Drug-induced hyperinsulinemic hypoglycemia: An update on pathophysiology and treatment

The initial step for the differential diagnosis of hypoglycemia is to determine whether it is hyperinsulinemic or non hyperinsulinemic. Existing literature discusses drug-related hypoglycemia, but it misses a focus on drug-induced hyperinsulinemic hypoglycemia (DHH). Here we reviewed the association existing between drugs and hyperinsulinemic hypoglycemia. We primarily selected on the main electronic databases (MEDLINE, EMBASE, Web of Science, and SCOPUS) the reviews on drug-induced hypoglycemia. Among the drugs listed in the reviews, we selected the ones linked to an increase in insulin secretion. For the drugs missing a clear association with insulin secretion, we investigated the putative mechanism underlying hypoglycemia referring to the original papers. Our review provides a list of the most common agents associated with hyperinsulinemic hypoglycemia (HH), in order to facilitate both the recognition and the prevention of DHH. We also collected data about the responsiveness of DHH to diazoxide or octreotide.

Drug-Induced Hypoglycemia in Neonates Born to Nondiabetic Women Treated with Medications during the Pregnancy or the Labor: A Systematic Review of the Literature

The prompt identification of at-risk newborns for drug-induced hypoglycemia can minimize the risk for adverse side effects, inappropriate investigations, and considerable unnecessary costs. Existing literature discusses drug-induced hypoglycemia, but a systematic description of neonatal hypoglycemia induced or exacerbated by maternal medications is missing. We reviewed the association between neonatal hypoglycemia and maternal medications. We systematically searched the literature according to the PICOS model on drug-induced hypoglycemia in neonates born to nondiabetic women treated with medications during the pregnancy or the labor. The main outcomes of the review were: (1) prevalence of hypoglycemia, (2) risk factors and potential confounders, (3) time at onset and severity of hypoglycemia, (4) dose-response gradient, (5) metabolic features of hypoglycemia, (6) modalities to treat hypoglycemia, and (7) quality of the studies. We included 69 studies in this review and we identified 11 groups of maternal drugs related to neonatal hypoglycemia. Results were classified for each outcome. Our review aims at supporting clinicians in the identification of the newborn at risk for hypoglycemia and in the differential diagnosis of neonatal hypoglycemia. Further studies are necessary to assess the risk of neonatal hypoglycemia associated with common maternal medications. KEY POINTS: · A systematic description of neonatal hypoglycemia induced or exacerbated by maternal medications is missing.. · In our review we identified 11 groups of maternal drugs related to neonatal hypoglycemia.. · Our review aims at supporting clinicians in the identification of the newborn at risk for hypoglycemia..

The Role of IgLON Cell Adhesion Molecules in Neurodegenerative Diseases

In the brain, cell adhesion molecules (CAMs) are critical for neurite outgrowth, axonal fasciculation, neuronal survival and migration, and synapse formation and maintenance. Among CAMs, the IgLON family comprises five members: Opioid Binding Protein/Cell Adhesion Molecule Like (OPCML or OBCAM), Limbic System Associated Membrane Protein (LSAMP), neurotrimin (NTM), Neuronal Growth Regulator 1 (NEGR1), and IgLON5. IgLONs exhibit three N-terminal C2 immunoglobulin domains; several glycosylation sites; and a glycosylphosphatidylinositol anchoring to the membrane. Interactions as homo- or heterodimers in cis and in trans, as well as binding to other molecules, appear critical for their functions. Shedding by metalloproteases generates soluble factors interacting with cellular receptors and activating signal transduction. The aim of this review was to analyse the available data implicating a role for IgLONs in neuropsychiatric disorders. Starting from the identification of a pathological role for antibodies against IgLON5 in an autoimmune neurodegenerative disease with a poorly understood mechanism of action, accumulating evidence links IgLONs to neuropsychiatric disorders, albeit with still undefined mechanisms which will require future thorough investigations.

Negr1-Derived Peptides Trigger ALK Degradation and Halt Neuroblastoma Progression In Vitro and In Vivo

Neuroblastoma is among the most common childhood cancers. Neuroblastoma in advanced stages is one of the most intractable pediatric cancers, notwithstanding the recent therapeutic advances. ALK mutations are among the leading cause of hereditary neuroblastoma and account for more than 14% of the somatically acquired alterations. ALK kinase activity is currently one of the main targets for pharmacological strategies. However, evidence from ALK fusion-positive lung cancer studies has shown that resistance to ALK inhibition arises during the therapy, causing a relapse within several years. IgLONs are membrane-bound proteins involved in cell-to-cell adhesion. The expression of the IgLON family results altered in different cancers. We found that the IgLON member Negr1 is downregulated in neuroblastoma. The ectopic overexpression of Negr1 impairs neuroblastoma growth in vitro and in vivo. Negr1 exists as a GPI-anchored membrane-bound protein and as a soluble protein released upon metalloprotease cleavage. We generated and characterized a panel of Negr1-derived peptides. The treatment with Negr1 protein and derived peptides induce ALK downregulation and halt neuroblastoma progression in vitro and in vivo.

Changes in gut microbiota composition after 12 weeks of a home-based lifestyle intervention in breast cancer survivors during the COVID-19 lockdown

Background

Breast cancer (BC) is the second-leading cause of cancer-related death worldwide. This study aimed to investigate the effects of a 12-week home-based lifestyle intervention (based on nutrition and exercise) on gut microbial composition in twenty BC survivors of the MoviS clinical trial (protocol: NCT04818359).

Methods

Gut microbiota analysis through 16S rRNA gene sequencing, anthropometrics, Mediterranean Diet (MD) adherence, and cardiometabolic parameters were evaluated before (Pre) and after (Post) the lifestyle intervention (LI).

Results

Beneficial effects of the LI were observed on MD adherence, and cardiometabolic parameters (pre vs post). A robust reduction of Proteobacteria was observed after LI, which is able to reshape the gut microbiota by modulating microorganisms capable of decreasing inflammation and others involved in improving the lipid and glycemic assets of the host. A significant negative correlation between fasting glucose and Clostridia_vadinBB60 (r = -0.62), insulin and homeostatic model assessment (HOMA) index and Butyricicoccus genera (r = -0.72 and -0.66, respectively), and HDL cholesterol and Escherichia/Shigella (r = -0.59) have been reported. Moreover, positive correlations were found between MD adherence and Lachnospiraceae_ND3007 (r = 0.50), Faecalibacterium (r = 0.38) and Butyricimonas (r = 0.39).

Conclusion

These data suggest that adopting a healthy lifestyle, may contribute to ameliorate several biological parameters that could be involved in the prevention of cancer relapses through the modulation of gut microbiota.

