Carcinogenic Krebs-Cycle Enzyme Mutations Supporting Ketolytic-Dependent Tumors

Tumors incorporate much glucose for overcoming glycolytic pyruvate-kinase and pyruvate-dehydrogenase inhibitions; they form lactate, rather than oxidative acetyl-CoA. Tumors also need to synthetize fatty acids, which automatically turns-off their mitochondrial degradation into acetyl-CoA. Thus, ketolysis becomes their major acetyl-CoA supply. Carcinogenic mutations or deficiencies of Krebs-cycle enzymes support the ketolytic dependency of tumors.

Changes in energetic metabolism and lysosomal destruction in the skeletal muscle and cardiac tissues of pigeons (Columba livia f. urbana) from urban areas of the northern Pomeranian region (Poland)

The aim of the present study was to evaluate the biochemical responses of the skeletal muscle and cardiac tissues of the urban pigeon as a bioindicator organism tested in diverse environments (Szpęgawa as a rural environment and Słupsk as an urban environment, Pomeranian Voivodeship, northern Poland), resulting in changes in the level of lipid peroxidation at the initial and final stages of this process and the activities of Krebs cycle enzymes (succinate dehydrogenase, pyruvate dehydrogenase, isocitrate dehydrogenase, and alfa-ketoglutarate dehydrogenase). Szpęgawa village was chosen due to the intensive use of the European motorway A1 with significant traffic and pollution levels. The concentration of Pb was higher in the soil and feathers of pigeons nesting in the polluted areas (Szpęgawa). Our studies have shown that the presence of lead in soil and feathers of the pigeons resulted in the activation of lipid peroxidation, destabilization and increased activity of lysosomal membranes, and activation of mitochondrial enzymes of the Krebs cycle with energy deficiency (reduction of ATP levels) in cardiac and skeletal muscle tissues simultaneously.

Novel Germline SUCLG2 Mutations in Patients With Pheochromocytoma and Paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from neural crest cells that are frequently linked to mutations including those in Krebs cycle enzymes, particularly succinate dehydrogenase (SDH). Succinyl-CoA ligase (SUCL) catalyzes reversible conversion of succinyl-CoA to succinate providing the substrate for SDH. While mitochondrial diseases were documented for the mutations in SUCL subunits G1 and A2, the association of GDP/GTP-specific subunit SUCLG2 mutations with specific pathologies including cancer have not been reported. In our study, 352 patients with apparently sporadic PPGLs underwent genetic testing using a panel of 54 genes developed at the National Institutes of Health. Additionally, human pheochromocytoma (hPheo1) cells were used for gene manipulation to produce SUCLG2 knock-out (KO). Tumor tissues and hPheo1 SUCLG2 KO cells were used for further analysis focusing on mechanism of germline variants effect on mitochondrial functions. We detected eight germline SUCLG2 mutations in 15 patients which represents 4.3% of the cohort. Germline variants together with LOH led to decreased levels of SDH subunit B resulting in aberrant respiration and accumulation of succinate, well recognized oncometabolite. Manipulation of SUCLG2 in hPheo1 cells confirmed decrease in SDHB leading to faulty assembly of mitochondrial complex II and alteration of its respiration and activity. In summary, our study identified an association between SUCLG2 and PPGL. Larger scale sequencing and uncovering additional cases bearing SUCLG2 variants will further clarify the relationship between SUCLG2 and SDHx, particularly SDHB, as well as their role in disease etiology.

Dietary Mg2+ Intake and the Na+/Mg2+ Exchanger SLC41A1 Influence Components of Mitochondrial Energetics in Murine Cardiomyocytes

Cardiomyocytes are among the most energy-intensive cell types. Interplay between the components of cellular magnesium (Mg) homeostasis and energy metabolism in cardiomyocytes is poorly understood. We have investigated the effects of dietary Mg content and presence/functionality of the Na+/Mg2+ exchanger SLC41A1 on enzymatic functions of selected constituents of the Krebs cycle and complexes of the electron transport chain (ETC). The activities of aconitate hydratase (ACON), isocitrate dehydrogenase (ICDH), α-ketoglutarate dehydrogenase (KGDH), and ETC complexes CI–CV have been determined in vitro in mitochondria isolated from hearts of wild-type (WT) and Slc41a1−/− mice fed a diet with either normal or low Mg content. Our data demonstrate that both, the type of Mg diet and the Slc41a1 genotype largely impact on the activities of enzymes of the Krebs cycle and ETC. Moreover, a compensatory effect of Slc41a1−/− genotype on the effect of low Mg diet on activities of the tested Krebs cycle enzymes has been identified. A machine-learning analysis identified activities of ICDH, CI, CIV, and CV as common predictors of the type of Mg diet and of CII as suitable predictor of Slc41a1 genotype. Thus, our data delineate the effect of dietary Mg content and of SLC41A1 functionality on the energy-production in cardiac mitochondria.

