18F-Fluorodeoxyglucose Positron Emission Tomography Tracks the Heterogeneous Brain Susceptibility to the Hyperglycemia-Related Redox Stress

CSF amino acid profiles in ICV-streptozotocin-induced sporadic Alzheimer's disease in male Wistar rat: a metabolomics and systems biology perspective

Alzheimer's disease (AD) is an increasingly important public health concern due to the increasing proportion of older individuals within the general population. The impairment of processes responsible for adequate brain energy supply primarily determines the early features of the aging process. Restricting brain energy supply results in brain hypometabolism prior to clinical symptoms and is anatomically and functionally associated with cognitive impairment. The present study investigated changes in metabolic profiles induced by intracerebroventricular-streptozotocin (ICV-STZ) in an AD-like animal model. To this end, male Wistar rats received a single injection of STZ (3 mg·kg-1) by ICV (2.5 μL into each ventricle for 5 min on each side). In the second week after receiving ICV-STZ, rats were tested for cognitive performance using the Morris Water Maze test and subsequently prepared for positron emission tomography (PET) to confirm AD-like symptoms. Tandem Mass Spectrometry (MS/MS) analysis was used to detect amino acid changes in cerebrospinal fluid (CFS) samples. Our metabolomics study revealed a reduction in the concentrations of various amino acids (alanine, arginine, aspartic acid, glutamic acid, glycine, isoleucine, methionine, phenylalanine, proline, serine, threonine, tryptophane, tyrosine, and valine) in CSF of ICV-STZ-treated animals as compared to controls rats. The results of the current study indicate amino acid levels could potentially be considered targets of nutritional and/or pharmacological interventions to interfere with AD progression.

Cyclic fasting bolsters cholesterol biosynthesis inhibitors' anticancer activity

Identifying oncological applications for drugs that are already approved for other medical indications is considered a possible solution for the increasing costs of cancer treatment. Under the hypothesis that nutritional stress through fasting might enhance the antitumour properties of at least some non-oncological agents, by screening drug libraries, we find that cholesterol biosynthesis inhibitors (CBIs), including simvastatin, have increased activity against cancers of different histology under fasting conditions. We show fasting's ability to increase CBIs' antitumour effects to depend on the reduction in circulating insulin, insulin-like growth factor-1 and leptin, which blunts the expression of enzymes from the cholesterol biosynthesis pathway and enhances cholesterol efflux from cancer cells. Ultimately, low cholesterol levels through combined fasting and CBIs reduce AKT and STAT3 activity, oxidative phosphorylation and energy stores in the tumour. Our results support further studies of CBIs in combination with fasting-based dietary regimens in cancer treatment and highlight the value of fasting for drug repurposing in oncology.

Crosstalk between the Rod Outer Segments and Retinal Pigmented Epithelium in the Generation of Oxidative Stress in an In Vitro Model

Dysfunction of the retinal pigment epithelium (RPE) is associated with several diseases characterized by retinal degeneration, such as diabetic retinopathy (DR). However, it has recently been proposed that outer retinal neurons also participate in the damage triggering. Therefore, we have evaluated the possible crosstalk between RPE and photoreceptors in priming and maintaining oxidative damage of the RPE. For this purpose, we used ARPE-19 cells as a model of human RPE, grown in normal (NG, 5.6 mM) or high glucose (HG, 25 mM) and unoxidized (UOx) or oxidized (Ox) mammalian retinal rod outer segments (OSs). ARPE-19 cells were efficient at phagocytizing rod OSs in both NG and HG settings. However, in HG, ARPE-19 cells treated with Ox-rod OSs accumulated MDA and lipofuscins and displayed altered LC3, GRP78, and caspase 8 expression compared to untreated and UOx-rod-OS-treated cells. Data suggest that early oxidative damage may originate from the photoreceptors and subsequently extend to the RPE, providing a new perspective to the idea that retinal degeneration depends solely on a redox alteration of the RPE.