Nucleoporin Nup358 Downregulation Tunes the Neuronal Excitability in Mouse Cortical Neurons

Nucleoporins (NUPs) are proteins that comprise the nuclear pore complexes (NPCs). The NPC spans the nuclear envelope of a cell and provides a channel through which RNA and proteins move between the nucleus and the cytoplasm and vice versa. NUP and NPC disruptions have a great impact on the pathophysiology of neurodegenerative diseases (NDDs). Although the downregulation of Nup358 leads to a reduction in the scaffold protein ankyrin-G at the axon initial segment (AIS) of mature neurons, the function of Nup358 in the cytoplasm of neurons remains elusive. To investigate whether Nup358 plays any role in neuronal activity, we downregulated Nup358 in non-pathological mouse cortical neurons and measured their active and passive bioelectrical properties. We identified that Nup358 downregulation is able to produce significant modifications of cell-membrane excitability via voltage-gated sodium channel kinetics. Our findings suggest that Nup358 contributes to neuronal excitability through a functional stabilization of the electrical properties of the neuronal membrane. Hypotheses will be discussed regarding the alteration of this active regulation as putatively occurring in the pathophysiology of NDDs.

Understanding the Pathogenesis of Cardiac Complications in Patients with Propionic Acidemia and Exploring Therapeutic Alternatives for Those Who Are Not Eligible or Are Waiting for Liver Transplantation

The guidelines for the management of patients affected by propionic acidemia (PA) recommend standard cardiac therapy in the presence of cardiac complications. A recent revision questioned the impact of high doses of coenzyme Q10 on cardiac function in patients with cardiomyopathy (CM). Liver transplantation is a therapeutic option for several patients since it may stabilize or reverse CM. Both the patients waiting for liver transplantation and, even more, the ones not eligible for transplant programs urgently need therapies to improve cardiac function. To this aim, the identification of the pathogenetic mechanisms represents a key point. Aims: This review summarizes: (1) the current knowledge of the pathogenetic mechanisms underlying cardiac complications in PA and (2) the available and potential pharmacological options for the prevention or the treatment of cardiac complications in PA. To select articles, we searched the electronic database PubMed using the Mesh terms "propionic acidemia" OR "propionate" AND "cardiomyopathy" OR "Long QT syndrome". We selected 77 studies, enlightening 12 potential disease-specific or non-disease-specific pathogenetic mechanisms, namely: impaired substrate delivery to TCA cycle and TCA dysfunction, secondary mitochondrial electron transport chain dysfunction and oxidative stress, coenzyme Q10 deficiency, metabolic reprogramming, carnitine deficiency, cardiac excitation-contraction coupling alteration, genetics, epigenetics, microRNAs, micronutrients deficiencies, renin-angiotensin-aldosterone system activation, and increased sympathetic activation. We provide a critical discussion of the related therapeutic options. Current literature supports the involvement of multiple cellular pathways in cardiac complications of PA, indicating the growing complexity of their pathophysiology. Elucidating the mechanisms responsible for such abnormalities is essential to identify therapeutic strategies going beyond the correction of the enzymatic defect rather than engaging the dysregulated mechanisms. Although these approaches are not expected to be resolutive, they may improve the quality of life and slow the disease progression. Available pharmacological options are limited and tested in small cohorts. Indeed, a multicenter approach is mandatory to strengthen the efficacy of therapeutic options.

An Integrated Approach to Skeletal Muscle Health in Aging

A decline in muscle mass and function represents one of the most problematic changes associated with aging, and has dramatic effects on autonomy and quality of life. Several factors contribute to the inexorable process of sarcopenia, such as mitochondrial and autophagy dysfunction, and the lack of regeneration capacity of satellite cells. The physiologic decline in muscle mass and in motoneuron functionality associated with aging is exacerbated by the sedentary lifestyle that accompanies elderly people. Regular physical activity is beneficial to most people, but the elderly need well-designed and carefully administered training programs that improve muscle mass and, consequently, both functional ability and quality of life. Aging also causes alteration in the gut microbiota composition associated with sarcopenia, and some advances in research have elucidated that interventions via the gut microbiota-muscle axis have the potential to ameliorate the sarcopenic phenotype. Several mechanisms are involved in vitamin D muscle atrophy protection, as demonstrated by the decreased muscular function related to vitamin D deficiency. Malnutrition, chronic inflammation, vitamin deficiencies, and an imbalance in the muscle-gut axis are just a few of the factors that can lead to sarcopenia. Supplementing the diet with antioxidants, polyunsaturated fatty acids, vitamins, probiotics, prebiotics, proteins, kefir, and short-chain fatty acids could be potential nutritional therapies against sarcopenia. Finally, a personalized integrated strategy to counteract sarcopenia and maintain the health of skeletal muscles is suggested in this review.

Movement and health beyond care, MoviS: study protocol for a randomized clinical trial on nutrition and exercise educational programs for breast cancer survivors

BACKGROUND

Breast cancer (BC) is the most common invasive cancer in women, and exercise can significantly improve the outcomes of BC survivors. MoviS (Movement and Health Beyond Care) is a randomized controlled trial aimed to evaluate the potential health benefits of exercise and proper nutritional habits. This study aims to assess the efficacy of aerobic exercise training in improving quality of life (QoL) and health-related factors in high-risk BC.

METHODS

One hundred seventy-two BC survivor women, aged 30-70 years, non-metastatic, stage 0-III, non-physically active, 6-12 months post-surgery, and post chemo- or radiotherapy, will be recruited in this study. Women will be randomly allocated to the intervention arm (lifestyle recommendations and MoviS Training) or control arm (lifestyle recommendations). The MoviS training consists of 12 weeks of aerobic exercise training (2 days/week of supervised and 1 day/week of unsupervised exercise) with a progressive increase in exercise intensity (40-70% of heart rate reserve) and duration (20-60 min). Both arms will receive counseling on healthy lifestyle habits (nutrition and exercise) based on the World Cancer Research Fund International (WCRF) 2018 guidelines. The primary outcome is the improvement of the QoL. The secondary outcomes are improvement of health-related parameters such as Mediterranean diet adherence, physical activity level, flexibility, muscular fitness, fatigue, cardiorespiratory fitness (estimated maximal oxygen uptake), echocardiographic parameters, heart rate variability (average of the standard deviations of all 5 min normal to normal intervals (ASDNN/5 min) and 24 h very low and low frequency), and metabolic, endocrine, and inflammatory serum biomarkers (glycemia, insulin resistance, progesterone, testosterone, and high-sensitivity C-reactive protein).

