A Roundtable seminar involving three Department of Biochemistry faculty members from the Sapienza University of Rome, all of whom do research on Alzheimer disease and Down syndrome (persons with DS nearly always exhibit Alzheimer disease neuropathology in brain and dementia later in life).

Prof. Fabio Di Domenico: Department of Biochemical Sciences “A. Rossi-Fanelli” - Sapienza University of Rome

Title: “Protein O-GlcNAc modification in the central nervous system: from nutrient sensing to the development of Alzheimer disease signatures.”

Abstract: Protein O-GlcNAc modification is a dynamic non-canonical form of protein O-Glycosylation considered a rheostat of cellular reprogramming under differential metabolic conditions. Alterations of nutrient availability in the brain, as observed in Alzheimer Disease and in other neurodegenerative disorders, lead to aberrant O-GlcNAc levels and trigger the development of neuropathological signatures. We analyzed by proteomics approaches the total and protein-specific levels of O-GlcNacylation, the O-GlcNAc cycling and the development of AD signatures in mouse models of both AD-like dementia (DS mice) and metabolic disease (high fat diet mice). Data on DS mice supported the presence of altered hippocampal O-GlcNAc levels and their implications in the AD-related neurodegenerative process. Accordingly, metabolic defects observed in high fat diet (HFD) mice promoted the impairment of protein O-GlcNAcylation, eventually resulting in mitochondrial defects, reduced energy consumption and in the development of AD signatures. By testing the effects of the O-GlcNAcylation inducer Thiamet-G to rescue brain alterations and AD development, we demonstrated its beneficial effect on cognition associated with the recovery of O-GlcNAc levels of protein belonging to key functional pathways, such as, neuronal architecture, stress response mechanisms and energy production. Our studies clarified the molecular mechanisms by which reduced protein O-GlcNAcylation promote the progression of brain pathology, thus laying the foundations to understand the main processes linking metabolic defects and neurodegenerative processes

Bio: Fabio Di Domenico is Full professor of Biochemistry at Sapienza University of Rome. He obtained his PhD degree in Biochemistry in 2009. Before gaining his current position, he performed his research under the supervision of Prof. Butterfield at University of Kentucky, where he has been involved in the application of redox proteomics to brain samples from Alzheimer patients. His research is currently focused in understanding the mechanisms that associates the alteration of protein homeostasis with the development of Alzheimer-like dementia. Collected data from his laboratory postulate that aberrant proteostasis, observed in both Alzheimer and Down syndrome patients, is strictly associated with the increase of oxidative damage as result of compromised antioxidant response and faulty protein degradative systems. Recently, his studies revealed that the reduction a nutrient sensing protein post translational modification, O-GlcNAc, might represents a key molecular link between metabolic defect and the development of Alzheimer Disease signatures.

Prof. Eugenio Barone: Sapienza University of Rome

Title: “Insulin signaling alterations impair mitochondrial bioenergetics in the brain: identification of a novel molecular mechanism linking metabolic and neurodegenerative diseases.”

Abstract: Brain insulin signaling acts as a key regulator for gene expression and cellular metabolism, both events sustaining neuronal activity and synaptic plasticity mechanisms. Alterations of this pathway, known as brain insulin resistance, are associated with an increased risk of developing age-related cognitive decline and neurodegeneration. Studies from our group and in collaboration with Dr. Butterfield's group uncovered the role of the enzyme biliverdin reductase A (BVRA) that, beyond its activity in the degradation pathway of heme, is a novel regulator of the insulin signaling. BVRA is a direct target of the insulin receptor (IR), similar to the insulin receptor substrate-1 (IRS1). IR phosphorylates BVRA on specific Tyr residues and activates BVRA to function as a Ser/Thr/Tyr kinase. Moreover, downstream from IRS1, BVRA works as a scaffold protein favoring: the translocation of GLUT4-containing vesicles to the plasma membrane (to increase glucose uptake in response to insulin), the AKT-mediated inhibition of GSK3β (that promotes cell survival) and the AMPK-mediated inhibition of MTOR (that is involved in autophagy). Moreover, we recently discovered that BVRA regulates mitochondrial bioenergetics in response to insulin, thus supporting cell metabolism. Ground-breaking findings from our group revealed that oxidative stress-induced impairment of BVRA is a key event driving insulin resistance development either in the brain or in peripheral tissues. Conversely, rescuing BVRA activity reduces oxidative stress levels and ameliorate brain insulin signaling activation, both events contributing to improved cognitive functions in animal models of neurodegeneration.  Overall, our data suggest that dysfunctions of BVRA are responsible for increased oxidative stress levels and the impairment of insulin signaling. Alterations of BVRA also impair energy metabolism thus contributing to create a harmful synergistic effect triggering the development of neurodegeneration.   