Mutated FANCA Gene Role in the Modulation of Energy Metabolism and Mitochondrial Dynamics in Head and Neck Squamous Cell Carcinoma

Fanconi Anaemia (FA) is a rare recessive genetic disorder characterized by a defective DNA repair mechanism. Although aplastic anaemia is the principal clinical sign in FA, patients develop a head and neck squamous cell carcinoma (HNSCC) with a frequency 500–700 folds higher than the general population, which appears more aggressive, with survival of under two years. Since FA gene mutations are also associated with a defect in the aerobic metabolism and an increased oxidative stress accumulation, this work aims to evaluate the effect of FANCA mutation on the energy metabolism and the relative mitochondrial quality control pathways in an HNSCC cellular model. Energy metabolism and cellular antioxidant capacities were evaluated by oximetric, luminometric, and spectrophotometric assays. The dynamics of the mitochondrial network, the quality of mitophagy and autophagy, and DNA double-strand damage were analysed by Western blot analysis. Data show that the HNSCC cellular model carrying the FANCA gene mutation displays an altered electron transport between respiratory Complexes I and III that does not depend on the OxPhos protein expression. Moreover, FANCA HNSCC cells show an imbalance between fusion and fission processes and alterations in autophagy and mitophagy pathways. Together, all these alterations associated with the FANCA gene mutation cause cellular energy depletion and a metabolic switch to glycolysis, exacerbating the Warburg effect in HNSCC cells and increasing the growth rate. In addition, the altered DNA repair due to the FANCA mutation causes a higher accumulation of DNA damage in the HNSCC cellular model. In conclusion, changes in energy metabolism and mitochondrial dynamics could explain the strict correlation between HNSCC and FA genes, helping to identify new therapeutic targets.

Effect of metformin on 18F-fluorodeoxyglucose uptake and positron emission tomographic imaging

Metformin is widely used to treat diabetes, but induces changes in glucose uptake in both normal organs and tumors. Here, we review the effects of metformin on the uptake of ¹⁸F-fludeoxyglucose (¹⁸F-FDG) in tissues and tumors, and its influence on ¹⁸F-FDG positron emission tomographic imaging (¹⁸F-FDG PET), as well as the mechanisms involved. This is an important issue, because metformin has diverse effects on tissue uptake of ¹⁸F-FDG, and this can affect the quality and interpretation of PET images. Metformin increases glucose uptake in the gastrointestinal tract, cerebral white matter, and the kidney, while regions of the cerebrum associated with memory show decreased glucose uptake, and the myocardium shows no change. Hepatocellular carcinoma and breast cancer show increased glucose uptake after metformin administration, while thyroid cancer shows decreased uptake, and colon and pancreatic cancers show no change. A high-energy diet increases ¹⁸F-FDG uptake, but this effect is blocked by metformin. Withdrawal of metformin 48 h before PET image acquisition is widely recommended. However, based on our review of the literature, we propose that the differentiation of metformin discontinuation could be reasonable. But future clinical trials are still needed to support our viewpoint.

The Role of Endoplasmic Reticulum in the Differential Endurance against Redox Stress in Cortical and Spinal Astrocytes from the Newborn SOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis

Recent studies reported that the uptake of [18F]-fluorodeoxyglucose (FDG) is increased in the spinal cord (SC) and decreased in the motor cortex (MC) of patients with ALS, suggesting that the disease might differently affect the two nervous districts with different time sequence or with different mechanisms. Here we show that MC and SC astrocytes harvested from newborn B6SJL-Tg (SOD1^G93A) 1Gur mice could play different roles in the pathogenesis of the disease. Spectrophotometric and cytofluorimetric analyses showed an increase in redox stress, a decrease in antioxidant capacity and a relative mitochondria respiratory uncoupling in MC SOD1^G93A astrocytes. By contrast, SC mutated cells showed a higher endurance against oxidative damage, through the increase in antioxidant defense, and a preserved respiratory function. FDG uptake reproduced the metabolic response observed in ALS patients: SOD1^G93A mutation caused a selective enhancement in tracer retention only in mutated SC astrocytes, matching the activity of the reticular pentose phosphate pathway and, thus, of hexose-6P dehydrogenase. Finally, both MC and SC mutated astrocytes were characterized by an impressive ultrastructural enlargement of the endoplasmic reticulum (ER) and impairment in ER–mitochondria networking, more evident in mutated MC than in SC cells. Thus, SOD1^G93A mutation differently impaired MC and SC astrocyte biology in a very early stage of life.