DISCUSSION

This trial aims to evaluate if supervised exercise may improve QoL and health-related factors of BC survivors with a high risk of recurrence. Findings from this project could provide knowledge improvement in the field of exercise oncology through the participation of a multidisciplinary team that will provide a coordinated program of cancer care to improve healthcare quality, improve prognosis, increase survival times and QoL, and reduce the risk of BC recurrence.

TRIAL REGISTRATION

ClinicalTrials.gov  NCT04818359 . Retrospectively registered on March 26, 2021.

A narrative review on pathogenetic mechanisms of hyperinsulinemic hypoglycemia in Kabuki syndrome

Objective. Kabuki syndrome (KS) is associated with hyperinsulinemic hypoglycemia (HH) in 0.3-4% of patients, thus exceeding the prevalence in the general population. HH association is stronger for KS type 2 (KDM6A-KS, OMIM #300867) than KS type 1 (KMT2D-KS, OMIM #147920). Both the disease-associated genes, KMD6A and KMT2D, modulate the chromatin dynamic. As such, KS is considered to be the best characterized pediatric chromatinopathy. However, the exact pathogenetic mechanisms leading to HH in this syndrome remain still unclear. Methods. We selected on the electronic database PubMed all articles describing or hypothesizing the mechanisms underlying the dysregulated insulin secretion in KS. Results. The impact on the gene expression due to the KDM6A or KMT2D function loss may lead to a deregulated pancreatic β-cell differentiation during embryogenesis. Moreover, both KMT2D gene and KDM6A gene are implicated in promoting the transcription of essential pancreatic β-cell genes and in regulating the metabolic pathways instrumental for insulin release. Somatic KMT2D or KDM6A mutations have also been described in several tumor types, including insulinoma, and have been associated with metabolic pathways promoting pancreatic cell proliferation. Conclusions. The impact of pathogenic variants in KDM6A and KDM2D genes on β-cell insulin release remains to be fully clarified. Understanding this phenomenon may provide valuable insight into the physiological mechanisms of insulin release and into the pathological cascade causing hyperinsulinism in KS. The identification of these molecular targets may open new therapeutic opportunities based on epigenetic modifiers.

Interventions on Gut Microbiota for Healthy Aging

In recent years, the improvement in health and social conditions has led to an increase in the average lifespan. Since aging is the most important risk factor for the majority of chronic human diseases, the development of therapies and intervention to stop, lessen or even reverse various age-related morbidities is an important target to ameliorate the quality of life of the elderly. The gut microbiota, that is, the complex ecosystem of microorganisms living in the gastrointestinal tract, plays an important role, not yet fully understood, in maintaining the host's health and homeostasis, influencing metabolic, oxidative and cognitive status; for this reason, it is also named "the forgotten endocrine organ" or "the second brain". On the other hand, the gut microbiota diversity and richness are affected by unmodifiable factors, such as aging and sex, and modifiable ones, such as diet, pharmacological therapies and lifestyle. In this review, we discuss the changes, mostly disadvantageous, for human health, induced by aging, in microbiota composition and the effects of dietary intervention, of supplementation with probiotics, prebiotics, synbiotics, psychobiotics and antioxidants and of physical exercise. The development of an integrated strategy to implement microbiota health will help in the goal of healthy aging.

Effect of individual characteristics and aerobic training on the %HRR-%V˙O2R relationship

This study aimed to assess if, during incremental exercise, considering individual characteristics can make the relationship between the percentages of heart rate (HRR) and oxygen uptake (VO₂R) reserve either 1:1 or more accurate. Cycle ergometer data of the maximal incremental exercise tests performed by 450 healthy and sedentary participants (17-66 years) of the HERITAGE Family Study, grouped for sex, ethnicity, age, body fat, resting HR, and VO_2max, were used to calculate the individual linear regressions between %HRR and %VO₂R. The mean slope and intercept of the individual linear regressions of each subgroup were compared with 1 and 0 (identity line), respectively, using Hotelling tests followed by post-hoc one-sample t-tests. Two multiple linear regressions were also performed, using either the slopes or intercepts of the individual linear regressions as dependent variables and sex, age, resting HR, and VO_2max as independent variables. The mean %HRR-%VO₂R relationships of all subgroups differed from the identity line. Moreover, individual linear regression intercepts (8.9±16.0) and slopes (0.971±0.190) changed (p<0.001) after 20 weeks of aerobic training (13.1±11.1 and 0.891±0.122). The multiple linear regressions could explain only 3.8% and 1.3% of the variance in the intercepts and slopes, whose variability remained high (standard error of estimate of 15.8 and 0.189). In conclusion, the %HRR-%VO₂R relationship differs from the identity line regardless of individual characteristics and their difference increased after aerobic training. Moreover, due to the high interindividual variability, using a single equation for the whole population seems not suitable for representing the %HRR-%VO₂R relationship of a given subject, even when several individual characteristics are considered.

Trafficking of the glutamate transporter is impaired in LRRK2-related Parkinson's disease

The Excitatory Amino Acid Transporter 2 (EAAT2) accounts for 80% of brain glutamate clearance and is mainly expressed in astrocytic perisynaptic processes. EAAT2 function is finely regulated by endocytic events, recycling to the plasma membrane and degradation. Noteworthy, deficits in EAAT2 have been associated with neuronal excitotoxicity and neurodegeneration. In this study, we show that EAAT2 trafficking is impaired by the leucine-rich repeat kinase 2 (LRRK2) pathogenic variant G2019S, a common cause of late-onset familial Parkinson’s disease (PD). In LRRK2 G2019S human brains and experimental animal models, EAAT2 protein levels are significantly decreased, which is associated with elevated gliosis. The decreased expression of the transporter correlates with its reduced functionality in mouse LRRK2 G2019S purified astrocytic terminals and in Xenopus laevis oocytes expressing human LRRK2 G2019S. In LRRK2 G2019S knock-in mouse brain, the correct surface localization of the endogenous transporter is impaired, resulting in its interaction with a plethora of endo-vesicular proteins. Mechanistically, we report that pathogenic LRRK2 kinase activity delays the recycling of the transporter to the plasma membrane via Rabs inactivation, causing its intracellular re-localization and degradation. Taken together, our results demonstrate that pathogenic LRRK2 interferes with the physiology of EAAT2, pointing to extracellular glutamate overload as a possible contributor to neurodegeneration in PD.

Effect of steady-state aerobic exercise intensity and duration on the relationship between reserves of heart rate and oxygen uptake

Background

The percentages of heart rate (%HRR) or oxygen uptake (%V̇O₂R) reserve are used interchangeably for prescribing aerobic exercise intensity due to their assumed 1:1 relationship, although its validity is debated. This study aimed to assess if %HRR and %V̇O₂R show a 1:1 relationship during steady-state exercise (SSE) and if exercise intensity and duration affect their relationship.

