Metabolic Rewiring in Glioblastoma Cancer: EGFR, IDH and Beyond

Glioblastoma multiforme (GBM), a highly invasive and incurable tumor, is the humans’ foremost, commonest, and deadliest brain cancer. As in other cancers, distinct combinations of genetic alterations (GA) in GBM induce a diversity of metabolic phenotypes resulting in enhanced malignancy and altered sensitivity to current therapies. Furthermore, GA as a hallmark of cancer, dysregulated cell metabolism in GBM has been recently linked to the acquired GA. Indeed, Numerous point mutations and copy number variations have been shown to drive glioma cells’ metabolic state, affecting tumor growth and patient outcomes. Among the most common, IDH mutations, EGFR amplification, mutation, PTEN loss, and MGMT promoter mutation have emerged as key patterns associated with upregulated glycolysis and OXPHOS glutamine addiction and altered lipid metabolism in GBM. Therefore, current Advances in cancer genetic and metabolic profiling have yielded mechanistic insights into the metabolism rewiring of GBM and provided potential avenues for improved therapeutic modalities. Accordingly, actionable metabolic dependencies are currently used to design new treatments for patients with glioblastoma. Herein, we capture the current knowledge of genetic alterations in GBM, provide a detailed understanding of the alterations in metabolic pathways, and discuss their relevance in GBM therapy.

Electrical stimulation of primary olfactory nerve induces two types of variations in the extracellular potassium activity within the glomerulus of the rat olfactory bulb in vivo

Primary olfactory nerve stimulation induces a two-step increase in extracellular potassium, as recorded by K+-sensitive microelectrodes inserted into single glomeruli of the rat olfactory bulb. The second rise in K+ (K-peak) occurs in a graded, activity-dependent manner at the basal pole of the glomerular neuropile. This phenomenon appears to be directly related to the rate of extracellular K+ accumulation and is accompanied by a substantial depression of the mitral cell firing rate.

Evidence for an absence of K+ spread in the glomerular layer of the rat olfactory bulb

Using K+-sensitive microelectrodes inserted into the olfactory bulb, the effects of distant K+ ejection on the extracellular K+ activity (aK), were monitored in the glomerular and plexiform layers. A ouabain-sensitive mechanism, which appeared to be markedly more efficient in the glomerular layer, prevents spread of distal ejected K+. The results are discussed on the basis of Na+,K+-pump activation in both glomerular neuronal networks and the glial capsule enclosing each glomerulus.

Odorant-evoked potassium changes in the frog olfactory epithelium

Electroolfactogram (EOG) and extracellular potassium activity (aK) measurements were carried out in frog olfactory epithelia in vivo. Odorant-evoked changes in aK were characterized on the basis of depth profile analysis. Following an olfactory stimulation with butanol vapours, an increase in aK was measured in the mucus and the proximal part of the epithelium; this response started after the beginning of the EOG and was proportional to the amplitude of the latter. In the deeper part of the epithelium, the aK response had complex waveforms showing an initial K decrease which was suppressed by local application of ouabain, suggesting the existence of a pumping mechanism at this level. The results are discussed in terms of extracellular accumulation of K ions following neuroreceptor activation with respect to EOG generation theories.

Na+,K(+)-ATPase in the rat olfactory bulb: evidence for a higher enzymatic activity in the glomerular layer

Protein content and ATPase activities have been determined in the superficial and deep layers of the rat olfactory bulb. Protein levels, Mg2(+)-ATPase and Na+,K(+)-ATPase activities were significantly higher in the whole homogenate for the superficial layers. These differences were amplified when activity was expressed on a wet weight basis in a crude microsomal preparation isolated by differential centrifugation. Specific activities, however, showed similar values in the microsomal fractions from superficial and deep layers. The results are discussed in terms of differences in the density of neuronal processes and efficiency of K+ reuptake mechanisms.

Influence of GABA, baclofen and bicuculline on the extracellular K+ activity in the olfactory bulb of the developing rat

gamma-Aminobutyric acid (GABA) and baclofen were iontophoresed into the glomerular and plexiform layers of the olfactory bulb of rats at different ages. Subsequent changes in K+ activity and mitral cell firing rates were monitored to specify GABA receptor activation. Only bicuculline-insensitive receptors are shown to be already present in the glomerular layer of the newborn rat. The possible distribution and maturation of GABA receptors on the olfactory nerve endings or on the dendrites of the mitral or periglomerular cells is discussed.

HOXDeRNA activates a cancerous transcription program and super enhancers via genome-wide binding

The role of long non-coding RNAs (lncRNAs) in malignant cell transformation remains elusive. We previously identified an enhancer-associated lncRNA, LINC01116 (named HOXDeRNA), as a transformative factor converting human astrocytes into glioma-like cells. Employing a combination of CRISPR editing, chromatin isolation by RNA purification coupled with sequencing (ChIRP-seq), in situ mapping RNA-genome interactions (iMARGI), chromatin immunoprecipitation sequencing (ChIP-seq), HiC, and RNA/DNA FISH, we found that HOXDeRNA directly binds to CpG islands within the promoters of 35 glioma-specific transcription factors (TFs) distributed throughout the genome, including key stem cell TFs SOX2, OLIG2, POU3F2, and ASCL1, liberating them from PRC2 repression. This process requires a distinct RNA quadruplex structure and other segments of HOXDeRNA, interacting with EZH2 and CpGs, respectively. Subsequent transformation activates multiple oncogenes (e.g., EGFR, miR-21, and WEE1), driven by the SOX2- and OLIG2-dependent glioma-specific super enhancers. These results help reconstruct the sequence of events underlying the process of astrocyte transformation, highlighting HOXDeRNA's central genome-wide activity and suggesting a shared RNA-dependent mechanism in otherwise heterogeneous and multifactorial gliomagenesis.