Role of mitochondria in the differential action of sodium deoxycholate and ursodeoxycholic acid on rat duodenum

Sodium deoxycholate (NaDOC) inhibits the intestinal Ca2+ absorption and ursodeoxycholic acid (UDCA) stimulates it. The aim of this study was to determine whether NaDOC and UDCA produce differential effects on the redox state of duodenal mitochondria altering the Krebs cycle and the electron transport chain (ETC) functioning, which could lead to perturbations in the mitochondrial dynamics and biogenesis. Rat intestinal mitochondria were isolated from untreated and treated animals with either NaDOC, UDCA, or both. Krebs cycle enzymes, ETC components, ATP synthase, and mitochondrial dynamics and biogenesis markers were determined. NaDOC decreased isocitrate dehydrogenase (ICDH) and malate dehydrogenase activities affecting the ETC and ATP synthesis. NaDOC also induced oxidative stress and increased the superoxide dismutase activity and impaired the mitochondrial biogenesis and functionality. UDCA increased the activities of ICDH and complex II of ETC. The combination of both bile acids conserved the functional activities of Krebs cycle enzymes, ETC components, oxidative phosphorylation, and mitochondrial biogenesis. In conclusion, the inhibitory effect of NaDOC on intestinal Ca2+ absorption is mediated by mitochondrial dysfunction, which is avoided by UDCA. The stimulatory effect of UDCA alone is associated with amelioration of mitochondrial functioning. This knowledge could improve treatment of diseases that affect the intestinal Ca2+ absorption.

Biochemical and Physiological Effects of Some Organic and Inorganic Chemical Agents in Capsicum spp.

Cultivation of vegetables is expected to increase in order to meet the demands of the expanding populations of the globe. Meanwhile, anthropic activities increase the concentrations of various chemical compounds in aquatic and terrestrial habitats. For productivity and food safety reasons, assessments of effects of pesticides and metals on crops should be performed. In the current paper, the presence of some heavy metals and a pesticide compound in the substrate altered the levels of some Krebs cycle enzymes activities in pepper plants cultivated in controlled conditions. The photosynthetic apparatus of the same plants appeared relatively unaffected, while the potential/actual soil dehydrogenases ratios were increased in all treatments.

Influence of oxygen on the Warburg effect: do cancer cells produce lactate only from glucose?

The common characteristics of many tumors is phenomenon termed the Warburg effect – the production of abundant amounts of lactate in the presence of sufficient oxygen. It is commonly accepted that lactate is synthesized from glucose; hence, the other term for this phenomenon is aerobic glycolysis. Hypoxia, frequently observed in solid tumors, results in an increased HIF 1 transcription factor activity, which stimulates lactate synthesis by activating the transcription of glucose transporters and glycolytic enzymes genes, while inhibiting mitochondrial pyruvate metabolism. However, under normoxic conditions, when the HIF-1 factor is inactive, the lactate is the product not only of glycolysis, but also of glutaminolysis. Both pathways are activated by the c-myc transcription factor. Glutaminolysis, the mitochondrial pathway involving Krebs cycle enzymes, provides energy to the cell and the pathway intermediates (L-glutamate, L-aspartate, acetyl CoA) are substrates for the synthesis of nucleic acids, proteins and lipids. Subsequently, the cytoplasmic oxaloacetate-malate-pyruvate-lactate axis provides redox cofactors - NADPH for lipid and DNA synthesis and for cellular antioxidant systems as well as NAD+ necessary for efficient glycolysis resulting in increased lactate synthesis from glucose at normoxia. Thus, oxygen as Krebs cycle activator enhances lactate synthesis as the end product of glutaminolysis as well as promotes glycolytic lactate synthesis. In conclusion, the Warburg effect is the result of oxygen-induced extensive lactate production in both glycolysis and glutaminolysis pathways. Thus, an increased lactate synthesis at normoxia is just not the result of the cellular shift to extramitochondrial metabolism, but a manifestation of transcriptionally regulated adaptive response, allowing the cancer cells to acquire the energy and nutrients necessary for growth and proliferation.

Diffuse Gliomas for Nonneuropathologists: The New Integrated Molecular Diagnostics

Diffuse gliomas comprise the bulk of “brain cancer” in adults. The recent update to the 4th edition of the World Health Organization's classification of tumors of the central nervous system reflects an unprecedented change in the landscape of the diagnosis and management of diffuse gliomas that will affect all those involved in the management and care of patients. Of the recently discovered gene alterations, mutations in the Krebs cycle enzymes isocitrate dehydrogenases (IDHs) 1 and 2 have fundamentally changed the way the gliomas are understood and classified. Incorporating information on a few genetic parameters (IDH, ATRX and/or p53, and chromosome 1p19q codeletion), a relatively straightforward diagnostic algorithm has been generated with robust and reproducible results that correlate with patients' survival far better than relying on conventional histology alone. Evidence also supports the conclusion that the vast majority of diffuse gliomas without IDH mutations (IDH–wild-type astrocytomas) behave like IDH–wild-type glioblastomas (“molecular GBM”). Together, these changes reflect a big shift in the practice of diagnostic neuropathology in which tumor risk stratification aligns better with molecular information than histology/grading. The purpose of this review is to provide the readers with a brief synopsis of the changes in the 2016 World Health Organization update with an emphasis on diffuse gliomas and to summarize key gene abnormalities on which these classifications are based. Practical points involved in day-to-day diagnostic workup are also discussed, along with a comparison of the various diagnostic tests, including immunohistochemistry, with an emphasis on targeted next-generation sequencing panel technology as a future universal approach.