Methods

Eight physically active males (age 22.6 ± 1.2 years) were enrolled. Pre-exercise and maximal HR and V̇O₂ were assessed on the first day. In the following 4 days, different SSEs were performed (running) combining the following randomly assigned durations and intensities: 15 min, 45 min, 60% HRR, 80% HRR. Post-exercise maximal HR and V̇O₂ were assessed after each SSE. Using pre-exercise and post-exercise maximal values, the average HR and V̇O₂ of the last 5 min of each SSE were converted into percentages of the reserves (%RES), which were computed in a 3-way RM-ANOVA (α = 0.05) to assess if they were affected by the prescription parameter (HRR or V̇O₂R), exercise intensity (60% or 80% HRR), and duration (15 or 45 min).

Results

The %RES values were not affected by the prescription parameter (p = 0.056) or its interactions with intensity (p = 0.319) or duration and intensity (p = 0.117), while parameter and duration interaction was significant (p = 0.009). %HRRs and %V̇O₂Rs did not differ in the 15-min SSEs (mean difference [MD] = 0.7 percentage points, p = 0.717), whereas %HRR was higher than %V̇O₂R in the 45-min SSEs (MD = 6.7 percentage points, p = 0.009).

Conclusion

SSE duration affects the %HRR-%V̇O₂R relationship, with %HRRs higher than %V̇O₂Rs in SSEs of longer duration.

Squalene-Based Nano-Assemblies Improve the Pro-Autophagic Activity of Trehalose

The disaccharide trehalose is a well-established autophagy inducer, but its therapeutic application is severely hampered by its low potency and poor pharmacokinetic profile. Thus, we targeted the rational design and synthesis of trehalose-based small molecules and nano objects to overcome such issues. Among several rationally designed trehalose-centered putative autophagy inducers, we coupled trehalose via suitable spacers with known self-assembly inducer squalene to yield two nanolipid-trehalose conjugates. Squalene is known for its propensity, once linked to a bioactive compound, to assemble in aqueous media in controlled conditions, internalizing its payload and forming nanoassemblies with better pharmacokinetics. We assembled squalene conjugates to produce the corresponding nanoassemblies, characterized by a hydrodynamic diameter of 188 and 184 nm and a high stability in aqueous media as demonstrated by the measured Z-potential. Moreover, the nanoassemblies were characterized for their toxicity and capability to induce autophagy in vitro.

Nutraceuticals and Physical Activity as Antidepressants: The Central Role of the Gut Microbiota

Major depressive disorder (MDD) is a common mental illness. Evidence suggests that the gut microbiota play an essential role in regulating brain functions and the pathogenesis of neuropsychiatric diseases, including MDD. There are numerous mechanisms through which the gut microbiota and brain can exchange information in a continuous, bidirectional communication. Current research emphasizes the interexchange of signals influenced by the gut microbiota that are detected and transduced in information from the gut to the nervous system involving neural, endocrine, and inflammatory mechanisms, suggesting a relationship between oxidative stress and the pathophysiology of MDD via the hyperactivation of inflammatory responses. Potential sources of inflammation in the plasma and hippocampus of depressed individuals could stem from increases in intestinal permeability. Some nutraceuticals, such as specific probiotics, namely psychobiotics, polyphenols, carotenoids, butyrate, and prebiotics, have been demonstrated to exert an antidepressant activity, but most of them need to be metabolized and activated by gut microorganisms. By inducing changes in the gut microbiota composition, physical exercise might also exert a role in alleviating depression-like symptoms. The mutual relationships among nutraceuticals, exercise, and depression will be discussed, and the potential role of the gut microbiota as a therapeutic target to treat depression will be explored.

Nine weeks of high-intensity indoor cycling training induced changes in the microbiota composition in non-athlete healthy male college students

Background

The gut microbiota constitutes a dynamic microbial system constantly challenged by environmental conditions, including physical exercise. Limited human studies suggest that exercise could play a beneficial role for gut health, increasing microbial diversity, even if the effects of exercise on gut microbial microorganisms depends on its intensity and duration. This study aimed to investigate the effects of nine weeks of high-intensity interval exercise on gut microbiota composition in healthy young adults.

Methods

The gut microbiota composition of seventeen healthy male college students was analysed before and after nine weeks of high-intensity interval cycling training by 16S rRNA amplicon sequencing. PERMANOVA for repeated measures was used to test pre-post differences in the relative abundance of all taxonomic levels, and correlations between variations in microbial composition and physical and dietary features were also assessed.

Results

Physical exercise induced changes in microbiota composition, at all taxonomic levels analysed (phyla: F _{[1, 32]}=3.97, p=0.029; classes: F _{[1, 32]}=3.39, p=0.033, orders: F _{[1, 32]}=3.17, p=0.044, families: F _{[1, 32]}=1.54, p=0.037, genera: F _{[1, 32]}=1.46, p=0.015, species: F _{[1, 32]}=1.38, p=0.007). Conversely, no differences were found between pre and post-training conditions for microbial community richness (Chao1: V=105, p=0.06) or diversity (Shannon index: V=62, p=0.52; Simpson index: V=59, p=0.43). Changes in the relative abundance of eighteen genera were correlated to changes of twenty environmental factors grouped in physical features, sport-related features, and dietary features.

Conclusions

Nine weeks of high-intensity exercise induced modifications in gut microbiota composition in healthy male college students, shifting the gut microbial population towards a healthier microbiome with benefit to human health in general.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12970-021-00471-z.

Hypoglycemia due to PI3K/AKT/mTOR signaling pathway defects: two novel cases and review of the literature

INTRODUCTION

The PI3K/AKT/mTOR signaling pathway is important for the regulation of multiple biological processes, including cellular growth and glucose metabolism. Defects of the PI3K/AKT/mTOR signaling pathway are not usually considered among the genetic causes of recurrent hypoglycemia in childhood. However, accumulating evidence links hypoglycemia with defects of this pathway.

CASE REPORTS AND REVIEW

We describe here two cases of macrocephaly and hypoglycemia bearing genetic defects in genes involved in the PI3K/AKT/mTOR pathway. The first patient was diagnosed with a PTEN hamartoma tumour syndrome (PTHS) due to the de novo germline missense mutation c.[492 + 1G > A] of the PTEN gene. The second patient presented the autosomal dominant mental retardation-35 (MDR35) due to the heterozygous missense mutation c.592G > A in the PPP2R5D gene. A review of the literature on hypoglycemia and PI3K/AKT/mTOR signaling pathway defects, with a special focus on the metabolic characterization of hypoglycemia, is included.