Astrocyte-to-microglia communication via Sema4B-Plexin-B2 modulates injury-induced reactivity of microglia

After central nervous system injury, a rapid cellular and molecular response is induced. This response can be both beneficial and detrimental to neuronal survival in the first few days and increases the risk for neurodegeneration if persistent. Semaphorin4B (Sema4B), a transmembrane protein primarily expressed by cortical astrocytes, has been shown to play a role in neuronal cell death following injury. Our study shows that after cortical stab wound injury, cytokine expression is attenuated in Sema4B-/- mice, and microglia/macrophage reactivity is altered. In vitro, Sema4B enhances the reactivity of microglia following injury, suggesting astrocytic Sema4B functions as a ligand. Moreover, injury-induced microglia reactivity is attenuated in the presence of Sema4B-/- astrocytes compared to Sema4B+/- astrocytes. In vitro experiments indicate that Plexin-B2 is the Sema4B receptor on microglia. Consistent with this, in microglia/macrophage-specific Plexin-B2-/- mice, similar to Sema4B-/- mice, microglial/macrophage reactivity and neuronal cell death are attenuated after cortical injury. Finally, in Sema4B/Plexin-B2 double heterozygous mice, microglial/macrophage reactivity is also reduced after injury, supporting the idea that both Sema4B and Plexin-B2 are part of the same signaling pathway. Taken together, we propose a model in which following injury, astrocytic Sema4B enhances the response of microglia/macrophages via Plexin-B2, leading to increased reactivity.

New insights into the cardio-renal benefits of SGLT2 inhibitors and the coordinated role of miR-30 family

Sodium-glucose co-transporter inhibitors (SGLTis) are the latest class of anti-hyperglycemic agents. In addition to inhibiting the absorption of glucose by the kidney causing glycosuria, these drugs also demonstrate cardio-renal benefits in diabetic subjects. miR-30 family, one of the most abundant microRNAs in the heart, has recently been linked to a setting of cardiovascular diseases and has been proposed as novel biomarkers in kidney dysfunctions as well; their expression is consistently dysregulated in a variety of cardio-renal dysfunctions. The mechanistic involvement and the potential interplay between miR-30 and SGLT2i effects have yet to be thoroughly elucidated. Recent research has stressed the relevance of this cluster of microRNAs as modulators of several pathological processes in the heart and kidneys, raising the possibility of these small ncRNAs playing a central role in various cardiovascular complications, notably, endothelial dysfunction and pathological remodeling. Here, we review current evidence supporting the pleiotropic effects of SGLT2is in cardiovascular and renal outcomes and investigate the link and the coordinated implication of the miR-30 family in endothelial dysfunction and cardiac remodeling. We also discuss the emerging role of circulating miR-30 as non-invasive biomarkers and attractive therapeutic targets for cardiovascular diseases and kidney diseases. Clinical evidence, as well as metabolic, cellular, and molecular aspects, are comprehensively covered.

Reducing Alzheimer's disease risk with SGLT2 inhibitors: From glycemic control to neuroprotection

Recent research has established a strong link between metabolic abnormalities and an increased risk of dementia. In parallel, there is growing epidemiological evidence supporting the neuroprotective effects of antidiabetic medications against cognitive impairments. Among these, sodium-glucose co-transporter (SGLT2) inhibitors have emerged as pharmacological candidates with promising potential in alleviating the burden of age-related diseases, particularly neurodegenerative diseases (NDD). SGLT2 inhibitor therapies are FDA-approved medications routinely prescribed to manage diabetes. This novel class was initially developed to address cardiovascular disorders and to reduce the risk of hypoglycemia associated with insulin-secretagogue agents. It subsequently attracted growing interest for its beneficial effects on central nervous system (CNS) disorders. However, the molecular mechanisms through which these glucose-lowering therapies mitigate cognitive decline and limit the progression of certain brain degenerative diseases remain largely unexplored. Consequently, the neuroscientific community needs further studies that gather, analyze, and critically discuss the available mechanistic evidence regarding the neuroprotective effects of SGLT2 inhibitors. This review aims to critically examine the most relevant published findings, both in vitro and in vivo, as well as human studies evaluating the impact of SGLT2 inhibitors exposure on Alzheimer's disease (AD). It seeks to integrate the current understanding of their beneficial effects at the molecular level and their role in addressing the pathophysiology and neuropathology of AD. These insights will help extend our knowledge of how SGLT2 inhibitor therapies are associated with reduced risk of dementia and thus shed light on the link between diabetes and AD.