and hepato-protective effects. Unfortunately, however, the underpinnings of such liver-pertinent VPA- and DHA-actions remain largely undefined. Accordingly, this study attempted to unveil the cellular and molecular triggers whereby VPA evokes, while DHA abates, hepatotoxicity. Methods: We evaluated activity and/or expression of cellular markers of oxidative stress, inflammation, and apoptosis in rat liver, following treatment with VPA (500 mg/kg/day) with and without concurrent treatment with DHA (250 mg/kg/day) for two weeks. Results and conclusion: VPA promoted hepatic oxidative stress as evidenced by enhancing activity/expression of NADPH-oxidase and its subunits, a ROS-generator, and by accumulation of lipid-peroxides. Moreover, VPA enhanced hepatic phosphorylation/activation of mitogen-activated protein kinase (MAPK), and expression of cyclooxygenase-2(COX-2), as proinflammatory signals. Besides, VPA promoted hepatocellular apoptosis, as attested by enhanced expression of cleaved caspase-9 and increased number of TUNEL-positive hepatocytes. Lastly, VPA upregulated levels of hypoxia-inducible factor-1-alpha (HIF-1α), a multifaceted modulator of hepatocytic biology, and activity of its downstream antioxidant enzyme heme-oxygenase-1(HO-1). These changes were significantly blunted by co-administration of DHA. Our findings demonstrate that VPA activated NADPH-oxidase and HIF-1α to induce oxidative-stress and hypoxia as initiators of hepatic injury. These changes were further aggravated by up-regulation of inflammatory (MAPK and COX-2) and apoptotic cascades, but could be partly lessened by HO-1 activation. Concurrent administration of DHA mitigated all VPA-induced anomalies.