CONCLUSIONS

PI3K/AKT/mTOR pathway defects should be included in the differential diagnosis of patients with hypoglycemia and macrocephaly. Clinical suspicion and molecular confirmation are important, not just for an accurate genetic counselling but also for defining the follow-up management, including cancer surveillance. The biochemical profile of hypoglycemia varies among patients. While most patients are characterized by low plasmatic insulin levels, hyperinsulinemia has also been observed. Large patient cohorts are needed to gain a comprehensive profile of the biochemical patterns of hypoglycemia in such defects and eventually guide targeted therapeutic interventions.

Trehalose-based neuroprotective autophagy inducers

A small set of trehalose-centered putative autophagy inducers was rationally designed and synthesized, with the aim to identify more potent and bioavailable autophagy inducers than free trehalose, and to acquire information about their molecular mechanism of action. Several robust, high yield routes to key trehalose intermediates and small molecule prodrugs (2-5), putative probes (6-10) and inorganic nanovectors (12a - thiol-PEG-triazole-trehalose constructs 11) were successfully executed, and compounds were tested for their autophagy-inducing properties. While small molecules 2-11 showed no pro-autophagic behavior at sub-millimolar concentrations, trehalose-bearing PEG-AuNPs 12a caused measurable autophagy induction at an estimated 40 μM trehalose concentration without any significant toxicity at the same concentration.

LRRK2 G2019S kinase activity triggers neurotoxic NSF aggregation

Parkinson's disease is characterized by the progressive degeneration of dopaminergic neurons within the substantia nigra pars compacta and the presence of protein aggregates in surviving neurons. The LRRK2 G2019S mutation is one of the major determinants of familial Parkinson's disease cases and leads to late-onset Parkinson's disease with pleomorphic pathology, including α-synuclein accumulation and deposition of protein inclusions. We demonstrated that LRRK2 phosphorylates N-ethylmaleimide sensitive factor (NSF). We observed aggregates containing NSF in basal ganglia specimens from patients with Parkinson's disease carrying the G2019S variant, and in cellular and animal models expressing the LRRK2 G2019S variant. We found that LRRK2 G2019S kinase activity induces the accumulation of NSF in toxic aggregates. Of note, the induction of autophagy cleared NSF aggregation and rescued motor and cognitive impairment observed in aged hG2019S bacterial artificial chromosome (BAC) mice. We suggest that LRRK2 G2019S pathological phosphorylation impacts on NSF biochemical properties, thus causing the formation of cytotoxic protein inclusions.

LRRK2 at the pre-synaptic site: A 16-years perspective

Parkinson's disease is a common neurodegenerative disorder and is clinically characterized by bradykinesia, rigidity, and resting tremor. Missense mutations in the leucine-rich repeat protein kinase-2 gene (LRRK2) are a recognized cause of inherited Parkinson's disease. The physiological and pathological impact of LRRK2 is still obscure, but accumulating evidence indicates that LRRK2 orchestrates diverse aspects of membrane trafficking, such as membrane fusion and vesicle formation and transport along actin and tubulin tracks. In the present review, we focus on the special relation between LRRK2 and synaptic vesicles. LRRK2 binds and phosphorylates key actors within the synaptic vesicle cycle. Accordingly, alterations in dopamine and glutamate transmission have been described upon LRRK2 manipulations. However, the different modeling strategies and phenotypes observed require a critical approach to decipher the outcome of LRRK2 at the pre-synaptic site.

HRR and V˙O2R Fractions Are Not Equivalent: Is It Time to Rethink Aerobic Exercise Prescription Methods?

INTRODUCTION

According to current guidelines, the intensity of health-enhancing aerobic exercise should be prescribed using a percentage of heart rate reserve (%HRR), which is considered to be more closely associated (showing a 1:1 relation) with the percentage of oxygen uptake reserve (%V˙O2R) rather than with the percentage of maximal oxygen uptake (%V˙O2max) during incremental exercise. However, the associations between %HRR and %V˙O2R and between %HRR and %V˙O2max are under debate; hence, their actual relationships were investigated in this study.

METHODS

Data from each stage of a maximal incremental exercise test performed by 737 healthy and physically inactive participants of the HERITAGE Family Study were screened and filtered then used to calculate the individual linear regressions between %HRR and either %V˙O2R or %V˙O2max. For each relationship, the mean slope and intercept of the individual linear regression were compared with 1 and 0 (i.e., the identity line), respectively, using one-sample t-tests. The individual root mean square errors of the actual versus the 1:1 predicted %HRR were calculated for both relationships and compared using a paired-sample t-test.

RESULTS

The mean slopes (%HRR-%V˙O2R, 0.972 ± 0.189; %HRR-%V˙O2max, 1.096 ± 0.216) and intercepts (%HRR-%V˙O2R, 8.855 ± 16.022; %HRR-%V˙O2max, -3.616 ± 18.993) of both relationships were significantly different from 1 and 0, respectively, with high interindividual variability. The average root mean square errors were high and revealed that the %HRR-%V˙O2max relationship was more similar to the identity line (P < 0.001) than the %HRR-%V˙O2R relationship (7.78% ± 4.49% vs 9.25% ± 5.54%).

CONCLUSIONS

Because both relationships are different from the identity line and using a single equation may not be appropriate to predict exercise intensity at the individual level, a rethinking of the relationships between the intensity variables may be necessary to ensure that the most suitable health-enhancing aerobic exercise intensity is prescribed.

Dietary Habits and Psychological States during COVID-19 Home Isolation in Italian College Students: The Role of Physical Exercise

Social isolation has adverse effects on mental health, physical exercise, and dietary habits. This longitudinal observational study aimed to investigate the effects of mood states and exercise on nutritional choices, on 176 college students (92 males, 84 females; 23 ± 4 years old) during the COVID-19 lockdown. During 21 days, nutrition and exercise were daily monitored, and the mood states assessed. A factor analysis was used to reduce the number of nutritional variables collected. The relationships between exercise, mood and nutrition were investigated using a multivariate general linear model and a mediation model. Seven factors were found, reflecting different nutritional choices. Exercise was positively associated with fruit, vegetables and fish consumption (p = 0.004). Depression and quality of life were, directly and inversely, associated with cereals, legumes (p = 0.005; p = 0.004) and low-fat meat intake (p = 0.040; p = 0.004). Exercise mediated the effect of mood states on fruit, vegetables and fish consumption, respectively, accounting for 4.2% and 1.8% of the total variance. Poorer mood states possibly led to unhealthy dietary habits, which can themselves be linked to negative mood levels. Exercise led to healthier nutritional choices, and mediating the effects of mood states, it might represent a key measure in uncommon situations, such as home-confinement.