Bio: Graduated in Pharmaceutical Chemistry and Technology in 2006 and got a PhD in Neuroscience in 2011. The overarching goal of his laboratory is to clarify the link between defects of neurotrophic signaling (insulin and GLP1) and increased cell damage during ageing and neurodegeneration. During the last years his research also focused on Down syndrome demonstrating for the first time that brain insulin resistance develops very early in DS, independently of peripheral alterations [Neurobiol Dis (2020); Free Rad Biol Med (2021); Alzheimer’s and Dementia (2021)].  Dr. Barone authored 92 publications, most of which dealing with the role of oxidative stress in neurodegenerative disorders, i.e., Alzheimer disease and DS. He was recipient of prestigious grants from the Alzheimer Association (2020-24), Jerome Lejeune Foundation (2019-21 and 2022-24), European Commission (2014-16) and Italian Ministry of Research (2015-18), among the others. Dr. Barone was one of the firsts two recipients of the SFRBM fellowship Awards (2010) while he was a visiting PhD student in the lab of Dr. Allan Butterfield at the University of Kentucky, and recipient of many international awards including those from:  SFRBM (2015 and 2016), EPHAR (2013), AAIC (2017) and T21RS (2017). In 2021 he was appointed as co-chair for the European Brain Research Area (EBRA) for the Trisomy 21 cluster. He serves as chair of the Strategic Alliances & Outreach Committee of the SfRBM and the chair of the Sponsoring and Membership Committee of the T21RS.

Dr. Antonella Tramutola: Department of Biochemical Sciences - Sapienza University of Rome

Title: “Intranasal insulin administration ameliorates learning and memory deficits by rescuing protein oxidative stress damage in Alzheimer disease.”

Abstract: Brain insulin resistance (bIR) heavily impacts on the core pathological processes of aging and Alzheimer disease (AD) since insulin regulates brain metabolism and cognitive functions. A close link among bIR, oxidative stress (OS) and mitochondrial defects exists, that contributes to brain dysfunctions observed in AD. Intriguingly, several studies suggest that intranasal insulin (INI) administration enhances cognitive performances and reduced AD neuropathology both in humans and animal models of neurodegeneration. We focused on the interplay between OS and bIR, by testing the hypothesis that rescuing brain insulin signaling activation by the mean of INI results in improved mitochondrial functions and reduced OS-induced damage to proteins and lipids in the brain of 3xTg-AD mice (a model of AD).

Methods. 12-month-old 3×Tg-AD and wild-type (non-Tg) mice were treated with INI (2 UI) or vehicle (saline) every other day for 2 months. At the end of the treatment mice underwent cognitive tests and then sacrificed to collected brain samples for biochemical analyses. Insulin signaling pathway and OS marker levels, i.e., PC, 4-HNE and 3-NT were evaluated in the frontal cortex. A redox proteomics approach was used to identify specific protein targets of 3-NT modifications. Mitochondrial functions were evaluated by measuring mitochondrial complexes (OXPHOS) protein levels and activities.

Results and Conclusions. INI administration led to a significant improvement of cognitive functions along with an amelioration of insulin signaling activation and reduced OS levels in 3xTg-AD mice. In particular, a consistent reduction of 3-NT levels was observed. Redox proteomics allowed to identify several proteins with reduced 3-NT modifications, that belong to key pathways, such as protein degradation and energy metabolism, known to be involved in the progression of AD. Remarkably, reduced 3-NT levels on mitochondrial proteins were responsible for the observed improvement of mitochondrial activity and brain energy metabolism in 3xTg-AD mice. We propose that INI represents a promising approach to reduce proteins OS-induced damage and restore mitochondrial bioenergetics in AD brain.

Bio: Antonella Tramutola is Assistant Professor of Biochemistry at the Department of Biochemical Sciences at Sapienza University of Rome. She obtained her PhD in Neuroscience at the Catholic University School of Medicine in Rome. In 2014, she spent 1 year as visiting researcher at Department of Chemistry at the University of Kentucky hosted by Professor D. Allan Butterfield. Her research is focused on exploring the role of the proteostasis network in neuronal death in Alzheimer Disease (AD) and Down Syndrome (DS), as they share common pathological hallmarks. She is examining the dysfunction of components of the protein quality control system, caused by oxidative damage, and the pathways involved in proteostasis such as mTOR signaling, the insulin cascade, and the autophagy-proteasome system. Through studying post-mortem brain tissue, cell culture, and animal models of AD or DS, her research is aimed at identifying common and divergent mechanisms of neurodegeneration. This could lead to investigating how these pathways could be targeted therapeutically to prevent neurodegenerative phenomena in DS and AD