Gut Microbiota Status in COVID-19: An Unrecognized Player?

Infection with the SARS-CoV-2 virus causes cardiopulmonary and vascular complications, ranging in severity. Understanding the pathogenic mechanisms of the novel SARS-CoV2 infection and progression can provide potential novel targets for its prevention and/or treatment. Virus microbiota reciprocal interactions have been studied in a variety of viral infections. For example, the integrity of Coronavirus particles can be disrupted by surfactin, a bacterial surface molecule that targets other viruses, including that of influenza A. In this light, intestinal microbiota likely influences COVID-19 virulence, while from its side SARS-CoV-2 may affect the intestinal microbiome promoting dysbiosis and other deleterious consequences. Hence, the microbiota pre-existing health status and its alterations in the course of SARS-CoV-2 infection, are likely to play an important, still underscored role in determining individual susceptibility and resilience to COVID-19. Indeed, the vast majority of COVID-19 worst clinical conditions and fatalities develop in subjects with specific risk factors such as aging and the presence of one or more comorbidities, which are intriguingly characterized also by unhealthy microbiome status. Moreover, these comorbidities require complex pharmacological regimens known as "polypharmacy" that may further affect microbiota integrity and worsen the resilience to viral infections. This complex situation may represent a further and underestimated risk with regard to COVID-19 clinical burden for the elderly and comorbid people. Here, we discuss the possible biological, physiopathological, and clinical implications of gut microbiota in COVID-19 and the strategies to improve/maintain its healthy status as a simple and adjunctive strategy to reduce COVID-19 virulence and socio-sanitary burden.

A reliable strategy for single-cell RNA sequencing analysis using cryoconserved primary cortical cells

BACKGROUND

The application of single-cell RNA sequencing (scRNASeq) represents a unique approach to identify hundreds to millions of cells in mammalian cortical multilayers at different stages of embryogenesis. ScRNASeq technology applied to neurological studies requires the use of fresh starting materials because standard cryopreservation methods do not guarantee high viability of cortical primary cells derived from dissected brain areas.

NEW METHOD

Here we set up and validate an innovative strategy to perform scRNASeq studies in cryopreserved primary cortical cells isolated from E15.5 mouse embryo. In order to freeze cortical primary cells, we have employed Neurostore, a medium able to guarantee high viability and cell composition of embryonic cortex after thawing.

COMPARISON WITH EXISTING METHODS

We showed for the first time the possibility to run scRNASeq experiments on primary cortical cells in an off-line set-up, ensuring cellular integrity and diversity.

RESULTS

By trypan blue assay and flow cytometry analysis, we found that Neurostore-cryopreserved cortical cells showed approximately 95 % of viability. Satisfactory RNA recovery and cDNA libraries were achieved. Transcriptome sequencing of 35,763 cryoconserved single cells yielded a robust data-set, identifying 25 cell clusters in three biological samples. Prevalence of peculiar neural populations before and after the cryopreservation-resuscitation procedure was verified by marker gene expression and immunofluorescence analysis.

CONCLUSIONS

Our findings support the evidence that frozen primary cortical cells can be successfully employed in scRNASeq experiments allowing an unprecedented flexibility in experimental procedures, such as sample preparation and subsequent processing steps performed in different locations.

Kinase inhibition of G2019S-LRRK2 enhances autolysosome formation and function to reduce endogenous alpha-synuclein intracellular inclusions

The Parkinson's disease (PD)-associated kinase Leucine-Rich Repeat Kinase 2 (LRRK2) is a crucial modulator of the autophagy-lysosome pathway, but unclarity exists on the precise mechanics of its role and the direction of this modulation. In particular, LRRK2 is involved in the degradation of pathological alpha-synuclein, with pathogenic mutations precipitating neuropathology in cellular and animal models of PD, and a significant proportion of LRRK2 patients presenting Lewy neuropathology. Defects in autophagic processing and lysosomal degradation of alpha-synuclein have been postulated to underlie its accumulation and onset of neuropathology. Thus, it is critical to obtain a comprehensive knowledge on LRRK2-associated pathology. Here, we investigated a G2019S-LRRK2 recombinant cell line exhibiting accumulation of endogenous, phosphorylated alpha-synuclein. We found that G2019S-LRRK2 leads to accumulation of LC3 and abnormalities in lysosome morphology and proteolytic activity in a kinase-dependent fashion, but independent from constitutively active Rab10. Notably, LRRK2 inhibition was ineffective upon upstream blockade of autophagosome-lysosome fusion events, highlighting this step as critical for alpha-synuclein clearance.

Multimodal MRI Longitudinal Assessment of White and Gray Matter in Different SPG Types of Hereditary Spastic Paraparesis

Hereditary spastic paraplegias (HSP) are a group of genetically and clinically heterogeneous neurologic disorders. Hereby we describe a relatively large group of patients (pts) affected by HSP studied at baseline (31 pts) and at follow-up (mean period 28.9 ± 8.4 months; 23 pts) with multimodal advanced MRI: high-resolution T1 images for voxel-based morphometry (VBM) analysis, magnetic resonance spectroscopy (MRS), and diffusion tensor imaging (DTI). An age-matched healthy control (HC) group underwent the same neuroimaging protocol in a time schedule matched with the HSP patients. At baseline, VBM showed gray matter (GM) reduction in HSP in the right pre-frontal cortex and bilaterally in the thalami. MRS at baseline depicted in HSP patients compared to the HC group reduction of NAA/Cr ratio in the right pre-frontal region, increase of Cho/Cr ratio in the right pre-central regions, and increase of mI/Cr ratio on the left pre-central area. At cross-sectional follow-up analysis and longitudinal evaluation, no VBM and MRS statistically significant results were obtained. Tract-based spatial statistics (TBSS) analysis showed widespread DTI brain white matter (WM) alterations in patients compared to HC at baseline, which are characterized by reduction of fractional anisotropy (FA) and increase of mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity, as confirmed on cross-analysis of the follow-up dataset. A longitudinal analysis with TBSS in HSP patients did not show significant variations, while upon applying region-based analysis we found increased FA and decreased MD and AD in specific brain WM fiber complex during follow-up. The changes were not correlated with the clinical presentation (pure vs complicated HSP), motor function, and motility indexes or history of specific treatments (botulinum toxin). In conclusion, the cross-sectional analysis of the multiparametric MRI data in our HSP patients confirmed the non-prominent involvement of the cortex in the primary motor regions but rather of other more associative areas. On the contrary, DTI demonstrated a widespread involvement of the brain WM, including the primary motor regions, which was confirmed at follow-up. The longitudinal analysis revealed an apparent inversion of tendency when considering the expected evolution of a neurodegenerative process: we detected an increase of FA and a decrease of MD and AD. These time-related modifications may suggest a repair attempt by the residual central WM fibers, which requires confirmation with a larger group of patients and with a longer time interval.

Formulation and Clinical Evaluation of Sodium Benzoate Oral Solution for the Treatment of Urea Cycle Disorders in Pediatric Patients

BACKGROUND

Sodium benzoate, a common food preservative, is used in the treatment of patients with urea cycle disorders (UCDs) as it stimulates ammonia removal by a non-urea cycle-based pathway. Despite its use in the clinical routine, no commercially available oral formulations currently exist. Liquid formulation is normally well accepted in pediatric age and allows precise dosage according to the children's needs.

AIMS

(1) To prepare an oral sodium benzoate solution in different tastes and determine its stability, palatability, and tolerability and (2) to describe the long-term follow-up of two pediatric patients with UCDs treated with our formulation.

METHODS

We prepared five oral solutions of sodium benzoate (200 mg/ml) by adding different flavoring agents. We measured drug concentration in the samples by high-performance liquid chromatography (HPLC). We evaluated palatability and tolerability with adult volunteers. Long-term drug compliance and metabolic control were appraised in two pediatric patients.

RESULTS

All the oral solutions remained stable at room temperature along the 96-day test period, and they were well tolerated. The mint-flavored solution resulted the most palatable and preferred by adult volunteers. We report good drug compliance and good metabolic outcomes for both pediatric patients during the entire follow-up.

CONCLUSIONS

Our study highlighted the stability and tolerability of flavored sodium benzoate oral solutions. These solutions were well accepted during a long-term follow-up and guaranteed a good metabolic control. Since taste attributes are critical to ensure acceptable medication adherence in the pediatric age, flavored liquid formulations of sodium benzoate may be an efficient strategy to achieve therapeutic outcomes in UCD pediatric patients.

The LRRK2 N-terminal domain influences vesicle trafficking: impact of the E193K variant

The LRRK2 protein consists of multiple functional domains, including protein-binding domains at its N and C-terminus. Mutations in the Leucine-rich repeat kinase 2 gene (LRRK2) have been linked to familial and sporadic Parkinson's disease (PD). We have recently described a novel variant falling within the N-terminal armadillo repeats, E193K. Herein, our aim is to investigate the functional impact of LRRK2 N-terminal domain and the E193K variant on vesicle trafficking. By combining Total Internal Reflection Fluorescence (TIRF) microscopy and a synaptopHluorin assay, we found that expression of a construct lacking the N-terminal domain increases the frequency and amplitude of spontaneous synaptic events. Complementary biochemical approaches showed that the E193K variant alters the binding properties of LRRK2, decreases LRRK2 binding to synaptic vesicles, and promotes vesicle fusion. Our results confirm the physiological and pathological relevance of the nature of the LRRK2-associated macro-molecular complex solidifying the idea that different pathological mutations critically alter the scaffolding function of LRRK2 resulting in a perturbation of the vesicular trafficking as a common denominator.

Effects of a commercially available branched-chain amino acid-alanine-carbohydrate-based sports supplement on perceived exertion and performance in high intensity endurance cycling tests

Background

Sports nutritional supplements containing branched-chain amino acids (BCAA) have been widely reported to improve psychological and biological aspects connected to central fatigue and performance in endurance exercise, although the topic is still open to debate. The aim of the present study was to determine whether the intake of a commercially available BCAA-based supplement, taken according to the manufacturer’s recommendations, could affect the rating of perceived exertion (RPE) and performance indexes at the beginning (1d) and end of a 9-week (9w) scheduled high intensity interval training program, with an experimental approach integrating the determination of psychometric, performance, metabolic and blood biochemical parameters.

Methods

This was a randomized double-blind placebo-controlled study. Thirty-two untrained, healthy young adults (20 males and 12 female) were enrolled. A high-intensity endurance cycling (HIEC) test was used to induce fatigue in the participants: HIEC consisted in ten 90 s sprints interspersed by ten 3 min recovery phases and followed by a final step time to exhaustion was used. In parallel with RPE, haematological values (creatine kinase, alanine, BCAA, tryptophan, ammonia and glucose levels), and performance indexes (maximal oxygen consumption - VO_2max, power associated with lactate thresholds - W_LT1, W_LT2 and time to exhaustion - TTE) were assessed. All subject took the supplement (13.2 g of carbohydrates; 3.2 g of BCAA and 1.6 g of L-alanine per dose) or placebo before each test and training session. Dietary habits and training load were monitored during the entire training period.

Results

The administration of the supplement (SU) at 1d reduced RPE by 9% during the recovery phase, as compared to the placebo (PL); at 9w the RPE scores were reduced by 13 and 21% during the sprint and recovery phase, respectively; at 9w, prolonged supplement intake also improved TTE and TRIMP. SU intake invariably promoted a rapid increase (within 1 h) of BCAA serum blood levels and prevented the post-HIEC tryptophan: BCAA ratio increase found in the PL group, at both 1d and 9w. There was no difference in dietary habits between groups and those habits did not change over time; no difference in glycemia was found between SU and PL. VO_2max, W_LT1 and W_LT2 values improved over time, but were unaffected by supplement intake.

Conclusions

On the whole, these results suggest that i) the intake of the BCAA-based commercially available supplement used in this study reduces RPE as a likely consequence of an improvement in the serum tryptophan: BCAA ratio; ii) over time, reduced RPE allows subjects to sustain higher workloads, leading to increased TRIMP and TTE.

Mutual Interactions among Exercise, Sport Supplements and Microbiota

The adult gut microbiota contains trillions of microorganisms of thousands of different species. Only one third of gut microbiota are common to most people; the rest are specific and contribute to enhancing genetic variation. Gut microorganisms significantly affect host nutrition, metabolic function, immune system, and redox levels, and may be modulated by several environmental conditions, including physical activity and exercise. Microbiota also act like an endocrine organ and is sensitive to the homeostatic and physiological changes associated with training; in turn, exercise has been demonstrated to increase microbiota diversity, consequently improving the metabolic profile and immunological responses. On the other side, adaptation to exercise might be influenced by the individual gut microbiota that regulates the energetic balance and participates to the control of inflammatory, redox, and hydration status. Intense endurance exercise causes physiological and biochemical demands, and requires adequate measures to counteract oxidative stress, intestinal permeability, electrolyte imbalance, glycogen depletion, frequent upper respiratory tract infections, systemic inflammation and immune responses. Microbiota could be an important tool to improve overall general health, performance, and energy availability while controlling inflammation and redox levels in endurance athletes. The relationship among gut microbiota, general health, training adaptation and performance, along with a focus on sport supplements which are known to exert some influence on the microbiota, will be discussed.

Levetiracetam treatment ameliorates LRRK2 pathological mutant phenotype

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of Parkinson's disease (PD). The LRRK2 physiological and pathological function is still debated. However, different experimental evidence based on LRRK2 cellular localization and LRRK2 protein interactors suggests that LRRK2 may be part and regulate a protein network modulating vesicle dynamics/trafficking. Interestingly, the synaptic vesicle protein SV2A is part of this protein complex. Importantly, SV2A is the binding site of the levetiracetam (LEV), a compound largely used in human therapy for epilepsy treatment. The binding of LEV to SV2A reduces the neuronal firing by the modulation of vesicle trafficking although by an unclear molecular mechanism. In this short communication, we have analysed the interaction between the LRRK2 and SV2A pathways by LEV treatment. Interestingly, LEV significantly counteracts the effect of LRRK2 G2019S pathological mutant expression in three different cellular experimental models. Our data strongly suggest that LEV treatment may have a neuroprotective effect on LRRK2 pathological mutant toxicity and that LEV repositioning could be a viable compound for PD treatment.

Ankyrin-G induces nucleoporin Nup358 to associate with the axon initial segment of neurons

Nup358 (also known as RanBP2) is a member of the large nucleoporin family that constitutes the nuclear pore complex. Depending on the cell type and the physiological state, Nup358 interacts with specific partner proteins and influences distinct mechanisms independent of its role in nucleocytoplasmic transport. Here, we provide evidence that Nup358 associates selectively with the axon initial segment (AIS) of mature neurons, mediated by the AIS scaffold protein ankyrin-G (AnkG, also known as Ank3). The N-terminus of Nup358 is demonstrated to be sufficient for its localization at the AIS. Further, we show that Nup358 is expressed as two isoforms, one full-length and another shorter form of Nup358. These isoforms differ in their subcellular distribution in neurons and expression level during neuronal development. Overall, the present study highlights an unprecedented localization of Nup358 within the AIS and suggests its involvement in neuronal function.This article has an associated First Person interview with the first author of the paper.

Nanolipid-Trehalose Conjugates and Nano-Assemblies as Putative Autophagy Inducers

The disaccharide trehalose is an autophagy inducer, but its pharmacological application is severely limited by its poor pharmacokinetics properties. Thus, trehalose was coupled via suitable spacers with squalene (in 1:2 and 1:1 stoichiometry) and with betulinic acid (1:2 stoichiometry), in order to yield the corresponding nanolipid-trehalose conjugates 1-Sq-mono, 2-Sq-bis and 3-Be-mono. The conjugates were assembled to produce the corresponding nano-assemblies (NAs) Sq-NA1, Sq-NA2 and Be-NA3. The synthetic and assembly protocols are described in detail. The resulting NAs were characterized in terms of loading and structure, and tested in vitro for their capability to induce autophagy. Our results are presented and thoroughly commented upon.

NEGR1 and FGFR2 cooperatively regulate cortical development and core behaviours related to autism disorders in mice

Autism spectrum disorders are neurodevelopmental conditions with diverse aetiologies, all characterized by common core symptoms such as impaired social skills and communication, as well as repetitive behaviour. Cell adhesion molecules, receptor tyrosine kinases and associated downstream signalling have been strongly implicated in both neurodevelopment and autism spectrum disorders. We found that downregulation of the cell adhesion molecule NEGR1 or the receptor tyrosine kinase fibroblast growth factor receptor 2 (FGFR2) similarly affects neuronal migration and spine density during mouse cortical development in vivo and results in impaired core behaviours related to autism spectrum disorders. Mechanistically, NEGR1 physically interacts with FGFR2 and modulates FGFR2-dependent extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) signalling by decreasing FGFR2 degradation from the plasma membrane. Accordingly, FGFR2 overexpression rescues all defects due to Negr1 knockdown in vivo. Negr1 knockout mice present phenotypes similar to Negr1-downregulated animals. These data indicate that NEGR1 and FGFR2 cooperatively regulate cortical development and suggest a role for defective NEGR1-FGFR2 complex and convergent downstream ERK and AKT signalling in autism spectrum disorders.

Leucine‐rich repeat kinase 2 phosphorylation on synapsin I regulates glutamate release at pre‐synaptic sites

Leucine-rich repeat kinase 2 (LRRK2) is a large multidomain scaffolding protein with kinase and GTPase activities involved in synaptic vesicle (SV) dynamics. While its role in Parkinson's disease has been largely investigated, little is known about LRRK2 physiological role and until now few proteins have been described as substrates. We have previously demonstrated that LRRK2 through its WD40 domain interacts with synapsin I, an important SV-associated phosphoprotein involved in neuronal development and in the regulation of neurotransmitter release. To test whether synapsin I is substrate for LRRK2 and characterize the properties of its phosphorylation, we used in vitro kinase and binding assays as well as cellular model and site-direct mutagenesis. Using synaptosomes in superfusion, patch-clamp recordings in autaptic WT and synapsin I KO cortical neurons and SypHy assay on primary cortical culture from wild-type and BAC human LRRK2 G2019S mice we characterized the role of LRRK2 kinase activity on glutamate release and SV trafficking. Here we reported that synapsin I is phosphorylated by LRRK2 and demonstrated that the interaction between LRRK2 WD40 domain and synapsin I is crucial for this phosphorylation. Moreover, we showed that LRRK2 phosphorylation of synapsin I at threonine 337 and 339 significantly reduces synapsin I-SV/actin interactions. Using complementary experimental approaches, we demonstrated that LRRK2 controls glutamate release and SV dynamics in a kinase activity and synapsin I-dependent manner. Our findings show that synapsin I is a LRRK2 substrate and describe a novel mechanisms of regulation of glutamate release by LRRK2 kinase activity.

Neurostore: A Novel Cryopreserving Medium for Primary Neurons

Primary neuronal culture from rodents is a key tool in neurobiology. However, the preparation of primary cultures requires precise planning, starting from animal mating. Furthermore, each preparation generates a high amount of cells that eventually go wasted. The possibility to cryopreserve primary neural cells represents a resource for in vitro studies and significantly reduces the sacrifice of animals. Here we describe that Neurostore buffer supports the cryopreservation of primary neurons.